Carbon sequestration in the uplands of Eastern China: An analysis with high-resolution model simulations

• SOC changes were estimated by polygon- and county-based databases modeling method.
• Coarse soil data may lead to large biases in SOC simulation.
• C sink of this study accounts 10.2% of the annual C sink of upland soils in China.
• Variations in N-fertilizer and manure applications affect the annual SOC change.

Using the DeNitrification-DeComposition (DNDC, version 9.5) model, we investigated the soil organic carbon (SOC) changes from 1980 to 2009 in Eastern China's upland-crop fields in northern Jiangsu Province. A currently most detailed high-resolution soil database, containing 17,024 polygons at a scale of 1:50,000, derived from 983 unique upland soil profiles, was used. A coarser county-level soil database was also used for a pair-wise simulation for comparison. We found that SOC changes modeled with the county-level soil database differ significantly from those with high-resolution soil data, with the deviation ranging from −64% to 8.0% in different counties. This implies that coarse soil data may lead to large biases in SOC simulation. With the high-resolution database, the model estimates a SOC increase of 37.89 Tg C in the top soils (0–50 cm) over the study area of 3.93 Mha for the past three decades, with an average rate of 322 kg C ha−1 year−1. The SOC accumulation in the study region accounts for 10.2% of annual national carbon sequestration of upland soils, compared with the fraction of 3.7% in the total upland area of China. This underscores its significance to national climate mitigation. The annual SOC change varied between 61 to 519 kg C ha−1 year−1, mainly driven by the variations in N-fertilizer and manure applications. This study highlights the significance of high-resolution soil databases in quantifying SOC changes. Our high-resolution estimates of SOC will support farming and carbon management in this region.