Occurrence, growth, and relative value of lodgepole pine and Engelmann spruce in the interior of British Columbia

The study was concerned with lodgepole pine, Pinus contorta Douglas and Engelmann spruce, Picea engelmannii Parry, particularly in the southern interior of British Columbia. Classifications of the forests of the Province as well as distribution, silvics, effects of fire upon succession, forest associations, and productivity classes of the two species were described. Sample plots were located in the Interior Douglas-fir and Engelmann Spruce - Alpine Fir Biogeoclimatic Zones. Hohenadl's form factor was used to compute volume growth by individual decades from stem analyses. On 124 plots, 137 trees were collected for stem analyses, 108 saplings were used for height - age studies, 100 point samples were made for determining basal area and stand volume and several hundred heights as well as diameters and borings at breast height, were taken. Thirty-four stand variables were subjected to multiple correlation analyses, particularly in regard to forest associations and growth of height, diameter at breast height and volume of the two species. Simple regressions were used to estimate height growth of several species on similar sites, and to compare several methods of volume calculation. Trees of the same diameter at breast height grown in different competitive positions (open, moderate to dense, and suppressed), contained different volumes. The largest volume of individual trees was found with trees grown in moderate to dense competitive position. Individual young lodgepole pines had a faster increment of height, diameter at breast height, and volume, than Engelmann spruces. This trend remained the same in yield tables based on individual tree studies and constructed for stands of good (average site index 100 ft. at 100 years), medium (average site index 70 ft. at 100 years), and poor (average site index 50 ft. at 100 years) productivity classes. The mean annual increment of volume of stands culminated earlier in lodgepole pine than in Engelmann spruce. The periods required were (in brackets are shown attained average diameters at breast height, total heights and volumes per acre). In the good productivity class in lodgepole pine 40 years (8.3 in., 58 ft., 6,700 cu.ft.) and in Engelmann spruce 75 years (10.0 in., 80 ft., 6,000 cu.ft.); in the medium productivity class in lodgepole pine 60 years (6.5 in., 50 ft., 4,600 cu.ft.) and in Engelmann spruce 130 years (9.0 in., 84 ft., 5,100 cu.ft.); in the poor productivity class in lodgepole pine 85 years (5.3 in., 45 ft., 3,100 cu.ft.) and in Engelmann spruce 150 years (6.3 in., 66 ft., 3,400 cu.ft.). Yield table volumes per acre in lodgepole pine were larger than those of Engelmann spruce, in the good productivity class, to the age of 120 years, in the medium productivity class to 150 years, and in the poor productivity class for an undetermined period. Present and suggested future trends of utilization and management of stands of the two species were reviewed. Generally, forest management in British Columbia shows a trend toward more intensive forest utilization, due to the increasing demand for wood. Smaller diameter trees and "smallwood" stands will be more and more frequently utilized. Utilization of whole trees, highly mechanized "harvesting" and transportation as well as intensified management of forest stands will compensate for increasing costs due to utilization of smaller diameters. Under intensive management, lodgepole pine deserves special consideration. It is as well-suited for artificial establishment of stands by planting as Engelmann spruce, but should cost less. Its value for the woodworking industry is similar to that of Engelmann spruce. However, on a rotation of maximal mean annual increment, its volume yield per acre unit will be higher than that of Engelmann spruce, and it should yield a higher rate of return on invested capital.

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