| Rocky desertification is the ultimate form of soil quality degradation and degradation in karst areas.It has become one of the most serious ecological and environmental problems that threaten human life,socio-economic development and ecological environment safety in this area.As a large area of rock is exposed,the soil layer is shallow and the distribution is not continuous,resulting in poor vegetation restoration.Zanthoxylum bungeanum,as a local economic species with strong ability to conserve water and soil,increase the income of local people.With the extension of planting time,whether Zanthoxylum bungeanum can continue to promote local soil quality and ecological restoration remains to be further studied.The soil microbial communities and functions are extremely sensitive to environmental changes and are important indicators for predicting the succession of the ecological environment.At present,there are few research reports on the succession rule of Zanthoxylum bungeanum rhizosphere soil microorganisms over time.In order to explore the interaction mechanism between the physical and chemical factors of rhizosphere soil-enzyme activity-microorganisms of Zanthoxylum bungeanum with the change of planting years.In this study,we selected healthy individuals of Zanthoxylum bungeanum at 5a,10 a,20a,and 30 a in Guanling,Guizhou,for a two-year research experiment.16 Sr RNA and indoor simulation experiments were used to analyze the bacterial community structure and ecological function of Zanthoxylum bungeanum rhizosphere soil in different years,and explored the rhizosphere.The relationship between soil physical and chemical factors-enzyme activity-bacterial microorganisms aims to provide a scientific basis for soil ecological protection and sustainable use of soil in karst areas.The main conclusions are as follows:(1)The physical and chemical factors of the rhizosphere soil of Zanthoxylum bungeanum were different in different years,but they did not reach a significant level(P>0.05).The diversity analysis of soil bacteria ? showed that the Observed?otus,Chaol,Shannon and Simpson indexes were different in different years,but they did not reach a significant level(P>0.05).The Shannon index increases with the increase of planting years,that is,5 a<10 a<20 a<30 a.The Simpson index reached its lowest value in 5 years and its highest value in 30 years.The Chao 1 index and Observed?otus index of the 10-year Zanthoxylum rhizosphere soil samples were the smallest compared with the other three planting years.The principal coordinate analysis showed that the bacterial communities in the rhizosphere soil of Zanthoxylum bungeanum became similar gradually with the increase of years;the difference indicator species analysis 5a,10 a,20a,and 30 a showed differences in indicator species.Redundancy analysis shows that organic matter is the primary influencing factor for the distribution of bacterial communities;non-metric multi-dimensional scale analysis shows that the rhizosphere soil of Zanthoxylum bungeanum abundant and rare taxa have obvious differences;potential correlation analysis shows that there are more positive correlations between abundant taxa and environmental factors,and rare taxa has stronger phylogenetic signals than abundant taxa.It shows that abundant taxa are more sensitive to changes in environmental factors,while rare taxa are more conservative in development.(2)With the increase of planting years,the activities of different enzymes in rhizosphere soils are different.Urease activity,phosphatase activity and invertase activity all show a trend of first decrease and then increase with the increase of years.Urease and invertase activities all have their lowest values in 20 a.Phosphatase activity reached its lowest value at 10 a.Catalase activity gradually increases with the increase of years.The activity of phosphatase in the rhizosphere of Zanthoxylum bungeanum was low at 10 a,which indicated that the conversion and absorption of phosphorus in the rhizosphere of Zanthoxylum bungeanum was slow.The activity of urease and invertase at 20 a were low,indicating that the rate of soil carbon and nitrogen conversion was reduced.Correlation analysis showed that urease activity was significantly positively correlated with soil organic matter and soil total nitrogen,and pH was significantly positively correlated with soil phosphatase activity.Catalase activity has a very significant positive correlation with water content,and a significant negative correlation with total carbon.The degree of correlation between soil enzyme activity and soil microbes is relatively high(the correlation coefficient is greater than0.4).Generally,the law of action is obvious.Studies have shown that changes in soil enzyme activity are closely related to the competition between microorganisms,and there are significant correlations between different phylum and their effects are more obvious.(3)The Bugbase biological phenotype prediction shows that with the increase of planting years,the aerobic in the rhizosphere soil of Zanthoxylum bungeanum increased,the facultatively-anaerobic gradually increased,the anaerobic gradually decreased,the forms-biofilms and the content-mobile-elements first decrease and then increase.Gram-positive bacteria and gram-negative bacteria have an antagonistic growth trend.Oxidative stress-tolerant bacteria are higher than 5a at 20 a and 30 a,and pathogenic bacteria at 10 a are lower than 5a and 10 a at 20 a and 30 a.It shows that the long-term planting of Zanthoxylum bungeanum affects the change of the soil environment and indirectly affects the bacterial groups in the rhizosphere soil.Therefore,it is recommended that proper plowing,improve soil permeability,and proper fertilization management are helpful to healthy and sustainable development. |
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