The function of ectomycorrhizal fungi in regenerating and mature forests

外生菌根（EM）真菌是根共生体，占北方森林土壤中微生物生物量的约30%，并介导60%的土壤碳通量。 EM真菌主要研究了它们通过增加营养供应来改变宿主生长的作用，但它们在营养循环中的潜在作用也越来越受到重视。继林分破坏的干扰，如野火或皆伐伐木，EM真菌的殖民幼苗在再生的立场是不同的，从那些殖民幼苗在原始森林。 我建议继续使用最近的皆伐作为一个模型系统来回答关于EM真菌群落如何在干扰后重新建立的基本问题。我们将研究是否EM真菌殖民幼苗皆伐不同生理，或有不同的传播机制，比真菌殖民幼苗在森林中。 具体来说，我们将使用稳定同位素的方法来研究氮的吸收和它的易位到幼苗EM真菌，以及这两组真菌的相对需求固定碳从他们的宿主植物。此外，我们将量化的相对重要性（一）气生孢子，（二）持久性繁殖体银行和（三）根到根菌丝传播接种源在山地云杉/松树林和皆伐。最近关于EM真菌的一个有趣的发现是，单个真菌个体可以同时在几棵相邻树木的根系中定植。 虽然研究已经调查了这些菌丝体网络如何影响地下碳和营养物质从一棵树转移到另一棵树，但我们将采取以真菌为中心的方法来询问哪些因素影响真菌向每个宿主分配矿物质营养物质。 我们将使用稳定同位素和量子点（荧光纳米粒子）作为实验室微观世界中这些营养素的示踪剂。 这两条研究线将增加我们的理解EM真菌，这是无处不在的加拿大混合和针叶林，影响生态系统服务和植物营养，以及如何森林管理可能会影响这些服务。将培养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.