Effects of shrub microhabitats on taxonomic and functional diversity of soil microarthropods under grazing regimes in desertified regions

Overgrazing is a major global disturbance affecting biological communities, resulting in a 10 % biodiversity loss. Shrub afforestation has been identified as an effective way to improve the recovery of soil biodiversity in overgrazed and desertified regions. The extent to which grazing activities can undermine the beneficial effects of shrubs on soil biodiversity in desertified areas remains unclear. To verify this, Acari and Collembola from soil microarthropods were collected from two distinct shrub microhabitats (i.e., shrub understory and open space between shrubs) in ungrazed and grazed plots in northwestern China. We extracted soil microarthropods using reformed Berlese-Tullgren funnels and identified them to the family or genus level. Here, taxonomic and functional diversity of soil microarthropods were examined. Soil properties and herbaceous plant performances were determined to explore the drivers of soil microarthropod communities under grazing regimes. The results revealed significantly higher abundance, group richness, Shannon index, and functional richness of soil microarthropods in shrub understory compared to open space in ungrazed plots. However, there was no significant difference in Shannon index and functional richness of soil microarthropods between both shrub microhabitats in grazed plots. Nevertheless, the functional evenness of soil microarthropods was found to be significantly lower in shrub understory compared to open space in both ungrazed and grazed plots. Correlation analysis and random forest regression models identified soil moisture in ungrazed plots and herbaceous plant height in grazed plots as the key factors shaping the taxonomic and functional diversity of soil microarthropods. In conclusion, grazing activities enhanced the refuge effects of shrubs for abundance of soil microarthropods but reduced both taxonomic and functional diversity in desertified regions.