HR: 10:50h
AN: B22C-03    [Abstracts]
TI: Hydrologic and Vegetative Effects on the Rate of Soil Carbon Accumulation in Restored Midwestern Grasslands
AU: * O'Brien, S L
EM: sobrie1@uic.edu
AF: Biological Sciences, University of Illinois at Chicago, 845 W. Taylor St M/C 066, Chicago, IL 60607, United States
AU: * O'Brien, S L
EM: sobrie1@uic.edu
AF: Biosciences Division, Argonne National Laboratory, 9700 S. Cass Ave, Argonne, IL 60439, United States
AU: Jastrow, J D
EM: jdjastrow@anl.gov
AF: Biosciences Division, Argonne National Laboratory, 9700 S. Cass Ave, Argonne, IL 60439, United States
AU: Gonzalez-Meler, M A
EM: mmeler@uic.edu
AF: Biological Sciences, University of Illinois at Chicago, 845 W. Taylor St M/C 066, Chicago, IL 60607, United States
AU: Grimley, D A
EM: grimley@isgs.uiuc.edu
AF: Illinois State Geological Survey, 615 E. Peabody Dr., Champaign, IL 61801, United States
AB: Revitalization of degraded landscapes may provide sinks for increasing atmospheric [CO2], especially where C inputs resulting from substantial belowground productivity are coupled with soil conditions that promote organic matter stabilization. For three decades, a chronosequence of restored prairies in northeastern Illinois has accumulated soil organic C, but the mechanisms controlling the rate and potential C accrual of the system are unknown. We used a repeated measures approach within the chronosequence to explore controls on C accumulation. The rate of soil C accrual was determined for each of four restored prairies and a field of Bromus inermis (a non-native C3 grass), which together represent a range of ages and drainage conditions. Soils were sampled over a 19-y interval at permanent stations in each plot. Stable isotope signatures of the soil C were used to determine accrual rates for C3- and C4-sourced C. Fifteen to 30 y after planting, prairies on poorly drained soils had accumulated more C in the surface 10 cm (6.8-9.4 Mg C ha-1) than better drained prairies (5.2-6.1 Mg C ha-1). Although the better drained B. inermis field apparently accrued C during the initial decade following establishment, it was at steady state with respect to soil C during the 19-y sampling interval. In the 10-20 cm layer, soil C declined initially but recovered with time, resulting in a total accumulation for the surface 20 cm of 5-7 Mg C ha-1 over the 19-y sampling interval. In the prairies, carbon derived from C4 plants appeared to contribute more to total soil C accumulation than C3-derived C. Variation in the rate of soil C accumulation was related to both soil magnetic susceptibility (a proxy for long-term drainage conditions) and proportion of C4-derived C. We hypothesize that the current absence of soil C accrual in the B. inermis field is due to plant community (lower amount and shorter duration of higher quality inputs) rather than moisture conditions. The faster rate of C accrual in poorly drained soils likely results from some long-term combination of reduced C mineralization during seasonally flooded periods and better plant growth during periods of moisture limitation.
DE: 0428 Carbon cycling (4806)
DE: 0481 Restoration
DE: 0486 Soils/pedology (1865)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting