FIRE EFFECTS GUIDE - National Wildfire Coordinating Group

establishment of seeds of plants of other species, are commonly found in the litter
beneath certain plant species, including chamise (McPherson and Muller 1969), Utah
juniper (Juniperus osteosperma), and singleleaf pinyon (Pinus monophylla) (Everett
1987a). Fire can volatilize these chemicals and allow additional seed germination.
Some species that must establish from seed may be temporarily eliminated from a
burned area because their establishment is not favored by conditions created by a fire.
They may require shade, have slow growth of their primary root, or a high water
requirement. Some tree species such as pinyon and juniper, may establish a few years
after a fire in the shade of plants that established first, but subsequently can grow in full
sun (Everett 1987b).
b. Seedbank. The seedbank, the supply of seeds present on a site, is composed of
buried seeds, those stored in the tree canopy, and those that are deposited annually.
Seeds of some species, such as willow, are very short-lived, and are part of the seed
bank for only a short time. Other species have extremely long-lived seeds, and become
a fixed member of the soil seedbank, once their seeds are dispersed.
Seed dispersal mechanisms vary. Light seeds may be windblown while heavier seeds
may skid across the surface of the snow. Some seeds have wing-like structures which
enhance their movement through the air. Seeds with barbs or hooks may be carried by
animals. Hard-coated seeds ingested along with their fruit may pass through the bird or
animal, with an enhanced likelihood of germination. Seed dispersal from unburned
areas depends on the amount of available seed, the distance of the seed source from
the burned area, the prevailing wind direction, and the type of seed.
The supply of seeds of a specific species can be greatly influenced by the amount of
annual seed production, which can vary significantly (Zasada et al. 1978).
Regeneration of conifers may be limited because cone crops are poor during the period
of time when exposed mineral soil seedbed is present.
Surviving plants on or near the burned area may not be old enough to produce seed
(Zasada 1971; Barney and Frischknecht 1974), or may be too old to produce much
viable seed.
The dispersal of seeds from plants occurs at a time that is characteristic for that plant,
and can last for different durations of time (Zasada 1986). The time of fire occurrence
with respect to seed dispersal can determine whether a species can regenerate
promptly. Heat from the fire may kill seeds in the canopy and seeds that have recently
been distributed onto the site. Seeds of a certain species may require a period of cold
before they can germinate, so seedlings of that species will not appear until the
following spring.
Seeds in immature cones in tree canopies may have survived the fire, and may
continue to ripen even though the foliage was killed (ponderosa pine) (Rietveld 1976),
or the bole was completely girdled by fire (white spruce) (Zasada 1985). Serotinous
lodgepole pine cones retain their seeds because of the presence of a resin bond
between the cone scales. These cones do not open and release their seeds unless
heated to 45 to 50C (113 to 122F), a temperature that melts the bond (Lotan 1976).
Numerous lodgepole pine seeds are often released after heating of the canopy during a