New study sounds alarm, provides hope for western redcedars
First peer-reviewed research links cedar death to climate, details which trees are dying, which are surviving and how the species might be saved
By Nathan Gilles. February 23, 2023. Columbia Insight
Though no one realized it at the time, the beginning of the end for many Pacific Northwest western redcedar trees began about a decade ago.
Drought had come.
Early on, the cedars did what trees do: they adapted to the dry conditions. They conserved water and grew less.
This strategy had worked during past droughts. This time would be different. Some trees wouldn’t make it.
The drought was relentless. One drought year followed the next. Multiple summers during these drought years would be uncommonly long, warm and dry, especially on the coast.
All of this stressed the region’s western redcedars until it become too much.
For many, growth, already sluggish, stopped entirely and death came.
In 2017 and 2018, Oregon and Washington western redcedars would experience “anomalously high mortality rates,” according to a new study currently under review at the scientific journal Global Change Biology.
“It’s repeated droughts that is causing this tree mortality,” says study lead author Robbie Andrus, postdoctoral researcher at the Washington State University.
To arrive at this conclusion, Andrus and his fellow researchers collected tree ring core samples from both living and dead western redcedars in Oregon and Washington.
They then compared the tree ring data to recent climate data recorded for each location where the rings were collected.
Drought was strongly correlated with slower tree growth (thinner tree rings) and eventually tree death (partial tree rings), according to the study.
The lag of four to five years, says Andrus, suggests it took multiple years of drought-induced stress to eventually kill the trees.
This pattern was so consistent that fully 80% of coastal western redcedars sampled by the researchers died in 2017 and 2018, just four to five years after the trees started slowing their growth in response to drought, according to the study.
Nathan Gilles 