Water table-driven divergent patterns and drivers of particulate and mineral-associated organic carbon in alpine peatlands

• Large-scale patterns and drivers of POC and MAOC in alpine peatland were revealed. • POC dominated SOC pools (58.4 %) in alpine peatlands. • POC was primarily regulated by plant-derived lignin phenols. • MAOC was more strongly impacted by mineral protection. • Water table drawdown reduced POC contribution but enhanced MAOC​​ contribution to SOC. Classifying soil organic carbon (SOC) into particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) can enhance the understanding of SOC vulnerability to environmental changes. However, the spatial patterns and drivers of POC and MAOC in peatlands remain poorly documented. Here, we collect topsoil samples (0–20 cm) from 43 representative sites exhibiting varying water table levels across the Zoige Plateau, the world’s largest alpine peatland. The mean value of POC and MAOC was 131.71 g kg soil −1 and 92.75 g kg soil −1 , respectively, with POC dominating the SOC contribution (58.4 %) in alpine peatlands compared to other terrestrial ecosystems. Multiple linear regression and random forest analyses identified SOC, soil total nitrogen, and lignin phenols as primary determinants of POC variation, whereas MAOC variation was mainly explained by SOC, iron-bound carbon, and non-crystalline iron oxides. Spatial predictions based on random forest models indicated that POC stocks (mean: 8.25 kg m −2 ) increased from southeast to northwest, whereas MAOC stocks (mean: 5.53 kg m −2 ) were higher in southeast on the Zoige Plateau. Rising water tables increased both POC stocks and their contribution to SOC, while declining water tables enhanced the contribution of MAOC stocks to SOC but reduced total SOC stocks. Our findings highlight divergent patterns and drivers of SOC fractions at large scales in alpine peatlands, provide evidence of how water table fluctuations influence their relative contributions to SOC stocks, and offer valuable insights into soil carbon formation and stability in these cold, climate-sensitive peatland ecosystems.