The Science

Current model simulations using version 1 of the Energy Exascale Earth System (E³SM) land model (ELM v1) show that the consideration of phosphorus availability leads to a smaller carbon sink associated with a carbon dioxide (CO₂) fertilization effect and lower carbon emissions resulting from land-use and land-cover changes (LULCC). These simulations suggest phosphorus limitation would significantly reduce the carbon sink associated with CO₂ fertilization effects through the 21st century.

The Impact

This study suggests that the Amazon tropical forests may offer less protection against future climate change than suggested by previous modeling studies due to phosphorus limitation.

Summary

The phosphorus-enabled ELM v1 model was used to investigate the effects of phosphorus cycle dynamics and phosphorus limitation on Amazon forest carbon sources and sinks. Historical simulations suggest that the consideration of phosphorus availability leads to (1) a smaller carbon sink associated with the CO₂ fertilization effect and (2) lower carbon emissions due to LULCC. When all environmental factors are considered, the study’s model simulations show a smaller carbon sink in the Amazon region when phosphorus limitation is considered. Modeling simulations from the Next-Generation Ecosystem Experiments (NGEE)–Tropics and Oak Ridge National Laboratory used with CO₂ concentrations from Representative Concentration Pathway scenarios RCP8.5 and RCP4.5 suggest that phosphorus limitation is critical for projecting future carbon uptake in tropical ecosystems. The predicted carbon sink in Amazon rainforests would be much smaller when phosphorus limitation is considered, suggesting that the Amazon tropical forests may offer less protection against future climate change than suggested by previous modeling studies.

Principal Investigator

Xiaojuan Yang
Oak Ridge National Laboratory
yangx2@ornl.gov

Program Manager

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

Funding

X. Yang, P. E. Thornton, D. M. Ricciuto, X. Shi, M. Xu, F. M. Hoffman, and R. Norby are supported by the Office of Biological and Environmental Research (BER), within the U.S. Department of Energy (DOE) Office of Science. This support includes funding from several BER programs and projects: Terrestrial Ecosystem Science program and its Next-Generation Ecosystem Experiments (NGEE)–Tropics activity; Earth System Modeling Development program (E³SM project), and the Regional and Global Model Analysis program [Reducing Uncertainty in Biogeochemical Interactions Through Synthesis and Computation (RUBISCO) Science Focus Area].

References