| In the study, slope cropland at different years at Dunshan watershed in loess hilly region was chosen as object, the approach of spatial sequence instead of temporal sequence was adopted to analyze the change of microbial properties in rhizosphere soil during vegetation succession after field investigation and laboratory determination. The change of microbial biomass, respiration and enzyme activities in rhizosphere soil of different vegetation and their effect on rhizosphere effects during succession sequence was also studied. The key rhizosphere microbial indicators of different vegetation were screened, on the basis of which rhizosphere microbial index (RMI) was put forward. The goal was to provide scientific reference and for vegetation rehabilitation and assessment of soil quality as well as biological effect in the hilly Loess Plateau. The main results are as follows:1. Soil phycio-chemical and biological properties of the abandoned slope cropland in loess hilly region were investigated. The results showed the contents of soil organic matter, total N, available N, available P, available K, microbial biomass C, microbial biomass N, Cmic/TOC, Nmic/TN, invertase, urease, alkaline phosphatase, cellulose, catalase, peroxidase in north slope increased to varying degree, while bulk density and pH generally dropped with extension of years. In sunny slope, soil organic matter, total N, available N, available K, microbial biomass C, microbial biomass N, induced respiration increased significantly, while catalase and peroxidase did not change obviously, polyphenol oxidase dropped with years.2. Evolution of microbial properties in different vegetation rhizosphere soil was analyzed. In north slope, microbial biomass C, microbial biomass N, invertase, urease, catalase in rhizosphere soil of Artemisia capillaries and Artemisia sacrorum increased significantly during succession, while basal respiration and induced respiration fluctuated dramatically, qCO2 gradually dropped with years and peroxidase did not change significantly. In sunny slope, microbial biomass C, microbial biomass N of Artemisia capillaries increased markedly, induced repiration, qCO2, alkaline phosphatase, catalase, polyphenol oxidase shown the trend of firstly rising and then dropping, invertase and cellulose decreased apparently in early 3 years, and there was not significant change in basal repiration. In rhizosphere soil of Stipa bungeana, microbial biomass C, microbial biomass N, urease, basal repiraton, induce respiration, invertase, alkaline phosphatase generally shown trend of drop-stable-rise.3. During the vegetation succession, the rhizosphere effects of Artemisia capillaries were significant such as microbial biomass C, microbial biomass N, basal respiration, induced respiration,invertase,alkaline phosphatase, catalase and peroxidase, while for the Artemisia sacrorum, microbial C, microbial biomass N, basal respiration, invertase, alkaline phosphatase, catalase and peroxidase are significant indicators. Except the induced respiration and qCO2, other indicators'rhizosphere effects are significant for Stipa bungeana. In north slope, rhizosphere effects of microbial C, microbial biomass N, basal respiration, invertase, peroxidase increased fast in early stage of succession, slow down in the middle and late stages in Artemisia capillaries, and in Artemisia sacrorum, microbial C, microbial biomass N, basal respiration, invertase and catalase rose significantly between 10-13 years, then dropped constantly 13 years later. In sunny slope, microbial C, microbial biomass N and catalase rhizosphere effects in Artemisia capillaries increased significantly with extension of restoration years, basal respiration and peroxidase rose in early stage and dropped later, alkaline phosphatase kept increasing in early 5 years, then dropped markedly. In Stipa bungeana, microbial C, microbial biomass N rhizopshere effects declined significantly and alkaline phosphatase, catalase, peroxidase took on rising firstly and dropping subsequently.With the development of succession, the early successional vegetation rhizosphere environment played a more significant role in rhizosphere effect of invertase, alkaline phosphatase, cellulose than later ones, while the effects of the later vegetation on basal respiration and induced repiration were more significant.4. During the process of succession, effects of late successional vegetation on rhizosphere soil microbial properties were more significant than that of previous ones, which could be shown in microbial biomass C, basal respiration, induced respiration, invertase, urease, alkaline phoshatase, cellulose and polyphenol oxidase in north slope, and in sunny slope, shown in microbial C, microbial biomass N, basal respiration, induce respiration, invertase, urease, alkaline phoshatase and peroxidase. Besdies, the effects of north slope on rhizosphere microbial properties were more significant than that of sunny slope.5. Based on principal component analysis, in north slope, microbial biomass C, microbial biomass N, qCO2, invertase, urease, cellulose and polyphenol oxidase can generally reflect the characteristics of the rhizosphere microbial properties of Artemisia capillaries and Artemisia sacrorum. In sunny slope, microbial biomass C, induced respiration, urease, cellulose as well as polyphenol oxidase are important rhziosphere soil factors for Artemisia capillaries and Stipa bungeana. From the discussion above, it can be concluded that whether in north slope or in sunny slope, the microbial biomass C, urease, cellulose and polyphenol oxidase were the key indicators for three different species during vegetation succession. The analysis of rhizophere microbial index (RMI) showed that RMI of Artemisia capillaries and Artemisia sacrorum in north slope, RMI of Artemisia capillaries in sunny slope took logarithmic growth with extension of years, while that of Artemisia sacrorum rose significantly in the early stage and then kept dropping.
|
PDF Full Text Request