The Essence of Illinois

Photos courtesy of the author.

While walking through an area in southern Illinois that had undergone a prescribed fire last year, I was struck at how the elements before me, individually and collectively, represented Illinois.

In a sunny clearing nearby were little bluestem grasses and other flowers reminiscent of prairies. At my feet numerous white oak seedlings were sprouting straight and tall, in dappled shade from mature white oaks that likely spawned them. White-tailed deer tracks crossed the opening in front of me. Illinois is nicknamed the Prairie State. The white oak is the state tree. The whitetail is the state mammal. These three elements would not have existed here if it were not for the fires that preceded them.

Historical Presence of Fire

Several lines of evidence demonstrate the recurrence of fires in our past. Telltale layers of charcoal have been identified in sediments going back thousands of years. Burn scars recorded on trees rings show frequent fire over the last few centuries. Journals of pioneers and early settlers depict Native Americans’ use of fire, and historical records show continued presence of fire on the landscape even after Euro-American contact and settlement. We inherited a landscape full of vegetation adapted to and frequently thriving because of fire.

In land surveys in the early 1800s, in what is now the Shawnee National Forest (Forest) in southern Illinois, most witness trees used to mark section corners were white oaks. Also, surveyors noted prairies and savannas in areas that today are densely forested. Researchers estimate the Forest had 3 to15 times fewer trees per acre then than it does now, although the total amount of wood growing on the landscape is nearly the same. Without periodic fires thinning some small trees and shrubs, this woody vegetation grew ever denser.

Ecosystems Evolved to this Disturbance Regime

Frequent fire gives oak trees a competitive advantage because they have thick bark, strong root systems, the ability to heal burn wounds and sprout repeatedly, and leaf chemistry and form that encourages fire. Many tree species can resprout once or twice, but multiple fires tend to select for oaks and other more fire tolerant species and thin out the understory. Plus, each burn consumes a bit more litter than the last, which allows a progressive change in the litter layers and understory. So, multiple prescribed fire treatments are needed to achieve the desired habitat structure.

The deep shade provided by most modern forest stands limits what tree seedlings and understory plants will grow there. In turn, this affects the type and abundance of insects, including pollinators, and the animals that prey on them.

“Native oaks are the most valuable tree for wildlife in 84 percent of the counties in the United States in which they occur,” says entomologist Doug Tallamy. According to Tallamy, oaks are the host plants for more than 1,000 kinds of moth and butterfly caterpillars, which are the most important protein that virtually all parent songbirds need to successfully raise their offspring. By contrast, native birch trees host just over 400 caterpillar species, while elms host about 200.

While we certainly had closed canopy (very shady) forests in bygone decades, it was probably proportionally much less than today. Currently, trees that are less adapted to fire have invaded nearly all landscapes. Fire, by thinning out undergrowth, selecting for certain species, and reducing litter depth, changes the structure and composition of the plant community. This affect is quite variable. Low-lying areas may burn lightly, if at all, whereas upper slopes, which are typically better drained and more exposed to sun and wind, may burn more intensely. The south side of slopes burn hotter than the north sides. Prairies, savannas, and areas with grassy vegetation burn more intensely and quickly than leaf litter, which itself is quite variable between species. This interplay of topography, existing vegetation, and the variable disturbance agent of fire can create many different outcomes to the natural environment. Therefore, fire provides enhanced biodiversity, especially when applied at the landscape scale.

The Shawnee National Forest Land and Resource Management Plan reflects this ecology. Among its natural resource goals, it emphasizes management for biodiversity, including diversity of species and natural communities including barrens, glades, open lands and oak-dominated forests within a matrix of upland and bottomland habitats. Further, it directs the agency to apply prescribed fire to achieve these ends and encourages its use at landscape scales, and with partners.

Prescribed Fire Treatments

As recognition of the “fire deficit” has been growing, the Shawnee has been increasing its use of prescribed fire. These are planned events, led by experienced and qualified individuals, where fire is applied to restore this critical disturbance agent to a landscape that was adapted to it. Prescribed fire plans consider the objectives of the project and the context of the area to be burned (vegetation, natural and cultural resources; structures, utilities, roads and public use in the area; and above all safety for fire personnel and the public). Based on these elements, the plan specifies the organization and equipment needed, notifications, contingency planning, smoke management, and the weather and environmental conditions needed to achieve all these goals. Because conditions must be just right, it isn’t surprising that the ones we cannot control – weather and smoke dispersal conditions – are the biggest limiting factors. The Shawnee typically conducts about 25 to 30 prescribed fire per year, primarily in the fall and early spring.

Partnerships

The Shawnee National Forest hasn’t been alone in its endeavors. Numerous state and local agencies, non-profit organizations, and private landowners have also been increasing their use of prescribed fire. The Illinois Prescribed Fire Council, a coalition of like-minded organizations with a mission to promote the safe and continued use of prescribed fire across the state, has been collecting such data for several years with the results available on their website.

Partnerships are key to the success of these programs. Some of these partners are landowners, such as the Illinois Department of Natural Resources or private landowners, that the Forest works with to plan and implement cross-boundary burns. Other partners provide staff, funding, research support, volunteers, or other things to help plan, implement, or monitor the results of projects.

Aerial Ignition

Managers usually use handheld devices called drip torches to ignite certain parts of the burn area in a planned sequence, using fire’s natural predilection for spreading faster up hills and with the wind to create the desired fire behavior – one that achieves the desired burn intensity and duration, but is still controllable. This requires knowledge and experience in fire behavior.

One way the Forest has increased its burn program is by using aerial ignition. This is a technique where small fires are started within by ignition devices dropped from aircraft. The advantage of this is that the burn can be done with fewer people, or those people can complete a burn much faster. This expands the benefits of the burn to a larger area, allows for completing burns on days when there may be fewer personnel available, and helps in reducing the duration of smoke impacts. This technique also allows fire to build upon itself, creating more intense burning conditions and higher smoke lift – crucial for minimizing impacts to nearby residences and communities.

Fire Combined with Other Tools

Often, fire alone is not enough to achieve the desired habitat structure or composition. While fire may reduce some invasive plants, others are unaffected or even encouraged by it. In these cases, prescribed fire treatments are best combined with other treatments, such as hand pulling or herbicide use.

Many of our forests have gone long enough without fire or other disturbance, that prescribed fire alone cannot provide the light needed for oaks to regenerate or grow into overstory trees. Thinning or timber harvests can be used in combination with prescribed fire to provide the optimum light levels, species composition and stand structure.

Combining fire with other treatments has been repeatedly shown to produce better results for some species. For instance, an average of one pair of red-headed woodpeckers, which are an Illinois species of conservation concern, are occurring on every 26 acres of thinned pine stands post-harvest and post-burn. Red-headed woodpeckers forage on the ground and respond positively to prescribed fire.

A Vision for the Future

While fire is known to be a crucial element for restoring and managing most natural communities in Illinois, experts acknowledge not nearly enough is occurring. The Illinois Prescribed Fire Council’s Fire Needs Assessment estimates more than 200,000 acres should be burned annually in the state just to maintain habitats on existing conservation lands.

Agencies, non-profit organizations, and individual landowners are working to improve this by informing the public about the need, by training landowners, fire departments, and others to safely manage properties with fire, and by analyzing and sharing the results of their work.

Above all, they are continuing to use fire to maintain natural environments and keep the legacy of prescribed fire handed down from earlier generations.

The next time you see a smoke column rising above the prairies, savannas, and forests of Illinois, it may be someone working to restore our state’s natural heritage.

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Scott Crist is the Fire Management Officer for the Shawnee National Forest. He has worked all over the country and for three different federal agencies, but for 20 years has primarily been responsible for planning and implementing prescribed fires and planning for and responding to wildfires in southern Illinois. He has specialized in studying fire behavior and fire ecology, developing future fire professionals, and working with partners to restore fire-adapted landscapes across ownership boundaries.