Equisetum arvense L. is a perennial pteridophyte that grows in open sites. In Tokyo, the plant has photosynthetic shoots from late March to November. However, in some populations, these shoots are lost before summer because of shading by taller plants. To investigate the contribution of shoots that remain on the plant for a certain duration, in terms of the maintenance of the E. arvense population, tubers were cultivated under different light conditions and the dry weight of growth, photosynthetic rates and respiration rates were measured. Individual growth was simulated on the basis of matter production and its partitioning. Biomass at the start of the next growing season (the initial size) was seriously decreased by shading before July. However, shading after July had little effect on the initial size of the next season plants. Thus, E. arvense can maintain its population if its shoots are retained until summer.

Sporophytes appeared on most gametophytes of Thelypteris palustris (Salisb.) Schott that reached a certain size, which is interpreted to be a critical size of gametophytes for the production of sporophytes. After sporophytes were produced, attached gametophytes ceased dry weight growth, but the gametophytes which did not produce sporophytes grew successively. It was hypothesized that matter produced by gametophytes was being supplied to young sporophytes. Photosynthesis and respiration of gametophytes with attached sporophytes were not significantly different from that of gametophytes without sporophytes. Photosynthetic activity of gametophytes dropped from 0.18 to 0.03 mu mol CO2 g(-1) s(-1) during the growth period. The higher photosynthetic rates of gametophytes in the early growth stage were important for reaching the critical size for sporophyte production in a short time. Sporophytes in the 'one leaf stage' averaged 0.14 mu mol CO2 g(-1) s(-1) of photosynthetic activity. The results show that sporophytes that had expanded the first leaf grow by their own photosynthetic production. Gametophytes allocated the photosynthate for sporophytes and it was an important aid before the one-leaf stage. The supportive role of gametophytes ended at that stage.

Camellia rusticana is an evergreen broad-leaved shrub found only in areas of heavy snowfall in Japan. The ecophysiological tolerance of this species to prolonged snow cover was studied in comparison with those of Camellia japonica found in areas of light snowfall. The shoots of C. rusticana and C. japonica were stored under a simulated snow cover for 1 year. During the experimental period, about 20% of the leaves of C. japonica defoliated after 90-140 days of storage and more than 80% of the leaves browned within 360 days. The proliferation of fungi was observed on all shoots of C. japonica after 200 days. In contrast, the leaves of C. rusticana showed no visible changes throughout the experimental period. The decline in the rate of soluble carbohydrate content in C. rusticana was about one-sixth of that in C. japonica. The photosynthetic capacity (O-2 exchange rates at saturated light and CO2 at 20 degrees C) of C. japonica dropped to about half its initial value after 140 days, while that of the C. rusticana did not change even after 360 days. Under dark conditions, the stomata of C. rusticana were always closed through the experiment, but those of C. japonica were not completely closed after 90 days. The differences in stomata characteristics and the consumption rate of soluble carbohydrates under snow-covered conditions between the two Camellia species are important factors for determining their habitat segregation by snow depth.

Nitrogen-fixing (acetylene-reducing) activity of intact saplings of Alnus maximowiczii was measured under natural conditions in the subalpine zone of Mt Fuji. The nitrogen-fixing activity was detected from the middle of June when expansion of leaves had just begun to the end of October when the shedding of leaves was almost completed. Diurnal changes in the activity were almost parallel with those of ground temperature. The measured nitrogen-fixing activity was related to ground temperature and total leaf area. Using this relation, annual nitrogen fixation was estimated from the data of ground temperature and leaf area measured in the field. The amount of annual nitrogen fixation was almost the same as that of nitrogen used for annual growth. It was concluded that nitrogen fixation by nodules made a considerable contribution to the nitrogen economy in the saplings of A. maximowiczii.

Net photosynthesis and dark respiration (CO2 flux) of Antarctic mosses were measured at Langhovde, East Antarctica, from 9 to 17 January 1988. Moss blocks were taken from communities in the Yukidori Valley (69°14′30″S, 39°46′00″E) at Langhovde. Each block was composed of Ceratodon purpureus and Bryum pseudotriquetrum, or B. pseudotriquetrum. The upper part of the block was used to measure net photosynthesis and dark respiration. The net photosynthesis of each sample was measured in the field for one or three days with two infrared CO2 gas analyzers and an assimilation chamber. The relationships of net photosynthetic rate and dark respiration rate, to the water content of the sample, the intensity of solar radiation and the moss temperature were estimated from the field data. The maximum rate of net photosynthesis was about 4 μmol CO2 m-2s-1 at saturating radiation intensity and at optimum temperature, about 10°C. Environmental features of moss habitats in the Yukidori Valley are discussed in relation to these results. © 1990 Ecological Society of Japan.

The distributions of carbon, nitrogen and phosphorus in a moss community-soil system developed on a naked region in Rundvågskollane (69050'S, 39009'E), East Antarctica, were investigated in order to analyze the flow of matter in an Antarctic terrestrial ecosystem. 1) The moss community was formed from many moss blocks of different sizes and was composed of Bryum pseudotriquetrum (Hedw.) Gaertn., Meyer et Scherb., Ceratodon purpureus (Hedw.) Brid. and Grimmia lawiana J. H. Willis. The surface of the community was covered with cyanobacteria. 2) It was estimated that nitrogen fixed by cyanobacteria flowed from these organisms to the moss and that little nitrogen was transported within the moss body. 3) A large amount of phosphorus existed in the soil. The moss community had a high phosphorus content although the amount itself was relatively little due to the small phytomass. 4) It seems that absorption of phosphorus from soil is difficult for moss, because of the paucity of water necessary for the movement of phosphorus and the suppressed growth of moss due to the arid conditions. © 1986 Ecological Society of Japan.

As part of the studies of the nitrogen flows in the Antarctic terrestrial ecosystems, nitrogen-fixing activities of moss communities, algae and lichens, collected in various ice-free areas near Syowa Station, East Antarctica, were measured by the acetylene reduction method. Moss communities which grew on the sand at dry habitats had dense cover of cyanobacteria and showed high nitrogen-fixing activities, while those at wet habitats near streams showed weak or no activity. Folious colonies of Nostoc sp. Showed significant activities. Some colonies of Chlorophyceae Prasiola crispa had weak activities which were probably due to associating cyanobacteria. No activity was detected for lichen species tested. The results suggest that nitrogen fixation by cyanobacteria, especially those epiphytic on mosses, plays an important role in the nitrogen budgets of terrestrial ecosystems developed in dry ice-free areas near Syowa Station.

To estimate the primary production in an Antarctic region, photosynthetic activity of moss communities was measured with an infrared gas analyzer at Syowa Station, east Antarctica, in January 1982. At the same time, air and moss temperatures and light intensity were measured. The moss community was composed of Ceratodon purpureus, Pottia heimii and Bryum pseudotriquetrum. The relations between gross photosynthetic rate and temperature, and/or light intensity were discussed.

本研究であつかったフジアザミは富士山南西斜面にひろがる宝永火山の噴出物であるスコリア上に生育している。植物の環境適応を研究する場合、植物にかかる環境ストレスが単純であり、かつ実験的に解析できることが望ましい。その意味から水不足、貧栄養、強光、基質の移動にさらされている富士山のフジアザミは最適な種のひとつと考えられる。富士山南西斜面に高度を違えて３個の調査区を設けた。上（標高2030m、25m×　30m）、中（標高2000m、35m×　35m）、下（標高1970m、30m×　30m）であった。標高2030mはフジアザミの分布限界に近く、５月末まで凍土層が残っていた。フジアザミは単独ロゼットあるいは数個のロゼットが集まった株をつくっていて、中区、下区では単独ロゼットが多かった。上区のロゼット密度は中区、下区の約1/3であった。ロゼット直径あるいは最大葉の長さで成長を表した場合、７月中旬までの相対成長速度は上区で大きかった。これは遅い芽吹きと関係あるものと推測される。７月中旬以降の各区の相対成長速度はほとんどゼロであった。ロゼットの最大葉の平均長は各区で有意差は認められなかったが、いずれの区でも1株１ロゼットのものの長さは小さかった。これは１株１ロゼットの個体が大きなロゼットをつくるだけの貯蔵物質を前年に蓄えられなかったことを意味する。繁殖努力の結果である花数について調べた。上区では１株のロゼット数が２，３個の場合、１ロゼットのつける花数は４個前後と多かった。中区では１株が３から５個のロゼットからなる場合に、１ロゼットあたりの花数は3.5個前後であり、それよりもロゼット数が増加しても減少しても花数は減少した。下区では１ロセットあたりの花数は他区に比べ少なかった。これらのことから、生育高度の限界に近い場所では、100mの高度差が個体群の構成、繁殖努力に大きな影響を与えていることが推測された。研究成果の発表：

　日本の火山荒原における一次遷移では、多くの場合シモフリゴケ（蘚類）やハイイロキゴケ（地衣類）が先駆植物のひとつとして出現している。これらは維管束植物と異なり、体中の水分を失っても死なず、水分を吸収すると生活活性を復活させるという乾燥耐性をもっている。乾燥耐性のある植物がその場に有機物を供給することにより、後続の出現種の苗床をつくり、遷移の進行を促進していると考えられる。富士山の御殿場側斜面は1600mあたりが森林限界になっていて、それ以上の高さでは一次遷移の初期段階にある。この地域では林縁や小群落周囲にシモフリゴケコロニーが分布し、その外側にハイイロキゴケコロニーが散在する。シモフリゴケコロニー中に見られる実生の種類は裸地やハイイロキゴケコロニー中で見られる種と同じであったが、数は裸地やハイイロキゴケコロニー中に比べ少なかった。まわりに種子供給親植物が存在することから、シモフリゴケに発芽抑制効果があることが推測された。抑制効果因子としてコケのもつ化学物質による作用、コケコロニーの構造に基づく物理的因子、動物の摂食効果などが考えられる。化学的因子の検討として、シモフリゴケの水浸出液、ハイイロキゴケの水浸出液を用いて、いずれの場所にも存在するイタドリ、クサボタン、シモツケソウ、カリヤスモドキの発芽実験を行った。その結果、浸出液（化学物質）による影響は認められなかった。次いで、構造を壊さないシモフリゴケコロニーに上記４種の種子を蒔き、常時湿った状態での発芽率を調べた。その結果、対象とした濾紙や礫上との違いは認められなかった。生育地では頻繁な乾燥と湿潤が繰り返されるので、そのような実験が必要とされる。現地調査では、発芽した個体の多くは乾燥と思われる原因で死亡していくが、シモフリゴケコロニーにおける死亡率は他に比べ、有意に低かった。このことは維管束植物が林縁あるいはパッチ周辺のシモフリゴケを介して、その分布域をひろげていくことを示唆している。

富士山御殿場登山口は標高約1450mにあり，これから上部は火山礫からなる裸地がひろがる。裸地にはフジアザミが散在し，イタドリ，オンタデ，ミヤマヤナギなどからなるパッチが海洋にある島のように点在する。よって，この地域は一次遷移初期の段階にあると言える。1500mから1650mにあるパッチの周縁にはシモフリゴケやハイスナゴケ（蘚類）が生育し，さらにその外側にハイイロキゴケ（地衣）が礫に付着している。 この研究ではシモフリゴケ，ハイイロキゴケの遷移に及ぼす影響を調べるために二つの目的を設定した。 1. パッチのまわりのシモフリゴケとハイイロキゴケの分布を決定している要因は何か。シモフリゴケはパッチに近いことによって良好な水環境を獲得しているのか。 2. シモフリゴケ，ハイイロキゴケは地表の突起物として，種子の捕獲に効果的であろう。そして，地表面を直射日光から遮るために，強度の乾燥を防ぎ，種子の発芽に効果をもつのではないか。 1について。1986年にシモフリゴケとハイイロキゴケの群集内に50cm四方の区画10個を設定した。以後，毎年これらの区画を真上から写真に撮り，ふたつの群集の境界の変化を記録した。これらの写真をCD-ROMにおとし，パソコンを使った画像解析によって，境界の変化を追跡した。現在解析中である。 2について。蘚あるいは地衣群集の中に維管束植物の幼個体や実生が少数認められる。これらの数は強度の乾燥，高温にさらされる裸地よりも多くはない。このことから蘚，地衣が発芽阻害あるいは成長阻害の作用をもつことが予想される。蘚あるいは地衣の水侵出液を使って，現地で採取したイタドリ，ススキ，クサボタン，フジアザミなどの種子の発芽テストを行っている。また，1995年10月に採取した種子を現地の蘚あるいは地衣の群集内につくった実験内に約300粒ずつ蒔いた。これらの発芽を1996年に観測する予定である。