Yellow-cedar are dying in Alaska: scientists now know why

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edfrank
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Yellow-cedar are dying in Alaska: scientists now know why

Post by edfrank » Fri Feb 03, 2012 2:36 pm

Yellow-cedar are dying in Alaska: scientists now know why

USDA Forest Service
Pacific Northwest Research Station
Dying yellow-cedar tree. Photo: Paul Hennon
Dying yellow-cedar tree. Photo: Paul Hennon
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Yellow-cedar in West Chichagof-Yakobi Wilderness Area, a pristine area of coastal Alaska, faces intensive mortality. Photo: Paul Hennon Yellow-cedar 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.
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.”

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.aibs.org/bioscience/current_issue.html
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 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
3b_cedar_map_cropped-sml.jpg (105.86 KiB) Viewed 1298 times
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Don
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Re: Yellow-cedar are dying in Alaska: scientists now know wh

Post by Don » Fri Feb 03, 2012 7:26 pm

Ed-
There are many signs that the seemingly minor changes in average temperatures (plus or minus 2 degrees F) have extensive regional impacts (Kenai Peninsula Spruce, numerous receding glaciers, and now yellow cedar decline).
Regarding the yellow spruce scenario where a cold snap happening in the absence of protective snow cover, this is not a common scenario in southeastern Alaska where the marine influence is immediate and pervasive. Southeastern Alaska is primarily an archipelago of islands with shoreline mainland, before ascending into Canada. Known primarily as a temperate rainforest, their precipitation is primarily in fluid state.
Further north, and from the perspective of a human occupant of Anchorage, the winter of 1995/1996, the first snowfall wasn't recorded until the fourth week in January, which prevented insulation of ground from severe cold temps in November/December...the result? Even in a municipality with building codes requiring water/sewer lines to be installed 10' below ground level, many contractors worked overtime repairing frozen/broken pipes.

One of the takehome messages for me from this article, is that any management activities that impact soil stability MUST be reconsidered and prevented. While money spent trying to protect the yellow cedar should be resisted, any money spent that imperils it should be halted. We shouldn't be adding to the problem.
-Don
Don Bertolette - President/Moderator, WNTS BBS
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