Community Composition And Metabolic Characteristics Of Soil Microbes Under Differenty Egetation Restorations And Its Influencing Factors

In the past,the study of vegetation restoration focused on the above-ground ecosystem process,lack of understanding of soil microbial community,and the study about differences in soil microbial community and influencing factors was rare.Aiming at solving the problem mentioned above,this study choses the Samachang small watershed in the upper reaches of the Yangtze River.In this study,five kinds of vegetation types were studied:grassland(herb layer + shrub + small tree)?Pinus yunnanensis forest(coniferous forest)?coniferous and broadleaved mixed forest?evergreen broad-leaved forest(broadleaf mixed forest)and Eucalyptus forest(artificial forest).Compares the difference of soil microbial composition and carbon metabolism under different vegetation types based on the method of phospholipid fatty acid(PLFA)and Biolog Eco microplate.The results are as follows:(1)The total amount of soil microbes,bacteria,fungi and actinomycetes biomass in evergreen broad-leaved forest and coniferous and broad-leaved mixed forest were significantly larger than other vegetation types.The evergreen broad-leaved forest's total amount of soil microbes,bacteria,fungi and actinomycetes biomass was 2.47,2.79,1.88 and 2.58 times as Eucalyptus forest.The microbial biomass of the three groups was as follows:bacteria>fungi>actinomycetes.The results of cluster analysis showed that evergreen broad-leaved forest and mixed forest is a class,grassland,Eucalyptus forest and Pinus yunnanensis forest is another class.(2)The carbon metabolism diversity of soil microbes is characterized by carbon source utilization and functional diversity index.The soil microbial carbon source utilization of evergreen broad-leaved forest and grassland was stronger than that of other vegetation types,the other as fellow:mixed forest>Eucalyptus forest>Pinus yunnanensis forest.The Shannon index(H')as fellow:evergreen broad-leaved forest>mixed forest>glassland>Eucalyptus forest>Pinus yunnanensis forest;evergreen broad-leaved forest has the highest carbon metabolism diversity,Pinus yunnanensis forest is the smallest.(3)The RDA analysis of soil microbial community composition and structure showed that the physical and chemical properties of the soil and litter can explain the soil microbial composition of the amount of variation of 75.2%.The results showed that the soil organic matter,soil C:P,soil total nitrogen,soil N:P and soil bulk density were the controlling factors of soil microbial community structure.The RDA analysis of soil microbial carbon metabolism diversity showed that the soil microbial community composition and characteristic of the soil and litter can explain the soil microbial composition of the amount of variation of 92.7%,soil microbial biomass and soil organic matter,total nitrogen,total phosphorus,soil C:N,soil C:P and litter organic matter were the controlling factors of soil microbial carbon source utilization ability.There was a significant positive correlation between plant species diversity and soil microbial diversity.(4)There were significant differences in soil nutrient content and stoichiometry of vegetation types under different restoration methods(P<0.05).The contents of soil organic matter,total nitrogen and total phosphorus in evergreen broad-leaved forest were significantly higher than those in other vegetation types.The soil C:N,C:P and N:P were significantly higher than those of other vegetation types.The soil C:P,N:P in the vegetation type was significantly lower than that of other vegetation types.Compared with other studies,there was nitrogen restriction in the soil of the Samachang area,and the restriction of the eucalyptus forest was the strongest.(5)Differences in litter nutrient content and stoichiometry of vegetation under different restoration measures were significant(P<0.05).Litter nitrogen in grassland and evergreen broad-leaved forest were significantly higher than that of other vegetation types,which were 7.916±0.646mg/g and 7.759 ± 1.017mg/g.Litter C:N ratio of mixed conifer and Pinus yunnanensis forest was significantly greater than that of other vegetation types,and the N:P ratio of evergreen broad-leaved forest was significantly higher than other vegetation types,which was 4.438±0.579.Litter phosphorus in Samachang region was relative surplus compared to other studies' results.Our findings showed that there were significant differences in soil microbial composition and carbon metabolic diversity under different vegetation restoration methods.This difference was caused by soil and above vegetation.Among these factors,soil nutrient content and metering ratio were the most important factors.It is certain that the vegetation restoration mode acts on the whole of the ecosystem,and different vegetation restoration methods will bring about the difference of soil,litter and species diversity,and these differences shape the soil microbial community characteristics in different degrees.Therefore,in the process of vegetation restoration,we should focus on the restoration of the integrity of the ecosystem,broad-leaved mixed recovery can be more comprehensive to improve the quality of vegetation restoration.