Data from: Intraspecific variation in seed dispersal of a Neotropical tree and its relationship to fruit and tree traits

The distribution of wind-dispersed seeds around a parent tree depends on
diaspore and tree traits, as well as wind conditions and surrounding
vegetation. This study of a neotropical canopy tree, Platypodium elegans,
explored the extent to which parental variation in diaspore and tree
traits explained (1) rate of diaspore descent in still air, (2)
distributions of diaspores dispersed from a 40-m tower in the forest, and
(3) natural diaspore distributions around the parent tree. The geometric
mean rate of descent in still air among 20 parents was highly correlated
with geometric mean wing loading1/2 (r = 0.84). However, diaspore traits
and rate of descent predicted less variation in dispersal distance from
the tower, although descent rate−1 consistently correlated with dispersal
distance. Measured seed shadows, particularly their distribution edges,
differed significantly among six parents (DBH range 62–181 cm) and were
best fit by six separate anisotropic dispersal kernels and surveyed
fecundities. Measured rate of descent and tree traits, combined in a
mechanistic seed dispersal model, did not significantly explain variation
among parents in natural seed dispersal distances, perhaps due to the
limited power to detect effects with only six trees. Seedling and sapling
distributions were at a greater mean distance from the parents than seed
distributions; saplings were heavily concentrated at far distances.
Variation among parents in the distribution tails so critical for
recruitment could not be explained by measured diaspore or tree traits
with this sample size, and may be determined more by wind patterns and the
timing of abscission in relation to wind conditions. Studies of wind
dispersal need to devote greater field efforts at recording the “rare”
dispersal events that contribute to far dispersal distances, following
their consequences, and in understanding the mechanisms that generate
them.

风传种子在母树周围的分布取决于传播体（diaspore）与树木性状，以及风况与周边植被状况。本研究以新热带冠层树木优雅扁轴木（Platypodium elegans）为对象，探究母树的传播体与树木性状的种间变异在多大程度上可解释：（1）静风环境下传播体的下落速率；（2）森林中40米高塔释放的传播体的空间分布；（3）母树周围自然状态下的传播体分布。对20株母树的静风下落速率几何均值分析显示，其与翼载荷（wing loading）几何均值的平方根呈高度相关（相关系数r=0.84）。不过，传播体性状与下落速率对高塔释放的传播体扩散距离变异的解释度较低，尽管下落速率的倒数始终与扩散距离呈显著相关。实测的种子雨（seed shadow）分布，尤其是其分布边界，在6株母树（胸径DBH，diameter at breast height，范围62~181 cm）间存在显著差异，且可通过6个独立的各向异性扩散核（anisotropic dispersal kernels）结合实测结实量得到最优拟合。将实测下落速率与树木性状整合进机械论种子扩散模型（mechanistic seed dispersal model）后，该模型未能显著解释母树间自然种子扩散距离的变异，这可能是因为仅6株的样本量有限，难以检测到显著效应。幼苗与幼树的空间分布平均距离母树的距离显著大于种子分布；幼树高度集中于更远的扩散距离处。对于种群更新（recruitment）至关重要的分布尾部变异，在本次样本量下无法通过实测的传播体或树木性状得到解释，其更可能受局地风场格局以及与风况相关的种子脱落（abscission）时机调控。风传扩散相关研究需投入更多野外工作，以记录那些贡献远距离扩散的“稀有”扩散事件，追踪其生态后果，并阐明其产生机制。