Observational Constraints on Mycorrhizal Nutrient Acquisition Reduce Future Land Carbon Sink Projections

Abstract

Accurately projecting the global carbon cycle requires Earth System Models (ESMs) to represent plant nutrient acquisition and associated carbon costs. However, most ESMs either neglect or oversimplify the role of mycorrhizal fungi, despite their key function in mediating plant-soil nutrient exchanges. Here, we integrate global satellite and field-based datasets on mycorrhizal distributions, soil nitrogen content, and carbon allocation to fungi to constrain nutrient acquisition costs in a land surface model, the Community Land Model (CLM). Incorporating these spatially explicit mycorrhizal costs reduces projected global carbon uptake by 15% over the 21st century. We find that mycorrhizal efficiency varies strongly by biome, with especially high carbon costs in boreal and semi-arid ecosystems. Model performance also improves by 5% in reproducing observed energy, water, and carbon fluxes. These results highlight the critical role of mycorrhizal symbioses in shaping ecosystem carbon balance and underscore the need to integrate fine-scale belowground data together with remote sensing into ESM frameworks for more accurate climate projections.

Authors 11

1. Renato K. Braghiere corresponding

   Jet Propulsion Laboratory

   Affiliation as printed

   Jet Propulsion Laboratory

2. Michael E. Van Nuland

   Society for the Protection of Underground Networks

   Affiliation as printed

   Society for the Protection of Underground Networks

3. E. Toby Kiers

   Vrije Universiteit Amsterdam

   Affiliation as printed

   Vrije Universiteit Amsterdam

4. Heidi‐Jayne Hawkins

   University of Cape Town

   Affiliation as printed

   University of Cape Town

5. Rosie A. Fisher

   CICERO Center for International Climate Research

   Affiliation as printed

   CICERO Center for International Climate Research

6. Joshua B. Fisher

   Chapman University

   Affiliation as printed

   Chapman University

7. Nadia Soudzilovskaia Aachen

   Leiden University

   Affiliation as printed

   Leiden University

8. A. Anthony Bloom

   Jet Propulsion Laboratory

   Affiliation as printed

   Jet Propulsion Laboratory, California Institute of Technology

9. Richard P. Phillips

   Indiana University Bloomington

   Affiliation as printed

   Indiana University Bloomington

10. Woodward W. Fischer

    California Institute of Technology

    Affiliation as printed

    California Institute of Technology

11. Christian Frankenberg

    California Institute of Technology

    Affiliation as printed

    California Institute of Technology