ZLV Online

Abstract

The effect of the first thinning in fir thickets 3–5 years after the intervention was evaluated at eleven sites. Two sub-plots were established at each site: one control and one thinned. One thousand promising fir trees per hectare in each plot were marked. These trees were then released from 1–2 competitors. The average annual increment of the mean stem diameter, slenderness ratio and crown ratio were evaluated on a set of target trees (1,000 silver-fir trees per hectare). The first thinning resulted in an acceleration of the diameter growth of the released target trees at most sites. Higher average diameter growth on the thinned treatment was recorded at ten of the eleven sites. On the thinned treatment, the mean slenderness ratio of the target firs was slightly more favourable at 82 compared to the control 87 (difference = -5.3; DF = 1,8; SE = 1.40; p = 0.005), and their mean crown ratio was also higher at 0.73 compared to the control at 0.68 (difference = 0.05; DF= 1,8; SE = 0.015; p = 0.02).