USDA Forest Service
 

Fire and Environmental Research Applications Team

 
 

Fire and Environmental Research Applications Team
Pacific Wildland Fire Sciences Laboratory

400 N 34th Street, Suite 201
Seattle, WA 98103

(206) 732-7800

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United States Department of Agriculture Forest Service.

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FCCS Inferred Variables

The FCCS inferred variables are internal datasets used to calculate physical characteristics of wildland fuels. Inferred variables are used in association with a plant species or type designation (e.g., moss type, duff derivation). Inferred variables by species are listed in this downloadable database. They cannot be modified by users and include fuel chemistry, heat content, particle density, and bulk density values. Nomenclature for many of the inferred variables were derived in the development of the Rothermel fire spread model (Rothermel 1972, Scott and Burgan 2005) and the Van Wagner crown fire model (Van Wagner 1977, Scott and Reinhardt 2001). Their values are based on published and unpublished data where available. Defaults were estimated when no data were available (Sandberg, pers. comm. 2005). Questions about the inferred variables database should be directed to Susan Prichard.

 

 
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Webpage (.htm)
Excel file (.xls)
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(.doc)
Table S1: List of inferred variables, definitions, and defaults.

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Table S2: Inferred variables by species (English units). For ID codes, see Definitions worksheet.

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Table S2: Inferred variables by species (metric units). For ID codes, see Definitions worksheet.

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Table S3: Inferred variables by type (English units)

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Table S3: Inferred variables by type (metric units)

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Table S4: Shrub allometric biomass equations. (English units)

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Table S4: Shrub allometric biomass equations (metric units)

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Inferred Variables by Species

Bulk density (ρb; lb/ft3)—Crown bulk density data are taken from published sources such as the Natural Fuels Photo Series (Ottmar et al. 2004), Anderson (1969), Pagni and Peterson (1973), and expert opinion (Ottmar 2007).

Crown packing ratio (β; dimensionless)—Packing ratio (β) of tree crowns by species; defined as the fraction of crown volume occupied by fuel.

Crown shape (CSF; dimensionless)—A geometrical adjustment factor used to differentiate crown shapes of coniferous and broadleaf trees in volume and loading calculations.

Flammability (dimensionless)—The flammability index allows for the designation of species with special properties with respect to fire. Accelerant species are those that have extractives (e.g., terpenes, fats, waxes, and oils [particularly terpenoid hydrocarbons and lipids]) which provide a ready source of combustible volatiles. High heat of combustion, volatility, and lower limits of flammability increase flammability of accelerant species (Pyne et al. 1996). Neutral species do not contribute to fire behavior. There are no retardant species in FCCS v. 2.0.

Foliage particle density (ρf; lb/ft3)—Taken from standard sources (e.g., Hoadley 1991, Wenger 1984); however, a default value of 25.0 lb/ft3 is used when values are not available.

Low fuel heat content (h; Btu/lb)—Heat of a material produced by combustion (Byram 1959).

Rotten wood particle density (ρr; lb/ft3)—Taken from standard sources (e.g., Hoadley 1991, Wenger 1984); however, a default value of 18.7 lb/ft3 is used when values are not available.

Sound wood particle density (ρs; lb/ft3)—Taken from standard sources (e.g., Hoadley 1991, Wenger 1984); however, a default value of 25.0 lb/ft3 is used when values are not available.

Surface-area-to-volume ratio (σ; ft2/ft3)—The ratio of surface area to volume based on data for cylinders and was described by Fons (1946).

 

Citations

 

Anderson, H.E. 1969. Heat transfer and fire spread. Gen. Tech Rep. INT-69. Ogden, UT: U.S.
Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment
Station. 20 p

Fons, W.L. 1946. Analysis of fire spread in light forest fuels. Journal of Agricultural Research. 72: 93-121.

Hoadley, R.B. 1991. Identifying wood: accurate results with simple tools. Newtown, CT: Taunton Press. 240 p.

Ottmar et al 2004

Ottmar, R.D. 2007. Personal communication. Research forester, Pacific Northwest Research Station, 400 N 34th
Street, Suite 201, Seattle, WA 98103.

Pagni, P.J.; Peterson, T.G. 1973. Flame spread through porous fuels. In: Proceedings of the 14th International
Symposium on Combustion. Pittsburgh, PA: The Combustion Institute: 1099–1107. Link to abstract

Pyne, S.J.; Andrews, P.L.; Laven, R.D. 1996. Introduction to wildland fire. 2nd ed. New York: John Wiley & Sons.
804 p.

Rothermel, Richard C.  1972.  A mathematical model for predicting fire spread in wildland fuels.   Res. Pap. INT-115. Ogden, UT: U.S. Department of Agriculture, Intermountain Forest and Range Experiment Station. 40 p. Abstract and full text

Sandberg, D.V. 2005. Personal communication. Research physical scientist emeritis, Pacific Northwest Research Station.

Scott, J.H.; Burgan, R.E. 2005 Standard fire behavior fuel models; a comprehensive set for use with Rothermel's surface fire spread model. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. Abstract and full text

Scott, Joe H.; Reinhardt, Elizabeth D.  2001.  Assessing crown fire potential by linking models of surface and crown fire behavior.   Res. Pap. RMRS-RP-29. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 59 p. Abstract and full text

Van Wagner, C.E. 1977. Conditions for the start and spread of crown fire. Canadian Journal of Forest Rsearch. 7: 23-34. Full text

Wenger, K.F., ed. 1984. Forestry handbook. New York: John Wiley and Sons. 1335 p.

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