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Microbial limitation

Project team: Manon Rumeau (Université de Pau et des Pays de l’Adour), Fotis Sgouridis (University of Bristol), Catriona A. Macdonald (Western Sydney University), Paola Pisetta Raupp (Western Sydney University), Charles Warren, (University of Sydney) Michaela K. Reay (University of Bristol), A. Rob MacKenzie (University of Birmingham), Sami Ullah (University of Birmingham) and Yolima Carrillo (Western Sydney University)

Project period: 2022 – 2026

You can find contacts to the Western Sydney University members of the project here

Summary

We aimed to determine whether the limiting factors for soil decomposer microbes were altered under elevated CO₂. We determined the limiting factor for soil microbes 

Key findings: We found that soil microbial growth under ambient CO₂ was primarily limited by C and secondarily limited by P. Microbial C limitation was enhanced under elevated CO₂ , though we expected that increased plant-derived C inputs under elevated CO₂  could reduce microbial C limitation. The enhanced C limitation was attributed to a higher C demand of a fast‑growing, copiotrophic decomposer community under eCO₂ . 

This conceptual figure illustrates how elevated CO₂ (eCO₂) influence microbial resource limitation and it feedback to responses of mature forest ecosystems to eCO₂, incorporating both previous findings (in blue) and new insights from the present study (in yellow). Under ambient CO₂, plant growth is primarily limited by phosphorus (P), and the current study reveals that microbial growth is primarily limited by carbon (C) and secondarily limited by P. Under eCO₂, increased photosynthesis enhances C input to the soil, stimulating microbial growth. Further, this acceleration leads to greater microbial demand for resources, intensifying both microbial C and P limitation. It explains the intensified competition for P between plants and microorganisms. Further, the intensified P competition may reduce C sequestration by primary production and increase C emissions from the soil, potentially diminishing the long-term capacity of ecosystems to act as C sinks under elevated CO₂.

Publications

It is completed and a paper has just been accepted by Communications Earth & Environment Mar 17, 2026. “Could soil decomposer microbes determine the ecosystem response to rising atmospheric CO2?“

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