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Abstract
A commercial thinning and fertilization experiment using 2x6 factorial design was initiated in a 68-year-old lodgepole pine stand in Alberta. Commercial thinning to remove 50% basal area from below was combined with nitrogen fertilization at five levels (No fertilizer, 200 kg/ha N Urea +boron, 200 kg/ha N+blend, 400 kg/ha N+boron, 400 kg/ha N+blend and 400 kg/ha N ammonium nitrate+boron). This study reports results from re-measurement 20 years later. At the stand level, commercial thinning had no impact on the final stand volume but did increase the cumulative merchantable volume (volume removed at time of thinning + final standing volume). Individual DBH growth was increased by thinning and fertilization treatments individually and additively meaning that individual tree growth was greatest for trees that were both thinned and had high fertilization (400 levels). Individual tree diameter at thinning was the best single predictor of 20-year growth response with medium-sized trees responding to thinning alone and thinning and 400-level fertilization. Mortality was increased by fertilization on unthinned plots while thinning increased the proportion of large sawlogs (>20 cm DBH) by 20%. Overall, commercial thinning and fertilization can be used to increase merchantability in natural lodgepole pine stands, even during later rotation.
Published Version
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