Weakened by the recent droughts, large numbers of trees throughout southwestern Oregon are dying off and may continue to do so for months to come, experts say.
According to the U.S. Forest Service, conifers in the region are perishing from the long-lasting effects of intense summer heat and mild winters over the past three years. The extent of the die-offs has not yet been mapped.
The die-offs come despite this past winter which was marked as a return to normal weather and precipitation. But the damage may have already been done in the years prior when those replenishing winters never arrived, according to plant pathologist Ellen Goheen with the Rogue River-Siskiyou National Forest.
“Everyone recognizes that we had a good, snowy, wet earlier portion of the winter, so people are very surprised by what we’re seeing,” said Goheen. “But really the mortality and the damage we’re seeing is the result of dry conditions in 2013 and into 2014 and ‘15, and particularly last year where we had a very dry winter. That’s when the trees are used to getting their moisture.”
Die-offs such as these come in “pulses” forest officials say, when a run of consecutive drought years can be followed up by a string of rainy years. This summer is expected to be hotter than average again and the die-offs could get worse before they get better.
“It’s been a tough time for trees and we expect the damage to continue to show itself as we warm up into summer months,” said the Rogue-River Siskiyou National Forest in a recent release addressing the problem.
Various trees have died but locally it appears Douglas firs are most susceptible, dying across all age classes, Goheen said. Trees of smaller sizes are dying, as well, too weak to pull water from the soil.
More resilient trees like pine, oak and madrone are also stressed, fending off opportunistic pests and fungi. Bark beetles and flat-headed fir borers will invade an area and will eat away a tree’s ability to circulate what little water there is into its branches.
“Normally a healthy tree can withstand any kind of infection or infestation by some of these organisms,” Goheen said.
The afflicted trees pepper public and private land alike. The dying trees redden from the top-down before turning orange or brown. Mike Harris, a silviculturist with the Umpqua National Forest, said private landowners have called asking for help to save their trees.
Harris said landowners may see trees start overproducing sap — called “pitching out” — to ward away pests.
Bob Ragon, the executive director of Douglas Timber Operators, estimates 10 acres of his own small woodland property are plagued by dying trees, reddening from the top-down as they do.
“We’re seeing it all over the place,” Ragon said, pointing to shallower soils where trees are competing for moisture. “It looks like hell because the red needles show up really sharply.”
For Ragon, his dead trees are too young to provide any salvageable lumber or even firewood. Young Douglas fir wood burns quickly, he said, and they are less of a fire hazard if they are left standing instead of laying down.
“They are not sufficient size to make into lumber or anything like that and getting out there to make them into firewood or anything like that would be too expense and you would do more damage than good,” Ragon said. “... There’s no question there’s potential for some landowners (to salvage) and they will do that I’m sure. It depends on how old the trees are.”
Officials will have a stronger grasp on the scale of the die-off after a joint effort from the U.S. Forest Service and the Oregon Department of Forestry sends a plan to conduct aerial mapping over the region, which it does every year. The next scheduled trip is planned next month.