Exploring the potential of MODIS EVI for modeling gross primary production across African ecosystems
Sjöström M. | Ardo J. | Arneth A. | Boulain N. | Cappelaere B. | Eklundh L. | De Grandcourt A. | Kutsch W.L. | Merbold L. | Nouvellon Y. | Scholes R.J. | Schubert P. | Seaquist J. | Veenendaal E.M.
One of themost frequently appliedmethods for integrating controls on primary production through satellite data is the light use efficiency (LUE) approach,which links vegetation gross or net primary productivity (GPP or NPP) to remotely sensed estimates of absorbed photosynthetically active radiation (APAR). Eddy covariance towers provide continuousmeasurements of carbon flux, presenting an opportunity for evaluation of satellite estimates of GPP. Here we investigate relationships between eddy covariance estimated GPP, environmental variables derived fromflux towers,Moderate Resolution Imaging Spectroradiometer (MODIS) enhanced vegetation index (EVI) and GPP across African savanna ecosystems.MODIS GPP was found to underestimate GPP at themajority of sites, particularly at sites in the Sahel. EVIwas found to correlate well with estimated GPP on a site-by-site basis. Combining EVI with tower-measured PAR and evaporative fraction (EF, ameasure ofwater sufficiency) improved the direct relationship betweenGPP and EVI at themajority of the sites. The slope of this relationshipwas strongly related to site peak leaf area index (LAI). These results are promising for the extension of GPP through the use of remote sensing data to a regional or even continental scale. (Résumé d'auteur)
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