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Sample records for africa showing desert

  1. Namib Desert, Namibia, Africa

    NASA Technical Reports Server (NTRS)

    1990-01-01

    One of the driest regions on Earth, the Namib Desert, Namibia, Africa (23.0N, 15.0E) lies adjacent to the Atlantic coast but upwelling oceanic water causes a very stable rainless atmosphere. The few local inland rivers do not reach the sea but instead appear as long indentations where rivers penetrate the dune fields and end as small dry lakes. The vast dune fields are the result of sands deposited over millions of years by the stream flow.

  2. Namib Desert, Namibia, Africa

    NASA Technical Reports Server (NTRS)

    1990-01-01

    One of the driest regions on Earth, the Namib Desert, Namibia, Africa (23.0N, 15.0E) lies adjacent to the Atlantic coast but the upwelling oceanic water causes a very stable rainless atmosphere. The few local inland rivers do not reach the sea but instead, appear as long indentations where they penetrate the dune fields and end as small dry lakes. The vast dune fields are the result of sands deposited over millions of years by the stream flow.

  3. Libyan Desert, Libya, Africa

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Desert landscapes such as this part of the northern Sahara (27.0N, 11.0E) may be analogous to other planets which have no soil or plant growth. The dark rocks in this view are probably volcanic in origin and have many stream beds leading into the dune areas. These stream beds carry sediments towards the lower terrain where the water evaporates, leaving the sediments to be wind blown into the complex dune patterns. The red color comes from iron oxides.

  4. Fog Bank, Namib Desert, Namibia, Africa

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Fog is the only source of moisture for desert dwelling animals and plants living in the Namib Desert sand dune field, Namibia (23.5N, 15.0E). Coastal stratus clouds provide most of the life supporting moisture as fog droplets in this arid land where the usual annual rainfall is less than a quarter of an inch for decades at a time. In this view, the stratus clouds over the coast conform to the dune pattern proving that the fog is in ground contact.

  5. Holocene Paleoecology of the Western Tenere Desert, Niger, Africa

    NASA Astrophysics Data System (ADS)

    Sereno, P. C.; Caran, S. C.; Housh, T. B.

    2007-12-01

    Multiple paleontological, sedimentological, and isotopic/ionic geochemical indicators permit reconstruction of the Holocene ecology of the western Tenere Desert (southern Sahara hyper-desert). Modern precipitation is highly erratic, averaging 25 mm yearly, and vegetative cover is negligible. From the early to middle Holocene, however, grassland-shrublands and seasonal to permanent lakes and wetlands predominated, supporting diverse limnic, riparian, and upland communities. Annual precipitation probably was comparable to that of the modern southern Sahel, exceeding 350 mm. Coarse-grained sediment washed into the large lacustrine basin from exposures of metamorphic, plutonic, and volcanic rocks in the nearby Air Massif highland. Lake margins fluctuated in response to runoff and limited ground-water discharge. The water was non-saline and there is no evidence of evaporite deposition. Aquatic and riparian macrophytes thrived, as did an extensive lacustrine-palustrine macrofauna. A Sahelian flora of mixed grasses, thorn shrubs, and perhaps some larger woodland species occupied the contiguous uplands, supporting resident and migratory mammalian and avian faunas. Lake levels were high until 6300 to 5200 BP, possibly as late as 4800 BP locally. Deflation of lacustrine deposits during a subsequent dry period provided finer-grained eolian sediment accreting as proximal dunes. The composition of mineral sediment within the middle to late Holocene dunes is different from, but clearly a subset of the lacustrine deposits. Organic matter reworked from the lake sediment was deposited in the dunes and oxidized in situ, generating CO2 that dissolved in soil moisture, producing bicarbonate. The bicarbonate reacted with calcium from weathered minerals, producing calcic cementation about 5100 BP. The resulting petrocalcic horizon was later exposed, weathered, and colonized by sparse terrestrial vegetation for one or more brief periods. A late phase of pedogenesis concurrent with or

  6. What is the impact of Harmattan surges on desert dust emission in North Africa?

    NASA Astrophysics Data System (ADS)

    Fiedler, Stephanie; Kaplan, Michael L.; Knippertz, Peter

    2015-04-01

    Desert dust aerosols have important implications in the Earth system, but their emission amount has a large model uncertainty. Improving the most important meteorological processes for dust-emitting winds helps to reduce this uncertainty. However, the dominant meteorological mechanisms for the large dust emission during spring remain unclear. This time of year is characterized by mobile, long-lived cyclones and Harmattan surges which are capable to uplift dust aerosol for long-range atmospheric transport. Emission near to the centre of mobile, long-lived cyclones are associated with a small mass of dust emission over the northern Sahara in spring, despite their most frequent occurrence in this season. Harmattan surges are proposed to be more efficient in emitting dust aerosol in spring. These events manifest themselves as a postfrontal strengthening of near-surface winds with a continental impact on dust emission. The present study shows the first long-term climatology of dust emission associated with Harmattan surges over North Africa. Using a newly-developed automated identification, Harmattan surges are statistically analysed in 32 years of ERA-Interim re-analysis from the European Centre for Medium-Range Weather Forecasts. The results show 34 events per year in the annual mean. Spring is herein the most active season with the largest mean number and duration of Harmattan surges, in contrast to summer with virtually no activity. The offline dust emission model by Tegen et al (2002) is used to calculate emissions with ERA-Interim data. Combining these results with the Harmattan surges allows a first quantitative estimate of the associated emission mass. The results highlight that a fraction of 32 % of the total emission is associated with these events, annually and spatially averaged across North Africa. This amount exceeds the annual mean contribution of nocturnal low-level jets to dust emission, which is known as one of the most important drivers for North

  7. Remote sensing experiment in West Africa. [drought effects on desert agriculture and vegetation in Niger

    NASA Technical Reports Server (NTRS)

    Macleod, N. H.

    1974-01-01

    There are substantial needs of the Sahelien Zone to detail the state of regional agricultural resources in the face of a sixth year of serious drought conditions. While most of the work has been done in the Republic of Niger, the principles which have emerged from the analysis seem to be applicable to much of the Sahel. The discussion relates to quite specific rehabilitation and development initiations under consideration in Niger which are based in part upon direct analysis of ERTS imagery of the country, in part on field surveys and on discussions with Nigerian officials and technicians. Again, because the entire Sahelien Zone (including Niger) has large zones of similar ecologic characteristics, modificiations of the approaches suggested for Niger are applicable to the solution of rehabilitation of the desert, the savannah and the woodlands of West Africa in general.

  8. A study of morphology, provenance, and movement of desert sand seas in Africa, Asia, and Australia

    NASA Technical Reports Server (NTRS)

    Mckee, E. D. (Principal Investigator); Breed, C. S.

    1973-01-01

    The author has identified the following significant results. Recent acquisition of generally high quality color prints for most of the test sites has enabled the project to make significant advances in preparing mosaics of sand desert areas under study. Computer enhancement of imagery of selected sites, where details of complex dune forms need to be determined, has been achieved with arrival of computer-compatible ERTS-1 tapes. Further, a comparator, recently received, gives precise visual measurements of width, length, and spacing of sand bodies and so improves comparison of patterns in various test sites. Considerable additional meteorological data recently received on sand-moving winds in China, Pakistan, Libya and other areas enabled much progress to be made in developing overlays for the dune mosaics. These data show direction, speed, and frequency of winds. Other new data for use in preparing overlays used with ERTS-1 image mosaics include ground truth on moisture control, geologic settings, and plant distribution. With the addition of visual observation data and prints from hand-held photography now being obtained by the Skylab mission, much progress in interpreting the patterns of sand seas for 17 desert sites is anticipated.

  9. A study of morphology, provenance, and movement of desert sand seas in Africa, Asia, and Australia

    NASA Technical Reports Server (NTRS)

    Mckee, E. D. (Principal Investigator); Breed, C. S.

    1974-01-01

    The author has identified the following significant results. Recent acquisition of generally high quality color prints for most of the test sites has enabled this project to make significant advances in preparing mosaics of sand desert areas under study. Computer enhancement of imagery, where details of complex dune forms need to be determined, has been achieved with arrival of computer-compatible ERTS-1 tapes. Further, a comparator, recently received, gives precise visual measurements of width, length, and spacing of sand bodies and so improves comparison of patterns in various test sites. Considerable additional meteorological data recently received on sand-moving winds in China, Pakistan, Libya, and other study areas enabled much progress to be made in developing overlays for the dune mosaics. These data show direction, speed, and frequency of winds. Other new data for use in preparing overlays used with ERTS-1 image mosaics include ground truth on moisture control, geologic settings, and plant distribution. With the addition of visual observation data and prints from hand-held photography now being obtained by the Skylab 4 mission, much progress in interpreting the patterns of sand seas for 17 desert sites is anticipated.

  10. Combining sky and earth: desert ants (Melophorus bagoti) show weighted integration of celestial and terrestrial cues.

    PubMed

    Legge, Eric L G; Wystrach, Antoine; Spetch, Marcia L; Cheng, Ken

    2014-12-01

    Insects typically use celestial sources of directional information for path integration, and terrestrial panoramic information for view-based navigation. Here we set celestial and terrestrial sources of directional information in conflict for homing desert ants (Melophorus bagoti). In the first experiment, ants learned to navigate out of a round experimental arena with a distinctive artificial panorama. On crucial tests, we rotated the arena to create a conflict between the artificial panorama and celestial information. In a second experiment, ants at a feeder in their natural visually-cluttered habitat were displaced prior to their homing journey so that the dictates of path integration (feeder to nest direction) based on a celestial compass conflicted with the dictates of view-based navigation (release point to nest direction) based on the natural terrestrial panorama. In both experiments, ants generally headed in a direction intermediate to the dictates of celestial and terrestrial information. In the second experiment, the ants put more weight on the terrestrial cues when they provided better directional information. We conclude that desert ants weight and integrate the dictates of celestial and terrestrial information in determining their initial heading, even when the two directional cues are highly discrepant. PMID:25324340

  11. Characterization of aerosolized bacteria and fungi from desert dust events in Mali, West Africa

    USGS Publications Warehouse

    Kellogg, C.A.; Griffin, Dale W.; Garrison, V.H.; Peak, K.K.; Royall, N.; Smith, R.R.; Shinn, E.A.

    2004-01-01

    Millions of metric tons of African desert dust blow across the Atlantic Ocean each year, blanketing the Caribbean and southeastern United States. Previous work in the Caribbean has shown that atmospheric samples collected during dust events contain living microbes, including plant and opportunistic human pathogens. To better understand the potential downwind public health and ecosystem effects of the dust microbes, it is important to characterize the source population. We describe 19 genera of bacteria and 3 genera of fungi isolated from air samples collected in Mali, a known source region for dust storms, and over which large dust storms travel.

  12. A study of morphology, provenance, and movement of desert sand seas in Africa, Asia, and Australia

    NASA Technical Reports Server (NTRS)

    Mckee, E. D. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. The most significant result to date is recongition that complexes are indeed visible on ERTS-1 images, and that the extent and nature of dune fields in many remote areas of the world can, for the first time, be observed almost simultaneously and directly compared. The primary scientific problem is to determine accurately the relationships among certain patterns, trends, and boundaries clearly revealed on ERTS-1 imagery to true surface configurations of desert landforms, and further, to relate the defined features to controlling factors such as wind direction and intensity, moisture in the air and on the ground and barriers to sand movement. It is hoped to produce, by photographic and cartographic extraction from ERTS-1 images, a set of thematic maps that will illustrate the relationships of optical appearance of various materials and effects of the color of various sand bodies upon ERTS-1 images.

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

    USGS Publications Warehouse

    Prose, D.V.

    1986-01-01

    Land disturbances caused by these training exercises are still evident today throughout the designated training areas (Lathrop, 1983; Prose, 1985; Prose and Metzger, 1985). The World War II base-camp locations are easily identified because the networks of dirt roads are still used by campers, hunters, artifact seekers, and other visitors. Vehicle trails and single tracks remain on many relatively stable surfaces and are most conspicuous on surfaces composed of a veneer of stones (desert pavement).

  14. Genetic analysis shows low levels of hybridization between African wildcats (Felis silvestris lybica) and domestic cats (F. s. catus) in South Africa

    PubMed Central

    Le Roux, Johannes J; Foxcroft, Llewellyn C; Herbst, Marna; MacFadyen, Sandra

    2015-01-01

    Hybridization between domestic and wild animals is a major concern for biodiversity conservation, and as habitats become increasingly fragmented, conserving biodiversity at all levels, including genetic, becomes increasingly important. Except for tropical forests and true deserts, African wildcats occur across the African continent; however, almost no work has been carried out to assess its genetic status and extent of hybridization with domestic cats. For example, in South Africa it has been argued that the long-term viability of maintaining pure wildcat populations lies in large protected areas only, isolated from human populations. Two of the largest protected areas in Africa, the Kgalagadi Transfrontier and Kruger National Parks, as well as the size of South Africa and range of landscape uses, provide a model situation to assess how habitat fragmentation and heterogeneity influences the genetic purity of African wildcats. Using population genetic and home range data, we examined the genetic purity of African wildcats and their suspected hybrids across South Africa, including areas within and outside of protected areas. Overall, we found African wildcat populations to be genetically relatively pure, but instances of hybridization and a significant relationship between the genetic distinctiveness (purity) of wildcats and human population pressure were evident. The genetically purest African wildcats were found in the Kgalagadi Transfrontier Park, while samples from around Kruger National Park showed cause for concern, especially combined with the substantial human population density along the park's boundary. While African wildcat populations in South Africa generally appear to be genetically pure, with low levels of hybridization, our genetic data do suggest that protected areas may play an important role in maintaining genetic purity by reducing the likelihood of contact with domestic cats. We suggest that approaches such as corridors between protected areas

  15. Genetic analysis shows low levels of hybridization between African wildcats (Felis silvestris lybica) and domestic cats (F. s. catus) in South Africa.

    PubMed

    Le Roux, Johannes J; Foxcroft, Llewellyn C; Herbst, Marna; MacFadyen, Sandra

    2015-01-01

    Hybridization between domestic and wild animals is a major concern for biodiversity conservation, and as habitats become increasingly fragmented, conserving biodiversity at all levels, including genetic, becomes increasingly important. Except for tropical forests and true deserts, African wildcats occur across the African continent; however, almost no work has been carried out to assess its genetic status and extent of hybridization with domestic cats. For example, in South Africa it has been argued that the long-term viability of maintaining pure wildcat populations lies in large protected areas only, isolated from human populations. Two of the largest protected areas in Africa, the Kgalagadi Transfrontier and Kruger National Parks, as well as the size of South Africa and range of landscape uses, provide a model situation to assess how habitat fragmentation and heterogeneity influences the genetic purity of African wildcats. Using population genetic and home range data, we examined the genetic purity of African wildcats and their suspected hybrids across South Africa, including areas within and outside of protected areas. Overall, we found African wildcat populations to be genetically relatively pure, but instances of hybridization and a significant relationship between the genetic distinctiveness (purity) of wildcats and human population pressure were evident. The genetically purest African wildcats were found in the Kgalagadi Transfrontier Park, while samples from around Kruger National Park showed cause for concern, especially combined with the substantial human population density along the park's boundary. While African wildcat populations in South Africa generally appear to be genetically pure, with low levels of hybridization, our genetic data do suggest that protected areas may play an important role in maintaining genetic purity by reducing the likelihood of contact with domestic cats. We suggest that approaches such as corridors between protected areas

  16. Middle Palaeolithic occupation in the Thar Desert during the Upper Pleistocene: the signature of a modern human exit out of Africa?

    NASA Astrophysics Data System (ADS)

    Blinkhorn, James; Achyuthan, Hema; Petraglia, Michael; Ditchfield, Peter

    2013-10-01

    The Thar Desert marks the transition from the Saharo-Arabian deserts to the Oriental biogeographical zone and is therefore an important location in understanding hominin occupation and dispersal during the Upper Pleistocene. Here, we report the discovery of stratified Middle Palaeolithic assemblages at Katoati in the north-eastern Thar Desert, dating to Marine Isotope Stages (MIS) 5 and the MIS 4-3 boundary, during periods of enhanced humidity. Hominins procured cobbles from gravels at the site as evidenced by early stages of stone tool reduction, with a component of more formalised point production. The MIS 5c assemblages at Katoati represent the earliest securely dated Middle Palaeolithic occupation of South Asia. Distinctive artefacts identified in both MIS 5 and MIS 4-3 boundary horizons match technological entities observed in Middle Palaeolithic assemblages in South Asia, Arabia and Middle Stone Age sites in the Sahara. The evidence from Katoati is consistent with arguments for the dispersal of Homo sapiens populations from Africa across southern Asia using Middle Palaeolithic technologies.

  17. Early Cretaceous counterclockwise rotation of Northeast Africa within the equatorial zone: Paleomagnetic study on Mansouri ring complex, Southeastern Desert, Egypt

    NASA Astrophysics Data System (ADS)

    Lotfy, Hamza I.

    2015-06-01

    The Mansouri ring complex (132 Ma) is, paleomagnetically, studied to shed light on the paleo-tectonic position of Northeast Africa during the Early Cretaceous. Progressive thermal demagnetization of all samples verified a general bi-vectorial decay of the natural remanence. After the removal of the present-day field overprint, the decaying anchored component was either: A dual-polarity, shallow NW-SE directed component residing in magnetite (400-585 °C) of shiny fresh samples, or, A normal-polarity, medium-inclination, north-oriented component stored in haematite of few reddish ferruginous sites. This component was considered as chemical remagnetization carried by secondary haematite. Due to its steady stability, overwhelming existence in most sites, positive reversal test and its residence in fresh-samples' magnetite, the first dual-polarity, shallow NW-SE component, was considered as the characteristic remanent magnetization [ChRM] representing the paleomagnetic field during cooling of the Mansouri ring complex. The mean paleomagnetic pole of the isolated ChRM was at 47°N/259°E, Dp/Dm = 3.4°/6.6°. This Hauterivian pole from Egypt shows reasonable consistency with its coeval poles rotated from the main tectonic units to Northeast Africa. It reveals that in Early Cretaceous: Northeast Africa was equatorial, lying just south the Equator. Cairo, which is now at 30°N, was at -1.5° paleo-latitude. The Azimuth of the African Plate was NE-SW, about 30° clockwise with respect to the present-day N-S trend. Comparing this Hauterivian pole to that of the Wadi Natash basalts [107 ± 4 Ma], which was at [55°N/250°E] during the Albian, the African Plate seems to have rotated counter-clockwise about 10° with Northeast Africa moving northwards [Cairo was moving from 1.5°S to 1.5°N] within the equatorial zone, during the Early Cretaceous.

  18. Tectonic and provenance history of the Neotethyan margin in NE Africa recorded by detrital zircon (U-Th)/He thermochronometry from a borehole in the Western Desert, Egypt

    NASA Astrophysics Data System (ADS)

    Stockli, D.; Glauser, T.; Bosworth, W.; Maher, T.; Clare, A.

    2009-04-01

    The subsurface of the Western Desert of Egypt contains multiple stacked sedimentary basin deposits separated by major unconformities reflecting the long-lived tectonic evolution of the Neotethyan continental margin in eastern North Africa. In this study, zircon (U/Th)/He (ZHe) data were collected from cuttings from a ~15000 ft borehole that penetrated Tertiary and Cretaceous strata and a major erosional unconformity at 13000 ft that juxtaposes Cretaceous and Cambro-Ordovician strata. A total of 56 samples spanning the borehole from 750-15400 ft yielded >200 single-grain ZHe ages in order to elucidate the thermal evolution of the borehole and constrain the thermal history of detrital provenance. ZHe ages above the unconformity are significantly older than the depositional age, suggesting detrital ZHe ages that were not reset subsequent to deposition. ZHe ages from Cambro-Ordovician strata below the unconformity are substantially younger than the minimum depositional age suggesting major cooling and resetting of zircon (>200C) during the Hercynian orogeny. In detail, ZHe ages form Cretaceous strata above the unconformity show the following trends. (1) ZHe ages from 6000-9000 ft (Aptian-Early Cenomanian) are characterized by a ZHe age peak at ~450 Ma and a minor Albian peak, (2) samples from 9000-12000 ft (Late Hauterivian-Barremian) show two major detrital ZHe age peaks at ~450 and 350 Ma, while (3) samples from 12000-13000 ft (Early Hauterivian) exhibit three dominant ZHe age components at ~450 Ma, 350 Ma, and 170-200 Ma. Additional cuttings from an offset containing complete stratigraphy yielded ZHe ages that mainly represent a strong Hercynian input as well as Late Triassic and Early Jurassic components of Tethyan related input. These ZHe age peaks display provenance characteristics typical for cooling signatures of rocks from the eroding Arabian-Nubian Shield, a North-African Hercynian source, and eroded material from exhumed fault blocks along the Triassic

  19. Desert Survivors!

    ERIC Educational Resources Information Center

    Horton, Jessica; Friedenstab, Steve

    2013-01-01

    This article describes a special third-grade classroom unit based on the reality show "Survivor." The goal of this engaging and interactive unit was to teach students about physical and behavioral adaptations that help animals survive in various desert biomes. The activity combines research, argument, and puppet play over one week of…

  20. Africa.

    ERIC Educational Resources Information Center

    Happel, Sue; Loeb, Joyce

    Although the activities in this unit are designed primarily for students in the intermediate grades, the document's text, illustrations, and bibliographic references are suitable for anyone interested in learning about Africa. Following a brief introduction and map work, the document is arranged into six sections. Section 1 traces Africa's history…

  1. Africa.

    ERIC Educational Resources Information Center

    Martz, Carlton

    2001-01-01

    This publication explores issues related to Africa. It examines the U.S. response to the Barbary pirate states (Morocco, Algiers, Tunis, Tripoli) in the early 19th century; the current AIDS crisis in Africa; and 14th century Mali and other Islamic lands through the eyes of Ibn Battuta, who traveled throughout the Muslim world. Each article…

  2. Intercomparison and Validation of AIRS, MODIS, and ASTER Land Surface Emissivity Products over the Namib and Kalahari Deserts in Southern Africa

    NASA Astrophysics Data System (ADS)

    Hulley, G.; Hook, S.

    2008-12-01

    Land surface emissivity is a critical parameter for retrieving land surface temperatures from spaceborne Thermal Infrared (TIR) measurements. Land Surface Temperature and Emissivity (LST&E) data are key parameters in global climate change studies that involve climate modeling, ice dynamic analyses, surface- atmosphere interactions and land use, land cover change. The errors in retrievals of atmospheric temperature and moisture profiles from hyperspectral infrared radiances, such as those from the Atmospheric Infrared Sounder (AIRS) on NASA's Aqua satellite, are strongly dependent on using constant or inaccurate surface emissivities, particularly over arid and semi-arid regions where the variation in emissivity is large, both spatially and spectrally. LST&E products are available from spaceborne sensors such as AIRS, MODIS and ASTER at varying spatial, spectral, temporal resolutions, and using different retrieval algorithms. ASTER provides LST&E data with the highest spatial resolution (90 m), compared with AIRS (50 km) and MODIS (1 and 5 km). AIRS has the highest spectral sampling and both AIRS and MODIS acquire data at much higher temporal frequencies (every 2-3 days) compared with ASTER (every 16 days). In this paper we present validation and intercomparisons of AIRS, MODIS and ASTER emissivity products over the Namib and Kalahari deserts in Southern Africa. The Namib, Africa's second largest desert, and the Kalahari cover areas of 80,900 and 900, 000 km² respectively and consist of pure quartz, giving the sand a deep red color. The dunes provide excellent areas for validation as they have little or no vegetation, are spatially homogeneous with known composition, and have large spectral variations in TIR emissivity. MODIS and ASTER data will be upsampled to the AIRS spatial resolution, and then compared to the emissivities of in-situ sand samples collected at designated areas at Sossusvlei in the Namib dunes and Kgalagadi Transfrontier Park in the Kalahari. The

  3. Immune indexes of larks from desert and temperate regions show weak associations with life history but stronger links to environmental variation in microbial abundance.

    PubMed

    Horrocks, Nicholas P C; Hegemann, Arne; Matson, Kevin D; Hine, Kathryn; Jaquier, Sophie; Shobrak, Mohammed; Williams, Joseph B; Tinbergen, Joost M; Tieleman, B Irene

    2012-01-01

    Immune defense may vary as a result of trade-offs with other life-history traits or in parallel with variation in antigen levels in the environment. We studied lark species (Alaudidae) in the Arabian Desert and temperate Netherlands to test opposing predictions from these two hypotheses. Based on their slower pace of life, the trade-off hypothesis predicts relatively stronger immune defenses in desert larks compared with temperate larks. However, as predicted by the antigen exposure hypothesis, reduced microbial abundances in deserts should result in desert-living larks having relatively weaker immune defenses. We quantified host-independent and host-dependent microbial abundances of culturable microbes in ambient air and from the surfaces of birds. We measured components of immunity by quantifying concentrations of the acute-phase protein haptoglobin, natural antibody-mediated agglutination titers, complement-mediated lysis titers, and the microbicidal ability of whole blood. Desert-living larks were exposed to significantly lower concentrations of airborne microbes than temperate larks, and densities of some bird-associated microbes were also lower in desert species. Haptoglobin concentrations and lysis titers were also significantly lower in desert-living larks, but other immune indexes did not differ. Thus, contrary to the trade-off hypothesis, we found little evidence that a slow pace of life predicted increased immunological investment. In contrast, and in support of the antigen exposure hypothesis, associations between microbial exposure and some immune indexes were apparent. Measures of antigen exposure, including assessment of host-independent and host-dependent microbial assemblages, can provide novel insights into the mechanisms underlying immunological variation. PMID:22902379

  4. Ash from the Toba supereruption in Lake Malawi shows no volcanic winter in East Africa at 75 ka

    PubMed Central

    Lane, Christine S.; Chorn, Ben T.; Johnson, Thomas C.

    2013-01-01

    The most explosive volcanic event of the Quaternary was the eruption of Mt. Toba, Sumatra, 75,000 y ago, which produced voluminous ash deposits found across much of the Indian Ocean, Indian Peninsula, and South China Sea. A major climatic downturn observed within the Greenland ice cores has been attributed to the cooling effects of the ash and aerosols ejected during the eruption of the Youngest Toba Tuff (YTT). These events coincided roughly with a hypothesized human genetic bottleneck, when the number of our species in Africa may have been reduced to near extinction. Some have speculated that the demise of early modern humans at that time was due in part to a dramatic climate shift triggered by the supereruption. Others have argued that environmental conditions would not have been so severe to have such an impact on our ancestors, and furthermore, that modern humans may have already expanded beyond Africa by this time. We report an observation of the YTT in Africa, recovered as a cryptotephra layer in Lake Malawi sediments, >7,000 km west of the source volcano. The YTT isochron provides an accurate and precise age estimate for the Lake Malawi paleoclimate record, which revises the chronology of past climatic events in East Africa. The YTT in Lake Malawi is not accompanied by a major change in sediment composition or evidence for substantial temperature change, implying that the eruption did not significantly impact the climate of East Africa and was not the cause of a human genetic bottleneck at that time. PMID:23630269

  5. Isolation and characterization of a radiation-resistant bacterium from Taklamakan Desert showing potent ability to accumulate Lead (II) and considerable potential for bioremediation of radioactive wastes.

    PubMed

    Luo, Xuesong; Zeng, Xian-Chun; He, Zhancan; Lu, Xiaolu; Yuan, Jie; Shi, Jingjing; Liu, Ming; Pan, Yunfan; Wang, Yan-Xin

    2014-12-01

    Radioactive wastes always contain radioactive substances and a lot of Pb compound and other heavy metals, which severely contaminate soils and groundwater. Thus, search for radiation-resistant microorganisms that are capable of sequestering Pb contaminants from the contaminated sites is urgently needed. However, very few such microorganisms have been found so far. In the present study, we discovered a novel Gram-negative bacterium from the arid Taklamakan desert, which can strongly resist both radiation and Pb(2+). Phylogenetic and phenotypic analysis indicated that this bacterial strain is closely affiliated with Microvirga aerilata, and was thus referred to as Microvirga aerilata LM (=CCTCC AB 208311). We found that M. aerilata LM can effectively accumulate Pb and form intracellular precipitations. It also keeps similar ability to remove Pb(2+) under radioactive stress. Our data suggest that M. aerilata LM may offer an effective and eco-friendly in situ approach to remove soluble Pb contaminants from radioactive wastes. PMID:25182517

  6. Desert Communities.

    ERIC Educational Resources Information Center

    NatureScope, 1985

    1985-01-01

    Provides: (1) background information on desert communities, their similarities, and differences; (2) student activities on this topic; and (3) ready-to-copy student pages with pictures of desert animals and plants. Each activity includes objective(s), recommended age level(s), subject area(s), list of materials needed, and procedures. (DH)

  7. Desert Sojourn.

    ERIC Educational Resources Information Center

    Greenman, Geri

    1999-01-01

    Focuses on an activity in which the students in a beginning drawing class used middle-value brown paper and earthen shades of conte to draw pictures of bones in a desert environment. Discusses how the assignment teaches appreciation of the colors, sounds, and shapes of the desert. (CMK)

  8. Thar Desert

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This ASTER sub-scene covers an area of 12 x 15 km in NW India in the Thar Desert. The sand dunes of the Thar Desert constantly shift and take on new shapes. Located in northwestern India and eastern Pakistan, the desert is bounded on the south by a salt marsh known as the Rann of Kutch, and on the west by the Indus River plain. About 800 kilometers long and about 490 kilometers wide, the desert's terrain is mainly rolling sandhills with scattered growths of shrub and rock outcroppings. Only about 12 to 25 centimeters of rain fall on the desert each year, and temperatures rise as high as 52 degrees Celsius. Much of the population is pastoral, raising sheep for their wool. The image is located at 24.4 degrees north latitude and 69.3 degrees east longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  9. Deserts and Arid Lands

    NASA Astrophysics Data System (ADS)

    Brown, Glen F.

    The exponential growth of global population and often concomitant degradation of the environment has forced human expansion into the more hostile and less well-known terrains of arid lands and deserts. Drought in the African Sahel, with recent wholesale movement of tribes seeking survival, has focused interest in such regions. However, geologic and geomorphic knowledge of deserts has expanded slowly until the last few decades. For instance, the arid cycle of erosion, as conceived by William Morse Davis (now deceased; formerly, Harvard University, Cambridge, Mass.), with modifications by W. Penck (now deceased; formerly, Leipzig University, Leipzig, German Democratic Republic), and L. C. King (University of Natal and Durban, South Africa), has dominated desert geomorphological deductions until recently. Since World War II and the verification of plate tectonics, the knowledge of arid lands has increased dramatically, especially in synoptic mapping from remote sensing data and space photography, which transcends political boundaries, thanks to the open skies policy of the U.S. space pioneers.

  10. West Africa

    NASA Technical Reports Server (NTRS)

    2002-01-01

    With its vast expanses of sand, framed by mountain ranges and exposed rock, northwestern Africa makes a pretty picture when viewed from above. This image was acquired by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA's Terra spacecraft. The Canary Islands can be seen on the left side of the image just off Africa's Atlantic shore. The light brown expanse running through the northern two thirds of the image is the Sahara Desert. The desert runs up against the dark brown Haut Atlas mountain range of Morocco in the northwest, the Atlantic Ocean to the west and the semi-arid (light brown pixels) Sahelian region in the South. The Sahara, however, isn't staying put. Since the 1960s, the desert has been expanding into the Sahelian region at a rate of up to 6 kilometers per year. In the 1980s this desert expansion, combined with over cultivation of the Sahel, caused a major famine across west Africa. Over the summer months, strong winds pick up sands from the Sahara and blow them across the Atlantic as far west as North America, causing air pollution in Miami and damaging coral reefs in the Bahamas and the Florida Keys. The white outlines on the map represent country borders. Starting at the top-most portion of the map and working clockwise, the countries shown are Morocco, Western Sahara, Mauritania, Senegal, Mali, Burkina Fasso, Nigeria, Mali (again), and Algeria. Image by Reto Stockli, Robert Simmon, and Brian Montgomery, NASA Earth Observatory, based on data from MODIS

  11. Discovering Deserts.

    ERIC Educational Resources Information Center

    Braus, Judy, Ed.

    1985-01-01

    Ranger Rick's NatureScope is a creative education series dedicated to inspiring in children an understanding and appreciation of the natural world while developing the skills they will need to make responsible decisions about the environment. The topic of this issue is "Discovering Deserts." Contents are organized into the following sections: (1)…

  12. Active synchronous counterclockwise rotation and northwards translation of Africa toward Eurasia during the Late Cretaceous: A paleomagnetic study on the Alkaline volcanic field of Wadi Natash (ca. 100-86Ma), South Eastern Desert, Egypt

    NASA Astrophysics Data System (ADS)

    Lotfy, H.

    2009-04-01

    In order to shed light on the paleo-tectonic movement of Africa during the Late Cretaceous, the two end members of the alkaline volcanic field of Wadi Natash (ca. 100-86Ma) in the South Eastern Desert of Egypt were studied paleomagnetically. The Wadi Natash volcanic field (24.5°N-34.25°E) is made up of a succession of differentiated flows grading from alkali olivine basalt [AOB] to trachyte-phonolite [Tr/Ph]. The oldest flows of the AOB (104±7 Ma) and the youngest Tr/Ph plugs and ring dykes (86Ma) as well as the interflows sandstones [ previously know as Nubian sandstone were sampled allover the field > 400km2. The isothermal remanent magnetization [IRM] study revealed that the remanence in Wadi Natash volcanics reside mainly in magnetite with some subsidiary goethite/hematite sites. On the other hand, goethite/hematite are the sole remanence carriers in the Nubian-type interflow sandstone. After the progressive stepwise thermal demagnetization of all samples, the visual isolation and subsequent calculation of the best-fit line of the characteristic remanence [ChRM] direction of each sample, followed by the calculation of the site and rock-unit means revealed that: 1- In the tilt-corrected coordinates, the mean ChRM of the oldest AOB flows [N=12 sites

  13. Dust storm off Western Africa

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The impacts of Saharan dust storms reach far beyond Africa. Wind-swept deserts spill airborne dust particles out over the Atlantic Ocean where they can enter trade winds bound for Central and North America and the Caribbean. This Moderate Resolution Imaging Spectroradiometer (MODIS) image shows a dust storm casting an opaque cloud of cloud across the Canary Islands and the Atlantic Ocean west of Africa on June 30, 2002. In general it takes between 5 and 7 days for such an event to cross the Atlantic. The dust has been shown to introduce foreign bacteria and fungi that have damaged reef ecosystems and have even been hypothesized as a cause of increasing occurrences of respiratory complaints in places like Florida, where the amount of Saharan dust reaching the state has been increasing over the past 25 years.

  14. Atmospheric transport of mold spores in clouds of desert dust

    USGS Publications Warehouse

    Shinn, E.A.; Griffin, Dale W.; Seba, D.B.

    2003-01-01

    Fungal spores can be transported globally in clouds of desert dust. Many species of fungi (commonly known as molds) and bacteria--including some that are human pathogens--have characteristics suited to long-range atmospheric transport. Dust from the African desert can affect air quality in Africa, Europe, the Middle East, and the Americas. Asian desert dust can affect air quality in Asia, the Arctic, North America, and Europe. Atmospheric exposure to mold-carrying desert dust may affect human health directly through allergic induction of respiratory stress. In addition, mold spores within these dust clouds may seed downwind ecosystems in both outdoor and indoor environments.

  15. What Makes a Desert a Desert?

    ERIC Educational Resources Information Center

    NatureScope, 1985

    1985-01-01

    Presents background information and activities which focus on definition of a desert, locations of deserts, and factors influencing locations. Activities include objective(s), recommended age level(s), subject area(s), list of materials needed, and procedures. Two ready-to-copy pages with desert landforms and temperature/rainfall data are…

  16. Sharptooth catfish shows its metal: a case study of metal contamination at two impoundments in the Olifants River, Limpopo river system, South Africa.

    PubMed

    Jooste, Antoinette; Marr, Sean M; Addo-Bediako, Abraham; Luus-Powell, Wilmien J

    2015-02-01

    Clarias gariepinus is increasing in importance as a global aquaculture species with a 100 fold increase in production over the past decade but this species still remains one of the most important wild harvested freshwater food fish throughout rural Africa. However, this species has been shown to accumulate metals from contaminated inland waters. In this paper, the metal concentrations in muscle tissue of C. gariepinus from two main-stem impoundments in the Olifants River, Limpopo Basin, were measured and a desktop risk assessment based on the US-EPA methodology completed to evaluate whether long-term consumption of C. gariepinus from these impoundments may pose a health risk to rural communities. Our results show that metals are accumulating in the muscle tissue of C. gariepinus and have appeared to have increased in the last two decades. Risk assessment generated Hazard quotients (HQ) greater than 1 indicate that long term consumption of fish from these impoundments may cause adverse health impacts. We found that lead (HQ=9), antimony (HQ=14), cobalt (HQ=2) and chromium (HQ=1) at one impoundment and lead (HQ=2) at the other impoundment were above acceptable levels for weekly consumption of 150 g C. gariepinus muscle tissue. PMID:25463859

  17. South Africa

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This true-color image of South Africa was acquired on May 14, 2000, by NASA's Moderate-resolution Imaging Spectroradiometer, or MODIS. The image was produced using a combination of the sensor's 250-m and 500-m resolution visible wavelength bands. As part of the opening ceremony to begin the joint U.S.-South Africa SAFARI Field Experiment, NASA presented print copies of this image as GIFts to Dr. Ben Ngubane, Minister of Arts, Science and Technology, and Honorable Advocate Ngoaka Ramathlodi, Premier of the Northern Province, South Africa. The area shown in this image encompasses seven capital cities and a number of the region's distinctive geological features can be seen clearly. Toward the northern (top) central part of the image, the browns and tans comprise the Kalahari Desert of southern Botswana. The Tropic of Capricorn runs right through the heart of the Kalahari and the Botswanan capital city of Gaborone sits on the Limpopo River, southeast of the Kalahari. Along the western coastline of the continent is the country of Namibia, where the Namib Desert is framed against the sea by the Kaokoveld Mountains. The Namibian capital of Windhoek is obscured by clouds. Looking closely in the center of the image, the Orange River can be seen running from east to west, demarcating the boundary between Namibia and South Africa. On the southwestern corner of the continent is the hook-like Cape of Good Hope peninsula and Cape Town, the parliamentary capital of South Africa. Running west to east away from Cape Town are the Great Karroo Mountains. The shadow in this image conveys a sense of the very steep grade of the cliffs along the southern coast of South Africa. Port Elizabeth sits on the southeasternmost point of South Africa, and a large phytoplankton bloom can be seen in the water about 100 miles east of there. Moving northward along the east coast, the Drakensberg Mountains are visible. The two small nations of Lesotho and Swaziland are in this region, completely

  18. The Impact of Desert Dust Aerosol Radiative Forcing on Global and West African Precipitation

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Desert dust aerosols exert a radiative forcing on the atmosphere, influencing atmospheric temperature structure and modifying radiative fluxes at the top of the atmosphere (TOA) and surface. As dust aerosols perturb radiative fluxes, the atmosphere responds by altering both energy and moisture dynamics, with potentially significant impacts on regional and global precipitation. Global Climate Model (GCM) experiments designed to characterize these processes have yielded a wide range of results, owing to both the complex nature of the system and diverse differences across models. Most model results show a general decrease in global precipitation, but regional results vary. Here, we compare simulations from GFDL's CM2Mc GCM with multiple other model experiments from the literature in order to investigate mechanisms of radiative impact and reasons for GCM differences on a global and regional scale. We focus on West Africa, a region of high interannual rainfall variability that is a source of dust and that neighbors major Sahara Desert dust sources. As such, changes in West African climate due to radiative forcing of desert dust aerosol have serious implications for desertification feedbacks. Our CM2Mc results show net cooling of the planet at TOA and surface, net warming of the atmosphere, and significant increases in precipitation over West Africa during the summer rainy season. These results differ from some previous GCM studies, prompting comparative analysis of desert dust parameters across models. This presentation will offer quantitative analysis of differences in dust aerosol parameters, aerosol optical properties, and overall particle burden across GCMs, and will characterize the contribution of model differences to the uncertainty of forcing and climate response affecting West Africa.

  19. Desert Voices: Southwestern Children's Literature.

    ERIC Educational Resources Information Center

    Polette, Keith

    1997-01-01

    Examines three books with different ways of writing about the desert. Discusses: "Here Is the Southwestern Desert" by Madeline Dunphy, "The Desert Is My Mother" by Pat Mora, and "The Desert Mermaid" by Alberto Blanco. (PA)

  20. Does Jatropha curcas L. show resistance to drought in the Sahelian zone of West Africa? A case study from Burkina Faso

    NASA Astrophysics Data System (ADS)

    Bayen, P.; Sop, T. K.; Lykke, A. M.; Thiombiano, A.

    2015-05-01

    Land degradation is an environmental problem which weakens agro-sylvo-pastoral productivity in sub-Saharan Africa. The most common manifestation of land degradation is the appearance of denuded land. We carried out an experiment to test the effect of three soil and water conservation techniques on survival and growth of Jatropha curcas seedlings transplanted onto two completely denuded lands in the Sahelian and Sudanian zones of Burkina Faso. We implemented an experimental design with three replicates per restoration technique. A total of 174 seedlings were planted in each study site. The results showed that the soil water content varied according to the restoration technique used (df = 2; F = 53.21; p < 0.00) as well as according to study site (df = 1; F = 74.48; p < 0.00). Soil water content was significantly lower in the Sahel than in the Sudanian zone. Seedling survival rate varied significantly according to technique used (df = 2; F = 8.91; p = 0.000) and study site (df = 1; F = 9.74; p = 0.003). Survival rate, diameter and seedling height were highest at the Sudanian site. At the Sahelian site, all seedlings died 2 years after establishment. These results suggest that J. curcas is unsuited to denuded land in the Sahelian zone. Most of the plants died in the Sahel between April and May, which is the peak of the dry season; this may be an indication that J. curcas may not be as drought-resistant as suggested by the prolific literature which has reported on diverse claims surrounding this plant.

  1. Does Jatropha curcas L. show resistance to drought in the Sahelian zone of West Africa? A case study from Burkina Faso

    NASA Astrophysics Data System (ADS)

    Bayen, P.; Sop, T. K.; Lykke, A. M.; Thiombiano, A.

    2015-02-01

    Land degradation is an environmental problem which weakens agro-silvo-pastoral productivity in Sub-Saharan Africa. The most common manifestation of land degradation is the appearance of denuded land. We carried out an experiment to test the effect of three soil and water conservation techniques on survival and growth of Jatropha curcas seedlings transplanted onto two completely denuded lands in the Sahelian and Sudanian zones of Burkina Faso. We implemented an experimental design with three replicates per restoration technique. A total of 174 seedlings were planted in each study site. The results showed that soil water content varied according to the restoration technique used (df = 2; F = 53.21; p < 0.00) as well as according to study site (df = 1; F = 74.48; p < 0.00). Soil water content was significantly lower in the Sahel than in the Sudanian zone. Seedling survival rate varied significantly according to technique used (df = 2; F = 8.91; p = 0.000) and study site (df = 1; F = 9.74; p = 0.003). Survival rate, diameter and seedling height were highest at the Sudanian site. At the Sahelian site, all seedlings died two years after establishment. These results suggest that Jatropha curcas is unsuited to denuded land in the Sahelian zone. Most of the plants died in the Sahel between April and May, which is the peak of the dry season; this may be an indication that Jatropha may not be as drought-resistant as suggested by the prolific literature which has reported on diverse claims surrounding this plant.

  2. Multiple nuclide cosmogenic dating of very old desert pavements on the Puna Plateau, Northwest Argentina

    NASA Astrophysics Data System (ADS)

    Dortch, J.; Schoenbohm, L. M.

    2011-12-01

    Wind erosion of bedrock has been suggested to be responsible for the removal of more than 800 m of strata in the Qaidam Basin while wind deposition creates large-scale landforms such as the loess plateau. Wind eroded landforms, such as desert pavements in the Namibian Desert, Africa, form relic landscapes that are stable for more than 5 Ma. Desert pavements are of particular importance because of their widespread occurrence on terraces and fans, in mountains and coastal areas, and in hot and cold deserts including: Southwestern Africa, Antartic Dry valleys, Southwest USA, Denmark, Ireland, Israel, Sweden, and Central Tibet. Moreover, greater than 95 % of ventifacts on desert pavements are suspected to be late Quaternary to Holocene in age and are located on surfaces suitable for cosmogenic radionuclide dating. In spite of this, glacial, fluvial, and mass wasting systems have received far more attention than wind as an important geomorphic agent of erosion, deposition, and rock mass redistribution. Our goal is to: 1) quantify bedrock wind erosion rates; 2) quantify the ages of old, stable desert pavements; 3) and to identify which lithology-isotope pair provides the most accurate exposure ages for desert pavements in arid landscapes. The Puna Plateau, Argentina, is an ideal area to undertake this study because numerous wind eroded/deposited landforms are present, rates of fluvial erosion are low, and glaciation is limited. Mapping using remote sensed images shows that a significant portion of the Puna Plateau surface is covered by wind eroded or wind deposited landforms. These landforms align with the dominant wind direction (southeast) determined from ~450 ventifact measurements from 9 locations on the plateau. Twelve amalgamated samples sets that span six lithologies (granite, gneiss, quartzite, rhyolite, diabase, and basalt) using four cosmogenic isotopes (10Be, 26Al, 36Cl, 3He) on ventifacted clasts were collected from two surfaces to identify the most

  3. Aridification of the Sahara desert caused by Tethys Sea shrinkage during the Late Miocene.

    PubMed

    Zhang, Zhongshi; Ramstein, Gilles; Schuster, Mathieu; Li, Camille; Contoux, Camille; Yan, Qing

    2014-09-18

    It is widely believed that the Sahara desert is no more than ∼2-3 million years (Myr) old, with geological evidence showing a remarkable aridification of north Africa at the onset of the Quaternary ice ages. Before that time, north African aridity was mainly controlled by the African summer monsoon (ASM), which oscillated with Earth's orbital precession cycles. Afterwards, the Northern Hemisphere glaciation added an ice volume forcing on the ASM, which additionally oscillated with glacial-interglacial cycles. These findings led to the idea that the Sahara desert came into existence when the Northern Hemisphere glaciated ∼2-3 Myr ago. The later discovery, however, of aeolian dune deposits ∼7 Myr old suggested a much older age, although this interpretation is hotly challenged and there is no clear mechanism for aridification around this time. Here we use climate model simulations to identify the Tortonian stage (∼7-11 Myr ago) of the Late Miocene epoch as the pivotal period for triggering north African aridity and creating the Sahara desert. Through a set of experiments with the Norwegian Earth System Model and the Community Atmosphere Model, we demonstrate that the African summer monsoon was drastically weakened by the Tethys Sea shrinkage during the Tortonian, allowing arid, desert conditions to expand across north Africa. Not only did the Tethys shrinkage alter the mean climate of the region, it also enhanced the sensitivity of the African monsoon to orbital forcing, which subsequently became the major driver of Sahara extent fluctuations. These important climatic changes probably caused the shifts in Asian and African flora and fauna observed during the same period, with possible links to the emergence of early hominins in north Africa. PMID:25230661

  4. HIV-1 A1 Subtype Epidemic in Italy Originated from Africa and Eastern Europe and Shows a High Frequency of Transmission Chains Involving Intravenous Drug Users

    PubMed Central

    Lai, Alessia; Bozzi, Giorgio; Franzetti, Marco; Binda, Francesca; Simonetti, Francesco R.; De Luca, Andrea; Micheli, Valeria; Meraviglia, Paola; Bagnarelli, Patrizia; Di Biagio, Antonio; Monno, Laura; Saladini, Francesco; Zazzi, Maurizio; Zehender, Gianguglielmo; Ciccozzi, Massimo; Balotta, Claudia

    2016-01-01

    Background Subtype A accounts for only 12% of HIV-1 infections worldwide but predominates in Russia and Former Soviet Union countries of Eastern Europe. After an early propagation via heterosexual contacts, this variant spread explosively among intravenous drug users. A distinct A1 variant predominates in Greece and Albania, which penetrated directly from Africa. Clade A1 accounts for 12.5% of non-B subtypes in Italy, being the most frequent after F1 subtype. Aim Aim of this study was to investigate the circulation of A1 subtype in Italy and trace its origin and diffusion through phylogenetic and phylodynamic approaches. Results The phylogenetic analysis of 113 A1 pol sequences included in the Italian ARCA database, indicated that 71 patients (62.8%) clustered within 5 clades. A higher probability to be detected in clusters was found for patients from Eastern Europe and Italy (88.9% and 60.4%, respectively) compared to those from Africa (20%) (p < .001). Higher proportions of clustering sequences were found in intravenous drug users with respect to heterosexuals (85.7% vs. 59.3%, p = .056) and in women with respect to men (81.4% vs. 53.2%, p < .006). Subtype A1 dated phylogeny indicated an East African origin around 1961. Phylogeographical reconstruction highlighted 3 significant groups. One involved East European and some Italian variants, the second encompassed some Italian and African strains, the latter included the majority of viruses carried by African and Italian subjects and all viral sequences from Albania and Greece. Conclusions Subtype A1 originated in Central Africa and spread among East European countries in 1982. It entered Italy through three introduction events: directly from East Africa, from Albania and Greece, and from the area encompassing Moldavia and Ukraine. As in previously documented A1 epidemics of East European countries, HIV-1 A1 subtype spread in Italy in part through intravenous drug users. However, Eastern European women contributed

  5. Simulated distribution of an invasive grass, Lehmann lovegrass, in the Chihuahuan Desert under future climate scenarios

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Background/Question/Methods Lehmann lovegrass (Eragrostis lehmanniana), a perennial grass introduced to the Southwest US in the 1930s from South Africa, has had a limited distribution in the Chihuahuan Desert while it has dominated many grassland sites in the Sonoran Desert.  Previous observational ...

  6. Lake Chad, Chad, Africa

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The fluctuating water levels of Lake Chad, (13.0N, 15.0E) at the intersection of the borders of Chad, Niger and Cameroon in the Sahara Desert, is an index of the drought in Africa. The lake level continues to decrease as indicated by the growing number and extent of emerging islands as previously submerged ancient sand dunes become visible. The water impounded between the dunes is probably because of local rainfall rather than a reversal of desertification.

  7. Estimating agricultural yield gap in Africa using MODIS NDVI dataset

    NASA Astrophysics Data System (ADS)

    Luan, Y.; Zhu, W.; Luo, X.; Liu, J.; Cui, X.

    2013-12-01

    Global agriculture has undergone a period of rapid intensification characterized as 'Green Revolution', except for Africa, which is the region most affected by unreliable food access and undernourishment. Increasing crop production will be one of the most challenges and most effectual way to mitigate food insecurity there, as Africa's agricultural yield is on a much lower level comparing to global average. In this study we characterize cropland vegetation phenology in Africa based on MODIS NDVI time series between 2000 and 2012. Cumulated NDVI is a proxy for net primary productivity and used as an indicator for evaluating the potential yield gap in Africa. It is achieved via translating the gap between optimum attainable productivity level in each classification of cropping systems and actual productivity level by the relationship of cumulated NDVI and cereal-equivalent production. The results show most of cropland area in Africa have decreasing trend in cumulated NDVI, distributing in the Nile Delta, Eastern Africa and central of semi-arid to arid savanna area, except significant positive cumulated NDVI trends are mainly found between Senegal and Benin. Using cumulated NDVI and statistics of cereal equivalent production, we find remarkable potential yield gap at the Horn of East Africa (especially in Somalia), Northern Africa (Morocco, Algeria and Tunisia). Meanwhile, countries locating at the savanna area near Sahel desert and South Africa also show significant potential, though they already have a relatively high level of productivity. Our results can help provide policy recommendation for local government or NGO to tackle food security problems by identifying zones with high potential of yield improvement.

  8. Endolithic microbial life in hot and cold deserts

    NASA Technical Reports Server (NTRS)

    Friedmann, E. I.

    1980-01-01

    Endolithic microorganisms (those living inside rocks) occur in hot and cold deserts and exist under extreme environmental conditions. These conditions are discussed on a comparative basis. Quantitative estimates of biomass are comparable in hot and cold deserts. Despite the obvious differences between the hot and cold desert environment, survival strategies show some common features. These endolithic organisms are able to 'switch' rapidly their metabolic activities on and off in response to changes in the environment. Conditions in hot deserts impose a more severe environmental stress on the organisms than in the cold Antarctic desert. This is reflected in the composition of the microbial flora which in hot desert rocks consist entirely of prokaryotic microorganisms, while under cold desert conditions eukaryotes predominate.

  9. Fossil hyrax dung and evidence of Late Pleistocene and Holocene vegetation types in the Namib Desert

    NASA Astrophysics Data System (ADS)

    Scott, Louis; Marais, Eugene; Brook, George A.

    2004-12-01

    Pollen was derived from fossil dung of herbivorous hyraxes, deposited in a rock shelter on the highest mountain in Namibia, Dâures or Brandberg, situated on the Namib Desert margin. Radiocarbon dating ranging in age between modern times and 30 000 yr BP showed it represents the first empirical pollen evidence of continental palaeovegetation during the Late Pleistocene along the western escarpment of southern Africa. The initial results indicate Last Glacial Maximum vegetation differed totally from the current pattern as vegetation types were dominated by small Asteraceae shrubs, in contrast to those of the Holocene and modern times which show more succulents, grass and woody elements (arboreal pollen). The results suggest that Cape floral communities did not reach into the tropics along the western escarpment of Africa, despite such pollen types occurring in marine cores. Copyright

  10. Occurrences and Effects of Drought across Africa

    NASA Astrophysics Data System (ADS)

    Mwangi, M. N.

    2009-12-01

    Drought is a common occurrence in Africa and its effects vary temporally and spatially across the continent. The objective of this paper is to synthesize available information on droughts in Africa in order to discern emerging trends vis-à-vis spatiotemporal occurrences, impacts and adaptation. Drought forcings in the Sahelian region and southern Africa are predominately related to the passage of mid-latitude air masses while in locations near the equator is strongly linked to the position of ITCZ, except perhaps in the deserts where albedo may predominate. The review shows that drought occurrences have increased both temporally and spatially; its effects on the society vary across scales, and are influenced by political, economic, social, cultural, and ecological factors. The drought occurrence and its impacts varied spatially and temporally. The effect of drought also varied with socioeconomic sector; agriculture and pastoralism were the widely reported. The greater horn of Africa, specifically Kenya, has the most continuous record of droughts. The synthesis also reveals that a suite of drought adaptation strategies exists at the local scale; in contrasts, at the aggregate scale, coping strategies are scarce. Drought management tailored for specific livelihood system or societies are non-existent. The study found that occurrence of drought alongside issues related to the multiscale political economy affect the viability of most adaptation strategies used by societies across Africa. Drought management has been silent on the social, political, and economic dimensions that reasonably aggravate the vulnerability of lives and livelihood systems to this climatic hazard. The effect of drought and social pressures is relational and simultaneous to such a degree that differential vulnerability among communities across Africa is to be expected. Although scenarios about rainfall and drought vis-à-vis Africa are largely contested there is a general indication that most

  11. Desert Storm environmental effects

    NASA Astrophysics Data System (ADS)

    Kimball, E. W.

    It is noted that after more than six months of operation of the Patriot launch station in the Saudi Arabian desert no problems that were attributed to high temperature occurred. The environmental anomalies that did occur were cosmetic in nature and related to dust and salt fog. It was concluded that the Desert Storm environmental effects were typical of worldwide hot, dry climates.

  12. Animals of the Desert.

    ERIC Educational Resources Information Center

    NatureScope, 1985

    1985-01-01

    Provides background information and student activities on how desert animals have adapted to dryness and heat, how and when animals move on the desert, and nocturnal/diurnal animals. Each activity includes objective(s), recommended age level(s), subject area(s), list of materials needed, and procedures. Ready-to-copy pages are included for a…

  13. People and Deserts.

    ERIC Educational Resources Information Center

    NatureScope, 1985

    1985-01-01

    Provides: (1) background information on ways people affect deserts and ways deserts affect people; (2) student activities on this topic; and (3) ready-to-copy materials (culture match worksheet and causes worksheet). Each activity includes objective(s), recommended age level(s), subject area(s), list of materials needed, and procedures. (DH)

  14. Workshop on Extraterrestrial Materials from Cold and Hot Deserts

    NASA Technical Reports Server (NTRS)

    Schultz, Ludolf (Editor); Franchi, Ian A. (Editor); Reid, Arch M. (Editor); Zolensky, Michael E. (Editor)

    1999-01-01

    Since 1969 expeditions from Japan, the United States, and European countries have recovered more than 20,000 meteorite specimens from remote ice fields of Antarctica. They represent approximately 4000-6000 distinct falls, more than all non-Antarctic meteorite falls and finds combined. Recently many meteorite specimens of a new "population" have become available: meteorites from hot deserts. It turned out that suitable surfaces in hot deserts, like the Sahara in Africa, the Nullarbor Plain in Western and South Australia, or desert high plains of the U.S. (e.g., Roosevelt County, New Mexico), contain relatively high meteorite concentrations. For example, the 1985 Catalog of Meteorites of the British Museum lists 20 meteorites from Algeria and Libya. Today, 1246 meteorites finds from these two countries have been published in MetBase 4.0. Four workshops in 1982, 1985, 1988, and 1989 have discussed the connections between Antarctic glaciology and Antarctic meteorites, and the differences between Antarctic meteorites and modern falls. In 1995, a workshop addressed differences between meteorites from Antarctica, hot deserts, and modem falls, and the implications of possible different parent populations, infall rates, and weathering processes. Since 1995 many more meteorites have been recovered from new areas of Antarctica and hot deserts around the world. Among these finds are several unusual and interesting specimens like lunar meteorites or SNCs of probable martian origin. The Annual Meeting of the Meteoritical Society took place in 1999 in Johannesburg, South Africa. As most of the recent desert finds originate from the Sahara, a special workshop was planned prior to this meeting in Africa. Topics discussed included micrometeorites, which have been collected in polar regions as well as directly in the upper atmosphere. The title "Workshop on Extraterrestrial Materials from Cold and Hot Deserts" was chosen and the following points were emphasized: (1) weathering

  15. Workshop on Extraterrestrial Materials from Cold and Hot Deserts

    NASA Technical Reports Server (NTRS)

    Schultz, Ludolf (Editor); Franchi, Ian A. (Editor); Reid, Arch M. (Editor); Zolensky, Michael E. (Editor)

    2000-01-01

    Since 1969 expeditions from Japan, the United States, and European countries have recovered more than 20,000 meteorite specimens from remote ice fields of Antarctica. They represent approximately 4000-6000 distinct falls, more than all non-Antarctic meteorite falls and finds combined. Recently many meteorite specimens of a new "population" have become available: meteorites from hot deserts. It turned out that suitable surfaces in hot deserts, like the Sahara in Africa, the Nullarbor Plain in Western and South Australia, or desert high plains of the U.S. (e.g., Roosevelt County, New Mexico), contain relatively high meteorite concentrations. For example, the 1985 Catalogue of Meteorites of the British Museum lists 20 meteorites from Algeria and Libya. Today, 1246 meteorites finds from these two countries have been published in MetBase 4.0. Four workshops in 1982, 1985, 1988, and 1989 have discussed the connections between Antarctic glaciology and Antarctic meteorites, and the differences between Antarctic meteorites and modem falls. In 1995, a workshop addressed differences between meteorites from Antarctica, hot deserts, and modem falls, and the implications of possible different parent populations, infall rates, and weathering processes. Since 1995 many more meteorites have been recovered from new areas of Antarctica and hot deserts around the world. Among these finds are several unusual and interesting specimens like lunar meteorites or SNCs of probable martian origin. The Annual Meeting of the Meteoritical Society took place in 1999 in Johannesburg, South Africa. As most of the recent desert finds originate from the Sahara, a special workshop was planned prior to this meeting in Africa. Topics discussed included micrometeorites, which have been collected in polar regions as well as directly in the upper atmosphere. The title "Workshop on Extraterrestrial Materials from Cold and Hot Deserts" was chosen and the following points were emphasized: (1) weathering

  16. Role of remote sensing in desert locust early warning

    NASA Astrophysics Data System (ADS)

    Cressman, Keith

    2013-01-01

    Desert locust (Schistocerca gregaria, Forskål) plagues have historically had devastating consequences on food security in Africa and Asia. The current strategy to reduce the frequency of plagues and manage desert locust infestations is early warning and preventive control. To achieve this, the Food and Agriculture Organization of the United Nations operates one of the oldest, largest, and best-known migratory pest monitoring systems in the world. Within this system, remote sensing plays an important role in detecting rainfall and green vegetation. Despite recent technological advances in data management and analysis, communications, and remote sensing, monitoring desert locusts and preventing plagues in the years ahead will continue to be a challenge from a geopolitical and financial standpoint for affected countries and the international donor community. We present an overview of the use of remote sensing in desert locust early warning.

  17. Nitrate distribution in Mojave Desert soils

    SciTech Connect

    Hunter, R.B.; Romney, E.M.; Wallace, A.

    1982-07-01

    Extensive sampling shows high variability in nitrate concentration within profiles of Mojave Desert soils. This high variability greatly complicates studies of desert soil N and its ecological role. Patterns in nitrate distribution suggest effects of litter decomposition under shrubs, surface leaching in bare areas, and plant uptake in the root zone. Two mechanisms proposed to explain high concentrations found at seemingly random depths are concentration at drying fronts and distribution along water potential gradients.

  18. Are Food Deserts Also Play Deserts?

    PubMed

    Cohen, Deborah A; Hunter, Gerald; Williamson, Stephanie; Dubowitz, Tamara

    2016-04-01

    Although food deserts are areas that lack easy access to food outlets and considered a barrier to a healthy diet and a healthy weight among residents, food deserts typically comprise older urban areas which may have many parks and street configurations that could facilitate more physical activity. However, other conditions may limit the use of available facilities in these areas. This paper assesses the use of parks in two Pittsburgh food desert neighborhoods by using systematic observation. We found that while the local parks were accessible, they were largely underutilized. We surveyed local residents and found that only a minority considered the parks unsafe for use during the day, but a substantial proportion suffered from health limitations that interfered with physical activity. Residents also felt that parks lacked programming and other amenities that could potentially draw more park users. Parks programming and equipment in food desert areas should be addressed to account for local preferences and adjusted to meet the needs and limitations of local residents, especially seniors. PMID:27033184

  19. Potential for deserts to supply reliable renewable electric power

    NASA Astrophysics Data System (ADS)

    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

  20. What is Desert RATS?

    NASA Video Gallery

    The mission manager and test coordinators for the 2011 mission explain why Desert RATS was started 14 years ago, questions being studied in this year's activities, technologies being tested and the...

  1. Desert pavements and associated rock varnish in the Mojave Desert: How old can they be?

    NASA Astrophysics Data System (ADS)

    Quade, Jay

    2001-09-01

    Desert pavements are common features of arid landscapes and have been widely used as a relative age indicator of the geomorphic surfaces upon which they are developed. In this study I examined the patterns of pavement development as a function of elevation in the Mojave Desert as well as the causes for the gradual disappearance of pavement at high elevations. Pavement density, as measured by percentage of pebble coverage, decreases systematically with elevation gain by ˜3% per 100 m, from 95% coverage below 500 m to less than 60% at 1700 m. Plants appear to be the main agent of pavement disruption; plant density decreases as pavement density increases. Burrowing by rodents and crusting by cryptobiota also disrupt pavement development at higher elevation. During the last glacial maximum, plant communities were displaced 1000 1400 m downward in the Mojave Desert. Pavements today generally do not survive above the blackbush (Coleogyne ramossisma)-sagebrush (Artemisia tridentata) zone. Evidence from packrat middens shows that these and other plants typical of high elevations today grew as low as 300 400 m during the last glacial maximum. I suggest that during the last glacial maximum, desert pavements were confined to the lowest alluvial fans of Death Valley and adjoining low valleys. No alluvial desert pavements above ˜400 m in the region are older than the latest Pleistocene. By the same reasoning, desert varnish on desert pavements above 400 m may all be Holocene in age, except where developed on stable boulders.

  2. Origin of desert loess from some experimental observations

    NASA Technical Reports Server (NTRS)

    Whalley, W. B.; Smith, B. J.; Marshall, J. R.

    1982-01-01

    The aeolian attrition of angular quartz grains previously produced by weathering in deserts has been simulated, yielding abrasion products which show that both coarse and fine silt sizes are produced by this process. These results suggest that desert aeolian processes can produce loess, and it is speculated that while much of this material from many deserts has been deposited in the sea, the Chinese loess could have been produced in the Gobi desert. The finest of the particles produced by such attrition may serve as a source of silica for silcrete formation.

  3. Neogene desertification of Africa

    NASA Astrophysics Data System (ADS)

    Senut, Brigitte; Pickford, Martin; Ségalen, Loïc

    2009-08-01

    Throughout the Neogene, the faunas and floras in Africa recorded global climatic changes. We present an overview of Neogene desertification in Africa by tracing stable isotopes in eggshells and mammalian enamel, by faunal (changes in hypsodonty, etc.) and floral changes in sequences at the latitudinal extremities of the continent and the equator. This work reveals that desertification started in the southwest ca 17-16 Ma, much earlier than the region of the present-day Sahara (ca 8-7 Ma) and long before the deserts in East Africa (Plio-Pleistocene). A consequence of this history is that animals and plants inhabiting the South of the continent had a long period of time in which to adapt to arid, unstable climatic conditions. When parts of East Africa became arid during the Late Miocene and Plio-Pleistocene, several of these lineages expanded northwards and occupied developing arid niches before local lineages could adapt. Several of the latter became extinct, while others withdrew westwards as the tropical forest diminished in extent. It is proposed that the history of desertification in Africa was related to that of the polar ice caps (Antarctic, Arctic).

  4. South Africa, Namibia, and Botswana

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Pale green vegetation and red-brown deserts dominate this MODIS image of Namibia (left), Botswana (upper right), and the Republic of South Africa (bottom) acquired on June3, 2002. In central Namibia the mountainous terrain of Namaqualand is sandwiched between the Namib Desert on the Atlantic Coast and the Kalahari Desert to the interior, where white dots mark the location of small, impermanent lakes and ponds. Namaqualand is home to numerous rare succulent plants that can survive on the region.s scant rainfall as well as fog that blows in off the ocean. Namaqualand extends south of the Orange River, which runs along the border of Namibia and South Africa and into that country.s Northern Cape region. The Orange River extends almost all the way back through the country, and where it makes a sharp southward dip in this image (at lower right), it runs through the Asbestos Mountains, names for the naturally-occurring asbestos they contain. In southwestern South Africa, high plateaus, such as the Great Karoo become mountain ridges near the coast, and the city of Cape Town is visible as a grayish area of pixels on the north shores of the horseshoe-shaped False Bay at the Cape of Good Hope. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  5. Atmospheric Movement of Microorganisms in Clouds of Desert Dust and Implications for Human Health

    PubMed Central

    Griffin, Dale W.

    2007-01-01

    Billions of tons of desert dust move through the atmosphere each year. The primary source regions, which include the Sahara and Sahel regions of North Africa and the Gobi and Takla Makan regions of Asia, are capable of dispersing significant quantities of desert dust across the traditionally viewed oceanic barriers. While a considerable amount of research by scientists has addressed atmospheric pathways and aerosol chemistry, very few studies to determine the numbers and types of microorganisms transported within these desert dust clouds and the roles that they may play in human health have been conducted. This review is a summary of the current state of knowledge of desert dust microbiology and the health impact that desert dust and its microbial constituents may have in downwind environments both close to and far from their sources. PMID:17630335

  6. Atmospheric movement of microorganisms in clouds of desert dust and implications for human health

    USGS Publications Warehouse

    Griffin, Dale W.

    2007-01-01

    Billions of tons of desert dust move through the atmosphere each year. The primary source regions, which include the Sahara and Sahel regions of North Africa and the Gobi and Takla Makan regions of Asia, are capable of dispersing significant quantities of desert dust across the traditionally viewed oceanic barriers. While a considerable amount of research by scientists has addressed atmospheric pathways and aerosol chemistry, very few studies to determine the numbers and types of microorganisms transported within these desert dust clouds and the roles that they may play in human health have been conducted. This review is a summary of the current state of knowledge of desert dust microbiology and the health impact that desert dust and its microbial constituents may have in downwind environments both close to and far from their sources.

  7. Orbital scale vegetation change in Africa

    NASA Astrophysics Data System (ADS)

    Dupont, Lydie

    2011-12-01

    Palynological records of Middle and Late Pleistocene marine sediments off African shores is reviewed in order to reveal long-term patterns of vegetation change during climate cycles. Whether the transport of pollen and spores from the source areas on the continent to the ocean floor is mainly by wind or predominantly by rivers depends on the region. Despite the differences in transportation, accumulation rates in the marine sediments decline exponentially with distance to the shore. The marine sediments provide well-dated records presenting the vegetation history of the main biomes of western and southern Africa. The extent of different biomes varied with the climate changes of the glacial interglacial cycle. The Mediterranean forest area expanded during interglacials, the northern Saharan desert during glacials, and the semi-desert area in between during the transitions. In the sub-Saharan mountains ericaceous scrubland spread mainly during glacials and the mountainous forest area often increased during intermediate periods. Savannahs extended or shifted to lower latitudes during glacials. While the representation of the tropical rain forest fluctuated with summer insolation and precession, that of the subtropical biomes showed more obliquity variability or followed the pattern of glacial and interglacials.

  8. Sounds of the Desert.

    ERIC Educational Resources Information Center

    McCullough-Brabson, Ellen; Achilles, Elayne; Ashcraft, Joan

    1997-01-01

    Discusses the program called "Sounds of the Desert" that celebrates the Southwest indigenous culture and focuses on understanding music in relation to history and culture. Emphasizes the study of Mariachi music that is being taught alongside band, orchestra, and chorus from the third grade to senior high in many Tucson (Arizona) schools. (CMK)

  9. How desert varnish forms?

    NASA Astrophysics Data System (ADS)

    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.

  10. Plants of the Desert.

    ERIC Educational Resources Information Center

    NatureScope, 1985

    1985-01-01

    Provides background information and student activities on plants of the desert, including various adaptations for life with limited water supplies. Each activity includes objective(s), recommended age level(s), subject area(s), list of materials needed, and procedures. A ready-to-copy student worksheet is included. (DH)

  11. Mojave Desert Diary

    ERIC Educational Resources Information Center

    Breed, Allen F.

    1974-01-01

    This is an account of a trip to the Mojave Desert sponsored by the California Youth Authority's Community Parole Center for wards who are selected on the basis of their potential for growth and their ability to make a connection between what they do in the wilderness and what they do on the streets. (PD)

  12. A study of Desert Dermatoses in the Thar Desert Region

    PubMed Central

    Chatterjee, Manas; Vasudevan, Biju

    2015-01-01

    Introduction: Desert dermatology describes the cutaneous changes and the diseases affecting those living in the desert. Diurnal variation in temperature is high and is characteristic of the deserts. The lack of water affects daily activities and impacts dermatological conditions. Adaptation to the desert is therefore important to survival. This original article focuses on dermatoses occurring in a population in the Thar desert of India, predominantly located in Rajasthan. Materials and Methods: This is a descriptive study involving various dermatoses seen in patients residing in the Thar desert region over a duration of 3 years. Results: Infections were the most common condition seen among this population and among them fungal infections were the most common. The high incidence of these infections would be accounted for by the poor hygienic conditions due to lack of bathing facilities due to scarcity of water and the consequent sweat retention and overgrowth of cutaneous infective organisms. Pigmentary disorders, photodermatoses, leishmaniasis and skin tumors were found to be more prevalent in this region. Desert sweat dermatitis was another specific condition found to have an increased incidence. Conclusion: The environment of the desert provides for a wide variety of dermatoses that can result in these regions with few of these dermatoses found in much higher incidence than in other regions. The concept of desert dermatology needs to be understood in more details to provide better care to those suffering from desert dermatoses and this article is a step forward in this regard. PMID:25657392

  13. Deserts of China

    USGS Publications Warehouse

    Walker, Alta S.

    1982-01-01

    Improving arid land quality requires an understanding of the original state of the land and its relationship to wind, water, and plant regimes, as well as understanding of interactions within the present ecosystem.  Chinese scientists and local residents have made significant advances in improving arid environments in gobi and sandy deserts and in less arid sandy lands.  Wind patterns are being changed by planting forest belts to protect oases and sandy lands, and on a smaller scale by planting grasses and shrubs or constructing straw grids.  Research on reclamation of deserts is now focusing on how sand-fixing plants may be adapted to local environments, and how the resources of grazing land and water may be effectively exploited without being overused.

  14. Unchanging Desert Sand Dunes

    NASA Astrophysics Data System (ADS)

    Gadhiraju, S.; Banerjee, B.; Buddhiraju, K.; Shah, V.

    2013-12-01

    Deserts are one of the major landforms on earth. They occupy nearly 20% of the total land area but are relatively less studied. With the rise in human population, desert regions are being gradually occupied for settlement posing a management challenge to the concerned authorities. Unrestrained erosion is generally a feature of bare dunes. Stabilized dunes, on the other hand, do not undergo major changes in textures, and can thus facilitate the growth of vegetation. Keeping in view of the above factors, better mapping and monitoring of deserts and particularly of sand dunes is needed. Mapping dunes using field instruments is very arduous and they generate relatively sparse data. In this communication, we present a method of clustering and monitoring sand dunes through imagery captured by remote sensing sensors. Initially Radon spectrum of an area is obtained by decomposition of the image into various projections sampled at finer angular directions. Statistical features such as mode, entropy and standard deviation of Radon spectrum are used in delineation and clustering of regions with different dune orientations. These clustered boundaries are used to detect if there are any changes occurring in the dune regions. In the experiment's, remote sensing data covering various dune regions of the world are observed for possible changes in dune orientations. In all the cases, it is seen that there are no major changes in desert dune orientations. While these findings have implications for understanding of dune geomorphology and changes occurring in dune directions, they also highlight the importance of a wider study of dunes and their evolution both at regional and global scales. Results for Dataset 1 & Dataset 2 Results for Dataset 3

  15. The Desert Crossings of Mars

    NASA Astrophysics Data System (ADS)

    Cockell, C. S.

    Apart from the polar caps, the Martian volcanoes and the Valles Marineris, ~80% of the martian surface can essentially be classified as `desert'. The methods used to explore Mars, the scientific priorities and the philo- sophical and historical precedents that drive human exploration on Mars will primarily come from our experiences in terrestrial deserts. Here, the methods and approaches used for terrestrial desert expeditions are discussed with reference to Mars. Some of the physical challenges such as low temperature and frost formation will be akin to cold polar desert exploration on Earth. However, some challenges, such as dust storms and lack of liquid water will be akin to hot desert exploration. Expeditions that draw the appropriate lessons from both hot and cold desert terrestrial expeditions will succeed. Examples of major regions on Mars that might be regarded as significant exploratory challenges for expeditions are identified. Key parameters of these expeditions including distance and plausible scientific objectives are provided.

  16. Jeeps Penetrating a Hostile Desert

    ERIC Educational Resources Information Center

    Bailey, Herb

    2009-01-01

    Several jeeps are poised at base camp on the edge of a desert aiming to escort one of them as far as possible into the desert, while the others return to camp. They all have full tanks of gas and share their fuel to maximize penetration. In a friendly desert it is best to leave caches of fuel along the way to help returning jeeps. We solve the…

  17. Microbial origin of desert varnish.

    PubMed

    Dorn, R I; Oberlander, T M

    1981-09-11

    Scanning electron microscopy and energy dispersive x-ray analyses of desert varnish reveal that microorganisms concentrate ambient manganese that becomes greatly enhanced in brown to black varnish. Specific characteristics of desert varnish and of varnish bacteria support a microbial origin for manganese-rich films. Varnish microbes can be cultured and produce laboratory manganese films. Accordingly, natural desert varnish and also manganese-rich rock varnishes in nondesert environments appear to be a product of microbial activity. PMID:17744757

  18. Long Term MSU Tropospheric and Ground Temperature Trends (1979-2008) Over Africa

    NASA Astrophysics Data System (ADS)

    Prasad, A. K.; El-Askary, H.; Kafatos, M.

    2009-12-01

    Africa, the second largest and second most populous continent, is marked by an arid desert zone in the north (10°-40°N), dense forest and tropical climate in the central region (10°S to 10°N), and a southern temperate zone (10°-40°S). The African landmass, which is symmetrically distributed across the equator, shows differential heating and cooling atmospheric (lower- and mid-tropospheric) temperature trends. The northern arid region, a main source of major dust storms and mineral dust aerosols, shows a larger warming trend compared to the central region characterized by dense forest and forest fires. The mean annual lower- and mid-tropospheric temperature trend (Microwave Sounding Units MSU, 1979-2008) is found be 0.023±0.006 °K/year and 0.018±0.003 °K/year respectively over northern Africa (Saharan region) as compared to 0.010±0.003 °K/year and 0.009±0.002 °K/year over the central equatorial, and mostly forest-covered region (Figure 1). The southern region shows a mean annual lower- and mid-tropospheric temperature trend of 0.015±0.004 °K/year and 0.011±0.003 °K/year, which is lower than the desert region. The dense tropical forest region near the equator shows the lowest tropospheric temperature trend (lower: 0.011±0.003 °K/year; mid: 0.007±0.002 °K/year) over the Africa (Figure 1). The warmest temperature trend was observed over the eastern Saharan region, covering parts of Egypt, Libya, and the northern parts of Sudan, Chad and Niger. We have also compared the MSU-derived atmospheric temperature trends to ground-based temperature trends available for Egypt and some surrounding regions. The mean annual MSU tropospheric trends over the Saharan region are relatively low compared to other major Asian deserts, such as the Taklamakan and the Gobi Desert in the northern mid-latitudes, which show a trend of 0.037±0.008 °K/year (lower) and 0.025±0.006 °K/year (mid). The seasonal and month-to-month variability of temperature trends over Africa

  19. Travertine from Egypt's Western Desert: a terrestrial proxy for North African paleohydrology and paleoclimate during the Quaternary

    NASA Astrophysics Data System (ADS)

    Jimenez, G.; Crossey, L. J.; Karlstrom, K. E.; Polyak, V. J.; Asmerom, Y.

    2013-12-01

    , rather than correlating to glacial cycles. We also note the presence of significant deposition between 650 ka and 1 Ma (using modeled ages for travertine outside of U/Th analytical range), adding support to the notion that pluvial episodes in North Africa occurred before and during the mid-Pleistocene transition, although they are unclear in the sapropel record at this time. Finally, we suggest that decreasing travertine volume and elevation above modern base level throughout our 650 ka record, as well as the lack of travertine deposition at major oasis areas after ~70 ka, may imply declining pluvial strength through the late Pleistocene. Thus, our study shows travertine in Egypt's Western Desert to be a useful proxy for broad-scale changes in North African paleohydrology and paleoclimate, with the potential to determine the timing of wet periods as well as their moisture sources.

  20. West Africa

    Atmospheric Science Data Center

    2013-04-16

    ... article title:  Hazy and Dusty Skies over Western Africa     View Larger Image ... of agricultural fires that were burning throughout western Africa during December and early January, and was likely to have been ...

  1. Southern Africa

    Atmospheric Science Data Center

    2013-04-16

    article title:  Southern Africa     View larger JPEG image ... These Multi-angle Imaging SpectroRadiometer (MISR) images of Africa were acquired on August 25, 2000, during Terra orbit 3655. The left ... of smoke plumes and haze. The southern tip of South Africa is at the bottom of the image, and Zambia is at the top. Distinctive ...

  2. Extrafloral nectar fuels ant life in deserts

    PubMed Central

    Aranda-Rickert, Adriana; Diez, Patricia; Marazzi, Brigitte

    2014-01-01

    Interactions mediated by extrafloral nectary (EFN)-bearing plants that reward ants with a sweet liquid secretion are well documented in temperate and tropical habitats. However, their distribution and abundance in deserts are poorly known. In this study, we test the predictions that biotic interactions between EFN plants and ants are abundant and common also in arid communities and that EFNs are only functional when new vegetative and reproductive structures are developing. In a seasonal desert of northwestern Argentina, we surveyed the richness and phenology of EFN plants and their associated ants and examined the patterns in ant–plant interaction networks. We found that 25 ant species and 11 EFN-bearing plant species were linked together through 96 pairs of associations. Plants bearing EFNs were abundant, representing ca. 19 % of the species encountered in transects and 24 % of the plant cover. Most ant species sampled (ca. 77 %) fed on EF nectar. Interactions showed a marked seasonal pattern: EFN secretion was directly related to plant phenology and correlated with the time of highest ant ground activity. Our results reveal that EFN-mediated interactions are ecologically relevant components of deserts, and that EFN-bearing plants are crucial for the survival of desert ant communities. PMID:25381258

  3. Extrafloral nectar fuels ant life in deserts.

    PubMed

    Aranda-Rickert, Adriana; Diez, Patricia; Marazzi, Brigitte

    2014-01-01

    Interactions mediated by extrafloral nectary (EFN)-bearing plants that reward ants with a sweet liquid secretion are well documented in temperate and tropical habitats. However, their distribution and abundance in deserts are poorly known. In this study, we test the predictions that biotic interactions between EFN plants and ants are abundant and common also in arid communities and that EFNs are only functional when new vegetative and reproductive structures are developing. In a seasonal desert of northwestern Argentina, we surveyed the richness and phenology of EFN plants and their associated ants and examined the patterns in ant-plant interaction networks. We found that 25 ant species and 11 EFN-bearing plant species were linked together through 96 pairs of associations. Plants bearing EFNs were abundant, representing ca. 19 % of the species encountered in transects and 24 % of the plant cover. Most ant species sampled (ca. 77 %) fed on EF nectar. Interactions showed a marked seasonal pattern: EFN secretion was directly related to plant phenology and correlated with the time of highest ant ground activity. Our results reveal that EFN-mediated interactions are ecologically relevant components of deserts, and that EFN-bearing plants are crucial for the survival of desert ant communities. PMID:25381258

  4. Evolution and Functional Classification of Vertebrate Gene Deserts

    SciTech Connect

    Ovcharenko, I; Loots, G; Nobrega, M; Hardison, R; Miller, W; Stubbs, L

    2004-07-14

    Gene deserts, long stretches of DNA sequence devoid of protein coding genes, span approximately one quarter of the human genome. Through human-chicken genome comparisons we were able to characterized one third of human gene deserts as evolutionarily stable - they are highly conserved in vertebrates, resist chromosomal rearrangements, and contain multiple conserved non-coding elements physically linked to their neighboring genes. A linear relationship was observed between human and chicken orthologous stable gene deserts, where the human deserts appear to have expanded homogeneously by a uniform accumulation of repetitive elements. Stable gene deserts are associated with key vertebrate genes that construct the framework of vertebrate development; many of which encode transcription factors. We show that the regulatory machinery governing genes associated with stable gene deserts operates differently from other regions in the human genome and relies heavily on distant regulatory elements. The regulation guided by these elements is independent of the distance between the gene and its distant regulatory element, or the distance between two distant regulatory cassettes. The location of gene deserts and their associated genes in the genome is independent of chromosomal length or content presenting these regions as well-bounded regions evolving separately from the rest of the genome.

  5. Peoples of Africa, Topic 1. Africa South of the Sahara: A Program of Study for Secondary School Social Studies Students. (Teaching and Student Guides).

    ERIC Educational Resources Information Center

    Carnegie-Mellon Univ., Pittsburgh, PA. Project Africa.

    This teaching guide and student text for Project Africa's curriculum program, "Africa South of the Sahara," deal with how four typical contemporary African peoples acquired their present way of life: (1) the Hausa of Northern Nigeria, (2) the Kung Bushmen of the Kalahari Desert, (3) the Mech'a Galla of Ethiopa, and (4) the Kikuyu of Kenya.…

  6. Desert Dust and Monsoon Rain

    NASA Technical Reports Server (NTRS)

    Lau, William K. M.; Kim, Kyu-Myong

    2014-01-01

    For centuries, inhabitants of the Indian subcontinent have know that heavy dust events brought on by strong winds occur frequently in the pre-monsoon season, before the onset of heavy rain. Yet scientists have never seriously considered the possibility that natural dust can affect monsoon rainfall. Up to now, most studies of the impacts of aerosols on Indian monsoon rainfall have focused on anthropogenic aerosols in the context of climate change. However, a few recent studies have show that aerosols from antropogenic and natural sources over the Indian subcontinent may affect the transition from break to active monsoon phases on short timescales of days to weeks. Writing in Nature Geoscience, Vinoj and colleagues describe how they have shown that desert dust aerosols over the Arabian Sea and West Asia can strenghten the summer monsoon over the Indial subcontinent in a matter of days.

  7. Browning in Desert Boundaries in Asia in Recent Decades

    NASA Technical Reports Server (NTRS)

    Jeong, Su-Jong; Ho, Chang-Hoi; Brown, Molly E.; Kug, Jong-Seong; Piao, Shilong

    2011-01-01

    In this study, the changes in desert boundaries in Asia (Gobi, Karakum, Lut, Taklimakan, and Thar deserts) during the growing season (April October) in the years 1982 2008 were investigated by analyzing the normalized difference vegetation index (NDVI), precipitation, and temperature. In the desert boundary regions, the domain mean NDVI values increased by 7.2% per decade in 1982 1998 but decreased by 6.8% per decade thereafter. Accordingly, the bare soil areas (or nonvegetated areas) of the inside of the desert boundaries contracted by 9.8% per decade in the 1990s and expanded by 8.7% per decade in the 2000s. It is noted that the five deserts experience nearly simultaneous NDVI changes although they cover a very diverse area of Asia. In contrast, changes in temperature and precipitation in the deserts show rather diverse results. In desert boundaries located along 40 N (Gobi, Taklimakan, and Karakum), the decadal changes in vegetation greenness were mainly related to regional climate during the entire analysis period. Precipitation increased in the 1990s, providing favorable conditions for vegetation growth (i.e., greening), but precipitation reduced (19 mm per decade) and warming intensified (0.7 C per decade) in the 2000s, causing less moisture to be available for vegetation growth (i.e., browning). In desert boundaries below 40 N (Lut and Thar), although an increase in precipitation (8 mm per decade) led to greening in the 1990s, local changes in precipitation and temperature did not necessarily cause browning in the 2000s. Observed multidecadal changes in vegetation greenness in the present study suggest that under significant global and/or regional warming, changes in moisture availability for vegetation growth in desert boundaries are an important factor when understanding decadal changes in areas vulnerable to desertification over Asia.

  8. Active sand dunes are largest dust source in the Sahara Desert

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Atreyee

    2012-09-01

    Dried up lakebeds and playas in the Sahara Desert of North Africa are large sources of dust in the atmosphere. The Bodélé Depression at the southern edge of the Sahara Desert, for example, is the single largest source of dust in the world; on average, 100 dust storms a year originate from the Bodélé Depression. A new study by Crouvi et al., however, finds that active sand dunes could be even bigger sources of desert dust in the atmosphere. Atmospheric dust plays active roles in climate and biological processes in the ocean: It regulates heating at the surface of the Earth; modifies cloud properties that affect rainfall; and acts as the only source of iron, a critical nutrient for microorganisms in the ocean. Little is known about types of dust sources in the Sahara Desert, which alone accounts for more than 50% of the dust in the atmosphere.

  9. Desert landscape irrigation

    SciTech Connect

    Quinones, R.

    1995-06-01

    Industrialization can take place in an arid environment if a long term, overall water management program is developed. The general rule to follow is that recharge must equal or exceed use. The main problem encountered in landscape projects is that everyone wants a lush jungle setting, tall shade trees, ferns, with a variety of floral arrangements mixed in. What we want, what we can afford, and what we get are not always the same. Vegetation that requires large quantities of water are not native to any desert. Surprisingly; there are various types of fruit trees, and vegetables that will thrive in the desert. Peaches, plums, nut trees, do well with drip irrigation as well as tomatoes. Shaded berry plans will also do well, the strawberry being one. In summary; if we match our landscape to our area, we can then design our irrigation system to maintain our landscape and grow a variety of vegetation in any arid or semiarid environment. The application of science and economics to landscaping has now come of age.

  10. Supersymmetry without the Desert

    SciTech Connect

    Nomura, Yasunori; Poland, David

    2006-09-26

    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){sub 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.

  11. Aerosol direct radiative forcing in desert and semi-desert regions of northwestern China

    NASA Astrophysics Data System (ADS)

    Xin, Jinyuan; Gong, Chongshui; Wang, Shigong; Wang, Yuesi

    2016-05-01

    The optical properties of dust aerosols were measured using narrow-band data from a portable sun photometer at four desert and semi-desert stations in northwestern China from 2004 to 2007. Ground-based and satellite observations indicated absorbing dust aerosol loading over the region surrounded by eight large-scale deserts. Radiation forcing was identified by using the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model. The ranges of annual mean aerosol optical depth (AOD), Angström exponents, and single-scattering albedo (SSA) were from 0.25 to 0.35, from - 0.73 to 1.18, and from 0.77 to 0.86, respectively. The ranges of annual mean aerosol direct radiative forcing values at the top of the atmosphere (TOA), mid-atmosphere, and on the surface were from 3.9 to 12.0, from 50.0 to 53.1, and from - 39.1 to - 48.1 W/m2, respectively. The aerosols' optical properties and radiative characteristics showed strong seasonal variations in both the desert and semi-desert regions. Strong winds and relatively low humidity will lead dust aerosols in the atmosphere to an increase, which played greatly affected these optical properties during spring and winter in northwestern China. Based on long-term observations and retrieved data, aerosol direct radiative forcing was confirmed to heat the atmosphere (50-53 W/m2) and cool the surface (- 39 to - 48 W/m2) above the analyzed desert. Radiative forcing in the atmosphere in spring and winter was 18 to 21 W/m2 higher than other two seasons. Based on the dust sources around the sites, the greater the AOD, the more negative the forcing. The annual averaged heating rates for aerosols close to the ground (1 km) were approximately 0.80-0.85 K/day.

  12. Living on the edge: timing of Rand Flora disjunctions congruent with ongoing aridification in Africa

    PubMed Central

    Pokorny, Lisa; Riina, Ricarda; Mairal, Mario; Meseguer, Andrea S.; Culshaw, Victoria; Cendoya, Jon; Serrano, Miguel; Carbajal, Rodrigo; Ortiz, Santiago; Heuertz, Myriam; Sanmartín, Isabel

    2015-01-01

    The Rand Flora is a well-known floristic pattern in which unrelated plant lineages show similar disjunct distributions in the continental margins of Africa and adjacent islands—Macaronesia-northwest Africa, Horn of Africa-Southern Arabia, Eastern Africa, and Southern Africa. These lineages are now separated by environmental barriers such as the arid regions of the Sahara and Kalahari Deserts or the tropical lowlands of Central Africa. Alternative explanations for the Rand Flora pattern range from vicariance and climate-driven extinction of a widespread pan-African flora to independent dispersal events and speciation in situ. To provide a temporal framework for this pattern, we used published data from nuclear and chloroplast DNA to estimate the age of disjunction of 17 lineages that span 12 families and nine orders of angiosperms. We further used these estimates to infer diversification rates for Rand Flora disjunct clades in relation to their higher-level encompassing lineages. Our results indicate that most disjunctions fall within the Miocene and Pliocene periods, coinciding with the onset of a major aridification trend, still ongoing, in Africa. Age of disjunctions seemed to be related to the climatic affinities of each Rand Flora lineage, with sub-humid taxa dated earlier (e.g., Sideroxylon) and those with more xeric affinities (e.g., Campylanthus) diverging later. We did not find support for significant decreases in diversification rates in most groups, with the exception of older subtropical lineages (e.g., Sideroxylon, Hypericum, or Canarina), but some lineages (e.g., Cicer, Campylanthus) showed a long temporal gap between stem and crown ages, suggestive of extinction. In all, the Rand Flora pattern seems to fit the definition of biogeographic pseudocongruence, with the pattern arising at different times in response to the increasing aridity of the African continent, with interspersed periods of humidity allowing range expansions. PMID:25983742

  13. Living on the edge: timing of Rand Flora disjunctions congruent with ongoing aridification in Africa.

    PubMed

    Pokorny, Lisa; Riina, Ricarda; Mairal, Mario; Meseguer, Andrea S; Culshaw, Victoria; Cendoya, Jon; Serrano, Miguel; Carbajal, Rodrigo; Ortiz, Santiago; Heuertz, Myriam; Sanmartín, Isabel

    2015-01-01

    The Rand Flora is a well-known floristic pattern in which unrelated plant lineages show similar disjunct distributions in the continental margins of Africa and adjacent islands-Macaronesia-northwest Africa, Horn of Africa-Southern Arabia, Eastern Africa, and Southern Africa. These lineages are now separated by environmental barriers such as the arid regions of the Sahara and Kalahari Deserts or the tropical lowlands of Central Africa. Alternative explanations for the Rand Flora pattern range from vicariance and climate-driven extinction of a widespread pan-African flora to independent dispersal events and speciation in situ. To provide a temporal framework for this pattern, we used published data from nuclear and chloroplast DNA to estimate the age of disjunction of 17 lineages that span 12 families and nine orders of angiosperms. We further used these estimates to infer diversification rates for Rand Flora disjunct clades in relation to their higher-level encompassing lineages. Our results indicate that most disjunctions fall within the Miocene and Pliocene periods, coinciding with the onset of a major aridification trend, still ongoing, in Africa. Age of disjunctions seemed to be related to the climatic affinities of each Rand Flora lineage, with sub-humid taxa dated earlier (e.g., Sideroxylon) and those with more xeric affinities (e.g., Campylanthus) diverging later. We did not find support for significant decreases in diversification rates in most groups, with the exception of older subtropical lineages (e.g., Sideroxylon, Hypericum, or Canarina), but some lineages (e.g., Cicer, Campylanthus) showed a long temporal gap between stem and crown ages, suggestive of extinction. In all, the Rand Flora pattern seems to fit the definition of biogeographic pseudocongruence, with the pattern arising at different times in response to the increasing aridity of the African continent, with interspersed periods of humidity allowing range expansions. PMID:25983742

  14. Water capture by a desert beetle

    NASA Astrophysics Data System (ADS)

    Parker, Andrew R.; Lawrence, Chris R.

    2001-11-01

    Some beetles in the Namib Desert collect drinking water from fog-laden wind on their backs. We show here that these large droplets form by virtue of the insect's bumpy surface, which consists of alternating hydrophobic, wax-coated and hydrophilic, non-waxy regions. The design of this fog-collecting structure can be reproduced cheaply on a commercial scale and may find application in water-trapping tent and building coverings, for example, or in water condensers and engines.

  15. Inferences about winter temperatures and summer rains from the late Quaternary record of C4 perennial grasses and C3 desert shrubs in the northern Chihuahuan Desert

    USGS Publications Warehouse

    Holmgren, Camille A.; Norris, Jodi; Betancourt, Julio L.

    2007-01-01

    Late Quaternary histories of two North American desert biomes—C4 grasslands and C3 shrublands—are poorly known despite their sensitivity and potential value in reconstructing summer rains and winter temperatures. Plant macrofossil assemblages from packrat midden series in the northern Chihuahuan Desert show that C4 grasses and annuals typical of desert grassland persisted near their present northern limits throughout the last glacial-interglacial cycle. By contrast, key C3 desert shrubs appeared somewhat abruptly after 5000cal.yrBP. Bioclimatic envelopes for select C4 and C3 species are mapped to interpret the glacial-interglacial persistence of desert grassland and the mid-to-late Holocene expansion of desert shrublands. The envelopes suggest relatively warm Pleistocene temperatures with moist summers allowed for persistence of C4 grasses, whereas winters were probably too cold (or too wet) for C3 desert shrubs. Contrary to climate model results, core processes associated with the North American Monsoon and moisture transport to the northern Chihuahuan Desert remained intact throughout the last glacial-interglacial cycle. Mid-latitude effects, however, truncated midsummer (July-August) moisture transport north of 35° N. The sudden expansion of desert shrublands after 5000cal.yrBP may be a threshold response to warmer winters associated with increasing boreal winter insolation, and enhanced El Niño-Southern Oscillation variability.

  16. A Microscopists View of Desert Varnish from the Sonoran Desert

    NASA Astrophysics Data System (ADS)

    Garvie, L. A. J.; Burt, D. M.; Buseck, P. R.

    2009-03-01

    Nanometer-scale element mapping and spectroscopy of desert varnish reveals a dynamic disequilibrium system characterized by post-depositional mineralogical, chemical, and structural changes, activated by liquid water.

  17. Challenge of a desert: revegetation of disturbed desert lands

    SciTech Connect

    Wallace, A.; Romney, E.M.; Hunter, R.B.

    1980-01-01

    The revegetation of disturbed, arid lands is one of the great challenges of a desert. An attempt to encourage it is not an impossible task, however, if the natural and the man-made resources available are utilized and managed. Where rainfall and temperature conditions approach or exceed those of the Great Basin desert, restoration of disturbed land will occur through natural revegetation processes within a reasonable period of time. This is not generally the case in the more arid Mojave Desert areas where the moisture and temperature conditions are less favorable for germination and seedling survival. Restoration of vegetation by natural reseeding can, however, occur within local sites where moisture has concentrated as the result of terrain features forming catchment basins. Otherwise, the natural revegetation processes in the Mojave Desert areas require much longer periods of time (possibly decades or centuries) than are practical for meeting environmental protection standards imposed by current legislation. Through better understanding of the processes governing revegetation and the ability to control them, it is possible for man to more rapidly restore disturbed desert lands. Terrain manipulation to form moisture catchment basins, selection of seed from pioneering shrub species, preservation of existing shrub clump fertile islands in the soil, supplemental fertilization, irrigation, organic amendments, and transplanting vigorous shrub species are some of the important things that can be done to help restore disturbed desert land.

  18. Making silica rock coatings in the lab: synthetic desert varnish

    NASA Astrophysics Data System (ADS)

    Perry, Randall S.; Kolb, Vera M.; Philip, Ajish I.; Lynne, Bridget Y.; McLoughlin, Nicola; Sephton, Mark; Wacey, David; Green, Owen R.

    2005-09-01

    Desert varnish and silica rock coatings have perplexed investigators since Humboldt and Darwin. They are found in arid regions and deserts on Earth but the mechanism of their formation remains challenging (see Perry et al. this volume). One method of researching this is to investigate natural coatings, but another way is to attempt to produce coatings in vitro. Sugars, amino acids, and silicic acid, as well as other organic and (bio)organic compounds add to the complexity of naturally forming rock coatings. In the lab we reduced the complexity of the natural components and produced hard, silica coatings on basaltic chips obtained from the Mojave Desert. Sodium silicate solution was poured over the rocks and continuously exposed to heat and/or UV light. Upon evaporation the solutions were replenished. Experiments were performed at various pH's. The micro-deposits formed were analyzed using optical, SEM-EDAX, and electron microprobe. The coatings formed are similar in hardness and composition to silica glazes found on basalts in Hawaii as well as natural desert varnish found in US southwest deserts. Thermodynamic mechanisms are presented showing the theoretical mechanisms for overcoming energy barriers that allow amorphous silica to condense into hard coatings. This is the first time synthetic silica glazes that resemble natural coatings in hardness and chemical composition have been successfully reproduced in the laboratory, and helps to support an inorganic mechanism of formation of desert varnish as well as manganese-deficient silica glazes.

  19. Keeping the desert at bay

    SciTech Connect

    El-Kassas, M.

    1981-02-01

    Man-made desert (areas that are no longer productive) has increased the world's deserts from 36.3 to 43% of the land surface. Desertification involves ecological degradation that makes the land less productive or allows an uneconomic type of vegetation, such as mesquite, to replace an economic plant. The process was first thought to be an encroachment by expanding deserts, but, except for the movement of sand dunes, desertification is now viewed as productive land that deteriorated and was added to the desert. Land is lost to agriculture by erosion, loss of nutrients, compaction, salination, urban development, and pollution. The interacting biosphere, technosphere, and social sphere form the framework of man's existence. An understanding of this framework is crucial to those offering technological assistance to developing countries. (DCK)

  20. South Africa

    Atmospheric Science Data Center

    2013-04-16

    ... atmospheric and oceanic conditions. At Elands Bay in South Africa's Western Cape province, about 1000 tons of rock lobsters beached ... red tide. At the same time, people came from across South Africa to gather the undersized creatures for food. The effects of the losses ...

  1. "The Show"

    ERIC Educational Resources Information Center

    Gehring, John

    2004-01-01

    For the past 16 years, the blue-collar city of Huntington, West Virginia, has rolled out the red carpet to welcome young wrestlers and their families as old friends. They have come to town chasing the same dream for a spot in what many of them call "The Show". For three days, under the lights of an arena packed with 5,000 fans, the state's best…

  2. Living in biological soil crust communities of African deserts-Physiological traits of green algal Klebsormidium species (Streptophyta) to cope with desiccation, light and temperature gradients.

    PubMed

    Karsten, Ulf; Herburger, Klaus; Holzinger, Andreas

    2016-05-01

    Green algae of the genus Klebsormidium (Klebsormidiales, Streptophyta) are typical members of biological soil crusts (BSCs) worldwide. The phylogeny and ecophysiology of Klebsormidium has been intensively studied in recent years, and a new lineage called superclade G, which was isolated from BSCs in arid southern Africa and comprising undescribed species, was reported. Three different African strains, that have previously been isolated from hot-desert BSCs and molecular-taxonomically characterized, were comparatively investigated. In addition, Klebsormidium subtilissimum from a cold-desert habitat (Alaska, USA, superclade E) was included in the study as well. Photosynthetic performance was measured under different controlled abiotic conditions, including dehydration and rehydration, as well as under a light and temperature gradient. All Klebsormidium strains exhibited optimum photosynthetic oxygen production at low photon fluence rates, but with no indication of photoinhibition under high light conditions pointing to flexible acclimation mechanisms of the photosynthetic apparatus. Respiration under lower temperatures was generally much less effective than photosynthesis, while the opposite was true for higher temperatures. The Klebsormidium strains tested showed a decrease and inhibition of the effective quantum yield during desiccation, however with different kinetics. While the single celled and small filamentous strains exhibited relatively fast inhibition, the uniserate filament forming isolates desiccated slower. Except one, all other strains fully recovered effective quantum yield after rehydration. The presented data provide an explanation for the regular occurrence of Klebsormidium strains or species in hot and cold deserts, which are characterized by low water availability and other stressful conditions. PMID:26422081

  3. Epifluorescent direct counts of bacteria and viruses from topsoil of various desert dust storm regions.

    PubMed

    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. PMID:22989672

  4. Epifluorescent direct counts of bacteria and viruses from topsoil of various desert dust storm regions

    USGS Publications Warehouse

    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.

  5. Sonoran Desert: Fragile Land of Extremes

    USGS Publications Warehouse

    Produced and Directed by Wessells, Stephen

    2003-01-01

    'Sonoran Desert: Fragile Land of Extremes' shows how biologists with the U.S. Geological Survey work with other scientists in an effort to better understand native plants and animals such as desert tortoises, saguaro cacti, and Gila monsters. Much of the program was shot in and around Saguaro National Park near Tucson, Arizona. Genetic detective work, using DNA, focuses on understanding the lives of tortoises. Studies of saguaros over many decades clarify how these amazing plants reproduce and thrive in the desert. Threats from fire, diseases in tortoises, and a growing human population motivate the scientists. Their work to identify how these organisms live and survive is a crucial step for the sound management of biological resources on public lands. This 28-minute program, USGS Open-File Report 03-305, was shot entirely in high definition video and produced by the USGS Western Ecological Research Center and Southwest Biological Science Center; produced and directed by Stephen Wessells, Western Region Office of Communications.

  6. Mate desertion in the snail kite

    USGS Publications Warehouse

    Beissinger, S.R.; Snyder, N.F.R.

    1988-01-01

    Mate desertion during the breeding cycle was documented at 28 of 36 (78%) snail kite, Rostrhamus sociabilis nests in Florida between 1979 and 1983. Offspring mortality occurred at only one deserted nest, however. Parents that were deserted by their mates continued to care for their young until independence (3?5 additional weeks) and provided snails at a rate similar to that of both parents combined before desertion. Males and females deserted with nearly equal frequency, except in 1982 when more females deserted. No desertion occurred during drought years, whereas desertion occurred at nearly every nest during favourable conditions. The occurrence of mate desertion was generally related to indirect measures of snail abundance: foraging range, snail delivery rates to the young and growth rates. Small broods were deserted more frequently by females than by males and tended to be deserted earlier than large ones. After desertion, deserters had the opportunity to re-mate and nest again since breeding seasons were commonly lengthy, but whether they did so was impossible to determine conclusively in most cases. The deserted bird sometimes incurred increased energetic costs and lost breeding opportunities during periods of monoparental care.

  7. Simulation of bulk aerosol direct radiative effects and its climatic feedbacks in South Africa using RegCM4

    NASA Astrophysics Data System (ADS)

    Tesfaye, M.; Botai, J.; Sivakumar, V.; Mengistu Tsidu, G.; Rautenbach, C. J. deW.; Moja, Shadung J.

    2016-05-01

    In this study, 12 year runs of the Regional Climate Model (RegCM4) have been used to analyze the bulk aerosol radiative effects and its climatic feedbacks in South Africa. Due to the geographical locations where the aerosol potential source regions are situated and the regional dynamics, the South African aerosol spatial-distribution has a unique feature. Across the west and southwest areas, desert dust particles are dominant. However, sulfate and carbonaceous aerosols are primarily distributed over the east and northern regions of the country. Analysis of the Radiative Effects (RE) shows that in South Africa the bulk aerosols play a role in reducing the net radiation absorbed by the surface via enhancing the net radiative heating in the atmosphere. Hence, across all seasons, the bulk aerosol-radiation-climate interaction induced statistically significant positive feedback on the net atmospheric heating rate. Over the western and central parts of South Africa, the overall radiative feedbacks of bulk aerosol predominantly induces statistically significant Cloud Cover (CC) enhancements. Whereas, over the east and southeast coastal areas, it induces minimum reductions in CC. The CC enhancement and RE of aerosols jointly induce radiative cooling at the surface which in turn results in the reduction of Surface Temperature (ST: up to -1 K) and Surface Sensible Heat Flux (SSHF: up to -24 W/m2). The ST and SSHF decreases cause a weakening of the convectively driven turbulences and surface buoyancy fluxes which lead to the reduction of the boundary layer height, surface pressure enhancement and dynamical changes. Throughout the year, the maximum values of direct and semi-direct effects of bulk aerosol were found in areas of South Africa which are dominated by desert dust particles. This signals the need for a strategic regional plan on how to reduce the dust production and monitoring of the dust dispersion as well as it initiate the need of further research on different

  8. Quaternary climate change on the northern margins of Saharo-Arabian Desert with possible impact on human evolution, evidence from Negev Desert speleothems, Israel

    NASA Astrophysics Data System (ADS)

    Vaks, A.; Bar-Matthews, M.; Ayalon, A.; Matthews, A.; Halicz, L.; Frumkin, A.

    2006-12-01

    The Saharo-Arabian Desert belt is the largest and driest desert in the world and its margins are vulnerable to climatic change. The paleoclimate of the northern margins of Saharo-Arabian Desert is not yet fully understood, and it is the subject of our study. The Negev Desert, southern Israel, located in the northern part of the Saharo-Arabian Desert is ideal for paleoclimate research, because of its very steep north-south precipitation gradient and numerous caves rich with carbonate cave deposits (speleothems). Speleothems grow only when precipitation is high enough to enable meteoric water to reach the caves. No present day speleothem deposition occurs in the Negev Desert. The aims of the study were: timing of the humid periods by U-Th dating of the speleothem deposition periods; origin of the rainfall by speleothem δ18O and fluid inclusions δ2H; correlations between local and global climate changes and between the climate changes to out of Africa dispersals of Early Modern Humans (EMH). Speleothems were collected from 7 caves located on the north-south transect of the Negev Desert, between 300 mm to 30 mm isohyets. Whereas in the Mediterranean climate zone (>350 mm) of central and northern Israel the speleothem deposition was continuous, in the Negev Desert periods of speleothem deposition alternated with multiple hiatuses. In the mildly arid transition zone of northern Negev (300 to 150 mm) speleothem deposition occurred most of the time during the last 210 ka, with hiatuses at 150-144 ka, ~140 ka, 117-96 ka, 93-85 ka, 25- 23 ka, and 14-0 ka. In present-day arid and hyper-arid zone of central and southern Negev (150 to 30 mm) no speleothem deposition occurred most of the last 350 ka, with humid intervals at 350-290 ka, 220-190 ka, 137- 110 ka, and ~85 ka. The origin of the precipitation in the Negev Desert during these intervals was from Eastern Mediterranean Sea, i. e. mid-latitude cyclones (as present day). The latter conclusion is based on three evidences

  9. Desert and desertification in Iran

    NASA Astrophysics Data System (ADS)

    Bahrami, M.

    2009-04-01

    One of the greatest environmental concerns in Iran as in other arid and semiarid countries is the transformation of once productive, or marginally productive, land to deteriorated land and soil unable to support plants and animals. Because the land becomes barren and dry, the process is described as desertification, which occurs as a sequence of events. The area of deserts in Iran is about 340,000 Km2 (less than one fifth of its total area), of which 100,000 Km2 is being used for some cultivation, 120,000 Km2 is subjected to moving sands about 40 % of which is active sand dunes. Most of features and processes usual in world famous deserts are also observed in Iran: low precipitation, high evaporation, poor or lack of vegetation, saline and alkaline soils, low population and small and sparse oases. The deserts of Iran are generally classified in the subtropical, warm, arid and semiarid group, but the effect and presence of some geographical and geoclimatical factors such as height, vicinity to Indian Ocean and so on do some changes in climatic conditions and geographical features causing some local and regional differences in them. Geographically, two groups of deserts have been known in Iran: (1) Coastal deserts which, like a ribbon with variable width, stretch from extreme southeast to extreme southwest, at the north parts of Oman Sea and Persian Gulf. One important feature of these deserts is relatively high humidity which differentiates them from other deserts. This causes an increase in vegetation coverage and hence a decrease in eolian erosion and also a dominance of chemical weathering to that of physical. (2) internal deserts, which rest in central, eastern and southeastern plateau of the country and in independent and semi dependent depressions. This situation, which is due to the surrounding high mountains, blocks humidity entry and causes the aridity of these deserts. Wind as a dominant process in the area causes deflated features such as Reg (desert

  10. Physiological Conjunction of Allelochemicals and Desert Plants

    PubMed Central

    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. PMID:24339945

  11. Physiological conjunction of allelochemicals and desert plants.

    PubMed

    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. PMID:24339945

  12. Africa: "Yonondio."

    ERIC Educational Resources Information Center

    Bendetson, Jane

    1996-01-01

    Recounts a teacher's experiences on a trip to Africa. Describes her pleasant moments with her fellow travelers; her appreciation of the natural setting; her visit to an impoverished native school; and her confrontation with a Maasai warrior. (TB)

  13. The provenance of Taklamakan desert sand

    NASA Astrophysics Data System (ADS)

    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

  14. Estimation of saltation emission in the Kubuqi Desert, North China.

    PubMed

    Du, Heqiang; Xue, Xian; Wang, Tao

    2014-05-01

    The Kubuqi Desert suffered more severe wind erosion hazard. Every year, a mass of aeolian sand was blown in the Ten Tributaries that are tributaries of the Yellow River. To estimate the quantity of aeolian sediment blown into the Ten Tributaries from the Kubuqi Desert, it is necessary to simulate the saltation processes of the Kubuqi Desert. A saltation submodel of the IWEMS (Integrated Wind-Erosion Modeling System) and its accompanying RS (Remote Sensing) and GIS (Geographic Information System) methods were used to model saltation emissions in the Kubuqi Desert. To calibrate the saltation submodel, frontal area of vegetation, soil moisture, wind velocity and saltation sediment were observed synchronously on several points in 2011 and 2012. In this study, a model namely BEACH (Bridge Event And Continuous Hydrological) was introduced to simulate the daily soil moisture. Using the surface parameters (frontal area of vegetation and soil moisture) along with the observed wind velocities and saltation sediments for the observed points, the saltation model was calibrated and validated. To reduce the simulate error, a subdaily wind velocity program, WINDGEN was introduced in this model to simulate the hourly wind velocity of the Kubuqi Desert. By incorporating simulated hourly wind velocity, and model variables, the saltation emission of the Kubuqi Desert was modeled. The model results show that the total sediment flow rate was 1-30.99 tons/m over the last 10years (2001-2010). The saltation emission mainly occurs in the north central part of the Kubuqi Desert in winter and spring. Integrating the wind directions, the quantity of the aeolian sediment that deposits in the Ten Tributaries was estimated. Compared with the observed data by the local government and hydrometric stations, our estimation is reasonable. PMID:24534701

  15. Phytoremediation for Oily Desert Soils

    NASA Astrophysics Data System (ADS)

    Radwan, Samir

    This chapter deals with strategies for cleaning oily desert soils through rhizosphere technology. Bioremediation involves two major approaches; seeding with suitable microorganisms and fertilization with microbial growth enhancing materials. Raising suitable crops in oil-polluted desert soils fulfills both objectives. The rhizosphere of many legume and non-legume plants is richer in oil-utilizing micro-organisms than non-vegetated soils. Furthermore, these rhizospheres also harbour symbiotic and asymbiotic nitrogen-fixing bacteria, and are rich in simple organic compounds exuded by plant roots. Those exudates are excellent nutrients for oil-utilizing microorganisms. Since many rhizospheric bacteria have the combined activities of hydrocarbon-utilization and nitrogen fixation, phytoremediation provides a feasible and environmentally friendly biotechnology for cleaning oil-polluted soils, especially nitrogen-poor desert soils.

  16. Simulated climate and biomes of Africa during the late quaternary: comparison with pollen and lake status data

    NASA Astrophysics Data System (ADS)

    Jolly, D.; Harrison, S. P.; Damnati, B.; Bonnefille, R.

    New compilations of African pollen and lake data are compared with climate (CCM1, NCAR, Boulder) and vegetation (BIOME 1.2, GSG, Lund) simulations for the last glacial maximum (LGM) and early to mid-Holocene (EMH). The simulated LGM climate was ca 4°C colder and drier than present, with maximum reduction in precipitation in semi-arid regions. Biome simulations show lowering of montane vegetation belts and expansion of southern xerophytic associations, but no change in the distribution of deserts and tropical rain forests. The lakes show LGM conditions similar or drier than present throughout northern and tropical Africa. Pollen data indicate lowering of montane vegetation belts, the stability of the Sahara, and a reduction of rain forest. The paleoenvironmental data are consistent with the simulated changes in temperature and moisture budgets, although they suggest the climate model underestimates equatorial aridity. EMH simulations show temperatures slightly less than present and increased monsoonal precipitation in the eastern Sahara and East Africa. Biome simulations show an upward shift of montane vegetation belts, fragmentation of xerophytic vegetation in southern Africa, and a major northward shift of the southern margin of the eastern Sahara. The lakes indicate conditions wetter than present across northern Africa. Pollen data show an upward shift of the montane forests, the northward shift of the southern margin of the Sahara, and a major extension of tropical rain forest. The lake and pollen data confirm monsoon expansion in eastern Africa, but the climate model fails to simulate the wet conditions in western Africa.

  17. Should I Stay or Should I Go? Dispersal and Population Structure in Small, Isolated Desert Populations of West African Crocodiles

    PubMed Central

    Campos, João Carlos; Brito, José Carlos

    2014-01-01

    The maintenance of both spatial and genetic connectivity is paramount to the long-term persistence of small, isolated populations living in environments with extreme climates. We aim to identify the distribution of genetic diversity and assess population sub-structuring and dispersal across dwarfed desert populations of Crocodylus suchus, which occur in isolated groups, usually less than five individuals, along the mountains of Mauritania (West Africa). We used both invasive and non-invasive sampling methods and a combination of mitochondrial DNA (12 S and ND4) and microsatellite markers (32 loci and a subset of 12 loci). Our results showed high genetic differentiation and geographic structure in Mauritanian populations of C. suchus. We identified a metapopulation system acting within four river sub-basins (high gene flow and absence of genetic structure) and considerable genetic differentiation between sub-basins (FST range: 0.12–0.24) with rare dispersal events. Effective population sizes tend to be low within sub-basins while genetic diversity is maintained. Our study suggests that hydrographic networks (temporal connections along seasonal rivers during rainy periods) allow C. suchus to disperse and maintain metapopulation dynamics within sub-basins, which attenuate the loss of genetic diversity and the risk of extinction. We highlight the need of hydrographic conservation to protect vulnerable crocodiles isolated in small water bodies. We propose C. suchus as an umbrella species in Mauritania based on ecological affinities shared with other water-dependent species in desert environments. PMID:24740183

  18. Should I stay or should I go? Dispersal and population structure in small, isolated desert populations of West African crocodiles.

    PubMed

    Velo-Antón, Guillermo; Godinho, Raquel; Campos, João Carlos; Brito, José Carlos

    2014-01-01

    The maintenance of both spatial and genetic connectivity is paramount to the long-term persistence of small, isolated populations living in environments with extreme climates. We aim to identify the distribution of genetic diversity and assess population sub-structuring and dispersal across dwarfed desert populations of Crocodylus suchus, which occur in isolated groups, usually less than five individuals, along the mountains of Mauritania (West Africa). We used both invasive and non-invasive sampling methods and a combination of mitochondrial DNA (12 S and ND4) and microsatellite markers (32 loci and a subset of 12 loci). Our results showed high genetic differentiation and geographic structure in Mauritanian populations of C. suchus. We identified a metapopulation system acting within four river sub-basins (high gene flow and absence of genetic structure) and considerable genetic differentiation between sub-basins (FST range: 0.12-0.24) with rare dispersal events. Effective population sizes tend to be low within sub-basins while genetic diversity is maintained. Our study suggests that hydrographic networks (temporal connections along seasonal rivers during rainy periods) allow C. suchus to disperse and maintain metapopulation dynamics within sub-basins, which attenuate the loss of genetic diversity and the risk of extinction. We highlight the need of hydrographic conservation to protect vulnerable crocodiles isolated in small water bodies. We propose C. suchus as an umbrella species in Mauritania based on ecological affinities shared with other water-dependent species in desert environments. PMID:24740183

  19. Saharan Desert Dust Sources: New Insights Based on Aerosol Vertical Profiles Retrieved from Thermal Infrared Measurements by IASI

    NASA Astrophysics Data System (ADS)

    Vandenbussche, S.; Kumps, N.; Vandaele, A. C.; De Maziere, M.

    2015-06-01

    Desert dust is a major actor in the climate and one of the least characterized with respect to its radiative forcing, both direct and indirect. Studies of dust atmospheric load and sources are therefore of great scientific interest. In the last years, we have developed and improved a retrieval strategy to obtain desert dust aerosols vertical profiles, from thermal infrared measurements by IASI. This strategy has been used to process significant amount of IASI data above North Africa. This dataset allows a new insight in the study of Saharan desert dust sources: it provides twice a day, at interesting times considering the dust emission diurnal cycle, vertical profiles of desert dust (not only optical depth), making possible to distinguish local emissions from transported dust.

  20. Water capture by a desert beetle.

    PubMed

    Parker, A R; Lawrence, C R

    2001-11-01

    Some beetles in the Namib Desert collect drinking water from fog-laden wind on their backs. We show here that these large droplets form by virtue of the insect's bumpy surface, which consists of alternating hydrophobic, wax-coated and hydrophilic, non-waxy regions. The design of this fog-collecting structure can be reproduced cheaply on a commercial scale and may find application in water-trapping tent and building coverings, for example, or in water condensers and engines. PMID:11689930

  1. Evidence for photochemical production of reactive oxygen species in desert soils.

    PubMed

    Georgiou, Christos D; Sun, Henry J; McKay, Christopher P; Grintzalis, Konstantinos; Papapostolou, Ioannis; Zisimopoulos, Dimitrios; Panagiotidis, Konstantinos; Zhang, Gaosen; Koutsopoulou, Eleni; Christidis, George E; Margiolaki, Irene

    2015-01-01

    The combination of intense solar radiation and soil desiccation creates a short circuit in the biogeochemical carbon cycle, where soils release significant amounts of CO2 and reactive nitrogen oxides by abiotic oxidation. Here we show that desert soils accumulate metal superoxides and peroxides at higher levels than non-desert soils. We also show the photogeneration of equimolar superoxide and hydroxyl radical in desiccated and aqueous soils, respectively, by a photo-induced electron transfer mechanism supported by their mineralogical composition. Reactivity of desert soils is further supported by the generation of hydroxyl radical via aqueous extracts in the dark. Our findings extend to desert soils the photogeneration of reactive oxygen species by certain mineral oxides and also explain previous studies on desert soil organic oxidant chemistry and microbiology. Similar processes driven by ultraviolet radiation may be operating in the surface soils on Mars. PMID:25960012

  2. Water use sources of desert riparian Populus euphratica forests.

    PubMed

    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. PMID:24816539

  3. Chemical Alterations in Martian Meteorites from Cold and Hot Deserts

    NASA Astrophysics Data System (ADS)

    Dreibus, G.; Huisl, W.; Spettel, B.; Haubold, R.; Jagoutz, E.

    2003-04-01

    Martian meteorites (SNC) provide evidence of the magmatic fractionation processes of their parent body. As 23 of the total of 27 meteorites are finds, the influence of chemical alterations during their residence time on Earth must be considered, when interpreting the mineralogical, chemical, or isotopic features. Many basaltic shergottites and nakhlites were collected both in the cold desert, Antarctica, and in hot deserts of North Africa and Asia. To detect alteration processes in the finds we have to compare their analytical data with those obtained from the very scarce falls. In this way, we find an overabundance of iodine in meteorites from Antarctica. The iodine contamination is caused by aerosols adhering to the ice. Therefore, iodine can penetrate into the meteorite during its residence in Antarctica. The iodine content measured in the Antarctic shergottites varies from 0.060 to 4.6 ppm and seems to depend on their residence time on ice. The paired Yamato nakhlites Y-000593 and Y-000749 recently discovered in Antarctica also reveal an iodine overabundance compared to Nakhla, which is the only fall among the nakhlites. However, in Nakhla we have another problem of alteration. Nakhla has unusually high Br and Cl concentrations which could originate from terrestrial or parent body alterations. As Cl and Br are readily extracted during water leaching experiments we favor a terrestrial contamination. A Br overabundance was also found in many olivine-rich shergottite finds from hot deserts, DaG 476, Dhofar 019, and SaU 005. However, in the basaltic shergottite Dhofar 378 and in the nakhlite NWA 817 [1] no Br contamination was observed. The olivine phases of the shergottites seem to be preferably attacked by weathering reactions in the hot deserts. In the shergottites from hot deserts, the subchondritic La/U ratios are remarkable, indicating a U contamination. All these meteorites are covered with an evaporation product, caliche. Caliche has a high content of

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

    USGS Publications Warehouse

    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.

  5. Comparison of US Antarctic Meteorite Collection to Other Cold and Hot Deserts and Modern Falls

    NASA Technical Reports Server (NTRS)

    McBride, K. M.; Righter, K.

    2010-01-01

    The US Antarctic meteorite collection has grown close to 18,000 specimens, over 16,000 of which have been classified. Because of this growth, the parallel growth of Antarctic meteorite collections by Japan and China, and also the hot desert collections (from Africa and Australia), we will update the statistical overview of the US collection (last done in 1990 [1]), and make comparisons to other collections and modern falls.

  6. Modeling Soil Moisture in the Mojave Desert

    USGS Publications Warehouse

    Miller, David M.; Hughson, Debra; Schmidt, Kevin M.

    2008-01-01

    The Mojave Desert is an arid region of southeastern California and parts of Nevada, Arizona, and Utah; the desert occupies more than 25,000 square miles (fig. 1). Ranging from below sea level to over 5,000 feet (1,524 m) in elevation, the Mojave Desert is considered a ?high desert.? On the west and southwest it is bounded by the Sierra Nevada, the San Gabriel, and the San Bernardino Mountains. These imposing mountains intercept moisture traveling inland from the Pacific Ocean, producing arid conditions characterized by extreme fluctuations in daily temperatures, strong seasonal winds, and an average annual precipitation of less than six inches. The Mojave Desert lies farther south and at a lower elevation than the cooler Great Basin Desert and grades southward into the even lower and hotter Sonoran Desert.

  7. Desert Pathfinder at Work

    NASA Astrophysics Data System (ADS)

    2005-09-01

    The Atacama Pathfinder Experiment (APEX) project celebrates the inauguration of its outstanding 12-m telescope, located on the 5100m high Chajnantor plateau in the Atacama Desert (Chile). The APEX telescope, designed to work at sub-millimetre wavelengths, in the 0.2 to 1.5 mm range, passed successfully its Science Verification phase in July, and since then is performing regular science observations. This new front-line facility provides access to the "Cold Universe" with unprecedented sensitivity and image quality. After months of careful efforts to set up the telescope to work at the best possible technical level, those involved in the project are looking with satisfaction at the fruit of their labour: APEX is not only fully operational, it has already provided important scientific results. "The superb sensitivity of our detectors together with the excellence of the site allow fantastic observations that would not be possible with any other telescope in the world," said Karl Menten, Director of the group for Millimeter and Sub-Millimeter Astronomy at the Max-Planck-Institute for Radio Astronomy (MPIfR) and Principal Investigator of the APEX project. ESO PR Photo 30/05 ESO PR Photo 30/05 Sub-Millimetre Image of a Stellar Cradle [Preview - JPEG: 400 x 627 pix - 200k] [Normal - JPEG: 800 x 1254 pix - 503k] [Full Res - JPEG: 1539 x 2413 pix - 1.3M] Caption: ESO PR Photo 30/05 is an image of the giant molecular cloud G327 taken with APEX. More than 5000 spectra were taken in the J=3-2 line of the carbon monoxide molecule (CO), one of the best tracers of molecular clouds, in which star formation takes place. The bright peak in the north of the cloud is an evolved star forming region, where the gas is heated by a cluster of new stars. The most interesting region in the image is totally inconspicuous in CO: the G327 hot core, as seen in methanol contours. It is a truly exceptional source, and is one of the richest sources of emission from complex organic molecules in the

  8. Serologic and molecular evidence for Testudinid herpesvirus 2 infection in wild Agassiz's desert tortoises, Gopherus agassizii.

    PubMed

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

    2012-07-01

    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. PMID:22740541

  9. Comparative Metagenomic Analysis Reveals Mechanisms for Stress Response in Hypoliths from Extreme Hyperarid Deserts.

    PubMed

    Le, Phuong Thi; Makhalanyane, Thulani P; Guerrero, Leandro D; Vikram, Surendra; Van de Peer, Yves; Cowan, Don A

    2016-01-01

    Understanding microbial adaptation to environmental stressors is crucial for interpreting broader ecological patterns. In the most extreme hot and cold deserts, cryptic niche communities are thought to play key roles in ecosystem processes and represent excellent model systems for investigating microbial responses to environmental stressors. However, relatively little is known about the genetic diversity underlying such functional processes in climatically extreme desert systems. This study presents the first comparative metagenome analysis of cyanobacteria-dominated hypolithic communities in hot (Namib Desert, Namibia) and cold (Miers Valley, Antarctica) hyperarid deserts. The most abundant phyla in both hypolith metagenomes were Actinobacteria, Proteobacteria, Cyanobacteria and Bacteroidetes with Cyanobacteria dominating in Antarctic hypoliths. However, no significant differences between the two metagenomes were identified. The Antarctic hypolithic metagenome displayed a high number of sequences assigned to sigma factors, replication, recombination and repair, translation, ribosomal structure, and biogenesis. In contrast, the Namib Desert metagenome showed a high abundance of sequences assigned to carbohydrate transport and metabolism. Metagenome data analysis also revealed significant divergence in the genetic determinants of amino acid and nucleotide metabolism between these two metagenomes and those of soil from other polar deserts, hot deserts, and non-desert soils. Our results suggest extensive niche differentiation in hypolithic microbial communities from these two extreme environments and a high genetic capacity for survival under environmental extremes. PMID:27503299

  10. Reconstructing pathways of aeolian pollen transport to the marine sediments along the coastline of SW Africa

    NASA Astrophysics Data System (ADS)

    Dupont, Lydie M.; Wyputta, Ulrike

    2003-02-01

    The distribution of pollen in marine sediments is used to reconstruct pathways of terrigenous input to the oceans and provides a record of vegetation change on adjacent continents. The wind transport routes of aeolian pollen is comprehensively illustrated by clusters of trajectories. Isobaric, 4-day backward trajectories are calculated using the modelled wind-field of ECHAM3, and are clustered on a seasonal basis to estimate the main pathways of aeolian particles to sites of marine cores in the south-eastern Atlantic. Trajectories and clusters based on the modelled wind-field of the Last Glacial Maximum hardly differ from those of the present-day. Trajectory clusters show three regional, and two seasonal patterns, determining the pathways of aeolian pollen transport into the south-eastern Atlantic ocean. Mainly, transport out of the continent occurs during austral fall and winter, when easterly and south-easterly winds prevail. South of 25°S, winds blow mostly from the west and southwest, and aeolian terrestrial input is very low. Generally, a good latitudinal correspondence exists between the distribution patterns of pollen in marine surface sediments and the occurrence of the source plants on the adjacent continent. The northern Angola Basin receives pollen and spores from the Congolian and Zambezian forests mainly through river discharge. The Zambezian vegetation zone is the main source area for wind-blown pollen in sediments of the Angola Basin, while the semi-desert and desert areas are the main sources for pollen in sediments of the Walvis Basin and on the Walvis Ridge. A transect of six marine pollen records along the south-western African coast indicates considerable changes in the vegetation of southern Africa between glacial and interglacial periods. Important changes in the vegetation are the decline of forests in equatorial Africa and the north of southern Africa and a northward shift of winter rain vegetation along the western escarpment.

  11. Pollination ecology of the rare desert species Eremosparton songoricum (Fabaceae

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The pollination ecology of Eremosparton songoricum (Litv.) Vass., a rare desert species endemic to central Asia, was examined by a series of observational studies and manipulative experiments in two natural populations during 2007–2008. Results showed that the duration of flowering lasted 21 and 23 ...

  12. Morphodynamics of Planetary Deserts: A Laboratory Approach

    NASA Astrophysics Data System (ADS)

    Garcia, A.; Courrech Du Pont, S.; Rodriguez, S.

    2014-12-01

    Earth deserts show a rich variety of dune shapes from transverse to barchan, star and linear dunes depending on the history of wind regimes (strength and variability) and sand availability [1]. In desert, exposed to one wind direction, dunes perpendicular to the wind direction are found to be transverse or barchans, only sand availability plays a key role on their formation and evolution. However, the evolution time scale of such structures (several years) limits our investigation of their morphodynamics understanding. We use here, a laboratory experiment able to considerably reduce space and time scales by reproducing millimeter to centimeter subaqueous dunes by controlling environmental parameters such as type of wind (multi-winds, bimodal, quasi-bimodal or unidirectional wind) and amount of sediment [2,3]. This set up allows us to characterize more precisely the different modes of dune formation and long-term evolution, and to constrain the physics behind the morphogenesis and dynamics of dunes. Indeed, the formation, evolution and transition between the different dune modes are better understood and quantified thanks to a new setting experiment able to give a remote sediment source in continuous (closer to what happens in terrestrial desert): a sand distributor that controls the input sand flow. Firstly, in a one wind direction conditions, we managed to follow and quantify the growth of the instability of transverse dunes that break into barchans when the sand supply is low and reversely when the sand supply is higher, barchan fields evolve to bars dunes ending to form transverse. The next step will be to perform experiments under two winds conditions in order to better constrain the formation mode of linear dunes, depending also only on the input sand flux. Previous experiments shown that linear "finger" dunes can be triggered by the break of transverse dunes and then the elongating of one barchan's arm [4]. These studies can farther explain more precisely in

  13. Distribution of desert varnish in Arizona

    NASA Technical Reports Server (NTRS)

    Elvidge, Christopher D.

    1989-01-01

    Desert varnish is the dark coat of clay and ferromanganese oxides developed on exposed rock surfaces in arid regions. It forms from the accretion of material from windblown dust. The distribution of desert varnish was mapped in Arizona. It was discovered that desert varnish could be mapped on a regional scale. Well developed desert varnish is common on stable rock surfaces in areas having alkaline soils and less than about 25 cm of annual precipitation. Rock surfaces in areas having more than 40 cm of annual precipitation are generally devoid of desert varnish. An experiment was conducted with varnished desert pavement stone. The stones were broken in half and half was set on a roof in central Illinois from April until October. Removed from the alkaline desert environment, it only took seven months for the varnish to develop an eroded appearance. This experiment graphically illustrates the dependency of desert varnish on alkalinity. In this context, the zones of eroded desert varnish in Arizona indicate that the area of active desert varnish formation has fluctuated, expanding in drier times and contracting/eroding in wetter times.

  14. Ancient watercourses and biogeography of the Sahara explain the peopling of the desert

    PubMed Central

    Drake, Nick A.; Blench, Roger M.; Armitage, Simon J.; Bristow, Charlie S.; White, Kevin H.

    2011-01-01

    Evidence increasingly suggests that sub-Saharan Africa is at the center of human evolution and understanding routes of dispersal “out of Africa” is thus becoming increasingly important. The Sahara Desert is considered by many to be an obstacle to these dispersals and a Nile corridor route has been proposed to cross it. Here we provide evidence that the Sahara was not an effective barrier and indicate how both animals and humans populated it during past humid phases. Analysis of the zoogeography of the Sahara shows that more animals crossed via this route than used the Nile corridor. Furthermore, many of these species are aquatic. This dispersal was possible because during the Holocene humid period the region contained a series of linked lakes, rivers, and inland deltas comprising a large interlinked waterway, channeling water and animals into and across the Sahara, thus facilitating these dispersals. This system was last active in the early Holocene when many species appear to have occupied the entire Sahara. However, species that require deep water did not reach northern regions because of weak hydrological connections. Human dispersals were influenced by this distribution; Nilo-Saharan speakers hunting aquatic fauna with barbed bone points occupied the southern Sahara, while people hunting Savannah fauna with the bow and arrow spread southward. The dating of lacustrine sediments show that the “green Sahara” also existed during the last interglacial (∼125 ka) and provided green corridors that could have formed dispersal routes at a likely time for the migration of modern humans out of Africa. PMID:21187416

  15. The Solar Spectrum in the Atacama Desert

    PubMed Central

    Cordero, R. R.; Damiani, A.; Seckmeyer, G.; Jorquera, J.; Caballero, M.; Rowe, P.; Ferrer, J.; Mubarak, R.; Carrasco, J.; Rondanelli, R.; Matus, M.; Laroze, D.

    2016-01-01

    The Atacama Desert has been pointed out as one of the places on earth where the highest surface irradiance may occur. This area is characterized by its high altitude, prevalent cloudless conditions and relatively low columns of ozone and water vapor. Aimed at the characterization of the solar spectrum in the Atacama Desert, we carried out in February-March 2015 ground-based measurements of the spectral irradiance (from the ultraviolet to the near infrared) at seven locations that ranged from the city of Antofagasta (on the southern pacific coastline) to the Chajnantor Plateau (5,100 m altitude). Our spectral measurements allowed us to retrieve the total ozone column, the precipitable water, and the aerosol properties at each location. We found that changes in these parameters, as well as the shorter optical path length at high-altitude locations, lead to significant increases in the surface irradiance with the altitude. Our measurements show that, in the range 0–5100 m altitude, surface irradiance increases with the altitude by about 27% in the infrared range, 6% in the visible range, and 20% in the ultraviolet range. Spectral measurements carried out at the Izaña Observatory (Tenerife, Spain), in Hannover (Germany) and in Santiago (Chile), were used for further comparisons. PMID:26932150

  16. The Solar Spectrum in the Atacama Desert

    NASA Astrophysics Data System (ADS)

    Cordero, R. R.; Damiani, A.; Seckmeyer, G.; Jorquera, J.; Caballero, M.; Rowe, P.; Ferrer, J.; Mubarak, R.; Carrasco, J.; Rondanelli, R.; Matus, M.; Laroze, D.

    2016-03-01

    The Atacama Desert has been pointed out as one of the places on earth where the highest surface irradiance may occur. This area is characterized by its high altitude, prevalent cloudless conditions and relatively low columns of ozone and water vapor. Aimed at the characterization of the solar spectrum in the Atacama Desert, we carried out in February-March 2015 ground-based measurements of the spectral irradiance (from the ultraviolet to the near infrared) at seven locations that ranged from the city of Antofagasta (on the southern pacific coastline) to the Chajnantor Plateau (5,100 m altitude). Our spectral measurements allowed us to retrieve the total ozone column, the precipitable water, and the aerosol properties at each location. We found that changes in these parameters, as well as the shorter optical path length at high-altitude locations, lead to significant increases in the surface irradiance with the altitude. Our measurements show that, in the range 0-5100 m altitude, surface irradiance increases with the altitude by about 27% in the infrared range, 6% in the visible range, and 20% in the ultraviolet range. Spectral measurements carried out at the Izaña Observatory (Tenerife, Spain), in Hannover (Germany) and in Santiago (Chile), were used for further comparisons.

  17. The Solar Spectrum in the Atacama Desert.

    PubMed

    Cordero, R R; Damiani, A; Seckmeyer, G; Jorquera, J; Caballero, M; Rowe, P; Ferrer, J; Mubarak, R; Carrasco, J; Rondanelli, R; Matus, M; Laroze, D

    2016-01-01

    The Atacama Desert has been pointed out as one of the places on earth where the highest surface irradiance may occur. This area is characterized by its high altitude, prevalent cloudless conditions and relatively low columns of ozone and water vapor. Aimed at the characterization of the solar spectrum in the Atacama Desert, we carried out in February-March 2015 ground-based measurements of the spectral irradiance (from the ultraviolet to the near infrared) at seven locations that ranged from the city of Antofagasta (on the southern pacific coastline) to the Chajnantor Plateau (5,100 m altitude). Our spectral measurements allowed us to retrieve the total ozone column, the precipitable water, and the aerosol properties at each location. We found that changes in these parameters, as well as the shorter optical path length at high-altitude locations, lead to significant increases in the surface irradiance with the altitude. Our measurements show that, in the range 0-5100 m altitude, surface irradiance increases with the altitude by about 27% in the infrared range, 6% in the visible range, and 20% in the ultraviolet range. Spectral measurements carried out at the Izaña Observatory (Tenerife, Spain), in Hannover (Germany) and in Santiago (Chile), were used for further comparisons. PMID:26932150

  18. Evolutionary hotspots in the Mojave Desert

    USGS Publications Warehouse

    Vandergast, Amy G.; Inman, Richard D.; Barr, Kelly R.; Nussear, Kenneth E.; Esque, Todd C.; Hathaway, Stacie A.; Wood, Dustin A.; Medica, Philip A.; Breinholt, Jesse W.; Stephen, Catherine L.; Gottscho, Andrew D.; Marks, Sharyn B.; Jennings, W. Bryan; Fisher, Robert N.

    2013-01-01

    Genetic diversity within species provides the raw material for adaptation and evolution. Just as regions of high species diversity are conservation targets, identifying regions containing high genetic diversity and divergence within and among populations may be important to protect future evolutionary potential. When multiple co-distributed species show spatial overlap in high genetic diversity and divergence, these regions can be considered evolutionary hotspots. We mapped spatial population genetic structure for 17 animal species across the Mojave Desert, USA. We analyzed these in concurrence and located 10 regions of high genetic diversity, divergence or both among species. These were mainly concentrated along the western and southern boundaries where ecotones between mountain, grassland and desert habitat are prevalent, and along the Colorado River. We evaluated the extent to which these hotspots overlapped protected lands and utility-scale renewable energy development projects of the Bureau of Land Management. While 30–40% of the total hotspot area was categorized as protected, between 3–7% overlapped with proposed renewable energy project footprints, and up to 17% overlapped with project footprints combined with transmission corridors. Overlap of evolutionary hotspots with renewable energy development mainly occurred in 6 of the 10 identified hotspots. Resulting GIS-based maps can be incorporated into ongoing landscape planning efforts and highlight specific regions where further investigation of impacts to population persistence and genetic connectivity may be warranted.

  19. Episodic death across species of desert shrubs.

    PubMed

    Miriti, Maria N; Rodríguez-Buriticá, Susana; Wright, S Joseph; Howe, Henry F

    2007-01-01

    Extreme events shape population and community trajectories. We report episodic mortality across common species of thousands of long-lived perennials individually tagged and monitored for 20 years in the Colorado Desert of California following severe regional drought. Demographic records from 1984 to 2004 show 15 years of virtual stasis in populations of adult shrubs and cacti, punctuated by a 55-100% die-off of six of the seven most common perennial species. In this episode, adults that experienced reduced growth in a lesser drought during 1984-1989 failed to survive the drought of 2002. The significance of this event is potentially profound because population dynamics of long-lived plants can be far more strongly affected by deaths of adults, which in deserts potentially live for centuries, than by seedling births or deaths. Differential mortality and rates of recovery during and after extreme climatic events quite likely determine the species composition of plant and associated animal communities for at least decades. The die-off recorded in this closely monitored community provides a unique window into the mechanics of this process of species decline and replacement. PMID:17489450

  20. Dynamic response of desert wetlands to abrupt climate change

    PubMed Central

    Springer, Kathleen B.; Manker, Craig R.; Pigati, Jeffrey S.

    2015-01-01

    Desert wetlands are keystone ecosystems in arid environments and are preserved in the geologic record as groundwater discharge (GWD) deposits. GWD deposits are inherently discontinuous and stratigraphically complex, which has limited our understanding of how desert wetlands responded to past episodes of rapid climate change. Previous studies have shown that wetlands responded to climate change on glacial to interglacial timescales, but their sensitivity to short-lived climate perturbations is largely unknown. Here, we show that GWD deposits in the Las Vegas Valley (southern Nevada, United States) provide a detailed and nearly complete record of dynamic hydrologic changes during the past 35 ka (thousands of calibrated 14C years before present), including cycles of wetland expansion and contraction that correlate tightly with climatic oscillations recorded in the Greenland ice cores. Cessation of discharge associated with rapid warming events resulted in the collapse of entire wetland systems in the Las Vegas Valley at multiple times during the late Quaternary. On average, drought-like conditions, as recorded by widespread erosion and the formation of desert soils, lasted for a few centuries. This record illustrates the vulnerability of desert wetland flora and fauna to abrupt climate change. It also shows that GWD deposits can be used to reconstruct paleohydrologic conditions at millennial to submillennial timescales and informs conservation efforts aimed at protecting these fragile ecosystems in the face of anthropogenic warming. PMID:26554007

  1. Dynamic response of desert wetlands to abrupt climate change.

    PubMed

    Springer, Kathleen B; Manker, Craig R; Pigati, Jeffrey S

    2015-11-24

    Desert wetlands are keystone ecosystems in arid environments and are preserved in the geologic record as groundwater discharge (GWD) deposits. GWD deposits are inherently discontinuous and stratigraphically complex, which has limited our understanding of how desert wetlands responded to past episodes of rapid climate change. Previous studies have shown that wetlands responded to climate change on glacial to interglacial timescales, but their sensitivity to short-lived climate perturbations is largely unknown. Here, we show that GWD deposits in the Las Vegas Valley (southern Nevada, United States) provide a detailed and nearly complete record of dynamic hydrologic changes during the past 35 ka (thousands of calibrated (14)C years before present), including cycles of wetland expansion and contraction that correlate tightly with climatic oscillations recorded in the Greenland ice cores. Cessation of discharge associated with rapid warming events resulted in the collapse of entire wetland systems in the Las Vegas Valley at multiple times during the late Quaternary. On average, drought-like conditions, as recorded by widespread erosion and the formation of desert soils, lasted for a few centuries. This record illustrates the vulnerability of desert wetland flora and fauna to abrupt climate change. It also shows that GWD deposits can be used to reconstruct paleohydrologic conditions at millennial to submillennial timescales and informs conservation efforts aimed at protecting these fragile ecosystems in the face of anthropogenic warming. PMID:26554007

  2. Dynamic response of desert wetlands to abrupt climate change

    USGS Publications Warehouse

    Springer, Kathleen; Manker, Craig; Pigati, Jeff

    2015-01-01

    Desert wetlands are keystone ecosystems in arid environments and are preserved in the geologic record as groundwater discharge (GWD) deposits. GWD deposits are inherently discontinuous and stratigraphically complex, which has limited our understanding of how desert wetlands responded to past episodes of rapid climate change. Previous studies have shown that wetlands responded to climate change on glacial to interglacial timescales, but their sensitivity to short-lived climate perturbations is largely unknown. Here, we show that GWD deposits in the Las Vegas Valley (southern Nevada, United States) provide a detailed and nearly complete record of dynamic hydrologic changes during the past 35 ka (thousands of calibrated 14C years before present), including cycles of wetland expansion and contraction that correlate tightly with climatic oscillations recorded in the Greenland ice cores. Cessation of discharge associated with rapid warming events resulted in the collapse of entire wetland systems in the Las Vegas Valley at multiple times during the late Quaternary. On average, drought-like conditions, as recorded by widespread erosion and the formation of desert soils, lasted for a few centuries. This record illustrates the vulnerability of desert wetland flora and fauna to abrupt climate change. It also shows that GWD deposits can be used to reconstruct paleohydrologic conditions at millennial to submillennial timescales and informs conservation efforts aimed at protecting these fragile ecosystems in the face of anthropogenic warming.

  3. Desert dust suppressing precipitation: A possible desertification feedback loop

    PubMed Central

    Rosenfeld, Daniel; Rudich, Yinon; Lahav, Ronen

    2001-01-01

    The effect of desert dust on cloud properties and precipitation has so far been studied solely by using theoretical models, which predict that rainfall would be enhanced. Here we present observations showing the contrary; the effect of dust on cloud properties is to inhibit precipitation. Using satellite and aircraft observations we show that clouds forming within desert dust contain small droplets and produce little precipitation by drop coalescence. Measurement of the size distribution and the chemical analysis of individual Saharan dust particles collected in such a dust storm suggest a possible mechanism for the diminished rainfall. The detrimental impact of dust on rainfall is smaller than that caused by smoke from biomass burning or anthropogenic air pollution, but the large abundance of desert dust in the atmosphere renders it important. The reduction of precipitation from clouds affected by desert dust can cause drier soil, which in turn raises more dust, thus providing a possible feedback loop to further decrease precipitation. Furthermore, anthropogenic changes of land use exposing the topsoil can initiate such a desertification feedback process. PMID:11353821

  4. Saharan Dust Export towards the Caribbean: Dust Sources and Atmospheric Circulation over North Africa

    NASA Astrophysics Data System (ADS)

    Schepanski, Kerstin; Heinold, Bernd; Groß, Silke; Schäfler, Andreas; Weinzierl, Bernadett; Sauer, Daniel; Walser, Adrian; Tegen, Ina

    2015-04-01

    Studies analysing satellite observations illustrate the spatial and temporal distribution of emitting dust sources. Results show that high surface wind speeds related to the break-down of the nocturnal low-level jet (LLJ) occurring during the morning hours are frequent driving mechanism for dust uplift in the Sahara desert. Here, we present a study investigating atmospheric circulation pattern over North Africa favouring (a) dust entrainment into the boundary layer and (b) dust export towards the Caribbean Sea. Satellite-based information on the spatio-temporal distribution of dust source activation (DSA) events inferred from 15-minute Meteosat Second Generation (MSG) Spinning Enhanced Visible and InfraRed Imager (SEVIRI) dust observations are linked to atmospheric circulation regimes over North Africa. By means of air-mass trajectories, which map the dust export from North Africa toward the SALTRACE ground observation site at Barbados, cases are selected which link DSA regions with dust events observed at Barbados. These cases are then examined with regard to the atmospheric conditions during dust emission and geomorphologic dust source characteristic. Dust properties inferred from LIDAR observation using the POLIS system and measurements taken during Falcon research flights are compared to the different dust source locations and atmospheric conditions during dust emission. Altogether, the results from this study aim at illustrating the relevance of knowing the dust source locations in concert with the atmospheric circulation. Ultimately, this study addresses the question of what is finally transported across the Atlantic towards the Caribbean from which dust source region.

  5. The drought of the 1890s in south-eastern Africa

    NASA Astrophysics Data System (ADS)

    Pribyl, Kathleen; Nash, David; Klein, Jorgen; Endfield, Georgina

    2016-04-01

    During the second half of the 1890s south-eastern Africa, from modern day Zimbabwe and Botswana down to South Africa, was hit by a drought driven ecological crisis. Using instrumental observations and previously unexploited documentary records in the form of British administrative sources, reports and letters by various Protestant mission societies and newspapers, the extent, duration and severity of the drought are explored. Generally the period was marked by a delayed onset of the rainy season of several months; rainfall totals dropped and perennial rivers such as the Limpopo dried up. The delay of the rainy season negatively impacted the rain-fed agriculture. Recurrent drought conditions during the rainy season frequently withered the young crops. In the interior of southern Africa, on the border of the Kalahari desert, the drought was more severe and continuous than towards the coast of the Indian Ocean. The prolonged dry conditions furthered the outbreak of locust plagues and cattle disease, which in the 1890s took the disastrous form of Rinderpest. A model is established showing how the drought as the original driver of the crisis, triggered a cascade of responses from harvest failure to famine and finally leading to profound socio-economic change.

  6. Network topology of the desert rose

    NASA Astrophysics Data System (ADS)

    Hope, Sigmund; Kundu, Sumanta; Roy, Chandreyee; Manna, Subhrangshu; Hansen, Alex

    2015-09-01

    Desert roses are gypsum crystals that consist of intersecting disks. We determine their geometrical structure using computer assisted tomography. By mapping the geometrical structure onto a graph, the topology of the desert rose is analyzed and compared to a model based on diffusion limited aggregation. By comparing the topology, we find that the model gets a number of the features of the real desert rose right, whereas others do not fit so well.

  7. Groundwater sapping processes, Western Desert, Egypt.

    SciTech Connect

    Luo, W.; Arvidson, R.E.; Sultan, M.; Becker, R.; Crombie, M.K.; Sturchio, N.; El Alfy, Z.; Environmental Research; Washington Univ.; Egyptian Geological Survey and Mining Authority

    1997-01-01

    Depressions of the Western Desert of Egypt (specifically, Kharga, Farafra, and Kurkur regions) are mainly occupied by shales that are impermeable, but easily erodible by rainfall and runoff, whereas the surrounding plateaus are composed of limestones that are permeable and more resistant to fluvial erosion under semiarid to arid conditions. Scallop-shaped escarpment edges and stubby-looking channels that cut into the plateau units are suggestive of slumping of limestones by ground-water sapping at the limestone-shale interfaces, removal of slump blocks by weathering and fluvial erosion, and consequent scarp retreat. Spring-derived tufa deposits found near the limestone escarpments provide additional evidence for possible ground-water sapping during previous wet periods. A computer simulation model was developed to quantify the ground-water sapping processes, using a cellular automata algorithm with coupled surface runoff and ground-water flow for a permeable, resistant layer over an impermeable, friable unit. Erosion, deposition, slumping, and generation of spring-derived tufas were parametrically modeled. Simulations using geologically reasonable parameters demonstrate that relatively rapid erosion of the shales by surface runoff, ground-water sapping, and slumping of the limestones, and detailed control by hydraulic conductivity inhomogeneities associated with structures explain the depressions, escarpments, and associated landforms and deposits. Using episodic wet pulses, keyed by {delta}{sup 18}O deep-sea core record, the model produced tufa ages that are statistically consistent with the observed U/Th tufa ages. This result supports the hypothesis that northeastern African wet periods occurred during interglacial maxima. The {delta}{sup 18}O-forced model also replicates the decrease in fluvial and sapping activity over the past million years, as northeastern Africa became hyperarid. The model thus provides a promising predictive tool for studying long

  8. The age of the Taklimakan Desert.

    PubMed

    Sun, Jimin; Liu, Tungsheng

    2006-06-16

    The Taklimakan Desert is located in the foreland basin of the Tibetan Plateau. We report here the results of stratigraphic investigations of a 1626-meter-thick sequence with interbedded wind-blown silt from the southern marginal Taklimakan Desert. Because the studied section is located downwind of the desert, the eolian silt accumulation is closely linked to desert formation. Our new evidence indicates that shifting sand dunes prevailed in the Tarim Basin by at least 5.3 million years ago, as they do today. We attribute this event to late Cenozoic climatic deterioration, as well as to changes in atmospheric circulation induced by Tibetan Plateau uplift. PMID:16778048

  9. Smoke in Southern Africa

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This SeaWiFS true-color image acquired over Southern Africa on Sept. 4, 2000, shows a thick shroud of smoke and haze blanketing much of the southern half of the continent. The smoke in this scene is being generated by a tremendous number of fires burning over a large area across the countries of Angola, Zambia, Mozambique, Zimbabwe, Botswana, and the Northern Province of South Africa. In this image, the smoke (grey pixels) is easily distinguished from clouds (bright white pixels). Refer to the Images and Data section for a larger scale view of the fires in Southern Africa. Data from both the SeaWiFS and Terra satellites are being used by an international team of scientists participating in the SAFARI field experiment. The objective of SAFARI is to measure the effects of windblown smoke and dust on air quality and the Earth's radiant energy budget. This image was produced using SeaWiFS channels 6, 5, and 1 (centered at 670 nm, 555 nm , and 412 nm, respectively). The data were acquired and provided by the Satellite Applications Center in Pretoria, South Africa. Image courtesy Gene Feldman, SeaWiFS Project and Orbital Sciences

  10. Evaluation of seasonal climates of the Mediterranean and nothern Africa in the CMIP5 simulations

    NASA Astrophysics Data System (ADS)

    Perez-Sanz, A.; Li, G.; González-Sampériz, P.; Harrison, S. P.

    2013-09-01

    We analyze the spatial expression of seasonal climates of the Mediterranean and northern Africa in pre-Industrial (piControl) and mid-Holocene (midHolocene, 6 ka) simulations from the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Modern observations show four distinct precipitation regimes characterized by differences in the seasonal distribution and total amount of precipitation: an equatorial band characterized by a double peak in rainfall, the monsoon zone characterized by summer rainfall, the desert characterized by low seasonality and total precipitation, and the Mediterranean zone characterized by summer drought. Most models correctly simulate the position of the Mediterranean and the equatorial climates in the piControl simulations, but over-estimate the extent of monsoon influence and underestimate the extent of desert. However, most models fail to reproduce the amount of precipitation in each zone. Model biases in the simulated magnitude of precipitation are unrelated to whether the models reproduce the correct spatial patterns of each regime. In the midHolocene, the models simulate a reduction in winter rainfall in the equatorial zone, and a northward expansion of the monsoon with a significant increase in summer and autumn rainfall. Precipitation is slightly increased in the desert, mainly in summer and autumn, with northward expansion of the monsoon. Changes in the Mediterranean are small, although there is an increase in spring precipitation consistent with palaeo-observations of increased growing-season rainfall. Comparison with reconstructions shows that most models under-estimate the mid-Holocene changes in annual precipitation, except in the equatorial zone. Biases in the piControl have only a limited influence on midHolocene anomalies in ocean-atmosphere models; carbon-cycle models show no relationship between piControl bias and midHolocene anomalies. Biases in the prediction of the midHolocene monsoon expansion are unrelated

  11. Effects of drought on desert tortoise movement and activity

    USGS Publications Warehouse

    Duda, J.J.; Krzysik, A.J.; Freilich, J.E.

    1999-01-01

    We monitored movement and activity patterns of 38 desert tortoises (Gopherus agassizii) at 2 locations in the southcentral Mojave Desert during 2 consecutive years differing markedly in winter rainfall. During the first year, winter precipitation was 225% greater than the long-term average for this region, whereas a drought the following year resulted in precipitation that was 25% of the long-term average. These winter rains produced 2 distinct patterns of annual plant productivity: a bloom of annuals the first year, followed by their complete absence the second year. As measured by radiotelemetry, home range size, the number of different burrows used, average distances traveled per day, and levels of surface versus burrow activity were significantly reduced in both populations during the drought year. The pooled distribution of between-observation distances traveled showed a shift favoring shorter-distance movements during the drought year. Differences in levels of winter precipitation between years and the resulting variation of winter annual biomass in the spring appear to play a significant role in desert tortoise movement and activity patterns. Future management and conservation plans for the desert tortoise should consider weather and productivity as important factors influencing annual home range size, number of burrows used, average distances traveled, and activity levels.

  12. Elemental profiles and signatures of fugitive dusts from Chinese deserts.

    PubMed

    Zhang, Rong; Cao, Junji; Tang, Yanrong; Arimoto, Richard; Shen, Zhenxing; Wu, Feng; Han, Yongming; Wang, Gehui; Zhang, Jiaquan; Li, Guohui

    2014-02-15

    Elemental profiles were determined for size-separated fugitive dust particles produced from Chinese desert and gobi soils. Seventeen surface soil samples from six Chinese deserts were collected, composited, resuspended, and sampled through TSP, PM10, and PM2.5 inlets onto Teflon® filters, which were analyzed for twenty-six elements. Two major dust sources could be distinguished based on differences in crustal and enriched elements-the northwestern (NW) region (Taklimakan Desert, Xinjiang Gobi, and Anxinan Gobi) and northern (N) region (Ulan Buh Desert, Central Inner Mongolia Desert, and Erenhot Gobi). The N sources showed lower concentrations of mineral elements (Fe, K, Na, Ti, Mn, Cr, and Rb in PM10, and Fe, K, Ti, Mn, Co, and V in PM2.5) and higher levels of contaminants (S, Zn, Mo, Cu, Cr, Pb, Cd, and As) than the NW ones, especially in PM2.5. Enrichment factors for Cu, Cr, Zn, Pb, As, Mo, and Cd calculated relative to the upper continental crust showed enrichments of one to two orders-of-magnitude, and they were much higher for N sources than NW ones, implying stronger anthropogenic impacts in north China. Aerosol elemental concentrations during dust events at Horqin, Beijing, and Xi'an matched the mass percentages of mineral elements from their presumptive sources better than the alternative ones, validating the differences between the NW and N sources. Additionally, Na/S, Mg/S, Fe/Al, K/Al, Si/Fe, and Na/Al ratios were suggested to differentiate the two dust source regions. The elemental ratios of Ca/Al, K/Al, Fe/Al, and Ti/Fe in the source regions matched those in aerosols collected downwind, and they can be considered as possible source indicators. PMID:24361747

  13. Searching for Life in Death Valley (and Other Deserts) - Microchemical Investigations on Desert Varnish

    NASA Astrophysics Data System (ADS)

    Andreae, M. O.; Al-Amri, A. M.; Jochum, K. P.; Kappl, M.; Kilcoyne, A. D.; Macholdt, D.; Müller, M.; Pöhlker, C.; Weber, B.; Weigand, M.

    2014-12-01

    Desert varnishes are thin, shiny, blackish to brown coatings frequently found on the surfaces of exposed rocks in deserts around the globe. They have been proposed as terrestrial analogues of superficial hematite enrichments observed on Mars. While the first scientific studies of such varnishes go back to Darwin and von Humboldt, and intensive studies by a variety of techniques have been conducted over the last few decades, their origin is still a matter of debate. Microscopic and molecular studies have shown the presence of fungi and bacteria, but it is still unclear whether they are involved in the formation of the varnish material or just opportunistic colonizers on available surfaces. We have analysed samples of desert varnish from sites in Death Valley, the Mojave Desert, the Negev of Israel, Central Saudi Arabia, and the Succulent Karoo by a variety of microanalytical techniques. Measurements by UV-femtosecond Laser Ablation Inductively Coupled Plasma Mass Spectrometry show enrichments of manganese, iron, barium and other elements. Isotopic and trace chemical signatures show that these enriched elements cannot originate from the rocks that form the substrate on which the crusts have been deposited, but most likely are the result of (bio?)chemical transformation of windblown material. For a more detailed investigation of the internal structure of the crusts, we prepared ultra-thin sections (~100 nm) using focused ion beam slicing and analysed them by Scanning Transmission X-ray Microscopy with Near-Edge X-ray Absorption Fine Structure spectroscopy (STXM-NEXAFS). This technique revealed layered or chaotic structures consisting of alternating Mn and Fe-rich zones. Some of these layers are enriched in organic carbon with spectral features dominated by aromatic and carboxylate functionalities, indicating a biological origin of some of the crust material. Some crusts also show cavities that are lined with similar organic material. Since the age of these crusts is

  14. Deep arid system hydrodynamics: 1. Equilibrium states and response times in thick desert vadose zones

    USGS Publications Warehouse

    Walvoord, M.A.; Plummer, M.A.; Phillips, F.M.; Wolfsberg, A.V.

    2002-01-01

    Quantifying moisture fluxes through deep desert soils remains difficult because of the small magnitude of the fluxes and the lack of a comprehensive model to describe flow and transport through such dry material. A particular challenge for such a model is reproducing both observed matric potential and chloride profiles. We propose a conceptual model for flow in desert vadose zones that includes isothermal and nonisothermal vapor transport and the role of desert vegetation in supporting a net upward moisture flux below the root zone. Numerical simulations incorporating this conceptual model match typical matric potential and chloride profiles. The modeling approach thereby reconciles the paradox between the recognized importance of plants, upward driving forces, and vapor flow processes in desert vadose zones and the inadequacy of the downward-only liquid flow assumption of the conventional chloride mass balance approach. Our work shows that water transport in thick desert vadose zones at steady state is usually dominated by upward vapor flow and that long response times, of the order of 104-105 years, are required to equilibrate to existing arid surface conditions. Simulation results indicate that most thick desert vadose zones have been locked in slow drying transients that began in response to a climate shift and establishment of desert vegetation many thousands of years ago.

  15. The spatio-temporal variability of groundwater depth in a typical desert-oasis ecotone

    NASA Astrophysics Data System (ADS)

    Wang, Guohua; Zhao, Wenzhi

    2015-06-01

    Eight groundwater observation wells were installed along the river plain, where the landscapes varied from floodplain, to oasis farmland, to desert-oasis ecotone to desert, in a typical desert-oasis ecotone in northwestern China. Ten years of data were used to analyze temporal and spatial changes in the groundwater depth. The results indicated that in the last decade: (1) the groundwater depths in the floodplain (GW1) and the desert (GW8) were basically stable; (2) the groundwater depths in the oasis farmland (GW2, GW3, GW4) increased dramatically: the annual fluctuations were 1.43, 1.01 and 0.79 m respectively, with the groundwater depths increasing by 0.13-0.18 m every year; (3) the groundwater depths in the desert-oasis ecotone (GW5, GW6, GW7) also increased dramatically: the annual fluctuations were 1.10, 1.06 and 1.05 m respectively, and the depths increased by 0.10-0.15 m every year; (4) the influence distance between the river and both the farmland and the desert-oasis ecotone was about 1000-2000 m in the study area. These results show that the natural seasonal fluctuation influence on groundwater depths was not significant, but the human-induced fluctuations such as intensive irrigation caused a significant increase in groundwater depth in both the farmland and the desert-oasis ecotone, seriously affecting sustainable agriculture development and the environment, in the oasis.

  16. Can desert dust explain the outgoing longwave radiation anomaly over the Sahara during July 2003?

    NASA Astrophysics Data System (ADS)

    Haywood, Jim M.; Allan, Richard P.; Culverwell, Ian; Slingo, Tony; Milton, Sean; Edwards, John; Clerbaux, Nicolas

    2005-03-01

    Measurements of the top-of-the-atmosphere outgoing longwave radiation (OLR) for July 2003 from Meteosat-7 are used to assess the performance of the numerical weather prediction version of the Met Office Unified Model. A significant difference is found over desert regions of northern Africa where the model emits too much OLR by up to 35 Wm-2 in the monthly mean. By cloud-screening the data we find an error of up to 50 Wm-2 associated with cloud-free areas, which suggests an error in the model surface temperature, surface emissivity, or atmospheric transmission. By building up a physical model of the radiative properties of mineral dust based on in situ, and surface-based and satellite remote sensing observations we show that the most plausible explanation for the discrepancy in OLR is due to the neglect of mineral dust in the model. The calculations suggest that mineral dust can exert a longwave radiative forcing by as much as 50 Wm-2 in the monthly mean for 1200 UTC in cloud-free regions, which accounts for the discrepancy between the model and the Meteosat-7 observations. This suggests that inclusion of the radiative effects of mineral dust will lead to a significant improvement in the radiation balance of numerical weather prediction models with subsequent improvements in performance.

  17. Properties of Desert Sand and CMAS Glass

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Choi, Sung R.

    2014-01-01

    As-received desert sand from a Middle East country has been characterized for its phase composition and thermal stability. X-ray diffraction analysis showed the presence of quartz (SiO2), calcite (CaCO3), gypsum (CaSO4.2H2O), and NaAlSi3O8 phases in as-received desert sand and showed weight loss of approx. 35 percent due to decomposition of CaCO3 and CaSO4.2H2O when heated to 1400 C. A batch of as-received desert sand was melted into calcium magnesium aluminosilicate (CMAS) glass at approx. 1500 C. From inductively coupled plasma-atomic emission spectrometry, chemical composition of the CMAS glass was analyzed to be 27.8CaO-4MgO-5Al2O3-61.6SiO2-0.6Fe2O3-1K2O (mole percent). Various physical, thermal and mechanical properties of the glass have been evaluated. Bulk density of CMAS glass was 2.69 g/cc, Young's modulus 92 GPa, Shear modulus 36 GPa, Poisson's ratio 0.28, dilatometric glass transition temperature (T (sub g)) 706 C, softening point (T (sub d)) 764 C, Vickers microhardness 6.3 +/- 0.4 GPa, indentation fracture toughness 0.75 +/- 0.15 MPa.m (sup 1/2), and coefficient of thermal expansion (CTE) 9.8 x 10 (exp -6)/degC in the temperature range 25 to 700 C. Temperature dependence of viscosity has also been estimated from various reference points of the CMAS glass using the Vogel-Fulcher-Tamman (VFT) equation. The glass remained amorphous after heat treating at 850 C for 10 hr but crystallized into CaSiO3 and Ca-Mg-Al silicate phases at 900 C or higher temperatures. Crystallization kinetics of the CMAS glass has also been investigated by differential thermal analysis (DTA). Activation energies for the crystallization of two different phases in the glass were calculated to be 403 and 483 kJ/mol, respectively.

  18. Workshop on Extraterrestrial Materials from Cold and Hot Deserts

    NASA Technical Reports Server (NTRS)

    Buchanan, Paul C.

    1999-01-01

    The workshop was held July 6-8, 1999 before the Meteoritical Society meeting in Johannesburg, South Africa. The venue was Kwa Maritane Resort in the Pilanesburg Game Reserve. Conveners were Ludolf Schultz (Chair, MPI fur Chemie), Ian Franchi (Open University), Arch Reid (University of Houston), and Mike Zolensky (NASA JSC). Extended abstracts will be published as an LPI Technical Report. In the first session, Marvin discussed three African iron meteorites: Cape of Good Hope, Gibeon, and Hoba. Grady presented a statistical analysis of meteorites from hot and cold deserts. Wasson discussed types of Antarctic iron meteorites. Several presentations characterized populations of meteorites from individual desert areas: Libyan Desert (Weber et al.), Nullarbor Region (Bevan et al.), and Mojave Desert (Kring et al. and Verish et al). Pairing among EET87503-group howardites was discussed by Buchanan et al. Based on 14C terrestrial ages of Allan Hills ordinary chondrites, Bland et al. suggested that ice flow may be the principal sink for Antarctic meteorites. The effects of preterrestrial and terrestrial alteration were considered in the second session. Nakamura et al. and Lipschutz discussed asteroidal metamorphism of carbonaceous chondrites. Zolensky presented evidence for preterrestrial halide and sulfide in meteorites. Crozaz and Wadhwa described terrestrial alteration of Dar al Gani 476. Welten and Nishiizumi discussed terrestrial weathering of chondrites from Frontier Mountain, Antarctica. Most of the third session dealt with terrestrial meteorite ages. Based on 14C-10Be ages, Jull et al. discussed the exponential decay in numbers of meteorites with increased age. Nishiizumi et al. concluded that some Allan Hills meteorites have much older terrestrial ages than any meteorites from Lewis Cliffs. Welten et al. discussed terrestrial ages determined by 41Ca/36CI of metal separates from hot desert meteorites. Based on a comparison with large IDPs, Flynn et al. suggested that

  19. Desert Ants Learn Vibration and Magnetic Landmarks

    PubMed Central

    Buehlmann, Cornelia

    2012-01-01

    The desert ants Cataglyphis navigate not only by path integration but also by using visual and olfactory landmarks to pinpoint the nest entrance. Here we show that Cataglyphis noda can additionally use magnetic and vibrational landmarks as nest-defining cues. The magnetic field may typically provide directional rather than positional information, and vibrational signals so far have been shown to be involved in social behavior. Thus it remains questionable if magnetic and vibration landmarks are usually provided by the ants' habitat as nest-defining cues. However, our results point to the flexibility of the ants' navigational system, which even makes use of cues that are probably most often sensed in a different context. PMID:22412989

  20. Enhancing and restoring habitat for the desert tortoise (Gopherus agassizii)

    USGS Publications Warehouse

    Abella, Scott R.; Berry, Kristin H.

    2016-01-01

    Habitat has changed unfavorably during the past 150 years for the desert tortoise (Gopherus agassizii), a threatened species with declining populations in the Mojave 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 re-applying topsoil using effective techniques is among the more ecologically beneficial ways to initiate plant recovery after severe disturbance. Some plant species provide better-quality forage than others. Tortoises selectively forage on particular annual and herbaceous perennial species, such as legumes, with favored plants varying with phenological stage within years. Non-native grasses are non-preferred 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 non-native grasses are priorities for restoring most desert tortoise habitats. Reducing herbivory by non-native 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 re-contouring road berms to reestablish drainage patterns, vertical mulching ("planting" dead plant material), and creating barriers to prevent trespasses can assist natural recovery on decommissioned backcountry

  1. The Landscape Evolution of Ulan Buh Desert in North China during Late Quaternary

    NASA Astrophysics Data System (ADS)

    Chen, Fahu; Li, Guoqiang; Zhao, Hui; Jin, Ming; Fan, Yuxin; Madsen, David; Chun, Xi

    2013-04-01

    Desert evolution was one of the major environmental changes in northern China during Quaternary. Ulan Buh Desert (UBD), at margin of present summer monsoon, is one of main desert fields and dust source areas in the north and northwest China. In this paper we present the results of lithology, Optical Stimulated Luminescence (OSL) dates, grain-size, carbonate content, organic content and pollen analysis from the drilling cores in the different parts of UBD. Our results show that most area of the present Ulan Buh desert was covered by the Jilantai-Hetao mage-paleolake before ~90 ka ago, a uniform paleolake of about 34,000 km2 covering the whole Hetai palin, and sevrious eolian and desert environment was prevailing during the last glacial and early Holoccene. Then an Ulan Buh paleolake (UB paleolake), likely a desert-wetland enviroment, formed in the northern part of UBD and Jilantai salt lake at around 8-7 ka, leaving dry lake bed landform in northern UBD, while high dune landscape probably prevailed in south UBD. After that, the mordern UBD landscape formed. The Jilantai Salt Lake in western UBD continued to exist until present with high lake level during UB paleolake preiod. During the recent 2000 years aeolian sand from Badan Jaran desert invaded the north UBD through Langshan mountain to form dune landform covered on dry UB paleolake bed and seperated main Ulan Buh desert and Jilantai Salt Lake. Human activities such as changing low wetland to farmland and following abandonment resulted the formation of easten Ulan Buh desert in Han dynasty since 200 BC. The formation of UBD landfporms was suggedted to be relate to disintegration of Jilantai-Hetao mage-paleolake, and was also likely to corresponding to summer monsoon changes during during last glacial and Holocene.

  2. Desert Farming Benefits from Microbial Potential in Arid Soils and Promotes Diversity and Plant Health

    PubMed Central

    Köberl, Martina; Müller, Henry; Ramadan, Elshahat M.; Berg, Gabriele

    2011-01-01

    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 soil showed a higher

  3. Magnetic Analysis Techniques Applied to Desert Varnish

    NASA Technical Reports Server (NTRS)

    Schmidgall, E. R.; Moskowitz, B. M.; Dahlberg, E. D.; Kuhlman, K. R.

    2003-01-01

    Desert varnish is a black or reddish coating commonly found on rock samples from arid regions. Typically, the coating is very thin, less than half a millimeter thick. Previous research has shown that the primary components of desert varnish are silicon oxide clay minerals (60%), manganese and iron oxides (20-30%), and trace amounts of other compounds [1]. Desert varnish is thought to originate when windborne particles containing iron and manganese oxides are deposited onto rock surfaces where manganese oxidizing bacteria concentrate the manganese and form the varnish [4,5]. If desert varnish is indeed biogenic, then the presence of desert varnish on rock surfaces could serve as a biomarker, indicating the presence of microorganisms. This idea has considerable appeal, especially for Martian exploration [6]. Magnetic analysis techniques have not been extensively applied to desert varnish. The only previous magnetic study reported that based on room temperature demagnetization experiments, there were noticeable differences in magnetic properties between a sample of desert varnish and the substrate sandstone [7]. Based upon the results of the demagnetization experiments, the authors concluded that the primary magnetic component of desert varnish was either magnetite (Fe3O4) or maghemite ( Fe2O3).

  4. ECOLOGY OF DESERT SYSTEMS BOOK REVIEW

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The 12 chapters of Whitford's book, Ecology of Desert Systems, summarize the comprehensive experiences and knowledge of a scientist with an extensive research background on a wide variety of physical and biological aspects of desert ecology. The author illustrates facts and concepts presented in th...

  5. Notes from the Great American Desert

    ERIC Educational Resources Information Center

    Grady, Marilyn L.; LaCost, Barbara Y.

    2005-01-01

    In the good old days, the state that is Nebraska was identified as part of the Great American Desert. In many ways, in climate and terrain, it still bears a resemblance to a desert. As a frontier or a land of pioneers, it deserves recognition. Invisibility may be one of the greatest challenges women face. One of the great flaws in the writing of…

  6. Diversity and Ecology of Viruses in Hyperarid Desert Soils

    PubMed Central

    Zablocki, Olivier; Adriaenssens, Evelien M.

    2015-01-01

    In recent years, remarkable progress has been made in the field of virus environmental ecology. In marine ecosystems, for example, viruses are now thought to play pivotal roles in the biogeochemical cycling of nutrients and to be mediators of microbial evolution through horizontal gene transfer. The diversity and ecology of viruses in soils are poorly understood, but evidence supports the view that the diversity and ecology of viruses in soils differ substantially from those in aquatic systems. Desert biomes cover ∼33% of global land masses, and yet the diversity and roles of viruses in these dominant ecosystems remain poorly understood. There is evidence that hot hyperarid desert soils are characterized by high levels of bacterial lysogens and low extracellular virus counts. In contrast, cold desert soils contain high extracellular virus titers. We suggest that the prevalence of microbial biofilms in hyperarid soils, combined with extreme thermal regimens, exerts strong selection pressures on both temperate and virulent viruses. Many desert soil virus sequences show low values of identity to virus genomes in public databases, suggesting the existence of distinct and as-yet-uncharacterized soil phylogenetic lineages (e.g., cyanophages). We strongly advocate for amplification-free metavirome analyses while encouraging the classical isolation of phages from dominant and culturable microbial isolates in order to populate sequence databases. This review provides an overview of recent advances in the study of viruses in hyperarid soils and of the factors that contribute to viral abundance and diversity in hot and cold deserts and offers technical recommendations for future studies. PMID:26590289

  7. Diversity and Ecology of Viruses in Hyperarid Desert Soils.

    PubMed

    Zablocki, Olivier; Adriaenssens, Evelien M; Cowan, Don

    2016-02-01

    In recent years, remarkable progress has been made in the field of virus environmental ecology. In marine ecosystems, for example, viruses are now thought to play pivotal roles in the biogeochemical cycling of nutrients and to be mediators of microbial evolution through horizontal gene transfer. The diversity and ecology of viruses in soils are poorly understood, but evidence supports the view that the diversity and ecology of viruses in soils differ substantially from those in aquatic systems. Desert biomes cover ∼ 33% of global land masses, and yet the diversity and roles of viruses in these dominant ecosystems remain poorly understood. There is evidence that hot hyperarid desert soils are characterized by high levels of bacterial lysogens and low extracellular virus counts. In contrast, cold desert soils contain high extracellular virus titers. We suggest that the prevalence of microbial biofilms in hyperarid soils, combined with extreme thermal regimens, exerts strong selection pressures on both temperate and virulent viruses. Many desert soil virus sequences show low values of identity to virus genomes in public databases, suggesting the existence of distinct and as-yet-uncharacterized soil phylogenetic lineages (e.g., cyanophages). We strongly advocate for amplification-free metavirome analyses while encouraging the classical isolation of phages from dominant and culturable microbial isolates in order to populate sequence databases. This review provides an overview of recent advances in the study of viruses in hyperarid soils and of the factors that contribute to viral abundance and diversity in hot and cold deserts and offers technical recommendations for future studies. PMID:26590289

  8. South Africa.

    PubMed

    1985-05-01

    The 1983 population of South Africa was estimated at 31.1 million, with an annual growth rate of 2.5% (0.8% for whites, 1.8% for blacks and "coloreds," 1.8% for Asians, and 2.8% for Africans). The infant mortality rate was 14.9/1000 live births among whites, 80.6/1000 among blacks and coloreds, and 25.3/1000 among Asians. Life expectancy was 70 years for whites, 59 years for blacks and coloreds, 66 years for Asians, and 55 years for Africans. Racial discrimination has become increasingly institutionalized in South Africa since the ruling National Party came to power in 1948. The policy of apartheid calls for separate political institutions for the 4 major racial groups in the population. Africans are considered citizens of the homelands to which their tribal group is assigned, not permanent citizens of the country. Coloreds and Asians are considered citizens and given some political expression. The new political system envisions broad consensus among whites, coloreds, and Indians, and a parliamentary committee is considering possible abolition of laws against multiracial political activity. The work force totals 11 million, 30% of whom are engaged in agriculture, 29% are employed in industry and commerce, 34% work in the services sector, and 7% work in mining. The GNP in 1983 totalled US$75.5 billion and the GDP stood at US$73.2 billion. Per capita GNP was US$5239. PMID:12178120

  9. Desert Test Site Uniformity Analysis

    NASA Technical Reports Server (NTRS)

    Kerola, Dana X.; Bruegge, Carol J.

    2009-01-01

    Desert test sites such as Railroad Valley (RRV) Nevada, Egypt-1, and Libya-4 are commonly targeted to assess the on-orbit radiometric performance of sensors. Railroad Valley is used for vicarious calibration experiments, where a field-team makes ground measurements to produce accurate estimates of top-of-atmosphere (TOA) radiances. The Sahara desert test sites are not instrumented, but provide a stable target that can be used for sensor cross-comparisons, or for stability monitoring of a single sensor. These sites are of interest to NASA's Atmospheric Carbon Observation from Space (ACOS) and JAXA's Greenhouse Gas Observation SATellite (GOSAT) programs. This study assesses the utility of these three test sites to the ACOS and GOSAT calibration teams. To simulate errors in sensor-measured radiance with pointing errors, simulated data have been created using MODIS Aqua data. MODIS data are further utilized to validate the campaign data acquired from June 22 through July 5, 2009. The first GOSAT vicarious calibration experiment was conducted during this timeframe.

  10. Desert test site uniformity analysis

    NASA Astrophysics Data System (ADS)

    Kerola, Dana X.; Bruegge, Carol J.

    2009-08-01

    Desert test sites such as Railroad Valley (RRV) Nevada, Egypt-1, and Libya-4 are commonly targeted to assess the on-orbit radiometric performance of sensors. Railroad Valley is used for vicarious calibration experiments, where a field-team makes ground measurements to produce accurate estimates of top-of-atmosphere (TOA) radiances. The Sahara desert test sites are not instrumented, but provide a stable target that can be used for sensor cross-comparisons, or for stability monitoring of a single sensor. These sites are of interest to NASA's Atmospheric Carbon Observation from Space (ACOS) and JAXA's Greenhouse Gas Observation SATellite (GOSAT) programs. This study assesses the utility of these three test sites to the ACOS and GOSAT calibration teams. To simulate errors in sensor-measured radiance with pointing errors, simulated data have been created using MODIS Aqua data. MODIS data are further utilized to validate the campaign data acquired from June 22 through July 5, 2009. The first GOSAT vicarious calibration experiment was conducted during this timeframe.

  11. Rb-Sr And Sm-Nd Ages, and Petrogenesis of Depleted Shergottite Northwest Africa 5990

    NASA Technical Reports Server (NTRS)

    Shih, C. Y.; Nyquist, L. E.; Reese, Y.; Irving, A. J.

    2011-01-01

    Northwest Africa (NWA) 5990 is a very fresh Martian meteorite recently found on Hamada du Draa, Morocco and was classified as an olivine-bearing diabasic igneous rock related to depleted shergottites [1]. The study of [1] also showed that NWA 5990 resembles QUE 94201 in chemical, textural and isotopic aspects, except QUE 94201 contains no olivine. The depleted shergottites are characterized by REE patterns that are highly depleted in LREE, older Sm-Nd ages of 327-575 Ma and highly LREE-depleted sources with Nd= +35+48 [2-7]. Age-dating these samples by Sm-Nd and Rb-Sr methods is very challenging because they have been strongly shocked and contain very low abundances of light rare earth elements (Sm and Nd), Rb and Sr. In addition, terrestrial contaminants which are commonly present in desert meteorites will compromise the equilibrium of isotopic systems. Since NWA 5990 is a very fresh meteorite, it probably has not been subject to significant desert weathering and thus is a good sample for isotopic studies. In this report, we present Rb-Sr and Sm-Nd isotopic results for NWA 5990, discuss the correlation of the determined ages with those of other depleted shergottites, especially QUE 94201, and discuss the petrogenesis of depleted shergottites.

  12. Behavior of geladas and other endemic wildlife during a desert locust outbreak at Guassa, Ethiopia: ecological and conservation implications.

    PubMed

    Fashing, Peter J; Nguyen, Nga; Fashing, Norman J

    2010-07-01

    Desert locust (Schistocerca gregaria) outbreaks have occurred repeatedly throughout recorded history in the Horn of Africa region, devastating crops and contributing to famines. In June 2009, a desert locust swarm invaded the Guassa Plateau, Ethiopia, a large and unusually intact Afroalpine tall-grass ecosystem, home to important populations of geladas (Theropithecus gelada), Ethiopian wolves (Canis simensis), thick-billed ravens (Corvus crassirostris), and other Ethiopian or Horn of Africa endemics. During the outbreak and its aftermath, we observed many animals, including geladas, ravens, and a wolf, feeding on locusts in large quantities. These observations suggest surprising flexibility in the normally highly specialized diets of geladas and wolves, including the potential for temporary but intensive insectivory during locust outbreaks. To our knowledge, Guassa is the highest elevation site (3,200-3,600 m) at which desert locusts, which require temperatures >20 degrees C for sustained flight, have been reported. Continued monitoring will be necessary to determine whether the June 2009 outbreak was an isolated incident or part of an emerging pattern in the Ethiopian Highlands linked to global warming. The intensive consumption of desert locusts by geladas, wolves, and ravens during the outbreak at Guassa raises concerns about pesticide-based locust control strategies and potential unintended adverse effects on endemic and endangered wildlife. PMID:20333438

  13. Effects of aerosols and surface shadowing on bidirectional reflectance measurements of deserts

    NASA Technical Reports Server (NTRS)

    Bowker, David E.; Davis, Richard E.

    1987-01-01

    Desert surfaces are probably one of the most stable of the Earth's natural targets for remote sensing. The bidirectional reflectance properties of the Saudi Arabian desert was investigated during the Summer Monsoon Experiment (Summer Monex). A comparison of high-altitude with near-surface measurements of the White Sands desert showed significant differences. These discrepancies have been attributed to forward scattering of the dust-laden atmosphere prevalent during Summer Monex. This paper is concerned in general with modeling the effects of atmospheric aerosols and surface shadowing on the remote sensing of bidirectional reflectance factors of desert targets, and in particular with comparing the results of these models with flight results. Although it is possible to approximate the latter, it is felt that a surface reflectance model with a smaller specular component would have permitted using a more realistic set of atmospheric conditions in the simulations.

  14. Intercomparison and interpretation of satellite-derived directional albedos over deserts

    NASA Technical Reports Server (NTRS)

    Cess, Robert D.; Vulis, Inna L.

    1989-01-01

    Issues related to the dependence of planetary albedo upon solar zenith angle are studied using Nimbus-7, GOES, and Meteosat data over deserts. Geographical variations of the planetary albedo are isolated from the albedo's solar zenith angle dependence. An atmospheric solar radiation model is coupled with desert surface bidirectional reflectance measurements to test the consistency of satellite-derived directional planetary albedos. Consideration is given to the use of narrowband versus broadband instruments, the impact of desert aerosols on the directional planetary albedo, and potential differences in the directional planetary albedo associated with different types of deserts. The results show that the directional planetary albedo is dominated by the directional surface albedo, although surface brightness influences the atmospheric limb brightening and limb darkening processes.

  15. Thermodynamic and pedogenic differences between desert microsites

    NASA Astrophysics Data System (ADS)

    Young, Michael; Caldwell, Todd; Lin, Henry

    2014-05-01

    taken along transects radiating from canopies of perennial shrubs into bare interspaces of structured soils. We augmented these measurements with ground-penetrating radar (GPR), laboratory analyses, and (in some cases) soil trenches. The results showed higher saturated conductivity under canopies versus interspaces, regardless of surface age, with the largest differences observed on older, developed soils. Bulk density, soil structure grade, and silt and clay content increased significantly away from the canopy, and organic content decreased toward interspaces. Trends in soil properties, from canopies to interspaces, were found to be predictable to a distance of 1.35 +/- 0.32 times the canopy radius, regardless of the size or genus of the shrub. The microsite environments, which are separated by only 10s of cm, release energy and mass at different rates—the fluxes differ by microsite locations. They exist with different thermodynamic gradients, with larger upward fluxes to support shrubs under canopy microsites and larger downward fluxes in interspaces. Armoured against change in interspaces can explain progressive structural evolution of pedons, a paradoxically reduced water infiltration capacity, and a contraction of canopy volumes and ecosystem production in older soils. We use these gradients to illustrate the importance of microsite location when considering complex feedbacks that result through currently-observed, time-dependent processes of pedogenesis in arid regions of the desert southwest.

  16. 75 FR 57761 - Desert Southwest Power, LLC; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-22

    ... Energy Regulatory Commission Desert Southwest Power, LLC; Notice of Filing September 14, 2010. Take notice that on September 10, 2010, Desert Southwest Power, LLC (Desert Southwest) filed responses to the... Commission's July 28, 2010 letter regarding Desert Southwest's petition for declaratory order...

  17. Thermal and water relations of desert beetles

    NASA Astrophysics Data System (ADS)

    Cloudsley-Thompson, J.

    2001-11-01

    The physical problems that living organisms have to contend with in hot deserts are primarily extremes of temperature, low humidity, shortage or absence of free water, and the environmental factors that accentuate these - such as strong winds, sand-storms, lack of shade, rocky and impenetrable soils. Climatic factors are particularly important to smaller animals such as arthropods on account of their relatively enormous surface to volume ratios. Nevertheless, beetles (especially Tenebrionidae and, to a lesser extent, Chrysomelidae) are among the most successful animals of the desert, and are often the only ones to be seen abroad during the day. Similar physical problems are experienced by insects in all terrestrial biomes, but they are much enhanced in the desert. Although climatic extremes are often avoided by burrowing habits coupled with circadian and seasonal activity rhythms, as well as reproductive phenology, several species of desert beetle are nevertheless able to withstand thermal extremes that would rapidly cause the death of most other arthropods including insects. The reactions of desert beetles to heat are largely behavioural whilst their responses to water shortage are primarily physiological. The effects of coloration are not discussed. In addition to markedly low rates of transpiration, desert beetles can also withstand a considerable reduction in the water content of their tissues. The study of desert beetles is important because it illustrates many of the solutions evolved by arthropods to the problems engendered, in an extreme form, by life in all terrestrial environments.

  18. Thermal and water relations of desert beetles.

    PubMed

    Cloudsley-Thompson, J L

    2001-11-01

    The physical problems that living organisms have to contend with in hot deserts are primarily extremes of temperature, low humidity, shortage or absence of free water, and the environmental factors that accentuate these--such as strong winds, sand-storms, lack of shade, rocky and impenetrable soils. Climatic factors are particularly important to smaller animals such as arthropods on account of their relatively enormous surface to volume ratios. Nevertheless, beetles (especially Tenebrionidae and, to a lesser extent, Chrysomelidae) are among the most successful animals of the desert, and are often the only ones to be seen abroad during the day. Similar physical problems are experienced by insects in all terrestrial biomes, but they are much enhanced in the desert. Although climatic extremes are often avoided by burrowing habits coupled with circadian and seasonal activity rhythms, as well as reproductive phenology, several species of desert beetle are nevertheless able to withstand thermal extremes that would rapidly cause the death of most other arthropods including insects. The reactions of desert beetles to heat are largely behavioural whilst their responses to water shortage are primarily physiological. The effects of coloration are not discussed. In addition to markedly low rates of transpiration, desert beetles can also withstand a considerable reduction in the water content of their tissues. The study of desert beetles is important because it illustrates many of the solutions evolved by arthropods to the problems engendered, in an extreme form, by life in all terrestrial environments. PMID:11771473

  19. Near eastern neolithic genetic input in a small oasis of the Egyptian Western Desert.

    PubMed

    Kujanová, Martina; Pereira, Luísa; Fernandes, Verónica; Pereira, Joana B; Cerný, Viktor

    2009-10-01

    The Egyptian Western Desert lies on an important geographic intersection between Africa and Asia. Genetic diversity of this region has been shaped, in part, by climatic changes in the Late Pleistocene and Holocene epochs marked by oscillating humid and arid periods. We present here a whole genome analysis of mitochondrial DNA (mtDNA) and high-resolution molecular analysis of nonrecombining Y-chromosomal (NRY) gene pools of a demographically small but autochthonous population from the Egyptian Western Desert oasis el-Hayez. Notwithstanding signs of expected genetic drift, we still found clear genetic evidence of a strong Near Eastern input that can be dated into the Neolithic. This is revealed by high frequencies and high internal variability of several mtDNA lineages from haplogroup T. The whole genome sequencing strategy and molecular dating allowed us to detect the accumulation of local mtDNA diversity to 5,138 +/- 3,633 YBP. Similarly, theY-chromosome gene pool reveals high frequencies of the Near Eastern J1 and the North African E1b1b1b lineages, both generally known to have expanded within North Africa during the Neolithic. These results provide another piece of evidence of the relatively young population history of North Africa. PMID:19425100

  20. Drought in West Africa

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Drought settled over West Africa's Ivory Coast region when wet season rains came late in 2007. Instead of beginning in February, the rainy season didn't start until March, and steady rains didn't start until late March, said the Famine Early Warning System Network. Though the rain had started to alleviate the drought, vegetation was still depressed in parts of Cote d'Ivoire (Ivory Coast) between March 22 and April 6, 2007, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured the data used to make this image. The image shows current vegetation conditions compared to average conditions recorded since 2000. Areas where plants are growing more slowly or more sparsely than average are brown, while areas where vegetation is denser than average are green. The brown tint that dominates the image indicates that plants through most of the country are more sparse than normal. Among the crops affected by the lack of rain was West Africa's cocoa crop. About 70 percent of the world's cocoa comes from West Africa, and Cote d'Ivoire is a top grower, said Reuters. Cocoa prices climbed as the crop fell short. Farmers called the drought the worst in living memory, Reuters said. The delay in rainfall also led to water shortages in parts of Cote d'Ivoire, according to the United Nations Office for the Coordination of Humanitarian Affairs.

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

    USGS Publications Warehouse

    Jacobson, Elliott R.; Berry, Kristin H.; Wellehan, James F. X., Jr.; 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.

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

    USGS Publications Warehouse

    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 (<1 kg) mammals and 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.

  3. Effects of added Zn, Ni and Cd on desert shrubs grown in desert soil

    SciTech Connect

    Patel, P.M.; Wallace, A.; Romney, E.M.; Alexander, G.V.

    1980-01-01

    Desert shrubs - Ambrosia dumosa, Lycium andersonii, Larrea tridenata, and Ephedra nevadensis wre grown in a glasshouse in desert (calcarous) soil with different levels of added Zn, Ni, and Cd. The objective was to study effects of the metals on growth and yield and uptake and translocation of metals in desert plant species which are common in the Mojave Desert (areas of Nevada and southeast California). Zinc and Cd considerably decreased yields of all four species. Yields of E. nevadensis were increased by Ni at 250 and 500 mg/kg applied to desert soil. Ephedra nevadensis was more tolerant of Ni than were the other three desert shrubs. Some interactions were observed among various elements: manganese concentration was increased in shrubs by Zn. Particularly, application of Ni reduced the concentrations of Zn and Mn over the control.

  4. Microphytic crusts: 'topsoil' of the desert

    USGS Publications Warehouse

    Belnap, Jayne

    1990-01-01

    Deserts throughout the world are the home of microphytic, or cryptogamic, crusts. These crusts are dominated by cyanobacteria, previously called blue-green algae, and also include lichens, mosses, green algae, microfungi and bacteria. They are critical components of desert ecosystems, significantly modifying the surfaces on which they occur. In the cold deserts of the Colorado Plateau (including parts of Utah, Arizona, Colorado, and New Mexico), these crusts are extraordinarily well-developed, and may represent 70-80% of the living ground cover.

  5. Impact and monitoring of dust storms in Taklimakan desert

    NASA Astrophysics Data System (ADS)

    Feng, G. G.; Li, X.; Zheng, Z.

    2012-12-01

    determined that the horizontal dust flux was 0.6 to 4.3 kg/m. Dust clouds are formed when the friction from high surface wind speeds (>6 m/s) lifts loose dust particles into the atmospheric boundary layer or above. Analysis shows that a dust storm in the Taklimakan desert on April 23th produced a huge atmospheric dust cloud, it was transported across the Pacific Ocean to reach the West Coast of North America 12 days later, corresponding to 6 m/s average transport speed. The observations in the Pacific Coast indicated that aerosol concentrations were elevated which resulted in Air Quality Index (AQI) to the yellow moderate category.

  6. Desert Dust Satellite Retrieval Intercomparison

    NASA Technical Reports Server (NTRS)

    Carboni, E.; Thomas, G. E.; Sayer, A. M.; Siddans, R.; Poulsen, C. A.; Grainger, R. G.; Ahn, C.; Antoine, D.; Bevan, S.; Braak, R.; Brindley, H.; DeSouza-Mchado, S.; Deuze, J. L.; Diner, D.; Ducos, F.; Grey, W.; Hsu, C.; Kalashnikova, O. V.; Kahn, R.; North, P. R. J.; Salustro, C.; Smith, A.; Tanre, D.; Torres, O.; Veihelmann, B.

    2012-01-01

    This work provides a comparison of satellite retrievals of Saharan desert dust aerosol optical depth (AOD) during a strong dust event through March 2006. In this event, a large dust plume was transported over desert, vegetated, and ocean surfaces. The aim is to identify and understand the differences between current algorithms, and hence improve future retrieval algorithms. The satellite instruments considered are AATSR, AIRS, MERIS, MISR, MODIS, OMI, POLDER, and SEVIRI. An interesting aspect is that the different algorithms make use of different instrument characteristics to obtain retrievals over bright surfaces. These include multi-angle approaches (MISR, AATSR), polarisation measurements (POLDER), single-view approaches using solar wavelengths (OMI, MODIS), and the thermal infrared spectral region (SEVIRI, AIRS). Differences between instruments, together with the comparison of different retrieval algorithms applied to measurements from the same instrument, provide a unique insight into the performance and characteristics of the various techniques employed. As well as the intercomparison between different satellite products, the AODs have also been compared to co-located AERONET data. Despite the fact that the agreement between satellite and AERONET AODs is reasonably good for all of the datasets, there are significant differences between them when compared to each other, especially over land. These differences are partially due to differences in the algorithms, such as as20 sumptions about aerosol model and surface properties. However, in this comparison of spatially and temporally averaged data, at least as significant as these differences are sampling issues related to the actual footprint of each instrument on the heterogeneous aerosol field, cloud identification and the quality control flags of each dataset.

  7. Desert potholes: Ephemeral aquatic microsystems

    USGS Publications Warehouse

    Chan, M.A.; Moser, K.; Davis, J.M.; Southam, G.; Hughes, K.; Graham, T.

    2005-01-01

    An enigma of the Colorado Plateau high desert is the "pothole", which ranges from shallow ephemeral puddles to deeply carved pools. The existence of prokaryotic to eukaryotic organisms within these pools is largely controlled by the presence of collected rainwater. Multivariate statistical analysis of physical and chemical limnologic data variables measured from potholes indicates spatial and temporal variations, particularly in water depth, manganese, iron, nitrate and sulfate concentrations and salinity. Variation in water depth and salinity are likely related to the amount of time since the last precipitation, whereas the other variables may be related to redox potential. The spatial and temporal variations in water chemistry affect the distribution of organisms, which must adapt to daily and seasonal extremes of fluctuating temperature (0-60 ??C), pH changes of as much as 5 units over 12 days, and desiccation. For example, many species become dormant when potholes dry, in order to endure intense heat, UV radiation, desiccation and freezing, only to flourish again upon rehydration. But the pothole organisms also have a profound impact on the potholes. Through photosynthesis and respiration, pothole organisms affect redox potential, and indirectly alter the water chemistry. Laboratory examination of dried biofilm from the potholes revealed that within 2 weeks of hydration, the surface of the desiccated, black biofilm became green from cyanobacterial growth, which supported significant growth in heterotrophic bacterial populations. This complex biofilm is persumably responsible for dissolving the cement between the sandstone grains, allowing the potholes to enlarge, and for sealing the potholes, enabling them to retain water longer than the surrounding sandstone. Despite the remarkable ability of life in potholes to persist, desert potholes may be extremely sensitive to anthropogenic effects. The unique limnology and ecology of Utah potholes holds great scientific

  8. A probabilistic model of insolation for the Mojave Desert area

    NASA Technical Reports Server (NTRS)

    Hester, O. V.; Reid, M. S.

    1978-01-01

    A discussion of mathematical models of insolation characteristics suitable for use in analysis of solar energy systems is presented and shows why such models are essential for solar energy system design. A model of solar radiation for the Mojave Desert area is presented with probabilistic and deterministic components which reflect the occurrence and density of clouds and haze, and mimic their effects on both direct and indirect radiation. Multiple comparisons were made between measured total energy received per day and the corresponding simulated totals. The simulated totals were all within 11 percent of the measured total. The conclusion is that a useful probabilistic model of solar radiation for the Goldstone, California, area of the Mojave Desert has been constructed.

  9. Mineralogical maturity in dunefields of North America, Africa and Australia

    USGS Publications Warehouse

    Muhs, D.R.

    2004-01-01

    Studies of dunefields in central and western North America show that mineralogical maturity can provide new insights into the origin and evolution of aeolian sand bodies. Many of the world's great sand seas in Africa, Asia and Australia are quartz-dominated and thus can be considered to be mineralogically mature. The Algodones (California) and Parker (Arizona) dunes in the southwestern United States are also mature, but have inherited a high degree of mineralogical maturity from quartz-rich sedimentary rocks drained by the Colorado River. In Libya, sediments of the Zallaf sand sea, which are almost pure quartz, may have originated in a similar fashion. The Fort Morgan (Colorado) and Casper (Wyoming) dunefields in the central Great Plains of North America, and the Namib sand sea of southern Africa have an intermediate degree of mineralogical maturity because their sources are large rivers that drained both unweathered plutonic and metamorphic rocks and mature sedimentary rocks. Mojave Desert dunefields in the southwestern United States are quite immature because they are in basins adjacent to plutonic rocks that were their sources. Other dunefields in the Great Plains of North America (those in Nebraska and Texas) are more mature than any possible source sediments and therefore reflect mineralogical evolution over time. Such changes in composition can occur because of either of two opposing long-term states of the dunefield. In one state, dunes are stable for long periods of time and chemical weathering depletes feldspars and other weatherable minerals in the sediment body. In the other state, which is most likely for the Great Plains, abrasion and ballistic impacts deplete the carbonate minerals and feldspars because the dunes are active for longer periods than they are stable. ?? 2003 Elsevier B.V. All rights reserved.

  10. Hydrological projections under climate change in the near future by RegCM4 in Southern Africa using a large-scale hydrological model

    NASA Astrophysics Data System (ADS)

    Li, Lu; Diallo, Ismaïla; Xu, Chong-Yu; Stordal, Frode

    2015-09-01

    This study aims to provide model estimates of changes in hydrological elements, such as EvapoTranspiration (ET) and runoff, in Southern Africa in the near future until 2029. The climate change scenarios are projected by a high-resolution Regional Climate Model (RCM), RegCM4, which is the latest version of this model developed by the Abdus Salam International Centre for Theoretical Physics (ICTP). The hydrological projections are performed by using a large-scale hydrological model (WASMOD-D), which has been tested and customized on this region prior to this study. The results reveal that (1) the projected temperature shows an increasing tendency over Southern Africa in the near future, especially eastward of 25°E, while the precipitation changes are varying between different months and sub-regions; (2) an increase in runoff (and ET) was found in eastern part of Southern Africa, i.e. Southern Mozambique and Malawi, while a decrease was estimated across the driest region in a wide area encompassing Kalahari Desert, Namibia, southwest of South Africa and Angola; (3) the strongest climate change signals are found over humid tropical areas, i.e. north of Angola and Malawi and south of Dem Rep of Congo; and (4) large spatial and temporal variability of climate change signals is found in the near future over Southern Africa. This study presents the main results of work-package 2 (WP2) of the 'Socioeconomic Consequences of Climate Change in Sub-equatorial Africa (SoCoCA)' project, which is funded by the Research Council of Norway.

  11. Biological effects of desert dust in respiratory epithelial cells and a murine model.

    PubMed

    Ghio, Andrew J; Kummarapurugu, Suryanaren T; Tong, Haiyan; Soukup, Joleen M; Dailey, Lisa A; Boykin, Elizabeth; Ian Gilmour, M; Ingram, Peter; Roggli, Victor L; Goldstein, Harland L; Reynolds, Richard L

    2014-04-01

    As a result of the challenge of recent dust storms to public health, we tested the postulate that desert dust collected in the southwestern United States imparts a biological effect in respiratory epithelial cells and an animal model. Two samples of surface sediment were collected from separate dust sources in northeastern Arizona. Analysis of the PM20 fraction demonstrated that the majority of both dust samples were quartz and clay minerals (total SiO₂ of 52 and 57%). Using respiratory epithelial and monocytic cell lines, the two desert dusts increased oxidant generation, measured by Amplex Red fluorescence, along with carbon black (a control particle), silica, and NIST 1649 (an ambient air pollution particle). Cell oxidant generation was greatest following exposures to silica and the desert dusts. Similarly, changes in RNA for superoxide dismutase-1, heme oxygenase-1, and cyclooxygenase-2 were also greatest after silica and the desert dusts supporting an oxidative stress after cell exposure. Silica, desert dusts, and the ambient air pollution particle NIST 1649 demonstrated a capacity to activate the p38 and ERK1/2 pathways and release pro-inflammatory mediators. Mice, instilled with the same particles, showed the greatest lavage concentrations of pro-inflammatory mediators, neutrophils, and lung injury following silica and desert dusts. We conclude that, comparable to other particles, desert dusts have a capacity to (1) influence oxidative stress and release of pro-inflammatory mediators in respiratory epithelial cells and (2) provoke an inflammatory injury in the lower respiratory tract of an animal model. The biological effects of desert dusts approximated those of silica. PMID:24669951

  12. Biological effects of desert dust in respiratory epithelial cells and a murine model

    USGS Publications Warehouse

    Ghio, Andrew J.; Kummarapurugu, Suryanaren T.; Tong, Haiyan; Soukup, Joleen M.; Dailey, Lisa A.; Boykin, Elizabeth; Gilmour, M. Ian; Ingram, Peter; Roggli, Victor L.; Goldstein, Harland L.; Reynolds, Richard L.

    2014-01-01

    As a result of the challenge of recent dust storms to public health, we tested the postulate that desert dust collected in the southwestern United States imparts a biological effect in respiratory epithelial cells and an animal model. Two samples of surface sediment were collected from separate dust sources in northeastern Arizona. Analysis of the PM20 fraction demonstrated that the majority of both dust samples were quartz and clay minerals (total SiO2 of 52 and 57%). Using respiratory epithelial and monocytic cell lines, the two desert dusts increased oxidant generation, measured by Amplex Red fluorescence, along with carbon black (a control particle), silica, and NIST 1649 (an ambient air pollution particle). Cell oxidant generation was greatest following exposures to silica and the desert dusts. Similarly, changes in RNA for superoxide dismutase-1, heme oxygenase-1, and cyclooxygenase-2 were also greatest after silica and the desert dusts supporting an oxidative stress after cell exposure. Silica, desert dusts, and the ambient air pollution particle NIST 1649 demonstrated a capacity to activate the p38 and ERK1/2 pathways and release pro-inflammatory mediators. Mice, instilled with the same particles, showed the greatest lavage concentrations of pro-inflammatory mediators, neutrophils, and lung injury following silica and desert dusts. We conclude that, comparable to other particles, desert dusts have a capacity to (1) influence oxidative stress and release of pro-inflammatory mediators in respiratory epithelial cells and (2) provoke an inflammatory injury in the lower respiratory tract of an animal model. The biological effects of desert dusts approximated those of silica.

  13. Fasting-induced daily torpor in desert hamsters (Phodopus roborovskii).

    PubMed

    Chi, Qing-Sheng; Wan, Xin-Rong; Geiser, Fritz; Wang, De-Hua

    2016-09-01

    Daily torpor is frequently expressed in small rodents when facing energetically unfavorable ambient conditions. Desert hamsters (Phodopus roborovskii, ~20g) appear to be an exception as they have been described as homeothermic. However, we hypothesized that they can use torpor because we observed reversible decreases of body temperature (Tb) in fasted hamsters. To test this hypothesis we (i) randomly exposed fasted summer-acclimated hamsters to ambient temperatures (Tas) ranging from 5 to 30°C or (ii) supplied them with different rations of food at Ta 23°C. All desert hamsters showed heterothermy with the lowest mean Tb of 31.4±1.9°C (minimum, 29.0°C) and 31.8±2.0°C (minimum, 29.0°C) when fasted at Ta of 23°C and 19°C, respectively. Below Ta 19°C, the lowest Tb and metabolic rate increased and the proportion of hamsters using heterothermy declined. At Ta 5°C, nearly all hamsters remained normothermic by increasing heat production, suggesting that the heterothermy only occurs in moderately cold conditions, perhaps to avoid freezing at extremely low Tas. During heterothermy, Tbs below 31°C with metabolic rates below 25% of those during normothermia were detected in four individuals at Ta of 19°C and 23°C. Consequently, by definition, our observations confirm that fasted desert hamsters are capable of shallow daily torpor. The negative correlation between the lowest Tbs and amount of food supply shows that heterothermy was mainly triggered by food shortage. Our data indicate that summer-acclimated desert hamsters can express fasting-induced shallow daily torpor, which may be of significance for energy conservation and survival in the wild. PMID:27215346

  14. Stemflow and its significant to the fertilizer islands in desert shrub area

    NASA Astrophysics Data System (ADS)

    Wang, Xinping; Wang, Zhengning; Pan, Yanxia; Zhang, Yafeng

    2010-05-01

    Stemflow is a spatially localized point input of precipitation and fine particles of airborne dust from vegetation canopy at the plant stem and is of hydrological and ecological significance in desert shrub ecosystems, where precipitation is the sole source of water replenishment to sustaining the desert ecosystem. In the present study, stemflow production and the fine particles associated with the stemflow of the two main xerophytic shrubs was quantified by aluminum foil collar method at the desert shrub area of Shapotou Desert Experimental Research Station, Chinese Academy of Sciences. The results indicated that stemflow yield and the thresholds for stemflow occurrence varied within shrub species. The relationship between funnelling ratios and gross precipitation indicated that a certain value of precipitation was required for the shrubs. There was a large variability of funnelling ratio for the rainfall events with intensity of less than 4 mm h-1, and the variability tended to decease when rainfall intensity was greater than 4 mm h-1. Significant positive linear relationships were found between stemflow production and precipitation for the shrubs, statistical analysis showed that stemflow and fine particle yield varies as a function of meteorological conditions, canopy size and structure. An accurate modeling of stemflow water and nutrient inputs into desert soils may result in the understanding of the formation mechanism of fertilizer islands. Keywords: Desert ecosystem; Hydrology; Stemflow; Xerophytic shrub

  15. Effects of short photoperiod on energy intake, thermogenesis, and reproduction in desert hamsters (Phodopus roborovskii).

    PubMed

    Zhang, Xueying; Zhao, Zhijun; Vasilieva, Nina; Khrushchova, Anastasia; Wang, Dehua

    2015-03-01

    Desert hamsters (Phodopus roborovskii) are the least known species in the genus Phodopus with respect to ecology and physiology, and deserve scientific attention, particularly because of their small body size. Here, the responses of energy metabolism and reproductive function to short photoperiods in desert hamsters were investigated. Male and female desert hamsters were acclimated to either long day (LD) (L:D 16:8 h) or short day (SD) photoperiods (L:D 8:16 h) for three months, and then the females were transferred back to an LD photoperiod for a further five months, while at the end of the SD acclimation the males were killed and measurements were taken for serum leptin as well as molecular markers for thermogenesis. We found that like the other two species from the genus Phodopus, the desert hamsters under SD decreased body mass, increased adaptive thermogenesis as indicated by elevated mitochondrial protein content and uncoupling protein-1 content in brown adipose tissue, and suppressed reproduction compared to those under LD. However, different from the other two species, desert hamsters did not show any differences in energy intake or serum leptin concentration between LD and SD. These data suggest that different species from the same genus respond in different ways to the environmental signals, and the desert adapted species are not as sensitive to change in photoperiod as the other two species. PMID:25311843

  16. Nanoclimate environment of cyanobacterial communities in China's hot and cold hyperarid deserts

    NASA Astrophysics Data System (ADS)

    Warren-Rhodes, Kimberley A.; Rhodes, Kevin L.; Liu, Shuangjiang; Zhou, Peijin; McKay, Christopher P.

    2007-03-01

    This paper analyzes linkages between lithic (lithobiontic, lithophytic) cyanobacterial community (LCC) abundance and climate across a wide range of environmental conditions and geographical distance in China's northwest region, an area containing some of the world's oldest, driest and most isolated deserts. In situ monitoring and long-term climate data show that extreme heterogeneity in liquid water availability characterizes the LCC environment across multiple spatial and temporal scales, with rainfall and snowmelt being the main moisture sources. Mean annual precipitation (MAP) primarily dictates LCC ecology across sites, but the interacting effects of temperature, moisture and light create a gradient of soil liquid water (ALW, 505-1839 hr yr-1) and conditions suitable for metabolic activity (200-922 hr yr-1) that also correlate with LCC abundance (0.99 ± 0.2% to 12.6 ± 1.8%). In situ soil temperatures indicate a minimum range of thermal tolerance for LCC in China's deserts of -23.8°C to 53.8°C. Through a comparison of similar available climate data for other deserts, we conclude that from a microbial physiological standpoint, although the hyperarid core of the Atacama Desert represents the driest nanoclimate environment recorded and the Dry Valleys in Antarctica represent the coldest desert conditions, it is the high-altitude deserts in the Qinghai-Tibetan Plateau that offer the coldest and driest recorded extremes for LCC on Earth.

  17. Desert date (Balanites aegyptiaca) as an arid lands sustainable bioresource for biodiesel.

    PubMed

    Chapagain, Bishnu P; Yehoshua, Yariv; Wiesman, Zeev

    2009-02-01

    The aim of this study was to assess the suitability of Desert date (Balanites aegyptiaca L. Delile) as an oil crop in arid lands for large-scale sustainable industrial biodiesel production. Characterization of the Desert date plant material showed that using proper cultivation practices with emphasis on low quality irrigation water trees can be extremely well developed in hyper-arid conditions of the Israeli Arava desert and yield oil-rich fruits. Best selected trees can yield date fruits up to 52 kg/trees. Desert date kernels oil content may reach up to 46.7% (based on dry weight). The oil is consisted on four major fatty acids: palmitic (16:0), stearic (18:0), oleic (18:1), and linoleic (18:2), constituting 98-100% of the total fatty acids in the oil of all tested genotypes. Linoleic acid was the most prevalent fatty acid, ranging from 31% to 51% of the fatty acids profile, very similar to soybean oil profile. In situ biodiesel production directly from oil-enriched powder was successfully developed. Yield efficiency for both conventional and in situ biodiesel production was about 90%. The qualities of the produced biodiesel well meet the international biodiesel standards. The present study clearly demonstrated Desert date as a model for the utilization of bioresources in the Israeli Arava desert and potentially other similar areas for cost-effective biodiesel production. PMID:18848776

  18. Evaluation of modern and mid-Holocene seasonal precipitation of the Mediterranean and northern Africa in the CMIP5 simulations

    NASA Astrophysics Data System (ADS)

    Perez-Sanz, A.; Li, G.; González-Sampériz, P.; Harrison, S. P.

    2014-03-01

    We analyse the spatial expression of seasonal climates of the Mediterranean and northern Africa in pre-industrial (piControl) and mid-Holocene (midHolocene, 6 yr BP) simulations from the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Modern observations show four distinct precipitation regimes characterized by differences in the seasonal distribution and total amount of precipitation: an equatorial band characterized by a double peak in rainfall, the monsoon zone characterized by summer rainfall, the desert characterized by low seasonality and total precipitation, and the Mediterranean zone characterized by summer drought. Most models correctly simulate the position of the Mediterranean and the equatorial climates in the piControl simulations, but overestimate the extent of monsoon influence and underestimate the extent of desert. However, most models fail to reproduce the amount of precipitation in each zone. Model biases in the simulated magnitude of precipitation are unrelated to whether the models reproduce the correct spatial patterns of each regime. In the midHolocene, the models simulate a reduction in winter rainfall in the equatorial zone, and a northward expansion of the monsoon with a significant increase in summer and autumn rainfall. Precipitation is slightly increased in the desert, mainly in summer and autumn, with northward expansion of the monsoon. Changes in the Mediterranean are small, although there is an increase in spring precipitation consistent with palaeo-observations of increased growing-season rainfall. Comparison with reconstructions shows most models underestimate the mid-Holocene changes in annual precipitation, except in the equatorial zone. Biases in the piControl have only a limited influence on midHolocene anomalies in ocean-atmosphere models; carbon-cycle models show no relationship between piControl bias and midHolocene anomalies. Biases in the prediction of the midHolocene monsoon expansion are unrelated to

  19. Sampling and handling of desert soils

    NASA Technical Reports Server (NTRS)

    Blank, G. B.; Cameron, R. E.

    1969-01-01

    Report on sampling and handling desert soils includes sections on selection, characterization, and photography of area, site, and soil, sterilization of sampling equipment and containers, and soil sample collection, transport, storage, and dispersal.

  20. Giant viruses of the Kutch Desert.

    PubMed

    Kerepesi, Csaba; Grolmusz, Vince

    2016-03-01

    The Kutch Desert (Great Rann of Kutch, Gujarat, India) is a unique ecosystem: in the larger part of the year it is a hot, salty desert that is flooded regularly in the Indian monsoon season. In the dry season, the crystallized salt deposits form the "white desert" in large regions. The first metagenomic analysis of the soil samples of Kutch was published in 2013, and the data were deposited in the NCBI Sequence Read Archive. At the same time, the sequences were analyzed phylogenetically for prokaryotes, especially for bacteria. In the present work, we identified DNA sequences of recently discovered giant viruses in the soil samples from the Kutch Desert. Since most giant viruses have been discovered in biofilms in industrial cooling towers, ocean water, and freshwater ponds, we were surprised to find their DNA sequences in soil samples from a seasonally very hot and arid, salty environment. PMID:26666442

  1. Desert R.A.T.S. 2011

    NASA Video Gallery

    Desert Research And Technology Studies (D-R.A.T.S) kicks off an exciting new year of field testing. The crew is back in action, testing communication scenarios for near-Earth asteroids, and two new...

  2. Magnetic Analysis Techniques Applied to Desert Varnish

    NASA Astrophysics Data System (ADS)

    Schmidgall, E. R.; Moskowitz, B. M.; Dahlberg, E. D.; Kuhlman, K. R.

    2003-03-01

    A vibrating sample magnetometer (VSM) and radio frequency superconducting quantum interference device (RF SQUID) have been used to measure the properties of magnetic carriers in samples of black and red rock varnish from the Mojave Desert.

  3. Microbial Fossils Detected in Desert Varnish

    NASA Astrophysics Data System (ADS)

    Flood, B. E.; Allen, C.; Longazo, T.

    2003-03-01

    Desert varnish, a mixture of clays, Mn-oxides, and Fe-oxides, is a potential terrestrial analogue to Martian hematite. A scanning electron microscopic examination of samples from Pilbara, Australia revealed evidence of microbial fossilization.

  4. 2011 Desert RATS Sights and Sounds

    NASA Video Gallery

    Watch scenes from the 2011 Desert Research and Technology Studies (RATS) analog field test, as NASA scientists and engineers drive the Space Exploration Vehicle, assemble equipment in the Habitat D...

  5. Education, Democracy and Poverty Reduction in Africa.

    ERIC Educational Resources Information Center

    Harber, Clive

    2002-01-01

    Authoritarian rule in Africa has exacerbated poverty levels in six ways. Achievement of greater democracy depends upon political culture and civil society in Africa becoming more democratic; education must play a part in teaching democratic values and behaviors. Examples show how education has not furthered democracy in Botswana, Zimbabwe, and…

  6. Palynology of Albian-Cenomanian strata in Mersa Matruh well, Western Desert, Egypt

    NASA Astrophysics Data System (ADS)

    Sultan, Ismail Z.

    Plant microfossils have been recovered from the Albian and lower Cenomanian strata encountered in Mersa Matruh well No. 1, drilled in the northern part of the Western Desert of Egypt. The microflora includes 56 miospore species belonging to 35 genera; most of them are derived from pteridophyte, gymnosperm and angiosperm vegetations. Differences in miospore assemblages of the Albian and Lower Cenomanian are described. Correlation with coeval palynofloral assemblages in West Africa and South and North America reveals that the Mersa Matruh area, Egypt belongs to the mid-Cretaceous African-South American phytogeoprovince.

  7. Desert varnish: an environmental recorder for Mars

    NASA Astrophysics Data System (ADS)

    Perry, Randall S.; Sephton, Mark A.

    2006-08-01

    With the prospect of a Mars Sample Return mission in the next two decades, attention is now focusing on the types of samples that would be most useful for returning to Earth for laboratory analysis. Recent data on desert varnish reveal that laminated coatings on rocks from extreme environments are a passive recorder of past and present environments. Martian desert varnish would contain a chronology of the martian setting, perhaps extending back to a wetter and more biologically active period.

  8. News Almost dry but never dull: ASE 2014 EuroPhysicsFun shows physics to Europe Institute of Physics for Africa (IOPfA) South Sudan Report October 2013 Celebrating the centenary of x-ray diffraction The Niels Bohr Institute—an EPS Historical Site Nordic Research Symposium on Science Education (NFSUN) 2014: inquiry-based science education in technology-rich environments Physics World Cup 2013

    NASA Astrophysics Data System (ADS)

    2014-03-01

    Almost dry but never dull: ASE 2014 EuroPhysicsFun shows physics to Europe Institute of Physics for Africa (IOPfA) South Sudan Report October 2013 Celebrating the centenary of x-ray diffraction The Niels Bohr Institute—an EPS Historical Site Nordic Research Symposium on Science Education (NFSUN) 2014: inquiry-based science education in technology-rich environments Physics World Cup 2013

  9. Late Quaternary history of the Atacama Desert

    USGS Publications Warehouse

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

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    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.

  11. Reconstructing Quaternary pluvial episodes and paleohydrology using travertines from Egypt's Western Desert

    NASA Astrophysics Data System (ADS)

    Jimenez, G.; Crossey, L. J.; Karlstrom, K. E.; Ricketts, J. W.; Tafoya, A. J.; Anan, T.; Mohammed, A.; Asmerom, Y.; Polyak, V.; Farouk, S.

    2012-12-01

    Quaternary climate in North Africa was marked by multiple wet periods overprinting extreme aridity, but pluvial drivers, as well as their timing and geographic extent, are poorly constrained. We address these factors in the first comprehensive analysis of travertine from Egypt's Western Desert, which represents a unique and under-utilized record of paleoclimate and paleohydrology. We infer large-volume travertine mound deposition along faults near the area's central limestone plateau to reflect times of high discharge (high groundwater head) from springs of the Nubian aquifer, likely associated with so-called Green Sahara pluvial episodes. Similarly, we assume that travertine platforms in depressions (oases) represent related marsh and lake deposition, including a widespread late Cenozoic dolostone of probable lacustrine origin in Farafra Oasis, which needs additional mapping. We present the results of uranium-series analysis of travertines from oasis areas spanning a north-south gradient through the Western Desert; we dated the tops and bottoms of inset deposits at different wadi (wash) elevations to resolve the inception and termination of high spring heads/pluvials as well as regional aggradation or incision patterns. Our dates, combined with published literature ages, suggest wet intervals around 100-115, 125-140, 180-200, 350-360, 450, and 600 ka. Heights of inset terrace travertines in wadis are potentially correlative between sites and are seen as approximately 5, 10, and 25 m above the modern wadi levels. Assuming that paleohydrological changes reflect paleoclimate changes, we examine correlations between times of travertine deposition, relative to glacial cycles or to more specific orbital forcings, acting on the North African summer monsoon. Initial comparison of travertine occurrence to glacial cycles shows no obvious correlation, although there are major travertine deposition episodes at important paleoclimate transitions such as MIS 6 to 5, 7 to 6, and

  12. Ancient Leishmaniasis in a Highland Desert of Northern Chile

    PubMed Central

    Costa, Maria Antonietta; Matheson, Carney; Iachetta, Lucia; Llagostera, Agustín; Appenzeller, Otto

    2009-01-01

    Background Leishmaniasis is an infectious disease endemic today in many areas of South America. Methodology We discovered morphologic and molecular evidence of ancient infections in 4 female skulls in the archaeological cemetery of Coyo Oriente, in the desert of San Pedro de Atacama, Northern Chile. The boney facial lesions visible in the skulls could have been caused by a number of chronic infections including chronic Leishmaniasis. This diagnosis was confirmed using PCR-sequenced analyses of bone fragments from the skulls of the affected individuals.Leishmaniasis is not normally found in the high-altitude desert of Northern Chile; where the harsh climate does not allow the parasite to complete its life cycle. The presence of Leishmaniasis in ancient skulls from the region implies infection by the protozoan in an endemic area–likely, in our subjects, to have been the lowlands of North-Eastern Argentina or in Southern Bolivia. Conclusions We propose that the presence of the disease in ancient times in the high altitude desert of San Pedro de Atacama is the result of an exogamic system of patrilocal marriages, where women from different cultures followed their husbands to their ancestral homes, allowing immigrant women, infected early in life, to be incorporated in the Atacama desert society before they became disfigured by the disease. The present globalization of goods and services and the extraordinary facile movement of people across borders and continents have lead to a resurgence of infectious diseases and re-emergence of infections such as Leishmaniasis. We show here that such factors were already present millennia ago, shaping demographic trends and the epidemiology of infections just as they do today. PMID:19746163

  13. Patton's tracks in the Mojave Desert, USA: An ecological legacy

    USGS Publications Warehouse

    Belnap, J.; Warren, S.D.

    2002-01-01

    Recovery of soil properties from World War II-era military training exercises in the Mojave Desert was measured approximately 55 years following disturbance. Tracks from military vehicles were still visible, particularly in areas of desert pavement. Soil penetrability was much lower in visible tracks than outside the tracks. Soils in tracks had fewer rocks in the top 10 cm of the soil profile than adjacent untracked soils. Larger particles (> 4.8 mm) formed a moderately well-developed pavement outside of the tracks, while smaller, loose particles (???4.8 mm) dominated the surface of the tracks. The time required to restore the desert pavement is likely to be measured in centuries. Based on biomass estimates, the cyanobacterial component of biological soil crusts had recovered 46-65% in tracks, compared to outside the tracks. Overall recovery of lichen cover has been much slower. Under plant canopies, cover of Collema tenax was not significantly different between areas inside and outside the tracks; however, recovery of Catapyrenium squamulosum was only 36%. In plant interspaces with less favorable moisture and temperature conditions, C. tenax showed a 6% recovery and C. squamulosum a 3% recovery. Assuming recovery of the biological soil crust is linear, and complete only when the most sensitive species (C. squamulosum) has fully recovered in the most limiting microhabitats (plant interspaces), it may require almost two millennia for full recovery of these areas.

  14. Study of the microwave emissivity characteristics over Gobi Desert

    NASA Astrophysics Data System (ADS)

    Yubao, Qiu; Lijuan, Shi; Wenbo, Wu

    2014-03-01

    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.

  15. Assessment of aerosol transport into the Mojave Desert. Final report

    SciTech Connect

    Myrup, L.O.; Flocchini, R.G.

    1986-02-01

    The objective of the project was to assess the transport of atmospheric aerosols into the Mojave Desert from the San Joaquin Valley (via Techachapi Pass), Los Angeles (via Soledad Canyon), and San Bernadino (via Cajon Pass). The authors conducted a field study in summer, 1983 to measure the concentrations of aerosols and the meteorology at these three sites. They measured particles in five size ranges with a six-hour time resolution, hourly average wind speed and direction, temperature, and humidity at two meters and ten meters above ground, upper air winds (pibals) at four-hour intervals, and boundary layer structure with continuous acoustic sounder. The upper air data were not used in the analysis. The authors developed two new analytical methods for the data set, the 8-sector binary method and the shaped acceptance window method. Both methods proved useful in analyzing the data. As expected, there is a net transport of aerosol from the population centers to the Mojave Desert at each of the three passes studied. Lead and sulfur aerosol transport was highest at night, and was primarily from the direction of the passes. Crustal elements did not show a directional influence, so most likely were generated locally from wind-dust in the Mojave Desert.

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

    SciTech Connect

    Mahowald, Natalie; Kloster, Silvia; Engelstaedter, S.; Moore, Jefferson Keith; Mukhopadhyay, S.; McConnell, J. R.; Albani, S.; Doney, Scott C.; Bhattacharya, A.; Curran, M. A. J.; Flanner, Mark G.; Hoffman, Forrest M; Lawrence, David M.; Lindsay, Keith; Mayewski, P. A.; Neff, Jason; Rothenberg, D.; Thomas, E.; Thornton, Peter E; Zender, Charlie S.

    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

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

    EPA Science Inventory

    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...

  18. Internal and External Adaptation in Army Families: Lessons from Operations Desert Shield and Desert Storm

    ERIC Educational Resources Information Center

    Pittman, Joe F.; Kerpelman, Jennifer L.; McFadyen, Jennifer M.

    2004-01-01

    This study examined 1,064 Army families reunited after a member's deployment for Operation Desert Shield and Operation Desert Storm. Postdeployment outcomes were conceptualized in terms of the "fit" between the family and the demands of Army life, especially the stress of deployment. A structural model was used to test the hypothesized effects of…

  19. Dating climatic change in hot deserts using desert varnish on meteorite finds

    NASA Astrophysics Data System (ADS)

    Lee, M. R.; Bland, P. A.

    2003-01-01

    A thin coating of desert varnish occurs on Forrest 009 and Nurina 004, both equilibrated ordinary chondrite (L6) finds from the Nullarbor Plain, Australia. This finely laminated deposit is chemically and petrographically comparable to the varnish found on terrestrial rocks. Forrest 009, which has a terrestrial age of 5.9 kyr, has a 100-130 μm thick coating of desert varnish that has a laterally consistent chemical microstratigraphy comprising a narrow Ba- and Mn-poor lower region, a thick Ba- and Mn-rich central area and a narrow outer zone almost devoid of both cations. The interior of the meteorite contains Fe-oxide and oxyhydroxide veins that have formed by chemical weathering of metals and sulphides. As these veins do not cross-cut the varnish, it must have accreted rapidly relative to the weathering rate of the meteorite. The ≤70 μm thick varnish on Nurina 004, which has a terrestrial age of 33.4 kyr, lacks a consistent chemical microstratigraphy, but it is cross-cut by Fe-oxide and oxyhydroxide veins, some of which have supplied Fe to the varnish. This implies that the chemical weathering rate of Nurina 004's interior was slow in comparison to the accretion rate of the varnish. The petrography and chemical composition of varnish on Forrest 009 indicates that this meteorite may have resided in a relatively humid environment for most of its 5.9 kyr terrestrial history and that the Nullarbor recently became more arid. This conclusion supports results from an analysis of Fe-bearing weathering products in the interior of the meteorite by Mössbauer spectroscopy, which also indicate that Forrest 009 experienced an early period of rapid weathering under relatively humid conditions. The petrography of varnish on Nurina 004 shows that the interior of the meteorite weathered relatively slowly, probably because it fell during an arid time, which is again in agreement with previous Mössbauer spectroscopy results. Results from both meteorites are in agreement with

  20. Africa: Prosperous times

    SciTech Connect

    1996-08-01

    Political instability and corruption is the rule, rather than the exception, in Africa`s main producing regions, but exploration and production prospects there are bright and attractive to foreign operators. The paper discusses exploration, drilling, resource development, and production in Nigeria, Libya, Algeria, Egypt, Angola, Congo, Gabon, and Tunisia. The other countries of Africa are briefly mentioned, i.e., Cameroon, Cote D`Ivoire, South Africa, Sudan, Namibia, Equatorial Guinea, Eritrea, Zaire, Mozambique, Ghana, Niger, and Seychelles.

  1. The influence of biological soil crusts on successional vegetation patterns in a revegetated desert area in the Tengger Desert, China

    NASA Astrophysics Data System (ADS)

    Lei, Huang; Zhi-shan, Zhang; Xin-rong, Li

    2014-05-01

    Biological soil crusts (BSCs) are an important cover in arid desert landscapes, and have a profound effect on the soil water redistribution, plant growth and vegetation succession. Although a large number of studies have focused on the single-process of BSCs experimentally, relatively few studies have examined the eco-hydrological mechanisms of BSCs influence on successional vegetation patterns in revegetated desert areas. In this study, based on the long term monitoring and focused research on sand-binding vegetation in the Shapotou region (southeastern edge of the Tengger Desert, China) since the 1950s, the characteristics of plant community and BSCs at different successional stages, and the soil water dynamics were investigated. Then a simplified mathematical model describing the coupled dynamics of soil moisture and vegetation in drylands was developed. And finally the role of BSCs on soil water dynamics and vegetation patterns were discussed. Results have showed that BSCs was closely associated with the vegetation succession, such as in the Caragana korshinskii community, moss crusts were the dominate species and in the Artemisia ordosica community, algae crusts were the dominate species. BSCs had a significant effect on soil water infiltration and it was one of the main driving forces to vegetation pattern formations, as algae crusts would induced the tiger bush stripes and moss crusts would lead to the leopard bush spots in arid ecosystems.

  2. Space Radar Image of Namib Desert in Southern Namib

    NASA Technical Reports Server (NTRS)

    1999-01-01

    This is a C-band, VV polarization radar image of the Namib desert in southern Namibia, near the coast of South West Africa. The image is centered at about 25 degrees South latitude, 15.5 degrees East longitude. This image was one of the first acquired by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) when it was taken on orbit 4 from the shuttle Endeavour on April 9, 1994. The area shown is approximately 78 kilometers by 20 kilometers. The dominant features in the image are complex sand dune patterns formed by the prevailing winds in this part of the Namib desert. The Namib desert is an extremely dry area formed largely because of the influence of the cold Benguela ocean current that flows northward along the coast of Namibia. The bright areas at the bottom of the image are exposed outcrops of Precambrian rocks. This extremely barren area is a region rich in diamonds that through the centuries have washed down from the mountains. The town of Luderitz is located just to the south of the area shown. Spaceborne Imaging Radar-C and X-Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by human activity. SIR-C was developed by NASA's Jet Propulsion Laboratory. X-SAR was developed by the Dornier and Alenia Spazio companies for the German space agency, Deutsche Agentur fuer Aumfahrtangelegenheiten (DARA), and the Italian space agency, Agenzia

  3. Remote sensing of desert dust aerosols over the Sahel : potential use for health impact studies

    NASA Astrophysics Data System (ADS)

    Deroubaix, A. D.; Martiny, N. M.; Chiapello, I. C.; Marticorena, B. M.

    2012-04-01

    Since the end of the 70's, remote sensing monitors the desert dust aerosols due to their absorption and scattering properties and allows to make long time series which are necessary for air quality or health impact studies. In the Sahel, a huge health problem is the Meningitis Meningococcal (MM) epidemics that occur during the dry season : the dust has been suspected to be crucial to understand their onsets and dynamics. The Aerosol absorption Index (AI) is a semi-quantitative index derived from TOMS and OMI observations in the UV available at a spatial resolution of 1° (1979-2005) and 0.25° (2005-today) respectively. The comparison of the OMI-AI and AERONET Aerosol Optical thickness (AOT) shows a good agreement at a daily time-step (correlation ~0.7). The comparison of the OMI-AI with the Particle Matter (PM) measurement of the Sahelian Dust Transect is lower (~0.4) at a daily time-step but it increases at a weekly time-step (~0.6). The OMI-AI reproduces the dust seasonal cycle over the Sahel and we conclude that the OMI-AI product at a 0.25° spatial resolution is suitable for health impact studies, especially at a weekly epidemiological time-step. Despite the AI is sensitive to the aerosol altitude, it provides a daily spatial information on dust. A preliminary investigation analysis of the link between weekly OMI AI and weekly WHO epidemiological data sets is presented in Mali and Niger, showing a good agreement between the AI and the onset of the MM epidemics with a constant lag (between 1 and 2 week). The next of this study is to analyse a deeper AI time series constituted by TOMS and OMI data sets. Based on the weekly ratios PM/AI at 2 stations of the Sahelian Dust Transect, a spatialized proxy for PM from the AI has been developed. The AI as a proxy for PM and other climate variables such as Temperature (T°), Relative Humidity (RH%) and the wind (intensity and direction) could then be used to analyze the link between those variables and the MM epidemics

  4. Geochemical and geomorphological evidence for the provenance of aeolian deposits in the Badain Jaran Desert, northwestern China

    NASA Astrophysics Data System (ADS)

    Hu, Fangen; Yang, Xiaoping

    2016-01-01

    Identifying provenance of aeolian deposits in the mid-latitude deserts of Asia is essential for understanding formation and changes of Earth surface processes due to palaeoclimatic fluctuations. While some earlier studies focused on the interpretation of palaeoenvironments on the basis of aeolian deposits mainly in the desert margins and inter-dune lacustrine sediments, research on provenance of desert sands in the vast Asian mid-latitude deserts is still rare. In this paper, we present new geochemical data which provide insight to the provenance of dune sands in the Badain Jaran Desert, northwestern China, an important part of this desert belt. We sampled aeolian and lacustrine sediments in various parts of the Badain Jaran Desert, and examined their major, trace and rare earth elements (REE) in bulk samples, coarse and fine fractions, respectively. In addition, we took and analyzed samples from a rarely known dune field with red sands, northeast of the Badain Jaran. Our results show that the sands from the Badain Jaran Desert are generally different from those in the red sand dune field in terms of REE pattern and geochemical characteristics, suggesting different sediment origins. Geochemical composition of the aeolian sand samples indicates these sediments should be mainly derived from mixed source rocks of granite, granitoids and granodiorite. Comparing the immobile trace elements and REE ratios of the samples from the Badain Jaran Desert, red sand dune field with rocks of granite, granitoids in their potential source areas, we conclude that: (1) The aeolian deposits in the Badain Jaran Desert are predominantly derived from the Qilian Mountains, northeastern Tibetan Plateau initially via fluvial processes; (2) The Altay Mountains and Mongolian Gobi are the ultimate source areas for the red sand dune field; (3) The Altai Mountains and Mongolian Gobi in the northwest, that could produce massive amounts of materials via intensive deflation and alluvial process

  5. Clockwise rotation of the western Mojave Desert

    NASA Technical Reports Server (NTRS)

    Golombek, Matthew P.; Brown, Laurie L.

    1988-01-01

    A study of paleomagnetic data from Miocene volcanic rocks in the western Mojave Desert, which suggests about 25 deg of clockwise rotation, is presented. A total of 166 oriented core samples of two types of basalt were taken from 19 sites in the region. After demagnetization to 40 or 60 mT, application of structural corrections, and inversion of reversed sites, the data yielded an average direction of 51.6 deg inclination and 15.6 deg declination. When compared with the expected direction for Miocene rocks for stable North America, the direction for these Mojave rocks shows a clockwise rotation of 23.8 deg + or - 11.3 deg and a flattening of about 2.1 deg, a rotation which agrees in direction with oroclinal bending of the southern Sierra Nevada due to right-lateral shear along the western margin of North America. Most of this rotation is constrained by other paleomagnetic and strucural information to have occurred soon after the sampled basalts were deposited (about 20 Ma) and before about 16 Ma. These clockwise declination anomalies indicate that any subsequent counterclockwise rotation is small and/or compensated by previous clockwise rotation.

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

    USGS Publications Warehouse

    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.

  7. AIDS in South Africa.

    PubMed

    Ijsselmuiden, C; Evian, C; Matjilla, J; Steinberg, M; Schneider, H

    1993-01-01

    The National AIDS Convention in South Africa (NACOSA) in October 1992 was the first real attempt to address HIV/AIDS. In Soweto, government, the African National Congress, nongovernmental organizations, and organized industry and labor representatives worked for 2 days to develop a national plan of action, but it did not result in a united effort to fight AIDS. The highest HIV infection rates in South Africa are among the KwaZulu in Natal, yet the Inkatha Freedom Party did not attend NACOSA. This episode exemplifies the key obstacles for South Africa to prevent and control AIDS. Inequality of access to health care may explain why health workers did not diagnose the first AIDS case in blacks until 1985. Migrant labor, Bantu education, and uprooted communities affect the epidemiology of HIV infection. Further, political and social polarization between blacks and whites contributes to a mindset that AIDS is limited to the other race which only diminishes the personal and collective sense of susceptibility and the volition and aptitude to act. The Department of National Health and Population Development's voluntary register of anonymously reported cases of AIDS specifies 1517 cumulative AIDS cases (October 1992), but this number is low. Seroprevalence studies show between 400,000-450,000 HIV positive cases. Public hospitals cannot give AIDS patients AZT and DDI. Few communities provided community-based care. Not all hospitals honor confidentiality and patients' need for autonomy. Even though HIV testing is not mandatory, it is required sometimes, e.g., HIV testing of immigrants. AIDS Training, Information and Counselling Centers are in urban areas, but not in poor areas where the need is most acute. The government just recently developed in AIDS education package for schools, but too many people consider it improper, so it is not being used. The poor quality education provided blacks would make it useless anyhow. Lifting of the academic boycott will allow South African

  8. Mapping the mineralogical composition of mineral dust in Western Africa

    NASA Astrophysics Data System (ADS)

    Formenti, Paola; Caquineau, Sandrine; Desboeufs, Karine; Klaver, Anne; Chevaillier, Servanne; Journet, Emilie; Rajot, Jean Louis

    2014-05-01

    In the last few years, several ground-based and airborne field campaigns have allowed exploring the properties and impacts of mineral dust in Western Africa, one of the major emission and transport areas worldwide. In this paper, we explore the synthesis of these observations to provide with a large-scale quantitative view of the mineralogical composition and its variability with time after transport and source region. This work reveals that mineral dust in Western Africa can be represented as a mixture of illite, kaolinite, quartz, iron and titanium oxides, representing at least 92% of the dust mass. Calcite ranged between 0.3 and 8.4% of the dust mass depending on the origin. Our data do not show a systematic dependence of the dust composition with origin, likely as in most of the cases they represent the composition of the atmospheric burden after 1-2 days after emission, when air masses mix and give raise to a more uniform dust load. This has implications for the representation of the mineral dust composition in regional and global circulation models, and satellite retrievals. We estimate that iron oxides account for 58 ± 7% of the mass of elemental Fe, and between 2 and 5% of the dust mass. We provide with first time estimates of the partitioning of hematite and goethite in major dust sources such as the Bodélé and the South Algeria deserts. Goethite represents between 47 and 71% of the iron oxide mass. Likewise, we found that titanium oxides account for between 1 and 2% of the dust mass. On the basis of these compositional data, we provide with estimates of the complex refractive index relevant to the direct effect of mineral dust on the radiative budget. Data presented in this paper are provided in numerical form upon email request while they are being implemented as a public database, the Dust-Mapped Archived Properties (DUST-MAP), an open repository for compositional data from other source regions in Africa and worldwide.

  9. Three climate cycles of millennial-scale vegetation change in Africa (Invited)

    NASA Astrophysics Data System (ADS)

    Dupont, L. M.

    2010-12-01

    Marine sediments can deliver long well-dated continuous sequences of environmental change, not only of the ocean but also of the continents. Vegetation records from these archives are often the only land-cover records to encompass several climate cycles. Comparing vegetation development during several cycles uncovers the structural and systematic differences between glacial and interglacial vegetation. Such data may help with the validation of the current earth system models including dynamic vegetation modules. A number of marine pollen records from the East Atlantic (ODP658, GIK16415, GIK16776, GIK16867, GeoB1016) and a new one from the Indian Ocean (MD96-2048) register the vegetation development in West and South Africa over a period of more than 300 thousand years covering at least three full glacial-interglacial cycles. From these dataset typical patterns of vegetation change in Africa are inferred and differences between cycles are discussed. Both latitudinal and altitudinal shifts in the vegetation have been recorded by pollen of e.g. Chenopods, Asteraceae (daisies), Ericaceae (heath), Podocarpus (yellow wood), Poaceae (grass), and lowland forest. While latitudinal shifts in the area of desert and savannah are typical in West Africa, altitudinal changes of the belt with mountainous forest and mountainous shrubs are more common in Southern Africa. During glacial times, vegetation includes ericaceous shrubs in Southern Africa, while desert shrubs expand in West Africa, and the area of the lowland forests is strongly reduced on the whole continent.

  10. Desert Amplification in a Warming Climate

    PubMed Central

    Zhou, Liming

    2016-01-01

    Here I analyze the observed and projected surface temperature anomalies over land between 50°S-50°N for the period 1950–2099 by large-scale ecoregion and find strongest warming consistently and persistently seen over driest ecoregions such as the Sahara desert and the Arabian Peninsula during various 30-year periods, pointing to desert amplification in a warming climate. This amplification enhances linearly with the global mean greenhouse gases(GHGs) radiative forcing and is attributable primarily to a stronger GHGs-enhanced downward longwave radiation forcing reaching the surface over drier ecoregions as a consequence of a warmer and thus moister atmosphere in response to increasing GHGs. These results indicate that desert amplification may represent a fundamental pattern of global warming associated with water vapor feedbacks over land in low- and mid- latitudes where surface warming rates depend inversely on ecosystem dryness. It is likely that desert amplification might involve two types of water vapor feedbacks that maximize respectively in the tropical upper troposphere and near the surface over deserts, with both being very dry and thus extremely sensitive to changes of water vapor. PMID:27538725

  11. Desert Amplification in a Warming Climate.

    PubMed

    Zhou, Liming

    2016-01-01

    Here I analyze the observed and projected surface temperature anomalies over land between 50°S-50°N for the period 1950-2099 by large-scale ecoregion and find strongest warming consistently and persistently seen over driest ecoregions such as the Sahara desert and the Arabian Peninsula during various 30-year periods, pointing to desert amplification in a warming climate. This amplification enhances linearly with the global mean greenhouse gases(GHGs) radiative forcing and is attributable primarily to a stronger GHGs-enhanced downward longwave radiation forcing reaching the surface over drier ecoregions as a consequence of a warmer and thus moister atmosphere in response to increasing GHGs. These results indicate that desert amplification may represent a fundamental pattern of global warming associated with water vapor feedbacks over land in low- and mid- latitudes where surface warming rates depend inversely on ecosystem dryness. It is likely that desert amplification might involve two types of water vapor feedbacks that maximize respectively in the tropical upper troposphere and near the surface over deserts, with both being very dry and thus extremely sensitive to changes of water vapor. PMID:27538725

  12. Leaf epidermal appendages of desert plant: an ecological perspective

    NASA Astrophysics Data System (ADS)

    Liu, Yubing; Li, Xinrong; Li, Mengmeng

    2014-05-01

    Desert plant often have few, tiny or no leaves, which reduces transpiration. The epidermis of their leaves is often ornamented outgrowths called trichomes or hairs and a thick waxy cuticle. Hairs on the leaf surface trap humidity in dry climates and waxy leaf surfaces reduce water loss. Our present study is to investigate the characteristics of trichomes and waxy cuticle in leaf surface of desert plant, which in the long term acclimation in semi-humid, semi-arid and arid ecosystems of Northern China, from east (Zhangwu county, Liaoning province) to west (Korla city, Xinjiang Uygur Autonomous Region), passing through several provinces including the Inner Mongolia Autonomous Region, Shanxi province, the Ningxia Hui Autonomous Region and Gansu province. 68 shrubs and 7 trees were selected in the natural habitats which were artificial sand fixing vegetation and the adjacent natural vegetation in sandy areas. The leaf epidermis was observed by scanning electron microscopy (SEM) and the cuticle thickness was calculated in the leaf cross-section by transmission electron microscopy (TEM). The results indicated that the epidermis of selected materials was divided into five categories: (1) Trichomes with different forms covered completely on the adaxial and abaxial surfaces of leaf, and any other epidermal appendages could not been observed. (2) Epicuticular wax crystals with different forms almost completely covered in the epistomatal chambers as well as on the surrounding epidermis, and there were no other appendages on the leaf surface. (3) A lot of warty hairs arranged neatly on the surface and the stomatal index was too low. (4) Several or even dozens of papillary epidermal cells covered with waxy crystals enclosed a sunken stomata chamber, therefore the stomatal density is very low. (5) Like ordinary terrestrial plants, epidermal cells and cell outline are clear, with epidermal hairs or not, and the stomata and waxy crystals are visible. TEM showed that desert plants

  13. Namibia [South-West Africa].

    PubMed

    1983-01-01

    Namibia, a country of 1,051,700 inhabitants of whom 85.6% are blacks of diverse ethnic and linguistic origins, 7.5% are white, and the rest are of mixed ancestry, has been illegally administered by South Africa since 1966, when a League of Nations mandate was revoked by the UN. The Namibian Desert was a barrier to European expansion until the late 18th century, when the area came under German and British influence. Efforts to bring about an orderly and peaceful transition to independent status are hampered at present by the lack of parallel progress toward withdrawal of Cuban combat forces from Angola. Beginning in 1980, considerable executive power was transferred from the administrator general appointed by the South African Government to an interim 3-tier system of elected representatives dividing responsibility between central, ethnic, and local authorities. The judicial structure has separate overlapping systems for whites, westernized blacks and coloreds and for indigenous blacks. Namibian society is highly politicized, with 4 white and about 40 nonwhite political groups. The South West Africa People's Organization (SWAPO) remains an active party inside Namibia despite simultaneous detention of its entire leadership in 1979 by the South African Government. Namibia's economy is dual, with a modern market sector of mining, ranching and fishing producing most of the wealth and a traditional subsistence sector supporting most of the labor force. About 60% of the work force of 500,000 in 1981 worked in agriculture, 19% in industry and commerce, 6% in mining, 8% in services, and 7% in government. Namibia's gross domestic product in 1980 was $1.712 billion, representing an average growth rate of 2.5% from 1970-80. However, real growth since 1978 has been negative because of persistent drought, political uncertainty, low demand for mineral products, and previous overfishing. Namibia has no separate representation in any international body. The country may have the

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

    PubMed Central

    Gomaa, Nasr H.

    2012-01-01

    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%). PMID:23961181

  15. Molecular markers of biomass burning, fungal spores and biogenic SOA in the Taklimakan desert aerosols

    NASA Astrophysics Data System (ADS)

    Fu, Pingqing; Zhuang, Guoshun; Sun, Yele; Wang, Qiongzhen; Chen, Jing; Ren, Lujie; Yang, Fan; Wang, Zifa; Pan, Xiaole; Li, Xiangdong; Kawamura, Kimitaka

    2016-04-01

    Biogenic primary organic aerosols (POA) and secondary organic aerosols (SOA) are important organic constituents of atmospheric particulate matter (PM). In order to better understand the atmospheric abundances, molecular compositions and sources of the desert aerosols, biomass-burning tracers (e.g. levoglucosan), primary saccharides including fungal spore tracers, and SOA tracers from the oxidation of biogenic volatile organic compounds (e.g. isoprene, monoterpenes and sesquiterpene) have been studied in ambient aerosols from the Taklimakan desert, using gas chromatography-mass spectrometry. Results showed that the total concentrations of biomass-burning tracers at Hetian (177-359 ng m-3, mean 233 ng m-3 in PM2.5) in the south rim of the desert were much higher than those at Tazhong (1.9-8.8 ng m-3 in PM2.5 and 5.9-32 ng m-3 in TSP) in the central Taklimakan desert. Molecular markers of fungal spores were also detected in all the desert aerosols, highlighting the importance of primary bioaerosols in the Asian dust particles. A specific pattern of the dominance of 2-methylglyceric acid over 2-methyltetrols and C5-alkene triols was found in the Taklimakan desert aerosols, especially during the dust storm events, which is different from the 2-methyltetrols-dominated pattern in other ambient aerosols. Our results provide direct evidence on the biogenic POA and SOA tracers in the Taklimakan desert region, which help to better understand their impact on the aerosol chemistry in the down-wind regions.

  16. Variation in heat shock proteins within tropical and desert species of poeciliid fishes.

    PubMed

    Norris, C E; diIorio, P J; Schultz, R J; Hightower, L E

    1995-11-01

    The 70-kilodalton heat shock protein (hsp70) family of molecular chaperones, which contains both stress-inducible and normally abundant constitutive members, is highly conserved across distantly related taxa. Analysis of this protein family in individuals from an outbred population of tropical topminnows, Poeciliopsis gracilis, showed that while constitutive hsp70 family members showed no variation in protein isoforms, inducibly synthesized hsp70 was polymorphic. Several species of Poeciliopsis adapted to desert environments exhibited lower levels of inducible hsp70 polymorphism than the tropical species, but constitutive forms were identical to those in P. gracilis, as they were in the confamilial species Gambusia affinis. These differences suggest that inducible and constitutive members of this family are under different evolutionary constraints and may indicate differences in their function within the cell. Also, northern desert species of Poeciliopsis synthesize a subset of the inducible hsp70 isoforms seen in tropical species. This distribution supports the theory that ancestral tropical fish migrated northward and colonized desert streams; the subsequent decrease in variation of inducible hsp70 may have been due to genetic drift or a consequence of adaptation to the desert environment. Higher levels of variability were found when the 30-kilodalton heat shock protein (hsp30) family was analyzed within different strains of two desert species of Poeciliopsis and also in wild-caught individuals of Gambusia affinis. In both cases the distribution of hsp30 isoform diversity was similar to that seen previously with allozyme polymorphisms. PMID:8524039

  17. Mars-Like Soils in the Atacama Desert, Chile (Alexander von Humboldt Medal lecture)

    NASA Astrophysics Data System (ADS)

    Navarro-Gonzalez, R.

    2009-04-01

    The Viking missions showed the martian soil to be lifeless and depleted in organic material and indicated the presence of one or more reactive oxidants. The presence of Mars-like soils have been documented in the extreme arid region of the Atacama Desert. The Atacama desert is one of the driest and oldest deserts of the world that extends across 1000 km from 30°S to 20°S along the Pacific coast of South America. Geological and soil mineralogical evidence suggest that extreme arid conditions have persisted in this desert for about 10-15 Myrs. The surface soil from this region has organic species only at trace levels and extremely low levels of culturable bacteria. Some samples from the extreme arid region were tested for DNA and none was recovered. Incubation experiments, patterned after the Viking labeled-release experiment but with separate biological and nonbiological isomers, show active decomposition of organic species in these soils by nonbiological processes. The Atacama Desert is now a valuable testing ground by NASA and ESA for instruments and experiments designed for future Mars missions for the search of life.

  18. Erosion Resistance Index (ERI) to Assess Surface Stability in Desert Environments

    SciTech Connect

    Hamada, Yuki; Grippo, Mark A.

    2015-11-01

    A new spectral index—erosion resistance index (ERI)—was developed to assess erosion risks in desert landscapes. The index was developed by applying trigonometry to the combination of the green/red band-ratio and the red/near infrared band-ratio from very high spatial resolution imagery. The resultant ERI maps showed spatially cohesive distributions of high and low index values across the study areas. High index values were observed over areas that were resistant to erosion (such as desert pavement and dense vegetation), while low index values overlapped with areas likely dominated by loose sandy soils, such as stream beds and access roads. Although further investigation is warranted, this new index, ERI, shows promise for the assessment of erosion risks in desert regions.

  19. Oxalosis in wild desert tortoises, Gopherus agassizii.

    PubMed

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

    2009-10-01

    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. PMID:19901374

  20. An Economic View of Food Deserts in the United States

    ERIC Educational Resources Information Center

    Bitler, Marianne; Haider, Steven J.

    2011-01-01

    Considerable policy and academic attention has been focused on the topic of food deserts. We consider this topic from an economic perspective. First, we consider how the components of a standard economic analysis apply to the study of food deserts. Second, using this economic lens, we revisit the empirical literature on food deserts to assess the…

  1. 75 FR 61467 - Desert Southwest Power, LLC; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-05

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Desert Southwest Power, LLC; Notice of Filing September 27, 2010. Take notice that on September 24, 2010, Desert Southwest Power, LLC (Desert Southwest) supplemented...

  2. A Reservoir of Nitrate Beneath Desert Soils

    USGS Publications Warehouse

    Walvoord, M.A.; Phillips, F.M.; Stonestrom, D.A.; Evans, R.D.; Hartsough, P.C.; Newman, B.D.; Striegl, R.G.

    2003-01-01

    A large reservoir of bioavailable nitrogen (upto ???104 kilograms of nitrogen per hectare, as nitrate) has been previously overlooked in studies of global nitrogen distribution. The reservoir has been accumulating in subsoil zones of and regions throughout the Holocene. Consideration of the subsoil reservoir raises estimates of vadose-zone nitrogen inventories by 14 to 71% for warm deserts and arid shrublands worldwide and by 3 to 16% globally. Subsoil nitrate accumulation indicates long-term leaching from desert soils, impelling further evaluation of nutrient dynamics in xeric ecosystems. Evidence that subsoil accumulations are readily mobilized raises concern about groundwater contamination after land-use or climate change.

  3. Slope Deposits and (Paleo)Soils as Geoarchives to Reconstruct Late Quaternary Environments of Southern Africa

    NASA Astrophysics Data System (ADS)

    Huerkamp, K.; Voelkel, J.; Heine, K.; Bens, O.

    2009-04-01

    Although it is clear that large, rapid temperature changes have occurred during the last glacial-interglacial cycle and the Holocene in southern Africa, we have only limited, and often imprecise, knowledge of how the major moisture-bearing atmospheric circulation systems have reacted to these changes. Using slope deposits and soils as palaeoclimatic geoarchives we will overcome these constraints. The role of many geoarchives in the reconstruction of the Quaternary climate in southern Africa remains controversial, since the paleoclimate data are based on evidence from marine cores, lake sediments, speleothems and spring sinter, fluvial sediments, aeolian sands and dust, colluvium, and coastal sediments. To elucidate climate controls on Quaternary landscape evolution and to use these data for palaeoclimatic reconstructions, thus far slope deposits and soils have been investigated. Climatic controls on these cycles are incompletely known. The availability of results from earlier fieldwork, micromorphology, Optical Stimulated Luminescence (OSL), 14C dating and stable carbon isotope analysis will permit a thorough assessment of slope deposits and soils in terms of their palaeoenvironmental potential. The knowledge of suitable areas and sites in different climatic zones of southern Africa where slope deposits and soils have already been found document the late Quaternary climatic history and even climatic anomalies (e.g. Younger Dryas period at Eksteenfontein, 8.2 ka event at Tsumkwe, 4 ka event in the Auob valley, Little Ice Age in the Namib Desert). The findings will show the late Quaternary history of precipitation fluctuations, of the shifting of the ITCZ (and the ABF - Agulhas-Benguela Front), of wind intensities and directions, and of extreme precipitation events. The project will employ state-of-the-art geoscience methodology to interpret the record of precipitation changes of the late Quaternary, including the shifting of the summer and winter rain belts, the

  4. Airborne desert dust and aeromicrobiology over the Turkish Mediterranean coastline

    USGS Publications Warehouse

    Griffin, Dale W.; Kubilay, Nilgün; Kocak, Mustafa; Gray, Mike A.; Borden, Timothy C.; Shinn, Eugene A.

    2007-01-01

    Between 18 March and 27 October 2002, 220 air samples were collected on 209 of 224 calendar days, on top of a coastal atmospheric research tower in Erdemli, Turkey. The volume of air filtered for each sample was 340 liters. Two hundred fifty-seven bacterial and 2598 fungal colony forming units (CFU) were enumerated from the samples using a low-nutrient agar. Ground-based dust measurements demonstrated that the region is routinely impacted by dust generated regionally and from North Africa and that the highest combined percent recovery of total CFU and African dust deposition occurred in the month of April (93.4% of CFU recovery and 91.1% of dust deposition occurred during African dust days versus no African dust present, for that month). A statistically significant correlation was observed (peak regional African dust months of March, April and May; rs=0.576, P=0.000) between an increase in the prevalence of microorganisms recovered from atmospheric samples on dust days (regional and African as determined by ground-based dust measurements), versus that observed on non-dust days. Given the prevalence of atmospherically suspended desert dust and microorganisms observed in this study, and that culture-based studies typically only recover a small fraction (

  5. Salt deliquescence drives photosynthesis in the hyperarid Atacama Desert.

    PubMed

    Davila, Alfonso F; Hawes, Ian; Ascaso, Carmen; Wierzchos, Jacek

    2013-08-01

    Endolithic cyanobacteria are found in halite nodules in the hyperarid core of the Atacama Desert. Using Pulse Amplitude Modulated Fluorometry, we show here that photosynthetic systems of these cyanobacteria become active when the relative humidity rises above 70% and the salt becomes wet by way of deliquescence. This is the first evidence of active metabolism in the hyperarid core of the Atacama, and supports the view of a microbial community sustained by deliquescence. Our results expand the water activity envelope of life on Earth. PMID:23864573

  6. Habitat drives dispersal and survival of translocated juvenile desert tortoises

    USGS Publications Warehouse

    Nafus, Melia G.; Esque, Todd; Averill-Murray, Roy C.; Nussear, Kenneth E.; Swaisgood, Ronald R.

    2016-01-01

    5.Synthesis and applications. Resource managers using translocations as a conservation tool should prioritize acquiring data linking habitat to fitness. In particular, for species that depend on avoiding detection, refuges such as burrows and habitat that improved concealment had notable ability to improve survival and dispersal. Our study on juvenile Mojave desert tortoises showed that refuge availability or the distributions of habitat appropriate for concealment are important considerations for identifying translocation sites for species highly dependent on crypsis, camouflage, or other forms of habitat matching.

  7. Ubiquity, diversity and physiological characteristics of Geodermatophilaceae in Shapotou National Desert Ecological Reserve

    PubMed Central

    Sun, Hong-Min; Zhang, Tao; Yu, Li-Yan; Sen, Keya; Zhang, Yu-Qin

    2015-01-01

    The goal of this study was to gain insight into the diversity of culturable actinobacteria in desert soil crusts and to determine the physiological characteristics of the predominant actinobacterial group in these crusts. Culture-dependent method was employed to obtain actinobacterial strains from desert soil samples collected from Shapotou National Desert Ecological Reserve (NDER) located in Tengger Desert, China. A total of 376 actinobacterial strains were isolated and 16S rRNA gene sequences analysis indicated that these isolates belonged to 29 genera within 18 families, among which the members of the family Geodermatophilaceae were predominant. The combination of 16S rRNA gene information and the phenotypic data allowed these newly-isolated Geodermatophilaceae members to be classified into 33 “species clusters,” 11 of which represented hitherto unrecognized species. Fermentation broths from 19.7% of the isolated strains showed activity in at least one of the six screens for antibiotic activity. These isolates exhibited bio-diversity in enzymatic characteristics and carbon utilization profiles. The physiological characteristics of the isolates from different types of crusts or bare sand samples were specific to their respective micro-ecological environments. Our study revealed that members of the family Geodermatophilaceae were ubiquitous, abundant, and diverse in Shapotou NDER, and these strains may represent a new major group of potential functional actinobacteria in desert soil. PMID:26483778

  8. 76 FR 50493 - Notice of Availability of the Record of Decision for the Desert Sunlight Holdings, LLC, Desert...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-15

    ... on April 15, 2011 (76 FR 21402). Publication of the Notice of Availability for the Final EIS... Holdings, LLC, Desert Sunlight Solar Farm (DSSF) and California Desert Conservation Area Plan Amendment... . SUPPLEMENTARY INFORMATION: Desert Sunlight Holdings, LLC, a wholly owned subsidiary of First Solar, Inc.,...

  9. Orbital radar studies of paleodrainages in the central Namib Desert

    USGS Publications Warehouse

    Lancaster, N.; Schaber, G.G.; Teller, J.T.

    2000-01-01

    Orbital radar images of the central Namib Desert show clearly the extent of relict fluvial deposits associated with former courses of the Tsondab and Kuiseb rivers. South of the Kuiseb River, radar data show the existence of a drainage network developed in calcrete-cemented late Tertiary fluvial deposits. The sand-filled paleovalleys are imaged as radar-dark tones in contrast to the radar-bright interfluves where the calcreted gravels occur. The drainage network developed as a result of local runoff from indurated gravels and channeled surface and subsurface flow to the sites of the many interdune lacustrine deposits found in the area. (C) Elsevier Science Inc., 2000.Orbital radar images of the central Namib Desert show clearly the extent of relict fluvial deposits associated with former courses of the Tsondab and Kuiseb rivers. South of the Kuiseb River, radar data show the existence of a drainage network developed in calcrete-cemented late Tertiary fluvial deposits. The sand-filled paleovalleys are imaged as radar-dark tones in contrast to the radar-bright interfluves where the calcreted gravels occur. The drainage network developed as a result of local runoff from indurated gravels and channeled surface and subsurface flow to the sites of the many interdune lacustrine deposits found in the area.

  10. Distribution, habitat and habits of the desert tortoise (Gopherus agassizii) in the eastern Mojave Desert

    SciTech Connect

    Esque, T.C.; Bury, R.B. ); Medica, P.A. )

    1990-01-01

    The desert tortoise is widely distributed across most of southern Nevada below 1500 meters elevation and then ranges northeast into the Arizona Strip and southwestern Utah. There are several large populations, but also many isolated groups of desert tortoises due to the rugged topography and, possibly, unsuitable soils. We suggest that the greatest threats to tortoises in the eastern Mojave Desert are with peripheral populations. Tortoises in the eastern Mojave Desert occupy a wide variety of habitats from flats and bajadas in lower elevation to rocky slopes bordering on blackbrush and juniper woodland. In winter they use shallow burrows near Las Vegas but frequent deep caves in the northeast edge of their range. Tortoises in all areas may occur in steep, rocky habitats. Climatic extremes are frequent in this region and rainfall can be spotty due to several major mountain ranges that cause rain shadows. Forage is highly variable and this species can be an opportunistic herbivore. 11 refs., 13 figs.

  11. Organic constituents in eolian dust and surface sediments from northwest Africa

    NASA Technical Reports Server (NTRS)

    Lepple, F. K.; Brine, C. J.

    1976-01-01

    Samples of eolian dust and comparably sized desert surface sediment samples collected over widely scattered regions of northwest Africa were analyzed for carbon, nitrogen, and hydrogen content and total carbohydrate. Infrared analysis and gas chromatographic analysis were also performed on organic components extracted from several of these samples. Although the total carbon content of the eolian dust samples varies from 2.8 to 7.0% by weight, the organic carbon component is relatively uniform at 2.9 + or - 0.5%. By comparison, the average organic carbon content of the African surface sediments is 0.7 + or - 0.5%. Total carbohydrate content averages 0.128% for the dust and 0.022% for the desert sediments. It is shown that these desert regions are not presently the principal sources of eolian material transported over the North Atlantic Ocean.

  12. A mathematical model on the optimal timing of offspring desertion.

    PubMed

    Seno, Hiromi; Endo, Hiromi

    2007-06-01

    We consider the offspring desertion as the optimal strategy for the deserter parent, analyzing a mathematical model for its expected reproductive success. It is shown that the optimality of the offspring desertion significantly depends on the offsprings' birth timing in the mating season, and on the other ecological parameters characterizing the innate nature of considered animals. Especially, the desertion is less likely to occur for the offsprings born in the later period of mating season. It is also implied that the offspring desertion after a partially biparental care would be observable only with a specific condition. PMID:17328918

  13. On the application of DInSAR to deformation monitoring in desert areas

    NASA Astrophysics Data System (ADS)

    Chang, Xiao-Tao; Guo, Jin-Yun; Zhang, Yong-Hong; Wang, Xiao-Qing

    2011-03-01

    The DInSAR technique is used for monitoring the desert height changes to study sandstorms. Hunshandake Sandy Land, as the test area, is one of the main sources of sandstorms in Beijing. In order to study the sandstorm source and its impact, a pair of EnviSat ASAR images of Oct. 11, 2005, and Oct. 26, 2004, is processed on the basis of analysis of six ERS-2 and EnviSat radar images. After the image configuration, flat earth effect correction, data filtering, phase unwrapping, and geo-coding, a deformation model over Hunshandake desert is built. According to the results, the height decreased in most areas and increased in a few areas, which basically coincides with the strong sandstorm appearing in Beijing in the Spring of 2005. The results show DInSAR has an important role in monitoring of desert surface deformation.

  14. Field Verification of the Prediction Model on Desert Locust Adult Phase Status From Density and Vegetation

    PubMed Central

    Cissé, S.; Ghaout, S.; Babah Ebbe, M. A; Kamara, S; Piou, C.

    2016-01-01

    Previous studies investigated the effect of vegetation on density thresholds of adult Desert Locust gregarization from historical data in Mauritania. We examine here the prediction of locust phase based on adult density and vegetation conditions using the statistical model from Cisse et al. compared with actual behavior of Desert Locust adults observed in the field in Mauritania. From the 130 sites where adult locusts were found, the model predicted the phase of Desert Locust adults with a relatively small error of prediction of 6.1%. Preventive locust control should be rational, based on a risk assessment. The staff involved in implementation of the preventive control strategy needs specific indicators for when or where chemical treatment should be done. In this respect, we show here that the statistical model of Cisse et al. may be appropriate. PMID:27432351

  15. Characterization of desert sand as a sensible thermal energy storage medium

    NASA Astrophysics Data System (ADS)

    Diago, Miguel; Iniesta, Alberto Crespo; Delclos, Thomas; Soum-Glaude, Audrey; Shamim, Tariq; Calvet, Nicolas

    2016-05-01

    Desert sand from the United Arab Emirates (UAE) is considered as a possible sensible heat, thermal energy storage (TES) material. Its thermal stability, specific heat capacity and tendency to agglomerate are studied at high temperatures. The analyses show that it is possible to use desert sand as a TES material up to 800-1000 °C. Above 800 °C, weak agglomeration effects start to become significant. The samples become solid above 1000 °C. This may represent a major operating limit depending on the handling mechanism in place for the possible transport of the sand. The sand chemical composition is analyzed with the XRF and XRD techniques, which reveal the dominance of quartz and carbonates. Finally, the spectral absorptivity of the samples is measured before and after a thermal cycle, as it may be possible to use the desert sand not only as a TES material but also as a direct solar absorber.

  16. Hypolithic and soil microbial community assembly along an aridity gradient in the Namib Desert.

    PubMed

    Stomeo, Francesca; Valverde, Angel; Pointing, Stephen B; McKay, Christopher P; Warren-Rhodes, Kimberley A; Tuffin, Marla I; Seely, Mary; Cowan, Don A

    2013-03-01

    The Namib Desert is considered the oldest desert in the world and hyperarid for the last 5 million years. However, the environmental buffering provided by quartz and other translucent rocks supports extensive hypolithic microbial communities. In this study, open soil and hypolithic microbial communities have been investigated along an East-West transect characterized by an inverse fog-rainfall gradient. Multivariate analysis showed that structurally different microbial communities occur in soil and in hypolithic zones. Using variation partitioning, we found that hypolithic communities exhibited a fog-related distribution as indicated by the significant East-West clustering. Sodium content was also an important environmental factor affecting the composition of both soil and hypolithic microbial communities. Finally, although null models for patterns in microbial communities were not supported by experimental data, the amount of unexplained variation (68-97 %) suggests that stochastic processes also play a role in the assembly of such communities in the Namib Desert. PMID:23397517

  17. Field Verification of the Prediction Model on Desert Locust Adult Phase Status From Density and Vegetation.

    PubMed

    Cissé, S; Ghaout, S; Babah Ebbe, M A; Kamara, S; Piou, C

    2016-01-01

    Previous studies investigated the effect of vegetation on density thresholds of adult Desert Locust gregarization from historical data in Mauritania. We examine here the prediction of locust phase based on adult density and vegetation conditions using the statistical model from Cisse et al. compared with actual behavior of Desert Locust adults observed in the field in Mauritania. From the 130 sites where adult locusts were found, the model predicted the phase of Desert Locust adults with a relatively small error of prediction of 6.1%. Preventive locust control should be rational, based on a risk assessment. The staff involved in implementation of the preventive control strategy needs specific indicators for when or where chemical treatment should be done. In this respect, we show here that the statistical model of Cisse et al. may be appropriate. PMID:27432351

  18. On the longevity of desert plants and the production of new fine roots

    NASA Astrophysics Data System (ADS)

    Vargas, R.; Czimczik, C. I.; Bullock, S.; Xu, X.; Djuricin, S.

    2012-12-01

    There is evidence that some plants in arid regions can live for several hundreds of years suggesting a strong resilience to climate variability including drought events. Therefore, an important question is: Which are the physiological mechanisms of survival that are present in long-lived plants? Recent studies have shown that plants are able to store nonstructural carbon (NSC) for several years and then allocate them for production of new structures such as fine roots. We established an experiment to measure the radiocarbon age of new fine roots of desert plants between 150 and 400 years old. The study site was located at the Central Desert of Baja California, Mexico and included individuals of Brahea armata, Washingtonia robusta, and Pachycereus pringlei. Our results showed that on average all the plant species were able to use stored old carbon for production of new fine roots. These results suggest that NSC pools are important in determining belowground responses of long-lived desert plants.

  19. Differentiating volcanic rock assemblages using Landsat Thematic Mapper data - Influence of petrochemistry and desert varnish

    NASA Technical Reports Server (NTRS)

    Spatz, D. M.; Taranik, J. V.; Hsu, L. C.

    1989-01-01

    An investigation has been conducted of the composition, distribution, spectral properties, and Landsat TM influences of desert varnish from three sites in southern Nevada. It is established that the TM signatures of diverse volcanic rock assemblages primarily depend on primary petrochemical characteristics. Desert varnish is found to exert a minimal influence on TM imagery at longer wavelengths, but absorbs the higher frequency radiation of TM bands 1-3, thereby leading to high TM band 5/2 values and dark contrast on 5/2 images over units with high rock-varnish albedo difference; highly evolved volcanic deposits show steep positive spectral slopes in the TM band 5-7 region.

  20. Anticancer attributes of desert plants: a review.

    PubMed

    Harlev, Eli; Nevo, Eviatar; Lansky, Ephraim P; Lansky, Shifra; Bishayee, Anupam

    2012-03-01

    The ever-increasing emergence of the resistance of mammalian tumor cells to chemotherapy and its severe side effects reduces the clinical efficacy of a large variety of anticancer agents that are currently in use. Thus, despite the significant progress in cancer therapeutics in the last decades, the need to discover and to develop new, alternative, or synergistic anticancer agents remains. Cancer prevention or chemotherapy based on bioactive fractions or pure components derived from desert plants with known cancer-inhibiting properties suggests promising alternatives to current cancer therapy. Plants growing on low nutrient soils and/or under harsh climatic conditions, such as extreme temperatures, intense solar radiation, and water scarcity, are particularly susceptible to attack from reactive oxygen species and have evolved efficient antioxidation defense systems. The many examples of desert plants displaying anticancer effects as presented here indicates that the same defensive secondary metabolites protecting them against the harsh environment may also play a protective or a curative role against cancer, as they also do against diabetes, neurodegenerative, and other acute and chronic diseases. The present review highlights a plethora of studies focused on the antineoplastic properties of desert plants and their prinicipal phytochemicals, such as saponins, flavonoids, tannins, and terpenes. Although many desert plants have been investigated for their antitumor properties, there are many that still remain to be explored - a challenge for the prospective cancer therapy of the future. PMID:22217921

  1. The Desert Tortoise: A Delicate Balance

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This award winning program looks at the efforts to preserve the desert tortoise in and around the Edwards Air Force Base, CA area. It also explains what people should do if they come in contact with a tortoise. This video was produced in cooperation with Edwards Air Force Base.

  2. Modelling emergent patterns of dynamic desert ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In many desert ecosystems vegetation is both patchy and dynamic: vegetated areas are interspersed with patches of bare ground, and both the positioning and the species composition of the vegetated areas exhibit change through time. These characteristics lead to the emergence of multi-scale patterns ...

  3. Metagenomes from the saline desert of kutch.

    PubMed

    Pandit, A S; Joshi, M N; Bhargava, P; Ayachit, G N; Shaikh, I M; Saiyed, Z M; Saxena, A K; Bagatharia, S B

    2014-01-01

    We provide the first report on the metagenomic approach for unveiling the microbial diversity in the saline desert of Kutch. High-throughput metagenomic sequencing of environmental DNA isolated from soil collected from seven locations in Kutch was performed on an Ion Torrent platform. PMID:24831151

  4. Metagenomes from the Saline Desert of Kutch

    PubMed Central

    Pandit, A. S.; Joshi, M. N.; Bhargava, P.; Ayachit, G. N.; Shaikh, I. M.; Saiyed, Z. M.; Saxena, A. K.

    2014-01-01

    We provide the first report on the metagenomic approach for unveiling the microbial diversity in the saline desert of Kutch. High-throughput metagenomic sequencing of environmental DNA isolated from soil collected from seven locations in Kutch was performed on an Ion Torrent platform. PMID:24831151

  5. Reclaiming freshwater sustainability in the Cadillac Desert

    PubMed Central

    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%. PMID:21149727

  6. Gopherus agassizii (desert tortoise). Burrow collapse

    USGS Publications Warehouse

    Loughran, Caleb L.; Ennen, Joshua; Lovich, Jeffrey E.

    2011-01-01

    In the deserts of the southwestern U.S., burrows are utilized by the Desert Tortoise to escape environmental extremes (reviewed by Ernst and Lovich 2009. Turtles of the United States and Canada. 2nd ed. Johns Hopkins Univ. Press, Baltimore, Maryland. 827 pp.). However, the potential for mortality through burrow collapse and entrapment is poorly documented. Nicholson and Humphreys (1981. Proceedings of the Desert Tortoise Council, pp. 163−194) suggested that collapse due to livestock trampling may cause mortality. In addition, Lovich et al. (2011. Chelon. Cons. Biol. 10[1]:124–129) documented a Desert Tortoise that used a steel culvert as a burrow surrogate. The culvert filled completely with sediment following a significant rain event, entombing the animal and ultimately resulting in its death. We note that this mortality was associated with an anthropogenic structure; because tortoises are prodigious diggers, one might hypothesize that they have the ability to dig out of collapsed natural burrows in most situations. Circumstances described here presented us with an opportunity to test this hypothesis.

  7. Desert Research and Technology Studies 2008 Report

    NASA Technical Reports Server (NTRS)

    Romig, Barbara; Kosmo, Joseph; Gernhardt, Michael; Abercromby, Andrew

    2009-01-01

    During the last two weeks of October 2008, the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) Advanced Extravehicular Activity (AEVA) team led the field test portion of the 2008 Desert Research and Technology Studies (D-RATS) near Flagstaff, AZ. The Desert RATS field test activity is the year-long culmination of various individual science and advanced engineering discipline areas technology and operations development efforts into a coordinated field test demonstration under representative (analog) planetary surface terrain conditions. The 2008 Desert RATS was the eleventh RATS field test and was the most focused and successful test to date with participants from six NASA field centers, three research organizations, one university, and one other government agency. The main test objective was to collect Unpressurized Rover (UPR) and Lunar Electric Rover (LER) engineering performance and human factors metrics while under extended periods of representative mission-based scenario test operations involving long drive distances, night-time driving, Extravehicular Activity (EVA) operations, and overnight campover periods. The test was extremely successful with all teams meeting the primary test objective. This paper summarizes Desert RATS 2008 test hardware, detailed test objectives, test operations, and test results.

  8. Desert varnish: the importance of clay minerals.

    PubMed

    Potter, R M; Rossman, G R

    1977-06-24

    Desert varnish has been characterized by infrared spectroscopy, x-ray diffraction, and electron microscopy. It is a distinct morphological entity having an abrupt boundary with the underlying rock. Clay minerals comprise more than 70 percent of the varnish. Iron and manganese oxides constitute the bulk of the remainder and are dispersed throughout the clay layer. PMID:17776923

  9. Reclaiming freshwater sustainability in the Cadillac Desert

    USGS Publications Warehouse

    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%.

  10. Antioxidant Activity of Sonoran Desert Bee Pollen

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bee products have been consumed by mankind since antiquity and their health benefits are becoming more apparent. Bee pollen (pollen collected by honey bees) was collected in the high intensity ultraviolet (UV) Sonoran desert and was analyzed by the anti-2,2-diphenyl-1-picryhydrazyl (DPPH) assay and...

  11. Desert Culture Area. Native American Curriculum Series.

    ERIC Educational Resources Information Center

    Ross, Cathy; Fernandes, Roger

    One in a series of Native American instructional materials, this booklet introduces elementary students to the history and culture of the Navajo, Pueblo, and other Indian tribes of the southwest desert. Written in simple language, the booklet provides background information, activities, legends, and illustrations. Topics include the climate of the…

  12. An Ecosystem Services Framework for Desert Landscapes

    EPA Science Inventory

    Governments, tribal leaders and citizens of the deserts in North America are facing unprecedented pressures from population growth and climate change. The dominant environmental and economic issue is to ensure that people have access to clean water and sanitation while vital ecos...

  13. Microflora in soils of desert regions

    NASA Technical Reports Server (NTRS)

    Cameron, R. E.

    1970-01-01

    Desert soil samples, collected using aseptic techniques, are low in organic matter and cation exchange capacity. Aerobic and microaerophilic bacteria are most abundant, next are algae and molds. Chemical and physical properties are determined by standard procedures, including the Kjeldahl method and the use of Munsell soil color charts.

  14. Cryophenomena in the Cold Desert of Atacama

    NASA Astrophysics Data System (ADS)

    Buchroithner, Dr.; Trombotto, Dr.

    2012-04-01

    The study area of the Valle de Barrancas Blancas in the High Atacama Andes of Chile (68°39' W, 27°02' S), a kind of Patagonian "bajo sin salida", shows well preserved landforms resulting from a combination of slope, eolian, lacustrine/litoral, fluvial, glacial and periglacial regimes. They permit the reconstruction of geomorphological processes within this isolated catchment of approximately 160 km2. The mean annual air temperature varies between -2 and -4 °C and the precipitation is approximately 150 mm/a. Snowfall is frequent but the snow is quickly sublimated, redeposited and/or covered by cryosediments, i.e. mainly pumice pebbles. Water bodies present icings, even in summer. Regarding its climatic conditions the study area represents an extremely cold desertic region. Extremophile microfauna was also found. The area displays both in situ mountain permafrost and creeping permafrost. The active layer is 30 to 45 cm thick. It is a periglacial macro-environment where interdependent processes, and not only cryogenic processes but also erosion and eolian deposition and the action of fluvial washout mainly caused by precipitation, accumulation, retransportation/redeposition and melting of snow, play an important role. The cryogenic geomorphology of the Valle de Barrancas Blancas is varied and contains microforms such as patterned ground and microforms caused by cryoturbation, as well as mesoforms like rockglaciers and cryoplanation surfaces. Slopes are strongly affected by gelifluction. New cryoforms in South America and in the Southern Hemisphere like the Atacama Pingo (Pingo atacamensis) and Permafrosted Dunes ("Dunas heladas") were found. Intense niveo-eolian processes participate in the erosion of preexisting landforms, in the formation of subterraneous ice layers, and the retransportation/redeposition of snow and sediments. Studies of this periglacial environment are crucial for the understanding of Tundrean paleoenvironments and Martian conditions.

  15. Climate change as a draw bridge between Africa and the Middle East

    NASA Astrophysics Data System (ADS)

    Issar, Arie S.

    2010-07-01

    Since the very beginning of the human race, the Middle East served as a bridge between Africa-where our species first evolved-and the rest of the world. The passage over this bridge opened and closed with the global fluctuations of climate. The first glacial periods at the beginning of the Quaternary caused the greenhouse of equatorial Africa to become less hospitable, while making the desert belt of the Middle East more humid, green, and thus passable. Flint tools found along the shores of dried up lakes and swamps in the Negev Desert provide evidence that members of the first wave, Homo erectus, as well as the last wave, Homo sapiens, camped there en route to all the other continents.

  16. East Africa

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This image shows the East African nations of Ethiopia, Eritrea, and Somalia, as well as portions of Kenya, Sudan, Yemen, and Saudi Arabia. Dominating the scene are the green Ethiopian Highlands. With altitudes as high as 4,620 meters (15,157 feet), the highlands pull moisture from the arid air, resulting in relatively lush vegetation. In fact, coffee-one of the world's most prized crops-originated here. To the north (above) the highlands is Eritrea, which became independent in 1993. East (right) of Ethiopia is Somalia, jutting out into the Indian Ocean. The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) captured this true-color image on November 29, 2000. Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  17. Colonization patterns of soil microbial communities in the Atacama Desert

    PubMed Central

    2013-01-01

    Background 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. Results 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 <0.001) and that communities from locations in the hyper-arid zone displayed the lowest levels of diversity. We found bacterial taxa similar to those found in other arid soil communities with an abundance of Rubrobacterales, Actinomycetales, Acidimicrobiales, and a number of families from the Thermoleophilia. The extremely low abundance of Firmicutes indicated that most bacteria in the soil were in the form of vegetative cells. Integrating molecular data with climate and soil geochemistry, we found that air relative humidity (RH) and soil conductivity significantly correlated with microbial communities’ diversity metrics (least squares linear regression for observed OTU0.03 and air RH and soil conductivity, P <0.001; UniFrac 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. Conclusions 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

  18. Holocene aeolian activities in the southeastern Mu Us Desert, China

    NASA Astrophysics Data System (ADS)

    Jia, Feifei; Lu, Ruijie; Gao, Shangyu; Li, Jinfeng; Liu, Xiaokang

    2015-12-01

    Aeolian deposits from three sites in the Mu Us Desert were used to reconstruct the history of aeolian activities during the Holocene. The results of the lithologies, chronologies and proxy indicators showed that aeolian activities occurred at ∼9.96 cal ka BP, 7.9-6.9 ka BP, 6.4 ka BP and 3.8 cal ka BP∼. The cold event that occurred around 6.4 ka BP interrupted the Holocene Optimum period, which is largely consistent with the findings from sediments in adjacent regions and the monsoon areas of China. Combined with punished OSL and 14C ages of aeolian deposits samples in this region, the environmental changes in the Mu Us Desert were divided into four stages. Active sand dunes dominated before 11 ka BP. Aeolian activities occurred regionally from 11 to 8.5 ka BP and typical sandy paleosol widely developed with episodic aeolian activities between 8.5 and 4 ka BP. Dunes have reactivated and active sand dunes have gradually increased since 4 ka BP. Comparisons with the other paleoclimatic records indicated that the evolution of the Mu Us Desert was closely related to the East Asian monsoon. Paleosol development depended more on the precipitation brought by the East Asian summer monsoon (EASM). The stronger East Asian winter monsoon (EAMW) and higher isolation resulted in the aeolian activities in the early Holocene, while during the mid-Holocene the fluctuating EAWM played a more important role in inducing episodic aeolian activities. The environmental deterioration during the late Holocene can be related to weakened EASM or to increased anthropogenic influence.

  19. Hot bats: extreme thermal tolerance in a desert heat wave

    NASA Astrophysics Data System (ADS)

    Bondarenco, Artiom; Körtner, Gerhard; Geiser, Fritz

    2014-08-01

    Climate change is predicted to increase temperature extremes and thus thermal stress on organisms. Animals living in hot deserts are already exposed to high ambient temperatures ( T a) making them especially vulnerable to further warming. However, little is known about the effect of extreme heat events on small desert mammals, especially tree-roosting microbats that are not strongly protected from environmental temperature fluctuations. During a heat wave with record T as at Sturt National Park, we quantified the thermal physiology and behaviour of a single free-ranging little broad-nosed ( Scotorepens greyii, henceforth Scotorepens) and two inland freetail bats ( Mormopterus species 3, henceforth Mormopterus) using temperature telemetry over 3 days. On 11 and 13 January, maximum T a was ˜45.0 °C, and all monitored bats were thermoconforming. On 12 January 2013, when T a exceeded 48.0 °C, Scotorepens abandoned its poorly insulated roost during the daytime, whereas both Mormopterus remained in their better insulated roosts and were mostly thermoconforming. Maximum skin temperatures ( T skin) ranged from 44.0 to 44.3 °C in Scotorepens and from 40.0 to 45.8 °C in Mormopterus, and these are the highest T skin values reported for any free-ranging bat. Our study provides the first evidence of extensive heat tolerance in free-ranging desert microbats. It shows that these bats can tolerate the most extreme T skin range known for mammals (3.3 to 45.8 °C) and delay regulation of T skin by thermoconforming over a wide temperature range and thus decrease the risks of dehydration and consequently death.

  20. Hot bats: extreme thermal tolerance in a desert heat wave.

    PubMed

    Bondarenco, Artiom; Körtner, Gerhard; Geiser, Fritz

    2014-08-01

    Climate change is predicted to increase temperature extremes and thus thermal stress on organisms. Animals living in hot deserts are already exposed to high ambient temperatures (T a) making them especially vulnerable to further warming. However, little is known about the effect of extreme heat events on small desert mammals, especially tree-roosting microbats that are not strongly protected from environmental temperature fluctuations. During a heat wave with record T as at Sturt National Park, we quantified the thermal physiology and behaviour of a single free-ranging little broad-nosed (Scotorepens greyii, henceforth Scotorepens) and two inland freetail bats (Mormopterus species 3, henceforth Mormopterus) using temperature telemetry over 3 days. On 11 and 13 January, maximum T a was ∼45.0 °C, and all monitored bats were thermoconforming. On 12 January 2013, when T a exceeded 48.0 °C, Scotorepens abandoned its poorly insulated roost during the daytime, whereas both Mormopterus remained in their better insulated roosts and were mostly thermoconforming. Maximum skin temperatures (T skin) ranged from 44.0 to 44.3 °C in Scotorepens and from 40.0 to 45.8 °C in Mormopterus, and these are the highest T skin values reported for any free-ranging bat. Our study provides the first evidence of extensive heat tolerance in free-ranging desert microbats. It shows that these bats can tolerate the most extreme T skin range known for mammals (3.3 to 45.8 °C) and delay regulation of T skin by thermoconforming over a wide temperature range and thus decrease the risks of dehydration and consequently death. PMID:25005222

  1. 10Be in Quartz Gravel from the Gobi Desert and Evolutionary History of Alluvial Sedimentation in the Ejina Basin, Inner Mongolia, China

    NASA Astrophysics Data System (ADS)

    Lyu, Y.

    2014-12-01

    Reconstructing the evolutionary history of the Gobi deserts developed from alluvial sediments in arid regions has great significance in unraveling changes in both tectonic activity and climate. However, such work is limited by a lack of suitable dating material preserved in the Gobi Desert, but cosmogenic 10Be has great potential to date the Gobi deserts. In the present study, 10Be in quartz gravel from the Gobi deserts of the Ejina Basin in Inner Mongolia of China has been measured to assess exposure ages. Results show that the Gobi Desert in the northern margin of the basin developed 420 ka ago, whereas the Gobi Desert that developed from alluvial plains in the Heihe River drainage basin came about during the last 190 ka. The latter developed gradually northward and eastward to modern terminal lakes of the river. These temporal and spatial variations in the Gobi deserts are a consequence of alluvial processes influenced by Tibetan Plateau uplift and tectonic activities within the Ejina Basin. Possible episodes of Gobi Desert development within the last 420 ka indicate that the advance/retreat of alpine glaciers during glacial/interglacial cycles might have been the dominant factor to influencing the alluvial intensity and water volume in the basin. Intense floods and large water volumes would mainly occur during the short deglacial periods.

  2. Climate variability and predictability in Northwest Africa

    NASA Astrophysics Data System (ADS)

    Baddour, O.; Djellouli, Y.

    2003-04-01

    Northwest Africa defined here as the area including Morocco, Algeria and Tunisia, occupies a large territory in North Africa with an area exceeding 3.5 million km2. The geographical contrast is very important: while most of the southern part is desert, the northern and northwestern parts exhibit a contrasting geography including large flat areas in the western part of Morocco, northern Algeria and eastern part of Tunisia and the formidable Atlas mountains barrier extends from south west of Morocco toward north west of Tunisia crossing central Morocco and north Algeria. Agriculture is one of major socio-economic activities in the region with an extensive cash-crop for exporting to Europe especially from Morocco and Tunisia. The influence of the recurring droughts during the 80s and 90s was very crucial for the economic and societal aspects of the region. In Morocco, severe droughts have caused GDP fluctuation within past 20 years from 10% increase down to negative values in some particular years. Recent studies have investigated seasonal rainfall variability and prediction over MOROCCO in the framework of regional and international collaboration. Results from this work has shown that the main general circulation feature associated with the rainfall variability within Morocco is the North Atlantic Oscillation. The relationship is in fact due to the major role played by the AZORES high pressure with its role in modulating the main position of the active synoptic systems in the north Atlantic area and therefore in modulating the frequency and the intensity of the weather systems that impact the western part of the region. Mediterranean sea plays also major role in the mid of the region. In this paper we applied EOF technique on 500 hPa. The data used are monthly reanalysis NCEP/NCAR analyses for November from 1960 to 1990 climatological time series. Correlation analysis is then performed between EOF time series and global 4x4 degre SST anomalies. The results we

  3. A combined observational and modeling approach to study modern dust transport from the Patagonia desert to East Antarctica

    NASA Astrophysics Data System (ADS)

    Gassó, S.; Stein, A.; Marino, F.; Castellano, E.; Udisti, R.; Ceratto, J.

    2010-09-01

    ~1500 km SW of South Africa five days after, the limited capabilities of existing satellite platforms to differentiate between aerosol types do not permit a definitive conclusion. In addition, the model simulations show dust lifting to the free troposphere as it travels south but it could not be confirmed by the satellite observations due to cloudiness. This work demonstrates that complementary information from existing transport models, satellite and surface data can yield a consistent picture of the dust transport from the Patagonia desert to Antarctica. It also illustrates the limitation of using any of these approaches individually to characterize the transport of dust in a heavily cloudy area.

  4. A Combined Observational and Modeling Approach to Study Modern Dust Transport from the Patagonia Desert to East Antarctica

    NASA Technical Reports Server (NTRS)

    Gasso, S.; Stein, A.; Marino, F.; Castellano, E.; Udisti, R.; Ceratto, J.

    2010-01-01

    presence of dust at approx.1500 km SW of South Africa five days after, the limited capabilities of existing satellite platforms to differentiate between aerosol types do not permit a definitive conclusion. In addition, the model simulations show dust lifting to the free troposphere as it travels south but it could not be confirmed by the satellite observations due to cloudiness. This work demonstrates that complementary information from existing transport models, satellite and surface data can yield a consistent picture of the dust transport from the Patagonia desert to Antarctica. It also illustrates the limitation of using any of these approaches individually to characterize the transport of dust in a heavily cloudy area.

  5. Multiscale drivers of spatially variable grass production and loss in the Chihuahuan Desert

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Historic regime shifts from grass- to shrub-dominated states have been widespread in the Chihuahuan Desert and other arid and semiarid regions globally. These patterns of grass production and shifts to shrub dominance are spatially variable, and show a weak correlation with precipitation, suggesting...

  6. Hybrid engineered materials with high water-collecting efficiency inspired by Namib Desert beetles.

    PubMed

    Zhu, Hai; Guo, Zhiguang

    2016-05-21

    Inspired by Namib Desert beetles, a hybrid superhydrophobic surface was fabricated, showing highly efficient fog harvesting with a water collection rate (WCR) of 1309.9 mg h(-1) cm(-2). And, the surface possessed an excellent robustness and self-cleaning property. PMID:27125658

  7. Mass spectral determination of phenylacetonitrile (PAN) levels in body tissues of adult desert locust, Schistocerca gregaria

    Technology Transfer Automated Retrieval System (TEKTRAN)

    : Wings and legs of the gregarious desert locust, Schistocerca gregaria have been shown to be release sites of phenylacetonitrile (PAN), the major adult male-produced pheromone. However, there is limited information on the distribution of PAN within the locust. Here we show, using gas chromatograph...

  8. Feedbacks between aeolian processes, vegetation productivity, and nutrient flux in deserts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind is a key abiotic factor that influences the dynamics of arid and semiarid systems. A series of experiments and models will be presented that show the important feedbacks that exist between Aeolian processes and biotic process in deserts. Wind impacts vegetation by both changing the composition ...

  9. Clay Mineral Composition of Sediments in Some Desert Lakes in Nevada, California, and Oregon.

    PubMed

    Droste, J B

    1961-06-16

    X-ray analyses of some Recent desert lacustrine sediments in Nevada, California, and Oregon show that illite and montmorillonite are the most abundant clay minerals and that chlorite and kaolinite are present in subordinate amounts in the sediments of many of the lakes. These clay suites are derived from source rocks. PMID:17738874

  10. Potential source regions of dust accumulated in northern Africa

    NASA Astrophysics Data System (ADS)

    Wasowska, S.; Woronko, B.

    2012-04-01

    Sahara is the largest source of the dust in the world. The material sampled from dust storms in Tunisia (Nefta Oasis, El Kantoui Harbor), north Egypt (Alexandria) and Morocco (Mhamid Oasis) (March 2001, March and April 2009) was taken to identify the potential sources of dust accumulation and transport paths in North Africa. The samples were analyzed on grain size, micromorphology of silt grain surfaces in Scanning Electron Microscope (SEM), elemental composition of grains and their surface crusts, loss on ignition, mineralogical composition of samples and carbonate content. Additionally the meteorological situation was analyzed during the dust storm occurrences and preceding periods. The results of grain size analyses show that all studied sediments belong to the small dust type, and dust accumulated in Mhamid is the clay mineral agglomerated (CMA) dust. The source of the CMA are the old dry lake beds. Dust particles are mobilized as aggregates of clay minerals, what is controlled by structure (particle packing) of the original lake sediment, and accumulation is dry and wet as well. The results of the analysis of the quartz grain surface micromorphology, the elemental composition and loss on ignition indicate that dust accumulated in Morocco originated from a relatively homogenous sediment source and, on the other hand, dust found in Alexandria comes from a diversified source. Dust sampled in Tunisia is characterized by the highest content of carbonates and organic matter which suggests the intensive dispelling acting on the weathered material from carbonate rocks and local Mediterranean soil covers rich in CaCO3. The analyses of meteorological conditions during the dust storms and the analyses of the textural characteristics of deposits show that it is highly probable that analysed aeolian dust was transported both for shorter and longer distances. Hypothetic source areas of dust accumulated in Mhamid could be the old ergs, some located 300-500 km away like

  11. Global Retrieval of Aerosol Properties over Desert and Semi-Desert Regions from SeaWiFS and MODIS

    NASA Technical Reports Server (NTRS)

    Hsu, Nai-Yung; Tsay, Si-Chee; King, M. D.; Herman, J. R.

    2005-01-01

    Mineral aerosols (dust) play an important role in both climate forcing and oceanic productivity throughout the entire year. Due to the relatively short lifetime (a few hours to about a week), the distributions of these airborne dust particles vary extensively in both space and time. Consequently, satellite observations are needed over both source and sink regions for continuous temporal and spatial sampling of dust properties. However, despite their importance, the high spatial resolution satellite measurements of dust near its source have been lacking. In this paper, we will demonstrate the capability of a new satellite algorithm to retrieve aerosol optical thickness and single scattering albedo over bright-reflecting surfaces such as urban areas and deserts. Such retrievals have been difficult to perform using previously available algorithms that use wavelengths from the mid-visible to the near IR because they have trouble separating the aerosol signal from the contribution due to the bright surface reflectance. The new algorithm, called Deep Blue, utilizes blue-wavelength measurements from instruments such as SeaWiFS and MODIS to infer the properties of aerosols, sinre the stirfare reflectance nver land in the blue part of the spectrum is much lower than for longer wavelength channels. We have validated the satellite retrieved aerosol optical thickness with data from AERONET sunphotometers over desert and semi-desert regions. The comparisons show reasonable agreements between these two. These new satellite products will allow scientists to determine quantitatively the aerosol properties near sources using high spatial resolution measurements from SeaWiFS and MODIS-like instruments.

  12. Language in South Africa.

    ERIC Educational Resources Information Center

    Mesthrie, Rajend, Ed.

    This collection of 24 papers focuses on language and society in South Africa. Part 1, "The Main Language Groupings," includes (1) "South Africa: A Sociolinguistic Overview" (R. Mesthrie); (2) "The Khoesan Languages" (A. Traill); (3) "The Bantu Languages: Sociohistorical Perspectives" (Robert K. Herbert and Richard Bailey); (4) "Afrikaans:…

  13. Generation 2030/Africa

    ERIC Educational Resources Information Center

    You, Danzhen; Hug, Lucia; Anthony, David

    2014-01-01

    Until relatively recently, much of Africa has been among the economically least developed and least densely populated places on earth, replete with villages and rural communities. Africa is changing rapidly, in its economy, trade and investment; in climate change; in conflict and stability; in urbanization, migration patterns, and most of all in…

  14. Dearth of short-period Neptunian exoplanets: A desert in period-mass and period-radius planes

    NASA Astrophysics Data System (ADS)

    Mazeh, T.; Holczer, T.; Faigler, S.

    2016-05-01

    A few studies have reported a significant dearth of exoplanets with Neptune mass and radius with orbital periods below 2-4 d. This cannot be explained by observational biases because many Neptunian planets with longer orbital periods have been detected. The existence of this desert is similar to the appearance of the so-called brown-dwarf desert that suggests different formation mechanisms of planets and stellar companions with short orbital periods. Similarly, the Neptunian desert might indicate different mechanisms of formation and evolution for hot Jupiters and short-period super-Earths. We here follow a previous study and examine the location and shape of the desert in both the period-mass and period-radius planes, using the currently available large samples of planets. The desert in the period-mass plane has a relatively sharp upper edge, with a planetary mass that is inversely proportional to the planetary orbital period, while the lower, somewhat blurred, boundary is located along masses that are apparently linearly proportional to the period. The desert in the period-radius plane of the transiting planets is less clear. It seems as if the radius along the upper boundary is inversely proportional to the period to the power of one-third, while the lower boundary shows a radius that is proportional to the period to the power of two-thirds. The combination of the two upper bounds of the desert, in the period-mass and period-radius planes, yields a planetary mass-radius relation of Rp/RJup ≃ (1.2 ± 0.3)(Mp/MJup)0.27 ± 0.11 for 0.1 ≲ Mp/MJup ≲ 1. The derived shape of the desert, which might extend up to periods of 5-10 d, could shed some light on the formation and evolution of close-in planets.

  15. Let the show begin

    SciTech Connect

    Alperowicz, N.

    1993-01-27

    Major changes should occur in the European polyolefins industry this year. BASF's (Ludwigshafen) polypropylene (PP) deal with ICI is expected to be followed by that of Hoechst (Frankfurt) and Petrofina (Brussels). The two are engaged in feasibility studies for a possible joint venture in PP and are expected to make a decision in the second quarter of this year. Shell and Himont are on track to complete their feasibility study in the first quarter for a polyolefins joint venture. And Huels and PCD are still in talks. But two new possible deals, a polyolefins merger between Nests (Helsinki) and Statoil (Stavanger) and an alliance in PP involving Appryl, the Elf Atochem (51%)/BP Chemicals (49%) joint venture, and Solvay have been denied. The Hoechst/Fina venture would initially encompass only the two companies European plants - Hoechst's 550,000-m.t./year and Fina's 180,000 m.t./year. In addition, Fina would either build or acquire another PP plant. In the second stage, the partners could bring in their overseas plants. Fina has plants in the US, and Hoechst has a combined 100,000 m.t./year in south Africa and Australia. Neste's board member Jukka Viinanen says the only talks between Nests and Statoil center on renegotiations of ethylene supply contract at Stenungsund, Sweden. Nests wants a more flexible deal on quantity and price. It needs 400,000 m.t./year of ethylene for its downstream plants. Viinanen adds that he is worried about the European petrochemical industry and producers need to do everything to improve margins through pricing policies and obtaining a balance between supply and demand. On the possibility of a future link with Statoil he comments, One can never say never. It would take time. We don't feel in a very vulnerable position right now.

  16. Geometeorological data collected by the USGS Desert Winds Project at Desert Wells, Sonoran Desert, central-west Arizona, 1981 - 1996

    USGS Publications Warehouse

    Helm, Paula J.; Breed, Carol S.; Tigges, Richard; Creighton, Shawn

    1998-01-01

    The data in this report were obtained by instruments deployed on a GOES-satellite data collection station operated by the U.S. Geological Survey Desert Winds Project at Desert Wells (latitude 33° 42' 08" N, longitude 113° 48' 40" W), La Paz County, west-central Arizona. The elevation is 344 m (1,130 ft). From January 9, 1981 through May 31, 1995 the station recorded eight parameters: wind direction, wind speed, peak gust, air temperature, precipitation, humidity, barometric pressure, and soil temperature. On June 1, 1995, the station was upgraded by adding a SENSIT sand-flux sensor, which records grain impacts concurrently with wind speed and wind direction measurements. Included with the data is descriptive text on the geology, soils, climate, vegetation, and land use at the site, as well as text on data format, date retrieval software and instructions, and metadata

  17. Snow, the Great River, and the Desert

    NASA Astrophysics Data System (ADS)

    Rango, A.

    2005-12-01

    While many major rivers around the world originate from alpine snowpacks in mountain regions, some experience the extreme contrast of flowing through harsh desert environments downriver. One such stream is the Rio Grande which rises in the San Juan and the Sangre de Christo mountains of southern Colorado and northern New Mexico. Eventually, the snow fed Rio Grande flows through North America's largest desert, the Chihuahuan Desert in New Mexico, Texas, and Mexico, and simultaneously becomes part of the border between the United States and Mexico. As is often true, urban areas develop along the river corridors rather than in more inaccessible mountain regions. This demographic preference tends to isolate the vast majority of population in the Rio Grande, who are dependent on water for their livelihoods, from the mountain snowpacks where the flow is generated. Ironically then, snow is seldom viewed as the source of the much needed water flowing through the desert by the majority of the basin's population. In arid regions of the western U.S., water demand far exceeds the water supply, and water use is apportioned under the doctrine of prior appropriation with the oldest right getting the first use of water. The increasing population in urban areas does not usually have a right to use the water flowing through the desert unless water rights have been purchased by municipalities from the major category of water user in these basins, namely, irrigated agriculture. In the entire Rio Grande basin, irrigation makes up 80% of the consumptive use of water. Additionally, basin compacts and international treaties apportion water between states and countries. Because these formal agreements were based on above average runoff years, there is little flexibility in changing the use of water, particularly in dry to normal runoff years. Most of the older water rights in the Rio Grande, especially the upper basin, are supplied by snowmelt. This leaves the lower basin to depend upon

  18. Radiation, multiple dispersal and parallelism in the skinks, Chalcides and Sphenops (Squamata: Scincidae), with comments on Scincus and Scincopus and the age of the Sahara Desert.

    PubMed

    Carranza, S; Arnold, E N; Geniez, Ph; Roca, J; Mateo, J A

    2008-03-01

    Phylogenetic analysis using up to 1325 base pairs of mitochondrial DNA from 179 specimens and 30 species of Chalcides, Sphenops, Eumeces, Scincopus and Scincus indicates that Sphenops arose twice independently within Chalcides. It is consequently synonymized with that genus. Chalcides in this broader sense originated in Morocco, diversifying into four main clades about 10 Ma, after which some of its lineages dispersed widely to cover an area 40 times as large. Two separate lineages invaded the Canary Islands and at least five main lineages colonized southern Europe. At least five more spread across northern Africa, one extending into southwest Asia. Elongate bodies with reduced limbs have evolved at least four times in Chalcides, mesic 'grass-swimmers' being produced in one case and extensive adaptation to life in loose desert sand in two others. In clade, Chalcides striatus colonized SW Europe from NW Africa 2.6 Ma and C. chalcides mainland Italy 1.4 Ma, both invasions being across water, while C. c. vittatus reached Sardinia more recently, perhaps anthropogenically, and C. guentheri spread 1200km further east to Israel. C. minutus is a composite, with individuals from the type locality forming a long independent lineage and the remaining ones investigated being most closely related to C. mertensi. In the Northern clade, C. boulengeri and C. sepsoides spread east through sandy habitats north of the Sahara about 5 Ma, the latter reaching Egypt. C. bedriagai invaded Spain around the same time, perhaps during the Messinian period when the Mediterranean was dry, and shows considerable diversification. Although it is currently recognized as one species, the C. ocellatus clade exhibits as much phylogenetic depth as the other main clades of Chalcides, having at least six main lineages. These have independently invaded Malta and Sardinia from Tunisia and also southwest Arabia C. o. humilis appears to have spread over 4000 km through the Sahel, south of the Sahara quite

  19. Biogeochemical inferences of mobility of early Holocene fisher-foragers from the Southern Sahara Desert.

    PubMed

    Stojanowski, Christopher M; Knudson, Kelly J

    2011-09-01

    North Africa is increasingly seen as an important context for understanding modern human evolution and reconstructing biocultural adaptations. The Sahara, in particular, witnessed a fluorescence of hunter-gatherer settlement at the onset of the Holocene after an extended occupational hiatus. Subsequent subsistence changes through the Holocene are contrary to those documented in other areas where mobile foraging gave way to settled agricultural village life. In North Africa, extractive fishing and hunting was supplanted by cattle and caprine pastoralism under deteriorating climatic conditions. Therefore, the initial stage of food production in North Africa witnessed a likely increase in mobility. However, there are few studies of paleomobility in Early Holocene hunter-gatherer Saharan populations and the degree of mobility is generally assumed. Here, we present radiogenic strontium isotope ratios from Early Holocene fisher-forager peoples from the site of Gobero, central Niger, southern Sahara Desert. Data indicate a relatively homogeneous radiogenic strontium isotope signature for this hunter-gather population with limited variability exhibited throughout the life course or among different individuals. Although the overall signature was local, some variation in the radiogenic strontium isotope data likely reflects transhumance into the nearby Aïr Massif. Data from Gobero were significantly less variable than in other worldwide hunter-gatherer populations, including those thought to be fairly sedentary. Strontium data from Gobero were also significantly different from contemporaneous sites in southwestern Libya. These patterns are discussed with respect to archaeological models of community organization and technological evolution. PMID:21766285

  20. 43 CFR 2524.6 - Desert-land entryman may proceed independently of Government irrigation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false Desert-land entryman may proceed... (2000) DESERT-LAND ENTRIES Desert-Land Entries Within a Reclamation Project § 2524.6 Desert-land... that a desert-land entryman who owns a water right and reclaims the land embraced in his entry...

  1. 43 CFR 2524.6 - Desert-land entryman may proceed independently of Government irrigation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false Desert-land entryman may proceed... (2000) DESERT-LAND ENTRIES Desert-Land Entries Within a Reclamation Project § 2524.6 Desert-land... that a desert-land entryman who owns a water right and reclaims the land embraced in his entry...

  2. 43 CFR 2524.6 - Desert-land entryman may proceed independently of Government irrigation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Desert-land entryman may proceed... (2000) DESERT-LAND ENTRIES Desert-Land Entries Within a Reclamation Project § 2524.6 Desert-land... that a desert-land entryman who owns a water right and reclaims the land embraced in his entry...

  3. 43 CFR 2524.6 - Desert-land entryman may proceed independently of Government irrigation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false Desert-land entryman may proceed... (2000) DESERT-LAND ENTRIES Desert-Land Entries Within a Reclamation Project § 2524.6 Desert-land... that a desert-land entryman who owns a water right and reclaims the land embraced in his entry...

  4. Modeling Optical Properties of Mineral Dust over "The Great Indian Desert"

    NASA Astrophysics Data System (ADS)

    Mishra, S.; Tripathi, S. N.

    2007-12-01

    The Thar desert, sometimes also described as 'The Great Indian Desert', lying in the Northwest part of India with an area of 0.32*106 km2, is known to be the source of natural mineral dust . The mineral dust particles are mostly non-spherical having sharp edges, which show different scattering signature compared to that of equivalent spheres while interacting with the radiation. Furthermore accurate mineralogical information, that governs their refractive indices, is essential for scattering calculations. The radiative impacts of dust particles therefore depend on their morphology and mineralogy. Most of the present satellites consider the particle to be spherical while retrieving their optical properties. Some newly launched spacecraft instruments such as MISR accounts for non spherical nature by including spheroid particles in its retrieval algorithm . Clearly there exits a need for improvement in dust model used in retrieval algorithm to account for their sharp edges together with their index of refraction based on the latest chemical composition at the sensing wavelengths. To the best of our knowledge no such attempt has been made to calculate the optical properties of dust particles over the Thar desert. In this study, the optical properties of mineral dust of the Thar desert has been modeled using T-matrix method with realistic dust shapes based on Scanning Electron Microscope images of the dust over the desert with particle size ranging from 0.1-1.0 ìm at wavelengths spanning from ultraviolet to near infrared (0.38-1.2ìm). Representative dust particles shapes considered are sphere, cylinder, spheroids and chebyshev together with realistic mineral dust composition. Mineralogical analysis of airborne dust over Northwest India has revealed the presence of only basic non-metallic minerals such as Quartz, Feldspar, Mica and Calcite, which posses negligible imaginary part of refractive index at considered wavelength domain, however, the subsequent dust sampling

  5. Effect of desertification on productivity in a desert steppe.

    PubMed

    Tang, Zhuangsheng; An, Hui; Deng, Lei; Wang, Yingying; Zhu, Guangyu; Shangguan, Zhouping

    2016-01-01

    Desertification, one of the most severe types of land degradation in the world, is of great importance because it is occurring, to some degree, on approximately 40% of the global land area and is affecting more than 1 billion people. In this study, we used a space-for-time method to quantify the impact of five different desertification regimes (potential (PD), light (LD), moderate (MD), severe (SD), and very severe (VSD)) on a desert steppe ecosystem in northern China to examine the relationship between the productivity of the vegetation and soil properties and to determine the mechanism underlying the effects of desertification on productivity. Our results showed that the effects of desertification on TP (total phosphorus) and AP (available phosphorus) were not significant, and desertification decreased productivity in the desert steppe as a result of direct changes to soil physical properties, which can directly affect soil chemical properties. Therefore, intensive grassland management to improve soil quality may result in the long-term preservation of ecosystem functions and services. PMID:27297202

  6. Highly specialized microbial diversity in hyper-arid polar desert

    PubMed Central

    Pointing, Stephen B.; Chan, Yuki; Lacap, Donnabella C.; Lau, Maggie C. Y.; Jurgens, Joel A.; Farrell, Roberta L.

    2009-01-01

    The McMurdo Dry Valleys in Antarctica are a cold hyperarid polar desert that present extreme challenges to life. Here, we report a culture-independent survey of multidomain microbial biodiversity in McKelvey Valley, a pristine example of the coldest desert on Earth. We demonstrate that life has adapted to form highly-specialized communities in distinct lithic niches occurring concomitantly within this terrain. Endoliths and chasmoliths in sandstone displayed greatest diversity, whereas soil was relatively depauperate and lacked a significant photoautotrophic component, apart from isolated islands of hypolithic cyanobacterial colonization on quartz rocks in soil contact. Communities supported previously unreported polar bacteria and fungi, but archaea were absent from all niches. Lithic community structure did not vary significantly on a landscape scale and stochastic moisture input due to snowmelt resulted in increases in colonization frequency without significantly affecting diversity. The findings show that biodiversity near the cold-arid limit for life is more complex than previously appreciated, but communities lack variability probably due to the high selective pressures of this extreme environment. PMID:19850879

  7. Slow recovery in desert perennial vegetation following prolonged human disturbance

    USGS Publications Warehouse

    Guo, Q.

    2004-01-01

    Questions: How long may it take for desert perennial vegetation to recover from prolonged human disturbance and how do different plant community variables (i.e. diversity, density and cover) change during the recovery process? Location: Sonoran Desert, Arizona, USA. Methods: Since protection from grazing from 1907 onwards, plant diversity, density and cover of perennial species were monitored intermittently on ten 10 m x 10 m permanent plots on Tumamoc Hill, Tucson, Arizona, USA. Results: The study shows an exceptionally slow recovery of perennial vegetation from prolonged heavy grazing and other human impacts. Since protection, overall species richness and habitat heterogeneity at the study site continued to increase until the 1960s when diversity, density and cover had been stabilized. During the same period, overall plant density and cover also increased. Species turnover increased gradually with time but no significant relation between any of the three community variables and precipitation or Palmer Drought Severity Index (PDSI) was detected. Conclusions: It took more than 50 yr for the perennial vegetation to recover from prolonged human disturbance. The increases in plant species richness, density, and cover of the perennial vegetation were mostly due to the increase of herbaceous species, especially palatable species. The lack of a clear relationship between environment (e.g. precipitation) and community variables suggests that site history and plant life history must be taken into account in examining the nature of vegetation recovery processes after disturbance.

  8. Effect of desertification on productivity in a desert steppe

    PubMed Central

    Tang, Zhuangsheng; An, Hui; Deng, Lei; Wang, Yingying; Zhu, Guangyu; Shangguan, Zhouping

    2016-01-01

    Desertification, one of the most severe types of land degradation in the world, is of great importance because it is occurring, to some degree, on approximately 40% of the global land area and is affecting more than 1 billion people. In this study, we used a space-for-time method to quantify the impact of five different desertification regimes (potential (PD), light (LD), moderate (MD), severe (SD), and very severe (VSD)) on a desert steppe ecosystem in northern China to examine the relationship between the productivity of the vegetation and soil properties and to determine the mechanism underlying the effects of desertification on productivity. Our results showed that the effects of desertification on TP (total phosphorus) and AP (available phosphorus) were not significant, and desertification decreased productivity in the desert steppe as a result of direct changes to soil physical properties, which can directly affect soil chemical properties. Therefore, intensive grassland management to improve soil quality may result in the long-term preservation of ecosystem functions and services. PMID:27297202

  9. Metagenomic analysis of the viral community in Namib Desert hypoliths.

    PubMed

    Adriaenssens, Evelien M; Van Zyl, Lonnie; De Maayer, Pieter; Rubagotti, Enrico; Rybicki, Ed; Tuffin, Marla; Cowan, Don A

    2015-02-01

    Hypolithic microbial communities are specialized desert communities inhabiting the underside of translucent rocks. Here, we present the first study of the viral fraction of these communities isolated from the hyperarid Namib Desert. The taxonomic composition of the hypolithic viral communities was investigated and a functional assessment of the sequences determined. Phylotypic analysis showed that bacteriophages belonging to the order Caudovirales, in particular the family Siphoviridae, were most prevalent. Functional analysis and comparison with other metaviromes revealed a relatively high frequency of cell wall-degrading enzymes, ribonucleotide reductases (RNRs) and phage-associated genes. Phylogenetic analyses of terL and phoH marker genes indicated that many of the sequences were novel and distinct from known isolates, and the class distribution of the RNRs suggests that this is a novel environment. The composition of the viral hypolith fraction containing many Bacillus-infecting phages was not completely consistent with Namib hypolith phylotypic surveys of the bacterial hosts, in which the cyanobacterial genus Chroococcidiopsis was found to be dominant. This could be attributed to the lack of sequence information about hypolith viruses/bacteria in public databases or the possibility that hypolithic communities incorporate viruses from the surrounding soil. PMID:24912085

  10. Tolerance of Photosynthesis to High Temperature in Desert Plants 1

    PubMed Central

    Downton, W. John S.; Berry, Joseph A.; Seemann, Jeffrey R.

    1984-01-01

    Winter- and summertime-active desert annual species were grown at different temperatures to assess their capacity for photosynthetic acclimation. Thermal stability of photosynthesis was determined from responses of chlorophyll fluorescence to increased temperature. Photosynthesis in winter ephemerals grown at 28°C/21°C became unstable close to 41°C in contrast to the summer annuals which were stable up to about 46°C. Growth at higher temperature (43°C/32°C) resulted in increases in thermal stability of 5 to 7°C for the winter annuals and 3 to 4°C for the summer annuals, showing that temperature can provide the primary stimulus for acclimation of the photosynthetic apparatus. The magnitude of these changes was very similar to the range of field values observed for the respective floras, indicating that the thermal acclimation response under field conditions was qualitatively similar to that occurring under controlled growth conditions. Perennial species, co-existing with these annuals in the desert, were on average more thermostable. The cacti were exceptionally heat stable, the threshold for fluorescence increase averaging 55°C. PMID:16663510

  11. Effect of desertification on productivity in a desert steppe

    NASA Astrophysics Data System (ADS)

    Tang, Zhuangsheng; An, Hui; Deng, Lei; Wang, Yingying; Zhu, Guangyu; Shangguan, Zhouping

    2016-06-01

    Desertification, one of the most severe types of land degradation in the world, is of great importance because it is occurring, to some degree, on approximately 40% of the global land area and is affecting more than 1 billion people. In this study, we used a space-for-time method to quantify the impact of five different desertification regimes (potential (PD), light (LD), moderate (MD), severe (SD), and very severe (VSD)) on a desert steppe ecosystem in northern China to examine the relationship between the productivity of the vegetation and soil properties and to determine the mechanism underlying the effects of desertification on productivity. Our results showed that the effects of desertification on TP (total phosphorus) and AP (available phosphorus) were not significant, and desertification decreased productivity in the desert steppe as a result of direct changes to soil physical properties, which can directly affect soil chemical properties. Therefore, intensive grassland management to improve soil quality may result in the long-term preservation of ecosystem functions and services.

  12. Volcanoes of the Tibesti massif (Chad, northern Africa)

    NASA Astrophysics Data System (ADS)

    Permenter, Jason L.; Oppenheimer, Clive

    2007-04-01

    The Tibesti massif, one of the most prominent features of the Sahara desert, covers an area of some 100,000 km2. Though largely absent from scientific inquiry for several decades, it is one of the world’s major volcanic provinces, and a key example of continental hot spot volcanism. The intense activity of the TVP began as early as the Oligocene, though the major products that mark its surface date from Lower Miocene to Quaternary (Furon (Geology of Africa. Oliver & Boyd, Edinburgh (trans 1963, orig French 1960), pp 1-377, 1963)); Gourgaud and Vincent (J Volcanol Geotherm Res 129:261-290, 2004). We present here a new and consistent analysis of each of the main components of the Tibesti Volcanic Province (TVP), based on examination of multispectral imagery and digital elevation data acquired from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). Our synthesis of these individual surveys shows that the TVP is made up of several shield volcanoes (up to 80 km diameter) with large-scale calderas, extensive lava plateaux and flow fields, widespread tephra deposits, and a highly varied structural relief. We compare morphometric characteristics of the major TVP structures with other hot spot volcanoes (the Hawaiian Islands, the Galápagos Islands, the Canary and Cape Verdes archipelagos, Jebel Marra (western Sudan), and Martian volcanoes), and consider the implications of differing tectonic setting (continental versus oceanic), the thickness and velocity of the lithosphere, the relative sizes of main volcanic features (e.g. summit calderas, steep slopes at summit regions), and the extent and diversity of volcanic features. These comparisons reveal morphologic similarities between volcanism in the Tibesti, the Galápagos, and Western Sudan but also some distinct features of the TVP. Additionally, we find that a relatively haphazard spatial development of the TVP has occurred, with volcanism initially appearing in the Central TVP and subsequently

  13. Desert tortoise annotated bibliography, 1991-2015

    USGS Publications Warehouse

    Berry, Kristin H.; Lyren, Lisa M.; Mack, Jeremy S.; Brand, L. Arriana; Wood, Dustin A.

    2016-01-01

    Agassiz’s Desert Tortoise (hereinafter called desert tortoise) is a state- and federally-listed threatened species (U.S. Fish and Wildlife Service, 1990; California Department of Fish and Game, 2015). The first population federally listed as threatened occurred on the Beaver Dam Slope, Utah (U.S. Fish and Wildlife Service, 1980). In 1990, the entire geographic range north and west of the Colorado River was federally listed as threatened (U.S. Fish and Wildlife Service, 1990), with the exception being a small population in northwestern Arizona. The purpose of this annotated bibliography is to support recovery efforts for the species, because populations have continued to decline in spite of designation of critical habitat and publication of a recovery plan (U.S. Fish and Wildlife Service, 1994). For example, between 2005 and 2014, populations in critical habitats declined about 50% (U.S. Fish and Wildlife Service, 2015).

  14. Organic chemicals from the Chihuahuan desert

    SciTech Connect

    Campos-Lopez, E.; Roman-Alemany, A.

    1980-03-01

    A consideration of social, economic, political, and technological factors in the search for new renewable sources of raw materials suggests the exploitation and development of the resources of marginal land regions. Desert regions on the North American continent, which cannot be used for food production, nonetheless, grow a variety of indigenous floral species which offer, in their chemical composition, possibilities for agroindustrial development. Prospects for utilization of the resources of the Chihuahuan Desert for the production of organic raw materials are presented. Research and development projects presently underway in Mexico for the commercialization of plants such as Guayule (Parthenium argentatum), Creosote Bush (Larrea tridentata), Candelilla (Euphorbia antisyphilitica), and Palma (Yucca filiera), among others, are documented. Raw materials obtained from such plants are characterized, with emphasis on the identification of components of industrial interest. Current bench and pilot plant activities, as well as process and product development requirements, are detailed.

  15. High performance robotic traverse of desert terrain.

    SciTech Connect

    Whittaker, William

    2004-09-01

    This report presents tentative innovations to enable unmanned vehicle guidance for a class of off-road traverse at sustained speeds greater than 30 miles per hour. Analyses and field trials suggest that even greater navigation speeds might be achieved. The performance calls for innovation in mapping, perception, planning and inertial-referenced stabilization of components, hosted aboard capable locomotion. The innovations are motivated by the challenge of autonomous ground vehicle traverse of 250 miles of desert terrain in less than 10 hours, averaging 30 miles per hour. GPS coverage is assumed to be available with localized blackouts. Terrain and vegetation are assumed to be akin to that of the Mojave Desert. This terrain is interlaced with networks of unimproved roads and trails, which are a key to achieving the high performance mapping, planning and navigation that is presented here.

  16. Consumption of atmospheric methane by desert soils

    USGS Publications Warehouse

    Striegl, R.G.; McConnaughey, T.A.; Thorstenson, D.C.; Weeks, E.P.; Woodward, J.C.

    1992-01-01

    ATMOSPHERIC concentrations of methane, a greenhouse gas, are increasing at a rate of about 1% yr-1 (refs 1-4). Oxidation by methylotrophic bacteria in soil is the largest terrestrial sink for atmospheric CH4, and is estimated to consume about 30?? 1012 g CH4 yr-1 (refs 4-6). Spatial and temporal variability in the rate of soil CH4 consumption are incompletely understood6-19, as are the apparent inhibitory12,13,18 or enhancing20 effects of changes in land use. Dry deserts, which constitute 20% of total land surface, are not currently included in global soil uptake estimates. Here we describe measurements of the rate of uptake of atmospheric CH4 by undisturbed desert soils. We observed rates as great as 4.38 mg CH4 m-2 day-1; 50% of the measured rates were between 0.24 and 0.92 mg CH4 m2 d-1. Uptake of CH4 by desert soil is enhanced by rainfall after an initial soil-drainage period - opposite to the response of temperate forest soils12. Methane is consumed to a depth of about 2 m, allowing for deep removal of atmospheric CH4 if near-surface conditions are unfavourable for consumption. On the basis of an annual average CH4 consumption rate of 0.66 mg CH4 m-2 d-1, we estimate that the global CH4 sink term needs to be increased by about 7 ?? 1012 g yr-1 to account for the contribution of desert soils.

  17. Linking Populus euphratica Hydraulic Redistribution to Diversity Assembly in the Arid Desert Zone of Xinjiang, China

    PubMed Central

    Yang, Xiao-Dong; Zhang, Xue-Ni; Lv, Guang-Hui; Ali, Arshad

    2014-01-01

    The hydraulic redistribution (HR) of deep-rooted plants significantly improves the survival of shallow-rooted shrubs and herbs in arid deserts, which subsequently maintain species diversity. This study was conducted in the Ebinur desert located in the western margin of the Gurbantonggut Desert. Isotope tracing, community investigation and comparison analysis were employed to validate the HR of Populus euphratica and to explore its effects on species richness and abundance. The results showed that, P. euphratica has HR. Shrubs and herbs that grew under the P. euphratica canopy (under community: UC) showed better growth than the ones growing outside (Outside community: OC), exhibiting significantly higher species richness and abundance in UC than OC (p<0.05) along the plant growing season. Species richness and abundance were significantly logarithmically correlated with the P. euphratica crown area in UC (R2 = 0.51 and 0.84, p<0.001). In conclusion, P. euphratica HR significantly ameliorates the water conditions of the shallow soil, which then influences the diversity assembly in arid desert communities. PMID:25275494

  18. Water regime history drives responses of soil Namib Desert microbial communities to wetting events

    PubMed Central

    Frossard, Aline; Ramond, Jean-Baptiste; Seely, Mary; Cowan, Don A.

    2015-01-01

    Despite the dominance of microorganisms in arid soils, the structures and functional dynamics of microbial communities in hot deserts remain largely unresolved. The effects of wetting event frequency and intensity on Namib Desert microbial communities from two soils with different water-regime histories were tested over 36 days. A total of 168 soil microcosms received wetting events mimicking fog, light rain and heavy rainfall, with a parallel “dry condition” control. T-RFLP data showed that the different wetting events affected desert microbial community structures, but these effects were attenuated by the effects related to the long-term adaptation of both fungal and bacterial communities to soil origins (i.e. soil water regime histories). The intensity of the water pulses (i.e. the amount of water added) rather than the frequency of wetting events had greatest effect in shaping bacterial and fungal community structures. In contrast to microbial diversity, microbial activities (enzyme activities) showed very little response to the wetting events and were mainly driven by soil origin. This experiment clearly demonstrates the complexity of microbial community responses to wetting events in hyperarid hot desert soil ecosystems and underlines the dynamism of their indigenous microbial communities. PMID:26195343

  19. Water regime history drives responses of soil Namib Desert microbial communities to wetting events.

    PubMed

    Frossard, Aline; Ramond, Jean-Baptiste; Seely, Mary; Cowan, Don A

    2015-01-01

    Despite the dominance of microorganisms in arid soils, the structures and functional dynamics of microbial communities in hot deserts remain largely unresolved. The effects of wetting event frequency and intensity on Namib Desert microbial communities from two soils with different water-regime histories were tested over 36 days. A total of 168 soil microcosms received wetting events mimicking fog, light rain and heavy rainfall, with a parallel "dry condition" control. T-RFLP data showed that the different wetting events affected desert microbial community structures, but these effects were attenuated by the effects related to the long-term adaptation of both fungal and bacterial communities to soil origins (i.e. soil water regime histories). The intensity of the water pulses (i.e. the amount of water added) rather than the frequency of wetting events had greatest effect in shaping bacterial and fungal community structures. In contrast to microbial diversity, microbial activities (enzyme activities) showed very little response to the wetting events and were mainly driven by soil origin. This experiment clearly demonstrates the complexity of microbial community responses to wetting events in hyperarid hot desert soil ecosystems and underlines the dynamism of their indigenous microbial communities. PMID:26195343

  20. Water regime history drives responses of soil Namib Desert microbial communities to wetting events

    NASA Astrophysics Data System (ADS)

    Frossard, Aline; Ramond, Jean-Baptiste; Seely, Mary; Cowan, Don A.

    2015-07-01

    Despite the dominance of microorganisms in arid soils, the structures and functional dynamics of microbial communities in hot deserts remain largely unresolved. The effects of wetting event frequency and intensity on Namib Desert microbial communities from two soils with different water-regime histories were tested over 36 days. A total of 168 soil microcosms received wetting events mimicking fog, light rain and heavy rainfall, with a parallel “dry condition” control. T-RFLP data showed that the different wetting events affected desert microbial community structures, but these effects were attenuated by the effects related to the long-term adaptation of both fungal and bacterial communities to soil origins (i.e. soil water regime histories). The intensity of the water pulses (i.e. the amount of water added) rather than the frequency of wetting events had greatest effect in shaping bacterial and fungal community structures. In contrast to microbial diversity, microbial activities (enzyme activities) showed very little response to the wetting events and were mainly driven by soil origin. This experiment clearly demonstrates the complexity of microbial community responses to wetting events in hyperarid hot desert soil ecosystems and underlines the dynamism of their indigenous microbial communities.

  1. Range and habitats of the desert tortoise

    USGS Publications Warehouse

    Germano, D.J.; Bury, R.B.; Esque, T.C.; Fritts, T.H.

    1994-01-01

    We determined the current range of the desert tortoise (Gopherus agassizii) based on the available latest data from government agencies, the literature, and our experience. We developed the first detailed range map of this species and summarized information about habitat preferences. New records of occurrences were incorporated, and some peripheral localities of questionable authenticity were deleted. The distribution oCG. agassizii covers the broadest range of latitude, climatic regimes, habitats, and biotic regions of any North American tortoise. The northern portion ofits range is in the Mojave Desert of sDuth"eastern California, southern Nevada, southwestern Utah, and northwestern Arizona. The central portion of the range consists of several subdivisions of the Sonaran Desert in southeastern California, western and southern Arizona, and western Sonora, Mexico. The southern edge of its range is in the semitropical Sinaloan thornscrub and Sinaloan deciduous forest of eastern Sonora and northern Sinaloa, Mexico. This species has marked geogi-aphic differences but seems to construct burrows throughout its range.

  2. Petroleum potential of Western Desert of Egypt

    SciTech Connect

    Wood, D.S.

    1984-09-01

    The Western Desert of Egypt, despite many discouragements, has major potential as a petroleum province. Approximately 150 exploratory wells have discovered nine commercial oil and gas fields, with flows of oil or gas recorded from an additional 21 wells. All discoveries have been in marine inner shelf sandstones and carbonates that range from Aptian to Turonian in age. Potential reservoir rocks are known in Paleozoic to Tertiary sedimentary rocks. Mature source rocks have been recognized in the Devonian and in Jurassic to Upper Cretaceous strata. Despite these favorable factors, in-place reserves of only 800 million bbl of oil and condensate, and up to 1185 bcf of natural gas have been found. Almost all exploration has been limited to the drilling of relatively small onshore structures and no giant fields have been found. New investigations utilizing a broad regional tectonic framework provide a means both of recognizing the more prospective provinces of the Western Desert and for understanding the structural evolution in terms of the timing of growth folding and growth faulting. Particular attention should be given to testing the lower part of the Cretaceous and Jurassic. The Paleozoic section also warrants further attention as demonstrated by a review of drilling results and by indications from gravity data. The new investigations indicate a considerable potential within the Western Desert for discovery of small to moderate-size accumulations of oil and gas. More exploration should test these features, which although high-risk leads, may contain giant fields.

  3. Wind modeling of Chihuahuan Desert dust outbreaks

    NASA Astrophysics Data System (ADS)

    Rivera Rivera, Nancy I.; Gill, Thomas E.; Gebhart, Kristi A.; Hand, Jennifer L.; Bleiweiss, Max P.; Fitzgerald, Rosa M.

    The Chihuahuan Desert region of North America is a significant source of mineral aerosols in the Western Hemisphere, and Chihuahuan Desert dust storms frequently impact the Paso del Norte (El Paso, USA/Ciudad Juarez, Mexico) metropolitan area. A statistical analysis of HYSPLIT back trajectory residence times evaluated airflow into El Paso on all days and on days with synoptic (non-convective) dust events in 2001-2005. The incremental probability—a measure of the areas most likely to have been traversed by air masses arriving at El Paso during dusty days—was only strongly positively associated with the region west-southwest of the city, a zone of known dust source areas. Focused case studies were made of major dust events on 15 April and 15 December 2003. Trajectories approached the surface and MM5 (NCAR/Penn State Mesoscale Model) wind speeds increased at locations consistent with dust sources observed in satellite imagery on those dates. Back trajectory and model analyses suggested that surface cyclones adjacent to the Chihuahuan Desert were associated with the extreme dust events, consistent with previous studies of dust storms in the Southern High Plains to the northeast. The recognition of these meteorological patterns serves as a forecast aid for prediction of dust events likely to impact the Paso del Norte.

  4. The Palm Desert renewable [hydrogen] transportation system

    SciTech Connect

    Chamberlin, C.E.; Lehman, P.

    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.

  5. Television Quiz Show Simulation

    ERIC Educational Resources Information Center

    Hill, Jonnie Lynn

    2007-01-01

    This article explores the simulation of four television quiz shows for students in China studying English as a foreign language (EFL). It discusses the adaptation and implementation of television quiz shows and how the students reacted to them.

  6. Poverty reduction in Africa

    PubMed Central

    Collier, Paul

    2007-01-01

    Poverty in Africa has been rising for the last quarter-century, while it has been falling in the rest of the developing world. Africa's distinctive problem is that its economies have not been growing. This article attempts to synthesize a range of recent research to account for this failure of the growth process. I argue that the reasons lie not in African peculiarities but rather in geographic features that globally cause problems but that are disproportionately pronounced in Africa. These features interact to create three distinct challenges that are likely to require international interventions beyond the conventional reliance on aid. PMID:17942702

  7. An experimental analysis of granivory in desert ecosystems

    SciTech Connect

    Davidson, D.W.

    1988-01-01

    In our studies of desert granivore ecology, we have outlined the network of interaction pathways linking granivore and resource species in a Chihuahuan Desert Ecosystem. Here, a major fraction of the primary productivity takes the form of the seeds of annual plants. These seeds support two major resident taxa of desert granivores, ants and rodents. Population responses to removal of various taxa of granivores or seasonal classes of resource species are described.

  8. Quantifying the role of biosphere-atmosphere feedbacks in climate change: coupled model simulations for 6000 years BP and comparison with palaeodata for northern Eurasia and northern Africa

    NASA Astrophysics Data System (ADS)

    Texier, D.; de Noblet, N.; Harrison, S. P.; Haxeltine, A.; Jolly, D.; Joussaume, S.; Laarif, F.; Prentice, I. C.; Tarasov, P.

    The LMD AGCM was iteratively coupled to the global BIOME1 model in order to explore the role of vegetation-climate interactions in response to mid-Holocene (6000 y BP) orbital forcing. The sea-surface temperature and sea-ice distribution used were present-day and CO2 concentration was pre-industrial. The land surface was initially prescribed with present-day vegetation. Initial climate ``anomalies'' (differences between AGCM results for 6000 y BP and control) were used to drive BIOME1; the simulated vegetation was provided to a further AGCM run, and so on. Results after five iterations were compared to the initial results in order to identify vegetation feedbacks. These were centred on regions showing strong initial responses. The orbitally induced high-latitude summer warming, and the intensification and extension of Northern Hemisphere tropical monsoons, were both amplified by vegetation feedbacks. Vegetation feedbacks were smaller than the initial orbital effects for most regions and seasons, but in West Africa the summer precipitation increase more than doubled in response to changes in vegetation. In the last iteration, global tundra area was reduced by 25% and the southern limit of the Sahara desert was shifted 2.5°N north (to 18°N) relative to today. These results were compared with 6000 y BP observational data recording forest-tundra boundary changes in northern Eurasia and savana-desert boundary changes in northern Africa. Although the inclusion of vegetation feedbacks improved the qualitative agreement between the model results and the data, the simulated changes were still insufficient, perhaps due to the lack of ocean-surface feedbacks.

  9. Synoptic climatology of major floods in the Negev Desert, Israel

    NASA Astrophysics Data System (ADS)

    Kahana, Ron; Ziv, Baruch; Enzel, Yehouda; Dayan, Uri

    2002-06-01

    This study examines the extent to which the floods in the Negev Desert, an area that constitutes the southern half of Israel, are not the outcome of purely local weather conditions but are, rather, the result of distinct synoptic-scale events. This was done through compiling and analysing a hydro-climatological database of all the major floods in the Negev, and then categorizing them manually into synoptic types that cause the major floods.The type analysis is based on the US National Meteorological Center data sets with 2.5° × 2.5° resolution analysed by GrADS. Data were compiled and studied for 52 floods for the period 1965-94, with peak discharge above the magnitude of 5 year recurrence intervals (RI > 5 years) in at least one drainage basin.Distinct extreme synoptic patterns are indeed associated with 42 of the 52 floods. They were grouped into four synoptic types, two of which were associated with 37 events: (a) an active Red Sea trough, defined as a surface trough extending from East Africa through the Red Sea toward the eastern Mediterranean, accompanied by a pronounced trough at the 500 hPa level over eastern Egypt: (b) a Syrian low, defined as a well-developed Mediterranean cyclone accompanied by a pronounced upper-level trough, both located over Syria. Each of the four synoptic types has its own evolution course, and a unique seasonal and spatial distribution of its associated flooded basins.These findings imply that the major floods in the Negev can be considered as signatures of exceptional synoptic-scale evolutions, and that major floods reflect extreme climatic events. Our results indicate that it is possible to use a set of dynamic and thermodynamic variables for predicting the occurrence and location of major flash floods.

  10. America's Atomic Army: The Historical Archaeology of Camp Desert Rock

    SciTech Connect

    Susan R. Edwards

    2007-11-02

    Established in 1951, Camp Desert Rock served as the training ground for America's 'Atomic Army'. For the next six years, U.S. ground troops traveled to the Nevada desert to participate in military maneuvers during atmospheric atomic weapons testing. Nearly 60,000 soldiers received physical and psychological training in atomic warfare. Abandoned when atmospheric testing ended, Camp Desert Rock was dismantled and its buildings moved to other locations. Today, the camp appears as a sterile expanse of desert marked by rock-lined tent platforms, concrete foundations, and trash scatters. Although visually unimposing, the site is rich with the history of America's nuclear testing program.

  11. Nationwide desert highway assessment: a case study in China.

    PubMed

    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. PMID:21845155

  12. Role of pioneer species in revegetation of disturbed desert areas

    SciTech Connect

    Wallace, A.; Romney, E.M.

    1980-01-01

    The northern Mojave Desert, as are many deserts, is characterized in part by small fertile islands in which exist individual shrub clumps each containing two or more plants. These fertile sites promote characteristic organization of both plant and animal activity in the desert. Destruction of these fertile sites make revegetation extremely difficult because most seedlings germinate in these sites. Some pioneer species do, however, germinate and survive in the bare areas between the fertile sites. Four such species in the northern Mojave Desert are Acamptopappus shockleyi Gray, Lepidium fremontii Wats., Sphaeralcea ambigua Gray, and Atriplex confertifolia (Torr. and Frem.) Wats. These four-species may have a role in starting new fertile islands.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    USGS Publications Warehouse

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

    1993-01-01

    hot desert areas are minimal and, according to a recent U.S. General Accounting Office study (1991), local economies do not depend on the grazing of public lands for economic survival. The economic analysis describes the economy in 1990, prior to designation, and estimates the effects of designation. The report estimates those incremental effects attributable to critical habitat designation. Impacts attributable to listing the species were not considered in this analysis. Although critical habitat units have been designated in nine counties, two counties are omitted from the economic analysis because of the small proportion of critical habitat acreage they include. Three key activities (cattle grazing, mineral extraction, and off-road vehicle use) were studied in detail. Even if livestock grazing and commercial off-road racing events were eliminated in the proposed critical habitat units, the potential incremental regional economic impacts would be extremely small. The findings in the report do not include the assumption that mining would be eliminated from critical habitat units, but rather that consultation may result in added mitigation and/or relocation of features. Studies show that society will realize benefits from preservation of species and ecosystems. Survey-based studies confirm that benefits exist and are substantial in size, although these benefits often are not measured in traditional economic markets. The total benefit to society of desert tortoise preservation includes several components. Biodiversity in the Mojave and Colorado Deserts will be improved, some recreation values may increase, and gains in intrinsic value will be realized. Critical habitat designation should result in the loss of fewer than 425 total jobs in the seven counties. These include 340 direct ranching jobs and 85 indirect jobs in other industries. This estimated employment loss will not be permanent for most laborers, it is anticipated that over 85% will be reemployed within two

  15. Women in Africa

    ERIC Educational Resources Information Center

    Spitzer, Manon

    1975-01-01

    The role and status of women in Africa has changed profoundly since the end of the colonial period. Many differences in women's status and role are based on geography, history, nationality, political and socioeconomic systems, culture, and religion. (JR)

  16. The Wordpath Show.

    ERIC Educational Resources Information Center

    Anderton, Alice

    The Intertribal Wordpath Society is a nonprofit educational corporation formed to promote the teaching, status, awareness, and use of Oklahoma Indian languages. The Society produces "Wordpath," a weekly 30-minute public access television show about Oklahoma Indian languages and the people who are teaching and preserving them. The show aims to…

  17. Age and isotopic constraints on pleistocene pluvial episodes in the Western Desert, Egypt.

    SciTech Connect

    Crombie, M. K.; Arvidson, R. E.; Sturchio, N. C.; El Alfy, Z.; Abu Zeid, K.; Environmental Research; Washington Univ.; Egyptian Geological Survey and Mining Authority

    1997-01-01

    North Africa has undergone drastic climatic changes over the past several hundred thousand years. The timing of humid intervals called pluvials was investigated by uranium-series disequilibrium dating of travertines from the Kurkur Oasis, Western Desert, Egypt. The youngest and best dated travertines (70-160 ka) are found in Wadi Kurkur and include spring and lacustrine units exposed as 2 to 3 m high terraces. Travertines having an age of approximately 191-220 ka are exposed by differential erosion as linear mounds produced by spring systems over fracture zones in ancient wadis. The oldest travertines, having ages >260 ka, are extensive, cap limestone units above the oasis, and were deposited in paludal and lacustrine environments. Oxygen isotope ratios were measured for the wadi travertines ({delta}{sup 18}O values ranging from 16.7 to 19.1{per_thousand} SMOW) and for spring mound travertines (18.5-20.5{per_thousand}). Equilibrium oxygen isotope fractionation calculations indicate that the Kurkur travertines were deposited from waters having {delta}{sup 18}O values similar to ancient Western Desert groundwaters ({approx} -11{per_thousand}). The ages of the travertines correspond to times of monsoonal maxima, eustatic sea level high stands and interglacial maxima. Rainfall producing these groundwaters (and travertines) was significantly fractionated during atmospheric transport, in contrast to modern meteoric waters (-2.09{per_thousand}), implying a distant source for the pluvial waters. Increased precipitation, recharge of Western Desert groundwaters, and resultant travertine deposition are interpreted to be consequences of Milankovitch insolation cycle forcing, through enhanced Atlantic and Indian Ocean monsoons during interglacial time periods.

  18. Observation (Geomorphology) of the largest mega sand of central Iran Desert, Lut, Using Remote sensing data

    NASA Astrophysics Data System (ADS)

    Abdollhai, A.; Yamani, M.

    2009-04-01

    It is believed that the Lut desert features, in elevation and volume, are unique (even in the world) in central Iran. These huge morphological features will be an excellent Sedimentary Archive in quaternary explaining the climate condition and distribution of desert surface features on the earth, meanwhile the attention less has gone on the Aeolian features in the area of interest because it is hard to access. This papers aims to present these unique features by remote sensing data. Remote sensing data including, Irs Aster, Srtm and Arial photograph data were used to measure the dune migration and other aspects of desert environment. Sand dune morphology encompasses almost all typical desert features including single, linear, pyramid, star sand and others. compressing remote sensing data between 1955 and 2000 approves the single Barkhan is being migrated at the rate of 22.65 M per year and accelerate at the last period between 2000 and 2008. A large part of scarce vegetation represents active and rapid migration creating huge morphological features. Linear dune elevation reaches more than 430 M and shows the highest elevation of dune activity on Earth. To evaluate surface temperature Aster 08 production were used. The surface temperature on the sand is probably the highest temperature received by solar energy around 84 Celsius degrees resulting High thermal cell in central Iran. This causes to create huge morphological features in central Iran reaching more than 400 m high due to repetition and reactivation under closed circumstance system.

  19. Leaf nitrogen and phosphorus of temperate desert plants in response to climate and soil nutrient availability

    PubMed Central

    He, Mingzhu; Dijkstra, Feike A.; Zhang, Ke; Li, Xinrong; Tan, Huijuan; Gao, Yanhong; Li, Gang

    2014-01-01

    In desert ecosystems, plant growth and nutrient uptake are restricted by availability of soil nitrogen (N) and phosphorus (P). The effects of both climate and soil nutrient conditions on N and P concentrations among desert plant life forms (annual, perennial and shrub) remain unclear. We assessed leaf N and P levels of 54 desert plants and measured the corresponding soil N and P in shallow (0–10 cm), middle (10–40 cm) and deep soil layers (40–100 cm), at 52 sites in a temperate desert of northwest China. Leaf P and N:P ratios varied markedly among life forms. Leaf P was higher in annuals and perennials than in shrubs. Leaf N and P showed a negative relationship with mean annual temperature (MAT) and no relationship with mean annual precipitation (MAP), but a positive relationship with soil P. Leaf P of shrubs was positively related to soil P in the deep soil. Our study indicated that leaf N and P across the three life forms were influenced by soil P. Deep-rooted plants may enhance the availability of P in the surface soil facilitating growth of shallow-rooted life forms in this N and P limited system, but further research is warranted on this aspect. PMID:25373739

  20. Translocation as a conservation tool for Agassiz's desert tortoises: survivorship, reproduction, and movements

    USGS Publications Warehouse

    Nussear, K.E.; Tracy, C.R.; Medica, P.A.; Wilson, D.S.; Marlow, R.W.; Corn, P.S.

    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 animals to upper elevation areas. We measured survivorship, reproduction, and movements of translocated and resident animals at each site. Survivorship was not significantly different between translocated and resident animals within and among sites, and survivorship was greater overall during non-drought years. The number of eggs produced by tortoises was similar for translocated and resident females, but differed among sites. Animals translocated to atypical habitat generally moved until they reached vegetation communities more typical of desert tortoise habitat. Even within typical tortoise habitat, tortoises tended to move greater distances in the first year after translocation than did residents, but their movements in the second or third year after translocation were indistinguishable from those of resident tortoises. Our data show that tortoises translocated into typical Mojave desert scrub habitats perform well; however, the large first-year movements of translocated tortoises have important management implications. Projects that employ translocations must consider how much area will be needed to contain translocated tortoises and whether roads need fencing to prevent the loss of animals.

  1. Satellite-based estimates of groundwater depletion in the Badain Jaran Desert, China

    NASA Astrophysics Data System (ADS)

    Jiao, Jiu Jimmy; Zhang, Xiaotao; Wang, Xusheng

    2015-03-01

    Despite prevailing dry conditions, groundwater-fed lakes are found among the earth's tallest sand dunes in the Badain Jaran Desert, China. Indirect evidence suggests that some lakes are shrinking. However, relatively few studies have been carried out to assess the regional groundwater conditions and the fate of the lakes due to the remoteness and severity of the desert environment. Here we use satellite information to demonstrate an ongoing slow decrease in both lake level and groundwater storage. Specifically, we use Ice, Cloud, and land Elevation Satellite altimetry data to quantify water levels of the lakes and show overall decreases from 2003 to 2009. We also use water storage changes from the Gravity Recovery and Climate Experiment and simulated soil and water changes from the Global Land Data Assimilation System to demonstrate long-term groundwater depletion in the desert. Rainfall increase driven by climate change has increased soil water and groundwater storage to a certain degree but not enough to compensate for the long-term decline. If countermeasures are not taken to control the pumping, many lakes will continue to shrink, causing an ecological and environmental disaster in the fragile desert oases.

  2. Satellite-based estimates of groundwater depletion in the Badain Jaran Desert, China.

    PubMed

    Jiao, Jiu Jimmy; Zhang, Xiaotao; Wang, Xusheng

    2015-01-01

    Despite prevailing dry conditions, groundwater-fed lakes are found among the earth's tallest sand dunes in the Badain Jaran Desert, China. Indirect evidence suggests that some lakes are shrinking. However, relatively few studies have been carried out to assess the regional groundwater conditions and the fate of the lakes due to the remoteness and severity of the desert environment. Here we use satellite information to demonstrate an ongoing slow decrease in both lake level and groundwater storage. Specifically, we use Ice, Cloud, and land Elevation Satellite altimetry data to quantify water levels of the lakes and show overall decreases from 2003 to 2009. We also use water storage changes from the Gravity Recovery and Climate Experiment and simulated soil and water changes from the Global Land Data Assimilation System to demonstrate long-term groundwater depletion in the desert. Rainfall increase driven by climate change has increased soil water and groundwater storage to a certain degree but not enough to compensate for the long-term decline. If countermeasures are not taken to control the pumping, many lakes will continue to shrink, causing an ecological and environmental disaster in the fragile desert oases. PMID:25760683

  3. Has climatic warming altered spring flowering date of Sonoran Desert shrubs?

    USGS Publications Warehouse

    Bowers, Janice E.

    2007-01-01

    With global warming, flowering at many locations has shifted toward earlier dates of bloom. A steady increase in average annual temperature since the late 1890s makes it likely that flowering also has advanced in the northern Sonoran Desert of the southwestern United States and northwestern Mexico. In this study, phenological models were used to predict annual date of spring bloom in the northern Sonoran Desert from 1894 to 2004; then, herbarium specimens were assessed for objective evidence of the predicted shift in flowering time. The phenological models were derived from known flowering requirements (triggers and heat sums) of Sonoran Desert shrubs. According to the models, flowering might have advanced by 20-41 d from 1894 to 2004. Analysis of herbarium specimens collected during the 20th century supported the model predictions. Over time, there was a significant increase in the proportion of shrub specimens collected in flower in March and a significant decrease in the proportion collected in May. Thus, the flowering curve - the proportion of individuals in flower in each spring month - shifted toward the start of the calendar year between 1900 and 1999. This shift could not be explained by collection activity: collectors showed no tendency to be active earlier in the year as time went on, nor did activity toward the end of spring decline in recent decades. Earlier bloom eventually could have substantial impacts on plant and animal communities in the Sonoran Desert, especially on migratory hummingbirds and population dynamics of shrubs.

  4. Profile of South Africa

    SciTech Connect

    Fox, G.J.; Tonneson, L.C.

    1996-08-01

    A broad overview of the Republic of South Africa`s nuclear energy program is presented. Economic aspects are the main focus of the article, and numerical data is provided for electricity generation and use and uranium production. The role of the molecular laser isotope process for enrichment is discussed. The research reactor program, waste disposal and decommissioning, mining history, uranium production, and nonproliferation policy are other highlighted topics.

  5. Astronomy Landscape in Africa

    NASA Astrophysics Data System (ADS)

    Nemaungani, Takalani

    2015-01-01

    The vision for astronomy in Africa is embedded in the African Space Policy of the African Union in early 2014. The vision is about positioning Africa as an emerging hub for astronomy sciences and facilities. Africa recognized the need to take advantage of its natural resource, the geographical advantage of the clear southern skies and pristine sites for astronomy. The Pan African University (PAU) initiative also presents an opportunity as a post-graduate training and research network of university nodes in five regions of Africa and supported by the African Union. The Southern African node based in South Africa concentrates on space sciences which also includes astronomy. The PAU aims to provide the opportunity for advanced graduate training and postgraduate research to high-performing African students. Objectives also include promoting mobility of students and teachers and harmonizing programs and degrees.A number of astronomy initiatives have burgeoned in the Southern African region and these include the Southern Africa Largest Optical Telescope (SALT), HESS (High Energy Stereoscopic System), the SKA (Square Kilometre Array) and the AVN (African Very Long Baseline Interferometer Network). There is a growing appetite for astronomy sciences in Africa. In East Africa, the astronomy community is well organized and is growing - the East African Astronomical society (EAAS) held its successful fourth annual conference since 2010 on 30 June to 04 July 2014 at the University of Rwanda. Centred around the 'Role of Astronomy in Socio-Economic Transformation,' this conference aimed at strengthening capacity building in Astronomy, Astrophysics and Space Science in general, while providing a forum for astronomers from the region to train young and upcoming scientists.

  6. Usutu virus in Africa.

    PubMed

    Nikolay, Birgit; Diallo, Mawlouth; Boye, Cheikh Saad Bouh; Sall, Amadou Alpha

    2011-11-01

    Usutu virus (USUV) was discovered in South Africa in 1959. Since then, it has been reported in several African countries including Senegal, Central African Republic, Nigeria, Uganda, Burkina Faso, Cote d'Ivoire, and Morocco. In 2001, USUV has been identified for the first time outside of Africa, namely in Europe, where it caused a significant mortality among blackbirds in Vienna, Austria. In 2009, the first two human cases of USUV infection in Europe have been reported in Italy, causing encephalitis in immunocompromised patients. The host range in Africa includes mainly Culex mosquitoes, birds, and also humans with one benign and one severe case. Given its role as a potential human pathogen and the similar appearance compared with other emerging arboviruses, it is essential to investigate the natural history and ecology of USUV in Africa. In this regard, we review the emergence of USUV in Africa, summarizing data about isolations, host range, and potential vectors, which should help to improve our understanding of the factors underlying the circulation of USUV in Europe and Africa. PMID:21767160

  7. Identifying Vulnerability Regions of Dust Outbreaks in East Asian Desert Areas: using SMOS, MODIS, and GLDAS

    NASA Astrophysics Data System (ADS)

    Choi, M.; Kim, H.; Cho, E.

    2015-12-01

    It is now well understood that water, carbon, and energy fluxes at the surface/atmosphere interface are highly dependent on soil moisture (SM). In addition, SM is required to be used as realistic initial states for the SM variables, for climate predictions and weather forecasting. As satellite remote-sensing have developed greatly, global surface SM datasets have been produced based on several satellites. Three satellites-based SM datasets were inter-compared under different land-cover over East Asia to select most reliable satellite for retrieving SM datasets in dust source regions. We estimated satellite sensors with 1) Soil Moisture and Ocean Salinity (SMOS), 2) Advanced Scatterometer (ASCAT), and 3) Advanced Microwave Scanning Radiometer 2 (AMSR2) and Global Land Data Assimilation System (GLDAS) was used as reference datasets. In case of arid areas (desert and semi-desert), SMOS-retrieved SM products showed best accuracy (radiometers have generally exhibited a better performance than scatterometers in dry areas). For this reason, SMOS SM products were utilized to retrieve SM over desert areas. The regions that are susceptible to dust outbreaks were investigated using the dust outbreak probability functions (DOPF). Based on DOPF, about 58% of the total number of dust events occurred in regions with a high level of vulnerability where dust outbreaks were predicted with a probability higher than 60%. The SMOS-based DOPF was calculated to be about 62.4% of the dust outbreak vulnerability (DOV) level of the desert areas. Interestingly, East Asian deserts showed an increasing tendency for a high level of DOV during the study period. Those areas were judged to be sources from which dust could be transported to neighboring countries (e.g., Korea and Japan) which can lead to Asian dust storms. These results may allow us to predict trends of dust outbreaks in order to prepare the corresponding disaster response systems.

  8. Mesozoic rift basins in western desert of Egypt, their southern extension and impact on future exploration

    SciTech Connect

    Taha, M.A. )

    1988-08-01

    Rift basins are a primary target of exploration in east, central, and west Africa. These intracratonic rift basins range in age from the Triassic to the Neogene and are filled with lagoonal-lacustrine sand-shale sequences. Several rift basins may be present in the Western Desert of Egypt. In the northeastern African platform, the Mesozoic Tethyan strand lines were previously interpreted to have limited southern extension onto the continent. This concept, based upon a relatively limited amount of subsurface data, has directed and focused the exploration for oil and gas to the northernmost 120 km of the Western Desert of Egypt. Recent well and geophysical data indicate a southerly extension of mesozoic rift basins several hundred kilometers inland from the Mediterranean Sea. Shushan/Faghur and Abu Gharadig/Bahrein basins may represent subparallel Mesozoic basins, trending northeast-southwest. Marine Oxfordian-Kimmeridgian sediments were recently reported from wells drilled approximately 500 km south of the present-day Mediterranean shoreline. The link of these basins with the Sirte basin to the southwest in Libya is not well understood. Exploration is needed to evaluate the hydrocarbon potential of such basins.

  9. Selection and characterization of Saharan and Arabian desert sites for the calibration of optical satellite sensors

    SciTech Connect

    Cosnefroy, H.; Briottet, X.; Leroy, M.

    1996-10-01

    Desert areas are good candidates for the assessment of multitemporal, multiband, or multiangular calibration of optical satellite sensors. This article describes a selection procedure of desert sites in North Africa and Saudi Arabia, of size 100 x 100 km{sup 2}, using a criterion of spatial uniformity in a series of Meteosat-4 visible data. Twenty such sites are selected with a spatial uniformity better than 3% in relative value in a multitemporal series of cloud-free images. These sites are among the driest sites in the world. Their meteorological properties are here described in terms of cloud cover with ISCCP data and precipitation using data from a network of meteorological stations. Most of the selected sites are large sand seas, the geomorphology of which can be characterized with Spot data. The temporal stability of the spatially averaged reflectance of each selected site is investigated at seasonal and hourly time scales with multitemporal series of Meteosat-4 data. It is found that the temporal variations, of typical peak-to-peak amplitude 8--15% in relative value, are mostly controlled by directional effects. Once the directional effects are removed, the residual rms variations, representative of random temporal variability, are on the order of 1--2% in relative value. The suitability of use of these selected sites in routine operational calibration procedures is briefly discussed.

  10. Direct radiative effects induced by intense desert dust outbreaks over the broader Mediterranean basin

    NASA Astrophysics Data System (ADS)

    Gkikas, Antonis; Obiso, Vincenzo; Vendrell, Lluis; Basart, Sara; Jorba, Oriol; Pérez Garcia-Pando, Carlos; Hatzianastassiou, Nikos; Gassó, Santiago; Baldasano, Jose Maria

    2016-04-01

    Throughout the year, under favorable conditions, massive loads of mineral particles originating in the northern African and Middle East deserts are transported over the Mediterranean basin. Due to their composition and size, dust aerosols perturb the Earth-Atmosphere system's energy budget interacting directly with the shortwave (SW) and longwave (LW) radiation. The present study aims to compute the Mediterranean dust outbreaks' direct radiative effects (DREs) as well as to assess the effect of including dust DREs in numerical simulations of a regional model. To this aim, 20 intense dust outbreaks have been selected based on their spatial coverage and intensity. Their identification, over the period 2000-2013, has been achieved through an objective and dynamic algorithm which utilizes as inputs daily satellite retrievals derived by the MODIS-Terra, EP-TOMS and OMI-Aura sensors. For each outbreak, two simulations of the NMMB/BSC-Dust model were made for a forecast period of 84 hours, with the model initialized at 00 UTC of the day when the dust outbreak was ignited, activating (RADON) and deactivating (RADOFF) dust-radiation interactions. The simulation domain covers the northern Africa, the Middle East and Europe at 0.25° x 0.25° horizontal resolution, for 40 hybrid sigma pressure levels up to 50 hPa. The instantaneous and regional DREs have been calculated at the top of the atmosphere (TOA), into the atmosphere (ATMAB), and at surface, for the downwelling (SURF) and the absorbed (NETSURF) radiation, for the SW, LW and NET (SW+LW) radiation. The interaction between dust aerosols and NET radiation, locally leads to an atmospheric warming (DREATMAB) by up to 150 Wm-2, a surface cooling (DRENETSURF) by up to 250 Wm-2 and a reduction of the downwelling radiation at the surface (DRESURF) by up to 300 Wm-2. At TOA, DREs are mainly negative (down to -150 Wm-2) indicating a cooling of the Earth-Atmosphere system, although positive values (up to 50 Wm-2) are encountered

  11. A Holographic Road Show.

    ERIC Educational Resources Information Center

    Kirkpatrick, Larry D.; Rugheimer, Mac

    1979-01-01

    Describes the viewing sessions and the holograms of a holographic road show. The traveling exhibits, believed to stimulate interest in physics, include a wide variety of holograms and demonstrate several physical principles. (GA)

  12. Impact of desert dust on the biogeochemistry of phosphorus in terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Okin, Gregory S.; Mahowald, Natalie; Chadwick, Oliver A.; Artaxo, Paulo

    2004-06-01

    Leaching, biomass removal, and partitioning of phosphorus (P) into reservoirs not available to plants can limit the long-term productivity of terrestrial ecosystems. We evaluate the importance of atmospheric P inputs to the world's soils by estimating the total soil P turnover time with respect to dustborne P additions. Estimated turnover times range from ˜104 to ˜107 years. Our estimates provide a unique perspective on the importance and patterns of aeolian deposition to terrestrial landscapes. Dust source regions are areas of intense soil P cycling on large scales, but are too water-limited for this rapid cycling to have a major influence on ecosystem dynamics. By contrast, semiarid desert margins receive significant aeolian P from neighboring deserts and are likely influenced by dustborne P additions for the long-term maintenance of productivity. This is particularly true for the semiarid steppes of Africa and Eurasia. The prevalence of large dust sources in Africa and Eurasia indicates that these areas may generally be more influenced by dustborne P additions than soils in the Americas. Significant western hemisphere exceptions to this pattern occur on very old landscapes, such as the forests of the southeastern United States and the Amazon Basin. The Amazon Basin is highly dependent on aeolian deposition for the maintenance of long-term productivity. Dust deposition to terrestrial environments has not been constant with time. Variability in past P deposition related to geologically recent climate change may provide the strongest controls on present and future soil P in the Amazon and elsewhere.

  13. Transport aloft drives peak ozone in the Mojave Desert

    NASA Astrophysics Data System (ADS)

    VanCuren, Richard

    2015-05-01

    Transport of anthropogenic pollution eastward out of the Los Angeles megacity region in California has been periodically observed to reach the Colorado River and the Colorado Plateau region beyond. In the 1980s, anthropogenic halocarbon tracers measured in and near the Las Angeles urban area and at a mountain-top site near the Colorado River, 400 km downwind, were shown to have a correlated seven-day cycle explainable by transport from the urban area with a time lag of 1-2 days. Recent short term springtime intensive studies using aircraft observations and regional modeling of long range transport of ozone from the Southern California megacity region showed frequent and persistent ozone impacts at surface sites across the Colorado Plateau and Southern Rocky Mountain region, at distances up to 1500 km, also with time lags of 1-2 days. However, the timing of ozone peaks at low altitude monitoring sites within the Mojave Desert, at distances from 100 to 400 km from the South Coast and San Joaquin Valley ozone source regions, does not show the expected time-lag behavior seen in the larger transport studies. This discrepancy is explained by recognizing ozone transport across the Mojave Desert to occur in a persistent layer of polluted air in the lower free troposphere with a base level at approximately 1 km MSL. This layer impacts elevated downwind sites directly, but only influences low altitude surface ozone maxima through deep afternoon mixing. Pollutants in this elevated layer derive from California source regions (the Los Angeles megacity region and the intensive agricultural region of the San Joaquin Valley), from long-range transport from Asia, and stratospheric down-mixing. Recognition of the role of afternoon mixing during spring and summer over the Mojave explains and expands the significance of previously published reports of ozone and other pollutants observed in and over the Mojave Desert, and resolves an apparent paradox in the timing of ozone peaks due to

  14. Analysis of channel evolution characteristics in the Hobq Desert reach of the Yellow River (1962-2000)

    NASA Astrophysics Data System (ADS)

    Pan, Baotian; Guan, Qingyu; Liu, Zibian; Gao, Hongshan

    2015-12-01

    A series of problems, resulting from sediment deposition and channel silting, have occurred on the Hetao Plain as a result of changes to the Hobq Desert reach of the Yellow River. Therefore, improved research on channel evolution in this reach is vitally important. Using profile data from 80 channel cross-sections obtained in 1962, 1982, 1991 and 2000 from the Yellow River in the Hobq Desert, we showed that there was serious sediment deposition here (especially for the tributary section in the eastern desert) and that maximum sediment deposition occurred during 1982-1991. As sediment was deposited along the mobile channel, the channel trunk shrank and moved to the north. The characteristics of river channel evolution are dramatically different between the western and the eastern Hobq Desert reaches of the Yellow River, which include desert and the tributary sections, respectively. Erosion mainly occurred in the desert section, whereas sediment deposition occurred in the tributary section, with peak values at the mouths of on Yellow River tributaries. The desert section had a larger average erosion rate and smaller accumulation rate than the tributary section. The influences of tectonic movement and stream gradient on channel evolution in this fluvial reach were minimal. The sediment inputs from ten Yellow River tributaries (especially during flood seasons) have dominated channel evolution in these tributaries. The building of artificial levées has intensified sediment deposition in the channel, whereas the reduction of mainstream discharge (especially in the flood seasons), caused by the operation of reservoirs and water diversion activities (such as for agricultural irrigation), has further intensified the sediment deposition in the river channel.

  15. The densest meteorite collection area in hot deserts: The San Juan meteorite field (Atacama Desert, Chile)

    NASA Astrophysics Data System (ADS)

    Gattacceca, Jérôme; Valenzuela, Millarca; Uehara, Minoru; Jull, A. J. Timothy; Giscard, Marlène; Rochette, Pierre; Braucher, Régis; Suavet, Clement; Gounelle, Matthieu; Morata, Diego; Munayco, Pablo; Bourot-Denise, Michèle; Bourles, Didier; Demory, François

    2011-09-01

    Abstract- We describe the geological, morphological, and climatic setting of the San Juan meteorite collection area in the Central Depression of the Atacama Desert (Chile). Our recovery activities yielded 48 meteorites corresponding to a minimum of 36 different falls within a 3.88 km2 area. The recovery density is in the range 9-12 falls km-2 depending on pairing, making it the densest among meteorite collection areas in hot deserts. This high meteorite concentration is linked to the long-standing hyperaridity of the area, the stability of the surface pebbles (> Ma), and very low erosion rates of surface pebbles (approximately 30 cm Ma-1 maximum). The San Juan meteorite population is characterized by old terrestrial ages that range from zero to beyond 40 ka, and limited weathering compared with other dense collection areas in hot desert. Chemical weathering in San Juan is slow and mainly controlled by the initial porosity of meteorites. As in the Antarctic and other hot deserts, there is an overabundance of H chondrites and a shortage of LL chondrites compared with the modern falls population, suggesting a recent (< few ka) change in the composition of the meteorite flux to Earth.

  16. Extensional collapse along the Sevier Desert reflection, northern Sevier Desert basin, western United States

    NASA Astrophysics Data System (ADS)

    Coogan, James C.; Decelles, Peter G.

    1996-10-01

    Newly released and previously published seismic reflection data from the northern Sevier Desert basin provide a complete seismic transect between the tilted western margin of the basin and the eastern breakaway zone. When tied to well and surface age data, the transect delineates a continuum of extensional fault and basin fill geometries that developed between late Oligocene and Pleistocene time across the basin. A minimum of 18 km of top-to-the-west normal displacement is estimated across the Sevier Desert from only the most conspicuous growth geometries and offsets across listric normal faults that sole downward into the Sevier Desert reflection (SDR). The SDR clearly marks a normal fault zone beneath the entire basin, where stratal truncations are imaged for 50% of the 39 km length of the reflection east of the Cricket Mountains block. Restoration of extensional displacement along this entire 39 km fault length is necessary to reconstruct the pre-Oligocene configuration and erosion level of Sevier thrust sheets across the Sevier Desert area. The SDR normal fault zone underlies the former topographic crest of the Sevier orogenic belt, where it accommodated extensional collapse after cessation of regional contractile tectonism.

  17. Genetic structure and differention of Suaeda acuminata population in oasis-desert transitional zone in Fukang, Xinjiang, China

    NASA Astrophysics Data System (ADS)

    Wang, Xumai; Xu, Li; Zhang, Linjing; Yue, Ming; Zhao, Guifang; Gu, Fengxue; Pan, Xiaoling

    2003-07-01

    RAPD technique was applied to study intraspecific genetic polymorphism and differentiation of Suaeda acuminata populations in oasis-desert transitional zone in Fukang, Xinjiang. By analysis of RAPD data, higher genetic variability was found in the populations of S. acuminata, with a percentage of polymorphic loci of 98.9%. Both estimations by Shannon diversity index and by Nei's gene diversity index from RAPD data, it was found identically that about 72% of molecular variation existed within the subpopulations, while about 28% of which existed among subpopulations. Analysis of genetic identity, genetic distance and cluster analysis showed that genetic differentiation has taken place in the populations of Suaeda acuminata in oasis-desert transitional zone in Fukang, Xinjiang, China. The correlation analytical result between the soil factures and the genetic diversity indicted that there was a significant positive relation between genetic diversity and concentrations of Mg++, conductivity (CO) and absorbed water(W) in soil, while there was no significant relation between genetic distance among subpopulations and geographical distance. Analysis of genetic identity, genetic distance and cluster analysis between the five subpopulations showed that genetic differentiation has taken place in the population of Suaeda acuminata in oasis-desert transitional zone in Fukang, Xinjiang. No correlation existed between genetic distance among subpopulations and their locations in oasis-desert transitional zone. Adaptation to its habitats and restricted gene flow among subpopulations may be a cause of genetic differentiation of Suaeda acuminata population in oasis-desert transitional zone in Fukang, Xinjiang.

  18. Genomic insights into salt adaptation in a desert poplar

    SciTech Connect

    Ma, Tao; Wang, Junyi; Zhou, Gongke; Yue, Zhen; Hu, Quanjun; Chen, Yan; Liu, Bingbing; Qiu, Qiang; Wang, Zhuo; Zhang, Jian; Wang, Kun; Jaing, Dechun; Gou, Caiyun; Yu, Lili; Zhan, Dongliang; Zhou, Ran; Luo, Wenchun; Ma, Hui; Yang, Yongzhi; Pan, Shengkai; Fang, Dongming; Luo, Yadan; Wang, Xia; Wang, Gaini; Wang, Juan; Wang, Qian; Lu, Xu; Chen, Zhe; Liu, Jinchao; Lu, Yao; Yin, Ye; Yang, Huanming; Abbott, Richard; Wu, Yuxia; Wan, Dongshi; Li, Jia; Yin, Tongming; Yin, Tongming; Lascoux, Martin; DiFazio, Steven P; Tuskan, Gerald A; Wang, Jun; Jianquan, Liu

    2013-01-01

    Despite the high economic and ecological importance of forests, our knowledge of the genomic evolution of trees under salt stress remains very limited. Here we report the genome sequence of the desert poplar, Populus euphratica, which exhibits high tolerance to sa lt stress. Its genome is very similar and collinear to that of the closely related mesophytic congener, P trichocarpa. However, we find that several gene families likely to be involved in tolerance to salt stress contain significantly more gene copies within the P euphratica lineage. Furthermore, genes showing evidence of positive selection are significantly enriched in functional categories related to salt stress. Some of these genes, and others within the same categories, are significantly upregulated under salt stress relative to their expression in another salt-sensitive poplar. Our results provide an important background for understanding tree adaptation to salt stress and facilitating the genetic improvement of cultivated poplars for saline soils.

  19. Distribution of calcium carbonate in desert soils: A model

    SciTech Connect

    Mayer, L.; McFadden, L.D.; Harden, J.W.

    1988-04-01

    A model that describes the distribution of calcium carbonate in desert soils as a function of dust flux, time, climate, and other soil-forming factors shows which factors most strongly influence the accumulation of carbonate and can be used to evaluate carbonate-based soil age estimates or paleoclimatic reconstructions. Models for late Holocene soils have produced carbonate distributions that are very similar to those of well-dated soils in New Mexico and southern California. These results suggest that (1) present climate is a fair representation of late Holocene climate, (2) carbonate dust flux can be approximated by its Holocene rate, and (3) changes in climate and/or dust flux at the end of the Pleistocene effected profound and complex changes in soil carbonate distributions. Both higher carbonate dust flux and greater effective precipitation are required during the latest Pleistocene-early Holocene to explain carbonate distributions in latest Pleistocene soils. 21 refs., 4 figs., 1 tab.

  20. Increasing of Mechanical Parameters of Desert Sand Using Pozzolanic Materia

    NASA Astrophysics Data System (ADS)

    Mahdi Sajjadi, Seyed; Fakhraldin Sajjadi, Seyed; Beheshti, Seyed Mohammad; Mehmannavaz, Taha

    2016-04-01

    Research on roads to increase the resistance of weak soils to build structures on it has been increased in recent years. The present article provide the effects of different mixtures containing microsilica, cement, polypropylene waste fiber and dune sand on mechanical parameters such as, compressibility, compressive strength, bending strength and durability characteristic. In this study also is investigated evaluation the effect of road subgrade based on proposed material. The used dune sand in this research was obtained from Kashan city where is located in central desert of Iran. The obtained results show that the microsilica and cement could play a major role in reducing the cost and required time for building roads and also building foundation on these types of soils.

  1. Detectability of minerals on desert alluvial fans using reflectance spectra

    NASA Technical Reports Server (NTRS)

    Shipman, Hugh; Adams, John B.

    1987-01-01

    The visible and near-infrared reflectance spectra of soil samples collected from desert alluvial and colluvial surfaces in the Cuprite mining district, Nevada, were analyzed. These surfaces are downslope from hydrothermally altered volcanic rocks that contain spectrally characteristic minerals such as alunite and kaolinite. Coarse fractions of the soils on the alluvial fans are mineralogically variable and express the upslope lithologies; fine fractions are remarkably similar mineralogically and spectrally in all samples because of dilution of local mineral components by regionally derived windblown dust. Theoretical models for spectral mixing and for particle-size effects were used to model the observed spectral variations. Diagnostic mineral absorption bands in the spectra of fan materials were enhanced by computationally removing the spectrum of the homogeneous fine-soil component. Results show that spectral mixing models are useful for analyzing data with high spectral resolution obtained by field and aircraft spectrometers.

  2. Geomorphic control of radionuclide diffusion in desert soils

    USGS Publications Warehouse

    Pelletier, J.D.; Harrington, C.D.; Whitney, J.W.; Cline, M.; DeLong, S.B.; Keating, G.; Ebert, T.K.

    2005-01-01

    Diffusion is a standard model for the vertical migration of radionuclides in soil profiles. Here we show that diffusivity values inferred from fallout 137CS profiles in soils on the Fortymile Wash alluvial fan, Nye County, Nevada, have a strong inverse correlation with the age of the geomorphic surface. This result suggests that radionuclide-bound particles are predominantly transported by infiltration rather than by bulk-mixing processes such as wetting/ drying, freeze/thaw, and bioturbation. Our results provide a preliminary basis for using soil-geomorphic mapping, point-based calibration data, and the diffusion model to predict radionuclide trans desert soils within a pedotransfer-function approach. Copyright 2005 by the American Geophysical Union.

  3. Summary of along-track data from the Earth radiation budget satellite for several major desert regions

    NASA Technical Reports Server (NTRS)

    Brooks, David R.; Fenn, Marta A.

    1988-01-01

    For several days in January and August 1985, the Earth Radiation Budget Satellite, a component of the Earth Radiation Budget Experiment (ERBE), was operated in an along-track scanning mode. A survey of radiance measurements is given for four desert areas in Africa, the Arabian Peninsula, Australia, and the Sahel region of Africa. Each overflight provides radiance information for four scene categories: clear, partly cloudy, mostly cloudy, and overcast. The data presented include the variation of radiance in each scene classification as a function of viewing zenith angle during each overflight of the five target areas. Several features of interest in the development of anisotropic models are evident, including day-night differences in longwave limb darkening and the azimuthal dependence of short wave radiance. There is some evidence that surface features may introduce thermal or visible shadowing that is not incorporated in the usual descriptions of the anisotropic behavior of radiance as viewed from space. The data also demonstrate that the ERBE scene classification algorithms give results that, at least for desert surfaces, are a function of viewing geometry.

  4. Education Rights, Education Policies and Inequality in South Africa

    ERIC Educational Resources Information Center

    Spreen, Carol Anne; Vally, Salim

    2006-01-01

    In this article we explore education policy changes in South Africa through a rights-based framework. We situate our analysis in the context of deepening poverty and inequality arguing that progress (or the lack thereof) in schools cannot be divorced from poverty and its consequences. We show that education reform in South Africa has been situated…

  5. Neisseria meningitidis Serogroup X in Sub-Saharan Africa

    PubMed Central

    Agnememel, Alain; Hong, Eva; Giorgini, Dario; Nuñez-Samudio, Viginia; Deghmane, Ala-Eddine

    2016-01-01

    The epidemiology of meningococcal disease varies by geography and time. Whole-genome sequencing of Neisseria meningitidis serogroup X isolates from sub-Saharan Africa and Europe showed that serogroup X emergence in sub-Saharan Africa resulted from expansion of particular variants within clonal complex 181. Virulence of these isolates in experimental mouse models was high. PMID:26982628

  6. Distance sampling for Sonoran Desert tortoises

    USGS Publications Warehouse

    Swann, D.E.; Averill-Murray, R. C.; Schwalbe, C.R.

    2002-01-01

    We used line transects and distance sampling in combination with radiotelemetry to estimate density of a desert tortoise (Gopherus agassizii) population in the Rincon Mountains near Tucson, Arizona, USA, as part of a long-term study evaluating the impact of urban development on tortoises. During 2000, 34 1-km transects were each sampled twice in the 368.5-ha study area. We observed 46 tortoises with midline carapace lengths ???150 mm (subadults and adults) plus 7 juveniles on transects. For subadults and adults, the encounter rate was 0.63 tortoises/km, and the mean proportion of tortoises observable during radiotelemetry, conducted concurrently with transect sampling, was 82%. Corrected mean density based on line transects and radiotelemetry was 0.523 tortoises/ha (CV = 22.99, 95% CI = 0.29-0.79), and absolute abundance in the study area was estimated to be 193 (CV = 23.0%, CI = 107-291). Using the 2 independent coverages of transects as separate samples, the Lincoln-Petersen mark-recapture estimator produced an abundance estimate of 224 subadult and adult tortoises (CV = 53.9%, CI = 72-440). Transects measured on the ground over uneven topography resulted in 3% smaller estimates of density when compared to analysis with transect lengths determined from coordinates plotted on a map. Distance sampling appears to be a feasible method of estimating density of Sonoran Desert populations of the desert tortoise, but transect lengths should be based on mapped rather than measured distances to prevent biases caused by uneven topography.

  7. The Palm Desert Renewable Hydrogen Transportation System

    SciTech Connect

    Lehman, P.

    1996-10-01

    The present paper describes, for purposes of the Department of Energy (DoE) Hydrogen Program Review, Schatz Energy Research Center (SERC) progress on the Palm Desert Renewable Hydrogen Transportation System Project for the period January through June 1996. This period represents the first six months of the three year project. The estimated cost over three years is $3.9M, $1.859M of which is funded by the DoE ($600 k for fiscal year 1996). The goal of the Palm Desert Project is to develop a clean and sustainable transportation system for a community. The project will demonstrate the practical utility of hydrogen as a transportation fuel and proton exchange membrane (PEM) fuel cells as vehicle power plants. This transportation system will be developed in the City of Palm Desert in southern California and will include a fleet of 8 fuel cell powered vehicles, solar and wind powered hydrogen generating facilities, a consumer-ready refueling station, and a service infrastructure. The system holds the promise of a clean environment and an energy supply that is predictable, domestic, safe, and abundant. During, the first part of 1996 SERC has nearly completed building a fuel cell powered personal utility vehicle, which features an upgraded safety and computer system; they have designed and built a test bench that is able to mimic golf cart loads and test fuel cell system auxiliary components; they have begun the design of the solar hydrogen generating station; they have worked with Sandia National Laboratory on an advanced metal hydride storage system; they have increased the power density of the SERC fuel cell by as much as 50%; and they have reached out to the rest of the world with a new fact sheet, world wide web pages, a press release, video footage for a television program. and instruction within the community.

  8. The primary role of active large sand seas in forming warm-desert loess sequences

    NASA Astrophysics Data System (ADS)

    Crouvi, O.; Enzel, Y.; Amit, R.; Gillespie, A.

    2009-12-01

    Loess is a widespread aeolian deposit in warm deserts and their semiarid margins. It is commonly dominated by coarse silts. Quartz particles, commonly angular, are the main component (commonly 50%-70%) of this coarse silt fraction. Despite intensive research during the past century on loess formation, the origin of these coarse quartz silts comprising most of desert loess remains one of the fundamental debated problems in sedimentology and Quaternary geology. The ongoing debate is focused on the first stage of loess formation - the production of the quartz silt grains. Therefore this debate influences interpretations of past environmental and climatic changes. Although laboratory experiments indicate the potential of spalling coarse silt grains from abrading sand grains during saltation, field-based evidence is rare and the concept has been minimized and even rejected. We examined in detail data available for several well-known loess zones in subtropical deserts (including: Sahara, Sinai-Negev, Arabia) and show that all these, desert loess sequences are located downwind of adjacent sand dunes/seas both during the late Pleistocene as indicated by dune directions and even at present as indicated by wind data and drift analyses. Additional observations include: (a) mineralogical similarity between the loess and the upwind sand dunes, (b) temporal association of intensified erg activity and loess formation, and (c) grain-size mode reduction of loess with distance from ergs. Where there is no loess sequence downwind of ergs, there is an ocean, sometimes with reported silts (interpreted as dust) in coastal and deeper sea cores. These observations suggest that sand dunes must have been an important source for desert loess. We postulate that the silt grains are generated through active aeolian abrasion of sand grains during episodes of intense windy conditions, in most cases in glacial times. Thus our findings stress that the primary role of active ergs and aeolian

  9. Productivity responses of desert vegetation to precipitation patterns across a rainfall gradient.

    PubMed

    Li, Fang; Zhao, Wenzhi; Liu, Hu

    2015-03-01

    The influences of previous-year precipitation and episodic rainfall events on dryland plants and communities are poorly quantified in the temperate desert region of Northwest China. To evaluate the thresholds and lags in the response of aboveground net primary productivity (ANPP) to variability in rainfall pulses and seasonal precipitation along the precipitation-productivity gradient in three desert ecosystems with different precipitation regimes, we collected precipitation data from 2000 to 2012 in Shandan (SD), Linze (LZ) and Jiuquan (JQ) in northwestern China. Further, we extracted the corresponding MODIS Normalized Difference Vegetation Index (NDVI, a proxy for ANPP) datasets at 250 m spatial resolution. We then evaluated different desert ecosystems responses using statistical analysis, and a threshold-delay model (TDM). TDM is an integrative framework for analysis of plant growth, precipitation thresholds, and plant functional type strategies that capture the nonlinear nature of plant responses to rainfall pulses. Our results showed that: (1) the growing season NDVIINT (INT stands for time-integrated) was largely correlated with the warm season (spring/summer) at our mildly-arid desert ecosystem (SD). The arid ecosystem (LZ) exhibited a different response, and the growing season NDVIINT depended highly on the previous year's fall/winter precipitation and ANPP. At the extremely arid site (JQ), the variability of growing season NDVIINT was equally correlated with the cool- and warm-season precipitation; (2) some parameters of threshold-delay differed among the three sites: while the response of NDVI to rainfall pulses began at about 5 mm for all the sites, the maximum thresholds in SD, LZ, and JQ were about 55, 35 and 30 mm respectively, increasing with an increase in mean annual precipitation. By and large, more previous year's fall/winter precipitation, and large rainfall events, significantly enhanced the growth of desert vegetation, and desert ecosystems

  10. Show What You Know

    ERIC Educational Resources Information Center

    Eccleston, Jeff

    2007-01-01

    Big things come in small packages. This saying came to the mind of the author after he created a simple math review activity for his fourth grade students. Though simple, it has proven to be extremely advantageous in reinforcing math concepts. He uses this activity, which he calls "Show What You Know," often. This activity provides the perfect…

  11. The Ozone Show.

    ERIC Educational Resources Information Center

    Mathieu, Aaron

    2000-01-01

    Uses a talk show activity for a final assessment tool for students to debate about the ozone hole. Students are assessed on five areas: (1) cooperative learning; (2) the written component; (3) content; (4) self-evaluation; and (5) peer evaluation. (SAH)

  12. Honored Teacher Shows Commitment.

    ERIC Educational Resources Information Center

    Ratte, Kathy

    1987-01-01

    Part of the acceptance speech of the 1985 National Council for the Social Studies Teacher of the Year, this article describes the censorship experience of this honored social studies teacher. The incident involved the showing of a videotape version of the feature film entitled "The Seduction of Joe Tynan." (JDH)

  13. Talk Show Science.

    ERIC Educational Resources Information Center

    Moore, Mitzi Ruth

    1992-01-01

    Proposes having students perform skits in which they play the roles of the science concepts they are trying to understand. Provides the dialog for a skit in which hot and cold gas molecules are interviewed on a talk show to study how these properties affect wind, rain, and other weather phenomena. (MDH)

  14. Stage a Water Show

    ERIC Educational Resources Information Center

    Frasier, Debra

    2008-01-01

    In the author's book titled "The Incredible Water Show," the characters from "Miss Alaineus: A Vocabulary Disaster" used an ocean of information to stage an inventive performance about the water cycle. In this article, the author relates how she turned the story into hands-on science teaching for real-life fifth-grade students. The author also…

  15. Showing What They Know

    ERIC Educational Resources Information Center

    Cech, Scott J.

    2008-01-01

    Having students show their skills in three dimensions, known as performance-based assessment, dates back at least to Socrates. Individual schools such as Barrington High School--located just outside of Providence--have been requiring students to actively demonstrate their knowledge for years. The Rhode Island's high school graduating class became…

  16. Experience Of A US Air Force Surgical And Critical Care Team Deployed In Support Of Special Operations Command Africa.

    PubMed

    Delmonaco, Brian L; Baker, Aaron; Clay, Jared; Kilbourn, James

    2016-01-01

    An eight-person team of conventional US Air Force (USAF) medical providers deployed to support US Special Operations Forces (SOF) in North and West Africa for the first time in November 2014. The predeployment training, operations while deployed, and lessons learned from the challenges of performing surgery and medical evacuations in the remote desert environment of Chad and Niger on the continent of Africa are described. The vast area of operations and far-forward posture of these teams requires cooperation between partner African nations, the French military, and SOF to make these medical teams effective providers of surgical and critical care in Africa. The continuous deployment of conventional USAF medical providers since 2014 in support of US Special Operations Command Africa is challenging and will benefit from more medical teams and effective air assets to provide casualty evacuation across the vast area of operations. PMID:27045506

  17. Lake Eyre, Simpson Desert, South Australia, Australia

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Lake Eyre, Simpson Desert, South Australia, Australia (27.0S, 136.0E) is normally a dry lakebed for years on end. However on rare occasions small amounts of rainfall are recorded and ponding can be seen in low parts of the lake, as in this image, where an algae bloom in the water is seen as a dark pink area on the lakebed. The Finke Riverbed intersects Lake Eyre but it is normally a dry wash and seldom contributes water to the lake.

  18. Elevation Derivatives for Mojave Desert Tortoise Habitat

    USGS Publications Warehouse

    Wallace, Cynthia S.A.; Gass, Leila

    2008-01-01

    This report describes the methods used to derive various elevation-derivative grids that were inputted to the Mojave Desert Tortoise Habitat model (L. Gass and others, unpub. data). These grids, which capture information on surface roughness and topographic characteristics, are a subset of the environmental datasets evaluated for the tortoise habitat model. This habitat model is of major importance to the U.S. Fish and Wildlife Service, which is charged with management of this threatened population, including relocating displaced tortoises to areas identified as suitable habitat.

  19. Desert tortoise use of burned habitat in the Eastern Mojave desert

    USGS Publications Warehouse

    Drake, Karla K.; Esque, Todd C.; Nussear, Kenneth E.; DeFalco, Lesley; Scoles, Sara; Modlin, Andrew T.; Medica, Philip A.

    2015-01-01

    Wildfires burned 24,254 ha of critical habitat designated for the recovery of the threatened Mojave desert tortoise (Gopherus agassizii) in southern Nevada during 2005. The proliferation of non-native annual grasses has increased wildfire frequency and extent in recent decades and continues to accelerate the conversion of tortoise habitat across the Mojave Desert. Immediate changes to vegetation are expected to reduce quality of critical habitat, yet whether tortoises will use burned and recovering habitat differently from intact unburned habitat is unknown. We compared movement patterns, home-range size, behavior, microhabitat use, reproduction, and survival for adult desert tortoises located in, and adjacent to, burned habitat to understand how tortoises respond to recovering burned habitat. Approximately 45% of home ranges in the post-fire environment contained burned habitat, and numerous observations (n = 12,223) corroborated tortoise use of both habitat types (52% unburned, 48% burned). Tortoises moved progressively deeper into burned habitat during the first 5 years following the fire, frequently foraging in burned habitats that had abundant annual plants, and returning to adjacent unburned habitat for cover provided by intact perennial vegetation. However, by years 6 and 7, the live cover of the short-lived herbaceous perennial desert globemallow (Sphaeralcea ambigua) that typically re-colonizes burned areas declined, resulting in a contraction of tortoise movements from the burned areas. Health and egg production were similar between burned and unburned areas indicating that tortoises were able to acquire necessary resources using both areas. This study documents that adult Mojave desert tortoises continue to use habitat burned once by wildfire. Thus, continued management of this burned habitat may contribute toward the recovery of the species in the face of many sources of habitat loss.

  20. Spreading Deserts--The Hand of Man. Worldwatch Paper 13.

    ERIC Educational Resources Information Center

    Eckholm, Erik; Brown, Lester R.

    The report identifies regions in which deserts and arid zones are increasing; discusses social and climatic causes of deserts; and suggests ways to cope with and reverse problems of famine, malnutrition, and drought. Increasingly, land is being sapped of its ability to sustain agriculture and human habitation north and south of the Sahara, in…

  1. Negev: Land, Water, and Life in a Desert Environment

    NASA Astrophysics Data System (ADS)

    Back, William

    In view of the continuing increased concern about the extreme fragility of deserts and desert margins, Negev provides a timely discussion of land-use practices compatible with the often conflicting goals of preservation and development. The success o f agricultural and hydrologic experiments in the Negev desert of Israel offers hope to the large percentage of the world's population that lives with an unacceptably low quality of life in desert margins. Deserts are the one remaining type of open space that, with proper use, has the potential for alleviating the misery often associated with expanding population.In addition to the science in the book, the author repeatedly reinforces the concept that “western civilization is inextricably bound to the Negev and its environs, from which it has drawn, via its desert-born religions—Judasium, Christianity, and Islam—many of the mores and concepts, and much of the imagery and love of the desert, including man's relation to nature and to ‘God’.” Deserts often are erroneously perceived to be areas of no water: In reality, these are areas in which a little rainfall occurs sporadically and unpredictably over time. This meager water supply can be meticulously garnered to produce nutritious crops and forage.

  2. WIND CHARACTERISTICS OF MESQUITE STREETS IN THE NORTHERN CHIHUAHUAN DESERT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Past research has shown that the most important areas for active sand movement in the northern part of the Chihuahuan Desert are mesquite-dominated desert ecosystems possessing sandy soil texture. The most active sand movement in the mesquite-dominated ecosystems has been shown to take place on elon...

  3. Nationwide Desert Highway Assessment: A Case Study in China

    PubMed Central

    Mao, Xuesong; Wang, Fuchun; Wang, Binggang

    2011-01-01

    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. PMID:21845155

  4. Food Deserts and Overweight Schoolchildren: Evidence from Pennsylvania

    ERIC Educational Resources Information Center

    Schafft, Kai A.; Jensen, Eric B.; Hinrichs, C. Clare

    2009-01-01

    The concept of the "food desert", an area with limited access to retail food stores, has increasingly been used within social scientific and public health research to explore the dimensions of spatial inequality and community well-being. While research has demonstrated that food deserts are frequently characterized by higher levels of poverty and…

  5. Resilience Mechanisms and Recovery in a Chihuahuan Desert Rangeland Ecosystem

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Background: Desert grassland ecosystems of the Chihuahuan Desert, and other parts of the southwestern U.S., underwent significant changes from the late 1800s through the 1950s. Most often, grassland states were converted to shrubland states. Such transitions have been associated with diminished live...

  6. Desalination of Ground Water Minerals (Case Study: Kashan Desert in Iran)

    NASA Astrophysics Data System (ADS)

    Mahani, S. E.; Esmaeli Mahani, M.; Siavoshi, F.; Jafari, M.

    2009-12-01

    The present study focuses on testing quality and desalination of minerals from ground water that is used as the only source of water supply particularly for drinking in the Kashan Desert in Iran. About 14.2 cubic meter water/year from 59 wells, with the average depth of 120 meter, are used for drinking and personal usage in the selected study area. To test the quality of ground water, in general, salinity of minerals such as: chloride (Cl), sulfate (SO4), carbonate (CO3), bicarbonate (HCO3), potassium (K), sodium (Na), calcium (Ca), and magnesium (Mg), as well as PH, Total Dissolved Solids (TDS), Electric Conductivity (EC), and Temperature (T) are measured. EC and TDS in the deserts and arid areas are usually very high because of lack of rainfall, higher temperature, and high rate of evaporation. If the TDS is greater than 1000 mg/l, ground water needs to be desalinated. The TDS of ground water samples in Kashan Desert is greater than 2500 mg/l, which is higher than international World Health Organization (WHO) and Environmental Protection Agency (EPA) standard values. Conventional treatment can not be the only solution for making Kashan Desert ground water that much pure that can be used as fresh water for drinking because EC, Mg, Na, Cl, and SO4 are also higher than standard values. Various techniques such as: Ion Exchange (IX), Microfiltration (MF), Ultra Filtration (UF), Nano Filtration (NF), Electro Dialysis (ED), and Reserve Osmosis (RO) are examined to desalinate above mentioned minerals. Based on molecular weight and diameter of chemical particles which should be removed, in addition to experiences of operational groups in Iran, the RO technique has been selected as the best methodology. The results show that the RO technique could improve the quality of Kashan Desert ground water by comparison with the standard fresh water up to 95% to 99%.

  7. A dynamic state variable model of mate desertion in Cooper's Hawks

    SciTech Connect

    Kelly, E.J. ); Kennedy, P.L. )

    1993-03-01

    In a 4-yr study of the reproductive strategies of Cooper's Hawks (Accipiter cooperii) nesting in north-central New Mexico, >50% of the females deserted during the fledgling-dependence period and did not renest. A dynamic state variable model was developed to study the females' brood-rearing strategies. In this model a strategy consisted of combinations of staying at the nest, hunting, and deserting. The modeling assumptions were: a female's strategy during brood rearing maximizes her reproductive fitness, defined as the weighted average of the expected probability of survival of her current offspring and her expected future reproduction; and the reproductive fitness function depends on the physical condition of the female and nestlings, the risks to the nestlings associated with each strategy, and the male's foraging capabilities. The model predictions were compared to the observations of female strategies in Cooper's Hawks. The best match between observations and predictions (84-96%) was obtained when the nestlings' survival and the female's future reproductive potential were equally weighted during the nestling stage, but weighted in favor of the female's reproductive potential during the fledgling stage. A sensitivity analysis showed that the model predictions corresponded well with the observations of staying and hunting. However, those combinations of parameter values that reflected conditions with the least pressure to desert missed 70-85% of the desertions. The sensitivity analysis also indicated that a key factor influencing the female's choise of strategy was the interaction between the threat to her future reproduction due to her poor physical condition and the nestlings' risk of death from predation and exposure. The agreement of model predictions and observed strategies supported the modeling assumptions. Dynamic state variable modeling is an excellent tool for studying mate desertion. 54 refs., 2 figs., 5 tabs.

  8. A vectorial capacity product to monitor changing malaria transmission potential in epidemic regions of Africa

    USGS Publications Warehouse

    Ceccato, Pietro; Vancutsem, Christelle; Klaver, Robert; Rowland, James; Connor, Stephen J.

    2012-01-01

    Rainfall and temperature are two of the major factors triggering malaria epidemics in warm semi-arid (desert-fringe) and high altitude (highland-fringe) epidemic risk areas. The ability of the mosquitoes to transmit Plasmodium spp. is dependent upon a series of biological features generally referred to as vectorial capacity. In this study, the vectorial capacity model (VCAP) was expanded to include the influence of rainfall and temperature variables on malaria transmission potential. Data from two remote sensing products were used to monitor rainfall and temperature and were integrated into the VCAP model. The expanded model was tested in Eritrea and Madagascar to check the viability of the approach. The analysis of VCAP in relation to rainfall, temperature and malaria incidence data in these regions shows that the expanded VCAP correctly tracks the risk of malaria both in regions where rainfall is the limiting factor and in regions where temperature is the limiting factor. The VCAP maps are currently offered as an experimental resource for testing within Malaria Early Warning applications in epidemic prone regions of sub-Saharan Africa. User feedback is currently being collected in preparation for further evaluation and refinement of the VCAP model.

  9. Psoriatic arthritis in a fifth-century Judean Desert monastery.

    PubMed

    Zias, J; Mitchell, P

    1996-12-01

    Psoriatic arthritis is a greatly underreported seronegative erosive arthropathy, due to the ambiguous lesions it leaves on bone in all but the most severe cases. For a confident diagnosis of psoriatic arthritis to be made, sacroiliac and intervertebral joint fusion must be present together with erosive lesions of the peripheral skeleton including most especially the terminal interphalangeal joints. In modern times it is only a small percentage of cases who experience such debilitating disease, which may explain who so few cases of psoriatic arthritis can confidently be identified from past populations. This report describes this pathological condition as observed in the comingled skeletal remains of nine males and one female from the tomb of Paulus in the Byzantine Monastery of Martyrius, in the Judean Desert. Visual study was complemented using radiographic techniques along with scanning electron microscopy. Two adult males show characteristic lesions of psoriatic arthritis, demonstrating the form known as arthritis mutilans. A third individual shows less widespread erosive lesions which may signify a pauciarticular example of psoriatic arthritis, as is true of most cases in modern times, or the remains may represent Reiter's disease. During the Byzantine period the earlier practise of expelling those with disfiguring diseases (biblical leprosy) evolved into a philanthropic, caring philosophy where the sick were housed and fed out of charity, often within monasteries. The presence of these cases of psoriatic arthritis within such a Judean Desert monastery confirms earlier suggestions that psoriasis was one of the diseases included by those in the ancient eastern Mediterranean under the umbrella term of biblical leprosy. PMID:9016363

  10. Health effects of particulate air pollution and airborne desert dust

    NASA Astrophysics Data System (ADS)

    Lelieveld, J.; Pozzer, A.; Giannadaki, D.; Fnais, M.

    2013-12-01

    Air pollution by fine particulate matter (PM2.5) has increased strongly with industrialization and urbanization. In the past decades this increase has taken place at a particularly high pace in South and East Asia. We estimate the premature mortality and the years of human life lost (YLL) caused by anthropogenic PM2.5 and airborne desert dust (DU2.5) on regional and national scales (Giannadaki et al., 2013; Lelieveld et al., 2013). This is based on high-resolution global model calculations that resolve urban and industrial regions in relatively great detail. We apply an epidemiological health impact function and find that especially in large countries with extensive suburban and rural populations, air pollution-induced mortality rates have been underestimated given that previous studies largely focused on the urban environment. We calculate a global premature mortality by anthropogenic aerosols of 2.2 million/year (YLL ≈ 16 million/year) due to lung cancer and cardiopulmonary disease. High mortality rates by PM2.5 are found in China, India, Bangladesh, Pakistan and Indonesia. Desert dust DU2.5 aerosols add about 0.4 million/year (YLL ≈ 3.6 million/year). Particularly significant mortality rates by DU2.5 occur in Pakistan, China and India. The estimated global mean per capita mortality caused by airborne particulates is about 0.1%/year (about two thirds of that caused by tobacco smoking). We show that the highest premature mortality rates are found in the Southeast Asia and Western Pacific regions (about 25% and 46% of the global rate, respectively) where more than a dozen of the most highly polluted megacities are located. References: Giannadaki, D., A. Pozzer, and J. Lelieveld, Modeled global effects of airborne desert dust on air quality and premature mortality, Atmos. Chem. Phys. Discuss. (submitted), 2013. Lelieveld, J., C. Barlas, D. Giannadaki, and A. Pozzer, Model calculated global, regional and megacity premature mortality due to air pollution by ozone

  11. NASA Desert RATS 2011 Education Pilot Project and Classroom Activities

    NASA Technical Reports Server (NTRS)

    Gruener, J. E.; McGlone, M.; Allen, J.; Tobola, K.; Graff, P.

    2012-01-01

    The National Aeronautics and Space Administration's (NASA's) Desert Research and Technology Studies (Desert RATS) is a multi-year series of tests of hardware and operations carried out annually in the high desert of Arizona, as an analog to future exploration activities beyond low Earth orbit [1]. For the past several years, these tests have occurred in the San Francisco Volcanic Field, north of Flagstaff. For the 2011 Desert RATS season, the Exploration Systems Mission Directorate (ESMD) at NASA headquarters provided support to develop an education pilot project that would include student activities to parallel the Desert RATS mission planning and exploration activities in the classroom, and educator training sessions. The development of the pilot project was a joint effort between the NASA Johnson Space Center (JSC) Astromaterials Research and Exploration Science (ARES) Directorate and the Aerospace Education Services Project (AESP), managed at Penn State University.

  12. Relief evolution of Africa since 300 Ma: outcomes of the TopoAfrica project

    NASA Astrophysics Data System (ADS)

    Guillocheau, François; Braun, Jean; TopoAfrica Working Group

    2013-04-01

    are available (paleosoils, wood and pollen analysis…) and difficult to quantify. On the other hand, most of the paleoclimate models are unable to predict the birth of the main desert of Africa at the right period and, then, cannot be used as an input for paleoprecipitation in our model of sediment production and transport. Keywords: Africa, Relief, Mantle dynamics, Paleoclimate, Mesozoic, Cenozoic

  13. Plague in Africa from 1935 to 1949

    PubMed Central

    Davis, D. H. S.

    1953-01-01

    The history of plague in Africa during the period 1935-49 is reviewed. Much of the information derives from a questionnaire sent to all African territories in 1950. The annual incidence of plague in Africa declined, particularly from 1946 onwards. In 1949, under 400 cases were reported, as compared with over 6,000 in 1935. By the end of 1949, plague was still active in the Belgian Congo, Kenya and Tanganyika, Madagascar, and southern Africa. No cases were reported from Egypt, Tunisia, Algeria, Morocco, Senegal, or Uganda during 1949. A comparison of the seasonal incidence of plague with prevailing atmospheric conditions (temperature and rainfall) in African territories shows that human plague is more frequent in warm moist weather—60°-80°F (15°-27°C)—than in hot dry, or cold, weather—over 80°F (27°C) or under 60°F (15°C). The highlands of equatorial Africa and of Madagascar appear to provide the optimum environment for the persistence of plague on the domestic (murine) plane and the high-veld and Kalahari of southern Africa on the sylvatic plane. The rat (Rattus rattus) and the multimammate mouse (R. (Mastomys) natalensis) and their fleas Xenopsylla brasiliensis and X. cheopis appear to be mainly responsible for the persistence of the reservoir in the East African highlands; R. rattus and X. cheopis play this role in Madagascar. The gerbils (Tatera and Desmodillus) and their burrow fleas X. philoxera and X. piriei are the main reservoirs of plague in southern Africa. Within these areas, Pasteurella pestis finds an environment suitable for its continued survival; the conditions seem to be comparable to those defined as obtaining in endemic centres in India. Elsewhere in Africa such endemic centres do not appear to exist. PMID:13115987

  14. Hantaviruses in Africa.

    PubMed

    Witkowski, Peter T; Klempa, Boris; Ithete, Ndapewa L; Auste, Brita; Mfune, John K E; Hoveka, Julia; Matthee, Sonja; Preiser, Wolfgang; Kruger, Detlev H

    2014-07-17

    This paper summarizes the progress in the search for hantaviruses and hantavirus infections in Africa. After having collected molecular evidence of an indigenous African hantavirus in 2006, an intensive investigation for new hantaviruses has been started in small mammals. Various novel hantaviruses have been molecularly identified not only in rodents but also in shrews and bats. In addition, the first African hantavirus, Sangassou virus, has been isolated and functionally characterized in cell culture. Less is known about the ability of these hantaviruses to infect humans and to cause diseases. To date, no hantavirus genetic material could be amplified from patients' specimens collected in Africa. Serological studies in West Africa, based on a battery of screening and confirmatory assays, led to the detection of hantavirus antibodies in the human population and in patients with putative hantavirus disease. In addition to this overview, we present original data from seroepidemiological and field studies conducted in the Southern part of Africa. A human seroprevalence rate of 1.0% (n=1442) was detected in the South African Cape Region whereas no molecular evidence for the presence of hantavirus was found in 2500 small animals trapped in South Africa and Namibia. PMID:24406800

  15. Taking in a Show.

    PubMed

    Boden, Timothy W

    2016-01-01

    Many medical practices have cut back on education and staff development expenses, especially those costs associated with conventions and conferences. But there are hard-to-value returns on your investment in these live events--beyond the obvious benefits of acquired knowledge and skills. Major vendors still exhibit their services and wares at many events, and the exhibit hall is a treasure-house of information and resources for the savvy physician or administrator. Make and stick to a purposeful plan to exploit the trade show. You can compare products, gain new insights and ideas, and even negotiate better deals with representatives anxious to realize returns on their exhibition investments. PMID:27249887

  16. Relationship Between Job Burnout and Neuroendocrine Indicators in Soldiers in the Xinjiang Arid Desert: A Cross-Sectional Study.

    PubMed

    Tao, Ning; Zhang, Jianjiang; Song, Zhixin; Tang, Jinhua; Liu, Jiwen

    2015-12-01

    The purpose of this study was to explore the relationship between job burnout and neuroendocrine indicators in soldiers living in a harsh environment. Three hundred soldiers stationed in the arid desert and 600 in an urban area were recruited. They filled in the Chinese Maslach Burnout Inventory questionnaire. One hundred soldiers were randomly selected from each group to measure their levels of noradrenaline, serotonin, heat shock protein (HSP)-70, adrenocorticotropic hormone, and serum cortisol. Job burnout was more common in soldiers from urban areas than those from rural areas. Job burnout was significantly higher among soldiers stationed in the arid desert than those in urban areas. For soldiers in the arid desert, the levels of HSP-70, serum cortisol, and adrenocorticotropic hormone were significantly higher than in soldiers in urban areas. Correlation analyses showed that the degree of job burnout was weakly negatively correlated with the level of HSP-70. Being an only child, HSP-70 levels, cortisol levels, and ACTH levels were independently associated with job burnout in soldiers stationed in the arid desert. A higher level of job burnout in soldiers stationed in arid desert and a corresponding change in neuroendocrine indicators indicated a correlation between occupational stress and neurotransmitters. PMID:26633442

  17. Relationship Between Job Burnout and Neuroendocrine Indicators in Soldiers in the Xinjiang Arid Desert: A Cross-Sectional Study

    PubMed Central

    Tao, Ning; Zhang, Jianjiang; Song, Zhixin; Tang, Jinhua; Liu, Jiwen

    2015-01-01

    The purpose of this study was to explore the relationship between job burnout and neuroendocrine indicators in soldiers living in a harsh environment. Three hundred soldiers stationed in the arid desert and 600 in an urban area were recruited. They filled in the Chinese Maslach Burnout Inventory questionnaire. One hundred soldiers were randomly selected from each group to measure their levels of noradrenaline, serotonin, heat shock protein (HSP)-70, adrenocorticotropic hormone, and serum cortisol. Job burnout was more common in soldiers from urban areas than those from rural areas. Job burnout was significantly higher among soldiers stationed in the arid desert than those in urban areas. For soldiers in the arid desert, the levels of HSP-70, serum cortisol, and adrenocorticotropic hormone were significantly higher than in soldiers in urban areas. Correlation analyses showed that the degree of job burnout was weakly negatively correlated with the level of HSP-70. Being an only child, HSP-70 levels, cortisol levels, and ACTH levels were independently associated with job burnout in soldiers stationed in the arid desert. A higher level of job burnout in soldiers stationed in arid desert and a corresponding change in neuroendocrine indicators indicated a correlation between occupational stress and neurotransmitters. PMID:26633442

  18. Dew condensation on desert beetle skin.

    PubMed

    Guadarrama-Cetina, J; Mongruel, A; Medici, M-G; Baquero, E; Parker, A R; Milimouk-Melnytchuk, I; González-Viñas, W; Beysens, D

    2014-11-01

    Some tenebrionind beetles inhabiting the Namib desert are known for using their body to collect water droplets from wind-blown fogs. We aim to determine whether dew water collection is also possible for desert insects. For this purpose, we investigated the infra-red emissivity, and the wetting and structural properties, of the surface of the elytra of a preserved specimen of Physasterna cribripes (Tenebrionidæ) beetle, where the macro-structure appears as a series of "bumps", with "valleys" between them. Dew formation experiments were carried out in a condensation chamber. The surface properties (infra-red emissivity, wetting properties) were dominated by the wax at the elytra surface and, to a lower extent, its micro-structure. We performed scanning electron microscope on histological sections and determined the infra-red emissivity using a scanning pyrometer. The emissivity measured (0.95±0.07 between 8-14 μm) was close to the black body value. Dew formation occurred on the insect's elytra, which can be explained by these surface properties. From the surface coverage of the condensed drops it was found that dew forms primarily in the valleys between the bumps. The difference in droplet nucleation rate between bumps and valleys can be attributed to the hexagonal microstructure on the surface of the valleys, whereas the surface of the bumps is smooth. The drops can slide when they reach a critical size, and be collected at the insect's mouth. PMID:25403836

  19. Microbiology and Moisture Uptake of Desert Soils

    NASA Astrophysics Data System (ADS)

    Kress, M. E.; Bryant, E. P.; Morgan, S. W.; Rech, S.; McKay, C. P.

    2005-12-01

    We have initiated an interdisciplinary study of the microbiology and water content of desert soils to better understand microbial activity in extreme arid environments. Water is the one constituent that no organism can live without; nevertheless, there are places on Earth with an annual rainfall near zero that do support microbial ecosystems. These hyperarid deserts (e.g. Atacama and the Antarctic Dry Valleys) are the closest terrestrial analogs to Mars, which is the subject of future exploration motivated by the search for life beyond Earth. We are modeling the moisture uptake by soils in hyperarid environments to quantify the environmental constraints that regulate the survival and growth of micro-organisms. Together with the studies of moisture uptake, we are also characterizing the microbial population in these soils using molecular and culturing methods. We are in the process of extracting DNA from these soils using MoBio extraction kits. This DNA will be used as a template to amplify bacterial and eukaryotic ribosomal DNA to determine the diversity of the microbial population. We also have been attempting to determine the density of organisms by culturing on one-half strength R2A agar. The long-range goal of this research is to identify special adaptations of terrestrial life that allow them to inhabit extreme arid environments, while simultaneously quantifying the environmental parameters that enforce limits on these organisms' growth and survival.

  20. Desert tortoise hibernation: Temperatures, timing, and environment

    USGS Publications Warehouse

    Nussear, K.E.; Esque, T.C.; Haines, D.F.; Tracy, C.R.

    2007-01-01

    This research examined the onset, duration, and termination of hibernation in Desert Tortoises (Gopherus agassizii) over several years at multiple sites in the northeastern part of their geographic range, and recorded the temperatures experienced by tortoises during winter hibernation. The timing of hibernation by Desert Tortoises differed among sites and years. Environmental cues acting over the short-term did not appear to influence the timing of the hibernation period. Different individual tortoises entered hibernation over as many as 44 days in the fall and emerged from hibernation over as many as 49 days in the spring. This range of variation in the timing of hibernation indicates a weak influence at best of exogenous cues hypothesized to trigger and terminate hibernation. There do appear to be regional trends in hibernation behavior as hibernation tended to begin earlier and continue longer at sites that were higher in elevation and generally cooler. The emergence date was generally more similar among study sites than the date of onset. While the climate and the subsequent timing of hibernation differed among sites, the average temperatures experienced by tortoises while hibernating differed by only about five degrees from the coldest site to the warmest site. ?? 2007 by the American Society of Ichthyologists and Herpetologists.

  1. Temporal 222Rn distributions to reveal groundwater discharge into desert lakes: Implication of water balance in the Badain Jaran Desert, China

    NASA Astrophysics Data System (ADS)

    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.

  2. Not a "reality" show.

    PubMed

    Wrong, Terence; Baumgart, Erica

    2013-01-01

    The authors of the preceding articles raise legitimate questions about patient and staff rights and the unintended consequences of allowing ABC News to film inside teaching hospitals. We explain why we regard their fears as baseless and not supported by what we heard from individuals portrayed in the filming, our decade-long experience making medical documentaries, and the full un-aired context of the scenes shown in the broadcast. The authors don't and can't know what conversations we had, what documents we reviewed, and what protections we put in place in each televised scene. Finally, we hope to correct several misleading examples cited by the authors as well as their offhand mischaracterization of our program as a "reality" show. PMID:23631336

  3. Controls on sediment production in two U.S. deserts

    USGS Publications Warehouse

    Belnap, Jayne; Walker, Beau J.; Munson, Seth M.; Gill, Richard A.

    2014-01-01

    Much of the world’s airborne sediment originates from dryland regions. Soil surface disturbances in these regions are ever-increasing due to human activities such as energy and mineral exploration and development, recreation, suburbanization, livestock grazing and cropping. Sediment production can have significant impacts to human health with particles potentially carrying viruses such as Valley Fever or causing asthma or other respiratory diseases. Dust storms can cause decreased visibility at the ground level, resulting in highway accidents, and reduced visual quality in park and wildland airsheds. Sediment production and deposition is also detrimental to ecosystem health, as production reduces soil fertility at its source and can bury plants and other organisms where it is deposited. Therefore, it is important to understand how we can predict what areas are prone to producing sediment emissions both before and after soil surface disturbance. We visited 87 sites in two deserts of the western U.S. that represented a range of soil texture and surface cover types. We used a portable wind tunnel to estimate the threshold friction velocity (TFV) required to initiate sediment transport and the amount of sediment produced by the tunnel at a set wind speed. Wind tunnel runs were done before and after soil surface disturbance with a four-wheel drive vehicle. Results show that most undisturbed desert soils are very stable, especially if covered by rocks or well-developed biological soil crusts, which make them virtually wind-erosion proof. Particles at disturbed sites, in contrast, moved at relatively low wind speeds and produced high amounts of sediment. Silt was an important predictor of TFV and sediment production across all sites, whereas the influence of rock cover and biological soil crusts was site-dependent. Understanding the vulnerability of a site after disturbance is important information for land managers as they plan land use activities and attempt to

  4. Controls on sediment production in two U.S. deserts

    NASA Astrophysics Data System (ADS)

    Belnap, Jayne; Walker, Beau J.; Munson, Seth M.; Gill, Richard A.

    2014-09-01

    Much of the world’s airborne sediment originates from dryland regions. Soil surface disturbances in these regions are ever-increasing due to human activities such as energy and mineral exploration and development, recreation, suburbanization, livestock grazing and cropping. Sediment production can have significant impacts to human health with particles potentially carrying viruses such as Valley Fever or causing asthma or other respiratory diseases. Dust storms can cause decreased visibility at the ground level, resulting in highway accidents, and reduced visual quality in park and wildland airsheds. Sediment production and deposition is also detrimental to ecosystem health, as production reduces soil fertility at its source and can bury plants and other organisms where it is deposited. Therefore, it is important to understand how we can predict what areas are prone to producing sediment emissions both before and after soil surface disturbance. We visited 87 sites in two deserts of the western U.S. that represented a range of soil texture and surface cover types. We used a portable wind tunnel to estimate the threshold friction velocity (TFV) required to initiate sediment transport and the amount of sediment produced by the tunnel at a set wind speed. Wind tunnel runs were done before and after soil surface disturbance with a four-wheel drive vehicle. Results show that most undisturbed desert soils are very stable, especially if covered by rocks or well-developed biological soil crusts, which make them virtually wind-erosion proof. Particles at disturbed sites, in contrast, moved at relatively low wind speeds and produced high amounts of sediment. Silt was an important predictor of TFV and sediment production across all sites, whereas the influence of rock cover and biological soil crusts was site-dependent. Understanding the vulnerability of a site after disturbance is important information for land managers as they plan land use activities and attempt to

  5. The Holocene Geoarchaeology of the Desert Nile in Northern Sudan

    NASA Astrophysics Data System (ADS)

    Woodward, Jamie; Macklin, Mark; Spencer, Neal; Welsby, Derek; Dalton, Matthew; Hay, Sophie; Hardy, Andrew

    2016-04-01

    Invited Paper Forty years ago Colin Renfrew declared that "every archaeological problem starts as a problem in geoarchaeology" (Renfrew, 1976 p. 2). With this assertion in mind, this paper draws upon the findings from field research in two sectors of the Nile Valley of Northern Sudan dedicated to the exploration of human-environment interactions during the middle and late Holocene. This part of the Nile corridor contains a rich cultural record and an exceptionally well preserved Holocene fluvial archive. A distinctive feature of these records is the variety of evidence for interaction between desert and river over a range of spatial and temporal scales. This interaction presented both challenges and opportunities for its ancient inhabitants. This paper will present evidence for large-scale landscape changes driven by shifts in global climate. It will also show how we have integrated the archaeological and geological records in the Northern Dongola Reach and at Amara West - where long-term field projects led by archaeologists from the British Museum have recognised the importance of a sustained commitment to interdisciplinary research to achieve a fully integrated geoarchaeological approach across a range of scales. The former project is a large-scale landscape survey with multiple sites across an 80 km reach of the Nile whilst the latter has a strong focus on a single New Kingdom town site and changes in its environmental setting. By combining multiple archaeological and geological datasets - and pioneering the use of OSL dating and strontium isotope analysis in the Desert Nile - we have developed a new understanding of human responses to Holocene climate and landscape change in this region. Renfrew, C. (1976) Archaeology and the earth sciences. In: D.A. Davidson and M.I. Shackley (eds) Geoarchaeology: Earth Science and the Past, Duckworth, London, 1-5.

  6. Abiotic Factors Shape Microbial Diversity in Sonoran Desert Soils

    PubMed Central

    Fitak, Robert R.; Munguia-Vega, Adrian; Racolta, Adriana; Martinson, Vincent G.; Dontsova, Katerina

    2012-01-01

    High-throughput, culture-independent surveys of bacterial and archaeal communities in soil have illuminated the importance of both edaphic and biotic influences on microbial diversity, yet few studies compare the relative importance of these factors. Here, we employ multiplexed pyrosequencing of the 16S rRNA gene to examine soil- and cactus-associated rhizosphere microbial communities of the Sonoran Desert and the artificial desert biome of the Biosphere2 research facility. The results of our replicate sampling approach show that microbial communities are shaped primarily by soil characteristics associated with geographic locations, while rhizosphere associations are secondary factors. We found little difference between rhizosphere communities of the ecologically similar saguaro (Carnegiea gigantea) and cardón (Pachycereus pringlei) cacti. Both rhizosphere and soil communities were dominated by the disproportionately abundant Crenarchaeota class Thermoprotei, which comprised 18.7% of 183,320 total pyrosequencing reads from a comparatively small number (1,337 or 3.7%) of the 36,162 total operational taxonomic units (OTUs). OTUs common to both soil and rhizosphere samples comprised the bulk of raw sequence reads, suggesting that the shared community of soil and rhizosphere microbes constitute common and abundant taxa, particularly in the bacterial phyla Proteobacteria, Actinobacteria, Planctomycetes, Firmicutes, Bacteroidetes, Chloroflexi, and Acidobacteria. The vast majority of OTUs, however, were rare and unique to either soil or rhizosphere communities and differed among locations dozens of kilometers apart. Several soil properties, particularly soil pH and carbon content, were significantly correlated with community diversity measurements. Our results highlight the importance of culture-independent approaches in surveying microbial communities of extreme environments. PMID:22885757

  7. Environmental impacts of pipeline corridors in the Mojave Desert, California

    SciTech Connect

    Wilshire, H.G. )

    1992-01-01

    Three recently-built gas and oil pipelines that cross the Mojave Desert have graded constructed zones averaging 107 feet wide (range 68--200) on terrain of low relief, and 135 feet (range 77--273) on steeper terrain. Where corridors overlap, the graded width of two pipelines combined averages 157 feet (range 100--388). Right Of Way (ROW) Grants stipulate ROWs 50 feet wide, with an extra 25 feet allowed for construction. Pre- and post-construction measurements on one pipeline show that the width of the graded corridor exceeds the surveyed width by about 21%. A moderate rainstorm of 4 hr duration in the Tehachapi Mtns. eroded about 120 tons/ac to 250 tons/ac of soil from one pipeline corridor, measured on 3 transects across steep slopes. Especially in the western Mojave Desert, the pipeline corridors remain vulnerable to wind erosion for at least 5 years, and thus pose hazards to traffic on nearby highways. Pipeline corridors that pass through areas of stable eolian deposits are undergoing active erosion that expands by undercutting roots and sandblasting plants on downwind sides of the corridors, and by burial of plants beneath drifts. Techniques used to clear vegetation from construction corridors range from deep bulldozing to those designed to remove foliage while leaving root systems intact; the former technique guarantees long-term impacts, but the latter technique may have been defeated by final grading. Problems arise from failure to implement existing mitigations, inadequacies in environmental stipulations, and inadequacies in engineering oversight. Environmental benefits can be achieved by reducing or eliminating the practice of mechanical grading of the corridor, and by placing ditch lines of subsequent pipelines within existing 50 ft. ROWs and limiting construction disturbance to the existing disturbed zone.

  8. Local and global navigational coordinate systems in desert ants.

    PubMed

    Collett, Matthew; Collett, Thomas S

    2009-04-01

    While foraging, the desert ant Cataglyphis fortis keeps track of its position with respect to its nest through a process of path integration (PI). Once it finds food, it can then follow a direct home vector to its nest. Furthermore, it remembers the coordinates of a food site, and uses these coordinates to return to the site. Previous studies suggest, however, that it does not associate any coordinates remembered from previous trips with familiar views such that it can produce a home vector when displaced to a familiar site. We ask here whether a desert ant uses any association between PI coordinates and familiar views to ensure consistent PI coordinates as it travels along a habitual route. We describe an experiment in which we manipulated the PI coordinates an ant has when reaching a distinctive point along a habitual route on the way to a feeder. The subsequent home vectors of the manipulated ants, when displaced from the food-site to a test ground, show that also when a route memory is evoked at a significant point on the way to a food site, C. fortis does not reset its PI coordinates to those it normally has at that point. We use this result to argue that local vector memories, which encode the metric properties of a segment of a habitual route, must be encoded in a route-based coordinate system that is separate from the nest-based global coordinates. We propose a model for PI-based guidance that can account for several puzzling observations, and that naturally produces the route-based coordinate system required for learning and following local vectors. PMID:19282486

  9. Abiotic factors shape microbial diversity in Sonoran Desert soils.

    PubMed

    Andrew, David R; Fitak, Robert R; Munguia-Vega, Adrian; Racolta, Adriana; Martinson, Vincent G; Dontsova, Katerina

    2012-11-01

    High-throughput, culture-independent surveys of bacterial and archaeal communities in soil have illuminated the importance of both edaphic and biotic influences on microbial diversity, yet few studies compare the relative importance of these factors. Here, we employ multiplexed pyrosequencing of the 16S rRNA gene to examine soil- and cactus-associated rhizosphere microbial communities of the Sonoran Desert and the artificial desert biome of the Biosphere2 research facility. The results of our replicate sampling approach show that microbial communities are shaped primarily by soil characteristics associated with geographic locations, while rhizosphere associations are secondary factors. We found little difference between rhizosphere communities of the ecologically similar saguaro (Carnegiea gigantea) and cardón (Pachycereus pringlei) cacti. Both rhizosphere and soil communities were dominated by the disproportionately abundant Crenarchaeota class Thermoprotei, which comprised 18.7% of 183,320 total pyrosequencing reads from a comparatively small number (1,337 or 3.7%) of the 36,162 total operational taxonomic units (OTUs). OTUs common to both soil and rhizosphere samples comprised the bulk of raw sequence reads, suggesting that the shared community of soil and rhizosphere microbes constitute common and abundant taxa, particularly in the bacterial phyla Proteobacteria, Actinobacteria, Planctomycetes, Firmicutes, Bacteroidetes, Chloroflexi, and Acidobacteria. The vast majority of OTUs, however, were rare and unique to either soil or rhizosphere communities and differed among locations dozens of kilometers apart. Several soil properties, particularly soil pH and carbon content, were significantly correlated with community diversity measurements. Our results highlight the importance of culture-independent approaches in surveying microbial communities of extreme environments. PMID:22885757

  10. Interannual variability of photosynthesis across Africa and its attribution

    NASA Astrophysics Data System (ADS)

    Williams, Christopher A.; Hanan, Niall P.; Baker, Ian; Collatz, G. James; Berry, Joseph; Denning, A. Scott

    2008-12-01

    Africa is thought to be a large source of interannual variability in the global carbon cycle, only vaguely attributed to climate fluctuations. This study uses a biophysical model, Simple Biosphere, to examine in detail what specific factors, physiological (acute stress from low soil water, temperature, or low humidity) and biophysical (low vegetation radiation use), are responsible for spatiotemporal patterns of photosynthesis across the African continent during the period 1982-2003. Acute soil water stress emerges as the primary factor driving interannual variability of photosynthesis for most of Africa. Southern savannas and woodlands are a particular hot spot of interannual variability in photosynthesis, owing to high rainfall variability and photosynthetic potential but intermediate annual rainfall. Surprisingly low interannual variability of photosynthesis in much of the Sudano-Sahelian zone derives from relatively low vegetation cover, pronounced humidity stress, and somewhat lower rainfall variability, whereas perennially wet conditions diminish interannual variability in photosynthesis across much of the Congo Basin and coastal West Africa. Though not of focus here, the coefficient of variation in photosynthesis is notably high in drylands and desert margins (i.e., Sahel, Greater Horn, Namib, and Kalahari) having implications for supply of food and fiber. These findings emphasize that when considering impacts of climate change and land surface feedbacks to the atmosphere, it is important to recognize how vegetation, climate, and soil characteristics may conspire to filter or dampen ecosystem responses to hydroclimatic variability.

  11. Estimates of percolation rates and ages of water in unsaturated sediments at two Mojave Desert sites, California-Nevada

    USGS Publications Warehouse

    Prudic, D.E.

    1994-01-01

    Thick unsaturated zones in arid regions increasingly are being sought for the burial of radioactive and other hazardous wastes. Estimating percolation rates of water from precipitation at proposed burial sites is important for site assessment. Chloride profiles in unsaturated sediments are used to show differences and similarities in the rates of perco- lation at two sites in the Mojave Desert of southern Nevada and southeastern California; the first is an existing burial site for low-level radioactive waste in the Amargosa Desert, and the second is a proposed waste-burial site in Ward Valley. The Mojave Desert is one of the most arid regions of the United States. Chloride concentrations in pore water of unsaturated sediments peak between depths of 2 and 3 meters at both the Amargosa Desert and Ward Valley, sites; maximum chloride concentration is 9,000 milligrams per liter at the Amargosa Desert site and 15,000 milligrams per liter at the Ward Valley, site. Below a depth of 10 meters, however, chloride concentrations at the Amargosa Desert site decrease to less than 50 milligrams per liter, whereas concentrations at the Ward Valley site are greater than 2,300 milligrams per liter. Estimated age of water at a depth of 10 meters at both sites is between ]6,000 and 33,000 years. Below a depth of 10 meters, estimated age of water in the sediments at the Ward Valley site is considerably older than at the Amargosa Desert site because of the greater chloride concentrations at the Ward Valley site. The dilute chloride concentrations in the pore water below a depth of 10 meters at the Amargosa Desert site could indicate that the sediments were flushed with water in the past. The climate in the region was wetter and cooler from about 30,000 to 18,000 years ago. Perhaps increased precipitation or more frequent flooding of the Amargosa River resulted in deep percolation at the site. Downward percolation of water since that time seems limited to the upper 10 meters. The

  12. Observation of local cloud and moisture feedbacks over high ocean and desert surface temperatures

    NASA Technical Reports Server (NTRS)

    Chahine, Moustafa T.

    1995-01-01

    New data on clouds and moisture, made possible by reanalysis of weather satellite observations, show that the atmosphere reacts to warm clusters of very high sea surface temperatures in the western Pacific Ocean with increased moisture, cloudiness, and convection, suggesting a negative feedback limiting the sea surface temperature rise. The reverse was observed over dry and hot deserts where both moisture and cloudiness decrease, suggesting a positive feedback perpetuating existing desert conditions. In addition, the observations show a common critical surface temperature for both oceans and land; the distribution of atmospheric moisture is observed to reach a maximum value when the daily surface temperatures approach 304 +/- 1 K. These observations reveal complex dynamic-radiative interactions where multiple processes act simultaneously at the surface as well as in the atmosphere to regulate the feedback processes.

  13. Alternate non-stop migration strategies of pied flycatchers to cross the Sahara desert.

    PubMed

    Ouwehand, Janne; Both, Christiaan

    2016-04-01

    Each year more than two billion songbirds cross the Sahara, but how they perform this formidable task is largely unknown. Using geolocation tracks from 27 pied flycatchers, a nocturnally migrating passerine, we show that most birds made diurnal flights in both autumn and spring. These diurnal flights were estimated to be part of non-stop flights of mostly 40-60 h. In spring, birds flew across the Sahara, while autumn migration probably circumpassed part of the desert, through a long oversea flight. Our data contradict claims that passerines cross the Sahara by intermittent flight and daytime resting. The frequent occurrence of long non-stop flights to cross the desert shows migrants' physiological abilities and poses the question why this would not be the general migration strategy to cross the Sahara. PMID:27072404

  14. Public medical shows.

    PubMed

    Walusinski, Olivier

    2014-01-01

    In the second half of the 19th century, Jean-Martin Charcot (1825-1893) became famous for the quality of his teaching and his innovative neurological discoveries, bringing many French and foreign students to Paris. A hunger for recognition, together with progressive and anticlerical ideals, led Charcot to invite writers, journalists, and politicians to his lessons, during which he presented the results of his work on hysteria. These events became public performances, for which physicians and patients were transformed into actors. Major newspapers ran accounts of these consultations, more like theatrical shows in some respects. The resultant enthusiasm prompted other physicians in Paris and throughout France to try and imitate them. We will compare the form and substance of Charcot's lessons with those given by Jules-Bernard Luys (1828-1897), Victor Dumontpallier (1826-1899), Ambroise-Auguste Liébault (1823-1904), Hippolyte Bernheim (1840-1919), Joseph Grasset (1849-1918), and Albert Pitres (1848-1928). We will also note their impact on contemporary cinema and theatre. PMID:25273491

  15. Childhood cancer in Africa.

    PubMed

    Kruger, Mariana; Hendricks, Marc; Davidson, Alan; Stefan, Cristina D; van Eyssen, Ann L; Uys, Ronelle; van Zyl, Anel; Hesseling, Peter

    2014-04-01

    The majority of children with cancer live in low- and middle-income countries (LMICs) with little or no access to cancer treatment. The purpose of the paper is to describe the current status of childhood cancer treatment in Africa, as documented in publications, dedicated websites and information collected through surveys. Successful twinning programmes, like those in Malawi and Cameroon, as well as the collaborative clinical trial approach of the Franco-African Childhood Cancer Group (GFAOP), provide good models for childhood cancer treatment. The overview will hopefully influence health-care policies to facilitate access to cancer care for all children in Africa. PMID:24214130

  16. Hematology in Africa.

    PubMed

    Makani, Julie; Roberts, David J

    2016-04-01

    This review of hematology in Africa highlights areas of current practice and the immediate needs for development and clinical research. Acute hematological practice is dominated by anemia, sickle cell disease, and the need to provide a safe and rapidly available supply of blood. There is a growing need for specialist services for bleeding and coagulation, hematological malignancy, and palliative care. There are many areas of practice where straightforward measures could yield large gains in patient care. There is an urgent need for good clinical research to describe the epidemiology, natural history, and management of hematological diseases in Africa. PMID:27040965

  17. Bioremediation of Crude Oil Contaminated Desert Soil: Effect of Biostimulation, Bioaugmentation and Bioavailability in Biopile Treatment Systems.

    PubMed

    Benyahia, Farid; Embaby, Ahmed Shams

    2016-02-01

    This work was aimed at evaluating the relative merits of bioaugmentation, biostimulation and surfactant-enhanced bioavailability of a desert soil contaminated by crude oil through biopile treatment. The results show that the desert soil required bioaugmentation and biostimulation for bioremediation of crude oil. The bioaugmented biopile system led to a total petroleum hydrocarbon (TPH) reduction of 77% over 156 days while the system with polyoxyethylene (20) sorbitan monooleate (Tween 80) gave a 56% decrease in TPH. The biostimulated system with indigenous micro-organisms gave 23% reduction in TPH. The control system gave 4% TPH reduction. The addition of Tween 80 led to a respiration rate that peaked in 48 days compared to 88 days for the bioaugmented system and respiration declined rapidly due to nitrogen depletion. The residual hydrocarbon in the biopile systems studied contained polyaromatics (PAH) in quantities that may be considered as hazardous. Nitrogen was found to be a limiting nutrient in desert soil bioremediation. PMID:26891314

  18. Bioremediation of Crude Oil Contaminated Desert Soil: Effect of Biostimulation, Bioaugmentation and Bioavailability in Biopile Treatment Systems

    PubMed Central

    Benyahia, Farid; Embaby, Ahmed Shams

    2016-01-01

    This work was aimed at evaluating the relative merits of bioaugmentation, biostimulation and surfactant-enhanced bioavailability of a desert soil contaminated by crude oil through biopile treatment. The results show that the desert soil required bioaugmentation and biostimulation for bioremediation of crude oil. The bioaugmented biopile system led to a total petroleum hydrocarbon (TPH) reduction of 77% over 156 days while the system with polyoxyethylene (20) sorbitan monooleate (Tween 80) gave a 56% decrease in TPH. The biostimulated system with indigenous micro-organisms gave 23% reduction in TPH. The control system gave 4% TPH reduction. The addition of Tween 80 led to a respiration rate that peaked in 48 days compared to 88 days for the bioaugmented system and respiration declined rapidly due to nitrogen depletion. The residual hydrocarbon in the biopile systems studied contained polyaromatics (PAH) in quantities that may be considered as hazardous. Nitrogen was found to be a limiting nutrient in desert soil bioremediation. PMID:26891314

  19. The Great Cometary Show

    NASA Astrophysics Data System (ADS)

    2007-01-01

    its high spatial and spectral resolution, it was possible to zoom into the very heart of this very massive star. In this innermost region, the observations are dominated by the extremely dense stellar wind that totally obscures the underlying central star. The AMBER observations show that this dense stellar wind is not spherically symmetric, but exhibits a clearly elongated structure. Overall, the AMBER observations confirm that the extremely high mass loss of Eta Carinae's massive central star is non-spherical and much stronger along the poles than in the equatorial plane. This is in agreement with theoretical models that predict such an enhanced polar mass-loss in the case of rapidly rotating stars. ESO PR Photo 06c/07 ESO PR Photo 06c/07 RS Ophiuchi in Outburst Several papers from this special feature focus on the later stages in a star's life. One looks at the binary system Gamma 2 Velorum, which contains the closest example of a star known as a Wolf-Rayet. A single AMBER observation allowed the astronomers to separate the spectra of the two components, offering new insights in the modeling of Wolf-Rayet stars, but made it also possible to measure the separation between the two stars. This led to a new determination of the distance of the system, showing that previous estimates were incorrect. The observations also revealed information on the region where the winds from the two stars collide. The famous binary system RS Ophiuchi, an example of a recurrent nova, was observed just 5 days after it was discovered to be in outburst on 12 February 2006, an event that has been expected for 21 years. AMBER was able to detect the extension of the expanding nova emission. These observations show a complex geometry and kinematics, far from the simple interpretation of a spherical fireball in extension. AMBER has detected a high velocity jet probably perpendicular to the orbital plane of the binary system, and allowed a precise and careful study of the wind and the shockwave

  20. Central and southern Africa

    SciTech Connect

    McGrew, H.J.

    1981-10-01

    Exploration in central and southern Africa continued to expand during 1980. The greatest concentration of activity was in Nigeria. However, there was considerable increase in the level of exploratory work in Cameroon and Congo. Significant new finds have been made in Ivory Coast. Geological and geophysical activity was carried out in 18 of the countries, with those in the western part having the largest share. Seismic work involved 225 party months of operation. Most of this time was spent on land, but marine operations accounted for 73,389 km of new control. Gravity and magnetic data were recorded during the marine surveys, and several large aeromagnetic projects were undertaken to obtain a total of 164,498 line km of data. Exploratory and development drilling accounted for a total of 304 wells and 2,605,044 ft (794,212 m) of hole. The 92 exploratory wells that were drilled resulted in 47 oil and gas discoveries. In development drilling 89% of the 212 wells were successful. At the end of the year, 27 exploratory wells were underway, and 34 development wells were being drilled for a total of 61. Oil production from the countries that this review covers was 918,747,009 bbl in 1980, a drop of about 9% from the previous year. Countries showing a decline in production were Nigeria, Gabon, Cabinda, and Zaire. Increases were recorded in Cameroon, Congo, and Ghana. A new country was added to the list of producers when production from the Belier field in Ivory Coast came on stream. 33 figures, 15 tables.

  1. Family Planning Programmes in Africa.

    ERIC Educational Resources Information Center

    Pradervand, Pierre

    The countries discussed in this paper are the francophone countries of West Africa and the Republic of Congo, with comparative references made to North Africa (mainly Morocco, Algeria, and Tunisia). Obstacles to the adoption of family planning in the countries of tropical Africa are a very high mortality rate among children; a socioeconomic…

  2. Telecommunications and Development in Africa.

    ERIC Educational Resources Information Center

    Kiplagat, B. A., Ed.; Werner, M. C. M., Ed.

    The Telecommunications Foundation of Africa (TFA) was created in 1992 out of a conviction that insufficient telecommunications in Africa are an impediment to economic growth, and that more resources could be mobilized to strengthen this sector. This volume was made by TFA for readers both inside and outside of Africa and the telecommunications…

  3. Country Energy Profile, South Africa

    SciTech Connect

    1995-08-01

    This country energy profile provides energy and economic information about South Africa. Areas covered include: Economics, demographics, and environment; Energy situation; Energy structure; Energy investment opportunities; Department of Energy (DOE) programs in South Africa; and a listing of International aid to South Africa.

  4. Landscape histories, livestock management, and mesquite expansion in the Chihuahuan Desert of New Mexico

    Technology Transfer Automated Retrieval System (TEKTRAN)

    During the past 125 years the northern Chihuahuan Desert has undergone a significant shift from desert grasslands to desert scrub conditions, with mesquite (Prosopis glandulosa) dramatically increasing in dominance during this period. The transition from desert grasslands is viewed as deleterious, ...

  5. 43 CFR 2524.1 - Conditions excusing entrymen from compliance with the desert-land laws.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... compliance with the desert-land laws. 2524.1 Section 2524.1 Public Lands: Interior Regulations Relating to... (2000) DESERT-LAND ENTRIES Desert-Land Entries Within a Reclamation Project § 2524.1 Conditions excusing entrymen from compliance with the desert-land laws. (a) By section 5 of the Act of June 27, 1906 (34...

  6. 43 CFR 2524.5 - Assignment of desert-land entries in whole or in part.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false Assignment of desert-land entries in whole... (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR LAND RESOURCE MANAGEMENT (2000) DESERT-LAND ENTRIES Desert-Land Entries Within a Reclamation Project § 2524.5 Assignment of desert-land entries...

  7. 43 CFR 2524.1 - Conditions excusing entrymen from compliance with the desert-land laws.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... compliance with the desert-land laws. 2524.1 Section 2524.1 Public Lands: Interior Regulations Relating to... (2000) DESERT-LAND ENTRIES Desert-Land Entries Within a Reclamation Project § 2524.1 Conditions excusing entrymen from compliance with the desert-land laws. (a) By section 5 of the Act of June 27, 1906 (34...

  8. 43 CFR 2524.5 - Assignment of desert-land entries in whole or in part.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false Assignment of desert-land entries in whole... (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR LAND RESOURCE MANAGEMENT (2000) DESERT-LAND ENTRIES Desert-Land Entries Within a Reclamation Project § 2524.5 Assignment of desert-land entries...

  9. 43 CFR 2524.1 - Conditions excusing entrymen from compliance with the desert-land laws.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... compliance with the desert-land laws. 2524.1 Section 2524.1 Public Lands: Interior Regulations Relating to... (2000) DESERT-LAND ENTRIES Desert-Land Entries Within a Reclamation Project § 2524.1 Conditions excusing entrymen from compliance with the desert-land laws. (a) By section 5 of the Act of June 27, 1906 (34...

  10. 43 CFR 2524.5 - Assignment of desert-land entries in whole or in part.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Assignment of desert-land entries in whole... (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR LAND RESOURCE MANAGEMENT (2000) DESERT-LAND ENTRIES Desert-Land Entries Within a Reclamation Project § 2524.5 Assignment of desert-land entries...

  11. 43 CFR 2524.5 - Assignment of desert-land entries in whole or in part.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false Assignment of desert-land entries in whole... (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR LAND RESOURCE MANAGEMENT (2000) DESERT-LAND ENTRIES Desert-Land Entries Within a Reclamation Project § 2524.5 Assignment of desert-land entries...

  12. 43 CFR 2524.1 - Conditions excusing entrymen from compliance with the desert-land laws.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... compliance with the desert-land laws. 2524.1 Section 2524.1 Public Lands: Interior Regulations Relating to... (2000) DESERT-LAND ENTRIES Desert-Land Entries Within a Reclamation Project § 2524.1 Conditions excusing entrymen from compliance with the desert-land laws. (a) By section 5 of the Act of June 27, 1906 (34...

  13. Conquering the Sahara and Arabian deserts: systematics and biogeography of Stenodactylus geckos (Reptilia: Gekkonidae)

    PubMed Central

    2012-01-01

    Background The evolutionary history of the biota of North Africa and Arabia is inextricably tied to the complex geological and climatic evolution that gave rise to the prevalent deserts of these areas. Reptiles constitute an exemplary group in the study of the arid environments with numerous well-adapted members, while recent studies using reptiles as models have unveiled interesting biogeographical and diversification patterns. In this study, we include 207 specimens belonging to all 12 recognized species of the genus Stenodactylus. Molecular phylogenies inferred using two mitochondrial (12S rRNA and 16S rRNA) and two nuclear (c-mos and RAG-2) markers are employed to obtain a robust time-calibrated phylogeny, as the base to investigate the inter- and intraspecific relationships and to elucidate the biogeographical history of Stenodactylus, a genus with a large distribution range including the arid and hyper-arid areas of North Africa and Arabia. Results The phylogenetic analyses of molecular data reveal the existence of three major clades within the genus Stenodactylus, which is supported by previous studies based on morphology. Estimated divergence times between clades and sub-clades are shown to correlate with major geological events of the region, the most important of which is the opening of the Red Sea, while climatic instability in the Miocene is hypothesized to have triggered diversification. High genetic variability is observed in some species, suggesting the existence of some undescribed species. The S. petrii - S. stenurus species complex is in need of a thorough taxonomic revision. New data is presented on the distribution of the sister species S. sthenodactylus and S. mauritanicus. Conclusions The phylogenetic hypothesis for the genus Stenodactylus presented in this work permits the reconstruction of the biogeographical history of these common desert dwellers and confirms the importance of the opening of the Red Sea and the climatic oscillations of the

  14. Africa Adult Education. Chronologies in Commonwealth Countries.

    ERIC Educational Resources Information Center

    Draper, James A., Ed.

    In this document, leading educators from 12 African Commonwealth countries trace the development of adult education in Africa and show how providers of adult education outside the formal education system (including government and nongovernment organizations, trade unions, women's groups, and religious organizations) have met the needs of their…

  15. Mastomys natalensis and Lassa fever, West Africa.

    PubMed

    Lecompte, Emilie; Fichet-Calvet, Elisabeth; Daffis, Stéphane; Koulémou, Kékoura; Sylla, Oumar; Kourouma, Fodé; Doré, Amadou; Soropogui, Barré; Aniskin, Vladimir; Allali, Bernard; Kouassi Kan, Stéphane; Lalis, Aude; Koivogui, Lamine; Günther, Stephan; Denys, Christiane; ter Meulen, Jan

    2006-12-01

    PCR screening of 1,482 murid rodents from 13 genera caught in 18 different localities of Guinea, West Africa, showed Lassa virus infection only in molecularly typed Mastomys natalensis. Distribution of this rodent and relative abundance compared with M. erythroleucus correlates geographically with Lassa virus seroprevalence in humans. PMID:17326956

  16. Mastomys natalensis and Lassa Fever, West Africa

    PubMed Central

    Fichet-Calvet, Elisabeth; Daffis, Stéphane; Koulémou, Kékoura; Sylla, Oumar; Kourouma, Fodé; Doré, Amadou; Soropogui, Barré; Aniskin, Vladimir; Allali, Bernard; Kan, Stéphane Kouassi; Lalis, Aude; Koivogui, Lamine; Günther, Stephan; Denys, Christiane; ter Meulen, Jan

    2006-01-01

    PCR screening of 1,482 murid rodents from 13 genera caught in 18 different localities of Guinea, West Africa, showed Lassa virus infection only in molecularly typed Mastomys natalensis. Distribution of this rodent and relative abundance compared with M. erythroleucus correlates geographically with Lassa virus seroprevalence in humans. PMID:17326956

  17. Climate and soil salinity in the deserts of Central Asia

    NASA Astrophysics Data System (ADS)

    Pankova, E. I.; Konyushkova, M. V.

    2013-07-01

    A comparative analysis of climatic and soil salinity characteristics of the deserts of Central Asia, including deserts of the Turan Depression, the Gobi Desert, and deserts of the Dzungar and Tarim depressions was performed. The climatic characteristics—the degree of aridity, the degree of continentality, and the amount and regime of precipitation—are different in these deserts. No direct relationships between the areas occupied by the automorphic salt-affected soils and the aridity of the climate are observed in the studied regions. In the automorphic landscapes of Asian deserts, the degree and chemistry of the soil salinization and the distribution of salt-affected soils are controlled by the history of the particular territories rather than by their modern climatic conditions. The presence and properties of the salt-bearing rocks and the eolian migration of salts play the most significant role. The deficit of moisture in the modern climate favors the preservation of salt accumulations in places of their origin. The specific features of the climate, including the regime of precipitation, affect the redistribution of salts in the profiles of automorphic salt-affected soils. An increase in the degree of climatic continentality is accompanied by the decrease in the intensity of weathering and initial accumulation of salts. A different situation is observed in the soils of hydromorphic desert landscapes, in which the degree of salinity of the surface horizons and the area occupied by salt-affected soils are directly influenced by the modern climatic conditions.

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

    USGS Publications Warehouse

    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.

  19. Baking black opal in the desert sun: The importance of silica in desert varnish

    NASA Astrophysics Data System (ADS)

    Perry, Randall S.; Lynne, Bridget Y.; Sephton, Mark A.; Kolb, Vera M.; Perry, Carole C.; Staley, James T.

    2006-07-01

    Desert varnish, a widespread black manganese-rich rock coating, contains labile organic compounds, but a mechanism for its formation and for their preservation remains unproven. Using Raman spectroscopy, X-ray diffraction, and scanning transmission electron microscopy, we analyzed varnish and found amorphous hydrated silica (opal) and the silica mineral moganite, similar to findings we have reported from siliceous hot-spring deposits. We suggest that the slow dissolution of silica from anhydrous and hydrous minerals, and its subsequent gelling, condensation, and hardening, provides a simple explanation of a formation mechanism for desert varnish and silica glazes and the incorporation of organic material from local environments. These chemical signatures, sequestered in silica, provide valuable information about terrestrial and extraterrestrial paleoenvironments.

  20. A Continuous High-Resolution Climate-Proxy Record of the past 2600 Years from the Central Sahara Desert

    NASA Astrophysics Data System (ADS)

    Verschuren, D.; Schuster, M.; Cocquyt, C.; Russell, J. M.; Engstrom, D. R.; Kroepelin, S.

    2004-12-01

    Persistent lack of high-quality climate-proxy records from the arid-subarid belt of North Africa has hampered analysis of decade-to-century-scale climate tele-connections between warm-temperate southern Europe and the monsoonal climate regimes of sub-Saharan tropical Africa. Here we report recovery of a finely laminated sediment record from Lake Yoa, a stratified hypersaline lake occupying a Pleistocene deflation basin at Ounianga Kebir in northeastern Chad (20.0°N; 20.5°E). It represents a continuous, annual-resolution record of climate and environmental change during the past 2600 14C years from the hyper-arid core of the Sahara desert where rainfall is erratic and annual evaporation exceeds 600 cm. Lake Yoa is one of the very few permanent waters in this region maintained today by sub-surface inflow of fossil groundwater from sandstone aquifers recharged during the early-Holocene humid period. Preliminary sedimentological, chronological and fossil-diatom data suggest that Lake Yoa has been poly- to hyper-saline throughout the sampled period, and with conditions of physical and chemical limnology similar to those prevailing today for at least the past 1000 years. Given that the desert landscape in a large area surrounding Ounianga probably lacked significant ground cover throughout this period, we surmise that variation in aeolian mineral sediment input to the lake, partly reflected in distinct sand layers, could be exploited as a proxy of past changes in the intensity of dry northeasterly trade winds over central North Africa.

  1. Geolab 2010: Desert Rats Field Demonstration

    NASA Technical Reports Server (NTRS)

    Evans, Cindy A.; Calaway, M. J.; Bell, M. S.

    2009-01-01

    In 2010, Desert Research and Technology Studies (Desert RATS), NASA's annual field exercise designed to test spacesuit and rover technologies, will include a first generation lunar habitat facility, the Habitat Demonstration Unit (HDU). The habitat will participate in joint operations in northern Arizona with the Lunar Electric Rover (LER) and will be used as a multi-use laboratory and working space. A Geology Laboratory or GeoLab is included in the HDU design. Historically, science participation in Desert RATS exercises has supported the technology demonstrations with geological traverse activities that are consistent with preliminary concepts for lunar surface science Extravehicular Activities (EVAs). Next year s HDU demonstration is a starting point to guide the development of requirements for the Lunar Surface Systems Program and test initial operational concepts for an early lunar excursion habitat that would follow geological traverses along with the LER. For the GeoLab, these objectives are specifically applied to support future geological surface science activities. The goal of our GeoLab is to enhance geological science returns with the infrastructure that supports preliminary examination, early analytical characterization of key samples, and high-grading lunar samples for return to Earth [1, 2] . Figure 1: Inside view schematic of the GeoLab a 1/8 section of the HDU, including a glovebox for handling and examining geological samples. Other outfitting facilities are not depicted in this figure. GeoLab Description: The centerpiece of the GeoLab is a glovebox, allowing for samples to be brought into the habitat in a protected environment for preliminary examination (see Fig. 1). The glovebox will be attached to the habitat bulkhead and contain three sample pass-through antechambers that would allow direct transfer of samples from outside the HDU to inside the glovebox. We will evaluate the need for redundant chambers, and other uses for the glovebox

  2. Desert Research and Technology Studies 2005 Report

    NASA Technical Reports Server (NTRS)

    Ross, Amy J.; Kosmo, Joseph J.; Janoiko, Barbara A.; Bernard, Craig; Splawn, Keith; Eppler, Dean B.

    2006-01-01

    During the first two weeks of September 2005, the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) Advanced Extravehicular Activity (AEVA) team led the field test portion of the 2005 Research and Technology Studies (RATS). The Desert RATS field test activity is the culmination of the various individual science and advanced engineering discipline areas year-long technology and operations development efforts into a coordinated field test demonstration under representative (analog) planetary surface terrain conditions. The purpose of the RATS is to drive out preliminary exploration concept of operations EVA system requirements by providing hands-on experience with simulated planetary surface exploration extravehicular activity (EVA) hardware and procedures. The RATS activities also are of significant importance in helping to develop the necessary levels of technical skills and experience for the next generation of engineers, scientists, technicians, and astronauts who will be responsible for realizing the goals of the Constellation Program. The 2005 Desert RATS was the eighth RATS field test and was the most systems-oriented, integrated field test to date with participants from NASA field centers, the United States Geologic Survey (USGS), industry partners, and research institutes. Each week of the test, the 2005 RATS addressed specific sets of objectives. The first week focused on the performance of surface science astro-biological sampling operations, including planetary protection considerations and procedures. The second week supported evaluation of the Science, Crew, Operations, and Utility Testbed (SCOUT) proto-type rover and its sub-systems. Throughout the duration of the field test, the Communications, Avionics, and Infomatics pack (CAI-pack) was tested. This year the CAI-pack served to provide information on surface navigation, science sample collection procedures, and EVA timeline awareness. Additionally, 2005 was the first

  3. Relationship between desert locust, Schistocerca gregaria (Forskål), infestation, environmental factors and control measures in Gazan and Makkah Regions, Saudi Arabia.

    PubMed

    Al-Ajlan, Abdulaziz M

    2007-10-15

    Desert Locust, Schistocerca gregaria (Forskål), is one of the most important insect pests in Saudi Arabia. Cultivated crops and the range lands are heavily affected by desert locust in some regions of Saudi Arabia. The objective of this study was to determine the extent of damage by the Desert Locust, Schistocerca gregaria (Forskål) to the range lands being used for grazing range animals in Gazan and Makkah regions of Saudi Arabia. However, it is very difficult to estimate accurately the total infested areas, which were sprayed with insecticides to control upsurges, outbreaks and plagues over the last five decades. Records of Desert Locust control are kept in the National Desert Locust Control and Research Center in Jeddah. Meteorological data was obtained from the Meteorology and Environmental Protection Administration (MEPA), Saudi Arabia. The data shows that the Desert Locust infestation was associated partially with the rainfall intensity in Gazan and Makkah regions. There was found a good relationship between Desert Locust infestation (Solitary phase), temperature and the relative humidity. The locust infestation was heavy during 1986-88, 1992-95 and 1997-98 and about 1.8 million ha were treated with insecticides. Out of the total breeding/infested area, 43% was treated in winter months (October-February) and the remaining 57% was treated in spring season (March-June). The infested area was sprayed with Marshall, Carbosulfan (20%), Malathion (96%, Clorpyrifos; (48%) Fipronil (12.5%), Sumithion (100%) and Decis (12.5%). The study showed an excellent potential to determine the active locust infestation period in relation to the environmental factors for its effective control with insecticide sprays to minimize crop damage. The study highlighted the needs for further investigations in other locust infested areas with different environmental factors for planning future desert locust control programs. PMID:19093456

  4. Geomorphometirc Segmentation of Shield Deserts by Self-Organizing Maps

    NASA Astrophysics Data System (ADS)

    Foroutan, M.; Kompanizare, M.; Ehsani, A. H.

    2015-12-01

    Shield deserts have developed on ancient crystalline bedrocks and mainly composed of folded and faulted rocks hardened by heat and pressure over millions of years. They were unearthed by erosion and form steep-sided hills and basins filled with sediments. The Sahara, Arabian, southern African, central Kavir and Australian deserts are in this group. Their ranges usually supply groundwater resources or in some regions contain huge oil reservoirs. Geomorphological segmentation of shield deserts is one of the fundamental tools in their land use or site investigation planning as well as in their surface water and groundwater management. In many studies the morphology of shield deserts has been investigated by limited qualitative and subjective methods using limited number of simple parameters such as surface elevation and slope. However the importance of these regions supports the need for their accurate and quantitative morphologic classification. The present study attempts to implement a quantitative method, Self-Organizing Map (SOM), for geomorphological classification of a typical shield desert within Kavir Desert, Iran. The area is tectonically stable and characterized by flat clay pans, playas, well-developed pediments around scattered and low elevation ranges. Twenty-two multi-scale morphometric parameters were derived from the first- to third-orders partial derivatives of the surface elevation. Seven optimized parameters with their proper scales were selected by Artificial Neural Networks, Optimum Index Factor, Davies-Bouldin Index and statistic models. Finally, the area was segmented to seven homogeneous areas by SOM algorithm. The results revealed the most distinguishing parameter set (MDPS) for morphologic segmentation of shield deserts. The same segmentation results through using MDPS for another shield deserts in Australia proves the applicability of MDPS for shield deserts segmentation.

  5. Africa: Myth and Reality.

    ERIC Educational Resources Information Center

    Brown, Barbara B.

    1994-01-01

    Reports on the Third International Social Studies Conference held in Nairobi, Kenya, in 1994. Discusses democracy, educational reform efforts, and the importance of tourism to the Kenyan economy. Asserts that U.S. teachers must use accurate and nonstereotypical instructional materials in teaching about Africa. (CFR)

  6. Education in Africa.

    ERIC Educational Resources Information Center

    Educational Documentation and Information, 1977

    1977-01-01

    This selected, annotated bibliography of information resources in English and/or French is divided into sections on books; documents and articles; UNESCO publications; reference works; and African periodicals. A list of institutions concerned with education in Africa is included, as well as educational documentation and information services in…

  7. AED in Africa

    ERIC Educational Resources Information Center

    Academy for Educational Development, 2004

    2004-01-01

    Founded in 1961, the Academy for Educational Development (AED) is an independent, nonprofit, charitable organization that operates development programs in the United States and throughout the world. This directory presents an overview of the AED programs in Africa since 1975. Current AED Programs include: (1) HIV/AIDS Prevention and Impact…

  8. AIDS and Africa. Introduction.

    PubMed

    Kopelman, Loretta M; van Niekerk, Anton A

    2002-04-01

    Sub-Saharan Africa is the epicenter of the HIV/AIDS epidemic, and in this issue of the Journal, seven authors discuss the moral, social and medical implications of having 70% of those stricken living in this area. Anton A. van Niekerk considers complexities of plague in this region (poverty, denial, poor leadership, illiteracy, women's vulnerability, and disenchantment of intimacy) and the importance of finding responses that empower its people. Solomon Benatar reinforces these issues, but also discusses the role of global politics in sub-Saharan Africa, especially discrimination, imperialism and its exploitation by first world countries. Given the public health crisis, Udo Schüklenk and Richard E. Ashcroft defend compulsory licensing of essential HIV/AIDS medications on consequentialist grounds. Keymanthri Moodley discusses the importance of conducting research and the need to understand a moderate form of communitarianism, also referred to as "ubuntu" or "communalism", to help some Africans understand research as an altruistic endeavour. Godfrey B. Tangwa also defends traditional African values of empathy and ubuntu, discussing how they should be enlisted to fight this pandemic. Loretta M. Kopelman criticizes the tendency among those outside Africa to dismiss the HIV/AIDS pandemic, attributing one source to the ubiquitous and misguided punishment theory of disease. The authors conclude that good solutions must be cooperative ventures among countries within and outside of sub-Saharan Africa with far more support from wealthy countries. PMID:11961693

  9. Anglicising Postapartheid South Africa

    ERIC Educational Resources Information Center

    Louw, P. Eric

    2004-01-01

    The apartheid state deliberately encouraged linguistic diversity and actively built cultural infrastructures which impeded Anglicisation. With the end of apartheid has come "de facto" Anglicisation. So although South Africa has, since 1994, had 11 official languages, in reality, English is swamping the other 10 languages. Afrikaans has, in…

  10. Pythiosis in Africa

    PubMed Central

    Rivierre, Christine; Laprie, Caroline; Guiard-Marigny, Olivier; Bergeaud, Patrick; Berthelemy, Madeleine

    2005-01-01

    We report the first case of pythiosis from Africa in an 8-month-old dog with a chronic and ulcerative cutaneous lesion. The etiologic agent belonged to the genus Pythium. Phylogenetic analysis placed the isolate in a sister group to the other P. insidiosum strains. However, the isolate may belong to a new Pythium species. PMID:15757572

  11. Photomontage. Water in Africa.

    ERIC Educational Resources Information Center

    McKoski, David

    The Water in Africa Project was realized over a 2-year period by a team of Peace Corps volunteers. As part of an expanded, detailed design, resources were collected from over 90 volunteers serving in African countries, photos and stories were prepared, and standards-based learning units were created for K-12 students. This unit, "Photomontage,"…

  12. Who Speaks for Africa?

    ERIC Educational Resources Information Center

    Nealy, Michelle

    2005-01-01

    Judging by the press coverage, it would seem that Europeans are the only ones concerned about conditions in Africa, but perhaps the media is not telling the whole story. According to Mark P. Fancher, chair of the National Conference of Black Lawyers' Section on International Affairs & World Peace and the author of "The Splintering of Global…

  13. Africa and Applied Linguistics.

    ERIC Educational Resources Information Center

    Makoni, Sinfree, Ed.; Meinhof, Ulrike H., Ed.

    2003-01-01

    This collection of articles includes: "Introducing Applied Linguistics in Africa" (Sinfree Makoni and Ulrike H. Meinhof); "Language Ideology and Politics: A Critical Appraisal of French as Second Official Language in Nigeria" (Tope Omoniyi); "The Democratisation of Indigenous Languages: The Case of Malawi" (Themba Moyo); "Classroom Code-Switching…

  14. Anatomy: Spotlight on Africa

    ERIC Educational Resources Information Center

    Kramer, Beverley; Pather, Nalini; Ihunwo, Amadi O.

    2008-01-01

    Anatomy departments across Africa were surveyed regarding the type of curriculum and method of delivery of their medical courses. While the response rate was low, African anatomy departments appear to be in line with the rest of the world in that many have introduced problem based learning, have hours that are within the range of western medical…

  15. Neonatal surgery in Africa.

    PubMed

    Chirdan, Lohfa B; Ngiloi, Petronilla J; Elhalaby, Essam A

    2012-05-01

    The management of neonatal surgical problems continues to pose considerable challenges, particularly in low-resource settings. The burden of neonatal surgical diseases in Africa is not well documented. The characteristics of some neonatal surgical problems are highlighted. Late presentation coupled with poor understanding of the milieu interior of the neonates by incompetent health care providers and poorly equipped hospitals combine to give rise to the unacceptable high morbidity and mortality in most parts of Africa. Proper training of all staff involved in neonatal health care coupled with community awareness must be vigorously pursued by all stakeholders. Various governments throughout the continent of Africa, in conjunction with international donor agencies, must not only provide an adequate budget for health care services and improve infrastructures, but must also deliberately encourage and provide funding for neonatal surgical care and research across the continent. The well-established pediatric surgical training programs, particularly in North and South Africa, should hold the moral responsibility of training all possible numbers of young surgeons from other African countries that do not have any existing pediatric surgical training programs or those countries suffering from remarkable shortage of trained pediatric surgeons. PMID:22475121

  16. Out of Africa

    ERIC Educational Resources Information Center

    Wilbert, Nancy Corrigan

    2009-01-01

    Karen Blixen (Isak Dinesen), author of "Out of Africa," said, "God made the world round so people would never be able to see too far down the road." The author embraced this wonderful thought by venturing on a three-week journey to Kenya and Tanzania in search of grand adventure. In this article, the author shares her adventure with her students…

  17. AED in Africa.

    ERIC Educational Resources Information Center

    Academy for Educational Development, Washington, DC.

    For 30 years, the Academy for Educational Development (AED) has worked to support African development. In Uganda, Tanzania, and Botswana AED promoted some of Africa's first AIDS prevention programs. AED is funding research in Ethiopia, Tanzania, and perhaps Zambia that will target stigma and its role in AIDS prevention. Working with governments…

  18. Topical Research: Africa.

    ERIC Educational Resources Information Center

    Lynn, Karen

    This lesson plan can be used in social studies, language arts, or library research. The instructional objective is for students to select a topic of study relating to Africa, write a thesis statement, collect information from media sources, and develop a conclusion. The teacher may assign the lesson for written or oral evaluation. The teacher…

  19. Libraries in Africa.

    ERIC Educational Resources Information Center

    Enyia, Christian O.; And Others

    1991-01-01

    Includes five articles that discuss library and information work in Africa. Highlights include computerization in Nigerian libraries; education for library and information services in Ghana; an evaluation of African librarianship; the role of Nigerian publishers in national development; and the role of information services in national development…

  20. Transport of desert dust mixed with North African industrial pollutants in the subtropical Saharan Air Layer

    NASA Astrophysics Data System (ADS)

    Rodríguez, S.; Alastuey, A.; Alonso-Pérez, S.; Querol, X.; Cuevas, E.; Abreu-Afonso, J.; Viana, M.; Pérez, N.; Pandolfi, M.; de La Rosa, J.

    2011-07-01

    An analysis of chemical composition data of particulate matter samples (TSP, PM10 and PM2.5) collected from 2002 to 2008 in the North Atlantic free troposphere at the Izaña Global Atmospheric Watch (GAW) observatory (Tenerife, Canary Islands) shows that desert dust is very frequently mixed with particulate pollutants in the Saharan Air Layer (SAL). The study of this data set with Median Concentrations At Receptor (MCAR) plots allowed the identification of the potential source regions of the dust and particulate pollutants. Areas located at the south of the southern slope of the Atlas mountains emerge as the most frequent source of the soil desert dust advected to the northern edge of the SAL in summer. Industrial emissions occurring in Northern Algeria, Eastern Algeria, Tunisia and the Atlantic coast of Morocco appear as the most important source of the nitrate, ammonium and a fraction of sulphate (at least 60 % of the sulphate <10 μm transported from some regions) observed in the SAL. These emissions are mostly linked to crude oil refineries, phosphate-based fertilizer industry and power plants. Although desert dust emissions appear as the most frequent source of the phosphorous observed in the SAL, high P concentrations are observed when the SAL is affected by emissions from open mines of phosphate and phosphate based fertilizer industry. The results also show that a significant fraction of the sulphate (up to 90 % of sulphate <10 μm transported from some regions) observed in the SAL may be influenced by soil emissions of evaporite minerals in well defined regions where dry saline lakes (chotts) are present. These interpretations of the MCAR plots are consistent with the results obtained with the Positive Matrix Factorization (PMF2) receptor modelling. The results of this study show that North African industrial pollutants may be mixed with desert dust and exported to the North Atlantic in the Saharan Air Layer.

  1. Transport of desert dust mixed with North African industrial pollutants in the subtropical Saharan Air Layer

    NASA Astrophysics Data System (ADS)

    Rodríguez, S.; Alastuey, A.; Alonso-Pérez, S.; Querol, X.; Cuevas, E.; Abreu-Afonso, J.; Viana, M.; Pandolfi, M.; de La Rosa, J.

    2011-03-01

    The chemical composition of particulate matter samples (TSP, PM10 and PM2.5) collected from 2002 to 2008 in the North Atlantic free troposphere at Izaña Global Atmospheric Watch (GAW) observatory (Tenerife, The Canary Islands) was studied. The analysis of the samples collected in the Saharan Air Layer (SAL) shows that soil desert dust is very frequently mixed with particulate pollutants. An analysis of this data set with Median Concentrations At Receptor (MCAR) plots allowed to identify the potential source regions of the dust and particulate pollutants. Areas located at the south of the Southern slope of Atlas emerge as the most frequent source of the soil desert dust advected to the northern edge of the SAL in summer. Industrial emissions occurring along the Atlantic coast of Morocco, Northern Algeria, Eastern Algeria and Tunisia appear as the most important source of the nitrate, ammonium and a fraction of sulphate (at least a 60% of the sulphate <10 μm transported from some regions) observed in the SAL. These emissions are mostly linked to crude oil refineries, phosphate-based fertilizer industry and power plants. Although desert dust emissions appear as the most frequent source of the phosphorous observed in the SAL, high P concentrations are observed when the SAL is affected by emissions from open mines of phosphate and phosphate based fertilizer industry. The results also show that a significant fraction of the sulphate (up to 90% of sulphate <10 μm transported from some regions) observed in the SAL is linked to soil emissions of evaporite minerals in well defined regions where dry saline lakes (chotts) are present. These interpretations of the MCAR plots are consistent with the results obtained with the Positive Matrix Factorization receptor modelling. The results of this study show that North African industrial pollutants may be mixed with desert dust and exported to the North Atlantic in the Saharan Air Layer.

  2. A study of morphology, provenance, and movement of desert sand seas in Africa, Asia, and Australia

    NASA Technical Reports Server (NTRS)

    Mckee, E. D.; Breed, C. S.; Harris, L. F. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Examination of sand samples from both dune and interdune areas at White Sands, New Mexico, indicates marked differences in composition and texture between these two types of facies. If these differences are characteristics of dune fields in general, information concerning them may help to explain the contrast in appearance of the two kinds of sand areas on ERTS imagery and to permit interpretation of similar features in remote areas, such as Saudi Arabia.

  3. A study of morphology, provenance, and movement of desert sand seas in Africa, Asia, and Australia

    NASA Technical Reports Server (NTRS)

    Mckee, E. D.; Breed, C. S. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. The regional studies of sand seas made possible by analysis of ERTS-1 imagery have established that widespread patterns of eolian sand deposition exist in many places and that similarities and differences in these patterns can be measured and compared, on a worldwide scale. Analysis of the relationships of depositional patterns to controlling factors will require completion of the color mosaics of the test sites, and acquisition of adequate supporting ground truth data, especially wind data. Once analyses are complete, the results will be applicable to the regional study of ancient eolian sandstones. Such sandstones were formed many millions of years ago under conditions believed to be identical to those under which the sand seas that are observed being formed today. The understanding of the deposition of eolian sands provided by analysis of ERTS-1 imagery will be applicable to an understanding of the structure and distribution of ancient eolian sandstones and their potential as reservoirs of oil and water.

  4. A study of morphology, provenance, and movement of desert sand seas in Africa, Asia, and Australia

    NASA Technical Reports Server (NTRS)

    Mckee, E. D.; Breed, C. S.

    1973-01-01

    A description and classification of major types of sand seas on the basis of morphological pattern and lineation are discussed. The steps involved in analyzing the patterns of deposits on ERTS-1 imagery, where the visible forms are mostly dune complexes rather than individual dunes are outlined. After completion of thematic maps portraying the pattern and lineation of the sand bodies, data on directions and intensity of prevailing and other winds are plotted on corresponding bases, as a preliminary to determination of internal structures through ground truth.

  5. A study of morphology, provenance, and movement of desert sand seas in Africa, Asia, and Australia

    NASA Technical Reports Server (NTRS)

    Mckee, E. D.; Breed, C. S.; Harris, L. F. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. The assembling of photomosaics from color prints of ERTS images has made possible the recognition and description of san patterns, and these are to be the basis of a worldwide classification of sand bodies. Progress has been as rapid as the acquisition of the bulk composite images will permit and for some areas the mosaics are now nearly complete. A second step, which consists of the accumulation and analysis of regional wind data, to be plotted as overlays for the dune patterns, is now underway and should soon give tangible results. Other aspects of the project include the gathering of ground truth in the form of air photographs, needed to interpret geomorphic forms and the sampling of sand deposits for analyzing the texture and composition of sand bodies. A start has been made on these studies in several selected areas.

  6. The Challenge of Modeling the Meteorology of Dust Emission: Lessons Learned from the Desert Storms Project

    NASA Astrophysics Data System (ADS)

    Knippertz, P.; Marsham, J. H.; Cowie, S. M.; Fiedler, S.; Heinold, B.; Jemmett-Smith, B. C.; Pantillon, F.; Schepanski, K.; Roberts, A. J.; Pope, R.; Gilkeson, C. A.; Hubel, E.

    2015-12-01

    Mineral dust plays an important role in the Earth system, but a reliable quantification of the global dust budget is still not possible due to a lack of observations and insufficient representation of relevant processes in climate and weather models. Five years ago, the Desert Storms project funded by the European Research Council set out to reduce these uncertainties. Its aims were to (1) improve the understanding of key meteorological mechanisms of peak wind generation in dust emission regions (particularly in northern Africa), (2) assess their relative importance, (3) evaluate their representation in models, (4) determine model sensitivities with respect to resolution and model physics, and (5) explore the usefulness of new approaches for model improvements. Here we give an overview of the most significant findings: (1) The morning breakdown of nocturnal low-level jets is an important emission mechanism, but details depend crucially on nighttime stability, which is often badly handled by models. (2) Convective cold pools are a key control on summertime dust emission over northern Africa, directly and through their influence on the heat low; they are severely misrepresented by models using parameterized convection. A new scheme based on downdraft mass flux has been developed that can mitigate this problem. (3) Mobile cyclones make a relatively unimportant contribution, except for northeastern Africa in spring. (4) A new global climatology of dust devils identifies local hotspots but suggests a minor contribution to the global dust budget in contrast to previous studies. A new dust-devil parameterization based on data from large-eddy simulations will be presented. (5) The lack of sufficient observations and misrepresentation of physical processes lead to a considerable uncertainty and biases in (re)analysis products. (6) Variations in vegetation-related surface roughness create small-scale wind variability and support long-term dust trends in semi-arid areas.

  7. The Challenge of Modelling the Meteorology of Dust Emission: Lessons Learned from the Desert Storms Project

    NASA Astrophysics Data System (ADS)

    Knippertz, Peter; Marsham, John H.; Cowie, Sophie; Fiedler, Stephanie; Heinold, Bernd; Jemmett-Smith, Bradley; Pantillon, Florian; Schepanski, Kerstin; Roberts, Alexander; Pope, Richard; Gilkeson, Carl; Hubel, Eva

    2016-04-01

    Mineral dust plays an important role in the Earth system, but a reliable quantification of the global dust budget is still not possible due to a lack of observations and insufficient representation of relevant processes in climate and weather models. Five years ago, the Desert Storms project funded by the European Research Council set out to reduce these uncertainties. Its aims were to (1) improve the understanding of key meteorological mechanisms of peak wind generation in dust emission regions (particularly in northern Africa), (2) assess their relative importance, (3) evaluate their representation in models, (4) determine model sensitivities with respect to resolution and model physics, and (5) explore the usefulness of new approaches for model improvements. Here we give an overview of the most significant findings: (1) The morning breakdown of nocturnal low-level jets is an important emission mechanism, but details depend crucially on nighttime stability, which is often badly handled by models. (2) Convective cold pools are a key control on summertime dust emission over northern Africa, directly and through their influence on the heat low; they are severely misrepresented by models using parameterized convection. A new scheme based on downdraft mass flux has been developed that can mitigate this problem. (3) Mobile cyclones make a relatively unimportant contribution, except for northeastern Africa in spring. (4) A new global climatology of dust devils identifies local hotspots but suggests a minor contribution to the global dust budget in contrast to previous studies. A new dust-devil parameterization based on data from large-eddy simulations will be presented. (5) The lack of sufficient observations and misrepresentation of physical processes lead to a considerable uncertainty and biases in (re)analysis products. (6) Variations in vegetation-related surface roughness create small-scale wind variability and support long-term dust trends in semi-arid areas.

  8. Intercomparison of MODIS-Aqua C051 and C006 Level 3 Deep Blue AOD and Ångström exponent retrievals over the Sahara desert and the Arabian Peninsula during the period 2002-2014

    NASA Astrophysics Data System (ADS)

    Gkikas, Antonis; Basart, Sara; Korras-Carraca, Marios; Papadimas, Christos; Hatzianastassiou, Nikos; Sayer, Andrew; Hsu, Christina; Baldasano, Jose Maria

    2015-04-01

    Dust loads emitted from the arid regions of Northern Africa and the Arabian Peninsula account for the major portion of the global dust aerosol burden. Depending on prevailing atmospheric circulation they can be transported far away from their source areas. Considering the key role of dust aerosols to weather and climate a better description of their spatial and temporal variability it is an issue of great importance. The main target of the present study is to describe aerosols' regime over Northern Africa and Arabian Peninsula using Deep Blue aerosol optical depth (AOD550nm) and Ångström exponent (α412-470nm) measurements. Given the applied changes to the retrieval algorithm, emphasis is also given to the inter-comparison between the data from Collections 051 and 006. The analysis is performed using MODIS-Aqua daily Level 3 data at 1°x1° spatial resolution over the period 2002-2014. The study region extends from 20°W to 60°E and from 0° to 40°N. The obtained long-term geographical distributions reveal many similarities between C051 and C006 AOD retrievals. They both indicate a zone of high AODs along the parallel of 15°N, extending from the western coasts of Africa to Chad where the maximum values (~1.3) are recorded. In the Arabian Peninsula, the maximum AODs (up to 0.6) are found in Iraq. On the contrary, more apparent differences between the two collections are found for α412-470nm. It is evident a reduction of C006 retrievals, which is more pronounced across the Sahara desert. In C006, the α412-470nm values over the deserts of Northern Africa and Middle East mostly vary from 0 to 0.6 while higher values (up to 1.5) are observed in sub-sahel regions, west coasts of Saudi Arabia and Iran. During the study period, in both collections, AOD has decreased by up to 93% in N. Africa (northern parts of Algeria) while it has increased by up to 70% in the Middle East (northern parts of Iraq). Reversed tendencies are found for the α412-470nm retrievals. For

  9. Rock Varnish: Recorder of Desert Wetness?

    NASA Astrophysics Data System (ADS)

    Broecker, W. S.; Liu, T.

    2001-12-01

    Rock varnish is a thin coating (<200 μ m) of a cocktail rich in Mn, Fe, and clay minerals that is ubiquitous in desert regions. It has become the center of a contentious controversy revolving around its use to date geomorphic surfaces and/or to evaluate past climate conditions. We observe pronounced temporal variations in Mn and Ba concentration that are similar over large regions and that likely relate to variations in paleo-wetness. The mode of formation of varnish remains uncertain, but anthropogenic Pb concentrated in outermost varnish layers indicates its continued formation, and experiments using cosmogenic Be suggest that, while precipitation is a primary control, dust, dew, and aerosols may also be important in delivering the ingredients of varnish. We suggest several steps that may lead to rejuvenation and future breakthrough in varnish studies.

  10. Perennial plant mortality in the Sonoran and Mojave Deserts in response to severe, multi-year drought

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Severe drought that began in late 1998 caused considerable mortality of shrubs in the Mojave and Sonoran deserts. A region-wide survey in 2003 of 15 sites in southwestern Arizona, southern California, and southern Nevada showed that in some places, mortality of the small, drought-deciduous shrubs A...

  11. Impacts of off-road vehicles on nitrogen cycles in biological soil crusts: Resistance in different U.S. deserts

    USGS Publications Warehouse

    Belnap, J.

    2002-01-01

    Biological soil crusts are an important component of desert ecosystems, as they influence soil stability and fertility. This study examined and compared the short-term vehicular impacts on lichen cover and nitrogenase activity (NA) of biological soil crusts. Experimental disturbance was applied to different types of soil in regions throughout the western U.S. (Great Basin, Colorado Plateau, Sonoran, Chihuahuan, and Mojave deserts). Results show that pre-disturbance cover of soil lichens is significantly correlated with the silt content of soils, and negatively correlated with sand and clay. While disturbance appeared to reduce NA at all sites, differences were statistically significant at only 12 of the 26 sites. Cool desert sites showed a greater decline than hot desert sites, which may indicate non-heterocystic cyanobacterial species are more susceptible to disturbance than non-heterocystic species. Sandy soils showed greater reduction of NA as sand content increased, while fine-textured soils showed a greater decline as sand content increased. At all sites, higher NA before the disturbance resulted in less impact to NA post-disturbance. These results may be useful in predicting the impacts of off-road vehicles in different regions and different soils. ?? 2002 Published by Elsevier Science Ltd.

  12. 2D Size Distribution of Chondrules and Chondritic Fragments of an Ordinary Chondrite from Lut Desert (Iran)

    NASA Astrophysics Data System (ADS)

    Pourkhorsandi, H.; Mirnejad, H.

    2014-09-01

    2D size measurement of chondrules and chondiritic fragments of a meteorite from Lut desert of Iran is conducted. Chondrules exhibit a size range of 55-1800 µm (average 437 µm). Chondiritic fragments show a size range of 46-1220 µm (average 261 µm).

  13. The interaction between vegetation dynamics and dust emissions over West Africa

    NASA Astrophysics Data System (ADS)

    Marcella, M. P.; Eltahir, E. A.

    2012-12-01

    Two thirty-year simulations of RegCM3 coupled to a desert dust emission/aerosol tracer model and a dynamic vegetation model are performed over West Africa. To discern the interaction between vegetation dynamics and dust emissions over West Africa and its monsoon and climate, one simulation includes radiatively active dust emissions with plant functional types that can compete and biomes that evolve, while another allows only for vegetation dynamics and no dust emissions. It is found that RegCM3-IBIS does well in capturing the spatial and temporal distribution of dust suspension when compared to MISR observations. In addition, the vegetation dynamic component of the land surface model does well in modeling the spatial distribution of vegetation biomes over West Africa; that is, the model simulates the rainforest by the Gulf of Guinea, deciduous forests further north, the savanna/grassland of the Sahel and the desert region of the Sahara. Overall, dust emissions over the Sahara and Sahel cause a reduction in the incoming shortwave radiation of 20-40 W/m^2 which results in a reduction in the net radiation at the surface and surface cooling of 1-1.5C over the summer months of JJA The two way interactions between dust and vegetation dynamics, and their impacts on the water and energy cycles will be discussed.

  14. Microbial colonization of the salt deposits in the driest place of the Atacama Desert (Chile).

    PubMed

    Stivaletta, Nunzia; Barbieri, Roberto; Billi, Daniela

    2012-06-01

    The Atacama Desert (Chile), one of the most arid places on Earth, shows hostile conditions for the development of epilithic microbial communities. In this study, we report the association of cyanobacteria (Chroococcidiopsis sp.) and bacteria belonging to Actinobacteria and Beta-Gammaproteobacteria and Firmicutes phyla inhabiting the near surface of salt (halite) deposits of the Salar Grande Basin, Atacama Desert (Chile). The halite deposits were investigated by using optical, confocal and field emission scanning electron microscopes, whereas culture-independent molecular techniques, 16S rDNA clone library, alongside RFLP analysis and 16S rRNA gene sequencing were applied to investigate the bacterial diversity. These microbial communities are an example of life that has adapted to extreme environmental conditions caused by dryness, high irradiation, and metal concentrations. Their adaptation is, therefore, important in the investigation of the environmental conditions that might be expected for life outside of Earth. PMID:22661023

  15. Discrimination of active and inactive sand from remote sensing - Kelso dunes, Mojave Desert, California

    NASA Technical Reports Server (NTRS)

    Paisley, Elizabeth C. I.; Lancaster, Nicholas; Gaddis, Lisa R.; Greeley, Ronald

    1991-01-01

    Landsat TM images, field data, and laboratoray reflectance spectra were examined for the Kelso dunes, Mojave Desert, California to assess the use of visible and near-infrared (VNIR) remote sensing data to discriminate aeolian sand populations on the basis of spectral brightness. Results show that areas of inactive sand have a larger percentage of dark, fine-grained materials compared to those composed of active sand, which contain less dark fines and a higher percentage of quartz sand-size grains. Both areas are spectrally distinct in the VNIR, suggesting that VNIR spectral data can be used to discriminate active and inactive sand populations in the Mojave Desert. Analysis of laboratory spectra was complicated by the presence of magnetite in the active sands, which decreases their laboratory reflectance values to those of inactive sands. For this application, comparison of TM and laboratory spectra suggests that less than 35 percent vegetation cover does not influence the TM spectra.

  16. Endolithic Cyanobacteria in Halite Rocks from the Hyperarid Core of the Atacama Desert

    NASA Astrophysics Data System (ADS)

    Wierzchos, Jacek; Ascaso, Carmen; McKay, Christopher P.

    2006-06-01

    In the driest parts of the Atacama Desert there are no visible life forms on soil or rock surfaces. The soil in this region contains only minute traces of bacteria distributed in patches, and conditions are too dry for cyanobacteria that live under translucent stones. Here we show that halite evaporite rocks from the driest part of the Atacama Desert are colonized by cyanobacteria. This colonization takes place just a few millimeters beneath the rock surface, occupying spaces among salt crystals. Our work reveals that these communities are composed of extremely resistant Chroococcidiopsis morphospecies of cyanobacteria and associated heterotrophic bacteria. This newly discovered endolithic environment is an extremely dry and, at the same time, saline microbial habitat. Photosynthetic microorganisms within dry evaporite rocks could be an important and previously unrecognized target for the search for life within our Solar System.

  17. Microbial Colonization of the Salt Deposits in the Driest Place of the Atacama Desert (Chile)

    NASA Astrophysics Data System (ADS)

    Stivaletta, Nunzia; Barbieri, Roberto; Billi, Daniela

    2012-06-01

    The Atacama Desert (Chile), one of the most arid places on Earth, shows hostile conditions for the development of epilithic microbial communities. In this study, we report the association of cyanobacteria ( Chroococcidiopsis sp.) and bacteria belonging to Actinobacteria and Beta-Gammaproteobacteria and Firmicutes phyla inhabiting the near surface of salt (halite) deposits of the Salar Grande Basin, Atacama Desert (Chile). The halite deposits were investigated by using optical, confocal and field emission scanning electron microscopes, whereas culture-independent molecular techniques, 16S rDNA clone library, alongside RFLP analysis and 16S rRNA gene sequencing were applied to investigate the bacterial diversity. These microbial communities are an example of life that has adapted to extreme environmental conditions caused by dryness, high irradiation, and metal concentrations. Their adaptation is, therefore, important in the investigation of the environmental conditions that might be expected for life outside of Earth.

  18. [Study on estimation of deserts soil total phosphorus content from thermal-infrared emissivity].

    PubMed

    Hou, Yan-jun; Tiyip, Tashpolat; Zhang, Fei; Sawut, Mamat; Nurmemet, Ilyas

    2015-02-01

    Soil phosphorus provides nutrient elements for plants, is one of important parameters for evaluating soil quality. The traditional method for soil total phosphorus content (STPC) measurement is not effective and time-consuming. However, remote sensing (RS) enables us to determine STPC in a fast and efficient way. Studies on the estimation of STPC in near-infrared spectroscopy have been developed by scholars, but model accuracy is still poor due to the low absorption coefficient and unclear absorption peak of soil phosphorus in near-infrared. In order to solve the deficiency which thermal-infrared emissivity estimate desert soil total phosphorus content, and could improve precision of estimation deserts soil total phosphorus. In this paper, characteristics of soil thermal-infrared emissivity are analyzed on the basis of laboratory processing and spectral measurement of deserts soil samples from the eastern Junggar Basin. Furthermore, thermal-infrared emissivity based RS models for STPC estimation are established and accuracy assessed. Results show that: when STPC is higher than 0.200 g x kg(-1), the thermal-infrared emissivity increases with the increase of STPC on the wavelength between 8.00 microm and 13 microm, and the emissivity is more sensitive to STPC on the wavelength between 9.00 and 9.6 microm; the estimate mode based on multiple stepwise regression was could not to estimate deserts soil total phosphorus content from thermal-infrared emissivity because the estimation effects of them were poor. The estimation accuracy of model based on partial least squares regression is higher than the model based on multiple stepwise regression. However, the accuracy of second-order differential estimation model based on partial least square regression is higher than based on multiple stepwise regression; The first differential of continuous remove estimation model based on partial least squares regression is the best model with R2 of correction and verification are up to

  19. A genetic assessment of the recovery units for the mojave population of the desert tortoise, Gopherus agassizii

    USGS Publications Warehouse

    Murphy, R.W.; Berry, K.H.; Edwards, T.; McLuckie, A.M.

    2007-01-01

    In the 1994 Recovery Plan for the Mojave population of the desert tortoise, Gopherus agassizii, the US Fish and Wildlife Service established 6 recovery units by using the best available data on habitat use, behavior, morphology, and genetics. To further assess the validity of the recovery units, we analyzed genetic data by using mitochondrial deoxyribonucleic acid (mtDNA) sequences and nuclear DNA microsatellites. In total, 125 desert tortoises were sampled for mtDNA and 628 for microsatellites from 31 study sites, representing all recovery units and desert regions throughout the Mojave Desert in California and Utah, and the Colorado Desert of California. The mtDNA revealed a great divergence between the Mojave populations west of the Colorado River and those occurring east of the river in the Sonoran Desert of Arizona. Some divergence also occurred between northern and southern populations within the Mojave population. The microsatellites indicated a low frequency of private alleles and a significant correlation between genetic and geographic distance among 31 sample sites, which was consistent with an isolation-by-distance population structure. Regional genetic differentiation was complementary to the recovery units in the Recovery Plan. Most allelic frequencies in the recovery units differed. An assignment test correctly placed most individuals to their recovery unit of origin. Of the 6 recovery units, the Northeastern and the Upper Virgin River units showed the greatest differentiation; these units may have been relatively more isolated than other areas and should be managed accordingly. The Western Mojave Recovery Unit, by using the new genetic data, was redefined along regional boundaries into the Western Mojave, Central Mojave, and Southern Mojave recovery units. Large-scale translocations of tortoises and habitat disturbance throughout the 20th century may have contributed to the observed patterns of regional similarity. ?? 2007 Chelonian Research

  20. Nephrology in Africa--not yet uhuru.

    PubMed

    Swanepoel, Charles R; Wearne, Nicola; Okpechi, Ikechi G

    2013-10-01

    Nephrology is a 'Cinderella speciality', a disregarded area of health care, in Africa. Other health issues have relegated the treatment of kidney diseases to a low priority status, and the cost of treating the more common and widespread communicable diseases, financial mismanagement and corruption in many countries has sounded the death knell for expensive therapies such as dialysis. The communicable diseases that have devastated the health systems around Africa are tuberculosis and HIV/AIDS. Until recently, very little information was available on the impact of HIV on acute and chronic dialysis admissions. Patients with acute kidney injury (AKI) in most of Africa are seldom treated because of great distances to travel, lack of expertise, poverty and poor sustainable funding for health matters. An acute peritoneal dialysis (PD) programme has now been initiated in Tanzania but the sustainability of this project will be tested in the future. The International Society of Nephrology (ISN) has developed a training programme for nephrologists from developing countries, which may now be bearing fruit. A report from the sub-Saharan Africa region shows that the numbers of patients on dialysis and those diagnosed with chronic kidney disease (CKD) has increased significantly. Other ISN-sponsored programmes such as Continuing Medical Education activities for physicians and community screening projects have had far-reaching positive effects. Government funding for a dialysis programme is well established in South Africa, but this funding is limited so that the numbers accepted for public dialysis are restricted. Consequently in the Western Cape province of South Africa, a 'category system' has been formulated to attempt to cope with this unacceptable and restrictive ruling. PMID:23958719

  1. Pitted and fluted rocks in the Western Desert of Egypt - Viking comparisons

    NASA Technical Reports Server (NTRS)

    Mccauley, J. F.; Breed, C. S.; Grolier, M. J.; El-Baz, F.; Whitney, M. I.; Ward, A. W.

    1979-01-01

    The Western Desert of Egypt is one of the most arid regions on earth and is probably the closest terrestrial analog to the surface of Mars. An expedition to the area in 1978 revealed an abundance of quartzite and basalt rocks that have been pitted and fluted by wind erosion and deflation of the desert surface. These pitted rocks are internally homogeneous, show no internal holes or vesicles, and are considered an important but neglected type of ventifact. They bear a striking resemblance to the pitted and fluted rocks seen by the Viking Landers, rocks that have generally been interpreted as vesicular basalts only slightly modified by wind erosion. Wind tunnel studies of the air flow over and around nonstreamlined hand specimens from the Western Desert show that windward abrasion coupled with negative flow, secondary flow, and vorticity in a unidirectional wind can explain the complex arrays of pits and flutes. These field and laboratory observations suggest that the pitted rocks at the Viking Lander sites are also ventifacts, and thus the Martian surface may be far more wind eroded than previously thought.

  2. 'Africa Alive Corridors': Forging a new future for the people of Africa by the people of Africa

    NASA Astrophysics Data System (ADS)

    Felix Toteu, Sadrack; Malcolm Anderson, John; de Wit, Maarten

    2010-11-01

    design of one Corridor (AAC 4 - through Cameroon and Nigeria) that we have named the ' African Pole of Rotation' Corridor. We outline its significance in Africa, and the world, and formulate an approach in forging its reality in the countries through which it passes. We show how the uniqueness of this and other Corridors, as "global heritage trails", might translate into holistic lasting benefit for all. AAC aims to draw all 900 million Africans of every background and persuasion into co-curating, co-documenting and together keeping alive their continent's unmatched heritage - an epic and unfolding story.

  3. South Africa as seen from STS-63 Discovery

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The southwest coast of southern Africa from St. Helena Bay (large bay at center), to Table Bay at Cape Town (bottom, with Robben Island near entrance). The pier at the naval base and fishing port of Saldhanaha Bay can be seen in the small bay (center). False Bay is cut off by the bottom edge of the frame. What NASA scientists think to be a phytoplankton bloom appears offshore in the cold upwelled water off the Atlantic coast. Farmland, especially that used for wine growing, is found near the coast occupying the Mediterranian-like climate of the Southwest Cape Province; but inland of the mountains of the Karroo Desert is home to sheep farmers and little agriculture.

  4. Black Beauty's Rainbow: Hyperspectral Imaging of Northwest Africa 7034

    NASA Astrophysics Data System (ADS)

    Cannon, K. M.; Mustard, J. F.; Agee, C. B.; Wilson, J. H.; Greenberger, R. N.

    2014-07-01

    Hyperspectral imaging is used to characterize the first basaltic breccia from Mars, Northwest Africa 7034. Initial results show the spectral character of NWA 7034 is unlike other SNC meteorites and may be more representative of average martian crust.

  5. Cholera outbreaks in Africa.

    PubMed

    Mengel, Martin A; Delrieu, Isabelle; Heyerdahl, Leonard; Gessner, Bradford D

    2014-01-01

    During the current seventh cholera pandemic, Africa bore the major brunt of global disease burden. More than 40 years after its resurgence in Africa in 1970, cholera remains a grave public health problem, characterized by large disease burden, frequent outbreaks, persistent endemicity, and high CFRs, particularly in the region of the central African Great Lakes which might act as reservoirs for cholera. There, cases occur year round with a rise in incidence during the rainy season. Elsewhere in sub-Saharan Africa, cholera occurs mostly in outbreaks of varying size with a constant threat of widespread epidemics. Between 1970 and 2011, African countries reported 3,221,050 suspected cholera cases to the World Health Organization, representing 46 % of all cases reported globally. Excluding the Haitian epidemic, sub-Saharan Africa accounted for 86 % of reported cases and 99 % of deaths worldwide in 2011. The number of cholera cases is possibly much higher than what is reported to the WHO due to the variation in modalities, completeness, and case definition of national cholera data. One source on country specific incidence rates for Africa, adjusting for underreporting, estimates 1,341,080 cases and 160,930 deaths (52.6 % of 2,548,227 estimated cases and 79.6 % of 209,216 estimated deaths worldwide). Another estimates 1,411,453 cases and 53,632 deaths per year, respectively (50 % of 2,836,669 estimated cases and 58.6 % of 91,490 estimated deaths worldwide). Within Africa, half of all cases between 1970 and 2011 were notified from only seven countries: Angola, Democratic Republic of the Congo, Mozambique, Nigeria, Somalia, Tanzania, and South Africa. In contrast to a global trend of decreasing case fatality ratios (CFRs), CFRs have remained stable in Africa at approximately 2 %. Early propagation of cholera outbreaks depends largely on the extent of individual bacterial shedding, host and organism characteristics, the likelihood of people coming into contact with

  6. Impact of land use practices on faunal abundance, nutrient dynamics and biochemical properties of desert pedoecosystem.

    PubMed

    Tripathi, G; Sharma, B M

    2005-11-01

    Increased dependence of resource-poor rural communities on soils of low inherent fertility are the major problem of desert agroecosystem. Agrisilviculture practices may help to conserve the soil biota for maintaining essential soil properties and processes in harsh climate. Therefore, the impacts of different land use systems on faunal density, nutrient dynamics and biochemical properties of soil were studied in agrisilviculture system of Indian desert. The selected fields had trees (Zizyphus mauritiana, Prosopis cineraria, Acacia nilotica) and crops (Cuminum cyminum, Brassica nigra, Triticum aestivum) in different combinations. Populations of Acari, Myriapoda, Coleoptera, Collembola, other soil arthropods and total soil fauna showed significant changes with respect to different land use practices and tree species, indicating a strong relation between above and below ground biodiversity. The Coleoptera exhibited greatest association with all agrisilviculture fields. The Z. mauritiana system indicated highest facilitative effects (RTE value) on all groups of soil fauna. Soil temperature, moisture, organic carbon, nitrate- and ammonical-nitrogen, available phosphorus, soil respiration and dehydrogenase activity were greater under tree than that of tree plus cropping system. It showed accumulation of nitrate-nitrogen in tree field and more utilization by crops in cultivated lands. Positive and significant correlation among organic carbon, nitrate- and ammonical-nitrogen, phosphorus, soil respiration and dehydrogenase activity clearly reflects increase in soil nutrients with the increase in microbial and other biotic activity. P. cineraria field was the best pedoecosystem, while C. cyminum was the best winter crop for cultivation in desert agroforestry system for soil biological health and soil sustainability. The increase in organic carbon, soil nutrients and microbial activity is associated with the increase in soil faunal population which reflect role of soil fauna

  7. Human origins: Out of Africa

    PubMed Central

    Tattersall, Ian

    2009-01-01

    Our species, Homo sapiens, is highly autapomorphic (uniquely derived) among hominids in the structure of its skull and postcranial skeleton. It is also sharply distinguished from other organisms by its unique symbolic mode of cognition. The fossil and archaeological records combine to show fairly clearly that our physical and cognitive attributes both first appeared in Africa, but at different times. Essentially modern bony conformation was established in that continent by the 200–150 Ka range (a dating in good agreement with dates for the origin of H. sapiens derived from modern molecular diversity). The event concerned was apparently short-term because it is essentially unanticipated in the fossil record. In contrast, the first convincing stirrings of symbolic behavior are not currently detectable until (possibly well) after 100 Ka. The radical reorganization of gene expression that underwrote the distinctive physical appearance of H. sapiens was probably also responsible for the neural substrate that permits symbolic cognition. This exaptively acquired potential lay unexploited until it was “discovered” via a cultural stimulus, plausibly the invention of language. Modern humans appear to have definitively exited Africa to populate the rest of the globe only after both their physical and cognitive peculiarities had been acquired within that continent. PMID:19805256

  8. Ecophysiology of two Sonoran Desert evergreen shrubs during extreme drought

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recent drought across the arid Southwest US may be especially problematic for evergreen desert species that maintain leaves through dry periods. In July, 2002 we compared the ecophysiogical performance of the microphyllous creosotebush (Larrea tridentata) to broadleaved jojoba (Simmondisa chinensis...

  9. Modeling Agassiz's Desert Tortoise Population Response to Anthropogenic Stressors

    EPA Science Inventory

    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...

  10. Camelid genomes reveal evolution and adaptation to desert environments.

    PubMed

    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

    2014-01-01

    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. PMID:25333821

  11. Assessing the Benefits of Urban Forestry in Mojave Desert Communities

    EPA Science Inventory

    As the climate and environment change due to human activity, an understanding of the existing natural resources becomes paramount. Urban forests of Mojave Desert communities have the potential to reduce air pollution, heat island effects, and energy consumption. Regions throughou...

  12. Desert Varnish -- Preservation of Biofabrics and Implications for Mars

    NASA Astrophysics Data System (ADS)

    Probst, L. W.; Allen, C. C.; Thomas-Keprta, K. L.; Clemett, S. J.; Longazo, T. G.; Nelman-Gonzalez, M. A.; Sams, C.

    2002-03-01

    Preliminary data suggest that biofabrics are preserved by Mn and Fe minerals (birnessite and hematite) in desert varnish. A martian hematite-rich deposit with indications of biological activity may prove to be a prime site for future sample return.

  13. Biotic Processes Regulating the Carbon Balance of Desert Ecosystems

    SciTech Connect

    R. S. Nowak; J. Arnone; L. Fenstermaker; and S. D. Smith

    2005-07-26

    This project provided the funding to operate and maintain the Nevada Desert FACE Facility. This support funds the CO{sub 2}, system repairs and maintenance, basic physical and biological site information, and personnel that are essential for the experiment to continue. They have continued to assess the effects of elevated CO{sub 2} on three key processes: (1) leaf- to plant-level responses of desert vegetation to elevated atmospheric CO{sub 2}; (2) ecosystem-level responses; and (3) integration of plant and ecosystem processes to understand carbon balance of deserts. The focus is the seminal interactions among atmospheric CO{sub 2}, water, and nitrogen that drive desert responses to elevated CO{sub 2} and explicitly address processes that occur across scales (biological, spatial, and temporal).

  14. Rodent-denuded areas of the northern Mojave desert

    SciTech Connect

    Hunter, R.B.; Romney, E.M.; Wallace, A.

    1980-01-01

    Populations of pocket gophers and rabbits regulate or control the perennial vegetation on relatively large sites in the northern Mojave Desert. Aboveground shoots are pruned and whole plants are killed by complete cutting of main roots.

  15. Evening Pass Over the Sahara Desert and the Middle East

    NASA Video Gallery

    This video over the Sahara Desert and the Middle East was taken by the crew of Expedition 29 aboard the International Space Station. This sequence of shots was taken on Oct. 6, 2011, from 19:46:23 ...

  16. Technical paper on energy farming of desert species

    SciTech Connect

    Felker, P.

    1980-01-01

    Properties of five desert tree legumes are tabulated. Potential resource areas are classified into 4 major areas by water supply and discussed in order of increasing resource potential. Conclusions and recommendations are presented. (MHR)

  17. Geothermal resources of the western arm of the Black Rock Desert, northwestern Nevada. Part I. Geology and geophysics

    SciTech Connect

    Schaefer, D.H.; Welch, A.H.; Maurer, D.K.

    1983-01-01

    Studies of the geothermal potential of the western arm of the Black Rock Desert in northwestern Nevada included a compilation of existing geologic data on a detailed map, a temperature survey at 1-meter depth, a thermal-scanner survey, and gravity and seismic surveys to determine basin geometry. The temperature survey showed the effects of heating at shallow depths due to rising geothermal fluids near the known hot spring areas. Lower temperatures were noted in areas of probable near-surface ground-water movement. The thermal-scanner survey verified the known geothermal areas and showed relatively high-temperature areas of standing water and ground-water discharge. The upland areas of the desert were found to be distinctly warmer than the playa area, probably due to the low thermal diffusivity of upland areas caused by low moisture content. Surface geophysical surveys indicated that the maximum thickness of valley-fill deposits in the desert is about 3200 meters. Gravity data further showed that changes in the trend of the desert axis occurred near thermal areas. 53 refs., 8 figs., 3 tabs.

  18. Geothermal resources of the western arm of the Black Rock Desert, northwestern Nevada; Part I, geology and geophysics

    USGS Publications Warehouse

    Schaefer, Donald H.; Welch, Alan H.; Mauzer, Douglas K.

    1983-01-01

    Studies of the geothermal potential of the western arm of the Black Rock Desert in northwestern Nevada included a compilation of existing geologic data on a detailed map, a temperature survey at 1-meter depth, a thermal-scanner survey, and gravity and seismic surveys to determine basin geometry. The temperature survey showed the effects of heating at shallow depths due to rising geothermal fluids near the known hot spring areas. Lower temperatures were noted in areas of probable near-surface ground-water movement. The thermal-scanner survey verified the known geothermal areas and showed relatively high-temperature areas of standing water and ground-water discharge. The upland areas of the desert were found to be distinctly warmer than the playa area, probably due to low thermal diffusivity resulting from low moisture content. The surface geophysical surveys indicated that the maximum thickness of valley-fill deposits in the desert is about 3,200 meters. Gravity data further showed that changes in the trend of the desert axis occurred near thermal areas. (USGS)

  19. Vertebrate paleontological exploration of the Upper Cretaceous succession in the Dakhla and Kharga Oases, Western Desert, Egypt

    NASA Astrophysics Data System (ADS)

    Sallam, Hesham M.; O'Connor, Patrick M.; Kora, Mahmoud; Sertich, Joseph J. W.; Seiffert, Erik R.; Faris, Mahmoud; Ouda, Khaled; El-Dawoudi, Iman; Saber, Sara; El-Sayed, Sanaa

    2016-05-01

    The Campanian and Maastrichtian stages are very poorly documented time intervals in Africa's record of terrestrial vertebrate evolution. Upper Cretaceous deposits exposed in southern Egypt, near the Dakhla and Kharga Oases in the Western Desert, preserve abundant vertebrate fossils in nearshore marine environments, but have not yet been the focus of intensive collection and description. Our recent paleontological work in these areas has resulted in the discovery of numerous new vertebrate fossil-bearing localities within the middle Campanian Qusier Formation and the upper Campanian-lower Maastrichtian Duwi Formation. Fossil remains recovered from the Campanian-aged Quseir Formation include sharks, rays, actinopterygian and sarcopterygian fishes, turtles, and rare terrestrial archosaurians, including some of the only dinosaurs known from this interval on continental Africa. The upper Campanian/lower Maastrichtian Duwi Formation preserves sharks, sawfish, actinopterygians, and marine reptiles (mosasaurs and plesiosaurs). Notably absent from these collections are representatives of Mammalia and Avialae, both of which remain effectively undocumented in the Upper Cretaceous rocks of Africa and Arabia. New age constraints on the examined rock units is provided by 23 nannofossil taxa, some of which are reported from the Duwi Formation for the first time. Fossil discoveries from rock units of this age are essential for characterizing the degree of endemism that may have developed as the continent became increasingly tectonically isolated from the rest of Gondwana, not to mention for fully evaluating origin and diversification hypotheses of major modern groups of vertebrates (e.g., crown birds, placental mammals).

  20. Dramatic Demand Reduction In The Desert Southwest

    SciTech Connect

    Boehm, Robert; Hsieh, Sean; Lee, Joon; Baghzouz, Yahia; Cross, Andrew; Chatterjee, Sarah

    2015-07-06

    This report summarizes a project that was funded to the University of Nevada Las Vegas (UNLV), with subcontractors Pulte Homes and NV Energy. The project was motivated by the fact that locations in the Desert Southwest portion of the US demonstrate very high peak electrical demands, typically in the late afternoons in the summer. These high demands often require high priced power to supply the needs, and the large loads can cause grid supply problems. An approach was proposed through this contact that would reduce the peak electrical demands to an anticipated 65% of what code-built houses of the similar size would have. It was proposed to achieve energy reduction through four approaches applied to a development of 185 homes in northwest part of Las Vegas named Villa Trieste. First, the homes would all be highly energy efficient. Secondly, each house would have a PV array installed on it. Third, an advanced demand response technique would be developed to allow the resident to have some control over the energy used. Finally, some type of battery storage would be used in the project. Pulte Homes designed the houses. The company considered initial cost vs. long-term savings and chose options that had relatively short paybacks. HERS (Home Energy Rating Service) ratings for the homes are approximately 43 on this scale. On this scale, code-built homes rate at 100, zero energy homes rate a 0, and Energy Star homes are 85. In addition a 1.764 Wp (peak Watt) rated PV array was used on each house. This was made up of solar shakes that were in visual harmony with the roofing material used. A demand response tool was developed to control the amount of electricity used during times of peak demand. While demand response techniques have been used in the utility industry for some time, this particular approach is designed to allow the customer to decide the degree of participation in the response activity. The temperature change in the residence can be decided by the residents by