A long-term vegetation history of the Mojave-Colorado Desert ecotone at Joshua Tree National Park

Science.gov (United States)

Holmgren, Camille A.; Betancourt, Julio L.; Rylander, Kate A.

2010-01-01

Thirty-eight dated packrat middens were collected from upper desert (930–1357 m) elevations within Joshua Tree National Park near the ecotone between the Mojave Desert and Colorado Desert, providing a 30 ka record of vegetation change with remarkably even coverage for the last 15 ka. This record indicates that vegetation was relatively stable, which may reflect the lack of invasion by extralocal species during the late glacial and the early establishment and persistence of many desert scrub elements. Many of the species found in the modern vegetation assemblages were present by the early Holocene, as indicated by increasing Sørenson's Similarity Index values. C4 grasses and summer-flowering annuals arrived later at Joshua Tree National Park in the early Holocene, suggesting a delayed onset of warm-season monsoonal precipitation compared to other Sonoran Desert and Chihuahuan Desert localities to the east, where summer rains and C4 grasses persisted through the last glacial–interglacial cycle. This would suggest that contemporary flow of monsoonal moisture into eastern California is secondary to the core processes of the North American Monsoon, which remained intact throughout the late Quaternary. In the Holocene, northward displacement of the jet stream, in both summer and winter, allowed migration of the subtropical ridge as far north as southern Idaho and the advection of monsoonal moisture both westward into eastern California and northward into the southern Great Basin and Colorado Plateau.

Data measured on water collected from eastern Mojave Desert, California

Energy Technology Data Exchange (ETDEWEB)

Rose, Tim P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2017-08-17

In March of 2000 field collection of water from the Eastern Mojave Desert resulted in the measurement of stable isotope, radiocarbon, tritium, and limited dissolved noble gases. This work was follow-on to previous studies on similar systems in southern Nevada associated with the Nevada Test Site (Davisson et al., 1999; Rose and Davisson, 2003). The data for groundwater from wells and springs was never formally published and is therefore tabulated in Table 1 in order to be recorded in public record. In addition 4 years of remote precipitation data was collected for stable isotopes and is included in Table 2. These studies, along with many parallel and subsequent ones using isotopes and elemental concentrations, are all related to the general research area of tracing sources and quantifying transport times of natural and man-made materials in the environment. This type of research has direct relevance in characterizing environmental contamination, understanding resource development and protection, designing early detection in WMD related terrorism, and application in forensics analysis.

Comparative phylogeography reveals deep lineages and regional evolutionary hotspots in the Mojave and Sonoran Deserts

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Wood, Dustin A.; Vandergast, Amy G.; Barr, Kelly R.; Inman, Richard D.; Esque, Todd C.; Nussear, Kenneth E.; Fisher, Robert N.

2013-01-01

Aim: We explored lineage diversification within desert-dwelling fauna. Our goals were (1) to determine whether phylogenetic lineages and population expansions were consistent with younger Pleistocene climate fluctuation hypotheses or much older events predicted by pre-Pleistocene vicariance hypotheses, (2) to assess concordance in spatial patterns of genetic divergence and diversity among species and (3) to identify regional evolutionary hotspots of divergence and diversity and assess their conservation status. Location: Mojave, Colorado, and Sonoran Deserts, USA. Methods: We analysed previously published gene sequence data for twelve species. We used Bayesian gene tree methods to estimate lineages and divergence times. Within each lineage, we tested for population expansion and age of expansion using coalescent approaches. We mapped interpopulation genetic divergence and intra-population genetic diversity in a GIS to identify hotspots of highest genetic divergence and diversity and to assess whether protected lands overlapped with evolutionary hotspots. Results: In seven of the 12 species, lineage divergence substantially predated the Pleistocene. Historical population expansion was found in eight species, but expansion events postdated the Last Glacial Maximum (LGM) in only four. For all species assessed, six hotspots of high genetic divergence and diversity were concentrated in the Colorado Desert, along the Colorado River and in the Mojave/Sonoran ecotone. At least some proportion of the land within each recovered hotspot was categorized as protected, yet four of the six also overlapped with major areas of human development. Main conclusions: Most of the species studied here diversified into distinct Mojave and Sonoran lineages prior to the LGM – supporting older diversification hypotheses. Several evolutionary hotspots were recovered but are not strategically paired with areas of protected land. Long-term preservation of species-level biodiversity would

Effects of high fire frequency in creosote bush scrub vegetation of the Mojave Desert

Science.gov (United States)

Brooks, M.L.

2012-01-01

Plant invasions can increase fire frequency in desert ecosystems where fires were historically infrequent. Although there are many resource management concerns associated with high frequency fire in deserts, fundamental effects on plant community characteristics remain largely unstudied. Here I describe the effects of fire frequency on creosote bush scrub vegetation in the Mojave Desert, USA. Biomass of the invasive annual grass Bromus rubens L. increased following fire, but did not increase further with additional fires. In contrast, density, cover and species richness of native perennial plants each decreased following fire and continued to decrease with subsequent fires, although not as dramatically as after the initial fire. Responses were similar 5 and 14 years post-fire, except that cover of Hymenoclea salsola Torr. & A. Gray and Achnatherum speciosa Trin. & Rupr. both increased in areas burnt once. These results suggest that control of B. rubens may be equally warranted after one, two or three fires, but revegetation of native perennial plants is most warranted following multiple fires. These results are valid within the scope of this study, which is defined as relatively short term vegetation responses (???14 years) to short fire return intervals (6.3 and 7.3 years for the two and three fire frequency levels) within creosote bush scrub of the Mojave Desert. ?? 2012 IAWF.

Estimating wildfire risk on a Mojave Desert landscape using remote sensing and field sampling

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Van Linn, Peter F.; Nussear, Kenneth E.; Esque, Todd C.; DeFalco, Lesley A.; Inman, Richard D.; Abella, Scott R.

2013-01-01

Predicting wildfires that affect broad landscapes is important for allocating suppression resources and guiding land management. Wildfire prediction in the south-western United States is of specific concern because of the increasing prevalence and severe effects of fire on desert shrublands and the current lack of accurate fire prediction tools. We developed a fire risk model to predict fire occurrence in a north-eastern Mojave Desert landscape. First we developed a spatial model using remote sensing data to predict fuel loads based on field estimates of fuels. We then modelled fire risk (interactions of fuel characteristics and environmental conditions conducive to wildfire) using satellite imagery, our model of fuel loads, and spatial data on ignition potential (lightning strikes and distance to roads), topography (elevation and aspect) and climate (maximum and minimum temperatures). The risk model was developed during a fire year at our study landscape and validated at a nearby landscape; model performance was accurate and similar at both sites. This study demonstrates that remote sensing techniques used in combination with field surveys can accurately predict wildfire risk in the Mojave Desert and may be applicable to other arid and semiarid lands where wildfires are prevalent.

Precipitation regime classification for the Mojave Desert: Implications for fire occurrence

Science.gov (United States)

Tagestad, Jerry; Brooks, Matthew L.; Cullinan, Valerie; Downs, Janelle; McKinley, Randy

2016-01-01

Long periods of drought or above-average precipitation affect Mojave Desert vegetation condition, biomass and susceptibility to fire. Changes in the seasonality of precipitation alter the likelihood of lightning, a key ignition source for fires. The objectives of this study were to characterize the relationship between recent, historic, and future precipitation patterns and fire. Classifying monthly precipitation data from 1971 to 2010 reveals four precipitation regimes: low winter/low summer, moderate winter/moderate summer, high winter/low summer and high winter/high summer. Two regimes with summer monsoonal precipitation covered only 40% of the Mojave Desert ecoregion but contain 88% of the area burned and 95% of the repeat burn area. Classifying historic precipitation for early-century (wet) and mid-century (drought) periods reveals distinct shifts in regime boundaries. Early-century results are similar to current, while the mid-century results show a sizeable reduction in area of regimes with a strong monsoonal component. Such a shift would suggest that fires during the mid-century period would be minimal and anecdotal records confirm this. Predicted precipitation patterns from downscaled global climate models indicate numerous epochs of high winter precipitation, inferring higher fire potential for many multi-decade periods during the next century.

Recovery of severely compacted soils in the Mojave Desert, California, USA

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Webb, R.H.

2002-01-01

Often as a result of large-scale military maneuvers in the past, many soils in the Mojave Desert are highly vulnerable to soil compaction, particularly when wet. Previous studies indicate that natural recovery of severely compacted desert soils is extremely slow, and some researchers have suggested that subsurface compaction may not recover. Poorly sorted soils, particularly those with a loamy sand texture, are most vulnerable to soil compaction, and these soils are the most common in alluvial fans of the Mojave Desert. Recovery of compacted soil is expected to vary as a function of precipitation amounts, wetting-and-drying cycles, freeze-thaw cycles, and bioturbation, particularly root growth. Compaction recovery, as estimated using penetration depth and bulk density, was measured at 19 sites with 32 site-time combinations, including the former World War II Army sites of Camps Ibis, Granite, Iron Mountain, Clipper, and Essex. Although compaction at these sites was caused by a wide variety of forces, ranging from human trampling to tank traffic, the data do not allow segregation of differences in recovery rates for different compaction forces. The recovery rate appears to be logarithmic, with the highest rate of change occurring in the first few decades following abandonment. Some higher-elevation sites have completely recovered from soil compaction after 70 years. Using a linear model of recovery, the full recovery time ranges from 92 to 100 years; using a logarithmic model, which asymptotically approaches full recovery, the time required for 85% recovery ranges from 105-124 years.

An Annual Plant Growth Proxy in the Mojave Desert Using MODIS-EVI Data.

Science.gov (United States)

Wallace, Cynthia S A; Thomas, Kathryn A

2008-12-03

In the arid Mojave Desert, the phenological response of vegetation is largely dependent upon the timing and amount of rainfall, and maps of annual plant cover at any one point in time can vary widely. Our study developed relative annual plant growth models as proxies for annual plant cover using metrics that captured phenological variability in Moderate-Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) satellite images. We used landscape phenologies revealed in MODIS data together with ecological knowledge of annual plant seasonality to develop a suite of metrics to describe annual growth on a yearly basis. Each of these metrics was applied to temporally-composited MODIS-EVI images to develop a relative model of annual growth. Each model was evaluated by testing how well it predicted field estimates of annual cover collected during 2003 and 2005 at the Mojave National Preserve. The best performing metric was the spring difference metric, which compared the average of three spring MODIS-EVI composites of a given year to that of 2002, a year of record drought. The spring difference metric showed correlations with annual plant cover of R² = 0.61 for 2005 and R² = 0.47 for 2003. Although the correlation is moderate, we consider it supportive given the characteristics of the field data, which were collected for a different study in a localized area and are not ideal for calibration to MODIS pixels. A proxy for annual growth potential was developed from the spring difference metric of 2005 for use as an environmental data layer in desert tortoise habitat modeling. The application of the spring difference metric to other imagery years presents potential for other applications such as fuels, invasive species, and dust-emission monitoring in the Mojave Desert.

An Annual Plant Growth Proxy in the Mojave Desert Using MODIS-EVI Data

Directory of Open Access Journals (Sweden)

Kathryn A. Thomas

2008-12-01

Full Text Available In the arid Mojave Desert, the phenological response of vegetation is largely dependent upon the timing and amount of rainfall, and maps of annual plant cover at any one point in time can vary widely. Our study developed relative annual plant growth models as proxies for annual plant cover using metrics that captured phenological variability in Moderate-Resolution Imaging Spectroradiometer (MODIS Enhanced Vegetation Index (EVI satellite images. We used landscape phenologies revealed in MODIS data together with ecological knowledge of annual plant seasonality to develop a suite of metrics to describe annual growth on a yearly basis. Each of these metrics was applied to temporally-composited MODIS-EVI images to develop a relative model of annual growth. Each model was evaluated by testing how well it predicted field estimates of annual cover collected during 2003 and 2005 at the Mojave National Preserve. The best performing metric was the spring difference metric, which compared the average of three spring MODIS-EVI composites of a given year to that of 2002, a year of record drought. The spring difference metric showed correlations with annual plant cover of R2 = 0.61 for 2005 and R2 = 0.47 for 2003. Although the correlation is moderate, we consider it supportive given the characteristics of the field data, which were collected for a different study in a localized area and are not ideal for calibration to MODIS pixels. A proxy for annual growth potential was developed from the spring difference metric of 2005 for use as an environmental data layer in desert tortoise habitat modeling. The application of the spring difference metric to other imagery years presents potential for other applications such as fuels, invasive species, and dust-emission monitoring in the Mojave Desert.

77 FR 39181 - Revisions to the California State Implementation Plan, Mojave Desert Air Quality Management...

Science.gov (United States)

2012-07-02

... the California State Implementation Plan, Mojave Desert Air Quality Management District (MDAQMD) and Yolo-Solano Air Quality Management District (YSAQMD) AGENCY: Environmental Protection Agency (EPA... Air Quality Management District. (1) Rule 1165, ``Glass Melting Furnaces,'' amended on August 25, 2008...

Economic analysis of critical habitat designation for the desert tortoise (Mojave population)

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Schamberger, Mel; MacGillvray, Timothy J.; Draper, Dirk D.

1993-01-01

The U.S. Fish and Wildlife Service emergency 1isted the Mojave population of the desert tortoise as endangered on August 4, 1989. The Mojave population formally was listed as threatened on April 2, 1990. The Endangered Species Act of 1973, as amended, requires that the economic benefits and costs and other relevant effects of critical habitat designation be considered. The Secretary of the Interior may exclude from designation areas where the costs of designation are greater than the benefits, unless the exclusion would result in extinction of the species. Desert tortoises are threatened by an accumulation of human-and disease-related mortality accompanied by habitat destruction, degradation, and fragmentation. Many desert tortoises are illegally collected for pets, food, and commercial trade. Others are accidentally struck and killed by vehicles on roads and highways or are killed by gunshot or vehicles traveling off-highway. Raven predation on hatchling desert tortoises has increased as raven populations in the desert have risen. An upper respiratory tract disease is suspected to be a major cause of mortality in the western Mojave Desert. This presumably incurable affliction presumably is thought to be spread through the release of infected tortoises into the desert. The Service has proposed designating critical habitat in nine counties within four states. The 12 critical habitat units encompass 6.4 million acres of land, more than 80% federally owned. This region is economically and demographically diverse. Most of the land is sparsely settled and characterized as a hot desert ecosystem. Major industries in the region include entertainment and lodging (primarily in Las Vegas), property development to accommodate the rapid population growth, and services. Millions of rural acres in the region are leased by the federal government for livestock grazing and used for mining. Overall economic benefits to the affected states derived from cattle and sheep grazing in the

Geochronology and paleoenvironment of pluvial Harper Lake, Mojave Desert, California, USA

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Garcia, Anna L.; Knott, Jeffrey R.; Mahan, Shannon; Bright, Jordan

2014-01-01

Accurate reconstruction of the paleo-Mojave River and pluvial lake (Harper, Manix, Cronese, and Mojave) system of southern California is critical to understanding paleoclimate and the North American polar jet stream position over the last 500 ka. Previous studies inferred a polar jet stream south of 35°N at 18 ka and at ~ 40°N at 17–14 ka. Highstand sediments of Harper Lake, the upstream-most pluvial lake along the Mojave River, have yielded uncalibrated radiocarbon ages ranging from 24,000 to > 30,000 14C yr BP. Based on geologic mapping, radiocarbon and optically stimulated luminescence dating, we infer a ~ 45–40 ka age for the Harper Lake highstand sediments. Combining the Harper Lake highstand with other Great Basin pluvial lake/spring and marine climate records, we infer that the North American polar jet stream was south of 35°N about 45–40 ka, but shifted to 40°N by ~ 35 ka. Ostracodes (Limnocythere ceriotuberosa) from Harper Lake highstand sediments are consistent with an alkaline lake environment that received seasonal inflow from the Mojave River, thus confirming the lake was fed by the Mojave River. The ~ 45–40 ka highstand at Harper Lake coincides with a shallowing interval at downstream Lake Manix.

Δ17O Isotopic Investigation of Nitrate Salts Found in Co-Occurrence with Naturally Formed Perchlorate in the Mojave Desert, California, USA and the Atacama Desert, Chile

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Lybrand, R. A.; Parker, D.; Rech, J.; Prellwitz, J.; Michalski, G.

2009-12-01

Perchlorate is both a naturally occurring and manmade contaminant that has been identified in soil, groundwater and surface water. Perchlorate directly affects human health by interfering with iodide uptake in the thyroid gland, which may in turn lower the production of key hormones that are needed for proper growth and development. Until recently, the Atacama Desert, Chile was thought to be the only location where perchlorate salts formed naturally. Recent work has documented the occurrence of these salts in several semi-arid regions of the United States. This study identified putatively natural sources of perchlorate in the Mojave Desert of California. Soil samples were collected from six field sites varying in geologic age. The co-occurrence of perchlorate and nitrate in caliches from the Atacama Desert and soils from the Mojave Desert was also investigated. Although the former are richer in NO3-, near-ore-grade (~5%) deposits occur in the vicinity of Death Valley National Park. Weak but significant correlations exist between ClO4- and NO3- at both locations, but the perchlorate levels are much higher (up to 800 mg/kg) in the Chilean samples than in California (atmospheric origin for the Atacama nitrate salts, and a mixture between biological nitrate and atmospherically-derived nitrate for the Mojave samples. When corrected for the percentage of atmospheric nitrate measured in the Atacama samples, the Mojave samples still contain much lower perchlorate concentrations than would be expected if the occurrence of perchlorate correlated strictly with atmospherically derived nitrate. These results indicate that the variation in the origins of the nitrate salts is not the only factor influencing perchlorate distribution in these environments. These findings suggest that there are other geologic differences in landform age and stability that are crucial to understanding the co-occurrence of nitrate and perchlorate between the two locations.

A mechanistic modeling and data assimilation framework for Mojave Desert ecohydrology

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Ng, Gene-Hua Crystal; Bedford, David R.; Miller, David M.

2014-06-01

This study demonstrates and addresses challenges in coupled ecohydrological modeling in deserts, which arise due to unique plant adaptations, marginal growing conditions, slow net primary production rates, and highly variable rainfall. We consider model uncertainty from both structural and parameter errors and present a mechanistic model for the shrub Larrea tridentata (creosote bush) under conditions found in the Mojave National Preserve in southeastern California (USA). Desert-specific plant and soil features are incorporated into the CLM-CN model by Oleson et al. (2010). We then develop a data assimilation framework using the ensemble Kalman filter (EnKF) to estimate model parameters based on soil moisture and leaf-area index observations. A new implementation procedure, the "multisite loop EnKF," tackles parameter estimation difficulties found to affect desert ecohydrological applications. Specifically, the procedure iterates through data from various observation sites to alleviate adverse filter impacts from non-Gaussianity in small desert vegetation state values. It also readjusts inconsistent parameters and states through a model spin-up step that accounts for longer dynamical time scales due to infrequent rainfall in deserts. Observation error variance inflation may also be needed to help prevent divergence of estimates from true values. Synthetic test results highlight the importance of adequate observations for reducing model uncertainty, which can be achieved through data quality or quantity.

A mechanistic modeling and data assimilation framework for Mojave Desert ecohydrology

Science.gov (United States)

Ng, Gene-Hua Crystal.; Bedford, David; Miller, David

2014-01-01

This study demonstrates and addresses challenges in coupled ecohydrological modeling in deserts, which arise due to unique plant adaptations, marginal growing conditions, slow net primary production rates, and highly variable rainfall. We consider model uncertainty from both structural and parameter errors and present a mechanistic model for the shrub Larrea tridentata (creosote bush) under conditions found in the Mojave National Preserve in southeastern California (USA). Desert-specific plant and soil features are incorporated into the CLM-CN model by Oleson et al. (2010). We then develop a data assimilation framework using the ensemble Kalman filter (EnKF) to estimate model parameters based on soil moisture and leaf-area index observations. A new implementation procedure, the “multisite loop EnKF,” tackles parameter estimation difficulties found to affect desert ecohydrological applications. Specifically, the procedure iterates through data from various observation sites to alleviate adverse filter impacts from non-Gaussianity in small desert vegetation state values. It also readjusts inconsistent parameters and states through a model spin-up step that accounts for longer dynamical time scales due to infrequent rainfall in deserts. Observation error variance inflation may also be needed to help prevent divergence of estimates from true values. Synthetic test results highlight the importance of adequate observations for reducing model uncertainty, which can be achieved through data quality or quantity.

Relationship between climate and vegetation and the stable carbon isotope chemistry of soils in the eastern Mojave Desert, Nevada

International Nuclear Information System (INIS)

Amundson, R.G.; Chadwick, O.A.; Sowers, J.M.; Doner, H.E.

1988-01-01

The relationship between the stable C-isotope composition of the soil environment and modern climate and vegetation was determined empirically along a present-day climatic transect in the eastern Mojave Desert. The δ 13 C of the soil CO 2 and carbonates decreased with increasing elevation and plant density, even though plant assemblages at all elevations were isotopically similar. Several factors, including differences in the ratios of pedogenic of limestone calcite and differences in past vegetation, were considered as explanations of this trend, However, it appears that in the sparsely vegetated Mojave Desert, the δ 13 C of pedogenic carbonate is controlled by differences in plant density and biological activity. This relationship may provide a tool for assessing past vegetational densities, as long as the vegetation is isotopically homogeneous. (author)

A study of the depth of weathering and its relationship to the mechanical properties of near-surface rocks in the Mojave Desert

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Stierman, D.J.; Healy, J.H.

1985-01-01

Weathered granite extends 70 m deep at Hi Vista in the arid central Mojave Desert of southern California. The low strength of this granite is due to the alteration of biotite and chlorite montmorillonite. Deep weathering probably occurs in most granites, although we cannot rule out some anomalous mechanisms at Hi Vista. Geophysical instruments set in these slightly altered rocks are limited by the unstable behavior of the rocks. Thus, tectonic signals from instruments placed in shallow boreholes give vague results. Geophysical measurements of these weathered rocks resemble measurements of granitic rocks near major faults. The rheology of the rocks in which instruments are placed limits the useful sensitivity of the instruments. ?? 1985 Birkha??user Verlag.

Evaluation of volatile organic compounds in two Mojave Desert basins-Mojave River and Antelope Valley-in San Bernardino, Los Angeles, and Kern Counties, California, June-October 2002

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Densmore, Jill N.; Belitz, Kenneth; Wright, Michael T.; Dawson, Barbara J.; Johnson, Tyler D.

2005-01-01

The California Aquifer Susceptibility Assessment of the Ground-Water Ambient Monitoring and Assessment Program was developed to assess water quality and susceptibility of ground-water resources to contamination from surficial sources. This study focuses on the Mojave River and the Antelope Valley ground-water basins in southern California. Volatile organic compound (VOC) data were evaluated in conjunction with tritium data to determine a potential correlation with aquifer type, depth to top of perforations, and land use to VOC distribution and occurrence in the Mojave River and the Antelope Valley Basins. Detection frequencies for VOCs were compiled and compared to assess the distribution in each area. Explanatory variables were evaluated by comparing detection frequencies for VOCs and tritium and the number of compounds detected. Thirty-three wells were sampled in the Mojave River Basin (9 in the floodplain aquifer, 15 in the regional aquifer, and 9 in the sewered subset of the regional aquifer). Thirty-two wells were sampled in the Antelope Valley Basin. Quality-control samples also were collected to identify, quantify, and document bias and variability in the data. Results show that VOCs generally were detected slightly more often in the Antelope Valley Basin samples than in the Mojave River Basin samples. VOCs were detected more frequently in the floodplain aquifer than in the regional aquifer and the sewered subset. Tritium was detected more frequently in the Mojave River Basin samples than in the Antelope Valley Basin samples, and it was detected more frequently in the floodplain aquifer than in the regional aquifer and the sewered subset. Most of the samples collected in both basins for this study contained old water (water recharged prior to 1952). In general, in these desert basins, tritium need not be present for VOCs to be present. When VOCs were detected, young water (water recharge after 1952) was slightly more likely to be contaminated than old water

Monitoring Springs in the Mojave Desert Using Landsat Time Series Analysis

Science.gov (United States)

Potter, Christopher S.

2018-01-01

The purpose of this study, based on Landsat satellite data was to characterize variations and trends over 30 consecutive years (1985-2016) in perennial vegetation green cover at over 400 confirmed Mojave Desert spring locations. These springs were surveyed between in 2015 and 2016 on lands managed in California by the U.S. Bureau of Land Management (BLM) and on several land trusts within the Barstow, Needles, and Ridgecrest BLM Field Offices. The normalized difference vegetation index (NDVI) from July Landsat images was computed at each spring location and a trend model was first fit to the multi-year NDVI time series using least squares linear regression.Â

The Mojave Desert: A Martian Analog Site for Future Astrobiology Themed Missions

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Salas, E.; Abbey, W.; Bhartia, R.; Beegle, L. W.

2011-01-01

Astrobiological interest in Mars is highlighted by evidence that Mars was once warm enough to have liquid water present on its surface long enough to create geologic formations that could only exist in the presense of extended fluvial periods. These periods existed at the same time life on Earth arose. If life began on Mars as well during this period, it is reasonable to assume it may have adapted to the subsurface as environments at the surface changed into the inhospitable state we find today. If the next series of Mars missions (Mars Science Laboratory, the ExoMars Trace Gas Orbiter proposed for launch in 2016, and potential near surface sample return) fail to discover either extinct or extant life on Mars, a subsurface mission would be necessary to attempt to "close the book" on the existence of martian life. Mars is much colder and drier than Earth, with a very low pressure CO2 environment and no obvious habitats. Terrestrial regions with limited precipitation, and hence reduced active biota, are some of the best martian low to mid latitude analogs to be found on Earth, be they the Antarctic dry valleys, the Atacama or Mojave Deserts. The Mojave Desert/Death Valley region is considered a Mars analog site by the Terrestrial Analogs Panel of the NSF-sponsored decadal survey; a field guide was even developed and a workshop was held on its applicability as a Mars analog. This region has received a great deal of attention due to its accessibility and the variety of landforms and processes observed relevant to martian studies.

Map showing areas of visible land disturbances caused by two military training operations in the Mojave Desert, California

Science.gov (United States)

Prose, D.V.

1986-01-01

This map shows areas that retain visible land disturbances produced during two military armored-vehicle training operations in the Mojave Desert, California. The map documents the lasting visual effects these operations have on this arid region and provides a data base for monitoring changes in the extent of visual disturbances in the future.

Preliminary study of the uranium favorability of Mesozoic intrusive and Tertiary volcanic and sedimentary rocks of the Central Mojave Desert, Kern and San Bernardino counties, California

International Nuclear Information System (INIS)

Leedom, S.H.; Kiloh, K.D.

1978-02-01

Numerous, small, low-grade, supergene uranium deposits are found in Tertiary volcanic and sedimentary rocks in the central Mojave Desert of southern California. Large thorium-to-uranium ratios in samples of Mesozoic intrusive rocks exposed in the area indicate that these rocks have been extensively weathered, eroded, and subsequently leached by ground waters, and that they may have been the primary source of uranium for the deposits. The uranium content of samples of volcanic intrusive and extrusive rocks is average for intermediate to silicic rocks, but samples of basalt flows in the area contain six times the average uranium content of mafic igneous rocks. Devitrified tuffs and tuffaceous sedimentary rocks, interbedded with calcareous units, are additional sources of uranium for supergene uranium deposits found in calcareous units. Uranium is also found in accessory minerals in a few Mesozoic quartz-rich pegmatite dikes. Uranium deposits in the central Mojave Desert have been formed by enrichment during diagenetic replacement of Tertiary carbonate rocks; by supergene enrichment along fractures, joints, and bedding planes in Tertiary volcanic and sedimentary rocks; during formation of Holocene caliche; and by deposition within hydrothermally altered shear zones. Within the area, the diagenetic replacement type of deposit has the greatest potential for large, low-grade uranium occurrences. The other type of uranium deposits are small, erratically distributed, and extensively covered by alluvium

CO2 EFFECTS ON MOJAVE DESERT PLANT INTERACTIONS

Energy Technology Data Exchange (ETDEWEB)

L. A. DEFALCO; G. C. FERNANDEZ; S. D. SMITH; R. S. NOWAK

2004-01-01

Seasonal and interannual droughts characteristic of deserts have the potential to modify plant interactions as atmospheric CO{sub 2} concentrations continue to rise. At the Nevada Desert FACE (free-air CO{sub 2} enrichment) facility in the northern Mojave Desert, the effects of elevated atmospheric C02 (550 vs. ambient {approx}360 {micro}mol mol{sup -1}) on plant interactions were examined during two years of high and low rainfall. Results suggest that CO{sub 2} effects on the interaction between native species and their understory herbs are dependent on the strength of competition when rainfall is plentiful, but are unimportant during annual drought. Seasonal rainfall for 1999 was 23% the long-term average for the area, and neither elevated CO{sub 2} nor the low production of herbaceous neighbors had an effect on relative growth rate (RGR, d{sup -1}) and reproductive effort (RE, number of flowers g{sup -1}) for Achnatherum hymenoides (early season perennial C{sub 3} grass), Pleuraphis rigida (late season perennial C{sub 4} grass), and Larrea tridentata (evergreen C{sub 3} shrub). In contrast, 1998 received 213% the average rainfall. Consequently, the decrease in RGR and increase in RE for Achnatherum, whose period of growth overlaps directly with that of its neighbors, was exaggerated at elevated CO{sub 2}. However, competitive effects of neighbors on Eriogonum trichopes (a winter annual growing in shrub interspaces), Pleuraphis and Larrea were not affected by elevated CO{sub 2}, and possible explanations are discussed. Contrary to expectations, the invasive annual neighbor Bromus madritensis ssp. rubens had little influence on target plant responses because densities in 1998 and 1999 at this site were well below those found in other studies where it has negatively affected perennial plant growth. The extent that elevated CO{sub 2} reduces the performance of Achnatherum in successive years to cause its loss from the plant community depends more on future pressure

Short-Term Space-Use Patterns of Translocated Mojave Desert Tortoise in Southern California.

Directory of Open Access Journals (Sweden)

Matthew L Farnsworth

Full Text Available Increasingly, renewable energy comprises a larger share of global energy production. Across the western United States, public lands are being developed to support renewable energy production. Where there are conflicts with threatened or endangered species, translocation can be used in an attempt to mitigate negative effects. For the threatened Mojave desert tortoise (Gopherus agassizii, we sought to compare habitat- and space-use patterns between short-distance translocated, resident, and control groups. We tested for differences in home range size based on utilization distributions and used linear mixed-effects models to compare space-use intensity, while controlling for demographic and environmental variables. In addition, we examined mean movement distances as well as home range overlap between years and for male and female tortoises in each study group. During the first active season post-translocation, home range size was greater and space-use intensity was lower for translocated tortoises than resident and control groups. These patterns were not present in the second season. In both years, there was no difference in home range size or space-use intensity between control and resident groups. Translocation typically resulted in one active season of questing followed by a second active season characterized by space-use patterns that were indistinguishable from control tortoises. Across both years, the number of times a tortoise was found in a burrow was positively related to greater space-use intensity. Minimizing the time required for translocated tortoises to exhibit patterns similar to non-translocated individuals may have strong implications for conservation by reducing exposure to adverse environmental conditions and predation. With ongoing development, our results can be used to guide future efforts aimed at understanding how translocation strategies influence patterns of animal space use.

Temperature and Heat-Related Mortality Trends in the Sonoran and Mojave Desert Region

Directory of Open Access Journals (Sweden)

Polioptro F. Martinez-Austria

2017-03-01

Full Text Available Extreme temperatures and heat wave trends in five cities within the Sonoran Desert region (e.g., Tucson and Phoenix, Arizona, in the United States and Ciudad Obregon and San Luis Rio Colorado, Sonora; and Mexicali, Baja California, in Mexico and one city within the Mojave Desert region (e.g., Las Vegas, Nevada were assessed using field data collected from 1950 to 2014. Instead of being selected by watershed, the cities were selected because they are part of the same arid climatic region. The data were analyzed for maximum temperature increases and the trends were confirmed statistically using Spearman’s nonparametric test. Temperature trends were correlated with the mortality information related with extreme heat events in the region. The results showed a clear trend of increasing maximum temperatures during the months of June, July, and August for five of the six cities and statically confirmed using Spearman’s rho values. Las Vegas was the only city where the temperature increase was not confirmed using Spearman’s test, probably because it is geographically located outside of the Sonoran Desert or because of its proximity to the Hoover Dam. The relationship between mortality and temperature was analyzed for the cities of Mexicali, Mexico and Phoenix. Arizona.

Ground-water recharge from small intermittent streams in the western Mojave Desert, California: Chapter G in Ground-water recharge in the arid and semiarid southwestern United States (Professional Paper 1703)

Science.gov (United States)

Izbicki, John A.; Johnson, Russell U.; Kulongoski, Justin T.; Predmore, Steven; Stonestrom, David A.; Constantz, Jim; Ferré, Ty P.A.; Leake, Stanley A.

2007-01-01

extend to the distal ends of all washes. Where urbanization had concentrated spatially distributed runoff into a small number of fixed channels, enhanced infiltration induced recharging conditions, mobilizing accumulated chloride.Estimated amounts of ground-water recharge from the studied reaches were small. Extrapolating on the basis of drainage areas, the estimated aggregate recharge from small intermittent streams is minor compared to recharge from the Mojave River. Recharge is largely controlled by streamflow availability, which primarily reflects precipitation patterns. Precipitation in the Mojave Desert is strongly controlled by topography. Cool moist air masses from the Pacific Ocean are mostly blocked from entering the desert by the high mountains bordering its southern edge. Storms do, however, readily enter the region through Cajon Pass. These storms generate flow in the Mojave River that often reaches Afton Canyon, more than 150 kilometers downstream. The isotopic composition of ground water reflects the localization of recharge beneath the Mojave River. Similar processes occur near San Gorgonio Pass, 75 kilometers southeast from Cajon Pass along the bounding San Andreas Fault.

Final Technical Report: Effects of Changing Water and Nitrogen Inputs on a Mojave Desert Ecosystem

Energy Technology Data Exchange (ETDEWEB)

Smith, Stanley, D.; Nowak, Robert S.; Fenstermaker, Lynn, F.; Young, Michael,H.

2007-11-30

In order to anticipate the effects of global change on ecosystem function, it is essential that predictive relationships be established linking ecosystem function to global change scenarios. The Mojave Desert is of considerable interest with respect to global change. It contains the driest habitats in North America, and thus most closely approximates the world’s great arid deserts. In order to examine the effects of climate and land use changes, in 2001 we established a long-term manipulative global change experiment, called the Mojave Global Change Facility. Manipulations in this study include the potential effects of (1) increased summer rainfall (75 mm over three discrete 25 mm events), (2) increased nitrogen deposition (10 and 40 kg ha-1), and (3) the disturbance of biological N-fixing crusts . Questions addressed under this grant shared the common hypothesis that plant and ecosystem performance will positively respond to the augmentation of the most limiting resources to plant growth in the Mojave Desert, e.g., water and nitrogen. Specific hypotheses include (1) increased summer rainfall will significantly increase plant production through an alleviation of moisture stress in the dry summer months, (2) N-deposition will increase plant production in this N-limited system, particularly in wet years or in concert with added summer rain, and (3) biological crust disturbance will gradually decrease bio-available N, with concomitant long-term reductions in photosynthesis and ANPP. Individual plant and ecosystem responses to global change may be regulated by biogeochemical processes and natural weather variability, and changes in plant and ecosystem processes may occur rapidly, may occur only after a time lag, or may not occur at all. During the first PER grant period, we observed changes in plant and ecosystem processes that would fall under each of these time-response intervals: plant and ecosystem processes responded rapidly to added summer rain, whereas most

Effectiveness of post-fire seeding in desert tortoise Critical Habitat following the 2005 Southern Nevada Fire Complex

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DeFalco, Lesley; Drake, Karla K.; Scoles-Sciulla, S. J.; Bauer, Kyla L.

2010-01-01

In June 2005, lightning strikes ignited multiple wildfires in southern Nevada. The Southern Nevada Fire Complex burned more than 32,000 acres of designated desert tortoise Critical Habitat and an additional 403,000 acres of Mojave Desert habitat characterized as potentially suitable for the tortoise. Mortalities of desert tortoises were observed after the fires, but altered habitat is likely to prolong and magnify the impacts of wildfire on desert tortoise populations. To accelerate the re-establishment of plants commonly used by tortoises for food and shelter, the Bureau of Land Management (BLM) distributed seeds of native annual and perennial species in burned areas within desert tortoise Critical Habitat. The U.S. Geological Survey (USGS) established monitoring plots to evaluate broadcast seeding as a means to restore habitat and tortoise activity compared with natural recovery. Within the standard three-year Emergency and Stabilization Response (ESR) monitoring timeline, seeding augmented perennial seed banks by four to six-fold within a year of seed applications compared with unseeded areas. By the end of the three-year monitoring period, seedling densities of seeded perennial species were 33% higher in seeded areas than in unseeded areas, particularly for the disturbance-adapted desert globemallow (Sphaeralcea ambigua) and desert marigold (Baileya multiradiata). Seeded annuals, in contrast, did not increase significantly in seed banks or biomass production, likely due to low seeding rates of these species. Production of non-native annuals that helped carry the fires was not reduced by seeding efforts but instead was strongly correlated with site-specific rainfall, as were native annual species. The short-term vegetation changes measured in seeded areas were not yet associated with a return of tortoise activity to unburned levels. By focusing on a combination of native species that can withstand disturbance conditions, including species that are found in

Status of groundwater quality in the Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts study unit, 2008-2010: California GAMA Priority Basin Project

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Parsons, Mary C.; Hancock, Tracy Connell; Kulongoski, Justin T.; Belitz, Kenneth

2014-01-01

Groundwater quality in the approximately 963-square-mile Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts study unit was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in southern California in San Bernardino, Riverside, San Diego, and Imperial Counties. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey and the Lawrence Livermore National Laboratory. The GAMA Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts study was designed to provide a spatially unbiased assessment of the quality of untreated (raw) groundwater in the primary aquifer system. The assessment is based on water-quality and ancillary data collected by the U.S. Geological Survey from 52 wells (49 grid wells and 3 understanding wells) and on water-quality data from the California Department of Public Health database. The primary aquifer system was defined by the depth intervals of the wells listed in the California Department of Public Health database for the Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts study unit. The quality of groundwater in the primary aquifer system may be different from that in the shallower or deeper water-bearing zones; shallow groundwater may be more vulnerable to surficial contamination. This study assesses the status of the current quality of the groundwater resource by using data from samples analyzed for volatile organic compounds (VOCs), pesticides, and naturally occurring inorganic constituents, such as major ions and trace elements. This status assessment is intended to characterize the quality of groundwater resources in the primary aquifer system of the Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts study unit, not the

Invasive species in southern Nevada [Chapter 4

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Mathew L. Brooks; Steven M. Ostoja; Jeanne C. Chambers

2013-01-01

Southern Nevada contains a wide range of topographies, elevations, and climatic zones emblematic of its position at the ecotone between the Mojave Desert, Great Basin, and Colorado Plateau ecoregions. These varied environmental conditions support a high degree of biological diversity (Chapter 1), but they also provide opportunities for a wide range of invasive species...

Multiple factors affect a population of Agassiz's desert tortoise (Gopherus agassizii) in the Northwestern Mojave Desert

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Berry, Kristin H.; Yee, Julie L.; Coble, Ashley A.; Perry, William M.; Shields, Timothy A.

2013-01-01

Numerous factors have contributed to declines in populations of the federally threatened Agassiz's Desert Tortoise (Gopherus agassizii) and continue to limit recovery. In 2010, we surveyed a low-density population on a military test facility in the northwestern Mojave Desert of California, USA, to evaluate population status and identify potential factors contributing to distribution and low densities. Estimated densities of live tortoises ranged spatially from 1.2/km2 to 15.1/km2. Although only one death of a breeding-age tortoise was recorded for the 4-yr period prior to the survey, remains of 16 juvenile and immature tortoises were found, and most showed signs of predation by Common Ravens (Corvus corax) and mammals. Predation may have limited recruitment of young tortoises into the adult size classes. To evaluate the relative importance of different types of impacts to tortoises, we developed predictive models for spatially explicit densities of tortoise sign and live tortoises using topography (i.e., slope), predators (Common Raven, signs of mammalian predators), and anthropogenic impacts (distances from paved road and denuded areas, density of ordnance fragments) as covariates. Models suggest that densities of tortoise sign increased with slope and signs of mammalian predators and decreased with Common Ravens, while also varying based on interaction effects involving these predictors as well as distances from paved roads, denuded areas, and ordnance. Similarly, densities of live tortoises varied by interaction effects among distances to denuded areas and paved roads, density of ordnance fragments, and slope. Thus multiple factors predict the densities and distribution of this population.

The Mojave vadose zone: a subsurface biosphere analogue for Mars.

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Abbey, William; Salas, Everett; Bhartia, Rohit; Beegle, Luther W

2013-07-01

If life ever evolved on the surface of Mars, it is unlikely that it would still survive there today, but as Mars evolved from a wet planet to an arid one, the subsurface environment may have presented a refuge from increasingly hostile surface conditions. Since the last glacial maximum, the Mojave Desert has experienced a similar shift from a wet to a dry environment, giving us the opportunity to study here on Earth how subsurface ecosystems in an arid environment adapt to increasingly barren surface conditions. In this paper, we advocate studying the vadose zone ecosystem of the Mojave Desert as an analogue for possible subsurface biospheres on Mars. We also describe several examples of Mars-like terrain found in the Mojave region and discuss ecological insights that might be gained by a thorough examination of the vadose zone in these specific terrains. Examples described include distributary fans (deltas, alluvial fans, etc.), paleosols overlain by basaltic lava flows, and evaporite deposits.

Invasive species in southern Nevada [Chapter 4] (Executive Summary)

Science.gov (United States)

Matthew L. Brooks; Steven M. Ostoja; Jeanne C.. Chambers

2013-01-01

Southern Nevada contains a wide range of topographies, elevations, and climatic zones that are emblematic of its position at the ecotone between the Mojave Desert, Great Basin, and Colorado Plateau ecoregions. These varied environmental conditions support a high degree of biological diversity, but they also provide opportunities for a wide range of invasive species. In...

Desert wildfire and severe drought diminish survivorship of the long-lived Joshua Tree (Yucca brevifolia; Agavaceae)

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DeFalco, L.A.; Esque, T.C.; Scoles-Sciulla, S. J.; Rodgers, J.

2010-01-01

Extreme climate events are transforming plant communities in the desert Southwest of the United States. Abundant precipitation in 1998 associated with El Ni??o Southern Oscillation (ENSO) stimulated exceptional alien annual plant production in the Mojave Desert that fueled wildfires in 1999. Exacerbated by protracted drought, 80% of the burned Yucca brevifolia, a long-lived arborescent monocot, and 26% of unburned plants died at Joshua Tree National Park by 2004. Many burned plants old adults with fewer opportunities for plant recruitment, thus imperiling the persistence of this unique plant community.

Soil water availability and microsite mediate fungal and bacterial phospholipid fatty acid biomarker abundances in Mojave Desert soils exposed to elevated atmospheric CO2

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Jin, V. L.; Schaeffer, S. M.; Ziegler, S. E.; Evans, R. D.

2011-06-01

Changes in the rates of nitrogen (N) cycling, microbial carbon (C) substrate use, and extracellular enzyme activities in a Mojave Desert ecosystem exposed to elevated atmospheric CO2 suggest shifts in the size and/or functional characteristics of microbial assemblages in two dominant soil microsites: plant interspaces and under the dominant shrub Larrea tridentata. We used ester-linked phospholipid fatty acid (PLFA) biomarkers as a proxy for microbial biomass to quantify spatial and temporal differences in soil microbial communities from February 2003 to May 2005. Further, we used the 13C signature of the fossil CO2 source for elevated CO2 plots to trace recent plant C inputs into soil organic matter (SOM) and broad microbial groups using δ13C (‰). Differences between individual δ13CPLFA and δ13CSOM for fungal biomarkers indicated active metabolism of newer C in elevated CO2 soils. Total PLFA-C was greater in shrub microsites compared to plant interspaces, and CO2 treatment differences within microsites increased under higher soil water availability. Total, fungal, and bacterial PLFA-C increased with decreasing soil volumetric water content (VWC) in both microsites, suggesting general adaptations to xeric desert conditions. Increases in fungal-to-bacterial PLFA-C ratio with decreasing VWC reflected functional group-specific responses to changing soil water availability. While temporal and spatial extremes in resource availability in desert ecosystems contribute to the difficulty in identifying common trends or mechanisms driving microbial responses in less extreme environments, we found that soil water availability and soil microsite interacted with elevated CO2 to shift fungal and bacterial biomarker abundances in Mojave Desert soils.

Deserts

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Belnap, Jayne; Webb, Robert H.; Esque, Todd; Brooks, Matthew L.; DeFalco, Lesley; MacMahon, James A.

2016-01-01

The deserts of California (Lead photo, Fig. 1) occupy approximately 38% of California’s landscape (Table 1) and consist of three distinct deserts: the Great Basin Desert, Mojave Desert, and Colorado Desert, the latter of which is a subdivision of the Sonoran Desert (Brown and Lowe 1980). The wide range of climates and geology found within each of these deserts result in very different vegetative communities and ecosystem processes and therefore different ecosystem services. In deserts, extreme conditions such as very high and low temperatures and very low rainfall result in abiotic factors (climate, geology, geomorphology, and soils) controlling the composition and function of ecosystems, including plant and animal distributions. This is in contrast to wetter and milder temperatures found in other ecosystems, where biotic interactions are the dominant driving force. However, despite the harsh conditions in deserts, they are home to a surprisingly large number of plants and animals. Deserts are also places where organisms display a wide array of adaptations to the extremes they encounter, providing some of the best examples of Darwinian selection (MacMahon and Wagner 1985, Ward 2009). Humans have utilized these regions for thousands of years, despite the relatively low productivity and harsh climates of these landscapes. Unlike much of California, most of these desert lands have received little high-intensity use since European settlement, leaving large areas relatively undisturbed. Desert landscapes are being altered, however, by the introduction of fire following the recent invasion of Mediterranean annual grasses. As most native plants are not fire-adapted, they Many do not recover, whereas the non-native grasses flourish. Because desert lands are slow to recover from disturbances, energy exploration and development, recreational use, and urban development will alter these landscapes for many years to come. This chapter provides a brief description of where the

Disturbance and Plant Succession in the Mojave and Sonoran Deserts of the American Southwest

Directory of Open Access Journals (Sweden)

Scott R. Abella

2010-03-01

Full Text Available Disturbances such as fire, land clearing, and road building remove vegetation and can have major influences on public health through effects on air quality, aesthetics, recreational opportunities, natural resource availability, and economics. Plant recovery and succession following disturbance are poorly understood in arid lands relative to more temperate regions. This study quantitatively reviewed vegetation reestablishment following a variety of disturbances in the Mojave and Sonoran Deserts of southwestern North America. A total of 47 studies met inclusion criteria for the review. The time estimated by 29 individual studies for full reestablishment of total perennial plant cover was 76 years. Although long, this time was shorter than an estimated 215 years (among 31 individual studies required for the recovery of species composition typical of undisturbed areas, assuming that recovery remains linear following the longest time since disturbance measurement made by the studies.

Polarization signatures for abandoned agricultural fields in the Manix Basin area of the Mojave Desert

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Ray, Terrill W.; Farr, Tom G.; Vanzyl, Jakob J.

1991-01-01

Polarimetric signatures from abandoned circular alfalfa fields in the Manix Basin area of the Mojave desert show systematic changes with length of abandonment. The obliteration of circular planting rows by surface processes could account for the disappearance of bright 'spokes', which seems to be reflection patterns from remnants of the planting rows, with increasing length of abandonment. An observed shift in the location of the maximum L-band copolarization return away from VV, as well as an increase in surface roughness, both occurring with increasing age of abandonment, seems to be attributable to the formation of wind ripple on the relatively vegetationless fields. A Late Pleistocene/Holocene sand bar deposit, which can be identified in the radar images, is probably responsible for the failure of three fields to match the age sequence patterns in roughness and peak shift.

Discriminating patterns and drivers of multiscale movement in herpetofauna: The dynamic and changing environment of the Mojave desert tortoise.

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Sadoti, Giancarlo; Gray, Miranda E; Farnsworth, Matthew L; Dickson, Brett G

2017-09-01

Changes to animal movement in response to human-induced changes to the environment are of growing concern in conservation. Most research on this problem has focused on terrestrial endotherms, but changes to herpetofaunal movement are also of concern given their limited dispersal abilities and specialized thermophysiological requirements. Animals in the desert region of the southwestern United States are faced with environmental alterations driven by development (e.g., solar energy facilities) and climate change. Here, we study the movement ecology of a desert species of conservation concern, the Mojave desert tortoise ( Gopherus agassizii ). We collected weekly encounter locations of marked desert tortoises during the active (nonhibernation) seasons in 2013-2015, and used those data to discriminate movements among activity centers from those within them. We then modeled the probability of movement among activity centers using a suite of covariates describing characteristics of tortoises, natural and anthropogenic landscape features, vegetation, and weather. Multimodel inference indicated greatest support for a model that included individual tortoise characteristics, landscape features, and weather. After controlling for season, date, age, and sex, we found that desert tortoises were more likely to move among activity centers when they were further from minor roads and in the vicinity of barrier fencing; we also found that movement between activity centers was more common during periods of greater rainfall and during periods where cooler temperatures coincided with lower rainfall. Our findings indicate that landscape alterations and climate change both have the potential to impact movements by desert tortoises during the active season. This study provides an important baseline against which we can detect future changes in tortoise movement behavior.

Biotic Processes Regulating the Carbon Balance of Desert Ecosystems - Final Report

Energy Technology Data Exchange (ETDEWEB)

Nowak, Robert S [UNR; Smith, Stanley D [UNLV; Evans, Dave [WSU; Ogle, Kiona [ASU; Fenstermaker, Lynn [DRI

2012-12-13

Our results from the 10-year elevated atmospheric CO{sub 2} concentration study at the Nevada Desert FACE (Free-air CO{sub 2} Enrichment) Facility (NDFF) indicate that the Mojave Desert is a dynamic ecosystem with the capacity to respond quickly to environmental changes. The Mojave Desert ecosystem is accumulating carbon (C), and over the 10-year experiment, C accumulation was significantly greater under elevated [CO{sub 2}] than under ambient, despite great fluctuations in C inputs from year to year and even apparent reversals in which [CO{sub 2}] treatment had greater C accumulations.

Polarization signatures for abandoned agricultural fields in the Manix Basin area of the Mojave Desert - Can polarimetric SAR detect desertification?

Science.gov (United States)

Ray, Terrill W.; Farr, Tom G.; Van Zyl, Jakob J.

1992-01-01

Radar backscatter from abandoned circular alfalfa fields in the Manix Basin area of the Mojave desert shows systematic changes with length of abandonment. The obliteration of circular planting rows by surface processes could account for the disappearance of bright spokes, which seem to be reflection patterns from remnants of the planting rows, with increasing length of abandonment. An observed shift in the location of the maximum L-band copolarization return away from VV, as well as an increase in surface roughness, both occurring with increasing age of abandonment, seems to be attributable to the formation of wind ripples on the relatively vegetationless fields.

Landscape-scale distribution and density of raptor populations wintering in anthropogenic-dominated desert landscapes

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Duerr, Adam E.; Miller, Tricia A.; Cornell Duerr, Kerri L; Lanzone, Michael J.; Fesnock, Amy; Katzner, Todd E.

2015-01-01

Anthropogenic development has great potential to affect fragile desert environments. Large-scale development of renewable energy infrastructure is planned for many desert ecosystems. Development plans should account for anthropogenic effects to distributions and abundance of rare or sensitive wildlife; however, baseline data on abundance and distribution of such wildlife are often lacking. We surveyed for predatory birds in the Sonoran and Mojave Deserts of southern California, USA, in an area designated for protection under the “Desert Renewable Energy Conservation Plan”, to determine how these birds are distributed across the landscape and how this distribution is affected by existing development. We developed species-specific models of resight probability to adjust estimates of abundance and density of each individual common species. Second, we developed combined-species models of resight probability for common and rare species so that we could make use of sparse data on the latter. We determined that many common species, such as red-tailed hawks, loggerhead shrikes, and especially common ravens, are associated with human development and likely subsidized by human activity. Species-specific and combined-species models of resight probability performed similarly, although the former model type provided higher quality information. Comparing abundance estimates with past surveys in the Mojave Desert suggests numbers of predatory birds associated with human development have increased while other sensitive species not associated with development have decreased. This approach gave us information beyond what we would have collected by focusing either on common or rare species, thus it provides a low-cost framework for others conducting surveys in similar desert environments outside of California.

Aeolian responses to climate variability during the past century on Mesquite Lake Playa, Mojave Desert

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Whitney, John W.; Breit, George N.; Buckingham, S.E.; Reynolds, Richard L.; Bogle, Rian C.; Luo, Lifeng; Goldstein, Harland L.; Vogel, John M.

2015-01-01

The erosion and deposition of sediments by wind from 1901 to 2013 have created large changes in surface features of Mesquite Lake playa in the Mojave Desert. The decadal scale recurrence of sand-sheet development, migration, and merging with older dunes appears related to decadal climatic changes of drought and wetness as recorded in the precipitation history of the Mojave Desert, complemented by modeled soil-moisture index values. Historical aerial photographs, repeat land photographs, and satellite images document the presence and northward migration of a mid-20th century sand sheet that formed during a severe regional drought that coincided with a multi-decadal cool phase of the Pacific Decadal Oscillation (PDO). The sand sheet slowly eroded during the wetter conditions of the subsequent PDO warm phase (1977–1998) due to a lack of added sediment. Sand cohesion gradually increased in the sand sheet by seasonal additions of salt and clay and by re-precipitation of gypsum, which resulted in the wind-carving of yardangs in the receding sand sheet. Smaller yardangs were aerodynamically shaped from coppice dunes with salt-clay crusts, and larger yardangs were carved along the walls and floor of trough blowouts. Evidence of a 19th century cycle of sand-sheet formation and erosion is indicated by remnants of yardangs, photographed in 1901 and 1916, that were found buried in the mid-20th century sand sheet. Three years of erosion measurements on the playa, yardangs, and sand sheets document relatively rapid wind erosion. The playa has lowered 20 to 40 cm since the mid-20th century and a shallow deflation basin has developed since 1999. Annually, 5–10 cm of surface sediment was removed from yardang flanks by a combination of wind abrasion, deflation, and mass movement. The most effective erosional processes are wind stripping of thin crusts that form on the yardang surfaces after rain events and the slumping of sediment blocks from yardang flanks. These wind

A Systematic Review of Wild Burro Grazing Effects on Mojave Desert Vegetation, USA

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Abella, Scott R.

2008-06-01

Wild burros ( Equus asinus), protected by the 1971 Wild Free-Roaming Horse and Burro Act on some federal lands but exotic animals many ecologists and resource mangers view as damaging to native ecosystems, represent one of the most contentious environmental management problems in American Southwest arid lands. This review synthesizes the scattered literature about burro effects on plant communities of the Mojave Desert, a center of burro management contentions. I classified 24 documents meeting selection criteria for this review into five categories of research: (i) diet analyses directly determining which plant species burros consume, (ii) utilization studies of individual species, (iii) control-impact comparisons, (iv) exclosure studies, and (v) forage analyses examining chemical characteristics of forage plants. Ten diet studies recorded 175 total species that burros consumed. However, these studies and two exclosure studies suggested that burros preferentially eat graminoid and forb groups over shrubs. One study in Death Valley National Park, for example, found that Achnatherum hymenoides (Indian ricegrass) was 11 times more abundant in burro diets than expected based on its availability. Utilization studies revealed that burros also exhibit preferences within the shrub group. Eighty-three percent of reviewed documents were produced in a 12-year period, from 1972 to 1983, with the most recent document produced in 1988. Because burros remain abundant on many federal lands and grazing may interact with other management concerns (e.g., desert wildfires fueled by exotic grasses), rejuvenating grazing research to better understand both past and present burro effects could help guide revegetation and grazing management scenarios.

Coupled Environmental Processes and Long-term Performance of Landfill Covers in the northern Mojave Desert

Energy Technology Data Exchange (ETDEWEB)

David Shafer; Michael Young; Stephen Zitzer; Eric McDonald; Todd Caldwell

2004-05-12

Evapotransiration (ET) covers have gained widespread acceptance as a closure feature for waste disposal sites, particularly in the arid and semi-arid regions of the southwestern U.S. But as landforms, ET covers are subject to change over time because of processes such as pedogenesis, hydrologic processes, vegetation establishment and change, and biological processes. To better understand the effects of coupled process changes to ET covers, a series of four primary analog sites in Yucca Flat on the Nevada Test Site, along with measurements and observations from other locations in the Mojave Desert, were selected to evaluate changes in ET covers over time. The analog sites, of varying ages, were selected to address changes in the early post-institutional control period, the 1,000-year compliance period for disposal of low-level and mixed low-level waste, and the 10,000-year compliance period for transuranic waste sites.

Coupled Environmental Processes and Long-term Performance of Landfill Covers in the northern Mojave Desert

International Nuclear Information System (INIS)

David Shafer; Michael Young; Stephen Zitzer; Eric McDonald; Todd Caldwell

2004-01-01

Evapotransiration (ET) covers have gained widespread acceptance as a closure feature for waste disposal sites, particularly in the arid and semi-arid regions of the southwestern U.S. But as landforms, ET covers are subject to change over time because of processes such as pedogenesis, hydrologic processes, vegetation establishment and change, and biological processes. To better understand the effects of coupled process changes to ET covers, a series of four primary analog sites in Yucca Flat on the Nevada Test Site, along with measurements and observations from other locations in the Mojave Desert, were selected to evaluate changes in ET covers over time. The analog sites, of varying ages, were selected to address changes in the early post-institutional control period, the 1,000-year compliance period for disposal of low-level and mixed low-level waste, and the 10,000-year compliance period for transuranic waste sites

Distribution of photosynthetically fixed 14C in perennial plant species of the northern Mojave Desert

International Nuclear Information System (INIS)

Wallace, A.; Cha, J.W.; Romney, E.M.

1980-01-01

The distribution of photosynthate among plant parts subsequent to its production is needed to fully understand behavior of vegetation in any ecosystem. The present study, undertaken primarily to obtain information on transport of assimilates into roots of desert vegetation, was conducted in the northern Mojave Desert, where the mean annual rainfall is about 10 cm. Shoots of Ambrosia dumosa (A. Gray) Payne plants were exposed to 14 CO 2 in 1971, and the distribution of 14 C in roots, stems, and leaves was subsequently measured at 1 week, 2 months, and 5 months. Only about 12 percent of the 14 C photosynthate was stored in the root. Much of that stored in stems was available for new leaf growth. Photosynthate was labeled with 14 C for 24 plants representing eight species in 1972. Results showed that after 127 days the mean percentage of 14 C in roots as compared with the estimate of that originally fixed was 11.8; the percentage in stems was 43.8. To check the validity of the 14 C data, root growth of eight perennial desert plants grown in the glasshouse was followed as plants increased in size. The mean percent of the whole plant that was root for eight species was 17.7 percent. The mean proportion of the increase in plant weights that went below ground for the eight species was 19.5 percent. This value is higher than the fraction of 14 C found below ground, and therefore the 14 C technique underestimates the movement of C to roots. Results of an experiment designed to test the value of the 14 C-pulse technique for determining current root growth for some perennial species from the desert indicated that the transition part of roots where root growth continued after exposure to 14 C was highly labeled. Old growth contained less 14 C than new growth

EFFECTS OF ELEVATED CO2 ON ROOT FUNCTION AND SOIL RESPIRATION IN A MOJAVE DESERT ECOSYSTEM

Energy Technology Data Exchange (ETDEWEB)

Nowak, Robert S.

2007-12-19

Increases in atmospheric CO{sub 2} concentration during the last 250 years are unequivocal, and CO{sub 2} will continue to increase at least for the next several decades (Houghton et al. 2001, Keeling & Whorf 2002). Arid ecosystems are some of the most important biomes globally on a land surface area basis, are increasing in area at an alarming pace (Dregne 1991), and have a strong coupling with regional climate (Asner & Heidebrecht 2005). These water-limited ecosystems also are predicted to be the most sensitive to elevated CO{sub 2}, in part because they are stressful environments where plant responses to elevated CO{sub 2} may be amplified (Strain & Bazzaz 1983). Indeed, all C{sub 3} species examined at the Nevada Desert FACE Facility (NDFF) have shown increased A{sub net} under elevated CO{sub 2} (Ellsworth et al. 2004, Naumburg et al. 2003, Nowak et al. 2004). Furthermore, increased shoot growth for individual species under elevated CO{sub 2} was spectacular in a very wet year (Smith et al. 2000), although the response in low to average precipitation years has been smaller (Housman et al. 2006). Increases in perennial cover and biomass at the NDFF are consistent with long term trends in the Mojave Desert and elsewhere in the Southwest, indicating C sequestration in woody biomass (Potter et al. 2006). Elevated CO{sub 2} also increases belowground net primary production (BNPP), with average increases of 70%, 21%, and 11% for forests, bogs, and grasslands, respectively (Nowak et al. 2004). Although detailed studies of elevated CO{sub 2} responses for desert root systems were virtually non-existent prior to our research, we anticipated that C sequestration may occur by desert root systems for several reasons. First, desert ecosystems exhibit increases in net photosynthesis and primary production at elevated CO{sub 2}. If large quantities of root litter enter the ecosystem at a time when most decomposers are inactive, significant quantities of carbon may be stored

The Riparianness of a Desert Herpetofauna

Science.gov (United States)

Charles H. Lowe

1989-01-01

Within the Mojave, Sonoran, and Chihuahuan Desert subdivisions of the North American Desert in the U.S., more than half of 143 total amphibian and reptilian species perform as riparian and/or wetland taxa. For the reptiles, but not the amphibians, there is a significant inverse relationship between riparianness (obligate through preferential and facultative to...

Groundwater quality in the Mojave area, California

Science.gov (United States)

Dawson, Barbara J. Milby; Belitz, Kenneth

2012-01-01

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. Four groundwater basins along the Mojave River make up one of the study areas being evaluated. The Mojave study area is approximately 1,500 square miles (3,885 square kilometers) and includes four contiguous groundwater basins: Upper, Middle, and Lower Mojave River Groundwater Basins, and the El Mirage Valley (California Department of Water Resources, 2003). The Mojave study area has an arid climate, and is part of the Mojave Desert. Average annual rainfall is about 6 inches (15 centimeters). Land use in the study area is approximately 82 percent (%) natural (mostly shrubland), 4% agricultural, and 14% urban. The primary crops are pasture and hay. The largest urban areas are the cities of Victorville, Hesperia, and Apple Valley (2010 populations of 116,000, 90,000 and 69,000, respectively). Groundwater in these basins is used for public and domestic water supply and for irrigation. The main water-bearing units are gravel, sand, silt, and clay derived from surrounding mountains. The primary aquifers in the Mojave study area are defined as those parts of the aquifers corresponding to the perforated intervals of wells listed in the California Department of Public Health database. Public-supply wells in the Mojave study area are completed to depths between 200 and 600 feet (18 to 61 meters), consist of solid casing from the land surface to a depth of 130 to 420 feet (40 to 128 meters), and are screened or perforated below the solid casing. Recharge to the groundwater system is primarily runoff from the mountains to the south, mostly through the Mojave River channel. The primary sources

Regional water table (2016) in the Mojave River and Morongo groundwater basins, southwestern Mojave Desert, California

Science.gov (United States)

Dick, Meghan; Kjos, Adam

2017-12-07

From January to April 2016, the U.S. Geological Survey (USGS), the Mojave Water Agency, and other local water districts made approximately 1,200 water-level measurements in about 645 wells located within 15 separate groundwater basins, collectively referred to as the Mojave River and Morongo groundwater basins. These data document recent conditions and, when compared with older data, changes in groundwater levels. A water-level contour map was drawn using data measured in 2016 that shows the elevation of the water table and general direction of groundwater movement for most of the groundwater basins. Historical water-level data stored in the USGS National Water Information System (https://waterdata.usgs.gov/nwis/) database were used in conjunction with data collected for this study to construct 37 hydrographs to show long-term (1930–2016) and short-term (1990–2016) water-level changes in the study area.

Demographic studies of Joshua trees in Mojave Desert National Parks: demography with emphasis on germination and recruitment

Science.gov (United States)

Esque, T.C.; Reynolds, B.; DeFalco, L.A.; Waitman, B.A.; Hughson, Debra

2010-01-01

The study of population change with regard to reproduction, seed dispersal, and germination, establishment, growth, and survival/mortality is known as demography. Demographic studies provide managers with information to assess future trends on the density, distribution, health, and population changes of importance or value, including Joshua trees (Yucca brevifolia). Demographic research provides the potential to understand the combined impacts of climate change and land-use practices and determine if strategies for protecting important species are likely to succeed or fall short of management goals and will identify factors that have the potential to de-stabilize populations outside the realm of natural variation so that management strategies can be developed to circumvent challenges for key species, processes, and ecosystems. The National Park Service and US Geological Survey are collaborating to collect demographic information about the demographics of Joshua tree in the Mojave Desert.

Gopherus agassizii: Desert tortoise

Science.gov (United States)

Berry, Kristen H.; Swingland, Ian Richard; Klemens, Michael W.

1989-01-01

The desert tortoise is one of four allopatric North American tortoises. It occurs in the Mojave and Sonoran deserts of the southwestern United States and Mexico.Auffenberg (1976) divided the genus Gopherus (consisting of four species, G. agassizi, G. berlandieri, G.flavomarginatus, and G. polyphemus) in two osteological groups. Bramble (1982), using morphological and palaeontological data, divided the genus Gopherus into two separate complexes, each with two species. He established a new genus, Scaptochelys, for agassizi and berlandieri, retaining Gopherus for polyphemus and flavomarginatus. Bour and Dubois (1984) noted that Xerobates Agassiz had priority over Scaptochelys Bramble. Using mitochondrial DNA (mtDNA), Lamb et al. (1989) evaluated the evolutionary relationships of the North American tortoises, particularly the desert tortoise. They concluded that the mtDNA analysis provides strong support for generic recognition of the two distinct species groups described by Bramble (1982).Until a few decades ago, the desert tortoise was widespread at lower elevations throughout the Mojave and Sonoran deserts of the U.S.A. In the northern and western parts of the geographic range, large and relatively homogeneous populations with densities exceeding 1,000/sq km extended throughout parts of California, and probably into Nevada and Utah. In terms of biomass, the tortoise played an important role in the ecosystems. In most areas, numbers have declined dramatically and the extent of populations has been reduced. Most populations are now isolated and low in numbers. Conservation of the desert tortoise is a highly visible and political issue in the U.S.A., but not in Mexico.

Gopherus agassizii (Desert Tortoise). Non-native seed dispersal

Science.gov (United States)

Ennen, J.R.; Loughran, Caleb L.; Lovich, Jeffrey E.

2011-01-01

Sahara Mustard (Brassica tournefortii) is a non-native, highly invasive weed species of southwestern U.S. deserts. Sahara Mustard is a hardy species, which flourishes under many conditions including drought and in both disturbed and undisturbed habitats (West and Nabhan 2002. In B. Tellman [ed.], Invasive Plants: Their Occurrence and Possible Impact on the Central Gulf Coast of Sonora and the Midriff Islands in the Sea of Cortes, pp. 91–111. University of Arizona Press, Tucson). Because of this species’ ability to thrive in these habitats, B. tournefortii has been able to propagate throughout the southwestern United States establishing itself in the Mojave and Sonoran Deserts in Arizona, California, Nevada, and Utah. Unfortunately, naturally disturbed areas created by native species, such as the Desert Tortoise (Gopherus agassizii), within these deserts could have facilitated the propagation of B. tournefortii. (Lovich 1998. In R. G. Westbrooks [ed.], Invasive Plants, Changing the Landscape of America: Fact Book, p. 77. Federal Interagency Committee for the Management of Noxious and Exotic Weeds [FICMNEW], Washington, DC). However, Desert Tortoises have never been directly observed dispersing Sahara Mustard seeds. Here we present observations of two Desert Tortoises dispersing Sahara Mustard seeds at the interface between the Mojave and Sonoran deserts in California.

Vegetation - Central Mojave Desert [ds166

Data.gov (United States)

California Natural Resource Agency — The Department of Defense and the other desert managers are developing and organizing scientific information needed to better manage the natural resources of the...

The Mojave Subsurface Bio-Geochemistry Explorer (MOSBE)

Science.gov (United States)

Guerrero, J.; Beegle, L.; Abbey, W.; Bhartia, R.; Kounaves, S.; Russell, M.; Towles, D.

2012-01-01

The MOSBE Team has developed a terrestrial field campaign to explore two subsurface biological habitats under the Mojave Desert. This field campaign will not only help us understand terrestrial desert biology, but also will develop methodologies and strategies for potential future Mars missions that would seek to explore the Martian subsurface. We have proposed to the ASTEP program to integrate a suite of field demonstrated instruments with a 20 m subsurface drill as a coherent unit, the Mojave Subsurface Bio-geochemistry Explorer. The ATK Space Modular Planetary Drill System (MPDS) requires no drilling fluid, which allows aseptic sampling, can penetrate lithic ground up to 20 meters of depth, and utilizes less than 100 Watts throughout the entire depth. The drill has been developed and demonstrated in field testing to a depth of 10 meters in Arizona, December 2002. In addition to caching a continuous core throughout the drilling depth, it also generates and caches cuttings and fines that are strata-graphically correlated with the core. As a core segment is brought to the surface, it will be analyzed for texture and structure by a color microscopic imager and for relevant chemistry and mineralogy with a UV fluorescence/Raman spectrometer. Organic and soluble ionic species will be identified through two instruments -- a microcapillary electrophoresis, and an ion trap mass spectrometer that have been developed under PIDDP, ASTID and MIDP funding.

Who's hot, who's not? Effects of concentrating solar power heliostats on soil temperature at Ivanpah Solar Electric Generating System, Mojave Desert, USA

Science.gov (United States)

Grodsky, S.; Hernandez, R. R.

2017-12-01

Solar energy development may function as a contemporary, anthropogenic driver of disturbance when sited in natural ecosystems. Orientation and density of solar modules, including heliostats at concentrating solar power (CSP) facilities, may affect soils via shading and altered surface-water flow. Meanwhile, soil attributes like temperature and moisture may affect nutrient cycling, plant germination and growth, and soil biota. We tested effects of CSP heliostats on soil temperature at Ivanpah Solar Electric Generating System (ISEGS) in the Mojave Desert, USA. We implemented experimental treatments based on preconstruction rare plant [e.g., Mojave milkweed (Asclepias nyctaginifolia)] protection areas (hereafter "halos"), site preparation activities, and heliostat density throughout three, replicated CSP blocks (i.e., tower and associated heliostats), including: (1) No Halos (Bladed) - high site preparation intensity, high heliostat density immediately surrounding towers; (2) No Halos (Mowed) - moderate site preparation intensity, moderate to low heliostat density as distance increases from towers; and (3) Halos - no site preparation, no heliostats. We also established control sites within 1,600 km of ISEGS in undisturbed desert. We observed significant differences in soil temperature across treatments. We recorded significantly lower soil temperatures in the No Halos (Bladed) treatments (26.7°C) and No Halos (Mowed) treatments (29.9°C) than in the Halos treatments (32.9°C) and controls (32.1°C). We also determined that soil temperatures in the Halos treatments and controls did not significantly differ. Our results indicated that shading from high-density heliostat configuration significantly reduced soil temperature relative to low-density heliostat configuration and areas without CSP. Shading from heliostats and consequential fluctuation in soil temperatures may affect local-scale distribution of flora and fauna, leading to altered "bottom-up" ecological

Middle Pleistocene infill of Hinkley Valley by Mojave River sediment and associated lake sediment: Depositional architecture and deformation by strike-slip faults

Science.gov (United States)

Miller, David; Haddon, Elizabeth; Langenheim, Victoria; Cyr, Andrew J.; Wan, Elmira; Walkup, Laura; Starratt, Scott W.

2018-01-01

Hinkley Valley in the Mojave Desert, near Barstow about 140 km northeast of Los Angeles and midway between Victorville Valley and the Lake Manix basin, contains a thick sedimentary sequence delivered by the Mojave River. Our study of sediment cores drilled in the valley indicates that Hinkley Valley was probably a closed playa basin with stream inflow from four directions prior to Mojave River inflow. The Mojave River deposited thick and laterally extensive clastic wedges originating from the southern valley that rapidly filled much of Hinkley Valley. Sedimentary facies representing braided stream, wetland, delta, and lacustrine depositional environments all are found in the basin fill; in some places, the sequence is greater than 74 m (245 ft) thick. The sediment is dated in part by the presence of the ~631 ka Lava Creek B ash bed low in the section, and thus represents sediment deposition after Victorville basin was overtopped by sediment and before the Manix basin began to be filled. Evidently, upstream Victorville basin filled with sediment by about 650 ka, causing the ancestral Mojave River to spill to the Harper and Hinkley basins, and later to Manix basin.Initial river sediment overran wetland deposits in many places in southern Hinkley Valley, indicating a rapidly encroaching river system. These sediments were succeeded by a widespread lake (“blue” clay) that includes the Lava Creek B ash bed. Above the lake sediment lies a thick section of interlayered stream sediment, delta and nearshore lake sediment, mudflat and/or playa sediment, and minor lake sediment. This stratigraphic architecture is found throughout the valley, and positions of lake sediment layers indicate a successive northward progression in the closed basin. A thin overlapping sequence at the north end of the valley contains evidence for a younger late Pleistocene lake episode. This late lake episode, and bracketing braided stream deposits of the Mojave River, indicate that the river

Effects of desert wildfires on desert tortoise (Gopherus agassizii) and other small vertebrates

Science.gov (United States)

Esque, T.C.; Schwalbe, C.R.; DeFalco, L.A.; Duncan, R.B.; Hughes, T.J.

2003-01-01

We report the results of standardized surveys to determine the effects of wildfires on desert tortoises (Gopherus agassizii) and their habitats in the northeastern Mojave Desert and northeastern Sonoran Desert. Portions of 6 burned areas (118 to 1,750 ha) were examined for signs of mortality of vertebrates. Direct effects of fire in desert habitats included animal mortality and loss of vegetation cover. A range of 0 to 7 tortoises was encountered during surveys, and live tortoises were found on all transects. In addition to desert tortoises, only small (reptiles (11 taxa) were found dead on the study areas. We hypothesize that indirect effects of fire on desert habitats might result in changes in the composition of diets and loss of vegetation cover, resulting in an increase in predation and loss of protection from temperature extremes. These changes in habitat also might cause changes in vertebrate communities in burned areas.

Stratigraphy, age, and depositional setting of the Miocene Barstow Formation at Harvard Hill, central Mojave Desert, California

Science.gov (United States)

Leslie, Shannon R.; Miller, David M.; Wooden, Joseph L.; Vazquez, Jorge A.

2010-01-01

New detailed geologic mapping and geochronology of the Barstow Formation at Harvard Hill, 30 km east of Barstow, CA, help to constrain Miocene paleogeography and tectonics of the central Mojave Desert. A northern strand of the Quaternary ENE-striking, sinistral Manix fault divides the Barstow Formation at Harvard Hill into two distinct lithologic assemblages. Strata north of the fault consist of: a green rhyolitic tuff, informally named the Shamrock tuff; lacustrine sandstone; partially silicified thin-bedded to massive limestone; and alluvial sandstone to pebble conglomerate. Strata south of the fault consist of: lacustrine siltstone and sandstone; a rhyolitic tuff dated at 19.1 Ma (U-Pb); rock-avalanche breccia deposits; partially silicified well-bedded to massive limestone; and alluvial sandstone and conglomerate. Our U-Pb zircon dating of the Shamrock tuff by SHRIMP-RG yields a peak probability age of 18.7 ± 0.1 Ma. Distinctive outcrop characteristics, mineralogy, remanent magnetization, and zircon geochemistry (Th/U) suggest that the Shamrock tuff represents a lacustrine facies of the regionally extensive Peach Spring Tuff (PST). Here we compare zircon age and geochemical analyses from the Shamrock tuff with those of the PST at Stoddard Wash and provide new insight into the age of zircon crystallization in the PST rhyolite. Results of our field studies show that Miocene strata at Harvard Hill mostly accumulated in a lacustrine environment, although depositional environments varied from a relatively deep lake to a very shallow lake or even onshore setting. Rock-avalanche breccias and alluvial deposits near the base of the exposed section indicate proximity to a steep basin margin and detrital studies suggest a southern source for coarse-grained deposits; therefore, we may infer a southern basin-margin setting at Harvard Hill during the early Miocene. Our geochronology demonstrates that deposition of the Barstow Formation at Harvard Hill extended from before

First results from the Mojave Volatiles Prospector (MVP) Field Campaign, a Lunar Polar Rover Mission Analog

Science.gov (United States)

Heldmann, J. L.; Colaprete, A.; Cook, A.; Deans, M. C.; Elphic, R. C.; Lim, D. S. S.; Skok, J. R.

2014-12-01

The Mojave Volatiles Prospector (MVP) project is a science-driven field program with the goal to produce critical knowledge for conducting robotic exploration of the Moon. MVP will feed science, payload, and operational lessons learned to the development of a real-time, short-duration lunar polar volatiles prospecting mission. MVP achieves these goals through a simulated lunar rover mission to investigate the composition and distribution of surface and subsurface volatiles in a natural and a priori unknown environment within the Mojave Desert, improving our understanding of how to find, characterize, and access volatiles on the Moon. The MVP field site is the Mojave Desert, selected for its low, naturally occurring water abundance. The Mojave typically has on the order of 2-6% water, making it a suitable lunar analog for this field test. MVP uses the Near Infrared and Visible Spectrometer Subsystem (NIRVSS), Neutron Spectrometer Subsystem (NSS), and a downward facing GroundCam camera on the KREX-2 rover to investigate the relationship between the distribution of volatiles and soil crust variation. Through this investigation, we mature robotic in situ instruments and concepts of instrument operations, improve ground software tools for real time science, and carry out publishable research on the water cycle and its connection to geomorphology and mineralogy in desert environments. A lunar polar rover mission is unlike prior space missions and requires a new concept of operations. The rover must navigate 3-5 km of terrain and examine multiple sites in in just ~6 days. Operational decisions must be made in real time, requiring constant situational awareness, data analysis and rapid turnaround decision support tools. This presentation will focus on the first science results and operational architecture findings from the MVP field deployment relevant to a lunar polar rover mission.

Maintenance of C sinks sustains enhanced C assimilation during long-term exposure to elevated [CO2] in Mojave Desert shrubs.

Science.gov (United States)

Aranjuelo, Iker; Ebbets, Allison L; Evans, R Dave; Tissue, David T; Nogués, Salvador; van Gestel, Natasja; Payton, Paxton; Ebbert, Volker; Adams, Williams W; Nowak, Robert S; Smith, Stanley D

2011-10-01

During the first few years of elevated atmospheric [CO(2)] treatment at the Nevada Desert FACE Facility, photosynthetic downregulation was observed in desert shrubs grown under elevated [CO(2)], especially under relatively wet environmental conditions. Nonetheless, those plants maintained increased A (sat) (photosynthetic performance at saturating light and treatment [CO(2)]) under wet conditions, but to a much lesser extent under dry conditions. To determine if plants continued to downregulate during long-term exposure to elevated [CO(2)], responses of photosynthesis to elevated [CO(2)] were examined in two dominant Mojave Desert shrubs, the evergreen Larrea tridentata and the drought-deciduous Ambrosia dumosa, during the eighth full growing season of elevated [CO(2)] treatment at the NDFF. A comprehensive suite of physiological processes were collected. Furthermore, we used C labeling of air to assess carbon allocation and partitioning as measures of C sink activity. Results show that elevated [CO(2)] enhanced photosynthetic performance and plant water status in Larrea, especially during periods of environmental stress, but not in Ambrosia. δ(13)C analyses indicate that Larrea under elevated [CO(2)] allocated a greater proportion of newly assimilated C to C sinks than Ambrosia. Maintenance by Larrea of C sinks during the dry season partially explained the reduced [CO(2)] effect on leaf carbohydrate content during summer, which in turn lessened carbohydrate build-up and feedback inhibition of photosynthesis. δ(13)C results also showed that in a year when plant growth reached the highest rates in 5 years, 4% (Larrea) and 7% (Ambrosia) of C in newly emerging organs were remobilized from C that was assimilated and stored for at least 2 years prior to the current study. Thus, after 8 years of continuous exposure to elevated [CO(2)], both desert perennials maintained their photosynthetic capacities under elevated [CO(2)]. We conclude that C storage, remobilization

Bidirectional recovery patterns of Mojave Desert vegetation in an aqueduct pipeline corridor after 36 years: I. Perennial shrubs and grasses

Science.gov (United States)

Berry, Kristin H.; Weigand, James F.; Gowan, Timothy A.; Mack, Jeremy S.

2015-01-01

We studied recovery of 21 perennial plant species along a severely disturbed aqueduct corridor in a Larrea tridentata-Ambrosia dumosa plant alliance in the Mojave Desert 36 years after construction. The 97-m wide corridor contained a central dirt road and buried aqueduct pipeline. We established transects at 0 m (road verge), 20 m and 40 m into the disturbance corridor, and at 100 m in undisturbed habitat (the control). Although total numbers of shrubs per transect did not vary significantly with distance from the verge, canopy cover of shrubs, species richness, and species diversity were higher in the control than at the verge and other distances. Canopy cover of common shrubs (Ericameria nauseosa, Ambrosia salsola, A. dumosa, L. tridentata, Grayia spinosa) and perennial grasses (Elymus elymoides, Poa secunda) also varied significantly by location. Discriminant analysis clearly separated the four distances based on plant composition. Patterns of recovery were bidirectional: secondary succession from the control into the disturbance corridor and inhibition from the verge in the direction of the control. Time estimated for species composition to resemble the control is dependent on location within the disturbance corridor and could be centuries at the road verge. Our findings have applications to other deserts.

Clustering of GPS velocities in the Mojave Block, southeastern California

Science.gov (United States)

Savage, James C.; Simpson, Robert W.

2013-01-01

We find subdivisions within the Mojave Block using cluster analysis to identify groupings in the velocities observed at GPS stations there. The clusters are represented on a fault map by symbols located at the positions of the GPS stations, each symbol representing the cluster to which the velocity of that GPS station belongs. Fault systems that separate the clusters are readily identified on such a map. The most significant representation as judged by the gap test involves 4 clusters within the Mojave Block. The fault systems bounding the clusters from east to west are 1) the faults defining the eastern boundary of the Northeast Mojave Domain extended southward to connect to the Hector Mine rupture, 2) the Calico-Paradise fault system, 3) the Landers-Blackwater fault system, and 4) the Helendale-Lockhart fault system. This division of the Mojave Block is very similar to that proposed by Meade and Hager. However, no cluster boundary coincides with the Garlock Fault, the northern boundary of the Mojave Block. Rather, the clusters appear to continue without interruption from the Mojave Block north into the southern Walker Lane Belt, similar to the continuity across the Garlock Fault of the shear zone along the Blackwater-Little Lake fault system observed by Peltzer et al. Mapped traces of individual faults in the Mojave Block terminate within the block and do not continue across the Garlock Fault [Dokka and Travis, ].

Drawing a line in the sand: Effectiveness of off-highway vehicle management in California's Sonoran desert

Science.gov (United States)

Custer, Nathan; Defalco, Lesley A.; Nussear, Kenneth E.; Esque, Todd C.

2017-01-01

Public land policies manage multiple uses while striving to protect vulnerable plant and wildlife habitats from degradation; yet the effectiveness of such policies are infrequently evaluated, particularly for remote landscapes that are difficult to monitor. We assessed the use and impacts of recreational vehicles on Mojave Desert washes (intermittent streams) in the Chemehuevi Desert Wildlife Management Area (DWMA) of southern California. Wash zones designated as open and closed to off-highway vehicle (OHV) activity were designed in part to protect Mojave desert tortoise (Gopherus agassizii) habitat while allowing recreation in designated areas. OHV tracks were monitored in washes located near access roads during winter and early spring holidays – when recreation is typically high – and at randomly dispersed locations away from roads. Washes near access roads had fewer vehicle tracks within closed than open zones; further away from roads, OHV tracks were infrequent and their occurrence was not different between wash designations. Washes were in better condition in closed zones following major holidays as indicated by less vegetation damage, presence of trash, and wash bank damage. Furthermore, the frequency of washes with live tortoises and their sign was marginally greater in closed than open wash zones. Collectively, these results suggest that low impacts to habitats in designated closed wash zones reflect public compliance with federal OHV policy and regulations in the Chemehuevi DWMA during our study. Future monitoring to contrast wash use and impacts during other seasons as well as in other DWMAs will elucidate spatial and temporal patterns of recreation in these important conservation areas.

Modeling Agassiz's Desert Tortoise Population Response to Anthropogenic Stressors

Science.gov (United States)

Mojave Desert tortoise (Gopherus agassizii) populations are exposed to a variety of anthropogenic threats, which vary in nature, severity, and frequency. Tortoise management in conservation areas can be compromised when the relative importance of these threats is not well underst...

Negative impacts of invasive plants on conservation of sensitive desert wildlife

Science.gov (United States)

Drake, K. Kristina; Bowen, Lizabeth; Nussear, Kenneth E.; Esque, Todd C.; Berger, Andrew J.; Custer, Nathan; Waters, Shannon C.; Johnson, Jay D.; Miles, A. Keith; Lewison, Rebecca L.

2016-01-01

Habitat disturbance from development, resource extraction, off-road vehicle use, and energy development ranks highly among threats to desert systems worldwide. In the Mojave Desert, United States, these disturbances have promoted the establishment of nonnative plants, so that native grasses and forbs are now intermixed with, or have been replaced by invasive, nonnative Mediterranean grasses. This shift in plant composition has altered food availability for Mojave Desert tortoises (Gopherus agassizii), a federally listed species. We hypothesized that this change in forage would negatively influence the physiological ecology, immune competence, and health of neonatal and yearling tortoises. To test this, we monitored the effects of diet on growth, body condition, immunological responses (measured by gene transcription), and survival for 100 captive Mojave tortoises. Tortoises were assigned to one of five diets: native forbs, native grass, invasive grass, and native forbs combined with either the native or invasive grass. Tortoises eating native forbs had better body condition and immune functions, grew more, and had higher survival rates (>95%) than tortoises consuming any other diet. At the end of the experiment, 32% of individuals fed only native grass and 37% fed only invasive grass were found dead or removed from the experiment due to poor body conditions. In contrast, all tortoises fed either the native forb or combined native forb and native grass diets survived and were in good condition. Health and body condition quickly declined for tortoises fed only the native grass (Festuca octoflora) or invasive grass (Bromus rubens) with notable loss of fat and muscle mass and increased muscular atrophy. Bromus rubens seeds were found embedded in the oral mucosa and tongue in most individuals eating that diet, which led to mucosal inflammation. Genes indicative of physiological, immune, and metabolic functions were transcribed at lower levels for individuals fed B

Stable isotope evidence for an atmospheric origin of desert nitrate deposits in northern Chile and southern California, U.S.A.

Science.gov (United States)

Böhlke, J.K.; Ericksen, G.E.; Revesz, K.

1997-01-01

Natural surficial accumulations of nitrate-rich salts in the Atacama Desert, northern Chile, and in the Death Valley region of the Mojave Desert, southern California, are well known, but despite many geologic and geochemical studies, the origins of the nitrates have remained controversial. N and O isotopes in nitrate, and S isotopes in coexisting soluble sulfate, were measured to determine if some proposed N sources could be supported or rejected, and to determine if the isotopic signature of these natural deposits could be used to distinguish them from various types of anthropogenic nitrate contamination that might be found in desert groundwaters. High-grade caliche-type nitrate deposits from both localities have ??15N values that range from -5 to +5???, but are mostly near 0???. Values of ??15N near 0??? are consistent with either bulk atmospheric N deposition or microbial N fixation as major sources of the N in the deposits. ??18O values of those desert nitrates with ??15N near 0??? range from about +31 to + 50??? (V-SMOW), significantly higher than that of atmospheric O2 (+ 23.5???). Such high values of ??18O are considered unlikely to result entirely from nitrification of reduced N, but rather resemble those of modern atmospheric nitrate in precipitation from some other localities. Assuming that limited modern atmospheric isotope data are applicable to the deposits, and allowing for nitrification of co-deposited ammonium, it is estimated that the fraction of the nitrate in the deposits that could be accounted for isotopically by atmospheric N deposition may be at least 20% and possibly as much as 100%. ??34S values are less diagnostic but could also be consistent with atmospheric components in some of the soluble sulfates associated with the deposits. The stable isotope data support the hypothesis that some high-grade caliche-type nitrate-rich salt deposits in some of the Earth's hyperarid deserts represent long-term accumulations of atmospheric deposition

Moisture-driven xylogenesis in Pinus ponderosa from a Mojave Desert mountain reveals high phenological plasticity.

Science.gov (United States)

Ziaco, Emanuele; Truettner, Charles; Biondi, Franco; Bullock, Sarah

2018-04-01

Future seasonal dynamics of wood formation in hyperarid environments are still unclear. Although temperature-driven extension of the growing season and increased forest productivity are expected for boreal and temperate biomes under global warming, a similar trend remains questionable in water-limited regions. We monitored cambial activity in a montane stand of ponderosa pine (Pinus ponderosa) from the Mojave Desert for 2 consecutive years (2015-2016) showing opposite-sign anomalies between warm- and cold-season precipitation. After the wet winter/spring of 2016, xylogenesis started 2 months earlier compared to 2015, characterized by abundant monsoonal (July-August) rainfall and hyperarid spring. Tree size did not influence the onset and ending of wood formation, highlighting a predominant climatic control over xylem phenological processes. Moisture conditions in the previous month, in particular soil water content and dew point, were the main drivers of cambial phenology. Latewood formation started roughly at the same time in both years; however, monsoonal precipitation triggered the formation of more false rings and density fluctuations in 2015. Because of uncertainties in future precipitation patterns simulated by global change models for the Southwestern United States, the dependency of P. ponderosa on seasonal moisture implies a greater conservation challenge than for species that respond mostly to temperature conditions. © 2018 John Wiley & Sons Ltd.

Serologic and molecular evidence for testudinid herpesvirus 2 infection in wild Agassiz’s desert tortoise, Gopherus agassizii

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Jacobson, Elliott R.; Berry, Kristin H.; Wellehan, James F. X.; Origgi, Francesco; Childress, April L.; Braun, Josephine; Schrenzel, Mark; Yee, Julie; Rideout, Bruce

2012-01-01

Following field observations of wild Agassiz’s desert tortoises (Gopherus agassizii) with oral lesions similar to those seen in captive tortoises with herpesvirus infection, we measured the prevalence of antibodies to Testudinid herpesvirus (TeHV) 3 in wild populations of desert tortoises in California. The survey revealed 30.9% antibody prevalence. In 2009 and 2010, two wild adult male desert tortoises, with gross lesions consistent with trauma and puncture wounds, respectively, were necropsied. Tortoise 1 was from the central Mojave Desert and tortoise 2 was from the northeastern Mojave Desert. We extracted DNA from the tongue of tortoise 1 and from the tongue and nasal mucosa of tortoise 2. Sequencing of polymerase chain reaction products of the herpesviral DNA-dependent DNA polymerase gene and the UL39 gene respectively showed 100% nucleotide identity with TeHV2, which was previously detected in an ill captive desert tortoise in California. Although several cases of herpesvirus infection have been described in captive desert tortoises, our findings represent the first conclusive molecular evidence of TeHV2 infection in wild desert tortoises. The serologic findings support cross-reactivity between TeHV2 and TeHV3. Further studies to determine the ecology, prevalence, and clinical significance of this virus in tortoise populations are needed.

The western pond turtle (Clemmys marmorata) in the Mojave River, California, USA: Highly adapted survivor or tenuous relict?

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Lovich, J.; Meyer, K.

2002-01-01

Aspects of the ecology of populations of the western pond turtle Clemmys marmorata were investigated in the Mojave River of the central Mojave Desert, California, U.S.A. One population occupied man-made ponds and the other occurred in natural ponds in the flood plain of the Mojave River. Both habitats are severely degraded as a result of ground water depletion from human activities along the river and one is infested with the exotic shrub saltcedar Tamarix ramosissima. Mean female carapace length (CL) was significantly greater (14.4 cm) than that of males (13.7 cm). Live juveniles were not detected during the period of study. Shelled eggs were visible in X-radiographs from 26 May to 14 July. Mean clutch size was 4.46 and ranged from 3 to 6 eggs. Clutch size did not vary between 1998 and 1999 but was significantly correlated with CL for both years combined, increasing at the rate of 0.548 eggs/cm CL. Gravid female CL ranged from 13.3-16.0 cm. Some females nested in both years. Mean X-ray egg width (21.8 mm) was not significantly correlated with CL or clutch size. X-ray egg width differed more among clutches than within, whether including CL as a co-variate or not. Nesting migrations occurred from 6 June to 8 July with minimum round trip distances ranging from 17.5-585 m with a mean of 195 m. Mean estimated time of departure as measured at the drift fence was 18:13. Most females returned to the ponds in the early morning. Nesting migrations required females to be out of the water for estimated periods of 0.83 to 86 h. The destination of nesting females was typically fluvial sand bars in the channel of the dry riverbed. Overall, the ecology of C. marmorata in the Mojave River is very similar to that reported for populations in less severe habitats along the west coast of the United States. Notable exceptions include long nesting migrations to sandbars in the dry river channel, a possible result of human modifications to the environment, and an apparent lack of

Factors controlling As and U in shallow ground water, southern Carson Desert, Nevada

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Welch, A.H.; Lico, M.S.

1998-01-01

Unusually high As and U concentrations (> 100 ??g/L) are widespread in shallow ground water beneath the southern Carson Desert. The high concentrations, which locally exceed 1000 ??g/L, are of concern from a human health standpoint because the shallow ground water is used for domestic supply. Possible affects on wildlife are also of concern because the ground water flows into shallow lakes and marshes within wildlife refuges. Arsenic and U concentrations in ground water of the southern Carson Desert appear to be affected by evaporative concentration, redox reactions, and adsorption. The relation of these elements with Cl suggest that most of the high concentrations can be attributed to evaporative concentration of Carson River water, the primary source of recharge. Some ground water contains higher As and U concentrations that cannot be explained by evaporative concentration alone. Oxidation-reduction reactions, involving metal oxides and sedimentary-organic matter, appear to contribute As, U, inorganic C, Fe and Mn to the ground water. Arsenic in Fe-oxide was confirmed by chemical extraction and is consistent with laboratory adsorption studies. Uranium in both sedimentary-organic C and Fe-oxide coatings has been confirmed by fission tracks and petrographic examination. Arsenic concentrations in the ground water and chemical extracts of aquifer sediments are broadly consistent with adsorption as a control on some dissolved As concentrations. An apparent loss of As from some ground water as evaporative concentration proceeds is consistent with adsorption as a control on As. However, evidence for adsorption should be viewed with caution, because the adsorption model used values for the adsorbent that have not been shown to be valid for the aquifer sediments throughout the southern Carson Desert. Hydrologic and geochemical conditions in the Carson Desert are similar to other areas with high As and U concentrations in ground water, including the Salton Sea basin and

Factors controlling As and U in shallow ground water, southern Carson Desert, Nevada

International Nuclear Information System (INIS)

Lico, M.S.; Welch, A.H.

1998-01-01

100 μg/L) are widespread in shallow ground water beneath the southern Carson Desert. The high concentrations, which locally exceed 1000 μg/L, are of concern from a human health standpoint because the shallow ground water is used for domestic supply. Possible affects on wildlife are also of concern because the ground water flows into shallow lakes and marshes within wildlife refuges. Arsenic and U concentrations in ground water of the southern Carson Desert appear to be affected by evaporative concentration, redox reactions, and adsorption. The relation of these elements with Cl suggest that most of the high concentrations can be attributed to evaporative concentration of Carson River water, the primary source of recharge.Some ground water contains higher As and U concentrations that cannot be explained by evaporative concentration alone. Oxidation-reduction reactions, involving metal oxides and sedimentary-organic matter, appear to contribute As, U, inorganic C, Fe and Mn to the ground water. Arsenic in Fe-oxide was confirmed by chemical extraction and is consistent with laboratory adsorption studies. Uranium in both sedimentary-organic C and Fe-oxide coatings has been confirmed by fission tracks and petrographic examination.Arsenic concentrations in the ground water and chemical extracts of aquifer sediments are broadly consistent with adsorption as a control on some dissolved As concentrations. An apparent loss of As from some ground water as evaporative concentration proceeds is consistent with adsorption as a control on As. However, evidence for adsorption should be viewed with caution, because the adsorption model used values for the adsorbent that have not been shown to be valid for the aquifer sediments throughout the southern Carson Desert.Hydrologic and geochemical conditions in the Carson Desert are similar to other areas with high As and U concentrations in ground water, including the Salton Sea basin and southern San Joaquin Valley of California

Contrasting long-term survival of two outplanted Mojave Desert perennials for post-fire revegetation

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Scoles-Sciulla, Sara J.; Defalco, Lesley A.; Esque, Todd C.

2015-01-01

Post-fire recovery of arid shrublands is typically slow, and planting greenhouse-raised seedlings may be a means of jump-starting this process. Recovery can be further accelerated by understanding the factors controlling post-planting survival. In fall 2007 and 2009, we outplanted seedlings of two contrasting native evergreen shrubs—fast-growing Nevada jointfir and slow-growing blackbrush—across five burned sites in the Mojave Desert. To increase soil moisture and optimize seedling survival, we experimentally applied and evaluated soil amendments and supplemental watering. We also evaluated two herbicides that reduce competitive invasive annual grasses and two types of herbivore protection. Survival of jointfir outplanted in 2007 was 61% after 43 months, and site largely influenced survival, while herbicide containing imazapic applied more than one year after outplanting reduced survival. Reduced survival of jointfir outplanted in 2009 coincided with delayed seasonal precipitation that intensified foliar damage by small mammals. In contrast, blackbrush survival was 4% after 43 months, and was influenced by site, type of herbivore protection, and greenhouse during the 2007 outplanting, and soil amendment during 2009. Counter to expectations, we found that supplemental watering and soil amendments did not influence long-term survival of either blackbrush or jointfir. Shrub species with rapid growth rates and broad environmental tolerances, such as jointfir, make ideal candidates for outplanting, provided that seedlings are protected from herbivores. Re-introduction of species with slow growth rates and narrow environmental tolerances, such as blackbrush, requires careful consideration to optimize pre- and post-planting conditions.

Measuring Dust Emission from the Mojave Desert (USA) by Daily Remote-Camera Observations and Wind-Erosion Measurements: Bearing on "Unseen" Sources and Global Dust Abundance

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Reynolds, R. L.; Urban, F.; Goldstein, H. L.; Fulton, R.

2017-12-01

A large gap in understanding the effects of atmospheric dust at all spatial scales is uncertainty about how much and whence dust is emitted annually. Digital recording of dust emission at high spatial and temporal resolution would, together with periodic flux measurements, support improved estimates of local-scale dust flux where infrastructure could support remote internet enabled cameras. Such recording would also elucidate wind-erosion dynamics when combined with meteorological data. Remote camera recording of dust-emitting settings on and around Soda Lake (Mojave Desert) was conducted every 15 minutes during daylight between 10 Nov. 2010 and 31 Dec. 2016 and images uploaded to a web server. Examination of 135,000 images revealed frequent dust events, termed "dust days" when plumes obscured mountains beyond source areas. Such days averaged 68 (sd=10) per year (2011 through 2016). We examined satellite retrievals (MODIS, GOES) for dust events during six cloudless days of highest and longest duration dust emission but none were observed. From Apr. 2000 through May 2013, aeolian sediments collected at three sites were sampled and weighed. Estimates of the emitted mass of silt- and clay-size fractions were made on the basis of measured horizontal mass flux, particle sizes of sediment in collectors, and roughly determined areas of dust generation. Over this period, nearly 4 Tg yr-1 of dust (as particulate matter flood in the basin in late Dec. 2010 that deposited flood sediment across the lake basin. Increased emission was likely related to the availability of fresh, unanchored flood sediment. Within the Mojave and Great Basin deserts of North America, many settings akin to those at Soda Lake similarly emit dust that is rarely detected in satellite retrievals. These findings strongly imply that local and regional dust emissions from western North America are far underestimated and that, by extension to relatively small dust-source areas across all drylands, global

VEGETATIVE GROWTH AND EARLY PRODUCTION OF SIX OLIVE CULTIVARS, IN SOUTHERN ATACAMA DESERT, CHILE

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Freddy MORA

2007-12-01

Full Text Available Tree survival, early fruit production, vegetative growth and alternate bearing were examined in six different olive cultivars (Barnea, Biancolilla, Coratina, Empeltre, Koroneiki and Leccino under intensive agronomic conditions i southern Atacama Desert, in the Coquimbo Region of Chile. The cultivars were evaluated over four successive years and had a high survival rate (93% confi rming their potential for these dry-lands. Fruit production (recorded over the growing seasons 2002-2003, vegetative growth (2000-2003 and alternate bearing differed signifi cantly among cultivars. Olive selection in intensively managed planting at the southern part of the Atacama Desert depends on matching specifi c cultivars to sites on which they perform the best.

Polyphasic characterization of Trichocoleus desertorum sp. nov. (Pseudanabaenales, Cyanobacteria) from desert soils and phylogenetic placement of the genus Trichocoleus

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Radka Muhlsteinova; Jeffrey R. Johansen; Nicole Pietrasiak; Michael P. Martin; Karina Osorio-Santos; Steven D. Warren

2014-01-01

Little is known about the taxonomic diversity of cyanobacteria in deserts, despite their important ecological roles in these ecosystems. In this study, cyanobacterial strains from the Atacama, Colorado, and Mojave Deserts were isolated and characterized using molecular, morphological, and ecological information. Phylogenetic placement of these strains was revealed...

Landscape genetic approaches to guide native plant restoration in the Mojave Desert

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Shryock, Daniel F.; Havrilla, Caroline A.; DeFalco, Lesley; Esque, Todd C.; Custer, Nathan; Wood, Troy E.

2016-01-01

Restoring dryland ecosystems is a global challenge due to synergistic drivers of disturbance coupled with unpredictable environmental conditions. Dryland plant species have evolved complex life-history strategies to cope with fluctuating resources and climatic extremes. Although rarely quantified, local adaptation is likely widespread among these species and potentially influences restoration outcomes. The common practice of reintroducing propagules to restore dryland ecosystems, often across large spatial scales, compels evaluation of adaptive divergence within these species. Such evaluations are critical to understanding the consequences of large-scale manipulation of gene flow and to predicting success of restoration efforts. However, genetic information for species of interest can be difficult and expensive to obtain through traditional common garden experiments. Recent advances in landscape genetics offer marker-based approaches for identifying environmental drivers of adaptive genetic variability in non-model species, but tools are still needed to link these approaches with practical aspects of ecological restoration. Here, we combine spatially-explicit landscape genetics models with flexible visualization tools to demonstrate how cost-effective evaluations of adaptive genetic divergence can facilitate implementation of different seed sourcing strategies in ecological restoration. We apply these methods to Amplified Fragment Length Polymorphism (AFLP) markers genotyped in two Mojave Desert shrub species of high restoration importance: the long-lived, wind-pollinated gymnosperm Ephedra nevadensis, and the short-lived, insect-pollinated angiosperm Sphaeralcea ambigua. Mean annual temperature was identified as an important driver of adaptive genetic divergence for both species. Ephedra showed stronger adaptive divergence with respect to precipitation variability, while temperature variability and precipitation averages explained a larger fraction of adaptive

Delta Chromium-53/52 isotopic composition of native and contaminated groundwater, Mojave Desert, USA

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Izbicki, John A.; Bullen, Thomas D.; Martin, Peter; Schroth, Brian

2012-01-01

Chromium(VI) concentrations in groundwater sampled from three contaminant plumes in aquifers in the Mojave Desert near Hinkley, Topock and El Mirage, California, USA, were as high as 2600, 5800 and 330 μg/L, respectively. δ53/52Cr compositions from more than 50 samples collected within these plumes ranged from near 0‰ to almost 4‰ near the plume margins. Assuming only reductive fractionation of Cr(VI) to Cr(III) within the plume, apparent fractionation factors for δ53/52Cr isotopes ranged from εapp = 0.3 to 0.4 within the Hinkley and Topock plumes, respectively, and only the El Mirage plume had a fractionation factor similar to the laboratory derived value of ε = 3.5. One possible explanation for the difference between field and laboratory fractionation factors at the Hinkley and Topock sites is localized reductive fractionation of Cr(VI) to Cr(III), with subsequent advective mixing of native and contaminated water near the plume margin. Chromium(VI) concentrations and δ53/52Cr isotopic compositions did not uniquely define the source of Cr near the plume margin, or the extent of reductive fractionation within the plume. However, Cr(VI) and δ53/52Cr data contribute to understanding of the interaction between reductive and mixing processes that occur within and near the margins of Cr contamination plumes. Reductive fractionation of Cr(VI) predominates in plumes having higher εapp, these plumes may be suitable for monitored natural attenuation. In contrast, advective mixing predominates in plumes having lower εapp, the highly dispersed margins of these plumes may be difficult to define and manage.

Pedological and geological relationships with soil lichen and moss distribution in the eastern Mojave Desert, CA, USA

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Belnap, Jayne; Miller, David M.; Bedford, David R.; Phillips, Susan L.

2014-01-01

Biological soil crusts (biocrusts) are ubiquitous in drylands globally. Lichens and mosses are essential biocrust components and provide a variety of ecosystem services, making their conservation and management of interest. Accordingly, understanding what factors are correlated with their distribution is important to land managers. We hypothesized that cover would be related to geologic and pedologic factors. We sampled 32 sites throughout the eastern Mojave Desert, stratifying by parent material and the age of the geomorphic surfaces. The cover of lichens and mosses on ‘available ground’ (L + Mav; available ground excludes ground covered by rocks or plant stems) was higher on limestone and quartzite-derived soils than granite-derived soils. Cover was also higher on moderately younger-aged geomorphic surfaces (Qya2, Qya3, Qya4) and cutbanks than on very young (Qya1), older-aged surfaces (Qia1, Qia2), or soils associated with coppice mounds or animal burrowing under Larrea tridentata. When all sites and parent materials were combined, soil texture was the most important factor predicting the occurrence of L + Mav, with cover positively associated with higher silt, very fine sand, and fine sand fractions and negatively associated with the very coarse sand fraction. When parent materials were examined separately, nutrients such as available potassium, iron, and calcium became the most important predictors of L + Mav cover.

X-36 in Flight over Mojave Desert during 5th Flight

Science.gov (United States)

1997-01-01

The unusual lines of the X-36 Tailless Fighter Agility Research Aircraft contrast sharply with the desert floor as the remotely-piloted aircraft flies over the Mojave Desert on a June 1997 research flight. The NASA/Boeing X-36 Tailless Fighter Agility Research Aircraft program successfully demonstrated the tailless fighter design using advanced technologies to improve the maneuverability and survivability of possible future fighter aircraft. The program met or exceeded all project goals. For 31 flights during 1997 at the Dryden Flight Research Center, Edwards, California, the project team examined the aircraft's agility at low speed / high angles of attack and at high speed / low angles of attack. The aircraft's speed envelope reached up to 206 knots (234 mph). This aircraft was very stable and maneuverable. It handled very well. The X-36 vehicle was designed to fly without the traditional tail surfaces common on most aircraft. Instead, a canard forward of the wing was used as well as split ailerons and an advanced thrust-vectoring nozzle for directional control. The X-36 was unstable in both pitch and yaw axes, so an advanced, single-channel digital fly-by-wire control system (developed with some commercially available components) was put in place to stabilize the aircraft. Using a video camera mounted in the nose of the aircraft and an onboard microphone, the X-36 was remotely controlled by a pilot in a ground station virtual cockpit. A standard fighter-type head-up display (HUD) and a moving-map representation of the vehicle's position within the range in which it flew provided excellent situational awareness for the pilot. This pilot-in-the-loop approach eliminated the need for expensive and complex autonomous flight control systems and the risks associated with their inability to deal with unknown or unforeseen phenomena in flight. Fully fueled the X-36 prototype weighed approximately 1,250 pounds. It was 19 feet long and three feet high with a wingspan of

Extensive summer water pulses do not necessarily lead to canopy growth of Great Basin and northern Mojave Desert shrubs.

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Snyder, K A; Donovan, L A; James, J J; Tiller, R L; Richards, J H

2004-10-01

Plant species and functionally related species groups from arid and semi-arid habitats vary in their capacity to take up summer precipitation, acquire nitrogen quickly after summer precipitation, and subsequently respond with ecophysiological changes (e.g. water and nitrogen relations, gas exchange). For species that respond ecophysiologically, the use of summer precipitation is generally assumed to affect long-term plant growth and thus alter competitive interactions that structure plant communities and determine potential responses to climate change. We assessed ecophysiological and growth responses to large short-term irrigation pulses over one to three growing seasons for several widespread Great Basin and northern Mojave Desert shrub species: Chrysothamnus nauseosus, Sarcobatus vermiculatus, Atriplex confertifolia, and A. parryi. We compared control and watered plants in nine case studies that encompassed adults of all four species, juveniles for three of the species, and two sites for two of the species. In every comparison, plants used summer water pulses to improve plant water status or increase rates of functioning as indicated by other ecophysiological characters. Species and life history stage responses of ecophysiological parameters (leaf N, delta15N, delta13C, gas exchange, sap flow) were consistent with several previous short-term studies. However, use of summer water pulses did not affect canopy growth in eight out of nine comparisons, despite the range of species, growth stages, and site conditions. Summer water pulses affected canopy growth only for C. nauseosus adults. The general lack of growth effects for these species might be due to close proximity of groundwater at these sites, co-limitation by nutrients, or inability to respond due to phenological canalization. An understanding of the connections between short-term ecophysiological responses and growth, for different habitats and species, is critical for determining the significance of

Soil Nematodes and Their Prokaryotic Prey Along an Elevation Gradient in The Mojave Desert (Death Valley National Park, California, USA

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Alyxandra Pikus

2012-10-01

Full Text Available We characterized soil communities in the Mojave Desert across an elevation gradient. Our goal was to test the hypothesis that as soil quality improved with increasing elevation (due to increased productivity, the diversity of soil prokaryotes and nematodes would also increase. Soil organic matter and soil moisture content increased with elevation as predicted. Soil salinity did not correlate to elevation, but was highest at a mid-gradient, alluvial site. Soil nematode density, community trophic structure, and diversity did not show patterns related to elevation. Similar results were obtained for diversity of bacteria and archaea. Relationships between soil properties, nematode communities, and prokaryotic diversity were site-specific. For example, at the lowest elevation site, nematode communities contained a high proportion of fungal-feeding species and diversity of bacteria was lowest. At a high-salinity site, nematode density was highest, and overall, nematode density showed an unexpected, positive correlation to salinity. At the highest elevation site, nematode density and species richness were attenuated, despite relatively high moisture and organic matter content for the soils. Our results support emerging evidence for the lack of a relationship between productivity and the diversity of soil nematodes and prokaryotes.

Molluscs as evidence for a late Pleistocene and early Holocene humid period in the southern coastal desert of Peru (14.5°S)

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Mächtle, Bertil; Unkel, Ingmar; Eitel, Bernhard; Kromer, Bernd; Schiegl, Solveig

2010-01-01

The southern Peruvian coastal desert around Palpa, southern Peru (14.5°S) is currently characterized by hyper-arid conditions. However, the presence of two species of molluscs ( Scutalus, Pupoides) and desert-loess deposits indicates the past development of semi-desert and grassland ecosystems caused by a displacement of the eastern desert margin due to hydrological changes. Radiocarbon dating shows that the transition to a semi-arid climate in the southern Peruvian coastal desert took place during the Greenland interstadial 1, ˜ 13.5 cal ka BP. At the beginning of the Holocene, the mollusc fauna vanished due to increasing humidity and the development of grasslands. Dust particles were fixed by the grasses, as indicated by abundant Poaceae phytoliths, and desert loess was formed. The humid period we observe here is out of phase with the palaeoenvironmental records from the Titicaca region, which indicates dry conditions at that time. This paper offers a new idea for this contradiction: an orbitally driven meridional shift of the Bolivian high might have altered the moisture supply across the Andes.

Spatial and temporal changes in desertification in the southern region of the Tengger Desert from 1973 to 2009

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Guan, Qingyu; Guan, Wenqian; Yang, Jing; Zhao, Shilei; Pan, Baotian; Wang, Lei; Song, Na; Lu, Min; Li, Fuchun

2017-07-01

The sandy land in the southern region of the Tengger Desert is adjacent to cities and towns, and land desertification poses a threat to the livelihood and production of local residents. To determine dynamic changes in local desertification, five periods (1973, 1987, 1992, 2001, and 2009) of remote sensing data are studied by remote sensing (RS) and geographic information system (GIS). The desert contraction area is primarily centered around three units (Wuwei, Gulang, and Jingtai) and nearby regions of Zhongwei City. The primary desert expansion areas include the west side of Helan Mountain (WSHM), the Central Mountainous Area (CMA), and the eastern and western Zhongwei units far from towns. From 1973 to 2009, the degree of change in the contracting part of the primary desert expansion unit showed an increasing trend; in brief, most of the desert (especially after 2001) has been developing in a direction in which desertification has been gradually controlled. The primary desert expansion areas are less affected by human activity, but they are primarily controlled by natural factors (especially wind and terrain). The desert contraction areas occur around the towns and nearby regions with frequent human activity; desertification is primarily controlled by human factors. With rapid economic development (especially after 2000), the scale of the cultivated area, town, and ecological protection engineering has gradually expanded, and the latter two are primarily built on a previous desert, which is the root cause of the reduction in the desert areas around the towns and the shrinkage toward north of border. Therefore, reasonable and effective human activity in the southern region of the Tengger Desert is playing a crucial role in preventing desertification.

Desert Dust Outbreaks in Southern Europe: Contribution to Daily PM10 Concentrations and Short-Term Associations with Mortality and Hospital Admissions

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Stafoggia, Massimo; Zauli-Sajani, Stefano; Pey, Jorge; Samoli, Evangelia; Alessandrini, Ester; Basagaña, Xavier; Cernigliaro, Achille; Chiusolo, Monica; Demaria, Moreno; Díaz, Julio; Faustini, Annunziata; Katsouyanni, Klea; Kelessis, Apostolos G.; Linares, Cristina; Marchesi, Stefano; Medina, Sylvia; Pandolfi, Paolo; Pérez, Noemí; Querol, Xavier; Randi, Giorgia; Ranzi, Andrea; Tobias, Aurelio; Forastiere, Francesco

2015-01-01

Background: Evidence on the association between short-term exposure to desert dust and health outcomes is controversial. Objectives: We aimed to estimate the short-term effects of particulate matter ≤ 10 μm (PM10) on mortality and hospital admissions in 13 Southern European cities, distinguishing between PM10 originating from the desert and from other sources. Methods: We identified desert dust advection days in multiple Mediterranean areas for 2001–2010 by combining modeling tools, back-trajectories, and satellite data. For each advection day, we estimated PM10 concentrations originating from desert, and computed PM10 from other sources by difference. We fitted city-specific Poisson regression models to estimate the association between PM from different sources (desert and non-desert) and daily mortality and emergency hospitalizations. Finally, we pooled city-specific results in a random-effects meta-analysis. Results: On average, 15% of days were affected by desert dust at ground level (desert PM10 > 0 μg/m3). Most episodes occurred in spring–summer, with increasing gradient of both frequency and intensity north–south and west–east of the Mediterranean basin. We found significant associations of both PM10 concentrations with mortality. Increases of 10 μg/m3 in non-desert and desert PM10 (lag 0–1 days) were associated with increases in natural mortality of 0.55% (95% CI: 0.24, 0.87%) and 0.65% (95% CI: 0.24, 1.06%), respectively. Similar associations were estimated for cardio-respiratory mortality and hospital admissions. Conclusions: PM10 originating from the desert was positively associated with mortality and hospitalizations in Southern Europe. Policy measures should aim at reducing population exposure to anthropogenic airborne particles even in areas with large contribution from desert dust advections. Citation: Stafoggia M, Zauli-Sajani S, Pey J, Samoli E, Alessandrini E, Basagaña X, Cernigliaro A, Chiusolo M, Demaria M, Díaz J, Faustini A

Desert Dust Outbreaks in Southern Europe: Contribution to Daily PM₁₀ Concentrations and Short-Term Associations with Mortality and Hospital Admissions.

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Stafoggia, Massimo; Zauli-Sajani, Stefano; Pey, Jorge; Samoli, Evangelia; Alessandrini, Ester; Basagaña, Xavier; Cernigliaro, Achille; Chiusolo, Monica; Demaria, Moreno; Díaz, Julio; Faustini, Annunziata; Katsouyanni, Klea; Kelessis, Apostolos G; Linares, Cristina; Marchesi, Stefano; Medina, Sylvia; Pandolfi, Paolo; Pérez, Noemí; Querol, Xavier; Randi, Giorgia; Ranzi, Andrea; Tobias, Aurelio; Forastiere, Francesco

2016-04-01

Evidence on the association between short-term exposure to desert dust and health outcomes is controversial. We aimed to estimate the short-term effects of particulate matter ≤ 10 μm (PM10) on mortality and hospital admissions in 13 Southern European cities, distinguishing between PM10 originating from the desert and from other sources. We identified desert dust advection days in multiple Mediterranean areas for 2001-2010 by combining modeling tools, back-trajectories, and satellite data. For each advection day, we estimated PM10 concentrations originating from desert, and computed PM10 from other sources by difference. We fitted city-specific Poisson regression models to estimate the association between PM from different sources (desert and non-desert) and daily mortality and emergency hospitalizations. Finally, we pooled city-specific results in a random-effects meta-analysis. On average, 15% of days were affected by desert dust at ground level (desert PM10 > 0 μg/m3). Most episodes occurred in spring-summer, with increasing gradient of both frequency and intensity north-south and west-east of the Mediterranean basin. We found significant associations of both PM10 concentrations with mortality. Increases of 10 μg/m3 in non-desert and desert PM10 (lag 0-1 days) were associated with increases in natural mortality of 0.55% (95% CI: 0.24, 0.87%) and 0.65% (95% CI: 0.24, 1.06%), respectively. Similar associations were estimated for cardio-respiratory mortality and hospital admissions. PM10 originating from the desert was positively associated with mortality and hospitalizations in Southern Europe. Policy measures should aim at reducing population exposure to anthropogenic airborne particles even in areas with large contribution from desert dust advections. Stafoggia M, Zauli-Sajani S, Pey J, Samoli E, Alessandrini E, Basagaña X, Cernigliaro A, Chiusolo M, Demaria M, Díaz J, Faustini A, Katsouyanni K, Kelessis AG, Linares C, Marchesi S, Medina S, Pandolfi P, P�

Natural resource mitigation, adaptation and research needs related to climate change in the Great Basin and Mojave Desert

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Hughson, Debra L.; Busch, David E.; Davis, Scott; Finn, Sean P.; Caicco, Steve; Verburg, Paul S.J.

2011-01-01

This report synthesizes the knowledge, opinions, and concerns of many Federal and State land managers, scientists, stakeholders, and partners from a workshop, held at the University of Nevada, Las Vegas, on April 20-22, 2010. Land managers, research scientists, and resource specialists identified common concerns regarding the potential effects of climate change on public lands and natural resources in the Great Basin and Mojave Desert and developed recommendations for mitigation, adaptation, and research needs. Water and, conversely, the effects of drought emerged as a common theme in all breakout sessions on terrestrial and aquatic species at risk, managing across boundaries, monitoring, and ecosystem services. Climate change models for the southwestern deserts predict general warming and drying with increasing precipitation variability year to year. Scientists noted that under these changing conditions the past may no longer be a guide to the future in which managers envision increasing conflicts between human water uses and sustaining ecosystems. Increasing environmental stress also is expected as a consequence of shifting ecosystem boundaries and species distributions, expansion of non-native species, and decoupling of biotic mutualisms, leading to increasingly unstable biologic communities. Managers uniformly expressed a desire to work across management and agency boundaries at a landscape scale but conceded that conflicting agency missions and budgetary constraints often impede collaboration. More and better science is needed to cope with the effects of climate change but, perhaps even more important is the application of science to management issues using the methods of adaptive management based on long-term monitoring to assess the merits of management actions. Access to data is essential for science-based land management. Basic inventories, spatial databases, baseline condition assessments, data quality assurance, and data sharing were identified as top

Water-resources and land-surface deformation evaluation studies at Fort Irwin National Training Center, Mojave Desert, California

Science.gov (United States)

Densmore-Judy, Jill; Dishart, Justine E.; Miller, David; Buesch, David C.; Ball, Lyndsay B.; Bedrosian, Paul A.; Woolfenden, Linda R.; Cromwell, Geoffrey; Burgess, Matthew K.; Nawikas, Joseph; O'Leary, David; Kjos, Adam; Sneed, Michelle; Brandt, Justin

2017-01-01

The U.S. Army Fort Irwin National Training Center (NTC), in the Mojave Desert, obtains all of its potable water supply from three groundwater basins (Irwin, Langford, and Bicycle) within the NTC boundaries (fig. 1; California Department of Water Resources, 2003). Because of increasing water demands at the NTC, the U.S. Geological Survey (USGS), in cooperation with the U.S. Army, completed several studies to evaluate water resources in the developed and undeveloped groundwater basins underlying the NTC. In all of the developed basins, groundwater withdrawals exceed natural recharge, resulting in water-level declines. However, artificial recharge of treated wastewater has had some success in offsetting water-level declines in Irwin Basin. Additionally, localized water-quality changes have occurred in some parts of Irwin Basin as a result of human activities (i.e., wastewater disposal practices, landscape irrigation, and/or leaking pipes). As part of the multi-faceted NTC-wide studies, traditional datacollection methods were used and include lithological and geophysical logging at newly drilled boreholes, hydrologic data collection (i.e. water-level, water-quality, aquifer tests, wellbore flow). Because these data cover a small portion of the 1,177 square-mile (mi2 ) NTC, regional mapping, including geologic, gravity, aeromagnetic, and InSAR, also were done. In addition, ground and airborne electromagnetic surveys were completed and analyzed to provide more detailed subsurface information on a regional, base-wide scale. The traditional and regional ground and airborne data are being analyzed and will be used to help develop preliminary hydrogeologic framework and groundwater-flow models in all basins. This report is intended to provide an overview of recent water-resources and land-surface deformation studies at the NTC.

Gopherus Agassizii (Desert Tortoise). Predation/Mountain Lions (Pre-Print)

Energy Technology Data Exchange (ETDEWEB)

Paul D. Greger and Philip A. Medica

2009-01-01

During a long-term study on tortoise growth within 3 fenced 9-ha enclosures in Rock Valley, Nevada Test Site (NTS), Nye County, Nevada, USA, tortoises have been captured annually since 1964 (Medica et al. 1975. Copeia 1975:630-643; Turner et al. 1987. Copeia 1987:974-979). Between early August and mid October 2003 we observed a significant mortality event. The Rock Valley enclosures were constructed of 6 x 6 mm mesh 1.2 m wide hardware cloth, buried 0.3 m in the soil with deflective flashing on both sides on the top to restrict the movement of small mammals and lizards from entering or leaving the enclosures (Rundel and Gibson 1996, Ecological communities and process in a Mojave Desert ecosystem: Rock Valley, Nevada, Cambridge University Press, Great Britain. 369 pp.). On August 6, 2003, the carcass of an adult female Desert Tortoise No.1411 (carapace length 234 mm when alive) was collected while adult male tortoise No.4414 (carapace length 269 mm) was observed alive and in good health on the same day. Subsequently the carcass of No.4414 was found on October 16, 2003. Between October 16-17, 2003, the remains of 6 (5 adult and 1 juvenile) Desert Tortoises were found, some within each of the 3 enclosures in Rock Valley. A seventh adult tortoise was found on September 26, 2006, its death also attributed to the 2003 mortality event based upon the forensic evidence. Each of the 7 adult Desert Tortoises had the central portion of their carapace broken open approximately to the dorsal portion of the marginal scutes while the plastron was still intact (Figure 1A). Adjacent to 7 of the 8 remains we located numerous bone fragments including parts of the carapace and limbs as well as dried intestines in a nearby Range Rhatany (Krameria parvifolia) shrub. The significance of the frequent use of this shrub is puzzling. Three of the Desert Tortoise shell remains possessed distinctive intercanine punctures measuring 55-60 mm center to center indicating that this was an adult

Relative abundance of desert tortoises on the Nevada Test Site

International Nuclear Information System (INIS)

Rautenstrauch, K.R.; O'Farrell, T.P.

1993-01-01

Seven hundred fifty-nine transects having a total length of 1,191 km were walked during 1981--1986 to determine the distribution and relative abundance of desert tortoises (Gopherus agassizii) on the Nevada Test Site (NTS). The abundance of tortoises on NTS was low to very low relative to other populations in the Mojave Desert. Sign of tortoises was found from 880 to 1,570 m elevation and was more abundant above 1,200 m than has been reported previously for Nevada. Tortoises were more abundant on NTS on the upper alluvial fans and slopes of mountains than in valley bottoms. They also were more common on or near limestone and dolomite mountains than on mountains of volcanic origin

GOPHERUS AGASSIZII (Desert Tortoise)

International Nuclear Information System (INIS)

JAMES L. BOONE, DANNY L. RAKESTRAW, AND KURT R. RAUTENSTRAUCH

1997-01-01

GOPHERLTS AGAISSIZII (Desert Tortoise). Predation. A variety of predators, most notably coyotes (Canis Iatrans) and Common Ravens (Corvis corau) have been reported to prey on hatchling desert tortoises (Emst et al. 1994). Turtles of the United States and Canada (Smithsonian Institution Press, Washington, D.C. 578 pp.). Here, we report an observation of a hatchling tortoise, fitted with a radiotransmitter, that was preyed upon by native fire ants (Solenopsis sp.) in the eastern Mojave Desert at Yucca Mountain, Nevada (36 degrees 50 minutes N, 116 degree 25 minutes E). On 8/27/94, tortoise No.9315 (carapace length = 45 mm, age = 5 d) was found alive with eyes, chin, and parts of the head and legs being eaten by ants. The tortoise was alive, but lethargic, and responded little when touched. Eight of 74 other radiomarked hatchlings monitored at Yucca Mountain during 1992-1994 were found dead with fire ants on their carcass 3-7 days after the hatchlings emerged from their nests. It is not known whether those tortoises were killed by ants or were being scavenged when found. While imported fire ants (S. invicta) have long been known to kill hatchling gopher tortoises (G. polyphemus; Mount 1981. J. Alabama Acad. Sci. 52: 71-78), native fire ants have previously not been implicated as predators of desert tortoises. However, only 1 of 75 (or at worst 9 of 75) was killed by fire ants, suggesting that although fire ants do kill hatchlings, they were not important predators on desert tortoises during this study. Tortoise specimens were deposited at the University of California at Berkeley

SEASONALITY OF ANNUAL PLANT ESTABLISHMENT INFLUENCES THE INTERACTIONBETWEEN THE NON-NATIVE ANNUAL GRASS BROMUS MADRITENSIS SSP. RUBENS AND MOJAVE DESERT PERENNIALS

Energy Technology Data Exchange (ETDEWEB)

L A. DEFALCO; G. C. FERNANDEZ; R. S. NOWAK

2004-01-01

Competition between native and non-native species can change the composition and structure of plant communities, but in deserts the timing of non-native plant establishment can modulate their impacts to native species. In a field experiment, we varied densities of the non-native annual grass Bromus madritensis ssp. rubens around individuals of three native perennials--Larrea iridentata, Achnatherum hymenoides, and Pleuraphis rigida--in either winter or spring. Additional plots were prepared for the Same perennial species and seasons, but with a mixture of native annual species. Relative growth rates of perennial shoots (RGRs) declined with increasing Bromus biomass when Bromus that was established in winter had 2-3 mo of growth and high water use before perennial growth began. However, this high water use did not significantly reduce water potentials for the perennials, suggesting Bromus that established earlier depleted other soil resources, such as N, otherwise used by perennial plants. Spring-established Bromus had low biomass even at higher densities and did not effectively reduce RGRs, resulting in an overall lower impact to perennials than when Bromus was established in winter. Similarly, growth and reproduction of perennials with mixed annuals as neighbors did not differ from those with Bromus neighbors of equivalent biomass, but densities of these annuals did not support the high biomass necessary to reduce perennial growth. Thus, impacts of native Mojave Desert annuals to perennials are expected to be lower than those of Bromus because seed dormancy and narrow requirements for seedling survivorship produce densities and biomass lower than those achieved by Bromus. In comparing the effects of Bromus among perennial species, the impact of increased Bromus biomass on RGR was lower for Larrea than for the two perennial grasses, probably because Lurrea maintains low growth rates throughout the year, even after Bromus has completed its life cycle. This contrasts

Opening up the solar box: Cultural resource management and actor network theory in solar energy projects in the Mojave Desert

Science.gov (United States)

Gorrie, Bryan F.

This project considers the ways that Actor-Network Theory (ANT) can be brought to bear upon Cultural Resource Management (CRM) practices on renewable energy projects. ANT is a way of making inquiry into scientific knowledge practices and as CRM is intended to preserve environmental, historic, and prehistoric resources, it necessarily involves certain kinds of knowledge generation about regions in which projects are being developed. Because the practice of CRM is complex, involving a range of actors from developers to biologists, native peoples to academics, private landholders to environmental and cultural activists, it is imperative to account for the interests of all stakeholders and to resist devolving into the polemical relations of winners and losers, good and bad participants, or simple situations of right and wrong. This project intends to account for the "matters of concern" of various actors, both primary and secondary, by examining the case study of a single solar installation project in the Mojave Desert. A theoretical description of ANT is provided at the beginning and the concerns of this theory are brought to bear upon the case study project through describing the project, discussing the laws governing CRM on federal lands and in the state of California, and providing the points of view of various interviewees who worked directly or indirectly on various aspects of CRM for the solar project. The creators of ANT claim that it is not a methodology but it does speak to ethnomethodologies in that it insists that there is always something more to learn from inquiring into and describing any given situation. These descriptions avoid generalizations, providing instead various points of entry, from diverse perspectives to the project. There is an invitation to avoid assuming that one knows all there is to know about a given situation and to choose instead to continue investigating and thus give voice to the more obscure, often marginalized, voices in the

Effects of subsidized predators, resource variability, and human population density on desert tortoise populations in the Mojave Desert, USA

Science.gov (United States)

Esque, Todd C.; Nussear, Kenneth E.; Drake, K. Kristina; Walde, Andrew D.; Berry, Kristin H.; Averill-Murray, Roy C.; Woodman, A. Peter; Boarman, William I.; Medica, Phil A.; Mack, Jeremy S.; Heaton, Jill S.

2010-01-01

Understanding predator–prey relationships can be pivotal in the conservation of species. For 2 decades, desert tortoise Gopherus agassizii populations have declined, yet quantitative evidence regarding the causes of declines is scarce. In 2005, Ft. Irwin National Training Center, California, USA, implemented a translocation project including 2 yr of baseline monitoring of desert tortoises. Unusually high predation on tortoises was observed after translocation occurred. We conducted a retrospective analysis of predation and found that translocation did not affect the probability of predation: translocated, resident, and control tortoises all had similar levels of predation. However, predation rates were higher near human population concentrations, at lower elevation sites, and for smaller tortoises and females. Furthermore, high mortality rates were not limited to the National Training Center. In 2008, elevated mortality (as high as 43%) occurred throughout the listed range of the desert tortoise. Although no temporal prey base data are available for analysis from any of the study sites, we hypothesize that low population levels of typical coyote Canis latrans prey (i.e. jackrabbits Lepus californicus and other small animals) due to drought conditions influenced high predation rates in previous years. Predation may have been exacerbated in areas with high levels of subsidized predators. Many historical reports of increased predation, and our observation of a range-wide pattern, may indicate that high predation rates are more common than generally considered and may impact recovery of the desert tortoise throughout its range.

Shrubland carbon sink depends upon winter water availability in the warm deserts of North America

Science.gov (United States)

Biederman, Joel A.; Scott, Russell L.; John A. Arnone,; Jasoni, Richard L.; Litvak, Marcy E.; Moreo, Michael T.; Papuga, Shirley A.; Ponce-Campos, Guillermo E.; Schreiner-McGraw, Adam P.; Vivoni, Enrique R.

2018-01-01

Global-scale studies suggest that dryland ecosystems dominate an increasing trend in the magnitude and interannual variability of the land CO2 sink. However, such model-based analyses are poorly constrained by measured CO2 exchange in open shrublands, which is the most common global land cover type, covering ∼14% of Earth’s surface. Here we evaluate how the amount and seasonal timing of water availability regulate CO2 exchange between shrublands and the atmosphere. We use eddy covariance data from six US sites across the three warm deserts of North America with observed ranges in annual precipitation of ∼100–400mm, annual temperatures of 13–18°C, and records of 2–8 years (33 site-years in total). The Chihuahuan, Sonoran and Mojave Deserts present gradients in both mean annual precipitation and its seasonal distribution between the wet-winter Mojave Desert and the wet-summer Chihuahuan Desert. We found that due to hydrologic losses during the wettest summers in the Sonoran and Chihuahuan Deserts, evapotranspiration (ET) was a better metric than precipitation of water available to drive dryland CO2 exchange. In contrast with recent synthesis studies across diverse dryland biomes, we found that NEP could not be directly predicted from ET due to wintertime decoupling of the relationship between ecosystem respiration (Reco) and gross ecosystem productivity (GEP). Ecosystem water use efficiency (WUE=GEP/ET) did not differ between winter and summer. Carbon use efficiency (CUE=NEP/GEP), however, was greater in winter because Reco returned a smaller fraction of carbon to the atmosphere (23% of GEP) than in summer (77%). Combining the water-carbon relations found here with historical precipitation since 1980, we estimate that lower average winter precipitation during the 21st century reduced the net carbon sink of the three deserts by an average of 6.8TgC yr1. Our results highlight that winter precipitation is critical to the annual carbon balance of these

Dust emission at Franklin Lake Playa, Mojave Desert (USA): Response to meteorological and hydrologic changes 2005-2008

Science.gov (United States)

Reynolds, Richard L.; Bogle, Rian; Vogel, John; Goldstein, Harland L.; Yount, James

2009-01-01

Playa type, size, and setting; playa hydrology; and surface-sediment characteristics are important controls on the type and amount of atmospheric dust emitted from playas. Soft, evaporite-rich sediment develops on the surfaces of some Mojave Desert (USA) playas (wet playas), where the water table is shallow (monitored between March 2005 and April 2008. The dust record, based on day-time remote digital camera images captured during high wind, and compared with a nearby precipitation record, shows that aridity suppresses dust emission. High frequency of dust generation appears to be associated with relatively wet periods, identified as either heavy precipitation events or sustained regional precipitation over a few months. Several factors may act separately or in combination to account for this relation. Dust emission may respond rapidly to heavy precipitation when the dissolution of hard, wind-resistant evaporite mineral crusts is followed by the development of soft surfaces with thin, newly formed crusts that are vulnerable to wind erosion and (or) the production of loose aggregates of evaporite minerals that are quickly removed by even moderate winds. Dust loading may also increase when relatively high regional precipitation leads to decreasing depth to the water table, thereby increasing rates of vapor discharge, development of evaporite minerals, and temporary softening of playa surfaces. The seasonality of wind strength was not a major factor in dust-storm frequency at the playa. The lack of major dust emissions related to flood-derived sediment at Franklin Lake playa contrasts with some dry-lake systems elsewhere that may produce large amounts of dust from flood sediments. Flood sediments do not commonly accumulate on the surface of Franklin Lake playa because through-going drainage prevents frequent inundation and deposition of widespread flood sediment.

The Landers earthquake; preliminary instrumental results

Science.gov (United States)

Jones, L.; Mori, J.; Hauksson, E.

1992-01-01

Early on the morning of June 28, 1992, millions of people in southern California were awakened by the largest earthquake to occur in the western United States in the past 40 yrs. At 4:58 a.m PDT (local time), faulting associated with the magnitude 7.3 earthquake broke through to earth's surface near the town of Landers, California. the surface rupture then propagated 70km (45 mi) to the north and northwest along a band of faults passing through the middle of the Mojave Desert. Fortunately, the strongest shaking occurred in uninhabited regions of the Mojave Desert. Still one child was killed in Yucca Valley, and about 400 people were injured in the surrounding area. the desert communities of Landers, Yucca Valley, and Joshua Tree in San Bernardino Country suffered considerable damage to buildings and roads. Damage to water and power lines caused problems in many areas. 

Tracing the Atmospheric Source of Desert Nitrates Using Δ 17O

Science.gov (United States)

Michalski, G. M.; Holve, M.; Feldmeier, J.; Bao, H.; Reheis, M.; Bockheim, J. G.; Thiemens, M. H.

2001-05-01

Mineral, caliche, and soil nitrates are found throughout the worlds deserts, including the cold dry Wright Valley of Antarctica, the Atacama desert in Chile and the Mojave desert in the southwest United States. Several authors have suggested biologic sources of these nitrates while others have postulated atmospheric deposition. A recent study utilizing 18O indicated that 30%, and perhaps 100%, of nitrates found in the Atacama and Mojave were of atmospheric origin [1]. A more quantitative assessment of the source strength of atmospheric nitrates was impossible because of the high variability of δ 18 18O of atmospheric nitrates and uncertainties in conditions of biologic production. Mass independently fractionated (MIF) processes are defined and quantified by the equation Δ 17O = δ 17O - .52x δ 18O. MIF processes are associated with the photochemistry of trace gases in the atmosphere and have been found in O3, N2O, CO, and sulfate aerosols . A large MIF (Δ 17O ~ 28 ‰ ) in nitrate aerosols collected in polluted regions was recently reported [2]. Here we extend measurements of MIF in nitrate to the dry deposition of nitrate in less polluted areas (Mojave desert). In addition we trace the MIF signal as it accumulates in the regolith as nitrate salts and minerals and is mixed with biologically produced nitrate (nitrification). Also examined were the isotopic composition of soil nitrates from Antarctic dry valleys. Dust samples were collected as part of the NADP program and soils were collected throughout the Mojave and Death Valley regions of California. Isotope analysis was done in addition to soluble ion content (Cl, NO3, SO4). Dust samples collected by dry deposition samplers showed a large MIF > 20‰ approaching values measured in urban nitrate aerosol. Soils collected throughout the region showed large variations in Δ 17O from ~ 0 to 18 ‰ . The low Δ 17O values are nitrates dominated by biologic nitrification and higher values are nitrates derived by

Neotectonics of the southern Amargosa Desert, Nye County, Nevada and Inyo County, California

International Nuclear Information System (INIS)

Donovan, D.E.

1991-05-01

A complex pattern of active faults occurs in the southern Amargosa Desert, southern Nye, County, Nevada. These faults can be grouped into three main fault systems: (1) a NE-striking zone of faults that forms the southwest extension of the left-lateral Rock Valley fault zone, in the much larger Spotted Range-Mine Mountain structural zone, (2) a N-striking fault zone coinciding with a NNW-trending alignment of springs that is either a northward continuation of a fault along the west side of the Resting Spring Range or a N-striking branch fault of the Pahrump fault system, and (3) a NW-striking fault zone which is parallel to the Pahrump fault system, but is offset approximately 5 km with a left step in southern Ash Meadows. These three fault zones suggest extension is occurring in an E-W direction, which is compatible with the ∼N10W structural grain prevalent in the Death Valley extensional region to the west

Vascular plants of the Nevada Test Site and Central-Southern Nevada: ecologic and geographic distributions

Energy Technology Data Exchange (ETDEWEB)

Beatley, J.C.

1976-01-01

The physical environment of the Nevada Test Site and surrounding area is described with regard to physiography, geology, soils, and climate. A discussion of plant associations is given for the Mojave Desert, Transition Desert, and Great Basin Desert. The vegetation of disturbed sites is discussed with regard to introduced species as well as endangered and threatened species. Collections of vascular plants were made during 1959 to 1975. The plants, belonging to 1093 taxa and 98 families are listed together with information concerning ecologic and geographic distributions. Indexes to families, genera, and species are included. (HLW)

Impact of the invasive species Elaeagnus Angustifolia L. on vegetation in Pontic desert steppe zone (Southern Ukraine)

NARCIS (Netherlands)

Sudnik-Wojcikowska, B.; Moysiyenko, I.; Slim, P.A.; Moraczewski, I.R.

2009-01-01

The Irano-Turanian species – Russian olive (Elaeagnus angustifolia L.) – is one of most commonly planted tree in the shelterbelts in southern Ukraine. The consequences of introduction of the species from windbreaks, into areas of different land use in west and central Pontic desert steppe zone are

Southern Peru desert shattered by the great 2001 earthquake: Implications for paleoseismic and paleo-El Niño–Southern Oscillation records

OpenAIRE

Keefer, David K.; Moseley, Michael E.

2004-01-01

In the desert region around the coastal city of Ilo, the great southern Peru earthquake of June 23, 2001 (8.2–8.4 moment magnitude), produced intense and widespread ground-failure effects. These effects included abundant landslides, pervasive ground cracking, microfracturing of surficial hillslope materials, collapse of drainage banks over long stretches, widening of hillside rills, and lengthening of first-order tributary channels. We have coined the term “shattered landscape” to describe th...

[Soil infiltration of snowmelt water in the southern Gurbantunggut Desert, Xinjiang, China].

Science.gov (United States)

Hu, Shun-jun; Chen, Yong-bao; Zhu, Hai

2015-04-01

Soil infiltration of snow-melt water is an important income item of water balance in arid desert. The soil water content in west slope, east slope and interdune of sand dune in the southern Gurbantunggut Desert was monitored before snowfall and after snow melting during the winters of 2012-2013 and 2013-2014. According to the principle of water balance, soil infiltration of snow-melt in the west slope, east slope, interdune and landscape scale was calculated, and compared with the results measured by cylinder method. The results showed that the soil moisture recharge from unfrozen layer of unsaturated soil to surface frozen soil was negligible because the soil moisture content before snowfall was lower, soil infiltration of snow-melt water was the main source of soil water of shallow soil, phreatic water did not evaporate during freezing period, and did not get recharge after the snow melting. Snowmelt water in the west slope, east slope, interdune and landscape scale were 20-43, 27-43, 32-45, 26-45 mm, respectively.

Identifying multiple timescale rainfall controls on Mojave Desert ecohydrology using an integrated data and modeling approach for Larrea tridentata

Science.gov (United States)

Ng, Gene-Hua Crystal; Bedford, David R.; Miller, David M.

2015-01-01

The perennial shrub Larrea tridentata is widely successful in North American warm deserts but is also susceptible to climatic perturbations. Understanding its response to rainfall variability requires consideration of multiple timescales. We examine intra-annual to multi-year relationships using model simulations of soil moisture and vegetation growth over 50 years in the Mojave National Preserve in southeastern California (USA). Ecohydrological model parameters are conditioned on field and remote sensing data using an ensemble Kalman filter. Although no specific periodicities were detected in the rainfall record, simulated leaf-area-index exhibits multi-year dynamics that are driven by multi-year (∼3-years) rains, but with up to a 1-year delay in peak response. Within a multi-year period, Larrea tridentata is more sensitive to winter rains than summer. In the most active part of the root zone (above ∼80 cm), >1-year average soil moisture drives vegetation growth, but monthly average soil moisture is controlled by root uptake. Moisture inputs reach the lower part of the root zone (below ∼80 cm) infrequently, but once there they can persist over a year to help sustain plant growth. Parameter estimates highlight efficient plant physiological properties facilitating persistent growth and high soil hydraulic conductivity allowing deep soil moisture stores. We show that soil moisture as an ecological indicator is complicated by bidirectional interactions with vegetation that depend on timescale and depth. Under changing climate, Larrea tridentata will likely be relatively resilient to shorter-term moisture variability but will exhibit higher sensitivity to shifts in seasonal to multi-year moisture inputs.

Home in the heat: Dramatic seasonal variation in home range of desert golden eagles informs management for renewable energy development

Science.gov (United States)

Braham, Melissa A.; Miller, Tricia A.; Duerr, Adam E.; Lanzone, Michael J.; Fesnock, Amy; LaPre, Larry; Driscoll, Daniel; Katzner, Todd E.

2015-01-01

Renewable energy is expanding quickly with sometimes dramatic impacts to species and ecosystems. To understand the degree to which sensitive species may be impacted by renewable energy projects, it is informative to know how much space individuals use and how that space may overlap with planned development. We used global positioning system–global system for mobile communications (GPS-GSM) telemetry to measure year-round movements of golden eagles (Aquila chrysaetos) from the Mojave Desert of California, USA. We estimated monthly space use with adaptive local convex hulls to identify the temporal and spatial scales at which eagles may encounter renewable energy projects in the Desert Renewable Energy Conservation Plan area. Mean size of home ranges was lowest and least variable from November through January and greatest in February–March and May–August. These monthly home range patterns coincided with seasonal variation in breeding ecology, habitat associations, and temperature. The expanded home ranges in hot summer months included movements to cooler, prey-dense, mountainous areas characterized by forest, grasslands, and scrublands. Breeding-season home ranges (October–May) included more lowland semi-desert and rock vegetation. Overlap of eagle home ranges and focus areas for renewable energy development was greatest when eagle home ranges were smallest, during the breeding season. Golden eagles in the Mojave Desert used more space and a wider range of habitat types than expected and renewable energy projects could affect a larger section of the regional population than was previously thought.

Regional and temporal variability of melts during a Cordilleran magma pulse: Age and chemical evolution of the jurassic arc, eastern mojave desert, California

Science.gov (United States)

Barth, A.P.; Wooden, J.L.; Miller, David; Howard, Keith A.; Fox, Lydia; Schermer, Elizabeth R.; Jacobson, C.E.

2017-01-01

Intrusive rock sequences in the central and eastern Mojave Desert segment of the Jurassic Cordilleran arc of the western United States record regional and temporal variations in magmas generated during the second prominent pulse of Mesozoic continental arc magmatism. U/Pb zircon ages provide temporal control for describing variations in rock and zircon geochemistry that reflect differences in magma source components. These source signatures are discernible through mixing and fractionation processes associated with magma ascent and emplacement. The oldest well-dated Jurassic rocks defining initiation of the Jurassic pulse are a 183 Ma monzodiorite and a 181 Ma ignimbrite. Early to Middle Jurassic intrusive rocks comprising the main stage of magmatism include two high-K calc-alkalic groups: to the north, the deformed 183–172 Ma Fort Irwin sequence and contemporaneous rocks in the Granite and Clipper Mountains, and to the south, the 167–164 Ma Bullion sequence. A Late Jurassic suite of shoshonitic, alkali-calcic intrusive rocks, the Bristol Mountains sequence, ranges in age from 164 to 161 Ma and was emplaced as the pulse began to wane. Whole-rock and zircon trace-element geochemistry defines a compositionally coherent Jurassic arc with regional and secular variations in melt compositions. The arc evolved through the magma pulse by progressively greater input of old cratonic crust and lithospheric mantle into the arc magma system, synchronous with progressive regional crustal thickening.

X-36 in Flight over Mojave Desert

Science.gov (United States)

1997-01-01

The unusual lines of the X-36 technology demonstrator contrast sharply with the desert floor as the remotely piloted aircraft scoots across the California desert at low altitude during a research flight on October 30, 1997. The NASA/Boeing X-36 Tailless Fighter Agility Research Aircraft program successfully demonstrated the tailless fighter design using advanced technologies to improve the maneuverability and survivability of possible future fighter aircraft. The program met or exceeded all project goals. For 31 flights during 1997 at the Dryden Flight Research Center, Edwards, California, the project team examined the aircraft's agility at low speed / high angles of attack and at high speed / low angles of attack. The aircraft's speed envelope reached up to 206 knots (234 mph). This aircraft was very stable and maneuverable. It handled very well. The X-36 vehicle was designed to fly without the traditional tail surfaces common on most aircraft. Instead, a canard forward of the wing was used as well as split ailerons and an advanced thrust-vectoring nozzle for directional control. The X-36 was unstable in both pitch and yaw axes, so an advanced, single-channel digital fly-by-wire control system (developed with some commercially available components) was put in place to stabilize the aircraft. Using a video camera mounted in the nose of the aircraft and an onboard microphone, the X-36 was remotely controlled by a pilot in a ground station virtual cockpit. A standard fighter-type head-up display (HUD) and a moving-map representation of the vehicle's position within the range in which it flew provided excellent situational awareness for the pilot. This pilot-in-the-loop approach eliminated the need for expensive and complex autonomous flight control systems and the risks associated with their inability to deal with unknown or unforeseen phenomena in flight. Fully fueled the X-36 prototype weighed approximately 1,250 pounds. It was 19 feet long and three feet high with

Effects of an invasive plant on a desert sand dune landscape

Science.gov (United States)

Barrows, C.W.; Allen, E.B.; Brooks, M.L.; Allen, M.F.

2009-01-01

Given the abundance of non-native species invading wildland habitats, managers need to employ informed triage to focus control efforts on weeds with the greatest potential for negative impacts. Our objective here was to determine the level of threat Sahara mustard, Brassica tournefortii, represents to meeting regional goals for protecting biodiversity. Sahara mustard has spread throughout much of the Mojave and lower Sonoran Deserts. It has occurred in southern California's Coachella Valley for nearly 80 years, punctuated by years of extremely high abundance following high rainfall. In those years the mustard has clear negative impacts on the native flora. Using mustard removal experiments we identified reductions in native plant reproduction, shifting composition increasingly toward Sahara mustard while decreasing the fraction of native species. High between-year variance in precipitation may be a key to maintaining biodiversity as the mustard is less abundant in drier years. Sahara mustard impacts to the native fauna were much less evident. Of the animal species evaluated, only the Coachella Valley fringe-toed lizard, Uma inornata, demonstrated a negative response to mustard abundance; however the impacts were short-lived, lasting no more than a year after the mustard's dominance waned. Without control measures the long-term impacts to desert biodiversity may rest on the changing climate. Wetter conditions or increased periodicity of high rainfall years will favor Sahara mustard and result in reduced biodiversity, especially of native annual plants. Drier conditions will keep the mustard from becoming dominant but may have other negative consequences on the native flora and fauna. ?? 2008 Springer Science+Business Media B.V.

Southern Peru desert shattered by the great 2001 earthquake: implications for paleoseismic and paleo-El Nino-Southern Oscillation records.

Science.gov (United States)

Keefer, David K; Moseley, Michael E

2004-07-27

In the desert region around the coastal city of Ilo, the great southern Peru earthquake of June 23, 2001 (8.2-8.4 moment magnitude), produced intense and widespread ground-failure effects. These effects included abundant landslides, pervasive ground cracking, microfracturing of surficial hillslope materials, collapse of drainage banks over long stretches, widening of hillside rills, and lengthening of first-order tributary channels. We have coined the term "shattered landscape" to describe the severity of these effects. Long-term consequences of this landscape shattering are inferred to include increased runoff and sediment transport during postearthquake rainstorms. This inference was confirmed during the first minor postearthquake rainstorm there, which occurred in June and July of 2002. Greater amounts of rainfall in this desert region have historically been associated with El Niño events. Previous studies of an unusual paleoflood deposit in this region have concluded that it is the product of El Niño-generated precipitation falling on seismically disturbed landscapes. The effects of the 2001 earthquake and 2002 rainstorm support that conclusion.

Microbial Community and Biochemical Dynamics of Biological Soil Crusts across a Gradient of Surface Coverage in the Central Mojave Desert

Directory of Open Access Journals (Sweden)

Rakesh Mogul

2017-10-01

Full Text Available In this study, we expand upon the biogeography of biological soil crusts (BSCs and provide molecular insights into the microbial community and biochemical dynamics along the vertical BSC column structure, and across a transect of increasing BSC surface coverage in the central Mojave Desert, CA, United States. Next generation sequencing reveals a bacterial community profile that is distinct among BSCs in the southwestern United States. Distribution of major phyla in the BSC topsoils included Cyanobacteria (33 ± 8%, Proteobacteria (26 ± 6%, and Chloroflexi (12 ± 4%, with Phormidium being the numerically dominant genus. Furthermore, BSC subsurfaces contained Proteobacteria (23 ± 5%, Actinobacteria (20 ± 5%, and Chloroflexi (18 ± 3%, with an unidentified genus from Chloroflexi (AKIW781, order being numerically dominant. Across the transect, changes in distribution at the phylum (p < 0.0439 and genus (p < 0.006 levels, including multiple biochemical and geochemical trends (p < 0.05, positively correlated with increasing BSC surface coverage. This included increases in (a Chloroflexi abundance, (b abundance and diversity of Cyanobacteria, (b OTU-level diversity in the topsoil, (c OTU-level differentiation between the topsoil and subsurface, (d intracellular ATP abundances and catalase activities, and (e enrichments in clay, silt, and varying elements, including S, Mn, Co, As, and Pb, in the BSC topsoils. In sum, these studies suggest that BSCs from regions of differing surface coverage represent early successional stages, which exhibit increasing bacterial diversity, metabolic activities, and capacity to restructure the soil. Further, these trends suggest that BSC successional maturation and colonization across the transect are inhibited by metals/metalloids such as B, Ca, Ti, Mn, Co, Ni, Mo, and Pb.

Microbial Community and Biochemical Dynamics of Biological Soil Crusts across a Gradient of Surface Coverage in the Central Mojave Desert.

Science.gov (United States)

Mogul, Rakesh; Vaishampayan, Parag; Bashir, Mina; McKay, Chris P; Schubert, Keith; Bornaccorsi, Rosalba; Gomez, Ernesto; Tharayil, Sneha; Payton, Geoffrey; Capra, Juliana; Andaya, Jessica; Bacon, Leonard; Bargoma, Emily; Black, David; Boos, Katie; Brant, Michaela; Chabot, Michael; Chau, Danny; Cisneros, Jessica; Chu, Geoff; Curnutt, Jane; DiMizio, Jessica; Engelbrecht, Christian; Gott, Caroline; Harnoto, Raechel; Hovanesian, Ruben; Johnson, Shane; Lavergne, Britne; Martinez, Gabriel; Mans, Paul; Morales, Ernesto; Oei, Alex; Peplow, Gary; Piaget, Ryan; Ponce, Nicole; Renteria, Eduardo; Rodriguez, Veronica; Rodriguez, Joseph; Santander, Monica; Sarmiento, Khamille; Scheppelmann, Allison; Schroter, Gavin; Sexton, Devan; Stephenson, Jenin; Symer, Kristin; Russo-Tait, Tatiane; Weigel, Bill; Wilhelm, Mary B

2017-01-01

In this study, we expand upon the biogeography of biological soil crusts (BSCs) and provide molecular insights into the microbial community and biochemical dynamics along the vertical BSC column structure, and across a transect of increasing BSC surface coverage in the central Mojave Desert, CA, United States. Next generation sequencing reveals a bacterial community profile that is distinct among BSCs in the southwestern United States. Distribution of major phyla in the BSC topsoils included Cyanobacteria (33 ± 8%), Proteobacteria (26 ± 6%), and Chloroflexi (12 ± 4%), with Phormidium being the numerically dominant genus. Furthermore, BSC subsurfaces contained Proteobacteria (23 ± 5%), Actinobacteria (20 ± 5%), and Chloroflexi (18 ± 3%), with an unidentified genus from Chloroflexi (AKIW781, order) being numerically dominant. Across the transect, changes in distribution at the phylum ( p < 0.0439) and genus ( p < 0.006) levels, including multiple biochemical and geochemical trends ( p < 0.05), positively correlated with increasing BSC surface coverage. This included increases in (a) Chloroflexi abundance, (b) abundance and diversity of Cyanobacteria, (b) OTU-level diversity in the topsoil, (c) OTU-level differentiation between the topsoil and subsurface, (d) intracellular ATP abundances and catalase activities, and (e) enrichments in clay, silt, and varying elements, including S, Mn, Co, As, and Pb, in the BSC topsoils. In sum, these studies suggest that BSCs from regions of differing surface coverage represent early successional stages, which exhibit increasing bacterial diversity, metabolic activities, and capacity to restructure the soil. Further, these trends suggest that BSC successional maturation and colonization across the transect are inhibited by metals/metalloids such as B, Ca, Ti, Mn, Co, Ni, Mo, and Pb.

Oxalosis in wild desert tortoises, Gopherus agassizii

Science.gov (United States)

Jacobson, Elliott R.; Berry, Kristin H.; Stacy, Brian; Huzella, Louis M.; Kalasinsky, Victor F.; Fleetwood, Michelle L.; Mense, Mark G.

2009-01-01

We necropsied a moribund, wild adult male desert tortoise (Gopherus agassizii) with clinical signs of respiratory disease and elevated plasma biochemical analytes indicative of renal disease (blood urea nitrogen [415 mg/dl], uric acid [11.8 mg/dl], sodium >180 mmol/l] and chloride [139 mmol/l]). Moderate numbers of birefringent oxalate crystals, based on infrared and electron microscopy, were present within renal tubules; small numbers were seen in colloid within thyroid follicles. A retrospective analysis of 66 additional cases of wild desert tortoises was conducted to determine whether similar crystals were present in thyroid and kidney. The tortoises, from the Mojave and Sonoran deserts, were necropsied between 1992 and 2003 and included juveniles and adults. Tortoises were classified as healthy (those that died due to trauma and where no disease was identified after necropsy and evaluation by standard laboratory tests used for other tortoises) or not healthy (having one or more diseases or lesions). For all 67 necropsied tortoises, small numbers of crystals of similar appearance were present in thyroid glands from 44 of 54 cases (81%) and in kidneys from three of 65 cases (5%). Presence of oxalates did not differ significantly between healthy and unhealthy tortoises, between age classes, or between desert region, and their presence was considered an incidental finding. Small numbers of oxalate crystals seen within the kidney of two additional tortoises also were considered an incidental finding. Although the source of the calcium oxalate could not be determined, desert tortoises are herbivores, and a plant origin seems most likely. Studies are needed to evaluate the oxalate content of plants consumed by desert tortoises, and particularly those in the area where the tortoise in renal failure was found.

Airborne dust transport to the eastern Pacific Ocean off southern California: Evidence from San Clemente Island

Science.gov (United States)

Muhs, D.R.; Budahn, J.; Reheis, M.; Beann, J.; Skipp, G.; Fisher, E.

2007-01-01

Islands are natural dust traps, and San Clemente Island, California, is a good example. Soils on marine terraces cut into Miocene andesite on this island are clay-rich Vertisols or Alfisols with vertic properties. These soils are overlain by silt-rich mantles, 5-20 cm thick, that contrast sharply with the underlying clay-rich subsoils. The silt mantles have a mineralogy that is distinct from the island bedrock. Silt mantles are rich in quartz, which is rare in the island andesite. The clay fraction of the silt mantles is dominated by mica, also absent from local andesite, and contrasts with the subsoils, dominated by smectite. Ternary plots of immobile trace elements (Sc-Th-La and Ta-Nd-Cr) show that the island andesite has a composition intermediate between average upper continental crust and average oceanic crust. In contrast, the silt and, to a lesser extent, clay fractions of the silt mantles have compositions closer to average upper continental crust. The silt mantles have particle size distributions similar to loess and Mojave Desert dust, but are coarser than long-range-transported Asian dust. We infer from these observations that the silt mantles are derived from airborne dust from the North American mainland, probably river valleys in the coastal mountains of southern California and/or the Mojave Desert. Although average winds are from the northwest in coastal California, easterly winds occur numerous times of the year when "Santa Ana" conditions prevail, caused by a high-pressure cell centered over the Great Basin. Examination of satellite imagery shows that easterly Santa Ana winds carry abundant dust to the eastern Pacific Ocean and the California Channel Islands. Airborne dust from mainland North America may be an important component of the offshore sediment budget in the easternmost Pacific Ocean, a finding of potential biogeochemical and climatic significance.

Hydrogeologic inferences from drillers' logs and from gravity and resistivity surveys in the Amargosa Desert, southern Nevada

International Nuclear Information System (INIS)

Oatfield, W.J.; Czarnecki, J.B.

1989-01-01

The Amargosa Desert of southern Nevada, in the Basin and Range province, is hydraulically downgradient from Yucca Mountain, the potential site of a repository for high-level nuclear waste. Ground-water flow paths and flow rates beneath the Amargosa Desert are controlled in part by the total saturated thickness and the hydraulic properties of basin-fill alluvial sediments. Drillers' logs of water wells completed in alluvium were analyzed to help characterize the hydrogeologic framework underlying the Amargosa Desert. Fractions of coarse-grained sediments, calculated from each of these logs, were contoured using a universal-kriging routine to interpolate values. Results from a previous electrical sounding survey also were contoured, including the estimated depth to Paleozoic basement rocks. The vertical electric sounding results were obtained from individual depth-to-resistivity profiles, from which the average resistivity of the total profile and the resistivity of the upper 75 meters were calculated. the distribution and variations in average resistivity of the total depth correlated reasonably well with the distribution of variations in regional gravity. 24 refs., 17 figs

Conservation Planning for Offsetting the Impacts of Development: A Case Study of Biodiversity and Renewable Energy in the Mojave Desert.

Science.gov (United States)

Kreitler, Jason; Schloss, Carrie A; Soong, Oliver; Hannah, Lee; Davis, Frank W

2015-01-01

Balancing society's competing needs of development and conservation requires careful consideration of tradeoffs. Renewable energy development and biodiversity conservation are often considered beneficial environmental goals. The direct footprint and disturbance of renewable energy, however, can displace species' habitat and negatively impact populations and natural communities if sited without ecological consideration. Offsets have emerged as a potentially useful tool to mitigate residual impacts after trying to avoid, minimize, or restore affected sites. Yet the problem of efficiently designing a set of offset sites becomes increasingly complex where many species or many sites are involved. Spatial conservation prioritization tools are designed to handle this problem, but have seen little application to offset siting and analysis. To address this need we designed an offset siting support tool for the Desert Renewable Energy Conservation Plan (DRECP) of California, and present a case study of hypothetical impacts from solar development in the Western Mojave subsection. We compare two offset scenarios designed to mitigate a hypothetical 15,331 ha derived from proposed utility-scale solar energy development (USSED) projects. The first scenario prioritizes offsets based precisely on impacted features, while the second scenario offsets impacts to maximize biodiversity conservation gains in the region. The two methods only agree on 28% of their prioritized sites and differ in meeting species-specific offset goals. Differences between the two scenarios highlight the importance of clearly specifying choices and priorities for offset siting and mitigation in general. Similarly, the effects of background climate and land use change may lessen the durability or effectiveness of offsets if not considered. Our offset siting support tool was designed specifically for the DRECP area, but with minor code modification could work well in other offset analyses, and could provide

Seed banks in a degraded desert shrubland: Influence of soil surface condition and harvester ant activity on seed abundance

Science.gov (United States)

DeFalco, L.A.; Esque, T.C.; Kane, J.M.; Nicklas, M.B.

2009-01-01

We compared seed banks between two contrasting anthropogenic surface disturbances (compacted, trenched) and adjacent undisturbed controls to determine whether site condition influences viable seed densities of perennial and annual Mojave Desert species. Viable seeds of perennials were rare in undisturbed areas (3-4 seeds/m2) and declined to importance of litter as an indicator of site degradation and recovery potential in arid lands.

Late Quaternary history of the Atacama Desert

Science.gov (United States)

Latorre, Claudio; Betancourt, Julio L.; Rech, Jason A.; Quade, Jay; Holmgren, Camille; Placzek, Christa; Maldonado, Antonio; Vuille, Mathias; Rylander, Kate A.; Smith, Mike; Hesse, Paul

2005-01-01

Of the major subtropical deserts found in the Southern Hemisphere, the Atacama Desert is the driest. Throughout the Quaternary, the most pervasive climatic influence on the desert has been millennial-scale changes in the frequency and seasonality of the scant rainfall, and associated shifts in plant and animal distributions with elevation along the eastern margin of the desert. Over the past six years, we have mapped modern vegetation gradients and developed a number of palaeoenvironmental records, including vegetation histories from fossil rodent middens, groundwater levels from wetland (spring) deposits, and lake levels from shoreline evidence, along a 1200-kilometre transect (16–26°S) in the Atacama Desert. A strength of this palaeoclimate transect has been the ability to apply the same methodologies across broad elevational, latitudinal, climatic, vegetation and hydrological gradients. We are using this transect to reconstruct the histories of key components of the South American tropical (summer) and extratropical (winter) rainfall belts, precisely at those elevations where average annual rainfall wanes to zero. The focus has been on the transition from sparse, shrubby vegetation (known as the prepuna) into absolute desert, an expansive hyperarid terrain that extends from just above the coastal fog zone (approximately 800 metres) to more than 3500 metres in the most arid sectors in the southern Atacama.

[Spatial variation of soil carbon and stable isotopes in the southern margin desert of Junggar Basin, China].

Science.gov (United States)

Wang, Na; Xu, Wen Qiang; Xu, Hua Jun; Feng, Yi Xing; Li, Chao Fan

2017-07-18

The southern margin desert of Junggar Basin in the central arid region of Asia was selec-ted as the study area. To gain insight into the distribution characteristic of stable carbon isotope and the relationship between the change of soil carbon and the distance to oasis of soil organic carbon (SOC) and soil inorganic carbon (SIC), three belt transects were set according to the distance between the desert and the oasis in edge, middle and hinterland of the desert respectively, and collected the soil profile samples with depth of 2 m. The results indicated that the SOC content reduced with the soil depth, and the variation with the distance to oasis was the edge> the middle> the hinterland. The δ 13 C value of SOC varied in the range of -21.92‰ to -17.41‰, and decreased with the depth; the range in the middle and hinterland was -25.20‰ to -19.30‰, and increased then declined with the depth. Therefore, we could infer that the C3 plants played a dominant role in the central of desert, and had experienced the succession from C3 plants to C4 plants. The average content of SIC was 38.98 g·kg -1 in the edge of desert, which was about 6.01 folds as large as the content in the hinterland. This indicated that a large number of SIC with 0-2 m depth were clustered in the edge of the desert. The δ 13 C value of SIC increased first then decreased with the soil depth, and enriched in the bottom layer, which was mainly affected by the original carbonate content and soil carbon dioxide.

Southern Peru desert shattered by the great 2001 earthquake: Implications for paleoseismic and paleo-El Niño–Southern Oscillation records

Science.gov (United States)

Keefer, David K.; Moseley, Michael E.

2004-01-01

In the desert region around the coastal city of Ilo, the great southern Peru earthquake of June 23, 2001 (8.2–8.4 moment magnitude), produced intense and widespread ground-failure effects. These effects included abundant landslides, pervasive ground cracking, microfracturing of surficial hillslope materials, collapse of drainage banks over long stretches, widening of hillside rills, and lengthening of first-order tributary channels. We have coined the term “shattered landscape” to describe the severity of these effects. Long-term consequences of this landscape shattering are inferred to include increased runoff and sediment transport during postearthquake rainstorms. This inference was confirmed during the first minor postearthquake rainstorm there, which occurred in June and July of 2002. Greater amounts of rainfall in this desert region have historically been associated with El Niño events. Previous studies of an unusual paleoflood deposit in this region have concluded that it is the product of El Niño-generated precipitation falling on seismically disturbed landscapes. The effects of the 2001 earthquake and 2002 rainstorm support that conclusion. PMID:15263069

Variation of Desert Soil Hydraulic Properties with Pedogenic Maturity

Science.gov (United States)

Nimmo, J. R.; Perkins, K. S.; Mirus, B. B.; Schmidt, K. M.; Miller, D. M.; Stock, J. D.; Singha, K.

2006-12-01

Older alluvial desert soils exhibit greater pedogenic maturity, having more distinct desert pavements, vesicular (Av) horizons, and more pronounced stratification from processes such as illuviation and salt accumulation. These and related effects strongly influence the soil hydraulic properties. Older soils have been observed to have lower saturated hydraulic conductivity, and possibly greater capacity to retain water, but the quantitative effect of specific pedogenic features on the soil water retention or unsaturated hydraulic conductivity (K) curves is poorly known. With field infiltration/redistribution experiments on three different-aged soils developed within alluvial wash deposits in the Mojave National Preserve, we evaluated effective hydraulic properties over a scale of several m horizontally and to 1.5 m depth. We then correlated these properties with pedogenic features. The selected soils are (1) recently deposited sediments, (2) a soil of early Holocene age, and (3) a highly developed soil of late Pleistocene age. In each experiment we ponded water in a 1-m-diameter infiltration ring for 2.3 hr. For several weeks we monitored subsurface water content and matric pressure using surface electrical resistance imaging, dielectric-constant probes, heat-dissipation probes, and tensiometers. Analysis of these data using an inverse modeling technique gives the water retention and K properties needed for predictive modeling. Some properties show a consistent trend with soil age. Progressively more developed surface and near-surface features such as desert pavement and Av horizons are the likely cause of an observed consistent decline of infiltration capacity with soil age. Other properties, such as vertical flow retardation by layer contrasts, appear to have a more complicated soil-age dependence. The wash deposits display distinct depositional layering that has a retarding effect on vertical flow, an effect that may be less pronounced in the older Holocene soil

Faulting and groundwater in a desert environment: constraining hydrogeology using time-domain electromagnetic data

Science.gov (United States)

Bedrosian, Paul A.; Burgess, Matthew K.; Nishikawa, Tracy

2013-01-01

Within the south-western Mojave Desert, the Joshua Basin Water District is considering applying imported water into infiltration ponds in the Joshua Tree groundwater sub-basin in an attempt to artificially recharge the underlying aquifer. Scarce subsurface hydrogeological data are available near the proposed recharge site; therefore, time-domain electromagnetic (TDEM) data were collected and analysed to characterize the subsurface. TDEM soundings were acquired to estimate the depth to water on either side of the Pinto Mountain Fault, a major east-west trending strike-slip fault that transects the proposed recharge site. While TDEM is a standard technique for groundwater investigations, special care must be taken when acquiring and interpreting TDEM data in a twodimensional (2D) faulted environment. A subset of the TDEM data consistent with a layered-earth interpretation was identified through a combination of three-dimensional (3D) forward modelling and diffusion time-distance estimates. Inverse modelling indicates an offset in water table elevation of nearly 40 m across the fault. These findings imply that the fault acts as a low-permeability barrier to groundwater flow in the vicinity of the proposed recharge site. Existing production wells on the south side of the fault, together with a thick unsaturated zone and permeable near-surface deposits, suggest the southern half of the study area is suitable for artificial recharge. These results illustrate the effectiveness of targeted TDEM in support of hydrological studies in a heavily faulted desert environment where data are scarce and the cost of obtaining these data by conventional drilling techniques is prohibitive.

Preliminary Surficial Geology of the Dove Spring Off-Highway Vehicle Open Area, Mojave Desert, California

Science.gov (United States)

Miller, David M.; Amoroso, Lee

2007-01-01

vegetation, biological soil crusts, compaction, and other information may be correlated with land use to identify possible ecological thresholds in OHV use that require monitoring. Surficial geology is relevant for several other studies of OHV impact, such as soil compaction, dust emissions, and acceleration of erosion. Compaction, reduced infiltration, and accelerated erosion have been documented in Dove Spring Canyon because of OHV use (Snyder and others, 1976) and elsewhere in the Mojave Desert (e.g., Webb, 1983; Langdon, 2000). A surficial geologic map enables the use of geomorphic process models, which when combined with measured soil properties, such as texture, nutrient chemistry, and bulk density, allows spatial extrapolation of the properties. Maps can be produced that predict compaction susceptibility, moisture conditions, dust emissions, flood hazards, and erodibility, among other applications.

An overview of the Southern Nevada Agency Partnership science and research synthesis: Chapter 1 in The Southern Nevada Agency Partnership science and research synthesis: science to support land management in southern Nevada

Science.gov (United States)

Chambers, Jeanne C.; Brooks, Matthew L.; Turner, Kent; Raish, Carol B.; Ostoja, Steven M.

2013-01-01

Maintaining and restoring the diverse ecosystems and resources that occur in southern Nevada in the face of rapid socio-economic and ecological change presents numerous challenged to Federal land managers. Rapid population growth since the 1980s, the land uses associated with that growth, and the interactions of those uses with the generally dry and highly variable climate result in numerous stresses to ecosystems, species, and cultural resource. In addition, climate models predict that the rate of temperature increase and, thus, changes in ecological processes, will be highest for ecosystems like the Mojave Desert. The Southern Nevada Agency Partnership (SNAP; http:www.SNAP.gov) was established in 1999 to address common issues pertaining to public lands in southern Nevada. Partners include the Bureau of Land Management, National Park Service, U.S. Fish and Wildlife Service, and USDA Forest Service and they work with each other, the local community, and other partners. SNAP agencies manage more than seven million acres of public lands in southern Nevada (95% of the land area). Federal land includes two national recreation areas, two national conservation area, four national wildlife refuges, 18 congressionally designated wilderness areas, five wilderness study areas, and 22 areas of critical environmental concern. The partnership's activities are mainly centered in Southern Nevada's Clark County (fig. 1.1), but lands managed by SNAP partner agencies also include portions of Lake Mead National Recreation Area in Mohave County, Arizona, U.S. Fish and Wildlife Service, and USDA Forest Service-managed lands in Lincoln and Nye Counties, Nevada, and all lands and activities managed by the Southern Nevada District Office of the Bureau of Land Management. These lands encompass nine distinct ecosystem types (fig. 1.2), support multiple species of management concern an 17 listed species, and are rich in cultural and historic resource. This introductory executive summary

How fault evolution changes strain partitioning and fault slip rates in Southern California: Results from geodynamic modeling

Science.gov (United States)

Ye, Jiyang; Liu, Mian

2017-08-01

In Southern California, the Pacific-North America relative plate motion is accommodated by the complex southern San Andreas Fault system that includes many young faults (faults and their impact on strain partitioning and fault slip rates are important for understanding the evolution of this plate boundary zone and assessing earthquake hazard in Southern California. Using a three-dimensional viscoelastoplastic finite element model, we have investigated how this plate boundary fault system has evolved to accommodate the relative plate motion in Southern California. Our results show that when the plate boundary faults are not optimally configured to accommodate the relative plate motion, strain is localized in places where new faults would initiate to improve the mechanical efficiency of the fault system. In particular, the Eastern California Shear Zone, the San Jacinto Fault, the Elsinore Fault, and the offshore dextral faults all developed in places of highly localized strain. These younger faults compensate for the reduced fault slip on the San Andreas Fault proper because of the Big Bend, a major restraining bend. The evolution of the fault system changes the apportionment of fault slip rates over time, which may explain some of the slip rate discrepancy between geological and geodetic measurements in Southern California. For the present fault configuration, our model predicts localized strain in western Transverse Ranges and along the dextral faults across the Mojave Desert, where numerous damaging earthquakes occurred in recent years.

77 FR 12495 - Revisions to the California State Implementation Plan, Antelope Valley Air Quality Management...

Science.gov (United States)

2012-03-01

... the California State Implementation Plan, Antelope Valley Air Quality Management District and Mojave Desert Quality Management District AGENCY: Environmental Protection Agency (EPA). ACTION: Direct final... Quality Management District (AVAQMD) and Mojave Desert Air Quality Management District (MDAQMD) portion of...

Radiotelemetry Study of a Desert Tortoise Population: Sand Hill Training Mea, Marine Corps Air Ground Combat Center, Twentynine Palms, California

Science.gov (United States)

1998-05-01

shallow caliche burrows. Mojave populations differ genetically ( Lamb et al. 1989), morphologically (Weinstein and Berry 1987), in burrow construction...34 Abstract in The Desert Tortoise Council Symposium (1995d), p 92. Lamb , T., J.C. Avise, and J.W. Gibbons, "Phylogeographic Patterns in Mitochondrial...ATTN: STEWS -EL US Army Envr Hygiene Agency ATTN:HSHB-ME 21010 US Army Environmental Center ATTN: SFIM-AEC 21010-5401 Defense Tech Info Center

Enhancing and restoring habitat for the desert tortoise

Science.gov (United States)

Abella, Scott R.; Berry, Kristin H.

2016-01-01

Habitat has changed unfavorably during the past 150 y for the desert tortoise Gopherus agassizii, a federally threatened species with declining populations in the Mojave Desert and western Sonoran Desert. To support recovery efforts, we synthesized published information on relationships of desert tortoises with three habitat features (cover sites, forage, and soil) and candidate management practices for improving these features for tortoises. In addition to their role in soil health and facilitating recruitment of annual forage plants, shrubs are used by desert tortoises for cover and as sites for burrows. Outplanting greenhouse-grown seedlings, protected from herbivory, has successfully restored (>50% survival) a variety of shrubs on disturbed desert soils. Additionally, salvaging and reapplying topsoil using effective techniques is among the more ecologically beneficial ways to initiate plant recovery after severe disturbance. Through differences in biochemical composition and digestibility, some plant species provide better-quality forage than others. Desert tortoises selectively forage on particular annual and herbaceous perennial species (e.g., legumes), and forage selection shifts during the year as different plants grow or mature. Nonnative grasses provide low-quality forage and contribute fuel to spreading wildfires, which damage or kill shrubs that tortoises use for cover. Maintaining a diverse “menu” of native annual forbs and decreasing nonnative grasses are priorities for restoring most desert tortoise habitats. Reducing herbivory by nonnative animals, carefully timing herbicide applications, and strategically augmenting annual forage plants via seeding show promise for improving tortoise forage quality. Roads, another disturbance, negatively affect habitat in numerous ways (e.g., compacting soil, altering hydrology). Techniques such as recontouring road berms to reestablish drainage patterns, vertical mulching (“planting” dead plant material

Chemical constituents of Cenchrus ciliaris L. from the Cholistan desert, Pakistan

OpenAIRE

Ashraf Muhammad Aqeel; Mahmood Karamat; Yusoff Ismail; Qureshi Ahmad Kaleem

2013-01-01

The Cholistan Desert is an extension of the Great Indian Desert, covering an area of 26,330 km2. The desert can be divided into two main geomorphic regions: the northern region, known as Lesser Cholistan, constituting the desert margin and consisting of a series of saline alluvial flats alternating with low sand ridges/dunes; and the southern region, known as Greater Cholistan, a wind-resorted sandy desert comprised of a number of old Hakra River terraces w...

Water developments and canids in two North American deserts: a test of the indirect effect of water hypothesis.

Directory of Open Access Journals (Sweden)

Lucas K Hall

Full Text Available Anthropogenic modifications to landscapes intended to benefit wildlife may negatively influence wildlife communities. Anthropogenic provisioning of free water (water developments to enhance abundance and distribution of wildlife is a common management practice in arid regions where water is limiting. Despite the long-term and widespread use of water developments, little is known about how they influence native species. Water developments may negatively influence arid-adapted species (e.g., kit fox, Vulpes macrotis by enabling water-dependent competitors (e.g., coyote, Canis latrans to expand distribution in arid landscapes (i.e., indirect effect of water hypothesis. We tested the two predictions of the indirect effect of water hypothesis (i.e., coyotes will visit areas with free water more frequently and kit foxes will spatially and temporally avoid coyotes and evaluated relative use of free water by canids in the Great Basin and Mojave Deserts from 2010 to 2012. We established scent stations in areas with (wet and without (dry free water and monitored visitation by canids to these sites and visitation to water sources using infrared-triggered cameras. There was no difference in the proportions of visits to scent stations in wet or dry areas by coyotes or kit foxes at either study area. We did not detect spatial (no negative correlation between visits to scent stations or temporal (no difference between times when stations were visited segregation between coyotes and kit foxes. Visitation to water sources was not different for coyotes between study areas, but kit foxes visited water sources more in Mojave than Great Basin. Our results did not support the indirect effect of water hypothesis in the Great Basin or Mojave Deserts for these two canids.

Fault tectonics and earthquake hazards in parts of southern California. [penninsular ranges, Garlock fault, Salton Trough area, and western Mojave Desert

Science.gov (United States)

Merifield, P. M. (Principal Investigator); Lamar, D. L.; Gazley, C., Jr.; Lamar, J. V.; Stratton, R. H.

1976-01-01

The author has identified the following significant results. Four previously unknown faults were discovered in basement terrane of the Peninsular Ranges. These have been named the San Ysidro Creek fault, Thing Valley fault, Canyon City fault, and Warren Canyon fault. In addition fault gouge and breccia were recognized along the San Diego River fault. Study of features on Skylab imagery and review of geologic and seismic data suggest that the risk of a damaging earthquake is greater along the northwestern portion of the Elsinore fault than along the southeastern portion. Physiographic indicators of active faulting along the Garlock fault identifiable in Skylab imagery include scarps, linear ridges, shutter ridges, faceted ridges, linear valleys, undrained depressions and offset drainage. The following previously unrecognized fault segments are postulated for the Salton Trough Area: (1) An extension of a previously known fault in the San Andreas fault set located southeast of the Salton Sea; (2) An extension of the active San Jacinto fault zone along a tonal change in cultivated fields across Mexicali Valley ( the tonal change may represent different soil conditions along opposite sides of a fault). For the Skylab and LANDSAT images studied, pseudocolor transformations offer no advantages over the original images in the recognition of faults in Skylab and LANDSAT images. Alluvial deposits of different ages, a marble unit and iron oxide gossans of the Mojave Mining District are more readily differentiated on images prepared from ratios of individual bands of the S-192 multispectral scanner data. The San Andreas fault was also made more distinct in the 8/2 and 9/2 band ratios by enhancement of vegetation differences on opposite sides of the fault. Preliminary analysis indicates a significant earth resources potential for the discrimination of soil and rock types, including mineral alteration zones. This application should be actively pursued.

The source, discharge, and chemical characteristics of selected springs, and the abundance and health of associated endemic anuran species in the Mojave network parks

Science.gov (United States)

Schroeder, Roy A.; Smith, Gregory A.; Martin, Peter; Flint, Alan L.; Gallegos, Elizabeth; Fisher, Robert N.; Martin, Peter; Schroeder, Roy A.

2015-01-01

Hydrological and biological investigations were done during 2005 and 2006 in cooperation with the U.S. National Park Service to investigate the source, discharge, and chemical characteristics of selected springs and the abundance and health of endemic anuran (frog and toad) species at Darwin Falls in Death Valley National Park, Piute Spring in Mojave National Preserve, and Fortynine Palms Oasis in Joshua Tree National Park. Discharge from the springs at these sites sustains isolated riparian habitats in the normally dry Mojave Desert. Data were collected on water quantity (discharge) and quality, air and water temperature, and abundance and health of endemic anuran species. In addition, a single survey of the abundance and health of endemic anuran species was completed at Rattlesnake Canyon in Joshua Tree National Park. Results from this study were compared to limited historical data, where they exist, and can provide a baseline for future hydrological and biological investigations to evaluate the health and sustainability of the resource and its response to changing climate and increasing human use.

Large-scale gravity sliding in the Miocene Shadow Valley Supradetachment Basin, Eastern Mojave Desert, California

Science.gov (United States)

Davis, G. A.; Friedmann, S. J.

2005-12-01

The Miocene Shadow Valley basin in the eastern Mojave Desert of California developed above the active west-dipping Kingston Range-Halloran Hills extensional detachment fault system between 13.5 and ca. 7 mybp. Although mass-wasting processes are common phenomena in supradetachment basins, the Shadow Valley basin is an exceptional locale for the study of such processes, especially rock-avalanches and gravity sliding. A score of megabreccias, interpreted as rock-avalanche deposits, and half that number of very large (> 1 km 2, up to 200 m thick), internally intact gravity-driven slide sheets are interbedded with various sedimentary facies. The slide sheets, variably composed of Proterozoic crystalline rocks and Proterozoic, Paleozoic, and Tertiary sedimentary strata, moved across both depositional and erosional surfaces in the basin. Although the majority consist of Paleozoic carbonate rocks, the largest slide sheet, the Eastern Star crystalline allochthon, contains Proterozoic gneisses and their sedimentary cover and is now preserved as klippen atop Miocene lacustrine and alluvial fan deposits over an area > 40 km 2. Estimates of slide sheet runouts into the basin from higher eastern and northern source terranes range from approximately a few km to > 10 km; in most cases the exact provenances of the slide blocks are not known. The basal contacts of Shadow Valley slide sheets are characteristically knife sharp, show few signs of lithologic mixing of upper- and lower-plate rocks, and locally exhibit slickensided and striated, planar fault-like bases. Pronounced folding of overridden Miocene lacustrine and fan deposits beneath the Eastern Star allochthon extends to depths up to 40 m at widely scattered localities. We conclude that this slow moving slide sheet encountered isolated topographic asperities (hills) and that stress transfer across the basal slide surface produced folding of footwall strata. Synkinematic gypsum veins in footwall playa sediments, with fibers

The Agassiz's desert tortoise genome provides a resource for the conservation of a threatened species.

Directory of Open Access Journals (Sweden)

Marc Tollis

Full Text Available Agassiz's desert tortoise (Gopherus agassizii is a long-lived species native to the Mojave Desert and is listed as threatened under the US Endangered Species Act. To aid conservation efforts for preserving the genetic diversity of this species, we generated a whole genome reference sequence with an annotation based on deep transcriptome sequences of adult skeletal muscle, lung, brain, and blood. The draft genome assembly for G. agassizii has a scaffold N50 length of 252 kbp and a total length of 2.4 Gbp. Genome annotation reveals 20,172 protein-coding genes in the G. agassizii assembly, and that gene structure is more similar to chicken than other turtles. We provide a series of comparative analyses demonstrating (1 that turtles are among the slowest-evolving genome-enabled reptiles, (2 amino acid changes in genes controlling desert tortoise traits such as shell development, longevity and osmoregulation, and (3 fixed variants across the Gopherus species complex in genes related to desert adaptations, including circadian rhythm and innate immune response. This G. agassizii genome reference and annotation is the first such resource for any tortoise, and will serve as a foundation for future analysis of the genetic basis of adaptations to the desert environment, allow for investigation into genomic factors affecting tortoise health, disease and longevity, and serve as a valuable resource for additional studies in this species complex.

Impacts of upper respiratory tract disease on olfactory behavior of the Mojave desert tortoise

Science.gov (United States)

Germano, Jennifer; Van Zerr, Vanessa E.; Esque, Todd C.; Nussear, Ken E.; Lamberski, Nadine

2014-01-01

Upper respiratory tract disease (URTD) caused by Mycoplasma agassizii is considered a threat to desert tortoise populations that should be addressed as part of the recovery of the species. Clinical signs can be intermittent and include serous or mucoid nasal discharge and respiratory difficulty when nares are occluded. This nasal congestion may result in a loss of the olfactory sense. Turtles are known to use olfaction to identify food items, predators, and conspecifics; therefore, it is likely that URTD affects not only their physical well-being but also their behavior and ability to perform necessary functions in the wild. To determine more specifically the impact nasal discharge might have on free-ranging tortoises (Gopherus agassizii), we compared the responses of tortoises with and without nasal discharge and both positive and negative for M. agassizii antibodies to a visually hidden olfactory food stimulus and an empty control. We found that nasal discharge did reduce sense of smell and hence the ability to locate food. Our study also showed that moderate chronic nasal discharge in the absence of other clinical signs did not affect appetite in desert tortoises.

Cumulative biological impacts framework for solar energy projects in the California Desert

Science.gov (United States)

Davis, Frank W.; Kreitler, Jason R.; Soong, Oliver; Stoms, David M.; Dashiell, Stephanie; Hannah, Lee; Wilkinson, Whitney; Dingman, John

2013-01-01

This project developed analytical approaches, tools and geospatial data to support conservation planning for renewable energy development in the California deserts. Research focused on geographical analysis to avoid, minimize and mitigate the cumulative biological effects of utility-scale solar energy development. A hierarchical logic model was created to map the compatibility of new solar energy projects with current biological conservation values. The research indicated that the extent of compatible areas is much greater than the estimated land area required to achieve 2040 greenhouse gas reduction goals. Species distribution models were produced for 65 animal and plant species that were of potential conservation significance to the Desert Renewable Energy Conservation Plan process. These models mapped historical and projected future habitat suitability using 270 meter resolution climate grids. The results were integrated into analytical frameworks to locate potential sites for offsetting project impacts and evaluating the cumulative effects of multiple solar energy projects. Examples applying these frameworks in the Western Mojave Desert ecoregion show the potential of these publicly-available tools to assist regional planning efforts. Results also highlight the necessity to explicitly consider projected land use change and climate change when prioritizing areas for conservation and mitigation offsets. Project data, software and model results are all available online.

77 FR 16447 - Approval and Promulgation of Implementation Plans; Designation of Areas for Air Quality Planning...

Science.gov (United States)

2012-03-21

... County, Western Mojave Desert, South Coast Air Basin, Eastern Kern County, and San Diego County. DATES... April 30, 2004 final rule, we designated the Western Mojave Desert area as a moderate nonattainment area... reclassification of several areas for the 1997 8-hour ozone standard. See 75 FR 24409 (May 5, 2010). The Western...

[Seasonal variation of Tamarix ramosissima and Populus euphratica water potentials in southern fringe of Taklamakan Desert].

Science.gov (United States)

Zeng, Fanjiang; Zhang, Ximing; Li, Xiangyi; Foetzki, Andrea; Runge, Michael

2005-08-01

The measurement of the seasonal and diurnal variations of Tamarix ramosissima and Populus euphratica water potentials in the southern fringe of Taklamakan Desert indicated that there was no apparent water stress for the two species during their growth period, with little change of predawn water potential and some extent decrease of midday water potential. Irrigation once or thinning had no significant effects on the water status of the plants, while groundwater appeared to be a prerequisite for the survival and growth of these species. It is very important to ensure a stable groundwater table for the restoration of Tamarix ramosissima and Populus euphratica in this area.

Does a decade of elevated [CO2] affect a desert perennial plant community?

Science.gov (United States)

Newingham, Beth A; Vanier, Cheryl H; Kelly, Lauren J; Charlet, Therese N; Smith, Stanley D

2014-01-01

Understanding the effects of elevated [CO2 ] on plant community structure is crucial to predicting ecosystem responses to global change. Early predictions suggested that productivity in deserts would increase via enhanced water-use efficiency under elevated [CO2], but the response of intact arid plant communities to elevated [CO2 ] is largely unknown. We measured changes in perennial plant community characteristics (cover, species richness and diversity) after 10 yr of elevated [CO2] exposure in an intact Mojave Desert community at the Nevada Desert Free-Air CO2 Enrichment (FACE) Facility. Contrary to expectations, total cover, species richness, and diversity were not affected by elevated [CO2]. Over the course of the experiment, elevated [CO2] had no effect on changes in cover of the evergreen C3 shrub, Larrea tridentata; alleviated decreases in cover of the C4 bunchgrass, Pleuraphis rigida; and slightly reduced the cover of C3 drought-deciduous shrubs. Thus, we generally found no effect of elevated [CO2] on plant communities in this arid ecosystem. Extended drought, slow plant growth rates, and highly episodic germination and recruitment of new individuals explain the lack of strong perennial plant community shifts after a decade of elevated [CO2]. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Erosion Potential of a Burn Site in the Mojave-Great Basin Transition Zone: Interim Summary of One Year of Measurements

Energy Technology Data Exchange (ETDEWEB)

Etyemezian, V.; Shafer, D.; Miller, J.; Kavouras, I.; Campbell, S.; DuBois, D.; King, J.; Nikolich, G.; Zitzer, S.

2010-05-18

A historic return interval of 100 years for large fires in deserts in the Southwest U.S. is being replaced by one where fires may reoccur as frequently as every 20 to 30 years. This increase in fires has implications for management of Soil Sub-Project Corrective Action Units (CAUs) for which the Department of Energy, National Nuclear Security Administration Nevada Site office (NNSA/NSO) has responsibility. A series of studies has been initiated at uncontaminated analog sites to better understand the possible impacts of erosion and transport by wind and water should contaminated soil sites burn over to understand technical and perceived risk they might pose to site workers and public receptors in communities around the NTS, TTR, and NTTR; and to develop recommendations for stabilization and restoration after a fire. The first of these studies was undertaken at the Jacob fire, a lightning-caused fire approximately 12 kilometers north of Hiko, Nevada, that burned approximately 200 ha between August 6-8, 2008, and is representative of a transition zone on the NTS between the Mojave and Great Basin Deserts, where the largest number of Soil Sub-Project CAUs/CASs are located.

Groundwater-quality data in the Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts study unit, 2008-2010--Results from the California GAMA Program

Science.gov (United States)

Mathany, Timothy M.; Wright, Michael T.; Beuttel, Brandon S.; Belitz, Kenneth

2012-01-01

Groundwater quality in the 12,103-square-mile Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts (CLUB) study unit was investigated by the U.S. Geological Survey (USGS) from December 2008 to March 2010, as part of the California State Water Resources Control Board (SWRCB) Groundwater Ambient Monitoring and Assessment (GAMA) Program's Priority Basin Project (PBP). The GAMA-PBP was developed in response to the California Groundwater Quality Monitoring Act of 2001 and is being conducted in collaboration with the SWRCB and Lawrence Livermore National Laboratory (LLNL). The CLUB study unit was the twenty-eighth study unit to be sampled as part of the GAMA-PBP. The GAMA CLUB study was designed to provide a spatially unbiased assessment of untreated-groundwater quality in the primary aquifer systems, and to facilitate statistically consistent comparisons of untreated-groundwater quality throughout California. The primary aquifer systems (hereinafter referred to as primary aquifers) are defined as parts of aquifers corresponding to the perforation intervals of wells listed in the California Department of Public Health (CDPH) database for the CLUB study unit. The quality of groundwater in shallow or deep water-bearing zones may differ from the quality of groundwater in the primary aquifers; shallow groundwater may be more vulnerable to surficial contamination. In the CLUB study unit, groundwater samples were collected from 52 wells in 3 study areas (Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts) in San Bernardino, Riverside, Kern, San Diego, and Imperial Counties. Forty-nine of the wells were selected by using a spatially distributed, randomized grid-based method to provide statistical representation of the study unit (grid wells), and three wells were selected to aid in evaluation of water-quality issues (understanding wells). The groundwater samples were analyzed for organic constituents (volatile

Approved wind energy sites - Kern County, CA (Tehachapi Mountains)

Energy Technology Data Exchange (ETDEWEB)

1984-01-01

Rising out of the California desert near Mojave, California, are the Tehachapi Mountains - a rugged chain of wind swept hills. Up until 1981, this land was used almost exclusively by local ranchers for grazing beef cattle. But, in a raging December blizzard, a dedicated band of men and women threw the switch and fed the first wind-generated electrical power into Southern California Edison's grid. That single event drastically changed land use patterns in the Tehachapi's.

The Mormon Peak and Tule Springs Detachments of Southern Nevada and Their Role in Interpreting the Subsurface Structure of the Sevier Desert Basin

Science.gov (United States)

Wernicke, B.; Axen, G. J.

2007-12-01

The eastern Sevier front is commonly overprinted by west-dipping normal faults that have been active through much of Cenozoic time. Although examples of disparate age and geometry abound, the Sevier Desert detachment stands out as being: (1) a very large, low-angle structure, (2) probably still active, and (3) at drillable depth, and hence is a prime target for scientific drilling. Among the closest surface-exposed analogs of the detachment are the Miocene Mormon Peak and Tule Springs detachments in southern Nevada, about 250 km SSW of the Sevier Desert. In both areas, the detachments developed within a few km of the basal Sevier thrust. The few traces of the southern Nevada detachments that were identified by reconnaissance mapping in the 1950s were first interpreted as underlying "rootless" gravity-slide masses. Detailed stratigraphic and structural mapping in the 1980s revealed the full extent of these detachments and their close relationship to the basal Sevier thrust. Construction and retrodeformation of cross sections through the two detachments demonstrated that neither fault could represent the base of a surficial slide mass. The key field relationship is the structural contiguity of the hanging walls of the detachments with large mountain range blocks in their down-dip directions. "Rootless" gravity-driven masses of equivalent or larger scale are widely documented, and in contrast to the southern Nevada detachments show clear evidence along their down-dip portions of either riding over the earth's surface (e.g. Heart Mountain, WY; Shadow Valley, CA) or having been internally shortened (e.g. Bearpaw Mountains, MT; Louisiana shelf). A rootless slide origin for the Mormon Peak detachment has been revived based on meso- and microstructural analysis of the fault surface (refs. 1, 2, and 3), but the hypothesis still fails the retrodeformation test at macroscopic scale. The retrodefomed sections indicate that the footwalls of the southern Nevada detachments

From Fireproof Desert to Flammable Grassland: Buffelgrass Invasion in the Sonoran Desert

Science.gov (United States)

Betancourt, J. L.

2007-12-01

Only a few decades ago, the Sonoran Desert of northwestern Mexico and southern Arizona was considered mostly fireproof, a case of not enough fine fuel to connect the dominant shrubs and cacti. This has changed with invasions by non-native, winter annual and summer-flower perennial grasses that are rapidly transforming fireproof desert into flammable grassland. Of particular concern is buffelgrass, Pennisetum ciliare, a fire-prone and invasive African perennial grass that has already converted millions of hectares across Sonora since the mid-1960s and has made quick headway in southern and central Arizona beginning in the 1980s. Near Tucson and Phoenix, AZ, buffelgrass invasion is proceeding exponentially, with population expansion (and the costs of mitigation) more than doubling every year. As this conversion progresses, there will be increased fire risks, lost tourist revenue, diminished property values, insurmountable setbacks to conservation efforts, and the threat of large ignition fronts in desert valleys routinely spreading into the mountains. Although somewhat belated, an integrated, multi-jurisdictional effort is being organized to reduce ecological and economic impacts. My presentation will summarize the history and context of buffelgrass introduction and invasion, the disconnect in attitudes and policies across state and international boundaries, ongoing management efforts, the role of science and responsibilities of scientists, accelerated spread with changing climate, and impacts to regional ecosystems and economies. This narrative may serve as a template for other semi-arid lands where buffelgrass and similar grasses have become invasive, including Australia, South America, and many islands in the Pacific Ocean (including Hawaii), Indian Ocean, and Caribbean Sea.

Lunar polar rover science operations: Lessons learned and mission architecture implications derived from the Mojave Volatiles Prospector (MVP) terrestrial field campaign

Science.gov (United States)

Heldmann, Jennifer L.; Colaprete, Anthony; Elphic, Richard C.; Lim, Darlene; Deans, Matthew; Cook, Amanda; Roush, Ted; Skok, J. R.; Button, Nicole E.; Karunatillake, S.; Stoker, Carol; Marquez, Jessica J.; Shirley, Mark; Kobayashi, Linda; Lees, David; Bresina, John; Hunt, Rusty

2016-08-01

The Mojave Volatiles Prospector (MVP) project is a science-driven field program with the goal of producing critical knowledge for conducting robotic exploration of the Moon. Specifically, MVP focuses on studying a lunar mission analog to characterize the form and distribution of lunar volatiles. Although lunar volatiles are known to be present near the poles of the Moon, the three dimensional distribution and physical characteristics of lunar polar volatiles are largely unknown. A landed mission with the ability to traverse the lunar surface is thus required to characterize the spatial distribution of lunar polar volatiles. NASA's Resource Prospector (RP) mission is a lunar polar rover mission that will operate primarily in sunlit regions near a lunar pole with near-real time operations to characterize the vertical and horizontal distribution of volatiles. The MVP project was conducted as a field campaign relevant to the RP lunar mission to provide science, payload, and operational lessons learned to the development of a real-time, short-duration lunar polar volatiles prospecting mission. To achieve these goals, the MVP project conducted a simulated lunar rover mission to investigate the composition and distribution of surface and subsurface volatiles in a natural environment with an unknown volatile distribution within the Mojave Desert, improving our understanding of how to find, characterize, and access volatiles on the Moon.

Estimating Natural Recharge in a Desert Environment Facing Increasing Ground-Water Demands

Science.gov (United States)

Nishikawa, T.; Izbicki, J. A.; Hevesi, J. A.; Martin, P.

2004-12-01

Ground water historically has been the sole source of water supply for the community of Joshua Tree in the Joshua Tree ground-water subbasin of the Morongo ground-water basin in the southern Mojave Desert. Joshua Basin Water District (JBWD) supplies water to the community from the underlying Joshua Tree ground-water subbasin, and ground-water withdrawals averaging about 960 acre-ft/yr have resulted in as much as 35 ft of drawdown. As growth continues in the desert, ground-water resources may need to be supplemented using imported water. To help meet future demands, JBWD plans to construct production wells in the adjacent Copper Mountain ground-water subbasin. To manage the ground-water resources and to identify future mitigating measures, a thorough understanding of the ground-water system is needed. To this end, field and numerical techniques were applied to determine the distribution and quantity of natural recharge. Field techniques included the installation of instrumented boreholes in selected washes and at a nearby control site. Numerical techniques included the use of a distributed-parameter watershed model and a ground-water flow model. The results from the field techniques indicated that as much as 70 acre-ft/yr of water infiltrated downward through the two principal washes during the study period (2001-3). The results from the watershed model indicated that the average annual recharge in the ground-water subbasins is about 160 acre-ft/yr. The results from the calibrated ground-water flow model indicated that the average annual recharge for the same area is about 125 acre-ft/yr. Although the field and numerical techniques were applied to different scales (local vs. large), all indicate that natural recharge in the Joshua Tree area is very limited; therefore, careful management of the limited ground-water resources is needed. Moreover, the calibrated model can now be used to estimate the effects of different water-management strategies on the ground

Environmental Assessment/Overseas Environmental Assessment for the F-35 Joint Strike Fighter Initial Operational Test and Evaluation

Science.gov (United States)

2009-09-01

shrub layer. White fir (Abies concolor) occurs at elevations above approximately 8,000 feet, with single leaf pinyon ( Pinus monophylla) and limber...pine ( Pinus flexilis). The South Range lies in the northeastern portion of the Mojave Desert. Creosote bush, white bursage, and saltbush...pools of water, of sufficient extent, to sustain populations during drought . Wildlife species associated with Mojave Desert habitats found in the

Inventory of Amphibians and Reptiles at Mojave National Preserve: Final Report

Science.gov (United States)

Persons, Trevor B.; Nowak, Erika M.

2007-01-01

As part of the National Park Service Inventory and Monitoring Program in the Mojave Network, we conducted an inventory of amphibians and reptiles at Mojave National Preserve in 2004-2005. Objectives for this inventory were to use fieldwork, museum collections, and literature review to document the occurrence of reptile and amphibian species occurring at MOJA. Our goals were to document at least 90% of the species present, provide one voucher specimen for each species identified, provide GIS-referenced distribution information for sensitive species, and provide all deliverables, including NPSpecies entries, as outlined in the Mojave Network Biological Inventory Study Plan. Methods included daytime and nighttime visual encounter surveys and nighttime road driving. Survey effort was concentrated in predetermined priority sampling areas, as well as in areas with a high potential for detecting undocumented species. We recorded 31 species during our surveys. During literature review and museum specimen database searches, we found records for seven additional species from MOJA, elevating the documented species list to 38 (two amphibians and 36 reptiles). Based on our surveys, as well as literature and museum specimen review, we estimate an overall inventory completeness of 95% for Mojave National Preserve herpetofauna; 67% for amphibians and 97% for reptiles.

76 FR 27344 - Water Resources Management Plan/Environmental Impact Statement, Mojave National Preserve, San...

Science.gov (United States)

2011-05-11

... and resource management activities must be guided by general principles that can be applied to... Resources Management Plan/Environmental Impact Statement, Mojave National Preserve, San Bernardino County... Management Plan/ Environmental Impact Statement for Mojave National Preserve. SUMMARY: In accordance with Sec...

Origins and ecological consequences of pollen specialization among desert bees.

Science.gov (United States)

Minckley, R L; Cane, J H; Kervin, L

2000-02-07

An understanding of the evolutionary origins of insect foraging specialization is often hindered by a poor biogeographical and palaeoecological record. The historical biogeography (20,000 years before present to the present) of the desert-limited plant, creosote bush (Larrea tridentata), is remarkably complete. This history coupled with the distribution pattern of its bee fauna suggests pollen specialization for creosote bush pollen has evolved repeatedly among bees in the Lower Sonoran and Mojave deserts. In these highly xeric, floristically depauperate environments, species of specialist bees surpass generalist bees in diversity, biomass and abundance. The ability of specialist bees to facultatively remain in diapause through resource-poor years and to emerge synchronously with host plant bloom in resource-rich years probably explains their ecological dominance and persistence in these areas. Repeated origins of pollen specialization to one host plant where bloom occurs least predictably is a counter-example to prevailing theories that postulate such traits originate where the plant grows best and blooms most reliably Host-plant synchronization, a paucity of alternative floral hosts, or flowering attributes of creosote bush alone or in concert may account for the diversity of bee specialists that depend on this plant instead of nutritional factors or chemical coevolution between floral rewards and the pollinators they have evolved to attract.

Air-Surface-Ground Water Cycling in an Agricultural Desert Valley of Southern Colorado

Science.gov (United States)

Lanzoni, M.

2017-12-01

In dryland areas around the world, vegetation plays an important role in stabilizing soil and encouraging recharge. In the Colorado high desert of the San Luis Valley, windstorms strip away topsoil and deposit dust on the surrounding mountain snowpack. Dust-on-snow lowers albedo and hastens melting, which in turn lowers infiltration and aquifer recharge. Since the 1990s, the San Luis Valley has experienced a sharp decline in aquifer levels due to over-development of its water resources. Where agricultural abstraction is significant, the unconfined aquifer has experienced a 9 m (30 ft) drop. Over the course of three years, this dryland hydrology study analyzed rain, snow, surface and ground water across a 20,000 km2 high desert area to establish a baseline of water inputs. δ18O and δ2H were analyzed to develop a LMWL specific to this region of the southern Rockies and isotopic differences were examined in relation to chemistry to understand environmental influences on meteoric waters. This work identifies a repeating pattern of acid rainfall with trace element contaminants, including actinides.To better understand how the area's dominant vegetation responds to a lowered water table, 76 stem water samples were collected from the facultative phreatophyte shrubs E. nauseosa and S. vermiculatus over the summer, fall, spring, and summer of 2015 and 2016 from study plots chosen for increasing depths to groundwater. This research shows distinct patterns of water capture strategy and seasonal shifts among the E. nauseosa and S. vermiculatus shrubs. These differences are most apparent where groundwater is most accessible. However, where the water table has dropped 6 m (20 feet) over the last decade, both E. nauseosa and S. vermiculatus survive only on near-surface snowmelt and rain.

Mapping Palaeohydrography in Deserts: Contribution from Space-Borne Imaging Radar

Directory of Open Access Journals (Sweden)

Philippe Paillou

2017-03-01

Full Text Available Space-borne Synthetic Aperture Radar (SAR has the capability to image subsurface features down to several meters in arid regions. A first demonstration of this capability was performed in the Egyptian desert during the early eighties, thanks to the first Shuttle Imaging Radar mission. Global coverage provided by recent SARs, such as the Japanese ALOS/PALSAR sensor, allowed the mapping of vast ancient hydrographic systems in Northern Africa. We present a summary of palaeohydrography results obtained using PALSAR data over large deserts such as the Sahara and the Gobi. An ancient river system was discovered in eastern Lybia, connecting in the past the Kufrah oasis to the Mediterranean Sea, and the terminal part of the Tamanrasett river was mapped in western Mauritania, ending with a large submarine canyon. In southern Mongolia, PALSAR images combined with topography analysis allowed the mapping of the ancient Ulaan Nuur lake. We finally show the potentials of future low frequency SAR sensors by comparing L-band (1.25 GHz and P-band (435 MHz airborne SAR acquisitions over a desert site in southern Tunisia.

Modeling Soil Moisture in Support of the Revegetation of Military Lands in Arid Regions.

Science.gov (United States)

Caldwell, T. G.; McDonald, E. V.; Young, M. H.

2003-12-01

The National Training Center (NTC), the Army's primary mechanized maneuver training facility, covers approximately 2600 km2 within the Mojave Desert in southern California, and is the subject of ongoing studies to support the sustainability of military lands in desert environments. Revegetation of these lands by the Integrated Training Areas Management (ITAM) Program requires the identification of optimum growing conditions to reestablish desert vegetation from seed and seedling, especially with regard to the timing and abundance of plant-available water. Water content, soil water potential, and soil temperature were continuously monitored and used to calibrate the Simultaneous Heat And Water (SHAW) model at 3 re-seeded sites. Modeled irrigation scenarios were used to further evaluate the most effective volume, frequency, and timing of irrigation required to maximize revegetation success and minimize water use. Surface treatments including straw mulch, gravel mulch, soil tackifier and plastic sheet

76 FR 45606 - Desert Renewable Energy Conservation Plan, Habitat Conservation Plan and Possible Land Use Plan...

Science.gov (United States)

2011-07-29

...-N131; 80221-1112-80221-F2] Desert Renewable Energy Conservation Plan, Habitat Conservation Plan and Possible Land Use Plan Amendment, Southern California: Environmental Impact Statement AGENCY: Fish and..., as amended, for the proposed Desert Renewable Energy Conservation Plan (DRECP). The EIS will be a...

A potential predator-prey interaction of an American badger and an Agassiz's desert tortoise with a review of badger predation on turtles

Science.gov (United States)

Smith, Amanda L.; Puffer, Shellie R.; Lovich, Jeffrey E.; Tennant, Laura A.; Arundel, Terry; Vamstad, Michael S.; Brundige, Kathleen D.

2016-01-01

The federally threatened Agassiz’s desert tortoise (Gopherus agassizii) was listed under the U.S. Endangered Species Act in 1990, but thus far, recovery efforts have been unsuccessful (U.S. Fish and Wildlife Service [USFWS] 2015). Predation has been identified as a contributing factor to declining G. agassizii populations range-wide (e.g., Esque et al. 2010, Lovich et al. 2014). Understanding and managing for predator-prey dynamics is thus an important part of the recovery and conservation of this threatened species (USFWS 2011). Desert tortoises have a host of predators at all stages of their life cycle. Over 20 species of birds, mammals, and reptiles have been recorded as known or suspected predators (Woodbury and Hardy 1948, Luckenbach 1982, Ernst and Lovich 2009). American badgers (Taxidea taxus, family: Mustelidae) are confirmed excavators of desert tortoise nests (Turner and Berry 1984). They are also suspected predators of adult desert tortoises, a possibility which has been presented in some studies but without empirical verification (Luckenbach 1982, Turner and Berry 1984). Active mostly at night, badgers are solitary, secretive predators (Lindzey 1978, 1982; Armitage 2004) that are extremely difficult to observe in predatory encounters. Recently, strong circumstantial evidence presented by Emblidge et al. (2015) suggests that badgers do prey on adult Agassiz’s desert tortoises based on observations of more than two dozen dead tortoises in the Western Mojave Desert of California. In this note, we present another case of potential badger predation on a large adult desert tortoise in the Sonoran Desert of California. Collectively, these recent two cases potentially indicate that badger predation may be more common and widespread than previously thought. In addition, we review the worldwide literature of badger predation on turtles in general and summarize reported badger observations in Joshua Tree National Park, where our observation occurred, over a

Chihuahuan Deserts Ecoregion: Chapter 27 in Status and trends of land change in the Western United States--1973 to 2000

Science.gov (United States)

Ruhlman, Jana; Gass, Leila; Middleton, Barry

2012-01-01

The Chihuahuan Desert is the largest of the North American deserts, extending from southern New Mexico and Texas deep into Mexico, with approximately 90 percent of its area falling south of the United States–Mexico border (Lowe, 1964, p. 24). The Chihuahuan Deserts Ecoregion covers approximately 174,472 km2 (67,364 mi2) within the United States, including much of west Texas, southern New Mexico, and a small portion of southeastern Arizona (Omernik, 1987; U.S. Environmental Protection Agency, 1997). The ecoregion is generally oriented from northwest to southeast, with the Madrean Archipelago Ecoregion to the west; the Arizona/New Mexico Mountains, Arizona/New Mexico Plateau, Southwestern Tablelands, and Western High Plains Ecoregions to the north; and the Edwards Plateau and Southern Texas Plains Ecoregions to the east (fig. 1).

Response of the desert shrub Krameria parvifolia after ten years of chronic gamma irradiation

International Nuclear Information System (INIS)

Vollmer, A.T.; Bamberg, S.A.

1975-01-01

A northern Mojave Desert shrub community was irradiated by a 137 Cs source for a ten-year period. Leaf and fruit production, cover, and percent live stem of Krameria parvifolia shrubs were found to respond significantly to a radiation gradient with exposure rates ranging from 0.1 to 10 R/day. Fruit and leaf production were greatly reduced at exposures over 6 R/day. Above 7 R/day 16% of the shrubs were dead compared to 1.2% in a non-irradiated area. Reduced cover, density and live stem values indicate a trend toward a lower status of Krameria in the community at cumulative exposures above 25 kR. Observations indicate that an equilibrium in response to irradiation has not yet occurred. Radiosensitivity of K. parvifolia is attributed in part to its phenology. (author)

Response of the desert shrub Krameria parvifolia after ten years of chronic gamma irradiation

Energy Technology Data Exchange (ETDEWEB)

Vollmer, A T; Bamberg, S A [California Univ., Los Angeles (USA). Lab. of Nuclear Medicine and Radiation Biology

1975-12-01

A northern Mojave Desert shrub community was irradiated by a /sup 137/Cs source for a ten-year period. Leaf and fruit production, cover, and percent live stem of Krameria parvifolia shrubs were found to respond significantly to a radiation gradient with exposure rates ranging from 0.1 to 10 R/day. Fruit and leaf production were greatly reduced at exposures over 6 R/day. Above 7 R/day 16% of the shrubs were dead compared to 1.2% in a non-irradiated area. Reduced cover, density and live stem values indicate a trend toward a lower status of Krameria in the community at cumulative exposures above 25 kR. Observations indicate that an equilibrium in response to irradiation has not yet occurred. Radiosensitivity of K. parvifolia is attributed in part to its phenology.

Cumulative drought and land-use impacts on perennial vegetation across a North American dryland region

Science.gov (United States)

Munson, Seth M.; Long, A. Lexine; Wallace, Cynthia; Webb, Robert H.

2016-01-01

Question The decline and loss of perennial vegetation in dryland ecosystems due to global change pressures can alter ecosystem properties and initiate land degradation processes. We tracked changes of perennial vegetation using remote sensing to address the question of how prolonged drought and land-use intensification have affected perennial vegetation cover across a desert region in the early 21st century? Location Mojave Desert, southeastern California, southern Nevada, southwestern Utah and northwestern Arizona, USA. Methods We coupled the Moderate-Resolution Imaging Spectroradiometer Enhanced Vegetation Index (MODIS-EVI) with ground-based measurements of perennial vegetation cover taken in about 2000 and about 2010. Using the difference between these years, we determined perennial vegetation changes in the early 21st century and related these shifts to climate, soil and landscape properties, and patterns of land use. Results We found a good fit between MODIS-EVI and perennial vegetation cover (2000: R2 = 0.83 and 2010: R2 = 0.74). The southwestern, far southeastern and central Mojave Desert had large declines in perennial vegetation cover in the early 21st century, while the northeastern and southeastern portions of the desert had increases. These changes were explained by 10-yr precipitation anomalies, particularly in the cool season and during extreme dry or wet years. Areas heavily impacted by visitor use or wildfire lost perennial vegetation cover, and vegetation in protected areas increased to a greater degree than in unprotected areas. Conclusions We find that we can extrapolate previously documented declines of perennial plant cover to an entire desert, and demonstrate that prolonged water shortages coupled with land-use intensification create identifiable patterns of vegetation change in dryland regions.

76 FR 53482 - Endangered and Threatened Wildlife and Plants; Notice of Availability of a Revised Recovery Plan...

Science.gov (United States)

2011-08-26

... and revised the recovery plan accordingly. The desert tortoise is a large, herbivorous reptile that... tortoise populations. Disease and increased incidence of fire in the Mojave Desert have also been... tortoises, there are few data available to evaluate or quantify the effects of threats on desert tortoise...

Supplementing seed banks to rehabilitate disturbed Mojave Desert shrublands: where do all the seeds go?

Science.gov (United States)

DeFalco, Lesley A.; Esque, Todd C.; Nicklas, Melissa B.; Kane, Jeffrey M.

2012-01-01

Revegetation of degraded arid lands often involves supplementing impoverished seed banks and improving the seedbed, yet these approaches frequently fail. To understand these failures, we tracked the fates of seeds for six shrub species that were broadcast across two contrasting surface disturbances common to the Mojave Desert—sites compacted by concentrated vehicle use and trenched sites where topsoil and subsurface soils were mixed. We evaluated seedbed treatments that enhance soil-seed contact (tackifier) and create surface roughness while reducing soil bulk density (harrowing). We also explored whether seed harvesting by granivores and seedling suppression by non-native annuals influence the success of broadcast seeding in revegetating degraded shrublands. Ten weeks after treatments, seeds readily moved off of experimental plots in untreated compacted sites, but seed movements were reduced 32% by tackifier and 55% through harrowing. Harrowing promoted seedling emergence in compacted sites, particularly for the early-colonizing species Encelia farinosa, but tackifier was largely ineffective. The inherent surface roughness of trenched sites retained three times the number of seeds than compacted sites, but soil mixing during trench development likely altered the suitability of the seedbed thus resulting in poor seedling emergence. Non-native annuals had little influence on seed fates during our study. In contrast, the prevalence of harvester ants increased seed removal on compacted sites, whereas rodent activity influenced removal on trenched sites. Future success of broadcast seeding in arid lands depends on evaluating disturbance characteristics prior to seeding and selecting appropriate species and seasons for application.

Palynology in a polar desert, eastern North Greenland

DEFF Research Database (Denmark)

Funder, Svend Visby; Abrahamsen, Niels

1988-01-01

history back to c. 7,000 years calBP (6,000 years convBP) in this·extreme environment, which presents the coldest thermal regime where vascular plants can grow. The diagram shows that polar desert developed from sparse high arctic tundra at c. 4,300 years calBP (3,900 years convBP), owing...... to reduced summer heat. Also adjacent parts of high arctic Greenland, Canada and Svalbard suffered environmental decline, and polar deserts- presently restricted to a narrow fringe of land at the shores of the Arctic Ocean-were even more restricted before this time. Like other arctic vegetation types, polar...... desert is highly sensitive to summer temperatures, and its southern limit coincides with the isotherm for mean July temperatures of 3.5'C, A comparison with the Northwest European ice-age pollen record shows no evidence of summers as cold as those now prevailing in the extreme north, and the results...

Tree planting in deserts and utilization of atomic energy

International Nuclear Information System (INIS)

Hattori, Sadao; Minato, Akio; Hashizume, Kenichi; Handa, Norihiko.

1991-01-01

Global environment problems are discussed actively, concretely, those are the warming of the earth, the advance of desertification, the damage due to acid rain, the decrease of tropical forests, the pollution of sea, the depletion of ozone layer and so on. Most of these phenomena advance gradually. However, the advance of desertification is different from other phenomena in that the people in the areas concerned are deprived of their living space and even their lives are threatened at this moment. Desertification is advancing on global scale, and its rate is estimated to be 60,000 km 2 yearly. Especially the area where the advance is remarkable is the southern edge of Sahara Desert, which advances southward at 10-30 km in one year. Recently also in Japan, the interest in the prevention of desertification has become high, and the experiment on tree planting in a desert using a huge desert dome of the Institute of Physical and Chemical Research, 'Desert Aquanet concept' of Shimizu Construction Co., Ltd., 'Sahara green belt project' of the Ministry of International Trade and Industry and so on were published. Water and energy for tree planting in deserts, utilization of atomic energy for seawater desalination and the technical fields to which Japan can contribute are reported. (K.I.)

Tree planting in deserts and utilization of atomic energy

Energy Technology Data Exchange (ETDEWEB)

Hattori, Sadao; Minato, Akio [Central Research Inst. of Electric Power Industry, Tokyo (Japan); Hashizume, Kenichi; Handa, Norihiko

1991-06-01

Global environment problems are discussed actively, concretely, those are the warming of the earth, the advance of desertification, the damage due to acid rain, the decrease of tropical forests, the pollution of sea, the depletion of ozone layer and so on. Most of these phenomena advance gradually. However, the advance of desertification is different from other phenomena in that the people in the areas concerned are deprived of their living space and even their lives are threatened at this moment. Desertification is advancing on global scale, and its rate is estimated to be 60,000 km{sup 2} yearly. Especially the area where the advance is remarkable is the southern edge of Sahara Desert, which advances southward at 10-30 km in one year. Recently also in Japan, the interest in the prevention of desertification has become high, and the experiment on tree planting in a desert using a huge desert dome of the Institute of Physical and Chemical Research, 'Desert Aquanet concept' of Shimizu Construction Co., Ltd., 'Sahara green belt project' of the Ministry of International Trade and Industry and so on were published. Water and energy for tree planting in deserts, utilization of atomic energy for seawater desalination and the technical fields to which Japan can contribute are reported. (K.I.).

The role of fire on soil mounds and surface roughness in the Mojave Desert

Science.gov (United States)

Soulard, Christopher E.; Esque, Todd C.; Bedford, David R.; Bond, Sandra

2013-01-01

A fundamental question in arid land management centers on understanding the long-term effects of fire on desert ecosystems. To assess the effects of fire on surface topography, soil roughness, and vegetation, we used terrestrial (ground-based) LiDAR to quantify the differences between burned and unburned surfaces by creating a series of high-resolution vegetation structure and bare-earth surface models for six sample plots in the Grand Canyon-Parashant National Monument, Arizona. We find that 11 years following prescribed burns, mound volumes, plant heights, and soil-surface roughness were significantly lower on burned relative to unburned plots. Results also suggest a linkage between vegetation and soil mounds, either through accretion or erosion mechanisms such as wind and/or water erosion. The biogeomorphic implications of fire-induced changes are significant. Reduced plant cover and altered soil surfaces from fire likely influence seed residence times, inhibit seed germination and plant establishment, and affect other ecohydrological processes.

Metformin, an Anthropogenic Contaminant of Seidlitzia rosmarinus Collected in a Desert Region near the Gulf of Aqaba, Sinai Peninsula

DEFF Research Database (Denmark)

Hassan, Ahmed R; El-Kousy, Salah M; El-Toumy, Sayed A

2017-01-01

A phytochemical investigation of Seidlitzia rosmarinus collected along the shoreline of the Gulf of Aqaba in the remote southern desert region of the Sinai peninsula has revealed the presence of the registered drug metformin (4). However, analysis of the (14)C content revealed the drug to be an a......A phytochemical investigation of Seidlitzia rosmarinus collected along the shoreline of the Gulf of Aqaba in the remote southern desert region of the Sinai peninsula has revealed the presence of the registered drug metformin (4). However, analysis of the (14)C content revealed the drug...

[Effects of different disturbance modes on the morphological characteristics and aboveground biomass of Alhagi sparsifolia in oasis-desert ecotone].

Science.gov (United States)

Li, Hai-Feng; Zeng, Fan-Jiang; Gui, Dong-Wei; An, Gui-Xiang; Liu, Zhen; Zhang, Li-Gang; Liu, Bo

2012-01-01

Taking Cele oasis at the southern fringe of Taklimakan Desert as a case, this paper studied the effects of different disturbances (burning in spring, cutting in spring, and cutting in fall) on the morphological characteristics and aboveground biomass of natural vegetation Alhagi sparsifolia in the ecotone of oasis-desert. Burning in spring decreased the A. sparsifolia plant height, crown width, and biomass significantly, being harmful to the regeneration and growth of the vegetation. Cutting in spring decreased the A. sparsifolia plant height, crown width, and biomass but increased the leaf biomass, thorn length, and thorn diameter, whereas cutting in fall decreased the plant height and crown width but increased the ramification amount and biomass of A. sparsifolia. Moderate cutting in fall could benefit the protection of A. sparsifolia at the southern fringe of Taklimakan Desert.

Population, desert expanding.

Science.gov (United States)

1992-01-01

The conditions of desert expansion in the Sahara are highlighted. On the southern border the desert is growing at a rate of 3-6 miles/year. This growth is encroaching on arable land in Ethiopia and Mauritania. The region loses up to 28,000 sq miles/year of farmland. 33% of Africa's fertile land is threatened. Land-use patterns are responsible for the deterioration of the soil. Traditional practices are not effective because the practices are not suitable for permanent farming. Farmers also have stopped environmentally sound practices such as letting the fields remain fallow in order to renew soil fertility. Nomads overgraze areas before moving on. A recent study by the World Bank's Africa Region Office was released; the report details some of the links between rapid population growth, poor agricultural performance, and environmental degradation. Soil conditions are such that valuable topsoil is blow away by the wind because the layer is too thin. Vegetation at the desert's edge is used for cooking purposes or for heating fuel. Tropical and savannah areas are depleted when tree replacement is inadequate. Only 9 trees are planted for every 100 removed. The report emphasized the role of women and children in contributing to population pressure by increased fertility. Women's work load is heavy and children are a help in alleviating some of the burden of domestic and agricultural work. There is hope in meeting demographic, agricultural, food security, and environmental objectives over the next 30 years if the needs of women are met. The needs include access to education for young women, lessening the work loads of women, and decreasing child mortality through improved health care and access to safe water.

1983 biotic studies of Yucca Mountain, Nevada Test Site, Nye County, Nevada

International Nuclear Information System (INIS)

O'Farrell, T.P.; Collins, E.

1984-04-01

A 27.5-square-mile portion of Yucca Mountain on and adjacent to the US Department of Energy's Nevada Test Site, Nye County, Nevada, is being considered as a potential location for a national high-level radioactive waste repository. Preliminary geologic and environmental characterization studies have been supported and more extensive studies are planned. Goals of the biotic surveys were to identify species of concern, describe major floral and faunal associations, and assess possible impacts of characterization and operational activities. Floral associations observed were characteristic of either the Mojave or Transition deserts that are widely distributed in southern Nevada. Diversity, in terms of total number of perennial species represented, was higher in Transition Desert associations than in Mojave Desert associations. Canopy coverage of associations fell within the range of reported values, but tended to be more homogeneous than expected. Annual vegetation was found to be diverse only where the frequency of Bromus rubens was low. Ground cover of winter annuals, especially annual grasses, was observed to be very dense in 1983. The threat of range fires on Yucca Mountain was high because of the increased amount of dead litter and the decreased amount of bare ground. Significant variability was observed in the distribution and relative abundance of several small mammal species between 1982 and 1983. Desert tortoise were found in low densities comparable with those observed in 1982. Evidence of recent activity, which included sighting of two live tortoises, was found in five areas on Yucca Mountain. Two of these areas have a high probability of sustaining significant impacts if a repository is constructed. Regeneration of aboveground shrub parts from root crowns was observed in areas damaged in 1982 by seismic testing with Vibroseis machines. These areas, which had been cleared to bare dirt by passage of the machines, also supported lush stands of winter annuals

Tamarisk control on public lands in the desert of southern California: two case studies

Science.gov (United States)

1994-01-01

As a land manager, the Federal Government faces enormous challenges from exotic pest invasions and associated changes to the structure and stability of native ecosystems (Bureau of Land Management, 1988). On public lands administered by the Bureau of Land Management (BLM) alone, it is estimated that almost three million hectares are occupied by invasive exotic plant species (weeds). Assuming an annual rate of invasion of 14 percent, 930 hectares of BLM-administered land are infested everyday by weeds (Jerry Asher, personal communication). When one considers the fact that BLM administers only about one-third of the public land in the United States (The Keystone Center, 1991), the magnitude of the problem assumes staggering proportions. The scenario described in the quote above portrays only some of the problems associated with the spread of the exotic plant tamarisk, a species on the California Exotic Pest Plant Council’s list of exotic pest plants of greatest concern (California Exotic Pest Plant Council, 1993). In this paper we review the threats posed by tamarisk invasion and proliferation and examine the traits that make the plant such a successful competitor. In addition, we highlight two tamarisk control efforts conducted by the Bureau of Land Management in the southern California desert.

diurnal and seasonal water relations of the desert phreatophyte prosopis-glandulosa (honey mesquite) in the Sonoran Desert of California

OpenAIRE

Nilsen, E. T.; Sharifi, M. R.; Rundel, P. W.; Jarrell, W. M.; Virginia, R. A.

1983-01-01

Diurnal and Seasonal water relations were monitored in a population of Prosopis glandulosa var. torreyana in the Sonoran Desert of southern California. Prosopis glandulosa at this research site acquired its water from a ground water source 4-6 m deep. Measurements of diurnal and seasonal cycles of aboveground environmental conditions, soil moisture, and soil water potential (to 6 m depth) were taken to ascertain environmental water availability and water stress. Leaf water potential, leaf con...

Predicting Pinus monophylla forest cover in the Baja California Desert by remote sensing

Directory of Open Access Journals (Sweden)

Jonathan G. Escobar-Flores

2018-04-01

Full Text Available The Californian single-leaf pinyon (Pinus monophylla var. californiarum, a subspecies of the single-leaf pinyon (the world’s only one-needled pine, inhabits semi-arid zones of the Mojave Desert (southern Nevada and southeastern California, US and also of northern Baja California (Mexico. This tree is distributed as a relict subspecies, at elevations of between 1,010 and 1,631 m in the geographically isolated arid Sierra La Asamblea, an area characterized by mean annual precipitation levels of between 184 and 288 mm. The aim of this research was (i to estimate the distribution of P. monophylla var. californiarum in Sierra La Asamblea by using Sentinel-2 images, and (ii to test and describe the relationship between the distribution of P. monophylla and five topographic and 18 climate variables. We hypothesized that (i Sentinel-2 images can be used to predict the P. monophylla distribution in the study site due to the finer resolution (×3 and greater number of bands (×2 relative to Landsat-8 data, which is publically available free of charge and has been demonstrated to be useful for estimating forest cover, and (ii the topographical variables aspect, ruggedness and slope are particularly important because they represent important microhabitat factors that can determine the sites where conifers can become established and persist. An atmospherically corrected a 12-bit Sentinel-2A MSI image with 10 spectral bands in the visible, near infrared, and short-wave infrared light region was used in combination with the normalized differential vegetation index (NDVI. Supervised classification of this image was carried out using a backpropagation-type artificial neural network algorithm. Stepwise multiple linear binominal logistical regression and Random Forest classification including cross validation were used to model the associations between presence/absence of P. monophylla and the five topographical and 18 climate variables. Using supervised

Desert tortoises (Gopherus agassizii are selective herbivores that track the flowering phenology of their preferred food plants.

Directory of Open Access Journals (Sweden)

W Bryan Jennings

Full Text Available Previous studies of desert tortoise foraging ecology in the western Mojave Desert suggest that these animals are selective herbivores, which alter their diet according to the temporal availability of preferred food plants. These studies, however, did not estimate availability of potential food plants by taking into account the spatial and temporal variability in ephemeral plant abundance that occurs within the spring season. In this study, we observed 18 free-ranging adult tortoises take 35,388 bites during the spring foraging season. We also estimated the relative abundance of potential food plants by stratifying our sampling across different phenological periods of the 3-month long spring season and by different habitats and microhabitats. This methodology allowed us to conduct statistical tests comparing tortoise diet against plant abundance. Our results show that tortoises choose food plants non-randomly throughout the foraging season, a finding that corroborates the hypothesis that desert tortoises rely on key plants during different phenological periods of spring. Moreover, tortoises only consumed plants in a succulent state until the last few weeks of spring, at which time most annuals and herbaceous perennials had dried and most tortoises had ceased foraging. Many species of food plants--including several frequently eaten species--were not detected in our plant surveys, yet tortoises located these rare plants in their home ranges. Over 50% of bites consumed were in the group of undetected species. Interestingly, tortoises focused heavily on several leguminous species, which could be nutritious foods owing to their presumably high nitrogen contents. We suggest that herbaceous perennials, which were rare on our study area but represented ~30% of tortoise diet, may be important in sustaining tortoise populations during droughts when native annuals are absent. These findings highlight the vulnerability of desert tortoises to climate change

Desert tortoises (Gopherus agassizii) are selective herbivores that track the flowering phenology of their preferred food plants

Science.gov (United States)

Jennings, Bryan W.; Berry, Kristin H.

2015-01-01

Previous studies of desert tortoise foraging ecology in the western Mojave Desert suggest that these animals are selective herbivores, which alter their diet according to the temporal availability of preferred food plants. These studies, however, did not estimate availability of potential food plants by taking into account the spatial and temporal variability in ephemeral plant abundance that occurs within the spring season. In this study, we observed 18 free-ranging adult tortoises take 35,388 bites during the spring foraging season. We also estimated the relative abundance of potential food plants by stratifying our sampling across different phenological periods of the 3-month long spring season and by different habitats and microhabitats. This methodology allowed us to conduct statistical tests comparing tortoise diet against plant abundance. Our results show that tortoises choose food plants non-randomly throughout the foraging season, a finding that corroborates the hypothesis that desert tortoises rely on key plants during different phenological periods of spring. Moreover, tortoises only consumed plants in a succulent state until the last few weeks of spring, at which time most annuals and herbaceous perennials had dried and most tortoises had ceased foraging. Many species of food plants—including several frequently eaten species—were not detected in our plant surveys, yet tortoises located these rare plants in their home ranges. Over 50% of bites consumed were in the group of undetected species. Interestingly, tortoises focused heavily on several leguminous species, which could be nutritious foods owing to their presumably high nitrogen contents. We suggest that herbaceous perennials, which were rare on our study area but represented ~30% of tortoise diet, may be important in sustaining tortoise populations during droughts when native annuals are absent. These findings highlight the vulnerability of desert tortoises to climate change if such changes

A new perspective on the geometry of the San Andreas Fault in southern California and its relationship to lithospheric structure

Science.gov (United States)

Fuis, Gary S.; Scheirer, Daniel S.; Langenheim, Victoria; Kohler, Monica D.

2012-01-01

The widely held perception that the San Andreas fault (SAF) is vertical or steeply dipping in most places in southern California may not be correct. From studies of potential‐field data, active‐source imaging, and seismicity, the dip of the SAF is significantly nonvertical in many locations. The direction of dip appears to change in a systematic way through the Transverse Ranges: moderately southwest (55°–75°) in the western bend of the SAF in the Transverse Ranges (Big Bend); vertical to steep in the Mojave Desert; and moderately northeast (37°–65°) in a region extending from San Bernardino to the Salton Sea, spanning the eastern bend of the SAF in the Transverse Ranges. The shape of the modeled SAF is crudely that of a propeller. If confirmed by further studies, the geometry of the modeled SAF would have important implications for tectonics and strong ground motions from SAF earthquakes. The SAF can be traced or projected through the crust to the north side of a well documented high‐velocity body (HVB) in the upper mantle beneath the Transverse Ranges. The north side of this HVB may be an extension of the plate boundary into the mantle, and the HVB would appear to be part of the Pacific plate.

Soil, plant, and structural considerations for surface barriers in arid environments: Application of results from studies in the Mojave Desert near Beatty, Nevada

Science.gov (United States)

Andraski, Brian J.; Prudic, David E.; ,

1997-01-01

The suitability of a waste-burial site depends on hydrologic processes that can affect the near-surface water balance. In addition, the loss of burial trench integrity by erosion and subsidence of trench covers may increase the likelihood of infiltration and percolation, thereby reducing the effectiveness of the site in isolating waste. Although the main components of the water balance may be defined, direct measurements can be difficult, and actual data for specific locations are seldom available. A prevalent assumption is that little or no precipitation will percolate to buried wastes at an arid site. Thick unsaturated zones, which are common to arid regions, are thought to slow water movement and minimize the risk of waste migration to the underlying water table. Thus, reliance is commonly placed on the natural system to isolate contaminants at waste-burial sites in the arid West.Few data are available to test assumptions about the natural soil-water flow systems at arid sites, and even less is known about how the natural processes are altered by construction of a waste-burial facility. The lack of data is the result of technical complexity of hydraulic characterization of the dry, stony soils, and insufficient field studies that account for the extreme temporal and spatial variations in precipitation, soils, and plants in arid regions. In 1976, the U.S. Geological Survey (USGS) began a long-term study at a waste site in the Mojave Desert. This paper summarizes the findings of ongoing investigations done under natural-site and waste-burial conditions, and discusses how this information may be applied to the design of surface barriers for waste sites in arid environments.The waste-burial site is in one of the most arid parts of the United States and is about 40 km northeast of Death Valley, near Beatty, Nev. (Figure 1). Precipitation averaged 108 mm/yr during 1981-1992. The water table is 85-115 m below land surface (Fischer, 1992). Sediments are largely alluvial

Structure and Deformation in the Transpressive Zone of Southern California Inferred from Seismicity, Velocity, and Qp Models

Science.gov (United States)

Hauksson, E.; Shearer, P.

2004-12-01

deeper and shows a more complex 3D distribution in areas exhibiting compressional tectonics within the Pacific plate. The VP values are 0.2 to 0.4 km/s too high to support an abundant occurrence of schist beneath the Mojave Desert and the San Gabriel Mountains. The models reflect mapped changes, from east to west, in the lithology of the Peninsular Ranges. The interface between the shallow Moho of the Continental Borderland and the deep Moho of the continent forms a broad zone to the north beneath the western Transverse Ranges, Ventura basin and the Los Angles Basin and a narrow zone to the south, along the Peninsular Ranges. Similarly, the 3D Qp model includes several features that correspond to regional tectonic features and possibly the thermal structure of the southern California crust. A clear low Qp zone extends from the San Bernardino Basin, across the Chino Basin, San Gabriel Valley, into the Los Angeles Basin. This zone is consistent with the geology and decreases with depth from east to west. The Peninsular Ranges have a high Qp zone consistent with the high velocities in the 3D VP model. There are also zones of high Qp in the southern Mojave and southern Sierras. Several clear transition zones of rapidly varying Qp, extend across major late Quaternary faults and connect regions of high and low Qp. The strongest low Qp zone coincides with the Salton Trough where near-surface low Qp is associated with the sediments and the deeper low Qp may be associated with elevated mid-crustal temperatures.

The floral hosts and distribution of a supposed creosote bush specialist, Colletes stepheni Timberlake (Hymenoptera: Colletidae)

Science.gov (United States)

Colletes stepheni Timberlake, previously thought to be a narrow oligolege of Larrea (creosote bush) of limited distribution in the Sonoran Desert, is found to be a much more widely distributed psammophile of the Sonoran, Mojave and Great Basin Deserts that utilizes two unrelated plant pollen sources...

ON PHYTOCOENOTICAL MAPPING OF CASPIAN DESERT REGION

Directory of Open Access Journals (Sweden)

I. SAFRONOVA

2004-05-01

Full Text Available The phytoecological map (l :2.500.000 for Desert Region, including the Caspian Lowland and the Mangyshlak. has been compiled. It gives an idea of latitudinal differentiation cf vegetation. Edaphic variants and lithological composition in low mountains. The legend has been constructed according to zonal-typological principle e using an ecological-phytocoenotic classification. Heterogeneity of vegetation is reflected by means of territoria1 units (complex, series, combination and additional marks above the vegetation background. In the northern subzone vegetation is fairly monotonous and characterized by prevalence of wormwood communities (Artemisia of subgenus Seriphidium, joined in three formations: Artemisia lerchiana, A. arenaria. A. pauciflora. Small areas are occupied by shrub deserts of Calligollum aphyllum and Tamarix ramosissima. To southward of 47° N in the middle subzone on the Caspian Lowland the communities of halophyte perennial saltworts essential1y dominate, and to less extent-wormwood communities of hemipsammophytic Artemisia terrae-albae and psammophytic Artemisia arenaria and A. lerchiana. Deserts of Mangyshlak are much diverse. Dwarf semishrubs are presented by species of perennial saltworts (Anabasis salsa, Nanophyton erinaceum,Arthrophytum lehnwnianum, Salsola orientaUs and wonnwood (Artemisia terrae-albae, A. gurganica. A. santolina. To southward of 43° N in the southern subzone dwarf semishrub Salsola gemmascens and Artemisia kemrudica corrnnunities prevail.

ON PHYTOCOENOTICAL MAPPING OF CASPIAN DESERT REGION

Directory of Open Access Journals (Sweden)

I. SAFRONOVA

2004-01-01

Full Text Available The phytoecological map (l :2.500.000 for Desert Region, including the Caspian Lowland and the Mangyshlak. has been compiled. It gives an idea of latitudinal differentiation cf vegetation. Edaphic variants and lithological composition in low mountains. The legend has been constructed according to zonal-typological principle e using an ecological-phytocoenotic classification. Heterogeneity of vegetation is reflected by means of territoria1 units (complex, series, combination and additional marks above the vegetation background. In the northern subzone vegetation is fairly monotonous and characterized by prevalence of wormwood communities (Artemisia of subgenus Seriphidium, joined in three formations: Artemisia lerchiana, A. arenaria. A. pauciflora. Small areas are occupied by shrub deserts of Calligollum aphyllum and Tamarix ramosissima. To southward of 47° N in the middle subzone on the Caspian Lowland the communities of halophyte perennial saltworts essential1y dominate, and to less extent-wormwood communities of hemipsammophytic Artemisia terrae-albae and psammophytic Artemisia arenaria and A. lerchiana. Deserts of Mangyshlak are much diverse. Dwarf semishrubs are presented by species of perennial saltworts (Anabasis salsa, Nanophyton erinaceum,Arthrophytum lehnwnianum, Salsola orientaUs and wonnwood (Artemisia terrae-albae, A. gurganica. A. santolina. To southward of 43° N in the southern subzone dwarf semishrub Salsola gemmascens and Artemisia kemrudica corrnnunities prevail.

EFFECTS OF PLANT SIZE ON PHOTOSYNTHESIS AND WATER RELATIONS IN THE DESERT SHRUB PROSOPIS GLANDULOSA (FABACEAE)

Science.gov (United States)

The Jornada del Muerto basin of the Chihuahuan Desert of southern New Mexico, USA, has undergone a marked transition of plant communities. Shrubs such as mesquite (Prosopis glandulosa) have greatly increased or now dominate in areas that were previously dominated by perennial gra...

Chemical composition and biological activities of Artemisia judaica essential oil from southern desert of Jordan.

Science.gov (United States)

Abu-Darwish, M S; Cabral, C; Gonçalves, M J; Cavaleiro, C; Cruz, M T; Zulfiqar, Ali; Khan, I A; Efferth, T; Salgueiro, L

2016-09-15

Artemisia judaica L. (Arabic name: Beithran), is a medicinal and aromatic plant growing in the valley bottoms of desert areas, particularly in the southern desert of Jordan nearest to the Jordan-Saudi Arabia borders and in Wadi Araba in the Southern Badia. In Jordan, A. judaica is widely used in traditional medicine being recommended by aboriginal Bedouins in the North Badia region of Jordan as calmative. Furthermore, it is used for the treatment of stomach ache, heart diseases, sexual weakness, diabetes, gastro-intestinal disorders and external wounding. Additionally, other folk medicines of the Arabic region commonly use this aromatic plant for the treatment of inflammatory-related diseases, for instance fungal infections, diabetes, atherosclerosis, cancer and arthritis. Considering the traditional medicinal uses and the lack of scientific studies addressing the cellular and molecular mechanisms behind A. judaica claimed activities, the present study was designed to validate some of the traditional uses ascribed to this species, specifically the antifungal and anti-inflammatory activities of A. judaica essential oil at doses devoid of cytotoxicity to mammalian cells. Chemical analysis of A. judaica essential oil isolated by hydrodistillation from aerial parts was carried out by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The antifungal activity (minimal inhibitory concentrations and minimal lethal concentrations) was evaluated against yeasts, dermatophyte and Aspergillus strains. In order to deeply explore the mechanisms behind the anti-fungal effect of the essential oil, the germ tube inhibition assay and the biofilms formation assay were evaluated using Candida albicans. The assessment of cell viability was accomplished using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in both hepatocytes and macrophages. Furthermore, the in vitro anti-inflammatory potential of A. judaica oil was evaluated by

1982 biotic survey of Yucca Mountain, Nevada Test Site, Nye County, Nevada

International Nuclear Information System (INIS)

O'Farrell, T.P.; Collins, E.

1983-02-01

In 1981 an extensive literature review was conducted to determine the current state of knowledge about the ecological characteristics of the Yucca Mountain study area and to identify what site-specific information was lacking. Based on the findings of the review a field study was initiated in 1982 to gather site-specific information on the ecological characteristics of the project area. The biota observed were representative of either the Mojave or Transition deserts that are widely distributed in southern Nevada and the arid Southwest. No unusual vegetation associations or assemblages of animals were observed. Based on observations of tracks and scats it was concluded that low numbers of both mule deer and feral burros used the area seasonally, and that neither species should be severely threatened by the proposed activities. The Mojave fishhook cactus and desert tortoise, both under consideration for federal protection as threatened species, were found to occur in the study area. The former was distributed in notable densities on the rocky ridgelines of Yucca Mountain in areas that should not be greatly disturbed by site characterization or future repository activities. Evidence of desert tortoise was observed throughout the project area to elevations of 5240 ft; however, relative densities were estimated to be low (less than 20 per square mile). Physical destruction of soils and native vegetation was determined to be the most significant negative effect associated with current and proposed characterization activities. Solution holes in exposed flat rock on ridgelines that served as passive collectors of precipitation and runoff were the only sources of free water observed. While these water supplies were not adequate to support riparian vegetation, there was evidence that they served as an important ephemeral source of water for wildlife

Rocks, climate and the survival of human societies in hyper-arid and arid environments - Are the human civilization in deserts at a permanent risk of collapse?

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Yoav, Avni; Noa, Avriel-Avni

2017-04-01

The great challenges of living in the arid and hyper arid regions worldwide are the shortage of water, limited resources and the permanent uncertainty of the desert climate. These challenges are known as the main weaknesses of desert societies that are prone, according to the existing paradigm, to a permanent risk of collapse. However, in the Middle East deserts, human societies are known since prehistoric times and during the entire hyper-dry Holocene. This hints that the simple paradigm of desert societies' high vulnerability to harsh desert environments needs to be better examined. In this context we examine three case studies: 1. The Southern Sinai region in Egypt: In this region, the annual precipitation fluctuates between 20-50 mm/y. However, in this highly mountainous area, desert agriculture plots including orchards were constructed, located mainly around the byzantine monastery of Santa Katerina. During the last 1500 years, much of the water supply needed for humans and agriculture was generated from runoff developed on exposed granite rocks. 2. The southern Jordan region south of Petra: Much of this wide area connecting the deserts of the Arabian Peninsula and southern Jordan receive only 20-30 mm/y. However, the main caravan route established by the Arabian tribes during the first millennia BC managed to cross this land, supplying the water needs of many camels. Most of this water was stored in large cisterns dug into the sandstone rock formations exposed along the route, especially within the Disi Formation. 3. The Negev Highlands of southern Israel: This region is divided between the hyper arid region to the south, receiving 70-80 mm/y, and the arid region to the north receiving 90-130 mm/y. During the last two millennia, the hyper arid area was used for camel grazing and goats herds, while the northern sector was used for the construction of agriculture plots, agriculture farms and even desert towns. All these activities were sustained by runoff

Temporal patterns in species flowering in Sky Islands of the Sonoran Desert ecoregion

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Theresa M. Crimmins; Michael A. Crimmins; C. David. Bertelsen

2013-01-01

Highly variable moisture conditions in the Sonoran Desert play a significant role in shaping the composition and phenology of plants in this water-limited region. The flowering patterns of plants of the Finger Rock trail, located in the Santa Catalina Mountains of southern Arizona, have been very carefully documented on approximately a weekly basis for nearly three...

Regional and Seasonal Diet of the Western Burrowing Owl in South-Central Nevada

Energy Technology Data Exchange (ETDEWEB)

Derek B. Hall, Paul D. Greger, Jeffrey R. Rosier

2009-04-01

We examined diets of Western Burrowing Owls (Athene cunicularia hypugaea) based on contents of pellets and large prey remains collected year-round at burrows in each of the 3 regions in south central Nevada (Mojave Desert, Great Basin Desert, and Transition region). The most common prey items, based on percent frequency of occurrence, were crickets and grasshoppers, beetles, rodents, sun spiders, and scorpions. The most common vertebrate prey was kangaroo rats (Dipodomys spp.). True bugs (Hemiptera), scorpions, and western harvest mice (Reithrodontomys megalotis) occurred most frequently in pellets from the Great Basin Desert region. Kangaroo rats (Dipodomys spp.) and pocket mice (Perognathinae) were the most important vertebrate prey items in the Transition and Mojave Desert regions, respectively. Frequency of occurrence of any invertebrate prey was high (>80%) in samples year-round but dropped in winter samples, with scorpions and sun spiders exhibiting the steepest declines. Frequency of occurrence of any vertebrate prey peaked in spring samples, was intermediate for winter and summer samples, and was lowest in fall samples. With the possible exception of selecting for western harvest mice in the Great Basin Desert region, Western Burrowing Owls in our study appeared to be opportunistic foragers with a generalist feeding strategy.

Arizona/New Mexico Plateau Ecoregion: Chapter 26 in Status and trends of land change in the Western United States--1973 to 2000

Science.gov (United States)

Ruhlman, Jana; Gass, Leila; Middleton, Barry

2012-01-01

Situated between ecoregions of distinctly different topographies and climates, the Arizona/New Mexico Plateau Ecoregion represents a large area of approximately 192,869 km2 (74,467 mi2) that stretches across northern Arizona, central and northwestern New Mexico, and parts of southwestern Colorado; in addition, a small part extends into southeastern Nevada (fig. 1) (Omernik, 1987; U.S. Environmental Protection Agency, 1997). Forested, mountainous terrain borders the ecoregion on the northeast (Southern Rockies Ecoregion) and southwest (Arizona/New Mexico Mountains Ecoregion). Warmer and drier climates exist to the south (Chihuahuan Deserts Ecoregion) and west (Mojave Basin and Range Ecoregion). The semiarid grasslands of the western Great Plains are to the east (Southwestern Tablelands Ecoregion), and the tablelands of the Colorado Plateau in Utah and western Colorado lie to the north (Colorado Plateaus Ecoregion). The Arizona/New Mexico Plateau Ecoregion occupies a significant portion of the southern half of the Colorado Plateau.

Plantation of desert and renewal of earth with small LMRs

International Nuclear Information System (INIS)

Hattori, Sadao; Minato, Akio; Handa, Norihiko; Hashizume, Kenichi.

1991-01-01

Desertification is advancing at rapid rate on the earth. The technical development for preventing the desertification has been requested for advanced countries. Particularly in the southern hemisphere, the energy which can restore green in deserts and supply the electric power required for living is necessary. In this paper, the supply of electric power using the small fast reactors which are excellent in the safety and maintainability and the desalting plants required for tree planting in deserts, and further, the regeneration of the earth accompanying it, are discussed. By desertification, yearly 6 million ha of lands are devastated to unrecoverable extent, and those concentrate in the districts where yearly rainfall is little. In order to prevent desertification, it is necessary to stabilize surface soil by tree planting. Further, in order to prevent the deforestation for obtaining energy, the dual purpose plants for power generation and desalting are important. In this paper, the concept of obtaining water resources from sea, carrying out the desalting, supplying the water to the forefront of deserts and forming green belts there by using fast reactors is considered. The present status of desertification, the desalting of seawater by nuclear power, small fast reactors aiming at ultra-safety, the production of green, and the regeneration of the earth are described. (K.I.)

Colonization patterns of soil microbial communities in the Atacama Desert.

Science.gov (United States)

Crits-Christoph, Alexander; Robinson, Courtney K; Barnum, Tyler; Fricke, W Florian; Davila, Alfonso F; Jedynak, Bruno; McKay, Christopher P; Diruggiero, Jocelyne

2013-11-20

The Atacama Desert is one of the driest deserts in the world and its soil, with extremely low moisture, organic carbon content, and oxidizing conditions, is considered to be at the dry limit for life. Analyses of high throughput DNA sequence data revealed that bacterial communities from six geographic locations in the hyper-arid core and along a North-South moisture gradient were structurally and phylogenetically distinct (ANOVA test for observed operating taxonomic units at 97% similarity (OTU0.03), P microbial communities' diversity metrics (least squares linear regression for observed OTU0.03 and air RH and soil conductivity, P PCoA Spearman's correlation for air RH and soil conductivity, P <0.0001), indicating that water availability and salt content are key factors in shaping the Atacama soil microbiome. Mineralization studies showed communities actively metabolizing in all soil samples, with increased rates in soils from the southern locations. Our results suggest that microorganisms in the driest soils of the Atacama Desert are in a state of stasis for most of the time, but can potentially metabolize if presented with liquid water for a sufficient duration. Over geological time, rare rain events and physicochemical factors potentially played a major role in selecting micro-organisms that are most adapted to extreme desiccating conditions.

Distance to human populations influences epidemiology of respiratory disease in desert tortoises

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Berry, Kristin H.; Ashley A. Coble (formerly Emerson), no longer USGS; Yee, Julie L.; Mack, Jeremy S.; Perry, William M.; Anderson, Kemp M.; Brown, Mary B.

2014-01-01

We explored variables likely to affect health of Agassiz's desert tortoises (Gopherus agassizii) in a 1,183-km2 study area in the central Mojave Desert of California between 2005 and 2008. We evaluated 1,004 tortoises for prevalence and spatial distribution of 2 pathogens, Mycoplasma agassizii and M. testudineum, that cause upper respiratory tract disease. We defined tortoises as test-positive if they were positive by culture and/or DNA identification or positive or suspect for specific antibody for either of the two pathogens. We used covariates of habitat (vegetation, elevation, slope, and aspect), tortoise size and sex, distance from another test-positive tortoise, and anthropogenic variables (distances to roads, agricultural areas, playas, urban areas, and centroids of human-populated census blocks). We used both logistic regression models and regression trees to evaluate the 2 species of Mycoplasma separately. The prevalence of test-positive tortoises was low: 1.49% (15/1,004) for M. agassizii and 2.89% (29/1,004) for M. testudineum. The spatial distributions of test-positive tortoises for the 2 Mycoplasma species showed little overlap; only 2 tortoises were test-positive for both diseases. However, the spatial distributions did not differ statistically between the 2 species. We consistently found higher prevalence of test-positive tortoises with shorter distances to centroids of human-populated census blocks. The relationship between distance to human-populated census blocks and tortoises that are test-positive for M. agassizii and potentially M. testudineum may be related to release or escape of captive tortoises because the prevalence of M. agassizii in captive tortoises is high. Our findings have application to other species of chelonians where both domestic captive and wild populations exist. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Extended Radio Emission in MOJAVE Blazars: Challenges to Unification

Science.gov (United States)

Kharb, P.; Lister, M. L.; Cooper, N. J.

2010-02-01

We present the results of a study on the kiloparsec-scale radio emission in the complete flux density limited MOJAVE sample, comprising 135 radio-loud active galactic nuclei. New 1.4 GHz Very Large Array (VLA) radio images of six quasars and previously unpublished images of 21 blazars are presented, along with an analysis of the high-resolution (VLA A-array) 1.4 GHz emission for the entire sample. While extended emission is detected in the majority of the sources, about 7% of the sources exhibit only radio core emission. We expect more sensitive radio observations, however, to detect faint emission in these sources, as we have detected in the erstwhile "core-only" source, 1548+056. The kiloparsec-scale radio morphology varies widely across the sample. Many BL Lac objects exhibit extended radio power and kiloparsec-scale morphology typical of powerful FRII jets, while a substantial number of quasars possess radio powers intermediate between FRIs and FRIIs. This poses challenges to the simple radio-loud unified scheme, which links BL Lac objects to FRIs and quasars to FRIIs. We find a significant correlation between extended radio emission and parsec-scale jet speeds: the more radio powerful sources possess faster jets. This indicates that the 1.4 GHz (or low-frequency) radio emission is indeed related to jet kinetic power. Various properties such as extended radio power and apparent parsec-scale jet speeds vary smoothly between different blazar subclasses, suggesting that, at least in terms of radio jet properties, the distinction between quasars and BL Lac objects, at an emission-line equivalent width of 5 Å, is essentially an arbitrary one. While the two blazar subclasses display a smooth continuation in properties, they often reveal differences in the correlation test results when considered separately. This can be understood if, unlike quasars, BL Lac objects do not constitute a homogeneous population, but rather include both FRI and FRII radio galaxies for

EXTENDED RADIO EMISSION IN MOJAVE BLAZARS: CHALLENGES TO UNIFICATION

International Nuclear Information System (INIS)

Kharb, P.; Lister, M. L.; Cooper, N. J.

2010-01-01

We present the results of a study on the kiloparsec-scale radio emission in the complete flux density limited MOJAVE sample, comprising 135 radio-loud active galactic nuclei. New 1.4 GHz Very Large Array (VLA) radio images of six quasars and previously unpublished images of 21 blazars are presented, along with an analysis of the high-resolution (VLA A-array) 1.4 GHz emission for the entire sample. While extended emission is detected in the majority of the sources, about 7% of the sources exhibit only radio core emission. We expect more sensitive radio observations, however, to detect faint emission in these sources, as we have detected in the erstwhile 'core-only' source, 1548+056. The kiloparsec-scale radio morphology varies widely across the sample. Many BL Lac objects exhibit extended radio power and kiloparsec-scale morphology typical of powerful FRII jets, while a substantial number of quasars possess radio powers intermediate between FRIs and FRIIs. This poses challenges to the simple radio-loud unified scheme, which links BL Lac objects to FRIs and quasars to FRIIs. We find a significant correlation between extended radio emission and parsec-scale jet speeds: the more radio powerful sources possess faster jets. This indicates that the 1.4 GHz (or low-frequency) radio emission is indeed related to jet kinetic power. Various properties such as extended radio power and apparent parsec-scale jet speeds vary smoothly between different blazar subclasses, suggesting that, at least in terms of radio jet properties, the distinction between quasars and BL Lac objects, at an emission-line equivalent width of 5 A, is essentially an arbitrary one. While the two blazar subclasses display a smooth continuation in properties, they often reveal differences in the correlation test results when considered separately. This can be understood if, unlike quasars, BL Lac objects do not constitute a homogeneous population, but rather include both FRI and FRII radio galaxies for

Estimating Winter Annual Biomass in the Sonoran and Mojave Deserts with Satellite- and Ground-Based Observations

Directory of Open Access Journals (Sweden)

Bradley C. Reed

2013-02-01

Full Text Available Winter annual plants in southwestern North America influence fire regimes, provide forage, and help prevent erosion. Exotic annuals may also threaten native species. Monitoring winter annuals is difficult because of their ephemeral nature, making the development of a satellite monitoring tool valuable. We mapped winter annual aboveground biomass in the Desert Southwest from satellite observations, evaluating 18 algorithms using time-series vegetation indices (VI. Field-based biomass estimates were used to calibrate and evaluate each algorithm. Winter annual biomass was best estimated by calculating a base VI across the period of record and subtracting it from the peak VI for each winter season (R2 = 0.92. The normalized difference vegetation index (NDVI derived from 8-day reflectance data provided the best estimate of winter annual biomass. It is important to account for the timing of peak vegetation when relating field-based estimates to satellite VI data, since post-peak field estimates may indicate senescent biomass which is inaccurately represented by VI-based estimates. Images generated from the best-performing algorithm show both spatial and temporal variation in winter annual biomass. Efforts to manage this variable resource would be enhanced by a tool that allows the monitoring of changes in winter annual resources over time.

Holocene slip rates along the San Andreas Fault System in the San Gorgonio Pass and implications for large earthquakes in southern California

Science.gov (United States)

Heermance, Richard V.; Yule, Doug

2017-06-01

The San Gorgonio Pass (SGP) in southern California contains a 40 km long region of structural complexity where the San Andreas Fault (SAF) bifurcates into a series of oblique-slip faults with unknown slip history. We combine new 10Be exposure ages (Qt4: 8600 (+2100, -2200) and Qt3: 5700 (+1400, -1900) years B.P.) and a radiocarbon age (1260 ± 60 years B.P.) from late Holocene terraces with scarp displacement of these surfaces to document a Holocene slip rate of 5.7 (+2.7, -1.5) mm/yr combined across two faults. Our preferred slip rate is 37-49% of the average slip rates along the SAF outside the SGP (i.e., Coachella Valley and San Bernardino sections) and implies that strain is transferred off the SAF in this area. Earthquakes here most likely occur in very large, throughgoing SAF events at a lower recurrence than elsewhere on the SAF, so that only approximately one third of SAF ruptures penetrate or originate in the pass.Plain Language SummaryHow large are earthquakes on the southern San Andreas Fault? The answer to this question depends on whether or not the earthquake is contained only along individual fault sections, such as the Coachella Valley section north of Palm Springs, or the rupture crosses multiple sections including the area through the San Gorgonio Pass. We have determined the age and offset of faulted stream deposits within the San Gorgonio Pass to document slip rates of these faults over the last 10,000 years. Our results indicate a long-term slip rate of 6 mm/yr, which is almost 1/2 of the rates east and west of this area. These new rates, combined with faulted geomorphic surfaces, imply that large magnitude earthquakes must occasionally rupture a 300 km length of the San Andreas Fault from the Salton Sea to the Mojave Desert. Although many ( 65%) earthquakes along the southern San Andreas Fault likely do not rupture through the pass, our new results suggest that large >Mw 7.5 earthquakes are possible on the southern San Andreas Fault and likely

Mapping habitat for multiple species in the Desert Southwest

Science.gov (United States)

Inman, Richard D.; Nussear, Kenneth E.; Esque, Todd C.; Vandergast, Amy G.; Hathaway, Stacie A.; Wood, Dustin A.; Barr, Kelly R.; Fisher, Robert N.

2014-01-01

Many utility scale renewable energy projects are currently proposed across the Mojave Ecoregion. Agencies that manage biological resources throughout this region need to understand the potential impacts of these renewable energy projects and their associated infrastructure (for example, transmission corridors, substations, access roads, etc.) on species movement, genetic exchange among populations, and species’ abilities to adapt to changing environmental conditions. Understanding these factors will help managers’ select appropriate project sites and possibly mitigate for anticipated effects of management activities. We used species distribution models to map habitat for 15 species across the Mojave Ecoregion to aid regional land-use management planning. Models were developed using a common 1 × 1 kilometer resolution with maximum entropy and generalized additive models. Occurrence data were compiled from multiple sources, including VertNet (http://vertnet.org/), HerpNET (http://www.herpnet.org), and MaNIS (http://manisnet.org), as well as from internal U.S. Geological Survey databases and other biologists. Background data included 20 environmental covariates representing terrain, vegetation, and climate covariates. This report summarizes these environmental covariates and species distribution models used to predict habitat for the 15 species across the Mojave Ecoregion.

Medicinal flora of the Cholistan desert: a review

International Nuclear Information System (INIS)

Hmeed, M.; Ashraf, M.; Nawaz, T.; Naz, N.; Ahmad, M.S.A.; Al-Quriany, F.; Younis, A.

2011-01-01

The Cholistan desert can be divided into two distinct regions on the basis of topography, soil type and texture, and vegetation structure: the northern Lesser Cholistan and southern Greater Cholistan. The desert is characterized by large saline compacted areas with alluvial clay, sandy ridges and dunes, and semi-stabilized to frequently shifting dunes. The climate is subtropical, harsh, hot and arid, and influenced by seasonal monsoons. Vegetation cover on the sand dunes is comprised by a few tussock-forming grasses including Cenchrus ciliaris, Panicum turgidum and Lasiurus scindicus, along with perennial shrubs Calligonum polygonoides, Leptadenia pyrotechnica and Aerva javanica. Interdunal flats are dominated by grasses, mainly Cymbopogon jwarancusa, Sporobolus ioclados, Panicum antidotale, and Ochthochloa compressa, and tall shrubs Calligonum polygonoides and Capparis decidua. Vegetation of saline patches is specific, dominated by halophytes mainly belonging to family Chenopodiaceae (Amaranthaceae). Many plants of the Cholistan desert, including Neurada procumbens, Aerva javanica, Capparis decidua, Cleome brachycarpa, Dipterygium glaucum, Gisekia pharnacioides, Suaeda fruticosa, Achyranthes aspera, Aerva javanica, Alhagi maurorum, Calotropis procera, Capparis decidua, Zaleya pentandra, Mollugo cerviana, Ziziphus mauritiana, Boerhavia procumbens, Cressa cretica and Crotalaria burhia, are frequently used by the local inhabitants to cure chronic and acute diseases. A variety of medicinally important chemical compounds have been extracted and identified from the plants of the Cholistan desert, including terpenes and triterpenoids, sterols and steroids, phenolics, flavonoids, gums and resins, quinones, anthocyanidines, saponins, antioxidants and fatty acids. Habitat degradation, intensive agricultural practices and over exploitation of resources pose a serious threat to the diversity of ethno botanically important plant species. Allopathic medicines are generally

Gravity, magnetic, and physical property data in the Smoke Creek Desert area, northwest Nevada

Science.gov (United States)

Tilden, Janet E.; Ponce, David A.; Glen, Jonathan M.G.; Chuchel, Bruce A.; Tushman, Kira; Duvall, Alison

2006-01-01

The Smoke Creek Desert, located approximately 100 km (60 mi) north of Reno near the California-Nevada border, is a large basin situated along the northernmost parts of the Walker Lane Belt (Stewart, 1988), a physiographic province defined by northwest-striking topographic features and strike-slip faulting. Because geologic framework studies play an important role in understanding the hydrology of the Smoke Creek Desert, a geologic and geophysical effort was begun to help determine basin geometry, infer structural features, and estimate depth to Pre-Cenozoic rocks, or basement. In May and June of 2004, and June of 2005, the U.S. Geological Survey (USGS) collected 587 new gravity stations, more than 160 line-kilometers (100 line-miles) of truck-towed magnetometer data, and 111 rock property samples in the Smoke Creek Desert and vicinity in northwest Nevada, as part of an effort to characterize its hydrogeologic framework. In the Smoke Creek Desert area, gravity highs occur over rocks of the Skedaddle Mountains, Fox Range, Granite Range, and over portions of Tertiary volcanic rocks in the Buffalo Hills. These gravity highs likely reflect basement rocks, either exposed at the surface or buried at shallow depths. The southern Smoke Creek Desert corresponds to a 25-mGal isostatic gravity low, which corresponds with a basin depth of approximately 2 km. Magnetic highs are likely due to granitic, andesitic, and metavolcanic rocks, whereas magnetic lows are probably associated with less magnetic gneiss and metasedimentary rocks in the region. Three distinctive patterns of magnetic anomalies occur throughout the Smoke Creek Desert and Squaw Creek Valley, likely reflecting three different geological and structural settings.

Application of Space Technology to Discovery of Ancient Desert Trade Routes in the Southern Arabian Peninsula

Science.gov (United States)

Blom, Ronald; Crippen, Robert; Hedges, George; Zarins, Juris

1997-01-01

Over the last decade, an unusual combination of historical research, traditional archaeology, and application of space technolgy has demonstrated the existence of trans-desert trade routes in the sourthern Arabian peninsula.

Introduction: Chapter 1

Science.gov (United States)

Esque, Todd C.; Nussear, Kenneth E.; Inman, Richard D.; Matocq, Marjorie D.; Weisberg, Peter J.; Dilts, Thomas E.; Leitner, Philip

2013-01-01

The Mohave ground squirrel (Xerospermophilus mohavensis), named just over a century ago (Merriam 1889), is precinctive to the western Mojave Desert in California, USA, and occupies portions of Kern, Los Angeles, Inyo and San Bernardino counties (Best 1995). Early estimates of the geographic range of the squirrel are just 20,000 km2 in area (Hall 1981, Zeiner et al. 1988‐ 1990), one of the smallest distributions among North American ground squirrel species (Hoyt 1972, P. Leitner – pers. obs.). The closest living relative of the Mohave ground squirrel (MGS) is the round‐tailed ground squirrel (Xerospermophilus tereticaudus). Mohave ground squirrels have a “shorter tail with distichous hairs and white undersurface”, but visual differences between the two species are subtle (Hafner and Yates 1983). Speciation likely occurred when portions of the parent population were isolated 4‐1.6 million years ago during the accelerated uplift of the Sierra Nevada, the Transverse Ranges and the Mojave River system, resulting in separation and isolation with MGS evolving in refugia (Hafner 1992, Bell et al. 2009). Subsequently, fluvial‐ lacustrine systems in the Mojave River basin provided vicariance features during the Pleistocene (Hafner 1992, Bell et al. 2009). Responding to previous climate change, the two species potentially migrated into their current ranges from southern refugia after the Last Glacial Maximum, eventually abutting each other along the Mojave River (Hafner and Yates 1983). The species are capable of hybridizing, but intercrosses appear to be rare, and sampling near the zones of potential hybridization remains limited (Bell and Matocq 2011). The only other similar sized squirrel occupying the range of MGS is the white‐tailed antelope ground squirrel (Ammospermophilus leucurus) whose range entirely overlaps MGS, but is easily distinguished by its bright white dorso‐lateral stripes (Best 1995)

Lut Desert, Iran

Science.gov (United States)

1981-01-01

Iran is a large country with several desert regions. In the Dasht-E-Lut (Lut Desert) (30.5N, 58.5E) an area known as Namak-Zar, about 100 miles east of the city of Kerman, is at the center of this photograph. Some of the world's most prominent Yardangs (very long, parallel ridges and depressions) have been wind eroded in these desert dry lake bed sediments. At the left of the photo is a large field of sand dunes at right angles to the wind.

Ground-water quality and geochemistry, Carson Desert, western Nevada

Science.gov (United States)

Lico, Michael S.; Seiler, R.L.

1994-01-01

Aquifers in the Carson Desert are the primary source of drinking water, which is highly variable in chemical composition. In the shallow basin-fill aquifers, water chemistyr varies from a dilute calcium bicarbonate-dominated water beneath the irrigated areas to a saline sodium chloride- dominated water beneath unirrigated areas. Water samples from the shallow aquifers commonly have dissolved solids, chloride, magnesium, sulfate, arsenic, and manganese concentrations that exceed State of Nevada drinking-water standards. Water in the intermediante basin-fill aquifers is a dilute sodium bicarbonate type in the Fallon area and a distinctly more saline sodium chloride type in the Soda Lake-Upsal Hogback area. Dissolved solids, chloride, arsenic, fluoride, and manganese concen- trations commonly exceed drinking-water standards. The basalt aquifer contains a dilute sodium bicarbonate chloride water. Arsenic concentrations exceed standards in all sampled wells. The concen- trations of major constituents in ground water beneath the southern Carson Desert are the result of evapotranspiration and natural geochemical reactions with minerals derived mostly from igneous rocks. Water with higher concentrations of iron and manganese is near thermodynamic equilibrium with siderite and rhodochrosite and indicates that these elements may be limited by the solubility of their respective carbonate minerals. Naturally occurring radionuclides (uranium and radon-222) are present in ground water from the Carson Desert in concen- tratons higher than proposed drinking-water standards. High uranium concentrations in the shallow aquifers may be caused by evaporative concentration and the release of uranium during dissolution of iron and manganese oxides or the oxidation of sedimentary organic matter that typically has elevated uranium concentrations. Ground water in the Carson Desert does not appear to have be contaminated by synthetic organic chemicals.

40 CFR 52.220 - Identification of plan.

Science.gov (United States)

2010-07-01

... (Mojave Desert AQMD only). (xx) Mariposa County APCD. (A) Previously approved on September 22, 1972 in.... (viii) Mariposa County APCD. (A) Rules 101, 102, 201, 202, 203 (a-f, h, i, and k), 204-216, 301-303, 305...

[Paleoclimatology studies for Yucca Mountain site characterization]. Final report

International Nuclear Information System (INIS)

1996-01-01

This report consists of two separate papers: Fernley Basin studies; and Influence of sediment supply and climate change on late Quaternary eolian accumulation patterns in the Mojave Desert. The first study involved geologic mapping of late Quaternary sediments and lacustrine features combined with precise control of elevations and descriptions of sediments for each of the major sedimentary units. The second paper documents the response of a major eolian sediment transport system in the east-central Mojave Desert: that which feeds the Kelso Dune field. Information from geomorphic, stratigraphic, and sedimentologic studies of eolian deposits and landforms is combined with luminescence dating of these deposits to develop a chronology of periods of eolian deposition. Both studies are related to site characterization studies of Yucca Mountain and the forecasting of rainfall patterns possible for the high-level radioactive waste repository lifetime

Solar cell degradation under open circuit condition in out-doors-in desert region

Directory of Open Access Journals (Sweden)

M. Boussaid

Full Text Available The reliability of solar cells is an important parameter in the design of photovoltaic systems and particularly for cost estimation. Solar cell degradation is the result of various operating conditions; temperature is one of most important factors. Installed PV modules in desert regions are subjected to various temperature changes with significant gradient leading to accelerated degradation. In the present work, we demonstrate the influence of open-circuit condition on the degradation of PV modules. The experiment is carried out in the desert region of ADRAR (southern Algeria using two modules IJISEL of single-crystal silicon. A continuous monitoring allows analysis of both performances of modules for duration of 330 days. The module in open-circuit condition reaches higher temperature means than the module in charging condition; therefore, it undergoes a higher degradation. By simulation, we found that the life of a PV module (whose power output is close to 50% in a condition of an open-circuit in the desert region could be reduced to 4 years, and that has a significant impact on economy. Keywords: WEIBULL, Photovoltaic, Degradation, Open-circuit, Single-crystal, Silicon

Metformin, an Anthropogenic Contaminant of Seidlitzia rosmarinus Collected in a Desert Region near the Gulf of Aqaba, Sinai Peninsula

DEFF Research Database (Denmark)

Hassan, Ahmed R.; El-Kousy, Salah M.; El-Toumy, Sayed A.

2017-01-01

A phytochemical investigation of Seidlitzia rosmarinus collected along the shoreline of the Gulf of Aqaba in the remote southern desert region of the Sinai peninsula has revealed the presence of the registered drug metformin (4). However, analysis of the (14)C content revealed the drug to be an a...

Chroococcidiopsis sp. strain AAB1, a new model from the Atacama desert for the understanding of extreme UV tolerance in an astrobiological context

International Nuclear Information System (INIS)

Azua-Bustos, A.; Arenas, C.; Paulino-Lima, I G.; Galante, D.

2012-01-01

Full text: The Atacama Desert in northern Chile is the driest and oldest desert on Earth. In a recently published report [Azua-Bustos, 2011] we showed that along its Coastal Range, fog can support hypolithic colonization rates of 80From these hypolithic communities we were able to obtain a previously unknown strain of Chroococcidiopsis which we characterized by morphological and molecular means. Due to the extreme tolerance of cyanobacteria of this genus to UV, and since the Atacama Desert has constantly high UV radiation levels all year long, we propose this strain as a pertinent model for understanding the limits UV tolerance for life as we know it. We have measured the viability of the isolate by using the DEAD/LIVE BacLight kit which allows the detection of dead cells by measuring the loss of integrity of the plasma membrane, and found that it remains almost unchanged with control cultures when desiccated. In addition, desiccated samples readily start new cultures. Transmission electron microscopy (TEM) of desiccated samples show no evident changes compared with controls. Pigments extracts from desiccated samples show a decrease in photosynthetic pigments like Chlorophyll-a, measured by fluorescence spectra and by tissue layer chromatography. Desiccated samples also synthesize sucrose, an intracellular compatible solute known to play a role in desiccation tolerance. As desiccation and extreme UV tolerance are thought to share similar metabolic routes [Rebecchi, 2007], we expect that our isolate (as suggested by preliminary experiments performed with our strain at LNLS in 2010) should be extremely tolerant to UV radiation. Future work include exposition of monolayers of our strain using the VUV line, and the determination of its comparative tolerance levels with a Chroococcidiopsis strain (N76) isolated from the Mojave Desert which we also have in culture. The experiments will consist of different exposition times in order to achieve increasing UV accumulation

Factors affecting the thermal environment of Agassiz’s Desert Tortoise (Gopherus agassizii) cover sites in the Central Mojave Desert during periods of temperature extremes

Science.gov (United States)

Mack, Jeremy S.; Berry, Kristin H.; Miller, David; Carlson, Andrea S.

2015-01-01

Agassiz's Desert Tortoises (Gopherus agassizii) spend >95% of their lives underground in cover sites that serve as thermal buffers from temperatures, which can fluctuate >40°C on a daily and seasonal basis. We monitored temperatures at 30 active tortoise cover sites within the Soda Mountains, San Bernardino County, California, from February 2004 to September 2006. Cover sites varied in type and structural characteristics, including opening height and width, soil cover depth over the opening, aspect, tunnel length, and surficial geology. We focused our analyses on periods of extreme temperature: in summer, between July 1 and September 1, and winter, between November 1 and February 15. With the use of multivariate regression tree analyses, we found cover-site temperatures were influenced largely by tunnel length and subsequently opening width and soil cover. Linear regression models further showed that increasing tunnel length increased temperature stability and dampened seasonal temperature extremes. Climate change models predict increased warming for southwestern North America. Cover sites that buffer temperature extremes and fluctuations will become increasingly important for survival of tortoises. In planning future translocation projects and conservation efforts, decision makers should consider habitats with terrain and underlying substrate that sustain cover sites with long tunnels and expanded openings for tortoises living under temperature extremes similar to those described here or as projected in the future.

77 FR 12526 - Revisions to the California State Implementation Plan, Antelope Valley Air Quality Management...

Science.gov (United States)

2012-03-01

... the California State Implementation Plan, Antelope Valley Air Quality Management District and Mojave Desert Quality Management District AGENCY: Environmental Protection Agency (EPA). ACTION: Proposed rule. SUMMARY: EPA is proposing to approve revisions to the Antelope Valley Air Quality Management District...

Place Attachment and Tourist Experience in the Context of Desert Tourism – the Case of Wadi Rum

Directory of Open Access Journals (Sweden)

Allan Mamoon

2016-06-01

Full Text Available This paper aims to explore the relationship between tourist experience and place attachment in a desert tourism experience. The current study was carried out with a sample of international and domestic visitors in Wadi Rum, Southern Jordan. The results show that there is a significant positive correlation between the nearby constructs of the study units such as the four tourist experience dimensions (education, esthetics, entertainment, and escapism, and the two dimensional place attachments measures (place identity and place dependence. Moreover, the findings also indicate that education factor had a significantly positive relationship with place identity, and there was a significantly positive relationship between escapism factor and place dependence. The findings can be used to develop the tourist experience and place attachment in the context of desert tourism experience. They further help tourism destinations managers, planners and marketers to provide appropriate marketing strategies and enrich their offers to desert tourism participants.

Organic matter composition and substrate diversity under elevated CO2 in the Mojave Desert

Science.gov (United States)

Tfaily, M. M.; Hess, N. J.; Koyama, A.; Evans, R. D.

2016-12-01

Little is known about how rising atmospheric CO2 concentration will impact long-term plant biomass or the dynamics of soil organic matter (SOM) in arid ecosystems. In this study, we investigated the change in the molecular composition of SOM by high resolution mass spectrometry after 10 years exposure to elevated atmospheric CO2 concentrations at the Nevada Desert FACE Facility. Samples were collected from soil profiles from 0 to 1m in 0.2m increments under the dominant evergreen shrub (Larrea tridentata). The differences in the composition of SOM were more evident in soils close to the surface and consistent with higher bulk soil organic carbon (C) and total nitrogen (N) concentrations under elevated than ambient CO2, reflecting increased net productivity of shrubs under elevated CO2, which could be attributed to increased litter input from above-ground biomass and/or shallow roots, root exudation and/or microbial residues. This was further supported by the significant increase in the abundance of amino sugars-, protein- and carbohydrate-like compounds. These compounds are involved in diverse pathways ranging from sugars and amino-acid metabolism to lipid biosynthesis. This indicates increased activity and metabolism under elevated CO2 and suggests that elevated CO2 have altered microbial C use patterns, reflecting changes in the quality and quantity of soil C inputs. A significant increase in the mineral-bound soil organic C was also observed in the surface soils under elevated CO2. This was accompanied by increased microbial residues as identified by mass spectrometry that supports microbial lipid analysis, and reflecting accelerated microbial turnover under elevated CO2. Fungal neutral lipid fatty acids (NLFA) abundance doubled under elevated CO2. When provided with excess labile compounds, such as root exudates, and with limited supply of nutrients, fungi assimilate the excess labile C and store it as NLFA likely contributing to increased total N

Impacts of climate change and renewable energy development on habitat of an endemic squirrel, Xerospermophilus mohavensis, in the Mojave Desert, USA

Science.gov (United States)

Inman, Richard D.; Esque, Todd C.; Nussear, Kenneth E.; Leitner, Philip; Matocq, Marjorie D.; Weisberg, Peter J.; Dilts, Thomas E.

2016-01-01

Predicting changes in species distributions under a changing climate is becoming widespread with the use of species distribution models (SDMs). The resulting predictions of future potential habitat can be cast in light of planned land use changes, such as urban expansion and energy development to identify areas with potential conflict. However, SDMs rarely incorporate an understanding of dispersal capacity, and therefore assume unlimited dispersal in potential range shifts under uncertain climate futures. We use SDMs to predict future distributions of the Mojave ground squirrel, Xerospermophilus mohavensis Merriam, and incorporate partial dispersal models informed by field data on juvenile dispersal to assess projected impact of climate change and energy development on future distributions of X. mohavensis. Our models predict loss of extant habitat, but also concurrent gains of new habitat under two scenarios of future climate change. Under the B1 emissions scenario- a storyline describing a convergent world with emphasis on curbing greenhouse gas emissions- our models predicted losses of up to 64% of extant habitat by 2080, while under the increased greenhouse gas emissions of the A2 scenario, we suggest losses of 56%. New potential habitat may become available to X. mohavensis, thereby offsetting as much as 6330 km2 (50%) of the current habitat lost. Habitat lost due to planned energy development was marginal compared to habitat lost from changing climates, but disproportionately affected current habitat. Future areas of overlap in potential habitat between the two climate change scenarios are identified and discussed in context of proposed energy development.

Morphology of calcite crystals in clast coatings from four soils in the Mojave desert region

Science.gov (United States)

Chadwick, Oliver A.; Sowers, Janet M.; Amundson, Ronald G.

1989-01-01

Pedogenic calcite-crystal coatings on clasts were examined in four soils along an altitudinal gradient on Kyle Canyon alluvium in southern Nevada. Clast coatings were studied rather than matrix carbonate to avoid the effects of soil matrix on crystallization. Six crystal sizes and shapes were recognized and distinguished. Equant micrite was the dominant crystal form with similar abundance at all elevations. The distributions of five categories of spar and microspar appear to be influenced by altitudinally induced changes in effective moisture. In the drier, lower elevation soils, crystals were equant or parallel prismatic with irregular, interlocking boundaries while in the more moist, higher elevation soils they were randomly oriented, euhedral, prismatic, and fibrous. There was little support for the supposition that Mg(+2) substitution or increased (Mg + Ca)/HCO3 ratios in the precipitating solution produced crystal elongation.

Ecology and behavior of pronghorn in the Red Desert, Wyoming with reference to energy development

International Nuclear Information System (INIS)

Deblinger, R.D.

1988-01-01

Pronghorn in the Red Desert were not negatively impacted by the Sweetwater Uranium Mining Project or other human activities associated with mining. A proportion of the pronghorn population habituated to the mine site and inhabited lands adjacent to the mine their entire lives. Other pronghorn remained wary of mining activities and migrated around the mine without difficulty. Distribution patterns in the Red Desert varied seasonally and yearly. Generally, pronghorn used northern portions of the study area during summer and central to southern portions during winter. Summer range was used traditionally, while winter ranges were chosen opportunistically. Initial fall migration movement and total distances traveled were dictated by weather. Specifically, snow accumulation and temperatures determined fall migration timing and length of travel. Similarly, pronghorn migrated back to summer ranges as soon as snow melted

Russian deserters of World War I

OpenAIRE

Os'kin Maksim

2014-01-01

Desertion is one of the most active forms of ordinary resistance of the people to the state pressure during the low-popular war which is conducting for the purposes unclear for the people. At the same time, mass desertion is a manifestation of «total» war in the world conflicts of the XX century. During World War I in all armies of the world there was the desertion often accepting mass character. In the Russian army, as well as in other, deserters appeared from the war beginning. Desertion sca...

76 FR 10914 - Notice of Public Meetings: Mojave-Southern Great Basin Resource Advisory Council, Nevada

Science.gov (United States)

2011-02-28

... Area (NCA) Visitor's Center, Las Vegas, Nevada; July 21, 2011, at the BLM Southern Nevada District... final meeting agenda that will be available two weeks prior to each meeting. FOR FURTHER INFORMATION... be raised by RAC members. The final agendas with any additions/corrections to agenda topics...

Minerals in deserts

International Nuclear Information System (INIS)

Smith, G.I.

1982-01-01

Almost any kind of mineral deposit can occur in desert areas, and the lack of vegetation and soil cover makes finding them easier. Some kinds of deposits, though, are more likely to occur in deserts than elsewhere. Some of these result from processes genetically related to the present desert climate that improved lower grade deposits of ore. One such process, termed secondary enrichment, is most effective in areas with deep water tables, and many low-grade copper, silver, and uranium deposits have been converted into mineable ore by the downward migration and redeposition of soluble metals. In a desert terrane, placer processes are effective whenever running water flowing over steep slopes erodes outcropping ore bodies and transports and concentrates the heavier ore minerals at lower levels, thus converting low-grade or hard-to-mine bedrock deposits into economically workable concentrations. Other kinds of deposits are better preserved in deserts because the lower rainfall at the surface, and the lower volume of flow and the greater depths to groundwater, result in less destruction of soluble ores; deposits of salines and phosphates are the most notable ores affected by these factors. Still other ore deposits are created as a consequence of the arid climate, mostly because the high evaporation rates operating on standing bodies of water produce brines that can lead directly to concentrations of salts and indirectly to secondary minerals, such as zeolites, that are produced by reaction of silicate minerals with saline waters

Navajo Code Talker Joe Morris, Sr. shared insights from his time as a secret World War Two messenger

Science.gov (United States)

2002-01-01

Navajo Code Talker Joe Morris, Sr. shared insights from his time as a secret World War Two messenger with his audience at NASA's Dryden Flight Research Center on Nov. 26, 2002. NASA Dryden is located on Edwards Air Force Base in California's Mojave Desert.

Russian deserters of World War I

Directory of Open Access Journals (Sweden)

Os'kin Maksim

2014-10-01

Full Text Available Desertion is one of the most active forms of ordinary resistance of the people to the state pressure during the low-popular war which is conducting for the purposes unclear for the people. At the same time, mass desertion is a manifestation of «total» war in the world conflicts of the XX century. During World War I in all armies of the world there was the desertion often accepting mass character. In the Russian army, as well as in other, deserters appeared from the war beginning. Desertion scales in the Russian army explained as objective factors - diffi cult fights, shortage of supply, defeat at the front, and subjective - unwillingness to participate in war, melancholy for the house, desire to help a family the work. Desertion in different years of war had various forms. If at the beginning of war there were mainly «self-arrows», in 1915, during defeats at the front - evasion from entrenchments. By the end of 1916, because of the general fatigue from war, desertion takes the real form - flight from the front to the back. After February revolution desertion becomes mass in which hundreds thousands military personnel take part already. Disorder of army and development of revolutionary process extremely strengthen desertion scales that is explained by the actual lack of punishment for this crime. Destruction of the Russian state during revolution became the main reason of coming to power of Bolsheviks, an exit of Russia from war and the army demobilization which essential part in 1917 already deserted from the front.

Pre-treating Seed to Enhance Germination of Desert Shrubs

Energy Technology Data Exchange (ETDEWEB)

W. K. Ostler; D. C. Anderson; D. J. Hansen

2002-06-01

Creosotebush [Larrea tridentata (D.C.) Cav.] and white bursage [Ambrosia dumosa (A. Gray) W.W. Payne] seeds were subjected to pre-treatments of rinsing and soaking in water and thiourea to enhance germination in laboratory experiments. The effects of darkness, temperature, seed source, and soil moisture were also evaluated in the laboratory. The best pre-treatment from the laboratory experiments, rinsing with water for 36 hours followed by drying, was field-tested at Fort Irwin, California. Two sites and two seeding dates (early March and mid April) were determined for each site. Five mulch treatments (no mulch, straw, gravel, chemical stabilizer, and plastic) were evaluated in combination with the seed pre-treatments. Field emergence was greatly enhanced with the seed pre-treatment for white bursage during the March (18-42% increase in germination) and April seedings (16-23% increase in germination). Creosotebush showed poor germination during March (2-5%) when soil temperatures averaged 15 C, but germination increased during the April trials (6-43%) when soil temperatures averaged 23 C. The seed pre-treatment during the April trials increased germination from 16-23%. The plastic mulch treatment increased germination dramatically during both the March and April trials. The plastic mulch increased soil temperatures (8-10 C)and maintained high humidity during germination. Both the chemical stabilizer and the gravel mulches improved germination over the control while the straw mulch decreased germination. These results suggest that seed pre-treatments combined with irrigation and mulch are effective techniques to establish these two dominant Mojave Desert species from seed.

Paleoproterozoic mojaveprovince in northwestern Mexico? Isotopic and U-Pb zircon geochronologic studies of precambrian and Cambrian crystalline and sedimentary rocks, Caborca, Sonora

Science.gov (United States)

Lang, Farmer G.; Bowring, S.A.; Matzel, J.; Maldonado, G.E.; Fedo, C.; Wooden, J.

2005-01-01

Whole-rock Nd isotopic data and U-Pb zircon geochronology from Precambrian crystalline rocks in the Caborca area, northern Sonora, reveal that these rocks are most likely a segment of the Paleoproterozoic Mojave province. Supporting this conclusion are the observations that paragneiss from the ??? 1.75 Ga Bamori Complex has a 2.4 Ga Nd model age and contains detrital zircons ranging in age from Paleo- proterozoic (1.75 Ga) to Archean (3.2 Ga). Paragneisses with similar age and isotopic characteristics occur in the Mojave province in southern California. In addition, "A-type" granite exposed at the southern end of Cerro Rajon has ca 2.0 Ga Nd model age and a U-Pb zircon age of 1.71 Ga, which are similar to those of Paleoproterozoic granites in the Mojave province. Unlike the U.S. Mojave province, the Caborcan crust contains ca. 1.1 Ga granite (Aibo Granite), which our new Nd isotopic data suggest is largely the product of anatexis of the local Precambrian basement. Detrital zircons from Neoproterozoic to early Cambrian miogeoclinal arenites at Caborca show dominant populations ca. 1.7 Ga, ca. 1.4 Ga, and ca. 1.1 Ga, with subordinate Early Cambrian and Archean zircons. These zircons were likely derived predominately from North American crust to the east and northeast, and not from the underlying Caborcan basement. The general age and isotopic similarities between Mojave province basement and overlying miogeoclinal sedimentary rocks in Sonora and southern California is necessary, but not sufficient, proof of the hypothesis that Sonoran crust is allochthonous and was transported to its current position during the Mesozoic along the proposed Mojave-Sonora megashear. One viable alternative model is that the Caborcan Precambrian crust is an isolated, autochthonous segment of Mojave province crust that shares a similar, but not identical, Proterozoic geological history with Mojave province crust found in the southwest United States ?? 2005 Geological Society of America.

Reproduction and pollination of the endangered dwarf bear-poppy Arctomecon humilis (Papaveraceae)across a quarter century: unraveling of a pollination web?

Science.gov (United States)

ABSTRACT.—Arctomecon humilis, a rare gypsophile of the extreme northeastern Mojave Desert, is restricted to a few isolated populations in Washington County, Utah, USA. At several times in the past quarter century, we have studied the breeding system and reproductive success of this endangered specie...

Exploration of hydro-geomorphological indices for coastal floodplain ...

African Journals Online (AJOL)

Ozdemir and Bird (2008) investigated morphometric parameters across two ... industries are dominant and across many rural communities, fishing and ... a high correlation with Species richness, pH, groundwater, soil moisture and ..... for Animal Habitat Analysis: A Case Study Using Bighorn Sheep in the Mojave Desert. The.

Respondence and feedback of modern sand deserts to climate change--A case study in Gurbantunggut Desert

Institute of Scientific and Technical Information of China (English)

无

2000-01-01

The research on the respondence and feedback of modern sand deserts to the climate change is an important component part in the studies on the global climate change. Deserts respond to the climate change, meanwhile, they affect the climate with their feedback of peculiar environment during the respondence. Many researches on desert climate have been carried out at home and abroad. However, there is little research on the respondence and feedback of modern fixed, semi-fixed and mobile deserts in arid areas to the climate change, in which the factor analysis as well as the parameter changing effects is especially the difficult problem all along. In this note, the parameters of the respondence and feedback of Gurbantunggut Desert to the climate change are measured and analyzed, some variable parameters of water-heat exchange are obtained, and a numerical model of desertification is developed according to a series of climate change of about 40 years and the variable relations of meteorological and physical features of the sand surface in Gurbantunggut Desert.

Influence of surface roughness of a desert

Science.gov (United States)

Sud, Y. C.; Smith, W. E.

1984-01-01

A numerical simulation study, using the current GLAS climate GCM, was carried out to examine the influence of low bulk aerodynamic drag parameter in the deserts. The results illustrate the importance of yet another feedback effect of a desert on itself, that is produced by the reduction in surface roughness height of land once the vegetation dies and desert forms. Apart from affecting the moisture convergence, low bulk transport coefficients of a desert lead to enhanced longwave cooling and sinking which together reduce precipitation by Charney's (1975) mechanism. Thus, this effect, together with albedo and soil moisture influence, perpetuate a desert condition through its geophysical feedback effect. The study further suggests that man made deserts is a viable hypothesis.

Nature and origin of secondary mineral coatings on volcanic rocks of the Black Mountain, Stonewall Mountain, and Kane Springs Wash volcanic centers, southern, Nevada

Science.gov (United States)

Taranik, James V.; Hsu, Liang C.; Spatz, David M.; Chenevey, Michael J.

1989-01-01

The following subject areas are covered: (1) genetic, spectral, and LANDSAT Thematic Mapper imagery relationship between desert varnish and tertiary volcanic host rocks, southern Nevada; (2) reconnaissance geologic mapping of the Kane Springs Wash Volcanic Center, Lincoln County, Nevada, using multispectral thermal infrared imagery; (3) interregional comparisons of desert varnish; and (4) airborne scanner (GERIS) imagery of the Kane Springs Wash Volcanic Center, Lincoln County, Nevada.

Animal ecology

International Nuclear Information System (INIS)

Turner, F.B.; Strojan, C.L.; Ackerman, T.L.; Maza, B.G.

1976-01-01

Progress is reported in the following areas of research: dynamics of trace elements in desert environments; sterility of female Uta stansburiana exposed to gamma radiation; behavior and metabolism of jackrabbits, Lepus californicus, in the Mojave desert; determination of 18 O in water contained in biological samples by charged particle activation; temperature maintenance and CO 2 concentration in a swarm of honey bees; energy and nitrogen budgets and water balance in lizards; distribution and abundance of soil arthropods; and water balance of the cockroach, arenivaga investigata

Artemisia pollen-indicated steppe distribution in southern China during the Last Glacial Maximum

Directory of Open Access Journals (Sweden)

Liu Hongyan

2013-07-01

Full Text Available The Last Glacial Maximum (LGM was the coldest period during the previous 20,000 years. There have been different points of views on steppe distribution during the LGM period in southern China, partly due to the different interpretations of Artemisia occurrences. To make a reliable interpretation of the pollen fossil Artemisia, the modern distribution of Artemisia species and the relationship of pollen with climate and vegetation over a large spatial scale in China was thoroughly analyzed. Information about Artemisia species and pollen distributions used in this paper were collected from published works completed by other researchers as well as ourselves. The southern limit of steppe vegetation during the LGM period was interpreted from the published contour map of Artemisia pollen percentages during the LGM. Artemisia species in China are mostly distributed either in the horizontally distributed steppe regions or in the vertically distributed desert-steppe in the desert region, which indicates a cold and dry climate. The steppe is a distribution center of Artemisia pollen. Fractions of Artemisia in surface pollen assemblages are lower in both the desert and the temperate forest. Neither high Artemisia species cover nor high percentages of Artemisia pollen were found in the coast areas of China. Twenty-five percent of Artemisia pollen in sediments might indicate a local occurrence of steppe vegetation. Percentages of Artemisia pollen in the subtropical and tropical forest are less than 10%. A close relationship between Artemisia pollen and temperate steppe in China is demonstrated. The southern edge of the steppe vegetation during the LGM might be along the middle reach of the Yangtze River. Our results support the hypothesis that the isolated high fraction of Artemisia pollen along the northern edge of the South China Sea was transported from a large source area.

Desertions in nineteenth-century shipping: modelling quit behaviour

OpenAIRE

Jari Ojala; Jaakko Pehkonen; Jari Eloranta

2013-01-01

Ship jumping in foreign ports was widespread throughout the age of sail. Desertion by seamen was illegal, it occurred abroad, and men who deserted only seldom returned home. We analyse desertion quantitatively and link it to the broader question of quit behaviour and labour turnover. Though the better wages paid at the foreign ports were the main reason for desertion, the regression model of the determinants of desertion indicates that outside opportunities, such as migration, and monetary in...

HIGH FOLIAR NITROGEN IN DESERT SHRUBS: AN IMPORTANT ECOSYSTEM TRAIT OR DEFECTIVE DESERT DOCTRINE?

Science.gov (United States)

Nitrogen concentrations in green and senesced leaves of perennial desert shrubs were compiled from a worldwide literature search to test the validity of the doctrine that desert shrubs produce foliage and leaf litter much richer in nitrogen than that in the foliage of plants from...

Biologic overview for the Nevada Nuclear Waste Storage Investigations, Nevada Test Site, Nye County, Nevada

International Nuclear Information System (INIS)

Collins, E.; O'Farrell, T.P.; Rhoads, W.A.

1982-01-01

The Nevada Nuclear Waste Storage Investigations project study area includes five major vegetation associations characteristic of the transition between the northern extent of the Mojave Desert and the southern extent of the Great Basin Desert. A total of 32 species of reptiles, 66 species of birds, and 46 species of mammals are known to occur within these associations elsewhere on the Nevada Test Site. Ten species of plants, and the mule deer, wild horse, feral burro, and desert tortoise were defined as possible sensitive species because they are protected by federal and state regulations, or are being considered for such protection. The major agricultural resources of southern Nye County included 737,000 acres of public grazing land managed by the Bureau of Land Management, and 9500 acres of irrigated crop land located in the Beatty/Oasis valleys, the Amargosa Valley, and Ash Meadows. Range lands are of poor quality. Alfalfa and cotton are the major crops along with small amounts of grains, Sudan grass, turf, fruits, and melons. The largest impacts to known ecosystems are expected to result from: extensive disturbances associated with construction of roads, seismic lines, drilling pads, and surface facilities; storage and leaching of mined spoils; disposal of water; off-road vehicle travel; and, over several hundred years, elevated soil temperatures. Significant impacts to off-site areas such as Ash Meadows are anticipated if new residential developments are built there to accommodate an increased work force. Several species of concern and their essential habitats are located at Ash Meadows. Available literature contained sufficient baseline information to assess potential impacts of the proposed project on an area-wide basis. It was inadequate to support analysis of potential impacts on specific locations selected for site characterization studies, mining an exploratory shaft, or the siting and operation of a repository

Rural childhoods in Egypt's desert lands

DEFF Research Database (Denmark)

Adriansen, Hanne Kirstine

Based on fieldwork in Egypt’s desert lands, this paper discusses rural childhoods in an area experiencing rapid social and cultural change. Since 1987, the Egyptian Government has made new villages in the desert as a means to increase agricultural production and solving problems of unemployment....... Many settlers move to the Mubarak villages in order to give their children a good start in life. The desert villages are associated with a type of ‘rural idyll’. The process of settling in the desert impacts upon the children’s possible pathways to adulthood and their identities and social......’s new roles impact upon the children’s lives. The social contexts shaping the desert childhoods are in some ways more similar to contexts in ‘developed’ countries than in other parts of rural Egypt. The paper ends up by contrasting ideas of rural childhoods in Egypt with those found in ‘developed...

Fine-Scale Human Population Structure in Southern Africa Reflects Ecogeographic Boundaries.

Science.gov (United States)

Uren, Caitlin; Kim, Minju; Martin, Alicia R; Bobo, Dean; Gignoux, Christopher R; van Helden, Paul D; Möller, Marlo; Hoal, Eileen G; Henn, Brenna M

2016-09-01

Recent genetic studies have established that the KhoeSan populations of southern Africa are distinct from all other African populations and have remained largely isolated during human prehistory until ∼2000 years ago. Dozens of different KhoeSan groups exist, belonging to three different language families, but very little is known about their population history. We examine new genome-wide polymorphism data and whole mitochondrial genomes for >100 South Africans from the ≠Khomani San and Nama populations of the Northern Cape, analyzed in conjunction with 19 additional southern African populations. Our analyses reveal fine-scale population structure in and around the Kalahari Desert. Surprisingly, this structure does not always correspond to linguistic or subsistence categories as previously suggested, but rather reflects the role of geographic barriers and the ecology of the greater Kalahari Basin. Regardless of subsistence strategy, the indigenous Khoe-speaking Nama pastoralists and the N|u-speaking ≠Khomani (formerly hunter-gatherers) share ancestry with other Khoe-speaking forager populations that form a rim around the Kalahari Desert. We reconstruct earlier migration patterns and estimate that the southern Kalahari populations were among the last to experience gene flow from Bantu speakers, ∼14 generations ago. We conclude that local adoption of pastoralism, at least by the Nama, appears to have been primarily a cultural process with limited genetic impact from eastern Africa. Copyright © 2016 by the Genetics Society of America.

Cost estimates for Operation Desert Shield/Desert Storm: a budgetary analysis

OpenAIRE

Johnson, J. Andrew.

1991-01-01

Operation Desert Shield/Desert Storm (DS/DS) presented unique challenges for estimating the cost of that conflict. This analysis reviews the cost estimates and methodologies developed for that purpose by DoD, CBO and GAO. It considers the budget climate and the role of foreign cash and in-kind contributions. Finally, it reviews the budgeting innovations used to provide and monitor DS/DS defense spending. At the outset of the crisis, costs were estimated to determine the defense funding requir...

Climate change induced by Southern Hemisphere desertification

Science.gov (United States)

Wang, Ye; Yan, Xiaodong

2017-12-01

Some 10-20% of global dry-lands are already degraded, and the ongoing desertification threatens the world's poorest populations. Studies on desertification effects are essential for humans to adapt to the environmental challenges posed by desertification. Given the importance of the much larger southern ocean to the global climate and the Southern Hemisphere (SH) climate changes in phase with those in the north, the biogeophysical effects of the SH desertification on climate are assessed using an Earth system model of intermediate complexity, MPM-2. This analysis focuses on differences in climate among the averages of simulations with desert expansion in different latitude bands by year 2000. The localized desertification causes significant global changes in temperature and precipitation as well as surface albedo. On the global scale, cooling dominates the SH desertification effects. However, the biogeophysical effects are most significant in regions with desertification, and the cooling is also prominent in northern mid-latitudes. Desert expansion in 15°-30°S reveals statistically most significant cooling and increased precipitation over the forcing regions during spring. The global and regional scale responses from desertification imply the climate teleconnection and address the importance of the effects from the SH which are contingent on the location of the forcing. Our study indicates that biogeophysical mechanisms of land cover changes in the SH need to be accounted for in the assessment of land management options especially for latitude band over 15°-30°S.

Effects of prolonged drought on the vegetation cover of sand dunes in the NW Negev Desert: Field survey, remote sensing and conceptual modeling

Science.gov (United States)

Siegal, Z.; Tsoar, H.; Karnieli, A.

2013-06-01

Luminescence dating of stable sand dunes in the large deserts of the world has shown several episodes of mobility during the last 30 k years. The logical explanation for the mobility of fixed dunes is severe drought. Though drought length can be estimated, the level of precipitation drop is unknown. The stabilized sand dunes of the northwestern Negev Desert, Israel have been under an unprecedented prolonged drought since 1995. This has resulted in a vast decrease of shrubs cover on the fixed sand dunes, which changes along the rainfall gradient. In the north, an average of 27% of the shrubs had wilted by 2009, and in the drier southern area, 68% of the shrubs had withered. This loss of shrubbery is not expected to induce dune remobilization because the existing bio-crust cover is not negatively affected by the drought. Eleven aerial photographs taken over the drier southern area from 1956 to 2005 show the change in shrub cover due to human impact and the recent severe drought.

Physiological adaptation in desert birds

NARCIS (Netherlands)

Williams, JB; Tieleman, BI; Williams, Joseph B.

We call into question the idea that birds have not evolved unique physiological adaptations to desert environments. The rate at which desert larks metabolize energy is lower than in mesic species within the same family, and this lower rate of living translates into a lower overall energy requirement

From Desert to Dessert: Why Australian Dust Matters.

Science.gov (United States)

Hunter, K. A.; Mackie, D. S.; Boyd, P. W.; McTainsh, G. H.

2006-12-01

The growth of some types of phytoplankton in several parts of the world ocean, including much of the Southern Ocean, is limited by the supply of iron. Large Australian dust storms uplift, transport and abrade soils, to produce aeolian dust that is a significant source iron to the Southern Ocean. Atmospheric processes that enhance the dissolution of iron from aeolian dusts are of interest and have been studied for material from major dust producing regions like the Sahara, Gobi and Australian deserts; the reported solubility of iron from aeolian dusts ranges from <0.01% to 80%. The characteristic red soils, sands and dusts from Australia are generally believed to consist of quartz grains with a coating of fine grains and crystals of iron oxides, primarily hematite and goethite. The precise mineralogy of soil and dust grain coatings is poorly understood and it also not well known how the coatings are altered during uplift and transport to the ocean. Current models to understand the processes operating during the transport and atmospheric processing of dust include some generalisations and simplifications that are not always warranted and our work has shown the overlooked complexity of the system. Models for aeolian-iron dissolution based on Northern Hemisphere data commonly include the pollutants SOx and NOx. The modern Southern Hemisphere is less polluted and thus resembles past environmental systems. The dissolution of iron from soils of the Saharan, Gobi and Australian deserts in the presence of protons only (i.e. without SOx and NOx) occurs in two phases. The first, faster phase, representing up to 20% of total iron is via a surface-controlled mechanism. The rate determining variable is the exposed surface area of the iron oxides and not the size of the underlying quartz grain. The second, slower, phase of dissolution occurs via the transport-controlled formation of a leached layer. During the simulated aeolian abrasion of Australian soils from dust producing

When the solar energy pays

International Nuclear Information System (INIS)

Laramee, V.

1997-01-01

In the californian desert of Mojave, the three biggest solar power plants in the world produce 90% of world solar electric power. They have been operating for ten years, and their managers go on to improve them. These installations beat the productivity record every year, proving that the thermal solar energy can be competitive. (N.C.)

Directional floral orientation in Joshua trees (Yucca brevifolia)

Science.gov (United States)

Steve Warren; L. Scott Baggett; Heather Warren

2016-01-01

Joshua tree (Yucca brevifolia Engelm.) is a large, arborescent member of the yucca genus. It is an endemic and visually dominant plant in portions of the Mojave Desert, USA. We document the unique and heretofore unreported directional orientation of its flower panicles. The flower panicles grow primarily at the tips of branches that are oriented to the south....

Impacts of atmospheric nitrogen deposition on vegetation and soils in Joshua Tree National Park

Science.gov (United States)

E.B. Allen; L. Rao; R.J. Steers; A. Bytnerowicz; M.E. Fenn

2009-01-01

The western Mojave Desert is downwind of nitrogen emissions from coastal and inland urban sources, especially automobiles. The objectives of this research were to measure reactive nitrogen (N) in the atmosphere and soils along a N-deposition gradient at Joshua Tree National Park and to examine its effects on invasive and native plant species. Atmospheric nitric acid (...

How desert varnish forms?

Science.gov (United States)

Perry, Randall S.; Kolb, Vera M.; Lynne, Bridget Y.; Sephton, Mark A.; Mcloughlin, Nicola; Engel, Michael H.; Olendzenski, Lorraine; Brasier, Martin; Staley, James T., Jr.

2005-09-01

Desert varnish is a black, manganese-rich rock coating that is widespread on Earth. The mechanism underlying its formation, however, has remained unresolved. We present here new data and an associated model for how desert varnish forms, which substantively challenges previously accepted models. We tested both inorganic processes (e.g. clays and oxides cementing coatings) and microbial methods of formation. Techniques used in this preliminary study include SEM-EDAX with backscatter, HRTEM of focused ion beam prepared (FIB) wafers and several other methods including XRPD, Raman spectroscopy, XPS and Tof-SIMS. The only hypothesis capable of explaining a high water content, the presence of organic compounds, an amorphous silica phase (opal-A) and lesser quantities of clays than previously reported, is a mechanism involving the mobilization and redistribution of silica. The discovery of silica in desert varnish suggests labile organics are preserved by interaction with condensing silicic acid. Organisms are not needed for desert varnish formation but Bacteria, Archaea, Eukarya, and other organic compounds are passively incorporated and preserved as organominerals. The rock coatings thus provide useful records of past environments on Earth and possibly other planets. Additionally this model also helps to explain the origin of key varnish and rock glaze features, including their hardness, the nature of the "glue" that binds heterogeneous components together, its layered botryoidal morphology, and its slow rate of formation.

Fog water chemistry in the Namib desert, Namibia

Science.gov (United States)

Eckardt, Frank D.; Schemenauer, Robert S.

This study documents the ion concentrations and ion enrichment relative to sea water, in Namib Desert fog water, with the purpose of establishing its suitability for future fogwater collection schemes, while also examining claims that Namib Desert fog water carries exceptionally high concentrations of sulphate, which may be responsible for the formation of gypsum deposits in the desert. The work suggests that Namibian fog water is at least as clean as has been reported from other coastal deserts in South America and Arabia, and provides a source of very clean water for the coastal desert region of south-western Africa. It does not appear that fog is an efficient sulphur source for the formation of the gypsum deposits, unless rare events with high concentrations of marine sulphur compounds occur.

A 30-year chronosequence of burned areas in Arizona: effects of wildfires on vegetation in Sonoran Desert Tortoise (Gopherus morafkai) habitats

Science.gov (United States)

Shryock, Daniel F.; Esque, Todd C.; Chen, Felicia C.

2015-01-01

Fire is widely regarded as a key evolutionary force in fire-prone ecosystems, with effects spanning multiple levels of organization, from species and functional group composition through landscape-scale vegetation structure, biomass, and diversity (Pausas and others, 2004; Bond and Keeley 2005; Pausas and Verdu, 2008). Ecosystems subjected to novel fire regimes may experience profound changes that are difficult to predict, including persistent losses of vegetation cover and diversity (McLaughlin and Bowers, 1982; Brown and Minnich, 1986; Brooks, 2012), losses to seed banks (Esque and others, 2010a), changes in demographic processes (Esque and others, 2004; DeFalco and others, 2010), increased erosion (Soulard and others, 2013), changes in nutrient availability (Esque and others, 2010b), increased dominance of invasive species (Esque and others, 2002; Brooks and others, 2004), and transitions to alternative community states (Davies and others, 2012). In the deserts of the Southwestern United States, fire size and frequency have increased substantially over the last several decades because of an invasive grass/fire feedback cycle (Schmid and Rogers, 1988; D’Antonio and Vitousek, 1992; Swantek and others, 1999; Brooks and Matchett, 2006; Esque and others, 2010a), in which invasive annual species are able to establish fuel loads capable of sustaining large-scale wildfires following years of high rainfall (Esque and Schwalbe, 2002). Native perennial vegetation is not well-adapted to fire in these environments, and widespread, physiognomically dominant species such as creosote bush (Larrea tridentata), Joshua tree (Yucca brevifolia), giant saguaro cactus (Carnegiea gigantea), and paloverde (Parkinsonia spp.) may be reduced or eliminated (Brown and Minnich, 1986; Esque and others, 2006; DeFalco and others, 2010), potentially affecting wildlife populations including the Sonoran and federally threatened Mojave Desert Tortoises (Gopherus morafkai and Gopherus agassizii

Nationwide desert highway assessment: a case study in China.

Science.gov (United States)

Mao, Xuesong; Wang, Fuchun; Wang, Binggang

2011-07-01

The natural environment affects the construction of desert highways. Conversely, highway construction affects the natural environment and puts the ecological environment at a disadvantage. To satisfy the variety and hierarchy of desert highway construction and discover the spatio-temporal distribution of the natural environment and its effect on highway construction engineering, an assessment of the natural regional divisions of desert highways in China is carried out for the first time. Based on the general principles and method for the natural region division, the principles, method and index system for desert highway assessment is put forward by combining the desert highway construction features and the azonal differentiation law. The index system combines the dominant indicator and four auxiliary indicators. The dominant indicator is defined by the desert's comprehensive state index and the auxiliary indicators include the sand dune height, the blown sand strength, the vegetation coverage ratio and the annual average temperature difference. First the region is divided according to the dominant indicator. Then the region boundaries are amended according to the four auxiliary indicators. Finally the natural region division map for desert highway assessment is presented. The Chinese desert highways can be divided into three sections: the east medium effect region, the middle medium-severe effect region, and the west slight-medium effect region. The natural region division map effectively paves the way for the route planning, design, construction, maintenance and ongoing management of desert highways, and further helps environmental protection.

Desert Pavement Studies

National Research Council Canada - National Science Library

Haff, Peter

2003-01-01

Combining plan view information from aerial photography showing details of stream channels on desert pavement surfaces with process-based erosion models, a high-resolution, synthetic topography DEM...

Desert Pavement Studies

National Research Council Canada - National Science Library

Haff, P

2003-01-01

Combining plan view information from aerial photography showing details of stream channels on desert pavement surfaces with process-based erosion models, a high-resolution, "synthetic topography" DEM...

Remote Sensing Field Guide - Desert

Science.gov (United States)

1991-09-01

experienced boatmen. Most river water, even in deserts, contains Giardia micro -organisms that can cause serious diarrhea. Sich water should be boiled...water. The solutes and suspended micro -matter can be moved up and down by an oscillating water table and redeposited or precipitated at differ- ent...McCauley, U.S. Geological Survey, Desert Studies Group, Flagstaff, AZ, Nov 1973. B. Servicio Aerofotografia Nacional del Peru (on back). / ...... CONN:MFI

Plant responses to an edaphic gradient across an active sand dune/desert boundary in the great basin desert.

NARCIS (Netherlands)

Rosenthal, D.M.; Ludwig, F.; Donovan, L.A.

2005-01-01

In arid ecosystems, variation in precipitation causes broad-scale spatial heterogeneity in soil moisture, but differences in soil texture, development, and plant cover can also create substantial local soil moisture heterogeneity. The boundary between inland desert sand dunes and adjacent desert

Chapter 8: Fire and nonnative invasive plants in the Interior West bioregion

Science.gov (United States)

Peter M. Rice; Guy R. McPherson; Lisa J. Rew

2008-01-01

The Interior West bioregion is bounded on the east by the eastern slope of the Rocky Mountains from Canada south to Mexico and on the west by the eastern foothills of the Cascade Range in Washington and Oregon and the eastern foothills of the Sierra Nevada in California. The bioregion includes the Chihuahuan, Sonoran, and Mojave hot deserts and the Great Basin cold...

Phylogenetic studies of Terfezia pfeilii and Choiromyces echinulatus (Pezizales) support new genera for southern African truffles: Kalaharituber and Eremiomyces.

Science.gov (United States)

Yael Ferdman; Sharon Aviram; Nurit Roth-Bejerano; James M. Trappe; Varda. Kagan-Zur

2005-01-01

The ITS region including the 5.8S rRNA gene as well as the 5' end of the 28S rRNA gene of hypogeous Pezizaceae and Tuberaceae were studied to clarify the generic placement of two southern African desert truffles, Terfezia pfeilii and Choiromyces echinulatus. The results show that...

The impact of desert solar power utilization on sustainable development

International Nuclear Information System (INIS)

Sadiq Ali Shah; Yang Zhang

2011-01-01

This paper evaluates the prospects of developing a solar based desert economy in the deserts of solar-rich countries. The potential deserts are analysed to study their positive impact on the sustainable development processes in these regions. The sustainability of the processes is established on the basis of self-contained nature of energy generation, environmental emission reduction and desert land reclamation. (authors)

Microbial ecology of hot desert edaphic systems.

Science.gov (United States)

Makhalanyane, Thulani P; Valverde, Angel; Gunnigle, Eoin; Frossard, Aline; Ramond, Jean-Baptiste; Cowan, Don A

2015-03-01

A significant proportion of the Earth's surface is desert or in the process of desertification. The extreme environmental conditions that characterize these areas result in a surface that is essentially barren, with a limited range of higher plants and animals. Microbial communities are probably the dominant drivers of these systems, mediating key ecosystem processes. In this review, we examine the microbial communities of hot desert terrestrial biotopes (including soils, cryptic and refuge niches and plant-root-associated microbes) and the processes that govern their assembly. We also assess the possible effects of global climate change on hot desert microbial communities and the resulting feedback mechanisms. We conclude by discussing current gaps in our understanding of the microbiology of hot deserts and suggest fruitful avenues for future research. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Biological and Proteolytic Variation in the Venom of Crotalus scutulatus scutulatus from Mexico

Directory of Open Access Journals (Sweden)

Miguel Borja

2018-01-01

Full Text Available Rattlesnake venoms may be classified according to the presence/absence and relative abundance of the neurotoxic phospholipases A 2 s (PLA 2 s, such as Mojave toxin, and snake venom metalloproteinases (SVMPs. In Mexico, studies to determine venom variation in Mojave Rattlesnakes (Crotalus scutulatus scutulatus are limited and little is known about the biological and proteolytic activities in this species. Tissue (34 and venom (29 samples were obtained from C. s. scutulatus from different locations within their distribution in Mexico. Mojave toxin detection was carried out at the genomic (by PCR and protein (by ELISA levels for all tissue and venom samples. Biological activity was tested on representative venoms by measuring LD 50 and hemorrhagic activity. To determine the approximate amount of SVMPs, 15 venoms were separated by RP-HPLC and variation in protein profile and proteolytic activity was evaluated by SDS-PAGE (n = 28 and Hide Powder Azure proteolytic analysis (n = 27. Three types of venom were identified in Mexico which is comparable to the intraspecific venom diversity observed in the Sonoran Desert of Arizona, USA: Venom Type A (∼Type II, with Mojave toxin, highly toxic, lacking hemorrhagic activity, and with scarce proteolytic activity; Type B (∼Type I, without Mojave toxin, less toxic than Type A, highly hemorrhagic and proteolytic; and Type A + B, containing Mojave toxin, as toxic as venom Type A, variable in hemorrhagic activity and with intermediate proteolytic activity. We also detected a positive correlation between SVMP abundance and hemorrhagic and proteolytic activities. Although more sampling is necessary, our results suggest that venoms containing Mojave toxin and venom lacking this toxin are distributed in the northwest and southeast portions of the distribution in Mexico, respectively, while an intergradation in the middle of both zones is present.

Growth responses of five desert plants as influenced by biological soil crusts from a temperate desert, China

Science.gov (United States)

Zhang, Yuanming; Belnap, Jayne

2015-01-01

In almost all dryland systems, biological soil crusts (biocrusts) coexist alongside herbaceous and woody vegetation, creating landscape mosaics of vegetated and biocrusted patches. Results from past studies on the interaction between biocrusts and vascular plants have been contradictory. In the Gurbantunggut desert, a large temperate desert in northwestern China, well-developed lichen-dominated crusts dominate the areas at the base and between the sand dunes. We examined the influence of these lichen-dominated biocrusts on the germination, growth, biomass accumulation, and elemental content of five common plants in this desert: two shrubs (Haloxylon persicum, Ephedra distachya) and three herbaceous plants (Ceratocarpus arenarius, Malcolmia africana and Lappula semiglabra) under greenhouse conditions. The influence of biocrusts on seed germination was species-specific. Biocrusts did not affect percent germination in plants with smooth seeds, but inhibited germination of seeds with appendages that reduced or eliminated contact with the soil surface or prevented seeds from slipping into soil cracks. Once seeds had germinated, biocrusts had different influences on growth of shrub and herbaceous plants. The presence of biocrusts increased concentrations of nitrogen but did not affect phosphorus or potassium in tissue of all tested species, while the uptake of the other tested nutrients was species-specific. Our study showed that biocrusts can serve as a biological filter during seed germination and also can influence growth and elemental uptake. Therefore, they may be an important trigger for determining desert plant diversity and community composition in deserts.

Fire history and moisture influences on historical forest age structure in the sky islands of southern Arizona, USA

Science.gov (United States)

Jose M. Iniguez; Thomas W. Swetnam; Christopher H. Baisan

2016-01-01

Aim: The purpose of this study was to examine the influence of moisture and fire on historical ponderosa pine (Pinus ponderosa Dougl. ex Laws.) age structure patterns. Location: We used a natural experiment created over time by the unique desert island geography of southern Arizona. Methods: We sampled tree establishment dates in two sites on Rincon Peak and...

The Use of Water During the Crew 144, Mars Desert Research Station, Utah Desert

Science.gov (United States)

De Morais Mendonca Teles, Antonio

2016-07-01

Well. from November 29th to December 14th, 2014, the author conducted astrobiological and geological surveys, as analog astronaut member of the international Crew 144, at the site of the Mars Society's Mars Desert Research Station, located at a remote location in the Utah desert, United States. The use of water for drinking, bathing, cleaning, etc., in the crew was a major issue for consideration for a human expedition to the planet Mars in the future. The author would like to tell about the factors of the rationalized use of water.

Desert dust,Ocean spray,Volcanoes,Biomass burning: Pathways of nutrients into Andean rainforests

Science.gov (United States)

Fabian, P.; Rollenbeck, R.; Spichtinger, N.; Dominguez, G.; Brothers, L.; Thiemens, M.

2009-04-01

Regular rain and fogwater sampling in the Podocarpus National Park, along an altitude profile between 1800 and 3185 m, has been carried out since 2002.The research area located in southern Ecuador on the wet eastern slopes of the Andes is dominated by trade winds from easterly directions. The samples, generally accumulated over 1-week intervals, have been analysed for pH,conductivity and major ions(K+,Na+,NH4+,Ca2+,Mg 2+,SO42-,NO3-,PO43). For all components a strong seasonal variation is observed,while the altitudinal gradient is less pronounced. About 35 % of the weekly samples had very low ion contents,at or below the detection limit, with pH generally above 5 and conductivity below 10 uS/cm.10 days back trajectories (FLEXTRA) showed that respective air masses originated in pristine continental areas,with little or no obvious pollution sources. About 65 %,however,were significantly loaded with cations and anions,with pH often as low as 3.5 to 4.0 and conductivity up to 50 uS/cm.Back trajectories showed that respective air masses had passed over areas of intense biomass burning,volcanoes,and the ocean,with even episodic Sahara and/or Namib desert dust interference. Enhanced SO4 2-and NO3- were identified,by combining satellite-based fire pixels with back trajectories,as predominantly resulting from biomass burning. Analyses of oxygen isotopes 16O ,17O ,and 18O of nitrate show that nitrate in fog samples is a product of atmospheric conversion of precursors.For most cases,by using emission inventories, anthropogenic precursor sources other than forest fires could be ruled out,thus leaving biomass burning as the main source of nitrate and sulphate in rain and fogwater. Some SO4 2- ,about 10 % of the total input,could be identified to originate from active volcanoes, whose plumes were sometimes encountered by the respective back trajectories. Enhanced Na +, K + ,and Cl - was found to originate from ocean spray sources.They were associated with strong winds providing

Sensitivity of Sahelian Precipitation to Desert Dust under ENSO variability: a regional modeling study

Science.gov (United States)

Jordan, A.; Zaitchik, B. F.; Gnanadesikan, A.

2016-12-01

Mineral dust is estimated to comprise over half the total global aerosol burden, with a majority coming from the Sahara and Sahel region. Bounded by the Sahara Desert to the north and the Sahelian Savannah to the south, the Sahel experiences high interannual rainfall variability and a short rainy season during the boreal summer months. Observation-based data for the past three decades indicates a reduced dust emission trend, together with an increase in greening and surface roughness within the Sahel. Climate models used to study regional precipitation changes due to Saharan dust yield varied results, both in sign convention and magnitude. Inconsistency of model estimates drives future climate projections for the region that are highly varied and uncertain. We use the NASA-Unified Weather Research and Forecasting (NU-WRF) model to quantify the interaction and feedback between desert dust aerosol and Sahelian precipitation. Using nested domains at fine spatial resolution we resolve changes to mesoscale atmospheric circulation patterns due to dust, for representative phases of El Niño-Southern Oscillation (ENSO). The NU-WRF regional earth system model offers both advanced land surface data and resolvable detail of the mechanisms of the impact of Saharan dust. Results are compared to our previous work assessed over the Western Sahel using the Geophysical Fluid Dynamics Laboratory (GFDL) CM2Mc global climate model, and to other previous regional climate model studies. This prompts further research to help explain the dust-precipitation relationship and recent North African dust emission trends. This presentation will offer a quantitative analysis of differences in radiation budget, energy and moisture fluxes, and atmospheric dynamics due to desert dust aerosol over the Sahel.

Distribution patterns of terricolous and saxicolous lichens in extreme desert conditions

Science.gov (United States)

Temina, M.

2012-04-01

The investigation of biodiversity in stressful habitats is of great interest because it elucidates relationships between organisms and their environment, as well as revealing the mechanisms of their survival and adaptation to extreme conditions. Deserts represent such stressful habitats where harsh climate and limited resources greatly influence the formation of biota. In order to understand the link between microscale environmental variability in extreme arid conditions and lichen biodiversity patterns, we conducted the present study. For this purpose, the structure and distribution of lichen communities on soil and cobbles at six stations at "Evolution Canyon" III (EC III), Nahal Shaharut, in the extreme southern Negev, Israel, were examined. The opposite slopes of the canyon represented specific ecological niches characterized by sharply different microclimatic conditions. The following characteristics of lichen communities were studied: species richness, systematic diversity, biogeographical elements, frequencies and distribution of species, their morphological and anatomical characteristics, reproductive strategy, and ecological peculiarities. In the research site three environmental variables were evaluated: soil moisture, and temperatures of soil and cobbles. The Canonical Correspondence Analysis was used to study the influence of these ecological variables on the distribution of lichen species. The lichen diversity of EC III was very poor and comprised 12 species (3 cyanoliches on soil vs. 9 phycolichens on cobbles). Most of them belong to a specific group of arid endemic elements, adapted to survive in extreme arid conditions in the deserts of the Levant. The harsh desert conditions of the canyon negatively influence the reproductive ability of lichens. This influence is expressed in the decreased sizes of fruit bodies in some species, and the frequent occurrence of sterile specimens among lichens found in the canyon. A comparative analysis of structure

Annual report on paleoclimate studies for the Yucca Mountain project site characterization conducted by the Desert Research Institute for the Department of Energy

International Nuclear Information System (INIS)

1994-01-01

The prospect that Yucca Mountain may become a repository for high-level radionuclides with especially long half-lives means that the intended waste containment area must be well beyond the reach of the hydrologic system for at least ten millennia. Through the integration of several avenues of paleoclimatic proxy data, the authors intend to arrive at definite conclusions regarding rates of change, and extremes and stabilities of past climate regimes. These will in turn lead to rough estimates of: the amounts of rainfall available for recharge during past periods of effectively wetter climate, and the durations and frequencies of recharge periods. The paper gives summaries of the following studies: Late Quaternary and Holocene climate derived from vegetation history and plant cellulose stable isotope records from the Great basin of western North America; Accomplishments of paleofaunal studies, 1993--1994; Geomorphology studies in the Great Basin; Alluvial fan response to climatic change, Buena Vista Valley, central Nevada; Sedimentology, stratigraphy, and chronology of lacustrine deposition in the Fernley Basin, west-central Nevada; Tree-rings, lake chronologies, alluvial sequences and climate--Implications for Great Basin paleoenvironmental studies; Stable isotopic validation studies--Fossil snails; and Late Pleistocene and Holocene eolian activity in the Mojave Desert

Long-Term Observations of Dust Storms in Sandy Desert Environments

Science.gov (United States)

Yun, Hye-Won; Kim, Jung-Rack; Choi, Yun-Soo

2015-04-01

Mineral dust occupies the largest portion of atmospheric aerosol. Considering the numerous risks that dust poses for socioeconomic and anthropogenic activities, it is crucial to understand sandy desert environments, which frequently generate dust storms and act as a primary source of atmospheric aerosol. To identify mineral aerosol mechanisms, it is essential to monitor desert environmental factors involving dust storm generation in the long term. In this study, we focused on two major environmental factors: local surface roughness and soil moisture. Since installments of ground observation networks in sandy deserts are unfeasible, remote sensing techniques for mining desert environmental factors were employed. The test area was established within the Badain Jaran and Kubuqi Deserts in Inner Mongolia, China, where significant seasonal aeolian processes emit mineral dust that influences all of East Asia. To trace local surface roughness, we employed a multi-angle imaging spectroradiometer (MISR) image sequence to extract multi-angle viewing (MAV) topographic parameters such as normalized difference angular index, which represents characteristics of the target desert topography. The backscattering coefficient from various space-borne SAR and stereotopography were compared with MAV observations to determine calibrated local surface roughness. Soil moisture extraction techniques from InSAR-phase coherence stacks were developed and compiled with advanced scatterometer (ASCAT) soil moisture data. Combined with metrological information such as the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA interim, correlations between intensity of sand dune activity as a proxy of aeolian processes in desert environments, surface wind conditions, and surface soil moisture were traced. Overall, we have confirmed that tracking sandy desert aeolian environments for long-term observations is feasible with space-borne, multi-sensor observations when combined with

Goods and services provided by native plants in desert ecosystems: Examples from the northwestern coastal desert of Egypt

Directory of Open Access Journals (Sweden)

Laila M. Bidak

2015-01-01

Full Text Available About one third of the earth’s land surface is covered by deserts that have low and variable rainfall, nutrient-poor soils, and little vegetation cover. Here, we focus on the goods and services offered by desert ecosystems using the northwestern coastal desert of Egypt extending from Burg El-Arab to El-Salloum as an example. We conducted field surveys and collected other data to identify the goods services and provided by native plant species. A total of 322 native plant species were compiled. The direct services provided by these native plants included sources of food, medicine, and energy; indirect vegetation services included promotion of biodiversity, water storage, and soil fertility. The plant diversity in this ecosystem provided economic service benefits, such as sources of fodder, fuel-wood, and traditional medicinal plants. Changes in land use and recent ill-managed human activities may influence the availability of these services and strongly impact biodiversity and habitat availability. Although deserts are fragile and support low levels of productivity, they provide a variety of goods and services whose continuing availability is contingent upon the adoption of rational land management practices.

Evaluating process domains in small arid granitic watersheds: Case study of Pima Wash, South Mountains, Sonoran Desert, USA

Science.gov (United States)

Seong, Yeong Bae; Larson, Phillip H.; Dorn, Ronald I.; Yu, Byung Yong

2016-02-01

and roofs for coyotes (Canis latrans) and gray fox (Urocyon Cinereoargenteus) dens on terrace scarps via stage 3 pedogenic carbonate. These four process domains occur in six other randomly selected granitic watersheds with drainage areas < 5 km2 in the Mojave and Sonoran Deserts. Results on rates of geomorphic processes in the Pima Wash watershed provide new insight in the desert geomorphology of small granitic watersheds. Catchment-wide denudation rates (CWDRs) recorded by 10Be sampled along the main ephemeral wash vary between 15 and 23 mm/ka and do not appear to be influenced by knickpoint or knickzone occurrence; instead slightly lower CWDRs appear to be associated with sediment contributions by subbasins with more abundance of bare bedrock forms. Resampling for CWDR after a 500-year flood event from hurricane moisture at two sites along the main ephemeral channel revealed no detectable changes; this finding confirms the average representativeness of CWDR as a long-term denudation proxy and also means that sediment transport on these arid granitic hillslopes must be incremental and without rapid crest to wash transport. The first reported measurements of incision rates into a small granitic Sonoran Desert watershed, using 10Be and VML, reveal rates on the order of 70-180 mm/ka in the lower quarter of Pima Wash for the last 60 ka - producing a narrow and deep trench. As this base-level fall propagates upstream, erosion focuses on weaker material with higher joint densities; this facilitates the emergence of domes and kopje landforms with more widely spaced jointing.

Aborigines of the nuclear desert

International Nuclear Information System (INIS)

Rujula, A. de

1985-01-01

The chart of 'stable nuclides' extends from Hydrogen, to Z proportional 98, A proportional 263. It contains another island of stability - neutron stars - in a narrow range around Z proportional 10 56 , A proportional 10 57 . In between lies a supposedly barren region encompassing more than 50 orders of magnitude. This desert may be populated by strange quark balls: Stable single bags containing similar proportions of u, d and s quarks. These balls are candidates for the constituency of the 'dark mass' in galaxies and in the Universe. We describe seven ways to search for these possible inhabitants of the nuclear desert. (orig.)

Renewable Energy Development on Fort Mojave Reservation Feasiblity Study

Energy Technology Data Exchange (ETDEWEB)

Russell Gum, ERCC analytics LLC

2008-03-17

The Ft. Mojave tribe, whose reservation is located along the Colorado River in the states of Arizona, California, and Nevada near the point where all three states meet, has a need for increased energy supplies. This need is a direct result of the aggressive and successful economic development projects undertaken by the tribe in the last decade. While it is possible to contract for additional energy supplies from fossil fuel sources it was the desire of the tribal power company, AHA MACAV Power Service (AMPS) to investigate the feasibility and desirability of producing power from renewable sources as an alternative to increased purchase of fossil fuel generated power and as a possible enterprise to export green power. Renewable energy generated on the reservation would serve to reduce the energy dependence of the tribal enterprises on off reservation sources of energy and if produced in excess of reservation needs, add a new enterprise to the current mix of economic activities on the reservation. Renewable energy development would also demonstrate the tribe’s support for improving environmental quality, sustainability, and energy independence both on the reservation and for the larger community.

78 FR 27256 - Meeting of the California Desert District Advisory Council

Science.gov (United States)

2013-05-09

..., from 8 a.m. to 4:30 p.m. in Ridgecrest, Calif. at a location to be announced later. There also will be a DAC Business Meeting on Friday, June 7, from noon to 4:30 p.m. at the Jawbone Station Visitors... Saturday meeting will include a focus on the West Mojave Plan, as well as updates by council members, the...

Early history and reactivation of the rand thrust, southern California

Science.gov (United States)

Postlethwaite, Clay E.; Jacobson, Carl E.

The Rand thrust of the Rand Mountains in the northwestern Mojave Desert separates an upper plate of quartz monzonite and quartzofeldspathic to amphibolitic gneiss from a lower plate of metagraywacke and mafic schist (Rand Schist). The Rand thrust is considered part of the regionally extensive Vincent/Chocolate Mountain thrust system, which is commonly believed to represent a Late Cretaceous subduction zone. The initial direction of dip and sense of movement along the Vincent/Chocolate Mountain thrust are controversial. Microfabrics of mylonites and quartzites from the Rand Mountains were analyzed in an attempt to determine transport direction for this region, but the results are ambiguous. In addition, the southwestern portion of the Rand thrust was found to have been reactivated as a low-angle normal fault after subduction. Reactivation might have occurred shortly after subduction, in which case it could account for the preservation of high-pressure mineral assemblages in the Rand Schist, or it could be related to mid-Tertiary extension in the western United States. In either event, the reactivation might be responsible for the complicated nature of the microfabrics. The Rand Schist exhibits an inverted metamorphic zonation. Isograds in the schist are not significantly truncated by the reactivated segment of the Rand thrust. This indicates that other segments of the Vincent/Chocolate Mountain thrust should be re-evaluated for the possibility of late movement, even if they show an apparently undisturbed inverted metamorphic zonation.

Ploidy race distributions since the Last Glacial Maximum in the North American desert shrub, Larrea tridentata

Science.gov (United States)

Hunter, K.L.; Betancourt, J.L.; Riddle, B.R.; Van Devender, T. R.; Cole, K.L.; Geoffrey, Spaulding W.

2000-01-01

1 A classic biogeographic pattern is the alignment of diploid, tetraploid and hexaploid races of creosote bush (Larrea tridentata) across the Chihuahuan, Sonoran and Mohave Deserts of western North America. We used statistically robust differences in guard cell size of modern plants and fossil leaves from packrat middens to map current and past distributions of these ploidy races since the Last Glacial Maximum (LGM). 2 Glacial/early Holocene (26-10 14C kyr BP or thousands of radiocarbon years before present) populations included diploids along the lower Rio Grande of west Texas, 650 km removed from sympatric diploids and tetraploids in the lower Colorado River Basin of south-eastern California/south-western Arizona. Diploids migrated slowly from lower Rio Grande refugia with expansion into the northern Chihuahuan Desert sites forestalled until after ???4.0 14C kyr BP. Tetraploids expanded from the lower Colorado River Basin into the northern limits of the Sonoran Desert in central Arizona by 6.4 14C kyr BP. Hexaploids appeared by 8.5 14C kyr BP in the lower Colorado River Basin, reaching their northernmost limits (???37??N) in the Mohave Desert between 5.6 and 3.9 14C kyr BP. 3 Modern diploid isolates may have resulted from both vicariant and dispersal events. In central Baja California and the lower Colorado River Basin, modern diploids probably originated from relict populations near glacial refugia. Founder events in the middle and late Holocene established diploid outposts on isolated limestone outcrops in areas of central and southern Arizona dominated by tetraploid populations. 4 Geographic alignment of the three ploidy races along the modern gradient of increasingly drier and hotter summers is clearly a postglacial phenomenon, but evolution of both higher ploidy races must have happened before the Holocene. The exact timing and mechanism of polyploidy evolution in creosote bush remains a matter of conjecture. ?? 2001 Blackwell Science Ltd.

Lizard burrows provide thermal refugia for larks in the Arabian desert

NARCIS (Netherlands)

Williams, JB; Tieleman, BI; Shobrak, M

A common perception is that desert birds experience greater extremes of heat and aridity than their mammalian counterparts, in part, because birds do not use burrows as a refuge from the desert environment. We report observations of Dunn's Larks (Eremalauda dunni), Bar-tailed Desert Larks (Ammomanes

Three-dimensional geologic mapping of the Cenozoic basin fill, Amargosa Desert basin, Nevada and California

Science.gov (United States)

Taylor, Emily M.; Sweetkind, Donald S.

2014-01-01

Understanding the subsurface geologic framework of the Cenozoic basin fill that underlies the Amargosa Desert in southern Nevada and southeastern California has been improved by using borehole data to construct three-dimensional lithologic and interpreted facies models. Lithologic data from 210 boreholes from a 20-kilometer (km) by 90-km area were reduced to a limited suite of descriptors based on geologic knowledge of the basin and distributed in three-dimensional space using interpolation methods. The resulting lithologic model of the Amargosa Desert basin portrays a complex system of interfingered coarse- to fine-grained alluvium, playa and palustrine deposits, eolian sands, and interbedded volcanic units. Lithologic units could not be represented in the model as a stacked stratigraphic sequence due to the complex interfingering of lithologic units and the absence of available time-stratigraphic markers. Instead, lithologic units were grouped into interpreted genetic classes, such as playa or alluvial fan, to create a three-dimensional model of the interpreted facies data. Three-dimensional facies models computed from these data portray the alluvial infilling of a tectonically formed basin with intermittent internal drainage and localized regional groundwater discharge. The lithologic and interpreted facies models compare favorably to resistivity, aeromagnetic, and geologic map data, lending confidence to the interpretation.

Community adaptations to an impending food desert in rural Appalachia, USA.

Science.gov (United States)

Miller, Wayne C; Rogalla, Denver; Spencer, Dustin; Zia, Nida; Griffith, Brian N; Heinsberg, Haylee B

2016-01-01

The United States Department of Agriculture (USDA) describes a food desert as an urban neighborhood or rural town without ready access to fresh, healthy, and affordable food. An estimated 2.3 million rural Americans live in food deserts. One goal of the USDA is to eliminate food deserts. However, at a time when some food deserts are being eliminated, hundreds of grocery stores are closing, causing other food deserts to arise. The literature is scarce on how a community adapts to an impending food desert. Alderson, West Virginia, USA (population 1184) rallied to face an impending food desert when the only grocery store in town closed in December 2014. This study investigated how this small rural community adapted to its oncoming food desert. A community member survey was administered to 155 Alderson families (49%) to determine how the new food desert affected family food acquisition and storage behaviors. A restaurant survey was given to the town's four restaurants to determine how the food desert affected their businesses. Sales data for a new food hub (Green Grocer) was obtained to see if this new initiative offset the negative effects of the food desert. ANOVA and t-tests were used to compare group numerical data. Two group response rates were compared by testing the equality of two proportions. Categorical data were analyzed with the χ2 or frequency distribution analysis. Group averages are reported as mean ± standard error of the mean. Significance for all analyses was set at pp=0.16) from the number before the food desert (2.8±0.3). Price comparisons among the Green Grocer and three distant supermarkets showed a 30% savings by traveling to distant supermarkets. Frequency of monthly restaurant visits did not change after the emergence of the food desert (2.98±0.54 vs 3.05±0.51, p=0.85). However, restaurant patrons requested to buy fresh produce and dairy from the restaurants to use for their own home cooking. Food pantry use increased by 43%, with

Investigations of the geohydrology of the waters of the Negev Desert using U-234/U-238 disequilibrium

International Nuclear Information System (INIS)

Kronfeld, J.

1977-11-01

The attempt to use uranium analysis of the ratio 234 U/ 238 U to investigate the flow pattern and the recharge mechanism of the Nubian Sandstone waters in the Negev Desert is reported. 105 water samples were collected from the Nubian Sandstone, the overlying aquifers and from crystalline rocks in Southern Sinai. The latter is supposed to be the recharge area of the Nubian Sandstone waters. Although the uranium value group discretes water bodies no conclusion can be drawn as to the origin of the Nubian Sandstone waters. Due to the results artesian leakage from the Nubian Sandstone into the overlying aquifers probably can be ruled out

Airborne particle accumulation and composition at different locations in the northern Negev desert.

NARCIS (Netherlands)

Offer, Z.Y.; Goossens, D.

2001-01-01

Atmospheric desert dust was collected over 36 months in ground-level collectors at four stations in the northern Negev desert, Israel. Three stations (Shivta, Sede Boqer and Avdat) are located in the desert itself whereas the fourth station (Sayeret Shaked) is situated at the desert fringe, in the

The effect of leaf beetle herbivory on the fire behaviour of tamarisk (Tamarix ramosissima Lebed.)

Science.gov (United States)

Drus, Gail M.; Dudley, Tom L.; Brooks, Matthew L.; Matchett, John R.

2012-01-01

The non-native tree, Tamarix spp. has invaded desert riparian ecosystems in the south-western United States. Fire hazard has increased, as typically fire-resistant native vegetation is replaced by Tamarix. The tamarisk leaf beetle, Diorhabda carinulata Desbrochers, introduced for biological control, may affect fire behaviour by converting hydrated live Tamarix leaves and twigs into desiccated and dead fuels. This potentially increases fire hazard in the short term before native vegetation can be re-established. This study investigates how fire behaviour is altered in Tamarix fuels desiccated by Diorhabda herbivory at a Great Basin site, and by herbivory simulated by foliar herbicide at a Mojave Desert site. It also evaluates the influence of litter depth on fire intensity. Fire behaviour was measured with a fire intensity index that integrates temperature and duration (degree-minutes above 70°C), and with maximum temperature, duration, flame lengths, rates of spread and vegetation removal. Maximum temperature, flame length and rate of spread were enhanced by foliar desiccation of Tamarix at both sites. At only the Mojave site, there was a trend for desiccated trees to burn with greater fire intensity. At both sites, fire behaviour parameters were influenced to a greater degree by litter depth, vegetation density and drier and windier conditions than by foliar desiccation.

The politics of accessing desert land in Jordan

NARCIS (Netherlands)

Naber, Al Majd; Molle, Francois

2016-01-01

With the dramatic increase of the population in Jordan, the value of land has rocketed up. Urban sprawl into semi-desert or desert areas, initially not surveyed or settled by the British and considered as state land, has brought to the surface the problematic status of those lands. Likewise, the

Phylogeographic patterns of the desert poplar in Northwest China shaped by both geology and climatic oscillations.

Science.gov (United States)

Zeng, Yan-Fei; Zhang, Jian-Guo; Abuduhamiti, Bawerjan; Wang, Wen-Ting; Jia, Zhi-Qing

2018-05-25

The effects of historical geology and climatic events on the evolution of plants around the Qinghai-Tibetan Plateau region have been at the center of debate for years. To identify the influence of the uplift of the Tianshan Mountains and/or climatic oscillations on the evolution of plants in arid northwest China, we investigated the phylogeography of the Euphrates poplar (Populus euphratica) using chloroplast DNA (cpDNA) sequences and nuclear microsatellites, and estimated its historical distribution using Ecological Niche Modeling (ENM). We found that the Euphrates poplar differed from another desert poplar, P. pruinosa, in both nuclear and chloroplast DNA. The low clonal diversity in both populations reflected the low regeneration rate by seed/seedlings in many locations. Both cpDNA and nuclear markers demonstrated a clear divergence between the Euphrates poplar populations from northern and southern Xinjiang regions. The divergence time was estimated to be early Pleistocene based on cpDNA, and late Pleistocene using an Approximate Bayesian Computation analysis based on microsatellites. Estimated gene flow was low between these two regions, and the limited gene flow occurred mainly via dispersal from eastern regions. ENM analysis supported a wider distribution of the Euphrates poplar at 3 Ma, but a more constricted distribution during both the glacial period and the interglacial period. These results indicate that the deformation of the Tianshan Mountains has impeded gene flow of the Euphrates poplar populations from northern and southern Xinjiang, and the distribution constriction due to climatic oscillations further accelerated the divergence of populations from these regions. To protect the desert poplars, more effort is needed to encourage seed germination and seedling establishment, and to conserve endemic gene resources in the northern Xinjiang region.

An Integrated Multi-Sensor Approach to Monitor Desert Environments by UAV and Satellite Sensors: Case Study Kubuqi Desert, China

Science.gov (United States)

Kim, J.; Lin, C. W.; vanGasselt, S.; Lin, S.; Lan, C. W.

2017-12-01

Expanding deserts have been causing significant socio-economical threats by, e.g., hampering anthropogenic activities or causing decline of agricultural productivity. Countries in the Asian-Pacific regions in particular have been suffering from dust storms originating in the arid deserts of China, Mongolia and central Asia. In order to mitigate such environmental interferences by means of, e.g. combat desertification activities and early warning systems, the establishment of reliable desert monitoring schemes is needed. In this study, we report on a remote sensing data fusion approach to constantly and precisely monitor desert environments. We have applied this approach over a test site located in the Kubuqi desert located in Northeast China and which is considered to be a major contributor of dust storms today. In order to understand spatial and temporal trends of desertification, the planimetric distribution and 3D shape and size of sand dunes were reconstructed using Digital Terrain Models (DTM) derived from stereo observations made by Unmanned Aerial Vehicles (UAV). Based on this, the volumetric change of sand dunes was directly estimated through co-registered DTMs. We furthermore derived and investigated topographic parameters, such as the aerodynamic roughness length, the protrusion coefficient, the Normalized Difference Angular Index, and the phase coherence derived from spaceborne optical/synthetic aperture radar (SAR) remote sensing assets with the calibration index from UAV observation. Throughout such a multi-data approach, temporal changes of a target's environmental parameters can be traced, analyzed and correlated with weather conditions. An improved understanding of aeolian processes in sand deserts will be a valuable contribution for desertification combat activities and early warning systems for dust storm generation. Future research needs to be conducted over more extensive spatial and temporal domains, also by combining investigations on the

Effects of altered temperature and precipitation on desert protozoa associated with biological soil crusts.

Science.gov (United States)

Darby, Brian J; Housman, David C; Zaki, Amr M; Shamout, Yassein; Adl, Sina M; Belnap, Jayne; Neher, Deborah A

2006-01-01

Biological soil crusts are diverse assemblages of bacteria, cyanobacteria, algae, fungi, lichens, and mosses that cover much of arid land soils. The objective of this study was to quantify protozoa associated with biological soil crusts and test the response of protozoa to increased temperature and precipitation as is predicted by some global climate models. Protozoa were more abundant when associated with cyanobacteria/lichen crusts than with cyanobacteria crusts alone. Amoebae, flagellates, and ciliates originating from the Colorado Plateau desert (cool desert, primarily winter precipitation) declined 50-, 10-, and 100-fold, respectively, when moved in field mesocosms to the Chihuahuan Desert (hot desert, primarily summer rain). However, this was not observed in protozoa collected from the Chihuahuan Desert and moved to the Sonoran desert (hot desert, also summer rain, but warmer than Chihuahuan Desert). Protozoa in culture began to encyst at 37 degrees C. Cysts survived the upper end of daily temperatures (37-55 degrees C), and could be stimulated to excyst if temperatures were reduced to 15 degrees C or lower. Results from this study suggest that cool desert protozoa are influenced negatively by increased summer precipitation during excessive summer temperatures, and that desert protozoa may be adapted to a specific desert's temperature and precipitation regime.

Evaluation of great deserts of the world for perpetual radiowaste storage

International Nuclear Information System (INIS)

Libby, L.M.; Wurtele, M.G.; Whipple, C.G.

1982-01-01

Desert sites with a history of seismic stability were studied for storage of radioactive wastes because of the attractive meteorology, proven longterm geological stability, and distance from human population centers. Specific deserts were to be representative of various kinds of world deserts, if substantial information about each desert was available, to examine with respect to transporting, handling, storing, and cooling the radioactive waste, and the site suitability as to geological conditions, water availability, alternative land use, airborne emissions of heat, accidental radioactive emission, and possible socioeonomic impacts. No significant technical obstacles to the use of the world deserts as sites for a retrievable storage facility for 500 years were found. However, given the relatively low level of effort that was allocated between the many technical issues listed above, this study is neither a full risk assessment nor a full environmental impact analysis of such a facility. Assessments for siting the facility were made for five deserts, chosen to be representative of Old World, New World, Australian, interior, coastal, foggy, hot and cold: the Nullarbor Plain of Australia, the Namib in Africa, the Great Basin of the United States represented by the Nevada Test Site, the North Slope of Alaska and Canada, and the Egyptian desert

Water use sources of desert riparian Populus euphratica forests.

Science.gov (United States)

Si, Jianhua; Feng, Qi; Cao, Shengkui; Yu, Tengfei; Zhao, Chunyan

2014-09-01

Desert riparian forests are the main body of natural oases in the lower reaches of inland rivers; its growth and distribution are closely related to water use sources. However, how does the desert riparian forest obtains a stable water source and which water sources it uses to effectively avoid or overcome water stress to survive? This paper describes an analysis of the water sources, using the stable oxygen isotope technique and the linear mixed model of the isotopic values and of desert riparian Populus euphratica forests growing at sites with different groundwater depths and conditions. The results showed that the main water source of Populus euphratica changes from water in a single soil layer or groundwater to deep subsoil water and groundwater as the depth of groundwater increases. This appears to be an adaptive selection to arid and water-deficient conditions and is a primary reason for the long-term survival of P. euphratica in the desert riparian forest of an extremely arid region. Water contributions from the various soil layers and from groundwater differed and the desert riparian P. euphratica forests in different habitats had dissimilar water use strategies.

Stable Isotopic Analysis on Water Utilization of Two Xerophytic Shrubs in a Revegetated Desert Area: Tengger Desert, China

OpenAIRE

Lei Huang; Zhishan Zhang

2015-01-01

Stable isotope studies on stable isotope ratios of hydrogen and oxygen in water within plants provide new information on water sources and water use patterns under natural conditions. In this study, the sources of water uptake for two typical xerophytic shrubs, Caragana korshinskii and Artemisia ordosica, were determined at four different-aged revegetated sites (1956, 1964, 1981, and 1987) in the Tengger Desert, a revegetated desert area in China. Samples from precipitation, soil water at dif...

Geology and geochemistry of the Atacama Desert.

Science.gov (United States)

Tapia, J; González, R; Townley, B; Oliveros, V; Álvarez, F; Aguilar, G; Menzies, A; Calderón, M

2018-02-14

The Atacama Desert, the driest of its kind on Earth, hosts a number of unique geological and geochemical features that make it unlike any other environment on the planet. Considering its location on the western border of South America, between 17 and 28 °S, its climate has been characterized as arid to hyperarid for at least the past 10 million years. Notably dry climatic conditions of the Atacama Desert have been related to uplift of the Andes and are believed to have played an important role in the development of the most distinctive features of this desert, including: (i) nitrates and iodine deposits in the Central Depression, (ii) secondary enrichment in porphyry copper deposits in the Precordillera, (iii) Li enrichment in salt flats of the Altiplano, and (iv) life in extreme habitats. The geology and physiography of the Atacama Desert have been largely shaped by the convergent margin present since the Mesozoic era. The geochemistry of surface materials is related to rock geochemistry (Co, Cr, Fe, Mn, V, and Zn), salt flats, and evaporite compositions in endorheic basins (As, B, and Li), in addition to anthropogenic activities (Cu, Mo, and Pb). The composition of surface water is highly variable, nonetheless in general it presents a circumneutral pH with higher conductivity and total dissolved solids in brines. Major water constituents, with the exception of HCO 3 - , are generally related to the increase of salinity, and despite the fact that trace elements are not well-documented, surface waters of the Atacama Desert are enriched in As, B, and Li when compared to the average respective concentrations in rivers worldwide.

Engineered Approaches to In Situ Bioremediation of Chlorinated Solvents: Fundamentals and Field Applications

Science.gov (United States)

2000-07-01

310-9000 Fax: (512) 310-8800 mail@micro-bac.com Harry Christensen Phone: (714) 666-0110 Fax: (714) 538-5134 micro@webworldinc.com Del Christensen...Strategies & Applications, Inc. Somerset, New Jersey S. Koenigsberg, Regenesis 1011 Calle Sombra San Clemente, CA 92672 181 Offutt Air Force Base, Fire...Mojave Desert, about 60 miles north of Los Angeles , covers approximately 301,000 and is used for aircraft research and development. From 1958 through 1967

Liquid Water Restricts Habitability in Extreme Deserts.

Science.gov (United States)

Cockell, Charles S; Brown, Sarah; Landenmark, Hanna; Samuels, Toby; Siddall, Rebecca; Wadsworth, Jennifer

2017-04-01

Liquid water is a requirement for biochemistry, yet under some circumstances it is deleterious to life. Here, we show that liquid water reduces the upper temperature survival limit for two extremophilic photosynthetic microorganisms (Gloeocapsa and Chroococcidiopsis spp.) by greater than 40°C under hydrated conditions compared to desiccated conditions. Under hydrated conditions, thermal stress causes protein inactivation as shown by the fluorescein diacetate assay. The presence of water was also found to enhance the deleterious effects of freeze-thaw in Chroococcidiopsis sp. In the presence of water, short-wavelength UV radiation more effectively kills Gloeocapsa sp. colonies, which we hypothesize is caused by factors including the greater penetration of UV radiation into hydrated colonies compared to desiccated colonies. The data predict that deserts where maximum thermal stress or irradiation occurs in conjunction with the presence of liquid water may be less habitable to some organisms than more extreme arid deserts where organisms can dehydrate prior to being exposed to these extremes, thus minimizing thermal and radiation damage. Life in extreme deserts is poised between the deleterious effects of the presence and the lack of liquid water. Key Words: Deserts-Extremophiles-Stress-High temperatures-UV radiation-Desiccation. Astrobiology 17, 309-318.

Water/Pasture Assessment of Registan Desert (Kandahar and Helmand Provinces)

OpenAIRE

Toderich, Kristina; Tsukatani, Tsuneo

2005-01-01

The desolate desert in Afghanistan's Kandahar and Helmand Provinces was previously populated by thousands of pastoralists until a devastating drought decimated animal herds and forced them to live as IDPs (Internally Displaced Persons) on land bordering the desert. Through funding from UNAMA (United Nations Assistance Mission in Afghanistan), this report assesses conditions in the Registan Desert and border regions to devise solutions to the problems facing Registan Kuchi nomads. A work plan ...

Strategy for the development and management of deserts

Energy Technology Data Exchange (ETDEWEB)

1978-02-01

Recommendations from the June 1977 Conference on Alternative Strategies for Desert Development and Management apply primarily to arid lands, although some can be applied to true desert with no vegetation as well. The causes of desertification are reviewed and corrective measures suggested for both developed and developing countries. A range of strategies is proposed, but all are based on the efficient use of water and most are concerned with water used for agricultural purposes. The conference papers also addressed water management, agricultural development, field crops versus animal husbandry, grazing, land use and allocation, wild life resources, industry coastal resources, tourism, energy and minerals, and establishing the infrastructure needed to improve and retain desert health.

Parabolic dune development modes according to shape at the southern fringes of the Hobq Desert, Inner Mongolia, China

Science.gov (United States)

Guan, Chao; Hasi, Eerdun; Zhang, Ping; Tao, Binbin; Liu, Dan; Zhou, Yanguang

2017-10-01

Since the 1970s, parabolic dunes at the southern fringe of the Hobq Desert, Inner Mongolia, China have exhibited many different shapes (V-shaped, U-shaped, and palmate) each with a unique mode of development. In the study area, parabolic dunes are mainly distributed in Regions A, B, and C with an intermittent river running from the south to the north. We used high-resolution remote-sensing images from 1970 to 2014 and RTK-GPS measurements to study the development modes of different dune shapes; the modes are characterized by the relationship between the intermittent river and dunes, formation of the incipient dune patterns, the predominant source supply of dunes, and the primary formation of different shapes (V-shaped, U-shaped, and palmate). Most parabolic dunes in Region A are V-shaped and closer to the bank of the river. The original barchans in this region exhibit "disconnected arms" behavior. With the sand blown out of the riverbed through gullies, the nebkhas on the disconnected arms acquire the external sand source through the "fertile island effect", thereby developing into triangular sand patches and further developing into V-shaped parabolic dunes. Most parabolic dunes in Regions B and C are palmate. The residual dunes cut by the re-channelization of river from transverse dune fields on the west bank are the main sand source of Region B. The parabolic dunes in Region C are the original barchans having then been transformed. The stoss slopes of V-shaped parabolic dunes along the riverbank are gradual and the dunes are flat in shape. The dune crest of V-shaped parabolic dune is the deposition area, which forms the "arc-shaped sand ridge". Their two arms are non-parallel; the lateral airflow of the arms jointly transport sand to the middle part of dunes, resulting in a narrower triangle that gradually becomes V-shaped. Palmate parabolic dunes have a steeper stoss slope and height. The dune crest of the palmate parabolic dune is the erosion area, which forms

The provenance of Taklamakan desert sand

Science.gov (United States)

Rittner, Martin; Vermeesch, Pieter; Carter, Andrew; Bird, Anna; Stevens, Thomas; Garzanti, Eduardo; Andò, Sergio; Vezzoli, Giovanni; Dutt, Ripul; Xu, Zhiwei; Lu, Huayu

2016-03-01

Sand migration in the vast Taklamakan desert within the Tarim Basin (Xinjiang Uyghur Autonomous region, PR China) is governed by two competing transport agents: wind and water, which work in diametrically opposed directions. Net aeolian transport is from northeast to south, while fluvial transport occurs from the south to the north and then west to east at the northern rim, due to a gradual northward slope of the underlying topography. We here present the first comprehensive provenance study of Taklamakan desert sand with the aim to characterise the interplay of these two transport mechanisms and their roles in the formation of the sand sea, and to consider the potential of the Tarim Basin as a contributing source to the Chinese Loess Plateau (CLP). Our dataset comprises 39 aeolian and fluvial samples, which were characterised by detrital-zircon U-Pb geochronology, heavy-mineral, and bulk-petrography analyses. Although the inter-sample differences of all three datasets are subtle, a multivariate statistical analysis using multidimensional scaling (MDS) clearly shows that Tarim desert sand is most similar in composition to rivers draining the Kunlun Shan (south) and the Pamirs (west), and is distinctly different from sediment sources in the Tian Shan (north). A small set of samples from the Junggar Basin (north of the Tian Shan) yields different detrital compositions and age spectra than anywhere in the Tarim Basin, indicating that aeolian sediment exchange between the two basins is minimal. Although river transport dominates delivery of sand into the Tarim Basin, wind remobilises and reworks the sediment in the central sand sea. Characteristic signatures of main rivers can be traced from entrance into the basin to the terminus of the Tarim River, and those crossing the desert from the south to north can seasonally bypass sediment through the sand sea. Smaller ephemeral rivers from the Kunlun Shan end in the desert and discharge their sediment there. Both river run

Water relations in grassland and desert ecosystems exposed to elevated atmospheric CO2.

Science.gov (United States)

Morgan, J A; Pataki, D E; Körner, C; Clark, H; Del Grosso, S J; Grünzweig, J M; Knapp, A K; Mosier, A R; Newton, P C D; Niklaus, P A; Nippert, J B; Nowak, R S; Parton, W J; Polley, H W; Shaw, M R

2004-06-01

Atmospheric CO2 enrichment may stimulate plant growth directly through (1) enhanced photosynthesis or indirectly, through (2) reduced plant water consumption and hence slower soil moisture depletion, or the combination of both. Herein we describe gas exchange, plant biomass and species responses of five native or semi-native temperate and Mediterranean grasslands and three semi-arid systems to CO2 enrichment, with an emphasis on water relations. Increasing CO2 led to decreased leaf conductance for water vapor, improved plant water status, altered seasonal evapotranspiration dynamics, and in most cases, periodic increases in soil water content. The extent, timing and duration of these responses varied among ecosystems, species and years. Across the grasslands of the Kansas tallgrass prairie, Colorado shortgrass steppe and Swiss calcareous grassland, increases in aboveground biomass from CO2 enrichment were relatively greater in dry years. In contrast, CO2-induced aboveground biomass increases in the Texas C3/C4 grassland and the New Zealand pasture seemed little or only marginally influenced by yearly variation in soil water, while plant growth in the Mojave Desert was stimulated by CO2 in a relatively wet year. Mediterranean grasslands sometimes failed to respond to CO2-related increased late-season water, whereas semiarid Negev grassland assemblages profited. Vegetative and reproductive responses to CO2 were highly varied among species and ecosystems, and did not generally follow any predictable pattern in regard to functional groups. Results suggest that the indirect effects of CO2 on plant and soil water relations may contribute substantially to experimentally induced CO2-effects, and also reflect local humidity conditions. For landscape scale predictions, this analysis calls for a clear distinction between biomass responses due to direct CO2 effects on photosynthesis and those indirect CO2 effects via soil moisture as documented here.

Global Warming: The Instability of Desert Climate is Enhancing in the Northwest Area in China: A Case Study in the Desert Area in Northwestern China

OpenAIRE

Zhao-Feng Chang; Shu-Juan Zhu; Fu-Gui Han; Sheng-Nnian Zhong; Qiang-Qiang Wang; Jian-Hui Zhang

2013-01-01

To disclose the relation between the sandstorms change and the temperature changes, a case study in the desert area in northwestern china is investigated. The results showed that: the instability of climate in Minqin desert area is enhancing in the arid desert region in northwest China. Mainly as follows: Variation the annual extreme maximum temperature increasing. Variation of extreme minimum temperature also an increasing trend. Average visibility of sandstorms significantly reduced and the...

Birds and conservation significance of the Namib Desert's least ...

African Journals Online (AJOL)

-long Namib Desert and it remains the least known coastal wetland on a desert coast rich in shorebirds. Two surveys of the Baia dos Tigres region in 1999 and 2001 indicated a rich wetland bird diversity consisting of 25 species, with a total of ...

In vitro germination of desert rose varieties(

OpenAIRE

Tatiane Lemos Varella; Gizelly Mendes Silva; Kaliane Zaira Camacho Maximiliano da Cruz; Andréia Izabel Mikovski; Josué Ribeiro da Silva Nunes; Ilio Fealho Carvalho; Maurecilne Lemes Silva

2015-01-01

The drought stress resistance is a characteristic of the desert rose and its estimable beauty flowers, which gave it great relevance in the ornamental market. However, the desert rose production and germination is hampered by possible sterility of their male and female flowers and frequent problems in pollination, so the tissue culture is a promising alternative to the propagation of these plants. This study aimed to evaluate the effect of gibberellic acid on four commercial varieties of dese...

Screening the Egyptian desert actinomycetes as candidates for new ...

African Journals Online (AJOL)

In a screening program to study the antimicrobial activities of desert actinomycetes as potential producers of active metabolites, 75 actinomycete strains were isolated from the Egyptian desert habitats and tested. Out of the isolated 75 organisms, 32 (42.67%) showed activity against the used test organisms.

Camelid genomes reveal evolution and adaptation to desert environments.

Science.gov (United States)

Wu, Huiguang; Guang, Xuanmin; Al-Fageeh, Mohamed B; Cao, Junwei; Pan, Shengkai; Zhou, Huanmin; Zhang, Li; Abutarboush, Mohammed H; Xing, Yanping; Xie, Zhiyuan; Alshanqeeti, Ali S; Zhang, Yanru; Yao, Qiulin; Al-Shomrani, Badr M; Zhang, Dong; Li, Jiang; Manee, Manee M; Yang, Zili; Yang, Linfeng; Liu, Yiyi; Zhang, Jilin; Altammami, Musaad A; Wang, Shenyuan; Yu, Lili; Zhang, Wenbin; Liu, Sanyang; Ba, La; Liu, Chunxia; Yang, Xukui; Meng, Fanhua; Wang, Shaowei; Li, Lu; Li, Erli; Li, Xueqiong; Wu, Kaifeng; Zhang, Shu; Wang, Junyi; Yin, Ye; Yang, Huanming; Al-Swailem, Abdulaziz M; Wang, Jun

2014-10-21

Bactrian camel (Camelus bactrianus), dromedary (Camelus dromedarius) and alpaca (Vicugna pacos) are economically important livestock. Although the Bactrian camel and dromedary are large, typically arid-desert-adapted mammals, alpacas are adapted to plateaus. Here we present high-quality genome sequences of these three species. Our analysis reveals the demographic history of these species since the Tortonian Stage of the Miocene and uncovers a striking correlation between large fluctuations in population size and geological time boundaries. Comparative genomic analysis reveals complex features related to desert adaptations, including fat and water metabolism, stress responses to heat, aridity, intense ultraviolet radiation and choking dust. Transcriptomic analysis of Bactrian camels further reveals unique osmoregulation, osmoprotection and compensatory mechanisms for water reservation underpinned by high blood glucose levels. We hypothesize that these physiological mechanisms represent kidney evolutionary adaptations to the desert environment. This study advances our understanding of camelid evolution and the adaptation of camels to arid-desert environments.

Jojoba could stop the desert creep

Energy Technology Data Exchange (ETDEWEB)

1982-03-25

The Sahara desert is estimated to be expanding at a rate of 5km a year. The Sudanese government is experimenting with jojoba in six different regions as the bush has the potential to stop this ''desert creep''. The plant, a native to Mexico, is long known for its resistance to drought and for the versatile liquid wax that can be extracted from its seeds. It is estimated that one hectare of mature plants could produce 3000 kg of oil, currently selling at $50 per litre, and so earn valuable foreign currency.

Closed bioregenerative life support systems: Applicability to hot deserts

Science.gov (United States)

Polyakov, Yuriy S.; Musaev, Ibrahim; Polyakov, Sergey V.

2010-09-01

Water scarcity in hot deserts, which cover about one-fifth of the Earth's land area, along with rapid expansion of hot deserts into arable lands is one of the key global environmental problems. As hot deserts are extreme habitats characterized by the availability of solar energy with a nearly complete absence of organic life and water, space technology achievements in designing closed ecological systems may be applicable to the design of sustainable settlements in the deserts. This review discusses the key space technology findings for closed biogenerative life support systems (CBLSS), which can simultaneously produce food, water, nutrients, fertilizers, process wastes, and revitalize air, that can be applied to hot deserts. Among them are the closed cycle of water and the acceleration of the cycling times of carbon, biogenic compounds, and nutrients by adjusting the levels of light intensity, temperature, carbon dioxide, and air velocity over plant canopies. Enhanced growth of algae and duckweed at higher levels of carbon dioxide and light intensity can be important to provide complete water recycling and augment biomass production. The production of fertilizers and nutrients can be enhanced by applying the subsurface flow wetland technology and hyper-thermophilic aerobic bacteria for treating liquid and solid wastes. The mathematical models, optimization techniques, and non-invasive measuring techniques developed for CBLSS make it possible to monitor and optimize the performance of such closed ecological systems. The results of long-duration experiments performed in BIOS-3, Biosphere 2, Laboratory Biosphere, and other ground-based closed test facilities suggest that closed water cycle can be achieved in hot-desert bioregenerative systems using the pathways of evapotranspiration, condensation, and biological wastewater treatment technologies. We suggest that the state of the art in the CBLSS design along with the possibility of using direct sunlight for

Investigating water resources of the desert: How isotopes can help

International Nuclear Information System (INIS)

Gonfiantini, R.

1992-01-01

Newspapers and magazines from time to time write about the enormous reserves of water stored underground in the Sahara, whose rational exploitation would allow the agricultural development of the desert. Although the practical implementation of such projects is rather problematic, it is true that groundwater is relatively abundant under most of the Sahara (as well as in other deserts in the world), but it is seldom easily accessible. What do we really know about these resources of groundwater and how they have accumulated in areas where rainfall is so scarce. What do we know of the hydrological history of the desert. These problems are important for the correct evaluation and use of the groundwater in the desert. Isotope techniques help in their solution, and are described in this document. 6 figs

Investigating water resources of the desert: how isotopes can help

International Nuclear Information System (INIS)

Gonfiantini, R.

1981-01-01

Newspapers and magazines from time to time write about the enormous reserves of water stored underground in the Sahara, whose rational exploitation would allow the agricultural development of the desert. Although the practical implementation of such projects is rather problematic, it is true that groundwater is relatively abundant under most of the Sahara (as well as in other deserts in the world), but it is seldom easily accessible. What do we really know about these resources of groundwater and how they have accumulated in areas where rainfall is so scarce. What do we know of the hydrological history of the desert. These problems are important for the correct evaluation and use of the groundwater in the desert. Isotope techniques help in their solution, and are described in this document

Reclaiming freshwater sustainability in the Cadillac Desert

Science.gov (United States)

Sabo, John L.; Sinha, Tushar; Bowling, Laura C.; Schoups, Gerrit H.W.; Wallender, Wesley W.; Campana, Michael E.; Cherkauer, Keith A.; Fuller, Pam L.; Graf, William L.; Hopmans, Jan W.; Kominoski, John S.; Taylor, Carissa; Trimble, Stanley W.; Webb, Robert H.; Wohl, Ellen E.

2010-01-01

Increasing human appropriation of freshwater resources presents a tangible limit to the sustainability of cities, agriculture, and ecosystems in the western United States. Marc Reisner tackles this theme in his 1986 classic Cadillac Desert: The American West and Its Disappearing Water. Reisner's analysis paints a portrait of region-wide hydrologic dysfunction in the western United States, suggesting that the storage capacity of reservoirs will be impaired by sediment infilling, croplands will be rendered infertile by salt, and water scarcity will pit growing desert cities against agribusiness in the face of dwindling water resources. Here we evaluate these claims using the best available data and scientific tools. Our analysis provides strong scientific support for many of Reisner's claims, except the notion that reservoir storage is imminently threatened by sediment. More broadly, we estimate that the equivalent of nearly 76% of streamflow in the Cadillac Desert region is currently appropriated by humans, and this figure could rise to nearly 86% under a doubling of the region's population. Thus, Reisner's incisive journalism led him to the same conclusions as those rendered by copious data, modern scientific tools, and the application of a more genuine scientific method. We close with a prospectus for reclaiming freshwater sustainability in the Cadillac Desert, including a suite of recommendations for reducing region-wide human appropriation of streamflow to a target level of 60%.

Oasis deposits in the southern margin of the Taklimakan Desert and abrupt environmental changes during the last 30 ka

Science.gov (United States)

Shu, P.; Li, B.; Wang, H.; Cheng, P.; An, Z.; Zhou, W.; Zhang, D. D.

2017-12-01

Taklimakan Desert, the largest arid landform in the Eurasia, is one of the most important dust sources in the world. Growing evidences shows that millennial-scale abrupt climate changes during the last glacial period in the region. However, records on millennial-scale climate and environmental changes remain poorly understood because dating eolian, lacustrine, and fluvial sediments and establishing the reliable environmental proxies from these records are always challenging. Here, we present 32 AMS 14C dates of bulk sediments, grain size, and Rb/Sr ratio parameters from the oasis sequence and dates of bulk loess and charcoal from the upstream source regions to examine the significance of oasis sediments on millennial-scale environmental changes in the Taklimakan Desert. We found that substantial reversal of radiocarbon dates on total organic carbon (TOC) was controlled by source region organic carbon input. Loess hills, alpine meadow north of the study region provided fluvial deposits along drainage system and deflation in the river valleys further provide eolain materials. We argue that early oasis deposits experienced deflation and re-deposition less severe than the younger oasis deposits. After refining radiocarbon age-depth relationships for an age model by Bacon package, proxy records show substantial abrupt fluctuations in climate and environments during the last glacial period, among which three wet intervals, two dry periods are identified. The wetter and warmer conditions during the Holocene facilitated human to occupy the oasis.

The Desert and the Sown Project in Northern Jordan

DEFF Research Database (Denmark)

Kerner, Susanne

2014-01-01

The desert and sown project, which started in 1999 and continued in 2008-2009, studied the region between the settled areas east of Irbid and Ramtha and the surrounding desert at Mafraq (northern Jordan). Large parts of the material comes from the Palaeolithic period, while some smaller tells date...

Observed 20th Century Desert Dust Variability: Impact on Climate and Biogeochemistry

Energy Technology Data Exchange (ETDEWEB)

Mahowald, Natalie [Cornell University; Kloster, Silvia [Cornell University; Engelstaedter, S. [Cornell University; Moore, Jefferson Keith [University of California, Irvine; Mukhopadhyay, S. [Harvard University; McConnell, J. R. [Desert Research Institute, Reno, NV; Albani, S. [Cornell University; Doney, Scott C. [Woods Hole Oceanographic Institution (WHOI), Woods Hole, MA; Bhattacharya, A. [Harvard University; Curran, M. A. J. [Antarctic Climate and Ecosystems Cooperative Research Centre; Flanner, Mark G. [University of Michigan; Hoffman, Forrest M [ORNL; Lawrence, David M. [National Center for Atmospheric Research (NCAR); Lindsay, Keith [National Center for Atmospheric Research (NCAR); Mayewski, P. A. [University of Maine; Neff, Jason [University of Colorado, Boulder; Rothenberg, D. [Cornell University; Thomas, E. [British Antarctic Survey, Cambridge, UK; Thornton, Peter E [ORNL; Zender, Charlie S. [University of California, Irvine

2010-01-01

Desert dust perturbs climate by directly and indirectly interacting with incoming solar and outgoing long wave radiation, thereby changing precipitation and temperature, in addition to modifying ocean and land biogeochemistry. While we know that desert dust is sensitive to perturbations in climate and human land use, previous studies have been unable to determine whether humans were increasing or decreasing desert dust in the global average. Here we present observational estimates of desert dust based on paleodata proxies showing a doubling of desert dust during the 20th century over much, but not all the globe. Large uncertainties remain in estimates of desert dust variability over 20th century due to limited data. Using these observational estimates of desert dust change in combination with ocean, atmosphere and land models, we calculate the net radiative effect of these observed changes (top of atmosphere) over the 20th century to be -0.14 {+-} 0.11 W/m{sup 2} (1990-1999 vs. 1905-1914). The estimated radiative change due to dust is especially strong between the heavily loaded 1980-1989 and the less heavily loaded 1955-1964 time periods (-0.57 {+-} 0.46 W/m{sup 2}), which model simulations suggest may have reduced the rate of temperature increase between these time periods by 0.11 C. Model simulations also indicate strong regional shifts in precipitation and temperature from desert dust changes, causing 6 ppm (12 PgC) reduction in model carbon uptake by the terrestrial biosphere over the 20th century. Desert dust carries iron, an important micronutrient for ocean biogeochemistry that can modulate ocean carbon storage; here we show that dust deposition trends increase ocean productivity by an estimated 6% over the 20th century, drawing down an additional 4 ppm (8 PgC) of carbon dioxide into the oceans. Thus, perturbations to desert dust over the 20th century inferred from observations are potentially important for climate and biogeochemistry, and our understanding

Pastoralist rock art in the Black Desert of Jordan

NARCIS (Netherlands)

Brusgaard, N.O.

2015-01-01

This paper discusses the current problems that exist with the rock art research of the Black Desert in Jordan and presents some preliminary field results of the author’s research on the petroglyphs. It also explore the possibilities that the rock art affords to learn more about the elusive desert

Are There High Meteorite Concentrations in the Atacama Desert/Chile?

Science.gov (United States)

Scherer, P.; Delisle, G.

1992-07-01

We have visited numerous regions of the Atacama desert between Copiapo (27 degrees, 15'S) and Calama (22 degrees, 25'S) to assess their potential as a high-yield meteorite concentration surface, easily exploitable by search efforts within a reasonable time frame. According to our observations, this desert is characterized by the following features: a) A high percentage of the desert consists of sloping surfaces on which soil movement occurs, presumably by very infrequent, though heavy rain. b) Vast areas of the desert are covered by a dm-thick sand layer of dark colour. Since the sand is too coarse-grained to be transported by wind it presumably resulted from in-situ weathering of rock debris derived from nearby mountains. We suspect that impacting smaller objects can easily penetrate the sand layer. c) The sand layer is typically dotted by rocks, fist-size or smaller, that are covered by a thick layer of desert paint (reddish-brown to black colour). Most country rocks are of volcanic origin (rhyolite, andesite, basalt) and are typically of grey to black colour. A noticeable colour contrast in particular to potential stony meteorites is almost nonexistent. d) Soil salts with a potential to speed up weathering processes are ubiquitous near the surface. e) The Pampa de Mejillones, 45 km north of Antofagasta, is one of the few light-coloured areas in the Atacama desert. The surface, being of Mio-Pliocene age, consists of an almost continuous layer of light-brown fossil shells (bivalves and gastropodes). Fluvially transported dark rocks from adjacent outcrops rest on top. The latter material is covered again by desert paint. Few meteorite discoveries have been reported from this area (Pampa (a),(b),(c)). f) Numerous old tire tracks, in particular around mines in operation, crisscross most areas of the Atacama. Undetected objects such as large masses of iron bodies are not likely to have remained undiscovered in great numbers any more. We conclude that the potential of

Strong genetic differentiation in the invasive annual grass Bromus tectorum across the Mojave-Great Basin ecological transition zone

Science.gov (United States)

Susan E. Meyer; Elizabeth A. Leger; Desiree R. Eldon; Craig E. Coleman

2016-01-01

Bromus tectorum, an inbreeding annual grass, is a dominant invader in sagebrush steppe habitat in North America. It is also common in warm and salt deserts, displaying a larger environmental tolerance than most native species. We tested the hypothesis that a suite of habitat-specific B. tectorum lineages dominates warm desert habitats. We sampled 30 B....

76 FR 8730 - Desert Southwest Customer Service Region-Rate Order No. WAPA-151

Science.gov (United States)

2011-02-15

... DEPARTMENT OF ENERGY Western Area Power Administration Desert Southwest Customer Service Region.... Jack Murray, Rates Manager, Desert Southwest Customer Service Region, Western Area Power Administration... ancillary service rates for the Desert Southwest Customer Service Region in accordance with section 302 of...

Production of desert rose seedlings in different potting media

Directory of Open Access Journals (Sweden)

Ronan Carlos Colombo

2017-09-01

Full Text Available Over the past decade the desert rose received fame in the flower market due to its striking and sculptural forms; however, the commercial production of these species is quite recent and little is known about its crop management, including substrates recommendation. The objectives of this study were to investigate the effect of different substrates on desert rose seed germination and production of its seedlings. Experiment I: freshly harvested seeds of desert rose were sown in different substrates e.g. sand, coconut fiber, semi-composted pine bark, sand + coconut fiber, semi-composted pine bark + sand and coconut fiber + semicomposted pine bark. These substrates were evaluated to study the emergence percentage of seeds, initial growth of seedlings and seedling emergence speed index (ESI. Experiment II: desert rose from the experiment I were transferred to plastic pots filled with the same substrates as in experiment I. The pH and electrical conductivity (EC of the substrates were noted every 30 days while the growth parameters of seedlings were recorded after 240 days. Results from experiment I showed higher germination rate and seedling growth in substrates containing semi-composted pine bark. Similarly, in experiment II, better quality seedlings were observed in substrates containing semi-composted pine bark. Thus, for desert rose seed germination and seedling growth, it is recommended to use substrates containing semi-composted pine bark.

Pollen spectrum, a cornerstone for tracing the evolution of the eastern Central Asian desert

Science.gov (United States)

Lu, Kai-Qing; Xie, Gan; Li, Min; Li, Jin-Feng; Trivedi, Anjali; Ferguson, David K.; Yao, Yi-Feng; Wang, Yu-Fei

2018-04-01

The temperate desert in arid Central Asia (ACA) has acted as a thoroughfare for the ancient Silk Road and today's Belt and Road, linking economic and cultural exchanges between East and West. The interaction between human sustainable development and the dynamic change in the desert ecosystem in this region is an area of concern for governments and scientific communities. Nevertheless, the lack of a pollen spectrum of the dominant taxa within the temperate desert vegetation and a corresponding relation between pollen assemblages and specific desert vegetation types is an obstacle to further understanding the formation and maintenance of this desert ecosystem. In this work, we link pollen assemblages to specific desert vegetation types with a new pollen spectrum with specific pollen grains, specific plant taxa and related habitats, providing a solid foundation for further tracing the evolution of the desert ecosystem in eastern arid Central Asia.

Ecosystem responses to warming and watering in typical and desert steppes

Science.gov (United States)

Xu, Zhenzhu; Hou, Yanhui; Zhang, Lihua; Liu, Tao; Zhou, Guangsheng

2016-10-01

Global warming is projected to continue, leading to intense fluctuations in precipitation and heat waves and thereby affecting the productivity and the relevant biological processes of grassland ecosystems. Here, we determined the functional responses to warming and altered precipitation in both typical and desert steppes. The results showed that watering markedly increased the aboveground net primary productivity (ANPP) in a typical steppe during a drier year and in a desert steppe over two years, whereas warming manipulation had no significant effect. The soil microbial biomass carbon (MBC) and the soil respiration (SR) were increased by watering in both steppes, but the SR was significantly decreased by warming in the desert steppe only. The inorganic nitrogen components varied irregularly, with generally lower levels in the desert steppe. The belowground traits of soil total organic carbon (TOC) and the MBC were more closely associated with the ANPP in the desert than in the typical steppes. The results showed that the desert steppe with lower productivity may respond strongly to precipitation changes, particularly with warming, highlighting the positive effect of adding water with warming. Our study implies that the habitat- and year-specific responses to warming and watering should be considered when predicting an ecosystem’s functional responses under climate change scenarios.

Monitoring of desert dune topography by multi angle sensors

Science.gov (United States)

Yun, J.; Kim, J.; Choi, Y.; Yun, H.

2011-12-01

Nowadays, the sandy desert is rapidly expanding world widely and results in a lot of risks in the socio-econimical aspects as well as the anthropogenic activities. For example, the increasing occurrences of mineral dust storm which presumably originated from the sandy deserts in northwest China become a serious threat in human activities as well as public health over Far East Asian area as the interpretation by the MODIS analysis (Zhang et al., 2007) and the particle trajectory simulation with HYSPLYT (HYbrid Single-Particle Lagrangian Integrated Trajectory) (Kim et al., 2011) identified. Since the sand dune activity has been recognized as an essential indicator of the progressive desertification, it is important to establish the monitoring method for the variations of topographic properties by the dune activities such as local roughness. Thus it will provide the crucial data about the extent and the transition of sandy desert. For example, it is well known the aerodynamic roughness lengths Zo which can be driven from the specialized sensor such as POLDER (POLarization and Directionality of the Earth's Reflectances) is essential to understand desert dune characteristics. However, for the multi temporal observation of dune fields, the availability of data set to extract Zo is limited. Therefore, we employed MISR (Multi angle imaging Spectro Radiometer) image sequence to extract multi angle topographic parameters such as NDAI (Normalized Difference Angular Index) or the variation of radiance with the viewing geometry which are representing the characteristics of target desert topography instead of Zo. In our approach, NDAI were expanded to the all viewing angles and then compared over the target sandy desert and the surrounding land covers. It showed very strong consistencies according to the land cover type and especially over the dynamic dune fields. On the other hands, the variation of NDAIs of sandy desert combining with the metrological observations were

Desert wetlands in the geologic record

Science.gov (United States)

Pigati, Jeff S.; Rech, Jason A.; Quade, Jay; Bright, Jordon; Edwards, L.; Springer, A.

2014-01-01

Desert wetlands support flora and fauna in a variety of hydrologic settings, including seeps, springs, marshes, wet meadows, ponds, and spring pools. Over time, eolian, alluvial, and fluvial sediments become trapped in these settings by a combination of wet ground conditions and dense plant cover. The result is a unique combination of clastic sediments, chemical precipitates, and organic matter that is preserved in the geologic record as ground-water discharge (GWD) deposits. GWD deposits contain information on the timing and magnitude of past changes in water-table levels and, therefore, are a potential source of paleohydrologic and paleoclimatic information. In addition, they can be important archeological and paleontological archives because desert wetlands provide reliable sources of fresh water, and thus act as focal points for human and faunal activities, in some of the world's harshest and driest lands. Here, we review some of the physical, sedimentological, and geochemical characteristics common to GWD deposits, and provide a contextual framework that researchers can use to identify and interpret geologic deposits associated with desert wetlands. We discuss several lines of evidence used to differentiate GWD deposits from lake deposits (they are commonly confused), and examine how various types of microbiota and depositional facies aid in reconstructing past environmental and hydrologic conditions. We also review how late Quaternary GWD deposits are dated, as well as methods used to investigate desert wetlands deeper in geologic time. We end by evaluating the strengths and limitations of hydrologic and climatic records derived from GWD deposits, and suggest several avenues of potential future research to further develop and utilize these unique and complex systems.

CAMEL REARING IN CHOLISTAN DESERT OF PAKISTAN

OpenAIRE

I. ALI, M. SHAFIQ CHAUDHRY1 AND U. FAROOQ

2009-01-01

The camel is one of the typical and the best adopted animals of the desert, capable of enduring thirst and hunger for days and is the most patient of land animals. For desert nomads of Pakistani Cholistan, it is a beloved companion, a source of milk and meat, transport facility provider and a racing/dancing animal, thus, playing an important role in the socioeconomic uplift of the local community. Camels of Marrecha or Mahra breed are mainly used for riding and load carrying but may be traine...

Bacterial succession within an ephemeral hypereutrophic mojave desert playa lake

Science.gov (United States)

Navarro, J.B.; Moser, D.P.; Flores, A.; Ross, C.; Rosen, Michael R.; Dong, H.; Zhang, G.; Hedlund, B.P.

2009-01-01

Ephemerally wet playas are conspicuous features of arid landscapes worldwide; however, they have not been well studied as habitats for microorganisms. We tracked the geochemistry and microbial community in Silver Lake playa, California, over one flooding/desiccation cycle following the unusually wet winter of 2004-2005. Over the course of the study, total dissolved solids increased by 10-fold and pH increased by nearly one unit. As the lake contracted and temperatures increased over the summer, a moderately dense planktonic population of 1 ?????106 cells ml-1 of culturable heterotrophs was replaced by a dense population of more than 1????????109 cells ml-1, which appears to be the highest concentration of culturable planktonic heterotrophs reported in any natural aquatic ecosystem. This correlated with a dramatic depletion of nitrate as well as changes in the microbial community, as assessed by small subunit ribosomal RNA gene sequencing of bacterial isolates and uncultivated clones. Isolates from the early-phase flooded playa were primarily Actinobacteria, Firmicutes, and Bacteroidetes, yet clone libraries were dominated by Betaproteobacteria and yet uncultivated Actinobacteria. Isolates from the late-flooded phase ecosystem were predominantly Proteobacteria, particularly alkalitolerant isolates of Rhodobaca, Porphyrobacter, Hydrogenophaga, Alishwenella, and relatives of Thauera; however, clone libraries were composed almost entirely of Synechococcus (Cyanobacteria). A sample taken after the playa surface was completely desiccated contained diverse culturable Actinobacteria typically isolated from soils. In total, 205 isolates and 166 clones represented 82 and 44 species-level groups, respectively, including a wide diversity of Proteobacteria, Bacteroidetes, Actinobacteria, Firmicutes, Gemmatimonadetes, Acidobacteria, and Cyanobacteria. ?? 2008 Springer Science+Business Media, LLC.

The evolution of deserts with climatic changes in China since 150 ka B.P.

Institute of Scientific and Technical Information of China (English)

董光荣; 陈惠忠; 王贵勇; 李孝泽; 邵亚军; 金炯

1997-01-01

According to the bioclimatic zones, dune mobility and the fabric characteristics of stratigraphic sedimentary facies, the deserts in China are divided into Eastern, Western, Central and Northwestern deserts. Based on the records of stratigraphical facies, climatic proxies, historical data, etc. in each desert region, the evolution of deserts with climatic changes in time and space since 150 ka B. P. in China are dealt with; then the evolution of deserts in relation to the glacial climatic fluctuations caused by solar radiation changes, underlying surface variation and their feedback mechanism is discussed through comparison with global records; finally, in consideration of global wanning due to increasing of greenhouse gases such as CO2, the possible tendency of the evolution of deserts and the climatic changes is discussed.

Aeromycobiota of Western Desert of Egypt | Ismail | African Journal ...

African Journals Online (AJOL)

The prevalence of airborne mycobiota at six different regions of Western desert (5 regions) and Eastern desert (1) of Egypt was determined using the exposed-plate method. A total of 44 genera, 102 species and one variety in addition to some unidentified yeasts and dark sterile mycelia were collected. Of the above, only 5 ...

[Academic stress, desertion, and retention strategies for students in higher education].

Science.gov (United States)

Suárez-Montes, Nancy; Díaz-Subieta, Luz B

2015-04-01

A systematic review was performed to specify the characteristics of academic stress that affect the mental health of the university population. To do this, recent publications regarding academic stress, student desertion, and retention strategies were examined. Throughout this text, we present the results of the review in terms of the definitions of academic stress, student desertion, and retention strategies. In the same way, we examine the interpretative models with regard to student desertion and approach retention strategies in higher education. We also review retention experiences of several other countries. In terms of Colombia, we present aspects related to student desertion and retention programs from the point of view of the National Ministry of Education and from the experience of some universities with consolidated programs.

Dust deposition effects on growth and physiology of the endangered Astragalus jaegerianus (Fabaceae)

Science.gov (United States)

Wijayratne, Upekala C.; Scoles-Sciulla, Sara J.; Defalco, Lesley A.

2009-01-01

Human expansion into the Mojave Desert is a significant threat to rare desert plants. While immediate habitat loss is often the greatest concern, rare plants situated near areas where soil surfaces experience frequent disturbance may be indirectly impacted when fine particulate dust accumulates on leaf surfaces. Remaining populations of the federally listed Astragalus jaegerianus (Lane Mountain milkvetch) occur on land open to expanding military activities and on adjacent public land with increasing recreational use. This study was initiated to determine whether dust accumulation could decrease the vigor and fitness of A. jaegerianus through reduced growth. Beginning in early May 2004, plants located on Bureau of Land Management (BLM) land were dusted bimonthly at canopy-level dust concentrations ranging from 0 to 32 g/m2, and physiology and growth were monitored until late June when plants senesced. The maximum experimental dust level simulates dust concentrations of Mojave Desert perennials neighboring military activities at a nearby army training center. Average shoot growth declined with increasing dust accumulation, but seasonal net photosynthesis increased. Further investigation of plants grown in a greenhouse supported similar trends. This pattern of greater net photosynthesis with increasing dust accumulation may be explained by higher leaf temperatures of dusted individuals. Ambient dust deposition measured in traps near field plants (May 2004–July 2004) ranged from 0.04–0.17 g/m2/ d, which was well below the lowest level of dust on experimental plants (3.95 g/m2/d). With this low level of ambient deposition, we expect that A. jaegerianus plants in this population were not greatly affected by the dust they receive at the level of recreational use during the study.

Geochemical evidence for airborne dust additions to soils in Channel Islands National Park, California

Science.gov (United States)

Muhs, D.R.; Budahn, J.R.; Johnson, D.L.; Reheis, M.; Beann, J.; Skipp, G.; Fisher, E.; Jones, J.A.

2008-01-01

There is an increasing awareness that dust plays important roles in climate change, biogeochemical cycles, nutrient supply to ecosystems, and soil formation. In Channel Islands National Park, California, soils are clay-rich Vertisols or Alfisols and Mollisols with vertic properties. The soils are overlain by silt-rich mantles that contrast sharply with the underlying clay-rich horizons. Silt mantles contain minerals that are rare or absent in the volcanic rocks that dominate these islands. Immobile trace elements (Sc-Th-La and Ta-Nd-Cr) and rare-earth elements show that the basalt and andesite on the islands have a composition intermediate between upper-continental crust and oceanic crust. In contrast, the silt fractions and, to a lesser extent, clay fractions of the silt mantle have compositions closer to average upper-continental crust and very similar to Mojave Desert dust. Island shelves, exposed during the last glacial period, could have provided a source of eolian sediment for the silt mantles, but this is not supported by mineralogical data. We hypothesize that a more likely source for the silt-rich mantles is airborne dust from mainland California and Baja California, either from the Mojave Desert or from the continental shelf during glacial low stands of sea. Although average winds are from the northwest in coastal California, easterly winds occur numerous times of the year when "Santa Ana" conditions prevail, caused by a high-pressure cell centered over the Great Basin. The eolian silt mantles constitute an important medium of plant growth and provide evidence that abundant eolian silt and clay may be delivered to the eastern Pacific Ocean from inland desert sources. ?? 2007 Geological Society of America.

Female offspring desertion and male-only care increase with natural and experimental increase in food abundance.

Science.gov (United States)

Eldegard, Katrine; Sonerud, Geir A

2009-05-07

In species with biparental care, one parent may escape the costs of parental care by deserting and leaving the partner to care for the offspring alone. A number of theoretical papers have suggested a link between uniparental offspring desertion and ecological factors, but empirical evidence is scarce. We investigated the relationship between uniparental desertion and food abundance in a natural population of Tengmalm's owl Aegolius funereus, both by means of a 5-year observational study and a 1-year experimental study. Parents and offspring were fitted with radio-transmitters in order to reveal the parental care strategy (i.e. care or desert) of individual parents, and to keep track of the broods post-fledging. We found that 70 per cent of the females from non-experimental nests deserted, while their partner continued to care for their joint offspring alone. Desertion rate was positively related to natural prey population densities and body reserves of the male partner. In response to food supplementation, a larger proportion of the females deserted, and females deserted the offspring at an earlier age. Offspring survival during the post-fledging period tended to be lower in deserted than in non-deserted broods. We argue that the most important benefit of deserting may be remating (sequential polyandry).

Groundwater mixing and mineralization processes in a mountain-oasis-desert basin, northwest China: hydrogeochemistry and environmental tracer indicators

Science.gov (United States)

Ma, Bin; Jin, Menggui; Liang, Xing; Li, Jing

2018-02-01

Hydrogeochemistry and environmental tracers (2H, 18O, 87Sr/86Sr) in precipitation, river and reservoir water, and groundwater have been used to determine groundwater recharge sources, and to identify mixing characteristics and mineralization processes in the Manas River Basin (MRB), which is a typical mountain-oasis-desert ecosystem in arid northwest China. The oasis component is artificial (irrigation). Groundwater with enriched stable isotope content originates from local precipitation and surface-water leakage in the piedmont alluvial-oasis plain. Groundwater with more depleted isotopes in the north oasis plain and desert is recharged by lateral flow from the adjacent mountains, for which recharge is associated with high altitude and/or paleo-water infiltrating during a period of much colder climate. Little evaporation and isotope exchange between groundwater and rock and soil minerals occurred in the mountain, piedmont and oasis plain. Groundwater δ2H and δ18O values show more homogeneous values along the groundwater flow direction and with well depths, indicating inter-aquifer mixing processes. A regional contrast of groundwater allows the 87Sr/86Sr ratios and δ18O values to be useful in a combination with Cl, Na, Mg, Ca and Sr concentrations to distinguish the groundwater mixing characteristics. Two main processes are identified: groundwater lateral-flow mixing and river leakage in the piedmont alluvial-oasis plain, and vertical mixing in the north oasis plain and the desert. The 87Sr/86Sr ratios and selected ion ratios reveal that carbonate dissolution and mixing with silicate from the southern mountain area are primarily controlling the strontium isotope hydrogeochemistry.

Nest site characteristics, nesting movements, and lack of long-term nest site fidelity in Agassiz's desert tortoises at a wind energy facility in southern California

Science.gov (United States)

Lovich, Jeffrey E.; Agha, Mickey; Yackulic, Charles B.; Meyer-Wilkins, Kathie; Bjurlin, Curtis; Ennen, Joshua R.; Arundel, Terry R.; Austin, Meaghan

2014-01-01

Nest site selection has important consequences for maternal and offspring survival and fitness. Females of some species return to the same nesting areas year after year. We studied nest site characteristics, fidelity, and daily pre-nesting movements in a population of Agassiz’s desert tortoises (Gopherus agassizii) at a wind energy facility in southern California during two field seasons separated by over a decade. No females returned to the same exact nest site within or between years but several nested in the same general area. However, distances between first and second clutches within a year (2000) were not significantly different from distances between nests among years (2000 and 2011) for a small sample of females, suggesting some degree of fidelity within their normal activity areas. Environmental attributes of nest sites did not differ significantly among females but did among years due largely to changes in perennial plant structure as a result of multiple fires. Daily pre-nesting distances moved by females decreased consistently from the time shelled eggs were first visible in X-radiographs until oviposition, again suggesting some degree of nest site selection. Tortoises appear to select nest sites that are within their long-term activity areas, inside the climate-moderated confines of one of their self-constructed burrows, and specifically, at a depth in the burrow that minimizes exposure of eggs and embryos to lethal incubation temperatures. Nesting in “climate-controlled” burrows and nest guarding by females relaxes some of the constraints that drive nest site selection in other oviparous species.

Observed 20th century desert dust variability: impact on climate and biogeochemistry

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N. M. Mahowald

2010-11-01

Full Text Available Desert dust perturbs climate by directly and indirectly interacting with incoming solar and outgoing long wave radiation, thereby changing precipitation and temperature, in addition to modifying ocean and land biogeochemistry. While we know that desert dust is sensitive to perturbations in climate and human land use, previous studies have been unable to determine whether humans were increasing or decreasing desert dust in the global average. Here we present observational estimates of desert dust based on paleodata proxies showing a doubling of desert dust during the 20th century over much, but not all the globe. Large uncertainties remain in estimates of desert dust variability over 20th century due to limited data. Using these observational estimates of desert dust change in combination with ocean, atmosphere and land models, we calculate the net radiative effect of these observed changes (top of atmosphere over the 20th century to be −0.14 ± 0.11 W/m² (1990–1999 vs. 1905–1914. The estimated radiative change due to dust is especially strong between the heavily loaded 1980–1989 and the less heavily loaded 1955–1964 time periods (−0.57 ± 0.46 W/m², which model simulations suggest may have reduced the rate of temperature increase between these time periods by 0.11 °C. Model simulations also indicate strong regional shifts in precipitation and temperature from desert dust changes, causing 6 ppm (12 PgC reduction in model carbon uptake by the terrestrial biosphere over the 20th century. Desert dust carries iron, an important micronutrient for ocean biogeochemistry that can modulate ocean carbon storage; here we show that dust deposition trends increase ocean productivity by an estimated 6% over the 20th century, drawing down an additional 4 ppm (8 PgC of carbon dioxide into the oceans. Thus, perturbations to desert dust over the 20th century inferred from observations are potentially important for climate and

Observation of water and heat fluxes in the Badain Jaran desert, China

NARCIS (Netherlands)

Zhang, T.; Wen, J.; Su, Z.; Tian, H.; Zeng, Y.

Badain Jaran Desert lie in the northwest of the Alashan plateau in western Inner Mongolia of China, between39o20'N to 41o30'N and 100oE to 104oE. It is the 4th largest desert in the world and the second largest desert in China, with an area of 49000 square kilometers and an altitude between 900 and

Biparentally deserted offspring are viable in a species with intense sexual conflict over care.

Science.gov (United States)

Pogány, Ákos; Kosztolányi, András; Miklósi, Ádám; Komdeur, Jan; Székely, Tamás

2015-07-01

Desertion of clutch (or brood) by both parents often leads to breeding failure, since in vast majority of birds care by at least one parent is required for any young to fledge. Recent works in a highly polygamous passerine bird, the Eurasian penduline tit (Remiz pendulinus), suggest that biparental clutch desertion is due to intense sexual conflict over care. However, an alternative yet untested hypothesis for biparental desertion is low offspring viability so that the parents abandon the offspring that have poor prospect for survival. Here we test the latter hypothesis in a common garden experiment by comparing the viability of deserted and cared for eggs. We show that embryonic development does not differ between deserted and cared for eggs. Therefore, sexual conflict over care remains the best supported hypothesis for biparental clutch desertion in penduline tits. Our work points out that conflict over care is a potential - yet rarely considered - cause of biparental nest desertion, and a strong alternative for the traditional explanations of low offspring viability, human disturbance or deteriorating ambient environment. Apart from a handful of species, the intensity of sexual conflict has not been quantified, and we call for further studies to consider sexual conflict as a cause of nest desertion. Copyright © 2015 Elsevier B.V. All rights reserved.

CAMEL REARING IN CHOLISTAN DESERT OF PAKISTAN

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I. ALI, M. SHAFIQ CHAUDHRY1 AND U. FAROOQ

2009-05-01

Full Text Available The camel is one of the typical and the best adopted animals of the desert, capable of enduring thirst and hunger for days and is the most patient of land animals. For desert nomads of Pakistani Cholistan, it is a beloved companion, a source of milk and meat, transport facility provider and a racing/dancing animal, thus, playing an important role in the socioeconomic uplift of the local community. Camels of Marrecha or Mahra breed are mainly used for riding and load carrying but may be trained for dancing or racing. Berella is another heavy and milch breed of camel famous for milk production and can produce upto 10-15 liters of milk per day. This breed is also suitable for draught purpose, though comparatively slow due to heavy body. The present paper also describes the traditional camel rearing system used by nomads of Cholistan desert. Some aspects of camel health, production, feeding, socio-economic values, marketing and some constraints and suggestions are also given so that the policy makers may consider them for the welfare of this animal.

Pastoralist rock art in the Black Desert of Jordan

OpenAIRE

Brusgaard, N.O.

2015-01-01

This paper discusses the current problems that exist with the rock art research of the Black Desert in Jordan and presents some preliminary field results of the author’s research on the petroglyphs. It also explore the possibilities that the rock art affords to learn more about the elusive desert societies and the limitations about studying rock art in archaeologically unfamiliar territories.

Condition-dependent clutch desertion in Great Tit (Parus major) females subjected to human disturbance

OpenAIRE

2011-01-01

Abstract Nest desertion behaviour in relation to body condition and timing of breeding was studied in Great Tit (Parus major) females during two breeding seasons. Desertion, most likely unintentionally provoked by catching females during the incubation period, occurred at a very high rate with 41.2 and 25.6% of deserted first clutches in the two study years. The association between desertion probability, body condition (index calculated as residuals from the regression of body mass...

Fine-grained quartz OSL dating chronology of loess sequence from southern Tajikistan: Implications for climate change in arid central Asia during MIS 2

Science.gov (United States)

Wang, Leibin; Jia, Jia; Li, Guoqiang; Li, Zaijun; Wang, Xin; Chen, Fahu

2018-04-01

The desert and semi-desert region of arid central Asia is one of the most important areas of middle-latitude dust emission and deposition in the Northern Hemisphere. Marine isotope stage 2 (MIS 2) was the latest and one of the most representative intervals of dust emission from the region, and it is especially important for research into processes of dust transportation and deposition. Here, we report the results of an optically stimulated luminescence study of the Hoalin section in southern Tajikistan, which was deposited during MIS 2. The fine-grained quartz single aliquot regeneration (SAR) approach was used and its reliability was verified by internal checks. In addition, grain-size analyses, calculated dust accumulation rates (DARs) and mass accumulation rates (MARs) were used to reconstruct the pattern of climate change during MIS 2. The mean DAR for southern Tajikistan during MIS 2 was 0.43 m/ka, and the corresponding average MAR was 673 g/cm2/a for a non-river-terrace site, which is higher than the average MARs estimated for the central and southern Chinese Loess Plateau (CLP). In contrast to previous suggestions, the high dust DARs and MARs during the LGM indicate a 'cold-dry' climatic pattern, rather than a 'cold-humid' pattern. Our results also confirm that the patterns of high dust emission and deposition during the LGM in the mid-latitude arid zone of Asia were synchronous.

Hydrological indications of aeolian salts in mid-latitude deserts of ...

Indian Academy of Sciences (India)

Hydrological indications of aeolian salts in mid-latitude deserts of northwestern China. B Q Zhu. Supplementary data. Figure S1. Photograph views of Quaternary and modern sediments of aeolian and lacustrine/fluvial facies that consisted of clay and sand/silt sand alternations in the Taklamakan and Badanjilin Deserts.

Mineral compositions and sources of the riverbed sediment in the desert channel of Yellow River.

Science.gov (United States)

Jia, Xiaopeng; Wang, Haibing

2011-02-01

The Yellow River flows through an extensive, aeolian desert area and extends from Xiaheyan, Ningxia Province, to Toudaoguai, Inner Mongolia Province, with a total length of 1,000 km. Due to the construction and operation of large reservoirs in the upstream of the Yellow River, most water and sediment from upstream were stored in these reservoirs, which leads to the declining flow in the desert channel that has no capability to scour large amount of input of desert sands from the desert regions. By analyzing and comparing the spatial distribution of weight percent of mineral compositions between sediment sources and riverbed sediment of the main tributaries and the desert channel of the Yellow River, we concluded that the coarse sediment deposited in the desert channel of the Yellow River were mostly controlled by the local sediment sources. The analyzed results of the Quartz-Feldspar-Mica (QFM) triangular diagram and the R-factor models of the coarse sediment in the Gansu reach and the desert channel of the Yellow River further confirm that the Ningxia Hedong desert and the Inner Mongolian Wulanbuhe and Kubuqi deserts are the main provenances of the coarse sediment in the desert channel of the Yellow River. Due to the higher fluidity of the fine sediment, they are mainly contributed by the local sediment sources and the tributaries that originated from the loess area of the upper reach of the Yellow River.

Long-term growth of Desert Tortoises (Gopherus agassizii) in a southern Nevada population

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Medica, P.A.; Nussear, Kenneth E.; Esque, Todd C.; Saethre, Mary B.

2012-01-01

Knowledge of growth rates, age at maturity, and longevity are important aspects of a species life history and are directly applicable to life table creation and population viability analyses. We measured the growth of a cohort of 17 semi-wild Desert Tortoises (Gopherus agassizii) located in Rock Valley, Nevada over a 47-yr period beginning in 1963. The tortoises were initially marked as hatchling and juvenile animals between the years 1963 and 1965 and ranged in size from 47 to 77 mm in plastron length. We assigned ages of 1-4 yr to the tortoises at initial capture based on their body size. These tortoises were recaptured, measured, and weighed approximately annually since their initial capture. Growth of male and female tortoises did not differ significantly until animals reached the age of 23-25 yr. Annual tortoise growth was correlated with the production of ephemeral vegetation, while accounting for size, sex, and repeated measurements of the animals as well as the interval between measurements. However, the production of ephemeral plants was likewise highly correlated (non-linearly) with winter rainfall. Stochastic predation events between 2003 and 2007 decimated this cohort of tortoises. The average age of the long-term surviving tortoises from this cohort was 43 yr with a range of 39-47 yr. Twelve of the tortoises survived to the age of 39 yr and 11 of the 12 reached 40 yr.

Rupture Propagation through the Big Bend of the San Andreas Fault: A Dynamic Modeling Case Study of the Great Earthquake of 1857

Science.gov (United States)

Lozos, J.

2017-12-01

The great San Andreas Fault (SAF) earthquake of 9 January 1857, estimated at M7.9, was one of California's largest historic earthquakes. Its 360 km rupture trace follows the Carrizo and Mojave segments of the SAF, including the 30° compressional Big Bend in the fault. If 1857 were a characteristic rupture, the hazard implications for southern California would be dire, especially given the inferred 150 year recurrence interval for this section of the fault. However, recent paleoseismic studies in this region suggest that 1857-type events occur less frequently than single-segment Carrizo or Mojave ruptures, and that the hinge of the Big Bend is a barrier to through-going rupture. Here, I use 3D dynamic rupture modeling to attempt to reproduce the rupture length and surface slip distribution of the 1857 earthquake, to determine which physical conditions allow rupture to negotiate the Big Bend of the SAF. These models incorporate the nonplanar geometry of the SAF, an observation-based heterogeneous regional velocity structure (SCEC CVM), and a regional stress field from seismicity literature. Under regional stress conditions, I am unable to produce model events that both match the observed surface slip on the Carrizo and Mojave segments of the SAF and include rupture through the hinge of the Big Bend. I suggest that accumulated stresses at the bend hinge from multiple smaller Carrizo or Mojave ruptures may be required to allow rupture through the bend — a concept consistent with paleoseismic observations. This study may contribute to understanding the cyclicity of hazard associated with the southern-central SAF.

Siting a low-level radioactive waste disposal facility in California

International Nuclear Information System (INIS)

Romano, S.A.; Gaynor, R.K.

1991-01-01

US Ecology is the State of California's designee to site, develop and operate a low-level radioactive waste disposal facility. In March 1988, a site in the Ward Valley of California's Mojave Desert was chosen for development. Strong local community support has been expressed for the site. US Ecology anticipates licensing and constructing a facility to receive waste by early 1991. This schedule places California well ahead of the siting milestones identified in Federal law. (author) 1 fig., 2 refs

A demographic approach to study effects of climate change in desert plants

Science.gov (United States)

Salguero-Gómez, Roberto; Siewert, Wolfgang; Casper, Brenda B.; Tielbörger, Katja

2012-01-01

Desert species respond strongly to infrequent, intense pulses of precipitation. Consequently, indigenous flora has developed a rich repertoire of life-history strategies to deal with fluctuations in resource availability. Examinations of how future climate change will affect the biota often forecast negative impacts, but these—usually correlative—approaches overlook precipitation variation because they are based on averages. Here, we provide an overview of how variable precipitation affects perennial and annual desert plants, and then implement an innovative, mechanistic approach to examine the effects of precipitation on populations of two desert plant species. This approach couples robust climatic projections, including variable precipitation, with stochastic, stage-structured models constructed from long-term demographic datasets of the short-lived Cryptantha flava in the Colorado Plateau Desert (USA) and the annual Carrichtera annua in the Negev Desert (Israel). Our results highlight these populations' potential to buffer future stochastic precipitation. Population growth rates in both species increased under future conditions: wetter, longer growing seasons for Cryptantha and drier years for Carrichtera. We determined that such changes are primarily due to survival and size changes for Cryptantha and the role of seed bank for Carrichtera. Our work suggests that desert plants, and thus the resources they provide, might be more resilient to climate change than previously thought. PMID:23045708

The Ocean deserts:salt budgets of northern subtropical oceans and their

KAUST Repository

Carton, Jim

2011-04-09

The Ocean deserts: salt budgets of northern subtropical oceans and their relationship to climate variability The high salinity near surface pools of the subtropical oceans are the oceanic deserts, with high levels of evaporation and low levels of precip

Mapping of Grocery Stores in Slovak Countryside in Context of Food Deserts

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Kristína Bilková

2015-01-01

Full Text Available The paper is focused on mapping grocery stores in the Slovak countryside with an emphasis on identifying potential food deserts in rural areas. Grocery stores are analyzed in the time period 2001–2011. Food deserts in rural areas are identified by two accessibility measures. The results show the development of food retailing in the Slovak countryside and in potentially threatened localities which can be defined as food deserts.

Soil seed bank in different habitats of the Eastern Desert of Egypt.

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Gomaa, Nasr H

2012-04-01

The floristic composition and species diversity of the germinable soil seed bank were studied in three different habitats (desert salinized land, desert wadi, and reclaimed land) in the Eastern Desert of Egypt. Moreover, the degree of similarity between the seed bank and the above-ground vegetation was determined. The seed bank was studied in 40 stands representing the three habitats. Ten soil samples (each 25 × 20 cm and 5 cm depth) were randomly taken per stand. The seed bank was investigated by the seedling emergence method. Some 61 species belonging to 21 families and 54 genera were identified in the germinable seed bank. The recorded species include 43 annuals and 18 perennials. Ordination of stands by Detrended Correspondence Analysis (DCA) indicates that the stands of the three habitats are markedly distinguishable and show a clear pattern of segregation on the ordination planes. This indicates variations in the species composition among habitats. The results also demonstrate significant associations between the floristic composition of the seed bank and edaphic factors such as CaCO3, electrical conductivity, organic carbon and soil texture. The reclaimed land has the highest values of species richness, Shannon-index of diversity and the density of the germinable seed bank followed by the habitats of desert wadi and desert salinized land. Motyka's similarity index between the seed bank and the above-ground vegetation is significantly higher in reclaimed land (75.1%) compared to desert wadi (38.4%) and desert salinized land (36.5%).

Desert farming benefits from microbial potential in arid soils and promotes diversity and plant health.

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Martina Köberl

Full Text Available BACKGROUND: To convert deserts into arable, green landscapes is a global vision, and desert farming is a strong growing area of agriculture world-wide. However, its effect on diversity of soil microbial communities, which are responsible for important ecosystem services like plant health, is still not known. METHODOLOGY/PRINCIPAL FINDINGS: We studied the impact of long-term agriculture on desert soil in one of the most prominent examples for organic desert farming in Sekem (Egypt. Using a polyphasic methodological approach to analyse microbial communities in soil as well as associated with cultivated plants, drastic effects caused by 30 years of agriculture were detected. Analysing bacterial fingerprints, we found statistically significant differences between agricultural and native desert soil of about 60%. A pyrosequencing-based analysis of the 16S rRNA gene regions showed higher diversity in agricultural than in desert soil (Shannon diversity indices: 11.21/7.90, and displayed structural differences. The proportion of Firmicutes in field soil was significantly higher (37% than in the desert (11%. Bacillus and Paenibacillus play the key role: they represented 96% of the antagonists towards phytopathogens, and identical 16S rRNA sequences in the amplicon library and for isolates were detected. The proportion of antagonistic strains was doubled in field in comparison to desert soil (21.6%/12.4%; disease-suppressive bacteria were especially enriched in plant roots. On the opposite, several extremophilic bacterial groups, e.g., Acidimicrobium, Rubellimicrobium and Deinococcus-Thermus, disappeared from soil after agricultural use. The N-fixing Herbaspirillum group only occurred in desert soil. Soil bacterial communities were strongly driven by the a-biotic factors water supply and pH. CONCLUSIONS/SIGNIFICANCE: After long-term farming, a drastic shift in the bacterial communities in desert soil was observed. Bacterial communities in agricultural

[Spatial change of the grain-size of aeolian sediments in Qira oasis-desert ecotone, Northwest China].

Science.gov (United States)

Lin, Yong Chong; Xu, Li Shuai

2017-04-18

In order to understand the environmental influence of oasis-desert ecotone to oasis ecological system, we comparatively analyzed the grain size characteristics of various aeolian sediments, including the sediments in oasis-desert ecotone, shelterbelt and the inside oasis and in Qira River valley. The results showed that the grain size characteristics (including grain-size distribution curve, grain size parameters, and content of different size classes) of sediments in the oasis-desert ecotone were consistent along the prevailing wind direction with a grain-size range of 0.3-200 μm and modal size of 67 μm. All of the sediments were good sorting and mainly composed of suspension components and saltation components, but not denatured saltation and creeping components (>200 μm). They were typically aeolian deposits being short-range transported. The grain sizes of sediments in oasis-desert ecotone were smaller than that in the material sources of Qira River valley and desert (0.3-800 μm), but very similar to those of the modern aeolian deposits in oasis-desert ecotone, shelterbelt and the inside oasis. The denatured saltation and creep components (>200 μm) were suppressed to transport into oasis-desert ecotone because of the high vegetation cover in oasis-desert ecotone. Therefore, like the shelterbelts, the oasis-desert ecotone could also block the invasion of desert. They safeguarded the oasis ecological environment together.

Desert Net-Structure and Aims of an International Network for Desertification Research

International Nuclear Information System (INIS)

Akhtar-Schuster, M.; San Juan Mesonada, C.

2009-01-01

Desert Net://www.european-desert net.eu) is an interdisciplinary scientific network which was established in October 2006 at the UN premises in Bonn, Germany, by a group of international scientists. The network strives to generate and enhance scientific knowledge and understanding of the biophysical and socio-economic processes of desertification. This international scientific network provides an international platform for scientifically based discussions and exchange of ideas, addressing knowledge gaps, and identifying research areas. Desert Net is also a think tank community which identifies issues and priorities for the sustainable development of dry lands. the paper outlines the current role of Desert Net in the international scientific community and it delineates its role to strengthen the Science/Policy Interface. (Author) 2 refs.

Cytogeography of Larrea tridentata at the Chihuahuan-Sonoran Desert ecotone

Science.gov (United States)

Robert G. Laport; Robert L.. Minckley

2013-01-01

The long separation of the Chihuahuan and Sonoran Deserts is reflected in the high species richness and endemism of their floras. Although many endemic species from both deserts reach their distributional limits where the Sierra Madre Occidental massif fragments into smaller mountain complexes in northern Mexico and adjoining areas of the United States, indicator...

Water appropriation and ecosystem stewardship in the Baja desert

OpenAIRE

de las Heras Alejandro; Rodriguez Mario A.; Islas-Espinoza Marina

2014-01-01

The UNESCO San Francisco Rock Paintings polygon within El Vizcaino Biosphere Reserve in the Baja California Peninsula derives its moisture from the North American monsoon. There, ranchers have depended on the desert since the 18th century. More recently, the desert has depended on the environmental stewardship of the ranchers who have allayed mining exploitation and archaeological looting. Using a Rapid Assessment Procedure (RAP), climate data, and geographical informa...

MX Siting Investigation. Gravity Survey - Sevier Desert Valley, Utah.

Science.gov (United States)

1981-01-24

Cheyenne, Wyoming. DMAHTC reduces the data to Simple Bouguer Anomaly (see Section A1.4, Appendix Al.0). The Defense Mapping Agency Aerospace Center...Desert Valley, Utah ......... 2 2 Topographic Setting - Sevier Desert Valley, Utah . 3 LIST OF DRAWINGS Drawing Number 1 Complete Bouguer Anomaly...gravity stations were distributed throughout the valley at an approxi- mate interval of 1.4 miles (2.3 km). Drawing 1 is a Complete Bouguer Anomaly

Reestablishing healthy food retail: changing the landscape of food deserts.

Science.gov (United States)

Karpyn, Allison; Young, Candace; Weiss, Stephanie

2012-02-01

The term "food desert" was formally introduced into the lexicon in 1995 and has come to describe areas with limited access to affordable nutritious foods, particularly areas in lower-income neighborhoods. The definition has led to the development of national and regional maps that focus efforts on equity in food access. Recognition of food deserts also marks a strategic change in public health's approach to obesity prevention. Today's emphasis on prevention has shifted away from individual responsibility to the role of the environment in health promotion. A number of solutions are underway to address food deserts, including public–private financing programs, industry commitments, as well as local and regional efforts to put healthy food within reach. The promise of financing programs to facilitate development of healthy food markets in underserved communities is rooted in their potential to alleviate the grocery gap and address underlying environmental contributors to obesity and diet-related diseases, such as obesity and diabetes. As food desert mapping and related interventions expand, there remains a need for ongoing investigation of impacts and the mechanisms by which impacts are achieved.

Liquid Water Restricts Habitability in Extreme Deserts

Science.gov (United States)

Cockell, Charles S.; Brown, Sarah; Landenmark, Hanna; Samuels, Toby; Siddall, Rebecca; Wadsworth, Jennifer

2017-04-01

Liquid water is a requirement for biochemistry, yet under some circumstances it is deleterious to life. Here, we show that liquid water reduces the upper temperature survival limit for two extremophilic photosynthetic microorganisms (Gloeocapsa and Chroococcidiopsis spp.) by greater than 40°C under hydrated conditions compared to desiccated conditions. Under hydrated conditions, thermal stress causes protein inactivation as shown by the fluorescein diacetate assay. The presence of water was also found to enhance the deleterious effects of freeze-thaw in Chroococcidiopsis sp. In the presence of water, short-wavelength UV radiation more effectively kills Gloeocapsa sp. colonies, which we hypothesize is caused by factors including the greater penetration of UV radiation into hydrated colonies compared to desiccated colonies. The data predict that deserts where maximum thermal stress or irradiation occurs in conjunction with the presence of liquid water may be less habitable to some organisms than more extreme arid deserts where organisms can dehydrate prior to being exposed to these extremes, thus minimizing thermal and radiation damage. Life in extreme deserts is poised between the deleterious effects of the presence and the lack of liquid water.

Lithology, fault displacement, and origin of secondary calcium carbonate and opaline silica at Trenches 14 and 14D on the Bow Ridge Fault at Exile Hill, Nye County, Nevada

International Nuclear Information System (INIS)

Taylor, E.M.; Huckins, H.E.

1995-01-01

Yucca Mountain, a proposed site for a high-level nuclear-waste repository, is located in southern Nevada, 20 km east of Beatty, and adjacent to the southwest comer of the Nevada Test Site (NTS) (fig. 1). Yucca Mountain is located within the Basin and Range province of the western United States. The climate is semiarid, and the flora is transitional between that of the Mojave Desert to the south and the Great Basin Desert to the north. As part of the evaluation, hydrologic conditions, especially water levels, of Yucca Mountain and vicinity during the Quaternary, and especially the past 20,000 years, are being characterized. In 1982, the US Geological Survey, in cooperation with the US Department of Energy (under interagency agreement DE-A104-78ET44802), excavated twenty-six bulldozer and backhoe trenches in the Yucca Mountain region to evaluate the nature and frequency of Quaternary faulting (Swadley and others, 1984). The trenches were oriented perpendicular to traces of suspected Quaternary faults and across projections of known bedrock faults into Quaternary deposits. Trench 14 exposes the Bow Ridge Fault on the west side of Exile Hill. Although the original purpose of the excavation of trench 14 was to evaluate the nature and frequency of Quaternary faulting on the Bow Ridge Fault, concern arose as to whether or not the nearly vertical calcium carbonate (the term ''carbonate'' in this study refers to calcium carbonate) and opaline silica veins in the fault zone were deposited by ascending waters (ground water). These veins resemble in gross morphology veins commonly formed by hydrothermal processes

The economics of hybrid power systems for sustainable desert agriculture in Egypt

DEFF Research Database (Denmark)

Kamel, S.M.; Dahl, C.

2005-01-01

Egypt has embarked on an ambitious desert land reclamation program in order to increase total food production. Energy planners for these desert agriculture locations have chosen diesel generation power technology because minimization of the initial capital cost of a power supply system is their top...... priority. This heavy reliance on diesel generation has negative effects on the surrounding environment including soil, groundwater, and air pollution. Although good solar and wind resource prospects exist for the use of cleaner hybrid power systems in certain desert locations, little research has been done...... to investigate the economic potential of such systems in Egypt’s desert agriculture sector. Using optimization software, we assess the economics of hybrid power systems versus the present diesel generation technology in a remote agricultural development area. We also consider the emission reduction advantages...

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African Journals Online (AJOL)

Southern African Journal of Environmental Education, Vol. ... savanna in the Sahel, and then to desert scrub in the southern fringes of the Sahara Desert at ... Guinea savanna .... In Hirji, R., Johnson, P., Maro, P. & Chiuta, T.M. (Eds), Defining.

Winter precipitation and fire in the Sonoran Desert

Energy Technology Data Exchange (ETDEWEB)

Rogers, G.F.; Vint, M.K.

1987-01-01

Historical fire and climate records from the Arizona Upland portion of the Tonto National forest were used to test the hypothesis that fires burn larger areas in the Sonoran Desert after two wet winters than after one. We found that many more hectares burn in years following two winters that are wetter than normal, than during any other years. We agree with other ecologists, that desert fire occurrence is probably related to increased production of winter annual plants, and we suggest ways that the relationship may be clarified.

Naturalisation, Desert, and the Symbolic Meaning of Citizenship

DEFF Research Database (Denmark)

Lægaard, Sune

2012-01-01

of naturalisation requirements as involving notions of desert and asks what these developments imply about the meaning of citizenship. Naturalisation marks the boundary of society understood as a political community, i.e. a civic rather than territorial boundary. How this boundary is policed and on the basis...... that the introduction of naturalisation tests and other desert-based naturalisation requirements imply that citizenship comes to have different symbolic meanings for native born citizens and naturalised citizens because such requirements distinguish between volitional or ‘earned’ and ascriptive or ‘natural’ citizenship...

A Dynamic Simulation Model of the Desert Tortoise (Gopherus agassizii) Habitat in the Central Mojave Desert

National Research Council Canada - National Science Library

Westervelt, James

1997-01-01

.... Across the nation, Army and civilian land management offices responsible for the management of natural resources, endangered species, water quality, aesthetics, and economic productivity of the land...

Vascular flora of saline lakes in the southern high plains of Texas and eastern New Mexico

Science.gov (United States)

Rosen, David J.; Conway, Warren C.; Haukos, David A.; Caskey, Amber D.

2013-01-01

Saline lakes and freshwater playas form the principal surface hydrological feature of the High Plains of the Southern Great Plains. Saline lakes number less than 50 and historically functioned as discharge wetlands with relatively consistent water availability due to the presence of one or more springs. Currently, less than ten saline lakes contain functional springs. A survey of vascular plants at six saline lakes in the Southern High Plains of northwest Texas and one in eastern New Mexico during May and September 2009 resulted in a checklist of 49 species representing 16 families and 40 genera. The four families with the most species were Asteraceae (12), Amaranthaceae (8), Cyperaceae (5), and Poaceae (12). Non-native species (Bromus catharticus, Poa compressa, Polypogon monspeliensis, Sonchus oleraceus, Kochia scoparia, and Tamarix ramosissima) accounted for 10% of the total species recorded. Whereas nearly 350 species of vascular plants have been identified in playas in the Southern High Plains, saline lakes contain a fraction of this species richness. The Southern High Plains saline lake flora is regionally unique, containing taxa not found in playas, with species composition that is more similar to temperate desert wetlands of the Intermountain Region and Gulf Coastal Plain of North America.

The water economy of South American desert rodents: from integrative to molecular physiological ecology.

Science.gov (United States)

Bozinovic, Francisco; Gallardo, Pedro

2006-01-01

Rodents from arid and semi-arid habitats live under conditions where the spatial and temporal availability of free water is limited, or scarce, thus forcing these rodents to deal with the problem of water conservation. The response of rodents to unproductive desert environments and water deficits has been intensively investigated in many deserts of the world. However, current understanding of the cellular, systemic and organismal physiology of water economy relies heavily on short-term, laboratory-oriented experiments, which usually focus on responses at isolated levels of biological organization. In addition, studies in small South American mammals are scarce. Indeed xeric habitats have existed in South America for a long time and it is intriguing why present day South American desert rodents do not show the wide array of adaptive traits to desert life observed for rodents on other continents. Several authors have pointed out that South American desert rodents lack physiological and energetic specialization for energy and water conservation, hypothesizing that their success is based more on behavioral and ecological strategies. We review phenotypic flexibility and physiological diversity in water flux rate, urine osmolality, and expression of water channels in South American desert-dwelling rodents. As far as we know, this is the first review of integrative studies at cellular, systemic and organismal levels. Our main conclusion is that South American desert rodents possess structural as well as physiological systems for water conservation, which are as remarkable as those found in "classical" rodents inhabiting other desert areas of the world.

Are Wildlife Detector Dogs or People Better at Finding Desert Tortoises (Gopherus Agassizii)?

National Research Council Canada - National Science Library

Nussear, Kenneth E; Esque, Todd C; Heaton, Jill S; Cablk, Mary E; Drake, Kristina K; Valentin, Cindee; Yee, Julie L; Medica, Philip A

2008-01-01

.... Recent studies highlight the effectiveness of trained detector dogs to locate wildlife during field surveys, including Desert Tortoises in a semi-natural setting. Desert Tortoises (Gopherus agassizii...

Are wildlife detector dogs or people better at finding Desert Tortoises (Gopherus agassizii)?

Science.gov (United States)

Nussear, K.E.; Esque, T.C.; Heaton, J.S.; Cablk, Mary E.; Drake, K.K.; Valentin, C.; Yee, J.L.; Medica, P.A.

2008-01-01

Our ability to study threatened and endangered species depends on locating them readily in the field. Recent studies highlight the effectiveness of trained detector dogs to locate wildlife during field surveys, including Desert Tortoises in a semi-natural setting. Desert Tortoises (Gopherus agassizii) are cryptic and difficult to detect during surveys, especially the smaller size classes. We conducted comparative surveys to determine whether human or detector dog teams were more effective at locating Desert Tortoises in the wild. We compared detectability of Desert Tortoises and the costs to deploy human and dog search teams. Detectability of tortoises was not statistically different for either team, and was estimated to be approximately 70% (SE = 5%). Dogs found a greater proportion of tortoises located in vegetation than did humans. The dog teams finished surveys 2.5 hours faster than the humans on average each day. The human team cost was approximately $3,000 less per square kilometer sampled. Dog teams provided a quick and effective method for surveying for adult Desert Tortoises; however, we were unable to determine-their effectiveness at locating smaller size classes. Detection of smaller size classes during surveys would improve management of the species and should be addressed by future research using Desert Tortoise detector dogs.

Vagrant western red-shouldered hawks: origins, natal dispersal patterns, and survival

Science.gov (United States)

Bloom, Peter H.; Scott, J. Michael; Papp, Joseph M.; Thomas, Scott E.; Kidd, Jeff W.

2011-01-01

We report the results of a 40-year study of the western Red-shouldered Hawk (Buteo lineatus elegans) involving the banding of 2742 nestlings in southern California from 1970 to 2009 (this study) plus 127 nestlings banded in other California studies (1956–2008) and the analyses of 119 records of subsequent recovery from the Bird Banding Laboratory (1957–2009). Of the Red-shouldered Hawks recovered, 109 (91.6%) moved 100 km (long-distance dispersers). Three (2.5%), all long-distance dispersers, were vagrants (recovered outside the species' range of residency), and were found 374 to 843 km northeast and south of their banding locations in the Mojave, Great Basin, and Vizcaino deserts. The distribution of directions of short-distance dispersal was bipolar, closely corresponding with the northwest—southeast orientation of the species' range in southern California, while that of long-distance dispersers was mainly to the north. One of 10 long-distance dispersers, a nonvagrant, survived well into the age of breeding (103.0 months), whereas eight of the other nine perished before 14.5 months. The implications of vagrancy for conservation of this resident subspecies are that a relatively small source area can contribute genetic material over a vastly larger receiving area but rarely does so because of high mortality rates. Nonetheless, the movements of vagrants we documented provide evidence for the species' potential to populate new landscapes in response to changing environmental conditions and to maintain genetic heterogeneity within existing populations.

Concentration of plutonium in desert plants from contaminated area

International Nuclear Information System (INIS)

Xu Hui; Jin Yuren; Tian Mei; Li Weiping; Zeng Ke; Wang Yaoqin; Wang Yu

2012-01-01

The investigation of plutonium in desert plants from contaminated sites contributes to the evaluation of its pollution situation and to the survey of plutonium hyper accumulator. The concentration of 239 Pu in desert plants collected from a contaminated site was determined, and the influence factors were studied. The concentration of 239 Pu in plants was (1.8±4.9) Bq/kg in dry weight, and it means that the plants were contaminated, moreover, the resuspension results in dramatic plutonium pollution of plant surface. The concentration of plutonium in plants depends on species, live stages and the content of plutonium in the rhizosphere soil. The concentration of plutonium in herbage is higher than that in woody plant, and for the seven species of desert plants investigated, it decreases in the order of Hexinia polydichotoma, Phragmites australis, Halostashys caspica, Halogeton arachnoideus, Lycium ruthenicum, Tamarix hispida and Calligonum aphyllum. (authors)

Problems with sampling desert tortoises: A simulation analysis based on field data

Science.gov (United States)

Freilich, J.E.; Camp, R.J.; Duda, J.J.; Karl, A.E.

2005-01-01

The desert tortoise (Gopherus agassizii) was listed as a U.S. threatened species in 1990 based largely on population declines inferred from mark-recapture surveys of 2.59-km2 (1-mi2) plots. Since then, several census methods have been proposed and tested, but all methods still pose logistical or statistical difficulties. We conducted computer simulations using actual tortoise location data from 2 1-mi2 plot surveys in southern California, USA, to identify strengths and weaknesses of current sampling strategies. We considered tortoise population estimates based on these plots as "truth" and then tested various sampling methods based on sampling smaller plots or transect lines passing through the mile squares. Data were analyzed using Schnabel's mark-recapture estimate and program CAPTURE. Experimental subsampling with replacement of the 1-mi2 data using 1-km2 and 0.25-km2 plot boundaries produced data sets of smaller plot sizes, which we compared to estimates from the 1-mi 2 plots. We also tested distance sampling by saturating a 1-mi 2 site with computer simulated transect lines, once again evaluating bias in density estimates. Subsampling estimates from 1-km2 plots did not differ significantly from the estimates derived at 1-mi2. The 0.25-km2 subsamples significantly overestimated population sizes, chiefly because too few recaptures were made. Distance sampling simulations were biased 80% of the time and had high coefficient of variation to density ratios. Furthermore, a prospective power analysis suggested limited ability to detect population declines as high as 50%. We concluded that poor performance and bias of both sampling procedures was driven by insufficient sample size, suggesting that all efforts must be directed to increasing numbers found in order to produce reliable results. Our results suggest that present methods may not be capable of accurately estimating desert tortoise populations.

Clean power from deserts. The DESERTEC concept for energy, water and climate security

Energy Technology Data Exchange (ETDEWEB)

NONE

2009-07-01

The main challenge for the future is to reclaim energy from renewable and clean sources in environmentally compatible ways. Here the deserts of the earth can play a key role. They receive about 700 times more energy from the sun than humankind consumes by burning fossil fuels, day by day. Deserts are the places with the best solar radiation conditions and with the least possible impact of collector deployment onto the biosphere on earth. In deserts, clean power can be produced by solar thermal power plants (CSP) in a truly sustainable way and at any volume of conceivable demand. Power can be transmitted with low losses by high voltage direct current (HVDC) lines to more than 90% of the world's population. This gives the deserts a new role: Together with the many other forms of accessible renewable energy the newly utilized desert would enable us to replace fossil fuels and thus end the ongoing destruction of our natural living conditions. To put this into practice, countries with deserts, countries with high energy demand and countries with technology competence must cooperate. This is an opportunity for the Mediterranean riparian regions of Europe, the Middle East and North Africa (EUMENA) to form a community for energy, water and climate security. With the political will, EUMENA countries could now launch 'EUMENA-DESERTEC' Program, to bring humankind back into balance with its environment, by putting deserts and technology into service for energy, water and climate security. This would be an important step towards creating a truly sustainable civilization.

Water Sources for Cyanobacteria Below Desert Rocks in the Negev Desert Determined by Conductivity

Science.gov (United States)

McKay, Christopher P.

2016-01-01

We present year round meteorological and conductivity measurements of colonized hypolithic rocks in the Arava Valley, Negev Desert, Israel. The data indicate that while dew is common in the Negev it is not an important source of moisture for hypolithic organisms at this site. The dominance of cyanobacteria in the hypolithic community are consistent with predictions that cyanobacteria are confined to habitats supplied by rain. To monitor the presence of liquid water under the small Negev rocks we developed and tested a simple field conductivity system based on two wires placed about 0.5 cm apart. Based on 21 replicates recorded for one year in the Negev we conclude that in natural rains (0.25 mm to 6 mm) the variability between sensor readings is between 20 and 60% decreasing with increasing rain amount. We conclude that the simple small electrical conductivity system described here can be used effectively to monitor liquid water levels in lithic habitats. However, the natural variability of these sensors indicates that several replicates should be deployed. The results and method presented have use in arid desert reclamation programs.

The Palm Desert renewable [hydrogen] transportation system

Energy Technology Data Exchange (ETDEWEB)

Chamberlin, C.E.; Lehman, P. [Humboldt State Univ., Arcata, CA (United States). Schatz Energy Research Center

1998-08-01

This paper describes the Schatz Energy Research Center (SERC) progress on the Palm Desert Renewable Hydrogen Transportation System Project for the period June 1997 through May 1998. The project began in March 1996. The goal of the Palm Desert Project is to develop a clean and sustainable transportation system for a community. The project demonstrates the practical utility of hydrogen as a transportation fuel and the proton exchange membrane (PEM) fuel cell as a vehicle power system. The project includes designing and building 4 fuel cell powered vehicles, a solar hydrogen generating and refueling station, and a fuel cell vehicle diagnostic center. Over this last year, SERC has built a fuel cell powered neighborhood electric vehicle and delivered it to the City of Palm Desert. The design of the hydrogen refueling station is near completion and it is anticipated that construction will be complete in the fall of 1998. The vehicles are currently being refueled at a temporary refueling station. The diagnostic center is being designed and maintenance procedures as well as computer diagnostic programs for the fuel cell vehicles are being developed. City employees are driving the vehicles daily and monitoring data are being collected. The drivers are pleased with the performance of the vehicles.

Use of space photographs in deciphering the origin and evolution of the desert

International Nuclear Information System (INIS)

El-Baz, F.

1989-01-01

Space photographs provide a very useful tool to study deserts and semiarid land because of their coverage and the amount of data they portray about vegetation-free terrain. This is a welcome contribution because we do not understand the desert as we do other types of terrain. Results of wind action, erosion and deposition are clearly portrayed in images obtained from spacecraft. They are indications of the state of the environment and should be studied well in all cases where economic development projects are instituted in deserts and semiarid lands. Furthermore, the history of evolution of the arid landscape in space and time must be considered in order to be able to use more of the desert for the benefit of mankind. (author). 33 refs, 14 figs

Loess deposits since early Pleistocene in northeast China and implications for desert evolution in east China

Science.gov (United States)

Sun, Miao; Zhang, Xujiao; Tian, Mingzhong; Liu, Ru; He, Zexin; Qi, Lin; Qiao, Yansong

2018-04-01

Loess deposits and deserts are regarded as coupled geological systems and loess deposits on the periphery of deserts can often be used to reconstruct desert evolution. Previous studies of desert evolution in Asia are mainly concentrated in northwest China and the China Loess Plateau, and little is known about long-term desert evolution in east China. In this study, we selected the Sishijiazi loess section in the Chifeng area in northeast China to study the long-term evolution of the desert in east China. A high-resolution magnetostratigraphy combined with optically stimulated luminescence dating indicated that the age of the section base is approximately 1.02 Ma. The Brunhes-Matuyama boundary is at the depth of 39.8 m in loess unit L8, and the upper boundary of the Jaramillo Subchron is at the depth of 60.8 m in paleosol S10. The results of grain-size analysis indicate a coarsening grain-size trend in the past 1.0 Ma. In addition, based on grain-size variations, the desert evolution in east China since ∼1.0 Ma can be divided into three stages: stability from 1.0 to 0.8 Ma, desert recession from 0.8 to 0.5 Ma, and gradual expansion since 0.5 Ma. Our results further indicate that the evolution of desert in east China was mainly controlled by changes in global ice volume, and that the uplift of the Tibetan Plateau may have had an additional effect.

Trace-element evidence for the origin of desert varnish by direct aqueous atmospheric deposition

Science.gov (United States)

Thiagarajan, Nivedita; Aeolus Lee, Cin-Ty

2004-07-01

Smooth rock surfaces in arid environments are often covered with a thin coating of Fe-Mn oxyhydroxides known as desert varnish. It is debated whether such varnish is formed (a) by slow diagenesis of dust particles deposited on rock surfaces, (b) by leaching from the underlying rock substrate, or (c) by direct deposition of dissolved constituents in the atmosphere. Varnishes collected from smooth rock surfaces in the Mojave Desert and Death Valley, California are shown here to have highly enriched and fractionated trace-element abundances relative to upper continental crust (UCC). They are highly enriched in Co, Ni, Pb and the rare-earth elements (REEs). In particular, they have anomalously high Ce/La and low Y/Ho ratios. These features can only be explained by preferential scavenging of Co, Ni, Pb and the REEs by Fe-Mn oxyhydroxides in an aqueous environment. High field strength elements (HFSEs: Zr, Hf, Ta, Nb, Th), however, show only small enrichments despite the fact that these elements should also be strongly scavenged by Fe-Mn oxyhydroxides. This suggests that their lack of enrichment is a feature inherited from a solution initially poor in HFSEs. The first two scenarios for varnish formation can be ruled out as follows. The high enrichment factors of Fe, Mn and many trace elements cannot be generated by mass loss associated with post-depositional diagenesis of dust particles because such a process predicts only a small increase in concentration. In addition, the highly fractionated abundance patterns of particle reactive element pairs (e.g., Ce/La and Y/Ho) rules out leaching of the rock substrate. This is because if leaching were to occur, varnishes would grow from the inside to the outside, and thus any particle-reactive trace element leached from the substrate would be quantitatively sequestered in the Fe-Mn oxyhydroxide layers, prohibiting any significant elemental fractionations. One remaining possibility is that the Fe, Mn and trace metals in varnish are

Temporal 222Rn distributions to reveal groundwater discharge into desert lakes: Implication of water balance in the Badain Jaran Desert, China

Science.gov (United States)

Luo, Xin; Jiao, Jiu Jimmy; Wang, Xu-sheng; Liu, Kun

2016-03-01

How lake systems are maintained and water is balanced in the lake areas in the Badain Jaran Desert (BJD), northeast of China have been debated for about a decade. In this study, continuous 222Rn measurement is used to quantify groundwater discharge into two representative fresh and brine water lakes in the desert using a steady-state mass-balance model. Two empirical equations are used to calculate atmospheric evasion loss crossing the water-air interface of the lakes. Groundwater discharge rates yielded from the radon mass balance model based on the two empirical equations are well correlated and of almost the same values, confirming the validity of the model. The fresh water and brine lakes have a daily averaged groundwater discharge rate of 7.6 ± 1.7 mm d-1 and 6.4 ± 1.8 mm d-1, respectively. The temporal fluctuations of groundwater discharge show similar patterns to those of the lake water level, suggesting that the lakes are recharged from nearby groundwater. Assuming that all the lakes have the same discharge rate as the two studied lakes, total groundwater discharge into all the lakes in the desert is estimated to be 1.59 × 105 m3 d-1. A conceptual model of water balance within a desert lake catchment is proposed to characterize water behaviors within the catchment. This study sheds lights on the water balance in the BJD and is of significance in sustainable regional water resource utilization in such an ecologically fragile area.

Lithium abundance patterns of late-F stars: an in-depth analysis of the lithium desert

Science.gov (United States)

Aguilera-Gómez, Claudia; Ramírez, Iván; Chanamé, Julio

2018-06-01

Aims: We address the existence and origin of the lithium (Li) desert, a region in the Li-Teff plane sparsely populated by stars. Here we analyze some of the explanations that have been suggested for this region, including mixing in the late main sequence, a Li dip origin for stars with low Li abundances in the region, and a possible relation with the presence of planets. Methods: To study the Li desert, we measured the atmospheric parameters and Li abundance of 227 late-F dwarfs and subgiants, chosen to be in the Teff range of the desert and without previous Li abundance measurements. Subsequently, we complemented those with literature data to obtain a homogeneous catalog of 2318 stars, for which we compute masses and ages. We characterize stars surrounding the region of the Li desert. Results: We conclude that stars with low Li abundances below the desert are more massive and more evolved than stars above the desert. Given the unexpected presence of low Li abundance stars in this effective temperature range, we concentrate on finding their origin. We conclude that these stars with low Li abundance do not evolve from stars above the desert: at a given mass, stars with low Li (i.e., below the desert) are more metal-poor. Conclusions: Instead, we suggest that stars below the Li desert are consistent with having evolved from the Li dip, discarding the need to invoke additional mixing to explain this feature. Thus, stars below the Li desert are not peculiar and are only distinguished from other subgiants evolved from the Li dip in that their combination of atmospheric parameters locates them in a range of effective temperatures where otherwise only high Li abundance stars would be found (i.e., stars above the desert). Full Tables 1 and 3 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/614/A55This paper includes observations collected at The McDonald Observatory and

Atmospheric Surface Layer Characterization: Preliminary Desert Lapse Rate Study 22-25 August 2000

National Research Council Canada - National Science Library

Elliott, Doyle

2003-01-01

Results of the August 2000 Desert Lapse Rate (DLR) Experiment are presented. The DLR Experiment was performed to document the night-to-day transition effects on the desert Atmospheric Surface Layer (ASL...

Soil stabilization by a prokaryotic desert crust - Implications for Precambrian land biota

Science.gov (United States)

Campbell, S. E.

1979-01-01

The ecology of the cyanophyte-dominated stromatolitic mat forming the ground cover over desert areas of Utah and Colorado is investigated and implications for the formation of mature Precambrian soils are discussed. The activation of the growth of the two species of filamentous cyanophyte identified and the mobility of their multiple trichromes upon wetting are observed, accompanied by the production and deposition of a sheath capable of accreting and stabilizing sand and clay particles. The formation of calcium carbonate precipitates upon the repeated wetting and drying of desert crust is noted, and it is suggested that the desert crust community may appear in fossil calcrete deposits as lithified microscopic tubes and cellular remains of algal trichromes. The invasion of dry land by both marine and freshwater algae on the model of the desert crust is proposed to be responsible for the accumulation, stabilization and biogenic modification of mature Precambrian soils.

Epifluorescent direct counts of bacteria and viruses from topsoil of various desert dust storm regions

Science.gov (United States)

Gonzalez-Martin, Cristina; Teigell-Perez, Nuria; Lyles, Mark; Valladares, Basilio; Griffin, Dale W.

2013-01-01

Topsoil from arid regions is the main source of dust clouds that move through the earth's atmosphere, and microbial communities within these soils can survive long-range dispersion. Microbial abundance and chemical composition were analyzed in topsoil from various desert regions. Statistical analyses showed that microbial direct counts were strongly positively correlated with calcium concentrations and negatively correlated with silicon concentrations. While variance between deserts was expected, it was interesting to note differences between sample sites within a given desert region, illustrating the 'patchy' nature of microbial communities in desert environments.

Bacterial Rhizosphere Biodiversity from Several Pioneer Desert Sand Plants Near Jizan, Saudi Arabia

KAUST Repository

Osman, Jorge R.; Zelicourt, Axel de; Bisseling, Ton; Geurts, Rene; Hirt, Heribert; DuBow, Michael S.

2016-01-01

Life in arid regions and, in particular, hot deserts is often limited due to their harsh environmental conditions, such as large temperature fluctuations and low amounts of water. These extreme environments can influence the microbial community present on the surface sands and any rhizosphere members surrounding desert plant roots. The Jizan desert area, located in Saudi Arabia, supports particular vegetation that grows in the large sandy flat terrain. We examined five different samples, four from the rhizosphere of pioneer plants plus a surface sand sample, and used pyrosequencing of PCR-amplified V1-V3 regions of 16S rDNA genes from total extracted DNA to reveal and compare the bacterial population diversity of the samples. The results showed a total of 3,530 OTUs in the five samples, calculated using ≥ 97% sequence similarity levels. The Chao1 estimation of the bacterial diversity fluctuated from 637 to 2,026 OTUs for a given sample. The most abundant members found in the samples belong to the Bacteroidetes, Firmicutes and Proteobacteria phyla. This work shows that the Jizan desert area of Saudi Arabia can contain a diverse bacterial community on the sand and surrounding the roots of pioneer desert plants. It also shows that desert sand microbiomes can vary depending on conditions, with broad implications for sandstone monument bacterial communities

Bacterial Rhizosphere Biodiversity from Several Pioneer Desert Sand Plants Near Jizan, Saudi Arabia

KAUST Repository

Osman, Jorge R.

2016-04-08

Life in arid regions and, in particular, hot deserts is often limited due to their harsh environmental conditions, such as large temperature fluctuations and low amounts of water. These extreme environments can influence the microbial community present on the surface sands and any rhizosphere members surrounding desert plant roots. The Jizan desert area, located in Saudi Arabia, supports particular vegetation that grows in the large sandy flat terrain. We examined five different samples, four from the rhizosphere of pioneer plants plus a surface sand sample, and used pyrosequencing of PCR-amplified V1-V3 regions of 16S rDNA genes from total extracted DNA to reveal and compare the bacterial population diversity of the samples. The results showed a total of 3,530 OTUs in the five samples, calculated using ≥ 97% sequence similarity levels. The Chao1 estimation of the bacterial diversity fluctuated from 637 to 2,026 OTUs for a given sample. The most abundant members found in the samples belong to the Bacteroidetes, Firmicutes and Proteobacteria phyla. This work shows that the Jizan desert area of Saudi Arabia can contain a diverse bacterial community on the sand and surrounding the roots of pioneer desert plants. It also shows that desert sand microbiomes can vary depending on conditions, with broad implications for sandstone monument bacterial communities

Potential for deserts to supply reliable renewable electric power

Science.gov (United States)

Labordena, Mercè; Lilliestam, Johan

2015-04-01

To avoid dangerous climate change, the electricity systems must be decarbonized by mid-century. The world has sufficient renewable electricity resources for complete power sector decarbonization, but an expansion of renewables poses several challenges for the electricity systems. First, wind and solar PV power are intermittent and supply-controlled, making it difficult to securely integrate this fluctuating generation into the power systems. Consequently, power sources that are both renewable and dispatchable, such as biomass, hydro and concentrating solar power (CSP), are particularly important. Second, renewable power has a low power density and needs vast areas of land, which is problematic both due to cost reasons and due to land-use conflicts, in particular with agriculture. Renewable and dispatchable technologies that can be built in sparsely inhabited regions or on land with low competition with agriculture would therefore be especially valuable; this land-use competition greatly limits the potential for hydro and biomass electricity. Deserts, however, are precisely such low-competition land, and are at the same time the most suited places for CSP generation, but this option would necessitate long transmission lines from remote places in the deserts to the demand centers such as big cities. We therefore study the potential for fleets of CSP plants in the large deserts of the world to produce reliable and reasonable-cost renewable electricity for regions with high and/or rapidly increasing electricity demand and with a desert within or close to its borders. The regions in focus here are the European Union, North Africa and the Middle East, China and Australia. We conduct the analysis in three steps. First, we identify the best solar generation areas in the selected deserts using geographic information systems (GIS), and applying restrictions to minimize impact on biodiversity, soils, human heath, and land-use and land-cover change. Second, we identify

Food deserts in Winnipeg, Canada: a novel method for measuring a complex and contested construct

Directory of Open Access Journals (Sweden)

Joyce Slater

2017-10-01

Full Text Available Introduction: "Food deserts" have emerged over the past 20 years as spaces of concern for communities, public health authorities and researchers because of their potential negative impact on dietary quality and subsequent health outcomes. Food deserts are residential geographic spaces, typically in urban settings, where low-income residents have limited or no access to retail food establishments with sufficient variety at affordable cost. Research on food deserts presents methodological challenges including retail food store identification and classification, identification of low-income populations, and transportation and proximity metrics. Furthermore, the complex methods often used in food desert research can be difficult to reproduce and communicate to key stakeholders. To address these challenges, this study sought to demonstrate the feasibility of implementing a simple and reproducible method of identifying food deserts using data easily available in the Canadian context. Methods: This study was conducted in Winnipeg, Canada in 2014. Food retail establishments were identified from Yellow Pages and verified by public health dietitians. We calculated two scenarios of food deserts based on location of the lowest-income quintile population: (a living ≥ 500 m from a national chain grocery store, or (b living ≥ 500 m from a national chain grocery store or a full-service grocery store. Results: The number of low-income residents living in a food desert ranged from 64 574 to 104 335, depending on the scenario used. Conclusion: This study shows that food deserts affect a significant proportion of the Winnipeg population, and while concentrated in the urban core, exist in suburban neighbourhoods also. The methods utilized represent an accessible and transparent, reproducible process for identifying food deserts. These methods can be used for costeffective, periodic surveillance and meaningful engagement with communities, retailers and policy

Vegetation dynamics at a Mojave Desert restoration site, 1992 to 2007

Science.gov (United States)

Jeffrey E. Ott; E. Durant McArthur; Stewart C. Sanderson

2011-01-01

The Twist Hollow restoration site on BLM land near St. George, Utah, had been badly disturbed by sand mining, rock quarrying, dumping, off-road vehicles and target shooting prior to its closure and treatment. In December 1992 the site was sculpted and drill seeded with Indian ricegrass (Stipa hymenoides), sand dropseed (Sporobolus cryptandrus), galleta (Hilaria jamesii...

Surficial geology and stratigraphy of Pleistocene Lake Manix, San Bernardino County, California

Science.gov (United States)

Reheis, Marith C.; Redwine, Joanna R.; Wan, Elmira; McGeehin, John P.; VanSistine, D. Paco

2014-01-01

Pluvial Lake Manix and its surrounding drainage basin, in the central Mojave Desert of California, has been a focus of paleoclimate, surficial processes, and neotectonic studies by the U.S. Geological Survey (USGS) since about 2004. The USGS initiated studies of Lake Manix deposits to improve understanding of the paleoclimatic record and the shifts in atmospheric circulation that controlled precipitation in the Mojave Desert. Until approximately 25,000 years ago, Lake Manix was the terminus of the Mojave River, which drains northeasterly from the San Bernardino Mountains; the river currently terminates in the Soda Lake and Silver Lake playas. Pleistocene Lake Manix occupied several subbasins at its maximum extent. This map focuses on the extensive exposures created by incision of the Mojave River and its tributaries into the interbedded lacustrine and alluvial deposits within the central (Cady) and northeastern (Afton) subbasins of Lake Manix, and extends from the head of Afton Canyon to Manix Wash. The map illuminates the geomorphic development and depositional history of the lake and alluvial fans within the active tectonic setting of the eastern California shear zone, especially interactions with the left-lateral Manix fault. Lake Manix left an extraordinarily detailed but complex record of numerous transgressive-regressive sequences separated by desiccation and deposition of fan, eolian, and fluvial deposits, and punctuated by tectonic movements and a catastrophic flood that reconfigured the lake basin. Through careful observation of the intercalated lacustrine and fan sequences and by determining the precise elevations of unit contacts, this record was decoded to understand the response of the lake and river system to the interplay of climatic, geomorphic, and tectonic forces. These deposits are exposed in steep badland topography. Mapping was carried out mostly at scales of 1:12,000, although the map is presented at 1:24,000 scale, and employs custom unit

Biodiversity analysis of vegetation on the Nevada Test Site

International Nuclear Information System (INIS)

Ostler, W. K.; Hansen, D. J.

2000-01-01

The Nevada Test Site (NTS), located in south-central Nevada, encompasses approximately 3,500 square kilometers and straddles two major North American deserts, Mojave and Great Basin. Transitional areas between the two desert types have been created by gradients in elevation, precipitation, temperature, and soils. From 1996 to 1998, more than 1,500 ecological landform units were sampled at the NTS for numerous biotic and abiotic parameters. The data provide a basis for spatial evaluations of biodiversity over landscape scales at the NTS. Biodiversity maps (species richness vs. species abundance) have been produced. Differences in biodiversity among ecoregions and vegetation alliances are presented. Spatial distribution maps of species' presence and abundance provide evidence of where transition zones occur and the resulting impact on biodiversity. The influences of abiotic factors, such as elevation, soil, and precipitation, on biodiversity are assessed

Detection of land degradation with polarimetric SAR

Science.gov (United States)

Ray, Terrill W.; Farr, Tom G.; Van Zyl, Jakob J.

1992-01-01

Multispectral radar polarimeter data were collected over the Manix Basin Area of the Mojave desert using an airborne SAR. An analysis of the data reveals unusual polarization responses which are attributed to the formation of wind ripples on the surfaces of fields that have been abandoned for more than 5 years. This hypothesis has been confirmed through field observations, and a second-order perturbation model is shown to effectively model the polarization responses. The results demonstrate the usefulness of remote sensing techniques for the study of land degradation at synoptic scales.

Metabolic rate, evaporative water loss and thermoregulatory state in four species of bats in the Negev desert.

Science.gov (United States)

Muñoz-Garcia, Agustí; Larraín, Paloma; Ben-Hamo, Miriam; Cruz-Neto, Ariovaldo; Williams, Joseph B; Pinshow, Berry; Korine, Carmi

2016-01-01

Life in deserts is challenging for bats because of their relatively high energy and water requirements; nevertheless bats thrive in desert environments. We postulated that bats from desert environments have lower metabolic rates (MR) and total evaporative water loss (TEWL) than their mesic counterparts. To test this idea, we measured MR and TEWL of four species of bats, which inhabit the Negev desert in Israel, one species mainly restricted to hyper-arid deserts (Otonycteris hemprichii), two species from semi-desert areas (Eptesicus bottae and Plecotus christii), and one widespread species (Pipistrellus kuhlii). We also measured separately, in the same individuals, the two components of TEWL, respiratory water loss (RWL) and cutaneous evaporative water loss (CEWL), using a mask. In all the species, MR and TEWL were significantly reduced during torpor, the latter being a consequence of reductions in both RWL and CEWL. Then, we evaluated whether MR and TEWL in bats differ according to their geographic distributions, and whether those rates change with Ta and the use of torpor. We did not find significant differences in MR among species, but we found that TEWL was lowest in the species restricted to desert habitats, intermediate in the semi-desert dwelling species, and highest in the widespread species, perhaps a consequence of adaptation to life in deserts. Our results were supported by a subsequent analysis of data collected from the literature on rates of TEWL for 35 bat species from desert and mesic habitats. Copyright © 2015 Elsevier Inc. All rights reserved.

Who Needs Religion When You Have The Desert?

DEFF Research Database (Denmark)

Sørensen, Bent

In my paper I propose to read so-called ‘post-ironic’ texts by authors associated with the Blank Generation and Generation X (including Bret Easton Ellis and Douglas Coupland, as well as less well-known authors such as K.S. Haddock) and examine their use of the desert as a trope for identity...... testing and summation. Perhaps surprisingly, one finds in novels such as Ellis’ Less Than Zero (1984) and Coupland’s Generation X (1991) a reliance on desert locations to provide an alternative to the numerous non-places (in Marc Augé’s sense of the term) that otherwise make up the setting of these works....

Natural product diversity of actinobacteria in the Atacama Desert.

Science.gov (United States)

Rateb, Mostafa E; Ebel, Rainer; Jaspars, Marcel

2018-02-14

The Atacama Desert of northern Chile is considered one of the most arid and extreme environment on Earth. Its core region was described as featuring "Mars-like" soils that were at one point deemed too extreme for life to exist. However, recent investigations confirmed the presence of diverse culturable actinobacteria. In the current review, we discuss a total of 46 natural products isolated to date representing diverse chemical classes characterized from different actinobacteria isolated from various locations in the Atacama Desert. Their reported biological activities are also discussed.

Water sources for cyanobacteria below desert rocks in the Negev Desert determined by conductivity

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Christopher P. McKay

2016-04-01

Full Text Available We present year round meteorological and conductivity measurements of colonized hypolithic rocks in the Arava Valley, Negev Desert, Israel. The data indicate that while dew is common in the Negev it is not an important source of moisture for hypolithic organisms at this site. The dominance of cyanobacteria in the hypolithic community is consistent with predictions that cyanobacteria are confined to habitats supplied by rain. To monitor the presence of liquid water under the small Negev rocks we developed and tested a simple field conductivity system based on two wires placed about 0.5 cm apart. Based on 21 replicates recorded for one year in the Negev we conclude that in natural rains (0.25 mm to 6 mm the variability between sensor readings is between 20 and 60% decreasing with increasing rain amount. We conclude that the simple small electrical conductivity system described here can be used effectively to monitor liquid water levels in lithic habitats. However, the natural variability of these sensors indicates that several replicates should be deployed. The results and method presented have use in arid desert reclamation programs.

Seismic calibration shots conducted in 2009 in the Imperial Valley, southern California, for the Salton Seismic Imaging Project (SSIP)

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Murphy, Janice; Goldman, Mark; Fuis, Gary; Rymer, Michael; Sickler, Robert; Miller, Summer; Butcher, Lesley; Ricketts, Jason; Criley, Coyn; Stock, Joann; Hole, John; Chavez, Greg

2011-01-01

Rupture of the southern section of the San Andreas Fault, from the Coachella Valley to the Mojave Desert, is believed to be the greatest natural hazard facing California in the near future. With an estimated magnitude between 7.2 and 8.1, such an event would result in violent shaking, loss of life, and disruption of lifelines (freeways, aqueducts, power, petroleum, and communication lines) that would bring much of southern California to a standstill. As part of the Nation's efforts to prevent a catastrophe of this magnitude, a number of projects are underway to increase our knowledge of Earth processes in the area and to mitigate the effects of such an event. One such project is the Salton Seismic Imaging Project (SSIP), which is a collaborative venture between the United States Geological Survey (USGS), California Institute of Technology (Caltech), and Virginia Polytechnic Institute and State University (Virginia Tech). This project will generate and record seismic waves that travel through the crust and upper mantle of the Salton Trough. With these data, we will construct seismic images of the subsurface, both reflection and tomographic images. These images will contribute to the earthquake-hazard assessment in southern California by helping to constrain fault locations, sedimentary basin thickness and geometry, and sedimentary seismic velocity distributions. Data acquisition is currently scheduled for winter and spring of 2011. The design and goals of SSIP resemble those of the Los Angeles Region Seismic Experiment (LARSE) of the 1990's. LARSE focused on examining the San Andreas Fault system and associated thrust-fault systems of the Transverse Ranges. LARSE was successful in constraining the geometry of the San Andreas Fault at depth and in relating this geometry to mid-crustal, flower-structure-like decollements in the Transverse Ranges that splay upward into the network of hazardous thrust faults that caused the 1971 M 6.7 San Fernando and 1987 M 5

Giant desiccation fissures on the Black Rock and Smoke Creek Deserts, Nevada

Science.gov (United States)

Willden, R.; Mabey, D.R.

1961-01-01

Open fissures, from 100 to several hundred feet apart, that have produced polygonal patterns on the Black Rock Desert, Nevada, are believed to be giant desiccation cracks resulting from a secular trend toward aridity in the last few decades. Similar features on the Smoke Creek Desert probably have the same origin.

The Chemistry and Mineralogy of Atacama Desert soils: A Possible Analog for Mars Soils

Science.gov (United States)

Sutter, B.; Amundson, R.; Ewing, S.; Rhodes, K. W.; McKay, C.

2002-12-01

The Atacama Desert of northern Chile is the driest desert in the world, having experienced its present hyper-arid climate since the Miocene. While Mars is vastly more dry and cold than the Atacama, the Atacama environment may be one of the best terrestrial Mars analog environments accessible to researchers. Because of the long-term hyperaridity, the soils retain atmospherically-derived elements, which accumulate to economically valuable quantities. The objective of this work was to examine physical and chemical evolution of the soils of the hyper-arid Atacama Desert to provide insight as to what soil properties may be found on Mars. Three soils were excavated and examined on widely representative landforms along a south to north transect (Copiapo > Altimira > Yungay) that coincides with decreasing moisture levels (~15mm to ~2 mm yr-1, south to north). Total chemical analyses were used to calculate strain (i.e. volume change) and elemental gains or losses (\\tau). Relative to parent material values, the Yungay and Altimira soils have expanded over 400% in certain horizons, while the Copiapo soil has collapsed by as much as 48%. The expansions are driven by elemental gains; the collapse by weathering losses. Calculations of \\tau indicate a 380 000% enrichment in Cl (halite) in the lower horizons, and S enrichments (anhydrite, gypsum) as high as 50 000% in the upper horizons, of the Yungay soil. The Altimira soil had a 110 000% enrichment of S (gypsum) and a 16,000% enrichment of carbonate, reflecting the higher precipitation and the relative solubility of salts. The southern, higher rainfall Copiapo soil had small \\tau values for S (283%) and Cl (63%) in the middle horizons, but significant gains of CaCO3 (\\tau values as high as 4 000% in certain horizons). In general, the type and depth of Cl, S, and CaCO3 enrichment in the soils varied predictably with rainfall. The results of this work, which document enormous atmospherically-derived elemental gains and

[Analysis of spectral features based on water content of desert vegetation].

Science.gov (United States)

Zhao, Zhao; Li, Xia; Yin, Ye-biao; Tang, Jin; Zhou, Sheng-bin

2010-09-01

By using HR-768 field-portable spectroradiometer made by the Spectra Vista Corporation (SVC) of America, the hyper-spectral data of nine types of desert plants were measured, and the water content of corresponding vegetation was determined by roasting in lab. The continuum of measured hyperspectral data was removed by using ENVI, and the relationship between the water content of vegetation and the reflectance spectrum was analyzed by using correlation coefficient method. The result shows that the correlation between the bands from 978 to 1030 nm and water content of vegetation is weak while it is better for the bands from 1133 to 1266 nm. The bands from 1374 to 1534 nm are the characteristic bands because of the correlation between them and water content is the best. By using cluster analysis and according to the water content, the vegetation could be marked off into three grades: high (>70%), medium (50%-70%) and low (<50%). The research reveals the relationship between water content of desert vegetation and hyperspectral data, and provides basis for the analysis of area in desert and the monitoring of desert vegetation by using remote sensing data.

Desert rose: building material of cupolas in the Souf in Algeria

Science.gov (United States)

Azil, C.; Djebri, B.; Rovero, L.

2018-05-01

In the Souf of Algeria, the roofs of all constructions are arranged like corbelled domes, built with local particular material to this region, which is the desert rose. These cupolas describe a unique landscape of historic centres. Such constructions include a widespread and precious heritage that deserves protection to save this urban landscape which constitutes an element of identity of heritage built upon the material as well as the immaterial of the local know-how. Unfortunately, these architectural elements have undergone alterations that devalue the urban landscape and destabilize the buildings. However, the structural system that provides stability and endurance to this day remains an open question. In this, paper, we describe the role of desert rose cupolas in the construction of a single urban landscape and we contribute to this knowledge. Then, we explain the role of the availability of the materials locals (desert rose and tafza) to appearance ad emergence of construction with cupolas typology. In addition, we describe these materials locals, and the method to them usage. In the end, we have traced the process of construction of these cupolas by corbelling which is mounted by successive courses of the desert rose and the plaster mortar.

Reconstructing the origin of Helianthus deserticola: Survival and selection on the desert floor

NARCIS (Netherlands)

Gross, B.L.; Kane, D.L.; Lexer, C.; Ludwig, F.; Rosenthal, D.R.; Donovan, L.A.; Rieseberg, L.H.

2004-01-01

The diploid hybrid species Helianthus deserticola inhabits the desert floor, an extreme environment relative to its parental species Helianthus annuus and Helianthus petiolaris. Adaptation to the desert floor may have occurred via selection acting on transgressive, or extreme, traits in early

Biological soil crusts as an integral component of desert environments

Science.gov (United States)

Belnap, Jayne; Weber, Bettina

2013-01-01

The biology and ecology of biological soil crusts, a soil surface community of mosses, lichens, cyanobacteria, green algae, fungi, and bacteria, have only recently been a topic of research. Most efforts began in the western U.S. (Cameron, Harper, Rushforth, and St. Clair), Australia (Rogers), and Israel (Friedmann, Evenari, and Lange) in the late 1960s and 1970s (e.g., Friedmann et al. 1967; Evenari 1985reviewed in Harper and Marble 1988). However, these groups worked independently of each other and, in fact, were often not aware of each other’s work. In addition, biological soil crust communities were seen as more a novelty than a critical component of dryland ecosystems. Since then, researchers have investigated many different aspects of these communities and have shown that although small to microscopic, biological soil crusts are critical in many ecological processes of deserts. They often cover most of desert soil surfaces and substantially mediate inputs and outputs from desert soils (Belnap et al. 2003). They can be a large source of biodiversity for deserts, as they can contain more species than the surrounding vascular plant community (Rosentreter 1986). These communities are important in reducing soil erosion and increasing soil fertility through the capture of dust and the fixation of atmospheric nitrogen and carbon into forms available to other life forms (Elbert et al. 2012). Because of their many effects on soil characteristics, such as external and internal morphological characteristics, aggregate stability, soil moisture, and permeability, they also affect seed germination and establishment and local hydrological cycles. Covering up to 70% of the surface area in many arid and semi-arid regions around the world (Belnap and Lange 2003), biological soil crusts are a key component within desert environments.

Variations in Vegetation Structure, Species Dominance and Plant Communities in South of the Eastern Desert-Egypt

Directory of Open Access Journals (Sweden)

Fawzy SALAMA

2014-03-01

Full Text Available For two successive years, the floristic diversity and vegetation composition in the southern part of the Eastern Desert ofEgypt were investigated through four transects (3 crossing the Eastern Desert and one along the Red Sea. The data collected from 142 stands covering the study area included the species composition, functional groups, chorology and occurrences (Qvalues. A total of 94 plant species belonging to 33 different families were recorded, with Asteracea, Zygophyllaceae, Fabaceae,Poaceae, Chenopodiaceae and Brassicaceae as the largest families. Shrubs represented the largest functional group (39.4%, while perennial herbs represented the smallest ones (12.8%. Species occurrence (Q-value revealed that Zilla spinosa, Acacia tortilis subsp raddiana, Morettia philaeana, Caroxylon imbricatum, Zygophyllum coccineum and Citrullus colocynthis had wide ecological range of distribution (dominant species, Q-values 0.2. Saharo-Arabian chorotype was highly represented (72.6 % in the flora of this area, eventually as mono, bi or pluriregional. Classification of the data set yielded 7 vegetation groups included: (A Zilla spinosa-Morettia philaeana, (B1 Zilla spinosa-Citrullus colocynthis-Morettia philaeana, (B2 Zilla spinosa, (C1Zygophyllum album-Tamarix nilotica, (C2 Zygophyllum coccineum-Tamarix nilotica, (D1 Zilla spinosa-Zygophyllum coccineum and (D2 Zilla spinosa-Acacia tortilis subsp. raddiana-Tamarix aphylla-Balanites aegyptiaca. Certain vegetation groups were assigned to one or more transects. Detrended Correspondence Analysis (DCA revealed that electrical conductivity, sodium, potassium, calcium, magnesium, chlorides, moisture content, sulphates, pH, organic matter and gravel were the soil variables that affect the species distribution in this study.

20th-Century Climate Change over Africa: Seasonal Variation in Hydroclimate Trends and Sahara Desert Extent

Science.gov (United States)

Nigam, S.; Thomas, N. P.

2017-12-01

Twentieth-century trends in seasonal temperature and precipitation over the African continent are analyzed from observational data sets and historical climate simulations. Given the agricultural economy of the continent, a seasonal perspective is adopted as it is more pertinent than an annual-average one which can mask off-setting but agriculturally-sensitive seasonal hydroclimate variations. Examination of linear trends in seasonal surface air temperature (SAT) shows that heat stress has increased in several regions, including Sudan and Northern Africa where largest SAT trends occur in the warm season. Broadly speaking, the northern continent has warmed more than the southern one in all seasons. Precipitation trends are varied but notable declining trends are found in the countries along the Gulf of Guinea, especially in the source region of Niger river in West Africa, and in the Congo river basin. Rainfall over the African Great Lakes - one of the largest freshwater repositories - has however increased. We show that the Sahara Desert has expanded significantly over the 20th century - by 12-20% depending on the season. The desert expanded southward in summer, reflecting retreat of the northern edge of the Sahel rainfall belt; and to the north in winter, indicating potential impact of the widening of the Tropics. Specific mechanisms driving the expansion in each season are investigated. Finally, this observational analysis is used to evaluate the state-of-the-art climate models from a comparison of the 20th-century hydroclimate trends with those manifest in historical climate simulations. The evaluation shows that modeling regional hydroclimate change over the Africa continent remains challenging.

Resource pulses in desert river habitats: productivity-biodiversity hotspots, or mirages?

Science.gov (United States)

Free, Carissa L; Baxter, Greg S; Dickman, Christopher R; Leung, Luke K P

2013-01-01

Resource pulses in the world's hot deserts are driven largely by rainfall and are highly variable in both time and space. However, run-on areas and drainage lines in arid regions receive more water more often than adjacent habitats, and frequently sustain relatively high levels of primary productivity. These landscape features therefore may support higher biotic diversity than other habitats, and potentially act as refuges for desert vertebrates and other biota during droughts. We used the ephemeral Field River in the Simpson Desert, central Australia, as a case study to quantify how resources and habitat characteristics vary spatially and temporally along the riparian corridor. Levels of moisture and nutrients were greater in the clay-dominated soils of the riverine corridor than in the surrounding sand dunes, as were cover values of trees, annual grasses, other annual plants and litter; these resources and habitat features were also greater near the main catchment area than in the distal reaches where the river channel runs out into extensive dune fields. These observations confirm that the riverine corridor is more productive than the surrounding desert, and support the idea that it may act as a refuge or as a channel for the ingress of peri-desert species. However, the work also demonstrates that species diversity of invertebrates and plants is not higher within the river corridor; rather, it is driven by rainfall and the accompanying increase in annual plants following a rain event. Further research is required to identify the biota that depend upon these resource pulses.

Resource Pulses in Desert River Habitats: Productivity-Biodiversity Hotspots, or Mirages?

Science.gov (United States)

Free, Carissa L.; Baxter, Greg S.; Dickman, Christopher R.; Leung, Luke K. P.

2013-01-01

Resource pulses in the world's hot deserts are driven largely by rainfall and are highly variable in both time and space. However, run-on areas and drainage lines in arid regions receive more water more often than adjacent habitats, and frequently sustain relatively high levels of primary productivity. These landscape features therefore may support higher biotic diversity than other habitats, and potentially act as refuges for desert vertebrates and other biota during droughts. We used the ephemeral Field River in the Simpson Desert, central Australia, as a case study to quantify how resources and habitat characteristics vary spatially and temporally along the riparian corridor. Levels of moisture and nutrients were greater in the clay-dominated soils of the riverine corridor than in the surrounding sand dunes, as were cover values of trees, annual grasses, other annual plants and litter; these resources and habitat features were also greater near the main catchment area than in the distal reaches where the river channel runs out into extensive dune fields. These observations confirm that the riverine corridor is more productive than the surrounding desert, and support the idea that it may act as a refuge or as a channel for the ingress of peri-desert species. However, the work also demonstrates that species diversity of invertebrates and plants is not higher within the river corridor; rather, it is driven by rainfall and the accompanying increase in annual plants following a rain event. Further research is required to identify the biota that depend upon these resource pulses. PMID:24124446

Microbial communities in a High Arctic polar desert landscape

Directory of Open Access Journals (Sweden)

Clare M McCann

2016-03-01

Full Text Available The High Arctic is dominated by polar desert habitats whose microbial communities are poorly understood. In this study, we used next generation sequencing to describe the α- and β-diversity of polar desert soils from the Kongsfjorden region of Svalbard. Ten phyla consistently dominated the soils and accounted for 95 % of all sequences, with Proteobacteria, Actinobacteria and Chloroflexi being the dominant lineages. In contrast to previous investigations of Arctic soils, Acidobacterial relative abundances were low as were the Archaea throughout the Kongsfjorden polar desert landscape. Lower Acidobacterial abundances were attributed to the circumneutral soil pH in this region which has resulted from the weathering of the underlying carbonate geology. In addition, we correlated previously measured geochemical variables to determine potential controls on the communities. Soil phosphorus, pH, nitrogen and calcium significantly correlated with β-diversity indicating a landscape scale lithological control of soil nutrients which in turn influenced community composition. In addition, soil phosphorus and pH significantly correlated with α- diversity, specifically the Shannon diversity and Chao 1 richness indices.

Predicting Treatment Windows for Invasive Buffelgrass in Southern Arizona using MODIS and Climate Data

Science.gov (United States)

Wallace, C.; Weltzin, J. F.; Skirvin, S. M.; Patrick-Birdwell, C.; Raichle, H.

2014-12-01

The increasing spread and abundance of an invasive perennial grass, buffelgrass (Pennisetum ciliare), represents an important shift in the vegetation composition of the Sonoran Desert in southern Arizona. Buffelgrass out-competes native species and alters fire regimes, and its control and management is a high-priority issue for resource managers who seek to preserve the unique and iconic Sonoran Desert flora. Herbicidal treatment of buffelgrass is most effective when the vegetation is actively growing; however, the erratic timing and length of active buffelgrass growth periods in southern Arizona confound effective management decision-making. The goal of our research is to enable the strategic application of buffelgrass herbicide by using remote sensing data to detect when and where buffelgrass is photosynthetically active. We integrated ground-based observations of buffelgrass phenology (green-up and senescence) in the Tucson, Arizona area with climate information and Moderate-resolution Imaging Spectroradiometer (MODIS) satellite imagery at 250m spatial and both 8-day and 16-day composite temporal resolution to understand dynamics, relationships and resonance between these disparate datasets during 2011 to 2013. Fourier harmonics analysis was used to derive land surface phenology (LSP) metrics from MODIS Enhanced Vegetation Index (EVI) greenness data and to quantify the temporal patterns of the climate and phenophase abundance datasets. Regression analyses and statistical tests were used to identify correlations between temporal patterns of the data sets. Our results reveal strong correlations between the observed greenness of in-situ buffelgrass and satellite LSP metrics, confirming that MODIS-EVI data can be a useful indicator of active buffelgrass growth at multiple scales. The analysis also reveals strong harmonics between precipitation and greenness, but with a lagged response, suggesting that precipitation can be a predictor of the location and intensity of

76 FR 28767 - Desert Southwest Customer Service Region-Rate Order No. WAPA-152

Science.gov (United States)

2011-05-18

... DEPARTMENT OF ENERGY Western Area Power Administration Desert Southwest Customer Service Region..., Desert Southwest Customer Service Region, Western Area Power Administration, P.O. Box 6457, Phoenix, AZ... Customer Service Region, Western Area Power Administration, P.O. Box 6457, Phoenix, AZ 85005-6457, (602...

Urban particle size distributions during two contrasting dust events originating from Taklimakan and Gobi Deserts

International Nuclear Information System (INIS)

Zhao, Suping; Yu, Ye; Xia, Dunsheng; Yin, Daiying; He, Jianjun; Liu, Na; Li, Fang

2015-01-01

The dust origins of the two events were identified using HYSPLIT trajectory model and MODIS and CALIPSO satellite data to understand the particle size distribution during two contrasting dust events originated from Taklimakan and Gobi deserts. The supermicron particles significantly increased during the dust events. The dust event from Gobi desert affected significantly on the particles larger than 2.5 μm, while that from Taklimakan desert impacted obviously on the particles in 1.0–2.5 μm. It is found that the particle size distributions and their modal parameters such as VMD (volume median diameter) have significant difference for varying dust origins. The dust from Taklimakan desert was finer than that from Gobi desert also probably due to other influencing factors such as mixing between dust and urban emissions. Our findings illustrated the capacity of combining in situ, satellite data and trajectory model to characterize large-scale dust plumes with a variety of aerosol parameters. - Highlights: • Dust particle size distributions had large differences for varying origins. • Dust originating from Taklimakan Desert was finer than that from Gobi Desert. • Effect of dust on the supermicron particles was obvious. • PM_1_0 concentrations increased by a factor of 3.4–25.6 during the dust event. - Dust particle size distributions had large differences for varying origins, which may be also related to other factors such as mixing between dust and urban emissions.

Dead Sea pollen provides new insights into the paleoenvironment of the southern Levant during MIS 6-5

Science.gov (United States)

Chen, Chunzhu; Litt, Thomas

2018-05-01

The paleoclimate of the southern Levant, especially during the last interglacial (LIG), is still under debate. Reliable paleovegetation information for this period, as independent evidence to the paleoenvironment, was still missing. In this study, we present a high-resolution pollen record encompassing 147-89 ka from the Dead Sea deep drilling core 5017-1A. The sediment profile is marked by alternations of laminated marl deposits and thick massive halite, indicating lake-level fluctuations. The pollen record suggests that steppe and desert components predominated in the Dead Sea surroundings during the whole investigated interval. The late penultimate glacial (147.3-130.9 ka) and early last glacial (115.5-89.1 ka) were cool and relatively dry, with sub-humid conditions confined to the mountains that sustained moderate amounts of deciduous oaks. Prior to the LIG optimum, a prevalence of desert components and a concomitant increase in frost-sensitive pistachio trees demonstrate the occurrence of an arid initial warming phase (130.9-124.2 ka). The LIG optimum (124.2 ka-115.5 ka) was initiated by an abrupt grass expansion that was followed by a rapid spread of woodlands in the mountains due to increased moisture availability. The remarkable sclerophyllous expansion points to a strong seasonal moisture deficit. These results contradict previous Dead Sea lake-level investigations that suggested pluvial glacials and a warm, dry LIG in the southern Levant. Prominent discrepancies between vegetation and Dead Sea lake stands are also registered at 128-115 ka, and the potential causes are discussed. In particular, while the pollen spectra mirror increased effective moisture during the LIG optimum, the massive halite deposition is indicative of an extremely low lake level. Given that the climate amelioration triggered the migration of early modern humans to the southern Levant, we speculate that the diverse ecosystems in the region provided great potential for their residence

Hydrochemical and isotopic characteristics of groundwater in the northeastern Tennger Desert, northern China

Science.gov (United States)

Wang, Liheng; Dong, Yanhui; Xu, Zhifang; Qiao, Xiaojuan

2017-12-01

Groundwater is typically the only water source in arid regions, and its circulation processes should be better understood for rational resource exploitation. Stable isotopes and major ions were investigated in the northeastern Tengger Desert, northern China, to gain insights into groundwater recharge and evolution. In the northern mountains, Quaternary unconsolidated sediments, exposed only in valleys between hills, form the main aquifer, which is mainly made of aeolian sand and gravel. Most of the mountain groundwater samples plot along the local meteoric water line (LMWL), with a more depleted signature compared to summer precipitation, suggesting that mountain groundwater was recharged by local precipitation during winter. Most of the groundwater was fresh, with total dissolved solids less than 1 g/L; dominant ions are Na+, SO4 2- and Cl-, and all mineral saturation indices are less than zero. Evaporation, dissolution and cation exchange are the major hydrogeochemical processes. In the southern plains, however, the main aquifers are sandstone. The linear regression line of δD and δ 18O of groundwater parallels the LMWL but the intercept is lower, indicating that groundwater in the plains has been recharged by ancient precipitation rather than modern. Both calcite and dolomite phases in the plains groundwater are close to saturation, while gypsum and halite can still be dissolved into the groundwater. Different recharge mechanisms occur in the northern mountains and the southern plains, and the hydraulic connection between them is weak. Because of the limited recharge, groundwater exploitation should be limited as much as possible.

Genetic Diversity and Population Genetics of Mosquitoes (Diptera: Culicidae: Culex spp. from the Sonoran Desert of North America

Directory of Open Access Journals (Sweden)

Edward Pfeiler

2013-01-01

Full Text Available The population genetics and phylogenetic relationships of Culex mosquitoes inhabiting the Sonoran Desert region of North America were studied using mitochondrial DNA and microsatellite molecular markers. Phylogenetic analyses of mitochondrial cytochrome c oxidase subunit I (COI from mosquitoes collected over a wide geographic area, including the Baja California peninsula, and mainland localities in southern Arizona, USA and Sonora, Mexico, showed several well-supported partitions corresponding to Cx. quinquefasciatus, Cx. tarsalis, and two unidentified species, Culex sp. 1 and sp. 2. Culex quinquefasciatus was found at all localities and was the most abundant species collected. Culex tarsalis was collected only at Tucson, Arizona and Guaymas, Sonora. The two unidentified species of Culex were most abundant at Navojoa in southern Sonora. Haplotype and nucleotide diversities in the COI gene segment were substantially lower in Cx. quinquefasciatus compared with the other three species. Analysis of molecular variance revealed little structure among seven populations of Cx. quinquefasciatus, whereas significant structure was found between the two populations of Cx. tarsalis. Evidence for an historical population expansion beginning in the Pleistocene was found for Cx. tarsalis. Possible explanations for the large differences in genetic diversity between Cx. quinquefasciatus and the other species of Culex are presented.

Genetic Diversity and Population Genetics of Mosquitoes (Diptera: Culicidae: Culex spp.) from the Sonoran Desert of North America

Science.gov (United States)

Pfeiler, Edward; Flores-López, Carlos A.; Mada-Vélez, Jesús Gerardo; Escalante-Verdugo, Juan; Markow, Therese A.

2013-01-01

The population genetics and phylogenetic relationships of Culex mosquitoes inhabiting the Sonoran Desert region of North America were studied using mitochondrial DNA and microsatellite molecular markers. Phylogenetic analyses of mitochondrial cytochrome c oxidase subunit I (COI) from mosquitoes collected over a wide geographic area, including the Baja California peninsula, and mainland localities in southern Arizona, USA and Sonora, Mexico, showed several well-supported partitions corresponding to Cx. quinquefasciatus, Cx. tarsalis, and two unidentified species, Culex sp. 1 and sp. 2. Culex quinquefasciatus was found at all localities and was the most abundant species collected. Culex tarsalis was collected only at Tucson, Arizona and Guaymas, Sonora. The two unidentified species of Culex were most abundant at Navojoa in southern Sonora. Haplotype and nucleotide diversities in the COI gene segment were substantially lower in Cx. quinquefasciatus compared with the other three species. Analysis of molecular variance revealed little structure among seven populations of Cx. quinquefasciatus, whereas significant structure was found between the two populations of Cx. tarsalis. Evidence for an historical population expansion beginning in the Pleistocene was found for Cx. tarsalis. Possible explanations for the large differences in genetic diversity between Cx. quinquefasciatus and the other species of Culex are presented. PMID:24302868

The Plant Genetic Engineering Laboratory For Desert Adaptation

Science.gov (United States)

Kemp, John D.; Phillips, Gregory C.

1985-11-01

The Plant Genetic Engineering Laboratory for Desert Adaptation (PGEL) is one of five Centers of Technical Excellence established as a part of the state of New Mexico's Rio Grande Research Corridor (RGRC). The scientific mission of PGEL is to bring innovative advances in plant biotechnology to bear on agricultural productivity in arid and semi-arid regions. Research activities focus on molecular and cellular genetics technology development in model systems, but also include stress physiology investigations and development of desert plant resources. PGEL interacts with the Los Alamos National Laboratory (LANL), a national laboratory participating in the RGRC. PGEL also has an economic development mission, which is being pursued through technology transfer activities to private companies and public agencies.

Mid-Cretaceous aeolian desert systems in the Yunlong area of the Lanping Basin, China: Implications for palaeoatmosphere dynamics and paleoclimatic change in East Asia

Science.gov (United States)

Li, Gaojie; Wu, Chihua; Rodríguez-López, Juan Pedro; Yi, Haisheng; Xia, Guoqing; Wagreich, Michael

2018-02-01

The mid-Cretaceous constitutes a period of worldwide atmospheric and oceanic change associated with slower thermohaline circulation and ocean anoxic events, possible polar glaciations and by a changing climate pattern becoming controlled by a zonal planetary wind system and an equatorial humid belt. During the mid-Cretaceous, the subtropical high-pressure arid climate belt of the planetary wind system controlled the palaeolatitude distribution of humid belts in Asia as well as the spatial distribution of rain belts over the massive continental blocks at mid-low latitudes in the southern and northern hemispheres. Additionally, the orographic effect of the Andean-type active continental margin in East Asia hindered the transportation of ocean moisture to inland regions. With rising temperatures and palaeoatmospheric conditions dominated by high pressure systems, desert climate environments expanded at the inland areas of East Asia including those accumulated in the mid-Cretaceous of the Simao Basin, the Sichuan Basin, and the Thailand's Khorat Basin, and leading the Late Cretaceous erg systems in the Xinjiang Basin and Jianghan Basin. This manuscript presents evidences that allow to reinterpret previously considered water-laid sediments to be accumulated as windblown deposits forming part of extensive erg (sandy desert) systems. Using a multidisciplinary approach including petrological, sedimentological and architectural observations, the mid-Cretaceous (Albian-Turonian) Nanxin Formation from the Yunlong region of Lanping Basin, formerly considered to aqueous deposits is here interpreted as representing aeolian deposits, showing local aeolian-fluvial interaction deposits. The palaeowind directions obtained from the analysis of aeolian dune cross-beddings indicates that inland deserts were compatible with a high-pressure cell (HPC) existing in the mid-low latitudes of East Asia during the mid-Cretaceous. Compared with the Early Cretaceous, the mid-Cretaceous had

Correlation of Aerogravity and BHT Data to Develop a Geothermal Gradient Map of the Northern Western Desert of Egypt using an Artificial Neural Network

Science.gov (United States)

Mohamed, Haby S.; Abdel Zaher, Mohamed; Senosy, Mahmoud M.; Saibi, Hakim; El Nouby, Mohamed; Fairhead, J. Derek

2015-06-01

The northern part of the Western Desert of Egypt represents the second most promising area of hydrocarbon potential after the Gulf of Suez province. An artificial neural network (ANN) approach was used to develop a new predictive model for calculation of the geothermal gradients in this region based on gravity and corrected bottom-hole temperature (BHT) data. The best training data set was obtained with an ANN architecture composed of seven neurons in the hidden layer, which made it possible to predict the geothermal gradient with satisfactory efficiency. The BHT records of 116 deep oil wells (2,000-4,500 m) were used to evaluate the geothermal resources in the northern Western Desert. Corrections were applied to the BHT data to obtain the true formation equilibrium temperatures, which can provide useful constraints on the subsurface thermal regime. On the basis of these corrected data, the thermal gradient was computed for the linear sections of the temperature-versus-depth data at each well. The calculated geothermal gradient using temperature log data was generally 30 °C/km, with a few local high geothermal gradients in the northwestern parts of the study area explained by potential local geothermal fields. The Bouguer gravity values from the study area ranged from -60 mGal in the southern parts to 120 mGal in the northern areas, and exhibited NE-SW and E-W trends associated with geological structures. Although the northern Western Desert of Egypt has low regional temperature gradients (30 °C/km), several potential local geothermal fields were found (>40 °C/km). The heat flow at each well was also computed by combining sets of temperature gradients and thermal conductivity data. Aerogravity data were used to delineate the subsurface structures and tectonic framework of the region. The result of this study is a new geothermal gradient map of the northern Western Desert developed from gravity and BHT log data.

Spatial probability models of fire in the desert grasslands of the southwestern USA

Science.gov (United States)

Fire is an important driver of ecological processes in semiarid environments; however, the role of fire in desert grasslands of the Southwestern US is controversial and the regional fire distribution is largely unknown. We characterized the spatial distribution of fire in the desert grassland region...

Site selection and directional models of deserts used for ERBE validation targets

Science.gov (United States)

Staylor, W. F.

1986-01-01

Broadband shortwave and longwave radiance measurements obtained from the Nimbus 7 Earth Radiation Budget scanner were used to develop reflectance and emittance models for the Sahara, Gibson, and Saudi Deserts. These deserts will serve as in-flight validation targets for the Earth Radiation Budget Experiment being flown on the Earth Radiation Budget Satellite and two National Oceanic and Atmospheric Administration polar satellites. The directional reflectance model derived for the deserts was a function of the sum and product of the cosines of the solar and viewing zenith angles, and thus reciprocity existed between these zenith angles. The emittance model was related by a power law of the cosine of the viewing zenith angle.

Exploring the Limits to Photosynthetic Life in the Hyperarid Atacama (Chile) and Taklimakan (China) Deserts

Science.gov (United States)

Warren-Rhodes, K.; Ewing, S.; McKay, C. P.; Rhodes, K. L.

2003-12-01

Photosynthetic microbes inhabiting the cracks or fissures (chasmoendoliths) and undersides (hypoliths) of translucent stones function as the sole primary producers in the world's driest deserts. This poster reports on our studies of the distribution and survival of these microorganisms in the hyperarid core of the Atacama Desert--an extreme environment previously considered too dry to support photosynthetic life--and the Taklimakan Desert in China--one of the oldest and driest deserts on the Earth. In both deserts, we measured colonization rates and microclimate variables across natural precipitation gradients in order to investigate the role of moisture in the ecology and survival of hypolithic and chasmoendolithic microorganisms. Our results show 1000-fold variations in colonization rates--from 12% in the wettest portions of the Taklimakan Desert to 3000 y. At slightly wetter sites in the Atacama, Δ 14C of hypolith soils was progressively more enriched in proportion to increased MAP, with corresponding turnover times of >600 y (Δ 14C = -73 ‰ at sites with ˜5-10 mm MAP and ˜1 y Δ 14C = +12 ‰ ) as annual rainfall increased to ˜25 mm. At all sites, Δ 14C signatures of non-hypolith soils corresponded to turnover times that were longer by an order of magnitude, indicating significantly slower OC cycling by non-hypoliths. In the hyperarid core of the Atacama Desert, the prolonged lack of rainfall (decadal scales of a few millimeters) is responsible for possibly the lowest hypolithic and chasmoendolithic colonization rates observed in deserts on the Earth. Microclimate data for rock and soil surface moisture from rainfall, dew and frost suggest the particular form of moisture and its frequency may also explain observed differences in hypolithic versus chasmoendolithic colonization modes. These results hold theoretical and practical considerations for both terrestrial ecology and as analogs for possible life on Mars.

Supersymmetry without the Desert

International Nuclear Information System (INIS)

Nomura, Yasunori; Poland, David

2006-01-01

Naturalness of electroweak symmetry breaking in weak scale supersymmetric theories may suggest the absence of the conventional supersymmetric desert. We present a simple, realistic framework for supersymmetry in which (most of) the virtues of the supersymmetric desert are naturally reproduced without having a large energy interval above the weak scale. The successful supersymmetric prediction for the low-energy gauge couplings is reproduced due to a gauged R symmetry present in the effective theory at the weak scale. The observable sector superpotential naturally takes the form of the next-to-minimal supersymmetric standard model, but without being subject to the Landau pole constraints up to the conventional unification scale. Supersymmetry breaking masses are generated by the F-term and D-term VEVs of singlet and U(1) R gauge fields, as well as by anomaly mediation, at a scale not far above the weak scale. We study the resulting pattern of supersymmetry breaking masses in detail, and find that it can be quite distinct. We construct classes of explicit models within this framework, based on higher dimensional unified theories with TeV-sized extra dimensions. A similar model based on a non-R symmetry is also presented. These models have a rich phenomenology at the TeV scale, and allow for detailed analyses of, e.g., electroweak symmetry breaking

Preliminary survey of bee (Hymenoptera: Anthophila) richness in the northwestern Chihuahuan Desert

Science.gov (United States)

Robert L. Minckley; John S. Ascher

2013-01-01

Museum records indicate that the peak number of bee species occurs around the Mediterranean Sea and in the warm desert areas of North America, whereas flowering plants are most diverse in the tropics. We examine this biogeographic pattern for the bee species known from a limited area of northeastern Chihuahuan Desert, Mexico/United States. This topographically complex...

Radiatively-driven processes in forest fire and desert dust plumes

Energy Technology Data Exchange (ETDEWEB)

Weinzierl, Bernadett Barbara

2008-07-01

The absorption of solar radiation by atmospheric aerosol particles is important for the climate effects of aerosols. Absorption by aerosol particles heats atmospheric layers, even though the net effect for the entire atmospheric column may still be a cooling. Most experimental studies on absorbing aerosols so far focussed mainly on the aerosol properties and did not consider the influence of the aerosols on the thermodynamic structure of the atmosphere. In this study, data from two international aircraft field experiments, the Intercontinental Transport of Ozone and Precursors study (ITOP) 2004 and the Saharan Mineral Dust Experiment (SAMUM) 2006 are investigated. The ITOP data were collected before the work on this thesis started, while the logistics and the instrument preparation of the SAMUM campaign, the weather forecast during SAMUM and the in-situ aerosol measurements during SAMUM were done within this thesis. The experimental data are used to explore the impact of layers containing absorbing forest fire and desert dust aerosol particles on the atmospheric stability and the implications of a changed stability on the development of the aerosol microphysical and optical properties during long-range transport. For the first time, vertical profiles of the Richardson number Ri are used to assess the stability and mixing in forest fire and desert dust plumes. Also for the first time, the conclusions drawn from the observations of forest fire and desert dust aerosol, at first glance apparently quite different aerosol types, are discussed from a common perspective. Two mechanisms, the selfstabilising and the sealed ageing effect, acting in both forest fire and desert dust aerosol layers, are proposed to explain the characteristic temperature structure as well as the aerosol properties observed in lofted forest fire and desert dust plumes. The proposed effects impact on the ageing of particles within the plumes and reduce the plume dilution, therefore extending the

Total vertical sediment flux and PM10 emissions from disturbed Chihuahuan Desert Surfaces

Science.gov (United States)

Desert surfaces are typically stable and represent some of the oldest landforms on Earth. For surfaces without vegetation, the evolution of a desert pavements of gravel protects the surface from erosive forces and vegetation further protects the surface in arid and semi-arid rangelands. The suscep...

Sedimentary architecture and palaeogeography of lower Slochteren Aeolian cycles from the Rotliegend desert-lake margin (Permian), the Markham area, Southern North Sea

NARCIS (Netherlands)

Belt, F.J.G. van den; Hulten, F.F.N. van

2011-01-01

The Rotliegend gas play in the Southern Permian Basin has yielded over 200 gas fields in the Netherlands; they are found in an E-W fairway along the southern flank of the basin. Sandstones generally pinch out basinward, but localized, isolated sands are present north of the main fairway. The

Water consumption in artificial desert oasis based on net primary productivity

Institute of Scientific and Technical Information of China (English)

无

2010-01-01

Analysis of the water consumption is the basis for water allocation in oasis. However, the method of estimating oasis water consumption remains a great challenge. Based on net primary productivity (NPP) and the transpiration coefficient, a vegetation water consumption model was developed to estimate the water consumption in desert oasis in ERDAS environment. Our results demonstrated that the ecosystem in the middle reaches of the Heihe oasis consumed water of 18.41×108-21.9×108 m3 for irrigation. Without taking precipitation into account, the water consumption in farmland accounted for 77.1%-77.8% (or about 13.97×108-16.84×108 m3) of the oasis vegetation water consumption and in the farmland protection system accounting for 22%. The growing period precipitation in desert environments is about 7.02×108 m3, and the total annual precipitation is about 8.29×108 m3. The modeled water consumption of desert vegetation, however, is about 4.57×108 m3, equivalent to only 65% of the growing period precipitation or 55% of the total annual precipitation. The modeled value equals to the cumulative precipitation of greater than 5 mm, which is defined as the effective precipitation in arid desert.

Validation of SWEEP for creep, saltation, and suspension in a desert-oasis ecotone

Science.gov (United States)

Wind erosion in the desert-oasis ecotone can accelerate desertification and thus impacts oasis ecological security. Little is known about the susceptibility of the desert-oasis ecotone to wind erosion in the Tarim Basin even though the ecotone is a major source of windblown dust in China. The object...

Local Extinction and Unintentional Rewilding of Bighorn Sheep (Ovis canadensis) on a Desert Island

Science.gov (United States)

Wilder, Benjamin T.; Betancourt, Julio L.; Epps, Clinton W.; Crowhurst, Rachel S.; Mead, Jim I.; Ezcurra, Exequiel

2014-01-01

Bighorn sheep (Ovis canadensis) were not known to live on Tiburón Island, the largest island in the Gulf of California and Mexico, prior to the surprisingly successful introduction of 20 individuals as a conservation measure in 1975. Today, a stable island population of ∼500 sheep supports limited big game hunting and restocking of depleted areas on the Mexican mainland. We discovered fossil dung morphologically similar to that of bighorn sheep in a dung mat deposit from Mojet Cave, in the mountains of Tiburón Island. To determine the origin of this cave deposit we compared pellet shape to fecal pellets of other large mammals, and extracted DNA to sequence mitochondrial DNA fragments at the 12S ribosomal RNA and control regions. The fossil dung was 14C-dated to 1476–1632 calendar years before present and was confirmed as bighorn sheep by morphological and ancient DNA (aDNA) analysis. 12S sequences closely or exactly matched known bighorn sheep sequences; control region sequences exactly matched a haplotype described in desert bighorn sheep populations in southwest Arizona and southern California and showed subtle differentiation from the extant Tiburón population. Native desert bighorn sheep previously colonized this land-bridge island, most likely during the Pleistocene, when lower sea levels connected Tiburón to the mainland. They were extirpated sometime in the last ∼1500 years, probably due to inherent dynamics of isolated populations, prolonged drought, and (or) human overkill. The reintroduced population is vulnerable to similar extinction risks. The discovery presented here refutes conventional wisdom that bighorn sheep are not native to Tiburón Island, and establishes its recent introduction as an example of unintentional rewilding, defined here as the introduction of a species without knowledge that it was once native and has since gone locally extinct. PMID:24646515

Local extinction and unintentional rewilding of bighorn sheep (Ovis canadensis on a desert island.

Directory of Open Access Journals (Sweden)

Benjamin T Wilder

Full Text Available Bighorn sheep (Ovis canadensis were not known to live on Tiburón Island, the largest island in the Gulf of California and Mexico, prior to the surprisingly successful introduction of 20 individuals as a conservation measure in 1975. Today, a stable island population of ∼500 sheep supports limited big game hunting and restocking of depleted areas on the Mexican mainland. We discovered fossil dung morphologically similar to that of bighorn sheep in a dung mat deposit from Mojet Cave, in the mountains of Tiburón Island. To determine the origin of this cave deposit we compared pellet shape to fecal pellets of other large mammals, and extracted DNA to sequence mitochondrial DNA fragments at the 12S ribosomal RNA and control regions. The fossil dung was 14C-dated to 1476-1632 calendar years before present and was confirmed as bighorn sheep by morphological and ancient DNA (aDNA analysis. 12S sequences closely or exactly matched known bighorn sheep sequences; control region sequences exactly matched a haplotype described in desert bighorn sheep populations in southwest Arizona and southern California and showed subtle differentiation from the extant Tiburón population. Native desert bighorn sheep previously colonized this land-bridge island, most likely during the Pleistocene, when lower sea levels connected Tiburón to the mainland. They were extirpated sometime in the last ∼1500 years, probably due to inherent dynamics of isolated populations, prolonged drought, and (or human overkill. The reintroduced population is vulnerable to similar extinction risks. The discovery presented here refutes conventional wisdom that bighorn sheep are not native to Tiburón Island, and establishes its recent introduction as an example of unintentional rewilding, defined here as the introduction of a species without knowledge that it was once native and has since gone locally extinct.

Local extinction and unintentional rewilding of bighorn sheep (Ovis canadensis) on a desert island

Science.gov (United States)

Wilder, Benjamin T.; Betancourt, Julio L.; Epps, Clinton W.; Crowhurst, Rachel S.; Mead, Jim I.; Ezcurra, Exequiel

2014-01-01

Bighorn sheep (Ovis canadensis) were not known to live on Tiburón Island, the largest island in the Gulf of California and Mexico, prior to the surprisingly successful introduction of 20 individuals as a conservation measure in 1975. Today, a stable island population of ~500 sheep supports limited big game hunting and restocking of depleted areas on the Mexican mainland. We discovered fossil dung morphologically similar to that of bighorn sheep in a dung mat deposit from Mojet Cave, in the mountains of Tiburón Island. To determine the origin of this cave deposit we compared pellet shape to fecal pellets of other large mammals, and extracted DNA to sequence mitochondrial DNA fragments at the 12S ribosomal RNA and control regions. The fossil dung was 14C-dated to 1476–1632 calendar years before present and was confirmed as bighorn sheep by morphological and ancient DNA (aDNA) analysis. 12S sequences closely or exactly matched known bighorn sheep sequences; control region sequences exactly matched a haplotype described in desert bighorn sheep populations in southwest Arizona and southern California and showed subtle differentiation from the extant Tiburón population. Native desert bighorn sheep previously colonized this land-bridge island, most likely during the Pleistocene, when lower sea levels connected Tiburón to the mainland. They were extirpated sometime in the last ~1500 years, probably due to inherent dynamics of isolated populations, prolonged drought, and (or) human overkill. The reintroduced population is vulnerable to similar extinction risks. The discovery presented here refutes conventional wisdom that bighorn sheep are not native to Tiburón Island, and establishes its recent introduction as an example of unintentional rewilding, defined here as the introduction of a species without knowledge that it was once native and has since gone locally extinct.

Ecosystem responses to warming and watering in typical and desert steppes

OpenAIRE

Zhenzhu Xu; Yanhui Hou; Lihua Zhang; Tao Liu; Guangsheng Zhou

2016-01-01

Global warming is projected to continue, leading to intense fluctuations in precipitation and heat waves and thereby affecting the productivity and the relevant biological processes of grassland ecosystems. Here, we determined the functional responses to warming and altered precipitation in both typical and desert steppes. The results showed that watering markedly increased the aboveground net primary productivity (ANPP) in a typical steppe during a drier year and in a desert steppe over two ...

Vegetation - Anza-Borrego Desert State Park [ds165

Data.gov (United States)

California Natural Resource Agency — The Anza Borrego Desert State Park (ABDSP) Vegetation Map depicts vegetation within the Park and its surrounding environment. The map was prepared by the Department...

Biodiversity Analysis of Vegetation on the Nevada Test Site

International Nuclear Information System (INIS)

W. K. Ostler; D. J. Hansen

2001-01-01

The Nevada Test Site (NTS) located in south central Nevada encompasses approximately 3,561 square kilometers and straddles two major North American deserts, Mojave and Great Basin. Transitional areas between the two desert types have been created by gradients in elevation, precipitation, temperature, and soils. From 1996-1998, more than 1,500 ecological landform units were sampled at the NTS for numerous biotic and abiotic parameters. These data provide a basis for spatial evaluations of biodiversity over landscape scales at the NTS. Species diversity maps (species richness vs. species abundance) have been produced. Differences in ecosystem diversity at the ecoregion, alliance, association, and ecological landform unit levels are presented. Spatial distribution maps of species presence and abundance provide evidence of where transition zones occur and the resulting impact on biodiversity. The influences of abiotic factors (elevation, soil, precipitation) and anthropogenic disturbance on biodiversity are assessed

Resistance to invasion and resilience to fire in desert shrublands of North America

Science.gov (United States)

Matthew L. Brooks; Jeanne C. Chambers

2011-01-01

Settlement by Anglo-Americans in the desert shrublands of North America resulted in the introduction and subsequent invasion of multiple nonnative grass species. These invasions have altered presettlement fire regimes, resulted in conversion of native perennial shrublands to nonnative annual grasslands, and placed many native desert species at risk. Effective...

Seeing desert as wilderness and as landscape—an exercise in visual thinking approaches

Science.gov (United States)

John Opie

1979-01-01

Based on the components and program of VRVA (Visual Resources Values Assessment), a behavioral history of the visitor's perception of the American desert is examined. Emphasis is placed upon contrasts between traditional eastern "garden-park" viewpoints and contemporary desert scenery experiences. Special attention is given to the influence of John...

Geospatial techniques to Identify the Location of Farmers Markets and Community Gardens within Food Deserts in Virginia

Science.gov (United States)

Sriharan, S.; Meekins, D.; Comar, M.; Bradshaw, S.; Jackson, L.

2017-12-01

Specifically, a food desert is defined as an area where populations live more than one mile from a supermarket or large grocery store if in an urban area or more than 10 miles from a supermarket or large grocery store if in a rural area (Ver Ploeg et al. 2012). According to the U.S. Department of Agriculture, a food desert is "an area in the United States with limited access to affordable and nutritious food, particularly such an area composed of predominately lower-income neighborhoods and communities" (110th Congress 2008). Three fourths of these food deserts are urban. In the Commonwealth of Virginia, Petersburg City is among the eight primary localities, where its population is living in a food desert. This project will compare those identified food deserts in Virginia (areas around Virginia State University) with focus to where farmers markets and community gardens are being established. The hypothesis of this study is that these minority groups do not get healthy food due to limited access to grocery stores and superstores. To address this problem, the community development activities should focus on partnering local Petersburg convenience stores with farmers and community gardeners to sell fresh produce. Existing data was collected on convenient stores and community gardens in Petersburg City and Chesterfield County. Rare data was generated for Emporia, Lynchburg and Hopewell. The data was compiled through field work and mapping with ArcGIS where markets and gardens are being established, and create a spatial analysis of their location We have localities that reflect both rural and urban areas. The project provides educational support for students who will find solution to community problems by developing activities to: (a) define and examine characteristics of food deserts, (b) identify causes and consequences of food deserts and determine if their community is a food desert, (c) research closest food desert to their school, and (d) design solutions to help

Thermal design of a fully equipped solar-powered desert home

KAUST Repository

Serag-Eldin, M.A.

2010-03-01

The paper presents a conceptual design and thermodynamic analysis of a solar-powered desert home. The home is airconditioned and provides all modern comforts and facilities. Electrical power, which drives the entire energy system, is generated by roof mounted photovoltaic modules. A detailed dynamic heat transfer analysis is conducted for the building envelope, coupled with a solar radiation model. A dynamic heat balance for a typical Middle-Eastern desert site, reveals that indeed such a design is feasible with present day technology; and should be even more attractive with future advances in technology.

The Plate Boundary Observatory Student Field Assistant Program in Southern California

Science.gov (United States)

Seider, E. L.

2007-12-01

Each summer, UNAVCO hires students as part of the Plate Boundary Observatory (PBO) Student Field Assistant Program. PBO, the geodetic component of the NSF-funded EarthScope project, involves the reconnaissance, permitting, installation, documentation, and maintenance of 880 permanent GPS stations in five years. During the summer 2007, nine students from around the US and Puerto Rico were hired to assist PBO engineers during the busy summer field season. From June to September, students worked closely with PBO field engineers to install and maintain permanent GPS stations in all regions of PBO, including Alaska. The PBO Student Field Assistant Program provides students with professional hands-on field experience as well as continuing education in the geosciences. It also gives students a glimpse into the increasing technologies available to the science community, the scope of geophysical research utilizing these technologies, and the field techniques necessary to complete this research. Students in the PBO Field Assistant Program are involved in all aspects of GPS support, including in-warehouse preparation and in-field installations and maintenance. Students are taught practical skills such as drilling, wiring, welding, hardware configuration, documentation, and proper field safety procedures needed to construct permanent GPS stations. These real world experiences provide the students with technical and professional skills that are not always available to them in a classroom, and will benefit them greatly in their future studies and careers. The 2007 summer field season in Southern California consisted of over 35 GPS permanent station installations. To date, the Southern California region of PBO has installed over 190 GPS stations. This poster presentation will highlight the experiences gained by the Southern California student field assistants, while supporting PBO- Southern California GPS installations in the Mohave Desert and the Inyo National Forest.

A New Infrared Desert Dust Index over French Guyana Rain forest: First results

Science.gov (United States)

Molinie, J.; Barnacin, E.; Henry, J. L.; Gobinddass, M. L.; Panechou-Pulcherie, K.; Feuillard, T.; Nagau, J.

2017-12-01

Recently a NASA researcher showed the role of desert dust contribution for the Amazonian rain forest. In another hand, desert dust impact population health when PM 10 level reached values around and upper the PM 10 threshold of the 50 µg m-3, established by the World Health Organization (WHO). Infrared Desert Dust Index (IDDI) developed by Legrand with Meteosat infrared images, allow the following of desert dust plumes over semi-arid land. In French Guiana the WHO threshold is currently overpass in measurements done by ORA air quality network, in the two main towns located close to the coast. For inland population, it is very difficult to have continuous dust measures due to the low infrastructure supplies. We need to develop a tools in order to follow the crossing of desert dust over the French Guyana rain forest, from the coast to inland villages. Following the IDDI concept and comparing with VIIRS AOT EDR result over the same area, a modified IDDI for Amazonian region (IDDI_A) has been proposed to identify the dusty pixels over the forest. Despite of high cloud presence, a good correlation between AOT EDR and IDDI_A was obtained. The IDDI_A calculation has been applied over French Guiana area for different PM 10 level at Cayenne, a town along the coast.

Characterizing dust aerosols in the atmospheric boundary layer over the deserts in Northwest China: monitoring network and field observation

Science.gov (United States)

He, Q.; Matimin, A.; Yang, X.

2016-12-01

TheTaklimakan, Gurbantunggut and BadainJaran Deserts with the total area of 43.8×104 km2 in Northwest China are the major dust emission sources in Central Asia. Understanding Central Asian dust emissions and the interaction with the atmospheric boundary layer has an important implication for regional and global climate and environment changes. In order to explore these scientific issues, a monitoring network of 63 sites was established over the vast deserts (Taklimakan Desert, Gurbantunggut Desert and Badain Jaran Desert) in Northwest China for the comprehensive measurements of dust aerosol emission, transport and deposition as well as the atmospheric boundary layer including the meteorological parameters of boundary layer, surface radiation, surface heat fluxes, soil parameters, dust aerosol properties, water vapor profiles, and dust emission. Based on the monitoring network, the field experiments have been conducted to characterize dust aerosols and the atmospheric boundary layer over the deserts. The experiment observation indicated that depth of the convective boundary layer can reach 5000m on summer afternoons. In desert regions, the diurnal mean net radiation was effected significantly by dust weather, and sensible heat was much greater than latent heat accounting about 40-50% in the heat balance of desert. The surface soil and dust size distributions of Northwest China Deserts were obtained through widely collecting samples, results showed that the dominant dust particle size was PM100within 80m height, on average accounting for 60-80% of the samples, with 0.9-2.5% for PM0-2.5, 3.5-7.0% for PM0-10 and 5.0-14.0% for PM0-20. The time dust emission of Taklimakan Desert, Gurbantunggut Desert and Badain Jaran Desert accounted for 0.48%, 7.3%×10-5and 1.9% of the total time within a year, and the threshold friction velocity for dust emission were 0.22-1.06m/s, 0.29-1.5m/s and 0.21-0.59m/s, respectively.

Geology, Water, and Wind in the Lower Helmand Basin, Southern Afghanistan

Science.gov (United States)

Whitney, John W.

2006-01-01

This report presents an overview of the geology, hydrology, and climate of the lower Helmand Basin, a large, closed, arid basin in southern Afghanistan. The basin is drained by the Helmand River, the only perennial desert stream between the Indus and Tigris-Euphrates Rivers. The Helmand River is the lifeblood of southern Afghanistan and has supported desert civilizations in the Sistan depression for over 6,000 years. The Helmand Basin is a structurally closed basin that began to form during the middle Tertiary as a consequence of the collision of several Gondwanaland fragments. Aeromagnetic studies indicate the basin is 3-5 kilometers deep over basement rocks. Continued subsidence along basin-bounding faults in Iran and Pakistan throughout the Neogene has formed the Sistan depression in the southwest corner of the basin. Lacustrine, eolian, and fluvial deposits are commonly exposed in the basin and were intruded by latest Miocene-middle Quaternary volcanoes, which indicates that depositional environments in the lower Helmand Basin have not substantially changed for nearly 10 million years. Lakes expanded in the Sistan depression during the Quaternary; however, the size and extent of these pluvial lakes are unknown. Climate conditions in the lower Helmand Basin likely mirrored climate changes in the Rajasthan Desert to the east and in Middle Eastern deserts to the west: greater aridity during global episodes of colder temperatures and increased available moisture during episodes of warmer temperatures. Eolian processes are unusually dominant in shaping the landscape in the basin. A strong wind blows for 120 days each summer, scouring dry lakebeds and creating dune fields from annual flood deposits. Nearly one-third of the basin is mantled with active or stabilized dunes. Blowing winds combined with summer temperatures over 50? Celsius and voluminous insect populations hatched from the deltaic wetlands create an environment referred to as the 'most odious place on

Translocation as a conservation tool for Agassiz's desert tortoises: Survivorship, reproduction, and movements

Science.gov (United States)

K. E. Nussear; C. R. Tracy; P. A. Medica; D. S. Wilson; R. W. Marlow; P. S. Corn

2012-01-01

We translocated 120 Agassiz's desert tortoises to 5 sites in Nevada and Utah to evaluate the effects of translocation on tortoise survivorship, reproduction, and habitat use. Translocation sites included several elevations, and extended to sites with vegetation assemblages not typically associated with desert tortoises in order to explore the possibility of moving...

78 FR 143 - Desert Mining, Inc., Eagle Broadband, Inc., Endovasc, Inc., Environmental Oil Processing...

Science.gov (United States)

2013-01-02

... SECURITIES AND EXCHANGE COMMISSION [File No. 500-1] Desert Mining, Inc., Eagle Broadband, Inc., Endovasc, Inc., Environmental Oil Processing Technology Corp., Falcon Ridge Development, Inc., Fellows... that there is a lack of current and accurate information concerning the securities of Desert Mining...

Influence of shrubs on soil chemical properties in Alxa desert steppe, China

Science.gov (United States)

Hua Fu; Shifang Pei; Yaming Chen; Changgui Wan

2007-01-01

Alxa desert steppe is one of severely the degraded rangelands in the Northwest China. Shrubs, as the dominant life form in the desert steppe, play an important role in protecting this region from further desertification. Chemical properties of three soil layers (0 to 10, 10 to 20 and 20 to 30 cm) at three locations (the clump center [A], in the periphery of shrub...

Evolution and ecology meet molecular genetics: adaptive phenotypic plasticity in two isolated Negev desert populations of Acacia raddiana at either end of a rainfall gradient

Science.gov (United States)

Ward, David; Shrestha, Madan K.; Golan-Goldhirsh, Avi

2012-01-01

Background and Aims The ecological, evolutionary and genetic bases of population differentiation in a variable environment are often related to the selection pressures that plants experience. We compared differences in several growth- and defence-related traits in two isolated populations of Acacia raddiana trees from sites at either end of an extreme environmental gradient in the Negev desert. Methods We used random amplified polymorphic DNA (RAPD) to determine the molecular differences between populations. We grew plants under two levels of water, three levels of nutrients and three levels of herbivory to test for phenotypic plasticity and adaptive phenotypic plasticity. Key Results The RAPD analyses showed that these populations are highly genetically differentiated. Phenotypic plasticity in various morphological traits in A. raddiana was related to patterns of population genetic differentiation between the two study sites. Although we did not test for maternal effects in these long-lived trees, significant genotype × environment (G × E) interactions in some of these traits indicated that such plasticity may be adaptive. Conclusions The main selection pressure in this desert environment, perhaps unsurprisingly, is water. Increased water availability resulted in greater growth in the southern population, which normally receives far less rain than the northern population. Even under the conditions that we defined as low water and/or nutrients, the performance of the seedlings from the southern population was significantly better, perhaps reflecting selection for these traits. Consistent with previous studies of this genus, there was no evidence of trade-offs between physical and chemical defences and plant growth parameters in this study. Rather, there appeared to be positive correlations between plant size and defence parameters. The great variation in several traits in both populations may result in a diverse potential for responding to selection pressures in

Should I stay or should I go? Female brood desertion and male counterstrategy in rock sparrows

DEFF Research Database (Denmark)

Griggio, Matteo; Matessi, Giuliano; Pilastro, Andrea

2005-01-01

petronia), a species in which females can desert their first brood before the nestlings from the first brood leave the nest. We predicted that the male would either desert the brood first or stay even if this implied the risk of caring for the brood alone. We found that males mated to loaded females did...... not leave but stayed and significantly increased their courtship rate and mate guarding. Unexpectedly, they also increased their food provisioning to the nestlings, even though loaded females did not reduce their nestling-feeding rate. The increase in male feeding rate may be explained as a way for the male...... to reduce the female's propensity to switch mate and desert or to increase her propensity to copulate with the male to obtain paternity in her next brood. Altogether, our results demonstrate that the perception of the risk of being deserted by the female does not necessarily induce males to desert first...

A Study to Determine the Mental Models in Preschool Children’s Conceptualization of a Desert Environment

Directory of Open Access Journals (Sweden)

Berat AHİ

2016-03-01

Full Text Available This study aimed to determine mental models and identify codes (schemes used in conceptualizing a desert environment. The sample for this study consisted of 184 – out of a total population of 3,630 - children in preschool education in the central district of Kastamonu, Turkey. Within the scope of this study, the children were initially asked to draw a desert-themed picture, followed by a semi-structured interview to seek their opinions about the drawing and clarify what a desert environment meant to them. According to the findings, the children referred to 38 different codes relevant to the conceptualization of a desert environment; the most frequently used were the sun (f= 160, 86.9%, sand (f= 100, 54.3%, cacti (f= 74, 35.3% and camels (f= 52, 28.6%. During the interview phase, 33 children described a desert as a place where there is no life, although a significant number of the children (f= 65, 39.1% did describe a desert as a place where plants and animals live. Moreover, the sun and its rays were disproportionately bigger in size, in order to emphasize the excessive heat associated with the specific ecosystem found in a desert environment; to reinforce this, humans drenched in sweat, the absence of trees and the prevalence of cacti and exotic wildlife, including camels, scorpions and lizards, were all features of the children’s drawings. Based on these findings, it was inferred that the mental models in some of the children (f= 72, 39.1% were scientifically informed, with a degree of accuracy, about a desert environment. On the basis of the findings, it is considered that determining mental models in children in relation to different ecological concepts can be beneficial to teachers and curriculum programmers involved in environmental education.

A study to determine the mental models in preschool children’s conceptualization of a desert environment

Directory of Open Access Journals (Sweden)

Berat Ahi

2016-03-01

Full Text Available This study aimed to determine mental models and identify codes (schemes used in conceptualizing a desert environment. The sample for this study consisted of 184 – out of a total population of 3,630 - children in preschool education in the central district of Kastamonu, Turkey. Within the scope of this study, the children were initially asked to draw a desert-themed picture, followed by a semi-structured interview to seek their opinions about the drawing and clarify what a desert environment meant to them. According to the findings, the children referred to 38 different codes relevant to the conceptualization of a desert environment; the most frequently used were the sun (f= 160, 86.9%, sand (f= 100, 54.3%, cacti (f= 74, 35.3% and camels (f= 52, 28.6%. During the interview phase, 33 children described a desert as a place where there is no life, although a significant number of the children (f= 65, 39.1% did describe a desert as a place where plants and animals live. Moreover, the sun and its rays were disproportionately bigger in size, in order to emphasize the excessive heat associated with the specific ecosystem found in a desert environment; to reinforce this, humans drenched in sweat, the absence of trees and the prevalence of cacti and exotic wildlife, including camels, scorpions and lizards, were all features of the children’s drawings. Based on these findings, it was inferred that the mental models in some of the children (f= 72, 39.1% were scientifically informed, with a degree of accuracy, about a desert environment. On the basis of the findings, it is considered that determining mental models in children in relation to different ecological concepts can be beneficial to teachers and curriculum programmers involved in environmental education.

76 FR 50493 - Notice of Availability of the Record of Decision for the Desert Sunlight Holdings, LLC, Desert...

Science.gov (United States)

2011-08-15

... DEPARTMENT OF THE INTERIOR Bureau of Land Management [CACA-48649, LLCAD06000 L51010000 ER0000... right-of-way (ROW) application CACA-48649 for the Desert Sunlight Solar Farm Project (DSSF). The DSSF is... (CACA-052682) where the project would interconnect with the SCE regional transmission system. The DSSF...

Preventing desert locust plagues: optimizing management interventions

NARCIS (Netherlands)

Huis, van A.; Cressman, K.; Magor, J.I.

2007-01-01

Solitarious desert locusts, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae), inhabit the central, arid, and semi-arid parts of the species¿ invasion area in Africa, the Middle East, and South-West Asia. Their annual migration circuit takes them downwind to breed sequentially where winter,

Divining Jordan's desert waters | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

... in the area have a long history of being water-conservers, and the idea of using the ... Dr Abu-Jaber examined is covered by an ancient, volcanic rock called basalt. ... When a desert cloudburst drops rain on the area, the raindrops quickly roll ...

A Proposal for Desert House Design in Egypt Using Passive Ground Cooling Techniques

Directory of Open Access Journals (Sweden)

Mohamed Medhat Dorra

2018-06-01

Full Text Available An area less than 5.5% of Egyptian territory is where most of Egypt‘s population lives in. A narrow strip of land forms the Nile Valley and Delta sector.The National Project for Desert Hinterlands is one of the urban projects targeting rehabilitation of the poor in alternative villages in the near desert to stop urban sprawl over agricultural land and decrease the congestion in the old habitats. Low cost energy efficient houses are the aim of the architect in similar projects taking in consideration the high electricity consumption of Egypt’s residential sector. Based on a literature review, this paper presents a proposal for designing desert dwellings   that accommodates the hot dry climate by incorporating passive elements and using stabilized earth blocks as a local building material. Furthermore, simulation is used to test alternative proposals. The results show that an underground constructed house with a sunken courtyard incorporating an Earth to Air Heat Exchanger System (EAHE can reduce between 42-72% of energy consumption used to achieve thermal comfort compared to contemporary desert housing projects.

Difference in luminescence sensitivity of coarse-grained quartz from deserts of northern China

International Nuclear Information System (INIS)

Zheng, C.X.; Zhou, L.P.; Qin, J.T.

2009-01-01

The luminescence sensitivity of coarse quartz extracted from desert sands in northern China was investigated. In general, the western deserts' samples are shown to be less sensitive than samples from the eastern deserts with respect to both OSL and the 110 deg. C TL peak. However, internal scatter among different aliquots of the same sample is observed for these two signals, which have already been normalized by weight. Laboratory dosing/bleach experiments indicate that earth surface processes, such as repeated burial and transportation can cause the sensitivity change and suggest that they may be responsible for the internal scatter. An intrinsic property of quartz was explored via the luminescence response to thermal activation to a maximum temperature of 700 deg. C. The thermal activation curves obtained with quartz from western and central deserts are similar, except one sample from Gurbantungut, which follows the pattern of eastern samples. The differences in quartz luminescence sensitivity exhibited by OSL/110 deg. C TL sensitivity and response to thermal activation are in accordance with the published results of geochemical studies.

Water sources for cyanobacteria below desert rocks in the Negev Desert determined by conductivity

OpenAIRE

McKay, Christopher P.

2016-01-01

We present year round meteorological and conductivity measurements of colonized hypolithic rocks in the Arava Valley, Negev Desert, Israel. The data indicate that while dew is common in the Negev it is not an important source of moisture for hypolithic organisms at this site. The dominance of cyanobacteria in the hypolithic community is consistent with predictions that cyanobacteria are confined to habitats supplied by rain. To monitor the presence of liquid water under the small Negev rocks ...

Water relations and photosynthesis in the cryptoendolithic microbial habitat of hot and cold deserts

Science.gov (United States)

Palmer, R. J. Jr; Friedmann, E. I.

1990-01-01

Two cryptoendolithic microbial communities, lichens in the Ross Desert of Antarctica and cyanobacteria in the Negev Desert, inhabit porous sandstone rocks of similar physical structure. Both rock types adsorb water vapor by physical mechanisms unrelated to biological processes. Yet the two microbial communities respond differently to water stress: cryptoendolithic lichens begin to photosynthesize at a matric water potential of -46.4 megaPascals (MPa) [70% relative humidity (RH) at 8 degrees C], resembling thallose desert lichens. Cryptoendolithic cyanobacteria, like other prokaryotes, photosynthesize only at very high matric water potentials [> -6.9 MPa, 90% RH at 20 degrees C].

Wind to Hydrogen in California: Case Study

Energy Technology Data Exchange (ETDEWEB)

Antonia, O.; Saur, G.

2012-08-01

This analysis presents a case study in California for a large scale, standalone wind electrolysis site. This is a techno-economic analysis of the 40,000 kg/day renewable production of hydrogen and subsequent delivery by truck to a fueling station in the Los Angeles area. This quantity of hydrogen represents about 1% vehicle market penetration for a city such as Los Angeles (assuming 0.62 kg/day/vehicle and 0.69 vehicles/person) [8]. A wind site near the Mojave Desert was selected for proximity to the LA area where hydrogen refueling stations are already built.

Environmental racism: the US nuclear industry and native Americans

International Nuclear Information System (INIS)

Lehtinen, Ulla

1997-01-01

The author argues that the United States nuclear industry has acted in a discriminatory fashion towards Native American peoples and the land they hold as reservations. Both uranium mining and nuclear weapons testing is commonplace and plans now exist to locate a low-level radioactive waste dump in the Mojave desert in California, a sacred site for many native people. Opposition to such plans is growing among the Native Americans, sharpened by their existing commitment to conservation of the environment, but on their own, they are not a lobby powerful enough to oppose the might of the nuclear industry. (UK)

Environmental racism: the US nuclear industry and native Americans

Energy Technology Data Exchange (ETDEWEB)

Lehtinen, Ulla [Organization of the Fourth World - First Peoples (Finland)

1997-03-01

The author argues that the United States nuclear industry has acted in a discriminatory fashion towards Native American peoples and the land they hold as reservations. Both uranium mining and nuclear weapons testing is commonplace and plans now exist to locate a low-level radioactive waste dump in the Mojave desert in California, a sacred site for many native people. Opposition to such plans is growing among the Native Americans, sharpened by their existing commitment to conservation of the environment, but on their own, they are not a lobby powerful enough to oppose the might of the nuclear industry. (UK).

Windblown sediment transport and loss in a desert-oasis ecotone in the Tarim Basin.

Science.gov (United States)

Pi, Huawei; Sharratt, Brenton; Lei, Jiaqiang

2017-08-10

The Tarim Basin is regarded as one of the most highly erodible areas in China. Desert comprises 64% of the land use in the Basin, but the desert-oasis ecotone plays a prominent role in maintaining oasis ecological security and stability. Yet, little is known concerning the magnitude of windblown sediment transport in a desert-oasis ecotone. Therefore, aeolian sediment transport and loss was assessed from a desert-oasis experimental site located near Alaer City in the northwestern Tarim Basin. Sediment transport and factors governing transport were measured during three high wind events in 2012 and four events in 2013. Sediment transport was measured to a height of 10 m using passive aeolian airborne sediment samplers. The mass flux profile over the eroding surface was well represented by the power-law (R 2  > 0.77). Sediment loss from the site ranged from 118 g m -2 for the 20-24Apr 2012 wind event to 2925 g m -2 for the 31Mar-11Apr 2012 event. Suspension accounted for 67.4 to 84.8% of sediment loss across all high wind events. Our results indicate the severity of wind erosion in a desert-oasis ecotone and thus encourage adoption of management practices that will enhance oasis ecological security.

[Risk factors for students desertion from the UASLP School of Medicine, México].

Science.gov (United States)

Hernández-Mata, José María; Hernández-Castro, Rodrigo; Nieto-Caraveo, Amado; Hernández-Sierra, Juan Francisco

2005-01-01

To obtain the profile of students that deserted from the Faculty of Medicine of the Autonomous University of San Luis Potosi, México. Cases and controls nested in a cohort. All students that voluntarily deserted between 1992 and 2002 were consulted. Each student was compared in an aleatory form with a regular student and a proper questionnaire was applied. The significantly associated factors to abandon the Faculty of Medicine were: high school of origin (OR=2.43), extra-ordinary exam (OR=3.13), and lack of vocation (OR=2.41). The subjacent factors for not deserting from the Faculty of Medicine were: study habits, capacity for sustained effort, and tolerance to frustration.

Disturbance to desert soil ecosystems contributes to dust-mediated impacts at regional scales

Science.gov (United States)

Pointing, Stephen B.; Belnap, Jayne

2014-01-01

This review considers the regional scale of impacts arising from disturbance to desert soil ecosystems. Deserts occupy over one-third of the Earth’s terrestrial surface, and biological soil covers are critical to stabilization of desert soils. Disturbance to these can contribute to massive destabilization and mobilization of dust. This results in dust storms that are transported across inter-continental distances where they have profound negative impacts. Dust deposition at high altitudes causes radiative forcing of snowpack that leads directly to altered hydrological regimes and changes to freshwater biogeochemistry. In marine environments dust deposition impacts phytoplankton diazotrophy, and causes coral reef senescence. Increasingly dust is also recognized as a threat to human health.

Desert Peak East Enhanced Geothermal Systems (EGS) Project

Energy Technology Data Exchange (ETDEWEB)

Zemach, Ezra [Ormat Technologies Inc., Reno, NV (United States); Drakos, Peter [Ormat Technologies Inc., Reno, NV (United States); Spielman, Paul [Ormat Technologies Inc., Reno, NV (United States); Akerley, John [Ormat Technologies Inc., Reno, NV (United States)

2013-09-30

This manuscript is a draft to replaced with a final version at a later date TBD. A summary of activities pertaining to the Desert Peak EGS project including the planning and resulting stimulation activities.

Molecular mechanisms of foliar water uptake in a desert tree.

Science.gov (United States)

Yan, Xia; Zhou, Maoxian; Dong, Xicun; Zou, Songbing; Xiao, Honglang; Ma, Xiao-Fei

2015-11-12

Water deficits severely affect growth, particularly for the plants in arid and semiarid regions of the world. In addition to precipitation, other subsidiary water, such as dew, fog, clouds and small rain showers, may also be absorbed by leaves in a process known as foliar water uptake. With the severe scarcity of water in desert regions, this process is increasingly becoming a necessity. Studies have reported on physical and physiological processes of foliar water uptake. However, the molecular mechanisms remain less understood. As major channels for water regulation and transport, aquaporins (AQPs) are involved in this process. However, due to the regulatory complexity and functional diversity of AQPs, their molecular mechanism for foliar water uptake remains unclear. In this study, Tamarix ramosissima, a tree species widely distributed in desert regions, was investigated for gene expression patterns of AQPs and for sap flow velocity. Our results suggest that the foliar water uptake of T. ramosissima occurs in natural fields at night when the humidity is over a threshold of 85 %. The diurnal gene expression pattern of AQPs suggests that most AQP gene expressions display a circadian rhythm, and this could affect both photosynthesis and transpiration. At night, the PIP2-1 gene is also upregulated with increased relative air humidity. This gene expression pattern may allow desert plants to regulate foliar water uptake to adapt to extreme drought. This study suggests a molecular basis of foliar water uptake in desert plants. Published by Oxford University Press on behalf of the Annals of Botany Company.

Out of the Desert: My Journey from Nomadic Bedouin to the Heart of Global Oil

KAUST Repository

Al-Naimi, Ali Ibrahim

2017-01-01

Arabian deserts. From his first job as a shepherd boy to his appointment to one of the most powerful political and economic jobs in the world, Out of the Desert charts Al-Naimi's extraordinary rise to power.

Water quality and hydrology of the Lac Vieux Desert watershed, Gogebic County, Michigan, and Vilas County, Wisconsin, 2002-04

Science.gov (United States)

Weaver, T.L.; Neff, B.P.; Ellis, J.M.

2005-01-01

Lac Vieux Desert is a prominent 6.6 square-mile lake that straddles the Michigan-Wisconsin border and forms the headwaters of the Wisconsin River. For generations, the Lac Vieux Desert Band of Lake Superior Chippewa Indians have used Lac Vieux Desert and the surrounding area for growing and harvesting wild rice, and hunting and fishing. The Lac Vieux Desert Band is concerned about the impact of lake-stage regulation on hydrology and ecology, and the impact on water quality of development along and near the shore, and recreational watercraft use and sport fishing. In 2005, the U.S. Geological Survey completed a water-resources investigation of the Lac Vieux Desert watershed in cooperation with the Lac Vieux Desert Band of Lake Superior Chippewa Indians.Water quality of Lac Vieux Desert is typical of many lakes in the northern United States. Trophic State Index calculations classify Lac Vieux Desert as a highly productive eutrophic lake. The pH of water in Lac Vieux Desert ranged from 6.5 to 9.5, and specific conductance ranged from 62 to 114 µs/cm. Chloride concentration was less than 1.5 mg/L, indicating little effect from septic-tank or road-salt input. Results indicate that the water can be classified as soft, with hardness concentrations reported as calcium carbonate ranging from 29 to 49 mg/L. Concentrations of calcium, magnesium, chloride, and other dissolved solids ranged from 47 to 77 mg/L. Alkalinity of Lac Vieux Desert ranged from 27 to 38 mg/L.Pervasive aquatic blooms, including a bloom noted during the September 2003 sampling, are apparently common in late summer. Biological productivity at Lac Vieux Desert does not appear to have changed appreciably between 1973 and 2004. In the current study, total phosphorus concentrations ranged from 0.01 to 0.064 mg/L and dissolved nitrite plus nitrate nitrogen concentrations ranged from at, or below detection limit to 0.052 mg/L. Overabundance of nutrients in Lac Vieux Desert, particularly nitrogen and phosphorus

Biotechnological Applications Derived from Microorganisms of the Atacama Desert

Directory of Open Access Journals (Sweden)

Armando Azua-Bustos

2014-01-01

Full Text Available The Atacama Desert in Chile is well known for being the driest and oldest desert on Earth. For these same reasons, it is also considered a good analog model of the planet Mars. Only a few decades ago, it was thought that this was a sterile place, but in the past years fascinating adaptations have been reported in the members of the three domains of life: low water availability, high UV radiation, high salinity, and other environmental stresses. However, the biotechnological applications derived from the basic understanding and characterization of these species, with the notable exception of copper bioleaching, are still in its infancy, thus offering an immense potential for future development.

The influence of vegetation, mesoclimate and meteorology on urban atmospheric microclimates across a coastal to desert climate gradient.

Science.gov (United States)

Crum, Steven M; Shiflett, Sheri A; Jenerette, G Darrel

2017-09-15

Many cities are increasing vegetation in part due to the potential for microclimate cooling. However, the magnitude of vegetation cooling and sensitivity to mesoclimate and meteorology are uncertain. To improve understanding of the variation in vegetation's influence on urban microclimates we asked: how do meso- and regional-scale drivers influence the magnitude and timing of vegetation-based moderation on summertime air temperature (T a ), relative humidity (RH) and heat index (HI) across dryland cities? To answer this question we deployed a network of 180 temperature sensors in summer 2015 over 30 high- and 30 low-vegetated plots in three cities across a coastal to inland to desert climate gradient in southern California, USA. In a followup study, we deployed a network of temperature and humidity sensors in the inland city. We found negative T a and HI and positive RH correlations with vegetation intensity. Furthermore, vegetation effects were highest in evening hours, increasing across the climate gradient, with reductions in T a and increases in RH in low-vegetated plots. Vegetation increased temporal variability of T a , which corresponds with increased nighttime cooling. Increasing mean T a was associated with higher spatial variation in T a in coastal cities and lower variation in inland and desert cities, suggesting a climate dependent switch in vegetation sensitivity. These results show that urban vegetation increases spatiotemporal patterns of microclimate with greater cooling in warmer environments and during nighttime hours. Understanding urban microclimate variation will help city planners identify potential risk reductions associated with vegetation and develop effective strategies ameliorating urban microclimate. Published by Elsevier Ltd.

Temporal dynamics of hot desert microbial communities reveal structural and functional responses to water input.

Science.gov (United States)

Armstrong, Alacia; Valverde, Angel; Ramond, Jean-Baptiste; Makhalanyane, Thulani P; Jansson, Janet K; Hopkins, David W; Aspray, Thomas J; Seely, Mary; Trindade, Marla I; Cowan, Don A

2016-09-29

The temporal dynamics of desert soil microbial communities are poorly understood. Given the implications for ecosystem functioning under a global change scenario, a better understanding of desert microbial community stability is crucial. Here, we sampled soils in the central Namib Desert on sixteen different occasions over a one-year period. Using Illumina-based amplicon sequencing of the 16S rRNA gene, we found that α-diversity (richness) was more variable at a given sampling date (spatial variability) than over the course of one year (temporal variability). Community composition remained essentially unchanged across the first 10 months, indicating that spatial sampling might be more important than temporal sampling when assessing β-diversity patterns in desert soils. However, a major shift in microbial community composition was found following a single precipitation event. This shift in composition was associated with a rapid increase in CO 2 respiration and productivity, supporting the view that desert soil microbial communities respond rapidly to re-wetting and that this response may be the result of both taxon-specific selection and changes in the availability or accessibility of organic substrates. Recovery to quasi pre-disturbance community composition was achieved within one month after rainfall.

Temporal dynamics of hot desert microbial communities reveal structural and functional responses to water input

Energy Technology Data Exchange (ETDEWEB)

Armstrong, Alacia; Valverde, Angel; Ramond, Jean-Baptiste; Makhalanyane, Thulani P.; Jansson, Janet K.; Hopkins, David W.; Aspray, Thomas J.; Seely, Mary; Trindade, Marla I.; Cowan, Don A.

2016-09-29

The temporal dynamics of desert soil microbial communities are poorly understood. Given the implications for ecosystem functioning under a global change scenario, a better understanding of desert microbial community stability is crucial. Here, we sampled soils in the central Namib Desert on sixteen different occasions over a one-year period. Using Illumina-based amplicon sequencing of the 16S rRNA gene, we found that α-diversity (richness) was more variable at a given sampling date (spatial variability) than over the course of one year (temporal variability). Community composition remained essentially unchanged across the first 10 months, indicating that spatial sampling might be more important than temporal sampling when assessing β-diversity patterns in desert soils. However, a major shift in microbial community composition was found following a single precipitation event. This shift in composition was associated with a rapid increase in CO2 respiration and productivity, supporting the view that desert soil microbial communities respond rapidly to re-wetting and that this response may be the result of both taxon-specific selection and changes in the availability or accessibility of organic substrates. Recovery to quasi pre-disturbance community composition was achieved within one month after rainfall.

Landscape-scale distribution and density of raptor populations wintering in anthropogenic-dominated desert landscapes

Science.gov (United States)

Adam E. Duerr; Tricia A. Miller; Kerri L. Cornell Duerr; Michael J. Lanzone; Amy Fesnock; Todd E. Katzner

2015-01-01

Anthropogenic development has great potential to affect fragile desert environments. Large-scale development of renewable energy infrastructure is planned for many desert ecosystems. Development plans should account for anthropogenic effects to distributions and abundance of rare or sensitive wildlife; however, baseline data on abundance and distribution of such...

Study of the microwave emissivity characteristics over Gobi Desert

International Nuclear Information System (INIS)

Yubao, Qiu; Lijuan, Shi; Wenbo, Wu

2014-01-01

The microwave emissivity represents the capacity of the thermal radiation of the surface, and it is the significant parameter for understanding the geophysical processes such as surface energy budget and surface radiation. Different land covers have different emissivity properties, and the Gobi Desert in Central Asia seriously impact the sandstorms occur and develop in China, because of its special geographical environment and surface soil characteristics. In this study half-month averaged microwave emissivity from March 2003 to February 2004 over the Gobi Desert has been estimated. Emissivities in this area at different frequencies, polarization and their seasonal variations are discussed respectively. The results showed that emissivity polarization difference decrease as the frequency increases, and the polarization difference is large (0.03–0.127). The H polarization emissivity increases with increasing frequency, but the V-polarized microwave emissivity is reduced with increasing frequency because of the body scattering. In winter, emissivity decreases sharply in snow covered area, especially for higher frequencies (such as 89GHz). In addition, we compared emissivity with MODIS NDVI data at the same time in the Gobi Desert, and the results indicate that NDVI derived the good negative correlation with microwave emissivity polarization difference at 37GHz

Isotopic characterization and genetic origin of crude oils from Gulf of Suez and western desert fields in Egypt

International Nuclear Information System (INIS)

Abd El Samie, S.G.

2006-01-01

Stable carbon isotopes were used to asses the general characteristics of the western desert and Gulf of Suez crude oils in accordance with hydrocarbon generation, source rocks, thermal gradient and maturation level. The carbon isotopic results of all the analyzed oil samples in both areas lie in the range from -29.62 to -24.11 %. The av. σ 13 C values in the Gulf of Suez reaches about -28.6% and -26.4% in western desert. It was accounted a marginal difference between the two areas by about 2.5 : 3% in carbon-13 isotope of the whole oil indicated two distinct oil types of different organic input and varies in the depositional environment. It was found that Gulf of Suez oils are dominated by marine organic matter (plankton algae) deposited in saline environment. The derived oils from the northern and central provinces of the Gulf are isotopically light, higher in sulfur content, lower in API gravity degree and have Pristane/Phytane (Pr/Ph) ratio less than or equal one (Pr/Ph = 1). In the southern province, about 0.5% isotopic enrichment was recorded in the produced oils from shallower depths, associated with gradual increment in API and maturity level as thermal gradient increase. However, low API gravity degree and less maturity of the Gulf of Suez oils could be related to the rifting temperature that forced and accelerated the expulsion rate and hydrocarbon generation prior reaching higher maturation levels. On the other hand, the produced oils from the western desert fields belong mostly to terrestrial organic debris (with minor marine fragment in some basins) deposited at deeper geological formations. It is characterized by isotopic enrichment, paraffinic waxy oils, low in sulphur content, have Pr/Ph = 1, high in API gravity and maturity level. Hydrocarbon generated from the western desert fields has been controlled by time-temperature effect in the source rocks and reservoirs where the humic organic matter are affected by high temperature over longer period of

Biological Communities in Desert Varnish and Potential Implications for Varnish Formation Mechanisms

Science.gov (United States)

Lang-Yona, Naama; Maier, Stefanie; Macholdt, Dorothea; Rodriguez-Caballero, Emilio; Müller-Germann, Isabell; Yordanova, Petya; Jochum, Klaus-Peter; Andreae, Meinrat O.; Pöschl, Ulrich; Weber, Bettina; Fröhlich-Nowoisky, Janine

2017-04-01

Desert varnishes are thin, orange to black coatings found on rocks in arid and semi-arid environments on Earth. The formation mechanisms of rock varnish are still under debate and the involvement of microorganisms in this process remains unclear. In this work we aimed to identify the microbial community occurring in rock varnish to potentially gain insights into the varnish formation mechanism. For this purpose, rocks coated with desert varnish were collected from the Anza-Borrego Desert, California, USA, as well as soils from underneath the rocks. DNA from both varnish coatings and soil samples was extracted and subsequently used for metagenomic analysis, as well as for q-PCR analyses for specific species quantification. The element composition of the varnish coatings was analyzed and compared to the soil samples. Rock varnish shows similar depleted elements, compared to soil, but Mn and Pb are 50-60 times enriched compared to the soil samples, and about 100 times enriched compared to the upper continental crust. Our genomic analyses suggest unique populations and different protein functional groups occurring in the varnish compared to soil samples. We discuss these differences and try to shed light on the mechanism of Mn oxyhydroxide production in desert varnish formation.

Female offspring desertion and male-only care increase with natural and experimental increase in food abundance

OpenAIRE

Eldegard, Katrine; Sonerud, Geir A.

2009-01-01

In species with biparental care, one parent may escape the costs of parental care by deserting and leaving the partner to care for the offspring alone. A number of theoretical papers have suggested a link between uniparental offspring desertion and ecological factors, but empirical evidence is scarce. We investigated the relationship between uniparental desertion and food abundance in a natural population of Tengmalm's owl Aegolius funereus, both by means of a 5-year observational study and a...

Abiotic drivers of Chihuahuan Desert plant communities

Science.gov (United States)

Laura Marie Ladwig

2014-01-01

Within grasslands, precipitation, fire, nitrogen (N) addition, and extreme temperatures influence community composition and ecosystem function. The differential influences of these abiotic factors on Chihuahuan Desert grassland communities was examined within the Sevilleta National Wildlife Refuge, located in central New Mexico, U.S.A. Although fire is a natural...

Regional Landscape System Protection in the Urbanising Desert Southwest: Lessons from the Phoenix Metropolitan Region, USA

Directory of Open Access Journals (Sweden)

Laura Musacchio

2004-06-01

Full Text Available Since the late nineteenth century, landscape protection in the deserts of the Southwest, United States of America, like many places worldwide, has been driven by the conservation of landscape icons, such as unusual geological features in wilderness areas. Yet, in the past two decades, leading conservation scholars worldwide have called for a shift in this paradigm to one that emphasises landscape systems, which is based on holistic landscape ecology. The shift in emphas is to landscape systems opens new opportunities to protect desert landscape systems at the regional scale rather than just remnant patches at the local scale. In this paper, the authors present, for public consideration, a typology of the five major desert landscapes that can be used as the bas is for protecting regional landscape systems in the deserts of the Southwest. As a case study, several representative examples of recent regional open space plans from the Phoenix metropolitan area are analysed and compared with the typology in order to understand how successfully the projects have addressed protection of the regional landscape system in the Sonoran Desert.

Anthropogenic water sources and the effects on Sonoran Desert small mammal communities

OpenAIRE

Aaron B. Switalski; Heather L. Bateman

2017-01-01

Anthropogenic water sources (AWS) are developed water sources used as a management tool for desert wildlife species. Studies documenting the effects of AWS are often focused on game species; whereas, the effects on non-target wildlife are less understood. We used live trapping techniques to investigate rodent abundance, biomass, and diversity metrics near AWS and paired control sites; we sampled vegetation to determine rodent-habitat associations in the Sauceda Mountains of the Sonoran Desert...

Physiological conjunction of allelochemicals and desert plants.

Science.gov (United States)

Yosef Friedjung, Avital; Choudhary, Sikander Pal; Dudai, Nativ; Rachmilevitch, Shimon

2013-01-01

Plants exchange signals with other physical and biological entities in their habitat, a form of communication termed allelopathy. The underlying principles of allelopathy and secondary-metabolite production are still poorly understood, especially in desert plants. The coordination and role of secondary metabolites were examined as a cause of allelopathy in plants thriving under arid and semiarid soil conditions. Desert plant species, Origanum dayi, Artemisia sieberi and Artemisia judaica from two different sources (cultivar cuttings and wild seeds) were studied in their natural habitats. Growth rate, relative water content, osmotic potential, photochemical efficiency, volatile composition and vital factors of allelopathy were analyzed at regular intervals along four seasons with winter showing optimum soil water content and summer showing water deficit conditions. A comprehensive analysis of the volatile composition of the leaves, ambient air and soil in the biological niche of the plants under study was carried out to determine the effects of soil water conditions and sample plants on the surrounding flora. Significant morpho-physiological changes were observed across the seasons and along different soil water content. Metabolic analysis showed that water deficit was the key for driving selective metabolomic shifts. A. judaica showed the least metabolic shifts, while A. sieberi showed the highest shifts. All the species exhibited high allelopathic effects; A. judaica displayed relatively higher growth-inhibition effects, while O. dayi showed comparatively higher germination-inhibition effects in germination assays. The current study may help in understanding plant behavior, mechanisms underlying secondary-metabolite production in water deficit conditions and metabolite-physiological interrelationship with allelopathy in desert plants, and can help cull economic benefits from the produced volatiles.