The Science

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.

The Impact

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.

Summary

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.

Principal Investigator

Joshua B. Fisher
UCLA, JPL
joshbfisher@gmail.com

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
daniel.stover@science.doe.gov

Funding

DOE BER Environmental System Science (formerly Terrestrial Ecosystem Science) program and the NSF Ecosystem Science program.

References