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 be affected by 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 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 were higher in overgrazing areas than in grazing prohibited ones. These results suggest that, in spring and summer, overgrazing reduces the ecological space utilization of rodent communities, but its effect on community resource utilization is more comprehensive. In autumn, overgrazing increases the ecological space utilization rate of rodent community but decreases the resource utilization rate. 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.

Methods
Using the trap-day method.Microsoft Excel was used to input and sort the original data and calculate the species diversity. A one-way analysis of variance (ANOVA) was performed using SPSS 20.0 software and plotted using OriginPro 8 software. The Species Accumulation Curve was calculated and plotted using the 'vegan' package of software R 4.2.0. The 'mFD' package of software R 4.2.0 was used to analyze the correlation between the functional axis and species traits, β diversity, Jaccard similarity coefficient, Kruskal-Wallis test and functional diversity index calculation, and the ' ggplot2 ' package was used for mapping.