Temporal Stability of Plant Species α-Diversity in Alpine Grasslands of the Tibetan Plateau and Their Implications for Biodiversity Conservation

The temporal stability of alpine plant $\mathsf{\alpha }$-diversity remains poorly understood, constraining predictions of biodiversity dynamics. Here, this study examined spatiotemporal patterns in the temporal stability of plant $\mathsf{\alpha }$-diversity (species richness, Shannon, Simpson, and Pielou) across the Tibetan grasslands from 2000 to 2020. The temporal stability of plant $\mathsf{\alpha }$-diversity was more sensitive to changes in elevation compared to longitude and latitude. The greater the temporal stability of a plant species’ Shannon, the higher its rate of increase under the combined effects of climate change and human activities. The spatial average temporal stability of plant $\mathsf{\alpha }$-diversity declined by 8.83–16.40% across all the grasslands of the Qinghai-Xizang Plateau, while 39.34–43.77% of the region exhibited increasing trends under the combined effects of climate change and human activities. Climate change and human activities dominated 44.12–48.71% and 51.24–55.84% of grassland areas of the change of temporal stability of plant $\mathsf{\alpha }$-diversity, respectively. Radiation variability exerted some exclusive effects on the temporal stability of plant $\mathsf{\alpha }$-diversity. The relative change in plant $\mathsf{\alpha }$-diversity did not exhibit simple linear relationships with the relative change in its temporal stability. Therefore, climate change and human activities resulted in the spatial heterogenization of the temporal stability of plant $\mathsf{\alpha }$-diversity. While the overall temporal stability of plant $\mathsf{\alpha }$-diversity declined, some areas experienced local increases. Human activities drove changes in temporal stability across a broader area than climate change. In addition to climate warming and precipitation changes, attention should also be paid to the impact of radiation variability on the temporal stability of plant $\mathsf{\alpha }$-diversity. The relationships between plant $\mathsf{\alpha }$-diversity and its temporal stability were not always characterized by a trade-off or synergy. In future grassland biodiversity conservation efforts, it is essential to consider the potential influence of global dimming on the temporal stability of plant $\mathsf{\alpha }$-diversity. Simultaneously monitoring both $\mathsf{\alpha }$-diversity and its temporal stability, especially in areas where both are declining, should be a priority.