Field-based tree mortality constraint reduces estimates of model-projected forest carbon sinks

• Published in: Nature communications 2022-04, Vol.13 (1), p.2094-2094, Article 2094
• Main Authors: Yu, Kailiang, Ciais, Philippe, Seneviratne, Sonia I., Liu, Zhihua, Chen, Han Y. H., Barichivich, Jonathan, Allen, Craig D., Yang, Hui, Huang, Yuanyuan, Ballantyne, Ashley P.
• Format: Article
• Language: English
• Subjects: 704/106/694/682; 704/158/2445; 704/47/4113; Atmospheric models; Biomass; Carbon; Carbon dioxide; Carbon Sequestration; Carbon sinks; Climate change; Climate models; Constraint modelling; Continental interfaces, environment; Ecosystem; Forests; Humanities and Social Sciences; Mortality; multidisciplinary; Net Primary Productivity; Ocean, Atmosphere; Science; Science (multidisciplinary); Sciences of the Universe; Sinkholes; South America; Tropical environment; Tropical environments; Tropical forests; Uncertainty
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-022-29619-4

Considerable uncertainty and debate exist in projecting the future capacity of forests to sequester atmospheric CO 2 . Here we estimate spatially explicit patterns of biomass loss by tree mortality (LOSS) from largely unmanaged forest plots to constrain projected (2015–2099) net primary productivity (NPP), heterotrophic respiration (HR) and net carbon sink in six dynamic global vegetation models (DGVMs) across continents. This approach relies on a strong relationship among LOSS, NPP, and HR at continental or biome scales. The DGVMs overestimated historical LOSS, particularly in tropical regions and eastern North America by as much as 5 Mg ha −1 y −1 . The modeled spread of DGVM-projected NPP and HR uncertainties was substantially reduced in tropical regions after incorporating the field-based mortality constraint. The observation-constrained models show a decrease in the tropical forest carbon sink by the end of the century, particularly across South America (from 2 to 1.4 PgC y −1 ), and an increase in the sink in North America (from 0.8 to 1.1 PgC y −1 ). These results highlight the feasibility of using forest demographic data to empirically constrain forest carbon sink projections and the potential overestimation of projected tropical forest carbon sinks. Here the authors use broad-scale tree mortality data to estimate biomass loss, constraining uncertainty of projected forest net primary productivity in 6 models, finding weaker tropical forest carbon sinks with climate change.