Research On Soil Microbial Communities And Functional Responses Under Different Vegetation Succession Conditions In Rocky Desertification Areas

Rocky desertification restricts the benign and sustainable development of economy and society in karst area of Southwest China.Vegetation restoration as the most effective measure to control rocky desertification can be promoted in Southwest China.In yunnan over big Montenegro rocky desertification area in different recovery stage after peak cluster depression Qi Geng farmland,grassland,natural secondary forest(15 years,30 years)and forest as the research object,the collection of rocky desertification in different succession stages in the process of vegetation restoration of soil samples,with 16 s and nif H nitrogen-fixing bacteria genes as target,use technical means such as high-throughput sequencing,heat trace observation of soil microbial community composition,abundance,diversity and metabolic heat index,study function of soil microbial community and the variation law of through bioinformatics analysis,combined with the different stages of vegetation restoration of soil microbial microcalorimetric,The response and feedback of soil microbial community and microheat in different succession stages during the restoration of rocky desertification vegetation were clarified.The main research conclusions are as follows:(1)Different vegetation conditions have significant effects on the diversity of soil microbial community in rocky desertification area;At the same time,there were significant differences in soil microbial biodiversity between different vegetation conditions.During the process of natural vegetation succession and restoration,the effects of vegetation conditions on soil microbial community composition did not show different trends with the different collection sites.In addition,according to the ecological network analysis,Rhodoplanes,Pirellula,Pedomicrobium,Planctomyces,etc.all played an important role in different vegetation conditions for specific bacteria genera,and as the dominant bacteria genera,they were more closely related to other bacteria genera.(2)The Chao1 index,Shannon index and species evenness index of nitrogen-fixing microorganisms in rocky desertification area were significantly different among different vegetation.At the same time,through the community structure,it can be found in the rocky desertification grassland,woodland and 30 years in 15 years,its nitrogen-fixing microbes community composition present a certain degree of similarity,conform to the natural vegetation succession process of recovering in farmland,woodland and 30 years of 15 years nitrogen fixation in the microbial community composition and the differences in the group is relatively stable.In addition,by species interactivity,the nitrogen-fixing soil microbial community structure in different vegetation conditions,slow rhizobia genera(Bradyrhizobium),soil bacillus(Geobacter),nitrogen fixation spirillum(Azospirillum),nitrogen fixation vibrios(Azoarcus),Burkholderia bacteria genera(Burkholderia)as appear in different vegetation under the condition of the dominant key species at the same time,under the condition of the vegetation to have played a role in nitrogen fixation.In the ecological network diagram,the positive and negative expressions showed a trend of decreasing first and then increasing,and a higher proportion of positive correlation indicated that soil nitrogen-fixing microbial community had higher resistance to environmental pressure.The primary forest,as the last stage of natural vegetation restoration and succession,has the highest positive correlation and the strongest resistance to environmental pressure,which meets the expectation.(3)The results of microcalorification under different vegetation conditions in rocky desertification area showed that the basal metabolic activity of microorganisms in the farmland soil was lower than that in the primary forest,and the potential maximum metabolic activity of microorganisms in the farmland soil was significantly different from that in the primary forest after substrate induction(P<0.05).Compared with the 15-year forest,the potential maximum metabolic activity of soil microorganisms in the 30-year forest had a significant advantage(P<0.05).It also took longer for the soil microbial community to reach its maximum activity in the 30-year forest than in the 15-year forest.There was no significant difference in the soil microbial growth rate between the two,which indicated that the soil microbial community structure of the two showed a certain correlation and trend after natural ecological evolution.Compared with the farmland soil microorganisms,the soil microbial basal metabolic activities in grassland had little difference and were less than that in woodland after 15 years.After substrate induction,the potential maximum metabolic activity of soil microorganisms in grassland was slightly higher than that in farmland and slightly lower than that in 15-year woodland.However,the time required for soil microbial community to reach maximum activity in grassland was not different from that in farmland,and was significantly higher than that in woodland for 15 years.In addition,the soil microbial growth rate of grassland was lower than that of farmland and woodland in 15 years.