Abstract: Changes in nutrients in edible plants of blue sheep (Pseudois nayaur) in the Helan Mountains are an important link to study of the distribution of their browsing areas, which has great significance for clarifying the relationship between blue sheep and natural environment. The spatial and temporal variations in edible plant nutrients of blue sheep along an altitudinal gradient (1100-2600 m above sea level) in the Helan Mountains across different seasons (June, August, and November) were analyzed. Results showed that plant nutritional value was the highest in August, and that each plant nutritional ingredient except for crude ash was significantly different among different seasons (P<0.05). In June, except ether extract, nutrient contents of edible plants significantly varied across different altitudes (P<0.05). In August, there were significant differences in the contents of all nutrients among altitudes (P<0.05). In November, the contents of all nutrients except crude protein were significantly different among different altitudes (P<0.05). There was an interactive effect of altitude and season on changes in the nutritional ingredient of edible plants (P<0.05). Considering altitudinal and temporal variations of plant nutritional value, it is suggested that the management and conservation strategy for blue sheep should be dependent on altitudes and seasons to promote the healthy and sustainable development of blue sheep population.

Key words: Helan Mountains, Pseudois nayaur, plant nutrition, altitudinal gradient, seasonal dynamics.