The Significant Impact of Lost Species' Identity, Number and Abundance on Functional Structure of Alpine Meadow.

Biodiversity, the cornerstone of ecosystem functions and services, faces threats from anthropogenic climate change. However, it remains unclear how species loss, including abundance, number, and identity of lost species, would alter the functional structure of alpine meadow plant communities. Through a species removal experiment conducted in an alpine meadow of the central Tibetan Plateau, we found that removing common species typically altered the functional structure of plant communities. Changes in community functional structure were highly positively correlated with both the number of species removed and the degree of abundance loss. Beyond this, species removal treatments had significant direct effects on community functional structure, as revealed by a partial least squares path modeling approach. This indicates that the effects of species identity are independent of the number of species lost and the degree of abundance loss. Especially, only the removal of species including Kobresia pygmaea significantly reduced community abundance when fewer than three species were removed. This indicates that the species Kobresia pygmaea occupies an exclusive ecological niche and is irreplaceable in alpine meadows, suggesting that the consequences of climate change-induced declines in K. pygmaea biomass may be underestimated. Moreover, ecological niche breadth rather than niche overlap played a primary indirect role in the pathway through which species loss influences functional structure. This indicates that harsh environmental filtering and species adaptation, rather than biotic interactions, dominate community assembly in alpine meadows. This study provided valuable insights for biodiversity conservation and adaptive management of alpine ecosystems.