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Fire in the oaks.

In the Midwest, the Smokey Bear mentality is grudgingly giving way to a system of planned burns that has woodland managers all fired up.

On a breezy morning back in 1989, four men approached a three-acre oak/hickory grove at Iowa's Indian Creek Nature Center. They were about to reenact ecological history.

On signal, Lumir Newmeister and Ralph Ahrens stuck burning matches into dry leaves on the grove's downhill edge. Within seconds flames were slowly licking their way uphill, consuming more than a century's accumulation of duff. An hour later, Tom Lackner and George Pederson easily snuffed out the weak flames along a trail that functioned as a fireline.

Years ago, forest ecologists in western coniferous woodlands learned that deliberately setting fires reduced accumulated litter, invigorated fire-dependent plants, and improved wildlife habitat. Prescribed burns have become common out West, but it has taken midwestern forest managers longer to learn that fire is a valuable tool for maintaining the diversity of oak/hickory forests. Planned burns are now being conducted in Indiana, Illinois, Missouri, Wisconsin, and Iowa, and results are impressive on most areas.

Many historians and ecologists now believe the Midwest's oak/hickory forest evolved under frequent fire and remains fire-dependent. Long-term fire protection--the put-'em-all-out philosophy--slowly degrades the forest community.

Experts seem to agree that today's forest is dramatically different from what existed on the same sites 200 years ago.

"I did extensive reading of the records of early land surveyors who walked over much of the Midwest in the early to mid-1800s," said Ethan Perkins, former land steward for the Iowa Chapter of The Nature Conservancy. "In most cases they were able to cover much more ground in a day than would be possible today with all the brush and vines that make walking in the woods a slow chore. They called it the begetation forest, but I believe they were describing savanna."

Drawings and paintings from the presettlement era also depict savanna, an ecological term that describes a grassland habitat that includes several scattered large trees per acre. In the Midwest savanna, prairie grasses, sedges, and wildflowers thrived under the ragged crowns of such fire-resistant trees as white and bur oak and shagbark hickory. It was an open and attractive ecosystem that supported elk, bison, deer, and a thriving Native American culture.

Current ecological thinking holds that fires were once set deliberately by Native Americans, in both grasslands and savannas. Flames roared across the land, killing small trees but stimulating grasses and prairie forbs. The frequency of burning is not known, and certainly varied considerably from site to site, but it's reasonable to believe that nearly every acre in the Midwest experienced at least an occasional fire. Oaks evolved under this fire regime and are amazingly resistant to flames. Even young oaks are able to survive fires that quickly kill most other woody species.

In a classic oak savanna, periodic fires invigorated the grasses hugging the ground and killed off tree and shrub species that might compete with resident oaks.

Unfortunately, settlement doomed the savanna. Early farmers valued their woods as a source of fuel, fence posts, and building materials. Fire was anathema and was suppressed. At the same time, early farmers quickly converted almost all the Midwest's tallgrass prairie to fields of corn, barley, wheat, and other crops. Like the bison and Native American, the prairie grass that had once carried fire from one patch of woods to another was gone.

Over the years, oak savanna woodlots gradually changed as woody understory plants were able to colonize. Without fire, shrubs thrived, and today many former savannas are a tangle of undergrowth beneath tall trees. Walking through the dense vines, bushes, and thorns of today's understory is a midsummer nightmare.

Other changes occurred. From Europe and Asia came shade-tolerant plants such as buckthorn and barberry. They moved right into the woodlots and created such a dense shade that newly sprouted oaks died in the darkness. A typical modern midwestern deciduous woods has a canopy of veteran oaks, a dense understory of various shrub and forb species from throughout the world, and hardly a single young oak. Come May, you're lucky to find even an anemic wildflower.

The future of oaks on these unburned woodlands is bleak. As age fells the old veterans, they are replaced by tree species that never existed on the site before.

Oaks aren't the only species to fade under fire suppression. Not long ago forest managers believed that native woodland wildflowers--anemones, bloodroot, hepatica, and others--needed deep shade and careful protection to thrive. However, studies at the Morton Arboretum, located just west of Chicago, and other areas have shown that fire protection brings a gradual reduction in wildflower density and health.

Much of the Arboretum study has been under the direction of Dr. Jerry Wilhelm.

"Since 1922, when the Morton Arboretum was founded, we have lost about 140 of the 300 species of plants that live in oak forests. That loss has been because of fire suppression," he said.

According to Wilhelm, the Arboretum's staff mowed the woods for many years to keep out the undergrowth, but protection from all disturbances began in the early 1970s. "Mowing is a poor substitute for burning, but it did keep the shrub layer down and let more light reach the forest floor. Probably most of our species loss has been since 1970," he said.

In recent years, the Arboretum has held a series of prescribed burns and is carefully monitoring results.

Ironically, many managers of woodland preserves have carefully protected their land from disturbance, believing that this would perpetuate a healthy forest community. Unfortunately, they are inadvertently damaging the habitat.

A standard method of managing midwestern natural areas is to mow firelines between forests and grasslands and manage them quite differently. Prescribed burns are held in the grassland every few years to stimulate prairie plants, while fire is carefully excluded from the woods.

There is no doubt that prairie plants respond well to fire. In fact, without occasional burns most prairies succeed into brushy patches of mulberry trees and multiflora rose. With burning, prairie plants are even able to outcompete exotic brome grass.

The problem has not been with burning prairies. It's been the creation of artificial firelines on the landscape and the exclusion of fires from the woods. A permanent fireline between the woods and grass creates an artificial situation. In presettlement days wooded areas blended into prairies with transition areas of varying width. There are few places where a blended transition exists today. The norm is the stark contrast of grass on one side of a firebreak and dense woods on the other. That was the situation at the Indian Creek Nature Center.

Back in 1988, the Center's board of directors enacted a woods-management plan that differed greatly from its previous one. Its goals were to increase the abundance and health of woodland wildflowers, erase artificial lines between grasslands and woodlands, remove much of the exotic shrub layer present in the woods, and enhance survival of young white oaks. If successful, the new woods management would give visitors a chance to see what the presettlement Iowa savanna looked like, while enhancing plant diversity.

Forest Ecologist Victoria Nuzzo of Rockford, Illinois, inspected the area and suggested a woodland burn that would be conducted as soon as the ground dried in the spring but before woodland wildflowers broke dormancy. In Iowa that occurs around the first of April. She suggested we burn each year and closely observe vegetation changes. Once exotic understory plants were declining and young oaks increasing, we'd decrease the burn frequency.

A woods burn was a new endeavor to the organization, and it evoked a lively board discussion and many questions. Could we control the fire? Might it move through our property and endanger the homes or woods of neighbors? Would we kill too many young trees? Would the public object?

Were it not for the ecological understanding and encouragement of Nuzzo and Peter Van der Linden of the Morton Arboretum, it is unlikely that the board would have approved the burn.

Based on its experience with grass fires, the Nature Center's staff felt it could handle the fire, and the first burn was conducted on April 3, 1989. Subsequent burns on the same site were held in early April of 1990 and 1991.

The burn crew selects a dry day with a light breeze blowing from the prairie up into the woods. The fire is started in the grassland and allowed to roar uphill toward the trees, jump the old trail/fireline, and burn through the oaks.

Burning a deciduous woods is much different from burning a grassland. Prairie fires tend to roar along with intense heat. Woods burns sputter along, producing more smoke than heat. The burn is generally blotchy, with large patches of untouched areas within the general burn area. Leaves beneath fire-resistant oaks burn well--they are crinkled and rest high enough over the soil surface to stay dry. Leaves from locust, maple, and elm lay flat, stay damp, and don't burn.

When the flames of the Nature Center's first fire reached the trail fireline, they completely burned themselves out. The workers stared at the black ash and wondered what impact there would be. In contrast to the prairie, the cool fire did not seem to impact anything very much, and we predicted a May and June landscape that looked like it had in previous unburned years.

How wrong we were! Within weeks ephemeral wildflowers shot up with vigor. Mayapples bloomed earlier on the burn than in any other nearby area, and Dutchman's breeches and bloodroot were unquestionably healthy. Summer revealed even more striking differences. Prickly ash, black locust, barberry, buckthorn, and maples in the shrub layer were killed, while young oaks appeared unaffected.

After three years of burning, the woods has opened considerably, and the site is obviously returning to savanna.

The Nature Center has been pleased by an increase in prairie plants appearing, as if by magic, in the woods. Results were exactly the same as those of other woodland managers who have tried burns.

After conducting a woods burn on the Shawnee National Forest in Illinois, Lawrence Stretch reported in the journal of the Society for Ecological Restoration that "the recovery of species that were not known to be present or had not flowered in recent years was spectacular, and many natural-areas enthusiasts came to see the results. The question we were asking was, where had they been?"

According to Jock Ingels, an Illinois forest and prairie restoration expert and nurseryman, many sites harbor a huge amount of plant material that can't be seen but is present as seeds buried in the soil. Many of these seeds may remain viable for a century or more. Ecologists call them the "seed bank." Create the right conditions, and they will quickly and miraculously appear.

In many midwest forests, fire creates just those conditions needed to stimulate the long-dormant seeds.

Jerry Wilhelm of the Morton Arboretum has found that long-term fire suppression can cause severe erosion in dense woods, and soil moving down-slope removes the buried seeds of the seed bank. As the tree density increases because of fire suppression--from 10 to 40 oaks per acre in savanna to 200 or more oaks, maples, and basswoods per acre in the protected woods--hardly any light reaches the soil. Few plants hug the ground, and erosion takes place. Restoring eroded sites may require both burning and the reintroduction of native species.

At the Indian Creek Nature Center, fire's impact on young white oaks has been dramatic. Before burning, acorns sprouted but baby oaks died from severe competition and dense shade. Following the burns, scattered healthy oak seedlings are present, surrounded by young grass and sedges--an indication that savanna conditions are being restored.

After three years of prescribed burns at the Center, it appears that all management goals will be met. And there has been an unexpected side benefit. With the creation of savanna, visibility through the woods has increased. Hikers enjoy a panorama of the Cedar River Valley that was previously hidden by dense underbrush.

Is woods burning as viable a forest-management practice in the Midwest as it is in the coniferous woods out West?

That's a question for forest managers and ecologists to answer, and it will take time. However, burning appears to greatly enhance diversity of native plants and wildlife in midwestern woodlands, and it will probably become a more common management technique in the years to come.

Rich Patterson is director of the Indian Creek Nature Center near Cedar Rapids, Iowa, and a freelance writer.
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Title Annotation:planned burning of coniferous forests
Author:Patterson, Rich
Publication:American Forests
Date:Nov 1, 1992
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