This 32-year-old experimental plantation, near Houston, B.C., is the oldest known espacement (or planting density) study of white spruce (Picea glauca [Moench] Voss) in western Canada. Individual tree and stand characteristics were periodically measured in permanent sample plots for espacements ranging from 420 to 6727 stems per hectare.
Pronounced growth differences among espacements were noted after 32 years. Wider espacements produced trees with larger diameters, crowns and branches. Basal area per hectare and total volume per hectare were greatest in the closest espacement.
Mean annual increment was estimated at 3.90-4.75 m3/ha per year using the unadjusted Ministry of Forests' yield model for natural stands. TIPSY 2.0 Beta, the Ministry's managed stand yield model, forecast merchantable volume yields of 4.9-6.7 m3/ha per year, depending on espacement. Mean annual increment and rotation age estimates were compared to those in other white spruce studies.
Of the four densities tested, the 1682 stems-per-hectare treatment provided the best compromise between individual stem growth and overall stand production. At the two lower planting densities, crown closure had not yet occurred and considerable variability in individual stem height existed. The 6727 stems-per-hectare planting density was impractically dense. The absence of planting densities between 1682 and 6727 stems-per-hectare in this study precluded direct comparisons for this density range. Based on present growth characteristics and TIPSY projections, an optimum plantation density range of between 1300-1600 stems per hectare is recommended.
Predictive equations for 19 tree and stand characteristics are presented for the complete density range of 420-6727 stems per hectare.
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Updated May 29, 2009