Climate change, species loss, and spring phenology in and around Acadia National Park, Maine

Anthropogenic climate change is altering phenology—the timing of biological events, including leafing and flowering—with repercussions for trophic interactions, competition, and species’ persistence. My dissertation aims to uncover, compile, and analyze resources documenting changes in species abundance and phenology in an iconic location (Acadia National Park and surrounding areas) in an understudied region of northern New England. I used the journal of a hunting guide living in Oxbow, Maine in the mid-20th century to document the climate sensitivity of leafing, flowering, and migratory bird arrivals. In Acadia National Park, Maine, I examined changes in the abundance of species by analyzing data from past and contemporary published floras for the park, and published analyses of floristic change from elsewhere in the northeastern United States. I used reciprocal transplants in common gardens and trail-side monitoring across elevation gradients in Acadia to examine inter- and intraspecific variation in plant phenology. Results showed that many native species declined in abundance or disappeared from the flora of Acadia over the past 120 years, similar to changes in floras elsewhere in New England. However, changes in the abundance of particular species in southern New England are not predictive of how they changed in Acadia. Some plant families (e.g. Orchidaceae and Liliaceae) declined disproportionately, but plant vulnerability was not related to habitat preference or range. The phenology of leaf out, flowering and migratory bird arrivals in and around Acadia demonstrate advances in response to warmer temperatures, albeit more slowly than plants in southern New England. Within Acadia, the temperature of local microclimates is a better predictor of plant phenology than elevation or aspect. Local adaption in leaf-out phenology sensitivity was not significant as populations from across a range of elevations responded similarly to different local microclimates in common gardens. This pattern contrasts with other montane systems where high elevation populations displayed reduced phenological sensitivity compared to low elevation populations. The results of this dissertation research underscore the importance of local data and of combining data from multiple sources (historical records, new field observations, and experiments) to describe changes in plant abundance and phenology, to assess species vulnerability, and to support decisions regarding future management and monitoring

We do not want to “cure plant blindness” we want to grow plant love

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150580/1/ppp310062_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150580/2/ppp310062.pd

Data from: Trails-as-transects: phenology monitoring across heterogeneous microclimates in Acadia National Park, Maine

Climate‐driven shifts in phenology, which are being observed worldwide, affect ecosystem services, trophic interactions, and community composition, presenting challenges to managers in protected areas. Resource management benefits from local, species‐specific phenology information. However, phenology monitoring programs in heterogeneous landscapes typically require serendipitous historical records or many years of contemporary data before trends in phenological responses to changes in climate can be analyzed. Here, we used a trails‐as‐transects approach to rapidly accumulate monitoring data across environmental gradients on three mountains in Acadia National Park, Maine, USA, and compared our results to phenological changes observed in Concord, Massachusetts, USA. In four years of intensive monitoring of transects on three mountains, we found large variability in spring temperatures across the mountains, but consistent patterns of advancing flower and leaf phenology in warmer microclimates. Reduced sampling intensity would have yielded similar results, but a shorter duration would not have revealed these patterns. The plants in Acadia responded to warming spring temperatures by shifting leaf and flower phenology in the same direction (earlier), but at a reduced rate (as measured in d/°C), in comparison with plants in southern New England (e.g., Concord, Massachusetts, USA). Our approach takes advantage of topographical complexity and associated microclimate gradients to substitute for long time series, allowing for rapid assessment of phenological response to climate. Other climate gradients (e.g., urban‐to‐rural, latitudinal, or coastal‐to‐inland) could work similarly. This intensive monitoring over a short time period quickly builds a robust dataset and can inform management decisions regarding future monitoring strategies, including sampling designs for citizen science‐based phenology monitoring programs

Leaf out and flowering phenology data from trails-as-transects in Acadia

Phenology data (first leaf out and first flower) recorded in the field along trails-as-transects in Acadia National Park, 2013-2016

Transect Temperature

The mean monthly temperatures for January-April recorded by HOBO temperature loggers located along hiking trails in Acadia National Par

Common Gardens and Control Plots

This file contains data on leaf out phenology and mean spring temperatures observed in local transplants and control plants (not transplanted) in our study. Temperatures were recorded by ibuttons located in the gardens and in adjacent control plots

Data from: Local environment, not local adaptation, drives leaf-out phenology in common gardens along an elevational gradient in Acadia National Park, Maine

PREMISE OF THE STUDY: Climate-driven changes in phenology are substantially affecting ecological relationships and ecosystem processes. The role of variation among species has received particular attention; for example, variation among species’ phenological responses to climate can disrupt trophic interactions and can influence plant performance. Variation within species in phenological responses to climate, however, has received much less attention, despite its potential role in ecological interactions and local adaptation to climate change. METHODS: We constructed three common gardens across an elevation gradient on Cadillac Mountain in Acadia National Park, Maine to test population-level responses in leaf-out phenology in a reciprocal transplant experiment. The experiment included three native species: low bush blueberry (Vaccinium angustifolium), sheep’s laurel (Kalmia angustifolia), and three-toothed cinquefoil (Sibbaldiopsis tridentata). KEY RESULTS: Evidence for local adaptation of phenological response to temperature varied among the species, but was weak for all three. Rather, variation in phenological response to temperature appeared to be driven by local microclimate at each garden site and year-to-year variation in temperature. CONCLUSIONS: Population-level adaptations in leaf-out phenology appear to be relatively unimportant for these species in Acadia National Park, perhaps a reflection of strong genetic mixing across elevations, or weak differences in selection on phenological response to spring temperatures at different elevations. These results concur with other observational data in Acadia and highlight the utility of experimental approaches to understand the importance of annual and local site variation in affecting phenology both among and within plant species

Phenology data for tree and wildflower species in Concord

Raw phenology data for tree and wildflower species in Concord, MA, USA

Daily carbon gain estimates

Daily carbon gain data used in carbon gain simulations under phenological mismatch. Data for 6 wildflower species were from field measurements taken in a common garden near Pittsburgh, PA (see Heberling, J.M., Cassidy, S.T., Fridley, J.D. & Kalisz, S. (2019) Carbon gain phenologies of spring-flowering perennials in a deciduous forest indicate a novel niche for a widespread invader. New Phytologist 221: 778-788)

Data from: Phenological mismatch with trees reduces wildflower carbon budgets

Interacting species can respond differently to climate change, causing unexpected consequences. Many understory wildflowers in deciduous forests leaf out and flower in the spring when light availability is highest before overstory canopy closure. Therefore, different phenological responses by understory and overstory species to increased spring temperature could have significant ecological implications. Pairing contemporary data with historical observations initiated by Henry David Thoreau (1850s), we found that overstory tree leaf out is more responsive to increased spring temperature than understory wildflower phenology, resulting in shorter periods of high light in the understory before wildflowers are shaded by tree canopies. Because of this overstory-understory mismatch, we estimate that wildflower spring carbon budgets in the northeastern United States were 12-26% larger during Thoreau’s era and project a 10-48% reduction during this century. This underappreciated phenomenon may have already reduced wildflower fitness and could lead to future population declines in these ecologically important species