Organic Carbon, Nitrogen And Enzyme Content Characteristics Of Rhizosphere Soils Under Four Suitable Plants In Alpine Sandy Land In Northwestern Sichuan

In recent years, grassland desertification has been one of the most serious environmental problems around northwest Sichuan due to long-term wind erosion, overgrazing, and human activity. Plant ecological rehabilitation is one of the important means to repair desertification soil. Screening plant material with strong recessive resistance and good controlling effect is the key of plant ecological rehabilitation. Reveal the rhizosphere soil organic carbon, nitrogen accumulation characteristics and soil biological characteristics of different alpine desertification land suitable plant is of great significance. Therefore, four typical suitable plants including Peucedanum praeruptorum, Ajania potaninii, Potentilia discolor and Carex atrata were chosen from the Northwestern Sichuan, to study the difference of carbon, nitrogen and enzyme activity characteristics of between the rhizosphere and non-rhizosphere soil by using field sampling and laboratory analysis. The results will provide important scientific basis and theoretical reference for revealing the response mechanism between rhizosphere soil quality changes and plants, screening suitable plant for governance of desertification, exploring the desertification soil repair mechanism and protecting ecological environment. The main research conclusions were as follows:（1） The average plant height, crown, root length and underground biomass and total biomass of four optimum plant in northwest Sichuan alpine sandy are the following trend:P. praeruptorum>A. potaninit>P. discolor> C. atrata （P<0.05）, while the ground biomass present A. potaninii> P. praernptorum>P. discolor> C. atrata （P<0.05）, indicting that P. praeruptorum and A. potaninii could accumulate relatively more dry matter and be suitable for the treatment of the desertified land.（2） The concentrations of soil total organic C （SOC）, dissolved organic C （DOC）, readily oxidation organic C （ROC）, particulate organic C （POC） and microbial biomass carbon （MBC） in rhizosphere soil were higher than that in non-rhizosphere among the four species of suitable plants in alpine sandy land in Northwestern Sichuan, which are obviously enrichment in the rhizosphere （P<0.05）. SOC, DOC and POC and ROC content in the rhizosphere soil between four kinds plants were significant difference （P<0.05）. among them for P. praeruptorum reached the highest of 4.06 g kg-1,38.75 mg kg-1,1.79g kg-1,1.17 g kg-1,114.53mg kg-1, followed by A. potaninii, P. discolor and C. atrata.（3） The soil total nitrogen （TN）, alkali solution nitrogen （AN） and ammonium nitrogen （NH₄⁺-N）. nitrate nitrogen （NO₃^--N）, dissolved organic nitrogen （DON）, and microbial biomass N （MBN） in the rhizosphere soil were higher than that in non-rhizosphere among the four species of suitable plants in alpine sandy land in Northwestern Sichuan, which are obviously enrichment in the rhizosphere（P<0.05）. TN, AN, NH₄⁺-N, NO₃^--N, DON, and MBN content in the rhizosphere soil between four kinds plants were significant difference. Among them, TN, AN, NH₄⁺-N, DON and MBNof P. praeruptorum reached 0.75 g kg-1,42.38 mg kg-1,7.90 mg kg-1,15.56 mg kg-1 and 20.63 mg kg-1, which were significantly higher than that of A. potaninii, P. discolor and C. atrata. While for NO₃^--N of rhizosphere soil followed:P. praeruptorum>A. potaninii>P. discolor> C. atrata. There was not significant difference between P. praeruptorum and A. potaninii, but were significantly higher than in P. discolor and C. atrata.（4） The soil cellulase, amylase, invertase, urease, and proteinase activity of nitrate reductase in the rhizosphere soil were higher than that in non-rhizosphere among the four species of suitable plants in alpine sandy land in Northwestern Sichuan. Between different plant rhizosphere soil invertase and protease activity of nitrate reductase appears P. praeruptorum>A. potaninii>P. discolor> C. atrata （P<0.05） There was not significant difference between soil cellulase, amylase. urease and proteinase activity of rhizosphere soil in P. praeruptorum and A. potaninii, but were significantly higher than in P. discolor and C. atrata （P<0.05）（5） P. praeruptorum, A. potaninii, P. discolor and C. atrata were all beneficial to the accumulation of soil organic carbon and enhance the soil enzyme activity, and could be used as the plant material for treatment of alpine sandy land in the Northwestern Sichuan. The optimization order of these plants followed by P.praeruptorum, A. potaninii, P. discolor and C. atrata based on the consideration of their biomass and the rhizosphere effect of soil total organic C, N and soil enzyme activity.（6） There were significant （P<0.05） or significantly （P<0.011） positive correlations between the soil organic C and soil basal respiration, NH₄⁺-N. cellulase, amylase. and urease in rhizosphere soil under the 4 species of suitable plants; while no significant correlations were observed between TN and other indicators （P>0.05）:There was no significant correlation between sucrase and other indicators （P>0.05）, besides POC （P< 0.05）; urease had an significant positive correlation with AN、NO₃^--N、NH₄⁺-N and MBN（P<0.05）; while nitratase had only an significantly positive correlation with NO₃^--N （P<0.01）. In the non-rhizosphere soil, only the SOC and sucrase; ROC and NH₄⁺-N; DOC and basic respiration intensity NO₃^--N, NH₄⁺-N, cellulase and protease; MBC and basic respiration intensity, NO₃^--N, NH₄⁺-N, DON were significant （P<0.05） or significantly （P<0.01） positive correlation, and the rest were not significant （P> 0.05）. However, in the all of N index, there was only significant negative correlation between TN and protease （P<0.05）, and significant...