Abstract: Plant height is a central part of plant ecological strategy. It is a potential way to analyze the regulation mechanism of plant population to herbivores. Based on a longterm grazing experiment in Sonid Right Banner, Xilingol, this study aimed to reveal the height response of desert grassland plant Stipa breviflora under grazing regulation through three different dimensions (i.e. leaf macroscopic traits, leaf anatomical traits, and leaf nutrient contents). The results showed that the plasticity index (PI) of S. breviflora leaf height was the largest and leaf length was the second. The leaf anatomical structure showed a higher PI of leaf thickness, and PIs of leaf traits were greater under heavy grazing than under moderate grazing. The PI of leaf phosphorus (P) content was greater than those of leaf nitrogen (N) and carbon (C) content. The PI of leaf N content was greater than that of C content. Leaf height of S. breviflora in the moderate grazing treatment was higher than in the nongrazing treatment, and nongrazing treatment had higher leaf height than heavy grazing treatment. The area of upper epidermis cell under heavy grazing was lower than those under the other treatments. The leaf N content was increased by grazing. Leaf height of S. breviflora was significantly positively correlated with leaf length, leaf width and leaf erection index, and negatively correlated with leaf rolling index. Furthermore, it was significantly positively correlated with upper epidermal cell surface area, upper epidermis cell thickness, and leaf C content.

Key words: alpine meadow, carbon and nitrogen, Zoige, carbon stable isotope, degradation