Abstract: The altitudinal gradient pattern of mountain biodiversity and its formation mechanism are hot topics in ecological research. The altitudinal variations of belowground invertebrates are less understood than aboveground plants and animals. With soil mites as the model soil animals, we investigated their distribution patterns from 1318 m to 2500 m above sea level in three mountains of Lyuliang Mountains based on species diversity and functional diversity. We used soil pH, total N, total P, total K, and organic matter content to identify potential drivers of soil mite communities and diversity along the altitudinal gradient. A total of 715 soil mites were collected, belonging to 3 orders, 27 families, 28 genera, and 29 species. Phthiracarus clemens, Geolaelaps praesternalis and Diapterobates humeralis were dominant mites. Non-metric multidimensional scaling showed that soil mites community composition varied significantly among different altitudes due to Epilohmannia ovata predominated in high altitude and P. clemens predominated in middle altitude. There were significant differences in individual density of soil mites among different altitudes. The Margalef, Shannon, and Simpson indices followed a unimodal distribution pattern along the altitudinal gradient. Functional richness and functional evenness showed a unimodal distribution pattern along the altitudinal gradient, while other functional diversity indices changed little with altitude. The RDA results indicated that total K and soil pH were the major drivers for the variations in soil mite communities. The Pielou index of soil mites was significantly positively correlated with soil pH, while functional evenness was negatively correlated with altitude. Individual density, species number, Margalef, Simpson and Shannon indices were significantly positively correlated with functional richness index. Species diversity and functional diversity of soil mites varied differently with altitude. In the future, we should strengthen long-term monitoring and dynamic functional properties of soil mites and the community assembly to deeply understand the relationship between biodiversity and ecosystem functions.

Key words: soil animal, soil mite, functional diversity, altitude gradient