Regional heterogeneity and vertical stratification of carbon dynamics in Chinese peatlands

Global peatlands store vast amounts of terrestrial carbon (C), yet the regional heterogeneity and subsurface C dynamics of Chinese peatlands remain poorly quantified. These data gaps limit potential model extrapolations and vulnerability assessments of peatlands from one region to another in a global perspective. Our systematic investigation of peat profiles across four major climate regimes in China revealed generally lower C content (38.4 +/- 7.2%, n = 957) than the global average. A widespread mismatch between surface vegetation and subsurface peat type was documented, with a paradox where high C accumulation rates coincided low C stocks in Sphagnum peats and vice versa in non-Sphagnum peats. Crucially, we identified a fundamental vertical stratification in drivers: geoclimatic factors exerted a stronger influence on shallow, 0-20 cm, C stocks, whereas microbial processing of labile C significantly governed only deeper >20 cm reservoirs. Thus, the vulnerability of deeper peat hinges primarily on the decomposition resistance of subsurface peat C, rather on surface conditions. Our findings highlight the need for a depth-resolved framework for managing and modeling these peatlands to accurately project their climatic responses.