| Soil microorganisms,as the main participants in the material cycle and energy flow of forest ecosystems,play an important role in regulating the decomposition and nutrient cycle of soil organic matter,directly affecting the storage capacity of soil nutrients,and then affecting the stability of ecosystems.Because of unreasonable land use patterns,forest types change and soil degradation are serious,resulting in a sharp decline in productivity.Therefore,it is imperative to improve soil nutrient status and storage capacity of soil nutrients,and increase forest productivity.However,there is a lack of understanding of soil microbial nutrient requirements and microbial community structure under different vegetation types and their influencing factors.Therefore,Daiyun Mountain Nature Reserve in Fujian Province was selected as the research plot,and three typical vegetation types were selected: coniferous forest of Pinus taiwanensis Hayata,broad-leaved forest of Castanopsis faberi Hance,Mixed Forest and Coniferous Forest.Soil samples of 0-10 cm and 10-20 cm in May and December 2017 were taken to determine the basic physical and chemical properties of soil,microbial biomass and soil enzyme activity,and to analyze the ecoenzymatic stoichiometry ratio to obtain microbial nutrient requirements.The distribution of bacteria and fungi in soils with different vegetation types was analyzed by 16 S rDNA and ITS sequencing techniques,which will help us understand how microorganisms regulate soil nutrient changes.The main results are as follows:1)The results of eco-enzyme stoichiometry showed that microorganisms in this area were limited by nitrogen(N)and phosphorus(P)nutrients,and there were significant differences in eco-enzyme stoichiometry among different vegetation types.The results of eco-enzyme stoichiometry showed that soil microorganisms in coniferous forests were most restricted by N and P,while those in broad-leaved forests were weakly restricted by N.The eco-enzyme stoichiometry of different vegetation types in summer is greater than that in winter.The main factors affecting the ecoenzymatic stoichiometry are N,P nutrients and microbial biomass stoichiometry.2)There were significant differences in diversity and structure of bacterial communities among different vegetation types.The dominant bacteria were Proteobacteria,Acidobacteria,Actinobacteria,Chloroflexi and Verrucomicrobia.The relative abundance of Proteus in broad-leaved forest was significantly lower than that in other vegetation,and the abundance of Acidobacteria was higher.The species richness of bacteria in different vegetation types showed obvious seasonal variation,and the relative abundance of Proteus and Acidobacteria had obvious seasonal difference.The main factors affecting the change of bacterial community are soil nitrogen and phosphorus nutrient content and nutrient stoichiometry.3)In summer,different vegetation types have significant effects on the diversity of fungal community,and there is no significant difference in community structure.There was no significant difference in fungal community diversity among different vegetation types in winter,but different vegetation types had significant influence on fungal community structure.The dominant phylum were Basidiomycota,Ascomycota and Zygomycota.The abundance of basidiomycetes in mixed forest was significantly higher than that in coniferous forest and mixed forest,but ascomycetes was the lowest.The species richness of broad-leaved forest and coniferous forest in summer was higher than that in winter,but there was no seasonal difference in species diversity and evenness.The main factors affecting fungal community change are soil carbon and nitrogen nutrient content and microbial biomass stoichiometry. |
