The hemlock woolly adelgid (Adelges tsugae) is an invasive aphid-like insect that is damaging the native hemlock trees on the East coast of the United States. In their study comparing valley and ridge-top hemlock stands, Hautaniemi and Link found that adelgids were significantly more abundant on ridge-top hemlock stands than in valley hemlock stands. Hautaniemi and Link also found that indicators of tree health (crown density and new growth) were significantly higher in valley hemlock stands than they were in ridge-top hemlock stands. What could be causing the hemlock trees to be in greater health in valleys and why are there more adelgids on ridge-tops? The purpose of this study is to analyze the data collected by Hautaniemi and Link, 2014 and to use ArcGIS to investigate the spatial variables of slope, aspect and elevation and their potential impacts on hemlock health and adelgid abundance. Trees were found to be healthier at lower elevations and at flatter slopes. Crown ratio was significantly higher in hemlock stands with lower elevations and flatter slopes and new growth was significantly higher at lower elevations. Crown density was lower at higher elevations and on steeper slopes. Adelgids were found to be more abundant on steeper slopes, where the crown density was lowest. Aspect was not found to be significantly correlated with tree health or adelgid abundance.
PDF of poster: HautaniemiGISPoster2