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TITLE:
Soil-Plant-Atmosphere Interaction Study in a Semi-Arid Environment
INVESTIGATORS:
Mexican team: Jean-Pierre Brunel, Ghani Chehbouni, Eric Elguero, Burno Monteny, Gilles Boulet, Oscar Hartogensis, Yann Nouvellon, Julio Rodriguez, Chris Watts.
OBJECTIVES:
The major scientific objectives of these study are:
1. Examine and estimate the spatio-temporal variations of surface energy and water balance over a heterogeneous surfaces.
2. Assess the effects of changes in the surface conditions on the partitioning of available energy at the surface into sensible and latent heat flux and of precipitation into runoff and infiltration.
3. Investigate the feasibility of assimilating remotely sensed measurement in a coupled SVAT-Vegetation Functioning model.
APPROACH:
To achieve these objectives, the following experimental setup with be implemented:
A. A transect, of 3 sites west of Morelos village, will be instrumented with 3 Bowen ratio systems:
Site 1 - Piedmont zone: patch with mixed grass and mesquite.
Site 2 - Plateau: slopey patch of grass.
Site 3 - Plateau: horizontal patch of grass collecting most of the runoff water.
One weather station is installed on the plateau (solar radiation, wind velocity and direction, air temperature, air humidity) with an automatic raingage.
B. Two Eddy correlation stations will be set up over two sites that represent the extreme stage in terms of vegetation degradation:
Site 4 - Healthy grass site (Zapata village).
Site 5 - A site completely dominated by the Mesquite (south of Morelos).
DATA COLLECTION:
Over each site, the following data will be collected:
1. Net radiation, sensible, latent and soil heat flux.
2. Soil temperature at different depths using thermocouples.
3. Soil moisture at different depths using gravimetric and TDR methods.
4. Precipitation.
5. Surface temperature.
6. Hydraulic conductivity at saturation, and saturated water content using the pounded infiltration test (during 3 periods : pre-monsoon, monsoon and post-monsoon).
7. Vegetation cover and height , LAI and Biomass over grass sites (site 2, 3, and 4).
Over Site (5), Sapflow system (4 sensors) will be installed to estimate the contribution of the Mesquite to the total ET. Additionally isotopic measurements will be made to determine the origin of water transpired by the mesquites.
Over the grass dominated sites (site 2, 3, and 4), multidirectional VIS, NIR and TIR based data will be taken at least once a week during the entire growing season.
B- A large aperture scintillometer will be set up for a period of 10 days or so over each site. During the August IFC , we will take it to the US site so that it can be used with the LIDAR measurement to estimate sensible and latent heat flux over a transect that includes grass, shrubs and a section of the riparian corridor.
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