Conservation practitioners depend on accurate assessments of climate change vulnerability in allocating limited resources to protect and steward natural resources. Globally, montane and alpine communities are highly vulnerable to climate change, however there is evidence that high elevations and coastal mountains in the northeastern United States are not warming as rapidly as the rest of the region. The subalpine plants on Acadia National Park’s open granite ridges have been interpreted as post-glacial tundra relicts, however paleoecological records above treeline are sparse and this assumption remains untested. Could subalpine plant communities in Acadia represent persistent microrefugia, perhaps indicating high resilience in the face of regional and global climate change? Here we bring together historical ecological data from a 19thcentury flora and paleoecological data from lake sediment cores to reconstruct vegetation assemblages on these ridges throughout the Holocene. We calculate floristic change over the past century at the species-level. We describe decadal-to-centennial vegetation dynamics from new pollen and macrofossil records collected at a high elevation pond.
Results/Conclusions
Subalpine plant communities in Acadia appear in historical and paleoecological records. Our floristic change analysis found that mountain species (3% of the total flora of Acadia) experienced a loss of 3 native taxa from 1894 to 2005 (10.7% of its historical flora). All habitat categories in the park lost statistically indistinguishable proportions of their species, between 8.1 and 13.8%. Our paleoecological fieldwork recovered 409.5 cm of sediment; we analyzed 103 pollen samples throughout this stratigraphy and sorted and identified macrofossils at 0.5 cm increments. Preliminary results from the paleoecological research indicates a mix of what contemporary ecologists note as "low elevation" and "high elevation" taxa appearing in the fossil record, including species not currently found at this pond. Both the historical and paleoecological data capture changes in the vegetation assemblages on these coastal ridges. This combination of historical and paleo-ecological research brings long temporal perspectives to conservation planning in Acadia National Park and managers working at high elevations across the northeast. Assessing the premise of subalpine and alpine communities as persistent tundra microrefugia will provide critical context about the vulnerability of these iconic plant communities and allow conservation practitioners to focus management actions and refine extinction risk estimates for alpine and subalpine plants.