Geospatial Modeling of Soil C Redistribution In Eroded Agricultural Landscapes.

Geospatial modeling of soil C redistribution in eroded agricultural landscapes D. Kroetsch, A.J. VandenBygaart, R. Burcher This study is part of a larger investigation to characterize and determine the quality, quantity, distribution and the relative and absolute age of buried soil organic matter (SOM) under varying climatic and management conditions at various sites in Canada. The first part of the study characterized and reconstructed the history of SOC redistribution and burial over the past 60 years at five locations across Canada. Soil pits were excavated at multiple landscape positions over hillslope catenae and into adjacent riparian areas if present. Soil was sampled in 5 cm increments to beyond the depth of the A horizon. Buried profiles varied in thickness from 45 cm to over 90 cm. The second component of this study included measurements every 2 m of the ‘A’ horizon thickness along 10 m transects established parallel, perpendicular and diagonally (45o and 325o) upslope and downslope of each soil pit along the slope. Comparison of SOC stocks to the thickness of the A horizons from the sample pits has yielded very high R2 values. Based on the A horizon measurements the SOC were estimated and interpolated for all transect points and further to all grid cells. Utilizing detailed Digital Elevation Model data (LiDAR for some sites) the landscape at each site was segmented into discrete landscape segments and the SOC stocks were calculated from each site along the slope to the landscape segment. The estimates of the amount of buried carbon and SOC stocks for each landscape segment and for all similar landscapes within the soil polygon containing the study site are presented for one of the study areas.