Vegetation and ecology of ice-free areas of Northern Victoria Land, Antarctica

Abstract

At Birthday Ridge, a small ice free area in northern Victoria Land (70°48′S, 167°00′E), cryptogamic vegetation is mostly confined to gaps between granitc rocks. The sheltering effect on lichens and mosses was analyzed by continuous measurements of the microclimate at various levels between the rocks. Although warming by solar radiation was favourable for the existence of cryptogams, rocks strongly insolated were mostly devoid of lichens and mosses. Lichens in the soaked active state were heated to above air temperature but did not reach more than 10°C. The presence of lichens was dependent on the moisture conditions of the habitat. It was observed that snow, the only source of moisture, accumulated in summer only in deeper levels between rocks, and that the snow rapidly melted on contact with the lichens. After a snow shower,Usnea sulphurea gained 67% andUmbilicaria decussata 94% of their maximum water capacity. During one quarter of the time period of 7 days the lichens were soaked and therefore capable of carrying out photosynthesis. The lichens in soaked state had always less than optimum temperatures for net photosynthesis. The rock gaps at Birthday Ridge form oases, the only localities where moisture is provided, and temperature is high enough to enable growth of lichens and mosses.Bryum is also able to exist in the upper 3 cm of soil.