Abstract:

The experiments were performed in Hengtoushan Forest Farm and Mengjiagang Forest Farm, Heilongjiang Province. The long, perceptible ring and missing ring of knots were analyzed for Pinus sylvertris var. mongolica plantation. The results showed that the long of knots ranged from 2 to 32 years (mean value is 12.3) and perceptible ring of knots ranged from 1 to 25 (mean value is 7.9) for P. sylvertris var. mongolica plantation. Most dead branches (or knots) (99.8%) have missing rings and the number of missing rings ranged from 0 to 22 (mean value is 4.4). There were 88.6% of all the knots have 1～7 missing rings and only 11.2% of all the knots have more missing rings (over 7). The phenomenon of missing ring for knots in the stand below 30 years was not obvious, but the number of missing rings increased rapidly with stand age increasing. The number of knots that have missing rings decreased with the increasing of knot height, but the long, perceptible ring and missing ring of knots increased with the increasing of knot height then reach a balance status after the peak value. The relationship between the number of ring and long of knots was positive linear. The missing rings increased with the increasing of knots long. The mean value of missing ring increased with the increasing of DBH and decreased with the increasing of crown width. The results of this research could provide the theory foundation of manual pruning for P. sylvertris var. mongolica plantation.

Key words: Pinus sylvestris var. mongolica, knot, long, annual ring, missing ring, pruning