Nitrogen cycling in an Antarctic ecosystem. 1. Biological nitrogen fixation in the vicinity of Syowa Station

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

COMPARISON OF NET PHOTOSYNTHESIS AND DARK RESPIRATION OF ANTARCTIC MOSSES MEASURED IN THE ANTARCTIC AND IN JAPAN (Eleventh Symposium on Polar Biology)

Net photosynthesis and dark respiration (CO_2 uptake) of Antarctic mosses were measured to investigate the effects of transportation in a frozen condition from the Antarctic to Japan. Moss blocks were collected from some Ceratodon purpureus communities in different habitats at the Yukidori Valley (69°14\u2730"S, 39°46\u2700"E) in Langhovde, East Antarctica, on January 16, 1988. The CO_2 uptake activities of the surface layer of the moss blocks were measured in the laboratory on the research ship SHIRASE with two infrared CO_2 gas analyzers and an assimilation chamber within a month after the collection. The relationships of net photosynthesis and dark respiration to water content, illumination intensity, and temperature were determined. After the measuring, the samples were frozen at-20℃ and transported to Japan. From May to August of 1988, each sample was defrosted in the laboratory of Waseda University and the same measurements were undertaken with the same equipment that had been used in the Antarctic. There was little difference between the optimum water content for net photosynthesis measured in the Antarctic and that measured in Japan. In some samples, the net photosynthetic rate at saturated illumination intensity and the dark respiration rate measured in the Antarctic differed from those measured in Japan. A little difference was recognized in the optimum temperature for net photosynthesis in some samples. It was concluded that storage in a frozen condition for a long period produced some undesirable effects on the photosynthetic and respiration activities of some Antarctic mosses

Field measurement of the photosynthesis of mosses with a portable CO2 porometer at Langhovde, East Antarctica

The photosynthesis of mosses was measured with a portable CO_2 porometer (modified Koito KIP9000) at Langhovde, East Antarctica in January 1988. An assimilation chamber, 10cm×10cm×6.5cm, which was made for this measurement, was used in collecting data for 9h in Sample 1 and 11h in Sample 2. Samples were mixed communities of Bryum pseudotriquetrum and Ceratodon purpureus (Sample 1) and C. purpureus (Sample 2) collected in the Yukidori Valley, Langhovde. Both samples had high respiration rates. Net photosynthetic rates were negative at low irradiance and changed to positive rates at high irradiance. Maximum photosynthetic rates were higher than those of other mosses measured with other equipment (analyzer : Horiba VIA-300,assimilation chamber : Koito MC-A3W) in the Yukidori Valley in the same period (Y. INO : Ecol. Res., 5,195,1990

ヒガシ ナンキョク ラングホブデ ニ オケル センルイ ノ ジュン セイサン セイ ノ スイテイ

1988年1月にラングホブデの雪鳥沢で採取したコケ塊(Grimmia lawiana, Bryum pseudotriquetrumおよびB. pseudotriquetrumとCeratodon purpureusの混生塊)の光合成, 呼吸速度を現地で2台の赤外線CO_2分析計と温度制御付き同化箱を使用して測定した。同時に光強度と蘚表層の温度を記録した。KAPPEN et al. (Polar Biol., 9,415,1988)の用いた重回帰式に基づいて, 純光合成速度とコケ温度・光強度との関係式をつくった。この重回帰式とOHTANI et al. (JARE Data Rep., 152,216p., 1990)によって測定された雪鳥沢の微気象データを使って, 雪鳥沢に生育するコケ塊の1988年1月から1989年1月までの年間の有機物生産量を計算し, 230g~296gdw・m^の値を得た。この値はDAVIS (Ecol. Monogr., 51,125,1981)によるシグニー島の群落で報告された純生産量の下限値に近い。Field measurements of net photosynthesis and dark respiration (CO_2 exchange) of moss colonies were carried out at Langhovde, East Antarctica from 9 to 17 January 1988. Each colony growing at the Yukidori Valley, Langhovde was composed of Grimmia lawiana, Bryum pseudotriquetrum or the mixture of Ceratodon purpureus and B. pseudotriquetrum. Microclimatic data (photosynthetic photon flux density and moss temperature) in the assimilation chamber were recorded at the same time. A simple model to estimate the net photosynthetic rate and dark respiration rate on the basis of the microclimatic data was developed on KAPPEN\u27S model (KAPPEN et al. : Polar Biol., 9,415 1988). Net primary production of these moss colonies was calculated with the microclimatic data recorded separately at the Yukidori Valley from January 1988 to January 1989 (OHTANI et al. : JARE Data Rep., 152,1990). The estimated net production rates of moss colonies growing in the upper reaches of the Yukidori Valley ranged from 8.8 to 11.3 mol CO_2m^・y^, or from 230 to 296 gdw m^・y^

Estimation of primary production in moss community on East Ongul Island, Antarctica

This investigation is a part of the works to make clear the function of an Antarctic ecosystem. The photosynthetic activity and the respiration of moss community sampled on East Ongul Island, East Antarctica, were measured in January 1982 at Syowa Station with an infrared gas analyzer. Three species of mosses, Ceratodon purpureus, Pottia heimii and Bryum pseudotriquetrum were included in the community. The surface of all moss communities was covered with blue-green algae and lichens, and the growth condition of moss communities looked very poor. Positive correlations were observed between the gross photosynthetic rate or respiration rate and the R-T index, which is the product of daily radiation amount and daily mean air temperature. The net production rates in summer, from November to March, were estimated by the use of meteorological data for 17 years. Mean net production rate of moss community was 3.7g dw/m^2・yr, and the maximum and the minimum rates were 12.8 and -16.2g dw/m^2・yr, respectively

ナンキョク ヒガシ オングル トウ コケ グンラク ノ カコ 17 ネンカン ノ イチジ セイサンリョウ ノ スイテイ

南極生態系の機構解明のため, コケ群落の一次生産量の推定を試みた。1982年1月に昭和基地で東オングル島産のコケ群落の光合成, 呼吸速度を赤外線ガス分析計を使って同化箱法で測定した。ヤノウエノアカゴケ(Ceratodon purpureus), キョクチセンボンゴケ(Pottia heimii), オオハリガネゴケ(Bryum pseudotriquetrum)の混生群落で, それらの表面はらん藻と地衣におおわれていた。総光合成速度と呼吸速度は, それぞれ日射量と気温との積(R-T index)に二次式で近似できた。1959年11月から1981年1月まで, 基地閉鎖期間を除く17回の夏(11月から3月)の昭和基地の気象資料を用いて, コケ群落の総生産量と呼吸消費量を計算した。両者の差を純生産量とすると, 平均純生産量は3.7g dw/m^2・yr, 最大値, 最小値は12.8,-16.2g dw/m^2・yrであった。This investigation is a part of the works to make clear the function of an Antarctic ecosystem. The photosynthetic activity and the respiration of moss community sampled on East Ongul Island, East Antarctica, were measured in January 1982 at Syowa Station with an infrared gas analyzer. Three species of mosses, Ceratodon purpureus, Pottia heimii and Bryum pseudotriquetrum were included in the community. The surface of all moss communities was covered with blue-green algae and lichens, and the growth condition of moss communities looked very poor. Positive correlations were observed between the gross photosynthetic rate or respiration rate and the R-T index, which is the product of daily radiation amount and daily mean air temperature. The net production rates in summer, from November to March, were estimated by the use of meteorological data for 17 years. Mean net production rate of moss community was 3.7g dw/m^2・yr, and the maximum and the minimum rates were 12.8 and -16.2g dw/m^2・yr, respectively