Data associated with traits

In this study, we investigate how the expansion of poisonous plants reshapes functional traits of plants, soil microbes, and soil fauna along climatic gradients on the Qinghai–Tibet Plateau, and how these shifts affect multi-trophic trait networks and ecosystem stability. We found that poisonous plant expansion induced coordinated acquisitive shifts in plant (larger size, thinner and softer leaves) and microbial traits (faster C and N cycling), but contrasting conservative shifts in soil fauna traits (larger body size, higher trophic level). Temperature moderated these effects by weakening acquisitive plant traits, whereas precipitation amplified conservative soil fauna traits. Network analyses revealed that poisonous plant expansion diminished connectivity, complexity, and robustness among plant–microbe–fauna trait modules, indicating reduced ecosystem stability. By integrating trait-based and network approaches across trophic levels, our study provides the first empirical evidence that trait mismatches across plant–microbe–fauna communities constitute a key mechanism reducing ecosystem robustness under global change, with implications for biodiversity conservation and ecological restoration.