Roser Matamala1, Elizabeth Smith2, Julie D. Jastrow1 R. Michael Miller1 and Miquel A. Gonzalez-Meler2

1 Environmental Research Division, ANL, Argonne IL-60439. 2 Dept. Biological Sciences, UIC, Chicago, IL-60607

Atmospheric CO₂ concentration has substantially increased since pre-industrial levels and is expected to reach near double current levels by the end of this century. Terrestrial ecosystems are an important sink of excess atmospheric C, motivating C sequestration studies in soils of natural and managed ecosystems. Natural ecosystem transformation to agriculture converts biomass to CO₂. Cultivation of soils also releases a large fraction of stored soil organic matter (SOM), adding large amounts of CO₂ to the atmosphere (Wilson, 1978). Therefore, restoration of soil carbon to pre-cultivation levels in abandoned crop fields represents a target for atmospheric carbon sequestration.

The aim of this study is to gain information on ecosystem processes that determine carbon cycling in restored croplands into tall grass prairie. Preliminary results suggest faster C3 carbon cycling as restored prairies become older than the C4 carbon. From these studies we hope to be able to quantify the role of ecosystem respiration (Re) in determining the amount of atmospheric C that can be retained in restored ecosystems, and to understand the mechanisms involved in soil carbon retention using nondestructive stable isotope methods.