Geomorphic-vegetation relationships in the Jornada Basin, southern New Mexico

TitleGeomorphic-vegetation relationships in the Jornada Basin, southern New Mexico
Publication TypeConference Paper
Year of Publication1997
AuthorsH. Monger C, Huenneke L., Havstad K
Conference NameInternational Symposium and Workshop Combating Desertification: Connecting Science with Community Action
Date PublishedMay 12-16, 1997
Conference LocationTucson, AZ
AbstractThe southern portion of the Jornada Basin is the locale of the Jomada Experimental Range and Jomada LTER site. This area is bound to the west by the Rio Grande Valley and to the east by the San Andres Mountains. The western half of the basin is the relic floodplain of the ancestral Rio Grande. The eastern half consists of a fan piedmont and exposed bedrock of the San Andres Mountains. Both the relic floodplain and the fan piedmont have been extensively modified by natural and human-induced wind erosion. Soil patterns in this setting are diverse. The age of soils ranges between 0.74 to 1.6 million years in the relic floodplain, based on Ar/Ar dating, to sediments currently being deposited by wind and arroyos. Ancient soils have massive indurated petrocalcic horizons in contrast to young soils that exhibit little difference between their surface and subsoil horizons. //Vegetation patterns are also diverse, ranging from communities dominated by single species (e.g., mesquite, creosotebush, or tarbush) to communities with a mosaic of highly diverse assemblages. In some cases vegetation patterns are highly correlated to geomorphic units. For example, mesquite is the dominant species in coppice dune terrain, creosotebush is the dominant species on some gravelly alluvial fans, and tobosa grass is the dominant species on some clayey playas. Vegetation records dating back to the mid-1800s, however, reveal a proliferation of shrubs and a decline of grasses across a variety of geomorphic units. // Several geomorphic variables, especially those involving soils and topography, influence the ability of vegetation to resist changes driven by environmental stresses. Important soil variables include particle-size distribution, available water capacity, shrink-swell properties, organic matter, microbial populations, fertility, and other soil chemical properties such as cation exchange capacity and pH. Topographic variables include aspect, runoff, and run-in characteristics that affect the distribution of soil moisture. Although the interactions of these variables are complex, some of the greatest vegetation change during the last 150 years was experienced by geomorphic units composed of sandy soils susceptible to wind erosion and by coarse shallow soils with low moisture capacities.