in West Chichagof-Yakobi Wilderness Area, a pristine area of coastal
Alaska, faces intensive mortality. Photo: Paul Hennon
PORTLAND, Ore. February
1, 2012. Yellow-cedar, a culturally and economically valuable
tree in southeastern Alaska and adjacent parts of British Columbia,
has been dying off across large expanses of these areas for the
past 100 years. But no one could say why—until now.
“The cause of tree death, called yellow-cedar decline, is
now known to be a form of root freezing that occurs during cold
weather in late winter and early spring, but only when snow is
not present on the ground,” explains Pacific Northwest Research
Station scientist Paul Hennon, co-lead of a synthesis paper recently
published in the February issue of the journal BioScience. “When
present, snow protects the fine, shallow roots from extreme soil
temperatures. The shallow rooting of yellow-cedar, early spring
growth, and its unique vulnerability to freezing injury also contribute
to this problem.”
Yellow-cedar decline affects about 60 to 70 percent of trees in
forests covering 600,000 acres in Alaska and British Columbia.
The paper, “Shifting Climate, Altered Niche, and a Dynamic
Conservation Strategy for Yellow-Cedar in the North Pacific Coastal
Rainforest,” summarizes 30 years of research and offers a
framework for a conservation strategy for yellow-cedar in Alaska.
Some key findings include:
- The complex cause of yellow-cedar decline
is related to reduced snow, site and stand characteristics, shallow
rooting, and the
unique vulnerability of the roots to freezing in low temperatures.
snow levels and poor soil drainage lead to impact root injury
and the eventual death of yellow-cedar trees. The tree thrives
in wet soils, but its tendency to produce shallow roots to
access nitrogen on these sites made it more vulnerable when spring snow
levels were reduced by climate warming.
- Yellow-cedar health
depends on changing snow patterns, thus locations for appropriate
conservation and management activities need
to follow the shifting snow patterns on the landscape.
- Some responses to shifting
climate are expected to be complex and difficult to anticipate.
Long-term multidisciplinary research
was needed to determine the true role of climate in the health of yellow-cedar
and untangle it from other processes and natural cycles in
The yellow-cedar is a slow-growing tree; many are 700 to 1,200
years old. The tree has long been culturally significant
to Native Alaskans who use it to make paddles, masks, dishes, and woven
items. The wood is also very valuable commercially (for
home and boat
building) because of its straight grain, durability, and
resistance to insects.
Attention is now directed toward a solution to protect
and manage yellow-cedar, as coastal Alaska is expected to experience
snow but a persistence of periodic cold weather events
in the future.
Scientists are working with partners in the Alaska Region of the
Forest Service to use this new information as the framework for
a comprehensive conservation strategy for yellow-cedar in Alaska
in the context of a changing climate.
We also have ongoing projects with colleagues in the Tongass National
Forest in Alaska on planting and thinning to favor yellow-cedar
on suitable habitat,” adds co-lead author and station scientist
Dave D’Amore, “especially on well-drained productive
soils where most of the commercial forestry exits. Silvicultural
techniques can be used to nudge the ecological niche of yellow-cedar,
making it more competitive on these favorable sites.”
Other coauthors of the synthesis are Paul Schaberg, U.S. Forest
Service, Northern Research Station; Dustin Wittwer, U.S. Forest
Service, Alaska Region; and Colin Shanley, The Nature Conservancy.
(Photos are available on request.) Read the paper online at http://www.treesearch.fs.fed.us/pubs/40035.
Yellow-cedar trees grow in California to Prince William
Sound in Alaska. Yellow-cedar decline occurs along a 600-mile
zone from British Columbia to southeast Alaska; and on about
one-half million acres in southeast Alaska. Map: Colin Shanley,
The Nature Conservancy
yellow-cedar tree. Photo: Paul Hennon
The PNW Research Station is headquartered in Portland, Oregon.
It has 11 laboratories and centers located in Alaska, Oregon,
and Washington and about 425 employees.