Lower soil organic carbon mineralization and temperature sensitivity along a freeze-thaw erosion gradient in permafrost soils

Abstract

Freeze-thaw erosion (FTE) is widespread in permafrost regions, yet its effects on soil organic carbon (SOC) dynamics remain unclear. Here, we investigated SOC fractions, physicochemical properties, microbial biomass and community composition, SOC-degradation functional genes, SOC mineralization rates and their temperature sensitivity (Q 10 ) in permafrost soils with and without FTE on the Qinghai-Tibetan Plateau (QTP). Compared with no erosion soils, FTE soils exhibited markedly lower SOC, particulate organic carbon (POC), and mineral-associated organic carbon (MAOC), indicating reduced soil carbon pools. The Q 10 of SOC mineralization was significantly lower in FTE soils (mean = 3.00) than in no erosion soils (mean = 7.14), reflecting a dampened microbial respiratory response to warming. FTE also reshaped microbial community structure and altered microbial functional potential. Variation in SOC mineralization and Q 10 was associated with soil carbon characteristics and specific microbial properties, suggesting their potential roles in SOC responses to FTE. Moreover, these responses varied with slope position, highlighting the importance of topography in mediating carbon redistribution and microbial responses under FTE. Overall, our findings show that FTE is associated with reduced SOC mineralization and temperature sensitivity, together with concurrent changes in soil carbon characteristics and microbial properties, providing new insights into SOC dynamics in degrading permafrost ecosystems.