Jerry C. Ritchie, USDA ARS Hydrology and Remote Sensing Laboratory, BARC-West Building-007, Beltsville, MD 20705, Albert Rango, USDA ARS Jornada Experimental Range, Las Cruces, NM 88003, and Thomas J. Schmugge, New Mexico State University, Gerald W. Thomas Professor of Water Resources, Las Cruces, NM 88003.
The USDA ARS Jornada Experimental Range (Jornada) in southern New Mexico and the Sevilleta National Wildlife Refuge (Sevilleta) in Central New Mexico are Long Term Ecological Research (LTER) sites that provide unique opportunities to study changing rangeland conditions using remote sensing techniques. A research program began in 1995 collecting remotely sensed data from ground, aircraft, and satellite platforms to provide spatial and temporal data on the radiometric, thermal, physical, and vegetative properties of ecosystems (grass, grass/shrub transition, and shrub) typical of arid rangeland of southwestern United States. Data from these different platforms are being used to evaluate the physical and vegetation changes over time and at different scales in these ecosystems. Reflectance and thermal measurements from all platforms indicate that the shrub ecosystems have greater reflectance and are warmer that the grass ecosystems. Comparison of ground (ASD), aircraft (MASTERS), and satellite (ASTER) reflectance measurements showed that they were measuring similar reflectance values for three dates and three different vegetation communities. Reflectance was highest from the shrub and shrub-grass transition communities and lowest from the grass community and was related to the amount of vegetation cover present. This has implications for the energy and water budgets in this region of the Chihuahuan desert where shrub communities with low ground cover are invading and replacing grass communities.