Rotation Age Results of Low Planting Density Effects in Loblolly Pine (Pinus taeda L.)

Planting density is the most important management decision made by a forester when establishing a loblolly pine ( Pinus taeda L.) plantation. Traditionally, planting densities were often chosen with the assumption that at least one mid-rotation thinning operation would provide intermediate cash flow(s) while also accelerating the growth of residual trees to more quickly provide solid wood products at future thinnings and final harvest. Recently, closures of pulpwood processing facilities throughout the southeastern USA have led to growers considering low planting density, no-thin management regimes. Using a designed experiment in Virginia, USA, three lower planting densities (494, 741, and 988 trees per hectare) were evaluated at rotation age (30 years) for common characteristics of interest to growers. Results indicated that the highest planting density yielded significantly greater (p-value < 0.05) total green weight, pulpwood and chip-n-saw green weights, and basal area, whereas lower densities produce significantly more ( p -value < 0.05) sawtimber green weight, the highest-value product. Effect sizes for these characteristics were all large (Partial— η ² η 2 > 0.70) and meaningful from a management perspective. All planting densities produced viable stands showing little competition-induced mortality and should be evaluated alongside more traditional planting densities using expected local market conditions and landowner management objectives.