Perilous
Times and Climate Change
Forestry officials shocked as Massive die off of
Yellow-cedar trees is hitting Alaska hard
by Staff Writers
Portland OR (SPX) Feb 06, 2012
Yellow-cedar in West Chichagof-Yakobi Wilderness Area, a pristine
area of coastal Alaska, faces intensive mortality. Credit: Paul
Hennon.
Yellow-cedar, a culturally and economically valuable tree in
southeastern Alaska and adjacent parts of British Columbia, have
been massively 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.
+ Low 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 forests.
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 less
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."