Study On Altitude Distribution Patterns And Driving Factors Of Soil Microbial Diversity In The Tropical Montane Rainforest Of Yinggeling National Nature Reserve In Hainan Island

Hainan Yinggeling National Nature Reserve,located in the middle of the Limu Mountains in the south-central part of Hainan Island,is a forest ecological type reserve which mainly protects the tropical rain forest and its ecosystem.Yinggeling nature reserve plays an irreplaceable role in water conservation,species protection,climate regulation,air purification and so on.It is the ecological core of the south-central part of Hainan.Previous studies have shown that the vegetation of Tropical Montane rain forest in Yinggeling Nature Reserve has obvious vertical distribution characteristics,but less research is involved in the distribution characteristics and driving factors of soil microbial community,which is closely related to the material conversion and energy flow in the tropical montane rain forest ecosystem.Based on this,this study took the tropical mountain rainforest in Yinggering nature reserve as the research object,and selected a total of eight fixed sample plots at different altitudes,and analyzed the characteristics of soil microbial functional diversity and community diversity at different altitudes by using Biolog-ECO micro-plate technology and Illumina miseq high-throughput sequencing technology.Through the correlation analysis with vegetation types,soil physical and chemical properties and soil enzyme activities,to explore the altitude distribution pattern and driving factors of soil microbial diversity in the tropical montane rainforest of Yinggeling,Hainan.The main results are as follows:（1）The plant community in the plot is rich in species,with a total of 61 families,146genera and 246 species.Fagaceae,Camellia,Euphorbiaceae and Lauraceae are the main dominant families.The elevation gradients of dominant families,genera and species in each plot are heterogeneous.The vegetation species richness and species diversity of the sample plot increased first and then decreased with the increase of altitude,which conformed to the pattern of“Middle Peak Distribution”and the theory of“Middle Height Expansion”,respectively.The diversity of plant communities on different slopes at the same altitude is mainly influenced by complex and changeable environmental factors such as water,heat and topography.The altitudinal gradient affects the distribution patterns of families and genera,the structure of plant community was different in different altitude plots,and the similarity of plant community was very different.The pantropic distribution of families is dominant,the pantropic,tropical Asia and north temperate distribution of genera are relatively high.（2）The physical and chemical properties of soil and litter and soil enzyme activities were significantly different in some elevations,and the southern slopes and the northern slopes were different.Except for soil alkali-hydrolysable nitrogen（A-h N）,there were significant correlations among other soil ecological factors.The altitude was very significantly positively correlated with soil organic matter,total nitrogen（TN）,ammonium nitrogen（NH₄⁺-N）and nitrate nitrogen（NO₃^--N）content,Catalase,Acid Phosphatase and Urease activities,while positively correlated with soil total phosphorus（TP）content and negatively correlated with soil p H.The altitude differences of soil and litter physical and chemical properties and soil enzyme activities and the correlation between soil environmental factors were mainly affected by comprehensive factors such as soil parent material,light,precipitation,temperature and plant community composition.（3）Biolog-ECO analysis showed that the functional diversity index of soil microbial community increased first and then decreased with the increase of altitude,which conformed to the pattern of“Middle Peak Distribution”,and the vertical zonal differences in the metabolic diversity of soil microbial carbon sources were mainly reflected in the utilization of carbohydrates,polymers and carboxylic acids,and the south slope and the north slope were different.The functional diversity of soil microbial community was significantly positively correlated with soil available phosphorus content,significantly negatively correlated with soil acid phosphatase and litter organic carbon content,and extremely significantly negatively correlated with soil catalase.There was also a significant difference between the north and south slopes.（4）The Alpha diversity of soil bacterial community did not change significantly with the increase of altitude,but the analysis of PCo A and NMDS showed that there were significant differences in bacterial communities among some plots at different altitudes.Proteobacteria,Acidobacteria and Actinobacteria were the dominant bacteria groups in soil communities at different altitudes.LEfse analysis revealed 57 differential bacteria,including54 species on the south slope and 10 species on the north slope.Through Tax4FUN analysis and PICRUST2 bacterial function prediction,we obtained 6944 homologous functional genes and 376 metabolic pathways.The number of genes was significantly enriched in the three metabolic pathways of carbohydrate metabolism,amino acid metabolism and global and overview maps,the results were consistent with the functional diversity of soil microbial community mentioned above.There was a positive correlation between soil community diversity and plant community diversity,and the south slope was different from the north slope.The diversity of soil bacterial community and plant community on the south slope and north slopes was significantly positively correlated and negatively correlated,respectively.RDA/CCA analysis showed that p H,available potassium（AK）and altitude were the main environmental factors affecting the soil bacterial communities.Correlation analysis found that the contents of total nitrogen（TN）and total potassium（TK）in litter were significantly correlated with the community composition of soil bacteria at different taxonomic levels.（5）The Alpha diversity of soil fungal community increased significantly with the increase of altitude,and the analysis of PCo A and NMDS showed that there were significant differences in fungal communities among sample plots at different altitudes.Basidiomycota and Ascomycota were the dominant fungal groups in soil communities at different altitudes.There was a positive correlation between soil fungal community diversity and plant community diversity,but the southern slopes and the northern slopes were different.Fun Guild function prediction found that the fungal trophotypes were mainly symbiotic and saprophytic,and there were significant differences between some altitudes.There was a significant positive correlation between soil fungal community diversity and plant community diversity on the southern slope,while no correlation on the the northern slope.RDA/CCA analysis found that the altitude,p H,total phosphorus（TP）and AK were the main environmental factors affecting the fungal communities.Correlation analysis found that the contents of TP and TN in litter were significantly correlated with the community composition of soil fugal at different taxonomic levels.In conclusion,the functional diversity of soil microbial community and the altitude distribution of soil microbial diversity in the tropical montane rainforest of Yinggeling are significantly different.The contents of soil available phosphorus,acid phosphatase and catalase,and litter organic carbon were the main factors affecting the functional diversification of soil microbial community with altitudes.The contents of TP,TN and TK in litter are significantly correlated with soil microbial community composition,and the plant community diversity was significantly correlated with soil microbial community diversity.Soil p H and AK content were the main influencing factors of bacterial community diversity with altitude,and the soil p H,TP and AK content were the main influencing factors of fungal community diversity with altitude.