Frontiers Summer 1999 ~ College of Biological Sciences

Resources for

Burning questions

U researchers crack nature's riddles in the outdoor lab of Itasca.

By Jennifer Amie

In 1998 helicopters hovered over the treetops of Itasca State Park, poised to drop an incendiary cargo on the land below. Ping-pong-sized balls of combustible chemicals rained on the forest, igniting Minnesota's largest controlled burn and sparking a fire that had been a long time smoldering. Since the late 1950s, ecology professor John Tester has known that forests and prairies are reborn in the crucible of fire. But it's taken four decades for that idea to become accepted forest-management practice.

Tester's roots in the Itasca region date to 1949 and 1950, when he worked at the University's Lake Itasca Forestry and Biological Station as an undergraduate. His doctoral thesis, completed in 1960, examined prairies west of the park, where he studied the effects of burning, grazing, and mowing as management tools.

At the time, his research on the beneficial effects of fire was considered radical. "In the late '50s and '60s, it was seen as pretty extreme," says Tester. "Using fire was not accepted as a management practice, but from a research standpoint we knew that fire was important. We felt that it should be implemented, but there was so much fear of fire that it couldn't be pulled off."

In forests, says Tester, fire is particularly important for the growth of pine trees. "Stands of white and red pine, which are the hallmark of Itasca State Park, all originated from fires in the past," he says. "The fires remove the litter on the ground and open up the canopy. If the pine seeds fall on a litter layer, they may germinate--but the litter layer is so thick that by the time the seed has sent its root down, the energy in the seed is exhausted. The root still hasn't hit the soil, so it can't get moisture and it can't get nutrients. By burning off the litter, you create bare soil--now the seed can get its roots into the soil and grow."

When pine seedlings do sprout, they face another danger--hungry deer. "Deer just love white pine seedlings," says Tester. At Itasca, where deer hunting was long prohibited, the lack of fire and abundance of deer conspired to suppress new pine growth for many years.

In the mid-1990s Minnesota Department of Natural Resources officials asked Tester to draft a management plan for the natural resources of Itasca State Park. Tester's concise, workable plan advocated controlled burns and a controlled deer population, freeing the way for the forest to return to its pre-settlement state. "I was really pleased to prepare this plan, because I love Itasca," says Tester. "I spent many summers there as part of the biological station and there was just no question in my mind what it needed."

Park managers began large controlled burns in 1996, culminating last year with Minnesota's largest burn. Tester's fire research has, at last, come full circle.

BUT ANOTHER OF HIS MAJOR projects has left a puzzling question unanswered. As an offshoot of his fire research on prairies in the 1950s, Tester began to examine the behavior of prairie toads west of Itasca. Working with former Bell Museum of Natural History director Walter Breckenridge, Tester set out to discover what happened to toads during the winter. "We had no idea where they spent the winter," he says. "We'd follow them during the summer, then we lost track of them." In hot pursuit, Breckenridge and Tester marked large numbers of toads with radioactive tags, about the size of a pencil lead, inserted under the skin. They used an instrument similar to a Geiger counter to track the toads after the frost set in.

"We started searching in the pond because we thought that's where the amphibians would spend the winter," says Tester, "but we never found any. So we started searching on the land. We'd walk around with this Geiger counter, and the needle would start to bounce and it would start clicking in our ears. But we couldn't see anything. We'd pull the grass away, and we still couldn't find anything. Finally, we concluded that they must be living underground. The toads must have dug into the ground, but there were no holes--no holes at all."

Eventually, Tester and Breckenridge discovered that the toads do not dig underground--they twist. "They sit with the head up in the air and the hind feet on the ground," says Tester. "They have calluses on their hind feet that act like little shovels and they literally twist themselves right down into the ground. It's just like they pull the hole in after them. You see the surface of the ground wiggle a little bit when the toad is out of sight and all of a sudden there's nothing."

The toads spend the winter above the water table but below the frost line, breathing oxygen through their moist skin. Their preferred abodes are prairie earth mounds, known as Mima mounds, which were once thought to be of Native American origin. Tester discovered that, in fact, the 30-foot mounds are created by burrowing animals and could house up to 3,000 toads during the winter.

Springtime brought another mystery--how the toads dig out of their dens. The question remains unanswered, says Tester, because no one has ever seen them emerge. "We've seen them go down. We've never seen them come up," he says. "We've tried. We've put soil between two panes of glass and forced the toads to dig down in it, but we never were there when they came up. We don't have any idea how they do it."

In the years since his toad research, Tester has moved on to other problems, including working with a team of University scientists to develop radio collar technology for tracking animals. Among his other well-known achievements is the book Minnesota's Natural Heritage: An Ecological Perspective, published in 1995. Tester officially retired from the University this past December, but is teaching a vertebrate ecology class at the Itasca station this summer, as he has done for 30 years.

The Itasca program, he says, lets students conduct significant research in a close-knit community. "The value of Itasca is the personal contact that the students have with the faculty and with each other. You get that magic camaraderie that comes from seeing somebody every day. You don't have to knock on their door, you don't have to make appointments. You drink coffee together, you eat meals together. I've seen so many students come away from Itasca with the confidence to become leaders on campus."