Plant-soil feedback and species coexistence: interactions among soil pathogens, irradiance, and species life histories

生态学家长期以来一直对如何在一片给定的森林中共存这么多树种感到困惑。该项目的主要目标是将两个看似无关但相互竞争的机制联系起来，这两个机制已被提出用于树种共存。这就是树种对光照可获得性以及同一物种中其他个体密度的增加或接近程度的反应。树木幼苗对土壤真菌的反应可能是树木幼苗对同一物种其他个体的光可获得性和密度反应的关键。在弱光环境中，许多物种的幼苗对与其自身物种相关的土壤病原菌的死亡率可能会增加，在被认为“不耐荫”的物种中更为普遍。此外，这些生物植物-土壤反馈可能在增强物种之间对光的反应方面的差异方面发挥了很大作用。这项研究可能有助于更好地定义遮荫耐受性和解释树种共存；这两个结果对于有效保护和管理温带森林至关重要。例如，对于有特殊光照要求或更新困难的树种，结果可能会对森林恢复或木材工业产生影响。此外，该项目将在植物和土壤微生物生态学方面对本科生进行教育、培训和指导，并向当地K-12教师和学生提供公共宣传。该项目的主要目标是研究生物植物-土壤反馈，这些反馈可以影响跨光梯度和具有不同生活史特征的树种之间依赖距离和密度的幼苗存活和生长。研究人员将采用一种新颖的田间移栽实验，使用真菌排除盆栽，该实验将研究树木幼苗对以下因素的反应机制：1)植物和土壤微生物群落之间的反馈作为光可获得性的函数，以及2)8种温带树种对弱光的反应作为这些反馈的函数，这些树种在苗木耐荫性、当地成虫丰度以及与丛枝和外生菌根真菌的联系方面存在差异。因此，这项研究将调查植物-土壤反馈不仅通过负密度依赖过程，而且作为物种光梯度分配的驱动因素，对物种共存的贡献程度。该项目还将调查哪些因素(例如，土壤病原体密度和组成，和/或苗木性状)在弱光下对疾病和植物-土壤反馈产生更大的负面影响。

Ecologists have long been puzzled about how so many tree species can coexist within a given forest. The main goal of the project is to link two seemingly unrelated and competing mechanisms that have been proposed for tree species coexistence. These are how tree species respond to light availability and to increasing density or proximity of other individuals of the same species. Tree seedling response to soil fungi may hold the key to tree seedling response to light availability and densities of other individuals of the same species. Seedling mortality to soil pathogens associated with their own species is likely enhanced in low light environments for many species, and much more prevalent in species considered 'shade intolerant'. In addition, these biotic plant-soil feedbacks may play a large role in heightening differences among species in their responses to light. This research may help to better define shade tolerance and explain tree species coexistence; both results are vital for effective conservation and management of temperate forests. For instance, results may have implications for forest restoration or the timber industry with regards to tree species with specific light requirements or regeneration difficulties. Additionally, this project will educate, train and mentor undergraduate students in plant and soil microbial ecology as well as provide public outreach to local K-12 teachers and students. The primary goal of the project is to investigate biotic plant-soil feedbacks that can affect distance- and density-dependent seedling survival and growth across light gradients and among tree species with varying life-history traits. The researchers will employ a novel field-based transplant experiment using fungal exclusion pots, which will investigate the mechanisms of tree seedling response to: 1) feedbacks between plants and the soil microbial community as a function of light availability, and 2) response to low light as a function of these feedbacks for eight temperate tree species that vary in seedling shade tolerance, local adult abundance and association with arbuscular and ectomycorrhizal fungi. Thus, this research will investigate the degree to which plant-soil feedbacks contribute to species coexistence through not only negative-density dependent processes, but also as a driver of species light gradient partitioning. The project will also investigate which factors (e.g., soil pathogen density and composition, and/or seedling traits) contribute to greater negative effects from disease and plant-soil feedback in low light.