Climate change and species phenology at three trophic levels
Ellwood, Elizabeth R.
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In response to warmer temperatures and altered precipitation, plants and animals have adjusted their phenologies, timing of annual biological events, over the past few decades. However, a long-term perspective is needed. I combined observations from Concord, MA from the journals of Henry David Thoreau in the 1850s with other naturalists, to create the longest-known record of migratory bird arrivals in North America. Twenty-two passerine species were found to be highly variable with some arriving earlier in warm years than cold years, and others not changing at all. Banding data from the Manomet Center for Conservation Sciences, in southeastern MA, provided a robust dataset from 1970 to the present to further explore more detailed patterns in bird migrations. Most bird species in this record are experiencing significant population declines, and several arrive earlier in warm years. However, closely related birds did not behave in a manner similar to one another, and there is little evidence to support the hypothesis that species with flexible migration times would be more successful, a pattern found in European species. It is important to consider phenological changes at multiple trophic levels. Investigation of insect emergence dates collected by the Japan Meteorological Agency provided the paradoxical result that insects that emerge earlier in warm years are emerging later now than they did 50 years ago, even though temperatures are getting warmer. Sampling issues associated with strong population decline are the likely explanation. Plants are known to be quite responsive to temperature, yet one of the most primitive groups of plants, ferns, has remained unstudied from the perspective of recent climate change. I examined phenological and physiological responses of two fern species to a range of experimental water and temperature regimes. The cinnamon fern, Osmunda cinnamomea , generally exhibited greater phenological flexibility and hardiness under higher temperatures and drought as compared to the royal fern, Osmunda regalis . Taken together, this dissertation research demonstrates that organisms at various trophic levels respond differently to climate change. Therefore, the response of each species needs to be evaluated individually and in relationship to other species.
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