News for those who live, work and play in the Santiam Canyon

Western redcedars challenged; plantings continue in Canyon

Reporter for The Canyon Weekly

The western redcedar, one of the key species in Pacific Northwest conifer forests, is facing challenges with climate change.

Recent droughts have led to higher mortality rates, scientists say, with a recent study led by a Washington State University (WSU) professor noting that in 2017 and 2018 80 percent of western redcedars at 11 coastal sites sampled ultimately died.

The study is currently under peer review by the scientific journal Global Change Biology. The lead author is Robbie Andrus, a researcher in WSU’s School of the Environment.

“Our findings forewarn that a warming climate and more frequent and severe seasonal droughts will likely increase the vulnerability of WRC to canopy dieback and mortality and possibly other drought-sensitive trees in one of the world’s largest carbon sinks,” wrote Andrus in the abstract for this study.

The researchers found that tree mortality usually was preceded by four to five years of declining radial growth. In addition to higher mortality rates the trees also can be subject to thinning crowns, yellowing, canopy dieback and flagging (dangling and falling branches).

Oregon Department of Forestry (ODF) officials noted failing redcedars also can be susceptible to insects and diseases although none are typically implicated as primary causes of tree mortality.

“Western redcedar is a species that prefers shade and moisture, but it has been struggling for years due to ongoing droughts,” said Christine Buhl, ODF’s forest entomologist. “Even if they are growing along streams or when we get a bit more moisture (as we saw some days in this last La Niña year) – trees are still dying from drought stress simply because they have been limping along for years of decreasing consistent moisture and increasing average temperatures relative to what they have been used to for the last 30-plus years.”

The ODF does regular plantings of redcedar in the Santiam State Forest, said John Walter, the agency’s young stand silvicultural specialist, although some 10- to 20-year-old cedar stands burned during the 2020 fires.

“ODF is in the process of replanting them now,” Walter said.  “Since the 2021 planting season ODF’s State Forests Division has planted (including this season) 84,000 WRC seedlings.  This is about four percent of the total seedlings planted in that time frame.”

Before 2020, the state forests would receive up to 7,000 seedlings per year, topping out at about 6 percent of the total seedlings planted. 

Walter added that some of the smaller seedlings also face challenges from feeding deer and elk, and the ODF often uses tubes to help protect the young trees.

Overall, he said, “with proper maintenance they have been growing well in the Santiam State Forest and the (agency) is still planning on planting cedar in the future in this area.”

Western redcedar usually grows in forests that also include Douglas fir, western hemlock and western white pine. Douglas fir also is the dominant tree in the Willamette National Forest. 

Western redcedar is one of more than a dozen other confers,including incense-cedar, western white pine, ponderosa pine, Pacific yew, western hemlock, mountain hemlock, and several species of fir that are present in the forest. 

Willamette National Forest officials did not respond by The Canyon Weekly’s presstime to questions regarding the health of western redcedar on forest land in the Santiam Canyon or elsewhere in the forest’s 1.67 million acres.

ABOUT THE TREE

What: Western redcedar (Thuja plicata)

Range: Mainly in the coastal regions of Oregon, Washington and British Columbia, with some in Northern California. Southeast Alaska, the Canadian Rockies and Idaho.

Size: Can grow taller than 100 feet with a trunk 9 feet in diameter.

Age: Some reach 1,500 years old.

Best growing conditions: Western redcedar is very shade tolerant. This species requires moist conditions and thrives in coastal fog belts and most inland areas up to about 4,000 feet of elevation.

Alternatives: Incense cedar, sequoia and big leaf maple in dry sites and western white pine, maple, alder, ash and cottonwood at wetter sites that do not dry out in the summer.

Factoid: Tools made of redcedar found in Yaquot, a small settlement on Vancouver Island, have been dated as far back as 4,000 years. Indigenous peoples still use the wood for a wide variety of purposes.

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