Carl E. Fiedler

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 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.

Invasive pathogen threatens bird–pine mutualism: implications for sustaining a high-elevation ecosystem

Human-caused disruptions to seed-dispersal mutualisms increase the extinction risk for both plant and animal species. Large-seeded plants can be particularly vulnerable due to highly specialized dispersal systems and no compensatory regeneration mechanisms. Whitebark pine (Pinus albicaulis), a keystone subalpine species, obligately depends upon the Clarks Nutcracker (Nucifraga columbiana) for dispersal of its large, wingless seeds. Clarks Nutcracker, a facultative mutualist with whitebark pine, is sensitive to rates of energy gain, and emigrates from subalpine forests during periods of cone shortages. The invasive fungal pathogen Cronartium ribicola, which causes white pine blister rust, reduces whitebark pine cone production by killing cone-bearing branches and trees. Mortality from blister rust reaches 90% or higher in some whitebark pine forests in the Northern Rocky Mountains, USA, and the rust now occurs nearly rangewide in whitebark pine. Our objectives were to identify the minimum level of cone production necessary to elicit seed dispersal by nutcrackers and to determine how cone production is influenced by forest structure and health. We quantified forest conditions and ecological interactions between nutcrackers and whitebark pine in three Rocky Mountain ecosystems that differ in levels of rust infection and mortality. Both the frequency of nutcracker occurrence and probability of seed dispersal were strongly related to annual whitebark pine cone production, which had a positive linear association with live whitebark pine basal area, and negative linear association with whitebark pine tree mortality and rust infection. From our data, we estimated that a threshold level of approximately 1000 cones/ha is needed for a high likelihood of seed dispersal by nutcrackers (probability > or = 0.7), and that this level of cone production can be met by forests with live whitebark pine basal area > 5.0 m2/ha. The risk of mutualism disruption is greatest in northern most Montana (USA), where three-year mean cone production and live basal area fell below predicted threshold levels. There, nutcracker occurrence, seed dispersal, and whitebark pine regeneration were the lowest of the three ecosystems. Managers can use these threshold values to differentiate between restoration sites requiring planting of rust-resistant seedlings and sites where nutcracker seed dispersal can be expected.

Restoring Fire-Dependent Ponderosa Pine Forests in Western Montana

| suppression. M any foresters and ecologists recognize that disruption of the historic pattern of frequent fires in ponderosa pine forests has resulted in major ecological changes, including increasingly severe wildfires and insect and disease epidemics (Weaver, 1943; Covington and Moore, 1992; Mutch and others, 1993; Everett, 1994). In response to this realization, there is increasing interest among natural resource managers, biologists, and the public in restoring ponderosa pine forests to more natural and sustainable conditions (American Forests, 1995). The Intermountain Research Station and the University of Montana’s School of Forestry, in cooperation with the Bitterroot and Lolo National Forests have been testing the effectiveness of different silvicultural and prescribed-fire treatments for restoring ponderosa pine forests, and we will report some observations and initial findings here. But first we will summarize ecological changes that have occurred and describe our restoration treatments. For thousands of years fire shaped the composition and structure of North American forests, favoring species such as ponderosa pine (Pinus ponderosa) that are fireresistant and require fire to regenerate and compete successfully with other species (Pyne, 1982, Agee, 1993). In the inland West, pure ponderosa pine and mixed ponderosa pine-fir types are the most extensive of the fire-dependent forests. Non-fire-dependent species associated with ponderosa pine are interior Douglas-fir (Pseudotsuga menziesii var. glauca), grand fir (Abies grandis), white fir (A. concolor), and incensecedar (Calocedrus decurrens). Pure and mixed ponderosa pine types cover about 40 million acres (16 million hectares) in the western United States, an area equal to that of the state of Washington (van Hooser and Keegan, 1988). Prior to the early 1900s these forests were characterized by frequent lowto moderate-intensity fires, mostly underbums that killed few overstory pines. Historically, fires at intervals averaging five to 30 years in most areas thinned small trees and helped produce open, park-like, fire-resistant stands (Amo, 1988). Today many of these forests have changed dramatically and are experiencing critical health problems as a result of 60-80 years of fire exclusion and logging of overstory pines. For example, more than a million acres in eastern Oregon’s Blue Mountains now consist mostly of dead or dying trees, primarily fir thickets impacted by insect and disease epidemics (Mutch and others, 1993). Also, large stand-destroying wildfires, formerly rare in the open ponderosa pine forests, have become common in the dense stands that have developed as a result of fire exclusion. Dense stands also provide fuel ladders that cause fires to increase in intensity and climb into tree crowns. Severe fires in ponderosa pine made up a large portion of the three million acres that burned in the inland West during 1994. Past logging, which selectively removed large pines and left understory trees has allowed rapid development of conifer thickets (Habeck, 1990). Extensive coni-

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.

Nitrogen Spatial Heterogeneity Influences Diversity Following Restoration in a Ponderosa Pine Forest, Montana

The resource heterogeneity hypothesis (RHH) is frequently cited in the ecological literature as an important mechanism for maintaining species diversity. The RHH has rarely been evaluated in the context of restoration ecology in which a commonly cited goal is to restore diversity. In this study we focused on the spatial heterogeneity of total inorganic nitrogen (TIN) following restoration treatments in a ponderosa pine (Pinus ponderosa)/Douglas-fir (Pseudotsuga menziesii) forest in western Montana, USA. Our objective was to evaluate relationships between understory species richness and TIN heterogeneity following mechanical thinning (thin-only), prescribed burning (burn-only), and mechanical thinning with prescribed burning (thin/burn) to discern the ecological and management implications of these restoration approaches. We employed a randomized block design, with three 9-ha replicates of each treatment and an untreated control. Within each treatment, we randomly established a 20 x 50 m (1000 m2) plot in which we measured species richness across the entire plot and in 12 1-m(2) quadrats randomly placed within each larger plot. Additionally, we measured TIN from a grid consisting of 112 soil samples (0-5 cm) in each plot and computed standard deviations as a measure of heterogeneity. We found a correlation between the net increase in species richness and the TIN standard deviations one and two years following restoration treatments, supporting RHH. Using nonmetric multidimensional scaling ordination and chi-squared analysis, we found that high and low TIN quadrats contained different understory communities in 2003 and 2004, further supporting RHH. A comparison of restoration treatments demonstrated that thin/burn and burn-only treatments created higher N heterogeneity relative to the control. We also found that within prescribed burn treatments, TIN heterogeneity was positively correlated with fine-fuel consumption, a variable reflecting burn severity. These findings may lead to more informed restoration decisions that consider treatment effects on understory diversity in ponderosa pine/Douglas-fir ecosystems.

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.

Tree squirrel habitat selection and predispersal seed predation in a declining subalpine conifer

Differential responses by species to modern perturbations in forest ecosystems may have undesirable impacts on plant-animal interactions. If such disruptions cause declines in a plant species without corresponding declines in a primary seed predator, the effects on the plant could be exacerbated. We examined one such interaction between Pinus albicaulis (whitebark pine), a bird-dispersed, subalpine forest species experiencing severe population declines in the northern part of its range, and Tamiasciurus hudsonicus (red squirrel), an efficient conifer seed predator, at 20 sites in two distinct ecosystems. Hypotheses about squirrel habitat preferences were tested to determine how changes in forest conditions influence habitat use and subsequent levels of predispersal cone predation. We performed habitat selection modeling and variable ranking based on Akaike’s information criterion; compared the level and variance of habitat use between two forest types (P. albicaulis dominant and mixed conifer); and modeled the relationship between P. albicaulis relative abundance and predispersal cone predation. T. hudsonicus did not demonstrate strong habitat preference for P. albicaulis, and thus, declines in the pine were not met with proportional declines in squirrel habitat use. P. albicaulis habitat variables were the least important in squirrel habitat selection. Squirrel habitat use was lower and varied more in P. albicaulis-dominant forests, and predispersal cone predation decreased linearly with increasing P. albicaulis relative abundance. In Northern Rocky Mountain sites, where P. albicaulis mortality was higher and abundance lower, squirrel predation was greater than in Central Rocky Mountain sites. In ecosystems with reduced P. albicaulis abundance, altered interactions between the squirrel and pine may lead to a lower proportion of P. albicaulis contributing to population recruitment because of reduced seed availability. Reducing the abundance of competing conifers will create suboptimal squirrel habitat, thus lowering cone predation in P. albicaulis and ensuring more seeds are available for avian dispersal.

Making fire and fire surrogate science available: a summary of regional workshops with clients /

Youngblood, Andrew; Bigler-Cole, Heidi; Fettig, Christopher J.; Fiedler, Carl; Knapp, Eric E.; Lehmkuhl, John F.; Outcalt, Kenneth W.; Skinner, Carl N.; Stephens, Scott L.; Waldrop, Thomas A. 2007. Making fire and fire surrogate science available: a summary of regional workshops with clients. Gen. Tech. Rep. PNW-GTR-727. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 59 p. Operational-scale experiments that evaluate the consequences of fire and mechanical “surrogates” for natural disturbance events are essential to better understand strategies for reducing the incidence and severity of wildfire. The national Fire and Fire Surrogate (FFS) study was initiated in 1999 to establish an integrated network of long-term studies designed to evaluate the consequences of using fire and fire surrogate treatments for fuel reduction and forest restoration. Beginning in September 2005, four regional workshops were conducted with selected clients to identify effective and efficient means of communicating FFS study findings to users. We used participatory evaluation to design the workshops, collect responses to focused questions and impressions, and summarize the results. We asked four overarching questions: (1) Who needs fuel reduction information? (2) What information do they need? (3) Why do they need it? (4) How can it best be delivered to them? Participants identified key users of FFS science and technology, specific pieces of information that users most desired, and how this information might be applied to resolve fuel reduction and restoration issues. They offered recommendations for improving overall science delivery and specific ideas for improving delivery of FFS study results and information. User groups identified by workshop participants and recommendations for science delivery are then combined in a matrix to form the foundation of a strategic plan for conducting science delivery of FFS study results and information. These potential users, their information needs, and preferred science delivery processes likely have wide applicability to other fire science research.

Managing for Old Growth in Frequent-Fire Landscapes

In this article, we discuss how to monitor the structural and functional attributes of old growth, as well as its associated plant communities and wildlife, both to determine the possible need for treatment and to assess post-treatment progress toward desired conditions. Monitoring can be used to detect conditions (or agents) that threaten existing old growth and also to document indicators of healthy, functioning old- growth systems.