Chlorophyll distribution within the carpets, CO z gas exchange under controlled conditions, and heat resistance of the snowbed bryophyte Antheliajuratzkana (Limpr.) Trev. were investigated. Also the gas-exchange parameters of the co-occurring Polytrichum sexangulare Floercke were assessed. Only the uppermost 4 mm layer of Anthelia carpets contains sufficient pigments for photosynthesis. At light saturation and optimal temperatures (6-11 °C) the maximum rates of CO 2 uptake are 0.7 mg CO 2 g-Xdw h -1 in Anthelia and 1.5 mg CO 2 g ldw h -1 in Polytrichum. Gas exchange reaches light saturation at about 300 ~tE m-2s-1 in both species. At + 2 °C the light compensation point is reached at ca. 10 ~tE m-2s-1 and increases significantly with increasing temperature. The lower temperature compensation point is reached at -4 °C in A n thelia and does not drop much below -5 °C in Polytrichum. Anthelia cannot sustain net photosynthesis beyond 30°C and Polytrichum not beyond 32°C.
Nine month storage under dark, cold and wet conditions does not affect the photosynthetic capability of A nthelia.
As a response, however, the net photosynthesis rate is depressed due to an increase of the respiration rates.
Polytrichum sexangulare did not tolerate the storage so well. The heat resistance limit of Anthelia is low (39 °C).