Decreased fire activity has been recognized as a main cause of expansion and infilling of North American woodlands. Piñon-juniper (Pinus-Juniperus) woodlands in the western United States have expanded in area 2–10-fold since the late 1800s.
The prevailing paradigm in the western U.S. is that the increase in stand-replacing wildfires in historically frequent-fire dry forests is due to unnatural fuel loads that have resulted from management activities including fire suppression, logging, and grazing, combined with more severe drought conditions and increasing temperatures.
Wildfire poses a rising threat in the western USA, fueled by synergies between historical fire suppression, changing land use, insects and disease, and shifts toward a drier, warmer climate. The rugged landscapes of northeast Oregon, with their historically forest- and resource-based economies, have been one of the areas affected.
Since Euro-American settlement, ponderosa pine forests throughout the western United States have shifted from high fire frequency and open canopy savanna forests to infrequent fire and dense, closed canopy forests. Managers at Zion National Park, USA, reintroduced fire to counteract these changes and decrease the potential for high-severity fires.
Smoke exposure is often an inevitable side effect of open vegetation fires (both planned and wild) and is an important public health concern.
Management strategies developed for Turnbull NWR call for the integration of a variety of techniques to restore natural stand conditions, reduce hazard fuels and improve wildlife habitat. These strategies include various types of thinning followed by the application of prescribed fire.
Prescribed fire is a critical tool for promoting restoration and increasing resilience in fire-adapted ecosystems, but there are barriers to its use, including a shortage of personnel with adequate ecological knowledge and operational expertise to implement prescribed fire across multijurisdictional landscapes.
Altered fuel conditions coupled with changing climate have disrupted fire regimes of forests historically characterised by high-frequency and low-to-moderate-severity fire. Managers use fuel treatments to abate undesirable fire behaviour and effects.
Mechanical fuel treatments are a common pre-fire strategy for reducing wildfire hazard that alters fuel structure by converting live canopy fuels to a compacted layer of dead surface fuels. Current knowledge concerning their effectiveness, however, comes primarily from forest-dominated ecosystems.
Thinning implemented with a cut-to-length system accompanied by on-site slash mastication and dispersal and followed by prescribed underburning were evaluated for their influences on individual tree and stand level growth in eastern Sierran mixed conifer. California white fir (Abies concolor var. lowiana [Gord.] Lemm.) dominated stand composition with Jeffrey pine (Pinus jeffreyi Grev.