Abstract: We examined the characteristics of soil macrofauna community and the niche width and niche overlap of major groups of soil macrofauna in four habitat types of the Nianchu River Basin, Tibet, including grassland, wetland, cropland, and seabuckthorn forest. In May (spring) and August (summer) of 2020, soil macrofauna were collected, with the specimens being stored in 75% alcohol solution. A total of 2048 soil macrofauna specimens were captured and classified into 52 groups, 37 families, 25 orders, 5 classes, and 3 phyla. The highest numbers of individual and group of soil macrofauna were found in wetland in spring and summer, and the lowest in the grassland. The diversity index was the highest in seabuckthorn forest in spring and summer. The dominance index was the highest in grassland and seabuckthorn forest in spring, and the highest in wetland in summer. The evenness index was the highest in grassland in spring, and the highest in cropland and seabuckthorn forest in summer. The similarity index of soil macrofauna communities among four habitats in spring ranged from extreme dissimilarity to medium dissimilarity, and ranged from medium dissimilarity to medium similarity in summer. The similarity index of soil macrofauna communities between spring and summer ranged from medium dissimilarity to medium similarity. Diptera larva had the largest niche width, while Pentatomidae, Phalangiidea, and Lymnaeidae had the smallest niche width in spring and summer. The distribution range of niche overlap value of soil macrofauna communities was \[0, 1\]. The high niche overlap value accounted for 23.07% of the total pairs, the moderate niche overlap value accounted for 16.67%, and the low niche overlap accounted for 73.07%. Formicidae, Carabidae, Lycosidae, and Lymnaeidae were the dominant taxa in the Nianchu River Basin. The characteristics of soil fauna community were different in spatial distribution, but the diversity index of soil fauna community showed no significant difference between seasons. Diptera larva and Lycosidae, the main components of soil fauna communities, had strong adaptability to soil environment and had a wide range of ecological adaptation. The degree of niche overlap in soil fauna communities was low, with low degree of similarity in resource utilization and weak inter-group competition, indicating a relatively stable community structure.

Key words: Nianchu River Basin, soil macrofauna, community characteristics, niche width, niche overlap value.