Comparative Patterns of Net Photosynthesis in an Assemblage of Mosses With Contrasting Microdistributions

Effects of plant water content, previous desiccation, photon flux density, and temperature on rate of net photosynthesis were measured in the common species in the assemblage of desiccationtolerant mosses that dominates the flora on granitic boulders at a semiarid site in the inland chaparral of San Diego County, California. Species differed significantly in their responses to water content, desiccation, and light. Species previously found to occur in microsites of lower water availability attained maximum net photosynthesis at lower water contents and showed greater ability to recover from prolonged desiccation. Species found in microsites of lower light availability had higher rates of net photosynthesis at low photon flux density. Results suggest that differences in potential rates of net photosynthesis partly determine relative ability of these species to colonize xeric or dark microsites, but that other factors also determine microdistribution.