The influence of age and crown position on growth efficiency along a Scots pine chronosequence

The study deals with the effects of age and crown position (either dominant or intermediate, as determined by Kraft's social class) on stemwood growth efficiency (GE), which is viewed as the ratio of annual stemwood volume increment of the previous five years to needle volume of the entire tree, in eight even-aged pure stands of Scots pine (Pinus sylvestris L.). The highest GE was observed in the youngest stands, and the lowest in the oldest ones. There was no clear interdependence of GE on the age of intermediate stands. GE was most variable in the youngest, the 25-year-old stand, and was the least variable in the 74-year-old stand. GE in dominant trees was lower in 25- 74- and 85-year-old stands and higher in 33-, 44-, 56-, 64- and 93-year-old stands. The GE ratios of dominant trees to intermediate trees in 25-, 33-, 44-, 56-, 64-, 74-, 85- and 93-year-old stands were 0.47:1, 1:0.93, 1:0.87, 1:0.81, 1:0.86, 0.88:1, 0.90:1 and 1:0.61, respectively. Tree age had a statistically significant effect on GE; however, the contribution of the age factor to GE was assessed as weak. Generally, the position of trees (whether dominant or intermediate) had no effect on GE, while age x position of trees had a statistically significant effect on GE, which means that the two factors interacted. The correlation between GE and tree height, diameter at breast height (DBH), and the needle volume of the entire empirical material was statistically significant with a negative sign; however, the situation varied among the particular stands.