Data-driven modeling indicates projected increase in plant production confines warming-induced topsoil organic carbon change in China within a small range in the 21st Century

Understanding the dynamics of soil organic carbon (SOC) in the topsoil, the most sensitive part of soil profile to climate change, under future climate trajectories is vital for achieving carbon neutrality in China. However, large uncertainties and controversies exist in Earth System Model (ESM) simulations. We used a data-driven model to assess the responses of SOC to future climate change and quantified the critical biomass carbon input (i.e., net primary production, NPP) to preserve the current SOC level. Our results suggest that future warming alone may reduce the national topsoil organic carbon stock by 605.3 Tg C (1.72 %) by the end of the 21st century under the representative concentration pathway 8.5 (RCP8.5). However, the projected increase in precipitation cannot offset the negative impact of warming under all climate trajectories. We estimate that 18.5 %, 38.0 %, and 46.5 % of additional NPP are required in the 2030s, 2060s, and 2090s to offset the national SOC loss under RCP8.5, respectively. Further simulations driven by the NPP projections of ESMs suggest that the increasing NPP can confine warming-induced SOC loss within a small range and even slightly increase SOC in the 2090s under RCP4.5 and 8.5. Nevertheless, SOC dynamics show large spatial discrepancy, and regions with high SOC levels, especially Northeast and Southwest of China, have a high potential of losing carbon and deserve more attention. This work extends our knowledge about the future dynamics of topsoil organic carbon in China and can be a reference for current ESMs to produce more robust regional predictions.