The Vital Role of Snow in Protecting Yellow-Cedar from an Extensive Forest Decline in Alaska

TitleThe Vital Role of Snow in Protecting Yellow-Cedar from an Extensive Forest Decline in Alaska
Publication TypeConference Proceedings
Year of Conference2007
AuthorsHennon, P. E.
Conference Name75th Annual Western Snow Conference
Series TitleProceedings of the 75th Annual Western Snow Conference
Date PublishedApril 2007
PublisherWestern Snow Conference
Conference LocationKailua-Kona, HI
KeywordsYellow cedar, tree mortality, spring freezing, snow depth, climate change

Yellow-cedar (Chamaecyparis nootkatensis) is a culturally and economically important tree in Alaska that has been suffering from a severe mortality problem. Recent research indicates that a number of site factors predispose yellow-cedar to freezing injury in spring. Aerial surveys identified nearly the entire broad distribution of decline, which covers about ½ million acres of forestland. This broad distribution of dead and dying forests aligns closely with the lowest snow accumulation zone in a regional snow model. At the mid-spatial scale, analysis of color infrared photographs revealed that cedar decline is limited to lower elevations, but extends somewhat higher on southerly aspects where snowmelt likely occurs earlier in spring. Measurements of forest trees, snow depth (by remote digital cameras), and hourly soil temperature at the finest spatial scale (small watershed) indicated that cedars remain healthy where snow persists through April. Snow apparently protects yellow-cedar in spring by either the delay of dehardening (loss of cold tolerance) by postponing the onset of soil warming, or by providing insulation from soil temperatures lethal to cedar roots (-5?C). Yellow-cedar decline serves as an early example of the damaging ecological consequences of climate warming and, particularly, the detrimental effects of reduced snow pack.