Data from: Landscape structure mediates zoochorous-dispersed seed rain under isolated pasture trees across distinct tropical regions

Context: Isolated pasture trees play an important role in forest recovery within fragmented tropical landscapes by attracting seed dispersers and facilitating seedling growth. However, studies with conflicting results have led to confusion about what drives variation in zoochorous-dispersed seed rain patterns under isolated tree canopies. Objectives: To assess the role of landscape and biological factors impacting zoochorous-dispersed seed rain under isolated pasture trees across three tropical regions of the world. Methods: We measured seed dispersal under 144 isolated pasture trees found in 12 fragmented tropical and sub-tropical landscapes in Australia, Colombia and Nigeria. Using linear mixed effect models, we modeled seed diversity, abundance, richness and evenness as functions of the biological features and landscape context of isolated trees. Results: Throughout all regions, the amount of woody vegetation surrounding trees in pastures was negatively related to rainforest seed diversity, evenness and abundance. Seed diversity and evenness increased significantly with the distance of isolated trees to forest fragments in the Australian sub-tropics, but elsewhere, seed diversity and evenness tended to decline with distance to forest, though not significantly. Conclusions: Our results suggest that the tree composition of landscapes surrounding isolated pasture trees is important for influencing zoochorous-dispersed seed rain, regardless of the region studied. Our study highlights the prominent role of landscape-scale, rather than local-scale factors on seed dispersal to isolated pasture trees, while providing strong evidence that early stage successional processes involving isolated pasture trees are similar throughout global tropical regions.

研究背景：孤立牧场树木（isolated pasture trees）可通过吸引种子传播者、促进幼苗生长，在破碎化热带景观的森林恢复过程中发挥关键作用。然而，现有相关研究结果存在分歧，导致学界对孤立树冠下动物传播（zoochorous-dispersed）的种子雨格局的变异驱动因素产生认知困惑。
研究目标：评估全球三大热带区域内，孤立牧场树木冠层下动物传播的种子雨所受景观因子与生物因子的影响作用。
研究方法：我们对澳大利亚、哥伦比亚与尼日利亚境内12处破碎化热带及亚热带景观中的144株孤立牧场树木开展冠下种子扩散监测。采用线性混合效应模型（linear mixed effect models），以孤立牧场树木的生物特征与景观背景为预测变量，构建种子多样性、丰度、物种丰富度及均匀度的响应模型。
研究结果：在所有研究区域中，牧场周边木本植被的覆盖量与雨林源种子的多样性、均匀度及丰度呈显著负相关关系。在澳大利亚亚热带区域，孤立牧场树木与森林片段的距离越大，种子多样性与均匀度显著升高；而在其余研究区域，种子多样性与均匀度虽随与森林片段的距离增加呈下降趋势，但未达到统计学显著水平。
研究结论：本研究结果表明，无论研究区域为何，孤立牧场树木周边景观的木本植被组成，均对动物传播的种子雨格局具有显著影响。本研究强调，景观尺度因子而非局地尺度因子，对孤立牧场树木的种子扩散过程具有主导作用；同时有力证实，涉及孤立牧场树木的早期演替过程在全球热带区域具有高度一致性。