The impact of closed depressions on soil organic carbon storage in eroded loess landscapes of E Poland

Soil erosion is an important problem in the loess landscapes of Europe, resulting in a lowering of soil quality and landscape changes. As a result of soil erosion, SOC is redistributed and stored in SOC pools within the landscape. Understanding the SOC dynamics is important because changes in the SOC stocks may have large impacts on global climate change. Closed depressions (CDs) in loess landscapes collect colluvial sediments resulting from soil erosion and constitute sediment stores enabling the calculation of soil erosion phases and rates. CDs are also SOC pools enabling assessing of SOC erosion and storage in loess landscapes over long periods. Colluvial sediments and fossil soils, infilling five representative CDs in the Polish loess areas used for agriculture during several millennia, were documented. The mean SOC content in CDs were calculated, the area of CDs at the regional scale were mapped. Between 11.66 and 31.78 Mg of SOC are stored in each CD. The SOC within CDs represents a significant SOC storage in the landscape of the studied region and can reach values between 178.96 and 206.73 Mg·ha-1(mean 192.85 Mg·ha-1), the SOC content in the soil cover of the surrounding eroded slopes and plateaus is 102.38 Mg·ha-1. This study indicates that CDs are a key morphological features for a better understanding of the spatial distribution of SOC in agricultural used loess landscapes of eastern Poland. SOC storage in CDs needs to be taken into account when calculating total soil carbon storage at the regional scale.