The surface-atmosphere exchange of carbon dioxide in tropical rainforests: Sensitivity to environmental drivers and flux measurement methodology

Fu Zheng, Gerken Tobias, Bromley Gabriel, Araújo Alessandro, Bonal Damien, Burban Benoit, Ficklin Darren, Fuentes Jose D., Goulden Michaël L., Hirano Takashi, Kosugi Yoshiko, Liddell Michael, Nicolini Giacomo, Niu Shuli, Roupsard Olivier, Stefani Paolo, Mi Chunrong, Tofte Zaddy, Xiao Jingfeng, Valentini Riccardo, Wolf Sebastian, Stoy Paul C.. 2018. The surface-atmosphere exchange of carbon dioxide in tropical rainforests: Sensitivity to environmental drivers and flux measurement methodology. Agricultural and Forest Meteorology, 263 : 292-307.

https://doi.org/10.1016/j.agrformet.2018.09.001

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Quartile : Q1, Sujet : FORESTRY / Quartile : Outlier, Sujet : AGRONOMY / Quartile : Q1, Sujet : METEOROLOGY & ATMOSPHERIC SCIENCES

Résumé : Tropical rainforests play a central role in the Earth system by regulating climate, maintaining biodiversity, and sequestering carbon. They are under threat by direct anthropogenic impacts like deforestation and the indirect anthropogenic impacts of climate change. A synthesis of the factors that determine the net ecosystem exchange of carbon dioxide (NEE) at the site scale across different forests in the tropical rainforest biome has not been undertaken to date. Here, we study NEE and its components, gross ecosystem productivity (GEP) and ecosystem respiration (RE), across thirteen natural and managed forests within the tropical rainforest biome with 63 total site-years of eddy covariance data. Our results reveal that the five ecosystems with the largest annual gross carbon uptake by photosynthesis (i.e. GEP > 3000 g C m−2 y-1) have the lowest net carbon uptake – or even carbon losses – versus other study ecosystems because RE is of a similar magnitude. Sites that provided subcanopy CO2 storage observations had higher average magnitudes of GEP and RE and lower average magnitudes of NEE, highlighting the importance of measurement methodology for understanding carbon dynamics in ecosystems with characteristically tall and dense vegetation. A path analysis revealed that vapor pressure deficit (VPD) played a greater role than soil moisture or air temperature in constraining GEP under light saturated conditions across most study sites, but to differing degrees from -0.31 to -0.87 μmol CO2 m−2 s-1 hPa-1. Climate projections from 13 general circulation models (CMIP5) under the representative concentration pathway that generates 8.5 W m−2 of radiative forcing suggest that many current tropical rainforest sites on the lower end of the current temperature range are likely to reach a climate space similar to present-day warmer sites by the year 2050, warmer sites will reach a climate not currently experienced, and all forests are likely to experience higher VPD. Results demonstrate the need to quantify if and how mature tropical trees acclimate to heat and water stress, and to further develop flux-partitioning and gap-filling algorithms for defensible estimates of carbon exchange in tropical rainforests.

Mots-clés Agrovoc : forêt tropicale humide, cycle du carbone

Mots-clés libres : Climate variability, Ecosystem respiration, Eddy covariance, Gross primary productivity, Net ecosystem carbon dioxide exchange, Tropical rainforest

Classification Agris : K01 - Foresterie - Considérations générales
P33 - Chimie et physique du sol
F40 - Écologie végétale

Champ stratégique Cirad : Axe 6 (2014-2018) - Sociétés, natures et territoires

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