Soil Carbon Budget of Newly Established Tall-grass Prairies in Previously Cultivated Mollisols.

In addition to their aesthetic and environmental qualities, prairie restorations can act as C sinks and potentially offset rising atmospheric CO₂. Research during the past ten years has shown repeatedly the benefits of prairie restorations to sequester soil organic C (SOC). The change in SOC content alone, however, does not determine whether a site is a net sink or a source for CO₂. The objectives of this study were to determine the potential for SOC sequestration in newly established prairies on previously cultivated land, and whether restored prairies act as sink or source for CO₂. We calculated Net Ecosystem Production (NEP) using a C budgeting approach that assessed SOC content, soil surface CO₂-C emission, and above and below ground plant biomass. Preliminary findings indicate that (i) differences between sites for total C potential input were only seen in root biomass contributions, (ii) total soil surface CO₂-C emissions increased as prairie age increased, (iii) the prairie remnant site had the greatest soil C content while the most recently established prairie site had least soil C, and (iv) soil C content increased as prairie age increased, although at a decreasing rate. Calculations of NEP show that the youngest prairie restorations had the greatest potential for sequestering atmospheric CO₂.  These soils, however, reached a steady state of C content within a decade. These results suggest that early established prairies can act as sinks for CO₂.