Effects of thinning and pruning on stem and crown characteristics of radiata pine (Pinus radiata D. Don)

Abstract

Simultaneous applications of thinning and pruning are common silvicultural practices in radiata pine (Pinus radiata) forest plantations. Their separate effects on tree growth and wood quality have been well studied, but their combined effect is not clear yet. The aim of this study is to identify how thinning and pruning together affect the stem structure and properties of the pruned but also the unpruned section of the trees (the portions formed immediately after the application of these management efforts). The effects of pruning and thinning on the number of growth units per year, internode length, number of branches, and branch diameters was analyzed in managed and unmanaged stands of radiata pine grown in Chile. When used jointly, these practices generated larger individual tree volumes (135% more) and clear wood in the pruned logs; however, they also reduced the sawn wood quality of the unpruned stem section for some years after the silvicultural interventions. The managed trees showed more growth units per annual shoot and shorter internodes, thus generating more knotty wood. Moreover, managed trees showed more taper. As trees of the managed stand restore the foliar biomass lost due to pruning, managed and unmanaged stands approach the same level of canopy closure, and differences minimize.