How do mycorrhizal fungal traits influence ecosystem functioning?

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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.