Am J Bot. 1998 May;85(5):675.
We used mathematical models for wind-dispersed seeds and wind-tunnel experiments to predict modal seed dispersal distance of the Neotropical orchid Brassavola nodosa under conditions approximating those found in its natural habitat: mangrove islands in Belize, Central America. Key variables in a simple ballistic model for predicting modal dispersal distance (xm) of an individual seed include: height of release (h); free-stream velocity (Uc); and terminal velocity of the seed (Ut): xm = h Uc/Ut. Modal dispersal distance of dust-like orchid seeds were predicted adequately by this ballistic model at low wind velocities and low release heights, but it underestimated the increasing importance of turbulence at higher wind velocities and greater release heights. We estimated the magnitude and relative importance of one measure of turbulence, vertical mixing velocity (W*), on xm in wind tunnel experiments. Our estimates of W* were within the same order of magnitude as those found for other small dust-like seeds and pollen. In high turbulence conditions, incorporation of vertical mixing velocity effects into the ballistic model of seed dispersal overestimated modal seed dispersal distances.
我们使用风传播种子的数学模型和风洞实验，来预测中美洲伯利兹红树林岛上，近似于兰花 Brassavola nodosa 自然栖息地条件下的种子模态扩散距离。预测单个种子模态扩散距离（xm）的简单弹道模型中的关键变量包括：释放高度（h）；自由流速度（Uc）；和种子的终端速度（Ut）：xm = h Uc/Ut。在低风速和低释放高度下，这种弹道模型可以充分预测粉状兰花种子的模态扩散距离，但在更高风速和更大释放高度下，它低估了湍流的重要性不断增加。我们在风洞实验中估计了湍流的一个度量标准，即垂直混合速度（W*），对 xm 的大小和相对重要性。我们对 W*的估计与其他小型粉状种子和花粉的估计处于同一数量级。在强湍流条件下，将垂直混合速度效应纳入种子扩散的弹道模型会高估种子的模态扩散距离。
