| Soil b acteria are an important part of forest ecosystem and play an important role in driving material cycle and energy flow.To better understand the diversity and spatial distribution mechanisms of soil bacterial communities in forest ecosystems,this study was based on dynamic monitoring plots in the Baiyun Mountain National Forest Park,this study adopted high-throughput sequencing technology to sequence the bacteria in 120 soil samples in the sample,and explored the spatial distribution mechanism and ecological process of soil bacteria under different bacterial taxas,altitude gradient,humidity gradient and different terrain habitats.The specific research results are as follows:(1)In order to compare the diversity and coexistence mechanism of bacterial habitat generalists,specialists,and neutral taxa,the spatial distribution,ecological process and environmental adaptability of different bacterial taxa were analyzed.The results showed as follows: 1)The diversity and community composition of the generalists and the specialists were significantly different;2)In forest ecosystems,the bacterial habitat specialists were affected by stochastic processes,while the generalists were more susceptible to deterministic processes.3)Network analysis showed that habitat specialists played a more important role than generalists in maintaining the stability of bacterial community co-occurrence network.4)Light and spatial eigenvectors(PCNM)are important driving factors for the generalists,specialists,neutral taxas and all species.The specialists are more sensitive to environmental filtering than the generalists,and changing the light and spatial factors may have a greater impact on the specialists.The differences in diversity and coexistence mechanisms between specialists and generalists may be due to their different adaptations to the environment.The spatial distribution patterns and community assembly mechanism of habitat specialists were different from generalists.(2)In order to investigate the distribution characteristics and driving mechanism of soil bacterial taxa at different altitudes gradients(high,middle and low altitudes gradient),the characteristics of bacterial community structure and its driving factors were investigated.The results showed that: 1)There were significant differences in soil bacterial community composition at different altitude gradients.According to the niche breadth index,767 OTUs were defined as generalists,6753 OTUs were defined as neutral taxas,and 5332 OTUs were defined as specialists.The diversity of the generalists and the specialists was significantly different in different altitude gradients.2)At different altitudes,stochastic processes play an important role in the bacterial community process.3)The main environmental factors affecting the whole bacterial community and other taxas were different in different altitude gradients.Altitude,slope,convexity,organic matter and alkali-hydrolyzed nitrogen were identified by RDA as significant influencing factors of the whole bacterial community(P <0.05),while the community composition of specialists,neutral taxas and generalists were significantly affected by altitude,slope,aspect,convexity,leaf area index,light transmittance,available phosphorus,alkali-hydrolyzed nitrogen,soil p H and soil water content(P < 0.05).More importantly,compared with soil and terrain,light is the dominant environmental factor driving the variation of entire bacterial communities and other groups at different elevations.The change of altitude gradient will lead to significant differences in the diversity and community composition of bacterial taxas.(3)In order to explore the diversity and coexistence mechanism of soil bacteria in different habitat types(ridge,valley,hillside),the spatial distribution and ecological process of bacterial groups in different habitats were analyzed.The results showed as follows: 1)The bacterial community composition was changed with the change of habitat type,and the bacterial diversity increased significantly with the change of ridge,hillside and valley;2)In the valleys,ridges and slopes of forest ecosystems,most of the distribution patterns of soil bacteria are not random,but specialized,and prefer to be distributed in valleys;3)The stochastic process played a dominant role in the bacterial community of different habitat types;4)Altitude,convexity,slope and canopy cover had significant effects on the distribution pattern of bacteria,and light was the main factor affecting the bacterial communities in different habitats.The change of habitat type will affect the diversity of soil bacterial community,and light is a major driver of bacterial community.(4)In order to explore the structural characteristics of soil bacterial communities under different humidity gradients(low humidity gradient,medium humidity gradient and high humidity gradient)and different taxa(abundant taxa and rare taxa),the spatial distribution,ecological process,co-occurrence pattern and environmental adaptability of different bacterial taxas were analyzed.The results showed that: 1)The diversity of all taxas,abundant and rare taxas were significantly different under different humidity gradients,and increased with the increase of humidity gradients;2)The co-occurrence network were dominated by rare communities,and the relationship between bacterial communities were mainly positive,which means that the rare groups play a more important role in the stability of the network;3)The stochastic and deterministic processes affect the bacterial community at different humidity gradients simultaneously.Stochastic processes dominated the combination of rare taxas with narrow niche widths,while deterministic processes contributed more to abundant taxas;4)RDA and Mantel tests showed that all bacterial,abundant and rare taxas were mainly affected by altitude,organic matter,soil alkaline-hydrolyzed nitrogen,soil p H,soil water content and available phosphorus.The variation of soil moisture significantly affected the diversity of abundant and rare taxa and the process of community assembly.In conclusion,this study explored the diversity and coexistence mechanism of soil bacteria under different bacterial taxa,altitude gradients,humidity gradients and different habitat types,the results indicated that habitat differentiation had an important effect on soil bacterial diversity.The results also indicated that habitat changes could alter the ecological processes and network stability of bacterial communities.The results may broaden the understanding of the dynamic structure,interaction and community construction of soil bacteria in soil ecosystem,and provide a theoretical basis for the sustainable development and management of soil bacteria. |
