| In grassland ecosystems, plant, soil and soil microorganism were interacting with each other and formed an organic whole. For a long time, the mainly focused research part about vegetation and soil physicochemical properties, but soil microorganism was understood very few. So, exploring the relationships between vegetation–soil–soil microorgnism is important significance of grassland ecosystems. In this thesis, comparative study between the main grassland types of Hulunbeier, includes the plant community, diversity coverage and grassland productivity, nutrition characteristics and photosynthetic pigments of main plant, soil physicochemical properties, soil enzyme activity and soil microbial diversity. The main results as follows:1. The study of vegetation characteristics of Hulunbeier main grassland types has show: the community coverage, species richness, Shannon-wiener index, Simpson index, Pielou evenness index of five grassland types were significantly different (P<0.05), and in addition to simpson index, the order of the other four indicators in five grassland types is: Filifolium sibiricum steppe (FSS)> Stipa baicalensis steppe(SBS)> Leymus chinensis steppe (LCS)> Stipa grandis steppe (SGS)> Stipa kryrowi steppe (SKS), Simpson index: FSS>LCS>SBS>SGS>SKS. The aboveground biomass of five grassland types is also significantly different (P<0.05), the order is: FSS>SBS>LCS>SGS>SKS. Correlation analysis between plant diversity index with aboveground biomass showed that plant diversity and aboveground biomass of five types grassland were positively related to the linear relationship and between plant diversity index was positively correlated (r>0.689).2. The study of plant characteristics and plant nutrients of Hulunbeier main grassland types (five different types of grassland) show that plant nutrients (total nitrogen, total phosphorus, soluble sugar content) and photosynthetic pigments content (chlorophyll a, chlorophyll b, carotenoids, total chlorophyll content) differences (P<0.05). Comparative analysis constructive species of five grassland types result is: plant total nitrogen content was LCS>FSS>SKS>SBS>SGS; total phosphorus was FSS>LCS>SGS>SKS>SBS; soluble sugar content in order to SGS>SBS>SKS>LCS>FSS; chlorophyll a content was LCS>FSS>SKS>SBS>SGS; chlorophyll b content was SKS>FSS>LCS>SBS>SGS; carotene content was LCS>SGS>FSS>SKS>SBS; total chlorophyll content was SKS>LCS>FSS>SBS>SGS. Nutrients with the photosynthetic pigments content of five grassland types analysis showed that plants total nitrogen, total phosphorus, soluble sugar with photosynthetic pigments content are positively correlated, and plant total nitrogen with photosynthetic pigments content was significant or highly significant.3. Soil properties research of Hulunbeier main grassland types showed that soil physical and chemical factors of five Hulunbeier grassland types were significantly different (P<0.05). Soil mositure: FSS>SBS>LCS>SGS>SKS, soil bulk density: SKS>SGS>LCS>SBS>FSS, pH value: LCS>SGS>SBS>SKS>FSS, total nitrgen: FSS>SBS>LCS>SGS>SKS, total phosphorus: FSS>LCS>SBS>SGS>SKS, ammonium nitrogen: FSS>LCS>SGS>SBS>SKS, nitrate nitrogen: SBS>SKS>FSS>SGS>LCS ,available phosphorus: FSS>SBS>SKS>SGS>LCS, organic matter: FSS>SBS>LCS> SGS>SKS. Vertical distribution of soil physical and chemical factors: pH value of the vertical did not change significantly and soil bulk density was 0-10cm> 10-20cm, the other physical and chemical properties of soil are 0-10cm <10-20cm. Soil physical and chemical factors related analysis showed that soil physical and chemical factors of Hulunbeier five grassland types have different degrees of relevance to each other.4. Results also showed that soil activity (soil urease, hydrogen peroxidase, phosphatase, invertase activity) reduced significantly (P<0.05) in different grasslands with 0-10 cm higher than 0-20 cm in the vertical distribution. Soil activitoes of hydrogen peroxidase and invertase activities of Filifolium sibiricum steppe were significantliy higher than Stipa grandis steppe, Stipa baicalensis steppe; Soil urease activity of Stipa kryrowi steppe was the highest and significantly different from Stipa grandis steppe, Filifolium sibiricum steppe, soil phosphatase activity in Leymus chinensis steppe was the highest and significantly different from others. Correlation analysis between soil enzyme activity showed that soil enzyme activities between the different degrees of relevance.5. The research of soil microbial diveisity for main grassland types on Hulunbeier shows that:(1) Soil microbial biomass C, N (SMBC, SMBN) reduced significantly (P<0.05) in different grasslands. The microbial biomass carbon and nitrogen in Filifolium sibiricum steppe soil were significantly higher than others, soil microbial biomass C and N in Stipa grandis steppe and Leymus chinensis steppe were lower.(2) The number of microorganisms in different types of grassland were in the same changing trends: bacteria>actinomycetes>fungi, but the number of each microorganism and composition reduced significantly (P<0.05). The bacteria number in 5 different types of glasslands was LCS>SBS>SKS>FSS>SGS, the fungi number was FSS>SKS>LCS> SBS>SGS, the actinomycetes number was SKS>LCS>FSS>SBS>SGS.(3) In the 5 types grassland on Hulunbeier, the Soil microorganisms ability of carbon sources utilization and carbon source utilization reduced difference (P<0.05), AWCD value of 5 types grassland on Hulunbeier was FSS>SBS>LCS>SGS>SKS.(4) The total phospholipid fatty acid (PLFA) content and various types of flora of PLFA content reduced significantly different in 5 types grassland on Hulunbeier(P<0.05). The total content of PLFA in 5 types grassland on Hulunbeier was FSS>SBS>LCS> SGS>SKS. Dominant groups of soil microorganisms between 5 types grassland on Hulunbeier were difference. dominant groups of Filifolium sibiricum steppe were 15:0, a15:0, i16:0, i18:0; Stipa baicalensis steppe were 15:0, a15:0, i16:0, 16:1ω7c; Leymus chinensis steppe were 15:0, i16:0,18:1ω9t, 18:1ω9c; Stipa grandis steppe were 15:0, a15: 0, i16:0; Stipa kryrowi steppe were 15:0,16:0, i16:0.(5) Soil bacterial community structure reduced differences in 5 different types grassland on Hulunbeier and they dominant group was Proteobateria. Filifolium sibiricum steppe, Stipa baicalensis steppe and Leymus chinensis steppe detected Nitrospirae and Bacteroidetes, Stipa grandis steppe detected Firmicutes and Gemmatimonadetes, Verrucomicrobia was peculiar group of Filifolium sibiricum steppe.(6) Soil microbial diversity reduced significantly different in 5 different types grassland(P<0.05). Shannon-wiener index of soil microbial functional diversity, structural diversity and genetic diversity(16S rDNA) was FSS>SBS>LCS>SGS>SKS.6. Correlation analysis of vegetation, soil and soil microbe indicated that soil microorganism (microorganisms, microbial biomass, microbial diveisity) with vegetation characteristics and soil properities have close relationship.
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