Exploring the potential of MODIS EVI for modeling gross primary production across African ecosystems |
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Authors: | M Sjöström J Ardö N Boulain L Eklundh WL Kutsch Y Nouvellon RJ Scholes J Seaquist |
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Affiliation: | a Department of Earth and Ecosystem Sciences, Lund University, Sölvegatan 12, 22362, Lund, Swedenb IRD, HydroSciences, BP 64501, 34394 Montpellier Cedex 5, Francec CIRAD, Persyst, UPR80, TA10/D, 34398 Montpellier Cedex 5, Franced CRDPI, BP 1291, Pointe-Noire, Republic of the Congoe Institute of Agricultural Climate Research, Johann Heinrich von Thünen-Institute, Bundesallee 50, 38116, Braunschweig, Germanyf Institute of Plant-, Animal and Agroecosystem Sciences, Grassland Sciences Group, ETH Zurich, Universitätstrasse 2, 8092, Zurich, Switzerlandg Natural Resources and Environment, CSIR, P.O. Box 395, Pretoria, South Africah Nature Conservation and Plant Ecology Group, Wageningen University, Droevendaalsesteeg 3a, 6700 AA Wageningen, The Netherlands |
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Abstract: | One of the most frequently applied methods 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 continuous measurements 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 from flux towers, Moderate Resolution Imaging Spectroradiometer (MODIS) enhanced vegetation index (EVI) and GPP across African savanna ecosystems. MODIS GPP was found to underestimate GPP at the majority of sites, particularly at sites in the Sahel. EVI was found to correlate well with estimated GPP on a site-by-site basis. Combining EVI with tower-measured PAR and evaporative fraction (EF, a measure of water sufficiency) improved the direct relationship between GPP and EVI at the majority of the sites. The slope of this relationship was 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. |
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Keywords: | Africa Gross primary production (GPP) Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced vegetation index (EVI) Evaporative fraction (EF) Leaf area index (LAI) |
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