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Title: AN ECOPHYSIOLOGICAL PROCESS MODEL FOR SEMI-ARID GRASSLANDS

Author
item NOUVELLON, Y - CIRAD, MONTPELLIER FRANCE
item RAMBAL, S - CEFE, CNRS, FRANCE
item BEGUE, A - CIRAD, MONTPELLIER FRANCE
item LHOMME, J - ORSTOM/CICTUS MEXICO
item Moran, Mary
item Qi, Jiaguo
item CHEHBOUNI, A - ORSTOM/IMADES MEXICO
item LOSEEN, D - CIRAD, MONTPELLIER FRANCE

Submitted to: American Meteorological Society of the Conference on Hydrology Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/15/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: In order to properly manage extensive rangeland regions, it is necessary to have regional information on rangeland extent and general health. An approach was developed to combine a grassland growth simulation model with images obtained from orbiting satellite sensors to map rangeland conditions, such as plant density, height and vigor. By combining the model with regional images, it was possible to obtain both temporal and spatial information about rangeland health. The results were encouraging because the simulated estimates of grassland biomass compared well with measured values at several sites in southeastern Arizona. Ultimately, this coupled modeling/remote sensing approach should result in accurate, timely information on rangeland health that can be used by researchers and ranchers to make intelligent management decisions at the regional scale.

Technical Abstract: In this study, we developed a model that describes the water and carbon budget of semi-arid grasslands at the regional scale. At this scale, satellite remote sensing can provide valuable information to improve simulation results. One approach consisted of assimilating radiometric data into the plant growth model by recalibration of the plant growth model parameters. This approach relies on a radiative transfer model that uses the canopy structural parameters (LAI, percent cover, plant height, ...) given by the plant-growth model to simulate temporal variations of surface reflectances. Simulated biomass and LAI for the period of 1990-1992 compared well with observations at a field site in southeastern Arizona. The ability to reproduce temporal variations of LAI is encouraging for operational application of this coupled radiative transfer model.