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Harvard Forest Symposium Abstract 2016

• Title: Are regionally synchronous disturbance events and forest dynamics embedded in complex old-growth forests of the Eastern U.S.?
• Primary Author: Neil Pederson (Harvard Forest)
• Additional Authors: Daniel Bishop (Harvard Forest); David Orwig (Harvard Forest); Neil Pederson (Harvard Forest)
• Abstract:

  Stand to intermediate-scale disturbances are seen as important drivers of forest composition, stand and age structure, and biomass production in the complex, broadleaf-dominated forests of the eastern US. Much of this knowledge is derived from studies of forest dynamics at these scales or, in the case of continental scale studies (i.e, remote-sensing, only 15-30 years of information is available). Studies at small spatial scales or short time scales, however, can miss a range of drivers from previous decades and centuries. These limitations can lead to the thought that these forests are rather insensitive to climate. In contrast, sediment core analysis has long revealed synchronous and large-scale changes in forests in response to disturbance or, often, climatic change. Recently, using tree-ring techniques, some of our research made several important findings regarding regional-scale disturbance in today’s old-growth forests. First, regional-scale disturbance events have been identified across many tree species throughout their lifetime; some of these events were severe. Second, an interaction of repeated, sustained drought events and a severe late frost event (May 1774) appear to be important triggers of elevated canopy mortality at a regional scale. Third, two disturbance events occurring 230 and 350 years ago are still exerting a detectable legacy in the age and stand structure of forests over 61,000 and ~1,400,000 km2 of the eastern US, respectfully. Considering the large number of tree species and types of disturbance in this region, that these disturbances still stand out over such a large area is surprising. One would expect that the more frequent disturbance events common to these forest types would erase these events. Yet, they do not and events from centuries ago still reverberate in the pattern and process of today’s forests in the eastern U.S. Through a network of >1300 trees developed as a part of PalEON that stretches from central New England to eastern New York State, we have begun to investigate disturbance histories at subregional scales using tree-ring analysis. Already we see some evidence for a rather synchronous recruitment of Quercus rubra. We are currently aiming to expand this network from Maine to Oklahoma to identify and disentangle drivers of local and large-scale disturbance.

• Research Category: Forest-Atmosphere Exchange
  Historical and Retrospective Studies
  Regional Studies