Conversion of rainforests into monoculture plantations alters soil animal diversity and leads to marked shifts in community composition. However, the extent to which these changes can be predicted by response traits and their associations with environmental variables remains poorly understood. Using 17 traits spanning seven functional dimensions of oribatid mites (reproduction, perception, secretion, feeding, protection, energy use and microhabitat adaptation), we identified those most responsive to environmental gradients mediating community assembly in litter and soil following rainforest conversion to rubber and oil palm plantations. This was achieved through iterative RLQ analyses and community assembly by trait selection (i.e., CATS) models. Traits related to reproduction, perception, feeding and secretion consistently responded to environmental variation in both litter and soil, whereas traits linked to protection and microhabitat adaptation showed distinct patterns between vertical layers. Variation in these traits across land-use and layer gradients was primarily associated with differences in litter amount, canopy openness, water content and food resource availability. These selected responsive traits had significant predictive power for species’ relative abundances. Communities in monoculture plantations were characterised by pronounced parthenogenesis, chelate-dentate chelicerae, sacculi, pteromorphs, strong sclerotization, multiple claws and large anal plates, but reduced porose areas, indicating shifts in reproductive strategy and diet alongside enhanced protection and microhabitat adaptation under drier and more unstable conditions. Response traits also predicted community differences between vertical layers: soil communities showed a higher incidence of parthenogenesis and porose areas but less frequent pelopsiform and attenuate-edentate chelicerae than litter communities, reflecting contrasting abiotic conditions and resource distributions between layers. Overall, our findings demonstrate the predictive power of functional traits in explaining oribatid mite community structure and highlight the role of environmental filters in selecting species with specific adaptive traits in response to land-use change.