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Harvard Forest Symposium Abstract 2011
- Title: Sensitivity of the New England tension zone to past environmental change
- Primary Author: Wyatt Oswald (Emerson College)
- Additional Authors: David Foster (Harvard University); Matts Lindbladh (Swedish University of Agriculture Sciences)
- Abstract:
Ecotones are transitional boundaries between adjacent but contrasting plant communities. Some evidence suggests that ecotones are particularly sensitive to environmental change. We explored this hypothesis using a retrospective study of the New England tension zone, an ecotone spanning northern MA, southwestern NH, and southern ME. Oak, pine, hickory, and chestnut are common south of the tension zone, whereas hemlock, beech, maple and spruce dominate north of the ecotone. We analyzed lake-sediment pollen records from sites located along the tension zone (Little Willey Pond, NH), south of the ecotone (Blood Pond, MA), and north of the tension zone (Knob Hill Pond, VT). All three sites featured spruce during the late-glacial interval and white pine during the early Holocene. Multivariate ordination analyses show that the sites can be differentiated based on their pollen spectra beginning 8000 years ago. After that time, Blood Pond pollen assemblages are dominated by oak, Knob Hill Pond assemblages feature high percentages of hemlock, beech, and birch, and Little Willey samples are intermediate in their composition. This result suggests that the New England tension zone arose at that time. We then assessed the sensitivity of the study sites to Holocene environmental variability by using a dissimilarity metric (squared chord distance) to measure rates of change between samples. At times of major changes in climate, Little Willey Pond did not exhibit greater compositional shifts than the other sites. This finding suggests that ecotones are not necessarily more sensitive than other ecological settings during times of environmental change.
- Research Category: Historical and Retrospective Studies
