How do mycorrhizal fungal traits influence ecosystem functioning?

菌根真菌（MF）与世界上大多数植物有关。它们接收植物光合作用产物的重要部分，并且作为交换，它们为宿主植物提供改善的营养和对生物和非生物胁迫的耐受性。鉴于MF接收的植物源碳（C）占很大比例，它们极有可能影响C循环的主要步骤。许多研究确实表明，MF可以通过改变凋落物分解或植物初级生产力来显著影响C循环。然而，不同种类的微生物量在其特征上存在很大差异，这可能会对碳循环和生态系统功能产生更广泛的影响。一个基于特征的框架是必要的，以更好地预测具体性状的MF如何影响生态系统过程。这是我研究计划的核心。我专注于一组特定的MF，即丛枝菌根（AM）真菌，这是最广泛的MF组。通过多种技术手段，本研究将有助于回答以下问题：1-AM真菌是否稳定土壤有机质？例如，我们将评估AM真菌对土壤团聚体中植物来源的C整合的影响，并确定AM真菌是否会对其他土壤真菌的分解活性产生负面影响。2-植物是否会招募具有特定性状的AM真菌？这项工作将大大推进我们对AM真菌生态学的理解，也是对植物生态学的理解：几位作者已经认识到，植物功能策略不仅整合了它们自己的性状或特征，而且还整合了它们的微生物共生体（如AM真菌）的性状。因此，我们可以预期植物和AM真菌之间的性状相关性。这将促进AM真菌在C循环模型中的整合，因为植物性状比真菌性状更容易测量：用前者估计后者会很方便。3-植物来源的碳在AM真菌组织中的停留时间是多少？鉴于大量的碳转移到AM真菌，我们必须更好地了解其在土壤中的命运。例如，如果快速生长的AM真菌迅速替换它们的组织，并迅速将植物来源的C呼吸回大气中，那么在全球机会下增加AM真菌的C分配可能不会转化为土壤C储存的增加。我们迫切需要在AM真菌组织中表征碳周转，在这方面，总的来说，我的研究计划将提供一个有凝聚力的尝试，以促进我们了解AM真菌如何驱动土壤碳循环。使用基于特征的方法，这里提出的工作也将为研究AM真菌的功能策略铺平道路。这本身将是该领域的一个重大进步：植物生态学是一个很好的例子，说明基于特征的方法如何在科学学科中带来新的问题和见解。我的目标是促进AM真菌生态学的类似飞跃。

Mycorrhizal fungi (MF) associate with a majority of plants worldwide. They receive a significant portion of plant photosynthesis products, and in exchange they provide their host plants with an improved nutrition and tolerance to biotic and abiotic stresses. Given the large fraction of plant-derived carbon (C) that MF receive, they are highly likely to influence major steps of the C cycle. Many studies have indeed showed that MF can drastically influence C cycling through the alteration of litter decomposition or of plant primary productivity. However, different species of MF vary considerably in their traits, which may translate into different impacts on C cycling and ecosystem functioning more broadly. A trait-based framework is necessary to better predict how specific traits of MF influence ecosystem processes. This is the core of my research program. I focus on a specific group of MF, namely arbuscular mycorrhizal (AM) fungi, which are the most widespread group of MF. Using a variety of techniques, my research will contribute to answer the following questions:1- Do AM fungi stabilize soil organic matter? We will assess, for example, the impact of AM fungi on the integration of plant-derived C within soil aggregates, and we will determine whether AM fungi negatively impact the decomposing activity of other soil fungi.2- Do plants recruit AM fungi with specific traits? This work will significantly advance our understanding of AM fungal ecology, but also of plant ecology: it has been recognized by several authors that plant functional strategies not only integrate their own traits or characteristics, but also the traits of their microbial symbionts, such as AM fungi. We may thus expect trait correlations between plants and AM fungi. This would facilitate the integration of AM fungi in C cycling models, because plant traits are much easier to measure than fungal traits: it would be convenient to estimate the latter with the former. 3- What is the residence time of plant-derived C in AM fungal tissues? Given the large amount of C transferred to AM fungi, we must better understand its fate in the soil. If fast-growing AM fungi quickly replace their tissues and rapidly respire back plant-derived C to the atmosphere, then an increased allocation of C to AM fungi under global chance might not translate into an increased soil C storage, for example. We urgently need to characterize C turnover in AM fungal tissue, in this regard.Overall, my research program will offer a cohesive attempt to advance our understanding how AM fungi drive soil C cycling. Using a trait-based approach, the work presented here will also pave the way for studying functional strategies in AM fungi This, in itself, will be a major advancement of the field: plant ecology is an excellent example of how a trait-based approach can bring novel questions and insights in a scientific discipline. My aim is to promote a similar leap forward in AM fungai ecology.