Abstract Mineral association is widely recognized as a fundamental mechanism of soil organic carbon (SOC) stabilization; however, its relative importance versus climatic and vegetation drivers, and the key controlling geochemical factors remain poorly quantified in arid and semi‐arid grasslands (mean annual precipitation, MAP < 400 mm). Combining a regional survey across the Mongolian Plateau ( n = 260) with a global data synthesis ( n = 2,097), we quantified the overwhelming dominance of mineral‐associated organic carbon (MAOC), which constituted 79.8 ± 0.6% of SOC and established a benchmark for Eurasian drylands. More critically, we establish a hierarchical framework for MAOC accumulation: macro‐scale environmental parameters (C:P ratio, pH) set the stabilization capacity, whereas localized geochemical actors (Fe, Ca) actuate this capacity via direct physiochemical interactions. In contrast, POC (particulate organic carbon) and CPOC (coarse particulate organic carbon) fractions were predominantly regulated by the C:P ratio, mean annual precipitation minus potential evapotranspiration (MAP‐PET), and aboveground plus belowground biomass (AGB + BGB), suggesting a stronger dependence on recent carbon inputs and decomposition. Effective moisture (MAP‐PET) served as the principal indirect control modulating both carbon inputs and mineral weathering. We thus propose a “mineral protection paradigm” for these ecosystems, wherein Fe and Ca directly enhance SOC sequestration through adsorption and cation bridging, forming a geochemically driven core process that is indirectly amplified by climate (MAP‐PET) through its influence on vegetation drivers (AGB + BGB). This study establishes a synergistic Climate‐Geochemistry‐Vegetation framework that provides a scientific basis for SOC management in arid grassland ecosystems.
Tang et al. (Sun,) studied this question.