Abstract
Accurate projections of the terrestrial carbon (C) sink are critical to understanding the future global C cycle and setting CO2 emission reduction goals. Current earth system models (ESMs) and dynamic global vegetation models (DGVMs) with coupled carbon-nitrogen cycles project that future terrestrial C sequestration will be limited by nitrogen (N) availability, but the magnitude of N limitation remains a critical uncertainty. Plants use multiple symbiotic nutrient acquisition strategies to mitigate N limitation, but current DGVMs omit these mechanisms. Fully coupling N-acquiring plant-microbe symbioses to soil organic matter (SOM) cycling within a DGVM for the first time, we show that increases in N acquisition via SOM decomposition and atmospheric N2 fixation could support long-term enhancement of terrestrial C sequestration at global scales under elevated CO2. The model reproduced elevated CO2 responses from two experiments (Duke and Oak Ridge) representing contrasting N acquisition strategies. N release from enhanced SOM decomposition supported vegetation growth at Duke, while inorganic N depletion limited growth at Oak Ridge. Global simulations reproduced spatial patterns of N-acquiring symbioses from a novel niche-based map of mycorrhizal fungi. Under a 100-ppm increase in CO2 concentrations, shifts in N acquisition pathways facilitated 200 Pg C of terrestrial C sequestration over 100 years compared to 50 Pg C for a scenario with static N acquisition pathways. Our results suggest that N acquisition strategies are important determinants of terrestrial C sequestration potential under elevated CO2 and that nitrogen-enabled DGVMs that omit symbiotic N acquisition may underestimate future terrestrial C uptake.
| Original language | English |
|---|---|
| Pages (from-to) | 501-523 |
| Number of pages | 23 |
| Journal | Global Biogeochemical Cycles |
| Volume | 33 |
| Issue number | 4 |
| DOIs | |
| State | Published - Apr 2019 |
Funding
This report was prepared by B. Sulman under award NA14OAR4320106 from the National Oceanic and Atmospheric Administration, U.S. Department of Commerce. This study was also supported by NOAA Climate Program Office's Atmospheric Chemistry, Carbon Cycle, and Climate program, award NA15OAR4310065. The statements, findings, conclusions, and recommendations are those of the authors and do not necessarily reflect the views of the National Oceanic and Atmospheric Administration or the U. S. Department of Commerce. B. Sulman was also supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research under contract number DE‐AC05‐00OR22725. E. Brzostek's contribution was supported by U.S. Department of Energy Office of Biological and Environmental Research, Terrestrial Ecosystem Science Program (award DESC0016188). X. Zhang's contribution was supported by Cooperative Institute for Climate Science, Princeton University under NOAA grant NA14OAR4320106. Thanks to Chiara Medici, Richard Phillips and Efrat Sheffer for helpful discussions. Data and code are posted on FigShare: doi:https://doi.org/10.6084/m9. figshare.6207578. These include ecosystem‐scale simulation output, species distribution model data, global model output underlying all global plots, model code specific to the processes described in this manuscript, and analysis and plotting code. Full GFDL land model code is available upon request through the GFDL code management system. This report was prepared by B. Sulman under award NA14OAR4320106 from the National Oceanic and Atmospheric Administration, U.S. Department of Commerce. This study was also supported by NOAA Climate Program Office's Atmospheric Chemistry, Carbon Cycle, and Climate program, award NA15OAR4310065. The statements, findings, conclusions, and recommendations are those of the authors and do not necessarily reflect the views of the National Oceanic and Atmospheric Administration or the U.S. Department of Commerce. B. Sulman was also supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research under contract number DE-AC05-00OR22725. E. Brzostek's contribution was supported by U.S. Department of Energy Office of Biological and Environmental Research, Terrestrial Ecosystem Science Program (award DESC0016188). X. Zhang's contribution was supported by Cooperative Institute for Climate Science, Princeton University under NOAA grant NA14OAR4320106. Thanks to Chiara Medici, Richard Phillips and Efrat Sheffer for helpful discussions. Data and code are posted on FigShare: doi:https://doi.org/10.6084/m9.figshare.6207578. These include ecosystem-scale simulation output, species distribution model data, global model output underlying all global plots, model code specific to the processes described in this manuscript, and analysis and plotting code. Full GFDL land model code is available upon request through the GFDL code management system.
Keywords
- carbon
- elevated CO
- global land model
- mycorrhizae
- nitrogen
- soil