FOREST TREES OF THE PACIFIC SLOPE. 81 



Grows fairly on dry soils, but usually gives way on porous soils to lodgepole pine, Douglas 

 fir, and to other trees requiring better drainage. Does well on retentive, line, loamy soils, 

 but attains best growth on deep, rich soils of gulches and river valleys. A shallow root- 

 system enables it to grow on thin soils of slopes and on wet margins of rivers, lakes, 

 and swamps. Forms extensive pure forests and also occurs in mixed stands. Pure stands 

 are somewhat more frequent in south than in north, where it chiefly meets tries of sim- 

 ilar silvical requirements but of less extended southern range. .Most generally with 

 alpine fir and sparingly with Douglas fir near its lower limits. In Blue Mountains of 

 Washington and Oregon, with western larch, lodgepole pine, alpine and lowland firs, and 

 Douglas fir. In Washington, occasionally in pure stands, but usually with amabilis fir, 

 alpine fir, Lyall larch, black hemlock, yellow cedar, and white-bark pine. In Cascades of 

 Oregon, with alpine, noble, and amabilis firs, Douglas fir, black hemlock, and lodgepole 

 pine. 



Climatic Conditions. — Subject to varied climatic conditions. Annual precipitation 

 averages over 25 inches; is largely snow. Seasonal temperature, with a minimum in 

 north of approximately 40° F., and maximum of about 95° F. in south. Daily range of 

 temperature great at upper levels, but less at lower altitudes and on north exposures. 

 Near timber line the growing season is about two months, and freezing occurs almost 

 nightly, resulting in very slow growth ; while at lower elevations the growing season is 

 about four months and frosts are less frequent, permitting a more rapid growth. 



Tolerance. — Very tolerant of shade, surpassing most of its associates in this respect ; 

 endures years of shading and makes good growth when released from suppression. Owing 

 to great tolerance, it forms close stands of many ages and preserves good forest condi- 

 tions. Somewhat more tolerant in youth than in old age. 



REPRODUCTION. — A prolific seeder over most of range. Heavy seed years occur locally 

 at 3-year intervals. Seed with high rate of germination and persistent vitality. Produces 

 seeds from about twenty-fifth year to an advanced age. Seeds germinate best in moist 

 mineral soil; seedlings rarely found in humus. Notwithstanding prolific seed produc- 

 tion, seedlings are not generally abundant. They are most numerous in small protected 

 openings in the forest. Low branches of isolated trees also favor germination and 

 protect seedlings, through which groups of trees are built up, and which combine with 

 other groups to form continuous stands. 



Sitka Spruce; Tideland Spruce. 

 Picca sitchensis (Kong.) Trautvetter and Mayer. 



DISTINGUISHING CHARACTERISTICS. 



Sitka spruce growing in dense stands is tall, and has short thin open conical 

 crowns of small branches and long clean trunks of only moderate taper. In 

 open stands, or as it occurs singly, it develops a shorter, but still tall, rapidly 

 tapering stem with branches down to or near the ground. The crown is still 

 open, narrow and sharp in its upper part, but very broad at the bottom, where 

 the huge branches are often 20 or 30 feet long. The branches have many hang- 

 ing slender side branchlets from U to 3$ feet long. It is a very large and 

 massive tree when fully grown, attaining a height, exceptionally, of from 160 to 

 ISO feet, wilii a diameter of from S to 12 feet, 5 or 6 feet above ground. Still 

 larger trees are reported. Ordinarily it is from SO to 125 feet high and from 

 40 to 70 inches in diameter. Forest-grown trees are clear of brandies for from 

 40 to 80 feet, or more. The bases of big trunks are swelled by enormous but- 

 tresses. The bark is scaly on very young trees; on large trees it is thin (one- 

 half inch thick), is dark purple or deep reddish brown, and has big thin, easily 

 detached scales. Twigs of the year are always smooth anil dark yellow-brown. 

 The foliage is a bright yellow-green. The bristling habit of the often keenly- 

 pointed leaves, which stand out straight .all around the branches (fig. 30), render 

 it prickly to the touch. The leaves are tiat. only very Indistinctly 1 angled, 

 stiff, and rather thick. The cones mature in one season, and hang down con- 

 spicuously from the branches. They vary in length from about 2 to 4 indies 

 dig. :'.()). Soon after maturity, during early fall, their thin papery scales open 

 and shed their small seeds (tig. 30, a) in a short time. Most of the cones fall 



