Changes in alpine plant communities under climate change: Dynamics of snow-meadow vegetation in northern Japan over the last 40 years

Question: Alpine plant communities are often distributed as a mosaic reflecting micro-scale heterogeneity of environmental conditions, indicating the importance of diverse habitats in maintaining species diversity in alpine ecosystems. Because snow-meadow vegetation is particularly sensitive to climate change, species composition and community structure may have changed over the last few decades in response to global warming. The aim of the present study is to quantify changes in species diversity and snow-meadow community composition over the last 40 years. Location: Taisetsu Mountains, Hokkaido, Japan. Methods: The presence and ground cover of plant species were surveyed in two snow-meadow sites in 1971-1972 (44 and 113 plots) and 2012 (85 and 115 plots). In addition, soil moisture and snowmelt time were measured in every plot in 2012. Changes in species richness, functional types and species composition between the survey periods were analysed. Results: Community structure of snow-meadow vegetation has changed significantly. Although the total number of species at each site was the same between the survey periods, Shannon's diversity index and species richness per plot have increased. Moreover, similarity in species composition among community types has been enhanced, indicating the mosaic structure of alpine vegetation has become obscure. The relative dominance of forbs (particularly tall herbaceous species) decreased, while that of shrubs increased. The distribution of community types reflected the snowmelt and soil moisture conditions. Conclusions: Significant changes have occurred in vegetation structure in the alpine snow-meadows, possibly due to accelerated snow melt and drier soil conditions linked to global warming. To predict the dynamics of alpine vegetation, we need to clarify how micro-scale heterogeneity of environmental conditions is modified by global change.