Loss of resource‐conservative species affects plant phylogenetic and functional structure under long‐term snow addition

Abstract Climate change and human activities are increasingly influencing ecological communities. Within this context, increasing extreme snow events and persistent livestock grazing are known to pose significant challenges to alpine ecosystems on the Tibetan Plateau. However, the mechanisms driving long‐term community assembly and structural changes under these concurrent pressures remain unclear. Here, we used a 16‐year field experiment in a Tibetan alpine grassland to investigate the effects of spring snow addition and yak grazing on taxonomic, phylogenetic and functional community diversity and structure. We found that snow addition was the primary driver of community structure, while the effects of grazing were less pronounced. Specifically, snow addition shifted the phylogenetic structure from being random to overdispersed. This shift was driven by the selective loss of species with conservative resource‐use strategies (i.e. those with high leaf dry matter content [LDMC] and low‐specific leaf area), which were phylogenetically more closely related to the residents than were the gained species. In contrast, communities remained functionally clustered under all treatments. This resulted from opposing structural shifts in individual traits, where LDMC became more overdispersed, while plant height and leaf nitrogen content (LNC) became more clustered, driven by the loss of taller species and the gain of species with low LNC. This decoupling between phylogenetic and functional responses suggests that environmental filtering selects for convergent functional adaptations among phylogenetically distant species. Synthesis . Our findings highlight the importance of considering multi‐faceted diversity metrics when exploring community assembly and provide the first experimental evidence that long‐term snow addition reshapes plant phylogenetic community structure on the Tibetan Plateau. Importantly, the loss of conservative species suggests that altered snow regimes may potentially shift key ecosystem functions in alpine grasslands. Our findings also demonstrate that integrating species gain and loss is essential for a predictive understanding of long‐term community dynamics under global change.