Effects of tree planting rectangularity on wood quality and growth of Lodgepole pine (Pinus contorta) in Sweden

Abstract: Lodgepole pine (Pinus contorta) was introduced on a production scale in Sweden during the mid 20th century. Traditional Swedish forestry practices include planting trees at evenly spaced rectangularities in order to maximize nutrient and light availability to individual trees, minimize branch diameter, and to encourage good stem form. In 1982, a study using Lodgepole pine was established to evaluate any differences in growth characteristics between planting rectangularities. This research study is a completely randomized block design rectangularity study where lodgepole pine was planted in three replications at five different rectangularities (0.8 x 5 m, 1 x 4 m, 1.33 x 3 m, 1.46 x 1.46 x 4 m, and 2 x 2 m) all at the same planting density of 2500 trees/hectare. At age 29, final harvest candidate trees were chosen in each rectangularity treatment, individual trees were divided into two competitive sectors relative to each dimension of the rectangularity, and growth differences were evaluated. Straightness and quality were positively correlated with each other in all rectangularities. Final harvest candidate branch diameter was correlated with branch angle, stem DBH, individual tree volume and the total number of branches per tree. Total height, height to live crown, individual stem volume, biggest branch in sector 2, sector location of the biggest branch, and average diameter at breast height all differed significantly among rectangularities at an α - level = 0.05. Rectangularities with higher competitive ratios displayed higher total tree heights, larger biggest branch and tree diameters, along with higher volume per hectare. Rectangularity 0.8 x 5 m produced the highest volume at age 29 while maintaining desirable wood quality measures.