Forester Explains Science, Tradeoffs Of Forest Management After A Wildfire
It’s been nearly a month since the Bridger Foothills Fire burned through people’s timbered properties northeast of Bozeman. Landowners now have to figure out if they want to play a role in shaping what their forests will look like, 10 to 100 years in the future. A forestry expert is helping them understand the science and the tradeoffs.
Peter Kolb walks up a steep slope covered in ash. This area was burned several weeks ago by the Bridger Foothills Fire.
“There's a little bit of a trail up here but it can be hazardous footing,” Kolb said. Kolb is the Montana State University Extension Forestry Specialist and an associate professor at the University of Montana.
He says there isn’t a right way or a wrong way for landowners to manage their land after a fire. It really depends on their values.
For the landowner he’s meeting today, those values include:
“Wildlife and aesthetics, legacy for future generations, a healthy forest,” Kolb said.
Kolb says an important first step to upholding those values is figuring out which trees are dead or dying and which ones have a chance of surviving.
“So here’s a giant big old Douglas fir tree that’s about, oh, 28, 30 inches in diameter at the base, and if I cord it and count the rings, this tree, it would probably be about 300 to 350 years old,” Kolb said.
The tree is shedding a lot of dry, brown needles, which Kolb says is a sign that it’s in repair mode. It’s similar to our skin peeling after a sunburn.
But the bark around its base is black. Kolb says Douglas firs don’t survive if more than a third of its circumference has been killed by heat.
To gather more clues, he takes out a small ax and chips away the black bark to look at the inner cambium layer.
“It's wet, and it's spongy, so this is what healthy tissue looks like,” Kolb said.
But when he checks a few other spots on the tree, the inner tissue is dry and yellow.
“It’s still in a process of dying,” Kolb said.
After a diagnosis, Kolb says it’s up to the landowner to decide the course of action, adding that everything has its pros and cons.
For example, this 350 year old dying Douglas fir could fall over and roll onto the driveway. One option is to cut it down.
“On the other hand, because it’s big, this is a great snag for wildlife," Kolb said.
Kolb tells the landowner it could provide habitat for woodpeckers and other cavity nesting birds for 50 to 100 years.
“So, this is one of those, do you want to leave it as a snag? It’s above your driveway," Kolb says.
"We could leave it for a number of years," the landowner says. "Do you think for a number of years, it will probably —"
"Big trees like this stand for a long time when they’re dead,” Kolb says.
The landowner decides to keep it as a snag for wildlife.
They go through this process of assessing and discussing trade offs for the rest of the morning. In some areas, they tie pink ribbons around middle aged trees that will likely survive.
In other sections of the forest, the landowner decides he doesn’t want a lot of fallen dead trees several years from now. He’s going to have RY Timber in Livingston come collect the salvage wood.
Kolb says this option can help cover the cost of buying tree seedlings and paying for restoration work.
“I mean if you just have to pay for the restoration work, you’re looking at upwards to a $1000 an acre. That’s a lot of money,” Kolb said.
Another area where landowners face tradeoffs is the ground beneath their feet.
Kolb leans down and runs his hand over a thick layer of ash.
“There’s no plants or organic matter holding it in place. I add water to this, this now is going to turn into this slurry of goo, and see how that’s wet and how underneath it’s powder dry,” Kolb said.
During a heavy rainstorm or spring snow melt, Kolb says the slurry of goo could slide down a mountainside. Erosion moves the forest’s nutrients offsite and can mess up the hydrology of streams and municipal watersheds.
“Erosion is a natural process but it’s not necessarily a beneficial process for what we want,” Kolb said.
If the landowner only cared about making money from the salvage wood, RY Timber would come and collect the tree stems. But since he also cares about preventing erosion, he’s worked out an agreement with the mill. The crew will use its ten ton machinery to press tree branches and other woody debris into the slope.
Kolb says doing this in a jigsaw pattern in the right amount can slow water runoff by 80 percent.
“There is this stereotype that logging causes erosion, causing damage. The act of logging is just removing wood for us to use. How you log it is what makes the difference,” Kolb said.
To further stabilize severely burned slopes through next spring, he says landowners could also plant certified weed free grass seed or even winter wheat.
Kolb emphasizes that every ecosystem is complex; every fire is different, and every land management decision should be site specific.
“I love my job because these systems, you never stop learning, never. You kind of start thinking you got a handle on it and then something else pops up. I like to learn,” Kolb said.
Kolb put together a photo guide for landowners to help them assess wildfire damage to trees and vegetation and think about different land management options. That guide is available here.
Montana State University also hosts three day forest stewardship workshops each year to help landowners learn about ecology and management, and come up with a plan based on their values.