Forest & Grassland Health

Brown Bear Damage to Yellow-Cedar

Ursus arctos L.

Host(s) in Alaska:

Yellow-cedar (Callitropsis nootkatensis)

Habitat(s): lower tree boles, often on the uphill side of tree

Photos

Click on image for larger version.

An older scar on a yellow-cedar tree bole caused by brown bear feeding.

An older scar on a yellow-cedar tree bole caused by brown bear feeding.

A very fresh bear scar on yellow-cedar.

A very fresh brown bear scar with teeth marks from Poison Cove on Chichagof Island in mid-May.

Teeth marks and peeled bark resulting from brown bear feeding on yellow-cedar.

Teeth marks and stripped bark caused by brown bear feeding damage to yellow-cedar.

 

Current Status & Distribution in Alaska (2018 Update)

Little is known about fluctuation in the incidence of spring brown bear damage to yellow-cedar tree boles from year to year. Damage occurs where the range of brown bears overlaps the range of yellow-cedar in Southeast Alaska, especially Baranof and Chichagof Islands.

Historic Activity

Surveys conducted in the 1980s found that over half of the yellow-cedar trees in some stands were scarred by brown bears while other tree species were unaffected (Hennon et al. 1990).

Symptoms, Biology & Impacts

Yellow-cedar trees on Baranof and Chichagof Islands are often wounded in the spring by brown bears. The incidence of bear damage tends to be greatest in productive stands with deep soils that are less likely to experience yellow-cedar decline. Brown bears use their teeth to rip away bark from lower tree boles, usually on the uphill side of the tree, apparently to feed on the inner bark tissue. Bear damage does not typically kill trees. Callus tissue slowly develops around wounds. Bear scars likely serve as entry points for stem decay fungi that reduce wood volume.

Survey Method

Most studies were conducted on Chichagof and Baranof Islands (northeast of Sitka at Peril Strait, Slocum Arm, and Kennel Creek) but also on Prince of Wales Island (near Control Lake) and Wrangell Island (near Rainbow Falls). It was important to include study locations where brown bears are rare or absent (Prince of Wales and Wrangell Islands) for comparison. The occurrence and size of basal scars were noted for 779 Alaska yellow-cedars as well as for other associated tree species. See Hennon et al. 1990 for more details.


Links to Resources & Publications

Hennon, P. E.; McKenzie, C. M.; D'Amore, D. V.; Wittwer, D. T.; Mulvey, R. L.; Lamb, M. S.; Biles, F. E.; Cronn, R. C. 2016. A climate adaptation strategy for conservation and management of yellow-cedar in Alaska. Gen. Tech. Rep. PNW-GTR-917. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 382 p. Available here, see page 77. 

Hennon, P.E.; Hansen, E.M.; Shaw, C.G., III. 1990. Causes of basal scars on Chamaecyparis nootkatensis in southeast Alaska. Northwest Science 64(2): 45–54. Available here.

 

Content prepared by Robin Mulvey, Forest Pathologist, Forest Health Protection, robin.mulvey@usda.gov.

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