Seasonal changes in labile organic matter as a function of environmental factors in a relict permafrost region on the Qinghai-Tibetan Plateau

Abstract Labile organic matterplays an important role in permafrost carbon cycling, however, little is known about the effects of permafroston labile organic matterdynamics. Here, we examined seasonal changes in the labile organic matterincluding light fraction carbon (LFC), water extractable organic carbon (WEOC), microbial biomass carbon (MBC) and nitrogen (MBN) contents in a relict permafrostregion on the eastern edge of the Qinghai-Tibetan Plateau (QTP), China. We selected three different areas including permafrost, boundary, and seasonally frozen ground area. The results showed that seasonal changes in labile organic matterwere not the result of soil heterogeneity. Among all three areas, depth strongly correlated with labile organic mattercontent. LFC was significantly associated with the soil organic carbon (SOC) content. The MBC contents, which were the lowest in permafrostarea but highest in seasonally frozen ground area, were strongly affected by temperature. Multiple linear regression models showed that temperature was a significant predictor for labile organic matterin the permafrostarea, but the effects of temperature were weaker in the boundary and seasonally frozen ground areas. Our results suggested that permafrostdegradation could decrease production but increase decomposition rates of labile organic matterin permafrostregions, and this process should be taken into consideration in permafrost carbon cyclemodels.