Soil Type and Management Effects on Organic Carbon Stocks and Soil Structure Quality in North Germany

Improvement of carbon sequestration in soils for a more sustainable environment and prevention of climate change require not only knowledge about soil organic carbon (SOC) stocks, but also about interactions between land use and total amount and distribution of carbon. In North Germany (state: Schleswig-Holstein) about 925 soil profiles in the four dominant geological regions [Weichselian glacial region, the sandy outwash region (Lower ―Geest, the Saalian glacial region (Higher ―Geest), and the marshland with alluvial deposits] were sampled down to at least the 90 cm depth. Carbon content, pH, bulk density, and grain size distribution were analyzed for the major characteristic soil horizons. The four dominant geological regions possess different SOC stocks as well as SOC contents. The total amount of SOC stored within the representative soil profiles down to the 90 cm depth was analyzed for three depths: 0 – 30, 30 – 60, 60 – 90 cm; for the total area of Schleswig Holstein (15.369 km²), they summed to 244 Mt. SOC stocks, however, differed depending on the land use management system and clay content. Arable soils were most sensitive to soil deformation and the higher the clay content the less rigid they were, if the SOC to clay ratio were used as an index for structural quality. Grassland topsoils showed the highest SOC stocks and a mediate structural quality. The latter was highest for forest soils, which, however, had a higher SOC content but, at the same time, a less fertile SOC composition (litter with high C: N ratio). Further research on the carbon composition (labile, active, intermediate, or passive pools) would help to get a better insight into the role of SOC on soil strength and soil functions.