UBC Undergraduate Research

Productivity of mixed-species vs. single-species forest stands : an analysis of a mixed lodgepole pine-interior hybrid spruce spacing trial in interior British Columbia Carsky, Grace


Though most forest plantations are planted with a single species, there has been a push in forest management to switch to mixed species stands. To further understand the effects of density and species mixture on size, growth, and yield in pure- and mixed-species plots, this thesis analyzes a 20-year-old mixed lodgepole pine – interior hybrid spruce installation across three densities (1000, 1500, and 2000 stems per hectare [SPH]) and five species mixtures (1:0, 3:1, 1:1, 1:3, and 0:1 Pine:Spruce [Pl:Sx]). Results show that there is no interaction between density and mixture, but both factors have a significant effect on total volume per hectare, merchantable volume per hectare, and total basal area per hectare. Differences in density and mixture levels were significant between 1000 and 2000 SPH and between mixtures 3:1 and 1:3 Pl:Sx, mixtures 1:0 and 1:3 Pl:Sx, and mixtures 1:0 and 1:1 Pl:Sx. Pure pine plots (1:0 Pl:Sx) at a density of 2000 SPH resulted in the highest yield, but the 3:1 Pl:Sx treatment at a density of 2000 SPH showed potential for higher yield. Although monocultures tend to yield higher total volumes, planting mixed-species stands that produce similar volumes provides additional increases to pest and disease resistance and biodiversity.

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