James D. McIver

Fire treatment effects on vegetation structure, fuels, and potential fire severity in western U.S. forests

Forest structure and species composition in many western U.S. coniferous forests have been altered through fire exclusion, past and ongoing harvesting practices, and livestock grazing over the 20th century. The effects of these activities have been most pronounced in seasonally dry, low and mid-elevation coniferous forests that once experienced frequent, low to moderate intensity, fire regimes. In this paper, we report the effects of Fire and Fire Surrogate (FFS) forest stand treatments on fuel load profiles, potential fire behavior, and fire severity under three weather scenarios from six western U.S. FFS sites. This replicated, multisite experiment provides a framework for drawing broad generalizations about the effectiveness of prescribed fire and mechanical treatments on surface fuel loads, forest structure, and potential fire severity. Mechanical treatments without fire resulted in combined 1-, 10-, and 100-hour surface fuel loads that were significantly greater than controls at three of five FFS sites. Canopy cover was significantly lower than controls at three of five FFS sites with mechanical-only treatments and at all five FFS sites with the mechanical plus burning treatment; fire-only treatments reduced canopy cover at only one site. For the combined treatment of mechanical plus fire, all five FFS sites with this treatment had a substantially lower likelihood of passive crown fire as indicated by the very high torching indices. FFS sites that experienced significant increases in 1-, 10-, and 100-hour combined surface fuel loads utilized harvest systems that left all activity fuels within experimental units. When mechanical treatments were followed by prescribed burning or pile burning, they were the most effective treatment for reducing crown fire potential and predicted tree mortality because of low surface fuel loads and increased vertical and horizontal canopy separation. Results indicate that mechanical plus fire, fire-only, and mechanical-only treatments using whole-tree harvest systems were all effective at reducing potential fire severity under severe fire weather conditions. Retaining the largest trees within stands also increased fire resistance.

The Effects of Forest Fuel-Reduction Treatments in the United States

The current conditions of many seasonally dry forests in the western and southern United States, especially those that once experienced low- to moderate-intensity fire regimes, leave them uncharacteristically susceptible to high-severity wildfire. Both prescribed fire and its mechanical surrogates are generally successful in meeting short-term fuel-reduction objectives such that treated stands are more resilient to high-intensity wildfire. Most available evidence suggests that these objectives are typically accomplished with few unintended consequences, since most ecosystem components (vegetation, soils, wildlife, bark beetles, carbon sequestration) exhibit very subtle effects or no measurable effects at all. Although mechanical treatments do not serve as complete surrogates for fire, their application can help mitigate costs and liability in some areas. Desired treatment effects on fire hazards are transient, which indicates that after fuel-reduction management starts, managers need to be persistent with repeated treatment, especially in the faster-growing forests in the southern United States.

The national Fire and Fire Surrogate study: effects of fuel reduction methods on forest vegetation structure and fuels

Changes in vegetation and fuels were evaluated from measurements taken before and after fuel reduction treatments (prescribed fire, mechanical treatments, and the combination of the two) at 12 Fire and Fire Surrogate (FFS) sites located in forests with a surface fire regime across the conterminous United States. To test the relative effectiveness of fuel reduction treatments and their effect on ecological parameters we used an information-theoretic approach on a suite of 12 variables representing the overstory (basal area and live tree, sapling, and snag density), the understory (seedling density, shrub cover, and native and alien herbaceous species richness), and the most relevant fuel parameters for wildfire damage (height to live crown, total fuel bed mass, forest floor mass, and woody fuel mass). In the short term (one year after treatment), mechanical treatments were more effective at reducing overstory tree density and basal area and at increasing quadratic mean tree diameter. Prescribed fire treatments were more effective at creating snags, killing seedlings, elevating height to live crown, and reducing surface woody fuels. Overall, the response to fuel reduction treatments of the ecological variables presented in this paper was generally maximized by the combined mechanical plus burning treatment. If the management goal is to quickly produce stands with fewer and larger diameter trees, less surface fuel mass, and greater herbaceous species richness, the combined treatment gave the most desirable results. However, because mechanical plus burning treatments also favored alien species invasion at some sites, monitoring and control need to be part of the prescription when using this treatment.

Environmental effects of postfire logging: literature review and annotated bibliography

The scientific literature on logging after wildfire is reviewed, with a focus on environmental effects of logging and removal of large woody structure. Rehabilitation, the practice of planting or seeding after logging, is not reviewed here. Several publications are cited that can be described as “commentaries,” intended to help frame the public debate. We review 21 postfire logging studies and interpret them in the context of how wildfire itself affects stands and watersheds. Results of this review are summarized in 16 major conclusions at the end of the text, most of which are based on results of no more than a handful of studies. The review is followed by an annotated bibliography and an index. Copies of all papers reviewed here are held by the Blue Mountains Natural Resources Institute, at the Forestry and Range Sciences Laboratory, Pacific Northwest Research Station, La Grande, Oregon.

Restoration of degraded lands in the interior Columbia River basin: passive vs. active approaches

Evidence for success of passive and active restoration is presented for interior conifer forest, sagebrush steppe, and riparian ecosystems, with a focus on the Columbia River basin. Passive restoration, defined as removal of the stresses that cause degradation, may be most appropriate for higher elevation forests, low-order riparian ecosystems, and for sagebrush steppe communities that are only slightly impaired. More active approaches, in which management techniques such as planting, weeding, burning, and thinning are applied, have been successful in forests with excessive fuels and in some riparian systems, and may be necessary in highly degraded sagebrush steppe communities. There is general agreement that true restoration requires not only reestablishment of more desirable structure or composition, but of the processes needed to sustain these for the long term. The challenge for the restorationist is to find a way to restore more desirable conditions within the context of social constraints that limit how processes are allowed to operate, and economic constraints that determine how much effort will be invested in restoration.

Ecological effects of alternative fuel-reduction treatments: Highlights of the National Fire and Fire Surrogate study (FFS)

The 12-site National Fire and Fire Surrogate study (FFS) was a multivariate experiment that evaluated ecological consequences of alternative fuel-reduction treatments in seasonally dry forests of the US. Each site was a replicated experiment with a common design that compared an un-manipulated control, prescribed fire, mechanical and mechanical + fire treatments. Variables within the vegetation, fuelbed, forest floor and soil, bark beetles, tree diseases and wildlife were measured in 10-ha stands, and ecological response was compared among treatments at the site level, and across sites, to better understand the influence of differential site conditions. For most sites, treated stands were predicted to be more resilient to wildfire if it occurred shortly after treatment, but for most ecological variables, short-term response to treatments was subtle and transient. Strong site-specificity was observed in the response of most ecosystem variables, suggesting that practitioners employ adaptive management at the local scale. Because ecosystem components were tightly linked, adaptive management would need to include monitoring of a carefully chosen set of key variables. Mechanical treatments did not serve as surrogates for fire for most variables, suggesting that fire be maintained whenever possible. Restoration to pre-settlement conditions will require repeated treatments over time, with eastern forests requiring more frequent applications.

The Sagebrush Steppe Treatment Evaluation Project (SageSTEP): a test of state-and-transition theory

The Sagebrush Steppe Treatment Evaluation Project (SageSTEP) is a comprehensive, integrated, long-term study that evaluates the ecological effects of fire and fire surrogate treatments designed to reduce fuel and to restore sagebrush (Artemisia spp.) communities of the Great Basin and surrounding areas. SageSTEP has several features that make it ideal for testing hypotheses from state-and-transition theory: it is long-term, experimental, multisite, and multivariate, and treatments are applied across condition gradients, allowing for potential identification of biotic thresholds. The project will determine the conditions under which sagebrush steppe ecological communities recover on their own following fuel treatment versus the communities crossing ecological thresholds, which requires expensive active restoration.

Fuel treatment impacts on estimated wildfire carbon loss from forests in Montana, Oregon, California, and Arizona

Using forests to sequester carbon in response to anthropogenically induced climate change is being considered across the globe. A recent U.S. executive order mandated that all federal agencies account for sequestration and emissions of greenhouse gases, highlighting the importance of understanding how forest carbon stocks are influenced by wildfire. This paper reports the effects of the most common forest fuel reduction treatments on carbon pools composed of live and dead biomass as well as potential wildfire emissions from six different sites in four western U.S. states. Additionally, we predict the median forest product life spans and uses of materials removed during mechanical treatments. Carbon loss from modeled wildfire-induced tree mortality was lowest in the mechanical plus prescribed fire treatments, followed by the prescribed fire-only treatments. Wildfire emissions varied from 10–80 Mg/ha and were lowest in the prescribed fire and mechanical followed by prescribed fire treatments at most sites. Mean biomass removals per site ranged from approximately 30–60 dry Mg/ha; the median lives of products in first use varied considerably (from 50 years). Our research suggests most of the benefits of increased fire resistance can be achieved with relatively small reductions in current carbon stocks. Retaining or growing larger trees also reduced the vulnerability of carbon loss from wildfire. In addition, modeled vulnerabilities to carbon losses and median forest product life spans varied considerably across our study sites, which could be used to help prioritize treatment implementation.

Delayed conifer mortality after fuel reduction treatments: interactive effects of fuel, fire intensity, and bark beetles

Many low-elevation dry forests of the western United States contain more small trees and fewer large trees, more down woody debris, and less diverse and vigorous understory plant communities compared to conditions under historical fire regimes. These altered structural conditions may contribute to increased probability of unnaturally severe wildfires, susceptibility to uncharacteristic insect outbreaks, and drought-related mortality. Broad-scale fuel reduction and restoration treatments are proposed to promote stand development on trajectories toward more sustainable structures. Little research to date, however, has quantified the effects of these treatments on the ecosystem, especially delayed and latent tree mortality resulting directly or indirectly from treatments. In this paper, we explore complex hypotheses relating to the cascade of effects that influence ponderosa pine (Pinus ponderosa) and Douglas-fir (Pseudotsuga menziesii) mortality using structural equation modeling (SEM). We used annual census and plot data through six growing seasons after thinning and four growing seasons after burning from a replicated, operational-scale, completely randomized experiment conducted in northeastern Oregon, USA, as part of the national Fire and Fire Surrogate study. Treatments included thin, burn, thin followed by burn (thin + burn), and control. Burn and thin + burn treatments increased the proportion of dead trees while the proportion of dead trees declined or remained constant in thin and control units, although the density of dead trees was essentially unchanged with treatment. Most of the new mortality (96%) occurred within two years of treatment and was attributed to bark beetles. Bark beetle-caused tree mortality, while low overall, was greatest in thin + burn treatments. SEM results indicate that the probability of mortality of large-diameter ponderosa pine from bark beetles and wood borers was directly related to surface fire severity and bole charring, which in turn depended on fire intensity, which was greater in units where thinning increased large woody fuels. These results have implications when deciding among management options for restoring ecosystem health in similar ponderosa pine and Douglas-fir forests.

Multidisciplinary, Multisite Evaluation of Alternative Sagebrush Steppe Restoration Treatments: The SageSTEP Project

This special issue presents short-term ecological effects of restoration treatments imposed as part of the Sagebrush Steppe Treatment Evaluation Project (SageSTEP), and summarizes public attitude survey results related to restoration efforts. Funded by the US Joint Fire Science Program (JFSP; 2005– 2011), the Bureau of Land Management (BLM; 2011 to present), the National Interagency Fire Center (2011 to present), and the US Fish and Wildlife Service (2010), SageSTEP was designed and implemented to provide treatment-related information to managers concerned about the rapidly changing condition of sagebrush steppe ecosystems in the US Interior West (McIver et al. 2010). At lower elevations, cheatgrass has become more dominant at the expense of native perennial bunchgrasses, in some locations shifting fire return intervals from.50–100 yr to,20 yr, and greatly increasing mean fire size (Whisenant 1990; Miller et al. 2011; Balch et al. 2012). At higher elevations, pinon pine and juniper woodlands have expanded and displaced sagebrush and other shrubs, in some places shifting fire return intervals from 10–50 yr to..50 yr, and significantly increasing mean fire severity (Miller and Heyerdahl 2008). Federal, state, and private land managers and owners have for many years attempted to arrest the conversion of sagebrush steppe communities into woodland and annual grassland and to restore native herbaceous communities by applying treatments such as prescribed fire, mowing, chaining, cutting, mastication, or herbicides. Substantial published information exists on the efficacy of such treatments in sagebrush steppe, but most studies are site-specific, short-term (Miller et al. 2013), and focused on few variables. Recognizing this, the BLM, in collaboration with the JFSP, solicited sagebrush steppe scientists and managers to design SageSTEP, a study that provides multisite, multidisciplinary, long-term information on treatment outcomes over a range of ecological conditions, and that also provides insight on cost and public acceptance of management practices. A planning grant was provided by JFSP in 2003 to design SageSTEP, and the study was ultimately funded by JFSP in 2005. SageSTEP addresses four principle objectives, each linked to one or more of the design features of the study: