Since the mid 1970s, forest losses in the northeast U.S. have increased significantly. Forest dieback attributable to varied causes is now 2.6 times higher than pre-1975 levels. Although some of the increase is associated with the larger total tree volume, there is the strong perception that disruptive weather, air quality factors, and the outbreak of exotic pest species have played a significant role. The response by the USDA Forest Service and State agencies has included a large and increasing commitment to forest health monitoring, and to research into better techniques of forest health management.

Monitoring networks such as the USDA Forest Service’s Forest Health Monitoring Program currently have no capability to anticipate or fully explain climate and air quality impacts. The network of field plot observations serves as a passive system that allows interpretation and response only after well-defined patterns emerge. In contrast, natural resource managers need frequent, updated assessments of current and potential future conditions upon which to base management decisions and respond to public concerns. No methodology has been developed to predict when a forest population might be at risk to specific local and regional climate and air pollution stressors.

Our approach is to integrate climate and air-quality information with forest health data obtained from the USDA Forest Service’s Forest Health Monitoring (FHM) Program plots. Ultimately, our goal is to provide predictions of potential forest health conditions based on weather, climate, and air quality forecasts. To achieve this, we are developing risk indices of four key climate and air quality variables relevant to tree injury and loss in the northeastern U.S. The indices include (1) winter and early spring thaw-freeze occurrence and severity, (2) winter and early spring root-freeze occurrence and severity, (3) extreme low temperature occurrence, and (4) regional episodes of high surface ozone concentrations. Spatial and temporal patterns of these indices are being correlated with observed incidence of crown dieback and ozone damage obtained from the FHM ground observation plots in the northeastern U.S. This study sets the foundation and framework for future studies that will develop additional climate and air quality risk indices relevant to forest health in the north central and northeastern U.S. (e.g. NOx and SOx deposition patterns, extreme precipitation events, drought occurrence). The ozone component of this study provides a vital link to the USDA Forest Service’s Landscape Change Integrated Program in the North Central Research Station where landscape change impacts on tropospheric ozone risk to forest health in the north central U.S. are being examined.