Belowground traits significantly differ between decreasing and increasing plant species in alpine meadows: implications for vegetation response to climate change

Understanding the relationships between functional traits and changes in the abundance of plant species is essential for estimating future species composition under climate change. Previous studies on the trait-based approach have attempted to explain plant performance using either aboveground or belowground traits at either the organ level or the whole-plant level. To understand the species-specific responses to climate change, however, it is crucial to examine various traits simultaneously and comprehensively, including both organ level and whole-plant-level traits of aboveground and belowground parts, within the same study. Changes in the abundance of plant species have been recorded in an alpine meadow of the Taisetsu Mountains, northern Japan, over a 40-year period. Based on the previous studies, we selected 4 species with decreasing trends and 8 species with increasing trend. Then, we compared 26 functional traits between the decreasing and increasing species to understand the underlying mechanisms that drove the different changes in abundance. Compared to the decreasing species, the increasing species had larger rhizomes and longer and thinner fine roots, suggesting that drought tolerance may be a key factor in understanding the differences in the abundance of alpine meadow plants. Our study demonstrated that belowground traits at the whole-plant level, as well as at the organ level, played essential roles in species-specific abundance changes in alpine meadow plants. This means that belowground traits are a crucial component predicting the changes in species diversity of alpine vegetation under global warming.