FOREST TREES OF THE PACIFIC SLOPE. 71 



of soil moisture ; best in deep, fresh, porous soils, but thrives on low, moist sites and in 

 dry, gravelly soils. 



Sometimes forms pure stands, but usually in mixed stands. Its best growth is in 

 northeastern Washington, northern Idaho, and northwestern Montana, where it often 

 occurs in pure open forests in valleys and slopes. In the Blue Mountains of Washington 

 and Oregon, on typical flats. Bere, also, anas of this larch and lodgepole pine are inter- 

 spersed through the forest of Engelmann spruce, white and lowland firs, and Douglas 

 fir ; the silvical characteristics of larch and lodgepole pine appear very similar in view of 

 common association. Of largest size at lower elevations along Priest River (Idaho), in 

 mixture with western white pine, western red cedar, Douglas fir, western hemlock, Engel- 

 mann spruce, and lowland fir. It is a more important part of Douglas fir forests some- 

 what higher up, where ir is associated also with lodgepole and western white pines, 

 lowland and alpine firs. Engelmann spruce, cottonwoods, and birches. In Bitterroot 

 mountains (northern Idaho), in pure stands or with slight admixtures of Douglas fir and 

 western yellow pine. 



Climatic Conditions. — Seasonal precipitation, from about 20 to about 30 inches, 

 with a moderately heavy snowfall remaining on ground until summer. Rains frequent 

 in spring and fall, but summers hot and dry. 



Tolerance. — Very intolerant of shade throughout life ; probably demands even more 

 light than western yellow pine. This intolerance partly compensated for by early rapid 

 height growth, which carries it above suppressing heavier-foliaged associates. Appears 

 more tolerant on moist than on dry soils. In moist sites it grows in fairly dense stands, 

 and is tall, with a clear bole, and its lower branches are early killed and dropped ; while 

 on drier soils open stands or isolated trees occur with branches often retained to 1 1n- 

 ground. 



Reproduction. — A prolific seeder, but locally variable in seed production ; sterile 

 periods of from one to several seasons are likely to intervene. Rarely bears seeds as 

 early as the 25tb year, but begins to bear prolifically at 40 or 50 years. Seed has a 

 fairly high rate of germination and moderately persistent vitality. The thin scales of 

 ripe cones open and close very readily with alternate dry and wet weather, so that the 

 period and the rapidity of seed dispersion vary somewhat with local climatic conditions. 

 Usually much seed is shed on snow. Abundant moisture required for germination and 

 growl h of seedlings. The chief competitor of larch is lodgepole pine, both finding suit- 

 able seed heils in burned-over areas with exposed mineral soil, where the kind of repro- 

 duction depends upon whether larch or pine has seeded first. If lodgepole pine has the 

 start, it shades out the more intolerant larch. If both species start together, larch may 

 preserve its numerical importance in the stand by more rapid growth. Its light foliage 

 can not prevent the growth of the pines, or of spruce and firs, and the typical occur- 

 rence of larch in mixed stands is a result. Favorite areas for pure larch reproduction 

 are those so thoroughly burned over as to preclude the immediate heavy reproduction of 

 lodgepole pine. 



Alpine Larch. 

 Larix lyallii Parlatore. 



DISTINGUISHING CHARACTERISTICS. 



The strictly alpine habitat of Alpine larch serves very largely to distinguish 

 it from the Western larch, which it resembles in some features. It is stunted in 

 appearance, from 30 to 40 feet high and from 10 to 24 inches in diameter, with a 

 long, broadly pyramidal, pointed crown. Some of the branches are very long and 

 big, forming an open unsymmetrical crown. Somewhat larger trees are some- 

 times found. As a rule, the ends of the branches turn upward, but frequently 

 they droop conspicuously, while, in contrast with the brittle branches of Western 

 larch, they are tougb anil withy. A notable character of the new branch shoots 

 is their dense coating of white, fine wool, which is retained, more or less, for 

 two seasons, and from which the tree gained the name of "woolly birch." 

 Trunks are clear of branches for only about one-third or one-half the tree's 

 height, and. as a result of exposure, are often crooked or bent. The bark of 

 mature trees is rarely more than seven-eighths of an inch thick. It is indis- 

 tinctly furrowed; the irregular. Hat ridges of loose scales are deep purplish or 

 reddish brown. On young trees the bark is usually unbroken until they are 5 

 or <; inches in diameter. Previously it is ashy gray, as are the crown branches 

 of older trees. The foliage is distinctly light hluish-greeu, turning bright lemon- 



