DISSERTATION RESEARCH: Effects of nitrogen addition on ectomycorrhizal communities in tropical montane forest

论文研究：氮添加对热带山地森林外生菌根群落的影响

• 批准号: 1501483
• 负责人: James Dalling
• 金额: $ 1.73万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-05-01 至 2016-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1501483&HistoricalAwards=false
• 关键词: DISSERTATION; RESEARCH; Effects; nitrogen; addition

Tropical forests are renowned for their high biodiversity, with hundreds or even thousands of tree species living together at a single site. In some tropical forests, however, a single tree species can outnumber all other species combined. Recent attempts to explain this one-species dominance have focused on the role of soil microbes in determining which tree species are common and which are rare. Attention has been on beneficial associations between trees and fungi in their roots, called mycorrhizas. A leading idea about why some tropical trees are so common is that they are uniquely capable of forming associations with particular types of mycorrhizal fungi that provide access to nitrogen that is unavailable to less common tree species. Experimental work from a forest in western Panama is consistent with this hypothesis, leading to the question of how this plant-mycorrhizal association, and therefore tree community composition, may be disrupted by increasing rates of nitrogen deposition from the atmosphere. Will this new and relatively plentiful form of nitrogen make mycorrhizal fungi unimportant? Effects of nitrogen on the plant-mycorrhizal association of a dominant tree will be addressed by comparing mycorrhizal fungal communities in forest plots with and without a treatment of nitrogen fertilization over the last eight years. This project will also provide training in fungal genetics and ecology to a graduate student, and research mentoring for undergraduate students. The ectomycorrhizal fungal community associated with a dominant canopy tree, Oreomunnea mexicana, will be characterized in eight forest plots located in lower montane forest at Fortuna, Panama. Four of the plots have received a nitrogen addition treatment four times per year since 2008. In each plot, root samples will be collected from Oreomunnea trees and ectomycorrhizal communities characterized using Illumina sequencing. It is predicted that nitrogen addition will reduce the diversity and infection frequency of ectomycorrhizal taxa and result in a shift in the composition and phylogenetic structure of ectomycorrhizal communities, favoring lineages known to contain nitrophilic taxa.

热带森林以其高度的生物多样性而闻名，数百甚至数千种树种共同生活在一个地点。然而，在一些热带森林中，一种树种的数量可能超过所有其他树种的总和。最近试图解释这种单一物种优势的尝试集中在土壤微生物在决定哪些树种是常见的，哪些是罕见的方面的作用。人们一直关注树木与其根部真菌（称为菌根）之间的有益联系。关于为什么一些热带树木如此普遍的一个主要观点是，它们具有独特的能力，能够与特定类型的菌根真菌形成联系，这些真菌可以提供不太常见的树种无法获得的氮。来自巴拿马西部森林的实验工作与这一假设是一致的，这导致了这样一个问题：这种植物与菌根的联系，以及树木群落的组成，是如何被大气中氮沉降速率的增加所破坏的。这种新的和相对丰富的氮形式会使菌根真菌变得不重要吗？通过比较近8年来施用氮肥和未施用氮肥的森林样地的菌根真菌群落，探讨氮对优势树植物-菌根关联的影响。该项目还将为研究生提供真菌遗传学和生态学方面的培训，并为本科生提供研究指导。本文对巴拿马Fortuna低山林的8个样地的外生菌根真菌群落进行了研究。自2008年以来，其中四个地块每年进行四次氮肥处理。在每个地块，将收集Oreomunnea树木和外生菌根群落的根样品，并使用Illumina测序进行鉴定。结果表明，氮素的添加会降低外生菌根群落的多样性和侵染频率，导致外生菌根群落的组成和系统发育结构发生改变，有利于已知含有亲氮类群的谱系。