Response of plant traits of Stipa breviflora to grazing intensity and fluctuation in annual precipitation in a desert steppe, northern China

Abstract

As a grassland type distributed in the desert steppe with warmer climate in the steppe region of central Asia, Stipa breviflora steppe has the following characteristics, i.e. transition and vulnerability. Therefore, it is susceptible to global climate changes and anthropogenic disturbances. The resistance and resilience of a plant community to the disturbances or climate changes mainly depend on plant functional traits of the dominant species. Yet there are few studies focus on the interaction between annual precipitation and grazing pressure on the variation of plant traits of desert steppe. We investigated the functional traits of S. breviflora under contrasting annual precipitations (wet and dry years) and different long-term grazing intensities (no grazing, light grazing, moderate grazing, MG, and heavy grazing, HG), and revealed the influence of grazing and the precipitation on the variability of functional traits of S. breviflora. Moreover, we discussed the vulnerable grassland type’s adaptation mechanism to grazing disturbances and precipitation changes, and its grazing adaptation strategy under different annual rainfall precipitation conditions. Plant height, coverage, above-ground biomass, leaf length, single leaf area of S. breviflora, were sensitive to grazing interference and precipitation, while leaf dry matter content, specific leaf area, and leaf nitrogen content were inert traits. S. breviflora’s resistance and resilience in response to grazing disturbance strongly depended on rainfall conditions. In the dry year, the functional traits of S. breviflora showed higher plasticity in responses to grazing treatment, in which moderate interference was favorable for the compensatory growth of S. breviflora. The functional traits of S. breviflora were not sensitive to the drastic changes of precipitation in grazing exclusion plot for many years. It was concluded that grazing in dry year had an adverse effect on S. breviflora desert steppe, and that light grazing or banning grazing in dry years is a better management practice for the desert steppe.