Rare and common species contribute disproportionately to alpine meadow community construction and functional...

It is widely accepted that rare species are the first species to become extinct after human-induced disturbances. However, the functional importance of rare species still needs to be better understood, especially in alpine meadow communities with harsher habitats, where the extinction rate of rare species may be higher. This study established a 1.85 × 10⁵ m² permanent research sample plot on the eastern Tibetan Plateau. We investigated data from 162 plots at 6 different sampling scales in alpine meadows to determine the contribution of rare and common species to alpine meadow communities' structural and functional variability. The results showed that (1) Asteraceae (Compositae) was the dominant family in the surveyed localities. The trends of species diversity indices were the same, and all of them increased with the increase of sampling scale, and the plant community showed apparent scale effects. (2) The community construction of rare species at small scales with high occupancy transitioned from neutral processes to ecological niche processes, while the community construction of common species at different sampling scales was all dominated by ecological niche processes. (3) The trait values of rare species at different sampling scales were different from those of common species, and their distribution in FEs (functional entities) was also different, indicating that they contributed differently to the ecological functions of the communities. Rare species with lower abundance in the surveyed communities had a higher proportion of FEs, indicating that rare species had a more significant proportion of contribution to FEs. The functional redundancy (FR) of rare species was lower than that of common species, and the functional vulnerability (FV) was higher than that of common species. Therefore, the loss of rare species is more likely to cause the loss of community ecological functions, affecting the function and resilience of alpine meadow ecosystems.