Effects of pruning intensity on the knot attributes in Cunninghamia lanceolata plantations
Studying the effects of different pruning intensities on the knot properties of Cunninghamia lanceolata (hereafter called C. lanceolata for short) is crucial for guiding pruning measures to improve wood quality and optimize forestry management. An experiment was conducted on a 4-year-old C. lanceolata plantation using a randomized block design. The trees were subjected to different pruning intensities,with annual pruning until the stems reached diameters of 6,8,10 cm,and 12 cm,and the pruning clear bole height of the stems reached 7 m. Unpruned trees served as the control check. After 22 years of pruning,a total of 15 average standard trees with different pruning intensities were selected and cut down. The stems below 7 m were removed and brought back to the laboratory. A total of 105 knot analysis discs were cut and dissected. The length,diameter,and angle of the knots,as well as the lengths of sound and loose knots,were measured and compared for differences. The results showed that knot and sound knot lengths with pruning intensities were ranked in the following sequence:6 cm<8 cm<10 cm<12 cm<CK. The knot diameter with pruning intensity was ranked in the following order:8 cm<6 cm<10 cm<12 cm<CK. The loose knot length with pruning intensity was ranked in the following order:6 cm<12 cm<10 cm<8 cm<CK. The knot angle with pruning intensity was ranked as follows:8 cm<12 cm<10 cm<6 cm<CK. Both the knot and sound knot lengths tended to decrease significantly with increasing pruning intensity. The knot length with a pruning intensity of 6 cm was almost half that of the control CK,and its loose knot length was only one-fourth that of the control CK. The significant effect of pruning intensity on knot attributes lasted for 22 years,and all four pruning intensities were significant in improving knot attributes,with pruning intensities of 6 cm and 8 cm being the most effective. Therefore,in the process of C. lanceolata cultivation,to obtain a smaller knot length,knot diameter,and sound knot length,pruning intensities of 6 cm and 8 cm can be used;a pruning intensity of 6 cm has the smallest knot length,and a pruning intensity of 8 cm has the smallest knot angle.
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