A study of vegetation changes in Wisconsin”s northwest sand country reveals a dramatic decline in pine barrens, pines and open habitats, and an increase in oak and aspen forests over the past 140 years.
David Mladenoff and Volker Radeloff of the University of Wisconsin Madison and Mark Boyce, formerly with the University of Wisconsin Stevens Point, studied the region, which covers 1,700 square miles that stretch northeast from Polk County almost to Bayfield. The forest scientists documented changes in the region, once an enormous island of prairie, savanna and pine forests on very poor soil surrounded by a sea of dense forests on better soils.
“We believe wildfires created a unique ecosystem and areas of open habitat in the northwest sands before settlement,” says Mladenoff, a forest landscape ecologist in the College of Agricultural and Life Sciences.
“The Wisconsin Department of Natural Resources has made the northwest sands one of its first projects for managing an entire ecological region,” says Gerald Bartelt, chief of the DNR”s wildlife and forestry research section. Pine Barrens are found in only a few places across the country and contain a rare mix of ecological communities that are disappearing because of fire suppression and settlement, according to Bartelt. Many of the species that are adapted to the habitat and landscape patterns that fires once created are declining. In Wisconsin, those animals include the sharp-tailed grouse, many grassland birds, and the endangered Karner blue butterfly.
The U.S. Environmental Protection Agency has funded a project to involve area citizens, interest groups, forest managers and scientists in a series of meetings to decide how best to manage the region to meet both economic and conservation goals.
“Our findings provide an important frame of reference for ecosystem management in the northwest sands,” says Mladenoff. “They are one source to consider as resource managers meet with the public and landowners in northwestern Wisconsin to discuss management of the region.”
The researchers based their assessment of pre-settlement vegetation on surveyor records from the U.S. General Land Office. During the surveys, completed between 1847 and 1859, surveyors established survey posts at corner locations on a grid at half-mile intervals. They marked and recorded the species, location and size of two to four “witness” trees near each post. The ecologists analyzed those data and compared the results to the makeup of the forests in 1987, which they determined by analyzing satellite information.
Before settlement, the northwest sands were prone to drought, frequent fires and epidemics of the jack pine budworm, an insect that can kill thousands of acres of trees during an outbreak, Radeloff explains. Those conditions produced a shifting mosaic of grasslands, shrubs, and pine and oak species that are adapted to fires.
Loggers began removing the region”s white and red pine for timber in the 1860s. Farmers settled soon after that. The loggers returned to harvest the jack pine for pulp about 1910. During the Great Depression, much of the land was abandoned when former owners couldn”t pay their tax bills. Large areas were reforested with jack pine plantations and became county, state, federal or industrial forests. Today the northern portion of the northwest sands is part of the Chequamegon National Forest; the central portion contains extensive county forests and private industrial forests; small private holdings and county forests are common in the southern section.
“Although jack pine remains the most abundant species in the northwest sands, it has decreased by 30 percent despite widespread jack pine reforestation in the 1930s,” Radeloff says. “Red pine has decreased by 80 percent, while oak abundance increased by 360 percent and aspen by 570 percent.” The trends are likely to continue, he says, unless people agree on actions aimed at restoring the mix of vegetation types once present.
There are a handful of restored wildlife areas where county, state and federal managers conduct periodic burns to encourage sharp-tailed grouse populations. However, those practices burn the same areas again and again. Mladenoff says current burns don”t mimic the shifting nature of fires, which created a mix of openings and pine stands of different ages. For example, red pine savannas have almost entirely vanished.
“One of our goals was to consider management options that might restore those communities,” Mladenoff says. “Large scale use of fire seems out of the question. Even with fire suppression, fires have continued to be a major concern to citizens in the region. There were two major fires between 1977 and 1980. One was 10,000 acres and the other 13,000 acres. The second burned an area more than five miles long. The two fires destroyed about 250 houses, cabins and other structures.”
“We know how to manage for dense forests by suppressing fires and we know how to create prairies with prescribed fires,” Radeloff says. “The really tricky question is how do we include management alternatives for the types of open forests and savannas that were present in the northwest sands at settlement.”
Between 1990 and 1995 a major outbreak of jack pine budworm occurred in the region. The outbreak, followed by clearcuts to salvage the trees for pulp, created open areas similar in size to those made by large fires.
“It appears that large clearcuts could create some of the landscape patterns that fires once caused,” Radeloff says. “We know logging doesn”t mimic fire, but this system was historically much more of an open habitat. We think it might be possible to combine large clearcuts followed by prescribed burns to more closely mimic natural disturbances.”
For his research on the northwest sands, Volker Radeloff will receive an Outstanding Doctoral Research Award from the International Union of Forestry Research Organizations. He will receive the award — one of only seven presented every four years — during the opening ceremony of the organization”s meeting in Malaysia next September.
The research was supported by: state funding to the UW-Madison College of Agricultural and Life Sciences and the UW-Stevens Point; and a grant from the Wisconsin Department of Natural Resources and a McIntire Stennis Grant from the College of Agricultural and Life Sciences.
Mark Boyce is now at the University of Alberta in Edmonton.