While large fires have had dramatic impacts in some Pacific Northwest forests, only about 10 percent of the forested lands in the eastern Cascades have burned in the last 30 years, and young trees and dense forests are continuing to grow at a rate that outstrips losses from disturbance, a recently published study says.
As a result, many forests across this region are becoming denser. Efforts to reduce their vulnerability to future high-severity fires — through tree thinning, prescribed burning and harvesting — have had little overall effect on forest structural conditions across the region as whole.
Those are among the results of a comprehensive analysis of forest structure and biodiversity based on satellite imagery and on-the-ground field work in the eastern Cascades of Washington, Oregon and Northern California from 1985 to 2010. Matthew Reilly, a former Ph.D. student in the College of Forestry at Oregon State University led the study, which was published in the journal Ecological Applications. Reilly is now a post-doctoral scientist at Humboldt State University.
Large fires in highly visible places such as the Columbia Gorge, Santiam Pass and the Northern California wine region capture public attention, said Reilly, but are not representative of what’s happening across the whole region. “We become fixated on losses associated with tree mortality and fire, but the gains from new growth are really important. They have the potential to offset those losses. This study zooms out beyond the perimeter of recent fires and considers them in the context of what else is going on in the forests and woodlands east of the Cascades.”
For forest managers, the findings emphasize the tradeoffs between two goals: dense forests that provide habitat for threatened species such as the northern spotted owl, and more open-canopy forest ecosystems that scientists call early seral (the youngest stage in forest development) with large, thick-barked trees that are considered less vulnerable to high-severity fire.
From KTVZ 21 News: https://www.ktvz.com/news/study-nw-forests-getting-denser-more-vulnerable-to-fire/656369135