March 23, 2019
Inclusion of Plant-Microbe Partnerships Enhances Global Land Models
Diverse mycorrhizal associations enhance terrestrial carbon storage in a global model.
Ecosystems remove CO2 from the atmosphere and in doing slow climate change. However, given that low availability of soil nitrogen can limit how much CO2 plants can take up, factors that control nitrogen cycling are key modulators of an ecosystem’s carbon uptake potential. Two groups of microbes that live in symbiosis with plants control nitrogen cycling in most ecosystems: fungi, which extract nitrogen from detritus and exchange it with plants, and bacteria, which take up atmospheric nitrogen from the atmosphere and exchange it with plants. Both mechanisms provide plants with sources of nitrogen that allow them to process more CO2, but these mechanisms have not been incorporated into existing climate models.
More accurate estimates of the amount of CO2 taken up terrestrial ecosystems can be reported by including plant-microbe symbioses in climate models. The findings from this paper suggest that ecosystems that depend on different nitrogen acquisition methods are key to understanding rates of future climate change. To reach an increase in global net production and higher CO2 use, there would need to be a shift to species with better nitrogen acquisition methods.
Simulations were run using an existing land model that simulates carbon cycling in vegetation and soil, as well as water and energy fluxes. This was combined with a new coupled carbon-nitrogen cycle framework and an explicit model of plant-microbial symbioses to create a more robust global land model that accounts for nitrogen constraints of vegetation responses to elevated CO2. Results of the new model illustrate the major drivers in carbon-nitrogen cycling, global patterns of nitrogen acquisition, and the global response to an increase in CO2.
Joshua B. Fisher
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
DOE BER Environmental System Science (formerly Terrestrial Ecosystem Science) program and the NSF Ecosystem Science program.
Sulman, B.N., et al. "Diverse Mycorrhizal Associations Enhance Terrestrial C Storage in a Global Model." Global Biogeochemical Cycles 33 (4), 501–523 (2019). https://doi.org/10.1029/2018GB005973.