Alter forest structure to reduce severity or extent of extreme weather events

EASTERN: Wind disturbance is a fundamental process in many forest ecosystems across the Midwest and Northeast. Wind events and the ensuing effects on forests are expected to become more frequent and severe under climate change, although there are many challenges in predicting the size, frequency, and intensity of these events. Some stands may have structures poorly suited to withstand projected increases in storm intensity. Silvicultural techniques exist to alter forest composition and structure for increased resistance to blowdown or ice damage, or to avoid sudden exposure of retained trees to wind. 

WESTERN: Climate change is expected to increase the occurrence, frequency and severity of extreme weather events, including drought, extreme precipitation, heat waves, and wind disturbances. Though such events are fundamental processes in many forest ecosystems, increases in frequency and severity can overstress and burden these systems. Periods of moderate to intense drought impact the magnitude of climatic water deficits and plant stress, and risk of fire; trees weakened by water limitation may be more susceptible to pathogens, disease, and pests. Heat waves driving abnormally high temperatures can further stress plants and contribute to transitions of forest plant species composition. Extreme precipitation events, such as atmospheric rivers and late season snowstorms, can disturb and burden aboveground plant structures, creating vulnerabilities, particularly in recently burned forests, to flooding, erosion, and the ensuing negative impacts on water quality. Increasing intensity and frequency of windstorms may negatively impact the ability of stands to endure these disturbances. Moreover, high-intensity wind events may interact with intermittent features such as heavy canopy snow to increase blowdown, which can increase the risk of damaging electrical equipment and sparking fire. Management actions to alter forest composition and structure for reduced stress, increased resistance to blowdown or ice damage, or to avoid sudden exposure of retained trees to wind, may minimize the impact of extreme weather events.

Climate change is projected to continue to increase the potential for severe disturbance events, such as uncharacteristically large and severe wildfires, floods, severe and extended drought, and insect outbreaks. These disturbances have the ability to alter community composition and structure, potentially for many decades or longer, over large landscapes. Disturbances can also interact with other stressors. For example, extreme drought can cause tree damage and mortality, which increase the risk of insect outbreaks and potentially influence wildfire behavior. Even as trends continue to emerge, management will need to adjust appropriately to the changes in natural disturbance dynamics.