ThinningPinus radiataplantation by operator selection: 1. Effects on the residual forest

Summary Field trials were undertaken in Pinus radiata plantation, in order to compare thinning where the harvesting machine operator selects the trees to be thinned without prior tree marking, with conventional tree-marked thinning, in terms of stand and tree parameters such as residual stocking and spacing, basal area, mean tree diameter, and frequency of damaged trees. These trials included first and second thinning on high and low site quality and two trials at operational scale. On the whole, operators thinned to the same stand density and tree diameter distribution as tree-marked thinning in comparable stands. The removal of undesirable trees was generally as good as in tree-marked thinning. In two trials operator selected thinning resulted in a better quality residual stand than tree-marked thinning. Trials at the operational level also indicate practicalities of two types of guidelines for operator selection thinning: a diameter limit; and spacing of residual trees.