The function of ectomycorrhizal fungi in regenerating and mature forests

外生菌根（EM）真菌是根共生体，约占北方森林土壤微生物生物量的30%，并介导60%的土壤碳通量。EM真菌的研究主要是关于它们通过增加养分供应来调节宿主生长的作用，但它们在养分循环中的潜在作用也越来越受到重视。在林分破坏干扰（如野火或砍伐）之后，在再生林分中定植幼苗的EM真菌与在原始森林中定植幼苗的真菌不同。我建议继续使用最近的砍伐作为模型系统来回答关于EM真菌群落如何在干扰后重建的基本问题。我们将研究在森林中定植幼苗的EM真菌是否在生理上与在森林中定植幼苗的真菌不同，或者具有不同的扩散机制。具体而言，我们将使用稳定同位素方法研究EM真菌对氮的吸收及其向幼苗的转运，以及这两类真菌对寄主植物固定碳的相对需求。此外，我们将量化(i)空中孢子，（ii）持久繁殖体库和（iii）作为接种源的根到根菌丝传播在山地云杉林/松林和砍伐地的相对重要性。最近一项关于EM真菌的有趣发现是，单个真菌个体可以同时在几棵邻近树木的根系中定植。虽然研究已经调查了这些菌丝体网络如何影响碳和营养物质从一棵树到另一棵树的地下转移，但我们将采取以真菌为中心的方法来研究影响真菌向每个宿主分配矿物质营养物质的因素。我们将在实验室中使用稳定同位素和量子点（荧光纳米粒子）作为这些营养物质微观世界的示踪剂。这两项研究将增加我们对EM真菌的理解，EM真菌在加拿大混交林和针叶林中无处不在，它们如何影响生态系统服务和植物营养，以及森林管理如何影响这些服务。将培训10名本科生和5名研究生。

Ectomycorrhizal (EM) fungi are root symbionts that account for approximately 30% of microbial biomass in boreal forest soils and mediate throughput of 60% of soil carbon. EM fungi have been studied primarily with respect to their role in modifying host growth by increasing nutrient supply but, increasingly, their potential role in nutrient cycling is also being appreciated. Following stand-destroying disturbances, such as wildfire or clearcut logging, EM fungi that colonize seedlings in regenerating stands are different from those that colonize seedlings in the original forest. I propose to continue to use recent clearcuts as a model system to answer fundamental questions about how EM fungal communities re-establish after disturbance. We will examine whether EM fungi that colonize young seedlings in clearcuts differ physiologically, or have different mechanisms of dispersal, than fungi that colonize seedlings in forests. Specifically, we will use stable isotope approaches to study the uptake of nitrogen and its translocation to seedlings by EM fungi, as well as the relative demands of these two groups of fungi for fixed carbon from their host plants. In addition, we will quantify the relative importance of (i) aerial spores, (ii) persistent propagule banks and (iii) root-to-root hyphal spread as sources of inocula in montane spruce/pine forests and clearcuts. A fascinating recent discovery about EM fungi is that a single fungal individual can concurrently colonize root systems of several neighbouring trees. While studies have investigated how these mycelial networks influence belowground transfer of carbon and nutrients from one tree to the other, we will take a fungus-centered approach to ask what factors influence the distribution of minerals nutrients by the fungus to each host. We will use stable isotopes and quantum dots (fluorescent nano-particles) as tracers for these nutrients in microcosms in the lab. Both these lines of research will increase our understanding how EM fungi, which are ubiquitous in Canadian mixed and coniferous forests, influence ecosystem services and plant nutrition, as well as how forest management may affect those services. Ten undergraduate and five graduate students will be trained.