HAL Id: hal-02801733
https://hal.inrae.fr/hal-02801733
Submitted on 5 Jun 2020
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What drives the interannual variations in C fluxes and balance in a tropical rainforest of French Guiana?
Damien Bonal, Maricar Aguilos, Benoît Burban
To cite this version:
Damien Bonal, Maricar Aguilos, Benoît Burban. What drives the interannual variations in C fluxes and balance in a tropical rainforest of French Guiana?. 5. International Conference on Climate Change Adaptation 2016, Oct 2016, Toronto, Canada. 2016. �hal-02801733�
II. Methods
Study site • French Guiana, South America – a tropical wet forest • 10 – 40 m above sea level • Ave. rainfall is 3041 mm; ave. air temperature is 25.7°C • Guyaflux experimental unit covers >400 ha of undisturbed forest • 620 tree ha1 tree density (DBH >0.1 m) • Tree species richness is 140 species ha1 • Mean tree height is 35 m; emergent trees >40m The CO2 flux monitoring tower • 55 m high • 20 m higher than overall canopy heightI. Introduction
•The Amazon basin occupies a central position in our ability to understand the major role it
plays in the global carbon cycles.
•It suffered exceptional droughts in 2005 and 2010, yet 2010 dry spell was more critical shifting
the unburned forests from a net carbon sink during a wet year to a carbon neutral status during the extreme drought year.
• Using an 11year (2004 – 2014) data from French Guiana’s GuyaFlux tower, how drought
affect the carbon dynamics in this tropical ecosystem was examined and the climatic drivers influencing the interannual variation in carbon fluxes was determined. Flux and meteorological measurements • CO2 and H2O concentrations • Air temperature and humidity • Rainfall • Wind direction and speed • Global and infrared incident and reflected radiations • Incident and reflected photosynthetic photon flux density • Atmospheric pressure • Soil temperature • Volumetric soil water content Interannual variation in GPP, RE and NEE
III. Results
Acknowledgments:SOERE-FORET, GIP-ECOFOR, INRA, CIRAD, Labex CEBA, Jena platform, Observatoire du Carbone,
12ème CPER-Guyane
IV. Conclusion
What drives the interannual variations in C
fluxes
and balance in a tropical rainforest of French
Guiana?
Maricar AGUILOS1, Benoit BURBAN1 , Damien BONAL2
1INRA, UMR Ecologie des Forêts de Guyane, BP 316 Avenue de France Kourou Cedex, French Guiana, and 2INRA, UMR EEF 1137, Champenoux, France •Fluctuations in total annual GPP vary from 3394.9 g C m−2 yr −1 to 4054.5 g C m−2 yr −1. RE is more varied than GPP (3057.4 g C m−2 yr −1 to 3425.9 g C m−2 yr −1). Yet, annual GPP is always higher than annual RE, and the forest has remained carbon sink in an annual basis although NEE has huge interannual variability, from 68.2 g C m−2 yr −1 to 596.2 g C m−2 yr −1. •Distinct seasonal patterns in RE and GPP partly explained this variability. •The pattern of annual NEE appears to be driven by a higher rate of increase in respiration during the dry season, with less comparable rise in photosynthetic activity. •Solar radiation mostly explain the GPP, NEE and RE annually and during wet season, soil water limits them during dry season. •Therefore, process models dealing with tropical ecosystems must consider sitespecific responses to drought to reduce uncertainties and to generate a more accurate projections on forest response to climate change. Relationship between GPP, RE and NEE and global radiation (a – f) annually and during wet season and with relative extractable water (g – i) during dry periods -5000 -4000 -3000 -2000 -1000 0 1000 2000 3000 4000 5000 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 Carbon fluxes (gC m -2 yr -1 ) GPP RE NEE emission absorption