SITKA spruce: uses, growth, management. 23 
which spreads quickly through the sound wood and renders much 
of the upper trunk unmerchantable. Damage from this cause is 
very common in trees over 300 years of age. Wind-shake is a me- 
chanical defect resulting from heavy stresses in the butt section 
which are caused by the action of severe winds, and is of infrequent 
occurrence in large trees. This circular or radial rupture of the 
wood considerably reduces the value of the tree for lumber. 
BURLS. 
Another injury is the formation of huge burls along the trunks. 
This defect has been found abundantly in a limited area in Oregon. 
The illustrations in Plate XIX are typical examples of the defect. 
Its cause is uncertain, though probably analogous to similar mal- 
formations in many other species. 
FIRE. 
Sitka spruce is fortunate in having as its habitat a region in 
which there is less forest-fire hazard than in most parts of the conif- 
erous forest regions of western North America. Frequent rains 
throughout the year in southeastern Alaska make fires in the virgin 
spruce woods there quite uncommon; farther south in Washington 
and Oregon there is more danger of forest fires in the short dry 
season. Fires in this region are apt to run in the crowns of the 
trees, and they do so even in the spring months when the surface 
litter is still too wet to burn. The moss that hangs on the branches 
of the hemlock, spruce, and fir trees is very inflammable and helps 
to carry fire. The spruce region of Oregon suffered from several 
very disastrous and widespread fires a few decades ago, as the 
" burns " of the Coast Range witness. 
Sitka spruce is very susceptible to fire. This is due chiefly to its 
thin bark, which at stump height is only a half -inch to an inch 
thick. Fire-scars are uncommon in Sitka spruce, for even a very 
light surface fire is sufficient to kill the cambium, and the trees, 
thus girdled, die. 
Although an individual tree of Sitka spruce is more susceptible 
to injury than a Douglas fir of the same size, the forest in which it 
grows along the coast is less subject to fire than the forest farther 
inland where Douglas fir predominates. Even though the danger of 
uncontrollable fires is less in the Coast Range than in the Cascade 
Range, careful fire protection in both regions is imperative. 
GROWTH. 
Sitka spruce is one of the most rapid-growing coniferous species 
in the Pacific Northwest. In keeping with the character of spruces 
in general, its growth during the first few years is less than that of 
