Wood removed in Southwestern US forest restoration treatments currently has limited markets and thus low value. One important property of wood in structural products is its stiffness (measured as modulus of elasticity), which is known to vary systematically within trees. Directly measuring wood stiffness is expensive, time consuming and destructive. Therefore, we tested samples of ponderosa pine (Pinus ponderosa var. scopulorum Engelm.) from northern Arizona destructively in bending and also non-destructively using acoustic velocity (AV) methods. In total, we tested multiple pith-to-bark small clear (2.54 × 2.54 × 40.64 cm) samples from up to four heights in 103 trees. We first measured the standing-tree AV of sample trees, then the AV of small clear samples, and finally measured wood stiffness using three point static bending tests. We found that a Michaelis–Menten curve was a good fit to the radial profile of wood stiffness, with a steep increase outward from the pith that approached an asymptote. The AV of small clear samples, coupled with measured volumetric density values, approximated the static modulus of elasticity values with high accuracy (r² = 0.86). At the stand level, a model predicting standing tree AV from tree morphology fit the data well (r² = 0.77). Results indicate that southwestern ponderosa pine contains outerwood with relatively high stiffness that could be suitable for structural products. However, when assessed using wood stiffness, the trees take a long time to reach maturity (~50 years) and thus the corewood proportion is large. AV measurements are a good way to assess variability within and among stands and thus could be employed to segregate the resource by expected stiffness values. Segregation could help identify stands not suitable for structural uses and direct them toward more appropriate products.

中文翻译：

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使用静态弯曲和声学测量来模拟黄松木材刚度的变化

目前，在美国西南部森林恢复处理中清除的木材市场有限，因此价值较低。木材在结构产品中的一项重要特性是其刚度（以弹性模量衡量），已知其在树木中会发生系统性变化。直接测量木材刚度昂贵，费时且具有破坏性。因此，我们测试了黄松（松黄松）的样品变种 来自亚利桑那州北部的scopulorum Engelm。）使用声速（AV）方法进行破坏性的弯曲处理，并且也进行了非破坏性的处理。总的来说，我们在103棵树中从多达四个高度测试了多个髓到树皮的小净度（2.54×2.54×40.64 cm）样品。我们首先测量样本树的立木AV，然后测量小的透明样本的AV，最后使用三点静态弯曲测试测量木材的刚度。我们发现，Michaelis-Menten曲线非常适合木材刚度的径向轮廓，并且从接近渐近线的髓向外急剧增加。小净样品的AV值与测得的体积密度值相结合，可以高精度近似静态弹性模量值（r ² = 0.86）。在林分水平上，从树的形态预测立木AV的模型很好地拟合了数据（r ²  = 0.77）。结果表明，西南美国黄松含有较硬的外木，可能适合结构性产品。但是，使用木材刚度评估时，树木要花很长时间才能成熟（约50年），因此芯材所占比例很大。AV测量是评估林分内和林间变异性的好方法，因此可用于通过预期的刚度值隔离资源。隔离可以帮助确定不适合结构用途的林分，并将它们引向更合适的产品。