Variation of response in Cleistogenes songorica above-ground part functional traits to long-term grazing in a desert steppe

Individual plants can react to grazing of different intensities with a variety of adaptions, including trade-offs of several functional traits. In order to study the responses of Cleistogenes songorica individual traits to long-term grazing, this study, conducted in a desert steppe (Inner Mongolia), focused on the individual functional traits, the relationship between individual above-ground biomass and its functional traits, and the effect of the functional traits on the individual above-ground biomass in the dominant species, C. songorica. The results showed that the leaf characteristic index, individual above-ground biomass, plant height, and crow (bundle) decreased significantly with the increase of grazing intensity. Apart from basal stem diameter and average leaf length, we found positive correlations of individual above-ground biomass, stem biomass, leaf biomass and phenotypic traits of stem and leaves with grazing intensity. Furthermore, a greater variability was observed among individual above-ground biomass components, while only a relatively low correlation coefficient of phenotypic traits with smaller variability, and individual above-ground biomass components was found. Among all phenotypic traits of above-ground biomass of C. songorica, the VIP (variable importance projection) of total leaf area, the total number of leaves, and the average leaf length was greater than 1, and its contribution rate to individual aboveground biomass approached 61.01%. Grazing resulted in significant difference among all functional traits of C. songorica, however, grazing pressure did not challenge its position as a dominant species in this desert steppe.