2022/09/25 更新

写真a

ヨコサワ マサユキ
横沢 正幸
所属
人間科学学術院 人間科学部
職名
教授
プロフィール
生態系は、不均質性、空間および時間スケールのダイナミックレンジの広さ、多数のサブシステムの相互作用などを内包しており複雑である。このため、素過程からのフォワードモデルが適切に構築できない場合も多く、データからいかにセンス良く本質的な構造と機能を抽出しうるかが、問題解決への道筋となると考える。この観点から、陸域生態系を対象として統計モデリングとデータ同化手法を援用して以下の研究を行っている。

・要素間の非線形相互作用によって創発される生態系の巨視的現象の解明
・植生のサイズ構造、空間分布の出現様式
・生態系における物質・エネルギー移行過程の解明
・生態系における炭素、熱、水の流れと貯留
・環境摂動に対する不確実性を考慮した生態系の resilience と vulnerability の評価
・気候変化と生態系との相互作用(影響、適応、対策)

兼担

  • 人間科学学術院   人間科学部通信課程

  • 人間科学学術院   大学院人間科学研究科

学内研究所等

  • 2021年
    -
    2022年

    データ科学センター   兼任センター員

学歴

  •  
     
     

    東京工業大学   理工学研究科   物理学  

  •  
     
     

    東京工業大学   理学部   物理学科  

学位

  • 東京大学   博士(学術)

  • 東京工業大学   理学修士

経歴

  • 2013年
    -
    2017年

    静岡大学   工学部   教授

  • 1987年
    -
    2013年

    農業環境技術研究所   研究員

  •  
     
     

    早稲田大学 人間科学学術院   教授

所属学協会

  •  
     
     

    American Geophysical Union

  •  
     
     

    日本物理学会

  •  
     
     

    日本農業気象学会

  •  
     
     

    人工知能学会

  •  
     
     

    日本生態学会

 

研究分野

  • 農業環境工学、農業情報工学

  • 環境影響評価

  • 環境負荷、リスク評価管理

  • 生態学、環境学

  • 農業環境工学、農業情報工学

研究キーワード

  • 空間分布

  • サイズ構造

  • 物質循環

  • モデリング

  • 環境変化

  • 食料生産

  • 生態系

▼全件表示

論文

  • A Bayesian inversion framework to evaluate parameter and predictive inference of a simple soil respiration model in a cool-temperate forest in western Japan

    Motomu Toda, Kazuki Doi, Masae I. Ishihara, Wakana A. Azuma, Masayuki Yokozawa

    ECOLOGICAL MODELLING   418   108918  2020年02月  [査読有り]

     概要を見る

    Careful modelling of soil carbon sequestration is essential to evaluate future terrestrial feedback to the earth climate system through atmosphere-surface carbon exchange. Few studies have evaluated, in bio- and geo-applications, parameter and predictive uncertainty of soil respiration models by considering the difference between observations and model predictions; i.e. residual error, which is assumed neither to be independent nor to be described by a normal (i.e. Gaussian) probability distribution with a mean of zero and constant variance. In this paper, we use 2-year observations of soil carbon flux from 2017 to 2018 (hereafter referred to as 'long-term simulation') obtained with two open-top chambers to estimate parameter and predictive uncertainty of a simple soil respiration model based on Bayesian statistics in a cool-temperate forest in western Japan. We also use a Gaussian innovative residual error model in which a generalised likelihood uncertainty estimation that accounts for correlated, heteroscedastic, non-normally distributed (i.e. non-Gaussian) residual error flexibly handles statistics varying in skewness and kurtosis. Results show that the effects of correlation and heteroscedasticity were eliminated adequately. Additionally, the posterior distribution of the residuals had a pattern intermediate to those of Gaussian and Laplacian (or double-exponential) distributions. Consequently, the predicted soil respiration rate, and range of uncertainty therein, well-matched the observational data. Furthermore, we compare results of parameter and predictive inference of the soil respiration model from the long-term simulation with those constrained of short-term simulations (i.e. 4-month subsets of the 2-year dataset) to determine the extent to which the approach used affects the estimation of parameter and predictive uncertainty. No significant difference in parameter estimates was found between the long-term simulation versus any of the short-term simulations, whereas short-term simulation analysis of the uncertainty at 50 %-i.e. between the lower (25 %) and upper (75 %) quartiles of the probability range-indicated distinctive variations in model parameters in summer when more vigorous activity of trees and organisms promotes carbon cycling between the atmosphere and ecosystem. Overall we demonstrate that the Bayesian inversion approach is useful as a means by which to evaluate effectively parameter and predictive uncertainty of a soil respiration model with precise representation of residual errors.

    DOI

  • Dynamic measurements of earthworm respiration

    Yonemura Seiichiro, Kaneda Satoshi, Kodama Naomi, Sakurai Gen, Yokozawa Masayuki

    Journal of Agricultural Meteorology   75   103 - 110  2019年03月  [査読有り]

  • Effectively tuning plant growth models with different spatial complexity: A statistical perspective

    Yoshiaki Nakagawa, Masayuki Yokozawa, Akihiko Ito, Toshihiko Hara

    ECOLOGICAL MODELLING   361   95 - 112  2017年10月  [査読有り]

     概要を見る

    Forest gap models (non-spatial, patch- and individual-based models) and size structure models (non spatial stand models) rely on two assumptions: the mean field assumption (A-I) and the assumption that plants in one patch do not compete with plants in other patches (A-II). These assumptions lead to differences in plant size dynamics between these models and spatially explicit models (or observations of real forests). Therefore, to more accurately replicate dynamics, these models require model tuning by (1) adjusting model parameter values or (2) introducing a correction term into models. However, these model tuning methods have not been systematically and statistically investigated in models using different patch sizes.
    We used a simple spatially explicit model that simulated growth and competition processes, and rewrote it as patch models. The patch sizes of the patch models were set between 4 and 1500 m(2). First, we estimated the parameter values (the intrinsic growth rate, metabolic loss, competition coefficient, and competitive asymmetry) of these models that best reproduce plant size growth under competition using field data from a Sakhalin fir stand, and compared the parameter values among the models. Second, we introduced correction terms into the patch models and estimated the optimal correction term for reproducing plant size growth under competition using the field data.
    The estimated parameter values of the patch models for all patch sizes differed greatly from those of the spatially explicit models. Therefore, parameter values should not be shared between spatially explicit models and patch models. In addition, the parameter value sets for the models with small patches differed from those with large patches. This is because parameter values for small patches mainly improve biases of A-II, while those for large patches mainly improve biases of A-I. Therefore, parameter values should not be shared between patch models with small patches and with large patches.
    The estimated correction term in the patch models with large patches excluded the competitive effects of small and medium-sized plants on their neighbors, even though these effects exist in real stands. This exclusion can be ascribed to the discrepancy between their competition in real plant populations and A-I. Therefore, the competitive effects of small and medium-sized plants should not be included in patch models with large patches. Finally, the reproducibility of the models tuned with correction terms was higher than those with adjusted parameters. (C) 2017 Elsevier B.V. All rights reserved.

    DOI

  • A model of silicon dynamics in rice: An analysis of the investment efficiency of Si transporters

    Gen Sakurai, Naoki Yamaji, Namiki Mitani-Ueno, Masayuki Yokozawa, Keisuke Ono, Jian Feng Ma

    Frontiers in Plant Science   8   E31-E34  2017年07月  [査読有り]

     概要を見る

    Silicon is the second most abundant element in soils and is beneficial for plant growth. Although, the localizations and polarities of rice Si transporters have been elucidated, the mechanisms that control the expression of Si transporter genes and the functional reasons for controlling expression are not well-understood. We developed a new model that simulates the dynamics of Si in the whole plant in rice by considering Si transport in the roots, distribution at the nodes, and signaling substances controlling transporter gene expression. To investigate the functional reason for the diurnal variation of the expression level, we compared investment efficiencies (the amount of Si accumulated in the upper leaf divided by the total expression level of Si transporter genes) at different model settings. The model reproduced the gradual decrease and diurnal variation of the expression level of the transporter genes observed by previous experimental studies. The results of simulation experiments showed that a considerable reduction in the expression of Si transporter genes during the night increases investment efficiency. Our study suggests that rice has a system that maximizes the investment efficiency of Si uptake.

    DOI

  • Complex network analysis reveals novel essential properties of competition among individuals in an even-aged plant population

    Yoshiaki Nakagawa, Masayuki Yokozaw, Toshihiko Hara

    ECOLOGICAL COMPLEXITY   26   95 - 116  2016年06月  [査読有り]

     概要を見る

    Little is known about the network structure of competition in large populations of plants, despite the importance of such knowledge for understanding population dynamics. In this study, we used complex network analysis to examine temporal changes in the network structure of competition in an even-aged multi-individual stand of the Sakhalin fir Abies sachalinensis in Hokkaido, Japan. Using census data, which were measured over 30 years (1948-1978; seedlings were planted in 1929), on the sizes and locations of these plants, we regarded a plant as a node and competition between plants as a link. We then introduced two indices, the binary and weighted out-degrees (BO and WO, respectively), to interpret complicated plant interactions. The BO of a plant represents the number of links from the target plant to its neighbors, and the WO is the total strength of competition from the target plant to its neighbors. The analysis showed that the distributions of BO and WO were heavy-tailed in all years and that large plants had large BO and WO. These results suggest that only a few (i.e., large) plants have a very large impact on the growth and survival of a much larger number of neighboring plants and thus on population dynamics, whereas most of the others (i.e., small and medium-sized plants) have only a small impact on a few neighbors. By introducing binary and weighted connectivities (BC and WC, respectively), we were able to identify the size classes of neighbors with which the target plant preferentially and strongly competed. The BC and WC results showed that large plants competed preferentially and more strongly with other large plants in 1948, but they competed more strongly with small plants after 1963. These results clarify targets of the very large impact of large plants, as shown by the results of BO and WO: the impact was exerted on the growth and survival of other large plants in 1948, whereas the impact was exerted on those of small plants after 1963. Our study demonstrates that the statistical properties of the competition network structure, which have been largely ignored in plant competition research, are important for understanding plant population dynamics. (C) 2016 Elsevier B.V. All rights reserved.

    DOI

  • Indirect facilitation induced by competition among plants.

    Nakagawa Y, Yokozawa M, Hara T

    Nonlinear Theory and Its Applications   7 ( 2 ) 126 - 145  2016年04月  [査読有り]

     概要を見る

    We examined the indirect positive effect of one plant on the growth of another via growth suppression of a shared competing plant as an indirect facilitation between plants. We simulated the dynamics of populations of 3600 competing plants and used absolute interaction intensity (AIIi,j), the causal effect of plant j on plant i. The positive effect due to indirect facilitation between two plants occurs at a short distance apart and increases with increasing average density. The indirect facilitation between plants becomes increasingly important with increasing average density to explain the dynamics of size structure in plant populations.

    DOI CiNii

  • 20pPSA-15 植物個体間の負の相互作用の連鎖から生まれる正の相互作用

    中河 嘉明, 横沢 正幸, 原 登志彦

    日本物理学会講演概要集   71   2915 - 2915  2016年

    DOI CiNii

  • Technological spillover in Japanese rice productivity under long-term climate change: evidence from the spatial econometric model

    Yoji Kunimitsu, Ryoji Kudo, Toshichika Iizumi, Masayuki Yokozawa

    PADDY AND WATER ENVIRONMENT   14 ( 1 ) 131 - 144  2016年01月  [査読有り]

     概要を見る

    Rice productivity will be affected by climate conditions not only in own region but also in neighboring regions through technological spillover. Measuring such direct and indirect influence of future climate change is important for policy making. This study analyzes socioeconomic and climate factors in rice total factor productivity (TFP) and evaluates technological spillover effects by using the spatial econometric model. To consider geographical situation, we use hydrological model in addition to crop-yield and crop-quality models. Results show that spatial autoregressive tendencies were observed in rice TFP, even though the influences of climate factors were removed. Such spatial dependence brings about synergistic effects among neighboring prefectures in northern Japan and depression effects, like a spatial trap, from neighbors in southern Japan. Substantial impacts of climate change were as high as socio-economic factors but different in degrees by regions. Also, future climate change estimated by the global climate model enlarged fluctuation degree in rice TFP because accumulative or cancel out effects of temperature and precipitation occurred year by year. Therefore, technological development in rice production and provision of precise climate prediction to farmers are important in order to ease and mitigate these influences.

    DOI

  • Microhabitat locality allows multi-species coexistence in terrestrial plant communities

    Jerrold M. Tubay, Keisuke Suzuki, Takashi Uehara, Satoshi Kakishima, Hiromu Ito, Atsushi Ishida, Katsuhiko Yoshida, Shigeta Mori, Jomar F. Rabajante, Satoru Morita, Masayuki Yokozawa, Jin Yoshimura

    SCIENTIFIC REPORTS   5   15376  2015年10月  [査読有り]

     概要を見る

    Most terrestrial plant communities exhibit relatively high species diversity and many competitive species are ubiquitous. Many theoretical studies have been carried out to investigate the coexistence of a few competitive species and in most cases they suggest competitive exclusion. Theoretical studies have revealed that coexistence of even three or four species can be extremely difficult. It has been suggested that the coexistence of many species has been achieved by the fine differences in suitable microhabitats for each species, attributing to niche-separation. So far there is no explicit demonstration of such a coexistence in mathematical and simulation studies. Here we built a simple lattice Lotka-Volterra model of competition by incorporating the minute differences of suitable microhabitats for many species. By applying the site variations in species-specific settlement rates of a seedling, we achieved the coexistence of more than 10 species. This result indicates that competition between many species is avoided by the spatial variations in species-specific microhabitats. Our results demonstrate that coexistence of many species becomes possible by the minute differences in microhabitats. This mechanism should be applicable to many vegetation types, such as temperate forests and grasslands.

    DOI

  • Modeling irrigation-based climate change adaptation in agriculture: Model development and evaluation in Northeast China

    Masashi Okada, Toshichika Iizumi, Gen Sakurai, Naota Hanasaki, Toru Sakai, Katsuo Okamoto, Masayuki Yokozawa

    JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS   7 ( 3 ) 1409 - 1424  2015年09月  [査読有り]

     概要を見る

    Replacing a rainfed cropping system with an irrigated one is widely assumed to be an effective measure for climate change adaptation. However, many agricultural impact studies have not necessarily accounted for the space-time variations in the water availability under changing climate and land use. Moreover, many hydrologic and agricultural assessments of climate change impacts are not fully integrated. To overcome this shortcoming, a tool that can simultaneously simulate the dynamic interactions between crop production and water resources in a watershed is essential. Here we propose the regional production and circulation coupled model (CROVER) by embedding the PRYSBI-2 (Process-based Regional Yield Simulator with Bayesian Inference version 2) large-area crop model into the global water resources model (called H08), and apply this model to the Songhua River watershed in Northeast China. The evaluation reveals that the model's performance in capturing the major characteristics of historical change in surface soil moisture, river discharge, actual crop evapotranspiration, and soybean yield relative to the reference data during the interval 1979-2010 is satisfactory accurate. The simulation experiments using the model demonstrated that subregional irrigation management, such as designating the area to which irrigation is primarily applied, has measurable influences on the regional crop production in a drought year. This finding suggests that reassessing climate change risk in agriculture using this type of modeling is crucial not to overestimate potential of irrigation-based adaptation.

    DOI

  • In Silico Simulation Modeling Reveals the Importance of the Casparian Strip for Efficient Silicon Uptake in Rice Roots

    Gen Sakurai, Akiko Satake, Naoki Yamaji, Namiki Mitani-Ueno, Masayuki Yokozawa, Francois Gabriel Feugier, Jian Feng Ma

    PLANT AND CELL PHYSIOLOGY   56 ( 4 ) 631 - 639  2015年04月  [査読有り]

     概要を見る

    Silicon (Si) uptake by the roots is mediated by two different transporters, Lsi1 (passive) and Lsi2 (active), in rice (Oryza sativa). Both transporters are polarly localized in the plasma membranes of exodermal (outer) and endodermal (inner) cells with Casparian strips. However, it is unknown how rice is able to take up large amounts of Si compared with other plants, and why rice Si transporters have a characteristic cellular localization pattern. To answer these questions, we simulated Si uptake by rice roots by developing a mathematical model based on a simple diffusion equation that also accounts for active transport by Lsi2. In this model, we calibrated the model parameters using in vivo experimental data on the Si concentrations in the xylem sap and a Monte Carlo method. In our simulation experiments, we compared the Si uptake between roots with various transporter and Casparian strip locations and estimated the Si transport efficiency of roots with different localization patterns and quantities of the Lsi transporters. We found that the Si uptake by roots that lacked Casparian strips was lower than that of normal roots. This suggests that the doublelayer structure of the Casparian strips is an important factor in the high Si uptake by rice. We also found that among various possible localization patterns, the most efficient one was that of the wild-type rice; this may explain the high Si uptake capacity of rice.

    DOI

  • Competition among plants can lead to an increase in aggregation of smaller plants around larger ones

    Yoshiaki Nakagawa, Masayuki Yokozawa, Toshihiko Hara

    ECOLOGICAL MODELLING   301   41 - 53  2015年04月  [査読有り]

     概要を見る

    We re-examined traditional explanations regarding relationships between competition among plants and spatial patterns. We focused particularly on the prevailing view, which is that competition between smaller plants and larger plants serves only as a repulsive force between neighbors, and always decreases the degree of aggregation between smaller plants and larger plants over time. We propose an alternative underlying mechanism explaining the observed spatial patterns using a spatially explicit, individualbased model with general assumptions regarding the nature of competition among plants. We statistically estimated parameters for the model from observed census data collected over 30 years in an even-aged experimental fir forest (Abies sachalinensis). The results of our simulations, based on field data, indicated that asymmetric competition among plants led to the aggregation of smaller plants around a larger plant (i.e., not toward a uniform spatial pattern). This spatial pattern was generated by the growth suppression of plants near larger plants during the early growth stages, and more importantly, by the existence of a zone with lower competition intensity (referred to as competition-induced shelter, CiS) around a larger plant after the early growth stages. Larger plants compete for resources with large and medium-sized neighbors to the extent that the neighbors die and are removed, resulting in CiS. The results also indicate that competition between smaller plants and larger plants in an even-aged population exerts not only the traditionally recognized repulsive force but also a pseudo-attractive force, such as CiS, which promotes aggregation of smaller plants around a larger plant. (C) 2015 Elsevier B.V. All rights reserved.

    DOI J-GLOBAL

  • Inversely Estimating the Vertical Profile of the Soil CO2 Production Rate in a Deciduous Broadleaf Forest Using a Particle Filtering Method

    Gen Sakurai, Seiichiro Yonemura, Ayaka W. Kishimoto-Mo, Shohei Murayama, Toshiyuki Ohtsuka, Masayuki Yokozawa

    PLOS ONE   10 ( 3 ) e0119001  2015年03月  [査読有り]

     概要を見る

    Carbon dioxide (CO2) efflux from the soil surface, which is a major source of CO2 from terrestrial ecosystems, represents the total CO2 production at all soil depths. Although many studies have estimated the vertical profile of the CO2 production rate, one of the difficulties in estimating the vertical profile is measuring diffusion coefficients of CO2 at all soil depths in a nondestructive manner. In this study, we estimated the temporal variation in the vertical profile of the CO2 production rate using a data assimilation method, the particle filtering method, in which the diffusion coefficients of CO2 were simultaneously estimated. The CO2 concentrations at several soil depths and CO2 efflux from the soil surface (only during the snow-free period) were measured at two points in a broadleaf forest in Japan, and the data were assimilated into a simple model including a diffusion equation. We found that there were large variations in the pattern of the vertical profile of the CO2 production rate between experiment sites: the peak CO2 production rate was at soil depths around 10 cm during the snow-free period at one site, but the peak was at the soil surface at the other site. Using this method to estimate the CO2 production rate during snow-cover periods allowed us to estimate CO2 efflux during that period as well. We estimated that the CO2 efflux during the snow-cover period (about half the year) accounted for around 13% of the annual CO2 efflux at this site. Although the method proposed in this study does not ensure the validity of the estimated diffusion coefficients and CO2 production rates, the method enables us to more closely approach the "actual" values by decreasing the variance of the posterior distribution of the values.

    DOI

  • FluxPro as a realtime monitoring and surveilling system for eddy covariance flux measurement

    Wonsik Kim, Akira Miyata, Ali Ashraf, Atsushi Maruyama, Amnat Chidthaisong, Chaiporn Jaikaeo, Daisuke Komori, Eiji Ikoma, Gen Sakurai, Hyeong-Ho Seoh, In Chang Son, Jaeil Cho, Jonghyeon Kim, Keisuke Ono, Korakod Nusit, Kyung Hwan Moon, Masayoshi Mano, Masayuki Yokozawa, Md. Abdul Baten, Montri Sanwangsri, Motomu Toda, Nittaya Chaun, Panya Polsan, Seiichiro Yonemura, Seong-Deog Kim, Shin Miyazaki, Shinjiro Kanae, Suban Phonkasi, Sukanya Kammales, Takahiro Takimoto, Taro Nakai, Toshichika Iizumi, Vanisa Surapipith, Warangluck Sonklin, Yong Lee, Yoshio Inoue, Youngwook Kim, Taikan Oki

    JOURNAL OF AGRICULTURAL METEOROLOGY   71 ( 1 ) 32 - 50  2015年03月  [査読有り]

     概要を見る

    To understand how terrestrial ecosystems respond to global climate change, researchers have globally measured the energy, water and carbon dioxide flux densities (F) globally over various types of vegetation by the eddy covariance (EC) method. However, the process of F calculation and the method of quality control and quality assurance (QCQA) are complex and site specific. Moreover, instantly maintaining remote EC flux measurement sites against instrumentation problems and administrative difficulties is laborious. To overcome these issues, particularly those of realtime F monitoring and prompt site management, FluxPro was created.
    FluxPro consists of three functional systems: 1) a gathering system that transports EC measurements from various sites to the FluxPro management server; 2) a cooking system that computes F and its frictional uncertainty (a) together with micrometeorological variables (V); and 3) a serving system that presents the results of the gathering and cooking systems as charts to be distributed over the internet in realtime. Consequently, FluxPro could become an appropriate system for realtime-multi-site management, since it not only automatically monitors F with a and V but also continuously surveils EC sites, including copious information and an email alert system.

    DOI J-GLOBAL

  • 22pPSB-54 競争による正の間接相互作用 : 植物個体間競争をネットワークの視点で見る

    横沢 正幸, 中河 嘉明

    日本物理学会講演概要集   70   3083 - 3083  2015年

    DOI CiNii

  • 植物個体間競争過程のモデリングと北方林への適用

    中河嘉明, 横沢正幸

    低温科学   73   93 - 104  2015年  [査読有り]

     概要を見る

    植物個体間競争過程のモデルに関する過去の研究例をレビューした結果, サイズ, 個体間距離, 競争のサイズ非対称性の関数である競争関数(CKF)は経験的に様々に表現されていた. 我々は, 北海道のトドマツ林の毎木データに基づいて, パラメータのベイズ推定およびモデル選択を行い新たなCKF を導出した. その関数型は個体間距離の-3.42乗に比例するものであり, 従来, 広く用いられてきた距離の-2乗に比例するものとは明らかに異なっていた. このようなデータに基づいた競争過程のモデルは, 植物個体の空間パターンや多種共存機構の解明ならびに定量的予測に有効である.In this review, we summarize research on modeling competition processes among plants;that is, how anindividual plant competes with its neighbors. Previous studies have empirically defined various types ofcompetition kernel function (CKF), which is a function of the size difference, distance, and competitive asymmetry between two plants. In this study, we proposed a new CKF and determined the parameters based on census data of Sakhalin fir in Hokkaido using Bayesian inference with the Markov Chain Monte Carlo algorithm (MCMC). Model selection was conducted with Deviation Information Criteria (DIC)to obtain the most plausible model. The selected CKF attenuates with r-3.42, where r denotes the distance between plants, while most previous studies have assumed that CKF decreases with inverse squared distance. The data-oriented CKF derived in this study could be used to elucidate and quantitatively predict temporal changes in spatial pattern andsize structure, conspecific clustering, and coexistence in plant communities.

    DOI CiNii

  • Journal of Advances in Modeling Earth Systems

    Okada Masashi, Iizumi Toshichika, Sakurai Gen, Hanasaki Naota, Sakai Toru, Okamoto Katsuo, Yokozawa Masayuki

    Journal of Advances in Modeling Earth Systems   7   1409 - 1424  2015年  [査読有り]

    DOI

  • Is long-term climate change beneficial or harmful for rice total factor productivity in Japan: evidence from a panel data analysis

    Yoji Kunimitsu, Toshichika Iizumi, Masayuki Yokozawa

    PADDY AND WATER ENVIRONMENT   12   S213 - S225  2014年11月  [査読有り]

     概要を見る

    Under global warming, influences of heat stress and flooding on rice production are becoming critical in Japan, but it is still under discussion whether future climate change is beneficial or harmful for Japanese rice production. This study aims to evaluate the impacts of long-term climate change on rice total factor productivity (TFP) by a panel data analysis. We estimate a regression model to link rice TFP to climate factors via yield, quality, and flood influence by using crop models, and then project future TFP levels from the results of the high-resolution model for interdisciplinary research on climate (MIROC). The results demonstrate that climate change has a positive effect in the northern regions, such as Hokkaido and Tohoku, but it decreases rice TFP in other regions, especially in the western regions, after the 2050s. Furthermore, climate change increases fluctuations in rice TFP of the western regions. To overcome negative impacts, a forward shift in the rice transplanting time is effective. Second, the potential impacts of climate factors, shown by the elasticity values of rice TFP, are 0.18 (via yield), 0.09 (via quality), and -0.03 (via flood influence), but these climate impacts are weaker than socio-economic factors, such as economies of scale and research and development capital stocks. Third, regional gaps in rice TFP are enlarged over time because of different impacts of climate factors as well as socio-economic factors. Such fact-findings can be used to reconsider agricultural policy.

    DOI

  • Dependency of parameter values of a crop model on the spatial scale of simulation

    Toshichika Iizumi, Yukiko Tanaka, Gen Sakurai, Yasushi Ishigooka, Masayuki Yokozawa

    JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS   6 ( 3 ) 527 - 540  2014年09月  [査読有り]

     概要を見る

    Reliable regional-scale representation of crop growth and yields has been increasingly important in earth system modeling for the simulation of atmosphere-vegetation-soil interactions in managed ecosystems. While the parameter values in many crop models are location specific or cultivar specific, the validity of such values for regional simulation is in question. We present the scale dependency of likely parameter values that are related to the responses of growth rate and yield to temperature, using the paddy rice model applied to Japan as an example. For all regions, values of the two parameters that determine the degree of yield response to low temperature (the base temperature for calculating cooling degree days and the curvature factor of spikelet sterility caused by low temperature) appeared to change relative to the grid interval. Two additional parameters (the air temperature at which the developmental rate is half of the maximum rate at the optimum temperature and the value of developmental index at which point the crop becomes sensitive to the photoperiod) showed scale dependency in a limited region, whereas the remaining three parameters that determine the phenological characteristics of a rice cultivar and the technological level show no clear scale dependency. These results indicate the importance of using appropriate parameter values for the spatial scale at which a crop model operates. We recommend avoiding the use of location-specific or cultivar-specific parameter values for regional crop simulation, unless a rationale is presented suggesting these values are insensitive to spatial scale.

    DOI

  • A modeling approach for assessing rice cropping cycle affected by flooding, salinity intrusion, and monsoon rains in the Mekong Delta, Vietnam

    Akihiko Kotera, Khang Duy Nguyen, Toshihiro Sakamoto, Toshichika Iizumi, Masayuki Yokozawa

    PADDY AND WATER ENVIRONMENT   12 ( 3 ) 343 - 354  2014年07月  [査読有り]

     概要を見る

    We developed a crop scheduling model for rice cultivation in the Vietnam Mekong Delta (VMD), focusing on the adaptive behavior of crop planning to various water resource constraints. In addition, we also examined the effects of environmental change on rice cultivation in the last decade. In the VMD, multiple rice cropping is practiced under a variety of adverse water conditions, including flooding, salinity intrusion, and irregular monsoon rains. These environmental changes influence the durations of growing seasons and the number of crops per year, resulting in changes in productivity. To validate the performance of the model, we compared model estimates for the heading date and changes in leaf area index at nine sites with estimates of these parameters derived from MODIS satellite time series data for the period 2002-2006. The root mean square errors of heading date between the modeled and satellite data in the upper, middle, and coastal regions of the delta were 17.6, 11.2, and 13.0 days, respectively. Based on the model, we examined case studies to assess the changes in cropping cycles and crop failures in the VMD due to extreme flooding in 2000 and salinity intrusion in 2004 by applying evaluation indices defined by available period for cultivation (APC) and safe margin for cropping (SMC) which is defined as the marginal time between APC and the period required for cultivation. Findings of case studies suggested that a small difference in the SMC of the cropping pattern is critical to the stability and productive capacity of the rice crop.

    DOI

  • 稲作の総合生産性に対する気候変動と空間的従属性の影響-空間計量経済モデルによる分析-

    國光洋二, 工藤亮治, 飯泉仁之直, 横沢正幸

    地域学研究   44   305 - 325  2014年06月  [査読有り]

  • Contributions of historical changes in sowing date and climate to US maize yield trend: An evaluation using large-area crop modeling and data assimilation

    Toshichika Iizumi, Gen Sakurai, Masayuki Yokozawa

    JOURNAL OF AGRICULTURAL METEOROLOGY   70 ( 2 ) 73 - 90  2014年06月  [査読有り]

     概要を見る

    The consequences of changes observed in climate and management to yield trends in major crop-producing regions have implications for future food availability. We present an assessment of the impacts of historical changes in sowing date and climate to the maize yield trend in the U.S. Corn Belt from 1980 to 2006 by using large-area crop modeling and a data assimilation technique (i.e., the model optimization based on the Markov chain Monte Carlo method). Calibrated at a regional scale, the model captured the major characteristics of the changes reported in yield as well as the timing and length of maize growth periods across the Corn Belt. The simulation results using the calibrated model indicate that while the climate change observed for the period likely contributed to a decreasing yield trend, the positive contribution from the reported shift to an earlier sowing date offset the negative impacts. With the given spread in the assessment results across previous studies and in this study, the conclusion that the negative impacts of climate change on U.S. maize yield trend more likely derive from a decreasing trend in growing-season precipitation than to an increasing trend in temperature.

    DOI

  • Impacts of El Nino Southern Oscillation on the global yields of major crops

    Toshichika Iizumi, Jing-Jia Luo, Andrew J. Challinor, Gen Sakurai, Masayuki Yokozawa, Hirofumi Sakuma, Molly E. Brown, Toshio Yamagata

    NATURE COMMUNICATIONS   5  2014年05月  [査読有り]

     概要を見る

    The monitoring and prediction of climate-induced variations in crop yields, production and export prices in major food-producing regions have become important to enable national governments in import-dependent countries to ensure supplies of affordable food for consumers. Although the El Nino/Southern Oscillation (ENSO) often affects seasonal temperature and precipitation, and thus crop yields in many regions, the overall impacts of ENSO on global yields are uncertain. Here we present a global map of the impacts of ENSO on the yields of major crops and quantify its impacts on their global-mean yield anomalies. Results show that El Nino likely improves the global-mean soybean yield by 2.1-5.4% but appears to change the yields of maize, rice and wheat by - 4.3 to +0.8%. The global-mean yields of all four crops during La Nina years tend to be below normal (- 4.5 to 0.0%). Our findings highlight the importance of ENSO to global crop production.

    DOI

  • How much has the increase in atmospheric CO2 directly affected past soybean production?

    Gen Sakurai, Toshichika Iizumi, Motoki Nishimori, Masayuki Yokozawa

    SCIENTIFIC REPORTS   4  2014年05月  [査読有り]

     概要を見る

    Understanding the effects of climate change is vital for food security. Among the most important environmental impacts of climate change is the direct effect of increased atmospheric carbon dioxide concentration ([CO2]) on crop yields, known as the CO2 fertilization effect. Although several statistical studies have estimated past impacts of temperature and precipitation on crop yield at regional scales, the impact of past CO2 fertilization is not well known. We evaluated how soybean yields have been enhanced by historical atmospheric [CO2] increases in three major soybean-producing countries. The estimated average yields during 2002-2006 in the USA, Brazil, and China were 4.34%, 7.57%, and 5.10% larger, respectively, than the average yields estimated using the atmospheric [CO2] of 1980. Our results demonstrate the importance of considering atmospheric [CO2] increases in evaluations of the past effects of climate change on crop yields.

    DOI

  • Historical changes in global yields: major cereal and legume crops from 1982 to 2006

    Toshichika Iizumi, Masayuki Yokozawa, Gen Sakurai, Maria Isabel Travasso, Vladimir Romanernkov, Pascal Oettli, Terry Newby, Yasushi Ishigooka, Jun Furuya

    GLOBAL ECOLOGY AND BIOGEOGRAPHY   23 ( 3 ) 346 - 357  2014年03月  [査読有り]

     概要を見る

    AimRecent changes in crop yields have implications for future global food security, which are likely to be affected by climate change. We developed a spatially explicit global dataset of historical yields for maize, soybean, rice and wheat to explore the historical changes in mean, year-to-year variation and annual rate of change in yields for the period 1982-2006.
    LocationThis study was conducted at the global scale.
    MethodsWe modelled historical and spatial patterns of yields at a grid size of 1.125 degrees by combining global agricultural datasets related to the crop calendar and harvested area in 2000, country yield statistics and satellite-derived net primary production. Modelled yields were compared with other global datasets of yields in 2000 (M3-Crops and MapSPAM) and subnational yield statistics for 23 major crop-producing countries. Historical changes in modelled yields were then examined.
    ResultsModelled yields explained 45-81% of the spatial variation of yields in 2000 from M3-Crops and MapSPAM, with root-mean-square errors of 0.5-1.8 t ha(-1). Most correlation coefficients between modelled yield time series and subnational yield statistics for the period 1982-2006 in major crop-producing regions were greater than 0.8. Our analysis corroborated the incidence of reported yield stagnations and collapses and showed that low and mid latitudes in the Southern Hemisphere (0-40 degrees S) experienced significantly increased year-to-year variation in maize, rice and wheat yields in 1994-2006 compared with that in 1982-93.
    Main conclusionsOur analyses revealed increased instability of yields across a broad region of the Southern Hemisphere, where many developing countries are located. Such changes are likely to be related to recent yield stagnation and collapses. Although our understanding of the impacts of recent climate change, particularly the incidence of climate extremes, on crop yields remains limited, our dataset offers opportunities to close parts of this knowledge gap.

    DOI J-GLOBAL

  • 中国東北部における作物生産量の気候変化影響と灌漑による適応策の評価

    岡田 将誌, 飯泉 仁之直, 櫻井 玄, 酒井 徹, 横沢 正幸

    水文・水資源学会研究発表会要旨集   27   100124 - 100124  2014年

     概要を見る

    農業において、天水から灌漑への切り替えは気候変化影響の有効な適応策と考えられている。しかしながら、実際に利用可能な水資源量を考慮して作物モデルシミュレーションを実施している研究は少ない。一方で、灌漑農地を扱っている広域水資源モデルの多くは、作物栽培期間における水収支各項や作物収量のモデル推定値の検証は十分とはいえない。そこで本研究では、作物生産性と水資源量の動的相互作用を考慮した作物生産性-水資源量予測結合モデルの構築を行った。このモデルは、広域スケールでの作物生育・収量形成モデル、PRYSBI2(Sakurai et al., 2014)に全球スケールでの水資源量を動的に推定することのできるモデル、H08(Hanasaki et al., 2008)との結合を行ったものである。水資源が作物生産性の主要な制約要因となる地域として、中国東北部を選定し、過去のダイズ収量、河川流量、土壌水分量、蒸発散量の観測データとの比較を行った。その結果、ダイズ生育期間における水収支各項とダイズ収量の過去の時系列変化を良好に再現できることを確認した。さらに、気候変化シナリオと灌漑面積を増加させる適応策シナリオを用いて中国東北部のダイズ生産量変動と灌漑水需給のリスク評価を行い、灌漑面積の増加が約2倍であれば、水需要を満たした上でダイズ生産量を増加できる可能性を示した。

    DOI CiNii

  • 全球作物統計データを用いた過去の気候変動の影響評価

    櫻井玄, 飯泉仁之直, 横沢正幸

    統計数理研究所共同研究リポート   320   25 - 36  2014年

  • Impact functions for land-use-induced surface warming, and their applications in uncertainty analysis

    Ryuhei Yoshida, Toshichika Iizumi, Motoki Nishimori

    Climate Research   59 ( 1 ) 77 - 87  2014年  [査読有り]

     概要を見る

    We developed statistical models (called impact functions) in this study that mimicked the responses of summer mean, maximum, and minimum surface temperatures to given land-use changes (LUC) simulated with a regional climate model (RCM). The island of Shikoku in western Japan was used as an example. The impact functions were based on the RCM-simulated sensitivity of temperatures to changes for each of 5 land-surface parameters (surface albedo, evaporative efficiency, roughness length, heat capacity, and thermal conductivity). Thus, the relative importance of a specific land-surface parameter for the local temperature (e.g. greater sensitivity of daily mean temperature to evaporative efficiency) determines the impact functions. We compared the impact functions to the independently evaluated RCM simulations to assess how well our results matched the historical LUC-induced RCM warming simulations in this area between 1987 and 2006. The impact function performance varied with grid size: the 10 km results matched the RCM simulations best, with an error of 10-15%. Next, the impact functions were used to estimate the potential warming range for different LUC scenarios. Given the geographical distribution of present-day land use/land cover, the Monte Carlo simulations with impact functions indicate that LUC-induced changes in summer mean temperature potentially range from -0.4 (when forest is converted to paddy) to +1.3 °C (when forest is converted to building lots). This result indicates that, on an area mean basis, the cooling achieved through land-use management is limited in its ability to offset climate change-induced warming in future decades. © Inter-Research 2014.

    DOI

  • Applicability of empirical solar radiation models to altered climate

    Masashi Okada, Toshichika Iizumi, Masayuki Yokozawa

    JOURNAL OF AGRICULTURAL METEOROLOGY   70 ( 1 ) 13 - 23  2014年  [査読有り]

     概要を見る

    This study is a global assessment of the performance of two empirical models for estimating daily global solar radiation (SR) in the present-day climate, as well as the applicability of these models for near-future climates. One empirical model is used to estimate SR from a diurnal temperature range (DTR) and is called the DTR-SR model, while the other is used to estimate SR from relative humidity (RH) and is called the RH-SR model. Using data from the reanalysis and atmosphere-ocean coupled global climate model (GCM) known as MIROC4, we found that the DTR-SR model operates more accurately over land than the RH-SR model, though the RH-SR model outperformed the DTR-SR model over the ocean. Based on an assessment using data from the decadal prediction performed by the GCM, the DTR-SR model could be applied to estimate GCM-simulated SR in altered climates until the year 2035 considered in this study, given the comparatively limited performance of the model during the winter and in arid and semi-arid regions. This suggests that the DTR-SR model is likely useful for data imputation if GCM-simulated SR data are unavailable.

    DOI

  • Prediction of seasonal climate-induced variations in global food production

    Toshichika Iizumi, Hirofumi Sakuma, Masayuki Yokozawa, Jing-Jia Luo, Andrew J. Challinor, Molly E. Brown, Gen Sakurai, Toshio Yamagata

    NATURE CLIMATE CHANGE   3 ( 10 ) 904 - 908  2013年10月  [査読有り]

     概要を見る

    Consumers, including the poor in many countries, are increasingly dependent on food imports(1) and are thus exposed to variations in yields, production and export prices in the major food-producing regions of the world. National governments and commercial entities are therefore paying increased attention to the cropping forecasts of important food-exporting countries as well as to their own domestic food production. Given the increased volatility of food markets and the rising incidence of climatic extremes affecting food production, food price spikes may increase in prevalence in future years(2-4). Here we present a global assessment of the reliability of crop failure hindcasts for major crops at two lead times derived by linking ensemble seasonal climatic forecasts with statistical crop models. We found that moderate-to-marked yield loss over a substantial percentage (26-33%) of the harvested area of these crops is reliably predictable if climatic forecasts are near perfect. However, only rice and wheat production are reliably predictable at three months before the harvest using within-season hindcasts. The reliabilities of estimates varied substantially by crop-rice and wheat yields were the most predictable, followed by soybean and maize. The reasons for variation in the reliability of the estimates included the differences in crop sensitivity to the climate and the technology used by the crop-producing regions. Our findings reveal that the use of seasonal climatic forecasts to predict crop failures will be useful for monitoring global food production and will encourage the adaptation of food systems to climatic extremes.

    DOI

  • Vertical soil-air CO2 dynamics at the Takayama deciduous broadleaved forest AsiaFlux site

    Seiichiro Yonemura, Masayuki Yokozawa, Gen Sakurai, Ayaka W. Kishimoto-Mo, Nayeon Lee, Shohei Murayama, Kentaro Ishijima, Yasuhito Shirato, Hiroshi Koizumi

    JOURNAL OF FOREST RESEARCH   18 ( 1 ) 49 - 59  2013年02月  [査読有り]

     概要を見る

    At the Takayama deciduous broadleaved forest Asiaflux site in Japan, the ecosystem carbon dynamics have been studied for more than two decades. In 2005, we installed non-dispersive infrared CO2 sensors in the soil below the site's flux tower to systematically study vertical soil-air CO2 dynamics and explain the behavior of soil surface CO2 efflux. Soil-air CO2 concentrations measured from June 2005 through May 2006 showed sinusoidal variation, with maxima in July and minima in winter, similar to the soil CO2 effluxes measured simultaneously using open-flow chambers. Soil-air CO2 concentrations increased with soil depth from 5 to 50 cm: from 2,000 to 8,000 ppm in the summer and from 2,000 to 3,000 ppm in the winter under snow. Summer soil-air CO2 concentrations were positively correlated with soil moisture on daily and weekly scales, indicating that the Oi, Oe, and A horizons, where decomposition is accelerated by high-moisture conditions, contributed substantially to CO2 emissions. This result is consistent with the short residence time (about 2 h) of CO2 in the soil and larger emissions in shallow soil layers based on our diffusion model. We revealed for the first time that soil-air CO2 concentrations in winter were correlated with both snow depth and wind speed. CO2 transfer through the snow was hundreds of times the gas diffusion rates in the soil. Our estimate of the CO2 efflux during the snow-cover season was larger than previous estimates at TKY, and confirmed the important contribution of the snow-cover season to the site's carbon dynamics.

    DOI

  • An ensemble approach to the representation of subgrid-scale heterogeneity of crop phenology and yield in coarse-resolution large-area crop models

    Toshichika Iizumi, Gen Sakurai, Masayuki Yokozawa

    JOURNAL OF AGRICULTURAL METEOROLOGY   69 ( 4 ) 243 - 254  2013年  [査読有り]

     概要を見る

    The grid interval of a global climate model (GCM) is generally hundreds of kilometers in latitude and longitude. The spatial heterogeneity of crop condition (e.g., phenology and yields) at that scale could be substantial. Because the atmosphere-cropland exchanges of energy, water, and materials are sensitive to crop condition, this issue poses a question: How can we simulate the condition of a crop of interest on a GCM grid scale while taking into account the spatial heterogeneity of crop condition at a sub-grid scale? We therefore proposed an ensemble approach that uses stochastic parameter values to represent the spatial variation in the phenological and biophysical characteristics of a crop within a given GCM grid box, and tested its feasibility with simulation experiments. The combination of the Soil and Water Assessment Tool (SWAT) applied to maize in the Central Great Plains, United States, and coarse-resolution (2.5 degrees x2.5 degrees) reanalysis data was taken as the example. The ensemble simulations successfully captured the spatial variation in the phenology and yield. Our conclusion is that the ensemble approach is feasible and expected to benefit large-area crop modeling when extending those models to include more information on the spatial heterogeneity of crop condition than ever.

    DOI

  • Impacts of land-use changes on surface warming rates and rice yield in Shikoku, western Japan

    Ryuhei Yoshida, Toshichika Iizumi, Motoki Nishimori, Masayuki Yokozawa

    GEOPHYSICAL RESEARCH LETTERS   39  2012年11月  [査読有り]

     概要を見る

    We evaluated the impacts of historical land-use changes (LUCs) from 1987 to 2006 on surface warming rates and rice yields on the island of Shikoku, Japan. We performed two types of numerical simulations (with historical LUCs and with fixed land uses) using a regional atmospheric model (JMA-NHM) and a large-area rice-growth model (PRYSBI). During our study period in Shikoku, the area of paddy fields decreased markedly and the area of building lots and roads increased. Our evaluation suggests that these LUCs caused warming rates in and around paddy fields that were five times those in and around other land uses. The simulated rice yield in 2006 was 0.27% lower (0.012 t ha(-1)) than in 1987 in response to the change in thermal and solar radiation conditions. These results suggest that decreases of crop yield due to environmental deterioration will be found in other regions where similar LUCs are occurring. Citation: Yoshida, R., T. Iizumi, M. Nishimori, and M. Yokozawa (2012), Impacts of land-use changes on surface warming rates and rice yield in Shikoku, western Japan, Geophys. Res. Lett., 39, L22401, doi:10.1029/2012GL053711.

    DOI

  • Evaluation of CO2 Exchange Rates in a Wetland Ecosystem Using the Closed Geosphere Experiment Facility

    Shizuo Suzuki, Masayuki Yokozawa, Kazuyuki Inubushi, Toshihiko Hara, Michitoshi Kimura, Shoichi Tsuga, Yasuhiro Tako, Yuji Nakamura

    JOURNAL OF HYDROMETEOROLOGY   13 ( 3 ) 966 - 980  2012年06月  [査読有り]

     概要を見る

    To evaluate annual CO2 exchange rates in a wetland ecosystem, ecosystem respiration rate (R-e), net ecosystem productivity (NEP), and gross primary productivity (GPP) were investigated using the Closed Geosphere Experiment Facility (CGEF) located in northeastern Japan. The CGEF is highly airtight and equipped with a Geosphere Module (GM). The GM has a ground area of 5.8 x 8.7 m(2) and an average height of 11.9 m, including a soil depth of 3.1 m. A wetland ecosystem dominated by Phragmites australis was introduced into the CGEF. Air temperature and CO2 concentration in the GM were controlled automatically. The hourly nighttime R-e increased exponentially with the hourly average air temperature. Both hourly NEP and GPP depended on hourly photosynthetic photon flux density (PPFD). In addition, daily ecosystem CO2 exchange rates (R-e, NEP, and GPP) were influenced by above-ground plant biomass. The annual NEP was found to be 64.2 +/- 19.2 g C m(-2) yr(-1) and it resulted from the annual GPP of 555.8 +/- 17.0 g C m(-2) yr(-1) and annual R-e of -491.6 +/- 15.6 g C m(-2) yr(-1). Therefore, the wetland ecosystem behaved as a CO2 sink for the entire year. The annual CO2 exchange rates obtained were reasonable values compared to the findings of published studies in P. australis-dominated wild wetlands using the eddy covariance technique and the combined method of internal gas pressures and flow measurements and harvesting.

    DOI

  • Inversely estimating temperature sensitivity of soil carbon decomposition by assimilating a turnover model and long-term field data

    Gen Sakurai, Mayuko Jomura, Seiichiro Yonemura, Toshichika Iizumi, Yasuhito Shirato, Masayuki Yokozawa

    SOIL BIOLOGY & BIOCHEMISTRY   46   191 - 199  2012年03月  [査読有り]

     概要を見る

    Change in temperature sensitivity of soil organic carbon (SOC) decomposition with change in soil qualities (i.e. decomposability or lability) is one of the most important issues to be evaluated for projection of future CO2 emissions from soils. We inversely estimated the temperature sensitivity of SOC decomposition rate by applying a hybrid of the Metropolis-Hasting algorithm and the particle filter method to the extended Rothamsted carbon model (RothC), together with long-term (9 years) experimental data on SOC obtained at five sites in Japanese upland soils. Contrary to the prediction of the Arrhenius kinetics theory, we found no significant differences in temperature sensitivity among soils with different qualities (represented as soil compartments in the RothC model). We also confirmed that there was a positive correlation between the relative temperature sensitivity of the humus compartment and future total CO2 emissions. The RothC model with default parameterization tended to overestimate future total CO2 emissions relative to the calibrated model, and the degree of overestimation was larger than that of underestimation. (C) 2011 Elsevier Ltd. All rights reserved.

    DOI

  • Statistical downscaling with Bayesian inference: Estimating global solar radiation from reanalysis and limited observed data

    Toshichika Iizumi, Motoki Nishimori, Masayuki Yokozawa, Akihiko Kotera, Nguyen Duy Khang

    INTERNATIONAL JOURNAL OF CLIMATOLOGY   32 ( 3 ) 464 - 480  2012年03月  [査読有り]

     概要を見る

    Daily global solar radiation (SR) is one of essential weather inputs for crop, hydrological, and other simulation models to calculate biomass production and potential evapotranspiration. The availability of long-term observed SR data is, however, limited, especially in developing countries. This hinders climate applications in various sectors in these countries. To overcome this difficulty, we here propose a method to infer the reasonable daily SR condition for past decades from global reanalysis and limited observed SR data. The method consists of the regression-based statistical downscaling method and two empirical models for estimating the SR condition (i.e. the S-model and the DTR/RH-model). These empirical models were independent in terms of the variables explaining the SR condition. The regression models were trained on the basis of the SR conditions estimated by the S-model and the DTR/RH-model instead of the observed SR data. The Markov Chain Monte Carlo (MCMC) technique was applied to determine the parameter values of these models that guide the models to provide SR conditions that are close in value to each other at both the site and domain-mean scales. After that, we computed the SR condition over the 30 years from 1978 through 2007 at 17 sites in the Vietnam Mekong Delta area using the determined parameter values. The inferred SR condition was close in value to the corresponding observations available from the literature. This suggests that the proposed method yielded a reasonable inference of the SR condition at the sites despite the limited availability of observed SR data. The provided estimates of the daily SR condition over the past 30 years are useful for climate applications in agricultural, hydrological, and other sectors in this area. Copyright (c) 2011 Royal Meteorological Society

    DOI J-GLOBAL

  • Estimation of the damage area due to tropical cyclones using fragility curves for paddy rice in Japan

    Y. Masutomi, T. Iizumi, K. Takahashi, M. Yokozawa

    ENVIRONMENTAL RESEARCH LETTERS   7 ( 1 )  2012年01月  [査読有り]

     概要を見る

    A method for estimating the area of crop damage due to tropical cyclones (TCs) by using fragility curves (FCs) is proposed. FCs, which represent the probability of damage caused by external forces, are one method considered appropriate for estimating structural damage caused by natural disasters. Here, FCs are applied to estimate the area of damage to paddy rice resulting from typhoons in Japan. The FCs for paddy rice are assumed to vary with growth stage. Statistical data on areas damaged by 42 typhoons that have struck Japan between 1991 and 2007, together with observed meteorological data, are used to derive the FCs. In general, our estimates agree with the reported areas of damage for the 42 typhoons, especially for typhoons that affected large areas of paddy rice. Moreover, from statistical data on crop damage due to typhoons, the proposed method successfully shows that the heading stage of paddy rice is the stage most vulnerable to typhoons, as found in earlier experimental studies and post-disaster investigations.

    DOI

  • Projecting Climate Change Impacts Both On Rice Quality And Yield In Japan

    Masashi Okada, Yousay Hayashi, Toshichika Iizumi, Masayuki Yokozawa

    Journal of Agricultural Meteorology   67 ( 4 ) 285 - 295  2011年09月  [査読有り]

     概要を見る

    This study examined the impacts of climate change both on rice quality and yield using a climatologically empirical rice quality model together with a process-based rice growth model. The target area is Kyushu in the western part of Japan, where the decline in rice quality already occurs at the present time. After confirming the model reproducibility, we made simulations to project the changes of rice quality under climate change scenarios. All the projections suggested that the rice quality would significantly deteriorate. We analyzed the results by distinguishing the direct and indirect effects of climate based on simulations with changing weather data. It suggested that the indirect effect induced by the shift of the grain-filling period is relatively larger than the direct effect by temperature rise. We also examined the effects of adaptation measure shifting the date of transplanting on rice quality and yield. It is shown that rice quality is more sensitive to the shifting transplanting date than rice yield
    consequently, shifting the transplanting date later might be an appropriate measure for the adaptation to climate change. © 2011, The Society of Agricultural Meteorology of Japan. All rights reserved.

    DOI

  • Probabilistic evaluation of climate change impacts on paddy rice productivity in Japan

    Toshichika Iizumi, Masayuki Yokozawa, Motoki Nishimori

    CLIMATIC CHANGE   107 ( 3-4 ) 391 - 415  2011年08月  [査読有り]

     概要を見る

    Projecting the impacts of climate change includes various uncertainties from physical, biophysical, and socioeconomic processes. Providing a more comprehensive impact projection that better represents the uncertainties is a priority research issue. We used an ensemble-based projection approach that accounts for the uncertainties in climate projections associated with general circulation models (GCMs) and biophysical and empirical parameter values in a crop model. We applied the approach to address the paddy rice yield change in Japan in the 2050s (2046-2065) and 2090s (2081-2100) relative to the 1990s (1981-2000). Seventeen climate projections, nine (eight) climate projections performed by seven (six) GCMs conditional on the Special Report on Emission Scenarios (SRES) A1B (A2), were included in this projection. In addition, 50 sets of biophysical and empirical parameter values of a large-scale process-based crop model for irrigated paddy rice were included to represent the uncertainties of crop parameter values. The planting windows, cultivation practices, and crop cultivars in the future were assumed to be the same as the level in the baseline period (1990s). The resulting probability density functions conditioned on SRES A1B and A2 indicate projected median yield changes of + 17.2% and + 26.9% in Hokkaido, the northern part of Japan, in the 2050s and 2090s with 90% probability intervals of (-aEuro parts per thousand 5.2%, + 40.3%) and (+ 6.3%, + 51.2%), relative to the 1990s mean yield, respectively. The corresponding values in Aichi, on the Pacific side of Western Japan, are 2.2% and -aEuro parts per thousand 0.8%, with 90% probability intervals of (-aEuro parts per thousand 15.0%, + 14.9%) and (-aEuro parts per thousand 33.4%, + 17.9%), respectively. We also provided geographical maps of the probability that the future 20-year mean yield will decrease and that the future standard deviation of yield for 20 years will increase. Finally, we investigated the relative contributions of the climate projection and crop parameter values to the uncertainty in projecting yield change in the 2090s. The choice of GCM yielded a relatively larger spread of projected yield changes than that of the other factors. The choice of crop parameter values could be more important than that of GCM in a specific prefecture.

    DOI

  • Modeling the multiple effects of temperature and radiation on rice quality

    Masashi Okada, Toshichika Iizumi, Yousay Hayashi, Masayuki Yokozawa

    ENVIRONMENTAL RESEARCH LETTERS   6 ( 3 )  2011年07月  [査読有り]

     概要を見る

    Ongoing climate change is likely to enhance the deterioration of rice quality that has been observed in western Japan, especially in Kyushu, since the 1990s. Therefore, it is important to examine the response of rice quality to environmental variation over a wide geographical domain. To that end, the aims of this study were (i) to propose a statistical model to predict rice quality based on temperature, total radiation during the ripening period, and their multiple effects; and (ii) to evaluate the model validity and uncertainty in prediction. A Bayesian calibration was adopted to account for uncertainty in the parameter values associated with non-climatic factors. The validation results showed that the model performed well in capturing the temporal trend and interannual variation in observed rice quality in all prefectures of Kyushu. We then performed the prediction experiment for rice quality in the extremely hot summer of the year 2010, which was omitted from the model calibration data. The results showed that the predictive capability of the statistical model is somewhat dependent on the calibration data, but this dependency does not necessarily mean that useful predictions for climates not in the calibration data are impossible.

    DOI J-GLOBAL

  • Dangerous levels of climate change for agricultural production in China

    Fulu Tao, Zhao Zhang, Masayuki Yokozawa

    REGIONAL ENVIRONMENTAL CHANGE   11   S41 - S48  2011年03月  [査読有り]

     概要を見る

    There are increasing attempts to define the measures of 'dangerous anthropogenic inference with the climate system' in context of Article 2 of the Framework Convention on Climate Change, due to its linkage to goals for stabilizing greenhouse gas concentrations. The criteria for identifying dangerous anthropogenic interference may be characterized in terms of the consequences of climate change. In this study, we use the water stress index (WSI) and agricultural net primary production (NPP) as indictors to assess where and when there might be dangerous effects arising from the projected climate changes for Chinese agricultural production. The results showed that based on HadCM3-based climate change scenarios, the region between the North China Plain and Northeast China Plain (34.25-47.75 degrees N, 110.25-126.25 degrees E) would be vulnerable to the projected climate change. The analyses on inter-annual variability showed that the agricultural water resources conditions would fluctuate through the period of 2001-2080 in the region under IPCC SRES A2 scenario, with the period of 2021-2040 as critical drought period. Agricultural NPP is projected to have a general increasing trend through the period of 2001-2080; however, it could decrease during the period of 2005-2035 in the region under the IPCC SRES A2 scenario, and during the period of 2025-2035 under IPCC SRES B2 scenario. Generally, while projected climate change could bring some potentially improved conditions for Chinese agriculture, it could also bring some critical adverse changes in water resources, which would affect the overall outcome. At this stage, while we have identified certain risks and established the general shape of the damage curve expressed as a function of global mean temperature increase, more works are needed to identify specific changes which could be dangerous for food security in China. Therefore, there is a need for the development of more integrated assessment models, which include social-economic, agricultural production and food trade modules, to help identify thresholds for impacts in further studies.

    DOI

  • The hot summers and rice in Japan

    Kazuhiko Kobayashi, Tsuneo Kuwagata, Mayumi Yoshimoto, Masayuki Yokozawa

    Journal of Agricultural Meteorology   67 ( 4 ) 205 - 207  2011年  [査読有り]

    DOI

  • Evaluation and intercomparison of downscaled daily precipitation indices over Japan in present-day climate: Strengths and weaknesses of dynamical and bias correction-type statistical downscaling methods

    Toshichika Iizumi, Motoki Nishimori, Koji Dairaku, Sachiho A. Adachi, Masayuki Yokozawa

    Journal of Geophysical Research Atmospheres   116 ( 1 )  2011年  [査読有り]

     概要を見る

    In this study, we evaluate the accuracy of four regional climate models (NHRCM, NRAMS, TRAMS, and TWRF) and one bias correction-type statistical model (CDFDM) for daily precipitation indices under the present-day climate (1985-2004) over Japan on a 20 km grid interval. The evaluated indices are (1) mean precipitation, (2) number of days with precipitation 1 mm/d (corresponds to number of wet days), (3) mean amount per wet day, (4) 90th percentile of daily precipitation, and (5) number of days with precipitation 90th percentile of daily precipitation. The boundary conditions of the dynamical models and the predictors of the statistical model are given from the single reanalysis data, i.e., JRA25. Both types of models successfully improved the accuracy of the indices relative to the reanalysis data in terms of bias, seasonal cycle, geographical pattern, cumulative distribution function of wet-day amount, and interannual variation pattern. In most aspects, NHRCM is the best model of all indices. Through the intercomparison between the dynamical and statistical models, respective strengths and weaknesses emerged. Briefly, (1) many dynamical models simulate too many wet days with a small amount of precipitation in humid climate zones, such as summer in Japan, relative to the statistical model, unless the cumulus convection scheme improved for such a condition is incorporated
    (2) a few dynamical models can derive a better high-order percentile of daily precipitation (e.g., 90th percentile) than the statistical model
    (3) both the dynamical and statistical models are still insufficient in the representation of the interannual variation pattern of the number of days with precipitation 90th percentile of daily precipitation
    (4) the statistical model is comparable to the dynamical models in the long-term mean geographical pattern of the indices even on a 20 km grid interval if a dense observation network is applicable
    (5) the statistical model is less accurate than the dynamical models in the temporal variation pattern due to the strong dependence of the predictand on the relatively less accurate predictor (daily reanalysis precipitation)
    and (6) the simple statistical model is less plausible in the physical sense because of the oversimplification of underlying physical processes compared to the dynamical models and more sophisticated statistical models. Copyright 2011 by the American Geophysical Union.

    DOI

  • Tolerance of eddy covariance flux measurement.

    Kim, Wonsik, Jaeil Cho, Daisuke Komori, Masatoshi Aoki, Masayuki Yokozawa, Shinjiro Kanae, Taikan Oki

    Hydrological Research Letters   5   73 - 77  2011年  [査読有り]

     概要を見る

    Eddy covariance (EC) flux measurement is the most-used technique for observation of the fluxes of sensible heat, latent heat, and carbon dioxide between the land surface and the atmospheric boundary layer. Despite the availability of plentiful EC data from numerous research projects, it is difficult to make meaningful comparisons of EC at different sites, to validate the models used, and to integrate observed data with models because the uncertainties of the method are inadequately defined. We developed a method to evaluate the uncertainties of the EC method without the need to consider individual site specifications and flux characteristics. We showed that the fractional error φ of EC (i.e., tolerance T) can be separated into random and illegitimate components. T can be used as a scale parameter for spatiotemporal stationarity, and can be defined as a rational function. We demonstrated a practical application of T analyses for two contrasting areas: a low-relief paddy field and an area of more complex land-forms where dramatic wind changes affect fluxes, and showed that T analysis provides an appropriate and effective method to determine the uncertainties in EC.<br>

    DOI CiNii

  • Varying temporal and spatial effects of climate on maize and soybean affect yield prediction

    Gen Sakurai, Toshichika Iizumi, Masayuki Yokozawa

    CLIMATE RESEARCH   49 ( 2 ) 143 - 154  2011年  [査読有り]

     概要を見る

    The relationship between climatic factors and crop yields for maize and soybeans in 3 major producing countries (the United States, Brazil, and China) was analyzed statistically. Temporal changes in the climate-yield relationship were considered, and the temporal and spatial variations were evaluated. County-level data from 1980 to 2006 were collected for each country and allocated to 1.125 x 1.125 grids. Data were analyzed for temporal changes in the effect of climate on yields using the particle filtering method for each grid. The 'current' effect of temperature on crop yields was shown to be geographically symmetric around the optimal temperatures (19.51 C for maize and 20.66 C for soybeans) in the Northern Hemisphere. In the Southern Hemisphere, the 'current' effect of precipitation was more influential than that of temperature. The effects of these climatic factors changed over time. Whereas the negative effect of high temperatures has been mitigated around the corn belt of the United States during the last 3 decades, it has intensified in Brazil, northern China, and the southern United States for maize. Consequently, predicted future yields differed marginally depending on the relationship (past or current effect) used for the prediction, even when they were summarized on country scales. This study suggests that temporal changes in the relationship between weather and crop yields should be considered for better future predictions.

    DOI

  • Evaluation and intercomparison of downscaled daily precipitation indices over Japan in present-day climate: Strengths and weaknesses of dynamical and bias correction-type statistical downscaling methods

    Toshichika Iizumi, Motoki Nishimori, Koji Dairaku, Sachiho A. Adachi, Masayuki Yokozawa

    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES   116  2011年01月  [査読有り]

     概要を見る

    In this study, we evaluate the accuracy of four regional climate models (NHRCM, NRAMS, TRAMS, and TWRF) and one bias correction-type statistical model (CDFDM) for daily precipitation indices under the present-day climate (1985-2004) over Japan on a 20 km grid interval. The evaluated indices are (1) mean precipitation, (2) number of days with precipitation &gt;= 1 mm/d (corresponds to number of wet days), (3) mean amount per wet day, (4) 90th percentile of daily precipitation, and (5) number of days with precipitation &gt;= 90th percentile of daily precipitation. The boundary conditions of the dynamical models and the predictors of the statistical model are given from the single reanalysis data, i.e., JRA25. Both types of models successfully improved the accuracy of the indices relative to the reanalysis data in terms of bias, seasonal cycle, geographical pattern, cumulative distribution function of wet-day amount, and interannual variation pattern. In most aspects, NHRCM is the best model of all indices. Through the intercomparison between the dynamical and statistical models, respective strengths and weaknesses emerged. Briefly, (1) many dynamical models simulate too many wet days with a small amount of precipitation in humid climate zones, such as summer in Japan, relative to the statistical model, unless the cumulus convection scheme improved for such a condition is incorporated; (2) a few dynamical models can derive a better high-order percentile of daily precipitation (e.g., 90th percentile) than the statistical model; (3) both the dynamical and statistical models are still insufficient in the representation of the interannual variation pattern of the number of days with precipitation &gt;= 90th percentile of daily precipitation; (4) the statistical model is comparable to the dynamical models in the long-term mean geographical pattern of the indices even on a 20 km grid interval if a dense observation network is applicable; (5) the statistical model is less accurate than the dynamical models in the temporal variation pattern due to the strong dependence of the predictand on the relatively less accurate predictor (daily reanalysis precipitation); and (6) the simple statistical model is less plausible in the physical sense because of the oversimplification of underlying physical processes compared to the dynamical models and more sophisticated statistical models.

    DOI

  • More asymmetric tree competition brings about more evapotranspiration and less runoff from the forest ecosystems: A simulation study

    Motomu Toda, Masayuki Yokozawa, Seita Emori, Toshihiko Hara

    ECOLOGICAL MODELLING   221 ( 24 ) 2887 - 2898  2010年12月  [査読有り]

     概要を見る

    The present paper reports how stand size-structure dynamics due to competition between differentsized trees affect long-term forested water balance in Japanese cool-temperate planted stands (evergreen coniferous Cryptomeria japonica and deciduous coniferous Larix kaempferi stands) using a fully coupled multi-layered meteorological surface physics-terrestrial ecosystems model. The simulation captured the well-known annual variation in leaf area index (LAI) accurately with stand age in monocultured and even-aged stands; the occurrence of maximum LAI during the early growth stage and then a gradual decline followed by a steady state after the maximum LAI. The simulations also detected a high dependency of annual evapotranspiration (AETr) on LAI with stand age that is well known by prior observational researches. In the C. japonica (shade-tolerant late-successional species) stand, the relationship between annual net primary productivity of an individual tree (NPPind) and individual tree mass (w) changed from linear to a convex curve during self-thinning, indicating that the degree of asymmetric tree competition intensified with forest stand development. The higher degree of competitive asymmetry characterized by the convex-shaped NPPind-w relationship produced greater size inequality, i.e., the formation of trees stratified by height. Under such conditions. AETr and annual transpiration (ATr) were mainly regulated by larger trees. On the other hand, the NPPind-w relationships in the L. kaempferi (shade-intolerant early-successional species) stand were linear throughout the simulated period, indicating the lower degree of competitive asymmetry. Under such conditions, the growth of intermediate-sized trees was enhanced and these trees became a dominant source of AETr (and also ATr) during self-thinning. Furthermore, the sensitivity analysis of the effects of ecophysiological parameters such as foliage profile (i.e., vertical distribution of leaf area density) of an individual tree (distribution pattern is described by the parameter eta), the maximum carboxylation velocity (V-cmaxo) and biomass allocation pattern of individual plant growth (mu(1)) on AETr, ATr and annual runoff (AR(off)) showed that the temporal trends of AETr, ATr, ARoff and NPPind-w relationships were completely the same as those in the control simulations. However, the NPPind-w relationship during self-thinning indicated higher degrees of competitive asymmetry when eta or Vcmaxo were greater than those in the control simulation and generated greater AETr and ATr and thus smaller AR(off). We found that more asymmetric tree competition brings about greater size inequality between different-sized trees and thus more evapotranspiration and less runoff in a forest stand. Overall, our simulation approach revealed that not only LAI dynamics but also plant competition, and thus size-structure dynamics, in a forest ecosystem are essential to long-term future projections of forested water balance.(C) 2010 Elsevier B.V. All rights reserved.

    DOI

  • 統計的ダウンスケーリングによる気候変化シナリオ作成入門

    飯泉仁之直, 西森基貴, 石郷岡康史, 横沢正幸

    農業気象   66 ( 2 ) 131 - 143  2010年09月  [査読有り]

    DOI

  • Diagnostics of Climate Model Biases in Summer Temperature and Warm-Season Insolation for the Simulation of Regional Paddy Rice Yield in Japan

    Toshichika Iizumi, Motoki Nishimori, Masayuki Yokozawa

    JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY   49 ( 4 ) 574 - 591  2010年04月  [査読有り]

     概要を見る

    This study quantifies the ranges of climate model biases in surface air temperature for July and August (summer temperature) and daily total insolation for May-October (warm-season insolation) that can give simulated regional paddy rice yields with a bias within +/- 2.5% of the 20-yr mean observed regional yield. The following four sets of three meteorological elements ( daily maximum and minimum temperatures and daily total insolation) from daily climate model outputs were used as meteorological inputs for a large-scale crop model for irrigated paddy rice: 1) raw climate model outputs of all meteorological elements, 2) bias-corrected temperatures and raw climate model outputs of insolation, 3) bias-corrected insolation and raw climate model outputs of temperatures, and 4) bias-corrected climate model outputs of all meteorological elements. These meteorological inputs were sourced from seven coupled general circulation models, one regional climate model, and one reanalysis dataset. Crop model simulations with artificially biased meteorological inputs were also used. By using the approximation formula derived from these crop model simulation results and the Monte Carlo simulation technique, it was found that climate model outputs with biases within +/- 0.6 degrees C and +/- 3% for summer temperature and warm-season insolation, respectively, could result in a simulated regional paddy rice yield with a bias within +/- 2.5% of the 20-yr mean observed regional yield. The simulated regional yield was less biased not only when the biases of two meteorological inputs were small but also when the cold or warm bias of summer temperature and the overestimation of warm-season insolation were balanced through the crop model processes. The methodology presented here will lead to a better and more comprehensive understanding of the nature of error propagation from a climate model to an application model and will facilitate the selection of climate models suitable for specific applications.

    DOI

  • Use of the RothC model to estimate the carbon sequestration potential of organic matter application in Japanese arable soils

    Masayuki Yokozawa, Yasuhito Shirato, Toshihiro Sakamoto, Seiichirou Yonemura, Makoto Nakai, Toshiaki Ohkura

    SOIL SCIENCE AND PLANT NUTRITION   56 ( 1 ) 168 - 176  2010年02月  [査読有り]

     概要を見る

    We estimated the carbon (C) sequestration potential of organic matter application in Japanese arable soils at a country scale by applying the Rothamsted carbon (RothC) model at a 1-km resolution. After establishing the baseline soil organic carbon (SOC) content for 1990, a 25-year simulation was run for four management scenarios: A (minimum organic matter application), B (farmyard manure application), C (double cropping for paddy fields) and D (both B and C). The total SOC decreased during the simulation in all four scenarios because the C input in all four scenarios was lower than that required to maintain the baseline 1990 SOC level. Scenario A resulted in the greatest depletion, reflecting the effects of increased organic matter application in the other scenarios. The 25-year difference in SOC accumulation between scenario A and scenarios B, C and D was 32.3, 11.1 and 43.4 Mt C, respectively. The annual SOC accumulation per unit area was similar to a previous estimate, and the 25-year averages were 0.30, 0.10 and 0.41 t C ha-1 year-1 for scenarios B, C and D, respectively. The system we developed in the present study, that is, linking the RothC model and soil spatial data, can be useful for estimating the potential C sequestration resulting from an increase in organic matter input to Japanese arable soils, although more feasible scenarios need to be developed to enable more realistic estimation.

    DOI CiNii J-GLOBAL

  • Variations of water resources in the Vietnam Mekong Delta subjected to climate change and its impacts on rice production

    Nguyen, D. K, A. Kotera, T. Iizumi, T. Sakamoto, M. Yokozawa

    Journal of Agricultural Meteorology   66   11 - 21  2010年  [査読有り]

    DOI

  • Potential predictability of local paddy rice yield variation using a crop model with local areal information

    Iizumi, T, K. Ishida, M. Yokozawa, M. Nishimori

    Agricultural Information Research   19 ( 2 ) 36 - 42  2010年  [査読有り]

     概要を見る

    This study examined the potential predictability of paddy rice yield variation on a local scale (approximately 2 km × 2 km) by using a prefectural-scale dynamic paddy rice simulation model (the PRYSBI model) with the local observed weather data, taking the 160 local areas in Tochigi Prefecture, Japan, as the study area. From the comparison of the simulated and observed local yields during the 11-year period (1993, 1995, 1998-2006), the PRYSBI model showed high capability to simulate the interannual variation of area-mean local yield over the study area with the quite large root-mean-square error (RMSE) of 2.1 Mg ha-1. However, the RMSE has the statistical-significant relationship with the local areal features on agriculture. We thereby incorporated the local areal features in the simulated yields in the manner of the multiplicative model approach. The parameter values of the multiplicative model were estimated by using the Bayesian approach, which can count the uncertainty of parameter value in a stochastic manner. By this means, the potential predictability in terms of the coefficient of determination (r2) and RMSE between the simulated and observed local yields improved from r2=0.430 to r2=0.527 and from RMSE=2.0 Mg ha-1 to RMSE=0.4 Mg ha-1 compared to the PRYSBI model alone. The potential predictability of local yield could improve by incorporating the local areal features in the output of crop model.<br>

    DOI CiNii

  • Projection of effects of climate change on rice yield and keys to reduce its uncertainties

    Yoshimoto, M, M. Yokozawa, T. Iizumi, M. Okada, M. Nishimori, Y. Masaki, Y. Ishigooka, T. Kuwagata, M. Kondo, T. Ishimaru, M. Fukuoka, T. Hasegawa

    Crop, Environment and Bioinformatics   7   260 - 268  2010年  [査読有り]

  • Foliage profiles of individual trees determine competition, self-thinning, biomass and NPP of a Ctyptomeria japonica forest stand: A simulation study based on a stand-scale process-based forest model

    Motomu Toda, Masayuki Yokozawa, Akihiro Sumida, Tsutomu Watanabe, Toshihiko Hara

    ECOLOGICAL MODELLING   220 ( 18 ) 2272 - 2280  2009年09月  [査読有り]

     概要を見る

    A simulation study was carried out to investigate simultaneously the effects of eco-physiological parameters on competitive asymmetry, self-thinning, stand biomass and NPP in a temperate forest using an atmosphere-vegetation dynamics interactive model (MINoSGI). In this study, we selected three eco-physiological relevant parameters as foliage profiles (i.e. vertical distribution of leaf area density) of individual trees (distribution pattern is described by the parameter eta), biomass allocation pattern in individual tree growth (chi) and the maximum carboxylation velocity (V(max)) The position of the maximal leaf area density shifts upward in the canopy with increasing eta. For scenarios with eta 4 (foliage concentrated in the lowest canopy layer) or eta &gt; 12 (foliage concentrated in the uppermost canopy layer), a low degree of competitive asymmetry was produced. These scenarios resulted in the survival of subordinate trees due to a brighter lower canopy environment when eta 4 or the generation of spatially separated foliage profiles between dominant and subordinate trees when eta &gt; 12. In contrast, competition between trees was most asymmetric when 4 &lt;= eta &lt;= 12 (vertically widespread foliage profile in the canopy), especially when eta = 8. In such cases, vertically widespread foliage of dominant trees lowered the opportunity of light acquisition for subordinate trees and reduced their carbon gain. The resulting reduction in carbon gain of subordinate trees yielded a higher degree of competitive asymmetry and ultimately higher mortality of subordinate trees. It was also shown that 4 &lt;= eta &lt;= 12 generated higher self-thinning speed, smaller accumulated NPP, litter-fall and potential stand biomass as compared with the scenarios with eta 4 or eta &gt; 12. In contrast, our simulation revealed small effects of chi or V(max) on the above-mentioned variables as compared with those of eta. In particular, it is notable that greater V(max) would not produce greater potential stand biomass and accumulated NPP although it has been thought that physiological parameters relevant to photosynthesis such as V(max) influence dynamic changes in forest stand biomass and NPP (e.g. the greater the V(max), the greater the NPP). Overall, it is suggested that foliage profiles rather than biomass allocation or maximum carboxylation velocity greatly govern forest dynamics, stand biomass, NPP and litter-fall. (C) 2009 Elsevier B.V. All rights reserved.

    DOI

  • Effects of soil nutrients on competition and morphological plasticity in an Impatiens balsamina population.

    Haraguchi A, Li Bo, Yokozawa M, Toda M, Hara T

    Icfai University Journal of Environmental Sciences   3 ( 3 ) 7 - 23  2009年08月  [査読有り]

  • Modelling the impacts of weather and climate variability on crop productivity over a large area: A new super-ensemble-based probabilistic projection

    Fulu Tao, Zhao Zhang, Jiyuan Liu, Masayuki Yokozawa

    AGRICULTURAL AND FOREST METEOROLOGY   149 ( 8 ) 1266 - 1278  2009年08月  [査読有り]

     概要を見る

    Estimates of climate change impacts are plague with uncertainties from many physical, biological, and social-economic processes. Among the urgent research priorities, more comprehensive assessments of impacts that better represent the uncertainties are needed. Here, we develop a new super-ensemble-based probabilistic projection approach to account for the uncertainties from CO(2) emission scenarios, climate change scenarios, and biophysical processes in impact assessment model. We demonstrate the approach in addressing the probabilistic changes of maize production in the North China Plain in future. The new process-based general crop model, MCWLA [Tao, F., Yokozawa, M. Zhang, Z., 2009. Modelling the impacts of weather and climate variability on crop productivity over a large area: a new process-based model development, optimization, and uncertainties analysis. Agric. For. Meteorol. 149,831-850], is used. MCWLA accounts for the key impact mechanisms of climate variability and is accurate over a large area. We use 10 climate scenarios consisting of the combinations of five GCMs and two emission scenarios, the corresponding atmospheric CO(2) concentration range, and 60 sets of crop model parameters representing the biophysical uncertainties from crop models. The planting window is set to allow planting shift within the window, although the crop cultivar and management practice in future were assumed to be same as the level during the baseline period. The resulting probability distributions indicate expected yield changes of -9.7, -15.7, -24.7% across the maize cultivation grids in Henan province during 2020s, 2050s, and 2080s, with 95% probability intervals of (-29.4,+15.8).(-45.7,+24.0), (-92.8, +20.3) in percent of 1961-1990 yields, respectively. The corresponding value in Shandong province is -9.1, -19.0. -25.5%, with 95% probability intervals of (-28.4, +17.4),(-45.4, +15.9),(-60.1, +12.8). We also investigate the temporal and spatial pattern of changes and variability in maize yield across the region. Besides the new findings on the probabilistic changes of maize productivity in the North China Plain, our study demonstrated an advanced super-ensemble-based probabilistic projection approach in addressing the impacts of climate variability (change) on regional agricultural production and the uncertainties. (C) 2009 Elsevier B.V. All rights reserved.

    DOI

  • Analysis of rapid expansion of inland aquaculture and triple rice-cropping areas in a coastal area of the Vietnamese Mekong Delta using MODIS time-series imagery

    Toshihiro Sakamoto, Cao Van Phung, Aikihiko Kotera, Khang Duy Nguyen, Masayuki Yokozawa

    LANDSCAPE AND URBAN PLANNING   92 ( 1 ) 34 - 46  2009年08月  [査読有り]

     概要を見る

    We applied a remote-sensing method using MODIS time-series imagery to detect the expansion of intensive farming systems (shrimp farming and triple rice cropping) in the Soc Trang and Bac Lieu provinces of the Vietnamese Mekong Delta (VMD). Field surveys for interpreting the estimates derived from the remote-sensing analyses were conducted in June and September 2007. From 2000 to 2006, there has been rapid expansion of inland aquaculture, especially shrimp farming, in the western part of the Bac Lieu province and the coastal regions of both the Bac Lieu and Soc Trang provinces. The triple rice-cropped area expanded concentrically from specific small locations in the Bac Lieu province from 2001 to 2006. The triple rice-cropped areas in Soc Trang province also expanded concentrically from 2001 to 2003, but some of these new triple rice-cropped areas returned to double rice cropping after 2004. interviews with farmers and ancillary hydrological monitoring data suggested that changes in the water environment and transmission of information about new farming systems are closely connected with the annual expansion of triple rice-cropped areas in both provinces. The availability of salt-free irrigation water in the dry season may have led some pioneering farmers to attempt full-scale dry-season cropping. Furthermore, successful dry-season harvests and recent increases in the price of rice might have encouraged neighboring farmers to follow suit. Based on MODIS time-series imagery with field interviews at land-use change hotspots, the spatial structure of coastal farming systems and their recent changes were revealed from a macroscopic view point. (C) 2009 Elsevier B.V. All rights reserved.

    DOI J-GLOBAL

  • Detection of Yearly Change in Farming Systems in the Vietnamese Mekong Delta from MODIS Time-Series Imagery

    Toshihiro Sakamoto, Phung Cao Van, Aikihiko Kotera, Khang Nguyen Duy, Masayuki Yokozawa

    JARQ-JAPAN AGRICULTURAL RESEARCH QUARTERLY   43 ( 3 ) 173 - 185  2009年07月  [査読有り]

     概要を見る

    This paper briefly introduces an integrated remote-sensing methodology based oil MODIS time-series imagery for detecting spatiotemporal changes in Vietnamese Mekong Delta (VIVID) farming systems. The integrated methodology consists of six parts, and uses a wavelet-based filter to smooth MODIS-derived time-series indexes (EVI, LSWI, and DVEL) from 2000 to 2008. Through a proposed decision tree using the smoothed indexes, we classified several farming systems, viz., triple rice cropping, two types of double rice cropping, shrimp-rice farming (rotational cropping), and inland aquaculture (monoculture). The MODIS-derived estimate of the total rice-planted area, shrimp-rice farming area, and inland aquaculture area agreed well with statistical data at the province level (R-2 &gt;= 0.96). However, in sonic provinces, the estimate has a large margin of error, probably because of the mixed-pixel effect due to the moderate spatial resolution of MODIS (250 m). According to the estimated spatial pattern of the farming systems in the whole VMD, inland aquaculture and shrimp-rice farming areas are distributed mostly in the coastal provinces. The areas of the farming systems steadily expanded until 2007, and double rice cropping systems in both Upper and coastal regions were replaced by triple rice cropping because of infrastructure improvements. The proportion of the triple rice cropping area peaked in 2005 and then declined steadily over the next 2 years. We discuss the advantage of the proposed methodology for detecting the spatiotemporal changes of land use patterns, especially of farming systems in a regional area.

    DOI

  • Soil CO2 concentrations and their implications in a plow-managed agricultural soil

    Yonemura S, Yokozawa M, Shirato Y, Nouchi I

    Journal of Agricultural Meteorology   65 ( 2 ) 141 - 149  2009年06月  [査読有り]

  • Modelling the impacts of weather and climate variability on crop productivity over a large area: A new process-based model development, optimization, and uncertainties analysis

    Fulu Tao, Masayuki Yokozawa, Zhao Zhang

    AGRICULTURAL AND FOREST METEOROLOGY   149 ( 5 ) 831 - 850  2009年05月  [査読有り]

     概要を見る

    Process-based crop models are increasingly being used to investigate the impacts of weather and climate variability (change) on crop growth and production, especially at a large scale. Crop models that account for the key impact mechanisms of climate variability and are accurate over a large area must be developed. Here, we present anew process-based general Model to capture the Crop-Weather relationship over a Large Area (MCWLA). The MCWLA is optimized and tested for spring maize on the Northeast China Plain and summer maize on the North China Plain, respectively. We apply the Bayesian probability inversion and a Markov chain Monte Carlo (MCMC) technique to the MCWLA to analyze uncertainties in parameter estimation and model prediction and to optimize the model. Ensemble hindcasts (by perturbing model parameters) and deterministic hindcasts (using the optimal parameters set) were carried out and compared with the detrended long-term yields series both at the crop model grid (0.5 degrees x 0.5 degrees) and province scale. Agreement between observed and modelled yield was variable, with correlation coefficients ranging from 0.03 to 0.88 (p &lt; 0.01) at the model grid scale and from 0.45 to 0.82 (p &lt; 0.01) at the province scale. Ensemble hindcasts captured significantly the interannual variability in crop yield at all the four investigated provinces from 1985 to 2002. MCWLA includes the process-based representation of the coupled CO2 and H2O exchanges; its simulations on crop response to elevated CO2 concentration agree well with the controlled-environment experiments, suggesting its validity also in future climate. We demonstrate that the MCWLA, together with the Bayesian probability inversion and a MCMC technique, is an effective tool to investigate the impacts of climate variability on crop productivity over a large area, as well as the uncertainties. (C) 2008 Elsevier B.V. All rights reserved.

    DOI J-GLOBAL

  • Climate change, land use change, and China's food security in the twenty-first century: an integrated perspective

    Fulu Tao, Masayuki Yokozawa, Jiyuan Liu, Zhao Zhang

    CLIMATIC CHANGE   93 ( 3-4 ) 433 - 445  2009年04月  [査読有り]

     概要を見る

    Food security in China, the world's most populous country, has long been a concern because of the challenges of population growth, water shortages, and loss of cropland through urbanization, soil degradation, and climate change. Here, we present an integrated analysis of China's food demand and supply under IPCC Special Report on Emissions Scenarios A1, A2, B1, and B2 in 2020, 2050, and 2080, based on official statistics and future development scenarios. Our analysis accounts for future socioeconomic, technological, and resource developments, as well the impact of climate change. We present a covariant relationship between changes in cereal productivity due to climate change and the cereal harvest area required to satisfy China's food demand. We also estimated the effects of changing harvested areas on the productivity required to satisfy the food demand; of productivity changes due to climate change on the harvest area required to satisfy food demand; and of productivity and land use changes on the population at risk of undernutrition. China could be able to feed herself without disturbing the global food market in the twenty-first century, but whether the government will choose self-sufficiency or increased food imports may depend on the cost of change, which remains unknown.

    DOI

  • Agro-ecological Interpretation of Rice Cropping Systems in Flood-prone Areas using MODIS Imagery

    Toshihiro Sakamoto, Phung Van Cao, Nhan Van Nguyen, Akihiko Kotera, Masayuki Yokozawa

    PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING   75 ( 4 ) 413 - 424  2009年04月  [査読有り]

     概要を見る

    This study attempts a new approach using Moderate Resolution Imaging Spectroradiometer (MODIS) time-series imagery to evaluate the agro-ecological interpretation of rice-cropping systems in flood-prone areas. A series of wavelet-based methodologies were applied to reveal the dynamic relationships among annual flood inundation, rice phenology, and land-use change in the Vietnamese Mekong Delta (VWD). The rice-heading dates of multi-cropping areas were estimated by detecting the local maximal points in smoothed Enhanced Vegetation Index (EVI) profiles, Using the Wavelet-based Filter for determining Crop Phenology (WFCP) and Wavelet-based Filter for evaluating the spatial distribution of Cropping Systems (WFCS) methods. The temporal information for annual flood intensity was determined for the six annual flood seasons over the period from 2000 to 2005 by the Wavelet-based Filter for detecting spatio-temporal changes in the Flood Inundation (WFFI) method. Analysis using remote sensing techniques revealed an interaction between the regional environment and agricultural activity in the VMD. First, comparing the estimated heading date of the winter-spring rice with the end date of flood inundation showed that the cropping season for the winter-spring rice in the flood-prone area fluctuates depending on the annual change in flood scale. This result implied that the onset Of winter-spring rice is spatially and temporally linked to the variable flood-recession season, and hence the annual change in flood scale. Secondly, the field survey study of the yearly change in the rice-cropping system in the An Giang province from 2000 to 2006 showed that the triple rice-cropped area in the An Giang province expanded from 2000 to 2005, because the construction of a ring-dyke system and water-resource infrastructure allowed an additional rice crop to be sustained during the flood season. However, the area of the third rice crop in the An Giang province decreased drastically in 2006 as a result of the management of pest outbreaks. Although the regional water-resource environment was gradually transformed by the construction of water-resource infrastructure, in order to achieve favorable conditions for a third rice crop during the flood season, the rapid change in land-use for agricultural activity may complicate the spatio-temporal configuration of the agricultural environment in the VMD. This case study used MODIS time-series imagery to help understand the functions of the macro-scale ecosystem, including annual flood regimes and human activity,.

  • Parameter estimation and uncertainty analysis of a large-scale crop model for paddy rice: Application of a Bayesian approach

    Toshichika Iizumi, Masayuki Yokozawa, Motoki Nishimori

    AGRICULTURAL AND FOREST METEOROLOGY   149 ( 2 ) 333 - 348  2009年02月  [査読有り]

     概要を見る

    A Bayesian approach, the Markov Chain Monte Carlo (MCMC) technique, was applied to a newly developed large-scale crop model for paddy rice to optimize a new set of regional-specific parameters and quantify the uncertainty of yield estimation associated with model parameters. The developed large-scale model is process-based and up-scaled from a conventional field-scale model to meet the intended spatial-scale of the large-scale model to the typical grid size of high-resolution climate models. The domain of the large-scale model covers all of Japan, but the crop simulation is conducted for each local governmental area in Japan. The MCMC technique exhibits powerful capability to optimize multiple parameters in a nonlinear and fairly complex model. The application of the Bayesian approach is useful to quantify the uncertainty of model parameters in a comprehensive manner when researchers on crop modeling analyze the uncertainty of yield estimation associated with model parameters under given observations. A sensitivity analysis of the large-scale model was conducted with the obtained posterior distribution of parameters and warming conditions that have never been experienced before to demonstrate the change in the uncertainty of yield estimation associated with the uncertainty of parameters of the large-scale model. The uncertainty of yield estimation under warming conditions was larger than that obtained under climate conditions that have been experienced before. This raises a concern that the uncertainty of impact assessment on crop yield may increase if future climate projections are fed to crop models with parameters optimized under current climate conditions. (C) 2008 Elsevier B.V. All rights reserved.

    DOI

  • Soil CO2 concentrations and their implications in conventional and no-tillage agricultural fields

    Senchiro Yonemura, Masayuki Yokozawa, Yasuhito Shirato, Seiichi Nishimura, Isamu Nouchi

    Journal of Agricultural Meteorology   65 ( 2 ) 141 - 149  2009年  [査読有り]

     概要を見る

    Soil CO2 concentrations to a depth of 50 cm depth were monitored with Vaisala CO2 probes from June 2004 to May 2005 in conventionally plowed and no-tillage agricultural plots and found to be generally higher in the former than the latter. Soil CO2 concentrations were also higher in summer and lower in winter, but were modulated by harvesting and the application of crop residues. Analysis of diurnal variations in soil CO2 concentrations, soil CO2 effluxes, and soil temperatures revealed distinct differences between plots. The relative amplitudes of the variation in CO2 concentrations peaked at a soil depth of 5 cm. Soil CO2 concentrations were higher when there was higher soil water content after precipitation, while soil CO2 effluxes were lower under the same circumstances. These two results relate to the lower diffusivity at higher soil water content, which restricts CO2 efflux, leading to higher soil CO2 concentrations. Calculations reveal that in the shallower soil layer (0-5 cm), CO2 production was greater in no-tillage plots, whereas in the deeper layer (15-25 cm), it was greater in conventional plots. © 2009, The Society of Agricultural Meteorology of Japan. All rights reserved.

    DOI

  • Mesh Climate Change Data of Japan Ver. 2 for Climate Change Impact Assessments Under IPCC SRES A1B and A2

    Masashi Okada, Toshichika Iizumi, Motoki Nishimori, Masayuki Yokozawa

    Journal of Agricultural Meteorology   65 ( 1 ) 97 - 109  2009年  [査読有り]

     概要を見る

    The Intergovernmental Panel on Climate Change (IPCC) published the Fourth Assessment Report (AR4) in 2007 and stated that recent climate change and variation are induced by increases in the atmospheric greenhouse gases (GHG) concentration due to anthropogenic activities. The report includes the results of impact assessments on a wide range of sectors. These assessments have been conducted based on future climate projections, which refer to aspects of the future climate evaluated by Atmosphere-Ocean Coupled General Circulation Models (CGCMs). The projection data used in the AR4 are archived under the Program for Climate Model Diagnosis and Intercomparison (PCMDI) promoted by the U.S. Department of Energy. We interpolated the projection data around Japan and constructed a dataset entitled the "Mesh climate change data of Japan Ver. 2" for the climate change impact study. Nine projections performed by seven models under the A1B and A2 of the Special Report on Emissions Scenarios (SRES) were implemented for the dataset. They consist of mesh data with a size of 7.5' in longitude and 5.0' in latitude, i.e. approximately 10×10 km (45" in longitude and 30" in latitude, approximately 1×1 km, for one high-resolution model). The dataset includes five climatic elements, i.e. the daily mean, maximum, and minimum surface air temperatures, daily total precipitation, and daily accumulated shortwave radiation for three periods, 1981-2000, 2046-2065, and 2081-2100. This article describes the details concerning the construction and characteristics of the data. © 2009, The Society of Agricultural Meteorology of Japan. All rights reserved.

    DOI

  • Development of impact functions on regional paddy rice yield in Japan for integrated impact assessment models

    Toshichika Iizumi, Masayuki Yokozawa, Motoki Nishimori

    Journal of Agricultural Meteorology   65 ( 2 ) 179 - 190  2009年  [査読有り]

     概要を見る

    For this study, we developed and validated two types of impact functions on regional paddy rice yield in six regions of Japan. One is simple, and the other is slightly detailed. An impact function has the following features: (1) it is a look-up table that shows the quantity of interest (regional paddy rice yield in this study) in response to various forcing conditions
    (2) it is provided by a mechanistic but heavy computational-load model
    and (3) it is implemented in integrated impact assessment models to reduce the simulation time. The developed impact functions will be submitted for use in integrated impact assessment models and will contribute to examining the target level of stabilization on greenhouse gas emissions. The impact functions were compared with the observation and the conventional crop model simulation (full-simulation). The slightly detailed (simple) impact function agreed with the observation with a mean-absolute-percentage (MAP) error of 7.8% (7.7%). Under warming conditions, the slightly detailed (simple) one was comparable to the full-simulation with a MAP difference of 4.5% (4.6%). The majority of the difference arose from the temperature fluctuation within a short time period of less than two months. These results indicate that the application of the impact functions is permissible for assessing the impact of the average climate change on regional yield. However, the impact functions tend not to be a very reliable tool for assessing the impacts of extreme climate events and interannual climate variation on regional yield. © 2009, The Society of Agricultural Meteorology of Japan. All rights reserved.

    DOI

  • 気候変化がわが国におけるコメ収量変動に及ぼす影響の広域評価

    横沢正幸, 飯泉仁之直, 岡田将誌

    地球環境   14   199 - 205  2009年  [査読有り]

  • A climatological analysis on the recent declining trend of rice quality in Japan

    Masashi OKADa, Yousay Hayashi, Toshichika Iizumi, Masayuki Yokozawa

    Journal of Agricultural Meteorology   65 ( 4 ) 327 - 337  2009年  [査読有り]

     概要を見る

    A remarkable declining trend in rice quality has already been observed in western Japan and the future global warming associated with climate change is likely to exacerbate such risk. In this study, a simple statistical model was constructed to estimate the rice quality, which is defined as the proportion of white immature grains on a prefectural scale, in terms of two major climate variables during the grain-filling stage: the cumulative weighted effective temperature δ and the cumulative solar radiation SR. In order to account for the uncertainties included in the processes involved, Bayesian inference was used to estimate the model parameters. The modeled time changes in rice quality correlated well to those observed. Specifically, the reproducibility of rice quality since 2000 was particularly high. These results suggested that a combination of the two climate factors was responsible for the recent variability in rice quality on a prefectural scale. Subsequently, the elasticity of rice quality relative to δ and SR was examined based on the model. The elasticity represents the relative change in rice quality in response to a change in δ or SR, with a positive (negative) sign indicating increased (decreased) quality. Consequently, the mean elasticity of the rice quality relative to SR was larger than that to δ in Kyushu. Moreover, the time changes of rice quality in Kyushu synchronized with that of SR under high temperature conditions, suggesting that rice plants become more sensitive to conditions of insufficient radiation if exposed to high temperatures. Consequently, it was concluded that the contribution of the radiation condition to the variation in rice quality become relatively larger along with the recent increase in temperature. © 2009, The Society of Agricultural Meteorology of Japan. All rights reserved.

    DOI

  • Climate-crop yield relationships at provincial scales in China and the impacts of recent climate trends

    Fulu Tao, Masayuki Yokozawa, Jiyuan Liu, Zhao Zhang

    CLIMATE RESEARCH   38 ( 1 ) 83 - 94  2008年12月  [査読有り]

     概要を見る

    Understanding climate-yield relationships and the impacts of recent climate trends on crop productivity on a large scale is an important step in predicting regional agricultural production. In this study we investigated climate-crop relationships, recent trends in seasonal climate (maximum and minimum temperatures, diurnal temperature range and precipitation) and their impacts on the yields of major crops (i.e. rice, wheat, maize and soybean) at provincial scales throughout China over the last few decades. We found that major crop yields were significantly related to growing season climate in the main production regions of China, and that growing season temperature had a generally significant warming trend. Due to the trends in growing season climate, total rice production in China was estimated to have increased by 3.2 x 10(5) t decade(-1) during the period 1951-2002; total production of wheat, maize and soybean changed by -1.2 x 10(5), -21.2 x 10(5) and 0.7 x 10(5) t decade(-1), respectively, during 1979-2002. The warming trend increased rice yield in northeast China and soybean in north and northeast China; however, it decreased maize yield in 7 provinces (autonomous region or municipality) and wheat yield in 3 provinces. Our analysis presents the general response patterns of regional agricultural productivity to seasonal climate variability and change over the last few decades. Crop response mechanisms to local seasonal climate change (and variability) need further investigation to better understand the patterns and predict future consequences of climate change and variability on regional agricultural production.

    DOI J-GLOBAL

  • Regional Consequences of Seawater Intrusion on Rice Productivity and Land Use in Coastal Area of the Mekong River Delta

    Akihiko Kotera, Toshihiro Sakamoto, Duy Khang Nguyen, Masayuki Yokozawa

    JARQ-JAPAN AGRICULTURAL RESEARCH QUARTERLY   42 ( 4 ) 267 - 274  2008年10月  [査読有り]

     概要を見る

    This study investigates rice productivity in the coastal area of the Mekong River Delta, Vietnam focusing on relationships with the influences of seawater intrusion and recent changes in the land use at regional scale. We examined the statistical data on rice production at 30 districts of 4 provinces in the coastal area for the years 2003-2005, together with the average salinity concentration observed at 48 points in canals and rivers during the dry season. As an index of the extent of seawater intrusion to be compared with rice statistical data in each district, average salinity of each district was derived by using spatial interpolation from the data in the observation points. It was shown that seawater intrusion was the major factor leading to regional differences in rice cropping systems and land use patterns in the region. Rice cropping intensities, which is defined as the ratio of planted area to district area, decreased with increasing salinity level in canal water, but rice yields averaged over the district are independent of the salinity level. To avoid salinity stress to rice growth, rice cultivation in the coastal area is mainly undertaken during the period when seawater intrusion is weakened by the seasonal decrease in salinity in the rainy season. Specifically, in districts with high salinity, the salinity-free duration required for rice cultivation is short. There, rice cropping intensities are potentially limited by the salinity. In addition, recently, the area of paddy fields in the coastal area has been decreased through land use conversion to aquaculture, especially shrimp farms. Intensity of aquaculture, which requires brackish water, was also limited by seawater intrusion. Thus., rice production in the coastal area of the Mekong Delta was limited by the interrelationship between seawater intrusion and land-use diversification.

    DOI

  • Regional Consequences of Seawater Intrusion on Rice Productivity and Land Use in Coastal Area of the Mekong River Delta

    Akihiko Kotera, Toshihiro Sakamoto, Duy Khang Nguyen, Masayuki Yokozawa

    JARQ-JAPAN AGRICULTURAL RESEARCH QUARTERLY   42 ( 4 ) 267 - 274  2008年10月  [査読有り]

     概要を見る

    This study investigates rice productivity in the coastal area of the Mekong River Delta, Vietnam focusing on relationships with the influences of seawater intrusion and recent changes in the land use at regional scale. We examined the statistical data on rice production at 30 districts of 4 provinces in the coastal area for the years 2003-2005, together with the average salinity concentration observed at 48 points in canals and rivers during the dry season. As an index of the extent of seawater intrusion to be compared with rice statistical data in each district, average salinity of each district was derived by using spatial interpolation from the data in the observation points. It was shown that seawater intrusion was the major factor leading to regional differences in rice cropping systems and land use patterns in the region. Rice cropping intensities, which is defined as the ratio of planted area to district area, decreased with increasing salinity level in canal water, but rice yields averaged over the district are independent of the salinity level. To avoid salinity stress to rice growth, rice cultivation in the coastal area is mainly undertaken during the period when seawater intrusion is weakened by the seasonal decrease in salinity in the rainy season. Specifically, in districts with high salinity, the salinity-free duration required for rice cultivation is short. There, rice cropping intensities are potentially limited by the salinity. In addition, recently, the area of paddy fields in the coastal area has been decreased through land use conversion to aquaculture, especially shrimp farms. Intensity of aquaculture, which requires brackish water, was also limited by seawater intrusion. Thus., rice production in the coastal area of the Mekong Delta was limited by the interrelationship between seawater intrusion and land-use diversification.

    DOI

  • Climate change impact on rice insurance payouts in Japan

    Toshichika Iizumi, Masayuki Yokozawa, Yousay Hayashi, Fujio Kimura

    JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY   47 ( 9 ) 2265 - 2278  2008年09月  [査読有り]

     概要を見る

    The authors constructed the framework for a preliminary assessment of climate change impact on the rice insurance payout in Japan. The framework consisted of various models ranging from climate projection downscaling, rice yield estimation, yield loss assessment, and rice insurance payout estimation. In this study, a simulation was conducted based on the dynamically downscaled regional climate projection with a lateral boundary condition given by the global climate projection of the Meteorological Research Institute Coupled General Circulation Model, version 2 (MRI CGCM2), under the A2 scenario of the Special Report on Emission Scenarios (SRES). Results indicated that rice yield in the 2070s will decrease slightly in central and western Japan and increase in northern Japan. The increase in yield was derived from a significant reduction in yield loss caused by cool-summer damage; on the other hand, the decrease in yield was caused by the increase in yield loss caused by heat stress and the shortening of the growth period induced by the temperature rise. The increase in the atmospheric CO2 concentration resulted in an increase in paddy rice biomass because of the fertilization effect; however, the increase in biomass was not enhanced much as a result of shortening of the growth period if early planting was not considered as an adaptation practice. Reflecting such changes in yield, the rice insurance payout significantly decreased in northern Japan but only slightly increased in the areas of central and western Japan. In total, the 9-yr mean payout in Japan in the 2070s decreased to 120.2 billion yen; the value corresponded to 87% of the payout averaged over 9 yr in the 1990s (1991-99).

    DOI CiNii J-GLOBAL

  • Sensitivity of Salinity Intrusion to Sea Level Rise and River Flow Change in Vietnamese Mekong Delta-Impacts on Availability of Irrigation Water for Rice Cropping

    Akihiko Kotera, Toshihiro Sakamoto, Masayuki Yokozawa, Nguyen Duy Khang

    Journal of Agricultural Meteorology   64 ( 3 ) 167 - 176  2008年  [査読有り]

     概要を見る

    The combined impact of sea level rise and reduction of the Mekong River flow in the dry season on salinity intrusion and rice cropping in the Vietnamese Mekong Delta was assessed in this study. The MIKE11 model was used to simulate flow and salinity intrusion from December to June for the medium-term (mid-2030s) and long-term (mid-2090s) scenarios using data derived from the SRES B2 climate change projection. The sea level rise values for two scenarios were +20 cm and +45 cm, while the rates of change for the Mekong River flow were -15% and -29%, respectively. The results obtained for the mid-2030s and mid-2090s scenarios show that the 2.5 g/L saline front is likely to shift upstream by 10 km and 20 km in the main river channels, and up to 20 km and 35 km in the paddy field, respectively. The simulated salinity intrusion results were then used to compute durations of available water for irrigating rice cropping. The results indicate that area where triple rice crops are possible, will be reduced by approximately 71,000 and 72,000 ha, while single crop areas will be increased by approximately 38,000 and 179,000 ha for the mid-2030s and mid-2090s scenarios, respectively. Using GIS techniques the delta was divided into three areas reflecting different rice crop vulnerability levels
    areas of high and medium vulnerability measured approximately 200,000 ha and 400,000 ha, respectively. © 2008, The Society of Agricultural Meteorology of Japan. All rights reserved.

    DOI

  • Research on carbon dynamics in a wetland ecosystem dominated by Phragmites australis using the Closed Geosphere Experiment Facility.

    Suzuki S, Inubushi K, Yokozawa M, Hara T, Tsuga S, Endo M, Nitta K

    Proceedings of the International Symposium on Application of a Closed Experimental System to Modeling of 14C Transfer in the Environment (Y. Tako, T. Tani, R. Arai, S. Nozoe & Y. Nakamura, Eds),Rokkasho, Aomori, Japan.     64 - 71  2008年

  • Combined Equations for Estimating Global Solar Radiation: Projection of Radiation Field over Japan under Global Warming Conditions by Statistical Downscaling

    Toshichika Iizumi, Motoki Nishimori, Masayuki Yokozawa

    Journal of Agricultural Meteorology   64 ( 1 ) 9 - 23  2008年  [査読有り]

     概要を見る

    For this study, we developed a new statistical model to estimate the daily accumulated global solar radiation on the earth's surface and used the model to generate a high-resolution climate change scenario of the radiation field in Japan. The statistical model mainly relies on precipitable water vapor calculated from air temperature and relative humidity on the surface to estimate seasonal changes in global solar radiation. On the other hand, to estimate daily radiation fluctuations, the model uses either a diurnal temperature range or relative humidity. The diurnal temperature range, calculated from the daily maximum and minimum temperatures, and relative humidity is a general output of most climate models, and pertinent observation data are comparatively easy to access. The statistical model performed well when estimating the monthly mean value, daily fluctuation statistics, and regional differences in the radiation field in Japan. To project the change in the radiation field for the years 2081 to 2100, we applied the statistical model to the climate change scenario of a high-resolution Regional Climate Model with a 20-km mesh size (RCM20) developed at the Meteorological Research Institute based on the Special Report for Emission Scenario (SRES)-A2. The projected change shows the following tendency: global solar radiation will increase in the warm season and decrease in the cool season in many areas of Japan, indicating that global warming may cause changes in the radiation field in Japan. The generated climate change scenario for the radiation field is linked to long-term and short-term changes in air temperature and relative humidity obtained from the RCM20 and, consequently, is expected to complement the RCM20 datasets for an impact assessment study in the agricultural sector. © 2008, The Society of Agricultural Meteorology of Japan. All rights reserved.

    DOI

  • Land surface phenology dynamics and climate variations in the North East China Transect (NECT), 1982-2000

    F. Tao, M. Yokozawa, Z. Zhang, Y. Hayashi, Y. Ishigooka

    INTERNATIONAL JOURNAL OF REMOTE SENSING   29 ( 19 ) 5461 - 5478  2008年  [査読有り]

     概要を見る

    Land surface phenology dynamics reflect the response of the Earth&apos;s biosphere to inter- and intra-annual dynamics of the Earth&apos;s climate and hydrologic regimes. Investigations of land surface phenology dynamics and its relation to long-term climate variation could help us to detect the response of regional vegetation to climate variation. The present study developed a new algorithm for detecting regional land surface phenology dynamics (ARLSPD) and demonstrated it in detecting the vegetation response to inter-annual climate variability in the North East China Transect (NECT), a mid-latitude semi-arid terrestrial transect with strong gradients in environmental conditions and vegetation formations. The spatial-temporal patterns of greenup-onset date, maturity date, and senescence date during the period of 1982-2000 are presented. The resultant spatial-temporal patterns of land surface phenology were quite consistent with the land-cover characteristics, moisture, and temperature gradients. The relations between inter-annual variations in phenology and seasonal climate were investigated. It was found that besides human disturbance, land surface phenology depended primarily on the combined effects of preseason temperature and precipitation. The relative influence of preseason temperature and precipitation on land surface phenology was changing, which led to the different responses of land surface dynamics to climate variation along the moisture gradient in the NECT. In the arid and semi-arid region of NECT, the dates of onset for phonological events in temperate typical grassland were most significantly related to the precipitation during the preceding 2-4 months. Temperature-induced drought stress during the preceding months could delay greenup onset in cropland/grassland mosaic, and advance senescence in temporal typical grassland, and in cropland/grassland mosaic. The regional phenology algorithm, theoretically also applicable for complex ecosystems characterized by annual multiple growth cycles, is expected to couple with large-scale biogeochemical models to regulate dynamically land surface phenology.

    DOI

  • Global warming, rice production, and water use in China: Developing a probabilistic assessment

    Fulu Tao, Yousay Hayashi, Zhao Zhang, Toshihiro Sakamoto, Masayuki Yokozawa

    AGRICULTURAL AND FOREST METEOROLOGY   148 ( 1 ) 94 - 110  2008年01月  [査読有り]

     概要を見る

    Uncertainties in global climate models (GCMs) and emission scenarios affect assessments of the impact of global warming as well as the communication of scientific results. Here, we developed a probabilistic technique to deal with the uncertainties and to simulate the impact of global warming on rice production and water use in China, against a global mean temperature (GMT) increase scale relative to 1961-1990 values. From 20 climate scenarios output from the Intergovernmental Panel on Climate Change Data Distribution Centre, we used Monte Carlo analysis to develop the most likely climate-change scenarios for representative stations and derived the CERES-Rice model of [Alocilja, E.C., Ritchie, R.T., 1988. Rice simulation and its use in multicriteria optimization, IBSNAT Research Report Series 01] to simulate rice production under baseline and future climate scenarios. Adaptation options such as automatic application of irrigation and fertilization were considered, although cultivars were assumed constant over the baseline and future. After assessing representative stations across China, we projected changes in rice yield, growing period, evapotranspiration, and irrigation-water use for GMT changes of 1, 2, and 3 degrees C in a probabilistic way. Without consideration of CO2-fertilization effects, our results indicate that the growing period would shorten with 100% probability; yield would decrease with a probability of 90%, 100%, and 100% for GMT change of 1, 2, and 3 degrees C, respectively. The median values of yield decrease ranged from 6.1% to 18.6%,13.5% to 31.9%, and 23.6% to 40.2% for GMT changes of 1, 2, and 3 degrees C, respectively. According to the median values of the projected changes, evapotranspiration and irrigation water use would decrease in most of the investigated stations. If CO2-fertilization effects were included, the rice growing period would also be reduced with 100% probability; across the stations the median values of yield changes ranged from -10.1% to 3.3%, -16.1% to 2.5%, and -19.3% to 0.18% for GMT changes of 1, 2, and 3 degrees C, respectively. Evapotranspiration and irrigation water use would decrease more and with higher probability in comparison with the simulations without consideration of CO2-fertilization effects. Our study presents a process-based probabilistic assessment of rice production and water use at different GMT increases, which is important for identifying which climate-change level is dangerous for food security. (c) 2007 Elsevier B.V. All rights reserved.

    DOI

  • Detecting temporal changes in the extent of annual flooding within the Cambodia and the Vietnamese Mekong Delta from MODIS time-series imagery

    Toshihiro Sakamoto, Nhan Van Nguyen, Akihiko Kotera, Hiroyuki Ohno, Naoki Ishitsuka, Masayuki Yokozawa

    REMOTE SENSING OF ENVIRONMENT   109 ( 3 ) 295 - 313  2007年08月  [査読有り]

     概要を見る

    This paper presents the methodology used to detect temporal changes in the extent of annual flooding within the Cambodia and the Vietnamese Mekong Delta (VMD) based on MODIS time-series imagery (Wavelet-based Filter for detecting spatio-temporal changes in Flood Inundation; WFFI). This methodology involves the use of a wavelet-based filter to interpolate missing information and reduce the noise component in the time-series data, as proposed in a previous study. The smoothed time profiles of Enhanced Vegetation Index (EVT), Land Surface Water Index (LSWI), and the Difference Value between EVI and LSWI (DVEL) are obtained from MOD09 8-day composite time-series data (resolution: 500 m; time period: 2000-2005). The proposed algorithm was applied to produce time-series inundation maps (WFFI products) for the five annual flood seasons over the period from 2000 to 2004. The WFFI products were validated via comparisons with Landsat-derived results and inundation maps based on RADARSAT images, hydrological data, and digital elevation model data. Compared with the RADARSAT-derived inundation maps at the province level, the obtained RMSE range from 364 to 443 km(2) and the determination coefficients [R-2] range from 0.89 to 0.92. Compared with Landsat-derived results at the 10-km grid level, the obtained RMSE range from 6.8 to 15.2 km(2) and the determination coefficients [R-2] range from 0.77 to 0.97. The inundated area of flooded forests/marsh to the northeast of Tonle Sap Lake were underestimated, probably because of extensive vegetation cover in this area. The spatial characteristics of the estimated start dates, end dates, and duration of inundation cycles were also determined for the period from 2000 to 2004. There are clear contrasts in the distribution of the estimated end dates and duration of inundation cycles between large-scale floods (2000-2002) and medium- and small-scale floods (2003 and 2004). At the regional scale, the estimated start dates for the southern part of An Giang Province during 2003 and 2004 was distinctly later than that for surrounding areas. The results indicate that these triple-cropping areas enclosed by dikes increased in extent from 2003 to 2004. In contrast, the estimated end dates of inundation at the Co Do and Song Hart State Farms were clearly earlier than those for surrounding areas, although the estimated start dates were similar. Temporal changes in the inundation area of Flood pixels in the Dong Thap and Long An Provinces are in excellent agreement with daily water-level data recorded at Tan Chan Station. The estimated area of Long-term water body increased in size from 2000 to 2004, especially in coastal areas of the Ca Mau and Bac Lieu Provinces. Statistical data for Vietnam indicate that this trend may reflect the expansion of shrimp-farming areas. The WFFI products enable an understanding of seasonal and annual changes in the water distribution and environment of the Cambodia and the VMD from a global viewpoint. (C) 2007 Elsevier Inc. All rights reserved.

    DOI CiNii J-GLOBAL

  • Simulating the carbon balance of a temperate larch forest under various meteorological conditions

    Motomu Toda, Masayuki Yokozawa, Akihiro Sumida, Tsutomu Watanabe, Toshihiko Hara

    Carbon Balance and Management   2 ( 1 ) 6  2007年05月  [査読有り]

     概要を見る

    Background: Changes in the timing of phenological events may cause the annual carbon budget of deciduous forests to change. Therefore, one should take such events into account when evaluating the effects of global warming on deciduous forests. In this article, we report on the results of numerical experiments done with a model that includes a phenological module simulating the timing of bud burst and other phenological events and estimating maximum leaf area index. Results: This study suggests that the negative effects of warming on tree productivity (net primary production) outweigh the positive effects of a prolonged growing season. An increase in air temperature by 3°C (5°C) reduces cumulative net primary production by 21.3% (34.2%). Similarly, cumulative net ecosystem production (the difference between cumulative net primary production and heterotrophic respiration) decreases by 43.5% (64.5%) when temperatures are increased by 3°C (5°C). However, the positive effects of CO2 enrichment (2 × CO2) outweigh the negative effects of warming (&lt
    5°C). Conclusion: Although the model was calibrated and validated for a specific forest ecosystem, the implications of the study may be extrapolated to deciduous forests in cool-temperate zones. These forests share common features, and it can be conjectured that carbon stocks would increase in such forests in the face of doubled CO2 and increased temperatures as long as the increase in temperature does not exceed 5°C. © 2007 Toda et al
    licensee BioMed Central Ltd.

    DOI J-GLOBAL

  • Assessing the impacts of climate change on rice yields in the main rice areas of China

    Fengmei Yao, Yinglong Xu, Erda Lin, Masayuki Yokozawa, Jiahua Zhang

    CLIMATIC CHANGE   80 ( 3-4 ) 395 - 409  2007年02月  [査読有り]

     概要を見る

    This paper assesses the impact of climate change on irrigated rice yield using B2 climate change scenario from the Regional Climate Model (RCM) and CERES-rice model during 2071--2090. Eight typical rice stations ranging in latitude, longitude, and elevation that are located in the main rice ecological zones of China are selected for impact assessment. First, Crop Estimation through Resource and Environment Synthesis (CERES)-rice model is validated using farm experiment data in selected stations. The simulated results represent satisfactorily the trend of flowering duration and yields. The deviation of simulation within +/- 10% of observed flowering duration and +/- 15% of observed yield. Second, the errors of the outputs of RCM due to the difference of topography between station point and grid point is corrected. The corrected output of the RCM used for simulating rice flowering duration and yield is more reliable than the not corrected. Without CO2 direct effect on crop, the results from the assessment explore that B2 climate change scenario would have a negative impact on rice yield at most rice stations and have little impacts at Fuzhou and Kunming. To find the change of inter-annual rice yield, a preliminary assessment is made based on comparative cumulative probability at low and high yield and the coefficient variable of yield between the B2 scenario and baseline. Without the CO2 direct effect on rice yield, the result indicates that frequency for low yield would increase and it reverses for high yield, and the variance for rice yield would increase. It is concluded that high frequency at low yield and high variances of rice yield could pose a threat to rice yield at most selected stations in the main rice areas of China. With the CO2 direct effect on rice yield, rice yield increase in all selected stations.

    DOI

  • 地球温暖化にともなう異常気象・集中豪雨などの気候学的な予測のための地域気候モデルによる現在気候再現実験

    西森 基貴, 木村 富士男, 飯泉 仁之直, 横沢 正幸

    地球環境シンポジウム講演論文集   15   177 - 182  2007年

     概要を見る

    To investigate the possibility of projection of unusual weathers such as hot and cool summer or disaster of heavy rainfall under the global warming condition, we have examined the reconstructed probability of extreme summertime high and low temperatures and local-scale heavy rainfall by using a regional climate model (RCM), Regional Atmospheric Modeling System (RAMS) modified in the Terrestrial Environmental Research Center (TERC). The TERC-RAMS is a nested RCM and has driven by a forcing general circulation field obtained from realistic re-analysis data or Global Climate Models. Preliminary experiments are intended to reconstruct mainly on daily rainfall amount and frequency, and daily maximum and minimum temperatures in Japan. The results showed that the TERC-RAMS could reconstruct the rainfall frequency in one month, but not project the absolute amount of heavy rainfall well. In addition, this model has a systematic bias for under-estimation of temperature. The model experiments have necessity to further development especially on radiation and surface soil/water conditions.

    DOI CiNii

  • 気候変動が農業へ及ぼす影響―日本と中国への影響を中心として―

    横沢正幸, 陶福禄, 飯泉仁之直

    国際農林業協力   30 ( 2 ) 10 - 20  2007年

    CiNii

  • Climate changes and trends in phenology and yields of field crops in China, 1981-2000

    Fulu Tao, Masayuki Yokozawa, Yinlong Xu, Yousay Hayashi, Zhao Zhang

    AGRICULTURAL AND FOREST METEOROLOGY   138 ( 1-4 ) 82 - 92  2006年08月  [査読有り]

     概要を見る

    A warming trend has become pronounced since the 1980s in China and is projected to accelerate in the future. Concerns about the vulnerability of agricultural production to climate change are increasing. The impact of future climate change on crop production has been widely predicted by using crop models and climate change scenarios, but little evidence of the observed impacts of climate change on crop production has been reported. In this study, we synthesized crop and climate data from representative stations across China during 1981-2000 to investigate whether there were significant trends in changes of climate variables in different regions, and whether theses changes have had significant impact on the development and production of the staple crops (i.e. rice, wheat, and maize). Our results showed that significant warming trends were observed at most of the investigated stations, and the changes in temperature have shifted crop phenology and affected crop yields during the two decades. The observed climate change patterns, as well their impacts on crop phenology and yields are spatially diverse across China. Our study also highlights the need for further investigations of the combined impacts of temperature and CO2 concentration on physiological processes and mechanisms governing crop growth and production. (c) 2006 Elsevier B.V. All rights reserved.

    DOI

  • Climate changes and trends in phenology and yields of field crops in China, 1981-2000

    Fulu Tao, Masayuki Yokozawa, Yinlong Xu, Yousay Hayashi, Zhao Zhang

    AGRICULTURAL AND FOREST METEOROLOGY   138 ( 1-4 ) 82 - 92  2006年08月

     概要を見る

    A warming trend has become pronounced since the 1980s in China and is projected to accelerate in the future. Concerns about the vulnerability of agricultural production to climate change are increasing. The impact of future climate change on crop production has been widely predicted by using crop models and climate change scenarios, but little evidence of the observed impacts of climate change on crop production has been reported. In this study, we synthesized crop and climate data from representative stations across China during 1981-2000 to investigate whether there were significant trends in changes of climate variables in different regions, and whether theses changes have had significant impact on the development and production of the staple crops (i.e. rice, wheat, and maize). Our results showed that significant warming trends were observed at most of the investigated stations, and the changes in temperature have shifted crop phenology and affected crop yields during the two decades. The observed climate change patterns, as well their impacts on crop phenology and yields are spatially diverse across China. Our study also highlights the need for further investigations of the combined impacts of temperature and CO2 concentration on physiological processes and mechanisms governing crop growth and production. (c) 2006 Elsevier B.V. All rights reserved.

    DOI

  • A chamber system with automatic opening and closing for continuously measuring soil respiration based on an open-flow dynamic method

    SU Suh, YM Chun, NY Chae, J Kim, JH Lim, M Yokozawa, MS Lee, JS Lee

    ECOLOGICAL RESEARCH   21 ( 3 ) 405 - 414  2006年05月  [査読有り]

     概要を見る

    We developed an automatic opening and closing chamber system (AOCC) based on an open-flow dynamic method (open-flow AOCC). The AOCC can be used during all four seasons, even at the surface of relatively deep snow. We compared the open-flow AOCC with two closed dynamic methods [the AOCC configured as a closed dynamic system (closed dynamic AOCC) and the LI-6400 system] under field conditions. The closed dynamic-AOCC and LI-6400 measurements were about 15.4% and 5.2% lower, respectively, than the values obtained with the open-flow AOCC. There was a significant difference in soil respiration rate between the open-flow AOCC and the closed dynamic AOCC system. In contrast, no significant difference in soil respiration rate was detected between the open-flow AOCC and the LI-6400 system. In the field, the open-flow AOCC permitted continuous long-term measurements under a range of temperature conditions and did a good job of reflecting the marked daily and seasonal variations in soil respiration as a function of soil temperature.

    DOI

  • Acid hydrolysis to partition plant material into decomposable and resistant fractions for use in the Rothamsted carbon model

    Y Shirato, M Yokozawa

    SOIL BIOLOGY & BIOCHEMISTRY   38 ( 4 ) 812 - 816  2006年04月  [査読有り]

     概要を見る

    Using various plant materials, we identified two conceptual pools of plant litter, decomposable plant material (DPM) and resistant plant material (RPM), in the Rothamsted Carbon Model (RothC) by comparing the default proportions of DPM and RPM in the RothC and proportions in plant material fractions as determined by two-step acid hydrolysis with H2SO4. We collected 37 plant samples from 15 species at six sites on arable land, grassland, or forest in Japan. Carbon in the plant materials was divided into three pools by acid hydrolysis: (a) Labile Pool I (LP I), obtained by hydrolysis with 5 N H2SO4 at 105 degrees C for 30 min; (b) Labile Pool II (LP II), obtained by hydrolysis with 26 N H-2 SO4 at room temperature overnight, and then with 2 N H2SO4 at 105 C for 3 h; and (c) Recalcitrant Pool (RP), the unhydrolyzed residue. The average proportion of LP I in crops and grasses was 59%, which was the same as the proportion of DPM defined in the RothC as the default value for crops and grasses. The remaining 41% (23% LP II + 18% RP) was consequently the same as the RPM proportion defined in the RothC. Similarly, the average proportion of LP I in all tree leaves (19%) was very close to the proportion of DPM in the RothC (20%) for trees. These results indicate that DPM in the RothC can be identified as LP I from the acid hydrolysis analysis and RPM as LP II+RP. We conclude that, at least theoretically, the use of an independent DPM:RPM ratio, as determined by acid hydrolysis analysis for each plant material, should enable more reliable modeling of SOM dynamics than the use of default DPM:RPM values provided by the model, even though the practical advantages of this method require further evaluation. (c) 2005 Elsevier Ltd. All rights reserved.

    DOI CiNii J-GLOBAL

  • How does long-term elevated CO2 alter size structure and competition in forest stands?

    Toda M, Yokozawa M, Hara T

    Proceedings of the 2nd Symposium on Water Cycle in Northern Eurasia (T. Ohata & T. Ohta, Eds). Sapporo, Japan.     31 - 32  2006年

  • How to analyze long-term insect population dynamics under climate change: 50-year data of three insect pests in paddy fields

    K Yamamura, M Yokozawa, M Nishimori, Y Ueda, T Yokosuka

    POPULATION ECOLOGY   48 ( 1 ) 31 - 48  2006年01月  [査読有り]

     概要を見る

    We can precisely predict the future dynamics of populations only if we know the underlying mechanism of population dynamics. Long-term data are important for the elucidation of such mechanisms. In this article we analyze the 50-year dynamics of annual light-trap catches of three insect pest species living in paddy fields in Japan: the rice stem borer, Chilo suppressalis (Walker) (Lepidoptera: Pyralidae); the green rice leafhopper, Nephotettix cincticeps (Uhler) (Hemiptera: Deltocephalidae); and the small brown planthopper, Laodelphax striatellus (Fallen) (Hemiptera: Delphacidae). We separate the long-term dynamics into two components by using locally weighted scatterplot smoothing: (1) the underlying dynamics of populations, and (2) the influence of the past changes in the environment. The former component is analyzed by response surface analysis and vector autoregression to evaluate the nonlinearity of density-dependence and the inter-specific influence of density, respectively. On the basis of these analyses, we perform the state-space model analyses. The state-space model selected by Akaike's information criterion indicates that the observed number of light-trap catches of C. suppressalis and N. cincticeps in summer increases with increasing temperatures in the previous winter. It also indicates that the influence of temperature is not carried over to the next year. We utilize the selected model to predict the impact of global warming on these species, by substituting the temperature predicted by a general circulation model.

    DOI

  • Impact of Global Warming on Rice Production in Japan Based on Five Coupled Atmosphere-Ocean GCMs

    Toshichika Iizumi, Masatake E. Hori, Masayuki Yokozawa, Hiroshi Nakagawa, Yousay Hayashi, Fujio Kimura

    SOLA   2   156 - 159  2006年  [査読有り]

     概要を見る

    This study updates the projection of global warming impact on rice production in Japan using five coupled Atmosphere-Ocean General Circulation Model (AOGCM) products under the SRES A1B scenario. Projection of daily maximum and minimum temperatures and daily total solar radiation for each AOGCM product are fed to a regional-scale rice model by which the rice heading day and yield are simulated. Most climate model results show that while the heading day becomes significantly earlier, the yield mostly remains in the range of inter-annual variability of the present climate. Projected future yield shows a distinct pattern of increase in the northern Japan and decrease in the southwestern Japan, with exception in parts of Kyushu. Projected yield change in the central Japan differs depending on the location of the prefecture. The trend of change in yield is consistent among simulation years in the northern and central Japan whereas it varies year-to-year in the southwestern Japan. The variance in yield over southwestern Japan possibly becomes larger due to heat stress as a result of global warming.

    DOI

  • Spatio-temporal distribution of rice phenology and cropping systems in the Mekong Delta with special reference to the seasonal water flow of the Mekong and Bassac rivers

    T Sakamoto, N Van Nguyen, H Ohno, N Ishitsuka, M Yokozawa

    REMOTE SENSING OF ENVIRONMENT   100 ( 1 ) 1 - 16  2006年01月  [査読有り]

     概要を見る

    Multi-temporal Moderate Resolution Imaging Spectroradiometer (MODIS) data was used to estimate the spatial distribution of heading date and rice-cropping system employed in the Mekong Delta relative to seasonal changes in water resources in 2002 and 2003. We improved a Wavelet-based Filter for determining Crop Phenology (WFCP) and developed a Wavelet-based Filter for evaluating the spatial distribution of Cropping Systems (WFCS) to the interpretation of MODIS time-series data to determine the spatial distribution of rice phenology and various rice-cropping systems from the seasonal Enhanced Vegetation Index (EVI) data. The findings correspond well the physical characteristics of the cropping system in the Mekong Delta, which have changed over time in response to localized and seasonal changes in water resources. One such example is the double-irrigated rice-cropping system commonly employed in the upper Mekong Delta in the dry season to avoid damage due to the subsequent floods. The shortage of suitable irrigation water and intrusion of saline water in the coastal regions during the dry season has constrained the practice dry-season cropping and has meant that the double- and single-rainfed rice-cropping systems are employed in the rainy season. A triple-irrigated rice-cropping system is used in the central part of the Mekong Delta which is located midway between the flood-prone and salinity intrusion areas. Analysis of annual changes in the rice cropping systems between 2002 and 2003 showed that the triple-cropped rice expanded to the flood- and salinity-intrusion areas. This expansion indicates that the implementation of measures to limit the extent of flooding and salinity intrusion by improved farming technologies and improvements in land management. The heading dates in the upper Mekong Delta in 2003 were earlier than in 2002 by approximately 20 to 30 days. The reasons for this would be due to decreased flood runoff in 2002 compared to 2001, and implementation of government policies regarding early sowing of dry-season crops. Subsequent analysis of the MODIS data confirmed that the spatial distribution of rice-cropping systems was closely related to seasonal changes in river runoff regime in the Mekong Delta. (C) 2005 Elsevier Inc. All rights reserved.

    DOI CiNii J-GLOBAL

  • Applying the Rothamsted Carbon Model for long-term experiments on Japanese paddy soils and modifying it by simple mining of the decomposition rate

    Y Shirato, M Yokozawa

    SOIL SCIENCE AND PLANT NUTRITION   51 ( 3 ) 405 - 415  2005年06月  [査読有り]

     概要を見る

    We applied the Rothamsted Carbon Model (RothC), which was developed for simulating the soil organic carbon (SOC) turnover in non-waterlogged soils, for long-term experiments (16-22 years) on Japanese paddy soils and modified it to accurately simulate the changes in the content of SOC with time in paddy soils. The RothC underestimated the SOC content in all the nine plots at five sites: Gley Soils in Akita and Shimane, Gray Lowland Soils in Toyama and Mie, and Yellow Soil in Oita prefecture. This may be mainly due to the slow decomposition rate of organic matter during the rice-growing season, when submerged soils are waterlogged and subjected to anaerobic conditions. On the other hand, the decomposition of organic matter might be inhibited, not only during the submergence period but also throughout the year in paddy soils because of the difference in the composition of microorganisms between upland and paddy soils. Taking these possibilities of differences in the decomposition rate between upland soils and paddy soils into account, we changed the decomposition rates of the RothC during the submergence period (summer) and the period without submergence (winter), separately. We ran the model many times by changing the decomposition rates for summer and winter separately and tried to identify the optimum combinations of the values of the factors required to change the default decomposition rate, so that the modeled SOC content would be consistent with the values observed in nine plots at five experimental sites. To determine the optimum combinations of the values of the factors, we used two statistical indices, the root mean square error (RMSE), which represents the degree of coincidence, and the mean difference (M), which is a measure of model bias. We found that the optimum combination of the values of the factors required to change the decomposition rate was 0.2 in summer and 0.6 in winter. The modified RothC for paddy soils by simple tuning of the decomposition rate using the values of the factors (0.2 and 0.6) resulted in a much better performance than that of the original RothC for simulating the changes in the SOC content with time in Japanese paddy soils under various climatic conditions, types of soil texture, and management systems. This modified model can be used for the estimation of carbon loss from soils as well as for the planning of suitable organic matter management, at least in Japanese paddy soils.

    DOI J-GLOBAL

  • A crop phenology detection method using time-series MODIS data

    T Sakamoto, M Yokozawa, H Toritani, M Shibayama, N Ishitsuka, H Ohno

    REMOTE SENSING OF ENVIRONMENT   96 ( 3-4 ) 366 - 374  2005年06月  [査読有り]

     概要を見る

    Information of crop phenology is essential for evaluating crop productivity and crop management. Therefore we developed a new method for remotely determining phenological stages of paddy rice. The method consists of three procedures: (i) prescription of multi-temporal MODIS/Terra data; (ii) filtering time-series Enhanced Vegetation Index (EVI) data by time-frequency analysis; and (iii) specifying the phenological stages by detecting the maximum point, minimal point and inflection point from the smoothed EVI time profile. Applying this method to MODIS data, we determined the planting date, heading date, harvesting date, and growing period in 2002. And we validated the performance of the method against statistical data in 30 paddy fields. As for the filtering, we adopted wavelet and Fourier transforms. Three types of mother wavelet (Daubechies, Symlet and Coiflet) were used in Wavelet transform. As the results of validation, the wavelet transform performed better than the Fourier transform. Specifically, the case using Coiflet (order=4) gave remarkably good results in determining phenological stages and growing periods. The root mean square errors of the estimated phenological dates against the statistical data were: 12.1 days for planting date, 9.0 days for heading date, 10.6 days for harvesting date, and 11.0 days for growing period. The method using wavelet transform with Coiflet (order=4) allows the determination of regional characteristics of rice phenology. We proposed this new method using the wavelet transform; Wavelet based Filter for determining Crop Phenology (WFCP). (c) 2005 Elsevier Inc. All rights reserved.

    DOI J-GLOBAL

  • Remote sensing of crop production in China by production efficiency models: models comparisons, estimates and uncertainties

    FL Tao, M Yokozawa, Z Zhang, YL Xu, Y Hayashi

    ECOLOGICAL MODELLING   183 ( 4 ) 385 - 396  2005年05月  [査読有り]

     概要を見る

    Regional estimates or prediction of crop production is critical for many applications such as agricultural lands management, food security warning system, food trade policy and carbon cycle research. Remote sensing offers great potential for regional production monitoring and estimates, yet uncertainties associated with are rarely addressed. Moreover, although crops are one of critical biomes in global carbon cycle research, few evidences are available on the performance of global models of terrestrial net primary productivity (NPP) in estimating regional crop NPP. In this study, we use high quality weather and crop data to calibrate model parameter. validate and compare two kinds of remote sensing based production efficiency models, i.e. the Carnegie-Ames-Stan ford-Approach (CASA) and Global Production Efficiency Model Version 2.0 (GLO-PEM2), in estimating maize production across China. Results show that both models intend to underestimate maize yields, although they also overestimate maize yields much at some regions. There are no significant differences between the results from CASA and GLO-PEM2 models in terms of both estimated production and spatial pattern. CASA model simulates better in the areas with dense crop and weather data for calibration. Otherwise GLO-PEM2 model does better. Whether the water soil-moisture down-regulator is used or not should depend on the percent of irrigation lands at the regions. The improved and validated models can be used for many applications. Further improvement can be expected by increasing remote sensing image resolution and the number of surface data stations. (c) 2004 Elsevier B.V. All rights reserved.

    DOI J-GLOBAL

  • Testing the Rothamsted Carbon Model against data from long-term experiments on upland soils in Thailand

    Y Shirato, K Paisancharoen, P Sangtong, C Nakviro, M Yokozawa, N Matsumoto

    EUROPEAN JOURNAL OF SOIL SCIENCE   56 ( 2 ) 179 - 188  2005年04月  [査読有り]

     概要を見る

    We tested the Rothamsted Carbon Model (RothC) against three long-term (27-28 years) experimental sites on Thai upland soils in order to see how this widely used 'temperate' soil carbon turnover model performed in a typical farming region in the tropics. We were able to verify - over a much longer period than had been examined in previous studies - that RothC performs well in a tropical region in plots used for continuous cropping experiments of maize and cassava without organic matter application. However, the model overestimated soil organic carbon (SOC) in some plots to which large amounts of organic matter (rice straw or cassava stalks) were applied. This overestimate could not be attributed to errors in estimating either the amount of C input to the soil or the ratio of decomposable plant materials to resistant plant materials entering the soil. Among many factors affecting SOC dynamics (e.g. weather conditions, soil characteristics, etc.), which are different in tropical regions from temperate regions, we conclude that the activity of soil fauna might be a major factor which makes the performance of RothC worse where much organic matter was applied. We suggest that care should be taken when applying RothC to tropical soils with large amounts of added organic matter.

    DOI

  • Future agricultural water resources and agricultural production in China - Interaction between climate change and soil degradation

    Journal of Agricultural Meteorology   60: 1169-1174  2005年

  • Risk analyses of rice yield to seasonal climate variability in China

    Journal of Agricultural Meteorology   60: 885-887  2005年

  • A perspective on water resources in China: Interactions between climate change and soil degradation

    FL Tao, M Yokozawa, Y Hayashi, ED Lin

    CLIMATIC CHANGE   68 ( 1-2 ) 169 - 197  2005年01月  [査読有り]

     概要を見る

    Water is one of the most critical resources in China. Climate change and soil degradation will be two major, interrelated environmental challenges faced by managers of water resources in coming decades. In this study, we used a water-balance model and updated databases to assess the interacting impacts of climate change and soil degradation on China's future water resources. We plotted the spatial pattern of changes in actual and potential evapotranspiration, soil moisture deficits, and surface runoff across China in the 2020s using a resolution of 0.5degrees latitude and longitude under scenarios based on climate change, soil degradation, and a combination of the two. The results showed that climate change would affect the magnitude and spatial pattern of water resources on a national scale. Some regions in central, southwestern, and northeastern China would become more vulnerable to disastrous drought and floods as a result of soil degradation. Under the combined impacts of climate change and soil degradation, soil moisture deficits would increase most in central, western, and southwestern China; surface runoff would increase most in southeastern China. More detailed process-based models are needed to capture feedback mechanisms more effectively.

    DOI J-GLOBAL

  • Variability in climatology and agricultural production in China in association with the East Asian summer monsoon and El Nino Southern Oscillation

    FL Tao, M Yokozawa, Z Zhang, Y Hayashi, H Grassl, CB Fu

    CLIMATE RESEARCH   28 ( 1 ) 23 - 30  2004年12月  [査読有り]

     概要を見る

    The East Asian monsoon (EAM) and the El Nino Southern Oscillation (ENSO) determine climate variability over much of East Asia, affecting vulnerable grain markets and food security in China. In this study, we investigated the variability of climate and of agricultural production in China in association with the East Asian summer monsoon (EASM) and ENSO. Data from China showed that a strong EASM decreased fall temperature in Gansu and Sichuan Provinces in western China, as well as winter temperature in Heilongjiang Province in NE China and in Shandong and Anhui Provinces in eastern China. Summer rainfall in Hunan Province in southern China increased in weak EASM years. Summer temperature increased in Heilongjiang in NE China and Gansu Province in NW China during the La Nina phase. Summer rainfall decreased in Gansu Province in NW China during the El Nino phase. Among staple crops in China (rice, wheat, maize), maize production was very vulnerable to a strong EASM and El Nino phase. In Henan Province in central China, seasonal climate variability associated with EASM and ENSO resulted in about 14.4 and 15.6 %, respectively, of maize yield variability. Maize Yield at the national scale decreased significantly by 5.2 % during the El Nino phase. Cropland area affected and damaged by floods in Hunan Province in southern China increased significantly by 11.3 and 8.5 %, respectively, in weak monsoon years. During the La Nina phase, total crop planting area increased significantly in Shandong, Henan and Anhui Provinces in central China, and in Heilongjiang Province in NE China; however, it decreased significantly in Sichuan Province in SW China. The large variability in seasonal climate and agricultural production in association with EASM and ENSO warrant applying EASM and ENSO information to agricultural and food market management.

    DOI

  • プロセスアプローチによる農地生態系の炭素収支比較

    関川清広, 木部剛, 横沢正幸, 小泉博, 鞠子茂

    第51回日本生態学会大会講演要旨集     124  2004年08月

  • Developing a Multilayered Integrated Numerical Model of Surface Physics - Growing Plants Interaction (MINoSGI)

    T Watanabe, M Yokozawa, S Emori, K Takata, A Sumida, T Hara

    GLOBAL CHANGE BIOLOGY   10 ( 6 ) 963 - 982  2004年06月  [査読有り]

     概要を見る

    This paper describes a Multilayered Integrated Numerical Model of Surface Physics - Growing Plants Interaction (MINoSGI), which represents interactions between the dynamics of forest ecosystems and microclimate. Aiming at a large-scale study in the future, we describe forest dynamics by using area-averaged prognostic equations for thedistributions of plant density and plant weight with respect to plant height classes, instead of individual-based treatments for small-scale forest patches. Growth and mortality of plants are modelled based on the carbon balance of each plant height class. The area-averaged microclimate (e.g., light, wind speed, temperature, humidity, CO2 concentration) within the forest canopy is simulated by a one-dimensional multilayer canopy model, which includes most of the physical and physiological processes that control the forest microclimate. Owing to its multilayered framework, a direct specification is possible for the difference in the growing environment among plants of different size and species. Given hourly meteorological conditions, the model outputs energy, water, CO2 and momentum fluxes to and from a forest, of which the structure changes through competition among plants. The model's performance was tested by comparing its outputs with observed data on the development of plant size distribution taken over a 5-year period in an evergreen coniferous (Cryptomeria japonica) forest. The model produced realistic estimates of the total biomass increments during the period. The ratio of net primary production to gross primary production (=0.45) was consistent with previous estimates for temperate forests. The bimodal seasonal pattern in net ecosystem production was similar to the seasonal trend in the CO2 flux measured over a forest of the same species. Although some limitations due to the one-dimensional representation of microclimate were noticeable, the model adequately simulated distributions of annual growth rate, plant weight and diameter across plant height classes. Since the basic equations can be extended to include the effect of spatial variability with marginal increase of computational costs, the present model framework is feasible for large-scale studies.

    DOI J-GLOBAL

  • Impact of global warming on environments for apple and satsuma mandarin production estimated from changes of the annual mean temperature

    T Sugiura, M Yokozawa

    JOURNAL OF THE JAPANESE SOCIETY FOR HORTICULTURAL SCIENCE   73 ( 1 ) 72 - 78  2004年01月  [査読有り]

     概要を見る

    This study was undertaken to assess the impact of global warming on the production in Japan of apple (Malus domestica Borkh.) and satsuma mandarin (Citrus unshiu Marc.). The annual mean temperature was used to simulate possible changes in favorable regions for the cultivation of apple and satsuma mandarin. The temperature ranges assumed to be appropriate for fruit production were 6-14 degreesC and 7-13 degreesC for apples and 15-18 degreesC for satsuma mandarins, respectively. The database of "Climate Change Mesh Data (Japan)" was used to calculate annual mean temperatures under the climate change scenario, derived from four Atmosphere-Ocean General Circulation Models (AOGCM) at all 10 X 10 km mesh. It was predicted that the favorable regions to cultivate apples and satsuma mandarins will gradually move northward. In 2060's the plains of central Tohoku will be unfavorable for apple cultivation, while most of Hokkaido will be suitable. The plains of northern Tohoku are predicted to attain the annual mean temperatures higher than those of the current main producing districts. By 2060's, the favorable areas for satsuma mandarin production will possibly move from the southern coastal sites to inland areas of western and southern Japan, the plains of Kanto and the littoral zones of the Japan Sea in the central and western Japan and in southern Tohoku. Therefore, global warming will greatly affect the cultivation environment of apples and satsuma mandarins in Japan by the middle of the 21st century.

    DOI

  • Changes in agricultural water demands and soil moisture in China over the last half-century and their effects on agricultural production

    F Tao, M Yokozawa, Y Hayashi, E Lin

    AGRICULTURAL AND FOREST METEOROLOGY   118 ( 3-4 ) 251 - 261  2003年09月  [査読有り]

     概要を見る

    It has become obvious in recent years that water is the most critical resource for Chinese agricultural ecosystems. Changes in agricultural water demands and soil moisture have significant implications for China's water supply, the potential for drought and flood, and agricultural production. In the studies, we explored the changing trends in agricultural water demands, the changing trends and variability in soil moisture associated with both drought and increased surface runoff in Chinese croplands during the last half-century, and their impacts on agricultural production. We plotted temporal and spatial changes in agricultural water demands, soil moisture, soil-moisture variability, soil-moisture deficit, yield index, and surface runoff on a grid of 0.5degrees resolution. We found a trend toward agricultural water demands increasing, soil drying and significant changes in soil-moisture variability on the North China Plain and the Northeast China Plain. There was a significant decrease in agricultural water demands and a significant increase in soil-moisture levels in Southwest China, and a generally insignificant increase or decrease trend in agricultural water demands and soil-moisture levels in Southeast China. These changes in agricultural water demands and soil-moisture levels had corresponding impacts on soil-moisture deficit, and consequently on agricultural production. Increased surface runoff was found in the mountainous areas of the southwest and northeast, and in some areas along the South Coast. (C) 2003 Elsevier Science B.V. All rights reserved.

    DOI J-GLOBAL

  • Changes in the Southwest Monsoon mean daily rainfall intensity in Sri Lanka: relationship to the El Nino-Southern Oscillation

    E Ranatunge, BA Malmgren, Y Hayashi, T Mikami, W Morishima, M Yokozawa, M Nishimori

    PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY   197 ( 1-2 ) 1 - 14  2003年08月  [査読有り]

     概要を見る

    Daily rainfall data for 187 stations in Sri Lanka spanning the period 1960-1996 were analyzed to investigate the spatial and temporal characteristics of the mean rainfall intensity (MRI) through this time interval with special focus on the Southwest Monsoon (May-September). Particular emphasis was laid on temporal changes in the MRI series. The mean and standard deviation (SD) of the MRI data showed considerable spatial variation. Regression analysis expressing precipitation as a function of time at the various stations revealed distinct spatial trends; the results point to hi-h MRI in lowland areas and low MRI in mountain areas. Principal Components Analysis of the temporal C relationships among a reduced set of stations located in an equal-sized grid showed that the three dominant principal components (PCs) are characterized by the maximum and minimum mean and SD of the MRI series together with the mean number of rainy days. The first, second and third PC modes show significant patterns of the MRI data series over the northern half. southern half and southwestern coastal belt of Sri Lanka, respectively. The time series pattern of the dominant PC modes revealed distinct changes in MRI over time. A noticeable higher value in MRI was found from 1977 to 1996, this tendency is most pronounced for the first PC mode. The time series of the Southern Oscillation Index was found to be closely related to changes in the MRI patterns associated with the first PC mode. In addition, El Nino years coincide with low values of the first PC mode. Some La Nina years show a positive response for the first and third PC modes, while there is no clear response for the MRI pattern identified by the second PC. (C) 2003 Elsevier Science B.V. All rights reserved.

    DOI

  • Future climate change, the agricultural water cycle, and agricultural production in China (vol 95, pg 203, 2003)

    FL Tao, M Yokozawa, Y Hayashi, ED Lin

    AGRICULTURE ECOSYSTEMS & ENVIRONMENT   97 ( 1-3 ) 361 - 361  2003年07月  [査読有り]

    DOI

  • Terrestrial water cycle and the impact of climate change

    FL Tao, M Yokozawa, Y Hayashi, E Lin

    AMBIO   32 ( 4 ) 295 - 301  2003年06月  [査読有り]

     概要を見る

    The terrestrial water cycle and the impact of climate change are critical for agricultural and natural ecosystems. In this paper, we assess both by running a macro-scale water balance model under a baseline condition and 2 General Circulation Model (GCM)-based climate change scenarios. The results show that in 2021-2030, water demand will increase worldwide due to climate change. Water shortage is expected to worsen in western Asia, the Arabian Peninsula, northern and southern Africa, northeastern Australia, southwestern North America, and central South America. A significant increase in surface runoff is expected in southern Asia and a significant decrease is expected in northern South America. These changes will have implications for regional environment and socioeconomics.

    DOI J-GLOBAL

  • Future climate change, the agricultural water cycle, and. agricultural production in China

    F Tao, M Yokozawa, Y Hayashi, E Lin

    AGRICULTURE ECOSYSTEMS & ENVIRONMENT   95 ( 1 ) 203 - 215  2003年04月  [査読有り]

     概要を見る

    Climate change would have a major impact on the hydrological cycle and consequently on available water resources, the potential for flood and drought, and agricultural productivity. In this study, the impacts of climate change on the agricultural water cycle and their implications for agricultural production in the 2020s were assessed by water-balance calculations for Chinese croplands. Temporal and spatial changes in potential evapotranspiration, actual evapotranspiration, soil-moisture, soil-moisture deficit, yield index, and cropland surface runoff under the baseline climate and a HADCM2 general circulation model (GCM) climate-change scenario were mapped on a grid of 0.5degrees latitude/longitude resolution. According to the analysis, agricultural water demand in south China is projected to decrease generally, and the cropland soil-moisture deficit would decrease due to climate change. However, in north China, agricultural water demand is expected to increase, and the soil-moisture deficit would increase generally. The changes in the water resources would have consequent impacts on the yield index. Cropland surface runoff during the growing period is expected to increase on some sloping croplands in the southwest mountain areas and in some areas along the south coast. These changes would have important implications for agricultural production. Particularly the rain-fed crops in the north China plain and northeast China would face water-related challenges in coming decades due to the expected increases in water demands and soil-moisture deficit,and decreases in precipitation. (C) 2002 Elsevier Science B.V. All rights reserved.

    DOI

  • The mode of competition and spatial pattern formation in plant communities

    M Yokozawa

    MORPHOGENESIS AND PATTERN FORMATION IN BIOLOGICAL SYSTEMS: EXPERIMENTS AND MODELS     237 - 246  2003年  [査読有り]

  • Mesh Climate Change Data for Evaluating Climate Change Impacts in Japan under Gradually Increasing Atmospheric CO2 Concentration

    Masayuki Yokozawa, Shinkichi Goto, Yousay Hayashi, Hiroshi Seino

    Journal of Agricultural Meteorology   59 ( 2 ) 117 - 130  2003年

     概要を見る

    General circulation models (GCMs) that can simulate global climate are used to predict climate changes caused by an increase in atmospheric cO2 concentration. However, the spatial resolutions of currently running models are rough with a resolution of about 3° to 6° in latitude/longitude. Thus, reducing the relatively large-scale climatic states that the GCM provides to smaller-scale ones is required to evaluate impacts of climate changes on agriculture and natural ecosystems at local and regional scales. We constructed a dataset, namely the mesh climate change data of Japan, using the inverse distance weighted interpolation against coupled atmosphere-ocean GCMs' (A-O GCMs) experiment results under gradually increasing atmospheric cO2 concentration. The A-O GCMs used in this article are ECHAM4/OPYC3 (Germany), CGCM1 (Canada), CSIRO-Mk2 (Australia), and CCSR/NIES (Japan). The dataset gives the average climate change scenarios in Japan for every 10-year period over the next 100 years with a resolution of 7.5' in longitude and 5' in latitude (approximately 10 by 10 km). This article describes the construction method and contents of the dataset. In order to demonstrate the characteristics of the dataset, we examined the transient changes in spatial distribution of accumulated surface air temperature, accumulated precipitation, and mean short wave radiation during the months of May through September, corresponding with the major crop cultivation period in Japan. © 2003, The Society of Agricultural Meteorology of Japan. All rights reserved.

    DOI

  • Multivariate Statistical Analysis of The Seasonal Rainfall Regimes of The Guinea-Fouta Djallon Mountains of West Africa

    Serrie Kamara, TilaCk Kuruppuarachchi, Edmond Ranga Ranatunge, Yousay Hayashi, Masayuki Yokozawa, Motoki Nishimori, Takehiko Mikami

    Journal of Agricultural Meteorology   58 ( 4 ) 171 - 183  2002年09月  [査読有り]

     概要を見る

    A study of the seasonal structure of rainfall organization in a humid tropical mountain region of West Africa using multivariate classification techniques revealed considerable variations in rainfall regimes from ultra-humid to sub-humid conditions. Principal Component Analysis produced a three-component model which was used to characterize and explain the seasonal rainfall variations within the region. These are the Dry Season component which accounts for most of the variance in the rainfall data and represents the December-April period
    the Wet Season component (June-September) and the Wet/Dry and Dry/Wet transitions component in October-November and May, respectively. Using the three components and a hierarchical clustering procedure, seven clusters representing the rainfall regimes were identified and characterized. A better understanding of the regional rainfall climate is important to West African countries whose economies depend largely on agriculture and related activities governed by the reliability of rainfall. © 2002, The Society of Agricultural Meteorology of Japan. All rights reserved.

    DOI

  • Diurnal and seasonal changes in soil respiration in a Japanese grapevine orchard and their dependence on temperature and rainfall

      18 ( 1 ) 44-54  2002年04月  [査読有り]

  • Prediction of a geographical shift in the prevalence of rice stripe virus disease transmitted by the small brown planthopper, Laodelphax striatellus (Fallen) (Hemiptera : Delphacidae), under global warming

    K Yamamura, M Yokozawa

    APPLIED ENTOMOLOGY AND ZOOLOGY   37 ( 1 ) 181 - 190  2002年02月  [査読有り]

     概要を見る

    Global warming may affect crop damage caused by insect pest, by changing the degree of synchronization between pest occurrence and the susceptible stage of crops. The epidemiological system of rice stripe virus disease (RSV disease) transmitted by the small brown planthopper, Laodelphax striatellus (Fallen), is greatly influenced by synchronization, because the susceptible stage for virus infection is within several weeks after transplanting. We calculated how the area potentially vulnerable to RSV disease will change under future global warming by using the results of the Global Climate Model (GCM) experiments reported by the Intergovernmental Panel on Climate Change. For simplicity, assuming that rice seedlings are transplanted from May to June, we made a map, in which the number of generations of the small brown planthopper on June 1 was plotted by calculating the effective cumulative temperature. The influence of solar radiation was also considered in this calculation. We judged that the area located near the boundary of generations is potentially vulnerable to disease prevalence, because planthoppers are in the adult stage there. Generation maps indicated that the Tohoku and Hokuriku districts, which are major districts of rice production in Japan, might be potentially vulnerable to disease infection under future global warming.

  • Diurnal changes of carbon dioxide flux from bare soil in agricultural field in Japan

    T Nakadai, M Yokozawa, H Ikeda, H Koizumi

    APPLIED SOIL ECOLOGY   19 ( 2 ) 161 - 171  2002年02月  [査読有り]

     概要を見る

    We measured diurnal changes of CO2 flux from bare soil in agricultural field in central Japan. Measurements of soil CO2 flux were made by the open-flow IRGA method. Temperature and ambient CO2 concentration, which are highly variable in time, were also monitored during the measurements. The Soil CO2 flux showed significant diurnal changes, and these patterns were highly correlated with the soil surface temperatures. The measured values ranged from 2.52 x 10(-2) to 8.54 x 10(-2) Mg CO2 m(-2) s(-1) in August and from -4.95 x 10(-3) to 1.13 x 10(-2) mg CO2 m(-2) s(-1) in February. Moreover, a negative linear relationship between soil CO2 flux and ambient CO2 concentration was found in diurnal fluctuations. To explore the mechanism of these daily cycles, we estimated Soil CO2 flux with a coupled model of soil microbial activity and gas diffusion. The parameter functions used in our calculation were obtained based on the measured values during the same time of soil respiration measurements. The soil CO2 production rates were obtained by laboratory experiments using the undisturbed soil core samples, which were taken from the field measuring soil respiration. The calculated soil CO2 flux ranged from 4.41 x 10(-2) to 7.78 x 10(-2) Mg CO2 m(-2) s(-1) in August and 1.14 x 10(-3) to 5.03 x 10(-3) mg CO2 m(-2) s(-1) in February. These patterns of diurnal variability were similar for the measured ones, and the daily amounts estimated by integrating the model outputs were almost equal to those from the measured values. However, the amplitude of the measured respiration rates was larger than that of the estimated ones. The differences between measured and estimated values were related with thermal gradient around soil surface. The calculation suggested that the soil horizon above 10 cm depth would be a major CO2 source of soil respiration at about 70% in August and 40% in February. The depth of soil horizon in which soil microbial activity was significantly higher was not settled and would have a seasonal variation. (C) 2002 Elsevier Science B.V. All rights reserved.

    DOI J-GLOBAL

  • Evaluation of changes in climatic indices using combined analysis of remote sensing and GIS

    K Okamoto, M Yokozawa, H Kawashima

    2001 INTERNATIONAL CONFERENCES ON INFO-TECH AND INFO-NET PROCEEDINGS, CONFERENCE A-G     A133 - A138  2001年  [査読有り]

     概要を見る

    We predicted the future condition of places in which major cereals are cultivated using satellite remote sensing data in combination with spatial analysis as provided by Geographical Information System (GIS). The Open Policy and Economic Reform have significantly accelerated economic growth of mainly in coastal regions of China. Economic growth in China will change the diet and will increase cereal demand. As a case study, we predicted the trend of major cereal production in China in the 21st century. We also predicted the agricultural productivity of existing fields cropped with major cereals based on climatic indices, i.e., the net primary productivity (NPP) and the balance between precipitation and potential evapotranspiration (P-PET), from the present to 2090s. The agricultural productivity in Central, Northern and Northeastern China will increase as a result of an increase in the NPP, while that in Southern China will not. The agricultural productivity in Western China will decline as a result of a decrease in P-PET. Desertification will be a problem in these regions. The result of this study suggests that combined analysis of satellite remote sensing and GIS data is effective for use in a comparative study of the present and the future conditions.

  • 温暖化が日本の水稲栽培の潜在的特性に及ぼすインパクト (特集:環境変動とアジアの稲作)

    林 陽生, 石郷岡 康史, 横沢 正幸

    地球環境   6 ( 2 ) 141 - 148  2001年

    CiNii

  • Interclonal differences, plasticity and trade-offs of life history traits of Cyperus esculentus in relation to water availability

    Bo Li, Tomoko Shibuya, Yasuhiro Yogo, Toshihiko Hara, Masayuki Yokozawa

    Plant Species Biology   16 ( 3 ) 193 - 207  2001年  [査読有り]

     概要を見る

    Cyperus esculentus is an exotic clonal (or pseudoannual) weed in Japan, and its range is steadily increasing. To investigate its interclonal variation and phenotypic plasticity in response to water availability, five clones of C. esculentus, collected from different sites in Japan, were grown singly in pots placed outdoors under dry and wet conditions. All the traits examined showed considerable variation among the five clones. However, two clones from Tochigi were similar to each other
    thus, they might have originated from the same founder population. The clone from Ibaraki was quite different from the others. Therefore, it is suggested that the Japanese populations of C. esculentus might have resulted from multiple introductions of genotypes from geographically separated and, hence, genetically differentiated, source populations. All the clones also showed considerable plasticity in response to water availability. Clones with a larger ramet number had a greater plasticity, whereas tuber size was invariant across water treatments. Highly plastic traits had generally low interclonal variation in plasticity. All the clones had high productivity and produced more ramets and tubers under wet conditions than under dry conditions. Moreover, water availability could partially regulate the mode of its reproduction
    wet conditions favored tuber production (vegetative propagation) while dry conditions favored sexual reproduction. A number of trade-offs occurred between the traits of clonal growth, storage and sexual reproduction, indicating that allocation among the competing functions/organs is mutually exclusive in plants. The results obtained here suggest that C. esculentus is more likely to invade wet habitats than dry habitats.

    DOI CiNii

  • A multi-layered integrated numerical model of surface physics-growing plants interaction, MINoSGI

    Hara, T, Watanabe, T, Yokozawa, M, Emori, S, Takata, K, Sumida, A

    Present and future of modeling global environment change: toward integrated modeling     173 - 185  2001年

  • Pluses and minuses of climate change on major cereal cultivation in Asia

    K Okamoto, M Yokozawa, H Kawashima

    ECOSYSTEMS AND SUSTAINABLE DEVELOPMENT III   10   79 - 88  2001年  [査読有り]

     概要を見る

    This paper describes the impacts of climate change on major cereal crops, i.e., rice, wheat and maize, in Asia using results from simulation studies using the CCSR (Center for Climate System Research, the University of Tokyo) GCM (Global Climate Model). Climate change could cause the air temperature and precipitation to become unsuitable for major cereal cultivation in Asia. To predict the impacts of climate change on sustainable cropping and agricultural development, we evaluated changes in climatic conditions in Asia in major cereal cropping seasons. We used the monthly average temperature and precipitation data from the 1961-90 mean climatology and CCSR GCM. We analyzed changes in the mean temperature and precipitation of major cereal-producing regions at different cropping seasons from the present through the 2090s. Climate change will generally increase both the air temperature and precipitation in Asia. The impacts of climate change have two sides: plus and minus. The increase in the air temperature and precipitation will be disadvantageous to wheat cropping in Asia. In contrast, some regions in subtropical Asia will have excess water resources during the rainy season. Precautionary measures against flooding will be needed in these areas.

  • Model analysis of the influence of gas diffusivity in soil on CO and H-2 uptake

    S Yonemura, M Yokozawa, S Kawashima, H Tsuruta

    TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY   52 ( 3 ) 919 - 933  2000年07月  [査読有り]

     概要を見る

    CO and H-2 uptake by soil was studied as a diffusion process. A diffusion model was used to determine how the surface fluxes (net deposition velocities) were controlled by in-situ microbial uptake rates and soil gas diffusivity calculated from the 3-phase system (solid, liquid, gas) in the soil. Analytical solutions of the diffusion model assuming vertical uniformity of soil properties showed that physical properties such as air-filled porosity and soil gas diffusivity were more important in the uptake process than in the emission process. To incorporate the distribution of in-situ microbial uptake, we used a 2-layer model incorporating "a microbiologically inactive layer and an active layer" as suggested from experimental results. By numerical simulation using the 7-layer node, we estimated the effect of several factors on deposition velocities. The variations in soil gas diffusivity due to physical properties, i.e., soil moisture and air-filled porosity, as well as to the depth of the inactive layer and in-situ microbial uptake, were found to be important in controlling deposition velocities. Tills result shows that the diffusion process in soil is critically important for CO and H-2 uptake by soil, at least in soils with higher in-situ uptake rates and/or with large variation in soil moisture. Similar uptake rates and the difference in deposition velocity between CO and H-2 may be attributable to differences in CO and H-2 molecular diffusivity. The inactive layer is resistant to diffusion and creates uptake limits in CO and H-2, by soil. The coupling of high temperature and a thick inactive layer, common in arid soils, markedly lowers net CO deposition velocity. The temperature for maximum uptake of CO changes with depth of the inactive layer.

    DOI

  • 通気法による土壌表面および雪面CO_2フラックスの測定

    鞠子 茂, 西村 格, 莫 文紅, 松井 嘉祐, 横沢 正幸, 関川 清広, 小泉 博

    環境科学会誌 = Environmental science   13 ( 1 ) 69 - 74  2000年  [査読有り]

    DOI CiNii

  • Trace gas absorption by soil - Simulation study on diffusion processes of trace gases, CO, H-2, and CH4 in soil

    S Yonemura, M Yokozawa, S Kawashima, H Tsuruta

    COMPUTATIONAL METHODS FOR FLOW AND TRANSPORT IN POROUS MEDIA   17   371 - 381  2000年  [査読有り]

     概要を見る

    A two-layered diffusion model was applied to the uptake process of trace gases as CO, H-2, and CH4 which are utilized by soil microorganisms or enzymes assuming that its uptake obey first-order kinetics about its concentration. Analytical solutions for mono-layered model,exhibit that the physical property as gas diffusivity in soil is more important for uptake process than emission process. The numerical simulation shows that the deposition of CO, H-2, and CH4 are limited by the combination of transport process and the localization of the soil uptake zone, within 0.06cm s(-1) for CO and 0.1cm s(-1) for H-2, respectively, which are in reasonable consistence with field measurements.

  • Concentrations of carbon monoxide and methane at two heights above a grass field and their deposition onto the field

    S Yonemura, A Miyata, M Yokozawa

    ATMOSPHERIC ENVIRONMENT   34 ( 29-30 ) 5007 - 5014  2000年  [査読有り]

     概要を見る

    To investigate whether wind is a significant driving force in the diffusion of CO and CH4 from the atmosphere into soil, we measured the concentrations of these two gases at two heights above a temperate grass field in Japan and estimated their deposition velocities using micrometeorological techniques. The concentrations were inversely correlated with wind speed, indicating that the local concentrations were influenced by ground sources. The CO and CH4 concentrations at 0.33 m were usually lower than those at 1.3 m. Although nocturnal data are suspected to be non-stationary, by selecting several periods when the changes of the concentrations were small but larger than analytical precision, we obtained a CO velocity of 2.9 and 3.9 x 10(-2) cm s(-1), agreeing with a CO deposition velocity, 3.4 x 10(-2) cm s(-1), obtained by applying a method using CO2 as a tracer. The CH4 influx obtained by the method using CO2 as a tracer was 13 ng m(-2) s(-1). The ranges of the CO deposition velocity and CH4 influx were similar to those obtained in previous studies in grassfields and in a nearby arable field using a closed-chamber technique. This shows that light winds do not greatly accelerate CO and CHS uptake by soil. (C) 2000 Elsevier Science Ltd. All rights reserved.

    DOI

  • Model Analysis to the Influences of Soil Diffusivity on CO and H〈sub〉2〈/sub〉 Uptake by Soil

    Tellus   B52: 919-933  2000年

  • Size hierarchy and stability in competitive plant populations

    M Yokozawa

    BULLETIN OF MATHEMATICAL BIOLOGY   61 ( 5 ) 949 - 961  1999年09月  [査読有り]

     概要を見る

    A neighbourhood-based competition model for plant individuals is studied to evaluate how a hierarchical structure related to size may emerge in plant communities. It is shown by numerical simulations and linear stability analysis that many stable states exist in the hierarchical structure when both the total number of individuals and the degree of asymmetry of competition are high. When the hierarchical structures are self-organized by the dynamic instability of the homogeneous state due to non-linearity of competition, it is proved that these states are always locally stable. The relevance of the results to size structures in real plant communities (boreal forests vs tropical and temperate forests) is discussed. This is suggested to be the mechanism responsible for the coexistence of species in plant communities. (C) 1999 Society for Mathematical Biology.

    DOI J-GLOBAL

  • Global versus local coupling models and theoretical stability analysis of size-structure dynamics in plant populations

    M Yokozawa, T Hara

    ECOLOGICAL MODELLING   118 ( 1 ) 61 - 72  1999年06月  [査読有り]

     概要を見る

    A local coupling model for growth dynamics of plant populations is proposed, in which each individual occupies a square lattice point and follows logistic growth with potential maximum relative growth rate c(0) being reduced by the competitive effects from eight interacting neighbours. The competitive effects are given by the competition function W, which describes the degree of competitive asymmetry between individuals, beta and the distance-dependent intensity of competition between individual i and j, alpha(ij), as a coupling constant. Then a global coupling model corresponding to the local coupling model is proposed, in which every individual interacts with all the other individuals in the field. In the global coupling model, the coupling constant alpha as the same parameter for all the individuals was employed instead of alpha(ij)'s in the local coupling model. alpha was given as an average of alpha(ij)'s of eight interacting neighbours in the local coupling model. Both the coupling constants were normalized by the number of interacting individuals to make simulation results comparable between the models. Numerical simulations revealed that the local coupling model can be simulated by the corresponding global coupling model fairly well if population growth dynamics are continuous without deaths or new recruits. In both the models, multi-layered structure of size distribution was more likely to emerge under asymmetric and/or intense competition than under symmetric and/or weak competition. This conforms to the widely known phenomenon of size-structure dynamics in plant populations. Since theoretical analysis is impossible for the local coupling model, linear stability analysis of size-structure dynamics was made for the global coupling model. It was theoretically shown that if alpha &lt; c(0)/(1 + beta), mono-layered size structure is stable; if alpha &gt; c(0)/(1 + beta), multi-layered size structure is stable. As alpha and/or beta increases (decreases), multi-layered (mono-layered) size structure gets stable. As c(0) (i.e. seedlings' relative growth rate) increases, the domain of stable mono-layered (multi-layered) size structure becomes larger (smaller). Therefore, the above simulation results were supported by linear stability analysis of the dynamical systems. Ecological implications of these theoretical results are discussed concerning the relationship between the stability of stand size structure and the degree of competitive asymmetry (multi-layered versus mono-layered). (C) 1999 Elsevier Science B.V. All rights reserved.

    DOI

  • Effects of competition mode on the spatial pattern dynamics of wave regeneration in subalpine tree stands

    M Yokozawa, Y Kubota, T Hara

    ECOLOGICAL MODELLING   118 ( 1 ) 73 - 86  1999年06月  [査読有り]

     概要を見る

    The effects of competition between individuals (the degree of competitive asymmetry and the intensity of competition; an endogenous biological factor) and the intensity of disturbance (unidirectional prevailing winds in the present paper; an exogenous environmental factor) on the spatial pattern dynamics of wave regeneration in subalpine regions were studied by using a coupled map lattice model (a lattice model with discrete time, discrete space and continuous state) of plant populations. It was shown by simulation that the wave-shaped spatial pattern of regeneration is more likely to emerge under symmetric competition than under asymmetric competition and that the likelihood of emergence increases with the intensity of disturbance, It was already shown both theoretically and by field data analysis that Abies undergoes symmetric competition and that Betula undergoes asymmetric competition. Therefore, a theoretical explanation can be given as to why the wave-shaped spatial pattern occurs in Abies forests but not in Betula forests although both the species occur in subalpine regions. Our theoretical study showed that the interaction between endogenous and exogenous factors determine the spatial pattern dynamics in relation to the regeneration of plant communities. (C) 1999 Elsevier Science B.V. All rights reserved.

    DOI

  • MRI‐CGCM気候変化シナリオから予測した日本における21世紀の水稲の潜在収量

    鳥谷均, 米村正一郎, 横沢正幸

    システム農学   15 ( 1 ) 8-10,10(1)-10(2),11-16 - 16  1999年04月  [査読有り]

    CiNii J-GLOBAL

  • 半導体アンモニアセンサーの較正と野外での検証

    米村正一郎, 川島茂人, 大嶋秀雄, 横沢正幸

    大気環境学会誌 34, 321-330, 1999   34 ( 4 ) 321 - 330  1999年  [査読有り]

    DOI J-GLOBAL

  • Hierarchical structures in competitive plant communities

    M Yokozawa

    ECOSYSTEMS AND SUSTAINABLE DEVELOPMENT II   2   25 - 34  1999年  [査読有り]

     概要を見る

    To explore how a stable size hierarchical structure may emerge in plant communities, a simple competition model for plant individuals with two types of competition mode, asymmetric and symmetric, is studied numerically and theoretically. The model incorporates size-ratio dependent interactions between individuals, which reflects the sensitivity of resource gain to differences in individual biomass at the seedling stage. From numerical simulations, the stability of the multi-layered size structure is determined by the relationships between the number of population, the degree of competitive asymmetry and the potential maximum relative growth rate (i.e. seedling's relative growth rate) as follows: (1) As the number of population and/or the degree of competitive asymmetry increases [decreases], multi-layered [mono-layered] size structure becomes stable; (2) As the potential maximum relative growth rate increases, the domain of stable mono-layered [multilayered] size structure becomes larger [smaller]. It is further shown that, when the potential maximum relative growth rate is fixed, (3) multi-layered size structure is more likely to be stable under asymmetric competition than under symmetric competition; (4) mono-layered size structure is more likely to be stable under symmetric competition than under asymmetric competition. When the hierarchical structures are self-organized by the dynamic instability of the homogeneous state due to nonlinearity of competition, it is proved by theoretical analysis that these states are always locally stable. This is also suggestive of the mechanisms of species coexistence in plant communities.

  • Effects of competition mode on spatial pattern dynamics in plant communities

    M Yokozawa, Y Kubota, T Hara

    ECOLOGICAL MODELLING   106 ( 1 ) 1 - 16  1998年02月  [査読有り]

     概要を見る

    The effects of the mode of competition between individual plants (symmetric versus asymmetric) and the gap formation caused by natural disturbances on the dynamics of spatial configuration pattern of individual size were investigated theoretically based on an individual growth model incorporating competitive effects of neighbouring individuals. The degree of spatial heterogeneity in local size distribution was represented by the CV (coefficient of variation) of averages of local size distributions (CVav), the average of CVs of local size distributions (AV(cv)) and the CV of CVs of local size distributions (CVcv). Without gap formation, CVav, AV(cv), and CVcv were larger under asymmetric competition than under symmetric one, suggesting a fine-scale mosaic spatial pattern in asymmetrically competing populations. With gap formation, these statistics under symmetric competition approached those values under asymmetric competition. The spatial configuration pattern of individual size also showed the same trend in terms of the semivariogram. The patchiness index was almost the same in both gap and non-gap cases irrespective of the mode of competition. The semivariogram and patchiness index showed the presence of more uniform and larger patches under symmetric competition than asymmetric competition. Gap formation therefore increased spatial heterogeneity in local size distribution especially under symmetric competition, but there was still a difference in spatial heterogeneity between the two modes of competition even in the gap formation case. The effects of gap formation on spatial pattern dynamics were larger under symmetric competition than under asymmetric competition; under asymmetric competition, the spatial pattern dynamics were similar in both gap and son-gap cases. Therefore, against spatial disturbances (i.e. gap formation), symmetric competition brings about a more variable system than asymmetric competition. These theoretical results can explain spatial pattern dynamics of natural forests (northern coniferous and temperate hardwood forests). In conclusion, both the disturbance regime (gap formation process) and the mode of competition between individuals should be investigated to study the spatial pattern dynamics and species diversity of plant communities. The implications of the mode of between-individual competition for conservation biology are discussed. It is suggested that symmetrically competing plant communities (e.g. northern coniferous forests) should be preserved in larger areas than asymmetrically competing ones (e.g. temperate hardwood forests) if the plant communities are subject to frequent natural disturbances. (C) 1998 Elsevier Science B.V. All rights reserved.

    DOI

  • The characteristics of time changes on rice production predicted by the MRI's CGCM

    H Toritani, M Yokozawa, S Yonemura

    ECOSYSTEMS AND SUSTAINABLE DEVELOPMENT   1   31 - 40  1998年  [査読有り]

     概要を見る

    We estimate the time change of the rice production for every 10 years for a period of 100 years by using the MRI's CGCM containing the transient CO, experiment,(12) and the crop model named SIMRIW.(5) On this estimation by these models, we choose the 'Koshihikari' as a representative cultivar and assume optimal cultivation technologies are adopted.
    Annual and summer seasonis mean air temperature increase almost linearly, and become 2.0 to 3.0 degree C higher after 70 years, 3.0 to 4.0 degree C higher after 100 years, and these temperature changes are almost 1.0 to 2.0 degree C smaller than the predictions of previous studies.(1). (7). (14) AS a result of this, the cultivated area of 'Koshihikari' is estimated to spread northward, and the yield in currently cultivated area is also simulated not to change toward a harsh condition for at least 100 years, under optimal cultivation technologies.

  • System analysis of the food supply and demand in China in the 21st century

    H Kawashima, K Okamoto, M Yokozawa, MA Halablab, MJ Bazin

    ECOSYSTEMS AND SUSTAINABLE DEVELOPMENT   1   13 - 24  1998年  [査読有り]

     概要を見る

    Economic, political, environmental and agricultural variables were incorporated into a model in order to predict food supply and demand in the 21st century. Market forces do not apply to agricultural products in domestic market and price is determined politically. Invisible hand are used in order to increase prices of agricultural products. Population, area of arable land and income in the agricultural sector are key factors which determine cereal prices. Scenario analysis using a numerical model was carried out to predict cereal prices in the People's Republic of China (PRC) in the 21st century. The analysis shows that cereal prices will increase in the PRC rapidly if the country continues it's high rate of economic growth. The Chinese government have announced that they will continue the policy of self-sufficiency for food, but importing cheap cereal from international markets would be attractive an option for providing low price food to the people living in cities.

  • Relationships between competitive asymmetry of individuals and local size distributions in plant communities

    M Yokozawa, Y Kubota, T Hara

    ECOSYSTEMS AND SUSTAINABLE DEVELOPMENT   1   467 - 476  1998年  [査読有り]

     概要を見る

    The effects of the mode of competition between individual plants (symmetric vs. asymmetric) and the gap formation caused by natural disturbances on the dynamics of spatial configuration size pattern of individuals were investigated theoretically based on an individual growth model incorporating competitive effects of neighbouring individuals. The degree of spatial heterogeneity in local size distribution was represented by the CV of averages of local size distributions (CVav) and the average of CVs of local size distributions (AVcv). Without gap formation, both the CVav and AVcv were larger under asymmetric competition than under the symmetric one, suggesting a fine-scale mosaic spatial pattern in the asymmetrically competing population. With gap formation, the CVav and AVcv, under symmetric competition, approached those values under asymmetric competition. Gap formation therefore increased spatial heterogeneity in local size distribution especially under symmetric competition, but there was still a difference in spatial heterogeneity between the two modes of competition even in the gap formation case. The effects of gap formation on spatial pattern dynamics were larger under symmetric competition than under asymmetric one; under the latter, the spatial pattern dynamics were similar in both gap and non-gap cases. Therefore, against spatial disturbances (i,e. gap formation), symmetric competition produces a more variable system than asymmetric competition. Both the disturbance regime (gap formation process) and the mode of competition between individuals should be investigated to study the spatial pattern dynamics and species diversity of plant communities. The implications of the mode of between-individual competition for conservation biology are discussed. It is suggested that symmetrically competing plant communities should be preserved in larger areas than asymmetrically competing ones if plant communities are subject to frequent natural disturbances.

  • A Weather Generator for the Prediction of Crop Yields under Changeable Climates

    Yousay Hayashi, Masayuki Yokozawa, Shuji Yamakawa, Hotoshi Toritani

    Journal of Agricultural Meteorology   52 ( 5 ) 745 - 748  1997年01月  [査読有り]

     概要を見る

    The objectives of this study are the development of a newly designed weather generator for daily mean air temperature and a description of its performance. Sequentially generated data of the temperature respond to occurrence frequencies of the pressure patterns in East Asia. The generator is effective as a practical and conjunctive model between GCM and crop productivity in the field. © 1997, The Society of Agricultural Meteorology of Japan. All rights reserved.

    DOI

  • Crown architecture and species coexistence in plant communities

    M Yokozawa, Y Kubota, T Hara

    ANNALS OF BOTANY   78 ( 4 ) 437 - 447  1996年10月  [査読有り]

     概要を見る

    The relationships between crown architecture and species coexistence were studied using the diffusion model and the canopy photosynthesis model for multi-species plant communities. The present paper deals with two species having different crown shapes [conic-canopy plant (CCP) and spheroidal-canopy plant (SCP)], for various initial mean sizes at the establishment stage and physiological parameter Values (photosynthetic rate, etc.). Recruitment processes were not incorporated into the model, and thus simulations were made for the effects on the pattern of species coexistence of either sapling competition starting from different sapling banks or competition in single-cohort stands with little continual establishment of species until a stand-replacement disturbance. The following predictions were derived: (1) SCPs can establish later/slowly in the lower canopy layer even if they are overtopped by a CCP which established first/rapidly; (2) if SCPs established first/rapidly and occupy the upper canopy layer, a CCP can rarely establish later/slowly in the lower canopy layer; (3) smallest-sized CCPs can persist well in the lowermost canopy layer overtopped by a SCP, suggesting a waiting strategy of CCP's saplings in the understorey of a crowded stand; (4) even if CCPs established first/rapidly and occupy the upper canopy layer, an SCP can establish later/slowly in the lower canopy layer. Therefore, the species diversity of SCPs which established first/rapidly and occupy the upper canopy layer limits the number of CCP species which can establish later/slowly. In contrast, the species diversity of CCPs which established first/rapidly and occupy the upper canopy layer does not affect the number of SCP species which can establish later/slowly. The combination of initial sizes of a CCP and,an SCP at the establishment stage (i.e. establishment timing) affects the segregation of vertical positions in the canopy between the two species with different crown shape, and not only species-specific physiological traits but also crown architecture greatly affects the coexistence pattern between species with different crown architectures. The theoretical predictions obtained here can explain coexistence patterns found in single-cohort conifer-hardwood boreal and sub-boreal forests, pointing to the significance of crown architecture for species coexistence. (C) 1996 Annals of Botany Company

    DOI

  • FOLIAGE PROFILE, SIZE STRUCTURE AND STEM DIAMETER PLANT HEIGHT RELATIONSHIP IN CROWDED PLANT-POPULATIONS

    M YOKOZAWA, T HARA

    ANNALS OF BOTANY   76 ( 3 ) 271 - 285  1995年09月  [査読有り]

     概要を見る

    The relationships between vertical foliage profile of an individual plant, competition between individuals, size structure and allocation pattern between stem diameter (D) and plant height (H) were investigated using canopy photosynthesis and two-dimensional continuity equation models including D and H as two independent variables. Broad-leaved type plants (more foliage mass in the upper layer than in the lower layer of the canopy of an individual when grown in isolation) showed curvilinear D-H relationship and bimodal H distribution, and underwent more asymmetric competition than coniferous type plants (more foliage mass in the lower layer than in the upper layer of the canopy of an individual when grown in isolation) under crowded conditions. Coniferous type plants showed almost linear D-X relationship (i.e. simple allometry) and unimodal H distribution, and underwent more symmetric competition than broad-leaved type plants under crowded conditions. However, in both the cases D distributions were unimodal. Allocation patterns between D and H affected these features only a little. These simulation results can explain many actual data already published. The value of eta for an individual plant (foliage profile parameter of an individual canopy representing a species-specific branching pattern and canopy morphology when grown in isolation) governs size structure (bimodal or unimodal), the mode of competition, D-H relationship and mean D-mean H trajectory with time under crowded conditions. Therefore, a simple view of the competition-allometry relationship that competition determines allometry should be re-evaluated incorporating the foliage profile of an individual. These theoretical results should also be important when studying species coexistence. The canopy tends to be multi-layered in broad-leaved type plants and mono-layered in coniferous type plants. Therefore, it is hypothesized that species coexistence in the former is mainly by way of separation of vertical space (i.e. niche separation under strongly asymmetric competition) and that species coexistence in the latter is due to nearly symmetric competition in a single canopy layer. (C) 1995 Annals of Botany Company

    DOI

  • Effects of Physiological and Environmental Variations of Size Structure dynamics in Plant Populations

    Annals of Botany   73 ( 1 ) 39 - 51  1994年01月  [査読有り]

    DOI

  • A Canopy Photosynthesis Model for the Dynamics of Size Structure and the Competition Mode in Plant Populations

    YOKOZAWA MASAYUKI, HARA TOSHIHIKO

    農業気象   48 ( 5 ) 827 - 830  1993年

     概要を見る

    A dynamic model for growth and mortality of individual plants in a stand is developed, based on the process of canopy photosynthesis, and assuming an allometric relationship between plant height and weight, i.e. an allocation-growth pattern of plant height and stem diameter. The following were shown by simulation: (i) competition between individuals in a crowded stand is never completely one-sided but always asymmetrically two-sided, even though competition is only for light; (ii) plants of the 'height-growth' type exhibit a greater asymmetry in competition than plants of the 'diameter-growth' type; (iii) the competition mode between plants of the 'height-growth' type becomes more asymmetric with increasing photosynthetic ability than with plants of the 'diameter-growth' type. These results can explain recent empirical results obtained from several natural plant communities.

    DOI CiNii

  • A CANOPY PHOTOSYNTHESIS MODEL FOR THE DYNAMICS OF SIZE STRUCTURE AND SELF-THINNING IN PLANT-POPULATIONS

    M YOKOZAWA, T HARA

    ANNALS OF BOTANY   70 ( 4 ) 305 - 316  1992年10月  [査読有り]

  • COMPETITION PROCESS AND SPATIAL PATTERN-FORMATION IN A BETULA ERMANII POPULATION

    T HARA, H VANRIJNBERK, H DURING, M YOKOZAWA, K KIKUZAWA

    SPATIAL PROCESSES IN PLANT COMMUNITIES     127 - 143  1990年  [査読有り]

  • COMPETITION BETWEEN THE NEEL AND THE EFFECTIVE SINGLET-STATES IN SPIN-1/2 ALTERNATING HEISENBERG-ISING ANTIFERROMAGNET IN ONE-DIMENSION

    H NISHIMORI, K OKAMOTO, M YOKOZAWA

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   56 ( 11 ) 4126 - 4133  1987年11月  [査読有り]

    DOI

▼全件表示

書籍等出版物

  • Indo-Pacific Climate Variability and Predictability

    Iizumi T, Yokozawa M, Sakurai G, Sakuma H, Luo J.J, Challinor A.J, Yamagata T( 担当: 共著)

    World Scientific Publishing  2016年01月

  • 地球環境変動の生態学

    横沢正幸, 櫻井 玄( 担当: 共著)

    共立出版  2014年03月

Misc

  • 求められる利水と治水のインターリンケージ:気候変動への適応の過程に注目して

    西原是良, 岡田将誌, 中河嘉明, 横沢正幸

    日本水文科学会学術大会発表要旨集   2021  2021年

    J-GLOBAL

  • 全球作物生産性予測モデルCROVERの信濃川流域への適用

    岡田将誌, 中河嘉明, 西原是良, 横沢正幸

    日本地理学会発表要旨集   ( 100 )  2021年

    J-GLOBAL

  • イネにおけるケイ素輸送モデルによる輸送体配置の影響分析

    櫻井玄, 山地直樹, 三谷奈見季, 小野圭介, 横沢正幸, 酒井英光, 吉本真由美, 馬建鋒

    日本土壌肥料学会講演要旨集(Web)   65  2019年

    J-GLOBAL

  • イネにおける作物体内ミネラル輸送ダイナミクスの解析手法の開発

    櫻井玄, 小野圭介馬建鋒, 山地直樹, 三谷奈見季, 横沢正幸

    農業環境変動研究センター研究成果情報    2018年03月

  • 気候変動に対応した循環型食料生産等の確立のためのプロジェクト 第1編 農業分野における温暖化緩和技術の開発 第1章 農地及び草地におけるモニタリング・モデリングと全国評価 3 全国スケールでの温暖化緩和ポテンシャルの評価

    白戸康人, 井上吉雄, 岡本勝男, 石塚直樹, 杉浦裕義, 高橋司, 小原繁, 川守田真紀, 岩淵幸治, 額田光彦, 根本知明, 折本善之, 飯村強, 藤田裕, 郷内武, 手塚誉裕, 加藤治, 榊英雄, 山田一宇, 橋本享子, 峯田絵里, 岸本文紅, 高田裕介, 三島慎一郎, 横沢正幸, 米村正一郎, 須藤重人, 矢ケ崎泰海, 木村園子ドロテア

    農林水産省農林水産技術会議事務局研究成果   ( 557 ) 64‐69  2016年03月

    J-GLOBAL

  • Characterizing the reliability of global crop prediction based on seasonal climate forecasts

    Toshichika Iizumi, Masayuki Yokozawa, Gen Sakurai, Hirofumi Sakuma, Jing-Jia Luo, Andrew J. Challinor, Toshio Yamagata

    World Scientific Series on Asia-Pacific Weather and Climate   7   281 - 304  2016年  [査読有り]

     概要を見る

    Reliable crop prediction based on seasonal climate forecasts can be achieved when a strong climate- crop relationship exists and there are reliable forecasts of the climatic constraints on crops. Here, we present global assessments of the climatic constraints on crops (maize, soybeans, rice, and wheat), the degree of the climate-crop relationship, and the reliability of seasonal forecasts of dominant climatic constraints based on statistical crop models and ensemble seasonal climate forecasts. We then classify the reliability of within-season crop prediction into four categories based on the degree of the climate-crop relationship and the reliability of the climate forecasting: (I) reliable
    (II) less reliable due to the low reliability of climate forecasting
    (III) not reliable due to the low reliability of climate forecasting and a weak climate-crop relationship
    and (IV) less reliable due to a weak climate-crop relationship. The results showed that a strong climate-crop relationship exists in the area that produces 24-38% of the global crop production. On a global scale, 51-59% of the maize and soybean production is sensitive to soil moisture level during the reproductive growth period, whereas 47-53% of the rice and wheat production is sensitive to temperature. Due to the greater reliability of temperature forecasts, crop prediction is reliable in those areas in which the crop yield is temperature-sensitive and temperature forecasts are reliable. The categorized reliability of crop prediction indicated that improvements of soil moisture forecasts in 30-50°N during July- October and in 30-40 ? S during February-April are needed for better maize and soybean prediction, whereas improved temperature forecasts in 20-60 ° N during March-August are keys to rice and wheat prediction. This study established a novel way of assessing the reliability of crop prediction, which will enable decision-making and allow researchers to prioritize the direction of new research to improve crop prediction in a given area for global food prediction.

    DOI

  • 森林の炭素動態モデル構築に向けて―リター及び土壌有機物分解サブモデルのパラメータ推定―

    鈴木静男, 鈴木静男, 永井勝, 小嵐淳, 安藤麻里子, 横沢正幸, 横沢正幸, 原登志彦, 日浦勉, 渡邉博史, 波松香苗, 多胡靖宏, 中村裕二, 久松俊一

    富士学会発表要旨集   ( 15 ) 10‐11  2015年09月

    J-GLOBAL

  • 土壌中CO2発生量鉛直分布の推定方法の開発

    櫻井玄, 米村正一郎, 横沢正幸, 岸本文紅, 村山昌平, 大塚俊之

    農業環境技術研究所研究成果情報   31   52 - 53  2015年03月

    J-GLOBAL

  • 根におけるケイ素吸収・輸送モデルの開発とイネがケイ素を多く吸収できるメカニズムの解明

    櫻井玄, 佐竹暁子, 山地直樹, 横沢正幸, FEUGIER Francois Gabriel, 三谷奈見季, 馬建鋒

    農業環境技術研究所研究成果情報   31  2015年

    J-GLOBAL

  • 環境変動が全休の同時不作確率に及ぼす影響のコピュラを用いた解析

    櫻井玄, 横沢正幸, 飯泉仁之直

    統計数理研究所共同研究リポート   343   39 - 49  2015年

    その他  

  • 環境変動と北方林生態系応答 (北半球寒冷圏陸域の気候・環境変動)

    戸田 求, 横沢 正幸, 原 登志彦

    気象研究ノート   ( 230 ) 159 - 167  2014年10月

    CiNii

  • イネのケイ素輸送におけるカスパリー線の役割とトランスポーター配置

    櫻井玄, 馬建鋒, 佐竹暁子, 横沢正幸, 山地直樹, 三谷奈見季

    日本植物生理学会年会要旨集   55th  2014年

    J-GLOBAL

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    櫻井 玄, 佐竹 暁子, 山地 直樹, 三谷 奈見季, 横沢 正幸, 馬 建鋒

    日本土壌肥料学会講演要旨集   60 ( 0 )  2014年

    CiNii

  • 気候変動にともなう大規模豪雨災害の稲作生産性に対する影響-空間計量経済モデルによる評価-

    國光洋二, 工藤亮治, 飯泉仁之直, 横沢正幸

    日本地域学会年次大会学術発表論文集(CD-ROM)   50th  2013年

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    岡田 将誌, 飯泉 仁之直, 櫻井 玄, 横沢 正幸

    大会講演予講集   104   459 - 459  2013年

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    金元植, 横沢正幸, 小森大輔, 徐炯鎬

    日本農業気象学会全国大会講演要旨   2013   95  2013年

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    横沢 正幸, 中河 嘉明, 原 登志彦

    日本物理学会講演概要集   67 ( 1 ) 328 - 328  2012年03月

    CiNii

  • P145 地表面日射量を推定する統計モデルの将来気候条件における適用可能性(ポスター・セッション)

    岡田 将誌, 飯泉 仁之直, 横沢 正幸

    大会講演予講集   102   229 - 229  2012年

    CiNii

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    鈴木静男, 横沢正幸, 犬伏和之, 原登志彦, 木村康倫, 津賀正一, 多胡靖宏, 中村裕二

    日本土壌肥料学会講演要旨集   57   16  2011年08月

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    白戸康人, 矢ケ崎泰海, 横沢正幸, 米村正一郎, 上村真由子, 岸本文紅, 和穎朗太

    農林水産省農林水産技術会議事務局研究成果   ( 483 ) 134 - 139  2011年07月

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  • 農業に関わる環境の長期モニタリング 温度が土壌からの温室効果ガスの発生・吸収に及ぼす影響を自動連続測定できる実験装置

    米村正一郎, 杜明遠, 横沢正幸, 岸本文紅, 和穎朗太

    農業環境技術研究所研究成果情報   27   74 - 75  2011年03月

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  • ヨシ優占湿地における1年間の総一次生産量,生態系呼吸量,純生態系生産量―閉鎖系施設を用いた評価―

    鈴木静男, 横沢正幸, 犬伏和之, 原登志彦, 木村康倫, 津賀正一, 多胡靖宏, 中村裕二

    日本生態学会大会講演要旨集   58th   203  2011年03月

    J-GLOBAL

  • 28aPS-26 植物個体群における個体間競争の時空間ネットワーク解析(28aPS 領域11ポスターセッション,領域11(統計力学,物性基礎論,応用数学,力学,流体物理))

    横沢 正幸, 中河 嘉明, 原 登志彦

    日本物理学会講演概要集   66 ( 1 ) 353 - 353  2011年03月

    CiNii

  • P326 日本の地点・日別気候変化シナリオデータセットから得られた農業気候指標の将来変化(ポスター・セッション)

    飯泉 仁之直, 横沢 正幸, 西森 基貴, 吉田 龍平

    大会講演予講集   100   470 - 470  2011年

    CiNii

  • フラジリティーカーブを用いた台風被害面積推計手法の開発

    増冨祐司, 飯泉仁之直, 高橋潔, 横沢正幸

    日本農業気象学会全国大会講演要旨   2011   198  2011年

    J-GLOBAL

  • 植物個体群における競争ネットワークの構造解析 (第6回生物数学の理論とその応用)

    中河 嘉明, 横沢 正幸, 原 登志彦

    数理解析研究所講究録   1704   68 - 75  2010年08月

    CiNii

  • 閉鎖系陸圏実験施設を用いたヨシ優占湿地における炭素収支の評価

    鈴木静男, 横沢正幸, 原登志彦, 犬伏和之, 木村康倫, 津賀正一, 多胡靖宏, 中村裕二

    生態工学会年次大会発表論文集   2010   65 - 66  2010年05月

    J-GLOBAL

  • 有機物施用が及ぼす農地土壌への炭素蓄積効果を全国推定

    白戸康人, 大倉利明, 横沢正幸, 米村正一郎, 坂本利弘, 中井信

    農業環境技術研究所研究成果情報   26   48 - 49  2010年03月

    J-GLOBAL

  • 21pPSB-27 個体サイズ構造を持つ植物群集における空間パターンの創発(21pPSB 領域11ポスターセッション,領域11(統計力学,物性基礎論,応用数学,力学,流体物理))

    横沢 正幸, 中河 嘉明, 原 登志彦

    日本物理学会講演概要集   65 ( 1 ) 321 - 321  2010年03月

    CiNii

  • 湿地生態系を対象とした炭素循環モデルのパラメータ決定―閉鎖系施設内の湿地生態系における炭素循環データを用いて―

    鈴木静男, 横沢正幸, 犬伏和之, 原登志彦, 津賀正一, 遠藤政弘, 多胡靖宏, 中村裕二, 新田慶治

    日本農業気象学会全国大会講演要旨   2010   159  2010年

    J-GLOBAL

  • P126 台風による水稲の被害面積推計モデルの開発(ポスター・セッション)

    増冨 祐司, 飯泉 仁之直, 高橋 潔, 横沢 正幸

    大会講演予講集   98   363 - 363  2010年

    CiNii

  • 23-37 土壌環境基礎調査・基準点調査データによるRothCモデルの性能検証(23.地球環境,2009年度京都大会)

    矢ヶ崎 泰海, 上村 真由子, 白戸 康人, 横沢 正幸

    日本土壌肥料学会講演要旨集   ( 55 ) 197 - 197  2009年09月

    CiNii

  • 23-36 RothCモデルを用いた有機物投入による土壌炭素量変化係数の作成(23.地球環境,2009年度京都大会)

    白戸 康人, 横沢 正幸

    日本土壌肥料学会講演要旨集   ( 55 ) 196 - 196  2009年09月

    CiNii

  • 累積密度分布に基づいた気候モデル日別データの補正

    飯泉仁之直, 西森基貴, 澤野真治, 横沢正幸

    農業環境工学関連学会合同大会講演要旨集(CD-ROM)   2009  2009年

    J-GLOBAL

  • Evaluation of seasonal changes in methane flux in a wetland ecosystem using the Closed Geosphere Experiment Facility

    Suzuki, S, Inubushi, K, Yokozawa, M, Hara, T, Nishidate, K, Tsuga, S, Tako, Y, Nakamura, N

    Geophysical Research Abstracts   11   EGU2009-3799-1  2009年

  • Assessing climate change impacts on rice production in Japan under stabilization levels of atmospheric GHG concentration

    Yokozawa Masayuki, Iizumi Toshichika, Nishimori Motoki, Hijioka Yasuaki, Takahashi Kiyoshi, Harasawa Hideo

    日本農業気象学会大会講演要旨   9 ( 0 ) 138 - 138  2009年

    DOI CiNii

  • 14-9 RothCモデルによる日本の農耕地土壌の炭素蓄積量変化の試算(14.土地分類利用・景域評価,2008年度愛知大会)

    白戸 康人, 横沢 正幸, 坂本 利弘, 米村 正一郎, 中井 信, 大倉 利明

    日本土壌肥料学会講演要旨集   ( 54 ) 120 - 120  2008年09月

    CiNii

  • 土壌の微量ガス代謝室内実験

    米村 正一郎, 山田 恵子, 莫 文紅, 北 一之, 井上 聡, 杜 明遠, 横沢 正幸

    日本農業気象学会大会講演要旨   8 ( 0 ) 29 - 29  2008年03月

    CiNii J-GLOBAL

  • P116 ベイズ推定と統計的ダウンスケーリングを併用したベトナム・メコンデルタ域の全天日射量の推定

    飯泉 仁之直, 西森 基貴, 横沢 正幸, 小寺 昭彦, Khang Nguyen Duy

    大会講演予講集   94   363 - 363  2008年

    CiNii

  • 衛星データを活用してメコンデルタの洪水と稲作の変化をみる

    坂本利弘, 石塚直樹, 大野宏之, 横沢正幸

    農業環境技術研究所年報   ( 24 ) 15 - 17  2007年12月

    J-GLOBAL

  • 衛星データを活用してメコンデルタの洪水と稲作の変化をみる

    坂本利弘, 石塚直樹, 大野宏之, 横沢正幸

    農環研ニュース   ( 76 ) 7 - 8  2007年10月

    J-GLOBAL

  • 高頻度観測衛星センサー(MODIS/Terra)を活用してメコンデルタの洪水と稲作を動的に捉える

    坂本利弘, 石塚直樹, 大野宏之, 横沢正幸

    農業環境技術研究所研究成果情報   23   44 - 45  2007年03月

    J-GLOBAL

  • 土壌炭素動態の温暖化応答解明のための高精度土壌加温システム

    岸本文紅, 米村正一郎, 横沢正幸

    農業環境技術研究所研究成果情報   23   38 - 39  2007年03月

    J-GLOBAL

  • 熱帯季節林域における二酸化炭素フラックスの季節変動

    金元植, 間野正厚, 横沢正幸, 小森大輔, 鼎信次郎, 沖大幹

    日本生態学会大会講演要旨集   54th   276  2007年03月

    J-GLOBAL

  • P391 温暖化による日射環境変化推定に用いる統計的ダウンスケーリング手法の構築

    飯泉 仁之直, 西森 基貴, 横沢 正幸

    大会講演予講集   92   536 - 536  2007年

    CiNii

  • 時系列衛星データ解析による農業的土地利用変化把握

    坂本利弘, 小寺昭彦, 大野宏之, 石塚直樹, 横沢正幸, VAN NHAN Nguyen

    日本写真測量学会学術講演会発表論文集   2007  2007年

    J-GLOBAL

  • MODIS時系列解析によるメコンデルタ洪水の時空間変動特性把握

    坂本利弘, NGUYEN Nhan Van, 小寺昭彦, 大野宏之, 石塚直樹, 横沢正幸

    システム農学会シンポジウム要旨集   2007  2007年

    J-GLOBAL

  • P326 高CO2が森林動態や大気-森林群落間の熱・水・CO2フラックスへ及ぼす影響

    戸田 求, 横沢 正幸, 隅田 明洋, 原 登志彦

    大会講演予講集   89 ( 0 ) 393 - 393  2006年04月

    CiNii

  • B309 TERC-RAMSを用いたアジア域における気候極値・異常気象の再現と予測(気候システムIII)

    西森 基貴, 木村 富士男, 飯泉 仁之直, 小寺 昭彦, 横沢 正幸

    大会講演予講集   90   132 - 132  2006年

    CiNii

  • ベトナム,メコンデルタ及び紅河デルタにおける水稲フェノロジー空間分布特性の把握

    坂本利弘, 小寺昭彦, 石塚直樹, 大野宏之, NGUYEN Nhan Van, 横沢正幸

    農業環境工学関連学会合同大会講演要旨集(CD-ROM)   2006  2006年

    J-GLOBAL

  • メコンデルタにおける水稲作付体系の把握

    坂本利弘, NGUYEN Nhan Van, 石塚直樹, 大野宏之, 横沢正幸

    システム農学会シンポジウム要旨集   2006  2006年

    J-GLOBAL

  • 県平均水稲収量の推定モデル

    横沢正幸, 飯泉仁之直, 小寺昭彦, 坂本利弘, 中川博視

    農業環境工学関連学会合同大会講演要旨集(CD-ROM)   2006   P1473  2006年

    J-GLOBAL

  • 気候変動が中国の水稲収量に及ぼす影響の予測

    中川博視, ZHU D, 横沢正幸, 堀江武

    日本作物学会講演会要旨・資料集   219th   80 - 81  2005年03月

    J-GLOBAL

  • リモートセンシングによる作物フェノロジー情報の広域推定

    坂本利弘, 横沢正幸, 鳥谷均, 芝山道郎, 石塚直樹, 大野宏之

    農業環境工学関連7学会合同大会講演要旨集   2005  2005年

    J-GLOBAL

  • 陸上生態系における炭素動態のモデリング : 土壌内の炭素の分配・流れを中心として(<特集2>陸上生態系における炭素フラックス調査法 現状と今後の課題).

    横沢 正幸, 米村 正一郎, 白戸 康人

    日本生態学会誌   55 ( 1 ) 167 - 171  2005年01月

    記事・総説・解説・論説等(学術雑誌)  

  • 土壌炭素動態モデルRothCの水田への適用の試み(1. 物質循環・動態, 2004年度大会講演要旨集)

    白戸 康人, 横沢 正幸

    日本土壌肥料学会講演要旨集   ( 50 ) 13 - 13  2004年09月

    CiNii

  • P101 環境変化が100年後における森林の群落動態・物質収支に及ぼす影響

    戸田 求, 渡辺 力, 横沢 正幸, 江守 正多, 高田 久美子, 隅田 昭洋, 原登 志彦

    大会講演予講集   85   223 - 223  2004年

    CiNii

  • MODIS画像時系列解析による水稲の生育モニタリング

    坂本利弘, 横沢正幸, 鳥谷均, 芝山道郎, 石塚直樹, 大野宏之

    システム農学会シンポジウム要旨集   2004  2004年

    J-GLOBAL

  • 地球温暖化が農林生態系に及ぼす影響 3. 大気CO_2濃度, 温度および水分環境の変化と作物の応答

    横沢 正幸

    日本土壌肥料學雜誌 = Journal of the science of soil and manure, Japan   74 ( 2 ) 229 - 236  2003年04月

     概要を見る

    いうまでもなく、CO2は地球上の緑色植物が行う光合成過程における最も本質的な物質である。しかし、人為活動によるCO2を含む温室効果ガスの放出により、地球の気候変化が引き起こされ、気温上昇、降水量変化といった、作物が生長する場の環境が変わりつつある。この地球規模の環境変化に対する作物の応答は、特定の地域だけではなく、世界の農業生産を変化させるであろう。そのような環境変化の影響を予測し、対策を立てるためには、次のような基本的な問いに答えることから始める必要があろう。すなわち、作物は現在の環境にどのように適応しているのか?大気CO2濃度および気温の上昇は作物の生長を促進するのか?作物の栽培にとって最適な環境条件は何か?環境の変化および変動は作物の生育・生長にどのような影響を与えるのか?このような作物の環境応答に関する基礎的な知見を踏まえて、はじめて気候変化が農業生産に及ぼす影響とその対応策の評価を総合的に行うことができる。本稿では、始めにCO2濃度、温度および水分環境の変化に対する作物の生理生態的機能の応答について概説する。次に、その基礎的知見に基づいて構築されたモデルを用いて気候変化の作物生産への影響評価を行った研究例について述べる。

    CiNii

  • Quasi-Biennial Zonal Wind Oscillation and Southern Oscillation Signals in the Monsoon Rainfall Periodicity in Sri Lanka

    HULUGALLA Ranatunge, MALMGREN Bjorn A., HAYASHI Yousay, MIKAMI Takehiko, YOKOZAWA Masayuki, MORISHIMA Wataru, NISHIMORI Motoki

    日本地理学会発表要旨集 = Proceedings of the General Meeting of the Association of Japanese Geographers   63   262 - 262  2003年03月

    CiNii

  • ENSO Signals in the Changes of Monsoon Rainfall in Sri Lanka during the Last 130 Years

    HULUGALLA Ranatunge, MALMGREN Bjorn A., HAYASHI Yousay, MIKAMI Takehiko, YOKOZAWA Masayuki, MORISHIMA Wataru, NISHIMORI Motoki

    日本地理学会発表要旨集 = Proceedings of the General Meeting of the Association of Japanese Geographers   63   261 - 261  2003年03月

    CiNii

  • 多時期衛星画像と気象観測データを用いた水稲の単収推定

    坂本利弘, 大野宏之, 石塚直樹, 鳥谷均, 岡本勝男, 横沢正幸

    システム農学会シンポジウム要旨集   2003  2003年

    J-GLOBAL

  • 気候変動の将来の見通しの向上を目指したエアロゾル・水・植生等の過程のモデル化に関する研究 (3) 地球温暖化における陸上生態系フィードバックに関する研究

    渡辺力, 溝口康子, 岡野通明, 横沢正幸, 近藤裕昭, 三枝信子, 沖大幹, 原登志彦, 隅田明洋

    気候変動の将来の見通しの向上を目指したエアロゾル・水・植生等の過程のモデル化に関する研究 平成12−14年度     71-97  2003年

    J-GLOBAL

  • 地球温暖化の生物圏への影響,適応,脆弱性評価に関する研究 (4) 影響の変動性・地域性を考慮した農業生態系のリスク評価に関する研究 (1) 温暖化影響の変動性・地域性を考慮した農業生態系のリスク評価手法の開発に関する研究

    林陽生, 谷山一郎, 横沢正幸, 大野宏之, 西森基貴, 白戸康人, 堀江武, 中川博視

    地球環境研究総合推進費 平成14年度研究成果 中間成果報告集 1/全5分冊     474 - 482  2003年

    J-GLOBAL

  • 21世紀の炭素管理に向けたアジア陸域生態系の統合的炭素収支研究 テーマI ボトムアップ(微気象・生態学的)アプローチによる陸域生態系の炭素収支解析に関する研究 (2) 土壌圏における炭素収支の定量的評価に関する研究

    小泉博, 秋山侃, 藤沼康実, 横沢正幸, 米村正一郎, 大塚俊之, 鞠子茂, 別宮有紀子, 関川清広

    地球環境研究総合推進費 平成14年度研究成果 中間成果報告集 1/全5分冊     143 - 155  2003年

    J-GLOBAL

  • 地球温暖化による年平均気温の変動がウンシュウミカンの栽培環境に及ぼす影響

    杉浦 俊彦, 横沢 正幸, 黒田 治之

    園芸学会雑誌. 別冊, 園芸学会大会研究発表   71 ( 1 ) 223 - 223  2002年04月

    CiNii

  • 24-23 ローザムステッド・カーボン・モデルによる日本の畑土壌の炭素収支の広域評価(24.地球環境)

    白戸 康人, 横沢 正幸, Coleman Kevin

    日本土壌肥料学会講演要旨集   ( 48 ) 166 - 166  2002年03月

    CiNii

  • 気候変動の将来の見通しの向上を目指したエアロゾル・水・植生等の過程のモデル化に関する研究 (3) 地球温暖化における陸上生態系フィードバックに関する研究 (環境省地球環境局S)

    渡辺力, 安田幸生, 岡野通明, 横沢正幸, 近藤裕昭, 三枝信子, 原登志彦, 隅田明洋, 県信次郎

    地球環境研究総合推進費 平成13年度研究成果 中間成果報告集 1/全4分冊     71-78  2002年

    J-GLOBAL

  • 地球温暖化による生物圏の脆弱性の評価に関する研究 (4) 農業生態系の脆弱性に関する研究 (環境省S)

    林陽生, 鳥谷均, 井上聡, 横沢正幸, 山村光司, 田中幸一, 内嶋善兵衛, 堀江武, 中川博視

    地球温暖化による生物圏の脆弱性の評価に関する研究 平成11-13年度     120 - 137  2002年

    J-GLOBAL

  • 気候変動・異常気象による日本の水稲単収変動の地域的変化

    西森基貴, 横沢正幸

    地球環境   6   149 - 158  2001年12月  [査読有り]

    速報,短報,研究ノート等(学術雑誌)  

  • 気候変動の将来の見通しの向上を目指したエアロゾル・水・植生等の過程のモデル化に関する研究 (3) 地球温暖化における陸上生態系フィードバックに関する研究 (環境省地球環境局S)

    渡辺力, 岡野通明, 横沢正幸, 近藤裕昭, 三枝信子, 原登志彦, 隅田明洋, 沖大幹, 鼎信次郎

    地球環境研究総合推進費 平成12年度研究成果 中間成果報告集 2/全4分冊     23-31  2001年

    J-GLOBAL

  • 地球温暖化による生物圏の脆弱性の評価に関する研究 (4) 農業生態系の脆弱性評価に関する研究 (環境省地球環境局S)

    林陽生, 横沢正幸, 西森基貴, 後藤慎吉, 井上聡, 山村光司, 内嶋善兵衛, 堀江武, 中川博視

    地球環境研究総合推進費 平成12年度研究成果 中間成果報告集 2/全4分冊     201 - 205  2001年

    J-GLOBAL

  • メタンと一酸化炭素の土壌による全球吸収量を求めるための過程モデル

    米村 正一郎, 横沢 正幸

    農業気象研究集録   41   5(149 - 170)  2000年12月

    CiNii

  • 一酸化炭素と水素の土壌による吸収に土壌のガス拡散係数が与える影響のモデル解析

    米村 正一郎, 横沢 正幸, 川島 茂人

    農業気象研究集録   41   6(919 - 933)  2000年12月

    CiNii

  • 草地上の二高度の一酸化炭素とメタンの濃度と地面への吸着

    米村 正一郎, 宮田 明, 横沢 正幸

    農業気象研究集録   41   3(5007 - 5014)  2000年12月

    CiNii

  • 陸上植生動態-気候間の相互作用のモデル化

    渡辺 力, 横沢 正幸, 江守 正多, 高田 久美子, 原 登志彦

    大会講演予講集   77   383 - 383  2000年05月

    CiNii

  • MRI‐CGCM気候変化シナリオから予測した日本における21世紀の水稲の潜在収量

    鳥谷均, 米村正一郎, 横沢正幸, 清野かつ

    農業環境技術研究所年報   ( 16 ) 59 - 67  2000年02月

    J-GLOBAL

  • MRI-CGCM気候変化シナリオから予測した日本における21世紀の水稲の潜在収量

    鳥谷 均, 米村 正一郎, 横沢 正幸

    農業気象研究集録   ( 40 ) 3(8 - 16)  1999年12月

    CiNii

  • 地球温暖化予測情報にもとづく水稲の潜在収量分布の変化 (農林水産省農業環境技術研究所S)

    鳥谷均, 林陽生, 後藤慎吉, 米村正一郎, 横沢正幸, 清野ひろし

    農業環境研究成果情報   15   65 - 66  1999年11月

    J-GLOBAL

  • 気候変動シナリオからみたアジアの農業生産力変動

    岡本 勝男, 横沢 正幸

    システム農学   15 ( 2 ) 104 - 110  1999年10月

    CiNii

  • MRI-CGCMによって予測された水稲の潜在収量の分布とその変化

    鳥谷 均, 横沢 正幸, 米村 正一郎, 清野 豁

    日本地理学会発表要旨集 = Proceedings of the General Meeting of the Association of Japanese Geographers   52   150 - 151  1997年10月

    CiNii

  • MRI-CGCMのCO_2漸増実験結果に基づいた水稲の潜在収量の変化

    鳥谷 均, 米村 正一郎, 横沢 正幸, 清野 豁

    大会講演予講集   71   116 - 116  1997年05月

    CiNii

  • 中部山岳域の高山帯におけるハイマツ群落の生理生態的機能 (文部省S)

    丸田恵美子, 中野隆志, 石田厚, 飯田肇, 増沢武弘, 横沢正幸, 米村正一郎

    本州中部山岳地帯における動植物相の保護・保全に関する研究 平成5-6年度 No.05304053     36 - 45  1995年

    J-GLOBAL

  • 個体の生理的特性,環境要因が植物個体群落の構造に及ぼす影響〔英文〕

    原 登志彦, 横沢 正幸

    農業気象研究集録   ( 35 ) 5(39 - 51)  1994年12月

    CiNii

  • 植物個体群におけるサイズ動態と自己間引きを表す群落光合成モデル〔英文〕

    横沢 正幸, 原 登志彦

    農業気象研究集録   ( 33 ) 11(305 - 316)  1992年12月

    CiNii

▼全件表示

受賞

  • 日本農業気象学会論文賞

    2015年03月  

共同研究・競争的資金等の研究課題

  • 樹木集団の空間不均一性を簡約化した森林生態系の環境応答モデル

    日本学術振興会  科学研究費助成事業 基盤研究(C)

    研究期間:

    2018年04月
    -
    2021年03月
     

    横沢 正幸

  • 異常気象による主要穀物の生産変動が世界の食料需給・貧栄養人口に及ぼす影響の解明

    日本学術振興会  科学研究費助成事業 基盤研究(B)

    研究期間:

    2014年08月
    -
    2018年03月
     

    横沢 正幸

講演・口頭発表等

  • Detecting changes in traits of forest after extreme climate episode using model data fusion

    M. yokozawa

    The International Society for Ecological Modelling Global Conference 2016  

    発表年月: 2016年05月

  • Modeling the climate change adaptation of crop production using irrigation over water-limited region

    Masashi Okada, Toshichika Iizumi, Gen Sakurai, Toru Sakai, Masayuki Yokozawa

    2014 AGU Fall Meeting  

    発表年月: 2014年12月

  • The past impact of climate change on major crop yield

    Gen Sakurai, Toshichika Iizumi, Motoki Nishimori, Masashi Okada, Masayuki Yokozawa  [招待有り]

    2014 AGU Fall Meeting  

    発表年月: 2014年12月

  • Evaluating the synchronicity in yield variations of staple crops at global scale

    Masayuki Yokozawa

    2014 AGU Fall Meeting  

    発表年月: 2014年12月

特定課題研究

  • 異常気象による作物生産性変動のナウキャスティングに向けたモデル開発

    2018年  

     概要を見る

     流域スケールの作物生産性変動をナウキャスト(作物の生産性を収穫の数ヶ月前に予測)するシステムに組み込むモデルのプロトタイプ開発を行った。対象であるサトウキビなど糖料作物はバイオマス量よりも植物体に含まれる糖度量の推定が経済的側面から重要であることから、作物の生育環境に応じた糖度特性決定に関するモデル化を行うとともに、JAMSTEC/APLから出力される気象環境データの時間空間分解能の観点からモデルに取り込む素過程の簡略化または高度化を行った。登熟過程に焦点をあてて、環境条件とスクロース貯蔵過程との関係の経験的モデルとして定式化した。そのモデルについて、貯蔵スクロース収量の環境応答を調べた。

 

現在担当している科目

▼全件表示

担当経験のある科目(授業)

  • 生物圏科学特別講義I

    北海道大学環境科学院  

  • 基礎生態学

    早稲田大学人間科学部  

  • 個体群生態学特論

    早稲田大学人間科学研究科  

  • 自然環境論

    群馬大学社会情報学部  

  • 生態モデリング特論

    早稲田大学人間科学研究科  

  • 農業気象学

    早稲田大学人間科学部  

  • 数理システム工学研究第二

    静岡大学  

  • 数理システム工学研究第一

    静岡大学  

  • 数理システム工学セミナー第二

    静岡大学  

  • 数理システム工学セミナー第一

    静岡大学  

  • 自然環境論

    静岡大学  

  • 環境シミュレーション特論

    静岡大学  

  • シミュレーション技法Ⅱ

    静岡大学  

  • システム工学応用実習Ⅱ

    静岡大学  

  • システム工学セミナー入門

    静岡大学  

  • システム工学セミナー

    静岡大学  

▼全件表示

 

委員歴

  • 2020年03月
    -
    継続中

    Global Change Biology, Editorial Advisory Board member

  • 2017年09月
    -
    継続中

    環境省  気候変動の影響観測・監視の推進に向けた検討チーム 座長

  • 2005年
    -
    2006年

    日本農業気象学会  評議員