Fire has historically played a fundamental ecological role in many of America’s wildland areas.
Mixed-conifer forests in the interior Pacific Northwest are subject to sporadic outbreaks of the western spruce budworm, the most destructive defoliator in western North America. Such outbreaks usually occur synchronously over broad regions and lead to widespread decreases in growth rates and low to moderate levels of mortality.
Quaking aspen, the most widespread tree species in North America, reproduces primarily by resprouting from roots. In some stands, mortality from fire encourages sprouting and prevents conifers from eventually replacing aspen. In other areas, aspen can form stable communities that do not require fire to regenerate or persist.
Forests dominated by Douglas-fir and western hemlock in the Pacific Northwest of the United States have strongly influenced concepts and policy concerning old-growth forest conservation.
During the 21st century, climate-driven changes in fire regimes will be a key agent of change in forests of the U.S. Pacific Northwest (PNW).
The “pyroclimatic hypothesis” proposed by F. Biondi and colleagues provides a basis for testable expectations about climatic and other controls of fire regimes. This hypothesis asserts an a priori relationship between the occurrence of widespread fire and values of a relevant climatic index.
The 12-site National Fire and Fire Surrogate study (FFS) was a multivariate experiment that evaluated ecological consequences of alternative fuel-reduction treatments in seasonally dry forests of the US. Each site was a replicated experiment with a common design that compared an un-manipulated control, prescribed fire, mechanical and mechanical + fire treatments.
Fire severity influences post-burn structure and composition of a forest and the potential for a future fire to burn through the area. The effects of fire on forests with mixed severity fire regimes are difficult to predict and interpret because the quantity, structure, and composition of forest fuels vary considerably.
In temperate conifer forests of the Western USA, there is active debate whether fuels reduction treatments and bioenergy production result in decreased carbon emissions and increased carbon sequestration compared to a no-action alternative.
The interaction of fires, where one fire burns into another recently burned area, is receiving increased attention from scientists and land managers wishing to describe the role of fire scars in affecting landscape pattern and future fire spread.