Abstract: Peatlands store approximately one-third of global soil organic carbon (SOC) and clarifying SOC sources is essential to assess soil C formation and stability in these C-rich ecosystems. However, large-scale patterns and drivers of plant- and microbial-derived C remain poorly understood in peatlands. This study applied lignin phenols and amino sugars as biomarkers for plant and microbial residues to investigate the regional distributions and controlling factors of plant- and microbial-derived C in surface peat (0–20 cm) across Zoige alpine peatlands. Our results showed that amino sugars contributed less while lignin phenols remained stable with SOC accrual, indicating the key role of plant-derived C in SOC accumulation. Soil nutrients and microbial properties explained the majority of the variation in lignin phenols, while soil nutrients and mineral protection played a more important role in amino sugars than microbial variables and climatic factors. Specifically, lignin phenols were negatively correlated with soil nutrients, fungal richness, and acid phosphatase activity, while showing a positive association with leucine aminopeptidase activity. In contrast, amino sugars were positively related to soil total phosphorus but negatively linked with Fe-associated C and Fe/Al-oxide. These findings provide the first empirical evidence of plant- and microbial-derived C and their divergent drivers in alpine peatlands over a broad scale, which advances our understanding of soil C formation and stability in these C-rich, climate-sensitive ecosystems.

Key words: lignin phenols, amino sugars, alpine peatlands, soil organic carbon, microbial necromass, surface soil