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Desert Environments (desert + environment)
Selected AbstractsDeserts and Desert Environments , By Julie LaityTHE GEOGRAPHICAL JOURNAL, Issue 1 2010Robert Bryant No abstract is available for this article. [source] Desert environments: landscapes and stratigraphyGEOLOGY TODAY, Issue 5 2009Peter G. Fookes It is common to think of hot deserts, i.e. hot arid or dry lands, as areas of little rain situated in the middle parts of the world, that are simply ,just there'. However, most of the world's deserts have a long geological history, sometimes of 50 million years or more and ways have been developing for some time now, particularly from geomorphological studies, of not only erecting the law of superposition of strata for the desert but also ,absolute' dating. The authors have often worked commercially in deserts world-wide but their recent experiences in the Oman have brought home to them the excellent work that has been going on in the last two or three decades in evaluating the geological history of deserts. The Oman experience is described in a feature in the next issue. [source] Processes controlling rapid temperature variations on rock surfaces,EARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2010Jamie L. Molaro Abstract In arid environments, thermal oscillations are an important source of rock weathering. Measurements of temperature have been made on the surface of rocks in a desert environment at a sampling interval of 0·375,s, with simultaneous measurements of wind speed, air temperature, and incoming shortwave radiation. Over timescales of hours, the temperature of the rock surface was determined primarily by shortwave radiation and air temperature, while rapid temperature variations, high dT/dt, at intervals of seconds or less, were determined by wind speed. The maximum values of temperature change and time spent above 2°C,min,1 increased at high measurement rates and were much higher than previously reported. The maximum recorded value of dT/dt was 137°C,min,1 and the average percentage time spent above 2°C,min,1 was ,70 ± 13%. Maximum values of dT/dt did not correlate with the maximum values of time spent above 2°C,min,1. Simultaneous measurements of two thermocouples 5·5,cm apart on a single rock surface had similar temperature and dT/dt values, but were not correlated at sampling intervals of less than 10,s. It is suggested that this is resulting from rapid fluctuations due to small spatial and timescale wind effects that are averaged out when data is taken at longer sampling intervals, ,10,s or greater. Published in 2010 by John Wiley & Sons, Ltd. [source] Multiyear to daily radon variability from continuous monitoring at the Amram tunnel, southern IsraelGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2010S. M. Barbosa SUMMARY Radon is a naturally occurring radioactive noble gas generated within mineral grains of uranium bearing rocks by alpha decay from radium. The Amram tunnel (A. Bloch Geophysical Observatory) is a particularly suitable location for the investigation of radon variability. Located in the arid environment of the Arava desert, near Elat, the 170 m tunnel that constitutes the observatory enables radon monitoring in a desert environment and under fairly stable environmental conditions. The analysis of the temporal variability of continuous measurements of radon and environmental parameters at the Amram tunnel over a period of several years shows a complex temporal pattern characterized by non-stationary and multiscale features. Radon concentrations exhibit multiyear variability in the form of a increasing trend of ,1000 Bq m,3 yr,1 in the mean and much larger trends up to ,2500 Bq m,3 yr,1 in the maximum radon levels. Radon concentrations also display strong seasonal patterns, with maxima in summer and minima in winter, ranging from 2.5 kBq m,3 in winter to 35 kBq m,3 in summer. Intraseasonal variability is characterized by very large radon anomalies, with sharp increases of more than 20 kBq m,3 relative to the base level, that occur in spring and summer and last for several days. Daily periodic variability with maxima around midnight appears also in spring and summer, being absent in the cold months. Radon variability at seasonal, intraseasonal and daily timescales is associated with the air temperature outside the tunnel, specifically the temperature gradient between the external environment and the more stable environment inside the tunnel where the measurements are performed. [source] Epidemiology of low back pain in the United Arab EmiratesINTERNATIONAL JOURNAL OF RHEUMATIC DISEASES, Issue 3 2004Abdulbari BENER Abstract Aims:, Low back pain (LBP), a common presenting problem in general practice in the United Arab Emirates (UAE), has received increasing attention in recent decades. We seek to investigate the prevalence of LBP and associated risk factors among people living in the typically hot, humid desert environment of the UAE. Methods:, A cross-sectional questionnaire survey was conducted. The setting was the Primary Health Care (PHC) Clinics in Al-Ain, UAE. The subjects were a multistage stratified sample of 1304 UAE nationals, 15,70 years of age, who attended PHC clinics for any reason. All subjects were invited to participate. The questionnaire used in the survey is a modified version of the Roland-Morris scale for evaluating low back pain. The questionnaires were administered during face-to-face interviews conducted in Arabic by qualified nurses. Results:, Of the total 1304 subject, 1103 (84.5%) living in both urban and rural areas agreed to participate and responded to the study; 586 (53.1%) were men and 517 (46.9%) women. The mean ages and SD of the subjects were 34.9 ± 13.4 years for the men and 33.5 ± 11.8 years for the women. The prevalence of LBP in the present study was 64.6% (95% CI = 60.7,68.5). The results revealed that there were statistically significant differences between men and women with respect to LBP and body mass index (BMI) (P < 0.001), marital status (P < 0.001), occupational status (P < 0.001), housing condition (P < 0.001), and smoking habits (P < 0.001). Back pain had a greater influence on the lifestyle habits of the women than men. Stepwise multiple regression analysis showed that only BMI (OR = 2.54, 95% CI = 2.30,281; P < 0.001), prolonged standing (OR = 6.22, 95% CI = 4.01,9.67; P < 0.0001), weakness in leg (OR = 2.11, 95% CI = 1.16,3.85; P = 0.0142), lifting heavy weights (OR = 6.34, 95% CI = 4.09,9.84; P = 0.019) regular exercise (OR = 12.47, 95% CI = 7.50,20.71; P < 0.001) and smoking habits (OR = 1.61, 95% CI = 1.08,2.38; P < 0.05) had a significant effect on the presence of LBP in these patients. Conclusions:, The study showed that the prevalence of back-related disability was higher among women than men in the UAE. Also, low socio-economic status and adverse lifestyle habits may constitute risk factors and predictors of LBP. [source] A petrologic and trace element study of Dar al Gani 476 and Dar al Gani 489: Twin meteorites with affinities to basaltic and lherzolitic shergottitesMETEORITICS & PLANETARY SCIENCE, Issue 2 2001M. WADHWA Having resided in a hot desert environment for an extended time, DaG 476 and DaG 489 were subjected to terrestrial weathering that significantly altered their chemical composition. In particular, analyses of some of the silicates show light rare earth element (LREE)-enrichment resulting from terrestrial alteration. In situ measurement of trace element abundances in minerals allows us to identify areas unaffected by this contamination and, thereby, to infer the petrogenesis of these meteorites. No significant compositional differences between DaG 476 and DaG 489 were found, supporting the hypothesis that they belong to the same fall. These meteorites have characteristics in common with both basaltic and lherzolitic shergottites, possibly suggesting spatial and petrogenetic associations of these two types of lithologies on Mars. However, the compositions of Fe-Ti oxides and the size of Eu anomalies in the earliest-formed pyroxenes indicate that the two Saharan meteorites probably experienced more reducing crystallization conditions than other shergottites (with the exception of Queen Alexandra Range (QUE) 94201). As is the case for other shergottites, trace element microdistributions in minerals of the DaG martian meteorites indicate that closed-system crystal fractionation from a LREE-depleted parent magma dominated their crystallization history. Furthermore, rare earth element abundances in the orthopyroxene megacrysts are consistent with their origin as xenocrysts rather than phenocrysts. [source] Preparation, swelling behaviors and application of polyacrylamide/attapulgite superabsorbent compositesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 1 2006Junping Zhang Abstract A series of superabsorbent composites, polyacrylamide/attapulgite (PAMA), were prepared from acrylamide (AM) and attapulgite micropowder in aqueous solution, using N,N,-methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator and then saponified with sodium hydroxide solution. This paper focuses on swelling behaviors of the PAMA superabsorbent composites in various saline solutions. The results indicate that saline solutions can weaken the swelling abilities of the PAMA compsites greatly. Water absorbency of the PAMA composites with 20 and 40,wt% attapulgite in aqueous chloride salt solutions has the following order: Li+,=,Na+,=,K+, Mg2+,>,Ca2+,=,Ba2+ all through the range of concentration investigated. However, swelling properties of the composites are complicated in CuCl2(aq), AlCl3(aq) and FeCl3(aq) solutions and are related to saline solutions concentration. The deswelling behavior of PAMA composites is more obvious in univalent chloride salt solutions than in divalent and trivalent ones. The influence of kind and valence of anions on swelling ability of the composites is limited and almost the same. Moreover, reswelling capability, practical water retention ability in sand soil of the composites and the effect of pH on water absorbency of the PAMA composites were investigated. The PAMA composite shows good water retention and reswelling ability in sand soil, and may be used as a recyclable water-managing material for the renewal of arid and desert environment. Copyright © 2006 John Wiley & Sons, Ltd. [source] Range size, taxon age and hotspots of neoendemism in the California floraDIVERSITY AND DISTRIBUTIONS, Issue 3 2010Nathan J. B. Kraft Abstract Aim, Sustaining biological diversity requires the protection of the ecological, evolutionary and landscape-level processes that generate it. Here, we identify areas of high neoendemism in a global diversity hotspot, the California flora, using range size data and molecular-based estimates of taxon age. Location, California, USA. Methods, We compiled distribution and range size data for all plant taxa endemic to California and internal transcribed spacer (ITS)-based age estimates for 337 putative neoendemics (15% of the endemic flora). This information was combined to identify areas in the state with high proportions of young and restricted-range taxa. We overlaid the distribution of neoendemic hotspots on maps of currently protected lands and also explored correlations between our diversity measures and climate. Results, The central coast of California, the Sierra Nevada and the San Bernardino Range contained endemics with the most restricted distributions on average, while areas in the Desert and Great Basin provinces found within the state were composed of the youngest neoendemics on average. Diversity measures that took age and range size into account shifted the estimate of highest endemic diversity in the state towards the Desert and Great Basin regions relative to simple counts of endemic species richness. Our diversity measures were poorly correlated with climate and topographic heterogeneity. Main conclusions, Substantial portions of California with high levels of plant neoendemism fall outside of protected lands, indicating that additional action will be needed to preserve the geographic areas apparently associated with high rates of plant diversification. The neoendemic flora of the deserts appears particularly young in our analyses, which may reflect the relatively recent origin of desert environments within the state. [source] Distribution, zoogeography and biology of the Murchison River hardyhead (Craterocephalus cuneiceps Whitley, 1944), an atherinid endemic to the Indian Ocean (Pilbara) Drainage Division of Western AustraliaECOLOGY OF FRESHWATER FISH, Issue 3 2005M. G. Allen Abstract , The Murchison River hardyhead (Craterocephalus cuneiceps) is endemic to the extremely arid Indian Ocean (Pilbara) Drainage Division of Western Australia, where it is found in the Greenough, Hutt, Murchison, Wooramel, Gascoyne and DeGrey rivers, but is absent from numerous rivers within its range. The most likely explanation for the disjunct contemporary distribution is that C. cuneiceps has simply never inhabited the rivers from which it is conspicuously absent (e.g. Ashburton and Fortescue). Biogeographical, geological and palaeoclimatic evidence is presented to support this hypothesis. In the Murchison River, breeding was extremely protracted with recruitment occurring throughout the year. The largest female and male specimens captured were 96 mm total length (TL; 7.73 g) and 86 mm TL (5.57 g), respectively. Sex ratio was 1.09 females:1 male. Batch fecundity ranged from 46 to 454 (mean 167.5 ± 25.7 SE). Estimates for the length at which 50 and 95% of females first spawned were 36.4 and 44.3 mm TL, respectively. Craterocephalus cuneiceps is essentially a detritivore, but also feeds on aquatic invertebrates. Rainfall in the Murchison River catchment is unpredictable and pH, salinity and temperature are variable. A specialised diet, small size and young age at maturity and protracted spawning period, coupled with serial spawning and high fecundity, allows the numerical dominance of this species in competitive, harsh, arid and unpredictable desert environments. Resumen 1. Craterocephalus cuneiceps es una especie endémica de las cuencas del Océano Indico (i.e., Pilbara) de Australia Occidental. Se encuentra en los ríos Greenough, Hutt, Murchison, Wooramel, Gascoyne y DeGrey pero está ausente en numerosos ríos dentro de su área de distribución. La explicación más probable para esta distribución separada en la actualidad es que C. cuneiceps no ha habitado nunca los ríos en los que está ausente tales como los ríos Ashburton y Fortescue. Presentamos evidencia bio-geográfica, geológica y paleo-climática para soportar esta hipótesis. 2. En el río Murchison, la reproducción es extremadamente prolongada con reclutamiento a lo largo de todo el año. Los mayores machos y hembras capturados alcanzaron 96 mm LT (7.73 g) y 86 mm LT (5.57 g), respectivamente. La proporción de sexos fue 1.09 hembras: 1 macho. La fecundidad varió entre 46 y 454 (media 167.5 ± 25.7 SE) y la longitudes a la que el 50 y el 95% de las hembras se reproducen por primera vez alcanzaron 36.4 y 44.3 mm LT, respectivamente. 3. C. cuneiceps es esencialmente detritívoro pero también se alimenta de invertebrados acuáticos. La lluvia sobre la cuenca del río Murchison es impredecible y el pH, la salinidad y la temperatura son variables. Una dieta especializada, pequeño tamaño, una edad joven en la madurez, y un período reproductivo prolongado, ademos de una freza seriada y alta fecundidad, permiten la dominancia numérica de la especie en ambientes competitivos, duros, áridos e impredecibles. [source] Desert water harvesting from takyr surfaces: assessing the potential of traditional and experimental technologies in the KarakumLAND DEGRADATION AND DEVELOPMENT, Issue 1 2007L. Fleskens Abstract From historical times the traditionally nomadic people in desert environments of Turkmenistan have applied a range of innovative technologies to secure water supply for consumptive and productive purposes. These technologies make use of takyrs, flat or slightly sloping dense clay surfaces which act as natural catchment areas. In recent history, these technologies have been neglected, in part due to a booming water supply through irrigation development, and takyr surfaces have suffered various degradation processes. However, the limited scope for further extension of irrigation systems presents a challenge to reconsider these traditional technologies. In this paper, results of cost-benefit analysis are presented by which an assessment is made of the potential of both traditional and experimental takyr use technologies. It is shown that they bear considerable potential for the future at relatively low investment cost, that they may help limit degradation processes and provide for a sustainable development pathway for the inhabitants of the desert. A main challenge in order to benefit from this potential is to find an appropriate management structure for maintenance and resource use of these water-harvesting technologies. Copyright © 2006 John Wiley & Sons, Ltd. [source] Range expansions in the flightless longhorn cactus beetles, Moneilema gigas and Moneilema armatum, in response to Pleistocene climate changesMOLECULAR ECOLOGY, Issue 4 2005CHRISTOPHER IRWIN SMITH Abstract Pollen cores and plant and animal fossils suggest that global climate changes at the end of the last glacial period caused range expansions in organisms indigenous to the North American desert regions, but this suggestion has rarely been investigated from a population genetic perspective. In order to investigate the impact of Pleistocene climate changes and glacial/interglacial cycling on the distribution and population structure of animals in North American desert communities, biogeographical patterns in the flightless, warm-desert cactus beetles, Moneilema gigas and Moneilema armatum, were examined using mitochondrial DNA (mtDNA) sequence data from the cytochrome oxidase I (COI) gene. Gene tree relationships between haplotypes were inferred using parsimony, maximum-likelihood, and Bayesian analysis. Nested clade analysis and coalescent modelling using the programs mdiv and fluctuate were used to identify demographically independent populations, and to test the hypothesis that Pleistocene climate changes caused recent range expansions in these species. A sign test was used to evaluate the probability of observing concerted population growth across multiple, independent populations. The phylogeographical and nested clade analyses reveal a history of northward expansion in both of these species, as well as a history of past range fragmentation, followed by expansion from refugia. The coalescent analyses provide highly significant evidence for independent range expansions from multiple refugia, but also identify biogeographical patterns that predate the most recent glacial period. The results indicate that widespread desert environments are more ancient than has been suggested in the past. [source] Seawater Greenhouses and the Sahara Forest ProjectARCHITECTURAL DESIGN, Issue 4 2009Ken Yeang Abstract In this issue, Ken Yeang joins forces with Michael Pawlyn of Exploration Architecture Ltd to investigate how seawater, when combined with the biological know-how of a beetle, might hold the key for creating fresh water in desert environments. Copyright © 2009 John Wiley & Sons, Ltd. [source] Seed supply as a limiting factor for granivorous bird assemblages in the Monte Desert, ArgentinaAUSTRAL ECOLOGY, Issue 4 2001Pedro G. Blendinger Abstract Seed availability may limit the size of granivorous bird populations, particularly in desert environments. Seasonal and annual fluctuations in the abundance of granivorous birds were studied at three sites in the Northern Monte Desert, Argentina. The way in which these changes were related to seed supply was also studied. Granivore abundance and biomass, as well as seed abundance, were greater in winter. Changes in total granivore abundance were mostly because of variations in numbers of the most mobile bird species, all of which were found to have similar patterns of variation in their abundance. Evidence suggests that during the non-breeding season, the most mobile species are able to track patches of high seed availability over long distances, whereas the abundance of less vagile species largely depends on the local ecological conditions. Seed supply is a proximate factor that limits the abundance of granivorous birds in the Monte Desert during the winter, but does not limit species richness. Granivore abundance was not correlated with seed supply in spring. [source] | |||||||||||||