Effects of desertification on temporal and spatial distribution of soil macro-arthropods in Horqin sandy grassland, Inner Mongolia

• Desertification led to obvious decrease in richness and density of soil arthropod.
• The largest richness and density of soil arthropod changed from summer to Autumn.
• The lowest richness and density changed from 20–30 cm soil to 10–20 cm soil.
• Effects of desertification on trophic groups differed among seasons and soil layer.
• Changes in soil arthropod were attributed to degradation of vegetation and soil.

The richness and density of soil macro-arthropods in 0–30 cm soil were investigated by a method of space-for-time substitution from spring to autumn of 2008–2009 in Horqin Sand Land, Inner Mongolia, to understand the effects of grassland desertification on the temporal and spatial distribution of the soil macro-arthropod community. The results showed that: 1) grassland desertification had a serious damage to the soil macro-arthropod community, more serious in the summer than in the spring and autumn, and resulting in obvious change on seasonal distribution pattern of the soil macro-arthropod community; 2) the effects of desertification on trophic groups differed among seasons, with greater effects on predators in spring, phytozoa in summer, and omnivores in autumn; 3) from large to small, the order of richness and density was 0–10 cm soil > 10–20 cm soil > 20–30 cm soil and 10–20 cm > 0–10 cm soil > 20–30 cm in non-desertified grassland, respectively, and both changed gradually to 0–10 cm soil ≥ 20–30 cm soil > 10–20 cm soil with desertification development; 4) with desertification development, the richness and density of phytozoa, predators, and omnivores all decreased significantly in different soil layers, with the magnitude of the decrease being lower for predators in 0–10 cm soil and omnivores in 10–20 cm and 20–30 cm soil and greatest for phytozoa in all three soil layers; 5) with desertification development, the dominant family in the community changed gradually and the dominance of the dominant family intensified significantly; and 6) changes in the soil macro-arthropod community were attributed to the degradation of vegetation and deterioration of the soil environment in the desertification process, including notable decreases in vegetation cover, litter, soil clay and silt, soil organic carbon, and soil N and P.