Subalpine and boreal moorlands are ecosystems that contribute to climate stability by reducing excess carbon as well as acting to help regulate the climate—both invaluable properties in a time of advancing climate change. Therefore, understanding how to maintain these communities in their natural state is imperative. However, the underlying mechanisms of community stability and how factors such as biodiversity within these communities affect their long-term stability is still not well understood.
Scientists in Japan have been studying subalpine and boreal moorland plant communities over an extended area in a national monitoring project, the 'Monitoring Site 1000.' Using this dataset researchers at YOKOHAMA National University analyzed the relationships between vascular plant species richness, species asynchrony, species stability, community compositional stability, bryophyte cover and the temporal stability of the community cover to understand what factors influence plant communities' stability.
They found "empirical evidence that species asynchrony, species stability, and compositional stability jointly stabilizes, while bryophyte cover destabilizes moorland community stability," said Shun Nonaka, one of the papers authors and a researcher at the College of Urban Sciences, YOKOHAMA National University.
Their results were published in the Science of The Total Environment on Feb. 27.
Community stability within a plant ecosystem may be affected by many different factors. In the study by researchers at YOKOHAMA National University on the subalpine and boreal communities, species asynchrony, species stability and compositional stability were the primary drivers in that system's stability.
Species asynchrony, the change in species abundance over time, evidences the multiple temporal niches that many of the different plants fill. Strengthening the overall community by introducing a diversity of temporal life strategies thereby increasing the probability that if an environmental change occurs some of the species would be able to survive.
Species stability in the moorlands was largely the result of the presence of the dominant species, for example Moliniopsis japonica. This is an important finding as many of these species are currently under threat from the encroachment of woody species and a loss of habitat. "Thus, the study findings highlight that dominant species with habitat specificity in moorlands (such as Moliniopsis japonica, Carex middendorffii, and Rhynchospora alba), which are increasingly threatened by the expansion of woody species and the reduction of areas occupied by moorlands, should be conserved regardless of their endangered status," said Nonaka
Compositional stability, the maintenance of the same groups with the community, increased the temporal stability of the community.
Species richness, the number of species within an area, generally has a positive effect on community stability. In the study they found that the role of species richness in community stability could not be determined. This may be due to the shorter time scales of this study. Future work in these areas should consider longer time scales in their research to clearly define the role of species richness.
The greatest negative influence on community stability was the bryophyte cover as the bryophytes, largely Sphagnum mosses, decreased species asynchrony. Sphagnum moss physiology has a very strong effect on nearby hydrology and biogeochemical cycles. This can very negatively affect the vascular plants thereby reducing the number of plants that may fill certain temporal niches.
"The factors that determine moorland community stability identified in this study underscore the importance of dominant species conservation and the critical role of biodiversity in conservation strategies for moorland ecosystems," said Takehiro Sasaki, the second author on the paper and a researcher at the Graduate School of Environment and Information Sciences, YOKOHAMA National University.
"This study also showed that the destabilizing effect of bryophyte may become more pronounced with increasing temperature fluctuations across time scales. Future study should evaluate the multifunctional stability of ecosystem functions and community stability on longer-term and broader spatiotemporal scales. In particular, the "Monitoring Site 1000" used in this study should continue to be monitored over a wider area and over a longer period of time in the future, and monitoring of easily measurable factors such as soil environmental factors such as pH and EC and plant traits such as leaf height and specific leaf area should also be incorporated into the protocol," said Sasaki.
This work was financially supported by a Fostering Joint International Research A (no. 19KK0393) and a Grant-in-Aid for Scientific Research B (grant no. 21H02567, 22H03791 and 24K03127) to TS from the Ministry of Education, Culture, Sports, Science and Technology of Japan.
