FIRE EFFECTS GUIDE - National Wildfire Coordinating Group

National Wildfire Coordinating Group
Fire Effects Guide
This page was last modified 05/31/01
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A. Introduction
CHAPTER VI - PLANTS
By Melanie Miller and Jean Findley
This chapter discusses the interaction of fire with plants. It explains the basic principles
and processes that determine how plants are affected by fire, and the factors that
control plant response after the fire. Documentation of burning conditions and fire
characteristics provides important information for understanding postfire vegetative
response. Use of appropriate techniques when monitoring specific effects of fire on
vegetation is necessary to detect changes that occur in the postfire plant community.
The goal is to enable managers to predict fire effects on plants based upon knowledge
of burning conditions and prefire species and community characteristics, and to
interpret the causes for observed variability in postfire vegetative response.
The response of plants to fire can vary significantly among fires and on different areas
of the same fire. Both variability in the heat regime of the fire and differences in plant
species' abilities to respond affect the postfire outcome. Fireline intensity, burn severity,
total duration of combustion, soil heating, time of the year, and time since the last fire
all influence mortality or survival of the plants, and thus subsequent recovery. Postfire
effects also depend upon the characteristics of the plant species on the site, their ability
to resist the heat of a fire, and the mechanisms by which they recover after fire. Plant
recovery can be affected by factors that vary with growing season, or age of the plant.
Whether the plants that first appear after a fire successfully establish on the site can be
influenced by external factors such as postfire weather, postfire animal use, and plant
competition.
The inherent abilities of plants to respond to fire depend partially on the fire regime to
which the plant community has adapted. For example, a community may
characteristically have been subject to frequent, low intensity, low severity understory
fires, or the site may have experienced infrequent high intensity fires that killed all
standing vegetation. Knowing the "natural" role of fire on a site gives an indication of
the type of plant adaptations to fire that may be present.
The most significant sources of heat from most fires are downed dead surface fuels,
litter, and duff layers. However, dead branches, leaves, or needles within a plant itself
can produce a considerable amount of heat. Old decadent stands of shrubs may
produce a more intense fire than a young shrub stand, which may have little dead or