Date of Award
Environmental Science and Policy
Eastern Hemlock, Hemlock Woolly Adelgid, Forest structure, Otsego County
The invasive hemlock woolly adelgid insect (Adelges tsugae, HWA) threatens eastern hemlock trees (Tsuga canadensis) throughout eastern North America and is an increasing threat in Otsego County, NY. Different management strategies can mitigate the spread and effect of HWA, but landowners need information on the distribution and characteristics of hemlock stands to inform their decision-making process. We used field sampling of stand structure combined with remotely sensed data to a) map eastern hemlock in Otsego County and b) model stand structural characteristics of these stands. This information will be used to develop and disseminate site-specific recommendations on mitigation options to land owners. During the summer of 2022 we used point sampling (n= 5-10 per stand) to measure basal area and density of all tree species from 21 hemlock dominated stands distributed across the county. Stand total basal areas were between 24 and 54 m2/ha with relative basal area of hemlock between 37 to 88 %. The majority of the stands were west to north facing and were at elevations ranging from 362m to 557m. Supervised classification was employed with the Semi-Automatic Classification Plugin in QGIS using Sentinel-2 imagery Level 1C ((09/02/2022) and Level 2A (11/06/2021)) on a training set of 81 plots. This classified the vegetation into categories of Cultivated Field, Hay Field, Deciduous Forest, Pine Stands, Spruce Stands and Eastern Hemlock Stands. We were able to map areas of majority eastern hemlock with 97% accuracy. Stepwise multiple regression results showed that Sentinel-2 bands can be used to estimate percent eastern hemlock, total basal area and total density all with more than 70% accuracy. Together a map of land cover classification and hemlock stand structural characteristics can inform land owner's decisions on mitigation of hemlock woolly adelgid either by cultural, chemical, silviculture and/or biological controls.
Drake, Emma, "Mapping Hemlock Stand Distribution and Structure in Otsego County, NY to Develop Site-specific Mitigation of Hemlock Woolly Adelgid" (2023). Honors Theses. 2702.