Carbon Isotopic Compositions of Plants and Sediments of Tide Marshes in the San Francisco Estuary

Abstract

Wetland sediments surrounding the San Francisco Bay Estuary contain a rich history of environmental change which can aid predictions of potential responses to future environmental change. Here we present results of a study of the stable carbon isotopic composition of modern surface sediments as they relate to the existing plant cover. The results indicate a strong correlation between the modern plant cover and the δ¹³C value of underlying surface sediments (RMS = 1.331). Reasons for residual differences between predicted and observed isotopic values of the surface soils include intraspecific changes in δ¹³C values of C3 plants, contributions to the carbon pool by algae, and effects of diagenesis on δ¹³C value of plant matter. The goal of this research is to provide a basis for interpreting isotopic data obtained from sediment cores in terms of changes in vegetation resulting from changes in environmental conditions.