杨树材性成熟龄模型的建立及树体内幼龄材的分布

Model for Maturation Age of Wood Property and Extend of Juvenile Wood Zone in Poplar Trunks

以小叶杨和北京杨的材性测定值(导管分子长度或木纤维长度或导管腔径)作为因变量,以年轮数作为自变量,建立材性成熟非线性模型,以此为依据讨论成熟龄问题,并对幼龄材在树体内的分布进行分析。导管分子长度、木纤维长度和导管腔径的成熟龄模型为应用分段回归分析方法拟合的二次方程和定数函数结合的非线性方程,方程的决定系数在0 85 7～0 991之间,并在0 1 %水平上达到显著。以导管分子长度作为材性指标,应用这个非线性模型分析的结果表明:材性成熟龄及幼龄材半径因树种、立地的灌溉条件不同存在差异。无灌溉北京杨6～1 0年达到成熟,幼龄材半径为5 2mm左右;无灌溉小叶杨2 4～2 9年达到成熟,幼龄材的半径为90mm左右;灌溉小叶杨1 3～1 5年左右达到成熟,幼龄材的半径为85mm左右。

Nonlinear models were established for two species of poplar ( Populus simonii and P.×beijingensis ) with the wood properties indices \[vessel element length (VEL) or wood fiber length (FL) or vessel lumen diameter (VLD)\] as the dependent variables and the ring number from pith to bark as independent variable. Based on this, the mature wood age and the distribution of juvenile wood in tree stems were discussed. The models that predict the maturation age according to vessel length, fiber length or the diameter of the vessel lumen were established using the segmented regression analysis which begins with a quadratic part and then reaches a plateau. The square of the correlation coefficient ( r 2 ) of nonlinear regression ranged from 0 857 to 0 991 and correlated significantly at 0 1% level in all cases. Using the fiber length as the wood property index, the models showed that variance of maturation age and the radius of juvenile wood existed between different species and different site conditions: for P.×beijingensis without irrigation, the maturation age and the radius of juvenile wood was about 6～10 a and 52 mm, while that for P. simonii without and with irrigation was 24～29 a and 90 mm, 13～15 a and 85 mm respectively.