川西亚高山典型灌丛土壤微生物量及其碳氮磷化学计量特征

Changes in soil microbial C:N:P stoichiometry in different shrub types in subalpine regions of western Sichuan Province,China

土壤微生物量及其碳氮磷化学计量比(C:N:P)受到植被类型的影响.为探讨川滇高山栎灌丛不同林型对土壤微生物量及其碳氮磷化学计量比的影响,以米亚罗林区川滇高山栎灌丛4种类型[川滇高山栎-粉背黄栌灌丛(QC)、川滇高山栎-华山松灌丛(QM)、川滇高山栎-云杉灌丛(QP)、川滇高山栎-陕甘花楸灌丛(QS)和杜鹃灌丛(CK)]为研究对象,分析灌丛林下表层(0-20 cm)土壤微生物量碳(MBC)、氮(MBN)和磷(MBP)含量及微生物熵(qMB)与微生物化学计量比(MBC:MBN:MBP)的变化特征.结果表明:(1)不同灌丛类型的土壤微生物量差异显著,MBC和MBN含量及其储量高低在川滇高山栎灌丛中表现为QC>QS>QM>QP,MBP及其储量则表现为QC>QM>QS>QP,其中MBC和MBP含量均显著低于CK.(2)MBC:MBN在不同灌丛植被类型中表现为CK>QM>QC>QS>QP(P<0.05);MBN:MBP则表现为QC>QS>QP>QM>CK(P<0.05);MBC:MBP变化趋势与MBN:MBP相似但未见显著性差异.(3)qMBC表现为QC>QM>QS>CK>QP(P<0.05),其中QP与CK无显著性差异;qMBN和qMBP在川滇高山栎灌丛中表现为QM>QC>QS>QP(P<0.05),CK的qMBN和qMBP分别低于和高于川滇高山栎灌丛.冗余分析表明,SOC和TP是影响土壤微生物量及其化学计量比和微生物熵的主要因素,说明土壤碳、磷含量是影响亚高山灌丛土壤微生物活性的主导因素.综上,不同灌丛植被类型具有不同的土壤微生物量和化学计量比,该研究区域土壤微生物量储量主要受到土壤有机碳、磷元素的影响.(图4表3参56)

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.