Estimating spatiotemporal variations of cropland soil organic carbon and its sequestration potential in central China from 1984 to 2019

Assessing spatial and temporal changes in soil organic carbon (SOC) over time is crucial for understanding soil fertility and its impact on the global carbon cycle. This study analyzed the spatiotemporal changes of SOC in a typical agricultural region of the North China Plain from 1984 to 2019 and explored the potential for SOC sequestration. A total of 411 soil samples were collected in 1984, with subsequent sampling in 2009 (411 samples) and 2019 (181 samples). Geostatistical Sequential Gaussian Simulation (SGS) was utilized to quantify the spatiotemporal trends of SOC changes from 1984 to 2019. The SOC sequestration potential (SOCp) was estimated using the Levenberg-Marquardt and Universal Global Optimization algorithms. The results revealed a significant elevation in mean SOC from 5.84 g kg(-1) in 1984 to 10.64 g kg(-1) in 2019, with an increasing trend observed from the northwest towards the southeast. The SOC increase rate during 2009-2019 (0.48 t/ha yr(-1)) surpassed that of 1984-2009 (0.32 t/ha yr(-1)). The fine-textured soil in the north showed a faster increase in SOC compared to coarse-textured soils in the south. Estimated SOCp ranged from 2.81 to 24.34 t C/ha, with a mean of 12.43 t C/ha across the area. Loam clay, silt clay, clay loam and loam in the north exhibited lower SOCp (0-10 t C/ha) compared to sandy loam in the south. The time required to reach SOC saturation (Ts) was high (>20 years) in the south, an area dominated by sandy loam, compared to the north, with a low Ts (0-20 years) covered by fine-textured soil. These findings suggest croplands might be a potential carbon sink to be developed through sustainable and efficient agricultural management in this typical agricultural region of the North China Plain, particularly in the sandy loam of the region's southern area.