Abstract

Foundational cushion plants sustain a prominent proportion of alpine biodiversity, but they are quite sensitive to climate warming hence their population dynamics have important implications for biodiversity. The potential biodiversity changes with the population dynamics of cushion plants in alpine ecosystems remain, however, unclear. Using eight communities along a climatic and community successional gradient, we assessed ecological drivers of population dynamics and associated plant diversity changes in alpine communities dominated by the foundational cushion plant Arenaria polytrichoides. The population degeneration of Arenaria is attributed to ecological constraints, including temperature, water and light availability, extreme climate events, and interspecific competition, at a series of life history stages. Once Arenaria populations completely degenerate, previously cushion-dominated communities shift to climax communities that are overwhelmingly dominated by sedges. Future degeneration of foundational cushion populations induced by climate warming will therefore induce a biodiversity collapse in alpine ecosystems.