Responses Of Soil Microbial Diversity To Different Disturbance Gradients In Mountain Forests In Guangzhou

The species composition and diversity of microbial communities in forest soils are closely related to the structure and function of the whole ecosystem,and play an important role in maintaining soil fertility,improving soil structure,synergistic plant growth,and other ecosystem services and functions.However,with the development of urbanization,the growing expansion of city scale,frequent agricultural production activities,domestic sewage and industrial waste discharge,and other human disturbancehave led to changes of soil physiochemical composition,soil structure,and consequent soil pollution.Therefore,study on forest soil microbial diversity under disturbance will help us to understand the role of soil microbes in the whole ecosystem,and to guarantee the stability of the whole ecosystem and the healthy development of the forest and the maintenance of biodiversity.In this paper,high-throughput sequencing techniques were used to identify soil microbes by analyzing the bacterial 16 S rDN A and fungal ITS genes in the soil,w ith the aim of studying species composition,community structure,and diversity of soil microbes under disturbance in a subtropical forest in Guangzhou.The Soil microbial diversity variation under disturbance,the relationship between woody plant diversit y and soil microbial diversity,and the correlations between environmental factors and soil microbial diversity were also tested.The main conclusions are as follows:(1)In 27 plots,a total of 13272 bacterial OTUs were identified from 32 known kingdom,169 families,and 428 genera and a total of 12907 fungal OTUs were identified from 6 known kingdoms,208 families and 529 genera.The richness of bacteria,fungi,and OTUs,the specific OTUs along a disturbance gradient were highest in gradient 3 and lowest in gradient 2.The cluster analysis of the dominant genus and the dominant OTU and Nonmetric Multidimensional Scaling(NMDS)analysis showedsignificant differences in species composition of soil microbes along a disturbance gradient,indicating that the community structure and species composition of soil microbes were significantly changed by human disturbance.(2)The soil microbial community showed strong adaptability and resistance against disturbance.The soil microbes can maintained a high diversity level largely by changing species composition and community structure in response to disturbance.Therefore,when facing human disturbance,the community structure of forest soil microbes will change significantly,while the diversity may not necessarily decrease.In contrast,intermediate disturbance can enhance the richness of soil microbes.(3)The richness of bacteria was more sensitive than that of fungi when facing the changes of soil pH,nutrients,heavy metals,physical properties.However,fungi s how better stability under the impact of plant diversity,representing its association with plants.The soil p H and soil organic matter,total nitrogen,available magnesium and manganese,soil water content,soil aeration porosity,soil temperature,and litter thickness were the main driving factors of forest soil microbial diversity.(3)Plant diversity was not significantly correlated with soil microbial diversity.In this paper,whether the above-ground plants can significantly affect soil microbial dive rsity depended on whether the above-ground plants can significantly change the soil physiochemical properties through their roots and litter.(5)The soil microbial richness decreased in the economic forest land with regular clear cutting,and increased in the presence of thinning interference,which indicated that the ?intermediate disturbance hypothesis? was equally applicable in soil microbial communities.Disturbance led to a decrease in the content of nutrients,such as organic matter,which reduced the abundance of the dominant species in the community and consequently made room for other species.