Changes in soil microbial C∶N∶P stoichiometry in different shrub types in subalpine regions of western Sichuan Province,China
The levels of soil microbial biomass carbon,nitrogen,and phosphorus(MBC,MBN,and MBP,respectively)and the dynamics of the MBC∶MBN∶MBP ratio are closely related to vegetation type.Shrubs are key components of the ecological system in the subalpine region of western Sichuan,China.However,the influence of different types of shrub vegetation on soil and microbial dynamics remains unclear.This study aimed to assess the influence of shrub vegetation types on soil microbial biomass and stoichiometry ratios in subalpine shrub ecosystems.Five typical shrub communities(Quercus aquifolioides shrub(QC,QM,QM,and QS)and Rhododendron faberi shrub(CK))were selected to monitor changes in soil microbial biomass contents and their stoichiometric ratios.The topsoil(0-20 cm)microbial biomass content was determined using the fumigation-extraction method.The stoichiometric characteristics and quotients,as well as soil properties(i.e.,soil organic carbon(SOC),total nitrogen(TN),total phosphorus(TP),water content(SW),and pH value).The results showed that soil microbial biomass content was significantly different among the different shrub types.The order of MBC and MBN contents and their stocks in the different Q.aquifolioides types was QC＞QS＞QM＞QP,whereas the order of MBP content and stocks was QC＞QM＞QS＞QP.The MBC and MBP contents were significantly lower in Q.aquifolioides types than in the CK.Higher MBC in CK supported significant higher MBC∶MBN,compared with those in different Q.aquifolioides types.Among the Q.aquifolioides types,the MBC∶MBN ratio significantly varied,following the order of QM＞QC＞QS＞QP,while the MBN∶MBP ratio was in the order of QC＞QS＞QP＞QM(P＜0.05).The variation tendencies of MBC∶MBP and MBN∶MBP were similar,with no differences among the different Q.aquifolioides types.qMBC was in the order QC＞QM＞QS＞CK＞QP(P＜0.05),whereas qMBC did not differ significantly between QP and CK(P＞0.05).qMBN and qMBP were in the order of QM＞QC＞QS＞QP(P＜0.05)in Q.aquifolioides types.However,in the control(CK)soil,qMBN was lower,while qMBP was higher,compared with those in the Q.aquifolioides types.The results of the redundancy analysis showed that changes in microbial biomass,stoichiometry,and qMB were mainly affected by SOC and TP.Overall,these results implied that shifts in soil microbial biomass and their stoichiometric characteristics were greatly affected by soil carbon and phosphorus elements in the different shrub types in subalpine areas.Different shrub vegetation types had different soil microbial biomass and stoichiometric ratios,indicating that soil microbial biomass stocks in the study area were different.The results of this study provide a scientific basis for the maintenance and management of shrubs.
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