ИСТИНА

Field studies were conducted in February and March 2008 in the vicinity of the Russian station "Bellingshausen" (62o12' S, 58o57'40'' W, 22 - 48 m asl) on the Fildes Peninsula (King George Island, West Antarctica). CO2 flows were measured with a portable infrared gas analyzer «Gas-Tech» (Japan) at a resolution of 25 ppm, in the cylindrical chambers 10 cm in diameter and 20 cm in height. Measurements were carried out in the most common types of plant communities: (a)separate spots of fruticose lichens on dry gravelly hills and stones (Hinantormia lugubris - Usnea aurantiaco-atra with moss Andreaea gainii Card.), (b) continuous moss mats and cushions in wet depressions (Bryum orbiculatifolium, Warnstorfia sarmentosa, Sanionia uncinata, S. georgicouncinata,Brachythecium austrosalebrosum), (c) algo-bacterial mats and (d) community with the dominance of the grass Deschampsia antarctica with mosses S. georgico-uncinata, Bryum pseudotriquetrum, Polytrichastrum alpinum, P. piliferum. Continuous permafrost was detected at a depth of 35 to 70 cm. Fluxes of CO2 emissions were recorded in all habitats and ranged from 0.58 to 134 mg C m-2 h-1. Gross primary production (GPP) flow was not detected at a vegetation-free ground. In habitats with pronounced vegetation the GPP values were higher than those of ecosystem breathing (EB) during a daytime – the sequestration of atmospheric C took place. The greatest values of GPP and EB were detected for tussock communities of Deschampsia antarctica. For comparison, in the Antarctic Dry valleys, in extreme conditions, close to Mars, the CO2 fluxes at the surface soils fluctuated from -4.3 to +6.5 mg m-2 h-1 (Parsons et al., 2004). The obtained results give the reason to conclude that the local plant-bacterial communities have a strong trend towards an increase in the EB response even to a small increase in temperature. It can be related to an adaptive strategy for species under conditions of extreme deficit of a heat. GPP and EB of moss communities are 4 times lower than that of communities of Deschampsia antarctica. However, mosses predominate among phytocenoses area, accounting for no less than 0.5% of the area of the island, and about 6% of its ice-free territory. These communities also exhibit significant sequestration of carbon (0.4 g C m-2 day-1). In spite of the very high (for cryogenic communities) values of GPP and EB during the growing season the Fildes Peninsula is generally weak, but significant source of C- CO2 to the atmosphere. This is due to the fact that a large part (95%) of an area is occupied by a barren ground, which contributes only in the EB. This area average value is about 0.01 g C m-2 day-1.