FIRE EFFECTS GUIDE - National Wildfire Coordinating Group

time is, in many cases, not true (Brown and See 1981). The amount of
forest fuel depends on stand history, whether the stand was visited by
insects, disease, wind, and fire, and at what intervals. The size and
pattern of disturbance, and amount of fuel that results, can vary with the
event, and tree and branch mortality can be compounded by drought.
Agee (1993) also relates the amount of forest fuel to stand disturbance.
Changes in the amount of fine and coarse woody fuels over time relate
to the amount of biomass present before a disturbance, the severity of
the disturbance, and successional patterns after the stand is disturbed
(ibid.).
(a) Relationship to stand disturbance. When a wildland fire occurs in a
forested stand, the severity of the impact on the stand, and resulting
amount of surface fuels and rate of their accumulation, can vary
(Muraro 1971 in Brown 1975). For example, if a fire occurs in a
lodgepole pine stand that burns only in surface litter layers, it can kill or
weaken many of the trees but not consume much of the foliage. Surface
fuels increase moderately as trees die and fall. A fire in a lodgepole
pine stand that burns into the duff layer can consume many structural
tree roots. This makes trees susceptible to rapid blowdown, and fine
fuels are added to the stand at a much higher rate than after a lower
severity fire. A high intensity crownfire in a lodgepole pine stand can
burn off many of the fine branches in the tree crowns. If it also burns
deeply into the duff layer, most of the trees will fall fairly quickly. Most of
the fuel added would be large diameter material. Because downed trees
are not supported by small diameter branchwood, they would come into
contact with forest floor sooner and decompose more readily.
Whether the young stand of lodgepole pine that establishes after fire
has a low or high dead fuel loading also depends on the frequency of
fire. The stand that develops after a fire that caused rapid blowdown of
trees with a lot of branchwood would have a high loading of dead fuel in
all size classes. If a fire occurs in this young stand of trees, much of the
crown-stored seed could be destroyed and most of the fuel consumed.
A sparse stand of lodgepole pine could subsequently establish that has
a much lower loading of dead woody fuel than the previous stand
(Muraro 1971 in Brown 1975).
(b) Varying patterns among live and dead fuels. Fuel succession is
more complicated if live and dead fuels are involved (Brown and See
1981). There may be an increase in one class of fuel while another is
decreasing or becoming unavailable. Dead woody fuel may decompose