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Discovery of distinct mid-elevational bands of blackbrush (Coleogyne ramosissima Torr.) shrublands on desert mountain slopes in the Mojave Desert caused an investigation of the relationships between environmental factors and Coleogyne distribution. Environmental factors were quantitatively examined to determine which were significant predictors of Coleogyne density at upper-elevational limits (ecotones) in the Spring Mountains of southern Nevada. Path analysis revealed significant, direct causal effects of air temperature, soil moisture, soil depth, and percent litter cover on the distribution of Coleogyne. Specifically, air temperature was a significant positive predictor, while soil moisture, soil depth, and percent...
Soil compaction from human trampling, biking, and off-road motor vehicle traffic was quantitatively investigated in a blackbrush (Coleogyne ramosissima) shrubland in Kyle Canyon of the Spring Mountains in southern Nevada. A significant difference was detected in soil compaction, bulk density, and percent pore space at a particular frequency of visits in each of 4 disturbance types. On average a single vehicle pass was equivalent to 10 human footprints. Ten and 100 footprints were equivalent to 1 motorcycle pass and 10 vehicle passes, respectively. Soil compaction is a product of increased bulk density and decreased pore space. The degree of soil compaction is a function of disturbance type and visit frequency when...
Differences in anatomical characteristics of blackbrush (Coleogyne ramosissima Torr.) leaves were quantitatively investigated along an elevational gradient in Lee Canyon of the Spring Mountains in southern Nevada. Three elevational sites were selected: a lower blackbrush ecotone, a nearly monospecific stand in the middle of the gradient, and an upper blackbrush ecotone. Stomatal density was significantly greater and palisade parenchyma was significantly shorter in the lower ecotone compared to the upper ecotone. Vessel diameters and areas were significantly smaller, while vessel density was higher with increasing aridity. Blackbrush shrubs exhibited upper and lower elevational ecotypes at the anatomical level in...
I investigated the individual and joint effects of simulated herbivory and interspecific competition on survival of Coleogyne ramosissima Torr. (blackbrush) seedlings. Seeds of C. ramosissima and Bromus rubens L. (red brome grass) were collected at mid-elevations (1220 to 1770 m) of the Spring Mountains in southern Nevada. A pot trial experiment was conducted for six months (27 wk) in a controlled environmental greenhouse. This trial experiment, consisting of a 2 � 2 factorial design with simulated rodent herbivory and interspecific competition with B. rubens as the main effects, resulted in four treatments. Herbivory on C. ramosissima by heteromyid and non-heteromyid species of rodents was simulated by clipping...
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This digital geologic map of the Nevada Test Site (NTS) and vicinity, as well as its accompanying digital geophysical maps, are compiled at 1:100,000 scale. The map compilation presents new polygon (geologic map unit contacts), line (fault, fold axis, metamorphic isograd, dike, and caldera wall) and point (structural attitude) vector data for the NTS and vicinity, Nye, Lincoln, and Clark Counties, Nevada, and Inyo County, California. The map area covers two 30 x 60-minute quadrangles-the Pahute Mesa quadrangle to the north and the Beatty quadrangle to the south-plus a strip of 7.5-minute quadrangles on the east side-72 quadrangles in all. In addition to the NTS, the map area includes the rest of the southwest Nevada...
Tags: 06027 = Inyo, 32003 = Clark, 32017 = Lincoln, 32023 = Nye, Amargosa Desert, All tags...
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The locations of principal faults and structural zones that may influence ground-water flow were compiled in support of a three-dimensional ground-water model for the Death Valley regional flow system (DVRFS), which covers 80,000 square km in southwestern Nevada and southeastern California. Faults include Neogene extensional and strike-slip faults and pre-Tertiary thrust faults. Emphasis was given to characteristics of faults and deformed zones that may have a high potential for influencing hydraulic conductivity. These include: (1) faulting that results in the juxtaposition of stratigraphic units with contrasting hydrologic properties, which may cause ground-water discharge and other perturbations in the flow system;...
Tags: 06027 = Inyo, 06029 = Kern, 06071 = San Bernardino, 32003 = Clark, 32009 = Esmeralda, All tags...


    map background search result map search result map Hydrostructural Maps of the Death Valley Regional Flow System, Nevada and California--Map A: Structural Framework, Neogene Basins, and Potentiometric Surface; Map B: Structural Framework, Earthquake Epicenters, and Potential Zones of Enhanced Hydraulic Conductivity Digital Geologic Map of the Nevada Test Site and Vicinity, Nye, Lincoln, and Clark Counties, Nevada, and Inyo County, California Digital Geologic Map of the Nevada Test Site and Vicinity, Nye, Lincoln, and Clark Counties, Nevada, and Inyo County, California Hydrostructural Maps of the Death Valley Regional Flow System, Nevada and California--Map A: Structural Framework, Neogene Basins, and Potentiometric Surface; Map B: Structural Framework, Earthquake Epicenters, and Potential Zones of Enhanced Hydraulic Conductivity