Seasonal Dynamics Of Rhizospheric And Root Endophytic Microbe Communities Of Pinus Tabulaeformis And Pinus Armandii In Qinling Huodingtang

Microbe, as an important part of the ecosystem, is a main driving force in biogeochemical cycles and plays a role in decomposition of organic matter, mineral nutrition releasing, nitrogen and carbon cycles. Microbial genetic diversity is important for maintaining the stability of terrestrial ecosystems. Soil factors(such as pH, organic matter content, etc.)and microbial community usually affects by seasons via changing of the micro-environment(such as temperature, moisture, sunlight, ultraviolet rays, etc.) and vegetation. Studies have shown that season influence the community structures and diversities of the rhizospheric soil microbes and root endophytic fungi by changing the climate, soil properties and vegetation.In this study, samples were also collected from the Pinus tabulaeformis and Pinus armandii forest plots at 1900 m in August 2014, November 2014, January 2015 and August2015, respectively. The impacts of season and tree species on micro-environment,rhizospheric soil physical and chemical properties, soil enzyme activity, mycorrhizal colonization rate, and communities of rhizospheric soil microbes and roots associated fungi were studied. Based on the results, the biogeographical distribution roles and seasonal dynamics of rhizospheric soil microbes and roots associated fungi were analyzed. In addition,the impacts of climate, soil and plant species on the distributions of soil microbes and root endophytic fungi also were simply analyzed. The main results were listed as follows:1. In P. tabulaeformis and P. armandii stands, rhizospheric soil physical and chemical properties, soil temperature and moisture were significant difference among four seasons except soil organic matter and carbon-nitrogen ratio. Only phosphatase and catalase activities were significantly associated with the seasons and no difference of soil mycelium density was found among seasons.2. Season was the main factor which caused changes in communities of pine rhizospheric soil microbes. Species Richness, Diversity and Evenness index of rhizospheric soil bacteria and fungi communities in summer were lower than the other seasons, and reached top in spring. Proteobacteria and Acidobacteria were the dominant population in pine tree rhizospheric soil bacterial communities with significant changes among the four seasons.Therefore, rhizospheric soil bacterial communities of pine tree were most impacted by season.In rhizospheric soil of pine trees, Basidiomycota were more than Ascomycota in both summer and autumn,, but decreased in winter and spring with along an increase of Ascomycota,suggesting Ascomycota has better tolerance to cold environment.3. Colonization rates of ectomycorrhizal(ECM) fungi in roots of P. tabulaeformis and P.armandii were affected by season, and microsclerotia colonization rate of dark septate endophytes(DSE) in roots of P. armandii was significant higher than in P. tabulaeformis’.The Species Richness, Diversity and Evenness index of pine root endophytic fungi also influenced by season, and the lowest value appeared in summer and the highest in spring. In P.tabulaeformis and P. armandii stands, ECM fungi grew faster than DSE in higher temperature spring and slowly down when temperature reduced in autumn, but DSE exhibited smaller changes. Therefore, ECM fungi preferred higher temperature environment, while DSE showed better tolerability to low temperature. Season was the main impact factor to the pine root endophytic fungal communities, and pine species showed a selection effect on root endophytic fungal communities.