In 1938, one of the last high-quality remnants of the nearly extinct Big Grove—an old-growth forest in Central Illinois with trees taller than church towers—was in danger of being logged. Members of the family that owned the land, the Brownfields, wanted to harvest the timber and sell the valuable property. But there was one holdout who argued for preserving the woods: an heir to the estate named Lelah Brownfield.
That year, Lelah wrote to University of Illinois zoology Professor Victor Shelford to let him know that her family was making plans to log the woods. Shelford, a pioneer in the field of ecology, was already an advocate for preserving the Brownfield site.
For more than two decades, Shelford had taken students into Brownfield Woods and another ancient forest patch nearby, Trelease Woods. At roughly sixty acres each and less than six miles from the campus, Brownfield and Trelease were ideal sites for ecological study. They were some of the last remnants of a vast deciduous woodland that once encompassed more than six thousand acres in Central Illinois. The university had purchased Trelease Woods in 1917-18, but in 1938, the Brownfield site was unprotected.
For another year, the Brownfield family and the university debated the value of the land. In January 1939, the university’s Committee on Natural Areas and Uncultivated Lands, which Shelford chaired, sent a letter to university President A.C. Willard urging him to purchase Brownfield Woods for over $10,000, a sum significantly higher than its appraised value. The letter described the woods as “an area of irreplaceable forest of great value for instruction and research in biology and soil science.” The university finally agreed, securing the site for future generations of research and learning.
If a tree falls
From their workshop near the woods, University of Illinois Urbana-Champaign natural areas coordinator Jamie Ellis and natural areas research specialist Nathan Hudson, both of the Illinois Natural History Survey, sometimes hear massive tree branches or whole trees crashing to earth during a rain or windstorm. Some of the trees get snagged on their way down and, unless they pose a risk to traffic at the borders of the property, remain in their half-fallen condition until another storm brings them down. The trees are left where they lie.
“What falls in the woods stays in the woods,” Ellis likes to say.
Brownfield Woods today feels like an anachronism, an island of towering trees in a sea of corn, soybeans, and houses. The woods are not open to the public, but professors regularly bring their classes to see and study the unique ecology of the site. While several giant trees have fallen in the eight-plus decades since the purchase of Brownfield Woods, dozens of the ancient “monarchs” remain. Over the decades, tens of thousands of Illinois students have walked among the giants of Brownfield Woods. This unparalleled outdoor laboratory is home to lessons in biology, entomology, forestry, soil science, and plant biology.
Leaving the fallen trees in place has yielded a treasure trove of opportunities for study as the decaying trees contribute to the natural ecology and evolution of the woods. Brownfield Woods used to be dominated by fire-adapted hardwood species like oaks and hickory, but maple trees now make up 65 percent of the woods. Ellis muses that reintroducing fire to Brownfield Woods could help maintain its historic character while interrupting the ascent of the maples. However, the university has traditionally left the Brownfield and Trelease Woods alone, allowing natural processes (other than fire) to occur within their boundaries without interference.
On a recent walk in Brownfield Woods, Ellis, Hudson, and Illinois entomology Professor Brian Allan, the current chair of the now named Committee on Natural Areas, pointed to a carpet of maple seedlings on the forest floor. Unlike young oaks, which need ample sunlight, young maples can flourish in sunny and shady areas as well as shade out other species. The number of oak trees has dwindled in Brownfield because deer, squirrels, and mice eat most of the acorns on the forest floor. All these circumstances have led to this gradual change in forest composition.
The Nature of Change
Several other factors have changed the nature of Brownfield and Trelease Woods. Tree deaths, including those caused by Dutch elm disease in the 1950s, increased the light in which sugar maples flourished while rarer species declined. More recently, the emerald ash borer has killed most of the ash trees.
Browsing deer also damage the emerging life on the forest floor, eating wildflowers and young oak trees. Plant biology professors James Dalling and Carol Augspurger see the large numbers of white-tailed deer as a primary threat to the quality of the woods and suggest deer management, including deer-proof fencing.
The forest edges are subject to tree-toppling winds and invasive plants. Ellis and Hudson combat the invasives at the forest’s edges, cutting back the large stems of bush honeysuckle, spraying the stumps with an herbicide in fall and winter when other plants are dormant, and uprooting smaller plants.
A less natural, but no less challenging, threat to Brownfield Woods and Trelease Woods comes from land the university doesn’t own. Property owners nearby sometimes put their holdings up for sale. The prospect of development just at their edges would likely degrade these ancient woodlands and, unless substantial barriers are erected around them, open them up to trespassers.
Allan and the other Illinois scientists actively teaching and researching in the woods say they would like to see large prairie or woodland buffers around Brownfield and Trelease so that the woods can continue sharing their riches with Illinois faculty, staff, and students.
“There is enough open land to the west of Brownfield Woods to bring back a thriving prairie grassland and even build an education research center there,” Allan said. That property is currently used to grow corn and soybeans.
“Most universities and other top-tier research institutions have a field station where faculty and students do ecological research,” Dalling said. “We don’t have one. We have Trelease Woods, and about a mile away we have Brownfield Woods. These are some of the only high-value protected forest areas that are under the control of the university within a short travel time from campus.”
A Century of Science
More than a hundred years after Shelford first saw the academic promise of Brownfield Woods, numerous ecological studies have been conducted and published. These include investigations of forest-dwelling bats, birds, foxes, mollusks, squirrels, and invertebrates such as beetles, centipedes, millipedes, and mosquitoes. The proximity of the woods to restored prairie also allows studies of the animals, plants, and fungi that live at the forest edges and rely on both habitats for their survival. For example, many species of wild bees nest and overwinter in forests but feed on prairie flowers.
Perhaps the greatest gift the woods offer, however, is to the ecological education of university students, said Augspurger, who has probably brought more students to the woods than any other professor in recent decades.
Visits to the forest laboratories “often awaken or reawaken younger students to the beauty and complexity of our native, old-growth forests,” Augspurger said. “Many have not been in nature often or not recently and realize how important it is to visit and protect these woods. They become comfortable in this new habitat and say how much they love being there. They also learn introductory scientific methods of how to test hypotheses explaining their observations, analyze data, write scientific manuscripts, and give oral presentations about their research.”
The more advanced students come up with their own testable hypotheses, gather data in the woods, analyze their findings and build their confidence in the science of ecology, Augspurger said.
“The fact that Brownfield Woods still exists and functions as a vibrant forest community island is a tribute to the university and the human community that has allowed it to remain,” she said.
“Brownfield Woods represents one of the best examples of a remnant prairie grove stand in east-central Illinois,” said Steve Buck, the former natural areas coordinator. “The soils, trees, nonwoody flora, insects, fungi, and so on are a unique collection that developed over centuries in that location. That in itself is a remarkable feat.”
Meet the scientists
Professor Victor Shelford
In 1915, Shelford was elected the first president of the Ecological Society of America. An activist and a scientist, Shelford formed the Committee for the Preservation of Natural Conditions for Ecological Study two years later. In the 1940s, Shelford and his colleagues split from the Society to focus on preservation and “direct action.” The group he formed ultimately became the Nature Conservancy, which continues to play a critical role in preserving and fighting the effects of climate change.
Professor Brian Allan, Entomology
Studies of forests worldwide find that insect diversity is greatest in those with “relict” trees—dead or fallen trees that are allowed to rot in place. Allan points out that Brownfield provides a hospitable environment for fungi, microbes, and insects that feast on rotting wood and the predators that feed on them. Because the forest provides so many types of habitat, the insect life there is also quite diverse. “You have the decomposers in the woody debris,” he said. “And then you have arboreal species distinct from your ground-level insects, which are distinct from those that live in the soil.”
Professor Emerita Carol Augspurger, Plant Biology
Augspurger has tracked the abundance of herbaceous plants on the forest floor of Trelease Woods and the timing of their emergence, flowering, and senescence over thirty-plus years. She also records changes in the community of woody species. Her study of herbaceous woodland plants found significant shifts in the timing of flowering that correspond to climate-related temperature shifts. These changes may disrupt the life cycle of pollinating insects that rely on the emergence of early flowering plants as a primary food source in the spring.
Steve Buck, Former Natural Areas Coordinator
Buck recorded every treefall in these parcels over a period of twenty-five years, starting in 1994. He wrote “obituaries” for the fallen trees, detailing the date they fell, their diameter, and notes about their condition and the probable cause of their fall. He and his team also tagged the fallen trees with metal disks numbered to correspond to locations on a grid established in Brownfield and Trelease woods in 1939. Ellis and Hudson continue the tradition of tagging and recording the treefalls.
Professor James Dalling, Plant Biology
Dalling turned to Brownfield and Trelease Woods to learn how deciduous trees contribute to a forest’s carbon-storage capacity. Buck’s earlier work in recording every treefall informed Dalling’s research. Dalling and his colleagues found that fallen oaks rot much more slowly than other trees in the forest, storing carbon for well over a century. Sugar maples and buckeyes disappear completely within decades.
