Member press delta T device :Leaf water potential

Li-Cor 6400 :Leaf photosynthesisLeal stomatal conductance

Porometer AP4 :Stomatal conductance

Overview of gas exchange measurements from leaf level to landscape scalein a semi-arid ecosystem (Mali)

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PPsystems closed dynamic soil chamber

Night-time CO2 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 (CO2, H2O, NO) have been performed from leaf to canopy scale. Data from eddy-covariance and from tethered balloon will be used to scale-up surface CO2.

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

NO fluxes, soil surface temperature and rain.

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30-juin 05-juil 10-juil 15-juilDate

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NO flux measurement

Rain

soil surf. temp.

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Details in poster by Delon et al.

Manual dynamic chambersNO chemiluminescence's analyser (ThermoEnvironnement 42 CTL).

Valérie Le Dantec1, Claire Damesin2, Daniel Epron3, Josiane Seghieri1, Jon Bennie4, Lina Mercado4, Claire Delon5, Richard Dupont5, Dominique Serça5, Colin Lloyd4, Laurent Kergoat1, Eric Mougin1

- To characterise light, temperature, VPD and CO2 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

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Zornia

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Details in poster by Seghieri et al

Light response curves for two main grass species :Zornia glochidiata (C3) and Cenchrus biflorus (C4)

Soil CO2 fluxes measurements To quantify CO2 fluxes response to environment and vegetation activity.To quantify soil contribution to net CO2 fluxes (canopy chamber, eddy covariance)Test existing soil organic matter models

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To estimate meso-scale night-time CO2 flux

To document night-time nocturnal boundary layer (monsoon flux)

P, Tair, Rh, wind and CO2 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 CO2 fluxes

To characterise response to environment and vegetation activity of net water and CO2 fluxes of herbaceous canopy.

To quantify Gross Primary Production/Respiration partition in net CO2 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 CO2 fluxes (FNC) of two monospecific herbaceous patches : Zornia glochidiata (C3) and Cenchrus biflorus (C4).

Net CO2 fluxes are negative in case of herbaceous canopy is a sink of carbon, positive when respiration is dominant.

To get integrative measurements of water,CO2 and energy fluxes at 200 m2 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