Plant-Plant Interactions With Fire
In this blog I will be discussing
the interactions between plants and fire. Aldo Leopold is considered to be the
godfather of conservation and has left a major impact on the wildlife
techniques that we use today. Leopold had five wildlife management techniques.
These techniques were an axe, cow, plow, match, and a gun. Aldo Leopold once said, “Fire
has always been part and parcel of the evolutionary background of our present
species in many regions.” Prescribed fires are commonly used to promote
plant growth and set back succession. Wildfires are fires that are burning out
of containment and can have various intensities. While some people view fire as
a detrimental thing to the environment, it can be very beneficial. For example,
the Great Smoky Mountain wildfire destroyed many homes and businesses but it
could result in the betterment of some of the ecosystems that were burned. Many
plant species rely on fire for their existence. These plants have many
adaptations that help them survive these fires. A few of these adaptations
include serotinous cones and thick bark. Fires also clear debris from the
soil’s surface allowing for seeds to be in contact with bare mineral soil. Fire
can have a major impact on the environment in many ways. If you have never seen
an area that has recently been burned, then you are in for a treat. What was
once a place that was not anesthetically pleasing and covered in plant litter
becomes a magnificent field of green plants emerging from the ground. Fire
impacts plant-plant interactions by allowing more sunlight to reach the ground
and by decreasing competition.
Many plant species have different
light tolerance. Some species may be shade intolerant while others may be shade
tolerant. It is up to the management objectives to determine what species
composition that they want. If an early successional/shade intolerant ecosystem
is desired, then prescribed fire can be a very useful tool to achieve those
conditions. According to the Oxford Dictionary, competition refers to the
“negative effects caused by the presence of neighbors, usually by reducing the
availability of resources.” Plants generally need water, light, phosphorus, and
nitrogen to survive. If plants don’t have these resources or other plants are
using up most of those resources, then those plants will most likely die off.
One of the most important factors that control plant communities is competition
(Bond et al. 1997). Fire helps reduce
plant competition by eliminating the majority of the mid-story and understory
of the ecosystem, which creates an increase in light penetrating to the forest
floor. A more intense fire can cause a significant change of woody vegetation
on the ecosystem (Langevelde et al. 2003). In 1966, the use of prescribed
burning was eliminated at Tall Timbers Research Station in Tallahassee,
Florida. After the first fifteen years of fire exclusion, the changes in
wildlife abundance and vegetation were obvious. The amount of groundcover
decreased from 85% to 21%, while the canopy cover increased from 43% to 91%
(Engstrom et al. 1984). Fire can
indirectly reduce the potential of future mortality through decreasing
competitive and self-shading pressure (Zimmermann et al. 2010). Fire can also
decrease plant cover, biomass and density of grass layers (Drewa et al. 2001).
Fire is used in many savannas and grasslands to stimulate plant growth and
control woody plant densities (McPherson, 1995).
So why do we care about plant-plant interactions with fire?
Plants need resources such as water, light, phosphorus, and nitrogen to
survive. Fire can be used to remove plants and open up space on the ground.
This open space can then be colonized by plants of the same or different
species (Begon et al. 1990). Fire can stimulate many plant species creating
enhanced seed germination, flowering, and seedling recruitment (Bond et al.
1997). Fire can help certain ecosystems strive in many ways. Not only does fire
have the ability to increase herbivory, it can influence plant survival and
growth (Crawley, 1983). Many plant species depend on fire for reproduction, and
without the presence of fire many of these plants could become extinct. A few
of these plant species include longleaf pines, wiregrass, and giant sequoias. It
is very important to understand that many plant and animal species depend on
fire. If an ecosystem has less competition, then many fire dependent plants can
colonize the area. Fire has the ability to set back succession and promote
plant growth. Fire can be used in a variety of ways such as agriculture,
woodlands, and fields. Fire has also been used as a management tool to restore
native grasslands. Fire is a very useful tool that can be used to reduce plant
competition and boost plant growth. The species composition that emerges after
a fire can also benefit wildlife.
A study performed by Zimmermann et
al. showed that increased standing dead biomass was associated with increased
tuft mortality through the presence of fire (Figure 1). Fire reduced the
standing dead biomass and created a less competitive environment.
Figure 1.
Predicted tuft
mortality depending on neighbor abundance quantified by the living basal area
of neighbors (NALBA), standing dead biomass
(SDB) and fire.
My research on plant-plant
interactions with fire has given me a better understanding of how fire impacts
plants. I have concluded that these interactions can be attributed to three key
points. 1) Fire can remove debris and litter from the ground that allows for
plants to establish. 2) Fire intensity is crucial for determining desired species
composition. 3) Fire can help reduce competition by killing some plants and
allowing sunlight to reach the ground. Fire impacts the environment through the
changes in plant communities and reducing plant competition. Fire can have a
major impact on the environment in both positive and negative ways. The use of
fire has been used as a management tool for hundreds of years. I have
personally used prescribed fires to burn around 2,000 acres, and I have seen
how many ecosystems strive after the application of fire. However, wildfires
can create a problem for the environment. I have found through my research that
the changes in plant communities and competition are related to fire.
Literature Cited
Engstrom, R.T., R. L. Crawford and W.
W. Baker. 1984. Breeding bird populations in relation to changing forest
structure following fire exclusion: A 15-year study. Wilson Bull. 96: 437-450.
Van Langevelde,
Frank, et al. "Effects of fire and herbivory on the stability of savanna
ecosystems." Ecology 84.2 (2003): 337-350.
P.B. Drewa, K.M. Havstad Effects of fire, grazing, and the presence of shrubs on
Chihuahuan desert grasslands Journal of Arid Environments, 48 (2001), pp. 429–443
G.R. McPherson The role of fire in the desert grasslands M.P. McClaran, T.R. van
Devender (Eds.), The Desert Grassland, The University of Arizona Press, Tucson
(1995), pp. 130–151
Zimmermann J., Higgins S., Grimm V. Grass
mortality in semi-arid savanna: The role of fire, competition and self-shading.
Perspectives in Plant Ecology, Evolution and
Systematics. 12.1 (2010), pp. 1-8.
W.J. Bond Fire R. Cowling, D. Richardson, S. Pierce (Eds.), Vegetation of
Southern Africa, Cambridge University Press, Cambridge (1997), pp. 421–446
Begon, M., J. L.
Harper, and C. R. Townsend. "Ecology: Individuals." Populations
and (1990).
Crawley, Michael
J. Herbivory. The dynamics of animal--plant interactions. Blackwell
Scientific Publications, 1983.
