The Influence of Stem density on the Productivity and Quality of Spruce (Picea abies [L.] Karst.) Wood in a Short Rotation Plantation in the Boreal Zone of North-West Russia

In the boreal zone of North-West Russia, a number of experimental short-rotation pulpwood spruce plantations have already reached the age for clear felling, so currently it is possible to draw conclusions about the effect of different stand density management regimes on the qualitative and quantitative characteristics of spruce wood. The aim of the project was to evaluate the effect of planting density and thinning on the productivity of a short-rotation spruce plantation and the quality of the produced spruce wood. Three variants of stand planting densities in two replications were investigated (1,000, 2,000, and 4,000 trees ha-1). On the replicated sample plots, thinning was carried out. Wood volume, wood density, and wood macro- and microstructure were evaluated and compared in accordance with planting density and thinning intensity. The best growth and stem biomass parameters were observed in the variant with the initial planting density of 2,000 trees ha-1 and the density of 1,065 trees ha-1 after thinning at the age of 25 aimed at retaining the best trees. The density of the spruce wood was mostly influenced by the macro- and microstructure of the early wood zone. The thinning of a stand led to a decrease in the average number of early wood cells in annual layers, with a simultaneous increase in cell wall thickness. The densest wood was formed in the variant with an initial density of 4,000 trees ha-1 and a final density of 1,050 trees ha-1 after thinning at the age of 25.