Location-optimized remediation measures for soil multifunctionality and carbon sequestration of saline-alkali land in China

Soil salinization-alkalization severely undermines soil multifunctionality (SMF) by disrupting essential biogeochemical and ecological processes. Remediating saline-alkali soils is therefore critical for enhancing SMF, safeguarding food security, and improving carbon storage. Although previous studies have applied meta-analysis to evaluate soil remediation strategies, the design of location-specific agricultural practices for rehabilitating saline-alkali lands and optimizing their carbon sequestration potential remains underexplored, largely due to China’s pronounced spatial heterogeneity. To address these gaps, this study presents the first integration of nationwide meta-analysis with machine learning-driven spatial predictive modeling to assess the effects of different remediation measures (i.e., physical, chemical, and biological) on soil organic carbon (SOC) content and SMF in saline-alkali lands. We produced spatial maps of effect sizes for SMF and SOC and categorized them into four regions (i.e., northwestern, northeastern, northern, and coastal) based on distinct climatic and hydrological conditions. The results indicate that the topsoil SOC stock in China’s saline-alkali lands is estimated at 126.05 Tg, which could be increased by up to 30% under biological remediation measures. A strong positive relationship was observed between SOC and SMF, with SOC enhancement indirectly boosting crop productivity in saline-alkali soils. On a national scale, chemical remediation proved to be the optimal management strategy for simultaneously promoting SMF and SOC sequestration. Biological measures showed comparable benefits, particularly in the northwestern, northeastern, and coastal regions. However, future changes in temperature and precipitation are projected to undermine SMF improvements while accelerating SOC accumulation under remediation, potentially weakening the SOC–SMF linkage in saline-alkali soils. These insights are vital for guiding future efforts to ensure food security and mitigate climate change.