Research On Plant Rhizosphere Microbial Communities And Theirdissolution Effects,in Jianshui Karst Area,Yunnan Province

Rocks in karst area are most soluble.Microorganisms can promote the rocks weathering,accelerate soil formation,improve soil fertility by influencing rock dissolution,which accelerated the restoration of ecological environment in karst areas.In present study,the soil samples were collected respectively in the rhizosphere of Eucalyptus robusta plantation,Pinus yunnanensis plantation and natural secondary forest growing up in karst and non-karst areas of Jianshui,Yunnan.In order to comprehensively understand the soil ecological environment in karst areas,we First explored the soil physical and chemical properties,soil enzyme activities,and the microbial community structure.Second,we examined the rate of dissolution in karst areas under natural conditions.Simulanting lab was perfomed to learn the effect of microorganisms on the dissolution of calcium carbonate rocks under mixed inoculation,then strains with strong dissolution ability were isolated,and the effects of the strain inoculation on the structure of soil microbial community and the dissolution of calcium carbonate rocks was studied through the pot experiments.Main contents and conclusions of this study are as follows:1.The result of soil research in Jianshui showed:(1)the number of actinomycetes was largest in karst areas.And the soil enzyme actitives were higher in karst areas than in non-karst areas.Soil enzyme activity positively correlated with moisture,organic matter and pH both in rainy season and dry season.(2)The structural diversity of rhizosphere microbial communities was analyzed in karst and non-karst areas,results showed significant differences in the composition and structure of microbial communities of the karst and non-karst areas,while the abundance of Actinomycetes class and Eurotiomycetes class was relatively higher in karst areas,the community structure in Pinus yunnanensis was similar to the natural secondary forest,the variations in microbial community structure are influenced by vegetation factors in a great degree.2.Exploring the rocks dissolution in karst area under natural conditions and the effect of mixed soil microorganisms on dissolution of calcium carbonate rocks in simulant condition:(1)it showed that the rocks dissolution were stronger in rainy season compared with dry season in the same plot,while in the same season,the dissolution of rocks in Pinus yunnanensis plantation was the greatest.(2)the effect of mixed soil microorganisms on dissolution of calcium carbonate rocks was higher in karst areas than in non-karst areas,which may conducted by the selective effect on the microbe under different geological conditions.(3)The treatment group with microbial inoculation was better than the control group in the rate of dissolution,which indicated that microorganisms could promote the weathering of calcium carbonate rocks and accelerate soil formation.3.We screened the microorganisms which can produce the carbonic anhydrase and applied it to the pot experiments:(1)it showed that In the rhizosphere soil,105 strains were obtained in this experiment.The CA activity and the dissolution of microbiology on dissolution of rocks was measured,and strain-KS289 with strong dissolution effect was obtained.The 16S rRNA gene sequencing identified the above strain as Serratia marcescens.(2)Pot experiments were conducted to investigate the effects of strain-KS289 inoculation on the functional diversity of edaphon communities and dissolution of rocks.The results showed that Serratia marcescens could change utilization ability of six carbon sources in microbial community,and promote the dissolution of calcium carbonate rocks.The dissolution of rocks in Pinus yunnanensis treated with Serratia marcescens on was the highest,the possible reason is KS289 has a co-existing relationship with the vegetation and promote the occurrence of dissolution effectively.This study provides a basis for understanding the soil conditions and microbial community structures in karst areas.And it accelerates the application of microorganisms in promoting soil formation and contributes to utilization of vegetation and microorganisms in environmental management in karst areas.