Abstract: Yak is one of the important livestock species in alpine animal husbandry of our country. Aliveweight dynamic model of grazing yak is established on the basis of its average liveweight data per month in alpine meadow ecosystem. Moreover, quantitative relationships between the liveweight and the intake, faeces, urine and methane are determined according to the results of experimental researches.

Key words: Alpine meadow ecosystem, Yak, Liveweight dynamic model, root branch order, Castanopsis platyacantha, root chemistry, nitrogen deposition, root morphology