Effects of plant community and altitude on food composition of during the withered grass period on the Tibetan Plateau, China.

How Tibetan red deer () acclimates to high altitude environment during the withered grass period is one of the challenges in maintaining their nutrient intake. It is an important basis to study the nutritional ecology of wild large ungulates in alpine ecosystems by investigating the changes in plant communities with altitude during the withered grass period and how these changes affect the food composition of Tibetan red deer. In this study, we selected the Tibetan red deer in Sangri County, Shannan region of Tibet as the research subject. We carried out field surveys on the altitude, plant communities, and feeding traces of the Tibetan red deer in March of 2021 and 2022 during the withered grass period on the Tibetan Plateau. Detrended correspondence analysis and canonical correspondence analysis were used to study altitudinal variations in plant communities and the regularity of food composition. The results showed that during the period of withered grass, Tibetan red deer ate primarily , var. and . . accounted for more than 50% of the food composition, as the main food resources for red deer in withered grass period. In the low altitude area (4100-4300 m), plant community included , . and , and Tibetan red deer mainly ate . , . and . In higher altitude area (4300-4600 m), plant community consisted of , , and , and Tibetan red deer mainly fed on . , , and . At different altitudes, the dominant plant species were the main food of Tibetan red deer. It is suggested that the changes of plant community composition with altitude directly affected food composition of Tibetan red deer, indicating different food composition patterns with altitude gradients.