In many temperate regions, winter climate is changing faster than that of other seasons, yet we often do not know the ecological influence of winter climate change relative to other driving forces. Although fire is important in prairies and savannas, it is not the sole driver of community change, therefore disentangling the influence of other factors, such as winter climate change, is important for understanding past and future community change. Climate change experiments help us untangle the interactions of climate and other drivers of community change, yet long-term observational data provide opportunities to evaluate patterns of change over ecologically relative time scales. To examine how past winter climate change influenced plant communities, we resurveyed prairie and savanna plant communities originally surveyed in the 1950s to ask, 1) Over the past 60 years, how have changes in snow fall timing, duration, and magnitude influenced prairie and savanna plant communities? and 2) How strong is the influence of changing winter weather relative to management history and environmental condition? Plant community change between 1950s and 2010s was compared to several potential drivers to test the relative influence of climate change, management history, and environmental condition.
Results/Conclusions
Over the past 60 years, both winter climate and plant communities changed. The first snow now arrives later at all 90 sites (mean 12d later) and the overall number of days with snow on the ground has decreased (mean 11d shorter). On average, mean snow depth decreased 2 cm, but direction of change was not consistent as some sites experienced increased snow depth while others experienced decreases. Plant communities also changed, with a mean Bray-Curtis dissimilarity of 0.68, ranging from 0.17 to 0.97 across sites. We predicted the sites that experienced more winter climate change to also have greater community change over the past 60 years, and this prediction was partially supported. The association between change in snow duration and community change was contingent on both management history and environmental condition. Over the past 60 years, changes in winter snow pack were associated with changes in prairie and savanna plant communities, and at most sites, as the duration of snow on the ground shortened, the plant community changed more. Given the potentially mix of gradual and stochastic ecological changes associated with winter climate change, both long-term observations and shorter experimentation are required for understanding ecological implications of winter climate change.