Wildfire is a keystone ecological process in many forests worldwide, but fire exclusion and suppression have driven profound shifts in forest structure (e.g., increased density, canopy cover, biomass) that have contributed to increases in large, high-severity fire in many seasonally dry forests and woodlands of the western United States.
Western U.S. wildfire area burned has increased dramatically over the last half‐century. How contemporary extent and severity of wildfires compare to the pre‐settlement patterns to which ecosystems are adapted is debated. We compared large wildfires in Pacific Northwest forests from 1984 to 2015 to modeled historic fire regimes.
Current conditions in dry forests of the western United State have given rise to policy mandates for accelerated ecological restoration on U.S. National Forest System and other public lands. In southwestern ponderosa pine (Pinus ponderosa Laws.) forests, mechanized tree thinning and prescribed fire are common restoration treatments but are not acceptable for all sites.
There is considerable interest in evaluating whether recent wildfires in dry conifer forests of western North America are burning with uncharacteristic severity—that is, with a severity outside the historical range of variability.
Reference ecological conditions offer important context for land managers as they assess the condition of their landscapes and provide benchmarks for desired future conditions. State-and-transition simulation models (STSMs) are commonly used to estimate reference conditions that can be used to evaluate current ecosystem conditions and to guide land management decisions and activities.