The thickness of bark (cork) is of utmost importance for its industrial processing and, therefore, for the sustainable management of cork oak ( Quercus suber L.) woodlands. Cork thickness has been reported to decrease from the stem base upwards but, to our knowledge, prediction models have not yet been presented. This study intended to develop reliable models to predict stem profiles of cork thickness. We addressed the relationship between bark thickness and stem height by measuring stem diameters and cork thickness at various stem heights in 76 trees. Through a repeated measure ANOVA, we selected the bark thickness response variables, cork-ring width and cork thickness. A mixed-effect modelling approach was used to fit linear bark thickness curves with stem height. Our results showed that the equations that performed better for cork thickness were functions of the stem relative height and cross-sectional cork area increment. The decreasing trend upwards the stem might lead to underestimation of cork thickness at the base, more than overestimate it at upper stem parts, in relation to the values at breast height, which are generally used to estimate the thickness of the whole cork plank. Furthermore, cork thickness curves were tree size-related, with larger trees exhibiting a steeper reduction in cork thickness upwards the stem.

中文翻译：

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葡萄牙西南部栓皮栎茎的树皮厚度变化建模

树皮（软木）的厚度对其工业加工至关重要，因此对于软木橡树（ Quercus suber L.）林地的可持续管理至关重要。据报道，软木厚度从茎基部向上减少，但据我们所知，尚未提出预测模型。这项研究旨在开发可靠的模型来预测软木厚度的茎轮廓。我们通过测量 76 棵树不同茎高处的茎直径和软木厚度来解决树皮厚度和茎高之间的关系。通过重复测量方差分析，我们选择了树皮厚度响应变量、软木环宽度和软木厚度。混合效应建模方法用于拟合线性树皮厚度曲线与茎高。我们的结果表明，对软木厚度表现更好的方程是茎相对高度和横截面软木面积增量的函数。相对于胸高值（通常用于估计整个软木板的厚度），茎向上的下降趋势可能导致基部软木厚度的低估，而不是上部茎部分的高估。此外，软木厚度曲线与树木大小有关，较大的树木在茎上表现出软木厚度的急剧减少。通常用于估算整个软木板的厚度。此外，软木厚度曲线与树木大小有关，较大的树木在茎上表现出软木厚度的急剧减少。通常用于估算整个软木板的厚度。此外，软木厚度曲线与树木大小有关，较大的树木在茎上表现出软木厚度的急剧减少。