Validation of Remote Sensed Soil Map Unit Boundaries, Sevilleta LTER, New Mexico.

There is increasing demand for more detailed information of rangeland soils for monitoring the impacts of climate change, environmental modeling, trafficability, land mine detection etc. Most soil maps of rangeland areas are level three soil maps at a scale of 1:24,000. The maps are developed through extensive use of aerial photographs, expert local knowledge of soil patterns and limited validation through soil pit descriptions. The technical limitations associated with producing larger scale soil maps means that remote sensing of soil properties is the only option for producing larger scale soil maps of rangeland areas.

We applied three different remote sensing techniques to a transect across a semi arid grassland on the Sevilleta LTER to identify existing soil map unit and landform boundaries. We used several Landsat images from different years, an algorithm for determining root zone soil moisture, SEBAL, and an electromagnetic induction meter (EM) along the same transect. Soil map unit boundaries were identified from Landsat and the SEBAL code using a split moving window technique. The existing soil map unit boundaries were identified; however several previously unmapped potential soil boundaries were also identified.. A field campaign was undertaken to determine the validity of the previously unidentified boundaries. We believe that most of the variability in the remote sensed data and thus the soil map boundaries reflects primarily changes in soil moisture especially for the SEBAL code and the EM. Field studies indicated changes in soil properties especially those that influence soil hydraulic properties such as the amount and distribution of calcium carbonate and soil texture along the transect. Overall, the use of multiple remotely sensed root zone soil moisture and Landsat images for soil boundary delineation shows great promise of becoming a valuable tool in the field of digital soil mapping