Accuracy of the AVHRR vegetation index as a predictor of biomass, primary productivity and net CO2 flux

Abstract

The Normalized Difference Vegetation Index (NDVI) or 'greenness index', based on the Advanced Very High Resolution Radiometer (AVHRR) aboard the NOAA-7 satellite, has been widely interpreted as a measure of regional to global vegetation patterns. This study provides the first rigorous, quantitative evaluation of global relationships between the NDVI and geographically representative vegetation data-bases, including field metabolic measurements and carbon-balance results from global simulation models. Geographic reliability of the NDVIis judged by comparing NDVIvalues for different surface types with a general global trend and by statistical analysis of relationships to biomass amounts, net and gross primary productivity, and actual evapotranspiration. NDVIdata appear to be relatively reliable predictors of primary productivity except in areas of complex terrain, for seasonal values at high latitudes, and in extreme deserts. The strength of the NDVI-productivity relationship seems comparable to that of earlier climate-based productivity models. Little consistent relationship was found, across different vegetation types, between NDVI and biomass amounts or net biospheric CO 2 flux.

Interannual variability of NDVI and species richness in Kenya

“…If a strong relationship can be shown between remotely sensed data and NPP, then more complete mapping and monitoring of NPP of terrestrial vegetation may be possible (Walker et al 1992). Normalized difference vegetation index (NDVI) has been related to NPP at broad spatial scales (Box et al 1989;Prince 1991). The chain of relationship from NDVI to NPP and NPP to species richness provides strong evidence that NDVI is related to species richness.…”

A Percolation‐Based Approach to Scaling Infiltration and Evapotranspiration

“…Furthermore, using total ET depths x g (instead of transpiration data, which is much less abundant) that range from 0.02 m (the Namibian desert at the dry end of the scale [39]) to 1.65 m (tropical rainforests and savannahs [40]) for a growing season of t g = 0.5 year, provides x = 0.02 m (t/180 days) 0.83 and x = 1.65 m (t/180 days) 0.83 , for a minimum and a maximum transpiration, or, equivalently, by Equation (7), for a minimum and maximum growing season plant height, respectively. As shown in Figure 2, these values of x (t g ) bound the world's plant heights [31] at a time corresponding to the length of the growing season, meaning that Equation (7) generates essentially identical scaling predictions of plant growth rates as depicted in Figure 1.…”

“…The hydraulic limit is postulated as a cavitation limit [47]. Note that the minimum and maximum scaling relationships could be equally expressed in terms of the limiting growing season transpiration values, 20 mm at the dry end of the spectrum [39] and 1650 mm at the wet end [40], which are plotted on the graph at the time of six months, a typical growing season. The correspondence between plant height and growing season transpiration suggests the viability of growth models in terms of growing season transpiration values.…”

Ecosystem greenspots pass the first test

“…Gross primary productivity (GPP), the rate per unit area at which new biomass is produced by the vegetation cover, can be monitored remotely using time series of satellite images (Box 1989). NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) sensor detects the energy reflected in distinct spectral bands from every part of the Earth's surface every 1-2 days.…”