Presenter: Dr. Greg Nowacki, USFS - Eastern Region
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Abstract: Witness trees provide information fundamental for restoration ecology, often serving as baselines for forest composition and structure. Furthermore, when categorized by fire relations, witness trees can shed light on past disturbance regimes. By applying a recently published method, we converted witness-tree points to a contiguous surface of pyrophilic percentage for four national forests in the northeastern United States. Fire was found to be an important disturbance agent on the Allegheny and Finger Lakes national forests, often corresponding to large river systems and lakesides where Native American activities were concentrated. In contrast, fire was relatively unimportant on the Green Mountain and White Mountain nataional forests based on the witness-tree record. There, the cool, moist year-around climate coupled with lower Native American population densities greatly subdued fire, supporting their local colloquialism as "asbestos" forests. When applying this method to town-level witness-tree data for the entire northeastern United States, a distinct east-west line dividing areas of high (south) and low (north) pyrophilic percentage was apparent. Known as the Tension Zone Line, the undulating character of this boundary, penetrating northward along major river valleys, underscores the importance of Native Americans as a disturbance agent on the presettlement landscape.