16 BULLETIN 1060, U. S. DEPARTMENT OF AGRICULTURE. 



LIGHT REQUIREMENTS. 



Sitka spruce, unlike other spruce, is somewhat intolerant of shade. 

 Compared with its associates, it is less tolerant than western hem- 

 lock and western red cedar and about as tolerant as Douglas fir. 

 Seedlings can endure heavy shade and on old burns and logged-over 

 areas establish themselves with little difficulty under the dense cover 

 of deciduous brush, such as salmonberry and huckleberry, and of 

 other coniferous seedling growth ; but strangely enough Sitka spruce 

 is seldom found under the heavy canopy of a mature stand. Here 

 temperature, not tolerance, is thought to be the governing factor, 

 and the coolness in the mature stands prevents, whereas the warmth 

 in the openings permits, the germination and establishment of spruce 

 seedlings. As the tree advances in age it demands overhead light, 

 and dies if long overtopped. 



The dead side branches, which are often moss-covered stubs 2 or 3 

 feet long and characteristically coarse and stiff, are very persistent 

 in young spruce. The shedding of the dead limbs and cleaning of 

 the bole starts when the trees are about 50 years old and often is not 

 completed for a century or more. (PL XII and PL XIII (fig. 1.)) 



REPRODUCTION. 



SEED PRODUCTION AND DISSEMINATION. 



Sitka spruce is a prolific seeder. Open-grown trees commence to 

 bear seed at 35 years of age, and trees of all sites are vigorous pro- 

 ducers of seed until maturity. Some seed is produced each year 

 and heavy crops are yielded every three or four years. The cones 

 mature in the early fall of the first year and, under normal condi- 

 tions, open and release the seed within a short period afterwards. A 

 mature tree with a full crown may produce, in a good seed year, 4 to 

 6 bushels of cones, which yield from 0.65 10 to 1.25 X1 pounds of clean 

 seed. A pound of these seeds will number between 200,000 and 300,- 

 000. Because of their small size and relatively large wings they are 

 often carried by the wind 400 feet or more from the base of the tree. 

 Many of the seeds filter into the deep duff of the forest floor and are 

 stored, their hard covering keeping them viable for several years. 

 The seed has a high percentage of germination. In tests 12 of fresh 

 commercial seed under greenhouse conditions, this amounts to 72 per 

 cent, and is higher than the germination percentage of western hem- 

 lock, western red cedar, and Douglas fir as determined in similar tests. 



10 " Sitka Spruce in Alaska," by B. E. Hoffman. Forest Service manuscript report, p. 9 

 1912. 



11 " Reforestation on the National Forests," by C. R. Tillotson. U. S. Dept. Agr. Bull. 

 475, p. 17, 1917. 



u " Seeding and Planting," by J. W. Tourney, p. 122, 1916. 



