Predicting Land Use & Climate Change Impacts on Soil Organic Carbon at Regional Scales.

Anthropogenic and climatic factors may convert a land surface into a source or sink of atmospheric CO_2. This presentation will provide several examples of using environmental variables, geospatial, and process-based modeling approaches to predict the landuse and climate change impacts on soil organic carbon (SOC) stocks at regional scales. The first study uses spatially varying estimates of SOC stocks to modify the Tier 2 IPCC carbon inventory approach to predict the impact of land use change on SOC pools. This approach showed the spatial distribution of SOC sequestration rates upon adoption of no-till and residue retention on the croplands of 7 states of the Midwest US. The second study combines process-based and geospatial modeling to predict the rainfed biomass productivity across the croplands of US. We predicted that cultivating miscanthus could result in SOC sequestration at the rate of 0.16–0.82 Mg C ha^-1 yr ^-1 across the US croplands primarily due to due to cessation of tillage and increased biomass and root carbon input into the soil system. Assuming temperature changes from the A1B Intergovernmental Panel on Climate Change emissions scenario, the final study predicts that the average 2100 Alaska active-layer thickness could deepen by 11 cm, resulting in a thawing of 13 Pg C currently in the permafrost layer of the soil profile. Our results indicated that the equilibrium SOC loss associated with this warming would be highest under continuous permafrost, followed by discontinuous, isolated, and sporadic permafrost areas. Our high-resolution predictions of SOC sequestration rates, biomass productivity, and movement of SOC stocks from permafrost to active-layer demonstrate the impacts of land use and climate change on soil carbon pool at management scales, which is critical for policy implications.