BACKGROUND AND AIMS In fragmented forests, proximity to forest edges can favor 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-specific leaf area (SLA), leaf dry matter content (LDMC), wood density, and seed size-explained interspecific differences in densities of seedling recruits with distance to 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 to 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 to 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.

中文翻译：

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边缘效应改变了真菌和昆虫在调节破碎热带森林幼苗功能组成和多样性方面的作用

背景和目标 在破碎的森林中，靠近森林边缘有利于建立资源获取型物种，而不是更多的资源保守型物种。在幼苗招募期间，资源获取性物种可能受益于更高的光照可用性或天敌较弱的自上而下效应。光和敌人对招募的相对重要性很少在边缘效应方面得到检验。方法在印度人工改造的湿热带森林中，我们首先研究了指示资源获取策略与资源节约策略的功能特征的具体叶面积 (SLA)、叶干物质含量 (LDMC)、木材密度和种子幼苗新兵密度与森林边缘距离的大小解释的种间差异。然后，我们检查了杀菌剂和杀虫剂处理以及冠层开放度（光照可用性的代理）是否解释了对性状介导的幼苗密度变化的边缘效应。最后，我们检查了光照可用性和天敌活动是否解释了对幼苗新兵功能多样性的边缘效应。主要结果距边缘 60 m 以内，募集密度随着种子大小的减小而增加，但在 90-100 m 处则不然，其中募集密度随着 SLA 的升高而增加。性状介导的募集密度变异仅在 90-100 m 处随农药发生变化：与对照地块相比，杀菌剂增加了低 SLA 物种的募集密度，杀虫剂增加了较小种子物种。对于 SLA、木材密度和种子大小，90-100 m 处新兵的功能多样性高于 0-5 m 处。在 90-100 m，与对照地块相比，杀菌剂降低了 SLA 的功能多样性，杀虫剂降低了种子大小的多样性。冠层开放度既不能解释与特征相关的招募密度变化，也不能解释功能多样性。结论 在森林碎片中幼苗补充过程中，改变的生物相互作用可以调节性状组成和功能多样性的局部变化，暗示下游对人工改造森林的结构和功能的影响。