Testing for Broader Effects of Foundation Species in Large Forest-Dynamics Plots

Event Type: Seminar

Date: 23 February 2021, 13:00 to 15:00

About the Event

A foundation species is a species (or group of functionally similar taxa) that dominates an assemblage numerically and in overall size (usually mass), determines the diversity of associated taxa through non-trophic interactions, and modulates fluxes of nutrients and energy at multiple control points in the ecosystem it defines. Recent advances in statistical methodology based on decades of observational and experimental work have identified two “fingerprints” of candidate foundation species in large forest dynamics plots: (1) they would be outliers from the expected “reverse-J” size-frequency distribution; and (2) their size or abundance would be negatively associated with the total abundance, alpha diversity of associated woody species at local spatial scales but positively associated with local-to-regional scale species turnover (beta diversity). The negative association between foundation species size or abundance and alpha diversity of associated woody species most likely results simply from crowding: at the local scale (e.g., in a 20×20-m subplot), when a foundation species dominates the basal area there is simply less room for any other stems. But foundation species also can enhance alpha diversity of other associated taxa, including microbes, invertebrate and vertebrate animals, and non-woody plant species. In this talk, I lay out a framework and sampling design for investigating effects of foundation species on other associated species. I then present initial data from a study that used these methods to investigate the relationship between the foundation tree species Tsuga candensis and diversity of associated ground-nesting ants in the ForestGEO plot at the Harvard Forest. These methods could be employed in any large forest dynamics plot to provide valuable new data on the importance of foundation species in controlling biodiversity at multiple scales.

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About the Speaker

Aaron Ellison

Aaron Ellison is the Senior Research Fellow in Ecology at Harvard University, Deputy Director of the Harvard Forest, and a semi-professional photographer, writer, and creative artist. He received his B.A. in East Asian Philosophy from Yale University in 1982 and his Ph.D. in Evolutionary Ecology from Brown University in 1986. After post-doctoral positions at Cornell and with the Organization for Tropical Studies in Costa Rica, Aaron taught for a year at Swarthmore College before moving to Mount Holyoke College in 1990. There, he was the Marjorie Fisher Assistant, Associate, and Full Professor of Environmental Studies, founding director of Mount Holyoke’s Center for Environmental Literacy, and then Associate Dean for Science, and he taught biology, environmental studies, and statistics until 2001. In 1992, Aaron received the National Science Foundation's Presidential Faculty Fellow award for "demonstrated excellence and continued promise both in scientific and engineering research and in teaching future generations of students to extend and apply human knowledge." Following a sabbatical year at Harvard in 2001-2002, Aaron assumed his current position at the Harvard Forest – Harvard’s 1500-hectare outdoor classroom and laboratory for ecological research. While continuing to work with undergraduate researchers as the director of the Harvard Forest Summer Research Program in Ecology (2004-2019), Aaron introduced the concept of foundation species to terrestrial ecology and continues to investigate their role in diversity and ecosystem function in forests throughout the world. Learn more about Aaron at harvardforest.fas.harvard.edu/aaron-ellison.