FIRE EFFECTS GUIDE - National Wildfire Coordinating Group

plant and the rate at which the litter burns. Fires have been observed in northwest
Colorado burning at windspeeds of 10 to 14 miles per hour (16 to 22.5 kilometers per
hour) with rates of spread greater than 88 feet/minute (27 meters/ minute) during dry
summer conditions. These fires charred only the tops of the crowns of bluebunch
wheatgrass and Indian ricegrass plants that were 4 to 5 inches (10 to 13 centimeters)
in diameter. Fire may have moved through grass litter too quickly to have a long
enough residence time to ignite grass crowns, and little grass mortality occurred
(Petersburg 1989).
(4) Relationship of damage to postfire sprouting. A fire may move quickly through a
bunchgrass stand with little residual burning. At the other extreme, the dead center of a
bunchgrass plant may ignite, smolder, and burn for hours. Conrad and Poulton (1966)
developed damage classes for bunchgrasses: 1) unburned, although foliage may be
scorched; 2) plants partially burned, but not within 2 inches (5 centimeters) of the
crown; 3) plants severely burned, but with some unburned stubble less than 2 inches;
4) plants extremely burned, all unburned stubble less than 2 inches and mostly
confined to an outer ring; 5) plants completely burned, no unburned material above the
root crown.
Postfire response of a bunchgrass plant can be related to these damage classes,
particularly for those species with meristems above the mineral soil surface (ibid.). The
highest postfire sprouting potential usually is found in those plants with only some
surface litter removed. The amount of sprouting tends to decrease as the amount of
basal litter consumption increases, with new shoots most likely to appear from the
outside edge of the bunch when little unburned stubble remains. Plant mortality is most
likely if all plant material above the root crowns is consumed. Survival and recovery
after a specific amount of fire caused damage must also be considered with respect to
phenology and other seasonal factors that affect plant response. (See Sections B.4.a.;
B.4.c.)
3. Seedling Establishment.
a. Seedbed. Requirements for successful germination and establishment vary for
different species. Organic seedbeds, even rotting logs, may be able to successfully
support seedling establishment and survival if water is not limiting during the growing
season (Zasada 1971). However, moss, litter, and duff are poor seedbeds in many
climates because they frequently dry out in the summer, killing the seedling if the root
has not yet reached mineral soil. Other attributes of organic seedbeds may also inhibit
seedlings (Zasada et al. 1983). For many species, the best seedbed is exposed
mineral soil, and microsites where most or all of the organic layer has been removed by
fire provide the greatest chance for seedling survival. Soil does not dry out as readily as
organic material, and nutrients may be more readily available in ash. Competition from
sprouting plants may be reduced.
On hot, dry, exposed sites, seedling germination and establishment may occur more
readily if some organic material remains as mulch, especially if the seeds are covered
(Clark 1986). Ponderosa pine seedlings are more likely to establish if seeds land on
bare mineral soil, and the ungerminated seeds are subsequently covered by litter
(McMurray 1988). Allelopathic chemicals, those that inhibit the germination and/or