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THE ASTORIAN • THURSDAY, NOVEMBER 25, 2021
Scientists take stock of forest damage after extreme heat
By KALE WILLIAMS
The Oregonian
The trees in Oregon
weren’t ready for the heat
that sweltered over the state
in late June.
The heat dome brought
record temperatures for three
consecutive days across
the Pacifi c Northwest, and
researchers are still working
to tally the damage several
months later.
The devastating human
toll was immediately clear,
as more than 100 people died
in Oregon, most of whom
were in Multnomah County,
alone and in dwellings with-
out fans or air conditioners.
Hundreds more were made ill
across the region by the high
temperatures.
The heat had its eff ect
on animals, as well. In East-
ern Oregon, dozens of baby
hawks jumped from their
nests to try to avoid the heat.
But some victims of the
sky-high temperatures were
less obvious in the immedi-
ate aftermath: Oregon’s for-
ests. That was the subject of
a meeting of tree experts —
foresters, silviculturists and
botanists — who gathered
virtually last week to discuss
the what’s to come for the
state’s scorched treescapes.
“These trees are not accli-
mated to this kind of heat,”
said Kat Olson, lead sil-
viculturist at GreenWood
Resources, an asset manage-
ment company that oversees
more than 150,000 acres of
forest in Oregon and Wash-
ington. “We know there
will be signifi cant growth
impacts.”
That was the goal of the
Friday meeting, convened by
the Oregon State University
College of Forestry, to begin
looking at how excessive heat
aff ects one of Oregon’s most
valuable and beloved natu-
ral resources. Some of the
scorched trees will undoubt-
edly recover — and scientists
at this point can’t say how
many — but the long-term
prognosis for the state’s for-
ests after a heat wave of such
epic proportions will require
more in-depth research.
An unprecedented heat
event
A strong ridge of high
pressure began building over
the Pacifi c Northwest during
the last week in June. The
ridge forced air in the atmo-
sphere down, compressing
it and warming it in a phe-
nomenon known as sub-
sidence. That warm air was
then trapped in place by the
high pressure, forming a heat
dome.
The heat dome coincided
with a slight off shore fl ow
with winds coming from the
east, pulling dry air from the
high desert of southeastern
Oregon, which heated more
easily than air with higher
moisture content. That air,
too, was forced downward
as it blew over the west-fac-
ing slopes of the Cascades,
further heating as it was
compressed.
Oregon and much of the
western U.S. were also com-
ing out of an exceptionally
dry spring, leaving plants and
soil bereft of the moisture
that usually evaporates into
the atmosphere and provides
a modest cooling eff ect.
All of this was taking place
right around the summer sol-
stice, so the Pacifi c North-
west was absorbing more of
the sun’s energy than it did at
any other time of year.
The combination of all
of those factors combined
to make for record-breaking
heat across Oregon, Wash-
ington and parts of British
Columbia.
In the wake of the event,
climate change experts said
a heat dome of that severity
was made 150 times more
likely because of global
warming.
John Nohr, the fi re chief
for parts of Clark and Cowlitz
counties in Washington,
was driving down Interstate
5 when another fi refi ghter
asked if he’d noticed the
trees.
Hailey Hoff man/The Astorian
Trees in timberland outside of Astoria were scorched brown
in the heat wave.
‘HAVING A HEAT WAVE ATOP
A DROUGHT IS LIKE PUTTING
YOUR FOOT ON THE GAS ...
TOWARD TREE MORTALITY.’
leaves and needles, mostly
on the south and west sides,
which were fully exposed to
the sun for the hottest parts
of the day. The nature of the
damage quickly helped them
rule out drought or pests as
the cause.
He began surveying from
a small plane above the for-
ests of the Willamette Valley
and the Coast Range, fl ying
in grid patterns and mapping
where the trees were visibly
scorched.
In his limited surveys,
DePinte said at least 229,000
acres showed some damage,
with about half rated as “very
severe.” He also noted that
surveying by plane is inher-
ently limited in scope, and
the damage was likely much
more widespread.
“I knew we were not get-
ting 100% of the damage,”
DePinte said.
All plants have an opti-
mal growing temperature,
and when the temperature
is exceeded, photosynthesis
slows and they stop respirat-
ing. The high temperatures
of the heat dome, coupled
with the ongoing drought in
the Pacifi c Northwest, likely
pushed some trees to the
brink, said Bill Hammond,
an ecophysiologist from the
University of Florida.
“Having a heat wave atop
a drought is like putting your
foot on the gas ... toward tree
mortality,” Hammond said.
Bill Hammond | an ecophysiologist from the University of Florida
Not just natural forests
It was June 29 — one day
after the hottest day in history
in both Portland and Vancou-
ver, Washington — and Nohr
turned to see the needles
on every fi r tree had turned
brown on the side facing the
sun, seemingly overnight.
On Interstate 205, he saw the
same.
Daniel DePinte, a for-
est health specialist with the
U.S. Forest Service, needed
to know more about how
Oregon’s trees had fared than
could be observed from the
side of the highway. He had
begun receiving reports of
damage to trees soon after the
heat dome dissipated across
numerous species, includ-
ing Douglas fi r, ponderosa
pine, giant sequoia, western
red cedar, spruce, maple and
western hemlock.
Thermal imaging from
some forests near the coast
showed bark temperatures
near 122 degrees.
After visiting several
sites on the ground, DePinte
and other researchers saw
the damage for themselves.
Many trees had scorched
Olson, the silviculturist
with GreenWood Resources,
began similarly surveying
GreenWood Resource’s for-
estlands after the heat dome.
Her team looked at about 220
stands of trees spread over
17,000 acres.
A quarter of the stands
had moderate to severe dam-
age on at least 40% of the
trees, she said, with the worst
damage on southwest facing
slopes closest to the coast.
Older trees fared better, she
said, while many saplings did
not survive.
“If you were a poor lit-
tle baby Douglas fi r, you got
pretty much zapped,” she
said. “They are just sticks
now.”
Olson said her com-
pany would likely be plant-
ing between 600,000 and
800,000 additional trees
this year to make up for the
expected mortality.
Chal Lundgren, a Christ-
mas tree specialist at Oregon
State University, said similar
impacts were seen at Christ-
mas tree farms across the
region. Because most Christ-
mas tree farms are run with-
out irrigation and the Pacifi c
Northwest was already suf-
fering through a drought,
many young trees did not
survive.
Older trees, especially the
Noble, Grand and Fraser fi rs,
suff ered some scorch and on
some trees, the leader — the
top branch atop which a top-
per is generally affi xed for
Christmas — were bent and
limp.
What remains to be seen,
nearly everyone at the sym-
posium agreed, is what the
long-term prognosis will be
for trees damaged by the heat
dome. For that, time, and
more research, will tell.
The Astoria City Council
wishes everyone a
SAFE AND JOYOUS
HOLIDAY SEASON!
Wear your mask and enjoy
the lights and holiday
festivities while social
distance shopping in
Downtown Astoria
www.astoriadowntown.com
Friday, November 26, 2021
to Saturday, January 1, 2022
Customers can park downtown
longer than posted time limits
(except in metered spaces)
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