Abstract:
Objective In order to improve the productivity and timber quality of Chinese fir (Cunninghamia lanceolata), a pruning experiment was carried out in a Chinese fir plantation. The impacts of pruning intensity on stem growth and knot free timber production were analyzed, which aims to provide guidance for cultivation of knot free timber.
Method In this study, we performed different pruning intensities in 8-year-old Chinese fir plantation, including light intensity pruning (retaining 75% of crown height, LP), heavy intensity pruning (retaining 50% of crown height, HP) and the control (unpruned, CK). The quantity and size of knots were measured by rotary cutting method. The differences of DBH, height, volume and the quantity or size of knot among different treatments were compared after 10 years of pruning.
ResultsResults showed that pruning had no significant effect on DBH, tree height, volume, plumpness, height of the first living branch and quantity of living branches of Chinese fir. Pruning substantially decreased the quantity of knot of self-pruning, so the diameter, length and volume of knot after pruning were lower than self-pruning knots. LP and HP remarkably reduced total diameter of knot per tree by 27.6% and 40.8%, and total length of knot per tree by 26.4% and 32.6%, and total volume of knot per tree by 27.8% and 45.0%, respectively. Moreover, compared with the knotted wood, the density of knot free timber was significantly decreased, and the compressive strength and bending strength were increased significantly.
Conclusion It is appropriate to take pruning measures in Chinese fir silviculture plantations, which can not only effectively reduce quantity and volume of knot, and improve the appearance grade and knot free timber , but also maintain the tree growth and stand volume.
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