Population Level Variation in Growth of the C3 Salt Marsh Sedge, Schoenoplectus americanus, and Its Potential Effects on Ecosystem Function

As environments change, evolution may modify plant growth, and thus influence ecosystem processes. Tidal salt marshes are productive ecosystems dominated by only a few plant species, including the C3 sedge, Schoenoplectus americanus. Although S. americanus marshes have been studied extensively, we know little about how evolutionary processes might affect marsh dynamics. We examined the effects of CO2, salinity, and competition on the growth of S. americanus. Growth characteristics were significantly influenced by CO2, salinity levels, and the initial planting mass of each vegetatively cloned individual. Competition had no effect on growth. Stem height, stem density and tissue carbon:nitrogen were significantly different between populations. Differences in growth among populations and genotypes resulted in differences in soil organic matter loss when examined in a heuristic model. Evolutionary variation could affect ecosystem processes like decomposition and marsh soil accretion as genotypes shift in abundance and distribution. This should be examined in other ecosystems.