THE TYPE. 



ECONOMIC IMPORTANCE. 



There can be no question of the economic importance of the com- 

 posite type, with its average yield of 14,100 board feet per acre, 

 especially in the forests of Arizona and New Mexico, where typical 

 stands of western yellow pine yield only from 4,000 to 7,000 board 

 feet. Moreover, a combination of three species, each having dif- 

 ferent requirements, makes possible a complete utilization of the 

 ground, thus satisfying one of the objects of silviculture — the pro- 

 duction of the greatest possible amount of timber per unit area. 



Economically, there is but little difference between Douglas fir 

 and western yellow pine. Douglas fir has a much larger percentage 

 of heartwood, and for some purposes will make better lumber. In 

 the Southwest, however, there is a strong prejudice against the tree, 

 though this can no doubt be overcome in the future. The spruce is 

 largely sapwood, and because of this and its small size is of little 

 value for lumber. It could, however, be utilized in mines after 

 preservative treatment. The white pine fails to develop into a good 

 timber tree, and the white fir, though often of good form, makes a 

 poor grade of lumber. In the event of timber sales these secondary 

 species could be utilized to some extent. 



FUTURE COMPOSITION. 



The reproductive capacity of the three chief species of the com- 

 posite type is the most important factor in determining the probable 

 composition of the forest after a cutting. Both spruce and Douglas 

 fir bear cones at more frequent intervals and probably at an earlier 

 age than western yellow pin,e. The interval between seed years of 

 spruce is shorter thfan for the other species, and for this reason the 

 total amount of seed produced is probably greater, though the germi- 

 nation per cent is no doubt considerably lower. 



Here, as on most forests in the Southwest, the reproduction which 

 succeeds in establishing itself is the result of a combination of good 

 seed years and favorable climatic conditions. Seedlings of yellow 

 pine establish themselves most readily in the larger openings, where 

 they receive the necessary amount of light. The quantity of seed 

 produced and the frequence of seed years are important factors, 

 since the climatic conditions of every season are by no means favor- 

 able to the growth of seedlings. With yellow pine, good seed years 

 occur at intervals of from three to five years. Blue spruce usually 

 bears some seed each year; Douglas fir every second or third year. 



Douglas fir and blue spruce, which are more tolerant, seldom if 

 ever compete with yellow pine seedlings in the larger openings. 

 These species germinate very well in dense shade, and will succeed 

 in growing for some time with but little direct sunlight. Douglas 

 fir seedlings are commonly found under mother trees, in aspen 

 thickets, and under groups of yellow pine seedlings and saplings 

 already large enough to cast an appreciable amount of shade. Blue 

 64473°— Bull. 125—13 2 



