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Spectral reflectance differences of Northern Chihuahuan Desert vegetation.
RITCHIE, JERRY*,1, SCHMUGGE, THOMAS1, JACOB, FREDERIC1, RANGO, ALBERT2, CHOPPING, MARK2, 1 USDA-ARS HYDROLOGY AND REMOTE SENSING LABORATORY, BELTSVILLE, MD2 USDA-ARS JORNADA EXPERIMENTAL RANGE, LAS CRUCES, NM
ABSTRACT- Spectral measurements of vegetation communities of the semiarid grasslands in the Jornada Experimental Range LTER and the Sevilleta LTER in New Mexico were measured at ground level using an Analytical Spectral Devices (ASD) Spectrometer on a 30x30 m grid at 5 m intervals, from an airplane with the MODIS/ASTER Simulator (MASTER) with a 3x3 m resolution, and from space with the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) with 15x15 m resolution in May 2001 and with the ASD and ASTER in September 2001. Four communities (Grass, Transition, Mesquite, Creosote) were sampled at the Jornada. Three communities (Grass, Transition, Creosote) were sampled at the Sevilleta. Reflectance increased from Grass to Transition to Shrub communities from all three platforms at both sites. Patterns of reflectance were similar from the three platforms with MASTER and ASTER having the similar absolute values. Comparison of absolute values of ASD ground measurements with MASTER and ASTER measurements differed with different vegetation communities but in general ASD measurement were slightly lower than MASTER or ASTER measurements. These differences are assumed to be related to the different sized footprints of the instruments. In general, as ground cover decreased from Grass to Transition to Shrub communities, reflectance increased indicating a potential for change in heat and water balance of these ecosystems if shrubs continue to expand into the Grass communities.
KEY WORDS: remote sensing, arid lands, spectral reflectance