Modelling the vulnerability of balsam fir forests to wind damage
Modelling the vulnerability of balsam fir forests to wind damage
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模拟香脂冷杉林对风害的脆弱性
DOI：
10.1016/j.foreco.2004.07.072
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发表时间：
2005
影响因子：
3.7
通讯作者：
S. Meunier
中科院分区：
文献类型：
--
作者：
A. Achim;Jean;B. Gardiner;G. Laflamme;S. Meunier
风对魁北克中部的森林造成了重大破坏，随着目前转向更精细的造林实践，人们越来越担心。本文研究了以香脂冷杉（Abies balsamea（L.）米尔。）含有少量的白色云杉（Picea glauca（Moench）Voss.），代表了加拿大东部北方森林的一大部分的主要特征。其目的是比较两个物种的树木的稳定性的中位和丰富的中位网站，然后比较在同一网站上的整个看台的风吹脆弱性。通过静态拔树试验测量稳定性。由此产生的临界转动力矩计算在干的基础上，并与一系列的树木描述符。干重和树重是相关系数最高的变量。地点和物种对临界转动力矩的影响不显著（P>0.05）。影响诊断并没有显示出需要将被拔出的采油树的稳定性与其失效模式分开。一个类似的分析也表明，在本研究中，茎基部腐烂的数量并没有显着影响风吹的脆弱性。利用为英国GALES模型开发的方法模拟了风抛脆弱性。利用表面空气阻力与空气动力学粗糙度之间的关系，将林冠上方的风速转化为树干根部的旋转力矩。临界风速，树木会推翻或管理单元，然后可以推断出典型的香脂冷杉站生长在两个网站指数对应的树木拉研究进行。间伐作业的直接效果是通过减少林分中的树干数量来模拟的。临界风速总是更高的茎断裂比倾覆。在后一种情况下，两个位点的信号强度都接近20 ms-1，然后在衰老时下降。去除30%基底面积的减薄处理将使该速度降低约4 ms-1。
Wind causes significant damage to forests in central Québec, and with the current move to more refined silvicultural practices, concerns are increasing. This study investigates the mechanisms of windthrow resistance in stands dominated by balsam fir (Abies balsamea (L.) Mill.) with a minor component of white spruce (Picea glauca (Moench) Voss.), representing the dominant feature of a large section of the Eastern Canadian boreal forest. The aim was to compare the stability of trees of both species on mesic and rich mesic sites and then to compare the windthrow vulnerability of the entire stands on the same sites. Stability was measured by static tree-pulling tests. The resulting critical turning moments were calculated at the base of the stem and were related to a series of tree descriptors. Stem mass and tree mass were the variables showing the highest correlation coefficients. The effects of the site and the species on the critical turning moments were non-significant (P>0.05). Influence diagnostics did not reveal the need for separating the stability of the pulled trees from their mode of failure. A similar analysis also showed that the amount of rot at the base of the stem did not affect significantly the vulnerability to windthrow in this study. Windthrow vulnerability was modelled using the methodology developed for the British GALES model. By using the relationship between the drag of the air on a surface and its aerodynamic roughness, the wind speed over a forest canopy was transformed into a resulting turning moment at the base of the stem. Critical wind speeds at which trees would overturn or snap could then be inferred for typical balsam fir stands growing on two site indices corresponding to those where the tree-pulling study was conducted. The immediate effect of a thinning operation was simulated by reducing the number of stems in the stands. The critical wind speeds were invariably higher for stem breakage than for overturning. In the later case, they were close to 20ms−1on both sites before declining at senescence. A thinning treatment removing 30% of the basal area would reduce this speed by approximately 4ms−1.