SITKA spruce: uses, growth, management. 15 
The underbrush, which in both the pure and mixed forests is 
extremely large and dense, is composed of salmonberry, huckleberry, 
vine maple, salal, devil's club, elderberry, and cascara, with a pre- 
ponderance of the first two species. The ground cover consists chiefly 
of braken. sword ferns, and moss. 
The volume of spruce per acre in the virgin stand varies greatly 
with the proportion of species, the density of stocking, and the quality 
of the site. The heaviest yields are naturally produced in properly 
stocked stands on sites where the best growth of individual trees is 
made. County cruise estimates indicate that the stand of merchant- 
able timber in what would be classed as spruce type (running all the 
way from 25 per cent to 65 per cent of spruce) varies from 20,000 to 
100,000 feet per acre over large areas. Very much heavier, as well as 
lighter, stands occur in the virgin woods. 
CLIMATIC AND SOIL REQUIREMENTS. 
Sitka spruce is very exacting in its soil and atmospheric moisture 
requirements. An abundance of rainfall, frequent fogs, and tempera- 
tures moderated by proximity to the sea are the climatic character- 
istics of the north Pacific coastal strip where this species grows. The 
yearly precipitation is 75 to 150 inches or more and comes chiefly in 
the form of rain, well distributed throughout the year, except for 
about two months in midsummer. Cloudy or partly cloudy days are 
frequent, and weather records show an average of 240 such days in a 
single year at one station in the heart of the spruce region. The tem- 
perature of the region is generally mild, the annual mean ranging 
from 38° F. in Alaska to 53° in northern California. Extreme tem- 
peratures of 15° below zero in Alaska and 102° above in California 
are encountered within the range of the tree ; but withal it may very 
readily be seen that Sitka spruce occurs only on areas that offer 
climatic advantages favorable for growth. 
Its soil requirements, however, are not so distinctly defined, and 
thin, rocky soils on the slopes, pure sand along the coast, and deep, 
rich alluvial deposits of rivers share equally, under similar condi- 
tions of climate, in the distribution of the species; but the trees are 
larger and reach better development on bottom lands of moist, friable, 
sandy loam. It is noteworthy that in Alaska the heaviest stands of 
spruce and those of best quality are found on limestone soils, perhaps 
partly because these are the deepest and most completely decomposed. 
Though this species demands a very great amount of soil moisture 
and can grow on swampy sites, it attains its best development on soils 
of good drainage. 
