The growth of styroblock, chemical and mechanical root pruned lodgepole pine seedlings in Interior British Columbia.

The one-year growth of lodgepole pine seedlings on two contrasting sites in interior British Columbia, a ploughed sandy nursery bed of low available moisture and a clayey wet forest soil, were investigated to evaluate the performance of seedlings subjected to chemical and mechanical root pruning techniques. Two sizes of chemically pruned seedlings were treated with a copper based paint (PCT 5-12 and PCT 4-10). The other treatments were containerized Styroblock (PSB) 4-15 seedling that were knife pruned in four ways (i.e. bottom plug removal = RPB, bottom plug removal and two lateral cuts = RPB+2, and lateral cutting with three cuts = RP3 and six cuts = RP6). Growths of pruned seedlings were compared to the un-pruned PSB 4-15 control group. While site soil conditions proved to be a stronger contributing factor to growth, pruning treatments induced different effects on seedlings particularly in root development. Root counts, root symmetry and proportion of direct large roots, showed greatest improvements. Root pruned seedlings also had better distribution of root growth throughout the plug. Among knife pruning treatments, lateral cutting methods were more favourable to early root growth with greater root counts after a twenty-one day period than bottom plug removal. The most extreme knife pruning treatment, consisting of six laterial cuts (RP6), had a mean of 60% removal of roots within the plug and showed no differences in height growth regardless of site. Also the RP6 seedlings had 100% survival. It shows that the PSB 4-15 seedling is to a great extent resilient to knife pruning, which should be encouraged where chemical root pruning is less useful as it improves rooting development in the early establishment of confer seedlings. Improved rooting establishment of planted seedlings may result to better adaptation to environmental conditions and competitive stresses, as well as improve stem morphology and long-term growth.--P.ii.