Plant phenology and vulnerability assessments in Acadia National Park, Maine

Background/Question/Methods: Changes in plant phenology are often hailed as a simple and straightforward signal of the ecological effects of climate change. Extensive observational and experimental studies have documented the correlations between advancing leaf out and flowering phenology and warming spring temperatures. However, phenological responses are not uniform across all plant taxa, and in Concord, Massachusetts plants with unresponsive flowering phenology were found more vulnerable to local extinctions. From this line of research, phenology has become a key plant trait included in many climate vulnerability assessment methods. These vulnerability assessments guide natural resources managers as they work to meet the conservation challenges posed by climate change. Often, the long-term, community-scale datasets required to document changes in phenology at the species level are not locally available. The relative importance of locally-sourced phenology data to determine vulnerability traits has not been assessed. We have documented patterns of species loss and spring phenology in Acadia National Park (ANP) through historical ecology and observational and experimental fieldwork. Here, we use ANP as a case study to evaluate phenology as a vulnerability trait and compare local measures of phenological responsiveness with those reported for conspecifics in Concord, Massachusetts.

Results/Conclusions: Over the past century ANP has lost nearly one-fifth of its wildflower species, an extinction rate that parallels Concord, Massachusetts. A Fisher’s exact test of the 254 species with historical abundances in both Concord and ANP found the status (i.e. decline, stable, or increase in abundance) of a species in Concord is not an indicator for its status in ANP over the same time period (p=0.082). We will use four years of data from observational transects in ANP to document local phenological responsiveness in days/°C for thirty species and compare these to records in Concord for a regional-scale assessment of phenology as a vulnerability trait. At the local level, our common garden experiment in ANP explores the role of population-level differences in phenological responses to microclimate. Each common garden was filled with transplants with provenances of low, mid-, and high elevation in ANP. An ANOVA of our first two years of leaf out data in the common gardens found that site (microclimate), species, and year were significant factors (p < 0.01 for each), while provenance was only significant as an interaction effect with these factors.