Soil Bacterial Diversity Under Different Land Use Types In The Yuanjiang Dry-Hot Valley

Soil microorganisms directly or indirectly participate in all soil processes and play a key role in the material circulation and energy conversion of the ecosystem.However,the influencing factors and controlling mechanisms of soil microbial diversity in different ecosystems and environments are uncertain.Therefore,in this study,three land use types including farmland,garden land and forestland were selected in typical dry-hot valley of Yuanjiang River,and soil samples were collected along four elevation gradients of<600 m.600-700 m,700-800 m and>800 m under each land use method.In this paper,soil bacterial 16S rDNA was sequenced based on Illumina HiSeq second-generation high-throughput gene sequencing technology.Based on the molecular variance analysis,single factor analysis of variance,redundancy analysis and typical correlation analysis,spearman rank correlation analysis and structural equation model.,and other statistical methods to analyze the typical dry-hot valleys area soil bacterial community composition structure and the influence factors of soil bacteria diversity.The main research results are as follows:(1)In each altitude gradient,the order of the number of soil bacteria OTU(Operational Taxonomic Units)is expressed as forestland>farmland>garden land,and both show significant differences only between forestland and garden land(p<0.05).The soil bacterial OTU of the three land use types is the largest at an altitude of<600 m or 600-700 m.The dominant phyla were Proteobacteria,Actinobacteria,Firmicutes,Chloroflexi,and Acidobacteria collectively accounting for more than 75%of bacterial relative abundance in all soil samples.(2)The soil bacterial community structure between different land uses shows different differences in altitude gradient.The soil bacterial community structure of forestland showed significant difference(p<0.05)between other altitude gradients except 600-700 m and 700-800 m;the soil bacterial community structure of the garden land was no significant difference between<600 m and>800 m,700-800 m and>800 m,and other altitude gradients showed significant differences(p<0.05).The soil bacterial community structure of the farmland showed no significant difference between the four altitude gradients(p<0.05).On the altitude gradients of<600 m and 600-700 m,soil bacterial community structure showed significant differences between forestland,garden land and farmland(p<0.01).(3)The Shannon and Simpson indices of soil bacteria showed a trend of decreasing with increasing altitude,but the ACE and chao1 indexes showed no obvious trend with the increase of altitude;only the Simpson index of agricultural soil bacteria showed an increase with altitude.The increasing trend;the four alpha diversity indices of the garden did not show a clear trend with the increase of altitude.On the gradient of<600 m,600-700 m,700-800 m,the order of Shannon,Simpson and ACE index of soil bacteria were expressed as forest land>farmland>garden land.(4)Redundancy analysis(RDA)indicates that land use is the main controlling factor of soil bacteria a diversity index in dry-hot valley regions.Structural equation modeling(SEM)analysis shows that both soil pH and soil available potassium content can have a significant impact on soil bacteria Shannon and ACE index.The typical correlation analysis showed that the soil bacterial community structure of forestland,garden land and farmland was mainly affected by soil moisture,soil bulk density,powder and C/N.