The "bug island" effect of shrubs and its formation mechanism in Horqin Sand Land, Inner Mongolia

In the moving sand dune of Horqin Sand Land (Inner Mongolia), the diversity of the soil macro-arthropod communities beneath the canopies of two shrub species (Caragana microphylla and Salix gordejevii) and in open areas was investigated in order to determine the effect of shrubs on these soil communities. The results showed that the shrubs facilitated the aggregation of soil macro-arthropods, resulting in significantly higher diversity and individual density of macro-arthropods in the soil beneath the shrub canopy compared to the open areas. This is known as the "bug island" effect. Although the dominant families in these three soil macro-arthropod communities were the same beneath the shrub canopy compared to open areas, many new macro-arthropod families also occurred in the shrub canopy communities, resulting in significant changes in the composition and structure of these soil communities. The "bug island" effect of the shrubs resulted from the "fertile island" effect generated by these shrubs, i.e., reduced wind velocity, retained dust and sand, increased soil litter biomass and soil moisture, improved soil texture and soil fertility. Between the two shrub species investigated C. microphylla had a greater "bug island" effect than S. gordejevii, as C. microphylla had a higher "fertile island" effect than S. gordejevii.