Thallus Temperature Research Articles

Net Photosynthesis and Respiration of Cladonia ecmocyna (Ach.) Nyl. from the Rocky Mountains and Comparison with Three Eastern Alpine Lichens

The dependence of net photosynthesis and dark respira- tion on irradiance, thallus temperature and hydration was examined in a western United States, subalpine population of Cladonia ecmocyna from near Loveland Pass, Colorado. Comparisons were made with eastern United States alpine populations of Cetraria nivalis, C. islandica, and Cladonia rangiferina from Mt. Washington, New Hampshire. Cladonia ecmocyna has: (1) lower optimum temperature for net photo- synthesis, (2) greater efficiency of utilization of high irradiance levels and (3) maximum photosynthesis at 70% relative water content, com- pared to maximal rates at or near full hydration, for the eastern popula- tions. These ecophysiological adaptations are related to environmental differences between eastern and western United States alpine and sub-