Climate Change in Acadia National Park and beyond: Long-term trends in flowering phenology and floral abundance

Background/Question/Methods:

Climate change and its long-term ecological effects have become the defining issues for biologists today.  Plant communities are expected to migrate north and shift their phenologies, but it unclear how this will occur with respect to pollinators and trophic interactions.  Recently, there has been proliferation of re-purposed historical datasets — published flora, herbaria specimens, and field journals — compiled for phenological analysis. This kind of interdisciplinary research has yielded a number of well-studied-flora, especially in the northeastern U.S.; among these disparate examples of warming-related shifts are some sophisticated phylogenetic analyses, while others simply re-survey old records.  With the addition of Acadia National Park’s flora, these well-studied flora could be better integrated.  There is a need for comparisons across species’ ranges for rates of phenological shifting between populations as well as an attempt to tease out differential sensitivities to photoperiod and temperature.  In addition, comparing floras could provide insights for conservation management: the flora fall along a spectrum of protected-ness from fragmented suburbia to a mosaic of easements to, with this study, a national park.  Are protected populations better able to survive warming conditions?  Or will climate change affect preserved and disturbed landscapes with similar levels of species loss and decline?

Results/Conclusions:

We found historical data on the abundance and flowering times of over 1,000 species of plants in Acadia National Park.  Over the past 115 years there is evidence of species loss (18.5%) and declines (20%) on par with Worcester, MA and Concord, MA.  However, there seem to be diverging patterns of abundance shifts between the Concord and Acadia flora.  The loss of species is not explained by land use changes in either landscape; species are being lost from every habitat.  The Acadia data has been used to create a subset of 500 species present in similar Concord, MA and Washington DC flowering phenology analyses (regressions of flowering date and average monthly spring temperatures).  Comparing the days flowering has shifted per °C rise in temperature across these three studies allows us to identify species that may be differentially responding to climate change across populations.  Lastly, we included a phylogenetic analysis of our flora to test for patterns of response among closely-related species.  This in-depth analysis of the Acadia flora in the context of other well-studied-flora in the northeast provides new perspectives on the shifting phenologies and changing abundances of plant communities under climate change.