Effect of thinning on wood density and tracheid properties of Scots pine on drained peatland stands

Abstract

The properties of wood and wood tracheids from trees growing in peatland stands are still insufficiently known. The long-term effects of thinning on wood and tracheid properties of Scots pine (Pinus sylvestris L.) were investigated in two thinning experiments on peatland sites in central Finland. The two sites were ditched for the first time in 1958 and 1973, and thinning experiments were established in 1987 and 1993, respectively. Thinning increased the basal area increment of the remaining trees by 20 per cent. No differences between the trees that were growing on the thinned plots and those that were growing on the unthinned control plots were found in the latewood proportion, wood density, tracheid diameter, cell wall thickness and tracheid length. Moreover, the wood and tracheid properties did not differ markedly from those of corresponding material originating from mineral soil sites. The results confirm the previous results on mineral soils, which showed that an increasing availability of resources primarily increases the rate of tracheid production but has no major effects on wood and tracheid properties.