CARBON BALANCE LIMITS THE MICRODISTRIBUTION OF GRIMMIA-LAEVIGATA, A DESICCATION-TOLERANT PLANT

Despite their ability to tolerate long and severe drought and extreme temperature, desiccation-tolerant plants are typically excluded from the most xeric microhabitats. It was hypothesized that this is due to an inability of the plants to maintain a positive cumulative C balance during repeated cycles of wetting and drying under highly xeric conditions. To test this hypothesis, the response of net CO2 flux to light, temperature, plant water content and previous desiccation were measured in the desiccation-tolerant moss G. laevigata, the dominant green plant on exposed granitic boulders in the inland chaparral of San Diego County, California [USA]. Patterns of net CO2 flux and results from a simple model of C balance were consistent with the hypothesis.