油松木材基本密度的变异

SPECIFIC GRAVITY VARIATION IN PINUS T ABULAEFORMIS

本文研究了山西中条山产油松木材基本密度的变异及影响其变异的因素,结果表明,基本密度的径向变异规律是,髓心向外逐渐递减到最小值后又递增;最大值出现在髓心附近,最小值位于第10生长轮附近.导致上述变异的主要原因是木材浸提物含量、管胞径弦向直径、胞壁厚度、单位面积管胞数目等综合作用所致.尽管油松木材髓心附近密度最大,但其顺纹抗拉强度、顺纹抗压强度、抗弯强度均最小,这主要是髓心附近纤丝角度最大,纤维素含量最低所致.基本密度纵向变异规律是,由基部向上递减,至顶部稍有增加的趋势.方差分析表明,株间不同高度、株间基本密度存在着显著性差异,但生长轮年龄相同.高度不同的5株样本有2株高度间的密度没有显著性差异.

Five trees of Pinus tabulaeformis were collected from a natural seeding stand of Zhongtiao Mountainsin hanxi Province.Sample disks(20cm thick)were cut from each tree ataix levels of height for determining their variation n specific gravity among trees and at differentheights of each tree.Radial variations in the tracheid diameter and wall hickness,extractivesand mechanical properties were also studied.The specific gravity is highest near the pith anddecreasing toward the 10 year,then increasing outward.Specific gravity is high at tree base,anddecreases pward o a certain height,then increases again near the top of the tree.From pith tobark,the tracheid diameter,all wall hickness,and mechanical properties increases,butextractives content decreases.Significant differences(0. 05 level)ere found in specific gravityvariation among trees,and at different heights of the same tree.The presence of high pecificgravity near the pith is due to small tracheid diameter,more tracheid number per sequaremillmeter and high xtractives content.Because of large microfibrill angel within the S2 layer ofthe secondary wall in tracheid and low ellulose content near the pith mechanical properties of thewood are lower.