ReviewObjectives and considerations for wildland fuel treatment in forested ecosystems of the interior western United States
Introduction
It is generally accepted that past management practices including the successful suppression of many wildland fires in some western United States ecosystems over the last 70 years have resulted in excessive accumulations of surface and canopy fuels which have, in turn, increased the potential for severe fires (Brown and Arno, 1991, Mutch et al., 1993, Kolb et al., 1998, Keane et al., 2002, Stephens and Ruth, 2005). Because productivity exceeds decomposition in most of the West, surface fuels tend to increase in the absence of disturbance. In most coniferous forests, canopy fuels also increase and become more available without disturbance as more shade-tolerant trees become established in the understory and overstory (Keane et al., 2002). Many scientists and natural resource agencies suggest extensive fuel treatments to reduce the possibility of severe and intense wildfires that could damage ecosystems, destroy property, and take human life (USDA Forest Service, 2000, GAO, 2003a, GAO, 2003b). However, there are a number of misconceptions and misunderstandings about fuel treatments and their use as a panacea for fire hazard reduction across the United States (Finney and Cohen, 2003, Franklin and Agee, 2003). This paper reviews some common misunderstandings about fuel treatments and discusses ecological and managerial realities. It is important to understand the strengths and limitations of fuel treatments so that they can be properly applied and their potential for achieving management objectives can be realized. We have synthesized relevant literature to establish a common ground for fuel treatment planning. We suggest that the primary objective for treating fuels is to make wildfire more acceptable, that is, less severe, rather than to reduce wildfire extent or make it easier to suppress.
In this paper we focus on forested ecosystems in the western United States. Many of the ideas presented here may apply to areas and other vegetation types, such as rangelands, where some fuel treatment work takes place.
The term fuel treatment, as used in this paper, describes any mechanical, silvicultural, or burning activity whose main objective is to reduce fuel loadings or change fuel characteristics to lessen fire behavior or burn severity (National Wildfire Coordinating Group, 2006). Examples include mastication (e.g., flailing, chipping, and breaking), thinning, raking, and, of course, prescribed fire used separately or in concert with the mechanical treatments (Graham et al., 2004, Agee and Skinner, 2005). Fuel treatments are usually implemented at the stand level, but an increasing number of agencies are conducting landscape-level fuel modification activities, especially as wildland fire use applications (Black, 2004). Fuels, as discussed here, are the live and dead surface and canopy biomass that are burned in wildland fire. Surface fuels include downed, dead woody biomass and live and dead shrub and herbaceous material (DeBano et al., 1998). Canopy fuels are aerial biomass primarily composed of tree branchwood and foliage, but also including arboreal mosses, lichens, and hanging dead material (e.g., needles and dead branches) (Scott and Reinhardt, 2001, Reinhardt et al., 2006). We recognize that fuel treatment objectives and design may differ between wildland and wildland–urban interface (WUI) areas (Radeloff et al., 2005) with fuel treatments in wildland areas mostly designed to mitigate the effects of large, severe wildfires and to restore fire-prone ecosystems. Wildland is considered to be an area in which development is essentially non-existent, except for roads, railroads, powerlines, and similar transportation facilities. Structures, if any, are widely scattered, while WUI is the zone where structures and other human development meet or intermingle with undeveloped wildland or vegetative fuels (National Wildland Fire Coordinating Group, 2006). The WUI area presents a special challenge to fuel treatment programs because it often contains lands with a variety of ownerships (both public and private) and objectives. Management of these boundary areas often attempts to reduce potential property loss as well as restoring or maintaining ecosystems. Prescribed fire and wildland fire use are the primary fuel treatment methods in wildland settings with a greater emphasis on mechanical fuel reduction treatments in WUI areas.
Planned fuel treatments, whether mechanical or prescribed fire, are only one part of a comprehensive fire management program that includes other tools such as wildland fire use. Wildland fire use is the management of naturally ignited wildland fires to accomplish specific prestated resource management objectives (http://www.fs.fed.us/fire/fireuse/index.html).
Section snippets
Objectives for treating wildland fuel
In general, fuel treatments are designed to alter fuel conditions so that wildfire is less difficult, disruptive, and destructive. However, implicitly and explicitly, managers, the public, special interest groups and policy makers often assume different specific objectives for fuel treatments. These differences in expectation can lead to polarization of what could be a non-divisive issue. In this section, we attempt to clarify some common misconceptions. While a number of authors provide
Other considerations for treating wildland fuel
Fuel treatments can involve a variety of strategies, including prescribed fire, thinning, and mechanical treatment of surface fuel, alone or in combination. Fuel treatment projects also involve decisions about placement, including the strategic placement of fuel treatments to accomplish as much as possible with limited resources. Specific fuel treatment needs vary with land use, current conditions, and the ecology of the site. In this section we outline the most pressing needs for enlightened
Treating fuels in the face of climate change
The world’s climate is changing, making increased resilience of forest stands an even more important goal. The effect of climate change on fire regimes remains somewhat uncertain, but many reports suggest that climates will become warmer and drier over the next century due to increased atmospheric carbon from anthropogenic sources, and the consequences of this change will be to increase (1) length of fire season, (2) severity and frequency of drought, (3) lightning ignitions, (4) amount of
Conclusions
Fuel treatment is an important management tool for reducing fire hazard. However, confusion exists as to the purpose and potential effectiveness of fuel treatment activities. We feel that fuel treatments should be used to reduce fire severity and intensity instead of fire occurrence. We also believe that fuel treatments should attempt to increase ecosystem resilience, especially in wildland settings. The range and variation of historical stand and landscape composition and structures should be
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