Effects Of Nitrogen Fertilization On Desert Grassland Ecosystem Biodiversity In Xinjiang

Greenhouse simulation experiment and wild field experiment were carried out to study effects of nitrogen(N) fertilizition on desert grassland plant, soil microbial species diversity, and population diversity, soil microbial function diversity and soil microbial genetic diversity of desert grassland in xinjiang. Different amount of N fertilizer were added in different three climatic conditions soils to research the desert grassland ecological diversity, and evaluate the effects of the climate type, N fertilization. There would be a better way to improve the desert grassland ecosystem diversity, soil quality, ground biomass. The study would provide theoretical support with main conclusions as follows:(1) N fertilization changed desert grassland plant community species composition and the advantage of plant on desert grassland in Xinjiang. It significantly increased the ground biomass of dry matter and reduced the species richness and diversity index, Shannon evenness index and Margalef richness index. Grass biomass of ground were increased slower with 2 years N fertilization than 1 year fertilization, and the species richness and diversity decreased slower too. Result showed that grass biomass were increased but plant community diversity were decreased with N fertilization.(2) N fertilization significantly improved numbers of soil bacteria, fungi, and actinomycetes. Soil microbial reproducted more with with 2 years N fertilization than 1 year fertilization. Numbers of soil microbial were decreased with soil depth, but were increased at the beginning and then decreased with increase of days after N fertilization and N application rates in the three soils. Numbers of soil microbial in higher precipitation were more than lower precipitation soil. Efficiency of N fertilization on soil microbial in higher precipitation area were more than lower precipitation area. Result showed that application of nitrogen could increase Numbers of soil microbial and soil microbial diversity.(3) N fertilization significantly promoted soil microbial biomass N and carbon, and soil urease, protease, invertase,alkaline phosphatase, polyphenol oxidase activities were significantly increased. Carbon sources utilization ability of soil microbes were increased with N application. The microbial biomass and the enzyme activities except polyphenol oxidase were decreased with soil depth, polyphenol oxidase activity in the soil 10-30cm were largest than other depth. The microbial biomass, urease, protease, invertase and alkaline phosphatase activities were increased at the beginning and then decreased with increase of days after N fertilization in the three soils, but polyphenol oxidase and catalase activities were increased. The soil enzyme activities changed rapidly with N application in higher precipitation area but changed slowly in lower precipitation area. Soil microbial function diversity were increased with N application(4) N Fertilization could significantly increased DGGE bands of the soil nitrous acid bacteria and ammonium oxidation bacteria.and there were more bands with 2 years N fertilization than 1 year fertilization. Shannon index, evenness index and stability index of the soil nitrous acid bacteria and ammonium oxidation bacteria were increased with N application treatments. The biological community diversity of nitrifying bacteria were increased with N Fertilization.