After Pagami Creek fire, worry accompanies BWCA forest renewalby Dan Kraker, Minnesota Public Radio
ISABELLA, Minn. — A year ago the Pagami Creek fire roared across a trail to the canoe landing at Isabella Lake, an entry point on the southern edge of the Boundary Waters Canoe Area, as 40 mph wind gusts drove the blaze an unprecedented 10 miles in one day.
Last summer's fire scorched 145 square miles of forest, mostly in the Boundary Waters area. In the fall, the burn area was filled with charcoal-black trees and soil, but tiny blades of grass had started to poke through the ash.
Today, the trees still stand like black pipes, their exposed roots clawing the ground. But the forest floor is lush and colorful, with moose maple and wild sarsaparilla.
Despite a striking amount of new growth, forest managers have major concerns, among them a huge loss of organic matter and the presence of invasive plants that already are taking root.
At first glance, however, the forest's renewal is overwhelming.
New aspen saplings are already 4 feet tall in places. Bright green birch leaves have sprouted at the bases of dead trees, a sharp contrast to the sheaves of blackened bark peeling from their trunks.
Even in late summer there is a patchwork quilt of colors: purple big leaf aster, pink fireweed. There's also a plant with jade green leaves called Bicknell's geranium that Bruce Anderson, forest monitoring coordinator for the Superior National Forest, calls a fire pioneering species.
"Once a fire goes through and exposes the soil, it germinates, and it may have been in the soil since the last fire, which may have been a hundred years or longer," Anderson said.
The plants will last three to five years. Then they will disappear again until the next fire, perhaps another hundred years from now.
It's all part of the renewal of the boreal forest after a wildfire. Anderson, who is studying how the forest has responded to the Cavity Lake and Ham Lake Fires in 2006 and 2007, and now the Pagami Creek fire, said the Cavity Lake Fire burned the most intensely of the three, feeding on downed timber from a 1999 blowdown. It also destroyed up to 90 percent of the soil's organic matter.
"After the fire," he said, "it was nothing but bedrock and ash."
But the forest has proved to be amazingly resilient.
"Five years later we identified over 30 species of plants that have come back in," Anderson said. "We had aspen and birch 15 to 20 feet tall. So the resiliency of these northern forests, even after an extremely severe wildfire like Cavity which burned through blowdown, was pretty striking."
Anderson anticipates an even faster recovery from the Pagami Creek fire. But some iconic species, among them red pine, have not come back, in part because all the new plants on the forest floor have stifled new tree growth, he said.
Of particular concern are invasive plants now in the fire area. They include a foot-high knapweed plant that Anderson pulled from the gravelly soil, a plant that "thrives in fire."
Knapweed is a thistle-like plant that produces a pinkish purple flower. It and hawkweed, another invasive plant, are native to Europe and Asia. Anderson said that not many native species feed on them. As a result they can quickly take over a burned area and out-compete native vegetation.
The key to eradicating them, he said, is to stop their spread early.
"Catch it when it's small," Anderson said. "You can get to the point of no return, particularly within wilderness. When it gets beyond a certain size, there's not a whole lot you can do in terms of management action."
Toward that end, crews are in the burn area, pulling weeds. When they flower next spring, workers will cut the stems and stick them in bags to prevent their seeds from spreading.
Forest officials describe it as a race to keep invasive plants at bay, so native plants have the time to slowly reclaim what the fire destroyed.
- Morning Edition, 09/10/2012, 7:24 a.m.