Accelerated Carbon and Water Cycles in the Amazon and Congo Basins Revealed From TRENDY Models and Remote Sensing Products

Journal Article · Fri Feb 13 00:00:00 EST 2026 · Global Biogeochemical Cycles

DOI:https://doi.org/10.1029/2025GB008747· OSTI ID:3018284

Shi, Mingjie ^[1]; Fang, Yilin ^[1]; McDowell, Nate G. ^[2]; Koven, Charlie D. ^[3]; Liu, Junjie ^[4]; Kuai, Le ^[5]; Sitch, Stephen ^[6]; Leung, Lai-Yung Ruby ^[1]

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1. Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
2. Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Washington State Univ., Pullman, WA (United States)
3. Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
4. California Institute of Technology (CalTech), Pasadena, CA (United States)
5. California Institute of Technology (CalTech), Pasadena, CA (United States). Jet Propulsion Laboratory (JPL)
6. Univ. of Exeter, Devon (United Kingdom)

Tropical forests play a vital role in the global carbon cycle and land–atmosphere interactions. Estimating tropical forest carbon–water dynamics is challenging due to observational and modeling uncertainties. This study leverages the “Trends and drivers of the regional scale terrestrial sources and sinks of carbon dioxide” (TRENDY) project models and satellite observations to assess changes (2003–2021) in vegetation carbon, gross primary production (GPP), evapotranspiration (ET), and net biosphere production (NBP) in the Amazon and Congo. Atmospheric CO₂, climate variability, and land use and land cover changes constrain these variables between 1700 and 2021 with the overall increasing trends of carbon stock and fluxes. The models overestimate vegetation carbon and GPP, while ET and NBP are consistent with observations. Fire-activated models predict lower values for vegetation carbon and GPP, ET, and NBP, aligning more closely with observations. The higher ET from fire-activated models may result from enhanced soil evaporation due to increased canopy openings. Fire-inactivated models could well estimate the magnitudes of NBP. The high vegetation carbon in nitrogen-enabled models points to simulation uncertainties and imbalance in model numbers regarding the nitrogen cycle. Although the nitrogen cycle enhances water use efficiency in both the Amazon and Congo, the models show a higher sensitivity to the nitrogen cycle in the Congo. This study highlights the challenges in accurately representing tropical biogeochemical cycles and the values of satellite products in model evaluations, underscoring the need for standard modeling protocols that address biogeochemical components (e.g., nutrient cycles) to better resolve process-based representations.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: National Aeronautics and Space Administration (NASA); USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: AC05-76RL01830
• Other Award/Contract Number: 71073; 80NM0018D0004; 80NSSC20K0215
• OSTI ID: 3018284
• Report Number(s): PNNL-SA--213345
• Journal Information: Global Biogeochemical Cycles, Journal Name: Global Biogeochemical Cycles Journal Issue: 2 Vol. 40; ISSN 0886-6236; ISSN 1944-9224
• Publisher: American Geophysical Union (AGU)
• Country of Publication: United States
• Language: English