Carbon isotope studies are commonly used to provide a proxy for past vegetation communities and for evaluating environmental change. Original studies suggested carbon isotope ratios of soil organic matter (SOM) faithfully preserved the isotopic composition of standing vegetation with little or no modification in the pedogenic and shallow burial environment. Recent studies of modern soils and laboratory experiments suggest that this may not necessarily be the case and that degradation of SOM in the burial environment may alter the original C-isotope ratio of bulk SOM. A first step in addressing the issue is to begin to understand the transformations of SOM in the burial environment; of particular interest in this study are transformations involving microbial residues. Sedimentary sequences with stacked buried soils afford the opportunity to study the changes that may occur through time and are especially useful if numerical ages and other environmental proxies are present.
The objective of this study is to thoroughly investigate the composition and quantity of organic matter that has been preserved in the surface and buried soils at the Claussen site, using Fourier Transform Infrared Spectroscopy (FTIR), which provides an estimate for the abundance of organic matter components preserved in each paleosol's SOM. We can trace the fate of bioavailable OM and determine the magnitude of preferential decay of SOM with time by first comparing the composition of bulk SOM to the composition of physically protected carbon, located in soil microaggregates (Christensen, 1992) of the stacked buried soils. The results of this project suggest differences in the composition of paleosol and surface soil SOM that could impact paleovegetation interpretations derived from δ13C values.