Soil carbon characterization in a subtropical drained peatland

•Organic matter and organic carbon decrease as soils get shallower.•The dominant carbon pool in the studied drained peatland is recalcitrant carbon.•Recalcitrant carbon is enriched in aromatic and depleted in O-alkyl C compounds.•Recalcitrant carbon is vulnerable to soil subsidence.•The addition of fresh biomass could minimize subsidence and labile carbon losses.