Wind profiles in and over trees

风速是森林生态系统研究中最为重要的变量之一,同时也是控制气流运输过程最基本的要素。由于树木生理指标和生长过程对风速的改变十分敏感,因此风速随高度的变化规律,即风速廓线的研究十分重要。一般认为,在裸地或林冠上的风廓线均呈对数规律变化,但是在单株树木和林分内风速随高度的变化则不呈对数规律。本文根据最近在海岸松林内风的研究结果,总结了针叶树种单株树木内、林分内和林冠上层以及海岸林区的风速廓线变化规律,其主要结论如下:1)单株针叶树树冠内的风速廓线呈指数形式分布,2)在林分内的风速廓线可用风的减弱系数来表示,3)[(\267\347)(\300\252\317\337\324\332\301\326\271\332\262\343)]上的分布可由风廓线参数(摩擦速度、粗糙长度、零平面位移)确定,4)在海岸林区,极端风速的分布可以使用了建筑上的风荷载模型进行预测。另外,本文提出了该研究领域尚需进一步探讨的问题,主要包括:1)风速廓线与树木特征及林分特征间的关系,2)利用简单的方法预测了风速廓线参数,3)风速廓线在树木生理、生态研究的作用、树木生长过程中风的微生态学效应以及森林生态和管理应用等方面。图4表1参60。

One of the most important and frequently studied variable in forests and the most basic element in governing transport processes of airflow is wind speed. The study of wind profile, defined as the change of wind velocity with height, and wind ve-locity are important because of tree physiological and developmental responses. Generally, wind profiles above the ground or at a canopy surface follow classical logarithm law, but wind profiles in a single tree and in a forest stand are not logarithmic. This paper summarizes the results of wind profile studies within a single tree, in a forest stand, above the forest canopy and in a forest area from recent research in a coastal pine forest. The results demonstrate that: 1) wind profiles with in a single conifer tree crown showed an exponential function with height, 2) wind profiles in forest stands were able to be expressed by attenuation coefficient of wind, 3) wind profiles over a forest canopy could be determined using profile parameters (friction velocity, rough-ness length and displacement), and 4) for a forest area, the extreme wind speed could be predicted reasonably using the methods developed for the design of buildings. More research will be required to demonstrate: 1) relationships between wind profiles and tree or stand characteristics, 2) the simple methods for predicting wind profile parameters, and 3) the applications of wind profile in studies of tree physiology, forest ecology and management, and the detail ecological effects of wind on tree growth.