Skip to main content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Glossary of Terms

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

- L -

Ladder Fuels:
Fuels which provide vertical continuity between strata, thereby allowing fire to carry from surface fuels into the crowns of trees or shrubs with relative ease. They help start and continue crowning on a fire.

Large Fire:
1) For statistical purposes, a fire burning more than a specified area of land; e.g., 100 acres. 2) A fire burning with a size and intensity such that its behavior is determined by interaction between its own convection column and weather conditions above the surface.

Lay Down:
A fire is said to "lay down," often at night, when temperatures drop and RH rises. Fires do not "lie down." It's a long-standing term in fire and means that the fire is burning less actively than it did during the day.

Lead Plane:
Aircraft used to make dry runs over a target area to check wind and smoke conditions and topography and to lead airtankers to targets and supervise their drops. Lead planes are mandatory with MAFFS operations.

Light Fuels:
Fast-drying fuels, generally with a comparatively high surface area-to-volume ratio, which are less than 1/4-inch in diameter and have a timelag of one hour or less. These fuels ignite readily and are rapidly consumed by fire when dry.

Lightning Activity Level (LAL):
A number, on a scale of 1 to 6, that reflects frequency and character of cloud-to-ground lightning. The scale is exponential, based on powers of 2 (i.e., LAL 3 indicates twice the lightning of LAL 2).

Line Scout:
A firefighter who determines the location or placement or route of a fireline to be built.

Top layer of the forest, scrubland, or grassland floor, directly above the fermentation layer. It's composed of loose debris including sticks, branches, twigs, and recently fallen leaves or needles, little altered in structure by decomposition.

Live Fuels:
Living plants, such as trees, grasses, and shrubs, in which the seasonal moisture content cycle is controlled largely by internal physiological mechanisms rather than by external weather influences.

Long-interval fire-adapted plant communities:
Plant communities that have developed under an environment infrequent but high intensity or mixed severity fire occurrence. Fuels accumulate at slow but steady rates between fire events but are subject to dramatic changes following each high intensity fire event. Also see short-interval fire-adapted plant communities.