Accurate measures of forest site productivity are essential for forest-management planning. The most common measure of site productivity is breast height–age site index (BHASI)—the expected height at a reference age. Error from including early growth in productivity estimates and limited applicability of any one BHASI model warrant development of alternative methods. Exploring alternatives may only be necessary if regional BHASI models are not accurately predicting growth rates. We compared modeled height growth rates for Rocky Mountain Douglas-fir (Pseudotsuga menziesii var. glauca) to felled-tree measurements to evaluate relative performance of a regional BHASI model. An orthogonal sampling design ensured samples were collected across a range of site factors known to influence Douglas-fir growth rates. Growth rates for each 10 m section were calculated and compared to BHASI modeled growth rates. The regional BHASI model underpredicted growth rates from breast height to 30 m. Observed growth rates from 10 to 30 m accounted for the majority of underprediction relative to BHASI modeled growth rates. An alternative multipoint method of defining site productivity is described. More research comparing BHASI and alternative methods is needed, given the growth rate error associated with one-point site productivity assessment.

中文翻译：

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身高年龄增长率的多点击倒树验证

准确测量林场生产力对森林管理规划至关重要。位置生产率的最常见度量是乳房身高–年龄部位指数（BHASI）-参考年龄的预期身高。由于生产率估计值的早期增长以及任何一种BHASI模型的适用性有限而引起的错误，都需要开发替代方法。仅当区域BHASI模型不能准确预测增长率时，才有必要探索替代方案。我们比较了洛矶山脉道格拉斯冷杉（模拟高度增长率花旗松变种青冈）进行砍伐树木测量，以评估区域BHASI模型的相对性能。正交采样设计可确保从已知影响道格拉斯冷杉生长速率的一系列地点因素中收集样本。计算每10 m断面的增长率，并将其与BHASI建模的增长率进行比较。区域BHASI模型低估了从胸高到30 m的增长率。与BHASI模拟的增长率相比，从10到30 m观察到的增长率是大部分低估的原因。描述了定义站点生产力的另一种多点方法。考虑到与单点现场生产力评估相关的增长率误差，需要开展更多的研究来比较BHASI和替代方法。