Smithsonian Environmental Research Center, 647 Contees Wharf Rd, Edgewater, MD, 21037, USA.
Department of Biological Sciences, University of Pittsburgh, A234 Langley Hall, 4249 Fifth Avenue, Pittsburgh, PA, 15260, USA.
New Phytol. 2017 Oct;216(1):99-112. doi: 10.1111/nph.14716. Epub 2017 Aug 7.
Producing and retaining leaves underlie the performance and survivorship of seedlings in deeply shaded tropical forests. These habitats are characterized by conditions ideal for foliar bacteria, which can be potent plant pathogens. Leaf production, retention and susceptibility to enemies may ultimately depend upon interactions among soil nutrients and foliar microbes, yet this has never been tested. We experimentally evaluated the degree that foliar bacteria and soil resource supply mediate leaf dynamics for five common tree species (five different families) in a Panamanian forest. We reduced foliar bacteria with antibiotics for 29 months and measured leaf production, retention and damage for seedlings nested within a replicated 15-yr factorial nutrient enrichment experiment (nitrogen, N; phosphorus, P; potassium, K). Our results demonstrate that when we applied antibiotics, soil nutrients - particularly N - always regulated seedling leaf production (and to a lesser extent herbivore damage) for all five tree species. In addition, it was common for two macronutrients together to negate or completely reverse the impact of applying either one alone. Our findings of frequent plant-microbe-nutrient interactions are novel and suggest that these interactions may reinforce plant species-environment associations, thereby creating a fairly cryptic and fine-scale dimension of niche differentiation for coexisting tree species.
在深阴影热带森林中，产生和保留叶子是幼苗表现和存活的基础。这些栖息地的特点是非常适合叶细菌生长的条件，而叶细菌可能是强大的植物病原体。叶片的产生、保留和对敌人的易感性最终可能取决于土壤养分和叶微生物之间的相互作用，但这一点从未得到过检验。我们通过实验评估了叶细菌和土壤资源供应在多大程度上影响了巴拿马森林中五种常见树种（五个不同的科）的叶片动态。我们用抗生素处理了 29 个月，以测量嵌套在重复 15 年养分富集实验（氮、磷、钾）中的幼苗的叶片产生、保留和损伤。我们的研究结果表明，当我们应用抗生素时，土壤养分——特别是氮——总是调节着所有五种树木的幼苗叶片产生（以及较小程度的食草动物损伤）。此外，两种大量营养素一起作用，通常会否定或完全扭转单独应用其中一种的影响。我们频繁发现植物-微生物-养分相互作用的结果是新颖的，这表明这些相互作用可能会加强植物与环境的联系，从而为共存的树种创造出一个相当隐蔽和精细的生态位分化维度。
