DENDROGEOMORPHIC ANALYSIS OF RECENT BEAVER IMPACT ON A STREAM CUTBANK, TYLER STATE PARK, PENNSYLVANIA

This study focuses on patterns of tree cutting (2018-2019) by North American beaver (Castor canadensis) along a 330-m-long stretch of the northeast bank of the Neshaminy Creek (Tyler State Park, Pennsylvania). The metrics included tree circumference and distance from the bank, bank height, tree height and slope of the cut, azimuth of treefall, and, where possible, the width of incisor marks (n=19). During the time of surveys (October 2019), the cutbank height was 1.5 m and exhibited dense vines and undergrowth. The affected trees were located from 0-4.86 m from the bank, with a slight preference of landward-sloping cut suggesting felling toward the creek. Small trees (circumference: ≤20.0 cm) tended to be felled within ±50° from the stream. Cut angles ranged from 9-74° and loosely negatively correlated with tree size. Our study demonstrates the importance of quantitative assessment of beaver impact along sensitive sections of the stream, as some trees were observed in progress of being felled. Some bark damage on larger trees indicates wide-ranging effects of increasing beaver activity.