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过去,沿用林带的透风系数、疏透度或林带的阻抗系数来评价林带防风的效应,在生产上应用有很大困难。为了解决这一问题,探讨直观的量值指标,中国林科院周士威等提出了评价林带防风效益的新指标,即隙高比(Xi),并探讨了以林带隙高比与林带行距、行数的关系,来判断林带的防风效应。 林带隙高比即株间平均树冠间隙与林带平均高的比值。在实际应用中的步骤是:首先将计划发展的树种,绘出树龄与树高、冠幅的关系曲线,从而查出逐年的树高和冠幅值;然后依设计的林带行数,从隙高比值表中查出该行所具有的最佳隙高比值;再按公式X=H×Xi;L=X+D冠计算各年应具有的株距。(式中X为平均树冠间隙;H为平均树高;L为株距;D冠为平均冠幅。
In the past, using the permeability coefficient of forest belts, the permeability or the impedance coefficient of forest belts to evaluate the windbreak effect of forest belts, it is very difficult to be applied in production. In order to solve this problem and discuss the direct and quantitative indicators, Zhou Shuiwei, a member of Chinese Academy of Forestry, put forward a new index to evaluate the windbreak effectiveness of forest belts, namely the gap height ratio (Xi) Number of relations to determine the windbreak effect of the forest belt. The ratio of forest gap height is the ratio of average canopy gap to average height of forest. The steps in practical application are as follows: firstly, the tree species planned to be developed and the relationship curve between the tree age and the height of the tree and the crown are plotted to find out the year-by-year tree height and crown amplitude; and then, High ratio table to find the line with the best ratio of the gap height; and then the formula X = H × Xi; L = X + D crown calculation each year should have the plant spacing. (Where X is the average canopy gap; H is the average tree height; L is the spacing; D crown is the average crown width.