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Seed-rain–successional feedbacks in wet tropical forests
Ecology ( IF 4.8 ) Pub Date : 2021-04-09 , DOI: 10.1002/ecy.3362
Nohemi Huanca Nuñez 1 , Robin L Chazdon 2 , Sabrina E Russo 1, 3
Affiliation  

Tropical forest regeneration after abandonment of former agricultural land depends critically on the input of tree seeds, yet seed dispersal is increasingly disrupted in contemporary human-modified landscapes. Here, we introduce the concept of seed-rain–successional feedbacks as a deterministic process in which seed rain is shaped by successional dynamics internal to a forest site and that acts to reinforce priority effects. We used a combination of time series and chronosequence approaches to investigate how the quantity and taxonomic and functional composition of seed rain change during succession and to evaluate the strength of seed-rain–successional feedbacks, relative to other deterministic and stochastic mechanisms, in secondary wet forests of Costa Rica. We found that both successional niches and seed-rain–successional feedbacks shaped successional trajectories in the seed rain. Determinism due to successional niche assembly was supported by the increasing convergence of community structure to that of a mature forest, in terms of both functional and taxonomic composition. With successional age, the proportions of large-seeded, shade-tolerant species in the seed rain increased, whereas the proportion of animal-dispersed species did not change significantly. Seed-rain–successional feedbacks increased in strength with successional age, as the proportion of immigrant seeds (species not locally represented in the site) decreased with successional age, and the composition of the seed rain became more similar to that of the adult trees at the forest site. The deterministic assembly generated by seed-rain–successional feedback likely contributed to the increasing divergence of secondary forest sites from each other during succession. To the extent that human modification of tropical forest landscapes reduces connectivity via factors such as forest cover loss, our results suggest that seed-rain–successional feedbacks are likely to increasingly shape regeneration trajectories in and amplify floristic heterogeneity among tropical secondary forests.

中文翻译:

湿热带森林中的种子-雨-连续反馈

废弃前农业用地后热带森林的再生在很大程度上取决于树木种子的输入,但在当代人工改造的景观中,种子传播越来越受到干扰。在这里,我们引入了种子雨连续反馈的概念,作为一个确定性过程,其中种子雨是由森林场地内部的连续动态形成的,并起到加强优先效应的作用。我们使用时间序列和时间序列方法的组合来研究种子雨的数量和分类学和功能组成如何在演替过程中发生变化,并评估种子雨 - 连续反馈的强度,相对于其他确定性和随机机制,在次生湿哥斯达黎加的森林。我们发现演替生态位和种子雨 - 连续反馈都塑造了种子雨的演替轨迹。在功能和分类组成方面,群落结构与成熟森林的结构日益趋同,支持了由于连续生态位组装而产生的确定性。随着演替年龄的增加,种子雨中大种子、耐阴物种的比例增加,而动物散布物种的比例没有显着变化。种子-雨-连续反馈强度随着年龄的增加而增加,因为移民种子(在该地点没有本地代表的物种)的比例随着年龄的增加而减少,种子雨的组成变得更类似于在森林站点。由种子-雨-连续反馈产生的确定性组装可能导致次生林在演替过程中彼此之间的差异越来越大。由于人类对热带森林景观的改造通过森林覆盖率丧失等因素降低了连通性,我们的研究结果表明,种子-雨-连续反馈可能会越来越多地塑造热带次生林中的再生轨迹并放大热带次生林之间的植物区系异质性。
更新日期:2021-04-09
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