Wildfires

Fire - Decay: Interactive Roles Regulating Wood Accumulation and Soil Development in the Northern Rocky Mountains

United States Department of Agriculture, Forest Service — Thu, 13 Jan 2011 15:18:41 PST

Decay and fire play interactive roles in recycling wood and other organic materials in forest ecosystems, and contribute to the development of high quality soils in the Northern Rocky Mountains. Decayed wood, charcoal, and other decomposed organic matter are the principal media for ectomycorrhizal and nonsymbiotic nitrogen fixing microbes. The activities of these microbes are critical to the growth of forest trees. The balance between decay and fire, as it affects the amount, distribution, and type of organic matter, controls the ability of forest soils to support the growth of trees.

Reexamination of Rothermel's Fire Spread Equations in No-wind and No-slope Conditions

United States Department of Agriculture, Forest Service — Wed, 15 Dec 2010 11:17:03 PST

Major revisions to Rothermel's fire spread equations include the propagating flux ratio, reaction velocity, and moisture damping coefficient. The reaction intensity is of the flames alone and specifically excludes energy derived from burning char whether or not it lies in the flaming zone. In this new formulation, moisture damping is completely divorced from fire extinction. Fire extinction is a probability function.

Fireline Production: A Conceptual Model

United States Department of Agriculture, Forest Service — Thu, 11 Nov 2010 14:29:26 PST

This report describes a conceptual model that provides a framework for the components of fireline production. Other conceptual or operational fire-related models may be linked with this production model. Major components and relationships are diagramed.

Fire Behavior in Nonuniform Fuels

United States Department of Agriculture, Forest Service — Thu, 11 Nov 2010 12:00:08 PST

For the purposes of this study, nonuniform fire behavior is predicted by modeling fire spread through a hexagonal network of fuel cells. Fire spread is assumed to be a process of contagious growth between cells. Fuel properties are allowed to vary from cell to cell in a prescribed manner but have uniform properties within the cell. Consequently, the nonuniformity of the actual fuel array is simulated through cell to cell variations and has a resolution limited by the cell size. Because of the nature of the modeling process, it is necessary to devise a scheme for collecting data describing nonuniformity and a scheme for filling the hexagonal cell array in a manner that simulates the actual fuel nonuniformity.

A Model for Predicting Lightning-Fire Ignition in Wildland Fuels

United States Department of Agriculture, Forest Service — Wed, 10 Nov 2010 12:27:47 PST

A model has been developed for predicting the number of lightning-fire ignitions in wildland fuels. The model is based on both stochastic and physical processes. Stochastic methods are used to generalize the lightning storm characteristics and site conditions that affect the potential for ignition. Physical processes are involved in determining the ignition probability of woody fuels by individual lightning events. Input required to operate the model includes lightning activity, upper air windspeed (storm movement), fuel moisture, and fuel bulk density. The model can be used either to predict ignitions at some future time by using forecast data or to estimate the number of fire ignitions actually occurring by using current data.

Relative Corrosivity of Currently Approved Wildland Fire Chemicals

United States Department of Agriculture, Forest Service — Tue, 02 Nov 2010 16:05:50 PDT

From the early stages of the development of chemicals for wildland fire control, damage from fire retardant corrosion was recognized as a serious problem. Extensive damage was done to equipment used in the handling, mixing, storing, and delivery of retardants (Davis and Phillips 1965; USDA FS 1964a). Corrosion-related damage, especially to aircraft, creates unsafe conditions. Preventing this damage reduces the potential risk of injury and death; moreover, everyone benefits from reduced expenditures for equipment repair and replacement.

Modeling Moisture Content of Fine Dead Wildland Fuels: Input to the BEHAVE Fire Prediction System

United States Department of Agriculture, Forest Service — Mon, 25 Oct 2010 12:40:52 PDT

A method for predicting the time-dependent nature of fine fuel moisture is badly needed to support fire behavior prediction systems used in fire management. Of the models available, none met all the requirements of the BEHAVE fire behavior prediction system. The Canadian Fire Fuel Moisture Code (FFMC) came closest to meeting our needs and was selected as a base model. Improvements to the FFMC were concentrated on providing a means of accounting for annual and diurnal variation due to solar heating of woody fuels. This was necessary because the FFMC was developed for fuels located within forest stands, a generally shaded condition. Solar heating raises the temperature of the fuel surface and lowers the relative humidity of the film of air surrounding the fuel particle. Formulas describing this near-fuel environment produce the temperature and relative humidity that are then used by FFMC to derive the moisture content. The solar intensity that drives the fuel temperature and relative humidity accounts for latitude, time of year, time of day, aspect, slope, elevation, atmospheric haze, and shade. Shade can be from clouds or overstory trees. Provisions are made to guide the user through tree descriptors necessary to determine expected amount of shade.

Visitor Attitudes Toward Wilderness Fire Management Policy -- 1971-84

United States Department of Agriculture, Forest Service — Mon, 25 Oct 2010 11:58:51 PDT

The historical role of naturally occurring fire in shaping the character of many American landscapes has become an accepted ecological principle. Prior to the coming of the Europeans, natural fires had a major influence in producing a variety of vegetational mosaics. Fire suppression policies of the 20th century, however, significantly changed the evolution of many landscapes compared to what would have occurred had natural fires been allowed to continue. Although natural fires can no longer be allowed to burn in many places because of resource values or danger to the public, such fires may be permitted in many wildernesses and National Parks under specified conditions -- if they achieve certain objectives.

Revegetation by Land Imprinter and Rangeland Drill

United States Department of Agriculture, Forest Service — Thu, 09 Sep 2010 09:17:54 PDT

The land imprinter and rangeland drill were compared for revegetation of a wildfire burn in the Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) vegetation type. Seeding trials were conducted on strips 152 m wide and 1.6 km long. Seeded species were fairway wheatgrass (Agropyron cristatum), luna pubescent wheatgrass (A. trichophorum), Russian wildrye (Elymus junceus), and Ladak alfalfa (Medicago sativa). Severe wind erosion on the study area occurred the first spring. Total seeded plant densities and cover were significantly higher with the imprinting treatment. Production of seeded plants was higher on the imprinted areas the first 2 years; thereafter, compensatory growth within the thinner drilled stand resulted in similar production levels between treatments. There was little difference in seeded plant establishment between soils.