Effects of soil redistribution on landscape patterns of organic carbon
de Jong, E.
Soil organic carbon (SOC) is important to soil productivity and is an important part of the global carbon cycle. Soil redistribution within hummocky landscapes has also resulted in SOC redistribution. Soil loss estimates using 137Cs techniques and SOC levels were measured on a 7x7 grid with a 100m sampling interval on a quarter section approximately 30 km east of Saskatoon. The quarter section has been under crop-fallow management for at least 50 years. 137Cs and SOC were also measured on a 5x6 grid (25m sampling interval) at a nearby native site as a reference for soil loss calculations. At the cultivated site, 34 out of the 49 sampling points had experience net erosion since 137Cs fallout (1960), 13 out of the 49 points were depositional, while 137Cs levels at the remaining two points were close to reference levels. A net soil loss of 7 Mg ha-’ yr“ was calculated based on the mean 137Cs concentration of the entire quarter section. Soil loss displayed a landscape pattern with footslope elements being areas of deposition and shoulder, backslope and level elements being eroded. SOC patterns followed soil loss patterns with depositional areas (footslopes) having higher levels of SOC than eroded areas. SOC that is not mineralized is redistributed within the landscape and concentrated into a relatively small area. As as a result, SOC levels over most of the quarter have been decreased substantially, indicating that there may be potential to sequester carbon over a larger area if management practices are changed.
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