Validating and Linking the GIMMS Leaf Area Index (LAI3g) with Environmental Controls in Tropical Africa
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
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.
Date Issued
2014-03-04
Date Acceptance
2014-02-25
Citation
Remote Sensing, 2014, 6 (3), pp.1973-1990
ISSN
2072-4292
Publisher
MDPI
Start Page
1973
End Page
1990
Journal / Book Title
Remote Sensing
Volume
6
Issue
3
Copyright Statement
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).
License URL
Subjects
Science & Technology
Technology
Remote Sensing
REMOTE SENSING
hemispherical images
Ethiopia
tropical landscapes
Kenya
Tanzania
essential climate variables
East Africa
field assessments
DIFFERENCE VEGETATION INDEX
HEMISPHERICAL PHOTOGRAPHY
GLOBAL ASSESSMENT
SOIL-MOISTURE
ABSORBED PAR
EAST-AFRICA
MODIS DATA
PRODUCTS
TRENDS
MODEL
Publication Status
Published