Species asynchrony, species stability, and compositional stability jointly stabilize, while bryophyte cover...

Given the benefits that human society derives from the functions and services provided by diverse ecosystems, it is imperative to gain insight into the underlying mechanisms of community stability in naturally assembled communities. Despite the potential of subalpine and boreal moorland ecosystems for global carbon sequestration and climate regulation, research on biodiversity-stability relationships and their underlying mechanisms in these ecosystems is lacking. Here, an extensive vegetation dataset collected from subalpine and boreal moorlands across Japan was used to analyze the relationships between plant species richness, species asynchrony, species stability, compositional stability, bryophyte cover, and the temporal stability of community cover. The results revealed that species asynchrony, species stability, and compositional stability were the primary drivers stabilizing moorland community. The positive indirect effect of species richness on community stability, through increased species asynchrony, was largely offset by its negative indirect effect on stability via decreased species stability. Bryophyte cover had a negative effect on species asynchrony, which, in turn, reduced moorland community stability. Vascular plants in bryophyte mats, including sedges and dwarf shrubs, may respond synchronously to fluctuating soil moisture conditions, depending on how Sphagnum mosses react to increased temperatures. We thus provide general empirical evidence that species asynchrony, species stability, and compositional stability jointly stabilize, while bryophyte cover destabilizes moorland community stability. Given that plant communities in subalpine and boreal moorland ecosystems in Japan are increasingly threatened by the expansion of woody species and the reduction of areas occupied moorlands, our study underscores the importance of proactive conservation strategies targeting dominant species with habitat specificity in moorlands and the pivotal role that biodiversity plays in maintaining species asynchrony.