Effects of overgrazing on the functional diversity of rodents in desert areas

Environmental stressors and disturbances can cause changes in an ecosystem's community structure, which can be reflected in its functional diversity. As grazing intensity increases, this causes changes in the environment that inevitably lead to changes in the community structure, which can especially affect rodents due to their sensitivity to the environment. The effects of grazing prohibition and overgrazing on the functional diversity of desert rodent communities in Alxa were studied in April, July, and October of 2018-2020. The trap-day method was used to study rodent communities in disturbed habitats. Five functional traits were selected and quantified: nutrition, life history, physiology, morphology, and activity rhythm. The results showed that: (1) The species composition of rodent communities in the Alxa Desert in spring and autumn was significantly correlated with the functional traits of the hibernation, reproductive cycle, and feeding habits. The species composition in the summer was only significantly correlated with the functional traits of reproductive cycle and diet. (2) The effects of overgrazing on the functional diversity of rodents in desert areas have significant temporal and spatial characteristics. (3) In spring and summer, overgrazing made the Functional Richness index of the rodent community lower than that of areas where grazing is prohibited, but the Functional Evenness index was higher than that of grazing-prohibition areas. In autumn, overgrazing increased the Functional Richness index of the rodent community and decreased the Functional Evenness index. The Functional Divergence index was higher in overgrazing areas than in grazing-prohibited ones. These results suggest that, in spring and summer, overgrazing reduced the ecological space utilization ability of rodent communities; however, the impact on the degree of utilization of community resources is more comprehensive. In autumn, overgrazing increases the ability of rodent communities to use ecological space but reduces resource efficiency. Overgrazing makes the niche differentiation of rodent communities higher, the degree of overlap lower, and the competition between species weaker. Therefore, overgrazing will affect the functional diversity of the community through the utilization of ecological space, resource utilization, interspecific competition, and niche. In this study, the dynamic processes of rodent communities under different disturbances in desert areas were compared, and the effects of disturbance on the functional structure of rodent communities were revealed from the perspective of functional traits.image