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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 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.

  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 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.

  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. 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

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. What do we know about effects of desert dust on air quality and human health in West Africa compared to other regions?

    PubMed

    De Longueville, Florence; Hountondji, Yvon-Carmen; Henry, Sabine; Ozer, Pierre

    2010-12-01

    This study aims to compare, on the one hand, the geographical distribution of the desert dust source areas, their contribution to quantities emitted into the atmosphere, the trajectories and the quantities deposited, with on the other hand the areas of research interest focused on the desert dust impacts on air quality and/or human health. Based on a systematic review of the literature using the ISI Web of Knowledge database, we found 231 articles published over the last decade on the desert dust impacts on air quality. Of these, 48% concerned Asian dust and 39% Saharan dust, with the remaining 13% divided between the other dust source areas. However, only one of these studies addressed the worsening air pollution in West Africa, even though it is very close to the Sahara, the greatest contributor to the global dust budget. Moreover, there have been very few studies (41) looking at the direct links between desert dust and human health; in this context too, no interest has been shown in West Africa. Yet this region is also among the areas in which morbidity rates have been noted to be far higher than those found in other regions of the world, and where respiratory infections alone account for more than 20% of the causes of infant mortality. This survey highlights a clear imbalance between those areas most exposed to dust and the most studied areas in terms of dust impacts. Given these findings and the often alarming results published about other regions of the world, we advocate a revival of interest in research on West Africa in order to achieve a better understanding of the desert dust impacts on air quality and health among the populations of this region.

  10. 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.

  11. Availability of water controls Crassulacean acid metabolism in succulents of the Richtersveld (Namib desert, South Africa).

    PubMed

    von Willert, D J; Brinckmann, E; Scheitler, B; Eller, B M

    1985-05-01

    Features of Crassulacean acid metabolism (CAM) were studied in a variety of different succulents in response to climatic conditions between March 1977 and October 1983 in the southern Namib desert (Richtersveld). A screening in 1977 and 1978 revealed that nearly all investigated succulents performed a CAM, but overnight accumulation of malate declined gradually with decreasing soil water potential, tissue osmotic potential, and leaf water content. This was further substantiated by an extended period of insufficient rainfall in 1979 and 1980 which damaged the evergreen CAM succulents between 80 and 100%. In most of the species still living, neither CO2-gas exchange nor diurnal acid fluctuation, indicative of CAM, could be detected unless an abundant rainfall restored both CAM features. Plants persisted in a stage of latent life.Water supply is one necessary prerequisite for CAM in the Richtersveld. But even well-watered plants with CAM were sensitive to short-term water stress caused by high water-vapour partialpressure deficit (VPD) in the night, which reduced or prevented CO2 uptake and resulted in a linear relation between overnight accumulated malate and VPD. The results do not support the opinion that, for the Namib succulents, CAM is an adaptive mechanism to water stress since long-term and short-term water stress stopped nocturnal malate synthesis, but instead lead to the conclusion that nocuturnal CO2 fixation is only performed when the water status of the plant can be improved simultaneously.

  12. 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).

  13. 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

  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. 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…

  16. 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…

  17. 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…

  18. 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

  19. 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.

  20. Africa.

    ERIC Educational Resources Information Center

    Crofts, Marylee

    1986-01-01

    Reviews myths, misconceptions, and unintentional biases about Africa in United States K-12 social studies textbooks. Summarizes common topics and recommends additions. Provides the names, addresses and phone numbers of 10 university-based African Studies centers. Concludes that improvements to textbooks must continue. (JDH)

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

    PubMed

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

    2013-05-14

    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.

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

    PubMed

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

    2013-05-14

    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

  3. 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

  4. 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)

  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. 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.

  7. 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.

  8. 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

  9. Desert Scrublands

    USGS Publications Warehouse

    Jones, L.L.C.; Halama, K.J.; Lovich, R.E.

    2016-01-01

    Desert scrublands comprise the lower to mid-elevation portions of four different ecosystems including the Chihuahuan, Great Basin, Mojave and Sonoran Deserts. Together the area inside their outer boundaries includes over 8% of the surface area of the United States. Despite significant differences in the flora and fauna of these bioregions they all share the common trait of being arid shrub-steppe ecosystems, receiving, on average, less than 254 mm of rain per year. The austere nature of these landscapes belies their significant biodiversity, the amazing behavioral and physiological adaptations of the biota, and the fragility of the ecosystems to human disturbances. For example, the Mojave Desert alone has at least 250 species of ephemeral plants, mostly winter annuals, and up to 90% are endemic.

  10. 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)…

  11. 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.

  12. 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.

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

    PubMed

    Shinn, Eugene A; Griffin, Dale W; Seba, Douglas B

    2003-08-01

    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.

  14. 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…

  15. Southwestern desert resources

    USGS Publications Warehouse

    Halvorson, William L.; van Riper, Charles; Schwalbe, Cecil R.

    2010-01-01

    The southwestern deserts stretch from southeastern California to west Texas and then south to central Mexico. The landscape of this region is known as basin and range topography featuring to "sky islands" of forest rising from the desert lowlands which creates a uniquely diverse ecology. The region is further complicated by an international border, where governments have caused difficulties for many animal populations. This book puts a spotlight on individual research projects which are specific examples of work being done in the area and when they are all brought together, to shed a general light of understanding the biological and cultural resources of this vast region so that those same resources can be managed as effectively and efficiently as possible. The intent is to show that collaborative efforts among federal, state agency, university, and private sector researchers working with land managers, provides better science and better management than when scientists and land managers work independently.

  16. 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

  17. 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.

  18. 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)

  19. 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.

  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. 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.

  2. 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 ...

  3. Test of Continental Drift by Comparison of Radiometric Ages: A pre-drift reconstruction shows matching geologic age provinces in West Africa and Northern Brazil.

    PubMed

    Hurley, P M; Rand, J R; Pinson, W H; Fairbairn, H W; de Almeida, F F; Melcher, G C; Cordani, U G; Kawashita, K; Vandoros, P

    1967-08-01

    1) The distribution of age values obtained by potassium-argon determinations and whole-rock rubidium-strontium determinations appears to be almost identical for West African rocks of the pervasive Eburnean Orogenic Cycle and basement rocks at opposite locations in South America. 2) There is also a close correlation, with respect to potassium-argon age determinations on micas, rubidium-strontium determinations on total-rock samples, and the extent to which these two sets of values differ, between rocks of the Pan-African Orogenic Cycle and rocks of the Caririan Orogenic Cycle in Brazil, where these two groups of rocks lie opposite each other in the two continents. 3) When Africa and South America are "fitted together," the sharply defined boundary between the Eburnean and the Pan-African age provinces in West Africa strikes directly toward the corresponding age boundary in northeast Brazil. 4) The transition from the 550-million-year Pan-African age province to the 2000-million-year age province in the Congo Craton in Cameroun-Gabon is matched in the rocks near the corresponding part of the east coast of Brazil. However the geological and age data are insufficient to do more than suggest the possibility of another age-boundary correlation here. 5) The evidence reported here supports the hypothesis of continental drift.

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. 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…

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. Deserts : geology and resources

    USGS Publications Warehouse

    Walker, Alta S.

    1996-01-01

    Approximately one-third of the Earth's land surface is desert, arid land with meager rainfall that supports only sparse vegetation and a limited population of people and animals. Deserts stark, sometimes mysterious worlds have been portrayed as fascinating environments of adventure and exploration from narratives such as that of Lawrence of Arabia to movies such as "Dune." These arid regions are called deserts because they are dry. They may be hot, they may be cold. They may be regions of sand or vast areas of rocks and gravel peppered with occasional plants. But deserts are always dry. Deserts are natural laboratories in which to study the interactions of wind and sometimes water on the arid surfaces of planets. They contain valuable mineral deposits that were formed in the arid environment or that were exposed by erosion. Because deserts are dry, they are ideal places for human artifacts and fossils to be preserved. Deserts are also fragile environments. The misuse of these lands is a serious and growing problem in parts of our world.

  14. Quantifying the Worldwide Digital Divide: The Emergence of Africa

    NASA Astrophysics Data System (ADS)

    Cottrell, Roger

    2011-04-01

    Africa is huge with over 1 billion people, speaking over 1000 languages, with huge rainforests and vast deserts. Yet as we shall show it badly lags behind the rest of the world in its Internet performance. This talk will show how we measure the Internet Performance. These measurements cover countries of the world containing over 99% of the world's Internet connected population. Using these measurements we illustrate the overall Internet performance for the world in particular for: throughput, losses, jitter, Round Trip Times, availability etc. We will demonstrate the performance trends for the last 13 years, in particular illustrating how Africa is not only behind all other regions and one to two decades behind developed regions, but worse is falling further behind. We also compare our results with the International Telecommunications Union's ICT Development Index (IDI) that measures the development for over 150 countries. We then focus on the promising emerging situation in Africa following the dramatic increases in performance due to submarine fibre connectivity that was driven partially by soccer's 2010 World Cup in South Africa. We conclude that despite the many challenges in Africa, there is promising potential for a dramatic improvement in the near future, but there is still a long way to go.

  15. New Insights in Preservation of Meteorites in Hot Deserts: The Oldest Hot Desert Meteorite Collection.

    NASA Astrophysics Data System (ADS)

    Hutzler, A.; Rochette, P.; Bourlès, D.; Gattacceca, J.; Merchel, S.; Jull, A. J. T.; Valenzuela, M.

    2016-08-01

    Terrestrial ages of a subset of a chilean meteorite collection have been determined with cosmogenic nuclides. We show here that provided the environnement is favorable enough, hot desert meteorites can survive over a million year.

  16. 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

  17. 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...

  18. 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.

  19. 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.

  20. 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

  1. Background-like nitrate in desert air

    NASA Astrophysics Data System (ADS)

    Wu, Feng; Zhang, Daizhou; Cao, Junji; Zhang, Ting; An, Zhisheng

    2014-02-01

    The atmospheric nitrogen cycle is a key process driving the earth's environmental evolution. Current model studies require knowledge of NOx soil emissions from various land types, but desert emissions remain unquantified or are not addressed with high confidence. Our measurements at two observatories in Taklimakan desert during a dust episode showed an approximately stable and dust-independent nitrate in the air. Its concentration estimated from PM2.5, PM10 and TSP samples under non-dust, floating dust and dust storm conditions was 3.81 ± 1.24 μg m-3, 2.95 ± 0.69 μg m-3, 4.99 ± 1.71 μg m-3, respectively, despite the more-than-one-order difference of dust loading. This concentration was much larger than that in remote marine and tropical forest air. Comprehensive investigation revealed a similar presence of nitrate in other desert air. The nitrate was hypothesized to be the consequence of the conversion of NOx released from desert soils. These results indicate a background-like nitrate and active reactions of nitrogen compounds in desert air.

  2. 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

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

    PubMed

    Griffin, Dale W

    2007-07-01

    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.

  4. 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.

  5. 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)

  6. 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.

  7. 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

  8. Historical Capsule: South Africa.

    ERIC Educational Resources Information Center

    Cole, Robert

    1988-01-01

    Briefly traces the history of South Africa from British acquisition in 1815 through the creation of the Union of South Africa in 1910. Presents a chronicle of the year 1900 to show part of the European achievement in close-up. Lists accomplishments in literature, fine arts, science, technology, music, theater, and dance. (GEA)

  9. Catastrophic desert formation in Daisyworld.

    PubMed

    Ackland, Graeme J; Clark, Michael A; Lenton, Timothy M

    2003-07-01

    Feedback between life and its environment is ubiquitous but the strength of coupling and its global implications remain hotly debated. Abrupt changes in the abundance of life for small changes in forcing provide one indicator of regulation, for example, when vegetation-climate feedback collapses in the formation of a desert. Here we use a two-dimensional "Daisyworld" model with curvature to show that catastrophic collapse of life under gradual forcing provides a testable indicator of environmental feedback. When solar luminosity increases to a critical value, a desert forms across a wide band of the planet. The scale of collapse depends on the strength of feedback. The efficiency of temperature regulation is limited by mutation rate in an analogous manner to the limitation of adaptive fitness in evolutionary theories. The final state of the system emerging from single-site rules can be described by two global quantities: optimization of temperature regulation and maximization of diversity, which are mathematically analogous to energy and entropy in thermodynamics.

  10. 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.

  11. Aquaporins in desert rodent physiology.

    PubMed

    Pannabecker, Thomas L

    2015-08-01

    Desert rodents face a sizeable challenge in maintaining salt and water homeostasis due to their life in an arid environment. A number of their organ systems exhibit functional characteristics that limit water loss above that which occurs in non-desert species under similar conditions. These systems include renal, pulmonary, gastrointestinal, nasal, and skin epithelia. The desert rodent kidney preserves body water by producing a highly concentrated urine that reaches a maximum osmolality nearly three times that of the common laboratory rat. The precise mechanism by which urine is concentrated in any mammal is unknown. Insights into the process may be more apparent in species that produce highly concentrated urine. Aquaporin water channels play a fundamental role in water transport in several desert rodent organ systems. The role of aquaporins in facilitating highly effective water preservation in desert rodents is only beginning to be explored. The organ systems of desert rodents and their associated AQPs are described.

  12. 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.

  13. 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…

  14. 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

  15. 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.

  16. 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

  17. 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.

  18. Southern Africa

    Atmospheric Science Data Center

    2013-04-16

    article title:  Southern Africa     View larger JPEG image ... visibility of smoke plumes and haze. The southern tip of South Africa is at the bottom of the image, and Zambia is at the top. ... MISR Team. Aug 25, 2000 - South Africa to Zambia including the Okavango Delta. project:  ...

  19. 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

  20. The origin of sulphur in gypsum and dissolved sulphate in the Central Namib Desert, Namibia

    NASA Astrophysics Data System (ADS)

    Eckardt, F. D.; Spiro, B.

    1999-02-01

    This study investigates the sulphur source of gypsum sulphate and dissolved groundwater sulphate in the Central Namib Desert, home to one of Africa's most extensive gypsum (CaSO 4·2H 2O) accumulations. It investigates previously suggested sulphate precursors such as bedrock sulphides and decompositional marine biogenic H 2S and studies the importance of other potential sources in order to determine the origin of gypsum and dissolved sulphate in the region. An attempt has been made to sample all possible sulphur sources, pathways and types of gypsum accumulations in the Central Namib Desert. We have subjected those samples to sulphur isotopic analyses and have compiled existing results. In addition, ionic ratios of Cl/SO 4 are used to determine the presence of non-sea-salt (NSS) sulphur in groundwater and to investigate processes affecting groundwater sulphate. In contrast to previous work, this study proposes that the sulphur cycle, and the formation of gypsum, in the Namib Desert appears to be dominated by the deposition of atmospheric sulphates of phytoplanktonic origin, part of the primary marine production of the Benguela upwelling cells. The aerosol sulphates are subjected to terrestrial storage within the gypsum deposits on the hyper-arid gravel plain and are traceable in groundwater including coastal sabkhas. The hypothesis of decompositional marine biogenic H 2S or bedrock sulphide sources, as considered previously for the Namib Desert, cannot account for the widespread accumulation of gypsum in the region. The study area in the Central Namib Desert, between the Kuiseb and Omaruru rivers, features extensive gypsum accumulations in a ca. 50-70 km wide band, parallel to the shore. They consist of surficial or shallow pedogenic gypsum crusts in the desert pavement, hydromorphic playa or sabkha gypsum, as thin isolated pockets on bedrock ridges and as discrete masses of gypsum selenite along some faults. The sulphur isotopic values (δ 34S ‰CDT) of these

  1. 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.

  2. 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.…

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Evaluation of the Landsat-5 TM radiometric calibration history using desert test sites

    NASA Astrophysics Data System (ADS)

    Markham, Brian L.; Barsi, Julia A.; Helder, Dennis L.; Thome, Kurtis J.; Barker, John L.

    2006-09-01

    The U.S. radiometric calibration procedure for the reflective bands of the Landsat-5 Thematic Mapper was updated in May 2003. This update was based on a model of the performance of the instrument developed from its response to the best-behaved internal calibration lamp and from a cross calibration with Landsat-7 ETM+ that occurred in June 1999. Since this update was performed, there have been continued attempts to validate the model. These validations have relied primarily upon data acquired over deserts of the world. These studies have been limited by the amount of data available over any one site for the 22-year life of the mission. Initial attempts over the desert Southwest of the United States were inconclusive, though they were suggestive of additional degradation occurring in the shorter wavelength channels. More recently, significant holdings from European Space Agency of data over North Africa have been made available for analysis. The North Africa test area results to date for one site in Libya are considerably less noisy than the North American datasets. They indicate an exponential-like decay of about 19%, 16%, 8% and 4% for TM bands 1, 2, 3 and 4, with the degradation, at least in bands 1 and 2 occurring throughout the mission. The current model shows changes of roughly the same magnitude, but with the change occurring more rapidly so that nearly all the change is completed in 4 years. These results are generally consistent with independent work going on outside of this effort. Additional sites are being analyzed as data become available.

  8. Evaluation of great deserts of the world for perpetual radiowaste storage

    SciTech Connect

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

    1982-12-31

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

  9. 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

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Desert speleothems reveal climatic window for African exodus of early modern humans

    NASA Astrophysics Data System (ADS)

    Vaks, Anton; Bar-Matthews, Miryam; Ayalon, Avner; Matthews, Alan; Halicz, Ludwik; Frumkin, Amos

    2007-09-01

    One of the first movements of early modern humans out of Africa occurred 130-100 thousand years ago (ka), when they migrated northward to the Levant region. The climatic conditions that accompanied this migration are still under debate. Using high-precision multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS) U-Th methods, we dated carbonate cave deposits (speleothems) from the central and southern Negev Desert of Israel, located at the northeastern margin of the Saharan-Arabian Desert. Speleothems grow only when rainwater enters the unsaturated zone, and this study reveals that a major cluster of wet episodes (the last recorded in the area) occurred between 140 and 110 ka. This episodic wet period coincided with increased monsoonal precipitation in the southern parts of the Saharan-Arabian Desert. The disappearance at this time of the desert barrier between central Africa and the Levant, and particularly in the Sinai-Negev land bridge between Africa and Asia, would have created a climatic “window” for early modern human dispersion to the Levant.

  19. 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.

  20. "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…

  1. 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.

  2. 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.

  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. 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.

  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. 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

  7. 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

  8. 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

  9. West Africa

    Atmospheric Science Data Center

    2013-04-16

    ... article title:  Hazy and Dusty Skies over Western Africa     View Larger Image ... the entire globe between 82 degrees north and 82 degrees south latitude. These data products were generated from a portion of the ...

  10. South Africa

    Atmospheric Science Data Center

    2013-04-16

    article title:  Red Tide Strands South African Rock Lobsters     ... and on atmospheric and oceanic conditions. At Elands Bay in South Africa's Western Cape province, about 1000 tons of rock lobsters beached ...

  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.

  12. 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

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. Profile storage of organic/inorganic carbon in soil: from forest to desert.

    PubMed

    Wang, Yugang; Li, Yan; Ye, Xuehua; Chu, Yu; Wang, Xinping

    2010-03-15

    Understanding the distribution of organic/inorganic carbon storage in soil profile is crucial for assessing regional, continental and global soil C stores and predicting the consequences of global change. However, little is known about the organic/inorganic carbon storages in deep soil layers at various landscapes. This study was conducted to determine the soil organic/inorganic carbon storage in soil profile of 0-3m at 5 sites of natural landscape from forest to desert. Landscapes are temperate forest, temperate grassland, temperate shrub-grassland, temperate shrub desert, and temperate desert. Root mass density and carbon contents at the profile were determined for each site. The results showed that considerable decrease in root biomass and soil organic carbon content at the soil profile of 0-3m when landscape varied from forest to desert along a precipitation gradient, while soil inorganic carbon content increased significantly along the precipitation gradient. Namely, for density of soil organic carbon: forest>grassland>shrub-grassland>shrub desert>desert; for density of soil inorganic carbon: forest, grasslanddesert (P<0.05 in all cases). In landscapes other than forest, more than 50% soil carbon storage was found in 1-3m depth. For grassland and shrub-grassland, the contribution from 1-3m was mainly in the form of organic carbon, while for shrub desert and desert the contribution from this depth was mainly in the form of inorganic carbon. The comparison of soil C storage between top 0-1m and 1-3m showed that the using top 1m of soil profile to estimate soil carbon storages would considerably underestimate soil carbon storage. This is especially true for organic soil carbon at grassland region, and for soil inorganic carbon at desert region.

  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. 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.

  20. 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.

  1. 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

  2. Path integration in desert ants, Cataglyphis fortis.

    PubMed

    Müller, M; Wehner, R

    1988-07-01

    Foraging desert ants, Cataglyphis fortis, continually keep track of their own posotions relative to home- i.e., integrate their tortuous outbound routes and return home along straight (inbound) routes. By experimentally manipulating the ants' outbound trajectories we show that the ants solve this path integration problem not by performing a true vector summation (as a human navigator does) but by employing a computationally simple approximation. This approximation is characterized by small, but systematic, navigational errors that helped us elucidate the ant's way of computing its mean home vector.

  3. 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

    2015-05-11

    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.

  4. 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

  5. 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.

  6. Incapacitation and just deserts as motives for punishment.

    PubMed

    Darley, J M; Carlsmith, K M; Robinson, P H

    2000-12-01

    What motivates a person's desire to punish actors who commit intentional, counternormative harms? Two possible answers are a just deserts motive or a desire to incarcerate the actor so that he cannot be a further danger to society. Research participants in two experiments assigned punishments to actors whose offenses were varied with respect to the moral seriousness of the offense and the likelihood that the perpetrator would commit similar future offenses. Respondents increased the punishment as the seriousness of the offense increased, but their sentences were not affected by variations in the likelihood of committing future offenses, suggesting that just deserts was the primary sentencing motive. Only in a case in which a brain tumor was identified as the cause of an actor's violent action, a case that does not fit the standard prototype of a crime intentionally committed, did respondents show a desire to incarcerate the actor in order to prevent future harms rather than assigning a just deserts based punishment.

  7. 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.

  8. Food insecurity and food deserts.

    PubMed

    Camp, Nadine L

    2015-08-15

    Food insecurity has been steadily increasing in the United States with prevalence at nearly 15% of all households. Nurse practitioners can assess for food insecurity and provide local resources for families living in neighborhoods without easy access to healthy foods, otherwise known as food deserts.

  9. On a Crowded Desert Island.

    ERIC Educational Resources Information Center

    Rothstein, Samuel

    1989-01-01

    Suggests reference sources most appropriate for a desert island. In addition to "Robinson Crusoe" (Daniel Defoe) and a reference guide to the literature of travel, the list includes basic books on reference work, guides to reference sources, journals, an almanac, encyclopedias, a guide to English usage, and a book of quotations. (14 references)…

  10. 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.

  11. 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

  12. 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

  13. 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.

  14. 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 ...

  15. 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.

  16. 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

  17. 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.

  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. 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

  20. 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

  1. 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.

  2. 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

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

    PubMed

    Rosenfeld, D; Rudich, Y; Lahav, R

    2001-05-22

    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.

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. Egypt western desert activity hits high gear

    SciTech Connect

    Petzet, G.A.

    1996-11-04

    Exploration in Egypt`s western desert is turning up large oil and gas reserves in several sub-basins. Though not a threat to the Gulf of Suez`s oil production dominance, the western desert`s output is climbing. And gas production is also set to rise as more pipelines are built. The paper describes the geology, Qarun field production, further exploration at Qarun and the Khalda/Obaiyed gas.

  9. 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.

  10. 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

  11. 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.

  12. Aerobiology and the global transport of desert dust

    USGS Publications Warehouse

    Kellogg, Christina A.; Griffin, Dale W.

    2006-01-01

    Desert winds aerosolize several billion tons of soil-derived dust each year, including concentrated seasonal pulses from Africa and Asia. These transoceanic and transcontinental dust events inject a large pulse of microorganisms and pollen into the atmosphere and could therefore have a role in transporting pathogens or expanding the biogeographical range of some organisms by facilitating long-distance dispersal events. As we discuss here, whether such dispersal events are occurring is only now beginning to be investigated. Huge dust events create an atmospheric bridge over land and sea, and the microbiota contained within them could impact downwind ecosystems. Such dispersal is of interest because of the possible health effects of allergens and pathogens that might be carried with the dust.

  13. Erosion resistance of bionic functional surfaces inspired from desert scorpions.

    PubMed

    Zhiwu, Han; Junqiu, Zhang; Chao, Ge; Li, Wen; Ren, Luquan

    2012-02-01

    In this paper, a bionic method is presented to improve the erosion resistance of machine components. Desert scorpion (Androctonus australis) is a typical animal living in sandy deserts, and may face erosive action of blowing sand at a high speed. Based on the idea of bionics and biologic experimental techniques, the mechanisms of the sand erosion resistance of desert scorpion were investigated. Results showed that the desert scorpions used special microtextures such as bumps and grooves to construct the functional surfaces to achieve the erosion resistance. In order to understand the erosion resistance mechanisms of such functional surfaces, the combination of computational and experimental research were carried out in this paper. The Computational Fluid Dynamics (CFD) method was applied to predict the erosion performance of the bionic functional surfaces. The result demonstrated that the microtextured surfaces exhibited better erosion resistance than the smooth surfaces. The further erosion tests indicated that the groove surfaces exhibited better erosion performance at 30° injection angle. In order to determine the effect of the groove dimensions on the erosion resistance, regression analysis of orthogonal multinomials was also performed under a certain erosion condition, and the regression equation between the erosion rate and groove distance, width, and height was established.

  14. 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.

  15. Prospects and constraints of desert agriculture: lessons from West Omdurman.

    PubMed

    El Gamri, Tarig

    2004-12-01

    Sudan is the largest country in Africa with an area of about 2.5 million km2; the country hosts a population of about 31 million people. About two-thirds of the country area is located within arid and semi-arid regions. Recently, especially during the last half of the previous century, these regions were subject to various forms of land degradation. This paper discusses the general prospects and constraints of desert agriculture. It also presents a detailed case study of West Omdurman, which is located in a semi-desert climatic zone. The ambitious plans to utilise the area for agricultural production were initiated because of the relatively fertile soil, availability of water and the proximity of the area to marketing and export centres. The paper discusses the different land use systems experienced in the area, reasons for failure are identified and possible remedies discussed. In addition, constraints facing the proposed West Omdurman Canal Project are also discussed. Finally, the paper reviews the major research findings of Rawakeeb Dryland Research Center with regard to promoting agricultural productivity.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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

  1. Desert ants learn vibration and magnetic landmarks.

    PubMed

    Buehlmann, Cornelia; Hansson, Bill S; Knaden, Markus

    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.

  2. 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

  3. 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

  4. 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).

  5. Off-Road and the Fragile Desert

    ERIC Educational Resources Information Center

    Stebbins, Robert C.

    1974-01-01

    Part one of a two-part article sets forth the dimensions and the political-cultural aspects of the use of off-road vehicles in desert areas. Presents arguments for and against off-road vehicle use on national-resource land as exemplified in the California Desert. (Editor/JR)

  6. 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…

  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. Diversity and Ecology of Viruses in Hyperarid Desert Soils.

    PubMed

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

    2015-11-20

    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.

  9. 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

  10. 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.

  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. 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.

  13. 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.

  14. 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...

  15. Nitrogen economy of endolithic microbial communities in hot and cold deserts.

    PubMed

    Friedmann, E I; Kibler, A P

    1980-06-01

    The source of combined nitrogen in endolithic microbial communities was studied in samples from desert localities in North and South America, the Middle East, South Africa, and Antarctica. Nitrogen fixation (acetylene reduction) seems to occur only exceptionally. Evidence suggests that, in general, the nitrogen source for endolithic microorganisms in deserts is abiotically fixed nitrogen produced by atmospheric electric discharges (lightning or aurorae), conveyed to the rock by atmospheric precipitation. Nitrogen is apparently not a limiting factor in these low-productivity communities. An incomplete nitrogen cycle seems to be present which includes the following pathways: supply of nitrates and ammonia from the atmosphere; decomposition of organic matter to ammonia; reassimilation of ammonia; ammonia volatilization; loss of organic matter through weathering (only in certain Antarctic rocks); biological nitrogen fixation (exceptional).

  16. 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.

  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. 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

  19. Dynamics and Resilience of Desert Ecosystems under Changing Climate

    NASA Astrophysics Data System (ADS)

    Stewart, J.; Wainwright, J.; Parsons, A. J.; Okin, G. S.; Bestelmeyer, B.; Fredrickson, E. L.; Schlesinger, W. H.

    2008-12-01

    Ecological models have been used to probe the causes of spatial complexity and predict specific responses of desert ecosystems. However, many models have been limited in their focus: models of dynamics have been developed with no consideration of the inherent patchiness or patterns in the vegetation, or else models have been developed to generate patterns with no consideration of the dynamics. Models that attempt to address both pattern and dynamics have been qualitative and descriptive. Furthermore, if, as is commonly believed, both dynamics and patterns/patchiness are a function of resource (specifically water) limitation, then there has been little integration of this relationship into such models. Consequently, these models have limited utility for understanding resilience of desert ecosystems. Here we present an integrated approach to the observed patchiness and dynamics in desert vegetation that is based on a sound process-based understanding and is formulated to accommodate previous conceptual models within an overarching framework. This framework is implemented as a mathematical model. Our contribution represents an advance over previous work in that we propose a general model framework for the analysis of ecosystem change in deserts that explicitly considers spatial interactions among multiple vegetation types and multiple resources, and predict specific responses to a variety of endogenous and exogenous disturbances. We present an application of this model to investigate conditions the conditions that would result in observed desert vegetation patterns in south-western desert systems of North America. In particular, we investigate the encroachment of shrubs (Larrea tridentata) into formerly pure stands of grass (Bouteloua eriopoda). We present the results of simulations that rest on rainfall data that was reconstructed for the Jornada Basin Long-Term Ecological Research site in southern New Mexico, USA based on 300-year tree- ring records. The results

  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. Mitochondrial DNA variability in Giraffa camelopardalis: consequences for taxonomy, phylogeography and conservation of giraffes in West and central Africa.

    PubMed

    Hassanin, Alexandre; Ropiquet, Anne; Gourmand, Anne-Laure; Chardonnet, Bertrand; Rigoulet, Jacques

    2007-03-01

    The giraffe (Giraffa camelopardalis) still survives in four countries of West and central Africa. The populations of Niger and Cameroon are generally assigned to the subspecies peralta, but those of Chad and the Central African Republic are taxonomically problematic, as they are referred to as either peralta, or antiquorum, or congoensis. In this study, a mitochondrial fragment of 1765 nucleotide sites, covering the complete cytochrome b gene, three transfer RNAs and a large part of the control region, was sequenced to assess the relationships between several populations of giraffe. The phylogenetic analyses performed on the 12 identified haplotypes indicate that northern giraffes constitute a natural group, distinct from that of southern giraffes. Surprisingly, the giraffes of Niger are found to be more closely related to the giraffes of East Africa (subspecies rothschildi and reticulata) than to those of central Africa. We conclude therefore that the subspecies peralta contains only the Niger giraffes, whereas the subspecies antiquorum includes all populations living in Cameroon, Chad, the Central African Republic, and southwestern Sudan. We suggest that the ancestor of the Nigerian giraffe dispersed from East to North Africa during the Quaternary period and thereafter migrated to its current Sahelian distribution in West Africa, in response to the development of the Sahara desert. This hypothesis implies that Lake Mega-Chad acted as a strong geographical barrier during the Holocene, preventing any contact between the subspecies peralta and antiquorum. Our study has direct implications for conservation management, as we show that no subspecies peralta is represented in any European zoos, only in Niger, with a small population of less than 200 individuals.

  2. Ecosystem responses to warming and watering in typical and desert steppes

    PubMed Central

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

    2016-01-01

    Global warming is projected to continue, leading to intense fluctuations in precipitation and heat waves and thereby affecting the productivity and the relevant biological processes of grassland ecosystems. Here, we determined the functional responses to warming and altered precipitation in both typical and desert steppes. The results showed that watering markedly increased the aboveground net primary productivity (ANPP) in a typical steppe during a drier year and in a desert steppe over two years, whereas warming manipulation had no significant effect. The soil microbial biomass carbon (MBC) and the soil respiration (SR) were increased by watering in both steppes, but the SR was significantly decreased by warming in the desert steppe only. The inorganic nitrogen components varied irregularly, with generally lower levels in the desert steppe. The belowground traits of soil total organic carbon (TOC) and the MBC were more closely associated with the ANPP in the desert than in the typical steppes. The results showed that the desert steppe with lower productivity may respond strongly to precipitation changes, particularly with warming, highlighting the positive effect of adding water with warming. Our study implies that the habitat- and year-specific responses to warming and watering should be considered when predicting an ecosystem’s functional responses under climate change scenarios. PMID:27721480

  3. 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.

  4. [Seasonal variations of soil organic carbon and microbial biomass carbon in degraded desert steppes of Inner Mongolia].

    PubMed

    Wu, Yong-Sheng; Ma, Wan-Li; L I, Hao; Lü, Gui-Fen; Lu, Ping

    2010-02-01

    Sampling sites were installed in Damao Banner, Siziwang Banner, and Sunite Right Banner of Inner Mongolia, which represented lightly, moderately, and heavily degraded desert steppes, respectively, and surface (0-20 cm) soil samples were collected to analyze the quantitative characteristics and seasonal dynamics of soil organic carbon (SOC) and microbial biomass carbon (MBC) in these steppes. The SOC and MBC contents decreased with the increasing degradation degree of desert steppe. The total amount of soil culturable microbes in lightly and moderately degraded desert steppes was higher than that in heavily degraded desert steppe, except in summer 2006, and the MBC content and the quantity of soil culturable microbes were higher in summer and autumn than in spring and winter. Correlation analysis showed that there was a significant positive correlation between SOC and MBC (P < 0.01), suggesting that both SOC and MBC could be used as the sensitive indicators to evaluate the degradation degree of desert steppe.

  5. 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.; 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. Desert wetlands—Archives of a wetter past

    USGS Publications Warehouse

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

    2015-12-16

    Scientists from the U.S. Geological Survey (USGS) are finding evidence of a much wetter past in the deserts of the American Southwest using a most unlikely source—wetlands. Wetlands form in arid environments where water tables approach or breach the ground surface. Often thought of as stagnant and unchanging, new evidence suggests that springs and wetlands responded dynamically to past episodes of abrupt climate change. Multiple cycles of deposition, erosion, and soil formation show that wetlands in the southwestern United States expanded and contracted many times during the past 35,000 years or so, before disappearing altogether as the last glacial period came to a close. USGS scientists are now studying the deposits to determine how closely conditions in the desert were tied to regional and global climate patterns in the past, and what it might mean for the fragile ecosystems in light of anticipated climate change in the future.

  12. 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.

  13. 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.

  14. 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.

  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.

  16. 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

  17. A comparison between desert and Mediterranean antlion populations: differences in life history and morphology.

    PubMed

    Scharf, I; Filin, I; Golan, M; Buchshtav, M; Subach, A; Ovadia, O

    2008-01-01

    We performed a transplant experiment to compare the life histories and morphologies of five geographically representative antlion Myrmeleon hyalinus populations along a sharp climatic gradient, from a Mediterranean climate in Israel's north to a desert climate in the south. Larvae were raised in two environmental chambers simulating Mediterranean and desert climates to investigate the extent to which the different populations exhibit phenotypic plasticity. Along the north-to-south climatic gradient, we observed a gradient in body mass prior to pupation and in pupation rate. Mediterranean populations suffered higher mortality rate when exposed to desert conditions, whereas the mortality rate of desert populations was consistent between Mediterranean and desert conditions. Our results regarding body mass, pupation rate and mortality rate suggest that Mediterranean populations had a more flexible response compared with desert populations. An analysis of digital photographs was used to measure population morphological differences, which were usually indicative of a decrease in trait size along the north-to-south gradient. We show how climatic gradients translate into phenotypic differences in an antlion population and provide a morphometric tool to distinguish between instar stages. PMID:18005016

  18. 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.

  19. 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

  20. 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…

  1. 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...

  2. 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.

  3. 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...

  4. 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

  5. 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.

  6. 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.

  7. Critical reflectance derived from MODIS: Application for the retrieval of aerosol absorption over desert regions

    NASA Astrophysics Data System (ADS)

    Wells, Kelley C.; Martins, J. Vanderlei; Remer, Lorraine A.; Kreidenweis, Sonia M.; Stephens, Graeme L.

    2012-02-01

    The determination of aerosol direct radiative forcing over desert regions requires accurate information about the aerosol single-scattering albedo (SSA); however, the brightness of desert surfaces in the visible and near-IR range complicates the retrieval of aerosol optical properties using passive space-based measurements. Here we use the critical reflectance method to retrieve spectral aerosol absorption from space over North Africa, a desert region that is predominantly impacted by absorbing dust and biomass burning aerosol. We examine the sensitivity of the critical reflectance parameter to aerosol physical and optical properties that are representative of the region, and we find that the critical reflectance has low sensitivity to assumptions of aerosol size and refractive index for dust-like particles, except at scattering angles near 180°, which should be avoided with this method. We use our findings to retrieve spectral SSA from critical reflectance derived from Moderate Resolution Imaging Spectroradiometer (MODIS) reflectances in the vicinity of two Aerosol Robotic Network (AERONET) stations: Tamanrasset, in the Algerian Sahara, and Banizoumbou, in the Sahel. We retrieve lower aerosol SSAs at Banizoumbou, which is often impacted by dust-smoke mixtures, and higher SSAs at Tamanrasset, where pure desert dust is the dominant aerosol. Our results generally fall within the AERONET uncertainty envelopes, although at Banizoumbou we retrieve a spectral dependence different from that of AERONET. On the basis of our analysis, we expect to be able to retrieve SSA from critical reflectance for pure dust with an uncertainty of 0.02 and to provide spatial and spectral SSA information that will help reduce current uncertainties in the aerosol radiative forcing over desert regions.

  8. A review on Balanites aegyptiaca Del (desert date): phytochemical constituents, traditional uses, and pharmacological activity

    PubMed Central

    Chothani, Daya L.; Vaghasiya, H. U.

    2011-01-01

    Balanites aegyptiaca Del. (Zygophyllaceae), known as ‘desert date,’ is spiny shrub or tree up to l0 m tall, widely distributed in dry land areas of Africa and South Asia. It is traditionally used in treatment of various ailments i.e. jaundice, intestinal worm infection, wounds, malaria, syphilis, epilepsy, dysentery, constipation, diarrhea, hemorrhoid, stomach aches, asthma, and fever. It contains protein, lipid, carbohydrate, alkaloid, saponin, flavonoid, and organic acid. Present review summarizes the traditional claims, phytochemistry, and pharmacology of B. aegyptiaca Del reported in scientific literature. PMID:22096319

  9. 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.

  10. 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

  11. Population growth and development planning in Africa.

    PubMed

    1980-12-01

    Some of the consequences of rapid population growth and their implications for the economic development of the Africa region in the 1980s are outlined. The total population of Africa was estimated to be 412 million in 1976, or 10.2% of the total world population of 4044 million. Population density of the region is comparatively low, but the crude density measure of 14 persons per square kilometer in 1977 obscures the very high percentage of Africa's land which is desert or otherwise not arable. Continued high fertility rates in the region coupled with substantial decline in mortality rates especially for infants and children has resulted in Africa having a youthful population. The growth of cities due primarily to rural-urban migration is 1 of the most pressing problems of the region. Some countries in the region maintain pronatalist policies because they have a small population and regard population growth as a stimulus to the socioeconomic development effort. Few countries such as Kenya, Mauritius, Egypt, and Morocco consider rapid population growth a constraint on their development efforts and are now implementing national policies which aim at reducing the rate of growth of their populations. Population problems in Africa arise mainly from the fact that additions to the population needing education, housing, employment and to be fed adequately are increasing at a rate far more than most African countries can cope with. To illustrate the potential impact of population factors on development, the potential relationships between population and health, education, food supply, labor force supply and employment are analyzed.

  12. 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.; Smith, Mike; Hesse, Paul

    2005-01-01

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

  13. 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.

  14. Fires in Central Africa

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Hundreds of fires are set every year during the dry season in Central Africa. This true color image from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) shows dozens of smoke plumes in the Democratic Republic of the Congo on June 29, 2000. Residents burn away scrub and brush annually in the woody savanna to clear land for farming and grazing. For more information, visit the SeaWiFS Home Page, Global Fire Monitoring Fact Sheet, and 4km2 Fire Data Image Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. Landmark guidance and vector navigation in outbound desert ants.

    PubMed

    Merkle, Tobias; Wehner, Rüdiger

    2008-11-01

    This study deals with the influence landmark information has on the foraging behaviour of the desert ant, Cataglyphis fortis, especially with the interaction of such landmark information with the ants' path integration system. We show in the first experiment that desert ants that are captured immediately after leaving their nest and then transferred to a remote test area search for the nest rather than activate their previous path integration vector. In a second experiment, the ants had been trained to a landmark corridor on their way to the feeder. In the critical test situation, they were again captured immediately after they had left the nest and transferred to a test field where they faced one of the following three situations: (1) the same landmark corridor as used during the training phase, (2) no landmarks at all and (3) a landmark corridor rotated by 90 deg. as compared with the training situation. Nearly all ants in test situation (1) eventually followed the landmark corridor but most of them never reached the fictive feeder. In situation (2), the ants searched around the nest entrance. In situation (3), approximately one half of the ants searched for the nest, whereas most of the other ants followed the landmark corridor, i.e. headed in a completely wrong direction. Hence, familiar landmarks do not only influence the foraging behaviour of desert ants, e.g. in making the ants start their foraging runs but can even out-compete the ants' path integration system.

  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. Hf-Nd-Sr isotopic fingerprinting of mineral dust from Asian and North African deserts

    NASA Astrophysics Data System (ADS)

    Ji, J.; Zhao, W.; Balsam, W.

    2015-12-01

    Mineral dust accounts for more than 50% of the atmospheric dust loading and plays an important role in the marine and terrestrial geochemical cycles. The deserts in North Africa, Northern China and Southern Mongolia are the major sources of mineral dust and have been studied intensively over past decades, especially with Sr, Nd and recently Hf isotopes which are seen as powerful tools to identify source areas. However, the isotopic compositions of dust are highly dependent on particle size hindering the ability to accurately identify dust provenance. The clay fraction (<2 μm) comprises about half of all mineral dust and has unique minerals phases dominanted by clay minerals. Once the clay-sized particles are deflated to the upper troposphere, they are transported over long distances and are removed from the atmosphere mainly by wet deposition. Thus, the clay-sized isotopic fingerprints from deserts may be ideal targets not only for tracking the provenance tracing of long-distance transported mineral dust, but also to provide an unparalleled window for understanding the global dust cycle, especially eolian dust preserved in deep-sea sediments and ice cores. In this work we investigate multivariate joint radiogenic Sr, Nd, and Hf isotopic compositions obtained from complete dissolution of clay-sized fractions of surface sediments from Asian and North African deserts. Asian dust source samples included the ten Northern China deserts and sandy lands - the Taklimakan, Gurbantunggut, Qaidam, Badaim Jaran, Tengger and Mu Us deserts, and the Hobq, Hulun Buirm, Onqin Daga and Horqin sandy land - and Mongolian Gobi desert. North African dust samples were from four transects in the Sahara and Sahel from Mali, Togo, Egypt and Morocco . Our results on the clay-sized isotopic measurements of these samples describe (1) the general characteristics of dusts from the Asian with ɛNd from -17.3 to 0.98, ɛHf from -5.95 to 3.68 and 87Sr/86Sr from 0.710113 to 0.73306, and North

  2. 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…

  3. 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...

  4. 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

  5. Forecasting droughts in East Africa

    NASA Astrophysics Data System (ADS)

    Mwangi, E.; Wetterhall, F.; Dutra, E.; Di Giuseppe, F.; Pappenberger, F.

    2014-02-01

    The humanitarian crises caused by the recent droughts (2008-2009 and 2010-2011) in East Africa have illustrated that the ability to make accurate drought forecasts with sufficient lead time is essential. The use of dynamical model precipitation forecasts in combination with drought indices, such as the Standardized Precipitation Index (SPI), can potentially lead to a better description of drought duration, magnitude and spatial extent. This study evaluates the use of the European Centre for Medium-Range Weather Forecasts (ECMWF) products in forecasting droughts in East Africa. ECMWF seasonal precipitation shows significant skill for March-May and October-December rain seasons when evaluated against measurements from the available in situ stations from East Africa. The forecast for October-December rain season has higher skill than for the March-May season. ECMWF forecasts add value to the consensus forecasts produced during the Greater Horn of Africa Climate Outlook Forum (GHACOF), which is the present operational product for precipitation forecast over East Africa. Complementing the original ECMWF precipitation forecasts with SPI provides additional information on the spatial extent and intensity of the drought event.

  6. Africa's Geomosaic under Stress.

    ERIC Educational Resources Information Center

    de Blij, H. J.

    1991-01-01

    Traces the transformation of Subsaharan Africa during the last 35 years. Contends that the domino effect hastened decolonization and increased polarization within South Africa. Argues that modernization is taking place only in South Africa's core and that the geopolitical framework appears stable but may collapse from within. (NL)

  7. 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

  8. 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.

  9. Energy expenditure and efficiency of energy use in rodents: desert and non-desert species.

    PubMed

    Degen, A A

    1998-01-01

    Feeding and the search for food are the predominant activities of most rodents. Since desert rodents inhabit regions of generally low food availability, it has been theorized that their energetic requirements would be lower and/or their efficiency to use energy for maintenance and growth would be higher than for rodents from more temperate regions. Indeed, the basal metabolic rate, average daily metabolic rate and field metabolic rate of desert rodents have been found to be lower than those of non-desert rodents. However, the ability to use energy intake for maintenance by desert rodents was calculated to be lower than that of non-desert rodents. In addition, granivores were not different from omnivores and herbivores in energy use efficiency, but herbivores were more efficient than omnivores.

  10. 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

  11. [The population situation in Africa].

    PubMed

    Li, Q L

    1981-07-01

    The population growth rate in Africa has been the highest in the world since 1970--about 2.7% annually. A lower mortality rate because of better health conditions, their tradition of early marriage and polygamy, and the predominantly agricultural economy are the main reasons. The lack of coordination of such rapid population growth with the slow economic development and backward industrial and agricultural conditions have caused a very serious unemployment problem and inhibit increases in the living standard. The vast areas of desert and equatorial forest are sparsely inhabited. The coastline, Nile delta, and the plateaus are the most densely populated areas of the world. The abnormally developed cities cause expansion of the urban population and serious problems in employment, housing, traffic, health, and education. Many leaders of African countries have begun to realize the seriousness of the rapid population growth, and a few have begun family planning programs. Most countries have no official policies concerning population control and a few even encourage population growth.

  12. 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

  13. Distribution of Natural Perchlorate in a Desert Landscape-Amargosa Desert Research Site, Nevada

    NASA Astrophysics Data System (ADS)

    Andraski, B. J.; Jackson, A.; Welborn, T.; Stonestrom, D. A.; Bohlke, J. K.

    2011-12-01

    Knowledge of perchlorate (ClO4-) occurrence is important due to health concerns, evolving groundwater-protection regulations, and for forensic investigations. The distribution of natural ClO4- is being studied at the U.S. Geological Survey's Amargosa Desert Research Site to improve understanding of factors that influence its accumulation and cycling in a desert landscape. The first part of the study evaluated the effect of plants on shallow (0-30 cm) soil concentrations in three settings-shoulder slope, footslope, and valley floor; samples were collected adjacent to plants and in interspaces 2.5-5 m from plants. For the valley-floor, there was a 17-fold decrease between interspace (5.0 μg/kg) and plant-adjacent (0.3 μg/kg) ClO4- concentrations. Chloride (Cl-) concentrations also showed large differences and indicated salt accumulation beneath the interspace desert pavement, but localized leaching adjacent to plants. For the shoulder and footslope, differences between interspace and plant-adjacent ClO4- concentrations were smaller (two fold on average) and inverted (interspace 2.0 μg/kg; plant-adjacent 3.8 μg/kg), and differences between interspace and plant-adjacent Cl- were negligible. Shoulder and footslope indications of a localized increase in ClO4- adjacent to plants suggest a cyclic mechanism of plant uptake, bioaccumulation, and leaf drop. The second part of the study examined ClO4- variability across a 9-ha hillslope. Data first were analyzed by assigning each sampling point to one of three elevation bands-upper, middle, or lower. Soil and plant data both showed trends of increasing ClO4- with decreasing elevation. Concentrations were, for soil (μg/kg): upper (1.6) < middle (2.7) < lower (4.9); for plants: upper (17,330) < middle (20,320) < lower (38,800). Soil Cl-, however, decreased with decreasing elevation, but differences were negligible (mg/kg): upper (4.2) > middle (3.9) > lower (3.6). Multiple-linear regression analyses also were used to

  14. The response of aboveground net primary productivity of desert vegetation to rainfall pulse in the temperate desert region of northwest China.

    PubMed

    Li, Fang; Zhao, Wenzhi; Liu, Hu

    2013-01-01

    Rainfall events can be characterized as "pulses", which are discrete and variable episodes that can significantly influence the structure and function of desert ecosystems, including shifts in aboveground net primary productivity (ANPP). To determine the threshold and hierarchical response of rainfall event size on the Normalized Difference Vegetation Index (NDVI, a proxy for ANPP) and the difference across a desert area in northwestern China with two habitats - dune and desert - we selected 17 independent summer rainfall events from 2005 to 2012, and obtained a corresponding NDVI dataset extracted from MODIS images. Based on the threshold-delay model and statistical analysis, the results showed that the response of NDVI to rainfall pulses began at about a 5 mm event size. Furthermore, when the rainfall event size was more than 30 mm, NDVI rapidly increased 3- to 6-fold compared with the response to events of less than 30 mm, suggesting that 30 mm was the threshold for a large NDVI response. These results revealed the importance of the 5 mm and 30 mm rainfall events for plant survival and growth in desert regions. There was an 8- to 16-day lag time between the rainfall event and the NDVI response, and the response duration varied with rainfall event size, reaching a maximum of 32 days. Due to differences in soil physical and mineralogical properties, and to biodiversity structure and the root systems' abilities to exploit moisture, dune and desert areas differed in precipitation responses: dune habitats were characterized by a single, late summer productivity peak; in contrast, deserts showed a multi-peak pattern throughout the growing season.

  15. 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

  16. Hydrotaxis of cyanobacteria in desert crusts.

    PubMed

    Pringault, O; Garcia-Pichel, F

    2004-05-01

    We studied the migration of cyanobacteria in desert crusts from Las Bárdenas Reales (Spain). The crusts were almost exclusively colonized by the filamentous cyanobacterium Oscillatoria, which formed a dense layer approximately 600 microm thick located between 1.5 and 2.1 mm deep. Laboratory and field experiments showed that saturation of the crust with liquid water induced a migration of the cyanobacteria leading to a significant greening of the surface within a few minutes. Under light and rapid evaporation, the green color rapidly disappeared and the crust surface was completely devoid of filaments within 60 min. In contrast, 260 min was required to recover the original white color of the crust when slow evaporation was experimentally imposed. The up and down migration following wetting and drying occurred also in the dark. This demonstrates that light was not a required stimulus. Addition of ATP synthesis inhibitors prevented the cyanobacterium from migrating down into the crust, with filaments remaining on the surface. Therefore, the disappearance of the green color observed during desiccation can only be attributed to an active cyanobacterial motility response to the decrease in the water content. The simplest explanation that can account for the evidence gathered is the presence of a mechanism that links, directly or indirectly, these motility responses to gradients in water content, namely a form of hydrotaxis. PMID:14605777

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. Desert Amplification in a Warming Climate.

    PubMed

    Zhou, Liming

    2016-08-19

    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.

  2. 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

  3. Desert Amplification in a Warming Climate

    NASA Astrophysics Data System (ADS)

    Zhou, Liming

    2016-08-01

    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.

  4. 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

  5. Desert basins of the Southwest

    USGS Publications Warehouse

    Leake, Stanley A.; Konieczki, Alice D.; Rees, Julie A.H.

    2000-01-01

    Ground water is among the Nation’s most important natural resources. It provides drinking water to urban and rural communities, supports irrigation and industry, sustains the flow of streams and rivers, and maintains riparian and wetland ecosystems. In many areas of the Nation, the future sustainability of ground-water resources is at risk from overuse and contamination. Because ground-water systems typically respond slowly to human actions, a long-term perspective is needed to manage this valuable resource. This publication is one in a series of fact sheets that describe ground-water-resource issues across the United States, as well as some of the activities of the U.S. Geological Survey that provide information to help others develop, manage, and protect ground-water resources in a sustainable manner. Ground-water resources in the Southwest are among the most overused in the United States. Natural recharge to aquifers is low and pumping in many areas has resulted in lowering of water tables. The consequences of large-scale removal of water from storage are becoming increasingly evident. These consequences include land subsidence; loss of springs, streams, wetlands and associated habitat; and degradation of water quality. Water managers are now seeking better ways of managing ground-water resources while looking for supplemental sources of water. This fact sheet reviews basic information on ground water in the desert basins of the Southwest. Also described are some activities of the U.S. Geological Survey (USGS) that are providing scientific information for sustainable management of ground-water resources in the Southwest. Ground-water sustainability is defined as developing and using ground water in a way that can be maintained for an indefinite time without causing unacceptable environmental, economic, or social consequences.

  6. 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

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

    PubMed

    Gomaa, Nasr H

    2012-04-01

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

  8. 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.

  9. The heat is on: desert tortoises and survival

    USGS Publications Warehouse

    Wessells, Stephen M.; Schwarzbach, Steven E.

    2010-01-01

    To highlight USGS scientists' research and build support for the work being done to help with desert tortoise recovery. To educate people about desert tortoises, their habitat needs, and what people might do to help. Length: 30 minutes

  10. 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

  11. Remobilization of southern African desert dune systems by twenty-first century global warming.

    PubMed

    Thomas, David S G; Knight, Melanie; Wiggs, Giles F S

    2005-06-30

    Although desert dunes cover 5 per cent of the global land surface and 30 per cent of Africa, the potential impacts of twenty-first century global warming on desert dune systems are not well understood. The inactive Sahel and southern African dune systems, which developed in multiple arid phases since the last interglacial period, are used today by pastoral and agricultural systems that could be disrupted if climate change alters twenty-first century dune dynamics. Empirical data and model simulations have established that the interplay between dune surface erodibility (determined by vegetation cover and moisture availability) and atmospheric erosivity (determined by wind energy) is critical for dunefield dynamics. This relationship between erodibility and erosivity is susceptible to climate-change impacts. Here we use simulations with three global climate models and a range of emission scenarios to assess the potential future activity of three Kalahari dunefields. We determine monthly values of dune activity by modifying and improving an established dune mobility index so that it can account for global climate model data outputs. We find that, regardless of the emission scenario used, significantly enhanced dune activity is simulated in the southern dunefield by 2039, and in the eastern and northern dunefields by 2069. By 2099 all dunefields are highly dynamic, from northern South Africa to Angola and Zambia. Our results suggest that dunefields are likely to be reactivated (the sand will become significantly exposed and move) as a consequence of twenty-first century climate warming.

  12. Establishing food site vectors in desert ants.

    PubMed

    Bolek, Siegfried; Wittlinger, Matthias; Wolf, Harald

    2012-02-15

    When returning to the site of a successful previous forage, where does one search for the goodies? Should one rely on experience from the previous homebound journey, or should one consider the outbound journey as well, or even exclusively? Desert ants are particularly well suited for pursuing this question because of their primary reliance on path integration in open and featureless desert habitats. Path integration has been studied particularly with regard to homing after lengthy foraging trips. The ants also use path integration to return to plentiful feeding sites, but what is memorised for revisiting the feeder remains controversial. Here, we demonstrate that desert ants consider, and indeed linearly average, both outbound and inbound travel for their return to a familiar feeder. This may be interpreted as a strategy to reduce navigation errors.

  13. New lakes in the Taklamakan Desert

    NASA Astrophysics Data System (ADS)

    Chen, Jiansheng; Wang, Chi-Yuen; Tan, Hongbing; Rao, Wenbo; Liu, Xiaoyan; Sun, Xiaoxu

    2012-11-01

    At the beginning of this century, some new lakes unexpectedly appeared in the Taklamakan Desert - one of the largest and driest deserts in the world. The origin of the water in the new lakes, however, has been a matter of debate. We test the hypotheses by analyzing water samples collected from the new lakes, the Bosten Lake and the foothills of the mountains that surround the desert. Using the isotopic composition of these waters as tracers, together with data from remote sensing, local weather stations and stream gauges, we infer that the new lakes may originate from increased recharge of groundwater from meltwater in the nearby mountains. We further speculate, supported by first-order simulation of earthquake-induced discharge of groundwater from mountains, that the source of this increased recharge may be related to earthquake-induced discharge of groundwater from nearby Altyn and Kunlun Mountains.

  14. 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.

  15. [Ultrasound in East Africa].

    PubMed

    Gysel, W

    2012-09-01

    Ultrasound is poorly established in East Africa because of missing finances and medical staff. The Foundation for medical know how transfer SmW installed in the last 3 years an ultrasound department in all District Hospitals in the South Province Mombasa in Kenya and was teaching the medical staff 2-3 times an year according the guidelines of SGUM and EFSUMB. The project is based on the idea that knowledge transfer is more efficient than money transfer. The project is supervised by public health studies. The first results show that non physicians are able to perform good quality ultrasound examinations. 75% of the obstetrical and 50% of the abdominal ultrasound examinations show therapy-relevant findings. Ultrasound is going to rise to the position of the most important imagine system in developing countries.

  16. Oxalosis in wild desert tortoises, Gopherus agassizii

    USGS Publications Warehouse

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

    2009-01-01

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

  17. 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...

  18. The Punitive Paradox: Desert and the Compulsion to Punish.

    ERIC Educational Resources Information Center

    Clear, Todd R.

    1996-01-01

    Explores the concept of a "just deserts" justice paradox in which carrying out a deserved penalty breaches the values that undergird the theory of just deserts. Examines whether it might ever be proper, from a desert perspective, to choose not to impose a deserved punishment. (KW)

  19. 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…

  20. 75 FR 19246 - Safety Zone; Desert Storm, Lake Havasu, AZ

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-14

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Desert Storm, Lake Havasu, AZ AGENCY: Coast... Havasu City, Arizona in support of the Desert Storm Exhibition Run. This temporary safety zone is... Purpose The Lake Racer LLC is sponsoring the Desert Storm Charity Poker Run and Exhibition Run, which...

  1. 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

  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. Desert Dust Properties, Modelling, and Monitoring

    NASA Technical Reports Server (NTRS)

    Kaskaoutis, Dimitris G.; Kahn, Ralph A.; Gupta, Pawan; Jayaraman, Achuthan; Bartzokas, Aristides

    2013-01-01

    This paper is just the three-page introduction to a Special Issue of Advances in Meteorology focusing on desert dust. It provides a paragraph each on 13 accepted papers, most relating to the used of satellite data to assess attributes or distribution of airborne desert dust. As guest Associate Editors of this issue, we organized the papers into a systematic whole, beginning with large-scale transport and seasonal behavior, then to regional dust transport, transport history, and climate impacts, first in the Mediterranean region, then India and central Asia, and finally focusing on transport model assessment and the use of lidar as a technique to constrain dust spatial-temporal distribution.

  4. A reservoir of nitrate beneath desert soils.

    PubMed

    Walvoord, Michelle A; Phillips, Fred M; Stonestrom, David A; Evans, R Dave; Hartsough, Peter C; Newman, Brent D; Striegl, Robert G

    2003-11-01

    A large reservoir of bioavailable nitrogen (up to approximately 10(4) 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 arid 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.

  5. 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 (

  6. Genetic connectivity across marginal habitats: the elephants of the Namib Desert.

    PubMed

    Ishida, Yasuko; Van Coeverden de Groot, Peter J; Leggett, Keith E A; Putnam, Andrea S; Fox, Virginia E; Lai, Jesse; Boag, Peter T; Georgiadis, Nicholas J; Roca, Alfred L

    2016-09-01

    Locally isolated populations in marginal habitats may be genetically distinctive and of heightened conservation concern. Elephants inhabiting the Namib Desert have been reported to show distinctive behavioral and phenotypic adaptations in that severely arid environment. The genetic distinctiveness of Namibian desert elephants relative to other African savanna elephant (Loxodonta africana) populations has not been established. To investigate the genetic structure of elephants in Namibia, we determined the mitochondrial (mt) DNA control region sequences and genotyped 17 microsatellite loci in desert elephants (n = 8) from the Hoanib River catchment and the Hoarusib River catchment. We compared these to the genotypes of elephants (n = 77) from other localities in Namibia. The mtDNA haplotype sequences and frequencies among desert elephants were similar to those of elephants in Etosha National Park, the Huab River catchment, the Ugab River catchment, and central Kunene, although the geographically distant Caprivi Strip had different mtDNA haplotypes. Likewise, analysis of the microsatellite genotypes of desert-dwelling elephants revealed that they were not genetically distinctive from Etosha elephants, and there was no evidence for isolation by distance across the Etosha region. These results, and a review of the historical record, suggest that a high learning capacity and long-distance migrations allowed Namibian elephants to regularly shift their ranges to survive in the face of high variability in climate and in hunting pressure. PMID:27648236

  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. Genetic connectivity across marginal habitats: the elephants of the Namib Desert.

    PubMed

    Ishida, Yasuko; Van Coeverden de Groot, Peter J; Leggett, Keith E A; Putnam, Andrea S; Fox, Virginia E; Lai, Jesse; Boag, Peter T; Georgiadis, Nicholas J; Roca, Alfred L

    2016-09-01

    Locally isolated populations in marginal habitats may be genetically distinctive and of heightened conservation concern. Elephants inhabiting the Namib Desert have been reported to show distinctive behavioral and phenotypic adaptations in that severely arid environment. The genetic distinctiveness of Namibian desert elephants relative to other African savanna elephant (Loxodonta africana) populations has not been established. To investigate the genetic structure of elephants in Namibia, we determined the mitochondrial (mt) DNA control region sequences and genotyped 17 microsatellite loci in desert elephants (n = 8) from the Hoanib River catchment and the Hoarusib River catchment. We compared these to the genotypes of elephants (n = 77) from other localities in Namibia. The mtDNA haplotype sequences and frequencies among desert elephants were similar to those of elephants in Etosha National Park, the Huab River catchment, the Ugab River catchment, and central Kunene, although the geographically distant Caprivi Strip had different mtDNA haplotypes. Likewise, analysis of the microsatellite genotypes of desert-dwelling elephants revealed that they were not genetically distinctive from Etosha elephants, and there was no evidence for isolation by distance across the Etosha region. These results, and a review of the historical record, suggest that a high learning capacity and long-distance migrations allowed Namibian elephants to regularly shift their ranges to survive in the face of high variability in climate and in hunting pressure.

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

    PubMed

    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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. Forecasting droughts in East Africa

    NASA Astrophysics Data System (ADS)

    Mwangi, Emmah; Wetterhall, Fredrik; Dutra, Emanuel; Di Giuseppe, Francesca; Pappenberger, Florian

    2014-05-01

    The humanitarian crisis caused by the recent droughts (2008-2009 and 2010-2011) in East Africa have illustrated that the ability to make accurate drought predictions with sufficient lead time is essential. The use of dynamical model forecasts in combination with drought indices, such as the Standardized Precipitation Index (SPI), can potentially to lead to a better description of drought duration, magnitude and spatial extent. This study evaluates the use of the European Centre for Medium-Range Weather Forecasts (ECMWF) products in forecasting droughts in East Africa. ECMWF seasonal precipitation shows significant skill for both rain seasons when evaluated against measurements from the available in-situ stations from East Africa. The forecast for October-December rain season has higher skill than for the March-May season. ECMWF forecasts add value to the statistical forecasts produced during the Greater Horn of Africa Climate Outlook Forums (GHACOF), which is the present operational product. Complementing the raw precipitation forecasts with SPI provides additional information on the spatial extent and intensity of the drought event.

  16. 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.

  17. 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

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. [Nutrition in Africa].

    PubMed

    Ganzin, M

    1985-01-01

    A certain number of countries in Africa south of the Sahara are suffering from severe food shortages and famine which have called the attention of the international public opinion. A review of the situation clearly shows that, not only the availability of food depends upon agricultural production and its various conditioning factors (soil, climate, fertility, agricultural technology, storage facilities, etc.), but that such socio-economic factors as population, migration, supplies to urban centres, transport, unemployment, inflation and debt also have a strong influence. With some variations in intensity, these factors and conditions are the same everywhere. It may therefore be said at the present time that political disorders and a poor understanding of nutritional problems are more often than not responsible for tragic situations.

  6. Habitat selection by juvenile Mojave Desert tortoises

    USGS Publications Warehouse

    Todd, Brian D; Halstead, Brian J.; Chiquoine, Lindsay P.; Peaden, J. Mark; Buhlmann, Kurt A.; Tuberville, Tracey D.; Nafus, Melia G.

    2016-01-01

    Growing pressure to develop public lands for renewable energy production places several protected species at increased risk of habitat loss. One example is the Mojave desert tortoise (Gopherus agassizii), a species often at the center of conflicts over public land development. For this species and others on public lands, a better understanding of their habitat needs can help minimize negative impacts and facilitate protection or restoration of habitat. We used radio-telemetry to track 46 neonate and juvenile tortoises in the Eastern Mojave Desert, California, USA, to quantify habitat at tortoise locations and paired random points to assess habitat selection. Tortoise locations near burrows were more likely to be under canopy cover and had greater coverage of perennial plants (especially creosote [Larrea tridentata]), more coverage by washes, a greater number of small-mammal burrows, and fewer white bursage (Ambrosia dumosa) than random points. Active tortoise locations away from burrows were closer to washes and perennial plants than were random points. Our results can help planners locate juvenile tortoises and avoid impacts to habitat critical for this life stage. Additionally, our results provide targets for habitat protection and restoration and suggest that diverse and abundant small-mammal populations and the availability of creosote bush are vital for juvenile desert tortoises in the Eastern Mojave Desert.

  7. 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…

  8. 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

  9. Desert pavement study at Amboy, California

    NASA Technical Reports Server (NTRS)

    Williams, S.; Greeley, R.

    1984-01-01

    Desert pavement is a general term describing a surface that typically consists of a thin layer of cm-sized rock fragments set on top of a layer of finer material in which no fragments are found. An understanding of desert pavement is important to planetary geology because they may play a major role in the formation and visibility of various aeolian features such as wind streaks, which are important on Mars and may be important on Venus. A field study was conducted in Amboy, California to determine the formation mechanism of desert pavements. The probable sequence of events for the formation and evolution of a typical desert pavement surface, based on this experiment and the work of others, is as follows. Starting with a layer of surface material consisting of both fine particles and rock fragments, aeolian deflation will rapidly erode the surface until an armored lag is developed, after which aeolian processes become less important. The concentration of fragments then slowly increases as new fragments are brought to the surface from the subsurface and as fragments move downslope by sheet wash. Sheet wash would be responsible for removing very fine particles from the surface and for moving the fragments relative to one another, forming interlocks.

  10. 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.

  11. 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.

  12. Reclaiming freshwater sustainability in the Cadillac Desert.

    PubMed

    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

    2010-12-14

    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

  13. 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%.

  14. 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 ...

  15. 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

  16. 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...

  17. 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.

  18. 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.

  19. Reclaiming freshwater sustainability in the Cadillac Desert.

    PubMed

    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

    2010-12-14

    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%.

  20. 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.

  1. Thermoregulation in the desert iguana Dipsosaurus dorsalis.

    PubMed

    McGinnis, S M; Dickson, L L

    1967-06-30

    The body temperature of desert iguanas implanted with miniature temperature-sensitive radio transmitters was continuously monitored in their natural habitat. Extensive thermoregulatory behavior occurred in retreat burrows prior to morning emergence. Such behavior permits the igluana to emerge from below ground at its preferred body temperature rather than suboptimal temperature at which activity in the burrow is initiated.

  2. 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.

  3. 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.

  4. Wood decay in desert riverine environments

    USGS Publications Warehouse

    Andersen, Douglas; Stricker, Craig A.; Nelson, S. Mark

    2016-01-01

    Floodplain forests and the woody debris they produce are major components of riverine ecosystems in many arid and semiarid regions (drylands). We monitored breakdown and nitrogen dynamics in wood and bark from a native riparian tree, Fremont cottonwood (Populus deltoides subsp. wislizeni), along four North American desert streams. We placed locally-obtained, fresh, coarse material [disks or cylinders (∼500–2000 cm3)] along two cold-desert and two warm-desert rivers in the Colorado River Basin. Material was placed in both floodplain and aquatic environments, and left in situ for up to 12 years. We tested the hypothesis that breakdown would be fastest in relatively warm and moist aerobic environments by comparing the time required for 50% loss of initial ash-free dry matter (T50) calculated using exponential decay models incorporating a lag term. In cold-desert sites (Green and Yampa rivers, Colorado), disks of wood with bark attached exposed for up to 12 years in locations rarely inundated lost mass at a slower rate (T50 = 34 yr) than in locations inundated during most spring floods (T50 = 12 yr). At the latter locations, bark alone loss mass at a rate initially similar to whole disks (T50 = 13 yr), but which subsequently slowed. In warm-desert sites monitored for 3 years, cylinders of wood with bark removed lost mass very slowly (T50 = 60 yr) at a location never inundated (Bill Williams River, Arizona), whereas decay rate varied among aquatic locations (T50 = 20 yr in Bill Williams River; T50 = 3 yr in Las Vegas Wash, an effluent-dominated stream warmed by treated wastewater inflows). Invertebrates had a minor role in wood breakdown except at in-stream locations in Las Vegas Wash. The presence and form of change in nitrogen content during exposure varied among riverine environments. Our results suggest woody debris breakdown in desert riverine ecosystems is primarily a microbial process with rates determined by landscape position

  5. Oil shales of Europe, North Africa, and the Near East

    SciTech Connect

    Troger, U.

    1984-04-01

    Oil shale deposits are known from almost all countries in Europe and range in age from Paleozoic to Eocene. The geology of Europe is well known, and the discovery of new and significant oil shale deposits is not anticipated. A considerably different situation exists in North Africa and the Near East, where sparsely tested areas in the Sahara and desert fringe might contain important oil shale deposits. Most of the oil shale deposits in these areas (1) are of Cretaceous age, (2) occur with phosphate deposits, and (3) owe their origin to sedimentary processes associated with upwelling. Oil shales can be found from Turkey to Morocco along a paleocoastline, and better definition of this feature could result in new discoveries. In contrast to the US, oil shale deposits in Europe are being used as energy sources and will probably serve the same purpose in North Africa and the Near East.

  6. 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.

  7. 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

  8. 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.

  9. Nonlinear responses of desert shrubs to episodic rainfall events

    NASA Astrophysics Data System (ADS)

    Ogle, K.; Reynolds, J. F.

    2001-12-01

    The physiological responses of desert shrubs to rapidly varying soil and atmospheric water status are equivocal. While much of the wide variations in observed responses in gas exchange and plant water potential can be readily attributed to nonlinear plant-soil-atmosphere couplings, there is a paucity of data to quantify these behaviors in the field. This motivated us to conduct an integrated field and modeling study on Larrea tridentata, the dominant shrub of North American warm deserts. We monitored photosynthesis, stomatal behavior, and water potential of 16 individual shrubs exposed to natural and simulated rainfall during two growing seasons at a field site in southern New Mexico. We use these field data to develop a new photosynthesis (A) model that explicitly links internal CO2 (Ci) and stomatal conductance (g). A threshold response is assumed for instantaneous g such that stomata operate at their maximum g (gmax) for low vapor pressure deficits (VPD); thereafter, g decreases nonlinearly with increasing VPD. Predawn water potential and growing temperature interact with VPD to affect g and gmax. Ci is a linear function of g and the intercept is the minimum achievable Ci, which varies with temperature and light intensity. This model is able to reproduce Larrea's responses to episodic soil and atmospheric water availability, capturing the large diurnal and seasonal fluctuations in A, g, and Ci. We use this model to show that the many conflicting conclusions regarding desert shrub responses to rainfall are explained by the lack of sufficient field data and by several key nonlinear plant-soil-atmosphere couplings.

  10. 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

  11. 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.

  12. Synergy of multispectral and multisensors satellite observations to evaluate desert aerosol transport and impact of dust deposition on inland waters: study case of Lake Garda

    NASA Astrophysics Data System (ADS)

    Di Nicolantonio, Walter; Cazzaniga, Ilaria; Cacciari, Alessandra; Bresciani, Mariano; Giardino, Claudia

    2015-01-01

    The capabilities of different Earth Observation multispectral satellites are employed for detecting and tracking of desert dust coming from North Africa toward the Northern Italy area and for evaluating the impact of Saharan dust deposition in inland waters, such as those of Lake Garda. Absorbing and scattering spectral optical properties of desert aerosol in the atmospheric windows in the ultraviolet, visible-near-infrared, and infrared spectral ranges are exploited in the dust retrieval performed by OMI/Aura, MODIS/Terra-Aqua, and SEVIRI/MSG satellite sensors. Therefore, the direct link between dust deposition and increase in phytoplankton abundance has been assessed retrieving MERIS-based chlorophyll-a (chl-a) concentration for the desert dust events. Estimates of the increased chl-a in the lake have been derived with values in concentration from 30% to 170%. AERONET sun-photometer measurements, gravimetric particulate matter samplings, in situ chl-a concentration and surface temperature are employed to select events and assess the presence of desert dust and recognize a corresponding increase of the phytoplankton abundance in the analyzed inland waters. The improved observational features that will be provided by the next European Sentinels missions, namely Sentinel-2, 3, 4, 5P, together with MTG-I (Imager) and MTG-S (Sounder) will allow better monitoring atmospheric constituents and studying the environmental impacts of desert dust transport.

  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. Teaching about Francophone Africa.

    ERIC Educational Resources Information Center

    Merryfield, Mary; Timbo, Adama

    Lessons and resources for Social Studies and French courses are included in this document. The major goals of these materials are to help students (1) explore the history and geography of Francophone Africa, (2) examine French influences in contemporary Africa, (3) recognize and appreciate cultural differences and similarities in values and…

  15. 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:…

  16. Multilingualism in Southern Africa.

    ERIC Educational Resources Information Center

    Peirce, Bonny Norton; Ridge, Stanley G. M.

    1997-01-01

    Reviews recent research in multilingualism in Southern Africa, focusing on the role of languages in education, sociolinguistics, and language policy. Much of the research is on South Africa. Topics discussed include language of instruction in schools, teacher education, higher education, adult literacy, language contact, gender and linguistic…

  17. 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.

  18. 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

  19. 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.

  20. 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...

  1. 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

  2. Geomorphology of MODIS-Visible Dust Plumes in the Chihuahuan Desert - Preliminary Results

    NASA Astrophysics Data System (ADS)

    Gill, T. E.; Mbuh, M. J.; Dominguez, M. A.; Lee, J. A.; Baddock, M. C.; Lee, C. E.; Whitehead, S. C.; Rivera Rivera, N. I.; Peinado, P.

    2009-12-01

    We identified 28 days since 2001 when blowing dust impacted El Paso, Texas and dust plumes were visible on NASA MODIS Terra/Aqua satellite images in the surrounding Chihuahuan Desert. Initiation points of >270 individual plumes were located on the MODIS images. Land use/land cover for each point was determined by field work, aerial photography, and/or soil/geological maps, and points were assigned to the geomorphic classes proposed by Bullard et al. (this session). Although dust plume identification is subjective (weak plumes, plumes obscured by clouds, and plumes occurring when the satellites are not overhead will be missed), these data provide preliminary information on the relationship between geomorphology and the initiation of major dust storms in the Chihuahuan Desert. Ephemeral lakes and alluvial low-relief non-incised lands are roughly equal producers of satellite-visible dust plumes in the Chihuahuan Desert. Anthropogenic modification of alluvial floodplains for cropping (primarily in the Casas Grandes and Del Carmen river basins) impacts dust generation, since about 2/3 of alluvial low-relief sites show evidence of agriculture. These agricultural fields are generally fallow during the November- April windy season. Not including agricultural lands, playas represent ~2x the number of sources as low-relief alluvial deposits. Aeolian sand deposits (predominantly coppice dunes and sand sheets overlaying alluvial or lacustrine sediments) account for about 1/7 of the points. These sands may act as erosional agents, providing saltating particles for sandblasting and bombardment of other sediments exposed nearby. Edges of ephemeral lakes are proportionally important sources (~10% of the points), likely due to the convergence of saltating sand, fine lacustrine sediments, and low roughness lengths of playa surfaces. Alluvial fans and alluvial uplands are minor dust sources compared to their overall prevalence in the region. Gobi/gibber/stony deposits are known dust

  3. Cyanobacterial composition and spatial distribution based on pyrosequencing data in the Gurbantunggut Desert, Northwestern China.

    PubMed

    Zhang, Bingchang; Li, Renhui; Xiao, Peng; Su, Yangui; Zhang, Yuanming

    2016-03-01

    Cyanobacteria are the primary colonizers and form a dominant component of soil photosynthetic communities in biological soil crusts. They are crucial in improving soil environments, namely accumulating soil carbon and nitrogen. Many classical studies have examined cyanobacterial diversity in desert crusts, but relatively few comprehensive molecular surveys have been conducted. We used 454 pyrosequencing of 16S rRNA to investigate cyanobacterial composition and distribution on regional scales in the Gurbantunggut Desert. The relationship between cyanobacterial distribution and environmental factors was also explored. A total of 24,973 cyanobacteria partial 16S rRNA gene sequences were obtained, and 507OTUs were selected, as most OTUs had very few reads. Among these, 347 OTU sequences were of cyanobacteria origin, belonging to Oscillatoriales, Nostocales, Chroococcales, and uncultured cyanobacterium clone, respectively. Microcoleus vaginatus, Chroococcidiopsis spp. and M. steenstrupii were the dominant species in most areas of the Gurbantunggut Desert. Compared with other desert, the Gurbantunggut Desert differed in the prominence of Chroococcidiopsis spp. and lack of Pseudanabaenales. Species composition and abundance of cyanobacteria also showed distinct variations. Soil texture, precipitation, and nutrients and salt levels affected cyanobacterial distribution. Increased precipitation was helpful in improving cyanobacterial diversity. A higher content of coarse sand promoted the colonization and growth of Oscillatoriales and some phylotypes of Chroococcales. The fine-textured soil with higher nutrients and salts supported more varied populations of cyanobacteria, namely some heterocystous cyanobacteria. The results suggested that the Gurbantunggut Desert was rich in cyanobacteria and that precipitation was a primary regulating factor for cyanobacterial composition on a regional scale.

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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...

  10. 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...

  11. 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...

  12. 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...

  13. Safe water for Africa (Africa-1000)

    SciTech Connect

    Dalton, R.; Kashkari, C.

    1996-12-31

    Africa-1000 is a program to provide safe water to thousands of villages in Africa. It is a formidable effort and needs the support of the international scientific community. Science and technology is the only hope for a solution of the African crisis. There are vast areas in the Sub-Saharan Africa that have water under the ground but due to lack of electric power, the water cannot be pumped. Thus the land is dry and barren and people are starving. The African continent has abundant renewable energy in the form of solar and wind energy. The technologies are well developed and available in the developed countries. Therefore, the solution is as follows: dig and drill wells and boreholes to reach underground water; install standardized solar or wind driven pumps to bring water to the surface; train village technicians to operate, maintain and repair these energy systems; and replicate these installations in thousands of villages, thus establishing standard water and energy systems across Africa.

  14. 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

  15. 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.

  16. 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.

  17. 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

  18. 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

  19. 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

  20. Feedbacks between woody plant encroachment and microclimate in desert grasslands

    NASA Astrophysics Data System (ADS)

    D'Odorico, P.; He, Y.; De Wekker, S.; Fuentes, J. D.; Collins, S. L.; Pockman, W.

    2011-12-01

    The encroachment of woody plants into grasslands is a global phenomenon that results from a variety of drivers related to land use and global environmental change. In the southwestern U.S., shrub encroachment can be associated with land degradation, soil erosion, and the formation of coppice dunes. In this region, the relatively abrupt character of grassland-to-shrubland transitions - both in time and in space - suggests that arid and semiarid rangelands may exhibit two alternative stable states characterized by either grass or shrub dominance. In these bistable landscapes, even small changes in environmental drivers may cause abrupt state transitions from grassland to shrubland, sustained by positive feedbacks with environmental drivers. We show that positive feedbacks between land cover change and microclimate may contribute to shrub encroachment in the southwestern US. Thus, we investigate changes in surface air temperature and energy balance resulting from grass-to-shrub transitions in the northern Chiuhuahuan desert. We find that the encroachment of native shrubs into desert grasslands modifies the surface energy balance with the overall net effect of increasing nighttime air temperatures, thereby favoring the establishment and growth of freeze-sensitive Larrea plants.

  1. 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

  2. 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

  3. 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).

  4. Desert tortoise annotated bibliography, 1991-2015

    USGS Publications Warehouse

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

    2016-03-01

    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).

  5. 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.

  6. Himalayan Mountain Range, Taklimakan Desert, China

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Looking north from Kashmir India (27.5N, 76.5E) into the Tibetan Plateau and beyond, the Taklimakan Desert of far western China appears to be covered with an extensive layer of haze that blankets the entire region. Reaching even into the western Siberian Plains of the CIS. This rugged land is one of the world's richest treasure troves of mineral wealth but the accessability into this remote area is so difficult that it is not yet economically feasible.

  7. Desert wetlands in the geologic record

    NASA Astrophysics Data System (ADS)

    Pigati, Jeffrey S.; Rech, Jason A.; Quade, Jay; Bright, Jordon

    2014-05-01

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

  8. Desert wetlands in the geologic record

    USGS Publications Warehouse

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

    2014-01-01

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

  9. 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.

  10. TDRS satellite over African Rift Valley, Kenya, Africa

    NASA Technical Reports Server (NTRS)

    1983-01-01

    This post deploy view of a TDRS satellite shows a segment of the African Rift Valley near Lake Baringo, Kenya, Africa (3.0S, 36.0E). The African Rift Valley system is a geologic fault having its origins in southern Turkey, through the near east forming the bed of the Jordan River, Gulf of Aqaba, the Red Sea and down through east Africa. The line of lakes and valleys of east Africa are the result of the faulting activity.

  11. 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

  12. 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.

  13. Range and habitats of the desert tortoise

    USGS Publications Warehouse

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

    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.

  14. 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.

  15. Photosynthetic strategies of two Mojave Desert shrubs

    SciTech Connect

    Kleinkopf, G.E.; Hartsock, T.L.; Wallace, A.; Romney, E.M.

    1980-01-01

    Photosynthetic production of two Mojave Desert shrubs was measured under natural growing conditions. Measurements of photosynthesis, transpiration, resistances to water vapor flux, soil moisture potential, and tissue water potential were made. Atriplex canescens (Pursh) Nutt., a member of the C/sub 4/ biochemical carbon dioxide fixation group was highly competitive in growth rate and production during conditions of adequate soil moisture. As soil moisture conditions declined to minus 40 bars, the net photosynthetic rate of Atriplex decreased to zero. However, the C/sub 3/ shrub species Larrea tridentata (Sesse and Moc. ex DC.) Cov. was able to maintain positive net photosynthetic production during conditions of high temperature and extreme low soil moisture through the major part of the season. The comparative advantages of the C/sub 4/ versus the C/sub 3/ pathway of carbon fixation was lost between these two species as the soil moisture potential declined to minus 40 bars. Desert plants have diffferent strategies for survival, one of the strategies being the C/sub 4/ biochemical carbon fixation pathway. However, many of the plants are members of the C/sub 3/ group. In this instance, the C/sub 4/ fixation pathway does not confer an added advantage to the productivity of the species in the Mojave Desert. Species distribution based on comparative photosynthetic production is discussed

  16. 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

  17. 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.

  18. 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

  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. Perspectives on history: army dietetics in southwest Asia during Operation Desert Shield/Desert Storm.

    PubMed

    Hodges, P A; Lyon, J M

    1996-06-01

    The Army dietitians deployed during Operation Desert Shield and Operation Desert Storm exemplified the commitment, dedication, patriotism, and professionalism of their predecessors. Although some were continuously on the move and all dealt with the extremes of a desert environment, were frequently handicapped with equipment shortages, and coped constantly with the monotony of limited ration variety, throughout their experiences these professionals expressed pride in participating in this national undertaking. The purposes of this article are to familiarize members of The American Dietetic Association with the responses of their colleagues in the US military to another of their nation's calls, to relate some aspects of Army dietetics experienced in Southwest Asia, and to identify the lessons learned in that engagement. PMID:8655908

  1. Apparent Brecciation Gradient, Mount Desert Island, Maine

    NASA Astrophysics Data System (ADS)

    Hawkins, A. T.; Johnson, S. E.

    2004-05-01

    Mount Desert Island, Maine, comprises a shallow level, Siluro-Devonian igneous complex surrounded by a distinctive breccia zone ("shatter zone" of Gilman and Chapman, 1988). The zone is very well exposed on the southern and eastern shores of the island and provides a unique opportunity to examine subvolcanic processes. The breccia of the Shatter Zone shows wide variation in percent matrix and clast, and may represent a spatial and temporal gradient in breccia formation due to a single eruptive or other catastrophic volcanic event. The shatter zone was divided into five developmental stages based on the extent of brecciation: Bar Harbor Formation, Sols Cliffs breccia, Seeley Road breccia, Dubois breccia, and Great Head breccia. A digital camera was employed to capture scale images of representative outcrops using a 0.5 m square Plexiglas frame. Individual images were joined in Adobe Photoshop to create a composite image of each outcrop. The composite photo was then exported to Adobe Illustrator, which was used to outline the clasts and produce a digital map of the outcrop for analysis. The fractal dimension (Fd) of each clast was calculated using NIH Image and a Euclidean distance mapping method described by Bérubé and Jébrak (1999) to quantify the morphology of the fragments, or the complexity of the outline. The more complex the fragment outline, the higher the fractal dimension, indicating that the fragment is less "mature" or has had less exposure to erosional processes, such as the injection of an igneous matrix. Sols Cliffs breccia has an average Fd of 1.125, whereas Great Head breccia has an average Fd of 1.040, with the stages between having intermediate values. The more complex clasts of the Sols Cliffs breccia with a small amount (26.38%) of matrix material suggests that it is the first stage in a sequence of brecciation ending at the more mature, matrix-supported (71.37%) breccia of Great Head. The results of this study will be used to guide isotopic

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Research Management in Africa.

    ERIC Educational Resources Information Center

    Benneh, George

    2002-01-01

    Examines research management, particularly within higher education institutions, in Africa including, research and current trends in knowledge production, institutional aspects, research funding, and good practice in research management. (EV)

  9. 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)

  10. 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.

  11. 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.

  12. Forecasting droughts in East Africa

    NASA Astrophysics Data System (ADS)

    Mwangi, E.; Wetterhall, F.; Dutra, E.; Di Giuseppe, F.; Pappenberger, F.

    2013-08-01

    The humanitarian crisis caused by the recent droughts (2008-2009 and 2010-2011) in the East African region have illustrated that the ability to make accurate drought predictions with adequate lead time is essential. The use of dynamical model forecasts and drought indices, such as Standardized Precipitation Index (SPI), promises to lead to a better description of drought duration, magnitude and spatial extent. This study evaluates the use of the European Centre for Medium-Range Weather Forecasts (ECMWF) products in forecasting droughts in East Africa. ECMWF seasonal precipitation shows significant skill for both rain seasons when evaluated against measurements from the available in-situ stations from East Africa. The October-December rain season has higher skill that the March-May season. ECMWF forecasts add value to the statistical forecasts produced during the Greater Horn of Africa Climate Outlook Forums (GHACOF) which is the present operational product. Complementing the raw precipitation forecasts with SPI provides additional information on the spatial extend and intensity of the drought event.

  13. Linking fog water use by plants in the coastal Namib Desert to carbon and nitrogen cycles along aridity gradients

    NASA Astrophysics Data System (ADS)

    Macko, S. A.; Soderberg, K.; Henschel, J.; Billmark, K.; Swap, R. J.

    2009-12-01

    A steep rainfall gradient exists across the Namib Desert in southern Africa, which is unique in that frequent coastal fog occurs in areas that receive the least rainfall. Overall, the Namib is hyper-arid in terms of rainfall (25-100mm mean annual rainfall, MAR), but areas within about 60km of the coast see up to 100 days of fog each year. This scenario has influenced the distribution of plant species and the behavior of Namib fauna. In this study, carbon and nitrogen isotopes are used to investigate the biogeochemistry of vegetation the Namib aridity gradient, and fog uptake by individual plants is estimated by comparing water isotopes (δ2H and δ18O) of fog, groundwater, rain, soil water and plant water. Using the natural aridity gradient as a basis for this investigation allows for observation of patterns that can potentially be related to controlling biogeochemical processes. Studies of carbon and nitrogen isotopes in vegetation along precipitation gradients have revealed similar patterns in the Kalahari of southern Africa and in West Australia. The Kalahari trend observed along a precipitation gradient of 200-1000mm MAR shows enriched δ13C values in drier areas, and this trend is only apparent in C3 vegetation. The West Australia gradient (<150 to >1000mm MAR) follows the same general pattern, but the values are quite variable below about 250mm MAR. The corresponding nitrogen isotope data in the Kalahari shows an enrichment in 15N with less rainfall, again only apparent in C3 vegetation. Although there are significant differences between the Namib and Kalahari setting - notably soils and climatology - the Namib aridity gradient could potentially extend the Kalahari data set to areas that receive less than 100mm MAR. The fog and the unique survival strategies of Namib plants may explain differences between the Namib and Kalahari patterns. For example, the C3/CAM species W. mirabilis has highly variable δ13C values (-17.5 to -24‰), with a slight enrichment

  14. 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

  15. Mesofaunal biodiversity and its importance in Thar desert.

    PubMed

    Tripathi, G; Kumari, R; Sharma, B M

    2007-04-01

    Soil animals are considered as important contributors to soil fertility However, there is paucity of such information for harsh climatic conditions. Therefore, the below ground faunal density and frequency have been studied in relation to physicochemical properties of soil in Thar desert. The selected soil systems were Vigna radiata--Cuminum cyminum, grassland, flower garden and Zizyphus mauritiana. Acari and other soil arthropods exhibited seasonal variation in their populations. There were two population peaks, one in February/March and other in August/September. The highest population was in flower garden, whereas lowest was in Z. mauritiana field. It clearly indicates that the soil fauna population develops in different degrees. The relative density showed that the acarines were more prevalent in comparison to other soil arthropods. The prostigmatids exhibited maximum relative density in comparison to cryptostigmatids and mesostigmatids in all fields. Pauropus showed higher relative density among all other soil arthropods. Acari had higher frequency of occurrence, while the other soil arthropods indicated lower frequency of occurrence in all systems. The highest frequency of occurrence was recorded in July/August and the lowest in May/June. The soil temperature, moisture, organic carbon, total nitrogen and carbon/nitrogen ratio varied significantly throughout the year The fluctuations in physicochemical characteristics of soil greatly influenced below ground faunal density in different fields. A highly significant and positive correlation was obtained among different soil fauna groups. Faunal population showed a significant positive correlation with soil moisture, organic carbon and total nitrogen. The abiotic factors such as temperature, pH and C/N ratio showed negative correlation with moisture, organic carbon and total nitrogen. However, moisture, organic carbon and total nitrogen had positive correlation among themselves. The present study suggests that the

  16. 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.

  17. 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

  18. The Response of Halophiles from the Atacama Desert to Humidity Changes

    NASA Astrophysics Data System (ADS)

    Allen, C.; Lera, M.; Chandra, J.; Webb, S.; Marcu, O.

    2011-12-01

    Survival of extremophiles in dry desert conditions implies adaptations to fluctuations in temperature, desiccation and radiation levels. The Atacama Desert, located in Chile, is the driest desert in the world. Despite the extreme desiccation conditions, cyanobacteria and heterotrophic bacteria are still able to survive in the evaporitic halite rocks that scatter the surface of the desert. The purpose of this study was to determine whether the extremely dry conditions cause cellular oxidative stress and to examine the adaptations that allow these extremophiles to survive. One potential adaptation is the import/export of redox metals which can scavenge reactive oxygen species, preventing oxidative stress. Another potential adaptation is based on changes in gene expression. Genes involved in the stress pathway, which help microorganisms combat intracellular oxidation and survive the harsh environment, are expected to have different expression levels based on the humidity and level of stress. The aims of this project were: 1. to characterize the elemental signature of cyanobacteria; 2. to identify possible intracellular elemental changes that may occur in response to changes in humidity; 3. to identify and quantify the expression of stress genes involved in the response to humidity changes. Here we will show the elemental composition of cells in the halite sample as determined by X-ray fluorescence imaging (microprobe beamline 2-3 at the Stanford Synchrotron Radiation Laboratory), real-time elemental fluctuations measured in live cells exposed to changing relative humidity values, and partial amplification of genes of interest using degenerate primers based on homologous cyanobacterial sequences.

  19. 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.

  20. 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.

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

    PubMed

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

    2014-11-06

    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.

  2. 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.

  3. The effects of drying following heat shock exposure of the desert moss Syntrichia caninervis.

    PubMed

    Xu, Shu-Jun; Liu, Chun-Jiang; Jiang, Ping-An; Cai, Wei-Min; Wang, Yan

    2009-03-15

    Desert mosses are components of biological soil crusts (BSCs) and their ecological functions make assessment and protection of these mosses a high-ranking management priority in desert regions. Drying is thought to be useful for desert mosses surviving heat shock. In this study, we investigated the role of drying by monitoring the responses of physiological characters and asexual reproduction in the typical desert moss Syntrichia caninervis. Heat significantly decreased chlorophyll content and weakened rapid recovery of photochemical activity, and increased carotenoid content and membrane permeability. Lethal temperatures significantly destroyed shoot regeneration potential. In comparison with heat alone, drying significantly increased protonema emergence time and depressed protonema emergence area. Drying combined with heat accelerated water loss, followed by a decrease of photosynthetic activity. Drying had different influences on membrane permeability at different temperatures. When moss leaves were subjected to a combined stress of drying and heat shock, photosynthesis was maintained mainly due to the effects of drying on physiological activity although the cellular morphological integrity was affected. Drying caused opposing effects on moss physiological and reproductive characteristics. On the one hand, drying caused a positive synergistic effect with heat shock when the temperature was below 40 degrees C. On the other hand, drying showed antagonism with heat shock when the moss was subjected to temperatures higher than 40 degrees C. These findings may help in understanding the survival mechanism of dessert mosses under heat shock stress which will be helpful for the artificial reconstruction of BSCs.

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

    PubMed

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

    2015-03-11

    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.

  5. Evaluation of barrier treatments on native vegetation in a southern California desert habitat.

    PubMed

    Britch, Seth C; Linthicum, Kenneth J; Wynn, Wayne W; Walker, Todd W; Farooq, Muhammad; Smith, Vincent L; Robinson, Cathy A; Lothrop, Branka B; Snelling, Melissa; Gutierrez, Arturo; Lothrop, Hugh D

    2009-06-01

    Treating perimeters with residual insecticides for protection from mosquito vectors has shown promise. These barrier treatments are typically evaluated in temperate or tropical areas using abundant vegetation as a substrate. However, there is an emerging interest to develop this technology to protect deployed US troops in extreme desert environments with sparse vegetation. We used a remote desert area in the Coachella Valley, California, to 1) evaluate bifenthrin barrier treatments on native xeric vegetation and 2) compare treatments applied with electrostatic and conventional spray technologies. Through a combination of laboratory bioassays on treated and control vegetation sampled at specific intervals over 63 days, synchronized with field surveillance of mosquitoes, we measured the temporal pattern of bioactivity of bifenthrin barriers under natural hot, dry, and dusty desert conditions. Regardless of spray technology, mosquito catch in treated plots was about 80% lower than the catch in control plots 1 day after treatment. This reduction in mosquito numbers in treated plots declined each week after treatment but remained at about 40% lower than control plots after 28 days. Field data were corroborated by results from bioassays that showed significantly higher mosquito mortality on treated vegetation over controls out to 28 days postspray. We concluded that barrier treatments in desert environments, when implemented as part of a suite of integrated control measures, may offer a significant level of protection from mosquitoes for deployed troops. Given the comparable performance of the tested spray technologies, we discuss considerations for choosing a barrier treatment sprayer for military scenarios.

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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)

  11. 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.

  12. 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.

  13. 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

  14. 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…

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. [Mitochondrial DNA sequence variations of Keriyan in the Taklamakan desert].

    PubMed

    Duan, Ran-Hui; Cui, Yin-Qiu; Zhou, Hui; Zhu, Hong

    2003-05-01

    The Keriyans live in the center of the Taklamakan desert of Xinjiang Province and they have never married with outsiders. Nobody knows clearly how they immigrated here and who was their origin. The mtDNA hypervariable segment I sequences were sequenced in 75 Keriyans. Seventy-one unique HVS I types were identified, varying at 68 nucleotide positions. Nucleotide diversity and the mean pairwise differences of Keriyan are intermediate between those reported for Eastern and Western populations. Keriyan's low Tajima's D statistics and bell-shaped pairwise-difference distributions can be interpreted as the hallmark of an ancient population expansion. Phylogenetic analysis shows Central Asian populations occupy a position intermediate between the Eastern and Western populations, moreover, the Keriyan presents shorter genetic distances to Xinjiang Uighur and Uighur in other places than to other populations.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  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. Palynological evidence for climatic and oceanic variability off NW Africa during the late Holocene

    NASA Astrophysics Data System (ADS)

    Bouimetarhan, Ilham; Dupont, Lydie; Schefuß, Enno; Mollenhauer, Gesine; Mulitza, Stefan; Zonneveld, Karin

    2009-09-01

    Pollen and organic-walled dinoflagellate cyst assemblages from core GeoB 9503-5 retrieved from the mud-belt (˜ 50 m water depth) off the Senegal River mouth have been analyzed to reconstruct short-term palaeoceanographic and palaeoenvironmental changes in subtropical NW Africa during the time interval from ca. 4200 to 1200 cal yr BP. Our study emphasizes significant coeval changes in continental and oceanic environments in and off Senegal and shows that initial dry conditions were followed by a strong and rapid increase in humidity between ca. 2900 and 2500 cal yr BP. After ca. 2500 cal yr BP, the environment slowly became drier again as indicated by slight increases in Sahelian savannah and desert elements in the pollen record. Around ca. 2200 cal yr BP, this relatively dry period ended with periodic pulses of high terrigenous contributions and strong fluctuations in fern spore and river plume dinoflagellate cyst percentages as well as in the fluxes of pollen, dinoflagellate cysts, fresh-water algae and plant cuticles, suggesting "episodic flash flood" events of the Senegal River. The driest phase developed after about 2100 cal yr BP.

  10. ZZYZX--The Last Word in Desert Studies

    ERIC Educational Resources Information Center

    Hill, Martin

    1977-01-01

    The mineral springs resort of Zzyzx in California is the site of a unique academic research center in high desert studies. It is being developed into a Desert Studies Center for seven southern campuses of the California State University and College System, and will provide field work opportunities for geology, geography, and anthropology students.…

  11. 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

  12. 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.

  13. 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…

  14. 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…

  15. 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.

  16. 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)

  17. 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…

  18. 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…

  19. 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…

  20. What Do Maps Show?

    ERIC Educational Resources Information Center

    Geological Survey (Dept. of Interior), Reston, VA.

    This curriculum packet, appropriate for grades 4-8, features a teaching poster which shows different types of maps (different views of Salt Lake City, Utah), as well as three reproducible maps and reproducible activity sheets which complement the maps. The poster provides teacher background, including step-by-step lesson plans for four geography…

  1. Obesity in show cats.

    PubMed

    Corbee, R J

    2014-12-01

    Obesity is an important disease with a high prevalence in cats. Because obesity is related to several other diseases, it is important to identify the population at risk. Several risk factors for obesity have been described in the literature. A higher incidence of obesity in certain cat breeds has been suggested. The aim of this study was to determine whether obesity occurs more often in certain breeds. The second aim was to relate the increased prevalence of obesity in certain breeds to the official standards of that breed. To this end, 268 cats of 22 different breeds investigated by determining their body condition score (BCS) on a nine-point scale by inspection and palpation, at two different cat shows. Overall, 45.5% of the show cats had a BCS > 5, and 4.5% of the show cats had a BCS > 7. There were significant differences between breeds, which could be related to the breed standards. Most overweight and obese cats were in the neutered group. It warrants firm discussions with breeders and cat show judges to come to different interpretations of the standards in order to prevent overweight conditions in certain breeds from being the standard of beauty. Neutering predisposes for obesity and requires early nutritional intervention to prevent obese conditions. PMID:24612018

  2. Show Me the Way

    ERIC Educational Resources Information Center

    Dicks, Matthew J.

    2005-01-01

    Because today's students have grown up steeped in video games and the Internet, most of them expect feedback, and usually gratification, very soon after they expend effort on a task. Teachers can get quick feedback to students by showing them videotapes of their learning performances. The author, a 3rd grade teacher describes how the seemingly…

  3. The Art Show

    ERIC Educational Resources Information Center

    Scolarici, Alicia

    2004-01-01

    This article describes what once was thought to be impossible--a formal art show extravaganza at an elementary school with 1,000 students, a Department of Defense Dependent School (DODDS) located overseas, on RAF Lakenheath, England. The dream of this this event involved the transformation of the school cafeteria into an elegant art show…

  4. 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)

  5. 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.

  6. 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

  7. 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

  8. Quantification of Iron Oxides and Hydroxides in Desert Aeolian Particles

    NASA Astrophysics Data System (ADS)

    Lafon, S.; Rajot, J.; Alfaro, S.; Gaudichet, A.

    2002-12-01

    Long range transport of desert dust over oceans constitute a source of iron for the surface water. Assessing the iron cycle and its biogeochemical implications in oceanic areas requires determination and quantification of the iron status in aeolian particles. Indeed, in such aerosols, the iron is either trapped in the silicate structure or present under the form of oxides and hydroxides (free iron). We propose a method to apportion iron between free and entrapped forms in mineral aerosols. It consists in the adaptation of a well known method used for soil characterization to the treatment of aerosol samples, which represent less than 1 mg of material collected by air filtration on polycarbonate filters. The iron oxides and hydroxides are extracted selectively using the combined action of reductive and complexant agents in a buffered solution. The iron content is measured before and after this chemical extraction using X ray fluorescence spectrometry. We attempt to give some values for three main desert source areas using aerosol samples collected near Niamey (Niger) either during Harmattan events or during local erosion events, and samples collected downwind of the Gobi desert in China. Results emphasize firstly that iron trapped in the structure of silicate minerals represents an important part of total iron content. This suggests that, regarding dissolution processes in sea water, total elemental iron content of aeolian dust can not be used directly to calculate the flux of iron available. Secondly, our results show that the free iron content vary according to the origin of dusts. Niger samples have contents in free iron of 4.4 % (SD = 0.8) for local erosion and 2.8 % (SD = 1.0) for Harmattan. Chinese samples contain 3.7 % (SD = 0.5) of free iron. These differences could be linked to the parent soil mineralogical composition that varies with geographical location, but for some of our samples it also could be linked to a size fractionation process occurring first

  9. Latest European coelacanth shows Gondwanan affinities.

    PubMed

    Cavin, Lionel; Forey, Peter L; Buffetaut, Eric; Tong, Haiyan

    2005-06-22

    The last European fossil occurrence of a coelacanth is from the Mid-Cretaceous of the English Chalk (Turonian, 90 million years ago). Here, we report the discovery of a coelacanth from Late Cretaceous non-marine rocks in southern France. It consists of a left angular bone showing structures that imply close phylogenetic affinities with some extinct Mawsoniidae. The closest relatives are otherwise known from Cretaceous continental deposits of southern continents and suggest that the dispersal of freshwater organisms from Africa to Europe occurred in the Late Cretaceous.

  10. 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.

  11. Retinitis pigmentosa in southern Africa.

    PubMed

    Greenberg, J; Bartmann, L; Ramesar, R; Beighton, P

    1993-11-01

    Retinitis pigmentosa (RP) is a heterogeneous group of inherited retinal disorders which are a common cause of genetic blindness. The relative frequencies of the different forms of RP in South Africa, as determined from the register at the DNA banking centre for RP at the Department of Human Genetics, University of Cape Town, are presented and discussed. Of the 125 families analysed, 29 (23%) showed autosomal dominant, 33 (27%) autosomal recessive and 3 (3%) X-linked inheritance. In 10 families the pedigree data were insufficient to allow accurate genetic subtyping and a further 50 patients were sporadic without a family history of RP or other syndromic features which would allow categorization.

  12. Agreement: Desert Community College District, College of the Desert Faculty Association CTA/NEA, January 13, 1989-June 30, 1989.

    ERIC Educational Resources Information Center

    Desert Community Coll. District, Palm Desert, CA.

    The collective bargaining agreement between the Desert Community College District and the College of the Desert Faculty Association/California Teachers Association/National Education Association is presented. This contract, covering the period from January 13, 1989 through June 30, 1989, deals with the following topics: bargaining agent…

  13. 76 FR 66354 - DesertXpress Enterprises, LLC and DesertXpress HSR Corporation-Construction and Operation...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-26

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF TRANSPORTATION Surface Transportation Board DesertXpress Enterprises, LLC and DesertXpress HSR Corporation-- Construction... under 49 U.S.C. 10502 from the prior approval requirements of 49 U.S.C. 10901 for...

  14. 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

  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.

  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. 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.

  19. Desert ecosystems: similarities, characteristics, and health benefits.

    PubMed

    Carpio-Obeso, M P; Shorr, M; Valdez-Salas, B

    1999-01-01

    Salty bodies of water in desert zones are known worldwide. The Salton Sea in California, USA, and the Dead Sea between Israel and Jordan are located in arid areas at approximately the same latitude, which might explain some similarities. Both the Salton and Dead Seas have ecosystems consisting of a singular saline sea/hot desert interface. The Salton Sea, the largest inland body of water in California, is a saline lake in the Coachella and Imperial Valleys. The Imperial Valley is one of the 10 top agricultural areas in the United States. Several thermoelectric plants exploiting geothermal wells operate around the Salton Sea, and some areas comprise a National Wildlife Refuge. The Dead Sea (Sea of Salt in Hebrew), the lowest saline lake on earth, contains high concentrations of salts and is a reservoir of minerals with a unique evaporation regime. The Dead Sea salts are the raw materials for the production of several chemical and health products. Magnesium salts and sulfur-containing mud are used for treating human skin disorders, allergies, arthritis, and respiratory diseases. After visiting both zones, we recorded, analyzed, and compared the similarities and differences between the areas. Some differences were found in the geographic, orographic, hydraulic, and climatic properties, but the main difference is in the economic-industrial aspect. The characteristics and health aspects are described in this report. PMID:10746738

  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. 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.

  2. 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.

  3. Calibration of vector navigation in desert ants.

    PubMed

    Collett, M; Collett, T S; Wehner, R

    1999-09-23

    Desert ants (Cataglyphis sp.) monitor their position relative to the nest using a form of dead reckoning [1] [2] [3] known as path integration (PI) [4]. They do this with a sun compass and an odometer to update an accumulator that records their current position [1]. Ants can use PI to return to the nest [2] [3]. Here, we report that desert ants, like honeybees [5] and hamsters [6], can also use PI to approach a previously visited food source. To navigate to a goal using only PI information, a forager must recall a previous state of the accumulator specifying the goal, and compare it with the accumulator's current state [4]. The comparison - essentially vector subtraction - gives the direction to the goal. This whole process, which we call vector navigation, was found to be calibrated at recognised sites, such as the nest and a familiar feeder, throughout the life of a forager. If a forager was trained around a one-way circuit in which the result of PI on the return route did not match the result on the outward route, calibration caused the ant's trajectories to be misdirected. We propose a model of vector navigation to suggest how calibration could produce such trajectories.

  4. Desert ecosystems: similarities, characteristics, and health benefits.

    PubMed

    Carpio-Obeso, M P; Shorr, M; Valdez-Salas, B

    1999-01-01

    Salty bodies of water in desert zones are known worldwide. The Salton Sea in California, USA, and the Dead Sea between Israel and Jordan are located in arid areas at approximately the same latitude, which might explain some similarities. Both the Salton and Dead Seas have ecosystems consisting of a singular saline sea/hot desert interface. The Salton Sea, the largest inland body of water in California, is a saline lake in the Coachella and Imperial Valleys. The Imperial Valley is one of the 10 top agricultural areas in the United States. Several thermoelectric plants exploiting geothermal wells operate around the Salton Sea, and some areas comprise a National Wildlife Refuge. The Dead Sea (Sea of Salt in Hebrew), the lowest saline lake on earth, contains high concentrations of salts and is a reservoir of minerals with a unique evaporation regime. The Dead Sea salts are the raw materials for the production of several chemical and health products. Magnesium salts and sulfur-containing mud are used for treating human skin disorders, allergies, arthritis, and respiratory diseases. After visiting both zones, we recorded, analyzed, and compared the similarities and differences between the areas. Some differences were found in the geographic, orographic, hydraulic, and climatic properties, but the main difference is in the economic-industrial aspect. The characteristics and health aspects are described in this report.

  5. 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

  6. Obesity in show dogs.

    PubMed

    Corbee, R J

    2013-10-01

    Obesity is an important disease with a growing incidence. Because obesity is related to several other diseases, and decreases life span, it is important to identify the population at risk. Several risk factors for obesity have been described in the literature. A higher incidence of obesity in certain breeds is often suggested. The aim of this study was to determine whether obesity occurs more often in certain breeds. The second aim was to relate the increased prevalence of obesity in certain breeds to the official standards of that breed. To this end, we investigated 1379 dogs of 128 different breeds by determining their body condition score (BCS). Overall, 18.6% of the show dogs had a BCS >5, and 1.1% of the show dogs had a BCS>7. There were significant differences between breeds, which could be correlated to the breed standards. It warrants firm discussions with breeders and judges in order to come to different interpretations of the standards to prevent overweight conditions from being the standard of beauty. PMID:22882163

  7. 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.

  8. 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.

  9. Tobacco in Africa.

    PubMed

    Yach, D

    1996-01-01

    Tobacco has been a common commodity in Africa for over three centuries. By 1993, some 500 000 tons of tobacco were being grown in 33 African countries, with only two countries exporting more than they import. Attempts to measure the current and potential impact of the tobacco business on health, society and the environment are still in their early stages, but the need for preventive action is already inescapably clear. Comprehensive control strategies are urgently required to prevent a major epidemic of tobacco-related disease in Africa. PMID:8820139

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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

  19. 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.

  20. 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…

  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. 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.

  3. 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.

  4. 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.

  5. 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

  6. The rural and the rotund? A critical interpretation of food deserts and rural adolescent obesity in the Canadian context.

    PubMed

    McPhail, Deborah; Chapman, Gwen E; Beagan, Brenda L

    2013-07-01

    Resting on the notion that rural spaces are "food deserts," rural adolescents are increasingly regarded as a "problem population" in Western obesity narratives. Using qualitative data gleaned from interviews with 51 teenage participants from rural areas across Canada, this paper focuses on the ways in which obesity is constructed as a rural disease in the Canadian context, demonstrating in particular how discourses of food deserts and related rural obesity rely on classist imaginings of obesity as a working-class embodiment. The paper will further question the understanding of the rural as a food desert, showing the ways in which rural teens acquire fresh, healthy foods in part through an informal economy of food growing and sharing.

  7. 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

  8. Bioremediation of Crude Oil Contaminated Desert Soil: Effect of Biostimulation, Bioaugmentation and Bioavailability in Biopile Treatment Systems.

    PubMed

    Benyahia, Farid; Embaby, Ahmed Shams

    2016-02-15

    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.

  9. 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

  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, 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...

  12. 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...

  13. 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...

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  18. 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

  19. Effects of dust storms on microwave radiation based on satellite observation and model simulation over the Taklamakan desert

    NASA Astrophysics Data System (ADS)

    Ge, J.; Huang, J.; Weng, F.; Sun, W.

    2008-04-01

    Effects of dust particles on microwave radiation over the Taklamakan desert are studied with use of measurements from the Advanced Microwave Scanning Radiometer (AMSR-E) on the EOS Aqua satellite and a microwave radiation transfer model. Eight observed cases show that the signal from atmospheric dust can be separated from the surface radiation by the fact that the dust particles produce stronger scattering at high frequencies and depolarize the background desert signature. This result of satellite data is consistent with the model simulation.

  20. Effects of dust storms on microwave radiation based on satellite observation and model simulation over the Taklamakan desert

    NASA Astrophysics Data System (ADS)

    Ge, J.; Huang, J.; Weng, F.; Sun, W.

    2008-08-01

    Effects of dust particles on microwave radiation over the Taklamakan desert are studied with use of measurements from the Advanced Microwave Scanning Radiometer (AMSR-E) on the EOS Aqua satellite and a microwave radiation transfer model. Eight observed cases show that the signal from atmospheric dust can be separated from the surface radiation by the fact that the dust particles produce stronger scattering at high frequencies and depolarize the background desert signature. This result of satellite data is consistent with the model simulation.

  1. 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…

  2. 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.

  3. Stretched View Showing 'Victoria'

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Stretched View Showing 'Victoria'

    This pair of images from the panoramic camera on NASA's Mars Exploration Rover Opportunity served as initial confirmation that the two-year-old rover is within sight of 'Victoria Crater,' which it has been approaching for more than a year. Engineers on the rover team were unsure whether Opportunity would make it as far as Victoria, but scientists hoped for the chance to study such a large crater with their roving geologist. Victoria Crater is 800 meters (nearly half a mile) in diameter, about six times wider than 'Endurance Crater,' where Opportunity spent several months in 2004 examining rock layers affected by ancient water.

    When scientists using orbital data calculated that they should be able to detect Victoria's rim in rover images, they scrutinized frames taken in the direction of the crater by the panoramic camera. To positively characterize the subtle horizon profile of the crater and some of the features leading up to it, researchers created a vertically-stretched image (top) from a mosaic of regular frames from the panoramic camera (bottom), taken on Opportunity's 804th Martian day (April 29, 2006).

    The stretched image makes mild nearby dunes look like more threatening peaks, but that is only a result of the exaggerated vertical dimension. This vertical stretch technique was first applied to Viking Lander 2 panoramas by Philip Stooke, of the University of Western Ontario, Canada, to help locate the lander with respect to orbiter images. Vertically stretching the image allows features to be more readily identified by the Mars Exploration Rover science team.

    The bright white dot near the horizon to the right of center (barely visible without labeling or zoom-in) is thought to be a light-toned outcrop on the far wall of the crater, suggesting that the rover can see over the low rim of Victoria. In figure 1, the northeast and southeast rims are labeled

  4. Primary health care in South Africa.

    PubMed

    Buch, E

    1989-01-01

    Even though most countries have committed to primary health care (PHC), South Africa, a middle-income country, has an inadequate PHC system. The poor system has roots in the colonial period and apartheid reinforces this system. Race, class, and place of residence determine the type of health care individuals receive. South Africa falls far short of all 5 principles of PHC. Just 12% of the health budget goes to 40% of the population who live in the homelands which shows the inequitable distribution of health care resources and inadequate quality health care for all. Similarly, South Africa has not altered its communication and education techniques to improve preventive and promotive health services. It has not implemented any successful national campaigns such as a campaign against diarrhea deaths. South Africa does not make good use of available appropriate technology such as breast feeding, oral rehydration, refrigeration, and the ventilated improved pit latrine which lead to health for all. People in South Africa discuss community participation but it is not likely to occur without general political democracy. Some people have made local attempts at community participation but they tend to use inflexible means and request either cash or contributions in kind from people who have little. The elite in South Africa has not recognized the need to correct socioeconomic inequalities. The Population Development Plan Programme among white farmer-owners has showed some support for a multisectoral approach to improve health care, however. For example, it acknowledges that non-health-care interventions such as better salaries, literacy, and living conditions, lead to better health. The Department of National Health has discussed improved coordination of the budget to allow priority determination of national PHD and manpower plans. Nongovernmental organizations are beginning to use the PHC approach instead of the charitable approach.

  5. 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

  6. 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.

  7. 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

  8. 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,"…

  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. 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…

  11. 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…

  12. 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)

  13. West and Central Africa.

    PubMed

    Lydie, N; Robinson, N J

    1998-01-01

    This article reviews scientific and other literature during the 1990s that links migration and mobility with the spread of sexually transmitted diseases (STDs), including HIV/AIDS. The focus is on key population groups linked to the spread of HIV and STDs in West and Central Africa: migrant laborers, truck drivers, itinerant traders, commercial sex workers (CSWs), and refugees. Countries with high emigration and immigration tend to have high levels of HIV infection, with the exception of Senegal. The main destination of immigrants are Senegal, Nigeria, and Cote d'Ivoire in West Africa and Cameroon, Congo, Gabon, and Congo in Central Africa. The risk of infection and the spread of HIV is variable among migrants. There is little in the literature that substantiates hypotheses about the strong association between migration and HIV-positive status. Information is needed on the duration, frequency of return visits, living conditions, sexual activities with multiple partners, and information before departure, along the routes, at final destination, and at the time of returns. Action-based research in five West African countries (Burkina Faso, Cote d'Ivoire, Mali, Niger, and Senegal) should produce results in late 1998. Comparable studies in Central Africa are unknown. Regional studies should be complemented by local studies. Prevention would benefit from studies on the relative size of these five population groups by geographic location.

  14. South Africa's Constitutional Change.

    ERIC Educational Resources Information Center

    Getman, Thomas

    1987-01-01

    Describes the striking dichotomy of South Africa's beauty and the squalor resulting from the apartheid policies of the government. Reviews reactions of black South Africans to recent constitutional changes and details efforts to secure more sweeping reform. Includes stories of several individuals who have taken actions which oppose the system of…

  15. Trends Abroad: South Africa

    ERIC Educational Resources Information Center

    Varley, Douglas H.

    1970-01-01

    In South Africa today there is a complex structure of laws and regulations which impose a variety of restrictions on individual liberties including the freedom to publish and read literary material. The successive steps by which this state of affairs has been reached are briefly described. (NH)

  16. 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…

  17. 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…

  18. 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.

  19. 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…

  20. Literacy in Francophone Africa.

    ERIC Educational Resources Information Center

    Kokora, Pascal D.

    1991-01-01

    Literacy in francophone Africa, where literacy is still a privilege, is reviewed in terms of the complex linguistic situation, effects of population change, concepts and definitions of literacy, promotion of literacy in adult nonformal settings (e.g., African language literacy materials, multilingual settings). (23 references) (LB)