Northeastern forests are being impacted by unprecedented environmental stressors, including acid deposition, invasive pests, and climate change. Forest health monitoring at a landscape scale is necessary to evaluate the changing condition of forest resources and to inform management of forest stressors. Traditional forest health monitoring is often limited to specific sites experiencing catastrophic decline or widespread mortality. Satellite remote sensing can complement these efforts by providing comprehensive forest health assessments over broad regions. Subtle changes in canopy health can be monitored over time by applying spectral vegetation indices to multitemporal satellite imagery. This project used historical archives of Landsat-5 TM imagery and geographic information systems to examine forest health trends in the northern Green Mountains of Vermont from 1984 to 2009. Results indicate that canopy health has remained relatively stable across most of the landscape, although decline was present in localized areas. Significant but weak relationships were discovered between declining forest health and spruce-fir-paper birch forests at high elevations. Possible causes of decline include the interacting effects of acid deposition, windthrow, and stressful growing environments typical of montane forests.

In spruce-fir forests, there are many biotic and abiotic disturbances that can alter stand structure and composition. Many of these disturbances can produce high percentages of tree mortality at different scales. Spruce beetle has been considered a devastating disturbance agent, capable of creating high levels of mortality that will alter fuel complexes that may affect fire behavior. For comparison, stand data were gathered in endemic (near Loa and Moab, UT), epidemic (near Loa and Fairview, UT), and post-epidemic (near Salina and Loa, UT) condition classes of spruce beetle activity. Generally, fine fuels were higher during the epidemic and returned to background levels during post-epidemic conditions. Also, herbaceous and shrub components increase following outbreak situations with an initial pulse of herbaceous material during epidemics followed by the expansion of shrub material in post-epidemic areas. Fuel bed bulk depth, large diameter woody material, sound and rotten, and duff did not significantly differ between spruce beetle condition classes. Available live canopy fuel, canopy bulk density, and canopy base height were significantly reduced from endemic when compared to epidemic and post-epidemic condition classes. The fuel complex alterations resulted in changes to calculated surface and crown fire behavior. Crown base height decreased in post-epidemic classes, which allowed for easier crown fire initiation. Due to large gaps in canopy continuity, no active crown fire was initiated. In endemic situations, canopy bulk density was adequate to maintain active crown fire runs, but crown base height was too high to initiate crown fire. Surface fire, estimated from the custom fuel models following fuel complex alterations, showed that fireline intensity and rates of spread were greater in post-epidemic areas, but mostly due to reduced overstory sheltering. When custom fuel models were compared with similar mid-flame wind speeds, epidemic and post-epidemic fire behavior predictions were similar, indicating that reduced sheltering was more dominant than the influence of the fuels complex or solar radiation. When custom fuel models were compared with established fuel models, none predicted the same fire behavior outputs.