How Can We Manage North Central Grasslands to Build SOC?.

Building SOC in temperate grasslands has been touted as part of the solution for stabilizing climate, improving water quality, and increasing farmer profitability. But, research shows where and when grasslands actually accumulate SOC is uncertain. Even more equivocal is whether SOC accumulation leads to stabilization of C such that it can actually be considered “sequestered”. Long-term research on Mollisols suggests that grasslands accumulate labile particulate organic matter, which may be mineralized if soil is disturbed or incorporated into organo-mineral complexes via microbial activity. We will present results from several experiments focused on understanding how management of grassland agroecosystems has led to gains or losses of SOC. A synthesis of these results indicates particular plant traits that seem to be important drivers of SOC change. If these traits are managed judiciously, cool-season pastures have the potential to maintain or accrue C, while warm-season grass stands are more likely to accumulate SOC because of deeper rooting systems. However, even warm-season stands can be net sources of C to the atmosphere depending on edaphic properties, climate, and management approaches. For example, landscape-scale heterogeneity in soil moisture and SOC concentrations can shift the annual ecosystem carbon balance between positive and negative. Hence, understanding how to build SOC requires a better understanding of plant traits likely to build SOC and decision support tools that integrate many environmental and management data layers to find “potential C sequestration hotspots” in complex landscape mosaics.