ROOT SPREAD CAN BE ESTIMATED FROM CROWN WIDTH OF DOUGLAS FIR, LODGEPOLE PINE, AND OTHER BRITISH COLUMBIA TREE SPECIES

Abstract

Knowledge of the relationships between lateral root spread and crown width is needed to guide plans for providing optimum space per tree during silvicultural operations. Crown width is a valuable indicator of root spread of open-grown Douglas fir, lodgepole and ponderosa pines, and white, Engelmann and Sitka spruces. The association between root spread and crown width is less reliable in forest-grown trees but still useful.Detailed studies of root systems were made by excavation of roots of trees blown down in the U.B.C. Campus Forest by a typhoon in October, 1962. Roots of 89 Douglas fir, 81 western hemlock, 61 western red cedar, and 33 red alder trees were mapped and analyzed in relation to 18 tree and stand variables. In addition, average and maximum root depth, number of main roots, the ratio of maximum to average root spread, and portion of rooting zone occupied by roots were studied.Average and maximum radius of roots of Douglas fir and lodgepole pine were analyzed in relation to crown width, d.b.h., height, age and other tree and stand characteristics. Appropriate regression and correlation analyses were completed for all species and the possible advantages of ratio estimates were noted.Ratios of root spread to crown width were influenced by species, stand density, and kind of soil. Ratios averaged 1.1 for open- and 0.9 for forest-grown Douglas fir but were 2.4 for both open- and forest-grown lodgepole pine on peat or poorly drained soils.