Soil carbon dynamics and carbon budget of newly reconstructed tall-grass prairies in south central Iowa

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Received for publication February 16, 2009. In addition to their aesthetic and environmental qualities, reconstructed prairies can act as C sinks and potentially offset rising atmospheric CO2 concentration. The objective of this study was to quantify C budget components of newly established prairies on previously cultivated land. Net ecosystem production (NEP) was estimated using a C budgeting approach that assessed SOC content, soil surface CO2–C emission, and above- and belowground plant biomass. Study was conducted in southern Iowa, in 2005 to 2007. Results show that differences between sites for potential total C input were primarily due to root biomass contributions, which ranged from 0.8 to 5.4 Mg C ha–1. Average potential aboveground biomass C input was 2.7 Mg C ha–1 in 2006 and 5.5 Mg C ha–1 in 2007. Total soil CO2–C emissions from heterotrophic respiration increased as prairie age increased from 2.9 to 4.0 Mg C ha–1 and 3.1 to 4.7 Mg C ha–1 in 2006 and 2007, respectively. Determination of NEP showed that the 1998 and 2003 reconstructed prairie sites had the greatest potential for soil C sequestration at 4.1 and 4.4 Mg C ha–1. Increases in SOC content were only observed in the youngest established prairie site (2003) and the no-till site in 2003 at 2.1 and 2.6 Mg C ha–1 yr–1, respectively. Declines of SOC sequestration rates occurred when potential C equilibrium was reached (Rh = NPP) within 10 yr since prairie establishment.

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