ATBC Online Web Program

O13-1
Integrating satellite and field measurement data to improve the understanding of carbon uptake by tree growth in French Guiana

Tuesday, 25 June 2013: 10:20
La Paz - B East (Herradura San Jose)
Fabien Wagner , CIRAD, UMR SELMET & EcoFoG, French Guiana
Vivien Rossi , CIRAD, UMR Ecologie des Forêts de Guyane, French Guiana
Clément Stahl , CIRAD, UMR SELMET & EcoFoG, French Guiana
Damien Bonal , Inra, UMR INRA-UHP Ecologie et Ecophysiologie Forestière, France
Bruno Herault , CIRAD, UMR Ecologie des Forêts de Guyane, French Guiana
Climate models predict a range of changes in the amazonian region, including increased frequency of extreme climatic events, increased average temperatures, increased atmospheric CO2 and reduced rainfall intensity. Understanding tree growth response to climate is important because wood production is the main way of carbon sequestration in the forest ecosystem. The response of tropical tree growth to changing climate could drive a change in the direction of the flux from terrestrial ecosystems to the atmosphere. Recently, the intra-annual variation of chlorophyll activity in Amazonia and in French Guiana was assessed with the Enhanced Vegetation Index (EVI) from the MODIS satellite data. Unexpectedly, the peak increase in biomass (early wet season), estimated by diameter growth, was not correlated with the peak in chlorophyll activity (early dry season) in French Guiana. This could reflect different timing in the use of photosynthesis products by the plant for leaf and wood production. Four datasets were used, MODIS EVI, modeled intra-annual biomass production, litter fall and climate data to analyze the timing of carbon use by the trees for leaf and wood production. At the French Guiana scale, we found that trees allocate carbon for leaf production in early dry season whereas wood is produced mainly in wet season. When leaf production is at its highest point wood production is minimal. The amount of carbon used for these processes is similar, 2.4 ± 1.38 Mg C ha−1 yr−1 for leaf production and 2.2 ± 0.4 Mg C ha−1 yr−1for wood production. Climate or endogenic drivers of this seasonality needs now to be disentangled to estimate the effect of climate change on the carbon entry in the forests of French Guiana.