James K. Agee

SPATIAL CONTROLS OF HISTORICAL FIRE REGIMES: A MULTISCALE EXAMPLE FROM THE INTERIOR WEST, USA

Our objective was to infer the controls of spatial variation in historical fire regimes. We reconstructed a multicentury history of fire frequency, size, season, and severity from fire scars and establishment dates of 1426 trees sampled on grids in four watersheds (-64 plots, over -1620 ha each) representative of the Blue Mountains, Oregon and Wash- ington, USA. The influence of regional climate, a top-down control, was inferred from among-watershed variation in fire regimes, while the influence of local topography, a bot- tom-up control, was inferred from within-watershed variation. Before about 1900, fire regimes varied among and within watersheds, suggesting that both top-down and bottom- up controls were important. At the regional scale, dry forests (dominated by ponderosa pine), burned twice as frequently and earlier in the growing season in southern watersheds than in northern watersheds, consistent with longer and drier fire seasons to the south. Mesic forests (dominated by subalpine fir or grand fir) probably also burned more frequently to the south. At the local scale, fire frequency varied with different parameters of topography in watersheds with steep terrain, but not in the watershed with gentle terrain. Frequency varied with aspect in watersheds where topographic facets are separated by significant barriers to fire spread, but not in watersheds where such facets interfinger without fire barriers. Frequency varied with elevation where elevation and aspect interact to create gradients in snow-cover duration and also where steep talus interrupts fuel continuity. Frequency did not vary with slope within any watershed. The presence of both regional- scale and local-scale variation in the Blue Mountains suggests that top-down and bottom- up controls were both important and acted simultaneously to influence fire regimes in the past. However, an abrupt decline in fire frequency around 1900 was much greater than any regional or local variation in the previous several centuries and indicates that 20th-century fire regimes in these watersheds were dramatically affected by additional controls such as livestock grazing and fire suppression. Our results demonstrate the usefulness of examining spatial variation in historical fire regimes across scales as a means for inferring their controls.

The use of shaded fuelbreaks in landscape fire management

Shaded fuelbreaks and larger landscape fuel treatments, such as prescribed fire, are receiving renewed interest as forest protection strategies in the western United States. The effectiveness of fuelbreaks remains a subject of debate because of differing fuelbreak objectives, prescriptions for creation and maintenance, and their placement in landscapes with differing fire regimes. A well-designed fuelbreak will alter the behavior of wildland fire entering the fuel-altered zone. Both surface and crown fire behavior may be reduced. Shaded fuelbreaks must be created in the context of the landscape within which they are placed. No absolute standards for fuelbreak width or fuel reduction are possible, although recent proposals for forested fuelbreaks suggest 400 m wide bands where surface fuels are reduced and crown fuels are thinned. Landscape-level treatments such as prescribed fire can use shaded fuelbreaks as anchor points, and extend the zone of altered fire behavior to larger proportions of the landscape. Coupling fuelbreaks with area-wide fuel treatments can reduce the size, intensity, and effects of wildland fires. # 2000 Elsevier Science B.V. All rights reserved.

An environmental narrative of Inland Northwest United States forests, 1800-2000

Fire was arguably the most important forest and rangeland disturbance process in the Inland Northwest United States for millennia. Prior to the Lewis and Clark expedition, fire regimes ranged from high severity with return intervals of one to five centuries, to low severity with fire-free periods lasting three decades or less. Indoamerican burning contributed to the fire ecology of grasslands and lower and mid-montane dry forests, especially where ponderosa pine was the dominant overstory species, but the extent of this contribution is difficult to quantify. Two centuries of settlement, exploitation, management, and climate variation have transformed the fire regimes, vegetation and fuel patterns, and overall functionality of these forests. We present a narrative that portrays conditions beginning at the first contact of Euro-American settlers with Indoamericans of the region and extending to the present. Due in part to its geographic isolation, the Inland Northwest was among the last regions to be discovered by Euro-Americans. In 200 years the region has undergone fur trapping and trading, sheep, cattle, and horse grazing, timber harvesting, mining, road construction, native grassland conversion to agricultural production, urban and rural area development, fire prevention, and fire suppression. We highlight key changes to forest landscape patterns and processes that occurred under these combined influences, discuss implications of the changes, and progress towards restoring sustainability. An adaptive ecosystem management model has been adopted by public land management agencies to remedy current conditions. Ecosystem management is a relatively new concept that emphasizes the integrity and sustainability of land systems rather than outputs from the land. Adaptive management emphasizes the twin notions that incomplete knowledge and high degrees of risk and uncertainty about earth and climate systems will always limit land and resource planning and management decisions, and that management is chiefly a learning and adapting process. We discuss current issues and future options associated with ecosystem management, including the low likelihood of social consensus concerning desired outcomes, the lack of integrated planning, analysis, and decision support tools, and mismatches between existing land management planning processes, Congressional appropriations, and complex management and restoration problems. Published by Elsevier Science B.V.

Simulation of long-term landscape-level fuel treatment effects on large wildfires

A simulation system was developed to explore how fuel treatments placed in topologically random and optimal spatial patterns affect the growth and behaviour of large fires when implemented at different rates over the course of five decades. The system consisted of a forest and fuel dynamics simulation module (Forest Vegetation Simulator, FVS), logic for deriving fuel model dynamics from FVS output, a spatial fuel treatment optimisation program, and a spatial fire growth and behaviour model to evaluate the performance of the treatments in modifying large fire growth. Simulations were performed for three study areas: Sanders County in western Montana, the Stanislaus National Forest in California, and the Blue Mountains in south-eastern Washington. For different spatial treatment strategies, the results illustrated that the rate of fuel treatment (percentage of land area treated per decade) competes against the rates of fuel recovery to determine how fuel treatments contribute to multidecade cumulative impacts on the response variables. Using fuel treatment prescriptions that simulate thinning and prescribed burning, fuel treatment arrangements that are optimal in disrupting the growth of large fires require at least 1 to 2% of the landscape to be treated each year. Randomly arranged units with the same treatment prescriptions require about twice that rate to produce the same fire growth reduction. The results also show that the topological fuel treatment optimisation tends to balance maintenance of previous units with treatment of new units. For example, with 2% landscape treatment annually, fewer than 5% of the units received three or more treatments in five decades with most being treated only once or twice and ~35% remaining untreated after five decades.

Managing Forests and Fire in Changing Climates

Policy focused on fire suppression only delays the inevitable. With projected climate change, we expect to face much more forest fire in the coming decades. Policy-makers are challenged not to categorize all fires as destructive to ecosystems simply because they have long flame lengths and kill most of the trees within the fire boundary. Ecological context matters: In some ecosystems, high-severity regimes are appropriate, but climate change may modify these fire regimes and ecosystems as well. Some undesirable impacts may be avoided or reduced through global strategies, as well as distinct strategies based on a forests historical fire regime.

Interpreting the Yellowstone Fires of 1988Ecosystem responses and management implications

Norman L. Christensen is a professor in the Department of Botany, Duke University, Durham, NC 27706. James K. Agee is a professor in the College of Forest Resources, University of Washington, Seattle, WA 98195. Peter F. Brussard is a professor in and the chairman of the Biology Department, University of Nevada, Reno, NV 89557. Jay Hughes is a professor in and dean of the College of Forestry and National Resources, Colorado State University, Fort Collins, CO 80523. Dennis H. Knight is a professor in the Department of Botany, University of Wyoming, Laramie, WY 82071. G. Wayne Minshall is a professor in the Department of Biology, Idaho State University, Pocatello, ID 83209. James M. Peek is a professor in the College of Forest Resources, Wildlife, and Range Science, University of Idaho, Moscow, ID 83843. Stephen J. Pyne is a professor in the Department of History, Arizona State University, West Campus, Phoenix, AZ 85017. Frederick J. Swanson is a senior research scientist in the USDA Forest Ser-

Ecological effects of large fires on US landscapes: benefit or catastrophe?

The perception is that todays large fires are an ecological catastrophe because they burn vast areas with high intensities and severities. However, little is known of the ecological impacts of large fires on both historical and contemporary landscapes. The present paper presents a review of the current knowledge of the effects of large fires in the United States by important ecosystems written by regional experts. The ecosystems are (1) ponderosa pine-Douglas-fir, (2) sagebrush-grasslands, (3) pinon-juniper, (4) chaparral, (5) mixed-conifer, and (6) spruce-fir. This review found that large fires were common on most historical western US landscapes and they will continue to be common today with exceptions. Sagebrush ecosystems are currently experiencing larger, more severe, and more frequent large fires compared to historical conditions due to exotic cheatgrass invasions. Historical large fires in south-west ponderosa pine forest created a mixed severity mosaic dominated by non-lethal surface fires while todays large fires are mostly high severity crown fires. While large fires play an important role in landscape ecology for most regions, their importance is much less in the dry pinon-juniper forests and sagebrush-grasslands. Fire management must address the role of large fires in maintaining the health of many US fire-dominated ecosystems.

FIRE AND VEGETATION HISTORY IN THE EASTERN CASCADE MOUNTAINS, WASHINGTON

Dendrochronological techniques were used to reconstruct a 433-yr fire his- tory, and to characterize the historical fire regime (frequency, size, season, severity) of the Teanaway River drainage in the eastern Cascade Mountains of Washington, USA. General Land Office section corner data were used to reconstruct aspects of the late-19th-century structure and composition of the forests in the study area. Systematic fire-scar surveys (;30 000 ha; 92 sites; 257 fire-scarred cross-sections; 1569 individual fire scars) revealed that fire frequency was quite variable spatially; Weibull median probability intervals ranged from seven to 43 years. Fire extent also varied widely; most fires were relatively small (,1000 ha), although several large fires (.4000 ha) were detected. Mean and median fire sizes were 1795 ha and 988 ha, respectively. Large fires occurred every 27 years, on average (every 11 years, on average, between 1708 and 1889), and coincided with periods of annual and seasonal drought (Palmer Drought Severity Index and winter Southern Oscillation Index). Intervals from 1 to 37 years occurred between fires of .4000 ha. Over 80% of fires occurred late in the growing season, or after the onset of cambial dormancy. Sampling locations in dry forest types (dominated by ponderosa pine) yielded fire-scarred cross- sections with numerous fire scars leading us to infer that most historical fires were of low intensity, leaving the overstory structure intact. This inference is corroborated by the com- position and structure of the historical forest, which was characterized by a preponderance of very large (.100-cm diameter) ponderosa pines. Mesic forest types (dominated by grand fir and Douglas-fir) likely exhibited a wider range of fire severities. Moderate and occasional high-severity understory fires or crown fires did occur within the study area, as indicated by the scarcity or lack of fire-scar evidence and the presence of relatively even-aged forests at several mesic forest sites. Historical section corner data indicate that small amounts of these forest types occurred in the study area. Fire frequency and size declined dramatically circa 1900, coincident with the advent of commercial timber harvesting, although most fires, despite their reduced number and size, continued to burn in the late summer or fall.

Forest Structure and Fire Hazard in Dry Forests of the Western United States

Peterson, David L.; Johnson, Morris C.; Agee, James K.; Jain, Theresa B.; McKenzie, Donald; Reinhardt, Elizabeth D. 2005. Forest structure and fire hazard in dry forests of the Western United States. Gen. Tech. Rep. PNW-GTR-628. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 30 p. Fire, in conjunction with landforms and climate, shapes the structure and function of forests throughout the Western United States, where millions of acres of forest lands contain accumulations of flammable fuel that are much higher than historical conditions owing to various forms of fire exclusion. The Healthy Forests Restoration Act mandates that public land managers assertively address this situation through active management of fuel and vegetation. This document synthesizes the relevant scientific knowledge that can assist fuel-treatment projects on national forests and other public lands and contribute to National Environmental Policy Act (NEPA) analyses and other assessments. It is intended to support science-based decisionmaking for fuel management in dry forests of the Western United States at the scale of forest stands (about 1 to 200 acres). It highlights ecological principles that need to be considered when managing forest fuel and vegetation for specific conditions related to forest structure and fire hazard. It also provides quantitative and qualitative guidelines for planning and implementing fuel treatments through various silvicultural prescriptions and surfacefuel treatments. Effective fuel treatments in forest stands with high fuel accumulations will typically require thinning to increase canopy base height, reduce canopy bulk density, reduce canopy continuity, and require a substantial reduction in surface fuel through prescribed fire or mechanical treatment or both. Long-term maintenance of desired fuel loadings and consideration of broader landscape patterns may improve the effectiveness of fuel treatments.

Reform forest fire management

Agency incentives undermine policy effectiveness Globally, wildfire size, severity, and frequency have been increasing, as have related fatalities and taxpayer-funded firefighting costs (1). In most accessible forests, wildfire response prioritizes suppression because fires are easier and cheaper to contain when small (2). In the United States, for example, 98% of wildfires are suppressed before reaching 120 ha in size (3). But the 2% of wildfires that escape containment often burn under extreme weather conditions in fuel-loaded forests and account for 97% of fire-fighting costs and total area burned (3). Changing climate and decades of fuel accumulation make efforts to suppress every fire dangerous, expensive, and ill advised (4). These trends are attracting congressional scrutiny for a new approach to wildfire management (5). The recent release of the National Cohesive Wildland Fire Management Strategy (NCWFMS) (6) and the U.S. Forest Services (USFSs) current effort to revise national forest (NF) plans provide openings to incentivize change. Although we largely focus on the USFS, which incurs 70% of national firefighting costs (7), similar wildfire policies and needed management reforms are relevant throughout the United States and fire-prone areas worldwide.