EVALUATING THE EFFECTS OF TOPOGRAPHIC POSITION ON SOIL CARBON CONTENT IN PRAIRIE POTHOLE AGRICULTURAL LANDSCAPES

Prairie potholes are depressional wetlands found throughout the northern Great Plains of the United States and Canada. These wetlands have potential to store large quantities of carbon, but many have been altered for agriculture. Conservation practices (e.g., no-till and cover crops) and programs (e.g., Conservation Reserve Program (CRP)) have focused on enhancing carbon storage in soils and aid in mitigating climate change. However, the effectiveness of these approaches across landscape positions are not well known, especially within the prairie pothole region (PPR).

This study evaluates the effects that topographic position has on soil carbon content in agricultural landscapes of the PPR. Methods include: 1) collecting 30-cm deep soil cores along toposequences from native grassland, CRP, and conservation and conventional agriculture sites; 2) quantifying total carbon content; 3) characterizing soil bulk density and particle size; and 4) evaluating relationships among total carbon, bulk density, and particle size by topographic position and land use.

Total carbon, clay, and silt content increased and bulk density and sand content decreased progressing from uplands to potholes, which follows standard hillslope soil development models, regardless of land use. Total carbon based on land use was complicated and more strongly influenced by other factors such as particle size, land use history, and pothole morphology and hydrology. This research highlights the importance of topographic position on soil carbon sequestration and storage, an often-overlooked variable, when implementing conservation and restoration practices in agricultural landscapes. Prairie potholes are carbon “hotspots” that can be a major source or sink of atmospheric carbon dioxide, while uplands are more degraded and are potential areas for restoration.