Contributions of Vegetation Restoration to Soil Organic Carbon Sequestration in Deserts of China: A Meta-Analysis

Abstract

Vegetation restoration has been widely used to curb desertification in northern and central desert shifting sandy lands of China. However, the general pattern, variability, and drivers of its effects on soil organic carbon (SOC) remain unclear. Here, we conducted a meta-analysis by synthesizing 332 paired observations from 32 publications to quantify the effects of vegetation restoration on SOC and to examine whether they were regulated by restoration characteristics (methods and durations) and edaphic-climatic conditions in northern and central desert shifting sandy lands of China. Overall, vegetation restoration significantly increased SOC in shifting sandy lands at the regional scale, but the magnitude of SOC responses varied across restoration methods, restoration durations, soil depths, and desertification types. In particular, it was greatest in tree-planted areas compared to other vegetation restoration methods, followed by shrub-planted, herb-sown, and enclosed areas; it displayed a positive relationship with restoration duration. We preliminarily found that SOC responses were stronger in surface soil and deep subsoil, while relatively weaker in middle soil layers. In addition, SOC was most pronounced in deserts, followed by degraded grassland, transitional zone, and desert steppe types. Random forest modeling and structural equation modeling revealed that soil sand fraction was the primary driver of SOC responses, followed by mean annual precipitation and restoration method. Soil physical properties (e.g., sand fraction, bulk density) were closely associated with SOC responses, while climate factors and restoration duration exerted indirect correlative influences on SOC responses via modifying soil physical properties. Overall, our study illuminated the divergent multidimensional responses of SOC to vegetation restoration in shifting sandy lands in northern and central Chinese desert shifting sandy lands and identified soil sand fraction and mean annual precipitation as the major regulatory factors of SOC responses. These findings can provide a fundamental basis for achieving coordinated advancement of regional desertification control and national carbon neutrality goals.