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Climate Change, Wildfire Transforming Northwest Forests

October 29, 2015

Portland State University Ph.D. student Charles Maxwell is studying forest type-shifts. Jes Burns, OPB/EarthFix.Much of the forestland above the Illinois River in southwest Oregon is a tangled mess of manzanita, shrubby hardwoods and ceanothus. Bushwhacking through it is a branch-to-the-face, boot-snagging, poison-oaky horror.  

And this is one of the easy spots, says Portland State University Ph.D. student Charles Maxwell.  

“Yeah, this one is a pretty accessible site relatively. Some are quite a bit further in,” he says.   

This is where the Biscuit Fire burned 13 years ago, and the site is one of dozens of research plots Maxwell bushwhacked into, measured and catalogued this summer.  

The tangled shrub cover was typical. Researchers found a good variety of species, but the pines and firs that grew on the land pre-fire are struggling to break through. And this is evident when Maxwell comes along a Douglas fir sapling, just over a foot tall.  

“This little guy, from what we've found from other Doug firs we've analyzed — this tree is probably 13 years old,” he says. “Its competition has severely over-topped it.”  

In the field, it’s difficult to know the actual age of this particular tree, because the rings are difficult to distinguish — but stunted trees weren’t out-of-the-ordinary on the plots.  

Through this research, Maxwell and others working on the project are trying to figure out if this 13-year dominance by shrubby vegetation is going to be permanent, and what causes a system to slip into one forest type or another. 

“With climate change, we may increase the prevalence of shrubs over forests and we might be headed more towards that tipping point of increasing more shrubs,” says Portland State researcher Melissa Lucash.  

Climate Connection

Previous modeling has shown that these Klamath and Siskiyou forests could experience a substantial long-term shift from conifer to this shrub-heavy chaparral.

The shift will likely not be the result of just one variable, because forests are complex systems and what human do in the forests complicates the equation. But climate change — and the warmer and sometimes drier conditions it brings — will play a big part.

Portland State’s Robert Scheller, who is leading the Klamath Climate and Wildfire study, says established trees can likely survive some warming.  Where climate change really kicks in is what vegetation comes back after large forest die-offs from wildfire, disease or bug infestation.  

“It's little trees. Those are the ones that really get hammered by drought.  And so if you get big wildfire, then you get some droughty years following that, that's where you get the replacement with shrub chaparral,” he says.  

And while the trees may ultimately take over the spot on top, the shrubs are believed to have the advantage in dry areas, and when fire returns regularly.  

“And they can keep a location in this shrub-chaparral state for decades, even centuries,” Scheller says.  

It’s not just these dry forests in southern Oregon that are threatened — it’s happening elsewhere as well. Scheller hypothesizes that any place in the Northwest outside of the moist Coast Range is at risk of flipping to some other forest system.  

Shifts are already becoming evident further north.  

“In case of ponderosa pine in British Columbia, they'd have to move 60 miles every decade north.  Well that's something like 10-times their normal rate of movement,” says Dick Waring, retired Oregon State University professor.  

Waring says the ponderosa in Canada need to move from the U.S. border all the way up to the Yukon, where the climate is predicted to be good for them. And that leaves a problem.    

“There's no way they can move that fast without assistance,” he says.  

These forest type shifts could have major implications for the region, according to University of British Columbia Forestry Professor Nicholas Coops.  

“Ultimately, the species that inhabit that forest, the biodiversity that’s in that forest, the ground cover, all of that will ultimately be shifting,” he says.  

“Now the caveat is it probably won't shift in one person's lifetime, but the trail that your grandkid walks will be a very different trail.”  

Economic Consequence

And the Northwest timber industry is not immune, says Oregon Forest Resources Institute Forester Mike Cloughesy.  

“The premise, that type shift is happening, is definitely true,” he says.  

But Cloughesy says the evidence is most evident on the edges of ranges amid higher elevation species: oak woodlands and conifers.    

“When you get way down in Southern Oregon and into California, you get tendency in areas that have burned repeatedly, that they shift from conifer forest to a brush,” he says. “If you're owning it, you're not going to get any type of income off that piece of ground.”  

But the primary managed timber species in the Northwest, Douglas fir and ponderosa pine, are a bit more secure because they’re adapted and bred to grow in a broad range of climate and on-the-ground conditions.  

Roseburg Forest Products owns timber lands in Oregon and Northern California. Manager Eric Geyer says they have not changed how they’re managing their land in anticipation of shifting forest types. Nor has it played into decisions about what land to buy and sell.    

“I would not say we're specifically looking at climate change.  That’s a whole body of science that's not our expertise. As people that look at forest as long term process, we don’t really think about smaller shifts; we think about big shifts. And that's anybody's guess as to what the climate may do over the next 30-40 years.”    

Carbon Consequence  

The shifts could also have an economic impact in other, less obvious ways.

“The first thing that comes to mind is the amount of carbon on landscape. There's going to be significantly less carbon stored in shrubs than in forests,” Maxwell says.

It’s about half as much. And that’s a big deal, says Jim Strittholt, president of the Conservation Biology Institute. The institute is working on cap and trade efforts, where businesses and governments are trying to put a price on carbon.

“And part of that relies on your ability to predict where your carbon stocks will be," he says. “Well, what if they're changing?”

The data gathered this summer by Maxwell will be used to help scientists better predict what forests across the globe will look like in the future, then what can potentially be done to change those outcomes for the better and to help Northwest forests weather the coming climate change.  

Whether that’s controlled burns, replanting, or even moving species, scientists are working to answer those questions.

"Anything we can do to really avoid really abrupt shifts or slow down the rate of change is valuable," Scheller says.

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Scientists walk through a shrub-dominated snag forest in the Biscuit Fire scar.

Jes Burns, OPB/Earthfix