A Landscape Scale Remote Sensing/GIS Tool to Assess Eastern Hemlock Vulnerability to Hemlock Woolly Adelgid Induced Decline
The hemlock woolly adelgid (Adelges tsugae Annand) (HWA) is an invasive insect pest that is causing widespread mortality of eastern hemlock (Tsuga canadensis). However, some stands remain living more than a decade after infestation. The ability to target management efforts in locations where hemlock is most likely to tolerate prolonged HWA infestation is critical to successful integrated pest-management programs. Here, we build a landscape-scale hemlock risk model for the Catskills region of New York based on coverage like slope and aspect derived from a traditional Digital Elevation Model (DEM). We also show that additional data layers derived from hyperspectral sensors such as NASA's Airborne Visible InfraRed Imaging Spectrometer (AVIRIS) can provide critical information for Geographic Information System (GIS) modeling. The initial landscape-only model was able to predict the rate of overall decline following HWA infestation for 21 plots across the Northeast with R2=0.35, p=0.027. Adding foliar N concentration to our model improved results to R2=0.79, p=0.0009. An AVIRIS-derived hemlock abundance coverage was then used to define the hemlock resource and its relative vulnerability to rapid decline. These results indicate that the inclusion of both landscape and chemical variables is critical to predicting hemlock vulnerability to HWA, and that landscape-scale modeling in a GIS platform is possible with the addition of hyperspectral remote sensing coverages. Whereas the resulting risk map covers only the Catskills region of New York, the relationships established here should be applicable to HWA infestation across the range of eastern hemlock, providing a basis for forest land management agencies to make informed management decisions.
- Introduction : Insect pests and pathogens represent the largest and most pervasive agents of natural disturbance in North American forests, with potentially significant economic, aesthetic, and ecological consequences for northern forest ecosystems.
- Objectives : The goal of this work was to build a data-driven, empirical decline model for hemlock vulnerability to HWA that could be applied to a spatially continuous GIS model.
- Methods : Plots in mature hemlock (where hemlock occupies >50 percent of the canopy) were established across a wide range of hemlock health, HWA infestation levels, site characteristics, and stand demographics. This included 48 sites characterizing the extremes of hemlock resistance and vulnerability to HWA from Pennsylvania to Maine.
- Results and Discussion : The final 3-term predictive model included aspect and slope.
- Conclusions : Creating an acceptable model of a complex, dynamic system is always challenging.
Encyclopedia ID: p3543
