1. Member press delta T device : Leaf water potential Li-Cor 6400 : Leaf photosynthesis Leal stomatal conductance Porometer AP4 : Stomatal conductance Overview of gas exchange measurements from leaf level to landscape scale in a semi-arid ecosystem (Mali) PPsystems closed dynamic soil chamber Night-time CO 2 fluxes from Nocturnal Boundary Layer budget. Details in poster by Kergoat et al. Intensives field campaigns have been conducted in the context of the Enhanced Observing period of AMMA. They are part of a complete land surface processes observing system. Knowledge of plant and soil processes is critical to understand land surface-atmosphere water exchanges. For this purpose, studies of plant and soil functioning have been conducted in a semi-arid ecosystem (super site Agoufou, Mali) coordinating and co-localising instruments and experimentations. The objectives were : - to improve understanding and modelling of mechanisms - to collect data to parameterise and to validate SVAT models at the local scale. During maximal plant growing period (July-August), intensive gas exchange measurements (CO 2, H 2 O, NO) have been performed from leaf to canopy scale. Data from eddy-covariance and from tethered balloon will be used to scale-up surface CO 2. soil NO fluxes measurements - Study the spatial variability of NO fluxes in tropical conditions. - Link to carbon cycle in soils and biogeochemistry. - Find new parameterization linking NO fluxes to environment with neural approach. - Quantify impact of emissions on atmospheric chemistry by adapting SVAT using new parameterization mean = 6.7 gN/ha/j (± 10.5) Details in poster by Delon et al. Manual dynamic chambers NO chemiluminescence's analyser (ThermoEnvironnement 42 CTL). Valérie Le Dantec 1, Claire Damesin 2, Daniel Epron 3, Josiane Seghieri 1, Jon Bennie 4, Lina Mercado 4, Claire Delon 5, Richard Dupont 5, Dominique Serça 5, Colin Lloyd 4, Laurent Kergoat 1, Eric Mougin 1 - To characterise light, temperature, VPD and CO 2 responses of dominant grass species - To screen other species for the maximal assimilation - To parameterize vegetation/SVAT models for areas where data are scarce or non-existent. Leaf level gas exchange 1 Centre d'Etudes Spatiales de la Biosphère, Toulouse (France) & Bamako (Mali) 2 Ecologie Systématique et Evolution, Université Paris XI, Orsay (France) 3 Ecologie et Ecophysiologie forestières, Université Nancy 1, Nancy (France) 4 Centre for Ecology and Hydrology, Wallingford (U.K.) 5 Laboratoire d'aérologie, Toulouse (France) Soil level gas exchange Details in poster by Seghieri et al Light response curves for two main grass species : Zornia glochidiata (C3) and Cenchrus biflorus (C4) Soil CO 2 fluxes measurements To quantify CO 2 fluxes response to environment and vegetation activity. To quantify soil contribution to net CO 2 fluxes (canopy chamber, eddy covariance) Test existing soil organic matter models UP SCALING To estimate meso-scale night-time CO 2 flux To document night-time nocturnal boundary layer (monsoon flux) P, Tair, Rh, wind and CO 2 recorded with a balloon-borne Vaisala sondes. Grass canopy level gas exchange Local scale level gas exchange Mesoscale level gas exchange Soil moisture and root biomass are the two main factors controlling soil CO 2 fluxes To characterise response to environment and vegetation activity of net water and CO 2 fluxes of herbaceous canopy. To quantify Gross Primary Production/Respiration partition in net CO 2 fluxes of herbaceous canopy To test existing process-models PPsystems closed dynamic canopy chamber Li-Cor 7500 Open-path system Light response curve of net CO 2 fluxes (FNC) of two monospecific herbaceous patches : Zornia glochidiata (C3) and Cenchrus biflorus (C4). Net CO 2 fluxes are negative in case of herbaceous canopy is a sink of carbon, positive when respiration is dominant. To get integrative measurements of water,CO 2 and energy fluxes at 200 m 2 scale. To test existing Soil-Vegetation-Atmosphere models To understand flux variations : Site specific composition of herbaceous canopy has been determined several times during growing season Frequent measurements of Leaf Area Index (LAI) have been performed to characterise its dynamic throughout season Surface soil moisture date have been collected along 1 km transect to characterise water stress at the site scale