Optimization yak grazing stocking rate in an alpine grassland of Qinghai-Tibetan Plateau, China

A simple yak (Bos grunniens) production model developed in this study was to evaluate the health of the intensive livestock production system in the three rivers headwaters region, on the Qinghai-Tibetan Plateau. An experiment conducted for 3 years showed that individual yak liveweight gain (kg/head) was negatively related to stocking rate (Sr) (head/ha). Yak liveweight gain per hectare (kg/ha) was modeled as a quadratic function of Sr, with an apparent optimum yak stocking rate (Sr_op). Following the model, the Sr_op rate was 1.67 heads/ha for the warm-season pasture (WSP), 0.72 head/ha for the cool-season pasture (CSP), and 0.63 head/ha for the yearlong periods grazing pastures, respectively. The corresponding maximum carrying capacity (when individual yak live weight gain was equal to zero) was 3.34, 1.44, and 1.26 head/ha for warm-season, cool-season, and yearlong periods grazing pasture, respectively. In comparison with modeled maximum stock carrying capacity, all the cold-season pasture in the three rivers headwaters region were overgrazed. By contrast, only 37.5 % of the warm-season rangeland area overgrazed. It indicated that reconstruction of the proportion of the seasonal rangeland area may be an effective strategy to prevent serious rangeland degradation in this alpine region. Moreover, adjustment of the stoking rate at optimum values may likely improve the income for local herders.