HR: 0830h
AN: B41C-0899    [PDF]
TI: Lifting the Green Veil: A Fresh Look at Synoptic Vegetation Dynamics
AU: * Henebry, G M
EM: ghenebry@calmit.unl.edu
AF: University of Nebraska-Lincoln, School of Natural Resources, 113 Nebraska Hall, Nebraska, NE 68588-0517 United States
AU: Vina, A
EM: avina@calmit.unl.edu
AF: University of Nebraska-Lincoln, School of Natural Resources, 113 Nebraska Hall, Nebraska, NE 68588-0517 United States
AU: Gitelson, A A
EM: gitelson@calmit.unl.edu
AF: University of Nebraska-Lincoln, School of Natural Resources, 113 Nebraska Hall, Nebraska, NE 68588-0517 United States
AB: Observing the dynamics of the vegetated land surface synoptically from spaceborne sensors plays a key role in understanding the global water, carbon, and nitrogen cycles, land cover and land use change, and biodiversity mapping. For the past three decades the study of global and regional vegetation dynamics has relied on satellite observations of the distinctive spectral contrast between red and near infrared reflectance exhibited by photosynthetically active green vegetation. It has long been recognized, however, that the spectral vegetation index with the widest currency-the Normalized Difference Vegetation Index (NDVI)-suffers a rapid decrease of sensitivity even at moderate Leaf Area Index (LAI) values of 2 to 4, as are commonly encountered in croplands and woodlands. This decrease in NDVI sensitivity casts a green veil over the land surface that obscures vegetation dynamics across vast areas during much of the growing season. This veil has important consequences for monitoring vegetation dynamics, developing land surface climatologies, and detecting significant changes. A straightforward modification of the NDVI, developed to increase its sensitivity under higher green biomass conditions, was applied to a standard, widely available AVHRR NDVI dataset for the conterminous US. The new Wide Dynamic Range Vegetation Index (WDRVI) exhibited increases in sensitivity between 30%-50% for Omernik Level III ecoregions dominated by woodlands, croplands, and grasslands. Ecoregions with lower aboveground net primary production, such as aridlands and semi-arid grasslands, showed no increase in sensitivity of the WDRVI over the NDVI. This powerful, new but simple approach creates an opportunity for a fresh look at the satellite data record. Further, it offers the possibility for significant improvements in the retrievals of canopy variables for carbon and nitrogen models, more accurate land surface characterizations for numerical weather prediction models, more sensitive analyses of land cover / land use change, and improvements in habitat mapping for biodiversity management.
DE: 1640 Remote sensing
DE: 1851 Plant ecology
DE: 3322 Land/atmosphere interactions
DE: 9350 North America
SC: Biogeosciences [B]
MN: 2003 Fall Meeting