Plant-biotic Interactions with Fire

Plant-Biotic 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 the biotic factors in the environment through the change of plant consumption and reduced competition.

The presence of fire is very important for herbivory. The great Aldo Leopold went on to say, “fire may well be the single most important factor in determining what animal and vegetable life will thrive in many areas.” Fire can help improve both the nutritional and quantity of food available to herbivores. This increase in food abundance can aid in the increase of carrying capacities, growth rates, and reproduction for many herbivores (Mellars, 1976).  The use of fire and grazing plays a vital role in both the maintenance and establishment of savannas and grasslands (Milchunas et al. 1988).  When fire occurs in an ecosystem, herbivores typically select recently burned areas (Vinton et al. 1993). Fire isn’t just used for forests and grasslands, but for agriculture as well. The severity of herbivore grazing is correlated to the intensity of the fire. If there is a large amount of grazing on an area there tends to be less fuel load for the fire, which will cause a less severe impact on the ecosystem. On the other hand, 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).

So why do we care about the plant-biotic interactions with fire? Animals need food to survive. In North America, two very important influences on the function and structure of grasslands are herbivore grazing and fire (Vinton et al. 1993). Ecosystems that have experienced a fire generally have a robust amount of vegetation in the understory. This in increase in plant abundance in the understory allows for animals to eat them more easily. An increase in plant consumption by animals can allow for them to have a higher carrying capacity, increased growth rates, and more successful reproduction. The increased amount of beneficial plant material located on the forest floor can also be attributed to the lack of plant competition that is caused by fire. Herbivore numbers and fire are two ways that landowners can meet their desired objectives (Levich et al. 2009). Sometimes land managers need to cut down valuable trees in order to increase sunlight to the forest floor. This is one of the management tools that is used that most of the public does not like. Most hunters want to hunt around oak trees and they think that cutting some of those trees down is a stupid idea, but what about the other eight or nine months that those trees aren’t producing mast? 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. So if you were a deer, would you rather have acorns to eat three or four months out of the year or would you rather have a robust amount of grasses, forbs, and seedlings to eat? Fire doesn’t just increase the amount of forage, it also provides specific habitat that some animals need to survive.

           

Animals need food, water, cover, and shelter to help then strive in an ecosystem. The presence of fire has the ability to create early successional habitat that some species desire. There are many species that depend on fire. A few of these species are white-tailed deer, wild turkey, northern bobwhite, red-cockaded woodpecker, and many other birds (Brennan et al. 1998). The Northern Bobwhite Quail is a perfect example of a species that depends on fire. Leopold stated that the northern bobwhite “was undoubtedly evolved in an environment that was always subject to occasional burning” Quail are also known as the “fire bird” and need fire to help create the necessary habitat that they need. Quail require fire every one to two years to help restore their habitat (Graves, personal communication).

It is very important to understand that many wildlife species need fire to be successful. The use of fire has decreased over the years, and as a result, so have the wildlife species that depend on them (Table 1). It is because of the lack of fire that many species are in decline, threatened, and even endangered (Table 1). The following table was produced from the findings that Brennan et al. 1998 found in their study of fire-dependent wildlife species without the presence of fire. 

Table 1. Terrestrial vertebrates from southern pine forests and savannas that have affinities for habitats maintained by frequent fire.

                            Species                                                   Current Status

Gopher tortoise	Threatened
Greater prairie-chicken	Endangered
Northern bobwhite	Declining
Red-cockaded woodpecker	Endangered
Bachman’s sparrow	Declining
Sherman’s fox squirrel	Declining
Eastern indigo snake	Threatened
Florida grasshopper sparrow	Endangered

 “Endangered and threatened status according to U.S. Fish and Wildlife Service listed vertebrate species index, January 31, 1998. Declining status determined from various sources.

My research on plant-biotic interactions with fire has given me a better understanding of how fire impacts plants and animals. I have concluded that these interactions can be attributed to three key points. 1) Many ecosystems and wildlife species depend on fire. 2) The use of fire has decreased, and as a result, many fire-dependent species are struggling. 3) Herbivores can influence the intensity of the fire by reducing the fuel load.

Fire impacts the environment through the changes in plant consumption and reduced 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 consumption and competition are related to fire.

Literature Cited

Mellars, Paul. "Fire ecology, animal populations and man: a study of some ecological relationships in prehistory." Proceedings of the Prehistoric Society. Vol. 42. Cambridge University Press, 1976.

Milchunas, D. G. , O. E. Sala , and W. K. Lauenroth . 1988. A generalized model of the effects of grazing by large herbivores on grassland community structure. Am. Nat. 132:87–106.

Vinton, M. A. , D. C. Hartnett , E. J. Finck , and J. M. Briggs . 1993. Interactive effects of fire, bison (Bison bison) grazing and plant community composition in tallgrass prairie. Am. Midl. Nat. 129:10–18.

Van Langevelde, Frank, et al. "Effects of fire and herbivory on the stability of savanna ecosystems." Ecology 84.2 (2003): 337-350.

Levick, Shaun R., et al. "The relative influence of fire and herbivory on savanna three-dimensional vegetation structure." Biological Conservation 142.8 (2009): 1693-1700.

Brennan, L.A.; Engstrom, R.T.; Palmer, W.E. 1998. Whither wildlife without fire?. Transactions of the 63rd North American Wildlife and Natural Resources conference; 1998 March 20-25; Orlando, FL. Washington, DC: Wildlife Management Institute: 402-414.

Graves, Chris. Personal Communication. 2016.

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.