XVI International Botanical Congess

This study evaluated the influence of microsite, seasonal, and genetic variation on carbon isotope discrimination (D) in peatmosses. Three species of Sphagnum that occupy hollow (S. recurvum), carpet (S. palustre), and hummock (S. tenerum) habitats were sampled for D and relative growth rates (RGR) during a growing season. Overall, D ranged from 19.0 to 27.1ë. This variation was unrelated to species (ANOVA, p=0.61). However, D varied seasonally (p<0.001), with lower discrimination in the spring (22.5ë), followed by summer (23.8ë) and winter (24.7ë). There was also significant microsite variability (p=0.015) which was eliminated when plants were grown in a common garden. In both spring and summer, microsite variability in D was inversely related to RGR (p<0.001). Thus, environmental, not genetic, causes control D in Sphagnum.