Organic carbon density and storage of the major black soil regions in northeast China

Abstract

Black soils in the Northeast Plain of China are characterized by high organic carbon (C) density and storage, which can infuence C sequestration in local cropland ecosystems. Using GIS, this study analyzed the temporal and spatial distribution and variation of cropland organic C density and storage in the arable layer (0-20 cm) of the major black soil regions in China's Northeast Plain (specifcally across the study region of Hailun, Shuangcheng and Gongzhuling counties) over the past 30 years. The results indicate an overall downward trend in soil organic C (SOC) density (SOCd, mean decrease of 0.64 kg m-2) and storage (SOCs, decrease of 4.65 Tg)*1 for the major black soil regions tested during the study period. The mean decrease in SOCd for Hailun, Shuangcheng and Gongzhuling counties was 0.68 kg m-2, 0.18 kg m-2 and 1.05 kg m-2, respectively, with total SOC decreases of 2.30 Tg, 0.49 Tg and 1.86 Tg, respectively. SOCd decreased to a greater extent during the frst twenty years in Hailun and Shuangcheng relative to Gongzhuling. Moreover, SOCd tended to stabilize and then slightly increase during the last ten years. There was a downward trend in SOCd and SOCs over the past 30 years for almost all soil types, but the most serious decline in SOCs was observed in black soils, which account for 57.92% of the cropland soil area in all study regions and which lost up to 2.91 Tg of SOC. Therefore, the major black soil region in Northeast China was presenting a C resource trend over the past 20-30 years.