Morphological characteristics of shrub coppice dunes in desert grasslands of southern New Mexico derived from scanning LIDAR

Since the 1880s rangeland vegetation in southern New Mexico has changed dra matically over widespread areas, typically with shrublands displacing nativ e grasslands. Coincident with these changes in vegetation dominance are inc reases in soil erosion, stream channel cutting, and shrub coppice dune form ation on sandy soil. Where marked transitions in, vegetation type from gras sland to honey mesquite shrubland have occurred, the local topography has b een transformed with previously flat mesa becoming rolling duneland. The si ze, distribution, and morphological characteristics of these dunes have an important impact on fluxes of energy and nutrients at the surface; they als o render the land far less useful as grazing land for domestic livestock. T hese shrub coppice dunes and the mesquite shrubs that grow on them may be c onsidered roughness elements. Quantifying their morphology is important for the calculation of aerodynamic roughness length and displacement height. T his article tests the ability of active scanning laser remote sensing techn iques to provide accurate estimates of the three-dimensional shapes and are al distributions of dune and interdune areas. It shows that scanning laser with a footprint diameter of 0.38 m and a sampling interval of 1.5 m to 2 m can be used to measure the morphological characteristics of shrub coppice dunes in the desert grasslands of southern New Mexico with acceptable accur acy and precision for a range of uses, including important geomorphological and hydrological applications. The use of scanning laser systems together with optical multi-spectral data is shown to be highly synergistic, providi ng information that is not easily obtainable via other surveying methods. ( C) Elsevier Science Inc., 2000.