Strong variations and shifting mechanisms of altitudal diversity and abundance patterns in soil oribatid mites (Acari: Oribatida) on the Changbai Mountain, China

Biological composition and structure vary strongly with elevation, however, the vertical distribution of soil fauna and its drivers have been rarely investigated. Oribatid mites play an essential role in soil faunal composition, where they can occur at high densities and mediate soil ecological processes and functions. Here, we comprehensively investigated the composition and diversity of soil oribatid mites, at nine altitudes (from 600 to 2200 m asl) and four vegetation types from forest to alpine tundra on the Changbai Mountain in July 2021. In total, 67 species were identified among 37,224 oribatid mite individuals. Oribatid mite species varied strongly with altitude and vegetation type, and only a few species overlapped between elevations. Species abundance and diversity declined significantly as altitude increased, while abundance exhibited a hump-shaped distribution along an elevational gradient, peaking at 1200 m. Beta diversity decomposition analyses revealed that species replacement processes dominated community compositional differences across all study sites (both between vegetation types and elevations). Meanwhile, soil oribatid mite community composition is greatly affected by elevation and vegetation type. Specifically, oribatid mite community varies with elevation across vegetation types. Twelve and twenty indicator species were found at different elevations and vegetation types, respectively. Our study shows that soil moisture content, total phosphorus, available phosphorus, ammonium nitrogen, and nitrate nitrogen are the most dominant drivers of oribatid mite composition patterns. These findings indicate oribatid mite assemblages have a distinct vertical distribution pattern and are coupled with different aboveground vegetation types, implying that changes in aboveground vegetation will cause shifts in soil fauna under future climate change.