藏北高寒草甸土壤有机碳矿化及微生物群落结构对外源碳添加的响应OA

Alpine meadow degradation significantly affects soil carbon stocks and stability.However,how the addition of exogenous carbon affects organic carbon mineralization in degraded and undegraded alpine meadow soils and the underlying microbial mechanisms remains unclear.In this study,degraded(dG)and undegraded(ndG)alpine meadow soils were used as research objects.Different concentrations of glucose solution(0‰、0.2‰、0.4‰,and 0.8‰)were added for constant temperature incubation to investigate the effects of glucose addition at various concentrations on soil organic carbon mineralization characteristics and the structure of related microbial communities.The results showed that a high concentration of glucose solution(0.8 ‰)exerted a positive priming effect on both dG and ndG soils and promoted soil organic carbon mineralization(the cumulative priming effect in ndG was 395 mg·kg-1).Fungi predominated in both dG and ndG soils(>80%).However,compared with ndG soils,the proportion of fungi decreased and actinomycetes increased in dG soils.Both F/B(fungi/bacteria)and F/A(fungi/actinomycetes)values showed a significant(P<0.05)increasing trend with incubation time.Most peaks in the total microbial growth rate occurred on day 3,and in dG soil,the total microbial growth rate reached 1 046.35%on day 3 at a glucose addition concentration of 0.8‰.The microbial diversity indices of dG soil were significantly higher than those of ndG soil throughout the incubation period(P<0.05).Structural equation modeling indicated that soil degradation had a direct negative effect mainly on fungi,whereas glucose addition had a direct positive effect on bacteria(P<0.05).Organic carbon mineralization was significantly(P<0.05)affected by microbial biomass,and changes in fungal communities inhibited the occurrence of the priming effect.These results indicate that readily degradable exogenous carbon exhibits a concentration threshold for stimulating soil organic carbon mineralization and the priming effect in alpine meadows.Microbial biomass is the primary driver of soil organic carbon mineralization,and changes in fungal communities suppress the priming effect.