Effects Of Grazing On The Soil Physical And Chemical Properties And Genetic Diversity Of Soil Actinomycetes Of Leymus Chinensis Steppe

As an important part of natural ecosystem, grassland ecosystem not only hasgreat value for the maintenance of ecological balance and the regional economy, butalso an important basis for human survival and sustainable economic development.In grassland ecosystem, grazing behavior is one way for human managingagriculture and livestock production through livestock grazing. Grazing ecosysteminclude herbivores, plants and soil microbes. As the core of the underground soilecosystem composition, soil microbes are complex, various and versatile. As thedecomposition of organic matter decomposition and transformation, nutrient cyclingand utilization, soil fertility and stability, soil microbes play a key role in themaintenance of grassland biodiversity, evaluation of grassland systems health, andits resources have enormous potential. Actinomycetes are an important class of soilmicroorganisms. Actinomycetes has many important ecological functions, such assoil organic matter decomposition and the conversion of soil nutrient carbon andnitrogen and phosphorus and other elements.In grazing systems, large herbivores through feeding on plants, changing soilphysical and chemical properties, affecting on soil rhizosphere, and then indirectlyaffect soil actinomycetes communities. Plants providing nutrients to the soilactinomycetes is an important source of energy to actinomycetes and then indirectlyimpact soil actinomycetes’ diversity by affecting soil physical environmental factorssuch as soil surface evaporation, soil element carbon and nitrogen content, watercontent, electrical conductivity, pH value, and so on. Plant is important forpromoting soil actinomycetes diversity. Therefore, the destruction of plant maychange actinomycetes community composition and reduce actinomycetes geneticdiversity.Subject to the limitation of the techniques and methods, researches about theactinomycetes are still not mature in the world now.85%to99%of themicroorganisms in nature is still not available in pure culture through traditionalmethods because the limitations of the traditional culture techniques, and now it hasbeen agreed that16SrRNA/rDNA gene sequences can be used to evaluate the diversity of microorganisms. Denaturing gradient gel electrophoresis (DGGE) can berepeated, quick and easy operation which is suitable for surveying the temporal andspatial variations of the investigation actinomyces.In this experiment, cattle and sheep are the large herbivores. The technologysurveying soil actinomycetes is16S rDNA-PCR-DGGE technology. Our study focuson researching the change of grassland soil physical and chemical properties andactinomycetes community under different grazing treatments (Control, Cattle, Sheepand Mixed grazing) and plant diversity levels (Low and High) to explore the highestdiversity of soil actinomycetes and reveal the effects of grazing treatments and plantdiversity levels on soil actinomyces community characters in L. chinensis grasslandecosystem.The results showed that different grazing treatments and plant diversity levels onsoil actinomycetes communities have different effects on soil actinomycetes geneticdiversity by DGGE profiles. At the low plant diversity level, the bands number ofactinomycetes under grazing treatments are all higher than control. Bands number ofactinomycetes under sheep grazing is highest and mixed grazing take the secondplace which means that different herbivores grazing on actinomycetes communitieshas a positive role in promoting community. At the high plant diversity level, bandsnumber of actinomycetes under mixed grazing is higher than cattle, sheep grazingand control. In all, mixed grazing is the optimal way for soil actinomycetes richnessand genetic diversity in grassland ecosystem.At the low plant diversity level, soil pH value under grazing treatments issignificantly higher than control; soil water content under cattle and sheep grazing issignificantly higher with mixed grazing; soil organic content under grazingtreatments is lower than control; soil total nitrogen under grazing treatments is alsolower than control; and there is an increase of soil total phosphorous under grazingtreatments comparing to control. At the high plant diversity level, soil water contentunder mixed grazing is highest; soil organic content under grazing treatments issignificantly higher than control; soil total nitrogen under grazing treatments issignificantly higher than control; soil total phosphorous under grazing treatments arealso higher than control. Several soil chemical factors affect the soil actinomycetescommunities together.