Simulated climate warming strongly constrains the seedling establishment of alpine cushion Arenaria oreophila.

Population shrinkage of alpine cushion plants with ongoing climate warming has been empirically confirmed. Since cushion plants play important roles in sustaining alpine plant community and ecosystem functions, their population dynamics may directly influence the future alpine ecosystems. However, little is known about how climate warming affect cushion population recruitment, especially at early life-history stages. In this study, we conducted a laboratory simulation of climate warming to detect the effects of warming temperature and associated moisture and light changes on seed germination and seedling growth of the typical alpine cushion plant Arenaria oreophila. Results suggested that increasing temperature indeed exerted strong constraints on the population recruitment processes. Specifically, increased temperatures could quickly initialize seed germination (4-6 days at higher temperatures vs. 29-32 days at low temperature, respectively, after sowing), accelerate them to reach the maximum germination percentage (9-19 days at higher temperatures vs. 57-86 days at low temperature, respectively, after sowing) and significantly accelerate seedling growth rate. However, higher temperatures accelerated seedling mortality (more than 80%). In addition, lower light availability also increased seedling mortality though it could generally increase the final seed germination percentage. The effects of water might be dependent on temperature and light. All results suggested that cushion A. oreophila is quite sensitive to climate warming which strongly constrains its seedling establishment process. We, therefore, speculate that the continuing climate warming in future will exert uncertain risks in the persistence of cushion A. oreophila, possibly by constraining the process of seedling recruitments.