The effects of factorial combinations of post-thinning density (600, 1100, and 1600 stems per hectare [sph]) and repeated fertilization on the growth and development of young lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) were investigated in central British Columbia. After 14 years, the effects of density and multi-nutrient fertilization (applied at 0, 5, and 10 years) on tree height were small relative to the effects on tree radial increment. Individual-tree bole growth was greatest at the lowest stand density, whereas per-hectare volume gains were greatest at the highest residual density and declined with decreasing stand density. Stand volume gains following fertilization were less, in both relative and absolute terms, at 600 sph than at 1100 or 1600 sph. Over 14 years, mean total bole volume increment in fertilized treatments was 13.9 m3/ha (39%), 29.2 m3/ha (56%), and 33.5 m3/ha (59%) greater than that in the unfertilized treatment at densities of 600, 1100, and 1600 sph, respectively. Low conifer site occupancy and vigorous response of understorey vegetation to nutrient additions may have reduced the effectiveness of fertilization in the low-density treatment at this site. Results indicate that the combined positive effects of thinning and repeated fertilization may substantially accelerate lodgepole pine stand development, thereby potentially shortening technical rotation length and mitigating the negative effects of the mountain pine beetle on midterm timber supply in the interior of British Columbia. However, the advantages of accelerated harvest and larger piece size must be weighed against the considerable thinning and fertilization costs and their effects on return on investment.
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Updated February 05, 2008