The big trees lean this way and that like preadolescents at a middle school dance who want to be seen together but aren’t quite ready to touch. The small stand – little over half a dozen oaks – is defined as much by the space around the trees as by the substantial bulk of their individual trunks. It is a classic example of an ecosystem known as oak savanna – or, I must hasten to add, what is left of one.
An undisturbed oak savanna is primarily grassland dotted with oaks. This remarkably diverse ecosystem once stretched in a wide belt from Minnesota to the Gulf of Mexico, creating a transition between the tallgrass prairie to the west and the dense broadleaf forest to the east. Unfortunately, of the 50 million acres that existed prior to European settlement little remains, almost none of it undisturbed.
This particular example stands facing Forest Home Avenue on the corner of a 2.5-acre parcel housing the historic Stahl-Conrad Homestead in Hales Corners. The property contains the eponymous homestead, consisting of a farmhouse and two outbuildings dating from around 1870. It is lovingly maintained by volunteers, members of the historical society dedicated to its preservation.
The ground beneath the oaks has recently burned. This was no accident. One of the ways a savanna has always been maintained is with fire. Prior to colonial settlement the indigenous tribes set the fires that kept the grasslands open, providing rich habitat for a wide variety of plants and animals. Fire-resistant oaks are among the few trees that survive these conditions. Today the primary purpose of burning is to remove invasive species and allow native grasses and wildflowers to spring up from the ashes.
I had come to the homestead to learn about oak savanna from two of the area’s leading experts. Randy Powers, a restoration ecologist and founder of Prairie Futures Seed Company, gave a slide lecture, after which arborist Jim Uhrinak led the group on a tour. The first stop on the tour was a back yard near the homestead. There we marveled at oaks with trunks up to five feet in diameter. “These trees can live hundreds of years,” Uhrinak told us. “They were here before the State of Wisconsin.”
He then pointed out a Norway maple and a row of pines crowding the oaks. He explained that these are trees that wouldn’t have grown in the historic savanna. They had been planted more recently, either by a farmer who settled here or a homeowner after the subdivision was developed. The soil too has changed. Once a rich loam would have supported the native tall grasses and a plethora of wildflowers we had seen in the slide program. Now the compacted ground held only a typical backyard lawn.
The second stop on the tour was the Indian Community School in Franklin. Our caravan of cars waited while interim principal Jason Dropik opened the gate for us. Our first treat, as we drove through, was the sight of the school’s resident pair of Sandhill cranes tending to their lanky chick. We parked around the back of the complex of school buildings and walked along a newly mulched path into what appeared more like a large woodland than a savanna.
While no grasses grew around the trees it quickly became apparent that we were not in a commonplace woodlot. There was little ground cover and an open understory. Here and there through younger, straighter trees we could see the massive, spreading forms of ancient oaks. In a typical forest setting, Uhrinak explained, tree trunks grow straight up to raise their crowns towards the sun at the canopy. The oaks in a grassy savanna, on the other hand, have room to spread their limbs.
Someone pointed to a particularly gargantuan oak nearby and we all stared in wonder at a limb thicker than your average tree extending horizontally for what must have been at least thirty feet. Farther along another great oak leaning out over the surface of a pond had a horizontal reach longer than it was tall.
The ground was strewn with shredded wood. Until recently the entire woodlot had been overgrown with invasive buckthorn and other small, weedy trees. In order to restore it to a more natural savanna-like appearance, a contractor hired by the school had brought in machinery to essentially mow down the forest around the desirable trees.
The advance of forestry clearing technology has made this practice more common, according to Uhrinak, but if the school is really committed to restoration of natural ecosystems, he said, a much more hands-on maintenance regimen is required. Buckthorn, for instance, will re-sprout in even greater abundance if not treated with an herbicide. However, great care is needed to avoid killing native flora along with invasive species.
Principal Dropik assured us that respect for the earth and natural ecology is not only a cultural tradition but also among the school’s educational goals. All members of the community are taught to be responsible stewards of the environment. “We want our students to experience nature and to feel a spiritual connection with the Earth and its creatures,” he said.
The Indian Community School is situated on 178 acres, about half of which has been retained as natural areas. However, Dropik added, until they undertake an environmental inventory of the property, planned to begin this spring and to last three years, no one actually knows what species are present. Much of it is in hard to access wetlands.
Recent rainfall had saturated much more of the area than usual and our group skirted numerous ephemeral ponds and muddy swales. The variety of oaks, including black, white and burr oak, were not the only desirable species in the forest. Uhrinak admired a particularly large stand of aspens, which, I was surprised to learn, has the largest natural range of any tree species in North America. Here and there flowering trees added splashes of color to the newly budding woodland.
The once vast oak savannas have nearly vanished because of their appeal and utility. Since these factors haven’t diminished along with the land, it will take an enormous effort of will to appreciate the little that remains for its inherent worth and to protect it from further decline. Fortunately, there are places like the Stahl-Conrad Homestead and the Indian Community School that are making this effort.