| Soils are rich in microbial resources and play an essential role in the material cycle and energy flow of ecosystems.This is of great theoretical and practical importance to the investigation of microbial diversity and communities in relation to microbial resource use,ecosystem conservation and global environmental issues such as rapid climate change.At present,research on forest soil microorganisms along the altitude gradient in China is mainly focused on the surface layer of the forest,but studies on deeper soil microorganisms are rare and controversial.Therefore,there is an urgent need to conduct comprehensive studies on forest soil microorganisms along the altitude and soil layers.The Huangshan Nature Reserve in Anhui Province,with its subtropical climate and rich biological resources,provides an ideal site for this study.In this thesis,soil samples from two soil layers under four elevations on the elevation gradient of the Jiulongfeng Forest Reserve(500～1100 m)were used to conduct a comprehensive study on the diversity and community structure of soil bacteria and fungi using second-generation sequencing techniques,combined with soil and vegetation information.The main results are as follows:1.soil bacterial diversity showed a U-shaped pattern with altitude,with greater diversity in the surface layer than in the sub-surface layer,and different dominant species in the community between soil layers;soil pH and fast-acting potassium had significant effects on bacterial diversity in the surface and sub-surface layers of the soil,respectively;bacterial community structure differed between both altitude and soil layers,and the effect of soil layer was greater than that of altitude,and soil reactive organic carbon was the most significant driver affecting the bacterial community in the surface layer,while Soil active organic carbon was the most significant driver of the surface bacterial community,while altitude was the driver of the surface bacterial community;the bacterial community building process in different soil layers at different altitudes was mainly dominated by stochastic processes.2.Soil fungal diversity did not follow a fixed pattern with increasing altitude and did not differ significantly between soil layers;there were differences in the dominant fungal phyla between soil layers;altitude,pH and water content were limiting factors for fungal diversity in the sub-surface layer,but not in the surface layer;soil fungal communities showed significant differences in structure after removing the high altitude sample sites;soil fastacting potassium was the main driver of fungal communities in the surface layer,but not in the sub-surface layer;fungal communities in the The fungal community is dominated by stochastic processes in both the inter-altitude and soil layers,diffusion-limited in the subsurface layer and non-dominated in the surface layer,with homogenous diffusion evident at high altitude.3.The network topology of both soil bacterial and fungal communities varies considerably at different altitudes,with bacterial coexistence networks being more complex in the surface layer than in the subsurface layer,while the opposite is true for fungi.Microorganisms differ between soil layers due to their environment and their own functions,resulting in different key species,and play different ecological functions between soil layers.In summary,this thesis presents a comprehensive analysis of soil microorganisms in surface and subsurface layers at different elevations in terms of diversity,community construction,drivers and network keystone species identification of soil bacteria and fungi,emphasizing the importance of stochastic processes in the construction of soil microorganisms,the different elevation patterns of microorganisms between different soil layers,and the large differences in networks and keystone species for subtropical forest This study provides a scientific basis for the driving mechanisms of soil microbial communities in subtropical forest ecosystems. |
