思茅松树干平均密度估计方法研究

为解决大径阶思茅松树干生物量测定问题，进行了树干平均密度的估计研究．依据估计密度的一般回归模型，在3种假设条件下分别对思茅松树干平均密度进行估计．通过比较确定最优估计方法，运用哑变量方法对思茅松树干不同部位、不同龄组之间密度的差异性进行检验．结果表明：思茅松木材密度的估计以方法3的效果最好，可以消除方差非齐次性的影响，而树皮密度的估计则应采用方法1；思茅松树干不同部位之间的木材密度无显著性的差异，而树皮密度除中部与下部无显著差异外，上部与中部、上部与下部之间的差异性显著；中龄林与近成熟龄林之间的木材与树皮均无显著性的差异．据此在利用材积密度法估计思茅松树干千重时，不同个体的木材均可采用统一的平均密度值．

Studies on Estimation Methods for Average Stem Density of Pinus kesiya var. langbianensis

The assessment of average stem density of Pinus kesiya var. langbianensis was conducted in order to measure stem biomass of large sized trees. The average stem density of Pinus kesiya var. langbianensis was evaluated under three hypotheses by the regular regression model for density assessment. The differences in the stem density among different positions on the stem and among varied age groups were verified by dummy variable method on the basis of selecting the best estimation method through comparison. The results showed： The best estimation of the stem density of Pinus kesiya var. langbianensis was obtained by method Ⅲ, by which the influence of heteroscedasticity could be eliminated. Method Ⅰ Was the best one for bark density estimation. There were no significant differences in the stem density among different positions on the stem, but there were significant differences in bark density among samples taken from the upper and middle, upper and lower parts of the trunk, although the bark density of the middle part of the trunk was not significantly different from the lower part. There were no significant differences in either timber or bark density between middle aged and premature plantations. It was proposed that the uniform value of the average stem density could be applied to estimate the dry Weight of Pinus kesiya var. langbianensis stems by volume density estimation method.