Effect of stand density on radial growth of branches of Scots pine in southern and central Finland

Abstract

Branch growth dynamics in Scots pine (Pinus sylvestris L.) were studied in 19 thinning experiments in southern and central Finland. Data were collected from 229 trees growing on sites of different fertility with different stand density, age, and canopy position. Radial increments were measured from discs from the base of the thickest branch on every fifth living whorl. Branch growth declined gradually from the upper part of the crown towards the crown base. Near the crown base, the effect of stand density was most apparent and branches remained alive without forming annual rings. After the thinnings, branch growth did not increase, but wider spacing delayed the reduction in branch growth and increased branch longevity. Correlation of branch increment between trees was greater in the upper whorls than in the lower crown. Correlation of the radial increment between whorls of different ages was greater between whorls near each other than between whorls from the upper and lower crown. Variation of the annual increments was similar in the stem and branches. A model was developed for predicting branch increment at different heights in the crown. The best independent variables for indicating branch increment were stem radial increment, height/diameter ratio, and branch age.