An increasing number of trees in the Anacortes Community Forest Lands are dying, even as others are doing just fine, and some thriving.
The cause is unclear, but certified arborist Dave Oicles, who is also forest lands maintenance supervisor, suspects periods of drought could be making an impact.
This was one of the observations he shared with a group Friday on a community hike focused on changing trees and forest health. Oicles, also known as Ranger Dave, takes care of the 2,800 acres of public forest and 50 miles of trails for the City of Anacortes.
The hike was hosted by Friends of the Forest.
Oicles told hikers he noticed an increase in dying Western Red Cedars and Hemlocks, marked by dramatic sections of orange, last summer.
In the Whistle Lake area, hikers stared up into the brown canopy, the color mellowed by winter.
“In the last 12 months, they’re losing their battle,” Oicles said of the trees.
The cause hasn’t been identified, but Oicles noted there has been a pattern of drought since 2012 — warmer, drier summers, with less rainfall throughout the year.
“We do know trees get stressed with a lack of water,” he said.
It isn’t necessarily an overall shortage of water but an issue of timing that could affect some trees.
“We’re getting the same amount of moisture, but not all 12 months,” he said.
These days, when he cuts into a newly dead tree, the trunk is dry and powdery, not what he would expect.
The problem may be more pronounced on Fidalgo Island, where soils are rocky, shallow and can’t hold water, and firs and cedars tend to have shallow roots, Oicles said. When there is not enough water in the ground, tree roots suck up air instead, causing a blockage or “air embolism.”
Above the blockage, the tree starts to die, causing it to die from the top-down, he said.
Elsewhere in the forest, trees are thriving. Like an estimated 600-year-old growth Douglas Fir that Oicles says is one of his favorites.
“We have trees that have lived through a lot,” he said. “We don’t know how (dead trees) are going to affect the forest lands.”
There may be a shift toward more drought-tolerant species, and positive effects, such as more sunlight reaching the forest floor that allows seeds of new species to germinate, he said.
Disease and fungus are also a possible concern.
“Sometimes trees can die directly from drought,” “said Daniel Omdal, a forest pathologist for the state Department of Natural Resources, by phone. “If (trees) don’t get moisture, it may not kill them, but when they’re thirsty they are pre-disposed to other agents.”
So far, there is limited data linking drought with dying trees, except one University of Washington study that found Big Leaf Maple decline in Washington associated with hotter, drier weather, Omdal said.
“Tree death is a natural phenomenon,” he said. “One of the challenging things is the extent of drought that is likely a result of a change in climate, and so these episodes of mortality are likely to become more frequent and severe.”
As far as more dead wood in the forest, Oicles said it’s not a concern.
Forty percent of wildlife make habitat out of dead wood, he said.
Woods need fire, and some plants depend on it, he said. Decades of fire suppression have resulted in hotter, more intense fires that threaten communities, such as the recent California fires. But in more isolated areas like the local forest lands, fire is not necessarily a bad thing, he said.
After a fire burned 18 acres of Little Cranberry Lake in 2016, there is now new growth in the understory.
“Walk through there now,” he said. “It’s amazing.”
A new citizen science project is hoping to document future changes in the forest. Volunteers from Transition Fidalgo & Friends, an Anacortes group focused on climate change issues, are developing a tree monitoring plan, with help from Oicles, for different areas of the forest lands. They also plan to monitor when leaf buds sprout, flowers grow and leaves drop, according to Eric Shen, a project organizer.