Historical and future dynamics of cropland soil organic carbon stocks in an intensive human-impacted area of southeastern China.

The dynamics of soil organic carbon stocks (SOCS) in croplands are highly sensitive to agricultural management practices, representing a crucial component of soil fertility and playing a pivotal role in regulating the global carbon cycle. However, the historical trajectory of SOCS in croplands and its future developments in response to agricultural management practices such as carbon inputs coupled with the impact of climate change, remain unclear, especially for the areas with intensive human activities. Here we collected a total of 1219 cropland SOCS data (0–20 cm) from the southern Jiangsu Province of China in 1980, 2000, and 2015, and the RothC-RFst model developed by integrating the RothC-predicted SOCS into the space-for-time random forest (RFst) was used to model spatiotemporal dynamic of cropland SOCS over the period of 1980–2015 and its future trend under three carbon input scenarios (CI+1, CI+0.6, and CI+0). Results showed that the historical change in SOCS from 1980 to 2015 was characterized as a significant increase of SOCS (+6.02 t C ha-1) before 2000 and SOCS decline (-5.05 t C ha-1) over the period of 2000–2015. The future trend of cropland SOCS under different CI scenarios were similar during 2024–2100, with substantial SOCS increases of 6 % and 4 % under CI+1 and CI+0.6, and almost unchanged SOCS (<1 %) for the baseline scenario (CI+0). The projected dynamics of SOCS indicated a constrained response to future climate change (e.g., the CMIP6 SSP1–1.9 and SSP5–8.5) under the CI-based scenarios. These findings highlight the significant role of the CI levels in preserving and enhancing cropland soil carbon sequestration potential. We believe that outputs from this study provide valuable insights for the development of cropland management strategies through effective economic and policy incentives, especially in areas heavily impacted by human activities. • Cropland soils functioned as important C sinks in the past. • The elevated CI promotes SOCS, even in the face of extreme climate constraints. • The SOCS is projected to increase by 6 % with annual growth rate of 1 % in CI levels. • SOCS dynamic remains dynamic balance under current CI and SSP1–1.9/SSP5–8.5. [ABSTRACT FROM AUTHOR]