Fire Treatment Effects on Vegetation Structure, Fuels, and Potential Fire Severity in Western US Forests

Forest structure and species composition in many western U. S. coniferous forests have been altered through. re 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,. re 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. re and mechanical treatments on surface fuel loads, forest structure, and potential. re severity. Mechanical treatments without. re 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;. re-only treatments reduced canopy cover at only one site. For the combined treatment of mechanical plus. re, all five FFS sites with this treatment had a substantially lower likelihood of passive crown. re 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. re severity under severe. re weather conditions. Retaining the largest trees within stands also increased. re resistance

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.Keywords: Oak, Prescribed fire, Frequent fire regimes, Pine, Mechanical treatment, Forest thinning, Dry forest management, Seasonally dry forest

Forest surveys and wildfire assessment in the Los Alamos Region; 1998-1999

To better understand the structural characteristics of vegetation in the Los Alamos region, the authors conducted two years of field surveys and associated analyses. This report introduces field methods, lists the summarized field data, and discusses the results of preliminary spatial analyses. During 1998 and 1999, seventy-six terrestrial plant communities were sampled for topographic characteristics, soil surface features, and vegetational conditions. A nested, randomized design was used to select the plot locations and to guide the sampling of the plot. The samples included a variety of fuel types, including surface fuels and ground fuels, shrubby and small tree fuels, and overstory fuels. Species composition data were also collected. The fuels data were summarized by vegetation type and evaluated for the topographic and spatial relationships of major field categories. The results of these analyses indicate that many of the fuels categories depend on topographic factors in a linear and curvilinear fashion. In particular, middle elevations within the Los Alamos region tend to support more surface fuels and ground fuels, whereas large-diameter trees are most dense at higher elevations and are specific to community types at these elevations. Small-diameter trees occur in more dense stands at lower and middle elevations and on specific soil and topographic conditions. Areas that burned in 1954 were found to be relatively free of fuels. The implications are that the western portions of the Los Alamos region are at risk from wildfire during dry, summer periods

A NATIONAL STUDY OF THE CONSEQUENCES OF FIRE AND FIRE SURROGATE TREATMENTS

Many U.S. forests, especially those with historically short-interval, low- to moderate-severity fire regimes, are too dense and have excessive quantities of fuels. Widespread treatments are needed to restore ecological integrity and reduce the high risk of destructive, uncharacteristically severe fires in these forests. Among possible treatments, however, the appropriate balance among cuttings, mechanical fuel treatments, and prescribed fire is often unclear. For improved decisionmaking, resource managers need much better information about the consequences of alternative management practices involving fire and mechanicaVmanual fire surrogates. Long-term, interdisciplinary research thus should be initiated to quantify the consequences and tradeoffs of alternative fire and fire surrogate treatments. Ecological, economic and social aspects must all be included as integral components. The research needs to be experimental, rather than retrospective or correlative, to permit stronger inferences about cause-and-effect relationships. Only through such research will it be possible to determine which ecosystem functions of fire can be emulated satisfactorily by other means, which may be irreplaceable, and the implications for management. The human dimensions of the problem are equally important. Treatment costs and utilization economics, as well as social and political acceptability, strongly influence decisions about treatment alternatives. Such research must be a cooperative effort, involving land managers, researchers, and other interested parties. A team of scientists and land managers has designed an integrated national network of long-term research sites to address this need, with support from the USDAIUSDI Joint Fire Science Program (http://www.nifc.gov/joint_fire_sci/index.html). The steering committee and other participants in this national FirelFire Surrogate (FFS) study represent a number of federal and state agencies, universities, and private entities, as well as a wide range of disciplines and geographic regions. The study will use a common experimental design to facilitate broad applicability of results

Appendix A. Characteristics of past management and treatments in the six western United States Fire and Fire Surrogate study sites.

Characteristics of past management and treatments in the six western United States Fire and Fire Surrogate study sites