边缘效应改变了真菌和昆虫在调节热带森林中幼苗补充功能组成和多样性方面的作用。

Edge effects alter the role of fungi and insects in mediating functional composition and diversity of seedling recruits in a fragmented tropical forest.

机构信息

School of Forestry and Environmental Studies, Yale University, New Haven, CT, USA.

Centre for Cellular and Molecular Biology, Habshiguda, Hyderabad, Telangana, India.

出版信息

Ann Bot. 2020 Nov 24;126(7):1181-1191. doi: 10.1093/aob/mcaa138.

DOI:10.1093/aob/mcaa138

PMID:32710752

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC7684699/

Abstract

BACKGROUND AND AIMS

In fragmented forests, proximity to forest edges can favour the establishment of resource-acquisitive species over more resource-conservative species. During seedling recruitment, resource-acquisitive species may benefit from either higher light availability or weaker top-down effects of natural enemies. The relative importance of light and enemies for recruitment has seldom been examined with respect to edge effects.

METHODS

In a human-modified wet tropical forest in India, we first examined how functional traits indicative of resource-acquisitive vs. resource-conservative strategies, i.e. specific leaf area (SLA), leaf dry matter content, wood density and seed size, explained interspecific differences in densities of seedling recruits with distance to the forest edge. Then, we checked whether fungicide and insecticide treatments and canopy openness (proxy for light availability) explained edge effects on trait-mediated changes in seedling density. Finally, we examined whether light availability and natural enemy activity explained edge effects on functional diversity of seedling recruits.

KEY RESULTS

Up to 60 m from edges, recruit densities increased with decreasing seed size, but not at 90-100 m, where recruit densities increased with higher SLA. Trait-mediated variation in recruit densities changed with pesticides only at 90-100 m: compared with control plots, fungicide increased recruit densities for low SLA species and insecticide increased smaller seeded species. For SLA, wood density and seed size, functional diversity of recruits was higher at 90-100 m than at 0-5 m. At 90-100 m, fungicide decreased functional diversity for SLA and insecticide reduced seed size diversity compared with control plots. Canopy openness explained neither variation in recruit density in relation to traits nor functional diversity.

CONCLUSIONS

Altered biotic interactions can mediate local changes to trait composition and functional diversity during seedling recruitment in forest fragments, hinting at downstream effects on the structure and function of human-modified forests.

摘要

背景和目的

在破碎化的森林中，靠近森林边缘可能有利于资源获取型物种的建立，而不利于资源保守型物种。在幼苗补充过程中，资源获取型物种可能受益于更高的光照可用性或较弱的天敌的下行效应。光照和天敌对幼苗补充的相对重要性很少根据边缘效应进行检验。

方法

在印度的一个人为干扰的热带湿地森林中，我们首先检查了资源获取型和资源保守型策略的功能特征（即比叶面积、叶干物质含量、木材密度和种子大小），如何解释距离森林边缘不同距离的幼苗补充的种间密度差异。然后，我们检查了杀菌剂和杀虫剂处理以及冠层开度（光照可用性的代理）是否解释了边缘效应对幼苗密度的特征介导变化的影响。最后，我们检查了光照可用性和天敌活动是否解释了边缘效应对幼苗补充的功能多样性的影响。

主要结果

在距离边缘 60 米以内，随着种子尺寸的减小，幼苗密度增加，但在 90-100 米处没有增加，在 90-100 米处，幼苗密度随着 SLA 的升高而增加。在 90-100 米处，只有在杀菌剂和杀虫剂处理的情况下，幼苗密度的特征介导变化才会发生变化：与对照小区相比，杀菌剂增加了 SLA 低的物种的幼苗密度，而杀虫剂增加了种子较小的物种的幼苗密度。对于 SLA、木材密度和种子大小，90-100 米处的幼苗补充功能多样性高于 0-5 米处。在 90-100 米处，杀菌剂降低了 SLA 的功能多样性，而杀虫剂降低了对照小区的种子大小多样性。冠层开度既不能解释与特征相关的幼苗密度变化，也不能解释功能多样性。