DENDROGEOMORPHOLOGICAL ANALYSIS OF THE VARYING EFFECTS OF SLOPE PROCESSES, LOWER BUCKS COUNTY, PA

Small forested tributaries along the Neshaminy Creek (Tyler State Park, Newtown, Pennsylvania) exhibit a variety of adjustment strategies of growing trees to slope processes. The reactive response of trunk growth has been examined for a number of tree species. Bank-parallel digital photographs of maximum trunk curvature were normalized for comparison of the shapes of the non-linear sections. Our analysis shows a range of exponential growth trajectories, which is likely the function of slope gradient and the rate of mass wasting processes that are dominated by slow creep. Analysis of tree ring asymmetry in an American Ash (Fraxinus americana) shows that the rings are narrower on the downslope side (0.89 mm) compared to upslope (0.98 mm). This suggests that the downslope compression during tilting, rather than bending, necessary for continued adjustment to slope processes. In contrast to tree throw or event-scale mass wasting (sharp trunk kinks), the rates of slow adjustment to slope processes on decadal time scales may be best assessed and quantified using a combination of traditional geomorphological and dendrological methods.