Joseph Back

“Prairies are a fire dependent ecosystem,” said Wisconsin Department of Natural Resources (DNR) Ecologist Dean Edlin when we asked him about a recent controlled burn evident in the western portion of the DNR owned Trenton Bluff Prairie State Natural Area, located along Highway 35 in southwestern Pierce County, just north of Hager City. “Without fire, you lose the prairies.” Edlin, a DNR ecologist for the eight county West Central Wisconsin District of which Pierce County is a member, said the recent controlled burn at the Trenton Bluff Prairie site had happened “approximately two weeks ago” when we reached him by telephone from his current home office over the past week. According to a description at the DNR website, the Trenton Bluff Prairie State Natural Area has at least five different grass species that are dominant and is contained within two different sections, an eastern one and a western one, with Great Plains species like plains muhly (Muhlenbergia cuspidata) and prairie larkspur (Delphinium carolinianum) among its chief residents. Additionally, there are several fern species in outcrop bluff crevices at Trenton Bluff, which rises 300 foot above the sandy river terrace below and puts both dolomite limestone and basal sandstone bedrock on display for passerby. But why are controlled burns held anyway? Wouldn’t fire destroy all this prairie plant diversity? Not necessarily.

“They’re held for many reasons,” Edlin said of the controlled burns by the Wisconsin DNR. At one time, fire was both a naturally occurring and planned phenomenon in Wisconsin from events like lightning strikes to the clearing of land by Native Americans, but with denser human settlement in the past 150 years from what previously held in the area, those naturally occurring wildfires have all but ceased—and that’s a bad thing if your own plant existence depends on just such fires to thrive.

“Trenton Bluff is one of the most diverse ecosystems in the area,” Edlin said, as he explained the rationale behind doing controlled burns periodically to rejuvenate the local grasslands. Without such fires, native eastern red cedar and invasive common buckthorn would take over the prairie hillside, producing the more common sight available along the Mississippi River Valley: bluff sides choked with tree growth, and little or no open spaces to enjoy in between. The fires are used to kill these eastern red cedar and common buckthorn trees, at least at the Trenton Bluff Prairie. But if prairie revitalization explains the ‘why?’, what of the ‘how?’ “That’s an involved process,” Edlin said when asked how the burns are carried out at places like Trenton Bluff. “First thing you do is you put fire breaks in.” By using leaf blowers to take away oak leaves and other fuel from a given boundary line, the potential of the fire to get out of control is greatly curtailed. In addition, participants in the controlled burn each have 60 pounds of water strapped to their back in case things start getting out of control, and other fire breaks are also used sometimes. For a steep hillside like that at Trenton Bluff, Edlin said, the next thing to do after putting in fire breaks is to start burning from the top down, then from the sides. Fire moves very quickly up a hillside, and with busy Highway 35 at the bottom, there’s an added reason to do things in a carefully staged pattern: smoke control. With cars passing by in two lanes and no guardrails on the roadsides, it’s not a good idea to have smoke drifting across the highway when the burn happens. But once the flames are out?

It makes for a great photo opportunity, and the green soon returns with the spring rains. When we drove past while on a recent paper run, the green shoots were already coming up through the devastation, from the ground upwards, showing if nothing else that you can’t keep a good prairie down—it just needs a bit of help to revitalize, now that the naturally occurring means are strictly controlled or stamped out by humans.

Photos contributed by Dean Edlin.