Key message

Cork porosity, due to lenticular channels, varied along the stem of Quercus suber L. Lenticular channels’ area, rather than their number, decreased upwards along the stem. Area decrease was observed regardless of tree size and of its intrinsic porosity.

Context

The cork of Quercus suber L. is radially crossed by lenticular channels, defining cork’s natural porosity. It has been suggested that porosity decreases from the stem base upwards, but studies on such variation have not yet been presented.

Aims

Three main research questions were addressed: (i) how large is the variation of cork porosity upwards along the stem; (ii) how does porosity variation relate with porosity traits, namely the size and number of lenticular channels and (iii) how much does porosity vary with stem height and between trees.

Methods

We set up a study at tree level to quantify the porosity of cork samples from fixed stem heights. Our statistical modelling approach was based on linear mixed-effects models, given the nested structure of the data. In the model fitting, porosity was described as a function of tree stem height, while the random effects explained the source of variability introduced by different tree size (as given by stem diameter at breast height, D_bh) and porosity (as given by intrinsic porosity, CP_bh).

Results

The lenticular channels’ area rather than their number consistently decreased up the stem. The area proportion of the lenticular channels in the cork tissue (i.e. porosity coefficient) decreased by about 1.4% per metre upwards along the stem, regardless of tree size and of its porosity.

Conclusion

Our findings highlight that the lenticular channels’ traits greatly vary among trees, much more than within-tree, which may be an important clue to predict variations in cork properties, for decision-making on cork oak management.

中文翻译：

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收割的软木栎树（栎木）上沿茎的软木孔隙率变化

关键信息

由于有扁豆状通道，软木孔隙度沿 栎栎 的茎部变化。沿着茎部，扁豆状通道的面积而不是数量有所减少。不论树木大小及其固有孔隙率如何，均观察到面积减少。

语境

栎属软木的软木塞通过透镜状通道径向交叉，从而确定了软木塞的自然孔隙度。已经提出，孔隙率从茎底部向上减小，但是尚未提出关于这种变化的研究。

目的

解决了三个主要的研究问题：（i）软木孔隙率沿茎向上的变化有多大；（ii）孔隙度变化与孔隙度特性如何相关，即柱状通道的大小和数量；以及（iii）孔隙度随茎高和树木之间变化多少。

方法

我们在树级别进行了一项研究，以从固定的茎高处量化软木样品的孔隙度。考虑到数据的嵌套结构，我们的统计建模方法基于线性混合效应模型。在模型拟合中，孔隙度被描述为树茎高度的函数，而随机效应则解释了由不同树尺寸（由胸高处的茎直径D _bh给出）和孔隙率（由内在_因子给出）引入的变异性来源。孔隙度，CP _bh）。

结果

柱状通道的面积而不是其数量一直沿茎减少。软木组织中的柱状通道的面积比例（即孔隙度系数）沿茎向上每米每米降低约1.4％，而与树木的大小和孔隙度无关。

结论

我们的研究结果突出表明，树木之间的透镜状通道特性差异很大，远比树木内差异大得多，这可能是预测软木特性变化的重要线索，从而有助于软木橡木的管理决策。