The influence of initial stocking on corewood stiffness in a clonal experiment of 11-year-old Pinus radiata D.Don.

Authors: J. P. Lasserre, E. Mason, M. Watt
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 2004, Issue N.Z.J.For. 49(2) 2004, pp 18-23, Aug 2004
Publisher: New Zealand Institute of Forestry

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Abstract: The influence of initial stocking on corewood stiffness of 11 year-old Pinus radiata D. Don was investigated at a Canterbury site. Dynamic stiffness was determined on standing trees using the stress wave method over the lower stem (0.2 to 2.0 m) of 135 trees. These trees were from two adjacent sub-experiments of the same age which comprised 10 different clones installed at three initial stockings of 833, 1250 and 2500 stem/ha.
Stiffness exhibited a significant (p<0.01) positive linear correlation with stocking. Values of stiffness significantly (p<0.05) varied between all stocking levels studied, with values of stiffness across clones ranging from 5.9 GPa at high stockings (2500 stem/ha) to 4.1 GPa at low stocking levels (833 stem/ha). Although stiffness significantly differed between clones (p<0.01) the clonal influence on stiffness was lower than that of stocking, with values ranging by on average 1.3 GPa (cf. 1.8 GPa for stocking) between the two clones representing the stiffness extremes. No significant interaction (p>0.05) was found between clone and stocking level. Tree diameter exhibited a significant (p<0.01,1^=0.5) negative correlation with stiffness. After the influence of diameter had been accounted for, stocking still had a significant (p<0.01) positive influence on stiffness.
These results highlight the importance of stocking in regulating Pinus radiata corewood stiffness and indicate that initial stocking and genotype can be used as complementary approaches for improving corewood stiffness.

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