MICROCLIMATIC CONDITIONS, MELTWATER MOISTENING, AND THE DISTRIBUTIONAL PATTERN OF BUELLIA-FRIGIDA ON ROCK IN A SOUTHERN CONTINENTAL ANTARCTIC HABITAT

The importance of snowmelt as a source of moisture for the crustose li chen Buellia frigida in the early austral summer was investigated at C ape Geology, Granite Harbour, southern Victoria Land (77 degrees 01'S, 162 degrees 32'E). Surface and air temperatures and irradiance were r ecorded on the surface of a slightly inclined granite boulder for 5 we eks. Observations were made of lichen thallus hydration during a 5-day period. The results confirmed the strong warming effect of high irrad iance; the rock surface and hydrated lichen were up to 19K above air t emperature and, overall, the rock surface averaged 5.5K warmer. Theref ore water condensation on the rock surface (dew or hoarfrost) was not possible during that period. Thalli were moistened by meltwater from b oth a small area of snow pack and from occasional snowfalls. The distr ibution of lichen thalli on the rock surface can be explained by the f requency and duration of meltwater moistening. Despite the very high i rradiance whilst moist, the lichens seem well adapted to the combinati on of hydration, low temperatures and strong light.