Landscape scale modeling of hemlock susceptibility to hemlock woolly adelgid (HWA) and drought stressors in New England

University of Maine School of Forest Resources; USDA Forest Service Northern Research Station

SUMMARY: Land managers need to effectively mitigate the potential stress complex of Hemlock Woolly Adelgid (HWA) and drought currently facing hemlock in the northeastern United States. The development of comprehensive landscape-scale, spatially continuous models of the hemlock resource and its susceptibility to HWA and drought stressors would greatly aid this goal. Multidiscipline research for this project, which began in May 2007, has the objectives of (1) developing field based models to predict the impacts of drought and HWA infestation on hemlock decline; (2) translating field based models to a landscape scale using Geographic Information Systems (GIS) layers; (3) assessing the accuracy of the models by independent validation using new sample plots; and (4) disseminating information on methods and the potential of such approaches to other researchers, land managers, and GIS specialists.

EFETAC's ROLE: This project is supported by EFETAC funding.

STATUS: Completed

PROGRESS: Researchers developed a quantitative model of various site, soil, stand, climatic and topographic variables to predict hemlock productivity and response to HWA and drought stressors. They also developed a landscape-scale GIS coverage of relative hemlock susceptibility for New England and sampled independent validation plots. Researchers performed a final accuracy assessment.

The study indicated that as HWA spreads northward, the impact will be less as the insect deals with colder winter temperatures. Hemlock growing on steeper slopes and with higher solar exposure will be more vulnerable to decline. In the locations used in the study, HWA frequently reached damaging levels (i.e., can reduce increment growth) several years before it was detected.



Updated November 2012

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