Fire Effects and Fire Ecology

Understory shrubs play important ecological roles in forests of the western US, but they can also impede early tree growth and lead to fire hazard concerns when very dense. Some of the more common genera (Ceanothus, Arctostaphylos, and Prunus) persist for long periods in the seed bank, even in areas where plants have been shaded out.

Aim Wildfire is often considered more severe now than historically in dry forestsof the western United States. Tree-ring reconstructions, which suggest that historicaldry forests were park-like with large, old trees maintained by low-severity fires,are from small, scattered studies.

Background. In forests subject to stand-replacing disturbances, conventional models of succession typically overlook early-seral stages as a simple re- organization/establishment period.

The National Wildfire Coordinating Group definition of extreme fire behavior (EFB) indicates a level of fire behavior characteristics that ordinarily precludes methods of direct control action. One or more of the following is usually involved: high rate of spread, prolific crowning/spotting, presence of fire whirls, and strong convection column.

Fire is a keystone process in many ecosystems of western North America. Severe fires kill and consume large amounts of above- and belowground biomass and affect soils, resulting in long-lasting consequences for vegetation, aquatic ecosystem productivity and diversity, and other ecosystem properties.

The results of this synthesis illustrate several important lessons. First, current forest structure is the result of decades of fire-suppression activities, and so restoration will require multiple treatments to bring forests to within the range of historic variation.

Dry forests throughout the United States are fire-dependent ecosystems, and much attention has been given to restoring their ecological function. As such, land managers often are tasked with reintroducing fire via prescribed fire, wildland fire use, and fire-surrogate treatments such as thinning and mastication.

Knowing when, where and how fire should be applied is critical for land managers planning to use fire prescriptively for land management goals, or allowing fires ignited naturally to burn. Myriad variables need to be taken into consideration to determine how fire will consume different fuels.

Technology is playing an increasingly pivotal role in the efficiency and effectiveness of fire management. The First Order Fire Effects Model (FOFEM) is a widely used computer application that predicts the immediate or ‘first-order’ effects of fire: fuel consumption, tree mortality, emissions, and soil heating.

Prescribed burning may be conducted at times of the year when fires were infrequent historically, leading to concerns about potential adverse effects on vegetation and wildlife. Historical and prescribed fire regimes for different regions in the continental United States were compared and literature on season of prescribed burning synthesized.