DEVELOPMENT OF WOOD DECAY IN WOUNDED WESTERN HEMLOCK AND SITKA SPRUCEIN SOUTHEAST ALASKA

Sixty-eight western hemlock (Tsuga heterophylla (Raf.) Sarg.) and 51 S itka spruce (Picea sitchensis (Bong.) Carriere) trees with bole wounds were selected from six locations in southeast Alaska. Each tree was d issected and measured for extent of internal stain and decay to determ ine wood volume losses over time caused by fungi. The margins of stain and decay associated with bole injuries that ranged from 1 to 80 year s old were marked on the surface of 30 cm long hole segments of each t ree and then photographed. Areas occupied by stain and decay were meas ured for each bole segment using AutoCAD digitizing techniques and the n the amount of affected volume was computed for each tree. In regress ion models, original scar width, original scar area, and a transformat ion of scar age are significantly correlated with the In(volume of sta in + decay) for hemlock; original scar length and a transformation of original scar width are significantly correlated with volume of stain + decay for spruce. Decay extended less than 1 m above wounds and cons umed less than 5% of gross tree volume in all but a few trees which ha d large, old scars. Decay development in hemlock was less extensive th an reported in Oregon and Washington; models from these areas greatly overestimate decay in wounded trees in southeast Alaska. Tangential ca llus growth (one side of the wound) was 2.1 and 1.7 mm/year for spruce and hemlock, respectively. Forest managers may use this information t o design stands with acceptable heart rot levels by predicting the dev elopment of decay in wounds and by altering schedules of stand thinnin g and final harvest of wounded trees.