Photosynthesis and Respiration of Alpine Lichens

Photosynthetic and respiratory rates were studied in Cetraria islandica, C. nivalis, and Cladonia rangiferina in the alpine zone of Mt. Washington, New Hampshire. Measurements were made in the field using an infrared gas analyzer; light, temperature, and thallus water content were varied. In all species, considerable reduction in photosynthesis and respiration occurred with drying, more rapidly in photosynthesis than respiration. Optimal photosynthetic rates in all 3 species occurred at 15–20 C with light levels of 1,600 ft‐c. Light compensation points ranged from 200 to 350 ft‐c. Optimal respiratory rates were attained at 15 C in the 2 species of Cetraria and at 20 C in Cladonia. The data indicate that these wide‐ranging, arctic‐alpine and arctic‐temperate lichens on Mt. Washington are quite well adapted to a moist, foggy environment with cool temperatures and low light levels, conditions which predominate in summer.