施肥对高寒草甸土壤微生物化学计量学及有机碳激发效应的影响

Fertilization-induced changes in soil microbial stoichiometry affect the priming effects (PEs), thus influence the soil organic carbon (SOC) content. In this study, we analyzed the effects of fertilization on soil microbial stoichiometry and PEs by using labelled glucose and vanillin (representing simple and complex carbon sources) to reveal the mechanism of the effect of fertilization (CK, N, P and NP) on SOC content in alpine meadows. The results showed that fertilization significantly reduced the ratio of microbial biomass carbon to microbial biomass phosphorus (MBC/MBP) and the ratio of microbial biomass nitrogen to microbial biomass phosphorus (MBN/MBP). It was reduced from 37.3 to 6.2-27.4 for MBC/MBP and from 9.1 to 1.2-4.7 for MBN/MBP after fertilization. The cumulative PEs with glucose and vanillin addition were increased by 697~1836% and 29-520% respectively compared to the control, with the highest PE under P fertilization. The decomposition of the two C sources also responded differently: fertilization decreased the decomposition of vanillin (by 9%, 21%and 29% for N, Pand NP, respectively) and increased the decomposition of glucose (by 45%, 36% and 28% for N, P and NP, respectively). The decompositionof exogenous carbon and PEs were significantly correlated with microbial stoichiometry. Both carbon source additions produced a positive net carbon balance, but fertilization reduced the net C balance. In conclusion, fertilization increased cumulative PEs and accelerated SOC decomposition by affecting microbial stoichiometry, reduced organic C accumulation, which would lower long-term SOC pool in alpine meadows.