Unearthing microbial “nutrient mining” as a driver of terrestrial biogeochemistry

Microorganisms break down soil organic matter (SOM), thus releasing nutrients to sustain global plant productivity.

I will investigate how microbial demand for limiting resources determines the balance between carbon (C), nitrogen (N) and phosphorus (P) release in soils, testing the hypothesis that microorganisms target specific components of SOM (microbial “nutrient mining”) to avoid resource limitation.

To do so, I will use state-of-the-art isotopic tools and a four-stage methodological approach, scaling up from simple to more complex systems.

Specifically, I will:Assess how the availability of limiting resources (C, N, P) affects how bacteria and fungi “mine” nutrients from SOM, using controlled microcosm systems; Examine how shifts in the balance of C:N:P at the ecosystem scale affect microbial mining for nutrients, using soils from fertilization and plant-input-and-removal field experiments;Validate findings from stages 1 and 2 using soils from natural fertility gradients;Synthesize the insights from stages 1–3 to develop a conceptual framework which describes: (i) the nutritional conditions under which microorganisms become limited by C, N or P, and (ii) how microbial demand for these limiting resources affects the balance of nutrient release from SOM to fuel plant growth.

Together, these advances will help inform Earth Systems Models used to predict the response of terrestrial ecosystems to future climate change.