Chapter 3 Large-scale patterns of forest fire occurrence across the 50 United States and the Caribbean territories, 2017This article is part of a larger document. View the larger document here.
As a pervasive disturbance agent operating at many spatial and temporal scales, wildland fre is a key abiotic factor affecting forest health both positively and negatively. In some ecosystems, for example, wildland fres have been essential for regulating processes that maintain forest health (Lundquist and others 2011). Wildland fre is an important ecological mechanism that shapes the distributions of species, maintains the structure and function of fre-prone communities, and acts as a signifcant evolutionary force (Bond and Keeley 2005). At the same time, wildland fres have created forest health (i.e., sustainability) problems in some ecosystems (Edmonds and others 2011). Specifcally, fre outside the historic range of frequency and intensity can impose extensive ecological and socioeconomic impacts. Current fre regimes on more than half of the forested area in the conterminous United States have been moderately or signifcantly altered from historical regimes, potentially altering key ecosystem components such as species composition, structural stage, stand age, canopy closure, and fuel loadings (Schmidt and others 2002). As a result of intensive fre suppression efforts during most of the 20th century, the forest area burned annually decreased from approximately 16–20 million ha (40–50 million acres) in the early 1930s to about 2 million ha (5 million acres) in the 1970s (Vinton 2004). Understanding existing fre regimes is essential for properly assessing the impact of fre on forest health because changes to historical fre regimes can alter forest developmental patterns, including the establishment, growth, and mortality of trees (Lundquist and others 2011).