The most common reasons for decreasing quality grade were rot and knots. The yield from aspen timber is best when relatively short components of sawn wood can be utilized. Regression models are presented for predicting the value of aspen logs. Lumber cutting length in the lumber grading criteria had the largest effect on grade yields and monetary values of the aspen logs.
參考答案:质量等级降低最通常的原意就是腐烂和节疤。 当短的锯木部件可被利用时，白杨可以达到最佳产量。回收的模型被用于预测白杨圆木的价值。 木料等级评定系统中木料切割长度对于白杨圆木的等级产量及货币值具有最大的影响。
