Environmental drivers shape soil mite communities along succession, with limited links to litter decomposition in upper Andean tropical forests

Abstract Mite composition varied among sites but was stable between wet and dry seasons. Succession altered mite composition but not abundance or richness. Microclimatic and edaphic factors drive mite communities, with group specific responses. Few associations between mites and litter decay rates were found. Mites exert a limited overall influence on decomposition in Andean montane forests. Mites contribute directly and indirectly to several ecosystem functions such as nutrient cycling, soil formation, litter decomposition, and biological control. Despite their importance, the processes driving mite community assembly remain poorly understood in tropical montane ecosystems, where mite composition is unique and environmental gradients are steep. Here, we examined the structure of mite communities, their ecological drivers, successional patterns, and their associations with litter decomposition in upper Andean tropical forests (UATF). We collected 168 soil samples (30 cm × 30 cm × 5 cm) across four climatic seasons (two wet, two dry) from 14 permanent plots in four UATF sites. Microclimatic data were recorded using dataloggers, forest and soil data were collected through field sampling and soil analysis, and decay rates of 15 plant species were measured using reciprocal litter experiments. In total, 1387 mites were collected, belonging to 31 families and 42 morphospecies. Mite communities varied markedly among sites but not between seasons, and were more abundant in the litter layer. While total Acari abundance and richness showed no significant differences along succession, Sarcoptiformes increased in abundance, reflecting their link to litter accumulation in old-growth forests. Community composition shifted strongly between mature and secondary forests. Total Acari were primarily associated with microclimatic conditions and soil nutrients, although responses varied among groups. Associations between mite attributes and decay rates were detected, but most litter species showed no link, suggesting a limited overall influence on decomposition. Our study provides a first step toward understanding the factors shaping mite communities and their associations with litter decay in UATF.