COMPARATIVE DENDROGEOMORPHOLOGY OF TREETHROW PATTERNS IN SE BUCKS COUNTY, PENNSYLVANIA: ASSESSING THE WINTER 2018 TRENDS

A field survey of treefall resulting from the 1-2 March 2018 winter storm at Tyler State Park and surrounding area (Bucks County, Pennsylvania) was used as a basis for comparison with that from an earlier event – the 2012 Superstorm Sandy. At several sites, oak and beech trees toppled by Sandy were overlain by freshly uprooted trunks, resulting in a clear relative chronology. Where isolated, the most recently broken or uprooted trees were identified by the lack of new leaves, fresh bark, and absence of ground vegetation in the pit below the root plate. Measurements included minimum original tree height (L), breast-height trunk diameter (D) and root-plate diameter (D_p). Along the east bank of the Neshaminy Creek, the fall direction of a broken trunk trended SSW, suggesting a more southerly force than a westerly downslope orientation. Three large trees (D=1.0-2.6 m) were oriented in SSE direction (~S22W), with two leaving pits with D_p=1.8 and 2.4 m. A massive double-treethrow (L=25 and 31; D_p >3.9 m) outside the park was oriented ESE and is visible on low-altitude satellite images due to their crowns extending into an open field. The dendrogeomorphic patterns produced by the 2018 nor’easter contrast with a largely westerly direction of treethrow (W and N80W) of Superstorm Sandy. At all of these previously studied sites, the bark was heavily weathered and partially infilled pits contained ground vegetation. In some instances, root plates and hollow trunks were exploited by semi-fossorial mammals for dwelling and shelter. Our findings emphasize the importance of repeat field surveys of dendrogeomorphic indicators for reconstructing windthrow resulting from severe storms.