Improving measurements of the falling trajectory and terminal velocity of wind-dispersed seeds

1. Seed dispersal by wind is one of the most important dispersal mechanisms in plants. The key seed trait affecting seed dispersal by wind is the effective terminal velocity (hereafter “terminal velocity”, Vt), the maximum falling speed of a seed in still air. Accurate estimates of Vt are crucial for predicting intra- and interspecific variation in seed dispersal ability. However, existing methods produce biased estimates of Vt for slow- or fast-falling seeds, fragile seeds, and seeds with complex falling trajectories.
2. We present a new video-based method that estimates the falling trajectory and Vt of wind-dispersed seeds. The design involves a mirror that enables a camera to simultaneously record a falling seed from two perspectives. Automated image analysis then determines three-dimensional seed trajectories at high temporal resolution. To these trajectories, we fit a physical model of free fall with air resistance to estimate Vt. We validated this method by comparing the estimated...

1. 风力传播是植物最为重要的种子传播机制之一。影响植物风力传播的关键种子性状为有效终端速度（effective terminal velocity，下称终端速度Vt），即种子在静止空气中的最大下落速度。准确估算Vt对于预测种子传播能力的种内与种间变异至关重要。然而现有方法针对下落速度过慢或过快的种子、脆弱种子以及下落轨迹复杂的种子，均会生成有偏的Vt估算结果。
2. 我们提出一种全新的基于视频的分析方法，可用于估算风播种子的下落轨迹与终端速度Vt。该方案通过加装反射镜，使单台摄像机可同时从两个视角记录下落中的种子。随后通过自动化图像分析，以高时间分辨率重建种子的三维下落轨迹。针对上述轨迹，我们拟合考虑空气阻力的自由落体物理模型以估算Vt。我们通过对比估算得到的相关结果，对该方法开展了有效性验证。