Validating and Linking the GIMMS Leaf Area Index (LAI3g) with Environmental Controls in Tropical Africa

Remote Sensing

Dereje Denu¹  Alemu Gonsamo²  Petri K. E. Pellikka³  Marion Pfeifer⁴  Veronique Lefebvre⁴  Rob Marchant⁵  Philip J. Platts⁵ 

[1] Department of Biology, Jimma University, Jimma 47, Ethiopia;Department of Geography and Program in Planning, University of Toronto,Toronto, ON M5S 3G3, Canada;Department of Geosciences and Geography, P.O. Box 64, University of Helsinki,Helsinki 00014, Finland;Department of Life Sciences, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire SL5 7PY, UK;Environment Department, University of York, Heslington, York YO10 5DD, UK;

关键词: hemispherical images;    tropical landscapes;    field assessments;    Kenya;    Ethiopia;    Tanzania;    East Africa;    essential climate variables;   

DOI  :  10.3390/rs6031973

来源: DOAJ

【 摘 要 】

The recent Global Inventory Modeling and Mapping Studies (GIMMS) LAI3g product provides a 30-year global times-series of remotely sensed leaf area index (LAI), an essential variable in models of ecosystem process and productivity. In this study, we use a new dataset of field-based LAITrue to indirectly validate the GIMMS LAI3g product, LAIavhrr, in East Africa, comparing the distribution properties of LAIavhrr across biomes and environmental gradients with those properties derived for LAITrue. We show that the increase in LAI with vegetation height in natural biomes is captured by both LAIavhrr and LAITrue, but that LAIavhrr overestimates LAI for all biomes except shrubland and cropland. Non-linear responses of LAI to precipitation and moisture indices, whereby leaf area peaks at intermediate values and declines thereafter, are apparent in both LAITrue and LAIavhrr, although LAITrue reaches its maximum at lower values of the respective environmental driver. Socio-economic variables such as governance (protected areas) and population affect both LAI responses, although cause and effect are not always obvious: a positive relationship with human population pressure was detected, but shown to be an artefact of both LAI and human settlement covarying with precipitation. Despite these complexities, targeted field measurements, stratified according to both environmental and socio-economic gradients, could provide crucial data for improving satellite-derived LAI estimates, especially in the human-modified landscapes of tropical Africa.

【 授权许可】

Unknown