PARENT SESSION
Oral Session #76: Ecosystem Ecology: Larger scale processes, geomorphology, soils.
Presiding: W. Straw
Thursday, August 8. 9:00 AM to 11:30 AM. Gila Meeting Room, TCC.

Evidence of different C3 and C4 carbon turnover rates in soils from a tallgrass prairie chronosequence.

Smith, Elizabeth^*,1, Matamala, Roser², Jastrow, Julie², Miller, R.², Gonzalez-Meler, Miquel¹, ¹ University of Illinois at Chicago, Chicago, Illinois² Argonne National Laboratory, Argonne, Illinois

ABSTRACT- Restoration of agricultural fields back to native vegetation has the potential to serve as a sink for atmospheric carbon and therefore mitigate the effects of elevated CO₂. At FermiLab (Batavia, IL), tallgrass prairies have been sequentially planted since the mid 1970s establishing a chronosequence in which soil carbon dynamics can be studied. Plant communities consist of forbs, shrubs, and C3 and C4 grasses, and the relative dominance of vegetation type depends on time of the season and restoration age. The different isotopic 13C signatures of C3 and C4 plant tissues are used to determine the C3 and C4 origin of belowground carbon dynamics. We measured soil respiration, root biomass, and soil organic matter (SOM) for five sites within the chronosequence at ages 3, 8, 15, and 23 years since restoration and results were compared to those from a remnant prairie (not cultivated for at least 500 years). Root biomass and soil respiration increased throughout the chronosequence coinciding with increased plant cover and C4 dominance in older plots. Throughout the chronosequence, the 13C of soil respired CO₂ had a larger proportion of C3 than C4 carbon, whereas the 13C of bulk SOM had a larger proportion of C4 carbon. Our results suggest that in soils of restored tallgrass prairies, C3 carbon cycles faster than C4 carbon. Implications for C sequestration are discussed.

KEY WORDS: Soil Carbon dynamics, Stable isotopes, C3 and C4 carbon