寒温带不同林龄白桦林根际与非根际土壤微生物生物量及生态化学计量季节性变化特征OA

To explore the characteristics of soil microbial biomass and ecological stoichiometry in the rhizosphere and non-rhizo-sphere soil of Betula platyphylla forests at different stand ages in the cold temperate zone,and to reveal the nutrient cycling mechanisms of B.platyphylla forests across distinct growth stages,this study was conducted.B.platyphylla forests of three stand ages((32±6),(47±4),and(68±7)a)were selected as the research objects.From May to September 2024,rhi-zosphere and non-rhizosphere soil samples were collected using the root-shaking method.Soil microbial biomass carbon(MBC),microbial biomass nitrogen(MBN),microbial biomass phosphorus(MBP),and other soil physical-chemical properties were determined.The microbial biomass and its stoichiometric characteristics in rhizosphere and non-rhizosphere soils were analyzed,and redundancy analysis(RDA)was employed to identify the key driving factors.The results showed that from May to September,the contents of MBC and MBN in the rhizosphere soil of B.platyphylla forests across the three stand ages exhibited a fluctuating variation trend,while MBP content presented a unimodal variation pattern with the peak value occurring in July.The contents of MBC,MBN,and MBP in rhizosphere soil were significantly higher than those non-rhizosphere soil(P<0.05).Stand age had a significant effect on soil microbial biomass.Specifically,the MBP content in both rhizosphere and non-rhizosphere soils of the 47-year-old B.platyphylla forest was significantly higher than that of the other two stand ages,whereas the MBC and MBN contents in both rhizosphere and non-rhizosphere soils of the 68-year-old forest were the highest.The ranges of MBC∶MBN,MBC∶MBP,and MBN∶MBP ratios in rhizosphere soil were 5.27-14.17,19.78-55.15,and 2.56-8.45,respectively,showing no significant differences from those non-rhizospheric soil.With the increase in stand age,the average contents of MBC∶MBN in both rhizosphere and non-rhizosphere soils de-creased gradually,while the contents of MBN∶MBP increased progressively.The order of MBC∶MBP contents in rhizo-sphere and non-rhizosphere soils across different stand ages from high to low was 32-year-old,68-year-old,and 47-year-old B.platyphylla forests.The microbial quotient of carbon(qMBC),microbial quotient of nitrogen(qMBN),and microbial quotient of phosphorus(qMBP)in rhizosphere soil were all lower than those in non-rhizospheric soil,indicating that rhizo-sphere microorganisms had a higher nutrient utilization efficiency.As stand age increased,the microbial C∶N stoichiomet-ric imbalance(C∶Nimb)and C∶P stoichiometric imbalance(C∶Pimb)in rhizosphere soil first increased and then de-creased,whereas the N∶P stoichiometric imbalance(N∶Pimb)showed an opposite trend of first decreasing and then in-creasing.Results of redundancy analysis revealed that available phosphorus(AP)and sucrase(SUC)were the key factors affecting soil microbial biomass.The microbial stoichiometric ratios in rhizosphere soil were mainly regulated by soil pH and SUC,while those in non-rhizosphere soil were dominated by SUC and dissolved organic carbon(DOC).Both rhizo-sphere effect and stand age had significant impacts on the contents of MBC,MBN,and MBP in soil.Soil microbial stoi-chiometric ratios were significantly affected by stand age,and with the increase in stand age,the microbial growth of B.platyphylla forest soil was increasingly limited by phosphorus(P).