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

Soil erosion in loess landscapes results in soil organic carbon (SOC) redistribution and storage in SOC pools. Understanding the SOC dynamics is important because changes in the SOC stocks may have impacts on global climate change. However, the topographic-related patterns controlling SOC storage are not well understood. Closed depressions are natural landforms in loess landscapes and preserve buried Holocene soils and SOC-rich colluvia resulting from soil erosion and are SOC pools. The aim of this study was to quantify the impact of natural closed depressions on SOC storage in the loess landscape of the Naleczow Plateau. Buried Holocene soils and colluvial sediments infilling five representative closed depressions were documented and the SOC stocks were calculated. Using GIS analysis SOC from all closed depressions was calculated and mapped. Between 13.5 and 229.78 Mg of SOC are in the entire soil profiles of the studied closed depressions, 10%-21% of the SOC stock is in the topsoils. The SOC stock in all closed depressions of the study area reaches 172.09-265.19 Mg ha(-1) and in the soil cover outside the closed depressions is 51.20-105.40 Mg ha(-1). SOC from closed depressions varies spatially and increases the SOC stock at regional scale by 0.1-90 Mg ha(-1). For about 21% of the study area, the SOC from closed depressions increases the SOC stock in the agricultural landscape by more than 10% (up to 60%). This study highlights the importance of closed depressions for SOC storage and provides a better understanding of its spatial distribution at the regional scale.