The Soil Biological Characteristics in Successional Sequence of Degraded Karst Area
|School||Nanjing Forestry University|
|Keywords||Degraded Karst vegetation Successional sequence Soil quality Soil-microbes Soil enzyme activity|
The restoration and reconstruction of degraded ecosystem has become one of the focused problems of modern ecology. The research on Karst degraded ecosystem concentrated mainly on individual ecology, natural restoration of degraded community and physics and chemistry characteristic of soil quality aspects. Some achievements in practical experience were obtained, and new theories of Karst vegetation restoration were proposed. However, the whole process lacked the systematic study about microbiology characteristic of soil quality during the southwest degraded Karst vegetation restoration. Therefore, this paper took the soil during degraded Karst vegetation restoration of Ecological Synthesis Control demonstrated Area in Huajiang Karst plateau of Guizhou as research object. We studied some indexes of microbial activity (including some kinds of soil microbial amount, soil biochemical function and soil microbial biomass carbon, microbial quotient, basal respiration, metabolic quotient, functional diversity of microbial community and the soil enzyme activity) of different habitats, the different layers and the rhizosphere, non-rhizosphere in four seasons. On the basis of the community features of degraded Karst vegetation and physical and chemical characteristic of soil quality which were studied by predecessor, the microbial mechanism of soil quality evolution during degraded Karst vegetation restoration and microbial ecological restoration mechanism between plant and soil system were discussed, at the same time, soil quality evaluation index system was established. This study not only enriched restoration ecology, but also provided scientific proof of soil microbiology for vegetation restoration and reconstruction of degraded ecosystem in south Karst mountain area. The main study results were as following:(1) The soil microbial and enzyme activity of different habitats, the different layers, the different seasons and the rhizosphere, non-rhizosphere increased gradually with the vegetation restoration during degraded Karst vegetation restoration, taking on arboreal community stage > shrubby community stage > herbaceous community stage > bare land stage. But change of the metabolic quotient was just opposite, it decreased with the vegetation restoration. The amount of soil microbes was different obviously, which was the bacteria > the antinomies > the fungi, the bacteria was the dominant group, accounts for above 90%; Ammonifiers > Nitrogen-fixing bacteria > Cellulose decomposing microbes > Nitrifying bacteria. The total soil microbial number of arboreal community stage was the highest, reaching 72.49×10~5 per gram dry soil; the bare land is lowest, account to 29.96×10~5 per gram dry soil. The microorganism did not gather obviously in the bare land, this because many microorganism population that was sensitive to the soil condition variety disappeared, and only a little microorganism of having stronger anti-negative was reserved(2) The research results of soil microbes and enzyme activity indicators in different habitats showed that: during degraded Karst vegetation restoration, the changes of the soil microbes and enzyme activity in different habitats overall performed the characteristics which stone gully was higher. It was because stone gully habitat characteristics were advantageous to breed soil microorganisms and animal groups.(3) The research results of soil microbes and enzyme activity indicators in the soil profile indicated that: the soil microbes and enzyme activity during degraded Karst vegetation restoration had the similar vertical change characteristic. they was weaken with the soil layer depth increasing, performing the vary characteristic of layer A > B layer. But change of the microbial quotient was just opposite to above microbial activity indicators, taking on the characteristic of layer A < B layer(4) The research results of soil microbes and enzyme activity indicators in the rhizosphere and non-rhizosphere showed that: the soil microbes and enzyme activity of the rhizosphere and non-rhizosphere had the similar change regulation, performing R > S, and rhizosphere effect R/S value was more than 1.0 and decreased with the vegetation restoration. But the microbial quotient was R < S change characteristic.(5) It can be seen from the seasonal change, the soil microbes and enzyme activity changed with the seasons changing during degraded Karst vegetation restoration and showed obvious seasonal characteristic. Except the seasonal dynamics of soil invertase and amylase activity was the biggest in autumn and minimum in winter. The other indexes performed the change characteristic that the summer was biggest and the winter smallest.(6) In this study, the system of soil biological evaluating indicators that degraded Karst vegetation restoration affected on soil biological characteristics was based by applying method of statistical analysis. The result showed that the soil microbial activity indicators, including the amount of bacteria, fungi, antinomies, total microbes, nitrifying bacteria, cellulose decomposing microbes, Nitrogen fixing bacteria, ammonification, nitrification, decomposition of cellulose, nitrogen fixation, microbial biomass carbon, basal respiration, AWCD, Shannon index, Simpson index, invertase, amylase, unease, phosphatase, catalase, polyphenoloxidase played a very important role to evaluate soil biological fertility quality; But the effect of ammonifiers amount, microbial quotient, metabolic quotient on evaluating soil biological fertility quality was smaller. In addition, the relations among the amount of soil microbes, soil biochemical intensity, soil microbial biomass carbon, microbial quotient, basal respiration, metabolic quotient, functional diversity of microbial community and the soil enzyme activity was very close. They depended on one another mutually, mutually influenced and played a decisive part to the stability and maintenance of soil ecosystem, as well as sustainability of soil productivity. It was impossible that the size of soil fertility was reflected accurately by single indicators of soil microbial activity or enzyme activity.(7) The sequence of soil biological fertility quality of different recovery stages evaluated by soil synthesis fertility index value (IFI)from high to low was A layer of arboreal community > A layer of shrubby community > A layer of herbaceous community > A layer of bare land > B layer of arboreal community > B layer of shrubby community > B layer of herbaceous community > B layer of bare land. The result of this index appraisal system was the same as the actual situation. It explained that the soil material cycling accelerated gradually, microbial activity increased gradually, the soil biological fertility enhanced gradually during degraded Karst vegetation restoration. This revealed that degraded Karst vegetation restoration improved the soil biological fertility and enhanced soil biological quality.