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Harvard Forest Symposium Abstract 2012
- Title: Pattern and ecological consequences of the catastrophic mortality of a foundation species due to interacting climatic and biotic stresses
- Primary Author: David Orwig (Harvard Forest)
- Additional Authors: David Foster (Harvard University); Brian Hall (Harvard Forest); Wyatt Oswald (Emerson College); Jonathan Thompson (Harvard Forest)
- Abstract:
Several HF scientists recently began a comprehensive research project examining forest tree species declines in response to successive years of defoliation by a suite of native and invasive insect pests combined with drought and interacting with natural and human disturbance. This research focuses on the catastrophic 2008-09 and ongoing mortality of oak across coastal New England and complements the broad theoretical, experimental, and modeling framework developed at Harvard Forest to examine historic and modern dynamics of foundation tree taxa in the eastern U.S. Ongoing analyses of pollen records from sites on Martha's Vineyard, including Harlock Pond, Duarte Pond, and Black Pond, suggest that the magnitude of the middle-Holocene oak decline varied across the coastal region, likely influenced by substrate and other landscape-scale processes. In 2008, we began examining the successional dynamics and community response following catastrophic oak mortality within twenty permanent plots on Martha’s Vineyard (Fig. 1). There were four general forest tree community types identified in the twenty vegetation sampling plots: post oak type, white oak type, black oak type, and a beech/mesic type with some overlap in community composition between them, with contrasting amounts of overstory-oak mortality. Oak mortality ranged from near zero to > 90% across the study area. Resin bag analysis suggests that total N capture from resin bags was higher in plots with higher oak mortality, despite high understory vegetation cover. Resin bags captured more NH4+ during both winters across all plots. In contrast, NO3 was captured in higher amounts in plots with > 60% oak mortality during the growing season. In terms of the almost 200 trees cored in the plots, oak trees killed by defoliation were very similar in diameter (average diameter = 27.8 cm) to trees that survived the defoliation event (avg. diameter = 27.1 cm). Annual radial growth rates are currently being measured in tree cores obtained from both live and dead trees to determine if growth prior to the most recent defoliation event was related to survival.
- Research Category: Historical and Retrospective Studies
Invasive Plants, Pests & Pathogens - Figures: MV fig1.jpg
