Print PageFinding long-term C storage in terrestrial ecosystems may be a key component of climate stabilization as greenhouse gases continue to accumulate in the atmosphere. Interest in restoring prairie and harvesting it as a bioenergy feedstock is growing because perennial polycultures should improve ecosystem services in agricultural landscapes. However, the capacity for restored prairies to accumulate C is uncertain. We conducted an experiment in two restored prairies (10- and 17-years-old) in southern Wisconsin to assess their carbon sequestration potential under naturally occurring gradients of C4 to C3 grass ratios. We quantified above- and below-ground net primary production and soil respiration for two years (30 plots each year) and used estimates of fine root turnover and the ratio of autotrophic to heterotrophic respiration to calculate annual net ecosystem production (NEP).
Results/Conclusions
Net ecosystem production was highly variable in magnitude and sign and driven by NPP. Site differences related to soil traits was the strongest predictor of NEP, but by analyzing sites separately, we determined that aboveground variables exerted the most influence on NPP at the more productive site while belowground variables were most important on the lower productivity site. Some weak evidence for the importance of species composition, in particular the abundance of the C4 grass, big bluestem, was observed. These results indicate that the capacity for C sequestration in restored prairie is highly variable and that their source-sink determination will be strongly influenced by agronomic intensification such as harvest, fertilization, and manipulation of the plant community.
