Four Forest Types Soil Nutrient And Microbial Community Studies In Middle Subtropical Region

Soil microorganisms are important drivers of organic matter decomposition and nutrient cycling,and play an important role in the process of vegetation growth.Subtropical forest is an important part of forest resources in China,and plays an important role in carbon sequestration and wood supply.Exploring the characteristics of soil nutrients and microbial communities of typical forest types in this region is of important reference significance for deeply understanding the forest-soil-microbial relationship and for efficient forest management.In this study,the composition,structure and diversity of soil microbial communities of different forest types were analyzed by using high-throughput sequencing technology in planted forests(Cunninghamia lanceolata(Lamb.)Hook.)(PF)and(Pinus massoniana Lamb.)(PM),secondary forests of Castanopsis eyrei(Champ.)Tutch.(CT)and mixed coniferous and broadleaved forests(MF)in the central subtropical region.The differences in soil microbial community composition,structure and diversity among different forest types were analyzed using high-throughput sequencing techniques(16S rRNA gene sequencing and ITS sequencing);Through Pearson correlation analysis and RDA(redundancy analysis)analysis,we will clarify the interrelationship between soil microbial community structure and function and soil physical and chemical characteristics of different forest types,and reveal the main drivers affecting the change in soil microbial community structure and function.In order to provide theoretical reference for forest cultivation soil management in this area.The main study results are presented as follows:(1)Among the four forest types,the soil moisture content(SWC)was higher in CT and MF than in PM and PF.The soil organic carbon(SOC),total nitrogen(TN)and total phosphorus(TP)contents were all higher in the four stand types:MF>PF>CT>PM>PM;The nitrate nitrogen(NO3-)was significantly higher in PM than in other stands,and the available potassium(AK)content was significantly higher in PF than in other stands.The C,N,and P ecological stoichiometry of plants,litter,and soil differed among the four stands,and the C:N and C:P of plant leaves were greater in both CT and MF than in PF and PM,with N:P showing:CT>PM>PF>MF;the N:P of plants litter was:CT>MF>PM>PF,indicating that the decomposition of litter in PM,CT,and MF was limited by P;the N:P of soil was:CT>PF>PM>MF,indicating that the soi lof CT,PF and PM was limited by phosphorus compared with mixed forest.(2)There were some differences in the diversity indices of soil microbial communities in different forest stand types.The diversity indices of soil bacterial and fungal communities were significantly higher in fir plantations than in other stands.The overall a diversity indices of soil bacterial and fungal microbial communities were:PF>PM>MF>CT.The β diversity of soil fungal and bacterial communities differed significantly among the four forest types,and the community structure was significantly different between PM and MF.(3)The structure of soil microbial community composition varied greatly among different forest types,mainly in the abundance of dominant phylum taxa.For soil bacterial communities,the dominant phyla were Acidiobacteria,Proteobacteria and Chloroflexi,at the level of fungal community families,Russulaceae The four fungal families,Russulaceae,Dermateaceae,Geminibasidiaceae and Mortierellaceae,differed significantly among different forest types.(4)There are five categories of primary functions and 34 categories of secondary functions in the biological metabolic pathway functions of soil bacterial communities in the four forest stands;among them,metabolic functions are dominant.The number of genes involved in nitrogen fixation in MF and CT was significantly higher than that in PM and PF,while the number of genes involved in nitrification,denitrification,nitrogen assimilation and reduction,and nitrogen dissimilation and reduction were significantly lower in CT and MF than in PM and PF.The soil fungal trophic type was mainly symbiotic,followed by saprophytic trophic type,and the pathotrophic type accounted for the smallest proportion in the four forest stands.The proportion of saprophytic trophic types was significantly higher in PF than in other stands,while the proportion of symbiotic trophic types was lower than in the other three stands.The proportion of endophytic fungal functional groups was significantly higher in MF and CT than in fir and PM.(5)Soil physical and chemical properties have a certain influence on the structure and diversity of soil microbial community,soil SWC,pH,SBD,SOC,TP,NH4+ all affect the soil microbial community structure,among which SWC,pH,SBD,TP,AK can explain the differences of soil microbial community structure.Ascomycota and Basidiomyceta showed a significant relationship with pH value and AK,and the differences in fungal composition and fungal functional groups between PF and the other three forests were caused by pH value and availiable potassium content.(6)Forest type had a significant effect on soil nutrient status and microbial community structure and function,and the dominant soil microbial community was closely related to soil nutrients.Compared with planted coniferous forests,mixed coniferous and broad-leaved forests were more favorable for the enhancement of soil organic carbon content and nitrogen fixation in this area.