RAPID: Topographic variation in tornado blowdown severity, and consequences for forest regeneration

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Ecologists have recently come to recognize that natural disturbances are an inherent part of the ebb and flow of forests, yet understanding of forest response to natural disturbances is patchy at best. There exists a good understanding of forest responses to fire, insect outbreaks, and hurricanes, but a poor grasp of forest response to ice storms, floods, and tornadoes. This project will examine forest damage caused by three long-track tornadoes that were part of the record-setting April 27-28, 2011 tornado outbreak. One tornado passed through the western section of Great Smoky Mountains National Park in southern Tennessee, and the other two through Chattahoochee National Forest in northern Georgia. The core goals of the project are to develop detailed inventories of the forest damage severity along these tornado tracks, and use that severity information to test three ecological models that hypothesize about how forests respond to different severity of disturbance. The study needs to begin promptly in order to accurately measure the severity of the disturbance and to identify the tree species that were blown down before they are salvage-logged or decompose. Once forest damage severity has been characterized along the tornado tracks, the recovery of the forests will be monitored, to see which model most accurately predicted the recovery of the forest. The model whose predictions are most accurate will be confirmed as the best understanding of how forests respond to wind disturbance. Knowledge of how forests respond to disturbance is important to society for a number of reasons: 1) guide management decisions, such as whether or not to log downed timber after disturbance; 2) project the likely future species composition after disturbance, i.e. will the tornado blowdown areas in 50 years be mostly cherry and maple, or mostly birch and hemlock?; 3) improve projections of carbon fixation in regrowing forests, a vitally important service provided by forests in a high-CO2 atmosphere; and, if future climate change brings increases in extreme weather events, 4) allow forecasts of how forests will change under the altered disturbance regime.