Genetic diversity and classification of domestic yaks inferred from mitochondrial DNA sequences Effects of Yaks Grazing Methods on the Community Characteristics of Kobresia pygmaea Meadow in Tibet Effects of Grazing Intensity on the Growth of Yaks Responses of contents of soil nutrient factors and water to stocking rates for yaks in Kobresia parva alpine meadow Ⅰresponses to contents of soil nutrient factors and water to stocking rates in summer pasture