Abstract
The response of net forest carbon uptake to warm extremes remains elusive. The year 2023 was at the time ‘the hottest year on record’ globally, with Canada’s forests experiencing warm anomalies of above 2 °C and unprecedented drought and wildfires, providing a unique case to examine the response of boreal forest net carbon uptake to climate extremes. Here we combine satellite-based atmospheric CO2 flux inversions with ground-based in situ observations of CO2 fluxes and concentrations to investigate Canada’s forest net carbon uptake and its underlying mechanisms in 2023. We find that, compared with 2015–2022, Canada’s forest net carbon uptake was enhanced by 0.28 ± 0.23 PgC, offsetting 38–48% of Canadian wildfire emissions in 2023. This enhanced net uptake was dominated by large ecosystem respiration reductions, mainly attributable to severe root-zone soil moisture deficits and the unimodal temperature response of respiration. However, most dynamic global vegetation models failed to simulate the respiration reductions and the responses to hydrothermal conditions well. This study improves our understanding of boreal forest net carbon uptake in response to climate extremes and highlights an urgent need to improve vegetation models under global warming.
| Original language | English |
|---|---|
| Journal | Nature Geoscience |
| DOIs | |
| State | Accepted/In press - 2026 |
Funding
This work is supported by the National Key R&D Program of China (grant no. 2023YFB3907404 to F.J.), the National Natural Science Foundation of China (grant nos. 42125105 to Yongguang Zhang and 42377102 to F.J.), the Jiangsu Provincial Science Fund for Distinguished Young Scholars (grant no. BK20231530 to F.J.), the German Federal Ministry of Education and Research (BMBF), project STEPSEC (grant no. 01LS2102A to T.N.), the Environment Research and Technology Development Fund (grant no. JPMEERF24S12206 to E.K.) and the NASA Early Career Investigator Program in Earth Science (grant no. 80NSSC24K1632 to L.M.). To generate the JSBACH TRENDYv13 data, resources of the Deutsches Klimarechenzentrum (DKRZ) granted by its Scientific Steering Committee (WLA) under project ID bm1241 were used. E3SM results for TRENDYv13 were supported as part of the Energy Exascale Earth System Model (E3SM) project, funded by the US Department of Energy, Office of Science, Office of Biological and Environmental Research Earth Systems Model Development Program area of Earth and Environmental System Modeling. We thank C. Rödenbeck at Max Planck Institute for Biogeochemistry, Y. Niwa at National Institute for Environmental Studies, Japan, L. Feng and P. Palmer at University of Edinburgh, A. Jacobson at the Cooperative Institute for Research in Environmental Sciences, D. Yang at Institute of Atmospheric Physics, Chinese Academy of Sciences, N. Chandra at Research Institute for Global Change, and P. Patra at Japan Agency for Marine-Earth Science and Technology for providing the GCB2024-in-situ inversions. The OCO-2 data are produced by the OCO project at the Jet Propulsion Laboratory, California Institute of Technology, and obtained from the data archive at the NASA Goddard Earth Science Data and Information Services Center. We acknowledge all atmospheric data providers to obspack_co2_1_GLOBALVIEWplus_v10.1_2024-11-13. We especially thank D. Worthy at Environment and Climate Change Canada for his/her great efforts on Canada’s CO observations and data sharing. We thank R. Staebler at Environment and Climate Change Canada, J. J. Brodeur at McMaster University, X. Zhang at Nanjing University and B. Johnson at University of Saskatchewan for help in processing the EC data. We thank A. P. Walker at Oak Ridge National Laboratory for his comments on an earlier version of the manuscript. We are also grateful to the High-Performance Computing Center (HPCC) of Nanjing University for conducting the GCAS-extra inversions on its blade cluster system. 2