Spatial distribution pattern of human-caused fires in Hulunbeir grassland Grazing effects on eco-stoichiometry of plant and soil in Hulunbeir, Inner Mogolia Desertification mechanisms and process of soil chemical and physical properties in Hulunbeir sandy grassland, Inner Mongolia Interspecific Niche Relationship of Artificial Sand-fixation Plants In Hulunbeir Desertification Grassland Study on Enclosing Effects and Biodiversity Variation of Desertification Grassland in Hulunbeir Steppe