Lianhong Gu, co-author, photosynthesis expert and distinguished staff scientist in ORNL’s Environmental Sciences Division, helped develop the project’s mesophyll conductance model, which represents numerically the diffusion of OCS in leaves, as well as the linkage between OCS diffusion and photosynthesis.
“Figuring out how much CO2 plants fix each year is a conundrum that scientists have been working on for a while,” Gu said. “The original estimate of 120 petagrams per year was established in the 1980s, and it stuck as we tried to figure out a new approach. It’s important that we get a good handle on global GPP since that initial land carbon uptake affects the rest of our representations of Earth’s carbon cycle.”
“We have to make sure the fundamental processes in the carbon cycle are properly represented in our larger-scale models,” Gu added. “For those Earth-scale simulations to work well, they need to represent the best understanding of the processes at work. This work represents a major step forward in terms of providing a definitive number.”
Pan-tropical rainforests accounted for the biggest difference between previous estimates and the new figures, a finding that was corroborated by ground measurements, Gu said. The discovery suggests that rainforests are a more important natural carbon sink than previously estimated using satellite data.
Understanding how much carbon can be stored in land ecosystems, especially in forests with their large accumulations of biomass in wood, is essential to making predictions of future climate change.
“Nailing down our estimates of GPP with reliable global-scale observations is a critical step in improving our predictions of future CO2 in the atmosphere, and the consequences for global climate” said Peter Thornton, Corporate Fellow and lead for the Earth Systems Science section at ORNL.
The results of this study point to the importance of including key processes, such as mesophyll conductance, in model representations of photosynthesis. DOE’s Next Generation Ecosystem Experiments in the Tropics has the goal of advancing model predictions of tropical forest carbon cycle response to climate change. These results can inform new model development that will reduce uncertainty in predictions of tropical forest GPP.
In addition to Cornell’s School of Integrative Plant Sciences, other collaborators on the project were Wageningen University and Research of The Netherlands, Carnegie Institution for Sciences, Colorado State University, University of California Santa Cruz and the NASA Jet Propulsion Laboratory.
Support came from Cornell, the National Science Foundation and the ORNL TES-SFA, sponsored by DOE’s Office of Science Biological and Environmental Research program.
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This Oak Ridge National Laboratory news article "Plant CO2 uptake rises by nearly one third in new global estimates" was originally found on https://www.ornl.gov/news