The function of ectomycorrhizal fungi in regenerating and mature forests

外生菌根真菌(EM)是北方森林土壤中约30%的微生物生物量和60%的土壤碳通量的根部共生体。EM真菌的研究主要是关于它们通过增加养分供应来改变寄主生长的作用，但越来越多地，它们在养分循环中的潜在作用也得到了重视。在野火或伐木等破坏林分的干扰之后，在更新林中定居幼苗的EM真菌与在原始森林中定居幼苗的EM真菌不同。我建议继续使用最近的Clearcuts作为一个模型系统来回答有关EM真菌群落在干扰后如何重建的基本问题。我们将研究在皆伐地定植幼苗的EM真菌是否与在森林中定植幼苗的真菌在生理上不同，或者具有不同的传播机制。具体地说，我们将使用稳定同位素方法来研究EM真菌对氮素的吸收及其向幼苗的转移，以及这两类真菌对宿主植物固定碳的相对需求。此外，我们将量化(I)气生孢子、(Ii)持久繁殖体库和(Iii)根到根的菌丝传播作为山地云杉/松林和砍伐林中接种物来源的相对重要性。最近关于EM真菌的一个有趣的发现是，一个真菌个体可以同时在几个相邻树木的根系上定居。虽然研究已经调查了这些菌丝网络如何影响地下碳和养分从一棵树到另一棵树的转移，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。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)作为这些营养物质的示踪剂。这两条研究路线都将增加我们对在加拿大混交林和针叶林中普遍存在的EM真菌如何影响生态系统服务和植物营养，以及森林管理可能如何影响这些服务的理解。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.