THE EFFECT OF DIFFERENT LEVELS OF GREEN PRUNING ON THE DIAMETER GROWTH OF PINUS-SYLVESTRIS L

It was hypothesized that maximum living crown removal can be determine d from experimental data using linear statistical models. Pruning expe riments were carried out in four Scots pine (Pinus sylvestris L.) stan ds. Zero to nine living branch whorls were removed in three stands in southern Finland, and 0-4.5 m of the living crown was removed in a sta nd in northern Finland. Only dead branch whorls were removed from the control trees. A total of 517 trees were analyzed. Diameter increment was measured five years after pruning. The growth reduction was statis tically significant when 40% or more of the living crown was removed b y pruning. According to the linear models, green pruning decreased dia meter growth by 0 to 33% at defoliation levels below 40%. This loss in diameter growth is, from an economical point of view, compensated by the knotfree timber resulting from pruning 2-3 years earlier.