The Burn Scars of the Sierra Foothills Tell a Story — and Offer Lessons

Blodgett Forest Research Station sits about 30 miles west of the southern tip of Lake Tahoe, amid commercial timber and U.S. Forest Service lands. A place for foresters and scientists to experiment with the care and management of forested lands, Blodgett is a prime study site because it’s representative of much of the forested Sierra — all the old growth trees were effectively logged out in the late 1800 and early 1900s. Mostly second growth exists now.

Researchers have practiced varying harvesting, thinning and prescribed burning techniques in study plots here since the 1930s, when the land was gifted to the University of California by a private timber company. One focus area of study is how to manage forest lands to be resilient to wildfire. Some of this is “really cutting edge stuff,” says research scientist Brandon Collins.

For the past 90 years, all fires on Blodgett have been intentionally set — carefully managed by people trained to bring them under control quickly if needed. That changed in September, when the Mosquito Fire, which started near a PG&E line on Sept. 6, burned rapidly and crossed the northern boundary of Blodgett on the morning of Sept. 9. The cause of the fire is still under investigation.

Blodgett staff had already been evacuated from the area for safety. The fire was considered fully contained on Blodgett by Sept. 11. It burned around 100 acres of the 3,000-acre property. All told, the Mosquito Fire burned 77,000 thousand acres in Placer and El Dorado counties.

While the fire damaged control plots for some long-term studies, it opened other opportunities for research. It also underlined the importance of preparing California’s forests for fires.

Save trees from fire by lighting fires?

Brandon Collins stands in front of what was recently a hillside of young trees, now burnt to blackened crisps by a wildfire. When these trees were alive, the trunks were barely the diameter of an arm or a calf. They now look like a crowd of knobby, emaciated skeletons. They are of no economic value and, unless replanted, risk becoming a field of brush rather than regrowing as a forest.

“I think about, if we go back in time, what could we have done differently to change the outcome?” asks Rob York, co-director of Berkeley Forests, which manages the study site. This area was clear-cut a few decades ago and left alone ever since. “It’s tricky, right? They’re vulnerable because they’re short trees. It doesn’t take a lot of fire intensity to cause a high-severity fire.”

Land managers at Blodgett could have thinned it with chain saws or a masticator (which is like a wood chipper on a tractor). Both of these options are tremendously expensive, up to $2,000 an acre, with no monetary return — placing them out of reach for almost all land managers, especially those managing for a commercial timber harvest to turn a profit.

Industrial timber managers sometimes spray herbicide (PDF) to kill competing vegetation in young stands of trees, again at a price. But the practice is unpopular among neighboring communities and can sicken exposed people.

Theoretically, some of the thinned material could be harvested as biomass and incinerated in a cogeneration facility, with profits from energy generation defraying the cost.

“But in this area and much of the Sierras,” says Ariel Roughton, research forest manager at Berkeley Forests, “that is not a viable option because the infrastructure doesn't exist. [...] There's not really a lot of good answers.”

Research on increasing forest resilience could not be more timely, with many acres of industrial timberland in the state looking similar — young trees growing back after a clear cut — and with the state’s wildfire problem accelerating in an era of climate change, drought and fire suppression. Over the coming years, the economic calculus of what makes financial sense for a timber company might change.

“If I could go back in time, I would go back two years ago and do a prescribed fire here,” says York, who is piloting this approach currently at Blodgett. “But it is hard to pull off a prescribed fire in this kind of [young forest] structure.”

Just the day prior to this interview, he conducted a prescribed burn in a forest that looked similar to this stand of trees pre-wildfire. Doing such a fire kills off and consumes some of the trees that could make for a future profit, but it can also inoculate the stand against being entirely destroyed by future fires.

“Nobody’s talking about putting [prescribed] fire in 30-year-old stands. It’s taboo, by the way, for classic forestry,” says Collins. “You'd be burning some of your crop and there are lots of risks and difficulties with doing fire. But maybe if fire loss increases, it'll start to look more viable.

“This is kind of leading a way to a new frontier in forest management.”

Sometimes it works, sometimes it doesn't

A few hundred feet away, over a dirt road, a patch of forest looks quite different from this walking graveyard of small, skinny trees. The Mosquito Fire reached it, too, but then quieted down and became a "surface fire," burning along the ground instead of torching the crowns of the trees.

Last spring they did a prescribed fire there. Roughton relays what happened when the Mosquito Fire passed from the untreated forest area to the location with the recent prescribed fire.

“The [wildfire] came up in this direction and the intensity changed, right? It was high, high-intensity here. And then over on this side,” she said, indicating the other side of the road, “we did see the fire effects change. It still killed some of these trees along the edge, but it did then drop to the ground.”

In addition to saving trees, the calmer fire behavior allowed firefighters to lay lines of containment.

But up the road, around a large bend, is a patch of forest that had been diligently treated with beneficial fires. When the Mosquito Fire, running uphill, slammed into it, many trees, even large older ones, still died. Viewed from the road, the trees are mostly dead.

"This is actually kind of a sad location for me,” says York, “because I had done the two prescribed fires here in the past, but yet we still see dead trees up in the canopy.”

Here, the researchers suspect the landscape had something to do with it. The fire had been making a long run uphill and crested like a powerful wave pounding ashore.

Fortunately, York says, deeper into the treated area, “we do start to see green trees. We saw the wildfire behaving like a low-severity fire caused by the prescribed fire we did.”

When wildfire is good fire

For the most part, the Mosquito Fire burned in a moderate, and even mild, way on Blodgett. In a low-intensity fire, stumps may be blackened but remain intact. In a moderate-intensity fire, stumps will be burned deep enough to form charcoal. In a high-severity fire, the stumps are gone.

“We were really fortunate that it didn't burn more of the property,” said Roughton. “It was, I think, a combination of our forest management, the weather helped us tremendously and then obviously the suppression folks who were out there.”

However, most of the acres that did burn don’t necessarily look too bad.

“One of the things that gets mischaracterized,” says Collins, “is the idea that a wildfire burns and it's all catastrophe, it’s all destroyed.”

In reality, he said, these forests are adapted to low- and moderate-severity fires. Even some patches of high-severity fire can be a benefit.

Test-driving new treatments

About a mile away, smoke is still rising like morning mist from a field, in a patch of forest. York burned it just the day before. It had looked similar to the high-density young forest seen at the start of the day, the one that burned up like a matchstick in the Mosquito Fire. Now, it’s opened up. You could walk through the stand without snagging your jacket on sticks.

“We let the fire kill all these small trees,” says York. “We just did it very cheaply and with an ecological process.”

York will be studying how this stand responds to the fire and whether the expected timber harvest to come from it is much reduced, which he says is still an open question. Heat can kill some parts of the tree’s crown and reduce growth. Yet, the additional space between trees may encourage bigger growth. This stand is also now less likely to be entirely lost in a future fire.

“I have some [forestry] friends who really focus on timber as their objective,” says York. “I think they would like this outcome primarily for that reason. We let the fire kill all these small trees. And that was a pretty cheap way to do it.”