| Abstract
| - The thallus nitrogen (N) concentration of two dominant macrolichens of continental Antarctica (Usnea sphacelata and Umbilicaria decussata) was estimated each month for 1 year on a low rounded knoll on Clark Peninsula, Windmill Islands, Wilkes Land, Antarctica. Thallus N was significantly higher in Umbilicaria decussata than in Usnea sphacelata and varied according to site. During the winter months, when the lichens were metabolically inactive, thalli gradually accumulated N. At the onset of warmer conditions, thallus N content fell dramatically in both species, with the timing of the decline being related to microclimatic conditions. The strongly seasonal pattern of metabolic activity in these species is reflected in their nitrogen relations. Copyright 2000 Annals of Botany Company
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