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Sample records for thar desert soils

  1. Microbial Diversity in Soil, Sand Dune and Rock Substrates of the Thar Monsoon Desert, India.

    Science.gov (United States)

    Rao, Subramanya; Chan, Yuki; Bugler-Lacap, Donnabella C; Bhatnagar, Ashish; Bhatnagar, Monica; Pointing, Stephen B

    2016-03-01

    A culture-independent diversity assessment of archaea, bacteria and fungi in the Thar Desert in India was made. Six locations in Ajmer, Jaisalmer, Jaipur and Jodhupur included semi-arid soils, arid soils, arid sand dunes, plus arid cryptoendolithic substrates. A real-time quantitative PCR approach revealed that bacteria dominated soils and cryptoendoliths, whilst fungi dominated sand dunes. The archaea formed a minor component of all communities. Comparison of rRNA-defined community structure revealed that substrate and climate rather than location were the most parsimonious predictors. Sequence-based identification of 1240 phylotypes revealed that most taxa were common desert microorganisms. Semi-arid soils were dominated by actinobacteria and alpha proteobacteria, arid soils by chloroflexi and alpha proteobacteria, sand dunes by ascomycete fungi and cryptoendoliths by cyanobacteria. Climatic variables that best explained this distribution were mean annual rainfall and maximum annual temperature. Substrate variables that contributed most to observed diversity patterns were conductivity, soluble salts, Ca(2+) and pH. This represents an important addition to the inventory of desert microbiota, novel insight into the abiotic drivers of community assembly, and the first report of biodiversity in a monsoon desert system.

  2. Desert Dermatoses (Thar Desert, India).

    Science.gov (United States)

    Chatterjee, Col Manas

    2017-01-01

    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. Infections are the most common conditions seen among this population, and among them, fungal infections are 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 are found to be more prevalent in this region. Desert sweat dermatitis was another specific condition found to have an increased incidence. 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.

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

    Science.gov (United States)

    Chatterjee, Manas; Vasudevan, Biju

    2015-01-01

    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. This is a descriptive study involving various dermatoses seen in patients residing in the Thar desert region over a duration of 3 years. 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. 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.

  4. Analyzing energy-water exchange dynamics in the Thar desert

    Science.gov (United States)

    Raja, P.; Singh, Nilendu; Srinivas, C. V.; Singhal, Mohit; Chauhan, Pankaj; Singh, Maharaj; Sinha, N. K.

    2017-07-01

    Regions of strong land-atmosphere coupling will be more susceptible to the hydrological impacts in the intensifying hydrological cycle. In this study, micrometeorological experiments were performed to examine the land-atmosphere coupling strength over a heat low region (Thar desert, NW India), known to influence the Indian summer monsoon (ISM). Within the vortex of Thar desert heat low, energy-water exchange and coupling behavior were studied for 4 consecutive years (2011-2014) based on sub-hourly measurements of radiative-convective flux, state parameters and sub-surface thermal profiles using lead-lag analysis between various E-W balance components. Results indicated a strong (0.11-0.35) but variable monsoon season (July-September) land-atmosphere coupling events. Coupling strength declined with time, becomes negative beyond 10-day lag. Evapotranspiration (LE) influences rainfall at the monthly time-scale (20-40 days). Highly correlated monthly rainfall and LE anomalies (r = 0.55, P memory linked to the local land surface state. Sensible heating (SH) during March and April are more strongly (r = 0.6-0.7) correlated to ISM rainfall than heating during May or June (r = 0.16-0.36). Analyses show strong and weak couplings among net radiation (Rn)-vapour pressure deficit (VPD), LE-VPD and Rn-LE switching between energy-limited to water-limited conditions. Consistently, +ve and -ve residual energy [(dE) = (Rn - G) - (SH + LE)] were associated with regional wet and dry spells respectively with a lead of 10-40 days. Dew deposition (18.8-37.9 mm) was found an important component in the annual surface water balance. Strong association of variation of LE and rainfall was found during monsoon at local-scale and with regional-scale LE (MERRA 2D) but with a lag which was more prominent at local-scale than at regional-scale. Higher pre-monsoon LE at local-scale as compared to low and monotonous variation in regional-scale LE led to hypothesize that excess energy and water

  5. Isolation and characterization of osmotolerant bacteria from thar desert of western Rajasthan (India).

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    Sharma, Ramavtar; Manda, Rajni; Gupta, Shikha; Kumar, Sushil; Kumar, Vinod

    2013-12-01

    The Thar Desert harsher environment harbors a limited diversity of life forms due to extreme conditions like low moisture of sandy soils and high soil temperature. In the present study, osmotolerant bacteria from the Thar soils were isolated and characterized. Bacteria were isolated from 20 soil samples (100 g), collected from sand dunes, suspended in water and absolute alcohol. A total of 11 biochemical and morphological tests were carried out for generic identification of bacteria. Osmotic tolerance capacity of isolates was examined on glycerol, NaCI and alcohol; and sequencing of 16S rRNA gene was also performed for bacterial identification. 16S to 23S rRNA internal transcribed spacer analysis (RISA) was done for phylogenetic analysis of isolates. The soil suspended in water contained 2.5 x 10(6) bacteria/g of soil while alcohol suspended soil had 4.4 x 10(4) bacteria/g. The 24 bacterial isolates were found tolerant to 26% glycerol, 14% NaCI and 10% of alcohol, and 22 out of 24 isolates were found Gram positive. The results showed that 45.83% and 41.67% bacteria belong to Bacillus spp. and Corynebacterium spp., respectively, while Acinetobacter spp., Aeromonas spp. and Staphylococcus spp. were in equal proportion (4.16% each). Six isolates were selected for 16S rRNA gene sequencing and five were found 95% similar with Bacillus licheniformis whereas one isolate was identified as B. subtilis. All the isolates showed good growth up to 50 degrees C with gradual reduction on subsequent increment of temperature. Out of 24 isolates, six could survive at 65 degrees C while one isolate could grow at 63 degrees C. Growth kinetic studies revealed that the reduction in generation time in solute(s) and temperature stress was more as compared to generation time in plain medium. This study suggests that virgin sand dunes may be a rich source of bacteria, tolerant to osmotrophic solutes, and can be examined for plant growth promotion activity in agriculture. Moreover, study

  6. Calcretes in the Thar desert: Genesis, chronology and ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    soil feature or as outcrops under a thin aeolian mantle (e.g., Dhir and Kolarkar 1977). At sev- eral locations, the solum over the calcretes was too thin vis-`a-vis calcrete development. This led. Dhir et al (1982) to suggest that their origin could not be purely by pedogenic processes. Courty et al (1987) and later Achyuthan and ...

  7. Fluoride ion contamination in the groundwater of Mithi sub-district, the Thar Desert, Pakistan

    Science.gov (United States)

    Rafique, Tahir; Naseem, Shahid; Bhanger, Muhammad I.; Usmani, Tanzil H.

    2008-11-01

    Groundwater samples were collected from various localities of Mithi sub-district of the Thar Desert of Pakistan and analysed for fluoride ion along with other chemical parameters. The area is mainly covered by sand dunes and kaolin/granite at variable depths. Results showed that collected water samples were severely contaminated by the presence of fluoride ion and most of the samples have higher concentration than prescribed WHO standards (1.5 mg/l) for drinking water. Fluoride ion concentrations ranged between 0.09 and 11.63 mg/l with mean and median values of 3.64 and 3.44 mg/l, respectively, in this area whereas, distribution pattern showed high concentrations in the vicinity of Islamkot and Mithi towns. The content of F- has also been correlated with other major ions found in the groundwater of the study area. The positive correlation of F- with Na+ and HCO3 - showed that the water with high Na+ and HCO3 - stabilizes F- ions in the groundwater of the Thar Desert. The pH versus F- plots signifies high fluoride concentration at higher pH values, implying that alkaline environment favours the replacement of exchangeable OH- with F- in the groundwater of Mithi area. The saturation indices (SI) of fluorite (CaF2) and calcite (CaCO3) in the groundwater samples showed that most of the samples are oversaturated with respect to calcite whereas majority of samples have been found under saturated with respect to fluorite. The log TDS and Na/Na+Ca ratio reflected supremacy of weathering of rocks, which promotes the availability of fluoride ions in the groundwater. Piper diagram has been used to classify the hydrofacies. In the cation triangle, all samples are Na-type, while the anion triangle reflects major dominance of Cl-type with a minor influence of HCO3 - and SO4 -.

  8. Environmental isotope studies on groundwater problems in the Thar Desert, India

    Energy Technology Data Exchange (ETDEWEB)

    Nair, A.R.; Navada, S.V.; Rao, S.M. [Bhabha Atomic Research Centre, Trombay, Mumbai (India). Isotope Division

    1997-10-01

    One of the groundwater problems encountered in arid areas like the Thar Desert in Rajasthan is to know whether the shallow groundwater is being actively recharged. Environmental isotopes particularly tritium are very useful in providing evidence of recent recharge. In the Barmer area, the shallow groundwaters have tritium levels generally in the range 3-6 TU showing modern recharge. Most of the recharge possibly occurs by direct infiltration of precipitation. Indirect recharge through wadis (river channels) could sometimes be an important mechanism of groundwater recharge. Environmental isotope study in Jalore area showed that the shallow groundwaters near the Sukri river course had {delta}{sup 2}H and {delta}{sup 18}O are depleted compared to present day precipitation but not as depleted as the present day Himalayan rivers. Carbon-24 values of some of these groundwaters are in the range of 54-58 pMC showing that they possibly represent old river with headwater connection outside the desert. In the Thar, the deep groundwaters which sometimes form the bulk of water supply are generally paleowaters as sown by environmental {delta}{sup 2}H, {delta}{sup 18}O, {sup 3}H and {sup 14}C. For example in the Barmer area, deep groundwaters (depth > 150m) have depleted {delta}{sup 2}H and {delta}{sup 18} O compared to the shallow groundwaters and present day precipitation. They have negligible {sup 3}H and {sup 14}C model ages ranging from 4000 to 9500 BP. Hence the isotope data of the deep groundwaters indicate they are paleowaters recharged during humid periods in the Holocene. Over-exploitation of deep groundwaters could lead to mixing of shallow and deep groundwaters or influx of waters from adjoining aquifers. In the Bikaner area similar {delta}{sup 2}H and {delta}{sup 18}O of the shallow and deep wells and young waters encountered in some of the deep wells indicated mixing between the two aquifers due to heavy exploitation of groundwaters in the area. In a limestone belt

  9. Combining molecular-marker and chemical analysis of Capparis decidua (Capparaceae) in the Thar Desert of Western Rajasthan (india).

    Science.gov (United States)

    Kumar, Sushil; Sharma, Ramavtar; Kumar, Vinod; Vyas, Govind K; Rathore, Abhishek

    2013-03-01

    The Thar Desert, a very inhospitable place, accommodates only plant species that survive acute drought, unpredictable precipitation, and those can grow in the limited moisture of sandy soils. Capparis decidua is among one of the few plants able to grow well under these conditions. This species is highly exploited and has been naturally taken, as local people use it for various purposes like food, timber and fuel, although, no management or conservation efforts have been established. The present study was conducted in this arid area of Western Rajasthan (India) with the aim to obtain preliminary molecular information about this group of plants. We evaluated diversity among 46 samples of C. decidua using chemical parameters and random amplified polymorphic DNA (RAPD) markers. Fourteen chemical parameters and eight minerals (total 22 variables) of this species fruits were estimated. A total of 14 RAPD primers produced 235 band positions, of which 81.27% were polymorphic. Jaccard's similarity coefficients for RAPD primers ranged from 0.34 to 0.86 with a mean genetic similarity of 0.50. As per observed coefficient of variation, NDF (Neutral Detergent Fiber) content was found to be the most variable trait followed by starch and soluble carbohydrate. The Manhattan dissimilarity coefficient values for chemical parameters ranged between 0.02-0.31 with an average of 0.092. The present study revealed a very low correlation (0.01) between chemical parameters and RAPD-based matrices. The low correlation between chemical- and RAPD-based matrices indicated that the two methods were different and highly variable. The chemical-based diversity will assist in selection of nutritionally rich samples for medicinal purpose, while genetic diversity to face natural challenges and find sustainable ways to promote conservation for future use.

  10. Conservation genetics of endangered medicinal plant Commiphora wightii in Indian Thar Desert.

    Science.gov (United States)

    Harish; Gupta, Amit Kumar; Phulwaria, Mahendra; Rai, Manoj Kumar; Shekhawat, Narpat Singh

    2014-02-10

    To ascertain the conservation priorities and strategies for Commiphora wightii, an endangered medicinal plant of Indian Thar Desert, genetic diversity was estimated within and among different populations. The total of 155 amplification products were scored using ten each of RAPD and ISSR primers, exhibiting an overall 86.72% polymorphism across 45 individuals representing eight populations. The cumulative data of two markers were used to compute pair-wise distances. The Neighbor-Joining tree revealed high genetic differentiation among populations except Kiradu population. Nei's gene diversity (h) ranged between 0.082 and 0.193 with total diversity at species level is 0.294. Shannon's information index (I) ranged between 0.118 and 0.275 with an overall diversity of 0.439. Analysis of molecular variance showed more diversity among population level (56.65%) than at within population level (43.35%). The low gene flow value (Nm=0.349) and high coefficient of genetic differentiation (GST=0.589) and high fixation index (FST=0.566) demonstrated elevated genetic differentiation among the population and can be predicted that these populations are not in Hardy-Weinberg proportions. Principal Co-ordinate Analysis confirms that Akal population has become phylogenetically more distinct and less diverse than the rest of the samples. Mantel's test revealed no correlation between genetic and geographical distances of populations (R(2)=0.122). Overall highest diversity was observed in the population of Machiya Safari Park and Kiradu, while lowest in Akal population, later may constitute an evolutionary significant unit, having merit for special management. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Chemical and genetic diversity among some wild stands of Calligonum polygonoides (Polygonaceae from the Thar Desert of Rajasthan

    Directory of Open Access Journals (Sweden)

    Govind K. Vyas

    2012-09-01

    Full Text Available The arid Western Rajasthan, where the Thar Desert of India is immersed, is mostly covered by sand dunes, a common landscape. The region has confronted with fragilities of natural resources, low, erratic and ill-distributed rainfall, and is covered up with many perennial hardy shrubs. Calligonum polygonoides, the most common perennial shrub, is widely present in some localities of this Thar Desert. In this study, we evaluated the diversity present among 54 wild Calligonum polygonoides plants, sampled from eight different locations within the Thar Desert. Our methods included chemical/nutritional characteristics and random amplified polymorphic DNA (RAPD. Both chemical and molecular methods produced wider range of diversity, however, RAPD detected comparatively more diversity. A total of 163 band positions were produced by ten RAPD primers, of which 147 were found polymorphic with 90.18% polymorphism. RAPD-based Jaccard’s similarity coefficients ranged from 0.43-0.89. The analysis of various chemical and mineral constituents revealed that phog is an excellent source of calcium, potassium and phosphorous while relatively poor in zinc. Among minerals, average potassium content was found maximum (2 430mg/100g with 0.14 CV. Zinc was observed comparably less in quantity while highest variable with CV 0.73. The chemical-based Manhattan dissimilarity coefficient values ranged from 0.01-0.22 with an average of 0.12. The comparison of the clusters obtained based on the chemical and mineral parameters with those of the RAPD data showed that the groups formed in both cases showed different patterns of relationships among the samples. Broader range of diversity might be due to the out breeding behavior of C. polygonoides and indicates the good adaptability of the plants in the region studied. However, low diversity observed in the Bikaner province is alarming and suggests that anthropogenic activities leading to heavy population disturbances can affect the

  12. Combining molecular-marker and chemical analysis of Capparis deciduas (Capparaceae in the Thar Desert of Western Rajasthan (India

    Directory of Open Access Journals (Sweden)

    Sushil Kumar

    2013-03-01

    Full Text Available The Thar Desert, a very inhospitable place, accommodates only plant species that survive acute drought, unpredictable precipitation, and those can grow in the limited moisture of sandy soils. Capparis decidua is among one of the few plants able to grow well under these conditions. This species is highly exploited and has been naturally taken, as local people use it for various purposes like food, timber and fuel, although, no management or conservation efforts have been established. The present study was conducted in this arid area of Western Rajasthan (India with the aim to obtain preliminary molecular information about this group of plants. We evaluated diversity among 46 samples of C. decidua using chemical parameters and random amplified polymorphic DNA (RAPD markers. Fourteen chemical parameters and eight minerals (total 22 variables of this species fruits were estimated. A total of 14 RAPD primers produced 235 band positions, of which 81.27% were polymorphic. Jaccard s similarity coefficients for RAPD primers ranged from 0.34 to 0.86 with a mean genetic similarity of 0.50. As per observed coefficient of variation, NDF (Neutral Detergent Fiber content was found to be the most variable trait followed by starch and soluble carbohydrate. The Manhattan dissimilarity coefficient values for chemical parameters ranged between 0.02-0.31 with an average of 0.092. The present study revealed a very low correlation (0.01 between chemical parameters and RAPD-based matrices. The low correlation between chemical- and RAPD-based matrices indicated that the two methods were different and highly variable. The chemical-based diversity will assist in selection of nutritionally rich samples for medicinal purpose, while genetic diversity to face natural challenges and find sustainable ways to promote conservation for future use.El desierto de Thar, un lugar muy inhóspito, alberga sólo a las especies de plantas capaces de resistir a condiciones de sequ

  13. Atmospheric aerosols size distribution properties in winter and pre-monsoon over western Indian Thar Desert location

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, Chhagan, E-mail: chhaganpanwar@gmail.com; Vyas, B. M. [Department of Physics, M.L. Sukhadia University, Udaipur-313001 (India)

    2016-05-06

    The first ever experimental results over Indian Thar Desert region concerning to height integrated aerosols size distribution function in particles size ranging between 0.09 to 2 µm such as, aerosols columnar size distribution (CSD), effective radius (R{sub eff}), integrated content of total aerosols (N{sub t}), columnar content of accumulation and coarse size aerosols particles concentration (N{sub a}) (size < 0.5 µm) and (N{sub c}) (size between 0.5 to 2 µm) have been described specifically during winter (a stable weather condition and intense anthropogenic pollution activity period) and pre-monsoon (intense dust storms of natural mineral aerosols as well as unstable atmospheric weather condition period) at Jaisalmer (26.90°N, 69.90°E, 220 m above surface level (asl)) located in central Thar desert vicinity of western Indian site. The CSD and various derived other aerosols size parameters are retrieved from their average spectral characteristics of Aerosol Optical Thickness (AOT) from UV to Infrared wavelength spectrum measured from Multi-Wavelength solar Radiometer (MWR). The natures of CSD are, in general, bio-modal character, instead of uniformly distributed character and power law distributions. The observed primary peaks in CSD plots are seen around about 10{sup 13} m{sup 2} μm{sup −1} at radius range 0.09-0.20 µm during both the seasons. But, in winter months, secondary peaks of relatively lower CSD values of 10{sup 10} to 10{sup 11} m{sup 2}/μm{sup −1} occur within a lower radius size range 0.4 to 0.6 µm. In contrast to this, while in dust dominated and hot season, the dominated secondary maxima of the higher CSD of about 10{sup 12} m{sup 2}μm{sup −3} is found of bigger aerosols size particles in a rage of 0.6 to 1.0 µm which is clearly demonstrating the characteristics of higher aerosols laden of bigger size aerosols in summer months relative to their prevailed lower aerosols loading of smaller size aerosols particles (0

  14. In vitro propagation of female Ephedra foliata Boiss. & Kotschy ex Boiss.: an endemic and threatened Gymnosperm of the Thar Desert.

    Science.gov (United States)

    Lodha, Deepika; Rathore, Nisha; Kataria, Vinod; Shekhawat, N S

    2014-07-01

    Ephedra foliata Boiss. & Kotschy ex Boiss., (family - Ephedraceae), is an ecologically and economically important threatened Gymnosperm of the Indian Thar Desert. A method for micropropagation of E. foliata using nodal explant of mature female plant has been developed. Maximum bud-break (90 %) of the explant was obtained on MS medium supplemented with 1.5 mg l(-1) of benzyl adenine (BA) + additives. Explant produces 5.3 ± 0.40 shoots from single node with 3.25 ± 0.29 cm length. The multiplication of shoots in culture was affected by salt composition of media, types and concentrations of plant growth regulators (PGR's) and their interactions, time of transfer of the cultures. Maximum number of shoots (26.3 ± 0.82 per culture vessel) were regenerated on MS medium modified by reducing the concentration of nitrates to half supplemented with 200 mg l(-1) ammonium sulphate {(NH4) 2SO4} (MMS3) + BA (0.25 mg l(-1)), Kinetin (Kin; 0.25 mg l(-1)), Indole-3-acetic acid (IAA; 0.1 mg l(-1)) and additives. The in vitro produced shoots rooted under ex vitro on soilrite moistened with one-fourth strength of MS macro salts in screw cap bottles by treating the shoot base (s) with 500 mg l(-1) of Indole-3-butyric acid (IBA) for 5 min. The micropropagated plants were hardened in the green house. The described protocol can be applicable for (i) large scale plant production (ii) establishment of plants in natural habitat and (iii) germplasm conservation of this endemic Gymnosperm of arid regions.

  15. Analysis of Seasonal and Annual Change of Vegetation in the Indian Thar Desert Using Modis Data

    Science.gov (United States)

    Santra, P.; Chkraborty, A.

    2011-09-01

    The western part of India, specifically the dry region, will play an important role in determining the Indian monsoon and even global climate patterns. Drastically change in land use pattern of the region has been observed during last few decades. In this paper, an effort was made to track the seasonal as well as annual changes of vegetation pattern in Jaisalmer district using MODIS normalized difference vegetation index (NDVI) products. Apart from this, ground data on vegetation were also collected under vegetation carbon pool assessment programme of ISRO-IGBP. It was found that during the hot summer month of May, the area under NDVI class 0-0.1 is reduced from 98% during 2003 to 95% during 2009 with a simultaneous increase in area under NDVI class 0.1-0.2 from 2 to 5%. During the month of September, area under NDVI class 0.2-0.3 increased from almost negligible during May to 34-39% during normal or surplus rainfall year but only to 3% during a deficit year. From the ground data on vegetation biomass, it was found that Prosopis juliflora and Acacia senegal are the most abundant trees in Jaisalmer region of the desert. The sites with NDVI value ≥ 0.2 were mostly found with Prosopis juliflora tree. Among shrubs, the most abundant species was Calotropis procera and Zizyphus numularia. From this study, it has been found that MODIS NDVI products may be used to quickly assess the vegetation changes in response to rainfall as well as due to anthroprogenic interventions in desert.

  16. Alluvial flash-flood stratigraphy of a large dryland river: the Luni River, Thar Desert, Western India

    Science.gov (United States)

    Carling, Paul; Leclair, Suzanne; Robinson, Ruth

    2017-04-01

    Detailed descriptions of the fluvial architecture of large dryland rivers are few, which hinders the understanding of stratigraphic development in aggradational settings. The aim of this study was to obtain new generic insight of the fluvial dynamics and resultant stratigraphy of such a river. The novelty of this investigation is that an unusually extensive and deep section across a major active dryland river was logged and the dated stratigraphy related to the behaviour of the discharge regimen. The results should help improve understanding of the stratigraphic development in modern dryland rivers and in characterizing oil, gas and groundwater reservoirs in the dryland geological record more generally. The Luni River is the largest river in the Thar desert, India, but yet details of the channel stratigraphy are sparse. Discharges can reach 14,000 m3s-1 but the bed is dry most of the year. GPS positioning and mm-resolution surveys within a 700m long, 5m deep trench enabled logging and photography of the strata associations, dated using optically-stimulated luminescence (OSL). The deposits consist of planar, sandy, upper-stage plane bed lamination and low-angle stratification, sandwiching less-frequent dune trough cross-sets. Mud clasts are abundant at any elevation. Water-ripple cross-sets or silt-clay layers occur rarely, usually near the top of sections. Aeolian dune cross-sets also appear sparsely at higher elevations. Consequently, the majority of preserved strata are due to supercritical flows. Localized deep scour causes massive collapse and soft-sediment deformation. Scour holes are infilled by rapidly-deposited massive sands adjacent to older bedded-deposits. Within bedform phase diagrams, estimated hydraulic parameters indicate a dominance of the upper-stage plane bed state, but the presence of dune cross-sets is also related to the flood hydrograph. Repeated deep scour results in units of deposition of different OSL ages (50 to 500 years BP) found at

  17. Study of atmospheric scattering and absorbing aerosols at 550 nm over nearby western Indian tropical sites of Thar Desert effected region

    Energy Technology Data Exchange (ETDEWEB)

    Vyas, B. M., E-mail: bmvyas@yahoo.com; Saxenna, Abhishek; Panwar, Chhagan [Department of Physics, M.L. Sukhadia University, Udaipur-313001 (India)

    2016-05-06

    The first time experimental results based on spaced satellite observations of different kinds of aerosols properties have been described over two different contrast environmental conditions locations in western tropical Indian region specifically first at Jaisalmer (26.90°N, 69.90°E, 220 m above mean sea level (amsl)) located in central Thar dessert vicinity of western Indian site over Indian Thar Desert region and another at Udaipur (24.6° N, 73.7° E, 560 m amsl) site concerning to semi-urban and semi arid place of hilly areas. The daily values of aerosols optical depth absorption at 500nm (AOD abs 500nm), aerosols optical depth extinction at 500nm (AOD ext 500nm) along with aerosols optical depth at 500nmon (AOD 500nm) of eleven year period from Jan., 2004 to Dec., 2014 are basis of primary database of the present investigation. From the synthesis if the above database and the basis of rigorous statistical approach, following some of interesting facts are noted (i) larger annual monthly AOD variation of 0.93 is noted over JSM when compared to observed annual monthly change in AOD cycle, over UDP, of only 0.50 clearly indicating the more impact of desert influence activities about more than double times over JSM than UDP (ii) The higher abundance of absorbing aerosols occurrences about two time higher are seen in JSM in comparison to UDP. It indicates the clear evidence of strong optical absorption properties of useful solar mid visible wavelength at 550nm as the results of presence of more availability of dust aerosols as mineral natural type in pre-monsoon to post-monsoon over JSM which is also more predominant over JSM than the UDP region located far away from desert activity regime (iii) The greater sharing of extinction solar radiation effect on aerosols are more effective in pre-monsoon in UDP in reference to over JSM, where as in case of UDP, the aerosols effect through the scattering mechanism gradually reduce from monsoon to winter months as compared

  18. Study of atmospheric scattering and absorbing aerosols at 550nm over nearby western Indian tropical sites of Thar Desert effected region

    Science.gov (United States)

    Vyas, B. M.; Saxenna, Abhishek; Panwar, Chhagan

    2016-05-01

    The first time experimental results based on spaced satellite observations of different kinds of aerosols properties have been described over two different contrast environmental conditions locations in western tropical Indian region specifically first at Jaisalmer (26.90°N, 69.90°E, 220 m above mean sea level (amsl)) located in central Thar dessert vicinity of western Indian site over Indian Thar Desert region and another at Udaipur (24.6° N, 73.7° E, 560 m amsl) site concerning to semi-urban and semi arid place of hilly areas. The daily values of aerosols optical depth absorption at 500nm (AOD abs 500nm), aerosols optical depth extinction at 500nm (AOD ext 500nm) along with aerosols optical depth at 500nmon (AOD 500nm) of eleven year period from Jan., 2004 to Dec., 2014 are basis of primary database of the present investigation. From the synthesis if the above database and the basis of rigorous statistical approach, following some of interesting facts are noted (i) larger annual monthly AOD variation of 0.93 is noted over JSM when compared to observed annual monthly change in AOD cycle, over UDP, of only 0.50 clearly indicating the more impact of desert influence activities about more than double times over JSM than UDP (ii) The higher abundance of absorbing aerosols occurrences about two time higher are seen in JSM in comparison to UDP. It indicates the clear evidence of strong optical absorption properties of useful solar mid visible wavelength at 550nm as the results of presence of more availability of dust aerosols as mineral natural type in pre-monsoon to post-monsoon over JSM which is also more predominant over JSM than the UDP region located far away from desert activity regime (iii) The greater sharing of extinction solar radiation effect on aerosols are more effective in pre-monsoon in UDP in reference to over JSM, where as in case of UDP, the aerosols effect through the scattering mechanism gradually reduce from monsoon to winter months as compared

  19. Climate variation in the Thar Desert since the Last Glacial Maximum and evaluation of the Indian Monsoon

    Directory of Open Access Journals (Sweden)

    Priyadarsi D. Roy

    2016-01-01

    Full Text Available El desierto de Thar está ubicado en la parte noroccidental de la India y es una región con escasez de lluvia (~500-100 mm/año. Los datos previamente publicados sobre la mineralogía, facies sedimentarias y cronología de radiocarbono han ayudado a reconstruir los cambios en el nivel lacustre y la salinidad de los cuerpos de agua en la escala orbital en cinco diferentes cuencas lacustres del desierto. Se evaluaron las condiciones hidrológicas en términos de la variación en la fuerza (cantidad y cobertura geográfica del monzón del suroeste desde el último máximo glacial (UMG. Entre el UMG y aproximadamente 15 ka cal AP, las cuencas de la parte oriental mantuvieron lagos salinos e hipersalinos y la parte occidental tuvo un lago intermitente. El cambio de una playa salina-hipersalina a un lago perenne con condiciones profundas ocurrió en la margen oriental alrededor de los 15 ka cal AP a medida que la insolación de verano aumentó tanto la temperatura superficial del mar (TSM del Océano Índico como la fuerza del monzón del suroeste. Durante la transición del Pleistoceno al Holoceno, la mayor insolación de verano y la alta TSM del Océano Índico aumentaron la cantidad de lluvia de verano y facilitaron la expansión del monzón a todo el desierto. Sin embargo, el predominio de las precipitaciones de invierno sobre las lluvias de verano durante el Holoceno temprano y medio mantuvieron lagos perennes a lo largo del desierto. Durante el Holoceno medio y tardío, las condiciones más secas en la región fueron contemporáneas a los intervalos de reducción en la insolación de verano, la ubicación de la Zona de Convergencia Intertropical en una latitud sureña y el aumento en la actividad de El Niño-Oscilación del Sur.

  20. Desert soil collection at the JPL soil science laboratory

    Science.gov (United States)

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

    1969-01-01

    Collection contains desert soils and other geologic materials collected from sites in the United States and foreign countries. Soils are useful for test purposes in research related to extraterrestrial life detection, sampling, harsh environmental studies, and determining suitable areas for training astronauts for lunar exploration.

  1. Climate and soil salinity in the deserts of Central Asia

    Science.gov (United States)

    Pankova, E. I.; Konyushkova, M. V.

    2013-07-01

    A comparative analysis of climatic and soil salinity characteristics of the deserts of Central Asia, including deserts of the Turan Depression, the Gobi Desert, and deserts of the Dzungar and Tarim depressions was performed. The climatic characteristics—the degree of aridity, the degree of continentality, and the amount and regime of precipitation—are different in these deserts. No direct relationships between the areas occupied by the automorphic salt-affected soils and the aridity of the climate are observed in the studied regions. In the automorphic landscapes of Asian deserts, the degree and chemistry of the soil salinization and the distribution of salt-affected soils are controlled by the history of the particular territories rather than by their modern climatic conditions. The presence and properties of the salt-bearing rocks and the eolian migration of salts play the most significant role. The deficit of moisture in the modern climate favors the preservation of salt accumulations in places of their origin. The specific features of the climate, including the regime of precipitation, affect the redistribution of salts in the profiles of automorphic salt-affected soils. An increase in the degree of climatic continentality is accompanied by the decrease in the intensity of weathering and initial accumulation of salts. A different situation is observed in the soils of hydromorphic desert landscapes, in which the degree of salinity of the surface horizons and the area occupied by salt-affected soils are directly influenced by the modern climatic conditions.

  2. Recovery of compacted soils in Mojave Desert ghost towns.

    Science.gov (United States)

    Webb, R.H.; Steiger, J.W.; Wilshire, H.G.

    1986-01-01

    Residual compaction of soils was measured at seven sites in five Mojave Desert ghost towns. Soils in these Death Valley National Monument townsites were compacted by vehicles, animals, and human trampling, and the townsites had been completely abandoned and the buildings removed for 64 to 75 yr. Recovery times extrapolated using a linear recovery model ranged from 80 to 140 yr and averaged 100 yr. The recovery times were related to elevation, suggesting freeze-thaw loosening as an important factor in ameliorating soil compaction in the Mojave Desert. -from Authors

  3. Biological soil crusts as an integral component of desert environments

    Science.gov (United States)

    Belnap, Jayne; Weber, Bettina

    2013-01-01

    The biology and ecology of biological soil crusts, a soil surface community of mosses, lichens, cyanobacteria, green algae, fungi, and bacteria, have only recently been a topic of research. Most efforts began in the western U.S. (Cameron, Harper, Rushforth, and St. Clair), Australia (Rogers), and Israel (Friedmann, Evenari, and Lange) in the late 1960s and 1970s (e.g., Friedmann et al. 1967; Evenari 1985reviewed in Harper and Marble 1988). However, these groups worked independently of each other and, in fact, were often not aware of each other’s work. In addition, biological soil crust communities were seen as more a novelty than a critical component of dryland ecosystems. Since then, researchers have investigated many different aspects of these communities and have shown that although small to microscopic, biological soil crusts are critical in many ecological processes of deserts. They often cover most of desert soil surfaces and substantially mediate inputs and outputs from desert soils (Belnap et al. 2003). They can be a large source of biodiversity for deserts, as they can contain more species than the surrounding vascular plant community (Rosentreter 1986). These communities are important in reducing soil erosion and increasing soil fertility through the capture of dust and the fixation of atmospheric nitrogen and carbon into forms available to other life forms (Elbert et al. 2012). Because of their many effects on soil characteristics, such as external and internal morphological characteristics, aggregate stability, soil moisture, and permeability, they also affect seed germination and establishment and local hydrological cycles. Covering up to 70% of the surface area in many arid and semi-arid regions around the world (Belnap and Lange 2003), biological soil crusts are a key component within desert environments.

  4. Abiotic regulators of soil respiration in desert ecosystems

    Science.gov (United States)

    Zhang, Lihua; Chen, Yaning; Li, Weihong; Zhao, Ruifeng

    2009-06-01

    Soil temperature and soil moisture are the most important environmental factors controlling soil respiration in mesic ecosystems. However, soil respiration and associated abiotic regulators have been poorly studied in desert ecosystems. In this study, soil respiration was measured using an automated CO2 efflux system (LI-COR 8100), and the effects of soil temperature and moisture on the rate of soil respiration were examined in six desert sites [three communities— Haloxylon ammodendron, Halostachys caspica and Anabasis aphylla at high (B) and low (A) vegetation coverage respectively]. It was found that soil respiration was significantly and positively correlated with soil surface temperature. A multi-variable model of soil temperature and soil moisture could explain 61.9% of temporal variation in soil CO2 efflux at a larger scale. There were significantly negative correlations between soil respiration and soil moisture in Haloxylon ammodendron B and Halostachys caspica B sites, which represented the driest and wettest sites, respectively. The results also showed that soil respiration displayed obvious diurnal and seasonal patterns during the growing season. The Q10 values for Haloxylon ammodendron A and B, Halostachys caspica A and B, and Anabasis aphylla A and B sites were 1.3, 1.34, 1.58, 1.65, 1.31 and 1.17, respectively, with a cross-site average of 1.39. The results showed that soil respiration was not positively correlated with soil moisture unlike in most mesic ecosystems. However, soil respiration in desert ecosystems is less sensitive to temperature variation than most mesic ecosystems as indicated by the lower Q10 values possibly due to energy limitation.

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

    Science.gov (United States)

    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. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

  6. Quaternary alluvial stratigraphy and palaeoclimatic reconstruction at the Thar margin

    DEFF Research Database (Denmark)

    Jain, M.; Tandon, S.K.

    2003-01-01

    /chlorite and smectite/illite of the alluvial palaeosols have been used as proxy indicators of climate change. These indicate wet phases during the OIS 5 and OIS 1. The overall stratigraphic development is discussed in the framework of fluvial response to climate change during the Late Pleistocene.......Quaternary alluvial record at the Thar desert margin has been examined using the exposed succession along Mahudi, Sabarmati river, Western India. Different alluvial facies, their associations and granulometry have been studied for palaeoenvironmental reconstruction. Clay mineral indices smectite...

  7. Browning in desert boundaries in Asia in recent decades

    Science.gov (United States)

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

    2011-01-01

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

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

    Science.gov (United States)

    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.

  9. Characteristics of Soil Environment Variation in Oasis–Desert Ecotone in the Process of Oasis Growth

    OpenAIRE

    Li, Haifeng; Zeng, Fanjiang; Gui, Dongwei; Lei, Jiaqiang

    2010-01-01

    International audience; Cele Oasis on the southern edge of Tarim Basin was used to investigate the impact of human activity on the soil environment of the oasis– desert ecotone during the oasis expansion process. Since farmland is extending into the oasis–desert ecotone during oasis expansion, reclaimed farmland and control plots within the ecotone were investigated. The variations in soil moisture, soil nutrients and soil particle-size distribution of the two plots to a depth range of 0–100 ...

  10. Diversity of bacterial communities along a petroleum contamination gradient in desert soils.

    Science.gov (United States)

    Abed, Raeid M M; Al-Kindi, Sumaiya; Al-Kharusi, Samiha

    2015-01-01

    Microbial communities in oil-polluted desert soils have been rarely studied compared to their counterparts from freshwater and marine environments. We investigated bacterial diversity and changes therein in five desert soils exposed to different levels of oil pollution. Automated rRNA intergenic spacer (ARISA) analysis profiles showed that the bacterial communities of the five soils were profoundly different (analysis of similarities (ANOSIM), R = 0.45, P desert soils are rich in aerobic and anaerobic bacteria that could potentially contribute to the degradation of hydrocarbons.

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

    Science.gov (United States)

    Zhang, Yuanming; Belnap, Jayne

    2015-01-01

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

  12. Remontant erosion in desert soils of Tamaulipas, México.

    Science.gov (United States)

    Rivera-Ortiz, P.; Andrade-Limas, E.; De la Garza-Requena, F.; Castro-Meza, B.

    2012-04-01

    REMONTANT EROSION IN DESERT SOILS OF TAMAULIPAS MÉXICO Rivera-Ortiz, P.1; Andrade-Limas, E.1; De la Garza-Requena, F.1 and Castro-Meza, B.1 1Facultad de Ingeniería y Ciencias, Universidad Autónoma de Tamaulipas, México The degradation of soil reduces the capacity of soils to produce food and sustain life. Erosion is one of the main types of soil degradation. Hydric erosion of remontant type can occur in soils located close to the channel of a river through the expansion of a gully that begins as a fluvial incision over the ravine of one side of the river. The incision takes place at the point of greatest flow of runoff from areas adjacent to empty into the river. The depth of the incision causes the growth of the gully by collapse to move their heads back, upstream. The soil loss by remontant erosion on land use in agriculture and livestock was estimated in order to understand the evolution of gullies formed by this type of erosion. Through measurements on satellite images and GPS (Global Positioning System) two gullies, developed on alluvial soils which drain into the river Chihue, were studied. The investigation was conducted during 2003 to 2010 period in the municipality of Jaumave, Tamaulipas, in northeastern Mexico. Soil loss in gullies developed by remontant erosion was large and it was caused by soil collapse and drag of soil on the headers. The estimated loss of soil by remontant erosion was 3500 t in the deeper gully during 2010 and nearly 1200 t per year in the period 2003-2009. New sections of gully of about 20 m length, with more than 3 m deep and up to 13 m wide, were formed each year. This degradation has significantly reduced the productive surface of soil that for many years has been used to the cultivation of maize (Zea mays) and beans (Phaseolus vulgaris) as well as pasture production.

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

    Directory of Open Access Journals (Sweden)

    Martina Köberl

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

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

    Science.gov (United States)

    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.

  15. Influence of shrubs on soil chemical properties in Alxa desert steppe, China

    Science.gov (United States)

    Hua Fu; Shifang Pei; Yaming Chen; Changgui Wan

    2007-01-01

    Alxa desert steppe is one of severely the degraded rangelands in the Northwest China. Shrubs, as the dominant life form in the desert steppe, play an important role in protecting this region from further desertification. Chemical properties of three soil layers (0 to 10, 10 to 20 and 20 to 30 cm) at three locations (the clump center [A], in the periphery of shrub...

  16. Soil CO2 Uptake in Deserts and Its Implications to the Groundwater Environment

    Directory of Open Access Journals (Sweden)

    Wenfeng Wang

    2016-09-01

    Full Text Available Recent studies of soil carbon cycle in arid and semi-arid ecosystems demonstrated that there exists an abiotic CO2 absorption by saline-alkali soils (Aa at desert ecosystems and suggested potential contributions of CO2 dissolution beneath deserts to the terrestrial ecosystems carbon balance. However, the overall importance of such soil CO2 uptake is still undetermined and its implications to the groundwater environment remain unaddressed. In this manuscript, a simple method is proposed for the direct computation of Aa from the total soil CO2 flux (Fa as well as for the evaluation of Aa importance to Fa. An artificial soil-groundwater system was employed to investigate the implications to groundwater environment and it was found that soil CO2 uptake in deserts can contribute a possible influence on the evolution of the groundwater environment, providing that the absorbed CO2 largely remained in the soil-groundwater system.

  17. Interactions between soil phototrophs and vascular plants in Himalayan cold deserts

    Czech Academy of Sciences Publication Activity Database

    Řeháková, Klára; Čapková, Kateřina; Dvorský, M.; Kopecký, M.; Altman, J.; Šmilauer, P.; Doležal, J.

    2017-01-01

    Roč. 115, Dec (2017), s. 568-578 ISSN 0038-0717 Institutional support: RVO:60077344 Keywords : cold desert * Himalaya * interactions * soil phototrophs Subject RIV: EH - Ecology, Behaviour Impact factor: 4.857, year: 2016

  18. Role of biological soil crusts in desert hydrology and geomorphology: Implications for military training operations

    Science.gov (United States)

    Steven D. Warren

    2014-01-01

    Biological soil crusts, composed of soil surfaces stabilized by a consortium of cyanobacteria, algae, fungi, lichens, and/or bryophytes, are common in most deserts and perform functions of primary productivity, nitrogen fixation, nutrient cycling, water redistribution, and soil stabilization. The crusts are highly susceptible to disturbance. The degree of perturbation...

  19. Soil fertility in deserts: a review on the influence of biological soil crusts and the effect of soil surface disturbance on nutrient inputs and losses

    Science.gov (United States)

    Reynolds, R.; Phillips, S.; Duniway, M.; Belnap, J.

    2003-01-01

    Sources of desert soil fertility include parent material weathering, aeolian deposition, and on-site C and N biotic fixation. While parent materials provide many soil nutrients, aeolian deposition can provide up to 75% of plant-essential nutrients including N, P, K, Mg, Na, Mn, Cu, and Fe. Soil surface biota are often sticky, and help retain wind-deposited nutrients, as well as providing much of the N inputs. Carbon inputs are from both plants and soil surface biota. Most desert soils are protected by cyanobacterial-lichen-moss soil crusts, chemical crusts and/or desert pavement. Experimental disturbances applied in US deserts show disruption of soil surfaces result in decreased N and C inputs from soil biota by up to 100%. The ability to glue aeolian deposits in place is compromised, and underlying soils are exposed to erosion. The ability to withstand wind increases with biological and physical soil crust development. While most undisturbed sites show little sediment production, disturbance by vehicles or livestock produce up to 36 times more sediment production, with soil movement initiated at wind velocities well below commonly-occurring wind speeds. Soil fines and flora are often concentrated in the top 3 mm of the soil surface. Winds across disturbed areas can quickly remove this material from the soil surface, thereby potentially removing much of current and future soil fertility. Thus, disturbances of desert soil surfaces can both reduce fertility inputs and accelerate fertility losses.

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

    National Research Council Canada - National Science Library

    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...

  1. Namib Desert Soil Microbial Community Diversity, Assembly, and Function Along a Natural Xeric Gradient.

    Science.gov (United States)

    Scola, Vincent; Ramond, Jean-Baptiste; Frossard, Aline; Zablocki, Olivier; Adriaenssens, Evelien M; Johnson, Riegardt M; Seely, Mary; Cowan, Don A

    2018-01-01

    The hyperarid Namib desert is a coastal desert in southwestern Africa and one of the oldest and driest deserts on the planet. It is characterized by a west/east increasing precipitation gradient and by regular coastal fog events (extending up to 75 km inland) that can also provide soil moisture. In this study, we evaluated the role of this natural aridity and xeric gradient on edaphic microbial community structure and function in the Namib desert. A total of 80 individual soil samples were collected at 10-km intervals along a 190-km transect from the fog-dominated western coastal region to the eastern desert boundary. Seventeen physicochemical parameters were measured for each soil sample. Soil parameters reflected the three a priori defined climatic/xeric zones along the transect ("fog," "low rain," and "high rain"). Microbial community structures were characterized by terminal restriction fragment length polymorphism fingerprinting and shotgun metaviromics, and their functional capacities were determined by extracellular enzyme activity assays. Both microbial community structures and activities differed significantly between the three xeric zones. The deep sequencing of surface soil metavirome libraries also showed shifts in viral composition along the xeric transect. While bacterial community assembly was influenced by soil chemistry and stochasticity along the transect, variations in community "function" were apparently tuned by xeric stress.

  2. Environmental conditions and soils of natural oases in the Alashan Gobi Desert, Mongolia

    Science.gov (United States)

    Pankova, E. I.

    2008-08-01

    Environmental conditions and soils of nine natural oases in the Alashan Gobi Desert of Mongolia are characterized. All these oases are allocated to the zones of tectonic faults, where the discharge of slightly saline groundwater takes place. The absolute heights are about 1500 m a.s.l. The oases are found on piedmont plains or in hilly areas occupied by true deserts with fragments of extremely arid deserts. With respect to geomorphological conditions, four types of oases can be distinguished: isolated (isle-type) oases, oases in large mesodepressions, oases formed in naturally ponded areas, and oases within terraced valleys. Each of these types is characterized by specific soil cover patterns controlled by the geomorphological features of the territory, the character of parent materials, and the groundwater depth. At the same time, some common soil properties are typical of all the oases. Hydromorphic soils—peat meadow-swampy soils, dark-colored nonsaline meadow soils, oasis solonchaks that developed in areas with shallow nonsaline groundwater, solonchaks with different degrees of hydromorphism that developed from mottled-colored salt-bearing Cretaceous and Paleogene deposits, and soddy alluvial (floodplain) soils—predominate in the central parts of the oases. Under conditions of deep groundwater, takyric and sandy desert soils are formed. The oases are encircled by desert ecosystems with gray-brown desert and extremely arid soils and with poorly developed stony soils that formed on the low residual mounts. In the period of the study (1991), irrigated farming was only developed within one of the studied oases. The main part of the land was used for pasturing. In some cases, the high grazing pressure led to degradation (desertification) of oasis ecosystems. A comparison of the oases studied in the Alashan Gobi with the Ekhiin-Gol oasis in the Transaltai Gobi attests to the similarity of their nature.

  3. Hydrogeological Issues Concerning the Thar Lignite Prospect

    Directory of Open Access Journals (Sweden)

    R. N. Singh

    2012-12-01

    Full Text Available The paper is concerned with the hydrogeological appraisal of the proposed mining operations in theThar lignite field in Sindh, Pakistan. The Thar coalfield covers an area of approximately 9000km2 andcontains three lignite seams lying at depth of 130m to 250 m. In the Thar lignite field, the presence ofthree main aquifers induces pore pressure in the rock mass surrounding the lignite seams and makes highwall slopes potentially unsafe. It is, therefore, necessary to dewater the rock mass before commencingmining excavations. The paper describes the proposed mine dewatering scheme to facilitatedepressurising of the rock mass surrounding the mining excavations. Inflow prediction of groundwater tothe surface mining excavation was carried out using a SEEP/W finite element software package. Thesimulation results show that the ground water inflow from the Top aquifer is 114m3/d, from theIntermediate confined aquifer is 141m3/d and from the Bottom confined aquifer is 1.28 x 105 m3 /d. Theseresults were compared with the analytical solutions which indicated that the relative error of estimation ofinflow quantities varies from 3.4 % to 6.4%.

  4. Microbial community response to hydration-desiccation cycles in desert soil.

    Science.gov (United States)

    Šťovíček, Adam; Kim, Minsu; Or, Dani; Gillor, Osnat

    2017-04-06

    Life in desert soil is marked by episodic pulses of water and nutrients followed by long periods of drought. While the desert flora and fauna flourish after rainfall the response of soil microorganisms remains unclear and understudied. We provide the first systematic study of the role of soil aqueous habitat dynamics in shaping microbial community composition and diversity. Detailed monitoring of natural microbial communities after a rainfall event revealed a remarkable decrease in diversity and a significant transition in community composition that were gradually restored to pre-rainfall values during soil desiccation. Modelling results suggest a critical role for the fragmented aqueous habitat in maintaining microbial diversity under dry soil conditions and diversity loss with wetting events that increase connectivity among habitats. This interdisciplinary study provides new insights into wetting and drying processes that promote and restore the unparalleled microbial diversity found in soil.

  5. Disturbance to desert soil ecosystems contributes to dust-mediated impacts at regional scales

    Science.gov (United States)

    Pointing, Stephen B.; Belnap, Jayne

    2014-01-01

    This review considers the regional scale of impacts arising from disturbance to desert soil ecosystems. Deserts occupy over one-third of the Earth’s terrestrial surface, and biological soil covers are critical to stabilization of desert soils. Disturbance to these can contribute to massive destabilization and mobilization of dust. This results in dust storms that are transported across inter-continental distances where they have profound negative impacts. Dust deposition at high altitudes causes radiative forcing of snowpack that leads directly to altered hydrological regimes and changes to freshwater biogeochemistry. In marine environments dust deposition impacts phytoplankton diazotrophy, and causes coral reef senescence. Increasingly dust is also recognized as a threat to human health.

  6. Seasonal and soil-type dependent emissions of nitrous oxide from irrigated desert soils amended with digested poultry manures.

    Science.gov (United States)

    Posmanik, Roy; Nejidat, Ali; Dahan, Ofer; Gross, Amit

    2017-09-01

    Expansion of dryland agriculture requires intensive supplement of organic fertilizers to improve the fertility of nutrient-poor desert soils. The environmental impact of organic supplements in hot desert climates is not well understood. We report on seasonal emissions of nitrous oxide (N2O) from sand and loess soils, amended with limed and non-limed anaerobic digestate of poultry manure in the Israeli Negev desert. All amended soils had substantially higher N2O emissions, particularly during winter applications, compared to unammended soils. Winter emissions from amended loess (10-175mgN2Om(-2)day(-1)) were markedly higher than winter emissions from amended sand (2-7mgN2Om(-2)day(-1)). Enumeration of marker genes for nitrification and denitrification suggested that both have contributed to N2O emissions according to prevailing environmental conditions. Lime treatment of digested manure inhibited N2O emissions regardless of season or soil type, thus reducing the environmental impact of amending desert soils with manure digestate. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Carbon and nitrogen contents in Desert Plants and Soil in the Yanqi basin of Northwestern China

    Science.gov (United States)

    Zhang, J.; Wang, X.; Wang, J.

    2011-12-01

    Carbon and nitrogen are two main elements in plant-soil systems. Here, we present a study of carbon and nitrogen contents in several typical desert plants and underlying soil, which was conducted in Yanqi basin, Xinjiang province of China. Our results show that carbon (C) content is around 30% in both aboveground tissues and belowground roots. Nitrogen (N) content in desert plants has a range of 0.5%-3.5%, and the aboveground tissue has higher nitrogen content (~2%) than the belowground root (~1%). As a result, the belowground root has higher C/N ratio (~35) than the aboveground tissue (~25). Especially, the C/N values in belowground roots are twice as much as their aboveground tissues in Acroption repens, Tamarix ramosissima Ledeb. and Halostachys caspica. In desert soils, the contents of soil organic carbon (SOC), total nitrogen (TN) with depth 0-50cm are range of 12.5-4.6 and 3.2-1.4 g/kg, respectively, different . As expected, the SOC and TN contents are declined with the depth increase. Meanwhile, our result indicated the soil TN is followed the SOC dynamic, as both elements are bond into the organic compounds. However, unlike the C/N ratios in aboveground tissue and roots, there is no significant difference of C/N ratios (2.95-3.46) in the soils within the 0-50 cm depth. The results inferred that in the desert plant C mainly storage in roots, but the C, N allocation between desert plant and soil has no significantly related.

  8. Impacts of tracked vehicles on sediment from a desert soil

    Science.gov (United States)

    Erek H. Fuchs; Karl M. Wood; Tim L. Jones; Brent Racher

    2003-01-01

    Off-road military vehicle traffic is a major consideration in the management of military lands. The objective of this study was to determine the impacts of military tracked M1A1 heavy combat tank vehicles on sediment loss from runoff, surface plant cover, and surface microtopography in a desert military training environment. A randomized block design was used which had...

  9. Diversity and feeding strategies of soil microfauna along elevation gradients in Himalayan cold deserts

    Czech Academy of Sciences Publication Activity Database

    Devetter, Miloslav; Háněl, Ladislav; Řeháková, Klára; Doležal, J.

    2017-01-01

    Roč. 12, č. 11 (2017), č. článku e0187646. E-ISSN 1932-6203 R&D Projects: GA MŠk(CZ) LTC17019 Institutional support: RVO:60077344 Keywords : diversity * feeding strategies * soil microfauna * Himalayan cold deserts Subject RIV: EH - Ecology, Behaviour OBOR OECD: Ecology Impact factor: 2.806, year: 2016

  10. The Impact of Rainfall on Soil Moisture Dynamics in a Foggy Desert.

    Science.gov (United States)

    Li, Bonan; Wang, Lixin; Kaseke, Kudzai F; Li, Lin; Seely, Mary K

    2016-01-01

    Soil moisture is a key variable in dryland ecosystems since it determines the occurrence and duration of vegetation water stress and affects the development of weather patterns including rainfall. However, the lack of ground observations of soil moisture and rainfall dynamics in many drylands has long been a major obstacle in understanding ecohydrological processes in these ecosystems. It is also uncertain to what extent rainfall controls soil moisture dynamics in fog dominated dryland systems. To this end, in this study, twelve to nineteen months' continuous daily records of rainfall and soil moisture (from January 2014 to August 2015) obtained from three sites (one sand dune site and two gravel plain sites) in the Namib Desert are reported. A process-based model simulating the stochastic soil moisture dynamics in water-limited systems was used to study the relationships between soil moisture and rainfall dynamics. Model sensitivity in response to different soil and vegetation parameters under diverse soil textures was also investigated. Our field observations showed that surface soil moisture dynamics generally follow rainfall patterns at the two gravel plain sites, whereas soil moisture dynamics in the sand dune site did not show a significant relationship with rainfall pattern. The modeling results suggested that most of the soil moisture dynamics can be simulated except the daily fluctuations, which may require a modification of the model structure to include non-rainfall components. Sensitivity analyses suggested that soil hygroscopic point (sh) and field capacity (sfc) were two main parameters controlling soil moisture output, though permanent wilting point (sw) was also very sensitive under the parameter setting of sand dune (Gobabeb) and gravel plain (Kleinberg). Overall, the modeling results were not sensitive to the parameters in non-bounded group (e.g., soil hydraulic conductivity (Ks) and soil porosity (n)). Field observations, stochastic modeling

  11. Soil microbial responses to temporal variations of moisture and temperature in a chihuahuan desert grassland.

    Science.gov (United States)

    Bell, Colin; McIntyre, Nancy; Cox, Stephen; Tissue, David; Zak, John

    2008-07-01

    Global climate change models indicate that storm magnitudes will increase in many areas throughout southwest North America, which could result in up to a 25% increase in seasonal precipitation in the Big Bend region of the Chihuahuan Desert over the next 50 years. Seasonal precipitation is a key limiting factor regulating primary productivity, soil microbial activity, and ecosystem dynamics in arid and semiarid regions. As decomposers, soil microbial communities mediate critical ecosystem processes that ultimately affect the success of all trophic levels, and the activity of these microbial communities is primarily regulated by moisture availability. This research is focused on elucidating soil microbial responses to seasonal and yearly changes in soil moisture, temperature, and selected soil nutrient and edaphic properties in a Sotol Grassland in the Chihuahuan Desert at Big Bend National Park. Soil samples were collected over a 3-year period in March and September (2004-2006) at 0-15 cm soil depth from 12 3 x 3 m community plots. Bacterial and fungal carbon usage (quantified using Biolog 96-well micro-plates) was related to soil moisture patterns (ranging between 3.0 and 14%). In addition to soil moisture, the seasonal and yearly variability of soil bacterial activity was most closely associated with levels of soil organic matter, extractable NH(4)-N, and soil pH. Variability in fungal activity was related to soil temperatures ranging between 13 and 26 degrees C. These findings indicate that changes in soil moisture, coupled with soil temperatures and resource availability, drive the functioning of soil-microbial dynamics in these desert grasslands. Temporal patterns in microbial activity may reflect the differences in the ability of bacteria and fungi to respond to seasonal patterns of moisture and temperature. Bacteria were more able to respond to moisture pulses regardless of temperature, while fungi only responded to moisture pulses during cooler seasons with

  12. The aeolian sedimentation record of the Thar desert

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    presented an interesting paradigm of periodic spa- tial shifts in dune forming climates. A similar dune shift of 1000km in Sahara and 300km in Arabia have been ..... urban settlements flourished due to the availability of water (e.g., at Kalibangan). The dune records suggest that the civilization flourished during a phase of ...

  13. Calcretes in the Thar desert: Genesis, chronology and ...

    Indian Academy of Sciences (India)

    . The better-developed calcrete horizons occur in pied- monts, interdunes or in areas that have sufficient groundwater. Deep sections in the region show phases of calcrete development in aeolian sand aggradation at ∼150, ∼100, ∼60 and ...

  14. The aeolian sedimentation record of the Thar desert

    Indian Academy of Sciences (India)

    Luminescence dating of sand has enabled quantification of the duration of the phases of sand aggradation and quiescence, time scales of dune migration and the dating of pedogenic carbonates. We demonstrate that the conventional wisdom of synchronicity of dune aggradation with glacial epoch is not true in the context ...

  15. Soil microbial community response to drought and precipitation variability in the Chihuahuan Desert.

    Science.gov (United States)

    Clark, Jeb S; Campbell, James H; Grizzle, Heath; Acosta-Martìnez, Veronica; Zak, John C

    2009-02-01

    Increases in the magnitude and variability of precipitation events have been predicted for the Chihuahuan Desert region of West Texas. As patterns of moisture inputs and amounts change, soil microbial communities will respond to these alterations in soil moisture windows. In this study, we examined the soil microbial community structure within three vegetation zones along the Pine Canyon Watershed, an elevation and vegetation gradient in Big Bend National Park, Chihuahuan Desert. Soil samples at each site were obtained in mid-winter (January) and in mid-summer (August) for 2 years to capture a component of the variability in soil temperature and moisture that can occur seasonally and between years along this watershed. Precipitation patterns and amounts differed substantially between years with a drought characterizing most of the second year. Soils were collected during the drought period and following a large rainfall event and compared to soil samples collected during a relatively average season. Structural changes within microbial community in response to site, season, and precipitation patterns were evaluated using fatty acid methyl ester (FAME) and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analyses. Fungal FAME amounts differed significantly across seasons and sites and greatly outweighed the quantity of bacterial and actinomycete FAME levels for all sites and seasons. The highest fungal FAME levels were obtained in the low desert scrub site and not from the high elevation oak-pine forests. Total bacterial and actinomycete FAME levels did not differ significantly across season and year within any of the three locations along the watershed. Total bacterial and actinomycete FAME levels in the low elevation desert-shrub and grassland sites were slightly higher in the winter than in the summer. Microbial community structure at the high elevation oak-pine forest site was strongly correlated with levels of NH4+-N, % soil moisture

  16. Soil microbial diversity, site conditions, shelter forest land, saline water drip-irrigation, drift desert.

    Science.gov (United States)

    Jin, Zhengzhong; Lei, Jiaqiang; Li, Shengyu; Xu, Xinwen

    2013-10-01

    Soil microbes in forest land are crucial to soil development in extreme areas. In this study, methods of conventional culture, PLFA and PCR-DGGE were utilized to analyze soil microbial quantity, fatty acids and microbial DNA segments of soils subjected to different site conditions in the Tarim Desert Highway forest land. The main results were as follows: the soil microbial amount, diversity indexes of fatty acid and DNA segment differed significantly among sites with different conditions (F soil microbial community (>84%), followed by actinomycetes and then fungi (soil microbial diversity were insignificant at 0-35 cm. Correlation analysis indicated that the forest trees grew better as the soil microbial diversity index increased. Therefore, construction of the Tarim Desert Highway shelter-forest promoted soil biological development; however, for enhancing sand control efficiency and promoting sand development, we should consider the effects of site condition in the construction and regeneration of shelter-forest ecological projects. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. The influence of surface soil physicochemistry on the edaphic bacterial communities in contrasting terrain types of the Central Namib Desert.

    Science.gov (United States)

    Gombeer, S; Ramond, J-B; Eckardt, F D; Seely, M; Cowan, D A

    2015-09-01

    Notwithstanding, the severe environmental conditions, deserts harbour a high diversity of adapted micro-organisms. In such oligotrophic environments, soil physicochemical characteristics play an important role in shaping indigenous microbial communities. This study investigates the edaphic bacterial communities of three contrasting desert terrain types (gravel plains, sand dunes and ephemeral rivers) with different surface geologies in the Central Namib Desert. For each site, we evaluated surface soil physicochemistries and used explorative T-RFLP methodology to get an indication of bacterial community diversities. While grain size was an important parameter in separating the three terrain types physicochemically and specific surface soil types could be distinguished, the desert edaphic bacterial communities displayed a high level of local spatial heterogeneity. Ten variables contributed significantly (P Desert and stress the importance of recording a wide variety of environmental descriptors to comprehensively assess the role of edaphic parameters in shaping microbial communities. © 2015 John Wiley & Sons Ltd.

  18. Desert grassland responses to climate and soil moisture suggest divergent vulnerabilities across the southwestern United States.

    Science.gov (United States)

    Gremer, Jennifer R; Bradford, John B; Munson, Seth M; Duniway, Michael C

    2015-11-01

    Climate change predictions include warming and drying trends, which are expected to be particularly pronounced in the southwestern United States. In this region, grassland dynamics are tightly linked to available moisture, yet it has proven difficult to resolve what aspects of climate drive vegetation change. In part, this is because it is unclear how heterogeneity in soils affects plant responses to climate. Here, we combine climate and soil properties with a mechanistic soil water model to explain temporal fluctuations in perennial grass cover, quantify where and the degree to which incorporating soil water dynamics enhances our ability to understand temporal patterns, and explore the potential consequences of climate change by assessing future trajectories of important climate and soil water variables. Our analyses focused on long-term (20-56 years) perennial grass dynamics across the Colorado Plateau, Sonoran, and Chihuahuan Desert regions. Our results suggest that climate variability has negative effects on grass cover, and that precipitation subsidies that extend growing seasons are beneficial. Soil water metrics, including the number of dry days and availability of water from deeper (>30 cm) soil layers, explained additional grass cover variability. While individual climate variables were ranked as more important in explaining grass cover, collectively soil water accounted for 40-60% of the total explained variance. Soil water conditions were more useful for understanding the responses of C3 than C4 grass species. Projections of water balance variables under climate change indicate that conditions that currently support perennial grasses will be less common in the future, and these altered conditions will be more pronounced in the Chihuahuan Desert and Colorado Plateau. We conclude that incorporating multiple aspects of climate and accounting for soil variability can improve our ability to understand patterns, identify areas of vulnerability, and predict

  19. Desert grassland responses to climate and soil moisture suggest divergent vulnerabilities across the southwestern US

    Science.gov (United States)

    Gremer, Jennifer; Bradford, John B.; Munson, Seth M.; Duniway, Michael C.

    2015-01-01

    Climate change predictions include warming and drying trends, which are expected to be particularly pronounced in the southwestern United States. In this region, grassland dynamics are tightly linked to available moisture, yet it has proven difficult to resolve what aspects of climate drive vegetation change. In part, this is because it is unclear how heterogeneity in soils affects plant responses to climate. Here, we combine climate and soil properties with a mechanistic soil water model to explain temporal fluctuations in perennial grass cover, quantify where and the degree to which incorporating soil water dynamics enhances our ability to understand temporal patterns, and explore the potential consequences of climate change by assessing future trajectories of important climate and soil water variables. Our analyses focused on long-term (20 to 56 years) perennial grass dynamics across the Colorado Plateau, Sonoran, and Chihuahuan Desert regions. Our results suggest that climate variability has negative effects on grass cover, and that precipitation subsidies that extend growing seasons are beneficial. Soil water metrics, including the number of dry days and availability of water from deeper (>30 cm) soil layers, explained additional grass cover variability. While individual climate variables were ranked as more important in explaining grass cover, collectively soil water accounted for 40 to 60% of the total explained variance. Soil water conditions were more useful for understanding the responses of C3 than C4 grass species. Projections of water balance variables under climate change indicate that conditions that currently support perennial grasses will be less common in the future, and these altered conditions will be more pronounced in the Chihuahuan Desert and Colorado Plateau. We conclude that incorporating multiple aspects of climate and accounting for soil variability can improve our ability to understand patterns, identify areas of vulnerability, and

  20. Trace elements assessment in agricultural and desert soils of Aswan area, south Egypt: Geochemical characteristics and environmental impacts

    Science.gov (United States)

    Darwish, Mohamed Abdallah Gad; Pöllmann, Hebert

    2015-12-01

    Determination of chemical elements, Al, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, P, Pb, Sc, Sr, Ti, Y, and Zn have been performed in agricultural and desert soils and alfalfa (Medicago sativa) at Aswan area. Consequently, the pollution indices, univariate and multivariate statistical methods have been applied, in order to assess the geochemical characteristics of these elements and their impact on soil environmental quality and plant, and to reach for their potential input sources. The investigation revealed that the mean and range values of all element concentrations in agricultural soil are higher than those in desert soil. Furthermore, the agricultural soil displayed various degrees of enrichment and pollution of Cd, Zn, Mo, Co, P, Ti, Pb. The geochemical pattern of integrated pollution indices gave a clear image of extreme and strong pollution in the agricultural soil stations, their poor quality with high risk to human health and considered as a tocsin for an alert. In contrast, the desert soil is the good environmental quality and safe for plant, animal and human health. Alfalfa is tolerant plant and considered as a biomarker for P and Mo in polluted agricultural soil. Four geochemical associations of analyzing elements in agricultural soil and three ones in desert soil have been generated, and their enhancements were essentially caused by various anthropogenic activities and geogenic sources. The investigation also revealed that the broad extended desert soil is fruitful and promising as cultivable lands for agricultural processes in the futures.

  1. The characteristics of phosphorus adsorption and desorption in gray desert soil of Xinjiang, China

    Science.gov (United States)

    Wang, B.; Sun, J. S.; Liu, H.; Ma, Y. B.

    2017-07-01

    The characteristics of phosphorus (P) adsorption and desorption in Xinjiang gray desert soil (0 - 200 mm) of China in the long-term fertilization condition is affected by the level of soil P content which studied through an isothermal adsorption and desorption experiments of P. The results stated that within the experimental concentration range, with the increase of the amount of outer-source phosphorus, P adsorption, desorption and desorption rate increased and adsorption rate decreased gradually in different Olsen-P levels of gray desert soil in Xinjiang, China. Olsen-P content is significantly correlated with the P adsorption saturation (DPS) of gray desert soil. The maximum adsorption capacity (Xm ) of the treatments followed an extremely significant decreasing order of CK>NPK≈NPKM>PK≈NPKS. The maximum buffer capacity (MBC) and adsorption constant (K) of the NPK treatment was much higher than NPKM, NPKS, PK and CK treatments. And, MBC value of CK treatment was extremely higher than NPKS and PK, however, the differences between NPKM and CK, NPKS and PK were not significant. The comparison between NPKM, NPKS, PK and CK treatments showed no significant difference in K value, but these four showed significantly lower than NPK treatments. The value of soil easy desorption P (RDP) of NPKS and NPKM was significantly higher than NPK and PK, and the chemical fertilizer with organic fertilizer was a best way to release the phosphorus for Xinjiang agricultural production, China.

  2. Spatial variability and stocks of soil organic carbon in the Gobi desert of Northwestern China.

    Directory of Open Access Journals (Sweden)

    Pingping Zhang

    Full Text Available Soil organic carbon (SOC plays an important role in improving soil properties and the C global cycle. Limited attention, though, has been given to assessing the spatial patterns and stocks of SOC in desert ecosystems. In this study, we quantitatively evaluated the spatial variability of SOC and its influencing factors and estimated SOC storage in a region (40 km2 of the Gobi desert. SOC exhibited a log-normal depth distribution with means of 1.6, 1.5, 1.4, and 1.4 g kg(-1 for the 0-10, 10-20, 20-30, and 30-40 cm layers, respectively, and was moderately variable according to the coefficients of variation (37-42%. Variability of SOC increased as the sampling area expanded and could be well parameterized as a power function of the sampling area. Significant correlations were detected between SOC and soil physical properties, i.e. stone, sand, silt, and clay contents and soil bulk density. The relatively coarse fractions, i.e. sand, silt, and stone contents, had the largest effects on SOC variability. Experimental semivariograms of SOC were best fitted by exponential models. Nugget-to-sill ratios indicated a strong spatial dependence for SOC concentrations at all depths in the study area. The surface layer (0-10 cm had the largest spatial dependency compared with the other layers. The mapping revealed a decreasing trend of SOC concentrations from south to north across this region of the Gobi desert, with higher levels close to an oasis and lower levels surrounded by mountains and near the desert. SOC density to depths of 20 and 40 cm for this 40 km2 area was estimated at 0.42 and 0.68 kg C m(-2, respectively. This study provides an important contribution to understanding the role of the Gobi desert in the global carbon cycle.

  3. Geochemistry, geomorphology, and soil petrology of the Mars-like soils from Pampas de la Joya hyper-arid desert

    Science.gov (United States)

    Valdivia-Silva, Julio E.; Ortega-Gutierrez, Fernando; Bonaccorsi, Rosalba

    2016-07-01

    Mars-like environments on Earth are used as a model to guide the investigation of possible habitable Martian environments. In this work we evaluate and analyze the geology, geomorphology and soil petrology of the Pampas de La Joya Desert in southern Peru, in order to understand the processes that transformed the region into a Mars-like environment. Using a multidisciplinary approach, we analyze the different soils that compose the floor of the desert, as well as describe and interpret the post-Oligocene landscape emphasizing some Mars-like features with respect to its acting geologic processes, the habitability potential under very low levels of nutrients and water, and its suitability to sustain microorganisms or their remains. Importantly, this work is part of a bigger project that use Mars-like soils, looking for new crops capable to grow in extreme environments.

  4. The response of soil microbial communities to variation in annual precipitation depends on soil nutritional status in an oligotrophic desert

    Directory of Open Access Journals (Sweden)

    Cristina Montiel-González

    2017-11-01

    Full Text Available Background Soil microbial communities (SMC play a central role in the structure and function of desert ecosystems. However, the high variability of annual precipitation could results in the alteration of SMC and related biological processes depending on soil water potential. The nature of the physiological adjustments made by SMC in order to obtain energy and nutrients remains unclear under different soil resource availabilities in desert ecosystems. In order to examine this dynamic, the present study examined the effects of variation in annual precipitation on physiological adjustments by the SMC across two vegetation-soil systems of different soil organic matter input in an oligotrophic desert ecosystem. Methods We collected soil samples in the Cuatro Ciénegas Basin (Mexico under two vegetation covers: rosetophylous scrub (RS and grassland (G, that differ in terms of quantity and quality of organic matter. Collections were conducted during the years 2011, 2012, 2013 and 2014, over which a noticeable variation in the annual precipitation occurred. The ecoenzymatic activity involved in the decomposition of organic matter, and the concentration of dissolved, available and microbial biomass nutrients, were determined and compared between sites and years. Results In 2011, we observed differences in bacterial taxonomic composition between the two vegetation covers. The lowest values of dissolved, available and microbial nutrients in both cover types were found in 2012. The G soil showed higher values of dissolved and available nutrients in the wet years. Significant positive correlations were detected between precipitation and the ratios Cmic:Nmic and Cmic:Pmic in the RS soil and Cmic:Pmic and Nmic:Pmic in the G soil. The slopes of the regression with Cmic and Nmic were higher in the G soil and lower in the RS soil. Moreover, the SMC under each vegetation cover were co-limited by different nutrients and responded to the sum of water stress and

  5. The response of soil microbial communities to variation in annual precipitation depends on soil nutritional status in an oligotrophic desert.

    Science.gov (United States)

    Montiel-González, Cristina; Tapia-Torres, Yunuen; Souza, Valeria; García-Oliva, Felipe

    2017-01-01

    Soil microbial communities (SMC) play a central role in the structure and function of desert ecosystems. However, the high variability of annual precipitation could results in the alteration of SMC and related biological processes depending on soil water potential. The nature of the physiological adjustments made by SMC in order to obtain energy and nutrients remains unclear under different soil resource availabilities in desert ecosystems. In order to examine this dynamic, the present study examined the effects of variation in annual precipitation on physiological adjustments by the SMC across two vegetation-soil systems of different soil organic matter input in an oligotrophic desert ecosystem. We collected soil samples in the Cuatro Ciénegas Basin (Mexico) under two vegetation covers: rosetophylous scrub (RS) and grassland (G), that differ in terms of quantity and quality of organic matter. Collections were conducted during the years 2011, 2012, 2013 and 2014, over which a noticeable variation in the annual precipitation occurred. The ecoenzymatic activity involved in the decomposition of organic matter, and the concentration of dissolved, available and microbial biomass nutrients, were determined and compared between sites and years. In 2011, we observed differences in bacterial taxonomic composition between the two vegetation covers. The lowest values of dissolved, available and microbial nutrients in both cover types were found in 2012. The G soil showed higher values of dissolved and available nutrients in the wet years. Significant positive correlations were detected between precipitation and the ratios Cmic:Nmic and Cmic:Pmic in the RS soil and Cmic:Pmic and Nmic:Pmic in the G soil. The slopes of the regression with Cmic and Nmic were higher in the G soil and lower in the RS soil. Moreover, the SMC under each vegetation cover were co-limited by different nutrients and responded to the sum of water stress and nutrient limitation. Soil community within both

  6. High Resolution Mapping of Soils and Landforms for the Desert Renewable Energy Conservation Plan (DRECP)

    Science.gov (United States)

    Potter, Christopher S.; Li, Shuang

    2014-01-01

    The Desert Renewable Energy Conservation Plan (DRECP), a major component of California's renewable energy planning efforts, is intended to provide effective protection and conservation of desert ecosystems, while allowing for the sensible development of renewable energy projects. This NASA mapping report was developed to support the DRECP and the Bureau of Land Management (BLM). We outline in this document remote sensing image processing methods to deliver new maps of biological soils crusts, sand dune movements, desert pavements, and sub-surface water sources across the DRECP area. We focused data processing first on the largely unmapped areas most likely to be used for energy developments, such as those within Renewable Energy Study Areas (RESA) and Solar Energy Zones (SEZs). We used imagery (multispectral and radar) mainly from the years 2009-2011.

  7. Spatiotemporal Distribution of Soil Moisture and Salinity in the Taklimakan Desert Highway Shelterbelt

    Directory of Open Access Journals (Sweden)

    Yuan Huang

    2015-08-01

    Full Text Available Salinization and secondary salinization often appear after irrigation with saline water. The Taklimakan Desert Highway Shelterbelt has been irrigated with saline ground water for more than ten years; however, soil salinity in the shelterbelt has not been evaluated. The objective of this study was to analyze the spatial and temporal distribution of soil moisture and salinity in the shelterbelt system. Using a non-uniform grid method, soil samples were collected every two days during one ten-day irrigation cycle in July 2014 and one day in spring, summer, and autumn. The results indicated that soil moisture declined linearly with time during the irrigation cycle. Soil moisture was greatest in the southern and eastern sections of the study area. In contrast to soil moisture, soil electrical conductivity increased from 2 to 6 days after irrigation, and then gradually decreased from 6 to 8 days after irrigation. Soil moisture was the greatest in spring and the least in summer. In contrast, soil salinity increased from spring to autumn. Long time drip-irrigation with saline groundwater increased soil salinity slightly. The soil salt content was closely associated with soil texture. The current soil salt content did not affect plant growth, however, the soil in the shelterbelt should be continuously monitored to prevent salinization in the future.

  8. Differences in ice nucleation behavior of arable and desert soil dust in deposition nucleation regime

    Science.gov (United States)

    Ullrich, Romy; Vogel, Franziska; Möhler, Ottmar; Höhler, Kristina; Schiebel, Thea

    2017-04-01

    Soil dust from arid and semi-arid regions is one of the most abundant aerosol types in the atmosphere with emission rates of about 1600 Tg per year (Andreae et al. (2009)). Therewith, soil dust plays an important role for the atmospheric radiative transfer and also for the formation of clouds. Soil dust refers to dust sampled from agricultural used areas, to dust from bare soil as well as to dust from desert regions. By mass-spectrometric measurements of the chemical composition of ice residuals, mineral dust as component of soil dust was found to be the major heterogeneous ice nucleating particle (INP) type (e.g. Cziczo et al. (2013)), in particular in the upper troposphere. Also in laboratory studies the ice nucleation efficiency of the different soil dusts was investigated. It was shown that desert dusts (Ullrich et al. (2017)) as well as soil dusts from arable regions (O'Sullivan et al. (2014), Tobo et al. (2014)) are efficient INP. However, there is still a lack of data for ice nucleation on soil dusts for temperatures below about 220 K. With the AIDA (Aerosol Interactions and Dynamics in the Atmosphere) cloud chamber, we are able to characterize the ice nucleation efficiency for different aerosol types to temperatures down to 180 K and high ice supersaturations. In order to extend the already existing AIDA data base for deposition nucleation on desert dusts and agricultural soil dusts, new experiments were done in the upper tropospheric temperature regime. This contribution will show the results of the new experiments with desert dust in comparison to existing data for higher temperatures. The first data analysis confirms the temperature dependent trend of the ice nucleation activity as discussed and parameterized in a recent paper by Ullrich et al. (2017). Furthermore, the update and extension of the recently published parameterization of deposition nucleation for desert dust to lower temperatures will be discussed. The experiments with agricultural soil

  9. Grazing Effects on Soil Nutrient Contents in Desert Oasis Ecotone of Haloxylon Ammodendron of Gan Jiahu

    Science.gov (United States)

    Li, Yanhong; Jiao, Li; Yang, Aixia

    2013-04-01

    This paper research different grazing strength on haloxylon ammodendron desert vegetation of soil nutrient effect in GanJiahu haloxylon ammodendron forest national nature reserv, in August 2009, November and May 2010, to Gan Jiahu Desert Oasis transition with for research district, results indicates that: (1) through on heavy degrees grazing of Reed wetland, and in the degrees grazing of salt of grass meadow and mild grazing of Populus euphratica forest comparison analysis: believes that grazing have effect on soil of organic matter, and full nitrogen, and full phosphorus, and quick-impact potassium, and quick-impact phosphorus, and alkali solutions nitrogen. And compared to mild degrees grazing, heavy degrees grazing affect obviously on soil organic matter, and quick-impact potassium, and quick-impact phosphorus, and alkali solutions nitrogen effect comparison significantly, on soil full nitrogen, and full phosphorus effect small; (2) different season on different grazing degree region of soil nutrient has much effect, different wet/dry quarter performance different, May and August soil of organic matter, with grazing degree increased full nitrogen, full phosphorus, quick-impact phosphorus, and alkali solutions nitrogen content are reduced, especially to August most significantly (Peffects of grazing on soil surface indicators of nutrient content significantly, various nutrient contents in the wet season (August), generally higher than that of the dry season in May and November, the accumulation of soil nutrient content in November.

  10. The stage of soil development modulates rhizosphere effect along a High Arctic desert chronosequence

    KAUST Repository

    Mapelli, Francesca

    2018-01-09

    In mature soils, plant species and soil type determine the selection of root microbiota. Which of these two factors drives rhizosphere selection in barren substrates of developing desert soils has, however, not yet been established. Chronosequences of glacier forelands provide ideal natural environments to identify primary rhizosphere selection factors along the changing edaphic conditions of a developing soil. Here, we analyze changes in bacterial diversity in bulk soils and rhizospheres of a pioneer plant across a High Arctic glacier chronosequence. We show that the developmental stage of soil strongly modulates rhizosphere community assembly, even though plant-induced selection buffers the effect of changing edaphic factors. Bulk and rhizosphere soils host distinct bacterial communities that differentially vary along the chronosequence. Cation exchange capacity, exchangeable potassium, and metabolite concentration in the soil account for the rhizosphere bacterial diversity. Although the soil fraction (bulk soil and rhizosphere) explains up to 17.2% of the variation in bacterial microbiota, the soil developmental stage explains up to 47.7% of this variation. In addition, the operational taxonomic unit (OTU) co-occurrence network of the rhizosphere, whose complexity increases along the chronosequence, is loosely structured in barren compared with mature soils, corroborating our hypothesis that soil development tunes the rhizosphere effect.

  11. Metagenomic characterization of biodiversity in the extremely arid desert soils of Kazakhstan

    Science.gov (United States)

    Kutovaya, O. V.; Lebedeva, M. P.; Tkhakakhova, A. K.; Ivanova, E. A.; Andronov, E. E.

    2015-05-01

    For the first time, the composition of microbiomes in the biological crust (AKL) horizons of extremely arid desert soils (Aridic Calcisols) developed from saline and nonsaline alluvial deposits in the Ili Depression (eastern Kazakhstan) was analyzed. To describe the diversity of microorganisms in the soil samples, a novel method of pyrosequencing (Roche/454 Life Sciences) was applied. It was shown that bacteria from the Proteobacteria, Actinobacteria, Firmicutes, Verrucomicrobia, Acidobacteria, and Bacteroidetes phyla predominate in all the samples; these are typical representatives of the microbiome of soil crusts. A distinctive feature of the extremely arid soils is the high contribution of cyanobacteria (25-30%) to the total DNA. In the soils developed from saline sediments, representatives from the Rubrobacteraceae, Streptococcaceae, and Caulobacteraceae families and from the Firmicutes phylum predominated. In the soils developed from nonsaline gypsiferous deposits, bacteria from the class of Acidobacteria, subgroup Gp3, of the Methylobacteriaceae family and the class of Subdivision 3 from the Verrucomicrobia phylum predominated.

  12. Impact of grazing on soil carbon and microbial biomass in typical steppe and desert steppe of Inner Mongolia

    National Research Council Canada - National Science Library

    Liu, Nan; Zhang, Yingjun; Chang, Shujuan; Kan, Haiming; Lin, Lijun

    2012-01-01

    ... (MBC) in Typical steppe and Desert steppe ecosystems, which are both important grassland resources for animal grazing and ecological conservation in China, and to derive region-specific soil C changes...

  13. Growing season net ecosystem CO2 exchange of two desert ecosystems with alkaline soils in Kazakhstan

    Science.gov (United States)

    Li, Longhui; Chen, Xi; van der Tol, Christiaan; Luo, Geping; Su, Zhongbo

    2014-01-01

    Central Asia is covered by vast desert ecosystems, and the majority of these ecosystems have alkaline soils. Their contribution to global net ecosystem CO2 exchange (NEE) is of significance simply because of their immense spatial extent. Some of the latest research reported considerable abiotic CO2 absorption by alkaline soil, but the rate of CO2 absorption has been questioned by peer communities. To investigate the issue of carbon cycle in Central Asian desert ecosystems with alkaline soils, we have measured the NEE using eddy covariance (EC) method at two alkaline sites during growing season in Kazakhstan. The diurnal course of mean monthly NEE followed a clear sinusoidal pattern during growing season at both sites. Both sites showed significant net carbon uptake during daytime on sunny days with high photosynthetically active radiation (PAR) but net carbon loss at nighttime and on cloudy and rainy days. NEE has strong dependency on PAR and the response of NEE to precipitation resulted in an initial and significant carbon release to the atmosphere, similar to other ecosystems. These findings indicate that biotic processes dominated the carbon processes, and the contribution of abiotic carbon process to net ecosystem CO2 exchange may be trivial in alkaline soil desert ecosystems over Central Asia. PMID:24455157

  14. Magnetic susceptibility of surface soils in the Mu Us Desert and its environmental significance

    Science.gov (United States)

    Liu, Xiaokang; Lu, Ruijie; Lü, Zhiqiang; Du, Jing; Jia, Feifei; Li, Tengfei; Chen, Lu; Wu, Yongqiu

    2017-04-01

    Magnetic susceptibility has been widely used as a climatic proxy in paleoclimatic research. In arid and semi-arid regions, the magnetic properties of modern surface soil are significantly influenced by precipitation. This is demonstrated by observed positive correlations between percentage frequency-dependent magnetic susceptibility (χfd%), which reflects the presence of fine-grained (superparamagnetic, SP) grains produced during weathering and pedogenesis, and regional mean annual precipitation (MAP). To further investigate this relationship, we measured the magnetic properties of 104 surface soil samples collected along two transects (AA and BB) spanning a rainfall gradient across the Mu Us Desert in northern China. There were no systematic trends in magnetic properties along transect BB; the χfd% values remained relatively low and stable, probably reflecting weak pedogenesis and the domination of the magnetic properties by lithology. In contrast, along transect AA there was a significant positive correlation (p modern Mu Us Desert. The results show that the variations of reconstructed precipitation are consistent with those of lithological properties, and they also confirm previous conclusions that paleosol development in the study area is dominated by precipitation. Overall the results further demonstrate the feasibility of using frequency-dependent magnetic susceptibility to quantitatively reconstruct regional paleo-precipitation, including within a geographically diverse desert area. In addition, they provide an improved understanding of the main sand provenance in Mu Us Desert.

  15. Profile Changes in the Soil Microbial Community When Desert Becomes Oasis

    Science.gov (United States)

    Li, Chen-hua; Tang, Li-song; Jia, Zhong-jun; Li, Yan

    2015-01-01

    The conversion of virgin desert into oasis farmland creates two contrasting types of land-cover. During oasis formation with irrigation and fertilizer application, however, the changes in the soil microbial population, which play critical roles in the ecosystem, remain poorly understood. We applied high-throughput pyrosequencing to investigate bacterial and archaeal communities throughout the profile (0–3 m) in an experimental field, where irrigation and fertilization began in 1990 and cropped with winter wheat since then. To assess the effects of cultivation, the following treatments were compared with the virgin desert: CK (no fertilizer), PK, NK, NP, NPK, NPKR, and NPKM (R: straw residue; M: manure fertilizer). Irrigation had a greater impact on the overall microbial community than fertilizer application. The greatest impact occurred in topsoil (0–0.2 m), e.g., Cyanobacteria (25% total abundance) were most abundant in desert soil, while Actinobacteria (26%) were most abundant in oasis soil. The proportions of extremophilic and photosynthetic groups (e.g., Deinococcus-Thermus and Cyanobacteria) decreased, while the proportions of R-strategy (e.g., Gammaproteobacteria including Xanthomonadales), nitrifying (e.g., Nitrospirae), and anaerobic bacteria (e.g., Anaerolineae) increased throughout the oasis profile. Archaea occurred only in oasis soil. The impact of fertilizer application was mainly reflected in the non-dominant communities or finer taxonomic divisions. Oasis formation led to a dramatic shift in microbial community and enhanced soil enzyme activities. The rapidly increased soil moisture and decreased salt caused by irrigation were responsible for this shift. Furthermore, difference in fertilization and crop growth altered the organic carbon contents in the soil, which resulted in differences of microbial communities within oasis. PMID:26426279

  16. Profile Changes in the Soil Microbial Community When Desert Becomes Oasis.

    Directory of Open Access Journals (Sweden)

    Chen-hua Li

    Full Text Available The conversion of virgin desert into oasis farmland creates two contrasting types of land-cover. During oasis formation with irrigation and fertilizer application, however, the changes in the soil microbial population, which play critical roles in the ecosystem, remain poorly understood. We applied high-throughput pyrosequencing to investigate bacterial and archaeal communities throughout the profile (0-3 m in an experimental field, where irrigation and fertilization began in 1990 and cropped with winter wheat since then. To assess the effects of cultivation, the following treatments were compared with the virgin desert: CK (no fertilizer, PK, NK, NP, NPK, NPKR, and NPKM (R: straw residue; M: manure fertilizer. Irrigation had a greater impact on the overall microbial community than fertilizer application. The greatest impact occurred in topsoil (0-0.2 m, e.g., Cyanobacteria (25% total abundance were most abundant in desert soil, while Actinobacteria (26% were most abundant in oasis soil. The proportions of extremophilic and photosynthetic groups (e.g., Deinococcus-Thermus and Cyanobacteria decreased, while the proportions of R-strategy (e.g., Gammaproteobacteria including Xanthomonadales, nitrifying (e.g., Nitrospirae, and anaerobic bacteria (e.g., Anaerolineae increased throughout the oasis profile. Archaea occurred only in oasis soil. The impact of fertilizer application was mainly reflected in the non-dominant communities or finer taxonomic divisions. Oasis formation led to a dramatic shift in microbial community and enhanced soil enzyme activities. The rapidly increased soil moisture and decreased salt caused by irrigation were responsible for this shift. Furthermore, difference in fertilization and crop growth altered the organic carbon contents in the soil, which resulted in differences of microbial communities within oasis.

  17. The influence of flint stones on a soil microbial community in the northern Negev Desert

    Directory of Open Access Journals (Sweden)

    Haggai Wasserstrom

    2017-07-01

    Full Text Available In the Negev Desert ecosystems, flint-stone cover on slopes acts as a barrier against water flow. As a result, soil moisture increases and organic matter accumulates under the stone and in the immediate surroundings, both affecting the duration of soil microbial activity. On the other hand, during the dry season (characterized by approximately 210 dew nights, flint-stone cover plays an important role in the formation of dew, which eventually trickles down beneath the stone, correspondingly enhancing biological activity. The present study examined the possible role of flint stones as hotspots for soil microbial-community activity and diversity. The results were compared with those obtained from the adjacent stone-free soils in the open spaces (OS, which served as controls. Microbial activity (respiration and biomass and functional diversity were determined by the MicroRespTM method. In addition, estimates of genetic diversity and viable counts of bacteria and fungi [colony-forming units (CFUs] were obtained. The soil was significantly wetter and contained more organic matter beneath the flint stones (BFS. As hypothesized, biological activity was enhanced under the stones, as described by CO2 evolution, microbial-community biomass functional diversity, and fungal phylogenetic diversity. BFS environments favored a greater range of catabolic functions. Taxa generally known for their stress resilience were found in the OS habitats. The results of this study elucidate the importance of flint-stone cover to soil microbial biomass, community activity, and functional diversity in the northern Negev Desert.

  18. Diel-scale temporal dynamics recorded for bacterial groups in Namib Desert soil

    Science.gov (United States)

    Gunnigle, Eoin; Frossard, Aline; Ramond, Jean-Baptiste; Guerrero, Leandro; Seely, Mary; Cowan, Don A.

    2017-01-01

    Microbes in hot desert soil partake in core ecosystem processes e.g., biogeochemical cycling of carbon. Nevertheless, there is still a fundamental lack of insights regarding short-term (i.e., over a 24-hour [diel] cycle) microbial responses to highly fluctuating microenvironmental parameters like temperature and humidity. To address this, we employed T-RFLP fingerprinting and 454 pyrosequencing of 16S rRNA-derived cDNA to characterize potentially active bacteria in Namib Desert soil over multiple diel cycles. Strikingly, we found that significant shifts in active bacterial groups could occur over a single 24-hour period. For instance, members of the predominant Actinobacteria phyla exhibited a significant reduction in relative activity from morning to night, whereas many Proteobacterial groups displayed an opposite trend. Contrary to our leading hypothesis, environmental parameters could only account for 10.5% of the recorded total variation. Potential biotic associations shown through co-occurrence networks indicated that non-random inter- and intra-phyla associations were ‘time-of-day-dependent’ which may constitute a key feature of this system. Notably, many cyanobacterial groups were positioned outside and/or between highly interconnected bacterial associations (modules); possibly acting as inter-module ‘hubs’ orchestrating interactions between important functional consortia. Overall, these results provide empirical evidence that bacterial communities in hot desert soils exhibit complex and diel-dependent inter-community associations. PMID:28071697

  19. Biodiversity of soil cyanobacteria in the hyper-arid Atacama Desert, Chile.

    Science.gov (United States)

    Patzelt, Dominik J; Hodač, Ladislav; Friedl, Thomas; Pietrasiak, Nicole; Johansen, Jeffrey R

    2014-08-01

    The cyanobacterial diversity of soils of the Atacama Desert (Chile) was investigated using 16S rRNA gene cloning/sequencing directly from soil samples and 16S rRNA gene sequencing from unialgal cultures. Within the hyper-arid Atacama Desert, one of the driest parts of the world, 10 sites with differing altitude and distance to the shore were sampled along a total air-line distance (from south to north) of ~1,100 km. Filamentous cyanobacteria belonging to Nostocophycideae and Synechococcophycideae were present. Oscillatoriophycideae exhibited the highest species richness among the subclasses of cyanobacteria, and included mostly filamentous species along with some coccoids (e.g., Chroococcidiopsis). Thirty species-level phylotypes could be recognized using a cut-off of 99% 16S rRNA sequence similarity within the 22 genera defined at 97% 16S rRNA sequence similarity. Eight of the 30 taxa could be detected by both clonal and culture sequences. Five taxa were observed only in cultures, whereas the cloning approach revealed 17 additional taxa, which might be in the collection but unsequenced, hard-to-cultivate, or entirely unculturable species using standard cultivation media. The Atacama Desert soils have a high diversity of phylotypes, among which are likely both new genera and new species awaiting characterization and description. © 2014 Phycological Society of America.

  20. Energy Crisis in Pakistan and Thar Coal is Untapped Wealth and Solution

    OpenAIRE

    Anwar Ali Shah G.Syed; Faiz M. Shaikh; Abdul Sattar Shah

    2014-01-01

    This research investigates the Energy crisis and Thar coal is untapped and solution to engery problem in Pakistan. Data were collected from various secondary sources i.e. Annual Reports, News prepard, magazine and Reports from Thar coal development authority. It was revealed that Thar coal that there is now some hope for economic uplift as its natural wealth is being tapped. Geological Survey of Pakistan (GSP), discovered huge deposits of coal in 1922 at Thar during the research program, assi...

  1. Soiling effects comparison between CPV plants in continental and desert climates

    Science.gov (United States)

    Calvo-Parra, Gustavo; Martínez, María; Sánchez, Daniel; de la Rubia, Ã.`scar; Chatenay, Pierre

    2017-09-01

    This paper presents the results obtained in the analysis of soiling effects in the energy production of CPV systems placed in desert areas (Abu Dhabi). These results are compared with the ones obtained from similar systems placed in continental climate areas, as it is the center of Spain at ISFOC headquarters. While the reduction in the energy generation because of soiling accumulation was less than a 10% at ISFOC, at Abu Dhabi it seems that it can reach values of 80% relatively fast, therefore a good cleaning policy becomes mandatory in climatic areas like Abu Dhabi.

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

    Energy Technology Data Exchange (ETDEWEB)

    Nowak, Robert S.

    2007-12-19

    belowground in relatively recalcitrant forms. Indeed, a model-based analysis predicted that the arid/semiarid southwestern bioclimatic region had one of the highest rates of net carbon storage in the United States over the past century (Schimel et al. 2000). Second, root systems of desert plants are often extensive (Foxx et al. 1984, Hartle et al. 2006) with relatively large proportions of roots deep in the soil (Schenk & Jackson 2002). Thus, an understanding of belowground processes in desert ecosystems provides information on the potential for terrestrial carbon sequestration in desert ecosystems.

  3. Exploring relationships between soil spectral and chemical properties along a climatic gradient in the Judean Desert

    Science.gov (United States)

    Shoshany, M. S.; Jarmer, T. J.

    2012-04-01

    Regions of rainfall gradients at desert margins are areas where eco-geomorphic changes and desertification in response to global warming and grazing are most intensive. Assessment and understanding consequences of global warming and human disturbance of these vulnerable ecosystems requires detailed information regarding spatial variation of soil and vegetation properties and their dependence on rainfall. Such detailed information is still of limited availability. This study aimed to rectify this shortcoming by analyzing data on chemical and spectral properties of soil samples collected along the Judean Desert climatic gradient. Six clusters of typical chemical soil properties were identified. Dependencies of the clusters' chemical properties of total iron, organic and inorganic carbon on annual rainfall amounts were found to be significant. Two spectral band ratios for Landsat TM bands were introduced to assess soil conditions and found to be significantly correlated with these chemical properties. While relationships between chemical properties and rainfall were relatively weak, spectral ratios were found higher correlated with average rainfall suggesting that spectral data may represent a broader range of chemical, physical and biological site properties. Examining the three-way relationships between soil chemical properties, their spectral reflectance characteristics and rainfall, facilitates better understanding of the generalized trends along the climatic gradient and more specifically modes of transition from semi-arid to arid zones.

  4. Dormancy cycling and persistence of seeds in soil of a cold desert halophyte shrub

    Science.gov (United States)

    Cao, Dechang; Baskin, Carol C.; Baskin, Jerry M.; Yang, Fan; Huang, Zhenying

    2014-01-01

    Background and Aims Formation of seed banks and dormancy cycling are well known in annual species, but not in woody species. In this study it was hypothesized that the long-lived halophytic cold desert shrub Kalidium gracile has a seed bank and dormancy cycling, which help restrict germination to a favourable time for seedling survival. Methods Fresh seeds were buried in November 2009 and exhumed and tested for germination monthly from May 2010 to December 2011 over a range of temperatures and salinities. Germination recovery and viability were determined after exposure to salinity and water stress. Seedling emergence and dynamics of the soil seed bank were investigated in the field. Key Results Seeds of K. gracile had a soil seed bank of 7030 seeds m−2 at the beginning of the growing season. About 72 % of the seeds were depleted from the soil seed bank during a growing season, and only 1·4 % of them gave rise to seedlings that germinated early enough to reach a stage of growth at which they could survive to overwinter. About 28 % of the seeds became part of a persistent soil seed bank. Buried seeds exhibited an annual non-dormancy/conditional dormancy (ND/CD) cycle, and germination varied in sensitivity to salinity during the cycle. Dormancy cycling is coordinated with seasonal environmental conditions in such a way that the seeds germinate in summer, when there is sufficient precipitation for seedling establishment. Conclusions Kalidium gracile has three life history traits that help ensure persistence at a site: a polycarpic perennial life cycle, a persistent seed bank and dormancy cycling. The annual ND/CD cycle in seeds of K. gracile contributes to seedling establishment of this species in the unpredictable desert environment and to maintenance of a persistent soil seed bank. This is the first report of a seed dormancy cycle in a cold desert shrub. PMID:24249808

  5. Dormancy cycling and persistence of seeds in soil of a cold desert halophyte shrub.

    Science.gov (United States)

    Cao, Dechang; Baskin, Carol C; Baskin, Jerry M; Yang, Fan; Huang, Zhenying

    2014-01-01

    Formation of seed banks and dormancy cycling are well known in annual species, but not in woody species. In this study it was hypothesized that the long-lived halophytic cold desert shrub Kalidium gracile has a seed bank and dormancy cycling, which help restrict germination to a favourable time for seedling survival. Fresh seeds were buried in November 2009 and exhumed and tested for germination monthly from May 2010 to December 2011 over a range of temperatures and salinities. Germination recovery and viability were determined after exposure to salinity and water stress. Seedling emergence and dynamics of the soil seed bank were investigated in the field. Seeds of K. gracile had a soil seed bank of 7030 seeds m(-2) at the beginning of the growing season. About 72 % of the seeds were depleted from the soil seed bank during a growing season, and only 1·4 % of them gave rise to seedlings that germinated early enough to reach a stage of growth at which they could survive to overwinter. About 28 % of the seeds became part of a persistent soil seed bank. Buried seeds exhibited an annual non-dormancy/conditional dormancy (ND/CD) cycle, and germination varied in sensitivity to salinity during the cycle. Dormancy cycling is coordinated with seasonal environmental conditions in such a way that the seeds germinate in summer, when there is sufficient precipitation for seedling establishment. Kalidium gracile has three life history traits that help ensure persistence at a site: a polycarpic perennial life cycle, a persistent seed bank and dormancy cycling. The annual ND/CD cycle in seeds of K. gracile contributes to seedling establishment of this species in the unpredictable desert environment and to maintenance of a persistent soil seed bank. This is the first report of a seed dormancy cycle in a cold desert shrub.

  6. Ammonia-oxidizing archaea respond positively to inorganic nitrogen addition in desert soils.

    Science.gov (United States)

    Marusenko, Yevgeniy; Garcia-Pichel, Ferran; Hall, Sharon J

    2015-02-01

    In soils, nitrogen (N) addition typically enhances ammonia oxidation (AO) rates and increases the population density of ammonia-oxidizing bacteria (AOB), but not that of ammonia-oxidizing archaea (AOA). We asked if long-term inorganic N addition also has similar consequences in arid land soils, an understudied yet spatially ubiquitous ecosystem type. Using Sonoran Desert top soils from between and under shrubs within a long-term N-enrichment experiment, we determined community concentration-response kinetics of AO and measured the total and relative abundance of AOA and AOB based on amoA gene abundance. As expected, N addition increased maximum AO rates and the abundance of bacterial amoA genes compared to the controls. Surprisingly, N addition also increased the abundance of archaeal amoA genes. We did not detect any major effects of N addition on ammonia-oxidizing community composition. The ammonia-oxidizing communities in these desert soils were dominated by AOA as expected (78% of amoA gene copies were related to Nitrososphaera), but contained unusually high contributions of Nitrosomonas (18%) and unusually low numbers of Nitrosospira (2%). This study highlights unique traits of ammonia oxidizers in arid lands, which should be considered globally in predictions of AO responses to changes in N availability. © FEMS 2014. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  7. The potential of established turf cover for cleaning oily desert soil using rhizosphere technology.

    Science.gov (United States)

    Mahmoud, H M; Suleman, P; Sorkhoh, N A; Salamah, S; Radwan, Samir S

    2011-02-01

    The rhizosphere of two turf cover sorts; Bermuda grass and American grass contained high numbers, 8.1 to 16.8 x 10(6) g(-1) of cultivable oil-utilizing and diazotrophic bacteria belonging predominantly to the genera Agrobacterium, Arthrobacter, Pseudomonas, Gordonia, and Rhodococcus. Those bacteria also grew on a nitrogen-free medium and demonstrated the ability to reduce acetylene to ethylene. These isolates grew on a wide range of n-alkanes (C9 to C40) and aromatic hydrocarbons, as sole sources of carbon. Quantitative determinations revealed that predominant bacteria consumed crude oil and representative aliphatic (n-octadecane) and aromatic (phenanthrene) hydrocarbons efficiently. The fact that those organisms had the combined activities of hydrocarbon-utilization and nitrogen-fixation makes them suitable tools for bioremediating oily desert areas that are normally poor in nitrogenous compounds. Phytoremediation experiments showed that spreading turf cover on oily desert soil inhibited oil volatilization and enhanced oil loss in soil by about 15%. Oil loss was also enhanced in turf free soil samples fertilized with NH4NO3. In conclusion, covering this oil-polluted soil with turf cover minimized atmospheric pollution, increased the numbers of the oil-utilizing/nitrogen-fixing bacteria by about 20 to 46% thus, encouraging oil attenuation.

  8. Connecting ecohydrology and hydropedology in desert shrubs: stemflow as a source of preferential flow in soils

    Directory of Open Access Journals (Sweden)

    Henry Lin

    2009-07-01

    Full Text Available Ecohydrology and hydropedology are two emerging fields that are interconnected. In this study, we demonstrate stemflow hydrology and preferential water flow along roots in two desert shrubs (H. scoparium and S. psammophila in the south fringe of Mu Us sandy land in North China. Stemflow generation and subsequent movement within soil-root system were investigated during the growing seasons from 2006 to 2008. The results indicated that the amount of stemflow in H. scoparium averaged 3.4% of incident gross rainfall with a range of 2.3–7.0%, while in S. psammophila stemflow averaged 6.3% with a range of 0.2–14.2%. Stemflow was produced from rainfall events with total amount more than 1 mm for both shrubs. The average funneling ratio (the ratio of rainfall amount delivered to the base of the tree to the rainfall that would have reached the ground should the tree were not present was 77.8 and 48.7 for H. scoparium and S. psammophila, respectively, indicating that branches and stems were fully contributing to stemflow generation and thereby provided sources of water for possible preferential flow into deeper soil layer. Analysis of Rhodamine-B dye distribution under the shrubs showed that root channels were preferential pathways for the movement of most stemflow water into the soil. Distribution of soil water content under the shrubs with and without stemflow ascertained that stemflow was conducive to concentrate and store water in deeper layers in the soil profiles, which may create favorable soil water conditions for plant growth under arid conditions. Accordingly, a clear linkage between aboveground ecohydrology and belowground hydropedology in the desert shrubs is worth noticing, whereby an increase in stemflow would result in an increase in soil hydrologic heterogeneity.

  9. Thermoregulatory value of cracking-clay soil shelters for small vertebrates during extreme desert conditions.

    Science.gov (United States)

    Waudby, Helen P; Petit, Sophie

    2017-05-01

    Deserts exhibit extreme climatic conditions. Small desert-dwelling vertebrates have physiological and behavioral adaptations to cope with these conditions, including the ability to seek shelter. We investigated the temperature (T) and relative humidity (RH) regulating properties of the soil cracks that characterize the extensive cracking-clay landscapes of arid Australia, and the extent of their use by 2 small marsupial species: fat-tailed and stripe-faced dunnarts (Sminthopsis crassicaudata and Sminthopsis macroura). We measured hourly (over 24-h periods) the T and RH of randomly-selected soil cracks compared to outside conditions, during 2 summers and 2 winters. We tracked 17 dunnarts (8 Sminthopsis crassicaudata and 9 Sminthopsis macroura) to quantify their use of cracks. Cracks consistently moderated microclimate, providing more stable conditions than available from non-crack points, which often displayed comparatively dramatic fluctuations in T and RH. Both dunnart species used crack shelters extensively. Cracks constitute important shelter for small animals during extreme conditions by providing a stable microclimate, which is typically cooler than outside conditions in summer and warmer in winter. Cracks likely play a fundamental sheltering role by sustaining the physiological needs of small mammal populations. Globally, cracking-clay areas are dominated by agricultural land uses, including livestock grazing. Management of these systems should focus not only on vegetation condition, but also on soil integrity, to maintain shelter resources for ground-dwelling fauna. © 2016 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.

  10. Kurtzmanomyces shapotouensis sp. nov., an anamorphic, basidiomycetous yeast isolated from desert soil crusts.

    Science.gov (United States)

    Zhang, Tao; Jia, Rong-Liang; Zhang, Yu-Qin; Liu, Hong-Yu; Su, Jing; Yu, Li-Yan

    2013-10-01

    Two yeast strains isolated from soil crusts in the Shapotou region of Tengger Desert (north-western China) were grouped in the genus Kurtzmanomyces based on morphological characteristics. rRNA gene sequence analyses (including the D1/D2 domain of the large subunit rRNA gene and internal transcribed spacer region) indicated that these two strains represented a novel species of the genus Kurtzmanomyces, for which the name Kurtzmanomyces shapotouensis sp. nov. is proposed (type strain: CPCC 300020(T) = DSM 26579(T) = CBS 12707(T)). The MycoBank number of the novel species is MB 804959.

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    Farid Benyahia

    2016-02-01

    Full Text Available 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.

  13. Soil water regulates the control of photosynthesis on diel hysteresis between soil respiration and temperature in a desert shrubland

    Science.gov (United States)

    Wang, Ben; Zha, Tian Shan; Jia, Xin; Gong, Jin Nan; Bourque, Charles; Feng, Wei; Tian, Yun; Wu, Bin; Qing Zhang, Yu; Peltola, Heli

    2017-09-01

    Explanations for the occurrence of hysteresis (asynchronicity) between diel soil respiration (Rs) and soil temperature (Ts) have evoked both biological and physical mechanisms. The specifics of these explanations, however, tend to vary with the particular ecosystem or biome being investigated. So far, the relative degree of control of biological and physical processes on hysteresis is not clear for drylands. This study examined the seasonal variation in diel hysteresis and its biological control in a desert-shrub ecosystem in northwest (NW) China. The study was based on continuous measurements of Rs, air temperature (Ta), temperature at the soil surface and below (Tsurf and Ts), volumetric soil water content (SWC), and photosynthesis in a dominant desert shrub (i.e., Artemisia ordosica) over an entire year in 2013. Trends in diel Rs were observed to vary with SWC over the growing season (April to October). Diel variations in Rs were more closely associated with variations in Tsurf than with photosynthesis as SWC increased, leading to Rs being in phase with Tsurf, particularly when SWC > 0.08 m3 m-3 (ratio of SWC to soil porosity = 0.26). However, as SWC decreased below 0.08 m3 m-3, diel variations in Rs were more closely related to variations in photosynthesis, leading to pronounced hysteresis between Rs and Tsurf. Incorporating photosynthesis into a Q10-function eliminated 84.2 % of the observed hysteresis, increasing the overall descriptive capability of the function. Our findings highlight a high degree of control by photosynthesis and SWC in regulating seasonal variation in diel hysteresis between Rs and temperature.

  14. Impact of environmental factors and biological soil crust types on soil respiration in a desert ecosystem.

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    Wei Feng

    Full Text Available The responses of soil respiration to environmental conditions have been studied extensively in various ecosystems. However, little is known about the impacts of temperature and moisture on soils respiration under biological soil crusts. In this study, CO2 efflux from biologically-crusted soils was measured continuously with an automated chamber system in Ningxia, northwest China, from June to October 2012. The highest soil respiration was observed in lichen-crusted soil (0.93 ± 0.43 µmol m-2 s-1 and the lowest values in algae-crusted soil (0.73 ± 0.31 µmol m-2 s-1. Over the diurnal scale, soil respiration was highest in the morning whereas soil temperature was highest in the midday, which resulted in diurnal hysteresis between the two variables. In addition, the lag time between soil respiration and soil temperature was negatively correlated with the soil volumetric water content and was reduced as soil water content increased. Over the seasonal scale, daily mean nighttime soil respiration was positively correlated with soil temperature when moisture exceeded 0.075 and 0.085 m3 m-3 in lichen- and moss-crusted soil, respectively. However, moisture did not affect on soil respiration in algae-crusted soil during the study period. Daily mean nighttime soil respiration normalized by soil temperature increased with water content in lichen- and moss-crusted soil. Our results indicated that different types of biological soil crusts could affect response of soil respiration to environmental factors. There is a need to consider the spatial distribution of different types of biological soil crusts and their relative contributions to the total C budgets at the ecosystem or landscape level.

  15. Preservation of Lipid Biomarkers Under Prolonged and Extreme Hyperaridity in Atacama Desert Soils

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    Wilhelm, Mary Beth

    2015-01-01

    Molecular biomarkers are the most direct biosignatures of life on early Earth and a key target in the search for life on Mars. Lipid biomarkers are of particular interest given their ability to survive oxidative degradation and record microbial presence and activity of microorganisms that occurred billions of years ago (Eigenbrode, 2008). Environmental conditions that suspend biotic and abiotic degradative processes prior to lithification can lead to enhanced biomolecular preservation over geological time-scales. The hyperarid core of the Atacama Desert in northern Chile offers a unique environment to investigate lipid biomarker taphonomy under extreme and prolonged dryness. We investigated the accumulation and degree of preservation of lipid biomarkers in million-year-old hyperarid soils where primarily abiotic conditions influence their taphonomy. Soils were extracted and free and membrane bound lipids were analyzed across a vertical profile of 2.5 meters in the Yungay hyper-arid core of the Atacama Desert. Due to the extremely low inventory of biomass in Atacama soils, samples were collected by scientists wearing cleanroom suits to minimize anthropogenic contamination during sampling. Fatty acids were found to be well preserved in Yungay soils, and were most abundant in the clay-rich soils at approx.2 m depth (approx.750 ng of fatty acid methyl ester/g of soil). These buried clays layers were fluvially deposited approximately 2 million years ago, and have been excluded from exposure to rainwater and modern surficial processes since their emplacement (Ewing et al., 2008). Monocarboxylic fatty acid, monohydroxy fatty acid, glycerol tetraether, and n-alkane hydrocarbon content was found to change with depth. Lipid biomarker content in deeper soil layers is suggestive of soils having been formed at a time when environmental conditions were capable of supporting active microbial communities and plants. In short, total lipid extracts reveal a remarkable degree of

  16. Response of desert biological soil crusts to alterations in precipitation frequency

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    Belnap, J.; Phillips, S.L.; Miller, M.E.

    2004-01-01

    Biological soil crusts, a community of cyanobacteria, lichens, and mosses that live on the soil surface, occur in deserts throughout the world. They are a critical component of desert ecosystems, as they are important contributors to soil fertility and stability. Future climate scenarios predict alteration of the timing and amount of precipitation in desert environments. Because biological soil crust organisms are only metabolically active when wet, and as soil surfaces dry quickly in deserts during late spring, summer, and early fall, the amount and timing of precipitation is likely to have significant impacts on the physiological functioning of these communities. Using the three dominant soil crust types found in the western United States, we applied three levels of precipitation frequency (50% below-average, average, and 50% above-average) while maintaining average precipitation amount (therefore changing both timing and size of applied events). We measured the impact of these treatments on photosynthetic performance (as indicated by dark-adapted quantum yield and chlorophyll a concentrations), nitrogenase activity, and the ability of these organisms to maintain concentrations of radiation-protective pigments (scytonemin, beta-carotene, echinenone, xanthophylls, and canthaxanthin). Increased precipitation frequency produced little response after 2.5 months exposure during spring (1 April-15 June) or summer (15 June-31 August). In contrast, most of the above variables had a large, negative response after exposure to increased precipitation frequency for 6 months spring-fall (1 April-31 October) treatment. The crusts dominated by the soil lichen Collema, being dark and protruding above the surface, dried the most rapidly, followed by the dark surface cyanobacterial crusts (Nostoc-Scytonema-Microcoleus), and then by the light cyanobacterial crusts (Microcoleus). This order reflected the magnitude of the observed response: crusts dominated by the lichen Collema

  17. Sonoran Desert winter annuals affected by density of red brome and soil nitrogen

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    Salo, L.F.; McPherson, G.R.; Williams, D.G.

    2005-01-01

    Red brome [Bromus madritensis subsp. rubens (L.) Husn.] is a Mediterranean winter annual grass that has invaded Southwestern USA deserts. This study evaluated interactions among 13 Sonoran Desert annual species at four densities of red brome from 0 to the equivalent of 1200 plants ma??2. We examined these interactions at low (3 I?g) and high (537 I?g NO3a?? g soila??1) nitrogen (N) to evaluate the relative effects of soil N level on survival and growth of native annuals and red brome. Red brome did not affect emergence or survival of native annuals, but significantly reduced growth of natives, raising concerns about effects of this exotic grass on the fecundity of these species. Differences in growth of red brome and of the three dominant non nitrogen-fixing native annuals at the two levels of soil N were similar. Total species biomass of red brome was reduced by 83% at low, compared to high, N levels, whereas that of the three native species was reduced by from 42 to 95%. Mean individual biomass of red brome was reduced by 87% at low, compared to high, N levels, whereas that of the three native species was reduced by from 72 to 89%.

  18. Two millennia of soil dynamics derived from ancient desert terraces using high resolution 3-D data

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    Filin, Sagi; Arav, Reuma; Avni, Yoav

    2017-04-01

    Large areas in the arid southern Levant are dotted with ancient terrace-based agriculture systems which were irrigated by runoff harvesting techniques. They were constructed and maintained between the 3rd - 9th centuries AD and abandoned in the 10th century AD. During their 600 years of cultivation, these terraces documented the gradual aggradation of alluvial soils, erosion processes within the drainage basins, as well as flashflood damage. From their abandonment and onwards, they documented 1000 years and more of land degradation and soil erosion processes. Examination of these installations presents an opportunity to study natural and anthropogenic induced changes over almost two millennia. On a global scale, such an analysis is unique as it is rare to find intact manifestations of anthropogenic influences over such time-scales because of landscape dynamics. It is also rare to find a near millennia documentation of soil erosion processes. We study in this paper the aggradation processes within intact agriculture plots in the region surrounding the world heritage Roman-Byzantine ancient city of Avdat, Negev Highlands. We follow the complete cycle of the historical desert agriculture, from the configuration pre-dating the first anthropogenic intervention, through the centuries of cultivation, and up to the present erosion phase, which spans over more than a millennium. We use high resolution 3-D laser scans to document the erosion and the environmental dynamics during these two millennia. The high-resolution data is then utilized to compute siltation rates as well as erosion rates. The long-term measures of soil erosion and land degradation we present here significantly improve our understanding of the mechanism of long-term environmental change acting in arid environments. For sustainable desert inhabitation, the study offers insights into better planning of modern agriculture in similar zones as well as insights on strategies needed to protect such historical

  19. Biological Soil Crusts Influence Hydrologic Function Differently in Various Deserts And Future Climate and Land Use will Affect These Relationships

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    Belnap, J.; Wilcox, B.; Barger, N.; Herrick, J.; van Soyoc, M.

    2012-04-01

    Biological soil crusts (biocrusts) can completely cover plant interspaces in dryland regions, and can constitute 70% or more of the living ground cover. In these areas, where precipitation is low and soils have low fertility, native plants often rely on intact biological soil crusts to provide water and nutrient flow to the broadly scattered vegetation. In cool desert systems, well-developed biocrusts (dominated by lichens and mosses) roughen the soil surface, increasing residence time of surface water flow. This results in increased and relatively homogenous infiltration of water into the soils. Filaments associated with cyanobacteria, fungi, mosses and lichens increase aggregate formation and stabilize soils, thus reducing sediment production, with well-developed biocrusts conferring much more stability on soils than less developed cyanobacterial dominated biocrusts. In hot and hyper-arid desert systems, biocrusts are generally less developed and dominated by cyanobacteria. These biocrusts generally increase runoff from plant interspaces to downslope vegetation. While reduced infiltration may seem to be negative, it can actually be advantageous to the downslope plants, as they may require small watersheds above them to provide the needed amount of water and nutrients required for their growth. Thus, infiltration and nutrient additions are more heterogenous than in cool desert systems. Soil surface disturbance and climate change have the potential to dramatically alter the species composition and thereby function of biological soil crusts in different deserts. Compressional disturbances results in reduced cover and a loss of lichen and moss species. Changes in climate regimes, such as an increase in temperature or a shift in the amount, timing, or intensity of rainfall, will influence the composition and physiological functioning of biological soil crusts, as various crust components have different photosynthetic and respiration responses to temperature and

  20. Using Agricultural Residue Biochar to Improve Soil Quality of Desert Soils

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    Yunhe Zhang

    2016-03-01

    Full Text Available A laboratory study was conducted to test the effects of biochars made from different feedstocks on soil quality indicators of arid soils. Biochars were produced from four locally-available agricultural residues: pecan shells, pecan orchard prunings, cotton gin trash, and yard waste, using a lab-scale pyrolyzer operated at 450 °C under a nitrogen environment and slow pyrolysis conditions. Two local arid soils used for crop production, a sandy loam and a clay loam, were amended with these biochars at a rate of 45 Mg·ha−1 and incubated for three weeks in a growth chamber. The soils were analyzed for multiple soil quality indicators including soil organic matter content, pH, electrical conductivity (EC, and available nutrients. Results showed that amendment with cotton gin trash biochar has the greatest impact on both soils, significantly increasing SOM and plant nutrient (P, K, Ca, Mn contents, as well as increasing the electrical conductivity, which creates concerns about soil salinity. Other biochar treatments significantly elevated soil salinity in clay loam soil, except for pecan shell biochar amended soil, which was not statistically different in EC from the control treatment. Generally, the effects of the biochar amendments were minimal for many soil measurements and varied with soil texture. Effects of biochars on soil salinity and pH/nutrient availability will be important considerations for research on biochar application to arid soils.

  1. Diversity and feeding strategies of soil microfauna along elevation gradients in Himalayan cold deserts.

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    Miloslav Devetter

    Full Text Available High-elevation cold deserts in Tibet and Himalaya are one of the most extreme environments. One consequence is that the diversity of macrofauna in this environment is often limited, and soil microorganisms have a more influential role in governing key surface and subsurface bioprocesses. High-elevation soil microfauna represent important components of cold ecosystems and dominant consumers of microbial communities. Still little is known about their diversity and distribution on the edge of their reproductive and metabolic abilities. In this study, we disentangle the impact of elevation and soil chemistry on diversity and distribution of rotifers, nematodes and tardigrades and their most frequent feeding strategies (microbial filter-feeders, bacterivores, fungivores, root-fungal feeders, omnivores along two contrasting altitudinal gradients in Indian NW Himalaya (Zanskar transect from 3805 to 4714 m a.s.l. and southwestern Tibet (Tso Moriri transect from 4477 to 6176 m a.s.l., using a combination of multivariate analysis, variation partitioning and generalized additive models. Zanskar transect had higher precipitation, soil moisture, organic matter and available nutrients than dry Tso Moriri transect. In total, 40 species of nematodes, 19 rotifers and 1 tardigrade were discovered. Species richness and total abundance of rotifers and nematodes showed mid-elevation peaks in both investigated transects. The optimum for rotifers was found at higher elevation than for nematodes. Diversity and distribution of soil microfauna was best explained by soil nitrogen, phosphorus and organic matter. More fertile soils hosted more diverse and abundant faunal communities. In Tso Moriri, bacterivores represented 60% of all nematodes, fungivores 35%, root-fungal feeders 1% and omnivores 3%. For Zanskar the respective proportions were 21%, 13%, 56% and 9%. Elevational optima of different feeding strategies occurred in Zanskar in one elevation zone (4400-4500 m

  2. Biological soil crusts are the main contributor to winter soil respiration in a temperate desert ecosystem of China

    Science.gov (United States)

    He, M. Z.

    2012-04-01

    Aims Biological soil crusts (BSCs) are a key biotic component of desert ecosystems worldwide. However, most studies carried out to date on carbon (fluxes) in these ecosystems, such as soil respiration (RS), have neglected them. Also, winter RS is reported to be a significant component of annual carbon budget in other ecosystems, however, we have less knowledge about winter RS of BSCs in winter and its contribution to carbon cycle in desert regions. Therefore, the specific objectives of this study were to: (i) quantify the effects of different BSCs types (moss crust, algae crust, physical crust) on the winter RS; (ii) explore relationships of RS against soil temperature and water content for different BSCs, and (iii) assess the relative contribution of BSCs to the annual amount of C released by RS at desert ecosystem level. Methods Site Description The study sites are located at the southeast fringe of the Tengger Desert in the Shapotou region of the Ningxia Hui Autonomous Region [37°32'N and 105°02'E, at 1340 m above mean sea level (a.m.s.l.)], western China. The mean daily temperature in January is -6.9°C , while it is 24.3°C in July. The mean annual precipitation is 186 mm, approximately 80% of which falls between May and September. The annual potential evaporation is 2800 mm. The landscape of the Shapotou region is characterized by large and dense reticulate barchans chains of sand dunes that migrate south-eastward at a velocity of 3-6 m per year. The soil is loose, infertile and mobile and can thus be classified as orthic sierozem and Aeolian sandy soil. Additionally, the soil has a consistent gravimetric water content that ranges from 3 to 4%. The groundwater in the study area is too deep (>60 m) to support large areas of the native vegetation cover; therefore, precipitation is usually the only source of freshwater. The predominant native plants are Hedysarum scoparium Fisch. and Agriophyllum squarrosum Moq., Psammochloa cillosa Bor, which scattered

  3. Large-scale downy brome treatments alter plant-soil relationships and promote perennial grasses in salt desert shrublands

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    The interrelationship between invasive annual grass abundance and soil resource availability varies spatially and temporally within ecosystems and may be altered by land treatments. We evaluated these relationships in two salt desert landscapes where the local abundance of Bromus tectorum L. (downy...

  4. Microbial Response to UV Exposure and Nitrogen Limitation in Desert Soil Crusts

    Science.gov (United States)

    Fulton, J. M.; Van Mooy, B. A.

    2016-12-01

    Microbiotic soil crusts have diverse biomarker distributions and C and N stable isotopic compositions that covary with soil type. Sparse plant cover and the relative lack of soil disturbance in arid/semi-arid landscapes allows populations of soil cyanobacteria to develop along with fungi and heterotrophic bacteria. Microbial communities in this extreme environment depend in part on the production of scytonemin, a UV protective pigment, by cyanobacteria near the top of the crust. N limitation of microbial growth also affects soil crust population dynamics, increasing the requirement of N2fixation by diazotrophic cyanobacteria. We collected 56 soil crust samples from 27 locations throughout the Great Salt Lake Desert, including four transects spanning high-elevation, erosion-dominated soils to lower elevation soils dominated by silt-accumulation. Erosion-dominated soil surfaces included rounded gravel and cobbles; in the interstices there were poorly-developed microbiotic crusts on sandy loam with low δ15N values near 0‰ that point toward microbial growth dependent on cyanobacterial N2 fixation. Nutrients regenerated by heterotrophic bacteria may have been eroded from the system, providing a positive feedback for N2 fixation. High scytonemin:chlorophyll a ratios suggest that cyanobacteria required enhanced protection from UV damage in these crusts. A similar increase in scytonemin:chlorophyll a ratio during soil crust rehydration experiments also points toward the importance of UV protection. Glycolipid:phospholipid ratios were lowest where N2 fixation was favored, however, suggesting that the cyanobacterial population was relatively small, possibly because of the metabolic cost of N2fixation. Microbiotic crusts on silt loam soils, on the other hand, had higher δ15N values between 3.5 and 7.8‰, consistent with heterotrophic growth and nutrient recycling. Lower scytonemin:chlorophyll a ratios suggest that relatively high photosynthetic activity was supported in

  5. Heterogeneity and loss of soil nutrient elements under aeolian processes in the Otindag Desert, China

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    Li, Danfeng; Wang, Xunming; Lou, Junpeng; Liu, Wenbin; Li, Hui; Ma, Wenyong; Jiao, Linlin

    2018-02-01

    The heterogeneity of the composition of surface soils that are affected by aeolian processes plays important roles in ecological evolution and the occurrence of aeolian desertification in fragile ecological zones, but the associated mechanisms are poorly understood. Using field investigation, wind tunnel experiments, and particle size and element analyses, we discuss the variation in the nutrient elements of surface soils that forms in the presence of aeolian processes of four vegetation species (Caragana microphylla Lam, Artemisia frigida Willd. Sp. Pl., Leymus chinensis (Trin.) Tzvel. and Stipa grandis P. Smirn) growing in the Otindag Desert, China. These four vegetation communities correspond to increasing degrees of degradation. A total of 40 macro elements, trace elements, and oxides were measured in the surface soil and in wind-transported samples. The results showed that under the different degradation stages, the compositions and concentrations of nutrients in surface soils differed for the four vegetation species. Aeolian processes may cause higher heterogeneity and higher loss of soil nutrient elements for the communities of Artemisia frigida Willd. Sp. Pl., Leymus chinensis (Trin.) Tzvel, and Stipa grandis P. Smirn than for the Caragana microphylla Lam community. There was remarkable variation in the loss of nutrients under different aeolian transportation processes. Over the past several decades, the highest loss of soil elements occurred in the 1970s, whereas the loss from 2011 to the present was generally 4.0% of that in the 1970s. These results indicate that the evident decrease in nutrient loss has played an important role in the rehabilitation that has occurred in the region recently.

  6. Assessing Organic Carbon Stabilization in Chihuahuan Desert Soils Using Sequential Density Fractionation

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    Throop, H. L.; Lajtha, K.; Sollins, P.; Monger, H. C.

    2008-12-01

    Stabilization of organic matter on mineral surfaces strongly affects rates of soil organic matter (SOM) accumulation and turnover. Controls over SOM are of particular interest in arid and semi-arid systems where the abundance of woody plants has increased globally over the past century. This proliferation of woody plants may lead to significant soil organic carbon (SOC) accumulation, although a large degree of uncertainty exists in the direction and magnitude of SOC pool responses to woody encroachment. We hypothesized that SOC accumulation from woody encroachment would be primarily due to increased light fraction C pools and also that soil parent material would strongly influence SOC stabilization. Previous studies at mesic sites have used sequential density fractionation to separate soil particles based on mineralology and to explore C stabilization via organo-mineral complexes that might affect particle density. We explored mechanisms of SOM stabilization in arid soils by density fractionating four Chihuahuan Desert soils. The soils differed in parent material (igneous vs. limestone alluvium), landscape position (bajada vs. basin floor), and dominant vegetative cover (intact grassland vs. shrubland in former grassland). We used sodium polytungstate to separate soils into seven fractions with density cutoffs of 1.68, 1.87, 1.98, 2.18, 2.47, 2.66, and >2.66 g cm-3 (hereafter F1-F7, respectively). Concentrations of C and N generally decreased with increasing particle density. Similar to findings from mesic sites, C:N decreased with increasing particle density. While F1 accounted for a small proportion of total mass (0.29-2.61%), a large proportion of total C was present in this fraction (25.3-39.2% of total) due to the high [C] (21-38%C). Carbon in these light fractions is likely to be primarily recently-derived plant material that turns over rapidly and is not stabilized on mineral surfaces. The basin floor sites contained a large proportion of the total C in F5

  7. Autochthonous bioaugmentation with environmental samples rich in hydrocarbonoclastic bacteria for bench-scale bioremediation of oily seawater and desert soil.

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    Ali, Nedaa; Dashti, Narjes; Salamah, Samar; Al-Awadhi, Husain; Sorkhoh, Naser; Radwan, Samir

    2016-05-01

    Oil-contaminated seawater and desert soil batches were bioaugmented with suspensions of pea (Pisum sativum) rhizosphere and soil with long history of oil pollution. Oil consumption was measured by gas-liquid chromatography. Hydrocarbonoclastic bacteria in the bioremediation batches were counted using a mineral medium with oil vapor as a sole carbon source and characterized by their 16S ribosomal RNA (rRNA)-gene sequences. Most of the oil was consumed during the first 2-4 months, and the oil-removal rate decreased or ceased thereafter due to nutrient and oxygen depletion. Supplying the batches with NaNO3 (nitrogen fertilization) at a late phase of bioremediation resulted in reenhanced oil consumption and bacterial growth. In the seawater batches bioaugmented with rhizospheric suspension, the autochthonous rhizospheric bacterial species Microbacterium oxidans and Rhodococcus spp. were established and contributed to oil-removal. The rhizosphere-bioaugmented soil batches selectively favored Arthrobacter nitroguajacolicus, Caulobacter segnis, and Ensifer adherens. In seawater batches bioaugmented with long-contaminated soil, the predominant oil-removing bacterium was the marine species Marinobacter hydrocarbonoclasticus. In soil batches on the other hand, the autochthonous inhabitants of the long-contaminated soil, Pseudomonas and Massilia species were established and contributed to oil removal. It was concluded that the use of rhizospheric bacteria for inoculating seawater and desert soil and of bacteria in long-contaminated soil for inoculating desert soil follows the concept of "autochthonous bioaugmentation." Inoculating seawater with bacteria in long-contaminated soil, on the other hand, merits the designation "allochthonous bioaugmentation."

  8. Three-dimensional structure and cyanobacterial activity within a desert biological soil crust.

    Science.gov (United States)

    Raanan, Hagai; Felde, Vincent J M N L; Peth, Stephan; Drahorad, Sylvie; Ionescu, Danny; Eshkol, Gil; Treves, Haim; Felix-Henningsen, Peter; Berkowicz, Simon M; Keren, Nir; Horn, Rainer; Hagemann, Martin; Kaplan, Aaron

    2016-02-01

    Desert biological soil crusts (BSCs) are formed by adhesion of soil particles to polysaccharides excreted by filamentous cyanobacteria, the pioneers and main producers in this habitat. Biological soil crust destruction is a central factor leading to land degradation and desertification. We study the effect of BSC structure on cyanobacterial activity. Micro-scale structural analysis using X-ray microtomography revealed a vesiculated layer 1.5-2.5 mm beneath the surface in close proximity to the cyanobacterial location. Light profiles showed attenuation with depth of 1%-5% of surface light within 1 mm but also revealed the presence of 'light pockets', coinciding with the vesiculated layer, where the irradiance was 10-fold higher than adjacent crust parts at the same depth. Maximal photosynthetic activity, examined by O2 concentration profiles, was observed 1 mm beneath the surface and another peak in association with the 'light pockets'. Thus, photosynthetic activity may not be visible to currently used remote sensing techniques, suggesting that BSCs' contribution to terrestrial productivity is underestimated. Exposure to irradiance higher than 10% full sunlight diminished chlorophyll fluorescence, whereas O2 evolution and CO2 uptake rose, indicating that fluorescence did not reflect cyanobacterial photosynthetic activity. Our data also indicate that although resistant to high illumination, the BSC-inhabiting cyanobacteria function as 'low-light adapted' organisms. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

  9. Biodiversity of species of Aspergillus section Fumigati in semi-desert soils in Argentina.

    Science.gov (United States)

    Giusiano, Gustavo E; Piontelli, Eduardo; Fernández, Mariana S; Mangiaterra, Magdalena L; Cattana, María E; Kocsubé, Sándor; Varga, János

    The distribution of Aspergillus species in soil has been widely studied all over the world. The aim of this study was the phenotypic and genotypic characterization of species Aspergillus belonging to section Fumigati present in soils from two Argentinian semi-desert areas having different geological conditions. Altogether, 23 isolates belonging to Aspergillus section Fumigati were recovered and identified using a polyphasic approach including phenotypic and molecular identifications. Aspergillus fumigatus sensu stricto and Aspergillus fumigatiaffinis had the highest frequency, of occurrence while isolates closely related to Aspergillus udagawae and Aspergillus felis were rarely observed. A. fumigatiaffinis and isolates closer to A. udagawae were isolated for the first time from Argentinian soils and this is the first report on the occurrence of species belonging to the A. felis clade in South America. Recent scientific interests in biodiversity, as well as the increasing importance of aspergilli as causative agents of human and animal diseases increase the need to understand the diversity and occurrence of these fungi in nature. Copyright © 2017 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

  10. Spatial variation in soil active-layer geochemistry across hydrologic margins in polar desert ecosystems

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    J. E. Barrett

    2009-12-01

    Full Text Available Polar deserts are characterized by severe spatial-temporal limitations of liquid water. In soil active layers of the Antarctic Dry Valleys, liquid water is infrequently available over most of the arid terrestrial landscape. However, soils on the margins of glacial melt-water streams and lakes are visibly wet during the brief Austral summer when temperatures permit the existence of liquid water. We examined the role of these hydrologic margins as preferential zones for the transformation and transport of nutrient elements and solutes in an environment where geochemical weathering and biological activity is strictly limited by the dearth of liquid water. We report on hydropedological investigations of aquatic-terrestrial transition zones adjacent to 11 stream and lake systems in the Antarctic Dry Valleys. Our results show that wetted zones extended 1–11 m from the edges of lotic and lentic systems. While capillary demand and surface evaporation drive a one-way flux of water through these zones, the scale of these transition zones is determined by the topography and physical characteristics of the surrounding soils. Nutrient concentrations and fluxes appear to be influenced by both the hydrology and microbial-mediated biogeochemical processes. Salt concentrations are enriched near the distal boundary of the wetted fronts due to evapo-concentration of pore water in lake margin soils, while organic matter, ammonium and phosphate concentrations are highest in stream channel sediments where potential for biological activity is greatest. Thus, in the Antarctic Dry Valleys, intermittently wet soils on the margins of streams and lakes are important zones of both geochemical cycling and biological activity.

  11. Experimental and numerical investigations of soil water balance at the hinterland of the Badain Jaran Desert for groundwater recharge estimation

    Science.gov (United States)

    Hou, Lizhu; Wang, Xu-Sheng; Hu, Bill X.; Shang, Jie; Wan, Li

    2016-09-01

    Quantification of groundwater recharge from precipitation in the huge sand dunes is an issue in accounting for regional water balance in the Badain Jaran Desert (BJD) where about 100 lakes exist between dunes. In this study, field observations were conducted on a sand dune near a large saline lake in the BJD to investigate soil water movement through a thick vadose zone for groundwater estimation. The hydraulic properties of the soils at the site were determined using in situ experiments and laboratory measurements. A HYDRUS-1D model was built up for simulating the coupling processes of vertical water-vapor movement and heat transport in the desert soil. The model was well calibrated and validated using the site measurements of the soil water and temperature at various depths. Then, the model was applied to simulate the vertical flow across a 3-m-depth soil during a 53-year period under variable climate conditions. The simulated flow rate at the depth is an approximate estimation of groundwater recharge from the precipitation in the desert. It was found that the annual groundwater recharge would be 11-30 mm during 1983-2012, while the annual precipitation varied from 68 to 172 mm in the same period. The recharge rates are significantly higher than those estimated from the previous studies using chemical information. The modeling results highlight the role of the local precipitation as an essential source of groundwater in the BJD.

  12. Atmospheric giant particles (iberulites) from African desert soils and human health

    Science.gov (United States)

    Párraga, Jesús; Delgado, Gabriel; Bech, Jaume; Martín-García, Juan Manuel; Delgado, Rafael

    2013-04-01

    Earth is twice as dusty as in 19th century. The amount of soil dust in the Earth's atmosphere has doubled over the last century. The circum-Mediterranean area has one of the highest dust accretion rates in the world. The larger deserts (Sahara, Gobi, Badai Jaran, etc.) are the primary sources of mobilized desert-dust top soil that move great distances through the troposphere each year. Erosion, atmospheric transport, and dust-sized soil particles deposition to earth's surface are important process in aeolian environments. Atmospheric dust is associated to global climate change. Iberulites are giant microspherulitic particles (87.9 × 27.6 µm) rounded and reddish, generated in the atmosphere (troposphere) by coalescence of smaller particles, finally falling to the earth's surface. The name comes from the Iberian Peninsula where they were discovered. An iberulite is a co-association with axial geometry, consisting of well-defined mineral grains, together with non-crystalline compounds, structured around a coarse-grained core with a smectite rind, only one vortex and pinkish color formed in the troposphere by complex aerosol-water-gas interactions. Sedimentable dust ("dry deposition") in the city of Granada (Spain) for 17 African dust intrusion events occurring in the summer months of 2010 has been studied. In all samples were detected (SEM, stereomicroscope) iberulites. Total dust and the iberulites are composed mainly by mineral particles of different nature (XRD and SEM-EDX) and size less than 10µm (laser technique), implying dangerousness by inhalation. In the total dust the dominant mineral is dolomite [CaMg(CO3)2], abundant in the surroundings of the city; in the iberulites dominates the quartz (SiO2), which indicates Saharan origin. The iberulites and the total dust are associated with metals (ICP-MS) that have a capacity to transport electrons with a high toxic potential in the body. The concentration of Cu and Pb in total dust were 5 and 2.5 times higher

  13. Desert soil clay content estimation using reflectance spectroscopy preprocessed by fractional derivative.

    Science.gov (United States)

    Wang, Jingzhe; Tiyip, Tashpolat; Ding, Jianli; Zhang, Dong; Liu, Wei; Wang, Fei; Tashpolat, Nigara

    2017-01-01

    Effective pretreatment of spectral reflectance is vital to model accuracy in soil parameter estimation. However, the classic integer derivative has some disadvantages, including spectral information loss and the introduction of high-frequency noise. In this paper, the fractional order derivative algorithm was applied to the pretreatment and partial least squares regression (PLSR) was used to assess the clay content of desert soils. Overall, 103 soil samples were collected from the Ebinur Lake basin in the Xinjiang Uighur Autonomous Region of China, and used as data sets for calibration and validation. Following laboratory measurements of spectral reflectance and clay content, the raw spectral reflectance and absorbance data were treated using the fractional derivative order from the 0.0 to the 2.0 order (order interval: 0.2). The ratio of performance to deviation (RPD), determinant coefficients of calibration ([Formula: see text]), root mean square errors of calibration (RMSEC), determinant coefficients of prediction ([Formula: see text]), and root mean square errors of prediction (RMSEP) were applied to assess the performance of predicting models. The results showed that models built on the fractional derivative order performed better than when using the classic integer derivative. Comparison of the predictive effects of 22 models for estimating clay content, calibrated by PLSR, showed that those models based on the fractional derivative 1.8 order of spectral reflectance ([Formula: see text] = 0.907, RMSEC = 0.425%, [Formula: see text] = 0.916, RMSEP = 0.364%, and RPD = 2.484 ≥ 2.000) and absorbance ([Formula: see text] = 0.888, RMSEC = 0.446%, [Formula: see text] = 0.918, RMSEP = 0.383% and RPD = 2.511 ≥ 2.000) were most effective. Furthermore, they performed well in quantitative estimations of the clay content of soils in the study area.

  14. Diurnal Freeze-Thaw Cycles Modify Winter Soil Respiration in a Desert Shrub-Land Ecosystem

    Directory of Open Access Journals (Sweden)

    Peng Liu

    2016-07-01

    Full Text Available Winter soil respiration (Rs is becoming a significant component of annual carbon budgets with more warming in winter than summer. However, little is known about the controlling mechanisms of winter Rs in dryland. We made continuous measurements of Rs in four microsites (non-crust (BS, lichen (LC, moss (MC, and a mixture of moss and lichen (ML in a desert shrub-land ecosystem northern China, to investigate the causes of Rs dynamics in winter. The mean winter Rs ranged from 0.10 to 0.17 µmol CO2 m−2·s−1 across microsites, with the highest value in BS. Winter Q10 (known as the increase in respiration rate per 10 °C increase in temperature values (2.8–19 were much higher than those from the growing season (1.5. Rs and Q10 were greatly enhanced in freeze-thaw cycles compared to frozen days. Diurnal patterns of Rs between freeze-thaw and frozen days differed. Although the freeze-thaw period was relatively short, its cumulative Rs contributed significantly to winter Rs. The presence of biocrust might induce lower temperature, thus having fewer freeze-thaw cycles relative to bare soil, leading to the lower Rs for microsites with biocrusts. In conclusion, winter Rs in drylands was sensitive to soil temperature (Ts and Ts-induced freeze-thaw cycles. The temperature impact on Rs varied among soil cover types. Winter Rs in drylands may become more important as the climate is continuously getting warmer.

  15. Selected Micrometeorological and Soil-Moisture Data at Amargosa Desert Research Site in Nye County Near Beatty, Nevada, 1998-2000

    National Research Council Canada - National Science Library

    Johnson, Michael J; Mayers, Charles J; Andraski, Brian J

    2002-01-01

    Selected micrometeorological and soil moisture data were collected at the Amargosa Desert Research Site adjacent to a low-level radioactive waste and hazardous chemical waste facility near Beatty, Nev., 1998 2000...

  16. EDTA addition enhances bacterial respiration activities and hydrocarbon degradation in bioaugmented and non-bioaugmented oil-contaminated desert soils.

    Science.gov (United States)

    Al Kharusi, Samiha; Abed, Raeid M M; Dobretsov, Sergey

    2016-03-01

    The low number and activity of hydrocarbon-degrading bacteria and the low solubility and availability of hydrocarbons hamper bioremediation of oil-contaminated soils in arid deserts, thus bioremediation treatments that circumvent these limitations are required. We tested the effect of Ethylenediaminetetraacetic acid (EDTA) addition, at different concentrations (i.e. 0.1, 1 and 10 mM), on bacterial respiration and biodegradation of Arabian light oil in bioaugmented (i.e. with the addition of exogenous alkane-degrading consortium) and non-bioaugmented oil-contaminated desert soils. Post-treatment shifts in the soils' bacterial community structure were monitored using MiSeq sequencing. Bacterial respiration, indicated by the amount of evolved CO2, was highest at 10 mM EDTA in bioaugmented and non-bioaugmented soils, reaching an amount of 2.2 ± 0.08 and 1.6 ± 0.02 mg-CO2 g(-1) after 14 days of incubation, respectively. GC-MS revealed that 91.5% of the C14-C30 alkanes were degraded after 42 days when 10 mM EDTA and the bacterial consortium were added together. MiSeq sequencing showed that 78-91% of retrieved sequences in the original soil belonged to Deinococci, Alphaproteobacteria, Gammaproteobacteia and Bacilli. The same bacterial classes were detected in the 10 mM EDTA-treated soils, however with slight differences in their relative abundances. In the bioaugmented soils, only Alcanivorax sp. MH3 and Parvibaculum sp. MH21 from the exogenous bacterial consortium could survive until the end of the experiment. We conclude that the addition of EDTA at appropriate concentrations could facilitate biodegradation processes by increasing hydrocarbon availability to microbes. The addition of exogenous oil-degrading bacteria along with EDTA could serve as an ideal solution for the decontamination of oil-contaminated desert soils. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Life at the hyperarid margin: novel bacterial diversity in arid soils of the Atacama Desert, Chile

    Science.gov (United States)

    Neilson, Julia W.; Quade, Jay; Ortiz, Marianyoly; Nelson, William M.; Legatzki, Antje; Tian, Fei; LaComb, Michelle; Betancourt, Julio L.; Wing, Rod A.; Soderlund, Carol A.; Maier, Raina M.

    2012-01-01

    Nearly half the earth's surface is occupied by dryland ecosystems, regions susceptible to reduced states of biological productivity caused by climate fluctuations. Of these regions, arid zones located at the interface between vegetated semiarid regions and biologically unproductive hyperarid zones are considered most vulnerable. The objective of this study was to conduct a deep diversity analysis of bacterial communities in unvegetated arid soils of the Atacama Desert, to characterize community structure and infer the functional potential of these communities based on observed phylogenetic associations. A 454-pyrotag analysis was conducted of three unvegetated arid sites located at the hyperarid-arid margin. The analysis revealed communities with unique bacterial diversity marked by high abundances of novel Actinobacteria and Chloroflexi and low levels of Acidobacteria and Proteobacteria, phyla that are dominant in many biomes. A 16S rRNA gene library of one site revealed the presence of clones with phylogenetic associations to chemoautotrophic taxa able to obtain energy through oxidation of nitrite, carbon monoxide, iron, or sulfur. Thus, soils at the hyperarid margin were found to harbor a wealth of novel bacteria and to support potentially viable communities with phylogenetic associations to non-phototrophic primary producers and bacteria capable of biogeochemical cycling.

  18. Resource islands predict the distribution of heterotrophic bacteria in chihuahuan desert soils.

    Science.gov (United States)

    Herman, R P; Provencio, K R; Herrera-Matos, J; Torrez, R J

    1995-05-01

    The resource island hypothesis predicts that soil resources such as nitrogen, phosphorus, and water will be distributed evenly in grasslands but have a patchy distribution focused around plants in shrublands. This hypothesis predicts that microorganism numbers will follow resources and be (i) evenly distributed in grasslands, (ii) concentrated around individual plants in shrublands, and (iii) higher where resources are higher when comparing the same vegetation type. This study enumerated total heterotrophic bacteria and a subset of these, the nitrogen-efficient guild (NEG), in three shrublands (playa fringe mesquite, tar bush, and creosote) and two grasslands (playa and bajada). Both heterotrophs and NEG members followed the distribution pattern predicted by the resource island hypothesis. There were no significant differences in heterotroph or NEG numbers comparing at-plant and interplant samples for both the playa and bajada grasslands. Furthermore, populations were generally higher in nutrient-rich playa grasslands than nutrient-poor bajada grasslands. In contrast, both heterotroph and NEG numbers were higher at shrubs than between shrubs in all three shrub sites. These results suggest that resource abundance in resource islands predicts the distribution of heterotrophic bacterial numbers in desert soils.

  19. Xeropreservation of Functionalized Lipid Biomarkers in Hyperarid Soils in the Atacama Desert

    Science.gov (United States)

    Wilhelm, Mary Beth; Davila, Alfonso F.; Eigenbrode, Jennifer L.; Parenteau, Mary N.; Jahnke, Linda L.; Liu, Xiao-Lei; Summons, Rogers E.; Wray, James J.; Stamos, Brian N.; O'Reilly, Shane S.; hide

    2016-01-01

    Our understanding of long-term organic matter preservation comes mostly from studies in aquatic systems. In contrast, taphonomic processes in extremely dry environments are relatively understudied and are poorly understood. We investigated the accumulation and preservation of lipid biomarkers in hyperarid soils in the Yungay region of the Atacama Desert. Lipids from seven soil horizons in a 2.5 m vertical profile were extracted and analyzed using GC-MS and LC-MS. Diagnostic functionalized lipids and geolipids were detected and increased in abundance and diversity with depth. Deeper clay units contain fossil organic matter (radiocarbon dead) that has been protected from rainwater since the onset of hyperaridity. We show that these clay units contain lipids in an excellent state of structural preservation with functional groups and unsaturated bonds in carbon chains. This indicates that minimal degradation of lipids has occurred in these soils since the time of their deposition between greater than 40,000 and 2 million years ago. The exceptional structural preservation of biomarkers is likely due to the long-term hyperaridity that has minimized microbial and enzymatic activity, a taphonomic process we term xeropreservation (i.e., preservation by drying). The degree of biomarker preservation allowed us to reconstruct major changes in ecology in the Yungay region that reflect a shift in hydrological regime from wet to dry since the early Quaternary. Our results suggest that hyperarid environments, which comprise 7.5 percent of the continental landmass, could represent a rich and relatively unexplored source of paleobiological informationon Earth.

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

    OpenAIRE

    Rakesh Mogul; Parag Vaishampayan; Mina Bashir; McKay, Chris P.; Keith Schubert; Rosalba Bornaccorsi; Ernesto Gomez; Sneha Tharayil; Geoffrey Payton; Juliana Capra; Jessica Andaya; Leonard Bacon; Emily Bargoma; David Black; Katie Boos

    2017-01-01

    In this study, we expand upon the biogeography of biological soil crusts (BSCs) and provide molecular insights into the microbial community and biochemical dynamics along the vertical BSC column structure, and across a transect of increasing BSC surface coverage in the central Mojave Desert, CA, United States. Next generation sequencing reveals a bacterial community profile that is distinct among BSCs in the southwestern United States. Distribution of major phyla in the BSC topsoils included ...

  1. Carbon and nitrogen fixation differ between successional stages of biological soil crusts in the Colorado Plateau and Chihuahuan Desert

    Science.gov (United States)

    Housman, D.C.; Powers, H.H.; Collins, A.D.; Belnap, J.

    2006-01-01

    Biological soil crusts (cyanobacteria, mosses and lichens collectively) perform essential ecosystem services, including carbon (C) and nitrogen (N) fixation. Climate and land-use change are converting later successional soil crusts to early successional soil crusts with lower C and N fixation rates. To quantify the effect of such conversions on C and N dynamics in desert ecosystems we seasonally measured diurnal fixation rates in different biological soil crusts. We classified plots on the Colorado Plateau (Canyonlands) and Chihuahuan Desert (Jornada) as early (Microcoleus) or later successional (Nostoc/Scytonema or Placidium/Collema) and measured photosynthesis (Pn), nitrogenase activity (NA), and chlorophyll fluorescence (Fv/Fm) on metabolically active (moist) soil crusts. Later successional crusts typically had greater Pn, averaging 1.2-1.3-fold higher daily C fixation in Canyonlands and 2.4-2.8-fold higher in the Jornada. Later successional crusts also had greater NA, averaging 1.3-7.5-fold higher daily N fixation in Canyonlands and 1.3-25.0-fold higher in the Jornada. Mean daily Fv/Fm was also greater in later successional Canyonlands crusts during winter, and Jornada crusts during all seasons except summer. Together these findings indicate conversion of soil crusts back to early successional stages results in large reductions of C and N inputs into these ecosystems.

  2. Contrasting diel hysteresis between soil autotrophic and heterotrophic respiration in a desert ecosystem under different rainfall scenarios.

    Science.gov (United States)

    Song, Weimin; Chen, Shiping; Zhou, Yadan; Wu, Bo; Zhu, Yajuan; Lu, Qi; Lin, Guanghui

    2015-11-30

    Diel hysteresis occurs often between soil CO2 efflux (R(S)) and temperature, yet, little is known if diel hysteresis occurs in the two components of R(S), i.e., autotrophic respiration (R(A)) and heterotrophic respiration (R(H)), and how diel hysteresis will respond to future rainfall change. We conducted a field experiment in a desert ecosystem in northern China simulating five different scenarios of future rain regimes. Diel variations of soil CO2 efflux and soil temperature were measured on Day 6 and Day 16 following the rain addition treatments each month during the growing season. We found contrasting responses in the diel hysteresis of R(A) and R(H) to soil temperature, with a clockwise hysteresis loop for R(H) but a counter-clockwise hysteresis loop for R(A). Rain addition significantly increased the magnitude of diel hysteresis for both R(H) and R(A) on Day 6, but had no influence on either on Day 16 when soil moisture was much lower. These findings underline the different roles of biological (i.e. plant and microbial activities) and physical-chemical (e.g. heat transport and inorganic CO2 exchange) processes in regulating the diel hysteresis of R(A) and R(H), which should be considered when estimating soil CO2 efflux in desert regions under future rainfall regime.

  3. A comparison of soil climate and biological activity along an elevation gradient in the eastern Mojave Desert.

    Science.gov (United States)

    Amundson, R G; Chadwick, O A; Sowers, J M

    1989-08-01

    Soil temperature, moisture, and CO2 were monitored at four sites along an elevation transect in the eastern Mojave Desert from January to October, 1987. Climate appeared to be the major factor controlling CO2 partial pressures, primarily through its influence of rates of biological reactions, vegetation densities, and organic matter production. With increasing elevation, and increasing actual evapotranspiration, the organic C, plant density, and the CO2 content of the soils increased. Between January and May, soil CO2 concentrations at a given site were closely related to variations in soil temperature. In July and October, temperatures had little effect on CO2, presumably due to low soil moisture levels. Up to 75% of litter placed in the field in March was lost by October whereas, for the 3 lower elevations, less than 10% of the litter placed in the field in April was lost through decomposition processes.

  4. A comparison of soil climate and biological activity along an elevation gradient in the eastern Mojave Desert

    Science.gov (United States)

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

    1989-01-01

    Soil temperature, moisture, and CO2 were monitored at four sites along an elevation transect in the eastern Mojave Desert from January to October, 1987. Climate appeared to be the major factor controlling CO2 partial pressures, primarily through its influence of rates of biological reactions, vegetation densities, and organic matter production. With increasing elevation, and increasing actual evapotranspiration, the organic C, plant density, and the CO2 content of the soils increased. Between January and May, soil CO2 concentrations at a given site were closely related to variations in soil temperature. In July and October, temperatures had little effect on CO2, presumably due to low soil moisture levels. Up to 75% of litter placed in the field in March was lost by October whereas, for the 3 lower elevations, less than 10% of the litter placed in the field in April was lost through decomposition processes. ?? 1989 Springer-Verlag.

  5. Methanogens at the top of the world: occurrence and potential activity of methanogens in newly deglaciated soils in high-altitude cold deserts in the Western Himalayas

    Directory of Open Access Journals (Sweden)

    Katrin eAschenbach

    2013-12-01

    Full Text Available Methanogens typically occur in reduced anoxic environments. However, in recent studies it has been shown that many aerated upland soils, including desert soils also host active methanogens. Here we show that soil samples from high–altitude cold deserts in the western Himalayas (Ladakh, India produce CH4 after incubation as slurry under anoxic conditions at rates comparable to those of hot desert soils. Samples of matured soil from three different vegetation belts (arid, steppe, and subnival were compared with younger soils originating from frontal and lateral moraines of receding glaciers. While methanogenic rates were higher in the samples from matured soils, CH4 was also produced in the samples from the recently deglaciated moraines. In both young and matured soils, those covered by a biological soil crust (biocrust were more active than their bare counterparts. Isotopic analysis showed that in both cases CH4 was initially produced from H2/CO2 but later mostly from acetate. Analysis of the archaeal community in the in situ soil samples revealed a clear dominance of sequences related to Thaumarchaeota, while the methanogenic community comprised only a minor fraction of the archaeal community. Similar to other aerated soils, the methanogenic community was comprised almost solely of the genera Methanosarcina and Methanocella, and possibly also Methanobacterium in some cases. Nevertheless, approximately 103 gdw-1 soil methanogens were already present in the young moraine soil together with cyanobacteria. Our results demonstrate that Methanosarcina and Methanocella not only tolerate atmospheric oxygen but are also able to survive in these harsh cold environments. Their occurrence in newly deglaciated soils shows that they are early colonisers of desert soils, similar to cyanobacteria, and may play a role in the development of desert biocrusts.

  6. Methanogens at the top of the world: occurrence and potential activity of methanogens in newly deglaciated soils in high-altitude cold deserts in the Western Himalayas.

    Science.gov (United States)

    Aschenbach, Katrin; Conrad, Ralf; Reháková, Klára; Doležal, Jiří; Janatková, Kateřina; Angel, Roey

    2013-01-01

    Methanogens typically occur in reduced anoxic environments. However, in recent studies it has been shown that many aerated upland soils, including desert soils also host active methanogens. Here we show that soil samples from high-altitude cold deserts in the western Himalayas (Ladakh, India) produce CH4 after incubation as slurry under anoxic conditions at rates comparable to those of hot desert soils. Samples of matured soil from three different vegetation belts (arid, steppe, and subnival) were compared with younger soils originating from frontal and lateral moraines of receding glaciers. While methanogenic rates were higher in the samples from matured soils, CH4 was also produced in the samples from the recently deglaciated moraines. In both young and matured soils, those covered by a biological soil crust (biocrust) were more active than their bare counterparts. Isotopic analysis showed that in both cases CH4 was initially produced from H2/CO2 but later mostly from acetate. Analysis of the archaeal community in the in situ soil samples revealed a clear dominance of sequences related to Thaumarchaeota, while the methanogenic community comprised only a minor fraction of the archaeal community. Similar to other aerated soils, the methanogenic community was comprised almost solely of the genera Methanosarcina and Methanocella, and possibly also Methanobacterium in some cases. Nevertheless, ~10(3) gdw(-1) soil methanogens were already present in the young moraine soil together with cyanobacteria. Our results demonstrate that Methanosarcina and Methanocella not only tolerate atmospheric oxygen but are also able to survive in these harsh cold environments. Their occurrence in newly deglaciated soils shows that they are early colonizers of desert soils, similar to cyanobacteria, and may play a role in the development of desert biocrusts.

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

    Directory of Open Access Journals (Sweden)

    Alyxandra Pikus

    2012-10-01

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

  8. The role of water tracks in altering biotic and abiotic soil properties and processes in a polar desert in Antarctica

    Science.gov (United States)

    Ball, Becky A.; Levy, Joseph

    2015-02-01

    Groundwater discharge via water tracks is a largely unexplored passageway routing salts and moisture from high elevations to valley floors in the McMurdo Dry Valleys (MDV) of Antarctica. Given the influence that water tracks have on the distribution of liquid water in seasonally thawed Antarctic soils, it is surprising how little is known about their role in structuring biotic and abiotic processes this cold desert ecosystem. Particularly, it is unclear how soil biota will respond to the activation of new water tracks resulting from enhanced active layer thickening or enhanced regional snowmelt. In the MDV, water tracks are both wetter and more saline than the surrounding soils, constituting a change in soil habitat suitability for soil biology and therefore the ecological processes they carry out. To investigate the net impact that water tracks have on Dry Valley soil biology, and therefore the ecosystem processes for which they are responsible, we analyzed microbial biomass and activity in soils inside and outside of three water tracks and relate this to the physical soil characteristics. Overall, our results suggest that water tracks can significantly influence soil properties, which can further impact biological biovolume and both biotic and abiotic fluxes of CO2. However, the nature of its impact differs with water track, further suggesting that not all water tracks can be regarded the same.

  9. Development of bacterial communities in biological soil crusts along a revegetation chronosequence in the Tengger Desert, northwest China

    Science.gov (United States)

    Liu, Lichao; Liu, Yubing; Zhang, Peng; Song, Guang; Hui, Rong; Wang, Zengru; Wang, Jin

    2017-08-01

    Knowledge of structure and function of microbial communities in different successional stages of biological soil crusts (BSCs) is still scarce for desert areas. In this study, Illumina MiSeq sequencing was used to assess the compositional changes of bacterial communities in different ages of BSCs in the revegetation of Shapotou in the Tengger Desert. The most dominant phyla of bacterial communities shifted with the changed types of BSCs in the successional stages, from Firmicutes in mobile sand and physical crusts to Actinobacteria and Proteobacteria in BSCs, and the most dominant genera shifted from Bacillus, Enterococcus and Lactococcus to RB41_norank and JG34-KF-361_norank. Alpha diversity and quantitative real-time polymerase chain reaction (PCR) analysis indicated that bacterial richness and abundance reached their highest levels after 15 years of BSC development. Redundancy analysis showed that silt + clay content and total K were the prime determinants of the bacterial communities of BSCs. The results suggested that bacterial communities of BSCs recovered quickly with the improved soil physicochemical properties in the early stages of BSC succession. Changes in the bacterial community structure may be an important indicator in the biogeochemical cycling and nutrient storage in early successional stages of BSCs in desert ecosystems.

  10. Development of bacterial communities in biological soil crusts along a revegetation chronosequence in the Tengger Desert, northwest China

    Directory of Open Access Journals (Sweden)

    L. Liu

    2017-08-01

    Full Text Available Knowledge of structure and function of microbial communities in different successional stages of biological soil crusts (BSCs is still scarce for desert areas. In this study, Illumina MiSeq sequencing was used to assess the compositional changes of bacterial communities in different ages of BSCs in the revegetation of Shapotou in the Tengger Desert. The most dominant phyla of bacterial communities shifted with the changed types of BSCs in the successional stages, from Firmicutes in mobile sand and physical crusts to Actinobacteria and Proteobacteria in BSCs, and the most dominant genera shifted from Bacillus, Enterococcus and Lactococcus to RB41_norank and JG34-KF-361_norank. Alpha diversity and quantitative real-time polymerase chain reaction (PCR analysis indicated that bacterial richness and abundance reached their highest levels after 15 years of BSC development. Redundancy analysis showed that silt + clay content and total K were the prime determinants of the bacterial communities of BSCs. The results suggested that bacterial communities of BSCs recovered quickly with the improved soil physicochemical properties in the early stages of BSC succession. Changes in the bacterial community structure may be an important indicator in the biogeochemical cycling and nutrient storage in early successional stages of BSCs in desert ecosystems.

  11. Soil texture as an influence on the distribution of the desert seed-harvester ants Pogonomyrmex rugosus and Messor pergandei.

    Science.gov (United States)

    Johnson, Robert A

    1992-01-01

    Pogonomyrmex rugosus and Messor pergandei are ecologically similar species of desert seed-harvester ants that coexist in numerous areas throughout the Sonoran and Mohave Deserts. However, these two species also commonly segregate along physical gradients, with each species predominating in areas that differ in soil texture and/or topographic relief. Along gradients that included bajada and alluvial flat habitats, P. rugosus occurred alone in coarse-textured soils near mountains, while M. pergandei occurred alone in finer-textured soils further away. Conversely, along a vegetation gradient that included creosote bush and saltbush habitats, P. rugosus occurred alone in finer-textured soils than those occupied by either M. pergandei alone or both species in coexistence. However, in both situations clay content was significantly higher in areas occupied by P. rugosus alone, and at the latter site clay content was correlated with relative abundance of each species. Moreover, local distribution pattern of these two species may be related to the effects of clay on water retention, with retention being highest in areas occupied by P. rugosus alone. Differences in reproductive ecology may also affect these patterns as P. rugosus reproductive flights follow summer monsoon rains, while those of M. pergandei occur during the milder winter and spring.

  12. DESERT PAVEMENTS AND SOILS ON BASALTIC PYROCLASTIC DEPOSITS AT LATHROP WELLS AND RED CONE VOLCANOES, SOUTHERN NEVADA

    Energy Technology Data Exchange (ETDEWEB)

    G.A. Valentine; C.D. Harrington

    2005-08-10

    Formation of desert pavement and accretionary soils are intimately linked in arid environments such as the Mojave Desert. Well-sorted fallout scoria lapilli at Lathrop Wells (75-80 ky) and Red Cone ({approx}1 Ma) volcanoes (southern Nevada) formed an excellent starting material for pavement, allowing infiltration of eolian silt and fine sand that first clogs the pore space of underlying tephra and then aggrades and develops vesicular A (Av) horizons. Variations in original pyroclast sizes provide insight into minimum and maximum clast sizes that promote pavement and soil formation: pavement becomes ineffective when clasts can saltate under the strongest winds, while clasts larger than coarse lapilli are unable to form an interlocking pavement that promotes silt accumulation (necessary for Av development). Contrary to predictions that all pavements above altitudes of {approx}400 m would have been ''reset'' in their development after late Pleistocene vegetation advances (about 15 ka), the soils and pavements show clear differences in maturity between the two volcanoes. This indicates that either the pavement soils develop slowly over many 10,000's of years and then are very stable, or that, if they are disrupted by vegetation advances, subsequent pavements are reestablished with successively more mature characteristics.

  13. Quantifying soil surface change in degraded drylands: shrub encroachment and effects of fire and vegetation removal in a desert grassland

    Science.gov (United States)

    Sankey, Joel B.; Ravi, Sujith; Wallace, Cynthia S.A.; Webb, Robert H.; Huxman, Travis E.

    2012-01-01

    Woody plant encroachment, a worldwide phenomenon, is a major driver of land degradation in desert grasslands. Woody plant encroachment by shrub functional types ultimately leads to the formation of a patchy landscape with fertile shrub patches interspaced with nutrient-depleted bare soil patches. This is considered to be an irreversible process of land and soil degradation. Recent studies have indicated that in the early stages of shrub encroachment, when there is sufficient herbaceous connectivity, fires (prescribed or natural) might provide some reversibility to the shrub encroachment process by negatively affecting shrub demography and homogenizing soil resources across patches within weeks to months after burning. A comprehensive understanding of longer term changes in microtopography and spatial patterning of soil properties following fire in shrub-encroached grasslands is desirable. Here, we investigate the changes in microtopography with LiDAR (light detection and ranging), vegetation recovery, and spatial pattering of soil properties in replicated burned, clipped, and control areas in a shrub-grass transition zone in the northern Chihuahuan Desert four years after prescribed fire or clipping. Results indicate a greater homogeneity in soil, microtopography, and vegetation patterning on burned relative to clipped and control treatments. Findings provide further evidence that disturbance by prescribed fire may allow for reversal of the shrub encroachment process, if the event occurs in the early stages of the vegetation shift. Improved understanding of longer-term effects of fire and associated changes in soil patterning can inform the use and role of fire in the context of changing disturbance regimes and climate.

  14. Effects of Simulated Nitrogen Deposition on Soil Respiration in a Populus euphratica Community in the Ebinur Lake Area, a Desert Ecosystem of Northwestern China.

    Directory of Open Access Journals (Sweden)

    Xuemin He

    Full Text Available One of the primary limiting factors for biological activities in desert ecosystems is nitrogen (N. This study therefore examined the effects of N and investigated the responses of an arid ecosystem to global change. We selected the typical desert plant Populus euphratica in a desert ecosystem in the Ebinur Lake area to evaluate the effects of N deposition on desert soil respiration. Three levels of N deposition (0, 37.5 and 112.5 kg·N·ha-1·yr-1 were randomly artificially provided to simulate natural N deposition. Changes in the soil respiration rates were measured from July to September in both 2010 and 2013, after N deposition in April 2010. The different levels of N deposition affected the total soil N, soil organic matter, soil C/N ratio, microorganism number, and microbial community structure and function. However, variable effects were observed over time in relation to changes in the magnitude of N deposition. Simulated high N deposition significantly reduced the soil respiration rate by approximately 23.6±2.5% (P<0.05, whereas low N deposition significantly increased the soil respiration rate by approximately 66.7±2.7% (P<0.05. These differences were clearer in the final growth stage (September. The different levels of N deposition had little effect on soil moisture, whereas N deposition significantly increased the soil temperature in the 0-5 cm layer (P<0.05. These results suggest that in the desert ecosystem of the Ebinur Lake area, N deposition indirectly changes the soil respiration rate by altering soil properties.

  15. Dormancy cycling and persistence of seeds in soil of a cold desert halophyte shrub

    National Research Council Canada - National Science Library

    Cao, Dechang; Baskin, Carol C; Baskin, Jerry M; Yang, Fan; Huang, Zhenying

    2014-01-01

    .... In this study it was hypothesized that the long-lived halophytic cold desert shrub Kalidium gracile has a seed bank and dormancy cycling, which help restrict germination to a favourable time for seedling survival...

  16. The effect of long-term exposure to elevated CO2 on nitrogen gas emissions from Mojave Desert soils

    Science.gov (United States)

    McCalley, Carmody K.; Strahm, Brian D.; Sparks, Kimberlee L.; Eller, Allyson S. D.; Sparks, Jed P.

    2011-09-01

    In arid regions, emissions of nitrogen (N) gases are important to long-term soil fertility and regional atmospheric chemistry, making alterations in N gas emissions an important aspect of ecosystem response to climate change. Studies at the Nevada Desert FACE Facility suggest that rising atmospheric CO2 concentrations impact ecosystems N dynamics in the Mojave Desert; our objective was to identify whether those responses translate into changes in trace N gas emissions. We measured soil fluxes of reactive N gases (NO, NOy, NH3) and N2O in plots receiving long-term fumigation with ambient and elevated (550 ppm) CO2. Reactive N gas emissions were significantly lower under elevated CO2 during high soil moisture conditions in the spring and fall. The strongest responses occurred in the islands of fertility created by the dominant shrub Larrea tridentata, where fluxes were 3-5 ng N m-2 s-1 lower in elevated CO2 plots. Changes in total N gas emissions were driven by reduced NO and NH3 emissions, with smaller changes in NOy efflux and little to no production of N2O. Lower N gas emissions under elevated CO2 reflect changes in plant and microbial demand for N, suggesting increased uptake or immobilization coupled with decreased rates of N mineralization and nitrification. This response of N gas efflux to elevated CO2 in the growing season suggests that in deserts, elevated CO2 promotes ecosystem retention of N during periods of peak biological demand. Concomitantly, exposure to elevated CO2 alters inputs of new reactive gases into the atmosphere, potentially impacting local atmospheric processes.

  17. Cervus elaphus Foraging Impacts on Plants and Soils at an Ungrazed Desert Grass/Shrubland in Northwestern New Mexico, USA

    Directory of Open Access Journals (Sweden)

    Louis C. Bender

    2015-01-01

    Full Text Available We evaluated Cervus elaphus herbivory and trampling impacts on plants and soils on Chaco Culture National Historical Park (Chaco, a desert grass/shrubland in northwestern New Mexico, USA, most (63% of which has been protected from grazing by domestic livestock since 1948. We conducted grazing, browse, and water infiltration surveys in areas which received different amounts of C. elaphus use (use and control, 2004–2007. Browse utilization was <32% on monitored species and Odocoileus hemionus use accounted for the majority of browsing. Live plant cover was greater on areas receiving more C. elaphus use, and no grass species were used above recommended levels. Stubble heights of Bouteloua spp. were positively related to relative C. elaphus use on some areas, suggesting possible stimulation of grassland productivity by C. elaphus grazing. Water infiltration rates either did not differ among use or control sites or were faster in use sites, indicating no impacts of C. elaphus use on soil compaction. At current C. elaphus densities (0.2–0.4/km2, negative impacts to plants and soils were not seen on Chaco, and some evidence suggests that light grazing is optimizing desert grasslands of Chaco.

  18. Surface biosolids application: effects on infiltration, erosion, and soil organic carbon in Chihuahuan Desert grasslands and shrublands.

    Science.gov (United States)

    Moffet, C A; Zartman, R E; Wester, D B; Sosebee, R E

    2005-01-01

    Land application of biosolids is a beneficial-use practice whose ecological effects depend in part on hydrological effects. Biosolids were surface-applied to square 0.5-m2 plots at four rates (0, 7, 34, and 90 dry Mg ha(-1)) on each of three soil-cover combinations in Chihuahuan Desert grassland and shrubland. Infiltration and erosion were measured during two seasons for three biosolids post-application ages. Infiltration was measured during eight periods of a 30-min simulated rain. Biosolids application affected infiltration rate, cumulative infiltration, and erosion. Infiltration increased with increasing biosolids application rate. Application of biosolids at 90 dry Mg ha(-1) increased steady-state infiltration rate by 1.9 to 7.9 cm h(-1). Most of the measured differences in runoff among biosolids application rates were too large to be the result of interception losses and/or increased hydraulic gradient due to increased roughness. Soil erosion was reduced by the application of biosolids; however, the extent of reduction in erosion depended on the initial erodibility of the site. Typically, the greatest marginal reductions in erosion were achieved at the lower biosolids application rates (7 and 34 dry Mg ha(-1)); the difference in erosion between 34 and 90 dry Mg ha(-1) biosolids application rates was not significant. Surface application of biosolids has important hydrological consequences on runoff and soil erosion in desert grasslands that depend on the rate of biosolids applied, and the site and biosolids characteristics.

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

    Science.gov (United States)

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

    2009-01-01

    We compared seed banks between two contrasting anthropogenic surface disturbances (compacted, trenched) and adjacent undisturbed controls to determine whether site condition influences viable seed densities of perennial and annual Mojave Desert species. Viable seeds of perennials were rare in undisturbed areas (3-4 seeds/m2) and declined to ant explained annual seed densities better than any other surface characteristics that were examined. Surface disturbances can have a varied impact on the condition of the soil surface in arid lands. Nevertheless, the consistently positive relationship between ground cover of litter and viable seed density emphasizes the importance of litter as an indicator of site degradation and recovery potential in arid lands.

  20. Hydrologic characterization of desert soils with varying degrees of pedogenesis: 2. Inverse modeling for eff ective properties

    Science.gov (United States)

    Mirus, B.B.; Perkins, K.S.; Nimmo, J.R.; Singha, K.

    2009-01-01

    To understand their relation to pedogenic development, soil hydraulic properties in the Mojave Desert were investi- gated for three deposit types: (i) recently deposited sediments in an active wash, (ii) a soil of early Holocene age, and (iii) a highly developed soil of late Pleistocene age. Eff ective parameter values were estimated for a simplifi ed model based on Richards' equation using a fl ow simulator (VS2D), an inverse algorithm (UCODE-2005), and matric pressure and water content data from three ponded infi ltration experiments. The inverse problem framework was designed to account for the eff ects of subsurface lateral spreading of infi ltrated water. Although none of the inverse problems converged on a unique, best-fi t parameter set, a minimum standard error of regression was reached for each deposit type. Parameter sets from the numerous inversions that reached the minimum error were used to develop probability distribu tions for each parameter and deposit type. Electrical resistance imaging obtained for two of the three infi ltration experiments was used to independently test fl ow model performance. Simulations for the active wash and Holocene soil successfully depicted the lateral and vertical fl uxes. Simulations of the more pedogenically developed Pleistocene soil did not adequately replicate the observed fl ow processes, which would require a more complex conceptual model to include smaller scale heterogeneities. The inverse-modeling results, however, indicate that with increasing age, the steep slope of the soil water retention curve shitis toward more negative matric pressures. Assigning eff ective soil hydraulic properties based on soil age provides a promising framework for future development of regional-scale models of soil moisture dynamics in arid environments for land-management applications. ?? Soil Science Society of America.

  1. Changes in soil aggregate dynamics following 18 years of experimentally increased precipitation in a cold desert ecosystem

    Science.gov (United States)

    De Graaff, M.; vanderVeen, J.; Germino, M. J.

    2011-12-01

    Climate change is expected to alter the amount and timing of precipitation in semiarid ecosystems of the intermountain west, which can alter soil carbon dynamics. Specifically, an increase in precipitation in arid ecosystems promotes microbial activity, which can increase soil aggregate formation and enhance sequestration of soil organic carbon within stable aggregates. This study was conducted to assess: (1) how precipitation shifts affect soil aggregate formation and associated soil organic carbon contents in semi arid ecosystems, and (2) how plants mediate precipitation impacts on soil aggregate dynamics. Soil samples were collected from a long-term ecohydrology study located in the cold desert of the Idaho National Lab, USA. Precipitation treatments delivered during the previous 18 years consist of three regimes: (1) a control (ambient precipitation), (2) 200 mm irrigation added during the growing season, and (3) 200 mm irrigation added during the cold dormant season. Experimental plots were planted with a diverse native mix of big sagebrush (Artemisia tridentate) and associated shrubs, grasses, and forbs, but had also become invaded by crested wheatgrass (Agropyron cristatum). Soils were collected in February (2011) with a 4.8 cm diameter soil corer to a depth of 15 cm. Across all precipitation treatments we sampled both directly beneath sagebrush and crested wheatgrass and from relatively bare plant-interspaces. Subsamples (100 g) were sieved (4.75 mm) and air dried. Then, the soils were fractionated into (1) macro aggregates (> 250 μm), (2) free micro aggregates (53-250 μm) and (3) free silt and clay fractions (fertility otherwise prevail.

  2. Factors Controlling Soil Microbial Biomass and Bacterial Diversity and Community Composition in a Cold Desert Ecosystem: Role of Geographic Scale.

    Directory of Open Access Journals (Sweden)

    David J Van Horn

    Full Text Available Understanding controls over the distribution of soil bacteria is a fundamental step toward describing soil ecosystems, understanding their functional capabilities, and predicting their responses to environmental change. This study investigated the controls on the biomass, species richness, and community structure and composition of soil bacterial communities in the McMurdo Dry Valleys, Antarctica, at local and regional scales. The goals of the study were to describe the relationships between abiotic characteristics and soil bacteria in this unique, microbially dominated environment, and to test the scale dependence of these relationships in a low complexity ecosystem. Samples were collected from dry mineral soils associated with snow patches, which are a significant source of water in this desert environment, at six sites located in the major basins of the Taylor and Wright Valleys. Samples were analyzed for a suite of characteristics including soil moisture, pH, electrical conductivity, soil organic matter, major nutrients and ions, microbial biomass, 16 S rRNA gene richness, and bacterial community structure and composition. Snow patches created local biogeochemical gradients while inter-basin comparisons encompassed landscape scale gradients enabling comparisons of microbial controls at two distinct spatial scales. At the organic carbon rich, mesic, low elevation sites Acidobacteria and Actinobacteria were prevalent, while Firmicutes and Proteobacteria were dominant at the high elevation, low moisture and biomass sites. Microbial parameters were significantly related with soil water content and edaphic characteristics including soil pH, organic matter, and sulfate. However, the magnitude and even the direction of these relationships varied across basins and the application of mixed effects models revealed evidence of significant contextual effects at local and regional scales. The results highlight the importance of the geographic scale of

  3. Draft Genome Sequence of Hymenobacter sp. Strain AT01-02, Isolated from a Surface Soil Sample in the Atacama Desert, Chile

    DEFF Research Database (Denmark)

    Hansen, Anders Cai Holm; Paulino-Lima, Ivan Glaucio; Fujishima, Kosuke

    2016-01-01

    Here, we report the 5.09-Mb draft genome sequence of Hymenobacter sp. strain AT01-02, which was isolated from a surface soil sample in the Atacama Desert, Chile. The isolate is extremely resistant to UV-C radiation and is able to accumulate high intracellular levels of Mn/Fe.......Here, we report the 5.09-Mb draft genome sequence of Hymenobacter sp. strain AT01-02, which was isolated from a surface soil sample in the Atacama Desert, Chile. The isolate is extremely resistant to UV-C radiation and is able to accumulate high intracellular levels of Mn/Fe....

  4. Properties of Subsurface Soil Cores from Four Geologic Provinces Surrounding Mars Desert Research Station, Utah: Characterizing Analog Martian Soil in a Human Exploration Scenario

    Science.gov (United States)

    Stoker, C. R.; Clarke, J. D. A.; Direito, S.; Foing, B.

    2011-01-01

    The DOMEX program is a NASA-MMAMA funded project featuring simulations of human crews on Mars focused on science activities that involve collecting samples from the subsurface using both manual and robotic equipment methods and analyzing them in the field and post mission. A crew simulating a human mission to Mars performed activities focused on subsurface science for 2 weeks in November 2009 at Mars Desert Research Station near Hanksville, Utah --an important chemical and morphological Mars analog site. Activities performed included 1) survey of the area to identify geologic provinces, 2) obtaining soil and rock samples from each province and characterizing their mineralogy, chemistry, and biology; 3) site selection and reconnaissance for a future drilling mission; 4) deployment and testing of Mars Underground Mole, a percussive robotic soil sampling device; and 5) recording and analyzing how crew time was used to accomplish these tasks. This paper summarizes results from analysis of soil cores

  5. Soil moisture control of sap-flow response to biophysical factors in a desert-shrub species, Artemisia ordosica

    Directory of Open Access Journals (Sweden)

    T. Zha

    2017-10-01

    Full Text Available The current understanding of acclimation processes in desert-shrub species to drought stress in dryland ecosystems is still incomplete. In this study, we measured sap flow in Artemisia ordosica and associated environmental variables throughout the growing seasons of 2013 and 2014 (May–September period of each year to better understand the environmental controls on the temporal dynamics of sap flow. We found that the occurrence of drought in the dry year of 2013 during the leaf-expansion and leaf-expanded periods caused sap flow per leaf area (Js to decline significantly, resulting in transpiration being 34 % lower in 2013 than in 2014. Sap flow per leaf area correlated positively with radiation (Rs, air temperature (T, and water vapor pressure deficit (VPD when volumetric soil water content (VWC was greater than 0.10 m3 m−3. Diurnal Js was generally ahead of Rs by as much as 6 hours. This time lag, however, decreased with increasing VWC. The relative response of Js to the environmental variables (i.e., Rs, T, and VPD varied with VWC, Js being more strongly controlled by plant-physiological processes during periods of dryness indicated by a low decoupling coefficient and low sensitivity to the environmental variables. According to this study, soil moisture is shown to control sap-flow (and, therefore, plant-transpiration response in Artemisia ordosica to diurnal variations in biophysical factors. This species escaped (acclimated to water limitations by invoking a water-conservation strategy with the regulation of stomatal conductance and advancement of Js peaking time, manifesting in a hysteresis effect. The findings of this study add to the knowledge of acclimation processes in desert-shrub species under drought-associated stress. This knowledge is essential in modeling desert-shrub-ecosystem functioning under changing climatic conditions.

  6. Soil moisture control of sap-flow response to biophysical factors in a desert-shrub species, Artemisia ordosica

    Science.gov (United States)

    Zha, Tianshan; Qian, Duo; Jia, Xin; Bai, Yujie; Tian, Yun; Bourque, Charles P.-A.; Ma, Jingyong; Feng, Wei; Wu, Bin; Peltola, Heli

    2017-10-01

    The current understanding of acclimation processes in desert-shrub species to drought stress in dryland ecosystems is still incomplete. In this study, we measured sap flow in Artemisia ordosica and associated environmental variables throughout the growing seasons of 2013 and 2014 (May-September period of each year) to better understand the environmental controls on the temporal dynamics of sap flow. We found that the occurrence of drought in the dry year of 2013 during the leaf-expansion and leaf-expanded periods caused sap flow per leaf area (Js) to decline significantly, resulting in transpiration being 34 % lower in 2013 than in 2014. Sap flow per leaf area correlated positively with radiation (Rs), air temperature (T), and water vapor pressure deficit (VPD) when volumetric soil water content (VWC) was greater than 0.10 m3 m-3. Diurnal Js was generally ahead of Rs by as much as 6 hours. This time lag, however, decreased with increasing VWC. The relative response of Js to the environmental variables (i.e., Rs, T, and VPD) varied with VWC, Js being more strongly controlled by plant-physiological processes during periods of dryness indicated by a low decoupling coefficient and low sensitivity to the environmental variables. According to this study, soil moisture is shown to control sap-flow (and, therefore, plant-transpiration) response in Artemisia ordosica to diurnal variations in biophysical factors. This species escaped (acclimated to) water limitations by invoking a water-conservation strategy with the regulation of stomatal conductance and advancement of Js peaking time, manifesting in a hysteresis effect. The findings of this study add to the knowledge of acclimation processes in desert-shrub species under drought-associated stress. This knowledge is essential in modeling desert-shrub-ecosystem functioning under changing climatic conditions.

  7. Effects of Land Use Change on Soil Carbon Storage and Water Consumption in an Oasis-Desert Ecotone

    Science.gov (United States)

    Lü, Yihe; Ma, Zhimin; Zhao, Zhijiang; Sun, Feixiang; Fu, Bojie

    2014-06-01

    Land use and ecosystem services need to be assessed simultaneously to better understand the relevant factors in sustainable land management. This paper analyzed land use changes in the middle reach of the arid Heihe River Basin in northwest China over the last two decades and their impacts on water resources and soil organic carbon (SOC) storage. The results indicated that from 1986 to 2007: (1) cropland and human settlements expanded by 45.0 and 17.6 %, respectively, at the expense of 70.1, 35.7, and 4.1 % shrinkage on woodland, grassland, and semi-shrubby desert; (2) irrigation water use was dominant and increased (with fluctuations) at an average rate of 8.2 %, while basic human water consumption increased monotonically over a longer period from 1981 to 2011 at a rate of 58 %; and (3) cropland expansion or continuous cultivation led to a significant reduction of SOC, while the land use transition from grassland to semi-shrubby desert and the progressive succession of natural ecosystems such as semi-shrubby desert and grassland, in contrast, can bring about significant carbon sequestration benefits. The increased water consumption and decreased SOC pool associated with some observed land use changes may induce and aggravate potential ecological risks for both local and downstream ecosystems, including water resource shortages, soil quality declines, and degeneration of natural vegetation. Therefore, it is necessary to balance socioeconomic wellbeing and ecosystem services in land use planning and management for the sustainability of socio-ecological systems across spatiotemporal scales, especially in resource-poor arid environments.

  8. Diazotrophic Community Structure and Function in Two Successional Stages of Biological Soil Crusts from the Colorado Plateau and Chihuahuan Desert

    Science.gov (United States)

    Yeager, C.M.; Kornosky, J.L.; Housman, D.C.; Grote, E.E.; Belnap, J.; Kuske, C.R.

    2004-01-01

    The objective of this study was to characterize the community structure and activity of N2-fixing microorganisms in mature and poorly developed biological soil crusts from both the Colorado Plateau and Chihuahuan Desert. Nitrogenase activity was approximately 10 and 2.5 times higher in mature crusts than in poorly developed crusts at the Colorado Plateau site and Chihuahuan Desert site, respectively. Analysis of nifH sequences by clone sequencing and the terminal restriction fragment length polymorphism technique indicated that the crust diazotrophic community was 80 to 90% heterocystous cyanobacteria most closely related to Nostoc spp. and that the composition of N2-fixing species did not vary significantly between the poorly developed and mature crusts at either site. In contrast, the abundance of nifH sequences was approximately 7.5 times greater (per microgram of total DNA) in mature crusts than in poorly developed crusts at a given site as measured by quantitative PCR. 16S rRNA gene clone sequencing and microscopic analysis of the cyanobacterial community within both crust types demonstrated a transition from a Microcoleus vaginatus-dominated, poorly developed crust to mature crusts harboring a greater percentage of Nostoc and Scytonema spp. We hypothesize that ecological factors, such as soil instability and water stress, may constrain the growth of N2-fixing microorganisms at our study sites and that the transition to a mature, nitrogen-producing crust initially requires bioengineering of the surface microenvironment by Microcoleus vaginatus.

  9. Mycobiota of biological soil crusts in the Negev desert, Israel - differences on a regional and local scale

    Science.gov (United States)

    Grishkan, I.; Zaady, E.; Kidron, G.

    2012-04-01

    On a regional scale, we examined variations in microfungal communities inhabiting the biological soil crusts (BSC) and non-crusted soil of the northern and central Negev desert in 10 locations along a southward rainfall gradient (from 325 mm to 81 mm of annual rainfall). A total of 87 species from 49 genera were isolated using the soil dilution plate method. The mycobiota of BSC (80 species) was characterized by dominance of melanin-containing fungi, remarkable contribution of sexual Ascomycota, and low abundance of the typical soil genera Penicillium and Aspergillus. Morphological adaptations to the stressful desert environment were expressed in the prevalence of dark-colored microfungi with large, many-celled spores in the localities of the "drier" part of the rainfall gradient and in dark thick-walled fruit bodies of sexual ascomycetes. The abundance of melanin-containing species with multicellular spores was the only characteristic showed a highly significant (negative) correlation with the rainfall amount. We assume that the main factor influencing the content of these species was the latitudinal position of the locations, determining also the intensity of solar (UV) radiation. In the BSC communities, the xeric "desert" component (melanics, slow-reproducing fungi with large, thick-walled spores) was significantly more pronounced and the mesic "forest" component (Penicillium, fast-reproducing fungi with small, light-colored, and thin-walled spores) was much less represented than in the non-crusted shrub communities. In BSC, density of fungal isolates which can be considered an indirect characteristic of fungal biomass was significantly lower than in the non-crusted soil. Cluster analysis indicated that in most cases, the BSC and shrub localities, separated only by a few meters or less, differed on microfungal community structure much more significantly than BSC or shrub localities in the distance of tens of kilometers. The results of this analysis, together

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

    Science.gov (United States)

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

    2014-01-01

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

  11. Hierarchical analysis of vegetation dynamics over 71 years: soil-rainfall interactions in a Chihuahuan Desert ecosystem.

    Science.gov (United States)

    Browning, Dawn M; Duniway, Michael C; Laliberte, Andrea S; Rango, Albert

    2012-04-01

    Proliferation of woody plants in grasslands and savannas is a persistent problem globally. This widely observed shift from grass to shrub dominance in rangelands worldwide has been heterogeneous in space and time largely due to cross-scale interactions among soils, climate, and land-use history. Our objective was to use a hierarchical framework to evaluate the relationship between spatial patterns in soil properties and long-term shrub dynamics in the northern Chihuahuan Desert of New Mexico, USA. To meet this objective, shrub patch dynamics from 1937 to 2008 were characterized at patch and landscape scales using historical imagery and a recent digital soils map. Effects of annual precipitation on patch dynamics on two soils revealed strong correlations between shrub growth on deep sandy soils and above-average rainfall years (r = 0.671, P = 0.034) and shrub colonization and below-average rainfall years on shallow sandy soils (r = 0.705, P = 0.023). Patch-level analysis of demographic patterns revealed significant differences between shrub patches on deep and shallow sandy soils during periods of above- and below-average rainfall. Both deep and shallow sandy soils exhibited low shrub cover in 1937 (1.0% +/- 2.3% and 0.3% +/- 1.3%, respectively [mean +/- SD]) and were characterized by colonization or appearance of new patches until 1960. However, different demographic responses to the cessation of severe drought on the two soils and increased frequency of wet years after 1960 have resulted in very different endpoints. In 2008 a shrubland occupied the deep sandy soils with cover at 19.8% +/- 9.1%, while a shrub-dominated grassland occurred on the shallow sandy soils with cover at 9.3% +/- 7.2%. Present-day shrub vegetation constitutes a shifting mosaic marked by the coexistence of patches at different stages of development. Management implications of this long-term multi-scale assessment of vegetation dynamics support the notion that soil properties may constrain

  12. Soil wind erosion in ecological olive trees in the Tabernas desert (southeastern Spain): a wind tunnel experiment

    Science.gov (United States)

    Asensio, Carlos; Lozano, Francisco Javier; Gallardo, Pedro; Giménez, Antonio

    2016-08-01

    Wind erosion is a key component of the soil degradation processes. The purpose of this study is to find out the influence of material loss from wind on soil properties for different soil types and changes in soil properties in olive groves when they are tilled. The study area is located in the north of the Tabernas Desert, in the province of Almería, southeastern Spain. It is one of the driest areas in Europe, with a semiarid thermo-Mediterranean type of climate. We used a new wind tunnel model over three different soil types (olive-cropped Calcisol, Cambisol and Luvisol) and studied micro-plot losses and deposits detected by an integrated laser scanner. We also studied the image processing possibilities for examining the particles attached to collector plates located at the end of the tunnel to determine their characteristics and whether they were applicable to the setup. Samples collected in the traps at the end of the tunnel were analyzed. We paid special attention to the influence of organic carbon, carbonate and clay contents because of their special impact on soil crusting and the wind-erodible fraction. A principal components analysis (PCA) was carried out to find any relations on generated dust properties and the intensity and behavior of those relationships. Component 1 separated data with high N and OC contents from samples high in fine silt, CO3= and available K content. Component 2 separated data with high coarse silt and clay contents from data with high fine sand content. Component 3 was an indicator of available P2O5 content. Analysis of variance (ANOVA) was carried out to analyze the effect of soil type and sampling height on different properties of trapped dust. Calculations based on tunnel data showed overestimation of erosion in soil types and calculation of the fraction of soil erodible by wind done by other authors for Spanish soils. As the highest loss was found in Cambisols, mainly due to the effect on soil crusting and the wind

  13. Degradation of seed mucilage by soil microflora promotes early seedling growth of a desert sand dune plant.

    Science.gov (United States)

    Yang, Xuejun; Baskin, Carol C; Baskin, Jerry M; Zhang, Wenhao; Huang, Zhenying

    2012-05-01

    In contrast to the extensive understanding of seed mucilage biosynthesis, much less is known about how mucilage is biodegraded and what role it plays in the soil where seeds germinate. We studied seed mucilage biodegradation by a natural microbial community. High-performance anion-exchange chromatography (HPAEC) was used to determine monosaccharide composition in achene mucilage of Artemisia sphaerocephala. Mucilage degradation by the soil microbial community from natural habitats was examined by monosaccharide utilization tests using Biolog plates, chemical assays and phospholipid fatty acid (PLFA) analysis. Glucose (29.4%), mannose (20.3%) and arabinose (19.5%) were found to be the main components of achene mucilage. The mucilage was biodegraded to CO(2) and soluble sugars, and an increase in soil microbial biomass was observed during biodegradation. Fluorescence microscopy showed the presence of mucilage (or its derivatives) in seedling tissues after growth with fluorescein isothiocyanate (FITC)-labelled mucilage. The biodegradation also promoted early seedling growth in barren sand dunes, which was associated with a large soil microbial community that supplies substances promoting seedling establishment. We conclude that biodegradation of seed mucilage can play an ecologically important role in the life cycles of plants especially in harsh desert environments to which A. sphaerocephala is well-adapted. © 2011 Blackwell Publishing Ltd.

  14. Don’t bust the biological soil crust: Preserving and restoring an important desert resource

    Science.gov (United States)

    Sue Miller; Steve Warren; Larry St. Clair

    2017-01-01

    Biological soil crusts are a complex of microscopic organisms growing on the soil surface in many arid and semi-arid ecosystems. These crusts perform the important role of stabilizing soil and reducing or eliminating water and wind erosion. One of the largest threats to biological soil crusts in the arid and semi-arid areas of the western United States is mechanical...

  15. Spatial variation in edaphic characteristics is a stronger control than nitrogen inputs in regulating soil microbial effects on a desert grass

    Science.gov (United States)

    Chung, Y. Anny; Sinsabaugh, Robert L; Kuske, Cheryl R.; Reed, Sasha C.; Rudgers, Jennifer A.

    2017-01-01

    Increased atmospheric nitrogen (N) deposition can have wide-ranging effects on plant community structure and ecosystem function, some of which may be indirectly mediated by soil microbial responses to an altered biogeochemical environment. In this study, soils from a field N fertilization experiment that spanned a soil texture gradient were used as inocula in the greenhouse to assess the indirect effects of soil microbial communities on growth of a desert grass. Plant performance and interaction with soil microbiota were evaluated via plant above- and belowground biomass, leaf N concentration, and root fungal colonization. Nitrogen fertilization in the field increased the benefits of soil microbial inoculation to plant leaf N concentration, but did not alter the effect of soil microbes on plant growth. Plant-microbe interaction outcomes differed most strongly among sites with different soil textures, where the soil microbial community from the sandiest site was most beneficial to host plant growth. The findings of this study suggest that in a desert grassland, increases in atmospheric N deposition may exert a more subtle influence on plant-microbe interactions by altering plant nutrient status, whereas edaphic factors can alter the whole-plant growth response to soil microbial associates.

  16. Diversity and Abundance of Soil Animals as Influenced by Long-Term Fertilization in Grey Desert Soil, China

    OpenAIRE

    Maibo Jiang; Xihe Wang; Yunhao Liusui; Xueqing Sun; Chengyi Zhao; Hua Liu

    2015-01-01

    The relationship between soil fauna and different fertilizer management practices is of growing concern. The aim of this research was to investigate the response of soil fauna to fertilization regimes, to explore the relationships among the community of soil animals, soil moisture and crop yields. The application of organic fertilizers (i.e., sheep manure or crop residues) increased crop yields and promoted the number of individuals and species of soil fauna owing to the exogenous organic mat...

  17. Heterogeneity of Soil and Vegetation in the Urban Habitats of New Industrial Cities in the Desert Landscape of Egypt

    Directory of Open Access Journals (Sweden)

    Monier Abd EL-GHANI

    2015-03-01

    Full Text Available The relationship between vegetation and soil supporting the habitats in 4 new industrial cities were assessed. Five main habitats were distinguished from inner city toward outskirts: lawns, home gardens, public gardens, waste lands and desert outskirts. After application of Twinspan, 26 vegetation groups were identified in the 5 recognized habitats, demonstrating that some groups are chatracteristic of a certain city, e.g. Asphodelus aestivus - Deverra tortuosa - Thymelaea hirsuta group was confined to the desert habitat of Burg El-Arab city; Thymelaea hirsuta - Linaria albifrons and Atriplex halimus - Atriplex lindleyi subsp. inflata - Suaeda vermiculata - Typha domingensis groups were found in the waste lands of Burg El-Arab city; Conyza bonariensis - Cynodon dactylon - Sonchus oleraceus group in the home garden habitat of 10th Ranadan city; Cynodon dactylon group in the lawns of Burg El-Arab city; Bassia indica - Plantago major group in the public gardens of Burg El-Arab city; Oxalis corniculata - Plantago lagopus group in the public gardens of 10th Ramadan city; Sonchus oleraceus - Cynodon dactylon and Dactyloctenium aegyptium - Leptochloa fusca - Phragmites australis groups in the public gardens of 6th October city. Silt, clay, organic matter, carbonates and carbon contents showed significant diffrences among the 5 habitats.

  18. Diversity and Abundance of Soil Animals as Influenced by Long-Term Fertilization in Grey Desert Soil, China

    Directory of Open Access Journals (Sweden)

    Maibo Jiang

    2015-08-01

    Full Text Available The relationship between soil fauna and different fertilizer management practices is of growing concern. The aim of this research was to investigate the response of soil fauna to fertilization regimes, to explore the relationships among the community of soil animals, soil moisture and crop yields. The application of organic fertilizers (i.e., sheep manure or crop residues increased crop yields and promoted the number of individuals and species of soil fauna owing to the exogenous organic matter that fertilizers provided for the survival and development of soil fauna. Furthermore, the treatments that applied sheep manure (i.e., sheep manure only or nitrogen, phosphorus, potassium and sheep manure plus were significantly beneficial for increasing crop yields and diversity of soil fauna compared to treatments with crop residues returned (i.e., crop residues returned only or nitrogen, phosphorus, potassium and crop residues returned to the field (p < 0.05 due to the response of soil fauna to diverse exogenous nutrients and the effect of soil fertility. Therefore, the finding that soil fauna abundance is significantly positively correlated with soil moisture and crop yield may mean the effects of fertilizer applications on soil animals were partly masked by the soil moisture and crop yield.

  19. Spectral Exploration of Calcium Accumulation in Organic Matter in Gray Desert Soil from Northwest China

    National Research Council Canada - National Science Library

    Wang, Ping; Ma, Yucui; Wang, Xihe; Jiang, Hong; Liu, Hua; Ran, Wei; Shen, Qirong

    2016-01-01

    .... In this paper, soil samples from a long-term field experiment conducted from 1990 to 2013 at a research station in Urumqi, China by different fertilizer treatments, were used to determine soil...

  20. Dynamics of soil organic carbon and its fractions after revegetation on sand dunes in the Tengger Desert, Northern China

    Science.gov (United States)

    Li, X.; Liu, Y.; Li, X.

    2015-12-01

    Revegetation has become increasingly important for desertified land restoration in arid and semiarid regions. Little is known about the dynamics of soil organic carbon (SOC) after the establishment of shrubland on shifting sand dunes; especially the changes in SOC fractions following planting were poorly understood. 0-10 cm soil samples were collected along chronosequence plots were to: (1) quantitatively analyze the changes of SOC and its fractions over time following the establishment of shrublands on shifting sand dunes; (2) precisely assess the relative contribution of different components to total organic carbon at different times. The results showed that revegetation can promote SOC accumulation in desert regions. SOC increased from 0.33±0.11 g kg-1 in mobile sand dunes to 5.08±0.11 g kg-1 in 57-year shrublands, while the light fraction of organic C (LF-OC) ranged from 0.05±0.02 g kg-1 to 2.96±0.24 g kg-1, the dissolved organic C (DOC) increased from 5.95±0.42 mg kg-1 to 23.63±2.79 mg kg-1 and microbial biomass C (MBC) from 6.54±1.64 mg kg-1 to 135.35±19.49 mg kg-1. Their dynamics patterns can be divided into three stages, i.e. slow increase, fast increase and slow increase stages; especially, both SOC and its fractions showed no significant changes in the first 14 years, which suggested that soil restoration is a slow process in dry environments, and therefore the maintenance of soil habitat is a crucial for land management. Our results also demonstrated that revegetation can increase the ratio of labile to stable pools in desert regions. Although, the content of HF-OC significantly increased after afforestation, but its contribution to SOC decreased from 85.15% to 41.52%, implied that more SOC stocks were stabilized in labile pools with the elapse of time, this would give rise to the risk of significant SOC losses caused by potential global warming and human-induced disturbances.

  1. Fungal Diversity in Tomato Rhizosphere Soil under Conventional and Desert Farming Systems.

    Science.gov (United States)

    Kazerooni, Elham A; Maharachchikumbura, Sajeewa S N; Rethinasamy, Velazhahan; Al-Mahrouqi, Hamed; Al-Sadi, Abdullah M

    2017-01-01

    This study examined fungal diversity and composition in conventional (CM) and desert farming (DE) systems in Oman. Fungal diversity in the rhizosphere of tomato was assessed using 454-pyrosequencing and culture-based techniques. Both techniques produced variable results in terms of fungal diversity, with 25% of the fungal classes shared between the two techniques. In addition, pyrosequencing recovered more taxa compared to direct plating. These findings could be attributed to the ability of pyrosequencing to recover taxa that cannot grow or are slow growing on culture media. Both techniques showed that fungal diversity in the conventional farm was comparable to that in the desert farm. However, the composition of fungal classes and taxa in the two farming systems were different. Pyrosequencing revealed that Microsporidetes and Dothideomycetes are the two most common fungal classes in CM and DE, respectively. However, the culture-based technique revealed that Eurotiomycetes was the most abundant class in both farming systems and some classes, such as Microsporidetes, were not detected by the culture-based technique. Although some plant pathogens (e.g., Pythium or Fusarium) were detected in the rhizosphere of tomato, the majority of fungal species in the rhizosphere of tomato were saprophytes. Our study shows that the cultivation system may have an impact on fungal diversity. The factors which affected fungal diversity in both farms are discussed.

  2. Fungal Diversity in Tomato Rhizosphere Soil under Conventional and Desert Farming Systems

    Directory of Open Access Journals (Sweden)

    Elham A. Kazerooni

    2017-08-01

    Full Text Available This study examined fungal diversity and composition in conventional (CM and desert farming (DE systems in Oman. Fungal diversity in the rhizosphere of tomato was assessed using 454-pyrosequencing and culture-based techniques. Both techniques produced variable results in terms of fungal diversity, with 25% of the fungal classes shared between the two techniques. In addition, pyrosequencing recovered more taxa compared to direct plating. These findings could be attributed to the ability of pyrosequencing to recover taxa that cannot grow or are slow growing on culture media. Both techniques showed that fungal diversity in the conventional farm was comparable to that in the desert farm. However, the composition of fungal classes and taxa in the two farming systems were different. Pyrosequencing revealed that Microsporidetes and Dothideomycetes are the two most common fungal classes in CM and DE, respectively. However, the culture-based technique revealed that Eurotiomycetes was the most abundant class in both farming systems and some classes, such as Microsporidetes, were not detected by the culture-based technique. Although some plant pathogens (e.g., Pythium or Fusarium were detected in the rhizosphere of tomato, the majority of fungal species in the rhizosphere of tomato were saprophytes. Our study shows that the cultivation system may have an impact on fungal diversity. The factors which affected fungal diversity in both farms are discussed.

  3. Soil Formation and Transport Processes on Hillslopes along a Precipitation Gradient in the Atacama Desert, Chile

    OpenAIRE

    Owen, Justine J

    2009-01-01

    The climate-dependency of the rates and types of soil formation processes on level landforms has been recognized and documented for decades. In contrast, methods for quantifying rates of soil formation and transport on hillslopes have only recently been developed and the results suggest that these rates are independent of climate. One explanation for this discrepancy is that hillslopes and their soil mantles are dynamic systems affected by local and regional tectonic effects. Tectonics can ch...

  4. Compendium of dietary sources of vitamin A in the Thar desert

    Directory of Open Access Journals (Sweden)

    Desai Sanjiv

    1992-01-01

    Full Text Available The undisputed long term solution to prevent nutritional blindness lies in changing the dietary habits of a given population through nutritional education, nutritional supplementation, and nutritional rehabilitation. Before such strategies can be successfully implemented, it becomes necessary to study the existing dietary pattern of the population and to identify locally grown foods rich in vitamin A. Seventy eight rural women were interviewed to determine the common dietary items in western Rajasthan. These items were then matched with their B-carotene contents, only to discover that, 100 grams of any of them would not provide the RDA for a 1-3 year old child, with the exception of Suva (Peucedanum graveolens and Bathua (Chenopodium album leaves. The B-Carotene contents of several food items is unknown at present and there is an urgent need to evaluate them.

  5. Geoinformatics for the Mapping of Nexus Between Poverty and Land Degradation in Drylands of Thar Desert

    Science.gov (United States)

    Gaur, Mahesh

    2012-07-01

    Poverty and land degradation are major problems in majority of world dry lands, where meagre vegetative coverage (of forests and trees) contribute significantly to rural livelihoods. In order to eradicate poverty in the dry lands, it is important to protect the land from deforestation, fragmentation, degradation, drought and sometimes flash floods. Satellite remote sensing is a critical need for India - for spatial and temporal inter-linking of poverty and land degradation nexus and its prioritization. Remote sensing and geographical information system (GIS) is often used to generate and apply knowledge in the complex local context. Connecting natural resources and ecosystem services with attributes of poverty is amenable through Remote Sensing and GIS. Such linkages in a typical local context are important to recognize while building rural assets and natural resources conservation leading to poverty alleviation. A large proportion of the poor in the Rajasthan state live in resource poor western region who lack productive assets (especially land) and also lack adequate livelihoods skills or capacities due to illiteracy. People are inadequately organized to assert their rights and utilize available resources and services. The state also continues to be plagued by high levels of gender and caste discrimination (World Bank, 2007). Incidence of Poverty: The number of population below poverty line in Rajasthan in 2004-05 were 22.1 percent. The corresponding figures for rural areas are 18.7 percent. In urban areas, the number of poor people are 32.9 percent. Rural poverty situation is significantly better than urban poverty. (HDR, 2008) Despite the fact that poverty rates in Rajasthan are lower than the national average, the incidence of poverty in Western Rajasthan is nevertheless high. The incidence of poverty varies between 11.2% in Jodhpur to as much as 35.2% in Jalore. The poor households suffer from both lack of resources and the means to access them, which contributes to the relatively low Human Development Index (HDI) indicators. Besides the extreme deprivations in the normal course of life, the poor become particularly vulnerable at the time of recurrent drought induced crisis. (MPOWER, 2010) The present study demonstrates application of earth observations for the mapping of nexus between poverty and land degradation. The empirical study carried out by the investigator in the Pali district highlights that such technological inputs could be applied in support of the poor and marginal farming community in the different parts of State and the country at cadastral level.

  6. Dynamics of cover, UV-protective pigments, and quantum yield in biological soil crust communities of an undisturbed Mojave Desert shrubland

    Science.gov (United States)

    Belnap, Jayne; Phillips, Susan L.; Smith, Stanley D.

    2007-01-01

    Biological soil crusts are an integral part of dryland ecosystems. We monitored the cover of lichens and mosses, cyanobacterial biomass, concentrations of UV-protective pigments in both free-living and lichenized cyanobacteria, and quantum yield in the soil lichen species Collema in an undisturbed Mojave Desert shrubland. During our sampling time, the site received historically high and low levels of precipitation, whereas temperatures were close to normal. Lichen cover, dominated by Collema tenax and C. coccophorum, and moss cover, dominated by Syntrichia caninervis, responded to both increases and decreases in precipitation. This finding for Collema spp. at a hot Mojave Desert site is in contrast to a similar study conducted at a cool desert site on the Colorado Plateau in SE Utah, USA, where Collema spp. cover dropped in response to elevated temperatures, but did not respond to changes in rainfall. The concentrations of UV-protective pigments in free-living cyanobacteria at the Mojave Desert site were also strongly and positively related to rainfall received between sampling times (R2 values ranged from 0.78 to 0.99). However, pigment levels in the lichenized cyanobacteria showed little correlation with rainfall. Quantum yield in Collema spp. was closely correlated with rainfall. Climate models in this region predict a 3.5–4.0 °C rise in temperature and a 15–20% decline in winter precipitation by 2099. Based on our data, this rise in temperature is unlikely to have a strong effect on the dominant species of the soil crusts. However, the predicted drop in precipitation will likely lead to a decrease in soil lichen and moss cover, and high stress or mortality in soil cyanobacteria as levels of UV-protective pigments decline. In addition, surface-disturbing activities (e.g., recreation, military activities, fire) are rapidly increasing in the Mojave Desert, and these disturbances quickly remove soil lichens and mosses. These stresses combined are likely to

  7. Chemical composition of volatile oil from Artemisia ordosica and its allelopathic effects on desert soil microalgae, Palmellococcus miniatus.

    Science.gov (United States)

    Yang, Xiaolu; Deng, Songqiang; De Philippis, Roberto; Chen, Lanzhou; Hu, Chaozhen; Zhang, Weihao

    2012-02-01

    Plants have been used to restore vegetation in desert region in Shapotou, where naturally biological soil crusts (BSCs) have formed after planting for several years. However, few works have been done on the allelopathic effects between the plants and soil microalgae in BSCs currently. In this study, we investigated the chemical compositions of volatile oil of Artemisia ordosica and its allelopathic effects on photosynthetic system II (PSII) and antioxidant system of Palmellococcus miniatus, a green algae isolated from BSCs. 37 components, consisted of 17 terpenoids, 14 alcohols, 2 esters, 2 ketones and other 2 components were identified in the volatile oil from A. ordosica by GC-MS analysis. High concentration of volatile oil could significantly inhibit the growth and photosynthetic activity (Fv/Fm), and decreased the photosynthetic parameters by affecting photon absorption, electron transport and the reaction center of PSII of P. miniatus, and also cause the significant increase of superoxide dismutase (SOD; EC 1.15.1.) activity, peroxidase (POD; EC 1.11.1.7) activity, reactive oxygen evolution (ROS) and malondialdehyde (MDA) contents of P. miniatus through the combined effects of components in volatile oil. The results indicated that the emission of volatile oil of A. ordosica could inhibit the growth, photosynthesis of P. miniatus through the oxidative damage, and thus might negatively affect the development of BSCs. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

  8. Few apparent short-term effects of elevated soil temperature and increased frequency of summer precipitation on the abundance and taxonomic diversity of desert soil micro- and meso-fauna

    Science.gov (United States)

    Darby, B.J.; Neher, D.A.; Housman, D.C.; Belnap, J.

    2011-01-01

    Frequent hydration and drying of soils in arid systems can accelerate desert carbon and nitrogen mobilization due to respiration, microbial death, and release of intracellular solutes. Because desert microinvertebrates can mediate nutrient cycling, and the autotrophic components of crusts are known to be sensitive to rapid desiccation due to elevated temperatures after wetting events, we studied whether altered soil temperature and frequency of summer precipitation can also affect the composition of food web consumer functional groups. We conducted a two-year field study with experimentally-elevated temperature and frequency of summer precipitation in the Colorado Plateau desert, measuring the change in abundance of nematodes, protozoans, and microarthropods. We hypothesized that microfauna would be more adversely affected by the combination of elevated temperature and frequency of summer precipitation than either effect alone, as found previously for phototrophic crust biota. Microfauna experienced normal seasonal fluctuations in abundance, but the effect of elevated temperature and frequency of summer precipitation was statistically non-significant for most microfaunal groups, except amoebae. The seasonal increase in abundance of amoebae was reduced with combined elevated temperature and increased frequency of summer precipitation compared to either treatment alone, but comparable with control (untreated) plots. Based on our findings, we suggest that desert soil microfauna are relatively more tolerant to increases in ambient temperature and frequency of summer precipitation than the autotrophic components of biological soil crust at the surface.

  9. Implications of meltwater pulse events for soil biology and biogeochemical cycling in a polar desert

    Directory of Open Access Journals (Sweden)

    Becky A. Ball

    2011-12-01

    Full Text Available The McMurdo Dry Valleys are one of the most arid environments on Earth. Over the soil landscape for the majority of the year, biological and ecosystem processes in the dry valleys are constrained by the low temperatures and limited availability of water. The prevalence of these physical limitations in controlling biological and ecosystem processes makes the dry valleys a climate-sensitive system, poised to experience substantial changes following projected future warming. Short-duration increases in summer temperatures are associated with pulses of water from melting ice reserves, including glaciers, snow and permafrost. Such pulses alter soil geochemistry by mobilizing and redistributing soil salts (via enhanced weathering, solubility and mobility, which can alter habitat suitability for soil organisms. Resulting changes in soil community composition or distribution may alter the biogeochemical processes in which they take part. Here, we review the potential impacts of meltwater pulses and present new field data documenting instances of meltwater pulse events that result from different water sources and hydrological patterns, and discuss their potential influence on soil biology and biogeochemistry. We use these examples to discuss the potential impacts of future climate change on the McMurdo Dry Valley soil ecosystem.

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

    Science.gov (United States)

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

    1989-01-01

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

  11. Effect of biostimulation using sewage sludge, soybean meal and wheat straw on oil degradation and bacterial community composition in a contaminated desert soil

    Directory of Open Access Journals (Sweden)

    Sumaiya eAl-Kindi

    2016-03-01

    Full Text Available Waste materials have a strong potential in the bioremediation of oil-contaminated sites, because of their richness in nutrients and their economical feasibility. We used sewage sludge, soybean meal and wheat straw to biostimulate oil degradation in a heavily contaminated desert soil. While oil degradation was assessed by following the produced CO2 and by using gas chromatography-mass spectrometry (GC-MS, shifts in bacterial community composition were monitored using illumina MiSeq. The addition of sewage sludge and wheat straw to the desert soil stimulated the respiration activities more than the addition of soybean meal. GC-MS analysis revealed that the addition of addition of sewage sludge and wheat straw resulted in 1.7 to 1.8 fold increase in the degraded C14 to C30 alkanes, compared to only 1.3 fold increase in the case of soybean meal addition. The degradation of ≥ 90% of the C14 to C30 alkanes were measured in the soils treated with sewage sludge and wheat straw. MiSeq sequencing revealed that the majority (76.5-86.4% of total sequences of acquired sequences from the original soil belonged to Alphaproteobacteria, Gammaproteobacteria and Firmicutes. Multivariate analysis of operational taxonomic units (OTUs placed the bacterial communities of the soils after the treatments in separate clusters (ANOSIM R=0.66, P=0.0001. The most remarkable shift in bacterial communities was in the wheat straw treatment, where 95-98% of the total sequences belonging to Bacilli. We conclude that sewage sludge and wheat straw are useful biostimulating agents for the cleanup of oil-contaminated desert soils.

  12. Microbial secondary succession in soil microcosms of a desert oasis in the Cuatro Cienegas Basin, Mexico.

    Science.gov (United States)

    López-Lozano, Nguyen E; Heidelberg, Karla B; Nelson, William C; García-Oliva, Felipe; Eguiarte, Luis E; Souza, Valeria

    2013-01-01

    Ecological succession is one of the most important concepts in ecology. However for microbial community succession, there is a lack of a solid theoretical framework regarding succession in microorganisms. This is in part due to microbial community complexity and plasticity but also because little is known about temporal patterns of microbial community shifts in different kinds of ecosystems, including arid soils. The Cuatro Cienegas Basin (CCB) in Coahuila, Mexico, is an arid zone with high diversity and endemisms that has recently been threatened by aquifer overexploitation. The gypsum-based soil system of the CCB is one of the most oligotrophic places in the world. We undertook a comparative 16S rRNA 454 pyrosequencing study to evaluate microbial community succession and recovery over a year after disturbance at two sites. Results were related to concurrent measurements of humidity, organic matter and total C and N content. While each site differed in both biogeochemistry and biodiversity, both present similar pattern of change at the beginning of the succession that diverged in later stages. After one year, experimentally disturbed soil was not similar to established and undisturbed adjacent soil communities indicating recovery and succession in disturbed soils is a long process.

  13. Isolation of a significant fraction of non-phototroph diversity from a desert Biological Soil Crust

    Directory of Open Access Journals (Sweden)

    Ulisses eNunes da Rocha

    2015-04-01

    Full Text Available Biological Soil Crusts (BSCs are organosedimentary assemblages comprised of microbes and minerals in topsoil of terrestrial environments. BSCs strongly impact soil quality in dryland ecosystems (e.g., soil structure and nutrient yields due to pioneer species such as Microcoleus vaginatus; phototrophs that produce filaments that bind the soil together, and support an array of heterotrophic microorganisms. These microorganisms in turn contribute to soil stability and biogeochemistry of BSCs. Non-cyanobacterial populations of BSCs are less well known than cyanobacterial populations. Therefore, we attempted to isolate a broad range of numerically significant and phylogenetically representative BSC aerobic heterotrophs. Combining simple pre-treatments (hydration of BSCs under dark and light and isolation strategies (media with varying nutrient availability and protection from oxidative stress we recovered 402 bacterial and one fungal isolate in axenic culture, which comprised 116 phylotypes (at 97% 16S rRNA gene sequence homology, 115 bacterial and one fungal. Each medium enriched a mostly distinct subset of phylotypes, and cultivated phylotypes varied due to the BSC pre-treatment. The fraction of the total phylotype diversity isolated, weighted by relative abundance in the community, was determined by the overlap between isolate sequences and OTUs reconstructed from metagenome or metatranscriptome reads. Together, more than 8% of relative abundance of OTUs in the metagenome was represented by our isolates, a cultivation efficiency much larger than typically expected from most soils. We conclude that simple cultivation procedures combined with specific pre-treatment of samples afford a significant reduction in the culturability gap, enabling physiological and metabolic assays that rely on ecologically relevant axenic cultures.

  14. Rehabilitation of a lignite mine-disturbed area in the Indian Desert

    Science.gov (United States)

    Sharma, K.D.; Kumar, P.; Gough, L.P.; SanFilipo, J.R.

    2004-01-01

    Extensive lignite mining in the Indian (Thar) Desert commenced within the past decade. Accompanying extraction of this valuable resource there have been visible, important environmental impacts. The resultant land degradation has prompted concern from both public and regulatory bodies. This research assesses the success of rehabilitation plans implemented to revegetate a lignite mine-disturbed area, near the village of Giral in western Rajasthan State. Rehabilitation success was achieved within the environmental constraints of this northwest Indian hot-desert ecosystem using a combination of: (1) backfilling (abandoned pits) with minespoil and of covering the backfilled-surfaces with fresh topsoil to a thickness of about 0??30 m; (2) use of micro-catchment rainwater harvesting (MCWH) technique; (3) soil profile modification approaches; (4) plant establishment methodologies; and (5) the selection of appropriate germplasm material (trees, shrubs and grasses). Preliminary results indicate that the resulting vegetative cover will be capable of self-perpetuation under natural conditions while at the same time meeting the land-use requirements of the local people. The minespoil is alkaline in nature and has high electrical conductance. The average content of organic carbon, N, P and K is lower than in the regional topsoil. However, the concentration of Ca, Mg, Na and total S in the minespoil is much higher than in the topsoil. Further, the spoil material has no biological activity. Enhanced plant growth was achieved in MCWH plots, compared to control plots, where minespoil moisture storage was improved by 18-43 per cent. The rehabilitation protocol used at the site appears to have been successful because, in addition to the planted species, desirable native invasive species have become established. This study developed methods for the rehabilitation of lignite mine-disturbed areas and has also resulted in an understanding of rehabilitation processes in arid regions with

  15. Spatial-temporal variability of soil water content in a cropland-shelterbelt-desert site in an arid inland river basin of Northwest China

    Science.gov (United States)

    Shen, Qin; Gao, Guangyao; Hu, Wei; Fu, Bojie

    2016-09-01

    Knowledge of the spatial-temporal variability of soil water content (SWC) is critical for understanding a range of hydrological processes. In this study, the spatial variance and temporal stability of SWC were investigated in a cropland-shelterbelt-desert site at the oasis-desert ecotone in the middle of the Heihe River Basin, China. The SWC was measured on 65 occasions to a depth of 2.8 m at 45 locations during two growing seasons from 2012 to 2013. The standard deviation of the SWC versus the mean SWC exhibited a convex upward relationship in the shelterbelt with the greatest spatial variation at the SWC of around 22.0%, whereas a linearly increasing relationship was observed for the cropland, desert, and land use pattern. The standard deviation of the relative difference was positively linearly correlated with the SWC (p effect on the selection of the representative locations of the field mean SWC. This study provides useful information for designing the optimal strategy for sampling SWC at the oasis-desert ecotone in the arid inland river basin.

  16. EFFECTS OF REPEATED DROUGHTS ON SOIL MICROARTHROPOD COMMUNITIES IN THE NORTHERN CHIHUHUAN DESERT

    Science.gov (United States)

    Soil microarthropods were sampled in plots centered on creosotebushes(Larrea tridentata) and in plots centered on mesquite(Prosopis glandulosa) coppice dunes. Nine plots in each area were covered by rain-out shelters with greenhouse plastic roofs which excluded natural rainfall a...

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

    Science.gov (United States)

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

    2017-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Rakesh Mogul

    2017-10-01

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

  19. Temporal variation in community composition, pigmentation, and Fv/Fm of desert cyanobacterial soil crusts

    Science.gov (United States)

    Bowker, M.A.; Reed, S.C.; Belnap, J.; Phillips, S.L.

    2002-01-01

    Summers on the Colorado Plateau (USA) are typified by harsh conditions such as high temperatures, brief soil hydration periods, and high UV and visible radiation. We investigated whether community composition, physiological status, and pigmentation might vary in biological soil crusts as a result of such conditions. Representative surface cores were sampled at the ENE, WSW, and top microaspects of 20 individual soil crust pedicels at a single site in Canyonlands National Park, Utah, in spring and fall of 1999. Frequency of cyanobacterial taxa, pigment concentrations, and dark adapted quantum yield (Fv/Fm) were measured for each core. The frequency of major cyanobacterial taxa was lower in the fall compared to spring. The less-pigmented cyanobacterium Microcoleus vaginatus showed significant mortality when not in the presence of Nostoc spp. and Scytonema myochrous (Dillw.) Agardh. (both synthesizers of UV radiation-linked pigments) but had little or no mortality when these species were abundant. We hypothesize that the sunscreen pigments produced by Nostoc and Scytonema in the surface of crusts protect other, less-pigmented taxa. When fall and spring samples were compared, overall cyanobacterial frequency was lower in fall, while sunscreen pigment concentrations, chlorophyll a concentration, and Fv/Fm were higher in fall. The ratio of cyanobacterial frequency/chlorophyll a concentrations was 2-3 times lower in fall than spring. Because chlorophyll a is commonly used as a surrogate measure of soil cyanobacterial biomass, these results indicate that seasonality needs to be taken into consideration. In the fall sample, most pigments associated with UV radiation protection or repair were at their highest concentrations on pedicel tops and WSW microaspects, and at their lowest concentrations on ENE microaspects. We suggest that differential pigment concentrations between microaspects are induced by varying UV radiation dosage at the soil surface on these different

  20. Bioremediation of contaminated mixtures of desert mining soil and sawdust with fuel oil by aerated in-vessel composting in the Atacama Region (Chile)

    Energy Technology Data Exchange (ETDEWEB)

    Godoy-Faundez, Alex [Department of Chemical Engineering and Bioprocesses, Pontifica Universidad Catolica de Chile (Chile)], E-mail: agodoy@puc.cl; Antizar-Ladislao, Blanca [Department of Water and Environment Science and Technology, University of Bulevar Ronda Rufino Peon, 39316 Torrelavega, Cantabria (Spain)], E-mail: b_antizar@hotmail.com; Reyes-Bozo, Lorenzo [Department of Chemical Engineering and Bioprocesses, Pontifica Universidad Catolica de Chile (Chile); Camano, Andres [Minera Escondida Ltd. (Chile); Saez-Navarrete, Cesar [Department of Chemical Engineering and Bioprocesses, Pontifica Universidad Catolica de Chile (Chile)], E-mail: csaez@ing.puc.cl

    2008-03-01

    Since early 1900s, with the beginning of mining operations and especially in the last decade, small, although repetitive spills of fuel oil had occurred frequently in the Chilean mining desert industry during reparation and maintenance of machinery, as well as casual accidents. Normally, soils and sawdust had been used as cheap readily available sorbent materials of spills of fuel oil, consisting of complex mixtures of aliphatic and aromatic hydrocarbons. Chilean legislation considers these fuel oil contaminated mixtures of soil and sawdust as hazardous wastes, and thus they must be contained. It remains unknown whether it would be feasible to clean-up Chilean desert soils with high salinity and metal content, historically polluted with different commercial fuel oil, and contained during years. Thus, this study evaluated the feasibility of aerated in-vessel composting at a laboratory scale as a bioremediation technology to clean-up contaminated desert mining soils (fuel concentration > 50,000 mg kg{sup -1}) and sawdust (fuel concentration > 225,000 mg kg{sup -1}) in the Atacama Region. The composting reactors were operated using five soil to sawdust ratios (S:SD, 1:0, 3:1, 1:1, 1:3, 0:1, on a dry weight basis) under mesophilic temperatures (30-40 deg. C), constant moisture content (MC, 50%) and continuous aeration (16 l min{sup -1}) during 56 days. Fuel oil concentration and physico-chemical changes in the composting reactors were monitored following standard procedures. The highest (59%) and the lowest (35%) contaminant removals were observed in the contaminated sawdust and contaminated soil reactors after 56 days of treatment, respectively. The S:SD ratio, time of treatment and interaction between both factors had a significant effect (p < 0.050) on the contaminant removal. The results of this research indicate that bioremediation of an aged contaminated mixture of desert mining soil and sawdust with fuel oil is feasible. This study recommends a S:SD ratio 1

  1. Impacts of LUCC on soil properties in the riparian zones of desert oasis with remote sensing data: a case study of the middle Heihe River basin, China.

    Science.gov (United States)

    Jiang, Penghui; Cheng, Liang; Li, Manchun; Zhao, Ruifeng; Duan, Yuewei

    2015-02-15

    Large-scale changes in land use and land cover over long timescales can induce significant variations in soil physicochemical properties, particularly in the riparian zones of arid regions. Frequent reclamation of wetlands and grasslands and intensive agricultural activity have induced significant changes in both land use/cover and soil physicochemical properties in the riparian zones of the middle Heihe River basin of China. The present study aims to explore whether land use/land cover change (LUCC) can well explain the variations in soil properties in the riparian zones of the middle Heihe River basin. To achieve this, we mapped LUCC and quantified the type of land use change using remote sensing images, topographic maps, and GIS analysis techniques. Forty-two sites were selected for soil and vegetation sampling. Then, physical and chemical experiments were employed to determine soil moisture, soil bulk density, soil pH, soil organic carbon, total nitrogen, total potassium, total phosphorous, available nitrogen, available potassium, and available phosphorous. The Independent-Samples Kruskal-Wallis Test, principal component analysis, and a scatter matrix were used to analyze the effects of LUCC on soil properties. The results indicate that the majority of the parameters investigated were affected significantly by LUCC. In particular, soil moisture and soil organic carbon can be explained well by land cover change and land use change, respectively. Furthermore, changes in soil moisture could be attributed primarily to land cover changes. Changes in soil organic carbon were correlated closely with the following land use change types: wetlands-arable, forest-grasslands, and grasslands-desert. Other parameters, including pH and total K, were also found to exhibit significant correlations with LUCC. However, changes in soil nutrients were shown to be induced most probably by human agricultural activity (i.e. fertilize, irrigation, tillage, etc.), rather than by simple

  2. Resource Islands Predict the Distribution of Heterotrophic Bacteria in Chihuahuan Desert Soils

    OpenAIRE

    Herman, R P; Provencio, K. R.; Herrera-Matos, J.; Torrez, R. J.

    1995-01-01

    The resource island hypothesis predicts that soil resources such as nitrogen, phosphorus, and water will be distributed evenly in grasslands but have a patchy distribution focused around plants in shrublands. This hypothesis predicts that microorganism numbers will follow resources and be (i) evenly distributed in grasslands, (ii) concentrated around individual plants in shrublands, and (iii) higher where resources are higher when comparing the same vegetation type. This study enumerated tota...

  3. Implications of meltwater pulse events for soil biology and biogeochemical cycling in a polar desert

    OpenAIRE

    Ball, Becky A.; J. E. Barrett; Gooseff, Mike N.; Ross A. Virginia; Wall, Diana H

    2011-01-01

    The McMurdo Dry Valleys are one of the most arid environments on Earth. Over the soil landscape for the majority of the year, biological and ecosystem processes in the dry valleys are constrained by the low temperatures and limited availability of water. The prevalence of these physical limitations in controlling biological and ecosystem processes makes the dry valleys a climatesensitive system, poised to experience substantial changes following projected future warming. Short-duration increa...

  4. Study of potential impacts of using sewage sludge in the amendment of desert reclaimed soil on wheat and jews mallow plants

    Directory of Open Access Journals (Sweden)

    Ahmed Mazen

    2010-08-01

    Full Text Available This investigation was conducted to study the impacts of using sewage sludge at different concentrations (0, 10, 25, 50, 75% in amendment of desert reclaimed soil properties and some physiological aspects in wheat and jews mallow plants. Generally adding sewage sludge to desert soil improved the soil texture, raised the organic matter contents, water holding capacity and lowered pH value. The contents of NPK gradually increased as the ratio of sewage sludge increased. The fresh and dry weights and biosyntheses of pigment contents of the variously treated test plants were increased by increasing the sewage sludge levels in the soil. Also, total carbohydrate and protein contents of sewage sludge-treated test plants were positively affected. With respect to the proline content and total free amino acids, in most cases, it decreased significantly, expect at 75% sewage sludge, which was higher than that of other concentrations. Also, the accumulation of metal was generally higher, especially in the root than that in the shoot system in the test plant tissues.

  5. Non-biological fractionation of stable Ca isotopes in soils of the Atacama Desert, Chile

    Science.gov (United States)

    Ewing, Stephanie A.; Yang, Wenbo; DePaolo, Donald J.; Michalski, Greg; Kendall, Carol; Stewart, Brian W.; Thiemens, Mark; Amundson, Ronald

    2008-02-01

    We measured Ca stable isotope ratios (δ 44/40Ca) in an ancient (2 My), hyperarid soil where the primary source of mobile Ca is atmospheric deposition. Most of the Ca in the upper meter of this soil (3.5 kmol m -2) is present as sulfates (2.5 kmol m -2), and to a lesser extent carbonates (0.4 kmol m -2). In aqueous extracts of variably hydrated calcium sulfate minerals, δ 44/40Ca E values (vs. bulk Earth) increase with depth (1.4 m) from a minimum of -1.91‰ to a maximum of +0.59‰. The trend in carbonate-δ 44/40Ca in the top six horizons resembles that of sulfate-δ 44/40Ca, but with values 0.1-0.6‰ higher. The range of observed Ca isotope values in this soil is about half that of δ 44/40Ca values observed on Earth. Linear correlation among δ 44/40Ca, δ 34S and δ 18O values indicates either (a) a simultaneous change in atmospheric input values for all three elements over time, or (b) isotopic fractionation of all three elements during downward transport. We present evidence that the latter is the primary cause of the isotopic variation that we observe. Sulfate-δ 34S values are positively correlated with sulfate-δ 18O values ( R2 = 0.78) and negatively correlated with sulfate δ 44/40Ca E values ( R2 = 0.70). If constant fractionation and conservation of mass with downward transport are assumed, these relationships indicate a δ 44/40Ca fractionation factor of -0.4‰ in CaSO 4. The overall depth trend in Ca isotopes is reproduced by a model of isotopic fractionation during downward Ca transport that considers small and infrequent but regularly recurring rainfall events. Near surface low Ca isotope values are reproduced by a Rayleigh model derived from measured Ca concentrations and the Ca fractionation factor predicted by the relationship with S isotopes. This indicates that the primary mechanism of stable isotope fractionation in CaSO 4 is incremental and effectively irreversible removal of an isotopically enriched dissolved phase by downward

  6. Ambient and potential denitrification rates in marsh soils of Northeast Creek and Bass Harbor Marsh watersheds, Mount Desert Island, Maine

    Science.gov (United States)

    Huntington, Thomas G.; Culbertson, Charles W.; Duff, John H.

    2012-01-01

    Nutrient enrichment from atmospheric deposition, agricultural activities, wildlife, and domestic sources is a concern at Acadia National Park on Mount Desert Island, Maine, because of the potential problems of degradation of water quality and eutrophication in estuaries. Degradation of water quality has been observed at Bass Harbor Marsh estuary in the park but only minimally in Northeast Creek estuary. Previous studies at Acadia National Park have estimated nutrient inputs to estuaries from atmospheric deposition and surface-water runoff, and have identified shallow groundwater as an additional potential source of nutrients. Previous studies at Acadia National Park have assumed that a certain fraction of the nitrogen input was removed through microbial denitrification, but rates of denitrification (natural or maximum potential) in marsh soils have not been determined. The U.S. Geological Survey, in cooperation with Acadia National Park, measured in-place denitrification rates in marsh soils in Northeast Creek and in Bass Harbor Marsh watersheds during summer 2008 and summer 2009. Denitrification was measured under ambient conditions as well as after additions of inorganic nitrogen and glucose. In-place denitrification rates under ambient conditions were similar to those reported for other coastal wetlands, although they were generally lower than those reported for salt marshes having high ambient concentrations of nitrate (NO3). Denitrification rates generally increased by at least an order of magnitude following NO3 additions, with or without glucose (as the carbohydrate) additions, compared with the ambient treatments that received no nutrient additions. The treatment that added both glucose and NO3 resulted in a variety of denitrification responses when compared with the addition of NO3 alone. In most cases, the addition of glucose to a given rate of NO3 addition resulted in higher rates of denitrification. These variable responses indicate that the amount of

  7. [Content and evolution characteristics of organic carbon associated with particle-size fractions of grey desert soil under long-term fertilization].

    Science.gov (United States)

    Liu, Hua; Tong, Xiao-Gang; Ma, Xing-Wang; Wang, Xi-He; Zhang, Wen-Ju; Xu, Yong-Mei; Xu, Ming-Gang

    2010-01-01

    Physical fractionation technique was used to analyze the content, distribution, and temporal evolution of organic carbon associated with particle-size fractions of grey desert soil under long-term (1990-2007) fertilization. Compared with no fertilization, a combined application of manure and chemical fertilizers increased the organic carbon associated with particle-size fractions significantly, with the highest increment (0.34 g x kg(-1) x a(-1)) in sand. Following also increased the organic carbon associated with clay and silt significantly. Straw return to cropland only maintained the organic carbon content in different particle-size fractions, while long-term application of chemical fertilizers was not beneficial to the organic carbon increase in particle-size fractions. Coarse silt and coarse clay had the highest distribution rates of organic carbon (27.9% and 27.1%, respectively), being the important fractions in sequestrating organic carbon. When manure was applied with chemical fertilizers, the organic carbon in sand was significantly increased by 119.4%, while that in fine silt and coarse clay was significantly decreased by 40.3% and 37.9%, respectively, which resulted in the increase in the ratio of particulate organic carbon content (W(POC)) to mineral-associated organic carbon content (W(MOC)), and improvd soil carbon property. Long-term application of manure combined with chemical fertilizers was the best mode to increase the organic carbon content in particle-size fractions and improve the fertility of grey desert soil.

  8. The role of non-rainfall water on physiological activation in desert biological soil crusts

    Science.gov (United States)

    Zheng, Jiaoli; Peng, Chengrong; Li, Hua; Li, Shuangshuang; Huang, Shun; Hu, Yao; Zhang, Jinli; Li, Dunhai

    2018-01-01

    Non-rainfall water (NRW, e.g. fog and dew), in addition to rainfall and snowfall, are considered important water inputs to drylands. At the same time, biological soil crusts (BSCs) are important components of drylands. However, little information is available regarding the effect of NRW inputs on BSC activation. In this study, the effects of NRW on physiological activation in three BSC successional stages, including the cyanobacteria crust stage (Crust-C), moss colonization stage (Crust-CM), and moss crust stage (Crust-M), were studied in situ. Results suggest NRW inputs hydrated and activated physiological activity (Fv/Fm, carbon exchange, and nitrogen fixation) in BSCs but led to a negative carbon balance and low rates of nitrogen fixation in BSCs. One effective NRW event could hydrate BSCs for 7 h. Following simulated rainfall, the physiological activities recovered within 3 h, and net carbon gain occurred until 3 h after hydration, whereas NRW-induced physiological recovery processes were slower and exhibited lower activities, leading to a negative carbon balance. There were significant positive correlations between NRW amounts and the recovered values of Fv/Fm in all the three BSC stages (p < .001). The thresholds for Fv/Fm activation decreased with BSC succession, and the annual effective NRW events increased with BSC succession, with values of 29.8, 89.2, and 110.7 in Crust-C, Crust-CM and Crust-M, respectively. The results suggest that moss crust and moss-cyanobacteria crust use NRW to prolong metabolic activity and reduce drought stress more efficiently than cyanobacteria crusts. Therefore, these results suggest that BSCs utilize NRW to sustain life while growth and biomass accumulation require precipitation (rainfall) events over a certain threshold.

  9. Bacillus swezeyi sp. nov. and Bacillus haynesii sp. nov., isolated from desert soil.

    Science.gov (United States)

    Dunlap, Christopher A; Schisler, David A; Perry, Elizabeth B; Connor, Nora; Cohan, Frederick M; Rooney, Alejandro P

    2017-08-01

    Two isolates of Gram-reaction-positive, facultatively anaerobic, motile, rod-shaped, endospore-forming bacteria were identified during a survey of the diversity of strains belonging to the genus Bacillus deposited in the Agriculture Research Service Culture Collection. These strains were originally isolated from soil in Evolution Canyon III (Israel) in a survey of ecological diversification. Phylogenetic analysis of the 16S rRNA gene of strains NRRL B-41294T and NRRL B-41327T determined they were closely related to members of the Bacillus licheniformis clade. The genome of each strain was sequenced, and further analysis indicated that the strains represented unique species based on in silico DNA-DNA hybridization analyses. A phylogenomic analysis revealed that NRRL B-41294T and NRRL B-41327T were closely related to the group that includes B. licheniformis. In phenotypic characterization, both NRRL B-41294T and NRRL B-41327T were found to grow at temperatures of between 15 and 60 °C and tolerated up to 12 % NaCl (w/v). The predominant cellular fatty acids were anteiso-C15 : 0 and iso-C15 : 0, and peptidoglycan from cell walls contained meso-diaminopimelic acid. The DNA G+C content was 45.7 and 44.3 mol% for NRRL B-41327T and NRRL B-41294T, respectively. Furthermore, each strain had a unique carbon utilization pattern that distinguished it from its nearest phylogenetic neighbours. Based upon the consensus of phylogenetic and phenotypic analyses, we conclude that these strains represent two novel species within the genus Bacillus, for which the name Bacillus swezeyi sp. nov. is proposed, with type strain NRRL B-41294T (=CCUG 70177T), and the name Bacillus haynesii sp. nov. is proposed, with type strain NRRL B-41327T (=CCUG 70178T).

  10. Desert shrub responses to experimental modification of precipitation seasonality and soil depth: relationship to the two-layer model and ecohydrological niche

    Science.gov (United States)

    Germino, Matthew J.; Reinhardt, Keith

    2013-01-01

    1. Ecohydrological niches are important for understanding plant community responses to climate shifts, particularly in dry lands. According to the two-layer hypothesis, selective use of deep-soil water increases growth or persistence of woody species during warm and dry summer periods and thereby contributes to their coexistence with shallow-rooted herbs in dry ecosystems. The resource-pool hypothesis further suggests that shallow-soil water benefits growth of all plants while deep-soil water primarily enhances physiological maintenance and survival of woody species. Few studies have directly tested these by manipulating deep-soil water availability and observing the long-term outcomes. 2. We predicted that factors promoting infiltration and storage of water in deep soils, specifically greater winter precipitation and soil depth, would enhance Artemisia tridentata (big sagebrush) in cold, winter-wet/summer-dry desert. Sagebrush responses to 20 years of winter irrigation were compared to summer- or no irrigation, on plots having relatively deep or shallow soils (2 m vs. 1 m depths). 3. Winter irrigation increased sagebrush cover, and crown and canopy volumes, but not density (individuals/plot) compared to summer or no irrigation, on deep-soil plots. On shallow-soil plots, winter irrigation surprisingly decreased shrub cover and size, and summer irrigation had no effect. Furthermore, multiple regression suggested that the variations in growth were related (i) firstly to water in shallow soils (0-0.2 m) and secondly to deeper soils (> 1 m deep) and (ii) more by springtime than by midsummer soil water. Water-use efficiency increased considerably on shallow soils without irrigation and was lowest with winter irrigation. 4. Synthesis. Sagebrush was more responsive to the seasonal timing of precipitation than to total annual precipitation. Factors that enhanced deep-water storage (deeper soils plus more winter precipitation) led to increases in Artemisia tridentata that

  11. Does protection of desert tortoise habitat generate other ecological benefits in the Mojave Desert?

    Science.gov (United States)

    Matthew L. Brooks

    2000-01-01

    This paper summarizes the ecological effects of fenced habitat protection for the desert tortoise (Gopherus agassizii) at the Desert Tortoise Research Natural Area in the Mojave Desert. The following were higher inside than outside the natural area: (1) annual and perennial plant biomass, cover, diversity and dominance by natives, (2) soil seed...

  12. Weaving Ecosystem Service Assessment into Environmental Impact Assessments of Thar Coal Field: Impact of Coal Mining on Socio-Ecological Systems of Rural Communities.

    Science.gov (United States)

    Hina, A.

    2016-12-01

    The Research takes into account Block II Mining and Power Plant Project of Thar Coal field in Pakistan by carrying out ecosystem service assessment of the region to identify the impact on important ecosystem service losses and the contribution of mining companies to mitigate the socio-economic problems as a part of their Corporate Social Responsibility (CSR). The study area includes 7 rural settlements, around 921 households and 7000 individuals, dependent on agriculture and livestock for their livelihoods. Currently, the project has adopted the methods of strip mining (also called open-cut mining, open-cast mining, and stripping), undergoing removing the overburden in strips to enable excavation of the coal seams. Since the consequences of mine development can easily spill across community and ecological boundaries, the rising scarcity of some ecosystem services makes the case to examine both project impact and dependence on ecosystem services. A preliminary Ecosystem Service review of Thar Coal Field identifies key ecosystems services owing to both high significance of project impact and high project dependence are highlighted as: the hydrogeological study results indicate the presence of at least three aquifer zones: one above the coal zone (the top aquifer), one within the coal and the third below the coal zone. Hence, Water is identified as a key ecosystem service to be addressed and valued due to its high dependency in the area for livestock, human wellbeing, agriculture and other purposes. Crop production related to agricultural services, in association with supply services such as soil quality, fertility, and nutrient recycling and water retention need to be valued. Cultural services affected in terms of land use change and resettlement and rehabilitation factors are recommended to be addressed.

  13. Altered snowfall and soil disturbance influence the early life stage transitions and recruitment of a native and invasive grass in a cold desert.

    Science.gov (United States)

    Gornish, Elise S; Aanderud, Zachary T; Sheley, Roger L; Rinella, Mathew J; Svejcar, Tony; Englund, Suzanne D; James, Jeremy J

    2015-02-01

    Climate change effects on plants are expected to be primarily mediated through early life stage transitions. Snowfall variability, in particular, may have profound impacts on seedling recruitment, structuring plant populations and communities, especially in mid-latitude systems. These water-limited and frequently invaded environments experience tremendous variation in snowfall, and species in these systems must contend with harsh winter conditions and frequent disturbance. In this study, we examined the mechanisms driving the effects of snowpack depth and soil disturbance on the germination, emergence, and establishment of the native Pseudoroegnaria spicata and the invasive Bromus tectorum, two grass species that are widely distributed across the cold deserts of North America. The absence of snow in winter exposed seeds to an increased frequency and intensity of freeze-thaw cycles and greater fungal pathogen infection. A shallower snowpack promoted the formation of a frozen surface crust, reducing the emergence of both species (more so for P. spicata). Conversely, a deeper snowpack recharged the soil and improved seedling establishment of both species by creating higher and more stable levels of soil moisture availability following spring thaw. Across several snow treatments, experimental disturbance served to decrease the cumulative survival of both species. Furthermore, we observed that, regardless of snowpack treatment, most seed mortality (70-80%) occurred between seed germination and seedling emergence (November-March), suggesting that other wintertime factors or just winter conditions in general limited survival. Our results suggest that snowpack variation and legacy effects of the snowpack influence emergence and establishment but might not facilitate invasion of cold deserts.

  14. Development and Assessment of the Sand Dust Prediction Model by Utilizing Microwave-Based Satellite Soil Moisture and Reanalysis Datasets in East Asian Desert Areas

    Directory of Open Access Journals (Sweden)

    Hyunglok Kim

    2017-01-01

    Full Text Available For several decades, satellite-based microwave sensors have provided valuable soil moisture monitoring in various surface conditions. We have first developed a modeled aerosol optical depth (AOD dataset by utilizing Soil Moisture and Ocean Salinity (SMOS, Advanced Microwave Scanning Radiometer 2 (AMSR2, and the Global Land Data Assimilation System (GLDAS soil moisture datasets in order to estimate dust outbreaks over desert areas of East Asia. Moderate Resolution Imaging Spectroradiometer- (MODIS- based AOD products were used as reference datasets to validate the modeled AOD (MA. The SMOS-based MA (SMOS-MA dataset showed good correspondence with observed AOD (R-value: 0.56 compared to AMSR2- and GLDAS-based MA datasets, and it overestimated AOD compared to observed AOD. The AMSR2-based MA dataset was found to underestimate AOD, and it showed a relatively low R-value (0.35 with respect to observed AOD. Furthermore, SMOS-MA products were able to simulate the short-term AOD trends, having a high R-value (0.65. The results of this study may allow us to acknowledge the utilization of microwave-based soil moisture datasets for investigation of near-real time dust outbreak predictions and short-term dust outbreak trend analysis.

  15. Groundwater discharge by evapotranspiration, flow of water in unsaturated soil, and stable isotope water sourcing in areas of sparse vegetation, Amargosa Desert, Nye County, Nevada

    Science.gov (United States)

    Moreo, Michael T.; Andraski, Brian J.; Garcia, C. Amanda

    2017-08-29

    This report documents methodology and results of a study to evaluate groundwater discharge by evapotranspiration (GWET) in sparsely vegetated areas of Amargosa Desert and improve understanding of hydrologic-continuum processes controlling groundwater discharge. Evapotranspiration and GWET rates were computed and characterized at three sites over 2 years using a combination of micrometeorological, unsaturated zone, and stable-isotope measurements. One site (Amargosa Flat Shallow [AFS]) was in a sparse and isolated area of saltgrass (Distichlis spicata) where the depth to groundwater was 3.8 meters (m). The second site (Amargosa Flat Deep [AFD]) was in a sparse cover of predominantly shadscale (Atriplex confertifolia) where the depth to groundwater was 5.3 m. The third site (Amargosa Desert Research Site [ADRS]), selected as a control site where GWET is assumed to be zero, was located in sparse vegetation dominated by creosote bush (Larrea tridentata) where the depth to groundwater was 110 m.Results indicated that capillary rise brought groundwater to within 0.9 m (at AFS) and 3 m (at AFD) of land surface, and that GWET rates were largely controlled by the slow but relatively persistent upward flow of water through the unsaturated zone in response to atmospheric-evaporative demands. Greater GWET at AFS (50 ± 20 millimeters per year [mm/yr]) than at AFD (16 ± 15 mm/yr) corresponded with its shallower depth to the capillary fringe and constantly higher soil-water content. The stable-isotope dataset for hydrogen (δ2H) and oxygen (δ18O) illustrated a broad range of plant-water-uptake scenarios. The AFS saltgrass and AFD shadscale responded to changing environmental conditions and their opportunistic water use included the time- and depth-variable uptake of unsaturated-zone water derived from a combination of groundwater and precipitation. These results can be used to estimate GWET in other areas of Amargosa Desert where hydrologic conditions are similar.

  16. An approach to locate and map swelling soils around Sohag – Safaga road, Eastern Desert, Egypt using remote sensing techniques for urban development

    Directory of Open Access Journals (Sweden)

    Salwa F. Elbeih

    2015-10-01

    Full Text Available The detrimental consequences of swelling soils are most apparent in arid and semi-arid regions. Sedimentary clays are mixtures of illite, kaolinite and some montmorillonite. There are various soil types liable to swell such as shale, mudstone, siltstone and marl due to the presence of Smectite group in these soils. Large volume changes of these types of soils can cause extensive damages to civil engineering infrastructures; roads, airport pavements, pipelines and shallow foundations. A number of localities in Egypt are well-known by the presence of swelling soils. Sohag – Safaga highway in the Eastern Desert of Egypt is considered to be an investable transportation road and one of the most important lateral connections between Upper Egypt and the Red Sea area. The study area is located in a buffer zone of 25 km from both sides of the highway. This area is believed to be more influenced by the road and could be fully utilized to share in developing areas in the road vicinity. The research objectives are to use recent ASTER satellite imageries with the aid of field samples to map different swelling clay minerals and compare between the different sensors accuracy in locating them within the buffer zone. Certain engineering measures should be considered to enable construction over these types of swelling soils. The results confirmed the presence of montmorillonite in this buffer zone and in the 5 km buffer around the road which represents a hazard especially for the future planned projects within this area.

  17. Effect of stocking rate on soil-atmosphere CH4 flux during spring freeze-thaw cycles in a northern desert steppe, China.

    Directory of Open Access Journals (Sweden)

    Cheng-Jie Wang

    Full Text Available BACKGROUND: Methane (CH(4 uptake by steppe soils is affected by a range of specific factors and is a complex process. Increased stocking rate promotes steppe degradation, with unclear consequences for gas exchanges. To assess the effects of grazing management on CH(4 uptake in desert steppes, we investigated soil-atmosphere CH(4 exchange during the winter-spring transition period. METHODOLOGY/MAIN FINDING: The experiment was conducted at twelve grazing plots denoting four treatments defined along a grazing gradient with three replications: non-grazing (0 sheep/ha, NG, light grazing (0.75 sheep/ha, LG, moderate grazing (1.50 sheep/ha, MG and heavy grazing (2.25 sheep/ha, HG. Using an automatic cavity ring-down spectrophotometer, we measured CH(4 fluxes from March 1 to April 29 in 2010 and March 2 to April 27 in 2011. According to the status of soil freeze-thaw cycles (positive and negative soil temperatures occurred in alternation, the experiment was divided into periods I and II. Results indicate that mean CH(4 uptake in period I (7.51 µg CH(4-C m(-2 h(-1 was significantly lower than uptake in period II (83.07 µg CH(4-C m(-2 h(-1. Averaged over 2 years, CH(4 fluxes during the freeze-thaw period were -84.76 µg CH(4-C m(-2 h(-1 (NG, -88.76 µg CH(4-C m(-2 h(-1 (LG, -64.77 µg CH(4-C m(-2 h(-1 (MG and -28.80 µg CH(4-C m(-2 h(-1 (HG. CONCLUSIONS/SIGNIFICANCE: CH(4 uptake activity is affected by freeze-thaw cycles and stocking rates. CH(4 uptake is correlated with the moisture content and temperature of soil. MG and HG decreases CH(4 uptake while LG exerts a considerable positive impact on CH(4 uptake during spring freeze-thaw cycles in the northern desert steppe in China.

  18. Soil plus root respiration and microbial biomass following water, nitrogen, and phosphorus application at a high arctic semi desert

    DEFF Research Database (Denmark)

    Illeris, Lotte; Michelsen, Anders; Jonasson, Sven Evert

    2003-01-01

    CO2 emmision, Decomposition, Microbial biomass carbon, Soil organic matter, Tundra, Water and nutrient limitation......CO2 emmision, Decomposition, Microbial biomass carbon, Soil organic matter, Tundra, Water and nutrient limitation...

  19. Spectral Exploration of Calcium Accumulation in Organic Matter in Gray Desert Soil from Northwest China: e0145054

    National Research Council Canada - National Science Library

    Ping Wang; Yucui Ma; Xihe Wang; Hong Jiang; Hua Liu; Wei Ran; Qirong Shen

    2016-01-01

    .... In this paper, soil samples from a long-term field experiment conducted from 1990 to 2013 at a research station in Urumqi, China by different fertilizer treatments, were used to determine soil...

  20. The effect of the halophytic shrub Lycium ruthenium (Mutt) on selected soil properties of a desert ecosystem in central Iran

    Science.gov (United States)

    Gholam Ali Jalali; Hossein Akbarian; Charles Rhoades; Hamed Yousefzadeh

    2012-01-01

    We compared soil properties beneath naturally-occurring patches of Lycium ruthenicum Murray (fam. Solanaceae) to evaluate the shrub’s potential to improve the fertility of saline soils. Soil pH, total nitrogen and carbon and extractable potassium, magnesium and phosphorus were respectively significantly higher in the A and B horizons of Lycium shrub patches...

  1. Thermal volatilization (TV) of different hyperarid Mars like-soils from the Atacama Desert: Implications for the analysis of the Phoenix Mission

    Science.gov (United States)

    Valdivia-Silva, J. E.; Navarro-Gonzalez, R.; McKay, C. P.

    2008-09-01

    The Phoenix spacecraft will search for organics in the soil and ice in the Martian north polar regions using thermal volatilization (TV) followed by mass spectrometry (MS). This experiment is a combination of a high-temperature furnace and a mass spectrometer that will be use to analyze samples delivered to instrument via a robotic arm. The samples will be heated from ambient to 1000ºC while evolved gases, including organic molecules and fragments, if they are present, will be simultaneously measured by a magnetic sector mass spectrometer (1). Our laboratory has developed a sample characterization method using a pyrolizer integrated to a quadrupole mass spectrometer to support the interpretations of TV data. The Atacama Desert, on northern Chile and southern Peru, has been considered the most arid region over the world (2) and an excellent Mars-like soil analogous (3). These soils contain very low levels to organic matter (10-40 ppm of organic C), and exotic mineralogical composition including iron oxides, which are common characteristics expected on Mars. A previous paper that examined the release of organics from samples soils by flash TV (pyrolisis) coupled to GC-MS (4). This work showed low efficiency of flash TV in soils with low organics or high contents of iron minerals. In addition, other study of agricultural soils showed low correlation between organics concentration and TV response, when levels of total organic matter were below 50000 ppm C or high presence of iron oxides (5). However, the efficiency of gradual heating by TV analysis from hyperarid soils has not been investigated. Here we examine the thermal and evolved gas properties of six types of soils from the two hyperarid core regions from the Atacama Desert: Yungay (northern Chile) and Pampas de La Joya (southern Peru), in order to investigate the effect of soil matrix and low organics contents over TV response. Between 20 to 40 mg of soil was loaded in a capillary quartz tube and it was mounted

  2. Effects of grazing intensity on soil labile organic carbon fractions in a desert steppe area in Inner Mongolia

    OpenAIRE

    Cao, Jixin; Wang, Xiaoping; Sun, Xiangyang; Zhang, Lin; Tian, Yun

    2013-01-01

    Grazing can cause changes in soil carbon (C) level. This study aimed to elucidate the response of soil labile organic carbon (SLOC) under four different grazing intensities: non grazing (NG), 0 sheep·ha-1; light grazing (LG), 0.91 sheep·ha-1; moderate grazing (MG), 1.82 sheep·ha-1, and heavy grazing (HG), 2.73 sheep·ha-1. Results showed that there was no significant difference in total soil organic carbon (TOC) and soil inorganic carbon (SIC) content from three soil depths (0-15 cm, 15-30 cm,...

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

    NARCIS (Netherlands)

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

    2005-01-01

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

  4. GIS application to identify the potential for certain irrigated agriculture uses on some soils in Western Desert, Egypt

    Directory of Open Access Journals (Sweden)

    M. Ismail

    2012-06-01

    The considered land suitability criteria for the aforementioned LUTs are: slope gradient, soil depth, soil erosion, soil drainage, soil infiltration rate, available water holding capacity (AWHC, surface stoniness (gravel, stones and boulders, stones in surface horizon, rock outcrop, soil salinity (EC, exchangeable sodium percent (ESP and calcium carbonate content. The suitability maps for each of the above criteria and the final land suitability maps of the study area for different LUTs were developed by multiplying the reclassified factors map and adding them by Raster calculator technique in spatial analyst module of Arc GIS 9.3 software. The values which are obtained from the result are classified into three classes. These classes were converted to suitability classes: moderately suitable (S2, marginally suitable (S3, and not suitable (NS. The most soil limiting factors in the study area for LUT1 are soil depth and drainage followed by slope gradient, salinity and AWHC. However, the most limiting factors for LUT2 and 3 are surface stones and soil depth followed by stone content of surface horizon and soil salinity. Land improvements are required to improve or reduce the severity of limitations exited in the study area.

  5. A Soil Carbon Cycle Without Life?: The Content and Residence Times of Organic and Inorganic Carbon in the Atacama Desert of Chile

    Science.gov (United States)

    Amundson, R. G.; Navarro-Gonzalez, R.; Ewing, S. A.

    2003-12-01

    The central Atacama Desert of Chile is nearly rainless and virtually devoid of biota. Precipitation increases steadily as one moves to more southern latitudes, providing a natural experiment to assess the role of water in the soil C cycle. We have established three research sites along this gradient, where the mean annual precipitation varies from nearly 0 to about 15 mm y-1. At the driest site, where plants are completely absent and soil microorganisms quite rare, trace quantities of organic C (OC) are present ( ˜0.009+/-0.0038%), and OC increases slightly with precipitation (and the increasing presence of vegetation) to 0.053%. The apparent radiocarbon age of the organic matter at the driest site is exceedingly old (> 7,000 y), suggesting C cycling rates on the order of 104 y. The source of the incoming C is being investigated, and may include a combination of marine aerosols and exceedingly rare cyanobacteria on the undersides of quartz clasts ("hypoliths"). Radiocarbon-based turnover times appear to increase to decadal scales with increasing rainfall, with annually cycling OC concentrated in coppice dunes (0.32% OC) and hypolith-associated soils (0.39% OC). The radiocarbon age of co-existing soil carbonate was ˜12,000 years at the driest site and thus older than that of the OC, suggesting limited weathering and incorporation of modern atmospheric CO2 with increasing precipitation. The character of the organic matter present in the soil was analyzed by pyrolysis-GC-MS. The main organic molecules released at 750° C in an inert atmosphere are benzene and formic acid. Their concentrations in the driest soil are in the ppb range, and decrease by about an order of magnitude with depth. This suggests that either the environmental conditions in the past were much more severe or else that there are slow downward fluxes of organic materials accompanied by decomposition (either biological or abiotic). In contrast, soil organic matter from the other two southern sites

  6. Effects of grazing intensity on soil labile organic carbon fractions in a desert steppe area in Inner Mongolia.

    Science.gov (United States)

    Cao, Jixin; Wang, Xiaoping; Sun, Xiangyang; Zhang, Lin; Tian, Yun

    2013-01-01

    Grazing can cause changes in soil carbon (C) level. This study aimed to elucidate the response of soil labile organic carbon (SLOC) under four different grazing intensities: non grazing (NG), 0 sheep·ha(-1); light grazing (LG), 0.91 sheep·ha(-1); moderate grazing (MG), 1.82 sheep·ha(-1), and heavy grazing (HG), 2.73 sheep·ha(-1). Results showed that there was no significant difference in total soil organic carbon (TOC) and soil inorganic carbon (SIC) content from three soil depths (0-15 cm, 15-30 cm, and 30-45 cm) under different grazing intensities. However, the SLOC including particulate organic carbon (POC), light fraction organic carbon (LFOC), and readily oxidizable carbon (ROC) content at a depth of 0-15 cm decreased with the increasing grazing intensity among LG, MG and HG. The SLOC content at depths of 15-30 cm under the NG and LG were significantly higher than that under the MG and the HG. The TOC and SLOC content decreased with increasing depths of soil horizons, but SIC content increased. The variation trend of the density of different soil carbon fractions and the ratio of individual SLOC fractions to TOC were similar to that of the soil carbon content of corresponding fractions. These results indicated that MG and HG treatments caused C loss at 0-30 cm; and SLOC was more sensitive than TOC in response to different grazing intensities.

  7. Desert Survivors!

    Science.gov (United States)

    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…

  8. Primary productivity as a control over soil microbial diversity along environmental gradients in a polar desert ecosystem

    Directory of Open Access Journals (Sweden)

    Kevin M. Geyer

    2017-07-01

    Full Text Available Primary production is the fundamental source of energy to foodwebs and ecosystems, and is thus an important constraint on soil communities. This coupling is particularly evident in polar terrestrial ecosystems where biological diversity and activity is tightly constrained by edaphic gradients of productivity (e.g., soil moisture, organic carbon availability and geochemical severity (e.g., pH, electrical conductivity. In the McMurdo Dry Valleys of Antarctica, environmental gradients determine numerous properties of soil communities and yet relatively few estimates of gross or net primary productivity (GPP, NPP exist for this region. Here we describe a survey utilizing pulse amplitude modulation (PAM fluorometry to estimate rates of GPP across a broad environmental gradient along with belowground microbial diversity and decomposition. PAM estimates of GPP ranged from an average of 0.27 μmol O2/m2/s in the most arid soils to an average of 6.97 μmol O2/m2/s in the most productive soils, the latter equivalent to 217 g C/m2/y in annual NPP assuming a 60 day growing season. A diversity index of four carbon-acquiring enzyme activities also increased with soil productivity, suggesting that the diversity of organic substrates in mesic environments may be an additional driver of microbial diversity. Overall, soil productivity was a stronger predictor of microbial diversity and enzymatic activity than any estimate of geochemical severity. These results highlight the fundamental role of environmental gradients to control community diversity and the dynamics of ecosystem-scale carbon pools in arid systems.

  9. Comparative activity and functional ecology of permafrost soils and lithic niches in a hyper-arid polar desert.

    Science.gov (United States)

    Goordial, Jacqueline; Davila, Alfonso; Greer, Charles W; Cannam, Rebecca; DiRuggiero, Jocelyne; McKay, Christopher P; Whyte, Lyle G

    2017-02-01

    Permafrost in the high elevation McMurdo Dry Valleys of Antarctica ranks among the driest and coldest on Earth. Permafrost soils appear to be largely inhospitable to active microbial life, but sandstone lithic microhabitats contain a trophically simple but functional cryptoendolithic community. We used metagenomic sequencing and activity assays to examine the functional capacity of permafrost soils and cryptoendolithic communities in University Valley, one of the most extreme regions in the Dry Valleys. We found metagenomic evidence that cryptoendolithic microorganisms are adapted to the harsh environment and capable of metabolic activity at in situ temperatures, possessing a suite of stress response and nutrient cycling genes to fix carbon under the fluctuating conditions that the sandstone rock would experience during the summer months. We additionally identified genes involved in microbial competition and cooperation within the cryptoendolithic habitat. In contrast, permafrost soils have a lower richness of stress response genes, and instead the metagenome is enriched in genes involved with dormancy and sporulation. The permafrost soils also have a large presence of phage genes and genes involved in the recycling of cellular material. Our results underlie two different habitability conditions under extreme cold and dryness: the permafrost soil which is enriched in traits which emphasize survival and dormancy, rather than growth and activity; and the cryptoendolithic environment that selects for organisms capable of growth under extremely oligotrophic, arid and cold conditions. This study represents the first metagenomic interrogation of Antarctic permafrost and polar cryptoendolithic microbial communities. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  10. Moramonas marocensis gen. nov., sp. nov.: a jakobid flagellate isolated from desert soil with a bacteria-like, but bloated mitochondrial genome.

    Science.gov (United States)

    Strassert, Jürgen F H; Tikhonenkov, Denis V; Pombert, Jean-François; Kolisko, Martin; Tai, Vera; Mylnikov, Alexander P; Keeling, Patrick J

    2016-02-01

    A new jakobid genus has been isolated from Moroccan desert soil. The cyst-forming protist Moramonas marocensis gen. nov., sp. nov. has two anteriorly inserted flagella of which one points to the posterior cell pole accompanying the ventral feeding groove and is equipped with a dorsal vane-a feature typical for the Jakobida. It further shows a flagellar root system consisting of singlet microtubular root, left root (R1), right root (R2) and typical fibres associated with R1 and R2. The affiliation of M. marocensis to the Jakobida was confirmed by molecular phylogenetic analyses of the SSU rRNA gene, five nuclear genes and 66 mitochondrial protein-coding genes. The mitochondrial genome has the high number of genes typical for jakobids, and bacterial features, such as the four-subunit RNA polymerase and Shine-Dalgarno sequences upstream of the coding regions of several genes. The M. marocensis mitochondrial genome encodes a similar number of genes as other jakobids, but is unique in its very large genome size (greater than 264 kbp), which is three to four times higher than that of any other jakobid species investigated yet. This increase seems to be due to a massive expansion in non-coding DNA, creating a bloated genome like those of plant mitochondria. © 2016 The Authors.

  11. [Long-Term Different Fertilizations Changed the Chemical and Spectrum Characteristics of DOM of the Irrigation-Desert Soil in North-Western China].

    Science.gov (United States)

    Chang, Dan-na; Cao, Wei-dong; Bag, Xing-guo; Bai, Jin-shun; Zhang, Jiu-dong; Lu, Bing-lin; Gao, Song-juan; Zeng, Nao-hua; Wang, Xue-cui; Katsuyoshi, Shimizu

    2016-01-01

    By using Ultraviolet-visible Spectrometry, Fourier Transform Infrared Spectrometer and Elemental Analyzer, spectrum and chemical characteristics of soil DOM affected by long-term different fertilizations were investigated in irrigation-desert soil in North-western China based on an experiment started from 1988. Four different fertilization treatments were included, i. e., organic fertilizer (OF), green manure (GM), chemical fertilizer (CF) and a control of no fertilization (CK). The results showed that fertilization could increase the contents of DOM. Compared to CK, the treatments of OF, GM, CF increased the dissolved organic carbon (DOC) by 37%, 29%, 16%; increased the dissolved nitrogen (DON) by 334%, 257%, 182%; increased the total carbohydrate (TCs) by 90%, 25%, 2%; and increased the total organic acids (TOAs) by 195%, 116%, 58%; respectively. Furthermore, DOC, DON, TCs, and TOAs in the OF treatment were significantly higher than those in CK, they were also significantly higher in the GM and CF treatments except for TCs. The ultraviolet-visible analysis showed that fertilizations enhanced the SUVA(254), SUVA(260), SUVA(272) and SUVA(280) of DOM, indicating that fertilizations increased the aromatic and hydrophobic percentage, humification degree, and average molecular weight, and thus resulting in more stability of DOM. Same trends were showed for all the 4 ultraviolet spectrum absorption values in different fertilizations, i. e., the strongest effect was found in the OF treatment, and then was the GM treatment and CF treatment successively. From the results by the Fourier Transform Infrared Spectrometry, the characteristic peak of aromatic in the OF treatment was observed shifting from 1 625 to 1 649 cm(-1), which was close to the characteristic peak of humin, suggesting that the aromaticity of DOM in the OF treatment was higher than the other treatments. The characteristic peaks of C-O at 1 260-1 000 cm(-1) belonging to sugar, alcohol, and carboxylic acid

  12. Dioszegia antarctica sp. nov. and Dioszegia cryoxerica sp. nov., psychrophilic basidiomycetous yeasts from polar desert soils in Antarctica

    Science.gov (United States)

    Rodriguez, Russell J.; Connell, L.; Redman, R.; Barrett, A.; Iszard, M.; Fonseca, A.

    2010-01-01

    During a survey of the culturable soil fungal population in samples collected in Taylor Valley, South Victoria Land, Antarctica, 13 basidiomycetous yeast strains with orange-coloured colonies were isolated. Phylogenetic analyses of internal transcribed spacer (ITS) and partial LSU rRNA gene sequences showed that the strains belong to the Dioszegia clade of the Tremellales (Tremellomycetes, Agaricomycotina), but did not correspond to any of the hitherto recognized species. Two novel species, Dioszegia antarctica sp. nov. (type strain ANT-03-116T =CBS 10920T =PYCC 5970T) and Dioszegia cryoxerica sp. nov. (type strain ANT-03-071T =CBS 10919T =PYCC 5967T), are described to accommodate ten and three of these strains, respectively. Analysis of ITS sequences demonstrated intrastrain sequence heterogeneity in D. cryoxerica. The latter species is also notable for producing true hyphae with clamp connections and haustoria. However, no sexual structures were observed. The two novel species can be considered obligate psychrophiles, since they failed to grow above 20 °C and grew best between 10 and 15 °C.

  13. Mycorrhizal fungi and ectomycorrhiza associated bacteria isolated from an industrial desert soil protect pine seedlings against Cd(II) impact.

    Science.gov (United States)

    Kozdrój, Jacek; Piotrowska-Seget, Zofia; Krupa, Piotr

    2007-08-01

    Effects of mycorrhization with Amanita rubescens or Hebeloma sinapizans and dual inoculation with the fungi and ectomycorrhiza associated bacteria (EMAB) Pseudomonas putida or Bacillus cereus on seedling growth and accumulation of Cd(II) in Pinus sylvestris were studied. Both fungal and bacterial species were isolated from roots of pines growing in an industrial area polluted with high concentrations of heavy metals. During mycorrhization, A. rubescens colonized higher number of pine seedlings than H. sinapizans, especially when EMAB were co-inoculated. In addition, the seedling biometric characteristics (i.e. root and shoot lengths and biomass) were stimulated by treatment with the fungal species alone and dual inoculation with the fungi and EMAB. Amanita rubescens was more efficient in this stimulation than H. sinapizans. The increased growth of pine seedlings was especially seen for co-inoculation with P. putida. Furthermore, elevated accumulation of Cd(II), ranging from 56 microg g(-1) to 72 microg g(-1) dry weight, in underground parts of the inoculated seedlings was found. The seedlings treated with A. rubescens accumulated higher concentrations of the metal than those inoculated with H. sinapizans. Additional treatment of pine seedlings with P. putida resulted in the higher accumulation of Cd(II) in the roots as compared with those inoculated with B. cereus. The results suggest that the growth of pine seedlings in Cd(II)-polluted soil may depend on fungal species forming ectomycorrhizae, species-specific co-inoculation with EMAB and specificity of fungal-EMAB interactions.

  14. The physiology mechanisms on drought tolerance and adaptation of biological soil crust moss Bryum argenteum and Didymodon vinealis in Tenger Desert

    Science.gov (United States)

    Zhao, X.; Shi, Y.; Chen, C.; Jia, R.; Li, X.

    2012-04-01

    Bryum argenteum Hedw. and Didymodon vinealis Brid are two dominant moss species in the restored vegetation area in Tenger Desert, which sampled from biological soil crusts and where is an extreme drought regions. We found that they resorted to different osmotic adjustment strategies to mitigate osmotic stress. Under the gradual drought stress, both Bryum argenteum and Didymodon vinealis accumulated K+ and soluble sugar such as sucrose and trehalose. Their glycine betaine contents both decreased, while their proline content had no significant change. With enhanced drought stress, Bryum argenteum's Na+ content was low and decreased significantly, whereas Didymodon vinealis's Na+ content increased sharply and reached to a high level. We found the different of the mechanism of between active oxygen scavenging on Enzymatic and non - enzymatic system in two species moss of Bryum argenteum Hedw and Didymodon vinealis Brid under extreme drought stress. The result showed that two species of Moss of SOD activity gradually enhanced, and they have the material basis for effectively eliminates in vivo of Superoxide free radical. POD in Didymodon nigrescen and CAT in Bryum argeneum are major resistance o oxidative stress effects. The content of GSH rise with the stress also enhanced. The mechanism of finding Bryum argenteum Hedw and Didymodon vinealis Brid tolerance of dehydration ability were focus on different direction, but they are all given positive response to stress and enhance resistance. We investigated the responses of signal transduction substances to gradual drought stress in Didymodon vinealis and Bryum argenteum. The results suggested that: under gradual drought stress, the activities of TP H+-ATPase and PM H+-ATPase of Didymodon vinealis and Bryum argenteum both increased, resulting in their increase of K+ contents and turgor pressures, and triggered biosynthesis of signal transduction substances. ABA had no obvious effect in signal transduction of Bryum argenteum

  15. Simulated climate effects of desert irrigation geoengineering

    Science.gov (United States)

    Cheng, Wei; Moore, John C.; Cao, Long; Ji, Duoying; Zhao, Liyun

    2017-04-01

    Geoengineering, the deliberate large-scale manipulation of earth’s energy balance to counteract global warming, is an attractive proposition for sparsely populated deserts. We use the BNU and UVic Earth system models to simulate the effects of irrigating deserts under the RCP8.5 scenario. Previous studies focused on increasing desert albedo to reduce global warming; in contrast we examine how extending afforestation and ecological projects, that successfully improve regional environments, fair for geoengineering purposes. As expected desert irrigation allows vegetation to grow, with bare soil or grass gradually becoming shrub or tree covered, with increases in terrestrial carbon storage of 90.3 Pg C (UVic-ESCM) - 143.9 Pg C (BNU-ESM). Irrigating global deserts makes the land surface temperature decrease by 0.48 °C and land precipitation increase by 100 mm yr-1. In the irrigated areas, BNU-ESM simulates significant cooling of up to 4.2 °C owing to the increases in low cloud and latent heat which counteract the warming effect due to decreased surface albedo. Large volumes of water would be required to maintain global desert irrigation, equivalent 10 mm/year of global sea level (BNU-ESM) compensate for evapotranspiration losses. Differences in climate responses between the deserts prompt research into tailored albedo-irrigation schemes.

  16. Microbial ecology of hot desert edaphic systems.

    Science.gov (United States)

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

    2015-03-01

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

  17. Methanogens at the top of the world: occurrence and potential activity of methanogens in newly deglaciated soils in high-altitude cold deserts in the Western Himalayas

    Czech Academy of Sciences Publication Activity Database

    Aschenbach, K.; Conrad, R.; Řeháková, Klára; Doležal, Jiří; Janatková, Kateřina; Angel, R.

    2013-01-01

    Roč. 4, Dec 2013 (2013), Ar.359 ISSN 1664-302X R&D Projects: GA ČR GA13-13368S Institutional support: RVO:67985939 Keywords : methanogens * desert areas * cold climate Subject RIV: EH - Ecology, Behaviour Impact factor: 3.941, year: 2013

  18. Desert Habitation History by 14C Dating of Soil Layers in Rural Building Structures (Negev, Israel) : Preliminary Results from Horvat Haluqim

    NARCIS (Netherlands)

    Bruins, Hendrik J.; van der Plicht, Johannes; Haiman, Mordechai

    2012-01-01

    Traditional archaeological approaches in the central Negev Desert used to employ excavation techniques in post-prehistoric periods in which stratigraphy is based on architecture, while material culture forms the basis for dating assessment and chronology. Such an approach was understandable, as it

  19. Desert dust hazards: A global review

    Science.gov (United States)

    Middleton, N. J.

    2017-02-01

    Dust storms originate in many of the world's drylands and frequently present hazards to human society, both within the drylands themselves but also outside drylands due to long-range transport of aeolian sediments. Major sources of desert dust include the Sahara, the Middle East, central and eastern Asia, and parts of Australia, but dust-raising occurs all across the global drylands and, on occasion, beyond. Dust storms occur throughout the year and they vary in frequency and intensity over a number of timescales. Long-range transport of desert dust typically takes place along seasonal transport paths. Desert dust hazards are here reviewed according to the three phases of the wind erosion system: where dust is entrained, during the transport phase, and on deposition. This paper presents a synthesis of these hazards. It draws on empirical examples in physical geography, medical geology and geomorphology to discuss case studies from all over the world and in various fields. These include accelerated soil erosion in agricultural zones - where dust storms represent a severe form of accelerated soil erosion - the health effects of air pollution caused by desert aerosols via their physical, chemical and biological properties, transport accidents caused by poor visibility during desert dust events, and impacts on electricity generation and distribution. Given the importance of desert dust as a hazard to human societies, it is surprising to note that there have been relatively few attempts to assess their impact in economic terms. Existing studies in this regard are also reviewed, but the wide range of impacts discussed in this paper indicates that desert dust storms deserve more attention in this respect.

  20. Properties of anthropogenic soils in ancient run-off capturing agricultural terraces in the Central Negev desert (Israel) and related effects of biochar and ash on crop growth

    NARCIS (Netherlands)

    Asperen, van H.L.; Bor, A.M.C.; Sonneveld, M.P.W.; Bruins, H.J.; Lazarovitch, N.

    2014-01-01

    In the Central Negev hills (Israel) many ancient terraced wadis exist, which captured run-off and caused gradual soil aggradation, which enabled agricultural practices. In these terraces, dark colored soil horizons were observed, containing charcoal, as can be found in Terra Preta soils, suggesting

  1. Restoration of eroded soil in the Sonoran Desert with native leguminous trees using plant growth-promoting microorganisms and limited amounts of compost and water.

    Science.gov (United States)

    Bashan, Yoav; Salazar, Bernardo G; Moreno, Manuel; Lopez, Blanca R; Linderman, Robert G

    2012-07-15

    Restoration of highly eroded desert land was attempted in the southern Sonoran Desert that had lost its natural capacity for self-revegetation. In six field experiments, the fields were planted with three native leguminous trees: mesquite amargo Prosopis articulata, and yellow and blue palo verde Parkinsonia microphylla and Parkinsonia florida. Restoration included inoculation with two of plant growth-promoting bacteria (PGPB; Azospirillum brasilense and Bacillus pumilus), native arbuscular mycorrhizal (AM) fungi, and small quantities of compost. Irrigation was applied, when necessary, to reach a rainy year (300 mm) of the area. The plots were maintained for 61 months. Survival of the trees was marginally affected by all supplements after 30 months, in the range of 60-90%. This variation depended on the plant species, where all young trees were established after 3 months. Plant density was a crucial variable and, in general, low plant density enhanced survival. High planting density was detrimental. Survival significantly declined in trees 61 months after planting. No general response of the trees to plant growth-promoting microorganisms and compost was found. Mesquite amargo and yellow palo verde responded well (height, number of branches, and diameter of the main stem) to inoculation with PGPB, AM fungi, and compost supplementation after three months of application. Fewer positive effects were recorded after 30 months. Blue palo verde did not respond to most treatments and had the lowest survival. Specific plant growth parameters were affected to varying degrees to inoculations or amendments, primarily depending on the tree species. Some combinations of tree/inoculant/amendment resulted in small negative effects or no response when measured after extended periods of time. Using native leguminous trees, this study demonstrated that restoration of severely eroded desert lands was possible. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. Physiographic soil map delineation for the Nile alluvium and desert outskirts in middle Egypt using remote sensing data of EgyptSat-1

    Directory of Open Access Journals (Sweden)

    A.A. Afify

    2010-12-01

    Full Text Available The objectives of this study are to produce a physiographic soil map with correlated attributes to be a base for extra modifiers within the land information system. This integrated data will serve the purposes of land use planning, precision farming practices and to be applied in other areas using the extrapolation approach. The Satellite data of EgyptSat-1 were projected on an area of Middle Egypt that represents unique physiographic features over portions of Beni Suef, El Fayoum, Helwan, and October Provinces. The spectral signatures of the land patterns were delineated by the visual interpretation using the physiographic approach, while soil taxa were categorized according to the key of Soil Taxonomy (USDA, 2010, resulting in two landscape categories. The first category includes older and developed parent materials, covering the following units: (a Pediplains of residual soils over limestone parent rock, having soils of Lithic Haplocalcids, loamy skeletal. (b Terraced old alluvial plains represent the formerly deposited alluvium that preceded the recent one of the River Nile alluvium. They includes soils of Typic Calcigypsids, loamy skeletal and old alluvial plain but are currently managed under cultivation. The soils are dominated by Typic Haplocalcids, loamy skeletal. (c Wadis that were shaped by the paleodrainage erosion, are currently subjected to the seasonal flush flooding and are sparsely vegetated including soils of Typic Torrifluvents, lamy skeletal (calcareous; Typic Torriorthents, sandy skeletal, and Typic Torriorthents, sandy. (d Aeolian plain “partly cultivated” includes soils of Typic Torripsamments (calcareous. The second category is a recent River Nile alluvium that formed the following units: (a Terraced recent alluvial plain “cultivated” includes soils of Entic Calcitorrerts, fine and Typic Haplotorrerts fine. (b Recent flat alluvial plain includes soils of Typic Haplotorrerts, fine. (c Meandering belt is aligning

  3. Carbon sequestration in response to grassland–shrubland–turfgrass conversions and a test for carbonate biomineralization in desert soils, New Mexico, USA

    Science.gov (United States)

    This study uses an experimental pedology approach to examine (i) how the conversion of native C4 grassland to C3 woody shrubs then to irrigated C4 turfgrass affects both soil organic C (SOC) and soil inorganic C (SIC) and (ii) whether SIC can be enhanced by microbial biomineralization. Three sites w...

  4. Paleomagnetism and Mineralogy of Unusual Silicate Glasses and Baked Soils on the Surface of the Atacama Desert of Northern Chile: A Major Airburst Impact ~12ka ago?.

    Science.gov (United States)

    Roperch, P. J.; Blanco, N.; Valenzuela, M.; Gattacceca, J.; Devouard, B.; Lorand, J. P.; Tomlinson, A. J.; Arriagada, C.; Rochette, P.

    2015-12-01

    Unusual silicate glasses were found in northern Chile in one of the driest place on earth, the Atacama Desert. The scoria-type melted rocks are littered on the ground at several localities distributed along a longitudinal band of about 50km. The silicate glasses have a stable natural remanent magnetization carried by fine-grained magnetite and acquired during cooling. At one locality, fine-grained overbank sediments were heated to form a 10 to 20 cm-thick layer of brick-type samples. Magnetic experiments on oriented samples demonstrate that the baked clays record a thermoremanent magnetization acquired in situ above 600°C down to more than 10cm depth and cooled under a normal polarity geomagnetic field with a paleointensity of 40μT. In some samples of the silicate glass, large grains of iron sulphides (troilite) are found in the glass matrix with numerous droplets of native iron, iron sulphides and iron phosphides indicating high temperature and strong redox conditions during melting. The paleomagnetic record of the baked clays and the unusual mineralogy of the silicate glasses indicate a formation mainly by in situ high temperature radiation. Paleomagnetic experiments and chemical analyses indicate that the silicate glasses are not fulgurite type rocks due to lightning events, nor volcanic glasses or even metallurgical slags related to mining activity. The existence of a well-developped baked clay layer indicates that the silicate glasses are not impact-related ejectas. The field, paleomagnetic and mineralogical observations support evidence for a thermal event likely related to a major airburst. The youngest calibrated 14C age on a charcoal sample closely associated with the glass indicates that the thermal event occurred around 12 to 13 ka BP. The good conservation of the surface effects of this thermal event in the Atacama Desert could provide a good opportunity to further estimate the threats posed by large asteroid airbursts.

  5. Leptochloa Fusca Cultivation for Utilization of Salt – affected Soil and Water Resources in Cholistan Desert / Cultivo de Leptochloa Fusca para a utilização de solos afetados por sais e recursos hídricos no Deserto de Cholistan

    Directory of Open Access Journals (Sweden)

    Farooq Ahmad

    2010-04-01

    Full Text Available In the Cholistan Desert, 0.44 million hectares are salt – affected low lying and clayey in nature locally known as ‘dhars’, where rainwater as well as saline groundwater could be utilized for growing salt tolerant grasses like Leptochloa fusca as forage during summer. L. fusca is a promising candidate grass for economic utilization and better management of sodic, high pH, saline soil and saline water resources of the Cholistan desert. L. fusca is known to be a versatile, halophytic, primary colonizer, easily propagatable, perennial, nutritive and palatable forage plant species. The grass has the good biomass producing potential and can grow equally well both under upland and submerged saline soil environment

  6. Military Review: Desert Shield/Desert Storm

    Science.gov (United States)

    1991-04-01

    Directorate However, this unprecedented conversion was ir- 5 of the US Army Combined Arms Support reversible . Most of the new hardware was in Co~mmand...the Logistcs Automation Directorate, US Army Desert Storm. CASCOM and DCL remain Comrined Arms Support Command, Fort Lee, committed to ensuring the

  7. Thermally evolved gas analysis (TEGA) of hyperarid soils doped with microorganisms from the Atacama Desert in southern Peru: Implications for the Phoenix mission

    Science.gov (United States)

    Valdivia-Silva, Julio E.; Navarro-González, Rafael; McKay, Christopher

    2009-07-01

    TEGA, one of several instruments on board of the Phoenix Lander, performed differential scanning calorimetry and evolved gas analysis of soil samples and ice, collected from the surface and subsurface at a northern landing site on Mars. TEGA is a combination of a high temperature furnace and a mass spectrometer (MS) that was used to analyze samples delivered to the instrument via a robotic arm. The samples were heated at a programmed ramp rate up to 1000 °C. The power required for heating can be carefully and continuously monitored (scanning calorimetry). The evolved gases generated during the process can be analyzed with the evolved gas analyzer (a magnetic sector mass spectrometer) in order to determine the composition of gases released as a function of temperature. Our laboratory has developed a sample characterization method using a pyrolyzer integrated to a quadrupole mass spectrometer to support the interpretations of TEGA data. Here we examine the evolved gas properties of six types of hyperarid soils from the Pampas de La Joya in southern Peru (a possible analog to Mars), to which we have added with microorganisms ( Salmonella typhimurium, Micrococcus luteus, and Candida albicans) in order to investigate the effect of the soil matrix on the TEGA response. Between 20 and 40 mg of soil, with or without ˜5 mg of lyophilized microorganism biomass (dry weight), were placed in the pyrolyzer and heated from room temperature to 1200 °C in 1 h at a heating rate of 20 °C/min. The volatiles released were transferred to a MS using helium as a carrier gas. The quadrupole MS was ran in scan mode from 10 to 200 m/z. In addition, ˜20 mg of each microorganism without a soil matrix were analyzed. As expected, there were significant differences in the gases released from microorganism samples with or without a soil matrix, under similar heating conditions. Furthermore, samples from the most arid environments had significant differences compared with less arid soils

  8. The concurrent use of novel soil surface microclimate measurements to evaluate CO2 pulses in biocrusted interspaces in a cool desert ecosystem

    Science.gov (United States)

    Tucker, Colin; McHugh, Theresa A.; Howell, Armin; Gill, Richard; Weber, Bettina; Belnap, Jayne; Grote, Ed; Reed, Sasha C.

    2017-01-01

    Carbon cycling associated with biological soil crusts, which occupy interspaces between vascular plants in drylands globally, may be an important part of the coupled climate-carbon cycle of the Earth system. A major challenge to understanding CO2 fluxes in these systems is that much of the biotic and biogeochemical activity occurs in the upper few mm of the soil surface layer (i.e., the ‘mantle of fertility’), which exhibits highly dynamic and difficult to measure temperature and moisture fluctuations. Here, we report a multi-sensor approach to simultaneously measuring temperature and moisture of this biocrust surface layer (0–2 mm), and the deeper soil profile, concurrent with automated measurement of surface soil CO2effluxes. Our results illuminate robust relationships between biocrust water content and field CO2 pulses that have previously been difficult to detect and explain. All observed CO2 pulses over the measurement period corresponded to surface wetting events, including when the wetting events did not penetrate into the soil below the biocrust layer (0–2 mm). The variability of temperature and moisture of the biocrust surface layer was much greater than even in the 0–5 cm layer of the soil beneath the biocrust, or deeper in the soil profile. We therefore suggest that coupling surface measurements of biocrust moisture and temperature to automated CO2flux measurements may greatly improve our understanding of the climatic sensitivity of carbon cycling in biocrusted interspaces in our study region, and that this method may be globally relevant and applicable.

  9. Joint by Design: The Western Desert Campaign

    Science.gov (United States)

    2015-05-21

    Introduction Seated in a dusty tent, finally cooling in the Egyptian night, the “Desert Fox” had a serious problem. German Lieutenant General Erwin...Ninth Air Force.” 8 foreign soil in Mexico and in Europe during the First World War, expeditionary operations in the Second World War had been...Benghazi and Tobruk, and the Egyptian port of Matruh were operating at 60 percent of their potential capacity. By the end of August, the Axis loss rate of

  10. A retrospective approach to assess human health risks associated with growing air pollution in urbanized area of Thar Desert, western Rajasthan, India.

    Science.gov (United States)

    Rumana, Harcharan Singh; Sharma, Ramesh Chandra; Beniwal, Vikas; Sharma, Anil Kumar

    2014-01-09

    : Air pollution has been a matter of great concern globally because of the associated health risks to individuals. The situation is getting worse in developing countries with more urbanization, industrialization and more importantly the rapidly growing population posing a threat to human life in the form of pulmonary, cardiovascular, carcinogenic or asthmatic diseases by accumulating toxic pollutants, harmful gases, metals, hydrocarbons etc. The present study was undertaken to assess the magnitude of ambient air pollutants and their human health risks like respiratory ailments, infectious diseases, cardiovascular diseases and cancer using a Retrospective Approach of Bart Ostra. The parameters PM2.5, PM10, NOx, SO2, NH3 and O3 were monitored at all selected study sites monitored through a high volume sampler (APM 451 Envirotech, Envirotech Instruments Pvt. Ltd., New Delhi, India). Retrospective Approach was used for assessment of risk factors and disease burden of respiratory and cardiopulmonary health problems. Environmental burden of disease showed that the problem of health related to air pollution is a main concern particularly in the growing cities of India. High to critical level of air pollution including PM10, PM2.5, NOx, SO2, NH3 and O3 was observed in all seasons at traffic intersections and commercial sites. The respiratory infections (25% incidence in population exposed to indoor smoke problems) and a prevalence of asthma/COPD (4.4%) in households exposed to high vehicular pollution along with signs of coronary artery/heart disease and/or hypertension and cancers (37.9-52.2%), were reported requiring preventive measures. The study reflects a great concern for the mankind with the need of having streamline ways to limit air pollution and emphasize upon efficiently determining the risk of illness upon exposure to air pollution.

  11. Re-sighting record of Fulvous Leaf-nosed Bat Hipposideros fulvus Gray, 1838 (Mammalia: Chiroptera: Hipposideridae from Thar Desert, Rajasthan, India

    Directory of Open Access Journals (Sweden)

    Sumit Dookia

    2017-01-01

    Full Text Available Here we report re-sighting records of the Fulvous Leaf-nosed Bat Hipposideros fulvus after a gap of almost four decades (37 years, from Rajasthan, India, on the basis of two male specimens collected from a cave dwelling colony of about 20 individuals from Jodhpur, Rajasthan, India.  This species has been once reported in 1979 from a man-made tunnel in Mandore Garden in Jodhpur and later the same sighting information was re-quoted by several researchers.  The present sighting from a new locality and the voucher specimen confirms the re-sighting of this species after a long gap. 

  12. Gas Chromatography Mass Spectrometry Profiling in Methanolic and Ethyl-acetate Root and Stem Extract ofCorbichonia decumbens(Forssk.) Exell from Thar Desert of Rajasthan, India.

    Science.gov (United States)

    Arora, Sunita; Saini, Manju

    2017-12-01

    Corbichonia decumbens (Forssk.) Exell ( Molluginaceae ), recently has moved to Lophiocarpaceae as per angiospermic plant group (APG) III system, is an annual or short-lived, dwarf, glabrous subshrub, prefers to grow on rocky places and on sand-stones in dry, hot areas of Rajasthan. This is the potential plant with medicinal properties. Vegetative organs under study show antioxidant, anti-inflammatory, antiulcer, antimicrobial, and antinociception activity. This study was carried out to identify the phytoconstituents present in the methanolic and ethyl-acetate extract of root and stem of C. decumbens by GC-MS analysis. Powdered test samples were sequentially extracted with methanol and ethyl-acetate. The compounds obtained as a result of GC-MS screening were identified on the basis of their retention time, peak area and compared with that of literature available and by interpretation of mass spectra. GC-MS analysis of a methanolic extract of root detected mome-inositol (49.53%), guanosine (20.91%), and cis-vaccenic acid (9.25%). While ethyl-acetate extract of root analyzed pentadecanoic acid (17.91%), octadecanoic acid (15.01%) and cis-vaccenic acid (12.04%). Methanolic extract of stem detected mome-inositol (75.47%), pentadecanoic acid (6.04%), and 7-tetradecenal, (Z) (4.54%) while ethyl-acetate extract of stem revealed the presence of 1-heptacosanol (17.35%), hexadecanoic acid (17.17%), and octadecanal (12.64%). The results suggest that C. decumbens (Forssk.) Exell is a plant of potential medicinal value, yielding various bioactive compounds that confirm the application of this plant as a plant-based drug in pharmacy-industry. Extraction is the most important step in the analysis of bioactive compounds present in botanical preparations. The strength of solvent plays a key role in this process, methanol as well as ethyl-acetate showed better response as far as extraction potency is concerned. Gas chromatography mass spectrometry analysis is highly reliable, and the interpretations of the results are of high-quality. This tool is in particular useful for confirming of the presence of bioactive-substances. The results suggest that Corbichonia decumbens (Forssk.) Exell can be used for drug formulations against some major disorders, i.e., cancer, ulcer, tuberculosis, arthritis, etc. Abbreviations Used: GC-MS: Gas Chromatography-Mass Spectrometry, kPa: Kilopascal, RT: Retention time, MF: Molecular formula, MW: Molecular weight.

  13. Soils

    Science.gov (United States)

    Emily Moghaddas; Ken Hubbert

    2014-01-01

    When managing for resilient forests, each soil’s inherent capacity to resist and recover from changes in soil function should be evaluated relative to the anticipated extent and duration of soil disturbance. Application of several key principles will help ensure healthy, resilient soils: (1) minimize physical disturbance using guidelines tailored to specific soil types...

  14. Enhancing and restoring habitat for the desert tortoise

    Science.gov (United States)

    Abella, Scott R.; Berry, Kristin H.

    2016-01-01

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

  15. Physiological conjunction of allelochemicals and desert plants.

    Science.gov (United States)

    Yosef Friedjung, Avital; Choudhary, Sikander Pal; Dudai, Nativ; Rachmilevitch, Shimon

    2013-01-01

    Plants exchange signals with other physical and biological entities in their habitat, a form of communication termed allelopathy. The underlying principles of allelopathy and secondary-metabolite production are still poorly understood, especially in desert plants. The coordination and role of secondary metabolites were examined as a cause of allelopathy in plants thriving under arid and semiarid soil conditions. Desert plant species, Origanum dayi, Artemisia sieberi and Artemisia judaica from two different sources (cultivar cuttings and wild seeds) were studied in their natural habitats. Growth rate, relative water content, osmotic potential, photochemical efficiency, volatile composition and vital factors of allelopathy were analyzed at regular intervals along four seasons with winter showing optimum soil water content and summer showing water deficit conditions. A comprehensive analysis of the volatile composition of the leaves, ambient air and soil in the biological niche of the plants under study was carried out to determine the effects of soil water conditions and sample plants on the surrounding flora. Significant morpho-physiological changes were observed across the seasons and along different soil water content. Metabolic analysis showed that water deficit was the key for driving selective metabolomic shifts. A. judaica showed the least metabolic shifts, while A. sieberi showed the highest shifts. All the species exhibited high allelopathic effects; A. judaica displayed relatively higher growth-inhibition effects, while O. dayi showed comparatively higher germination-inhibition effects in germination assays. The current study may help in understanding plant behavior, mechanisms underlying secondary-metabolite production in water deficit conditions and metabolite-physiological interrelationship with allelopathy in desert plants, and can help cull economic benefits from the produced volatiles.

  16. Physiological conjunction of allelochemicals and desert plants.

    Directory of Open Access Journals (Sweden)

    Avital Yosef Friedjung

    Full Text Available 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.

  17. Physiological Conjunction of Allelochemicals and Desert Plants

    Science.gov (United States)

    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

  18. Ecoregion sections of California deserts

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The dataset delineates ecological sections within California deserts. These deserts occupy the southeastern portion of California and include two ecoregional...

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

    Science.gov (United States)

    Gonzalez-Martin, Cristina; Teigell-Perez, Nuria; Lyles, Mark; Valladares, Basilio; Griffin, Dale W.

    2013-01-01

    Topsoil from arid regions is the main source of dust clouds that move through the earth's atmosphere, and microbial communities within these soils can survive long-range dispersion. Microbial abundance and chemical composition were analyzed in topsoil from various desert regions. Statistical analyses showed that microbial direct counts were strongly positively correlated with calcium concentrations and negatively correlated with silicon concentrations. While variance between deserts was expected, it was interesting to note differences between sample sites within a given desert region, illustrating the 'patchy' nature of microbial communities in desert environments.

  20. Sounds of the Desert.

    Science.gov (United States)

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

    1997-01-01

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

  1. Microbial Communities in a High Arctic Polar Desert Landscape.

    Science.gov (United States)

    McCann, Clare M; Wade, Matthew J; Gray, Neil D; Roberts, Jennifer A; Hubert, Casey R J; Graham, David W

    2016-01-01

    The High Arctic is dominated by polar desert habitats whose microbial communities are poorly understood. In this study, we used next generation sequencing to describe the α- and β-diversity of microbial communities in polar desert soils from the Kongsfjorden region of Svalbard. Ten phyla dominated the soils and accounted for 95% of all sequences, with the Proteobacteria, Actinobacteria, and Chloroflexi being the major lineages. In contrast to previous investigations of Arctic soils, relative Acidobacterial abundances were found to be very low as were the Archaea throughout the Kongsfjorden polar desert landscape. Lower Acidobacterial abundances were attributed to characteristic circumneutral soil pHs in this region, which has resulted from the weathering of underlying carbonate bedrock. In addition, we compared previously measured geochemical conditions as possible controls on soil microbial communities. Phosphorus, pH, nitrogen, and calcium levels all significantly correlated with β-diversity, indicating landscape-scale lithological control of available nutrients, which in turn, significantly influenced soil community composition. In addition, soil phosphorus and pH significantly correlated with α-diversity, particularly with the Shannon diversity and Chao 1 richness indices.

  2. Microbial communities in a High Arctic polar desert landscape

    Directory of Open Access Journals (Sweden)

    Clare M McCann

    2016-03-01

    Full Text Available The High Arctic is dominated by polar desert habitats whose microbial communities are poorly understood. In this study, we used next generation sequencing to describe the α- and β-diversity of polar desert soils from the Kongsfjorden region of Svalbard. Ten phyla consistently dominated the soils and accounted for 95 % of all sequences, with Proteobacteria, Actinobacteria and Chloroflexi being the dominant lineages. In contrast to previous investigations of Arctic soils, Acidobacterial relative abundances were low as were the Archaea throughout the Kongsfjorden polar desert landscape. Lower Acidobacterial abundances were attributed to the circumneutral soil pH in this region which has resulted from the weathering of the underlying carbonate geology. In addition, we correlated previously measured geochemical variables to determine potential controls on the communities. Soil phosphorus, pH, nitrogen and calcium significantly correlated with β-diversity indicating a landscape scale lithological control of soil nutrients which in turn influenced community composition. In addition, soil phosphorus and pH significantly correlated with α- diversity, specifically the Shannon diversity and Chao 1 richness indices.

  3. Active layer warming and deepening at Thule, Greenland during past decade: a comparison of a Polar Desert and a Polar Semi-desert site

    Science.gov (United States)

    Sletten, R. S.; Hagedorn, B.; Hallet, B.; Burnham, J. L.

    2013-12-01

    Microclimate and soil temperature/moisture monitoring at a Polar Desert and a Polar Semi-Desert site at Thule, Greenland reveals recent warming trends and distinct differences between these two sites. Approximately 5 C of warming occurred at the Polar Desert site from 2004 to 2009, while the Polar Semi-desert site warmed only about 3.5 C. Since 2009, the temperatures remain higher but stable. This warming trend is also reflected in the active layer, both in warming of the soil and in deepening of the active layer. Trends in soil temperatures and active layer depth are controlled substantially by the snow cover. For the Polar Semi-desert site, soil temperatures are measured both under natural snow accumulation conditions and under enhanced snow accumulation where a snow fence was installed. The insulating effect of the snow cover is effective and results in significantly warmer winter soils, as has been shown in other artificial snow cover studies. The warmer winter soils may allow greater respiration during the transition seasons thereby releasing more of the accumulated soil carbon in these sites than that we have previously documented. The trends in temperature and moisture may in part be controlled by the higher wind velocities at the Polar Desert site. These conditions are likely to be dominant controls on the ecosystem, along with differences in lithology which affects the cryoturbation of the soils. This in-depth microclimate study, along with our studies of the soils and soil water chemistry provides a detailed comparison of the adjacent ecosystems and may allow us to better predict how slight changes in climatic conditions may influence these systems and their subsequent feedback on carbon cycling.

  4. Mechanisms for maintenance of dominance in a nonclonal desert shrub

    Science.gov (United States)

    Stanley G. Kitchen; Susan E. Meyer; Stephanie L. Carlson

    2015-01-01

    Blackbrush (Coleogyne ramosissima: Rosaceae) is a slow-growing, non-clonal shrub that is regionally dominant on xeric, shallow soils in the North American Mojave Desert-Great Basin transition zone and southern Colorado Plateau. Blackbrush seed production is concentrated in mast years, and most seeds are cached and later consumed by heteromyid rodents....

  5. Is climate change mitigation the best use of desert shrublands?

    Science.gov (United States)

    Susan E. Meyer

    2011-01-01

    In a world where the metrics of the carbon economy have become a major issue, it may come as a surprise that intact cold desert shrublands can sequester significant amounts of carbon, both as biomass and in the form of SOC (soil organic carbon). Xerophytic shrubs invest heavily in belowground biomass, placing fixed carbon in an environment where it turns over only very...

  6. Long-Term Observations of Dust Storms in Sandy Desert Environments

    Science.gov (United States)

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

    2015-04-01

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

  7. Behavior of Boron and Boron Isotopes During Uptake by Atriplex canescens: Desert Plants as Samplers of Boron from Soils and Groundwater

    Science.gov (United States)

    Leenhouts, J. M.; Bassett, R. L.; Maddock, T.

    2002-12-01

    This research was conducted to determine if B isotope ratios (11B/10B) in plant tissue provide an isotopic "fingerprint" of imbibed groundwater and soil moisture. In essence, this work sought to ascertain whether plants can function as in situ samplers for B as an environmental isotope. Because very little is known about the transport and isotopic fractionation of B in plants, this study was designed to reveal any isotopic fractionation that might occur during root uptake and vascular transport by a specific arid-adapted species. The relation between the B isotope ratios sequestered in the leaves of Atriplex canescens and the growth conditions of the plant were investigated using a semihydroponic greenhouse experiment. Nutrient B concentration and solution pH were selected as experimental variables as these parameters span large ranges in nature. In addition, the transition of plant-available B species from neutrally charged to anionic as a function of pH provides a mechanism through which pH-dependent B isotope fractionation may occur. The experimental setup was a randomized factorial block design in which the plants were provided six different nutrient solutions with pH values that ranged from 7.5 to 9.5 and B concentrations that ranged from 0.1 mg/L to 10.0 mg/L. Boron concentration in the plant's leaf and stem samples followed expected patterns, with the highest B amount in the leaves of the plants fed the nutrient solution with 10.0 mg/L B. The stem samples of plants fed 0.1 mg/L B contained the least B. The ratio of B in plants fed 10.0 mg/L vs. 0.1 mg/L B was far less than the 100:1 ratio of B in the nutrients, which implies that a component of uptake is actively controlled by the plant. Negative thermal ionization mass spectrometry was used to analyze the minute amounts of B extracted from the plant tissue digests. Statistical tests indicated that no significant isotopic fractionation occurred during uptake at any treatment pH level. The results indicate

  8. Southwestern desert resources

    Science.gov (United States)

    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.

  9. Aquaporins in desert rodent physiology.

    Science.gov (United States)

    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. © 2015 Marine Biological Laboratory.

  10. Snow, the Great River, and the Desert

    Science.gov (United States)

    Rango, A.

    2005-12-01

    rainfall-produced runoff occurring mostly during the sporadic summer monsoon season. Water harvesting techniques which promote heterogeneous water accumulation or production can effectively make more water available in certain areas at the expense the expense of nearby areas. The use of water ponding dikes on arid rangeland can promote increased native vegetation productivity through increases in soil moisture. Stock tanks lined with impervious material are also used to collect whatever runoff that is generated for later use. Desert dwellers living along rivers must rely on conservation measures and ingenuity in order to come up with a very limited water resource to survive. This survival is continually in doubt because population(and consequently water demand) continues to grow in these arid regions while the water supply remains relatively constant.

  11. [Correlation Among Soil Organic Carbon, Soil Inorganic Carbon and the Environmental Factors in a Typical Oasis in the Southern Edge of the Tarim Basin].

    Science.gov (United States)

    Gong, Lu; Zhu, Mei-ling; Liu, Zeng-yuan; Zhang, Xue-ni; Xie, Li-na

    2016-04-15

    We analyzed the differentiation among the environmental factors and soil organic/inorganic carbon contents of irrigated desert soil, brown desert soil, saline soil and aeolian sandy soil by classical statistics methods, and studied the correlation between soil carbon contents and the environmental factor by redundancy analysis (RDA) in a typical oasis of Yutian in the southern edge of the Tarim Basin. The results showed that the average contents of soil organic carbon and soil inorganic carbon were 2.51 g · kg⁻¹ and 25.63 g · kg⁻¹ respectively. The soil organic carbon content of the irrigated desert soil was significantly higher than those of brown desert soil, saline soil and aeolian sandy soil, while the inorganic carbon content of aeolian sandy soil was significantly higher than those of other soil types. The soil moisture and nutrient content were the highest in the irrigated desert soil and the lowest in the aeolian sandy sail. All soil types had high degree of salinization except the irrigated desert soil. The RDA results showed that the impacts of environmental factors on soil carbon contents ranked in order of importance were total nitrogen > available phosphorus > soil moisture > ground water depth > available potassium > pH > total salt. The soil carbon contents correlated extremely significantly with total nitrogen, available phosphorus, soil moisture and ground water depth (P 0.05).

  12. Deserts and Arid Lands

    Science.gov (United States)

    Brown, Glen F.

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

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

    Science.gov (United States)

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

    2016-01-01

    Abstract 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

  14. Jeeps Penetrating a Hostile Desert

    Science.gov (United States)

    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…

  15. Desert Environmental Handbook. First Edition

    Science.gov (United States)

    1977-11-01

    21 3 Alix I SECTION 4. DESERT OPERATIONS Par’e 4.1 Heat Stress . . . . . . . . . . . . . ...... ...... . .. . . 4.2...0F)Surface Temperatures Floor Board : ¾-ton Truck 60^5 0 C 1410F 8-ton Goer 65 C 149OF Inside Cab: 8-ton Goer 57.20C 1350F Accelerator Pedal: ¾-ton...Experience in WWII, MS#P-129. 135 *)! Desert Effects (continued) Desert Convoy--Report of Environmental Operation, US Army Trans- portation Board

  16. Thar be Hematite!

    Science.gov (United States)

    2004-01-01

    This map of a portion of the small crater currently encircling the Mars Exploration Rover Opportunity shows where crystalline hematite resides. Red and orange patches indicate high levels of the iron-bearing mineral, while blue and green denote low levels. The northeastern rock outcropping lining the rim of the crater does not appear to contain much hematite. Also lacking hematite are the rover's airbag bounce marks. This image consists of data from Opportunity's miniature thermal emission spectrometer superimposed on an image taken by the rover's panoramic camera.

  17. Desert Experimental Range: Annotated bibliography

    Science.gov (United States)

    E. Durant McArthur; Stanley G. Kitchen

    2013-01-01

    Entries qualify for inclusion if they were conducted in whole or part at the Desert Experimental Range (DER, also known as the Desert Range Experiment Station) or were based on DER research in whole or part. They do not qualify merely by the author having worked at the DER when the research was performed or prepared. Entries were drawn from the original abstracts or...

  18. Physiological adaptation in desert birds

    NARCIS (Netherlands)

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

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

  19. Nelson's big horn sheep (Ovis canadensis nelsoni) trample Agassiz's desert tortoise (Gopherus agassizii) burrow at a California wind energy facility

    Science.gov (United States)

    Agha, Mickey; Delaney, David F.; Lovich, Jeffrey E.; Briggs, Jessica; Austin, Meaghan; Price, Steven J.

    2015-01-01

    Research on interactions between Agassiz's desert tortoises (Gopherus agassizii) and ungulates has focused exclusively on the effects of livestock grazing on tortoises and their habitat (Oldemeyer, 1994). For example, during a 1980 study in San Bernardino County, California, 164 desert tortoise burrows were assessed for vulnerability to trampling by domestic sheep (Ovis aries). Herds of grazing sheep damaged 10% and destroyed 4% of the burrows (Nicholson and Humphreys 1981). In addition, a juvenile desert tortoise was trapped and an adult male was blocked from entering a burrow due to trampling by domestic sheep. Another study found that domestic cattle (Bos taurus) trampled active desert tortoise burrows and vegetation surrounding burrows (Avery and Neibergs 1997). Trampling also has negative impacts on diversity of vegetation and intershrub soil crusts in the desert southwest (Webb and Stielstra 1979). Trampling of important food plants and overgrazing has the potential to create competition between desert tortoises and domestic livestock (Berry 1978; Coombs 1979; Webb and Stielstra 1979).

  20. The role of dew in Negev Desert plants.

    Science.gov (United States)

    Hill, Amber J; Dawson, Todd E; Shelef, Oren; Rachmilevitch, Shimon

    2015-06-01

    We investigated the possible use of dew as a water source for three desert plant species native to the Negev Desert: an annual Salsola inermis, and two perennials Artemisia sieberi and Haloxylon scoparium, with different rooting depths of 15, 30 and 90 cm, respectively. We quantified dew-water inputs and used stable isotope analyses to determine the proportion of dew as compared to the proportion of soil water each species utilized. Dew was isotopically enriched (δD values ranged from -25 to 5 ‰), relative to rainfall with δD values that ranged from -40 to -20 ‰ and relative to soil water with δD values that ranged from -65 to -35 ‰. Using a two-source isotope mixing model, we found that S. inermis, A. sieberi and H. scoparium used, on average, 56, 63 and 46 % of their water from dewfall, respectively. Our results suggest that dew-water utilization by Negev Desert plants is highly significant ecologically and thus may be more common than previously thought. In light of future predicted climate change, it may be increasingly important for plants of the Negev Desert to make use of dew as a water resource as it may play an important role in their ability to cope with the associated hydrological constraints predicted for the Negev region.

  1. Characterization of natural habitats and diversity of Libyan desert truffles.

    Science.gov (United States)

    Bouzadi, Mozidi; Grebenc, Tine; Turunen, Ossi; Kraigher, Hojka; Taib, Hassan; Alafai, Abdulhafied; Sbissi, Imed; Assad, Mamdouh El Haj; Bedade, Dattatray; Shamekh, Salem

    2017-10-01

    Desert truffles have traditionally been used as food in Libya. Desert truffle grows and gives fruit sporadically when adequate and properly distributed rainfall occurs with existence of suitable soil and mycorrhizal host plant. The present study aimed to identify and characterize two kinds of wild desert truffles from ecological and nutritional points that were collected from the studied area. The truffle samples were identified as Terfezia (known as red or black truffle) and Tirmania (known as white truffle). The nutritional values (protein, lipid and carbohydrate) of both Libyan wild truffle (Terfezia and Tirmania) were determined on a dry weight basis and result showed that Tirmania and Terfezia contained 16.3 and 18.5% protein, 6.2 and 5.9% lipid, 67.2 and 65% carbohydrate, respectively, in ascocarp biomass. The soil pH of the upper and lower regions of the Hamada Al-Hamra ranged between 8.2 and 8.5 giving suitable conditions for fructification. The plants, Helianthemum kahiricum and Helianthemum lippii were the dominant plants in Hamada Al-Hamra region found to form a mycorrhiza with desert truffles. The phylogenetic analysis of the genomic rDNA ITS region showed that, out of five collections three represented Tirmania pinoyi (Maire) Malencon, one Tirmania nivea (Desf.) Trappe, and one Terfezia boudieri Chatin.

  2. A Numerical Modeling Study on Desert Oasis Self-Supporting Mechanisms

    Science.gov (United States)

    2005-01-01

    soil, and biological resources have led to drought, salinization, and desertification and conse- quently have hindered the development of sustainable...water vapor flux is downward over the Gobi desert (Wang and Mitsuta, 1992). As part of HEIFE, the fundamental observational period observations were...NW–SE) by 25 km (NE–SW), and is surrounded by sandy and Gobi deserts. Small sensible heat-flux and dominating latent heat-flux in the surface energy

  3. Crude oil contamination of soil and groundwater in Kuwait

    OpenAIRE

    II, Hiroyuki; Kawaguchi, Masato; IWABUCHI, Masakazu; YABU, Shinobu

    1997-01-01

    [ABSTRACT] During the Gulf war seven hundreds of oil wells were destroyed by the retreating armies of Iraq. In particular, the Burgan oil field suffered heavy damage. Over 50millions of crude oil spilled out flooding the desert and as a result, extensive contamination of desert soils occurred. Field investigations indicated that crude oil penetrated the desert soils under the newly formed oil lakes to a depth of 150 cm for the 5 years following the Gulf war. The calculated penetration of this...

  4. Ecological zones of California deserts

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The dataset delineates ecological zones within California deserts. We derived ecological zones by reclassifying LANDFIRE vegetation biophysical setting types, plus...

  5. Large-Scale Physical Separation of Depleted Uranium from Soil

    Science.gov (United States)

    2012-09-01

    the garden versus approximately 18 months in the Catch Box); differences in soil chemistry (the DU garden was a desert soil, the Catch Box...increased tendency to burn after prolonged exposure to moist air. A few metals, such as thorium, uranium, and plutonium , emit ionizing radiation that...Catch Box), differences in soil chemistry (the DU garden was a desert soil, the Catch Box construction grade sand), and/or better aqueous drainage in

  6. Physiological ecology of desert iguana (Dipsosaurus dorsalis) eggs: temperature and water relations

    Energy Technology Data Exchange (ETDEWEB)

    Muth, A.

    1980-12-01

    The soil environment imposes constraints on the timing of oviposition and the location of suitable sites for egg burrows of the desert iguana (Dipsosaurus dorsalis). The effects of temperature and water potential on the developmental period and hatching success of eggs were determined. Eggs hatch normally between 28/sup 0/ and 38/sup 0/C at environmental water potentials between -50 and -1500 kPa. Predictions were derived for the timing and placement of egg clutches based on soil water potential and temperature profiles measured in the field and on the results of laboratory incubation experiments. The results suggest that egg burrows should be located at depths >22 cm in washes or possibly in sparsely vegetated areas away from creosote bushes. The biogeography of desert iguanas within the United States is discussed in relation to soil environments and tolerances of eggs. The physical factors affecting incubation may limit the geographical range of desert iguanas.

  7. Temporal dynamics of hot desert microbial communities reveal structural and functional responses to water input

    Energy Technology Data Exchange (ETDEWEB)

    Armstrong, Alacia; Valverde, Angel; Ramond, Jean-Baptiste; Makhalanyane, Thulani P.; Jansson, Janet K.; Hopkins, David W.; Aspray, Thomas J.; Seely, Mary; Trindade, Marla I.; Cowan, Don A.

    2016-09-29

    The temporal dynamics of desert soil microbial communities are poorly understood. Given the implications for ecosystem functioning under a global change scenario, a better understanding of desert microbial community stability is crucial. Here, we sampled soils in the central Namib Desert on sixteen different occasions over a one-year period. Using Illumina-based amplicon sequencing of the 16S rRNA gene, we found that α-diversity (richness) was more variable at a given sampling date (spatial variability) than over the course of one year (temporal variability). Community composition remained essentially unchanged across the first 10 months, indicating that spatial sampling might be more important than temporal sampling when assessing β-diversity patterns in desert soils. However, a major shift in microbial community composition was found following a single precipitation event. This shift in composition was associated with a rapid increase in CO2 respiration and productivity, supporting the view that desert soil microbial communities respond rapidly to re-wetting and that this response may be the result of both taxon-specific selection and changes in the availability or accessibility of organic substrates. Recovery to quasi pre-disturbance community composition was achieved within one month after rainfall.

  8. Diurnal pattern of the drying front in desert and its application for determining the effective infiltration

    Directory of Open Access Journals (Sweden)

    Y. Zeng

    2009-06-01

    Full Text Available Located in western Inner Mongolia, the Badain Jaran Desert is the second largest desert in China and consists of a regular series of stable megadunes, among which over 70 permanent lakes exist. The unexpected lakes in desert attracted research interests on exploring the hydrological process under this particular landscape; however, a very few literatures exist on the diurnal and spatial variation of the drying front in this area, which is the main issue in the desert hydrological process to characterize the movement of water in soil. In order to understand the drying front in the Badain Jaran Desert, a field campaign was conducted by the observations of soil physical parameters and micrometeorological parameters. With the field data, the performance of a vadose zone soil water balance model, the HYDRUS, was verified and calibrated. Then, the HYDRUS was used to produce the spatial and temporal information of coupled water, water vapour and heat transport in sand to characterize the variation pattern of the drying front before, during and after the rainfall. Finally, the deepest drying front was applied to determine the effective infiltration, which is defined as the amount of soil water captured by the sand beneath the deepest drying front by infiltrating water of an incident rainfall event.

  9. High concentrations of lead and barium in hair of the rural population caused by water pollution in the Thar Jath oilfields in South Sudan.

    Science.gov (United States)

    Pragst, Fritz; Stieglitz, Klaus; Runge, Hella; Runow, Klaus-Dietrich; Quig, David; Osborne, Robert; Runge, Christian; Ariki, John

    2017-05-01

    In the oil fields of Thar Jath, South Sudan, increasing salinity of drinking water was observed together with human incompatibilities and rise in livestock mortalities. Hair analysis was used to characterize the toxic exposure of the population. Hair samples of volunteers from four communities with different distance from the center of the oil field (Koch 23km, n=24; Leer 50km, n=26; Nyal 110km, n=21; and Rumbek 220km, n=25) were analyzed for altogether 39 elements by inductively coupled plasma-mass spectrometry. Very high concentrations and a toxic health endangerment were assessed for lead and barium. The concentration of lead increased steadily with decreasing distance from the oil field from Rumbek (mean 2.8μg/g) to Koch (mean 18.7μg/g) and was there in the same range as in highly contaminated mining regions in Kosovo, China or Bolivia. The weighting materials in drilling muds barite (BaSO4) and galena (PbS) were considered to be the sources of drinking water pollution and high hair values. The high concentrations of lead and barium in hair demonstrate clearly the health risk caused by harmful deposition of toxic industrial waste but cannot be used for diagnosis of a chronic intoxication of the individuals. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  10. Biological Communities in Desert Varnish and Potential Implications for Varnish Formation Mechanisms

    Science.gov (United States)

    Lang-Yona, Naama; Maier, Stefanie; Macholdt, Dorothea; Rodriguez-Caballero, Emilio; Müller-Germann, Isabell; Yordanova, Petya; Jochum, Klaus-Peter; Andreae, Meinrat O.; Pöschl, Ulrich; Weber, Bettina; Fröhlich-Nowoisky, Janine

    2017-04-01

    Desert varnishes are thin, orange to black coatings found on rocks in arid and semi-arid environments on Earth. The formation mechanisms of rock varnish are still under debate and the involvement of microorganisms in this process remains unclear. In this work we aimed to identify the microbial community occurring in rock varnish to potentially gain insights into the varnish formation mechanism. For this purpose, rocks coated with desert varnish were collected from the Anza-Borrego Desert, California, USA, as well as soils from underneath the rocks. DNA from both varnish coatings and soil samples was extracted and subsequently used for metagenomic analysis, as well as for q-PCR analyses for specific species quantification. The element composition of the varnish coatings was analyzed and compared to the soil samples. Rock varnish shows similar depleted elements, compared to soil, but Mn and Pb are 50-60 times enriched compared to the soil samples, and about 100 times enriched compared to the upper continental crust. Our genomic analyses suggest unique populations and different protein functional groups occurring in the varnish compared to soil samples. We discuss these differences and try to shed light on the mechanism of Mn oxyhydroxide production in desert varnish formation.

  11. Dynamic response of desert wetlands to abrupt climate change

    Science.gov (United States)

    Springer, Kathleen; Manker, Craig; 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.

  12. Investigation of Life in the Atacama Desert by Astrobiology Rover

    Science.gov (United States)

    Wettergreen, D.; Cabrol, N.

    2005-12-01

    The Atacama Desert is the most arid region on Earth and in several ways analogous to Mars. It has been suggested that the interior of the desert is the most lifeless place on Earth, yet it is known that microorganisms exist on rocks and in soils where the desert meets the coastal range. The Life in the Atacama (LITA) project is investigating the distribution and diversity of life and habitats in the desert using an rover guided by a remote science team. The Atacama Desert presents an excellent analogue to Mars because it is extremely dry, but also, like Mars it experiences high levels of ultraviolet radiation due to its altitude and atmospheric transparency. The soils in the Atacama have been found to be particularly high in oxidants, which lead to the rapid breakdown of organic material. The result is that in some regions of desert almost no biogenic material can be found on the surface. To the benefit of analogue studies for Mars exploration, the desert visually resembles Mars as seen through rover cameras. For these reasons: aridity, ultraviolet radiation and soil composition we believe the Atacama is analogous to Mars and an excellent location for rover field experiments. To support our astrobiologic investigation, we have created a mobile robot, Zo, that makes the measurement of the distribution and diversity of microorganisms possible. Mobility is crucial as habitats are hypothesized to depend on locally variable conditions including moisture, solar flux, and rock/soil composition. The ability to traverse tens to hundreds of kilometers while deploying sensors is a fundamental requirement because only by visiting many sites will the few in which organisms exist be found. Many observations provide the basis for statistically valid analysis of distribution. Zo's instrument payload combines complementary elements, some directed towards remote sensing of the environment (geology, morphology, mineralogy, climate) for the detection of conditions favorable to

  13. The economics of hybrid power systems for sustainable desert agriculture in Egypt

    DEFF Research Database (Denmark)

    Kamel, S.M.; Dahl, C.

    2005-01-01

    priority. This heavy reliance on diesel generation has negative effects on the surrounding environment including soil, groundwater, and air pollution. Although good solar and wind resource prospects exist for the use of cleaner hybrid power systems in certain desert locations, little research has been done...... to investigate the economic potential of such systems in Egypt’s desert agriculture sector. Using optimization software, we assess the economics of hybrid power systems versus the present diesel generation technology in a remote agricultural development area. We also consider the emission reduction advantages......Egypt has embarked on an ambitious desert land reclamation program in order to increase total food production. Energy planners for these desert agriculture locations have chosen diesel generation power technology because minimization of the initial capital cost of a power supply system is their top...

  14. Stone structures in the Syrian Desert

    CERN Document Server

    Sparavigna, Amelia Carolina

    2011-01-01

    An arid land, known as the Syrian Desert, is covering a large part of the Middle East. In the past, this harsh environment, characterized by huge lava fields, the "harraat", was considered as a barrier between Levant and Mesopotamia. When we observe this desert from space, we discover that it is crossed by some stone structures, the "desert kites", which were the Neolithic traps for the game. Several stone circles are visible too, as many Stonehenge sites dispersed in the desert landscape.

  15. Moving the Force: Desert Storm and Beyond

    Science.gov (United States)

    1994-12-01

    Desert Shield~ Desert Storm, we could have met our airlift deployment requirements 20 to 35 percent faster. ~° Similar analyses of the Somalian Restore...DATE DEC 1994 2. REPORT TYPE 3. DATES COVERED - 4. TITLE AND SUBTITLE Moving The Force: Desert Storm and Beyond 5a. CONTRACT NUMBER 5b...MOVING THE FORCE: Desert Storm and Beyond SCOTT W. CONRAD McNair Paper 32 December 1994 INSTITUTE FOR NATIONAL STRATEGIC STUDIES NATIONAL DEFENSE

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

    Science.gov (United States)

    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

  17. UV‐resistant yeasts isolated from a high‐altitude volcanic area on the Atacama Desert as eukaryotic models for astrobiology

    National Research Council Canada - National Science Library

    Pulschen, André A; Rodrigues, Fabio; Duarte, Rubens T. D; Araujo, Gabriel G; Santiago, Iara F; Paulino‐Lima, Ivan G; Rosa, Carlos A; Kato, Massuo J; Pellizari, Vivian H; Galante, Douglas

    2015-01-01

    The Sairecabur volcano (5971 m), in the Atacama Desert, is a high‐altitude extreme environment with high daily temperature variations, acidic soils, intense UV radiation, and low availability of water...

  18. Arbuscular mycorrhizal fungi (Glomales, Zygomycota of the Bledowska Desert, Poland

    Directory of Open Access Journals (Sweden)

    Janusz Błaszkowski

    2014-01-01

    Full Text Available The occurrence of arbuscular mycorrhizal fungi (AMF; Glomales, Zygomycetes associated with plants growing in sand dune soils of the Blędowska Desert, Poland, was investigated in 1995-1997. A total of 134 mixtures of soils and roots were sampled. The mixtures represented 26 plant species in 14 families and one unrecognized plant. Spores of AMF were found in 118 soil-root mixtures. The AMF spore populations comprised 20 described species of the genera Acaulospora, Gigaspora, Glomus and Scutellospora, as well as two undescribed morphospecies of the genus Glomus. The AMF most frequently occurring in the field-collected soils were members of the genus Scutellospora The AMF spore populations comprised 20 described species in the genera Acaulospora, Gigaspora, Glomus and Scutellospora, as well as two undescribed morpho-species of the genus Glomus. The fungal species most frequently and numerously found was Scutellospora armeniaca. The fungi relatively frequently present also were A. rugosa, A. lacunosa, G. aggregatum, an undescribed Glomus 142 and Sc. dipurpurescens. The overall spore abundance of AMF averaged 69.1 and ranged from 0 to 837 in 100 g dry soil. The highest abundance of spores occurred among roots of the families Cupressaceae, followed by the Rosaceae, Asteraceae and Poaceae. Of the plant species investigated two and more times, most spores harboured Juniperus communis. The overall average species richness was 2.4 and ranged from 0 to 6 in 100 g dry soil. Of the plant species sampled at lest two times, the highest average species diversity was found in the root zone of Salix arenaria. The plant species that hosted the highest overall number of species of AMF was Festuca rubra. Trap pot cultures with soilroot mixtures collected in 1997 revealed 10 species of AMF that were not found in field soils sampled in the same year. This suggests that a great part of AMF of Błędowska Desert is represented by rarely or non-sporulating species.

  19. On a Crowded Desert Island.

    Science.gov (United States)

    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)…

  20. Remote Sensing Field Guide - Desert

    Science.gov (United States)

    1991-09-01

    on the frame. A thin sandy crust can appear safe, but should be tested before use. When not covered by sand, an argillaceous sabkhah dries in the...McCauley, U.S. Geological Survey, Desert Studies Group, Flagstaff, AZ, Nov 1973. B. Servicio Aerofotografia Nacional del Peru (on back). / ...... CONN:MFI

  1. Fungal endophytes in above-ground tissues of desert plants: infrequent in culture, but highly diverse and distinctive symbionts

    OpenAIRE

    Massimo, Nicholas C.; Nandi Devan, MM; Arendt, Kayla R.; Wilch, Margaret H.; Riddle, Jakob M.; Furr, Susan H.; Steen, Cole; U?Ren, Jana M.; Sandberg, Dustin C.; Arnold, A. Elizabeth

    2015-01-01

    In hot deserts, plants cope with aridity, high temperatures, and nutrient-poor soils with morphological and biochemical adaptations that encompass intimate microbial symbioses. Whereas the root microbiomes of arid-land plants have received increasing attention, factors influencing assemblages of symbionts in above-ground tissues have not been evaluated for many woody plants that flourish in desert environments. We evaluated the diversity, host affiliations, and distributions of endophytic fun...

  2. Desert Pathfinder at Work

    Science.gov (United States)

    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

  3. Effects of artificial sand fixing on community characteristics of a rare desert shrub.

    Science.gov (United States)

    Liu, Huiliang; Tao, Ye; Qiu, Dong; Zhang, Daoyuan; Zhang, Yongkuan

    2013-10-01

    Eremosparton songoricum (Fabaceae) is a rare, native, clonal small shrub of the deserts of central Asia. Although human activities have greatly fragmented the distribution of E. songoricum, it occurs in areas where artificial sand fixing (AS) has been implemented. We sought to explore whether AS promotes survival and growth of E. songoricum. In the Gurbantunggut Desert of northwestern China in June 2010, we established 10 plots in an area where sand fixing occurred (5-10 years previously) and 11 plots on original sand substrate on which some plants had settled without fixing sand. Sand fixing changed soil properties and biological characteristics in sand-fixed plots. The soil surface where sand fixing occurred was covered by algal crusts and some lichen, but not bare sand (BS). Soil nutrients; water content of deep soil (30-150 cm); overall plant and herbaceous species richness, diversity, abundance, and cover; above- and belowground biomass; and cover, biomass, and height of E. songoricum in the sand-fixed plots were significantly greater than in plots of BS. However, distribution of E. songoricum individuals in the 2 types of plots did not differ. Our results indicate AS may enhance survival of E. songoricum and increase the overall diversity and stability of the desert plant community. We suggest AS as a way to protect this rare desert plant in situ. © 2013 Society for Conservation Biology.

  4. Desert environment and agriculture in the Central Negev and Kadesh-Barnea during historical times

    NARCIS (Netherlands)

    Bruins, H.J.

    1986-01-01

    A description is given of historic land-use and ancient agriculture in the arid desert environment of the central Negev and adjacent northeastern Sinai, based on archeaeological research and soil research.

    Relationships between the landscape, climatic and agricultural

  5. Desert environment and agriculture in the Central Negev and Kadesh-Barnea during historical times

    OpenAIRE

    Bruins, H.J.

    1986-01-01

    A description is given of historic land-use and ancient agriculture in the arid desert environment of the central Negev and adjacent northeastern Sinai, based on archeaeological research and soil research.

    Relationships between the landscape, climatic and agricultural history are evaluated.

  6. Land capability classification of some western desert Oases, Egypt, using remote sensing and GIS

    Directory of Open Access Journals (Sweden)

    Abd-Alla Gad

    2015-10-01

    It could be concluded that the desert Oases are sustainable areas, which might have potential importance supporting the national development programs. Integrating remote sensing data with digital soil map, using GIS, led to the elaboration of successful land capability classification mapping.

  7. WIND CHARACTERISTICS OF MESQUITE STREETS IN THE NORTHERN CHIHUAHUAN DESERT, NEW MEXICO, USA

    Science.gov (United States)

    The most active areas for sand movement in the mesquite-dominated ecosystems in the northern part of the Chihuahuan Desert are elongated bare soil patches referred to as "streets." Wind properties were measured at two flat mesquite sites having highly similar sandy textures but...

  8. A mechanistic modeling and data assimilation framework for Mojave Desert ecohydrology

    Science.gov (United States)

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

    2014-06-01

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

  9. Comparing three models to estimate transpiration of desert shrubs

    Science.gov (United States)

    Xu, Shiqin; Yu, Zhongbo; Ji, Xibin; Sudicky, Edward A.

    2017-07-01

    The role of environmental variables in controlling transpiration (Ec) is an important, but not well-understood, aspect of transpiration modeling in arid desert regions. Taking three dominant desert shrubs, Haloxylon ammodendron, Nitraria tangutorum, and Calligonum mongolicum, as examples, we aim to evaluate the applicability of three transpiration models, i.e. the modified Jarvis-Stewart model (MJS), the simplified process-based model (BTA), and the artificial neural network model (ANN) at different temporal scales. The stem sap flow of each species was monitored using the stem heat balance approach over both the 2014 and 2015 main growing seasons. Concurrent environmental variables were also measured with an automatic weather station. The ANN model generally produced better simulations of Ec than the MJS and BTA models at both hourly and daily scales, indicating its advantage in solving complicated, nonlinear problems between transpiration rate and environmental driving forces. The solar radiation and vapor pressure deficit were crucial variables in modeling Ec for all three species. The performance of the MJS and ANN models was significantly improved by incorporating root-zone soil moisture. We also found that the difference between hourly and daily fitted parameter values was considerable for the MJS and BTA models. Therefore, these models need to be recalibrated when applied at different temporal scales. This study provides insights regarding the application and performance of current transpiration models in arid desert regions, and thus provides a deeper understanding of eco-hydrological processes and sustainable ecosystem management at the study site.

  10. The Chameleon Concept: Modeling Quaternary Geomorphic Surfaces Using Laboratory, Field, and Imaging Spectrometry in the Lower Colorado Sonoran Desert

    Science.gov (United States)

    2005-11-01

    that overlies a thin, gravel-poor vesicular A (Av) soil horizon. Other major landforms on the installation in- clude alluvial fans and bajadas ...but transmits lithologic information in the 2000 to 2500 nanometer wavelengths. Surface soils on desert pavements consist of a layer of eolian dust...that overlies an accreting vesicular (Av) horizon. These soils have same structure and chemistry, and, therefore, the same hyperspectral signature

  11. [Effects of nitrogen addition on soil physico-chemical properties and enzyme activities in desertified steppe].

    Science.gov (United States)

    Su, Jie-Qiong; Li, Xin-Rong; Bao, Jing-Ting

    2014-03-01

    To investigate the impacts of nitrogen (N) enrichment on soil physico-chemical property and soil enzyme activities in desert ecosystems, a field experiment by adding N at 0, 1.75, 3.5, 7, or 14 g N x m(-2) a(-1) was conducted in a temperate desert steppe in the southeastern fringe of the Tengger Desert. The results showed that N addition led to accumulations of total N, NO(3-)-N, NH(4+)-N, and available N in the upper soil (0-10 cm) and subsoil (10-20 cm), however, reductions in soil pH were observed, causing soil acidification to some extent. N addition pronouncedly inhibited soil enzyme activities, which were different among N addition levels, soil depths, and years, respectively. Soil enzyme activities were significantly correlated with the soil N level, soil pH, and soil moisture content, respectively.

  12. Network topology of the desert rose

    Directory of Open Access Journals (Sweden)

    Sigmund Mongstad Hope

    2015-09-01

    Full Text Available 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.

  13. Network topology of the desert rose

    Science.gov (United States)

    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.

  14. Rural childhoods in Egypt's desert lands

    DEFF Research Database (Denmark)

    Adriansen, Hanne Kirstine

    Based on fieldwork in Egypt’s desert lands, this paper discusses rural childhoods in an area experiencing rapid social and cultural change. Since 1987, the Egyptian Government has made new villages in the desert as a means to increase agricultural production and solving problems of unemployment....... Many settlers move to the Mubarak villages in order to give their children a good start in life. The desert villages are associated with a type of ‘rural idyll’. The process of settling in the desert impacts upon the children’s possible pathways to adulthood and their identities and social...

  15. Nonlinear hydrological dynamics on a desert bajada

    Science.gov (United States)

    Wainwright, J.; Parsons, A. J.; Abrahams, A. D.

    2001-12-01

    Water movement forms an integral part of the dynamics of desert ecosystems, with important feedbacks with soil erosion and nutrient transport. Modelling the hydrological dynamics of such ecosystems is thus integral to their understanding. Field data have been collected at the Jornada Basin Long-Term Ecological Research site over the last seven years using rainfall-simulation experiments. These data have demonstrated important nonlinear relationships in the processes of rainfall interception, stemflow, infiltration, runoff dynamics, erosion and nutrient transport. In order to understand the impacts of these relationships at the bajada scale, monitoring of natural events in small catchments and over larger areas using stock ponds, have been carried out. The results from these sites are compared with model runs parameterized using the small-plot data. The dynamics at the bajada scale are shown to be primarily a function of the spatial and temporal pattern of rainfall events. Spatial connectivity of different vegetation zones and the pattern of bare ground and plants within them is shown to have a secondary effect.

  16. [Effects of short-term fencing on organic carbon fractions and physical stability of sandy sierozem in desert steppe of Northwest China].

    Science.gov (United States)

    Yang, Xin-Guo; Song, Nai-Ping; Li, Xue-Bin; Liu, Bing-Ru

    2012-12-01

    In order to explore the change patterns of organic carbon fractions and physical stability of sandy sierozem in desert steppe at the early stage of fencing, 0-40 cm soil samples were collected from a 5-year fenced desert steppe (inside the fence) and a free grazing steppe (outside the fence) in Yanchi County of Ningxia, Northwest China, with the soil organic carbon, labile organic carbon, and particulate organic carbon contents and soil particle composition analyzed. No significant differences were observed in the soil organic carbon content and soil particle composition inside and outside the fence. The average soil organic carbon inside and outside the fences was 3.25 g x kg(-1), the percentages of sand, silt, and clay were averagely 72%, 16%, and 12%, respectively, and the soil physical stability index was 1.30% -1.31%. The soil active organic carbon showed a significant change in 10-20 cm layer. The soil labile organic carbon content was 0.80 g x kg(-1) inside the fence, which was significantly higher than that outside the fence (0.62 g x kg(-1)). The percentage of soil particulate organic carbon was 50.9% inside the fence, which was also significantly higher than that outside the fence (31.7%). The soil texture inside the fence changed from sandy to loam, and the soil labile organic carbon content increased gradually; while the soil texture outside the fence was sandy, and its vertical change was relatively smooth. The organic carbon of sandy si- erozem in the desert steppe under the conditions of short-term fencing was still in a balance between consumption and accumulation, the soil texture was relatively stable, and the soil physical stability changed little. It was suggested that the soil active organic carbon content and its relative percentage in 10-20 cm layer could be used as the indicators of early soil quality change of desert steppe.

  17. Properties of New Reclaimed Soils in the Merowi Irrigation Project of North Sudan

    Directory of Open Access Journals (Sweden)

    Abdalla Elhagwa

    2007-10-01

    Full Text Available This study is a correlation analysis between main productivity limiting soil parameters of desert soils of North Sudan. The indications are based on data of 52 soil profiles representing the desert plain as the main land form of the region. The results show a high significant correlation of cation exchange capacity with both clay and silt in two soil depths. This positive correlation is a new guide for better understanding of the colloidal behaviour of desert soils. The salinity and sodicity interactions of the studied soils were tested via correlation analyses of ECe, ESP and SAR for salinity and sodicity, respectively. The high positive correlation between ECe and ESP indicates a strong association of saline and sodic soils in the desert plain of Northern Sudan. The high positive correlation of ESP and SAR enables a formula to estimate ESP by using the SAR data.

  18. Global Diversity of Desert Hypolithic Cyanobacteria.

    Science.gov (United States)

    Lacap-Bugler, Donnabella C; Lee, Kevin K; Archer, Stephen; Gillman, Len N; Lau, Maggie C Y; Leuzinger, Sebastian; Lee, Charles K; Maki, Teruya; McKay, Christopher P; Perrott, John K; de Los Rios-Murillo, Asunción; Warren-Rhodes, Kimberley A; Hopkins, David W; Pointing, Stephen B

    2017-01-01

    Global patterns in diversity were estimated for cyanobacteria-dominated hypolithic communities that colonize ventral surfaces of quartz stones and are common in desert environments. A total of 64 hypolithic communities were recovered from deserts on every continent plus a tropical moisture sufficient location. Community diversity was estimated using a combined t-RFLP fingerprinting and high throughput sequencing approach. The t-RFLP analysis revealed desert communities were different from the single non-desert location. A striking pattern also emerged where Antarctic desert communities were clearly distinct from all other deserts. Some overlap in community similarity occurred for hot, cold and tundra deserts. A further observation was that the producer-consumer ratio displayed a significant negative correlation with growing season, such that shorter growing seasons supported communities with greater abundance of producers, and this pattern was independent of macroclimate. High-throughput sequencing of 16S rRNA and nifH genes from four representative samples validated the t-RFLP study and revealed patterns of taxonomic and putative diazotrophic diversity for desert communities from the Taklimakan Desert, Tibetan Plateau, Canadian Arctic and Antarctic. All communities were dominated by cyanobacteria and among these 21 taxa were potentially endemic to any given desert location. Some others occurred in all but the most extreme hot and polar deserts suggesting they were relatively less well adapted to environmental stress. The t-RFLP and sequencing data revealed the two most abundant cyanobacterial taxa were Phormidium in Antarctic and Tibetan deserts and Chroococcidiopsis in hot and cold deserts. The Arctic tundra displayed a more heterogenous cyanobacterial assemblage and this was attributed to the maritime-influenced sampling location. The most abundant heterotrophic taxa were ubiquitous among samples and belonged to the Acidobacteria, Actinobacteria, Bacteroidetes

  19. Genomic characterization of Ensifer aridi, a proposed new species of nitrogen-fixing rhizobium recovered from Asian, African and American deserts.

    Science.gov (United States)

    Le Quéré, Antoine; Tak, Nisha; Gehlot, Hukam Singh; Lavire, Celine; Meyer, Thibault; Chapulliot, David; Rathi, Sonam; Sakrouhi, Ilham; Rocha, Guadalupe; Rohmer, Marine; Severac, Dany; Filali-Maltouf, Abdelkarim; Munive, Jose-Antonio

    2017-01-14

    Nitrogen fixing bacteria isolated from hot arid areas in Asia, Africa and America but from diverse leguminous plants have been recently identified as belonging to a possible new species of Ensifer (Sinorhizobium). In this study, 6 strains belonging to this new clade were compared with Ensifer species at the genome-wide level. Their capacities to utilize various carbon sources and to establish a symbiotic interaction with several leguminous plants were examined. Draft genomes of selected strains isolated from Morocco (Merzouga desert), Mexico (Baja California) as well as from India (Thar desert) were produced. Genome based species delineation tools demonstrated that they belong to a new species of Ensifer. Comparison of its core genome with those of E. meliloti, E. medicae and E. fredii enabled the identification of a species conserved gene set. Predicted functions of associated proteins and pathway reconstruction revealed notably the presence of transport systems for octopine/nopaline and inositol phosphates. Phenotypic characterization of this new desert rhizobium species showed that it was capable to utilize malonate, to grow at 48 °C or under high pH while NaCl tolerance levels were comparable to other Ensifer species. Analysis of accessory genomes and plasmid profiling demonstrated the presence of large plasmids that varied in size from strain to strain. As symbiotic functions were found in the accessory genomes, the differences in symbiotic interactions between strains may be well related to the difference in plasmid content that could explain the different legumes with which they can develop the symbiosis. The genomic analysis performed here confirms that the selected rhizobial strains isolated from desert regions in three continents belong to a new species. As until now only recovered from such harsh environment, we propose to name it Ensifer aridi. The presented genomic data offers a good basis to explore adaptations and functionalities that enable them

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

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, Yuki [Argonne National Lab. (ANL), Argonne, IL (United States); Grippo, Mark A. [Argonne National Lab. (ANL), Argonne, IL (United States)

    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.

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

    Science.gov (United States)

    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.

  2. Microenvironments and microscale productivity of cyanobacterial desert crusts

    Science.gov (United States)

    Garcia-Pichel, F.; Belnap, Jayne

    1996-01-01

    We used microsensors to characterize physicochemical microenvironments and photosynthesis occurring immediately after water saturation in two desert soil crusts from southeastern Utah, which were formed by the cyanobacteria Microcoleus vaginatus Gomont, Nostoc spp., and Scytonema sp. The light fields within the crusts presented steep vertical gradients in magnitude and spectral composition. Near-surface light-trapping zones were formed due to the scattering nature of the sand particles, but strong light attenuation resulted in euphotic zones only ca. 1 mm deep, which were progressively enriched in longer wavelengths with depth. Rates of gross photosynthesis (3.4a??9.4 mmol O2A?ma??2A?ha??1) and dark respiration (0.81a??3.1 mmol Oa??2A?ma??2A?ha??1) occurring within 1 to several mm from the surface were high enough to drive the formation of marked oxygen microenvironments that ranged from oxygen supersaturation to anoxia. The photosynthetic activity also resulted in localized pH values in excess of 10, 2a??3 units above the soil pH. Differences in metabolic parameters and community structure between two types of crusts were consistent with a successional pattern, which could be partially explained on the basis of the microenvironments. We discuss the significance of high metabolic rates and the formation of microenvironments for the ecology of desert crusts, as well as the advantages and limitations of microsensor-based methods for crust investigation.

  3. Road safety research in desert countries.

    NARCIS (Netherlands)

    Schreuder, D.A.

    1988-01-01

    Depending on the geographical location and the climatological situation, the rural areas in developing countries vary from dense jungles to deserts.The traffic situation varies accordingly. This chapter deals with developing countries in arid subtropical regions, where the rural areas are deserts

  4. Divining Jordan's desert waters | IDRC - International Development ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    To most people, a desert — by definition — is a place where water is practically nonexistent. But a team of researchers studying Jordan's badia — a large desert in the country's northwest corner — has uncovered a secret moving slowly beneath the area's vast arid expanses. Using satellite photos, knowledge of the local ...

  5. The Riparianness of a Desert Herpetofauna

    Science.gov (United States)

    Charles H. Lowe

    1989-01-01

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

  6. Namib Desert edaphic bacterial, fungal and archaeal communities assemble through deterministic processes but are influenced by different abiotic parameters.

    Science.gov (United States)

    Johnson, Riegardt M; Ramond, Jean-Baptiste; Gunnigle, Eoin; Seely, Mary; Cowan, Don A

    2017-03-01

    The central Namib Desert is hyperarid, where limited plant growth ensures that biogeochemical processes are largely driven by microbial populations. Recent research has shown that niche partitioning is critically involved in the assembly of Namib Desert edaphic communities. However, these studies have mainly focussed on the Domain Bacteria. Using microbial community fingerprinting, we compared the assembly of the bacterial, fungal and archaeal populations of microbial communities across nine soil niches from four Namib Desert soil habitats (riverbed, dune, gravel plain and salt pan). Permutational multivariate analysis of variance indicated that the nine soil niches presented significantly different physicochemistries (R 2  = 0.8306, P ≤ 0.0001) and that bacterial, fungal and archaeal populations were soil niche specific (R 2  ≥ 0.64, P ≤ 0.001). However, the abiotic drivers of community structure were Domain-specific (P Desert soil microbial communities, assembly is principally driven by deterministic processes.

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

    Science.gov (United States)

    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.

  8. Diversity and Distribution of Culturable Microbial Communities of Semiarid Desert Steppe and Cultivated Land in Northwestern China

    Directory of Open Access Journals (Sweden)

    LI Yan-lin CHEN Ji-xiang

    2016-05-01

    Full Text Available The diversity and community distribution of culturable bacteria, actinomycetes, fungi in semiarid desert steppe in northwestern part of China were studied by using dilution plate count, clone isolation and 16S rDNA sequence analysis methods. The results showed that the numbers of culturable bacteria, actinomycetes and fungi of desert steppe were 1.23×106 cfu·g-1, 0.19×106 cfu·g-1 and 0.18×106 cfu·g-1, respectively, compared with those of the cultivated land, whose numbers were 3.03×106 cfu·g-1, 0.53×106 cfu·g-1 and 0.05×106 cfu·g-1 respectively. The numbers of culturable bacteria and actinomycetes in the desert steppe soil were lower than those of the cultivated land, while the fungal number in desert steppe soil was higher than that of the cultivated land. A total of 14 bacterial strains were isolated from the desert steppe soil. The strains belonged to the following three phyla:γ-Proteobacteria(Psychrobacter), Actinobacteria(Kytococcus), and Firmicutes(Bacillus, Lysinibacillus, Solibacillus, Aerococcus). Among which Bacillus and Psychrobacter were the predominant genus. Nineteen bacterial strains were isolated from the cultivated land and were further affiliated to four phyla:ɑ-Proteobacteri(Rhizobium, Sinorhizobium), γ-Proteobacteria(Pseudomonas), Firmicutes(Bacillus) and Actinobacteria(Microbacterium, Arthrobacter, Micrococcus, Kocuria). Actinobacteria was the predominant phylum(occupied 57.9%). A total of 8 actinomycetes strains were isolated from the desert steppe soil and were identified to belong to three phylogenetic groups:Atreptomyces, Micromonspora, Intrasporangium. And Atreptomyces, Micromonspora were the dominant communities in cultivated land. The fungi strains from the desert steppe were identified and designated as Alternaria and Cladosporium. But Penicillium, Alternaria, Aspergillus, Mucor and Coniothecium were isolated from cultivated land. The results indicated that the

  9. Cyanobacterial ecology across environmental gradients and spatial scales in China's hot and cold deserts.

    Science.gov (United States)

    Warren-Rhodes, Kimberley A; Rhodes, Kevin L; Boyle, Linda Ng; Pointing, Stephen B; Chen, Yong; Liu, Shuangjiang; Zhuo, Peijin; McKay, Christopher P

    2007-09-01

    Lithic photoautotrophic communities function as principal primary producers in the world's driest deserts, yet many aspects of their ecology remain unknown. This is particularly true for Asia, where some of the Earth's oldest and driest deserts occur. Using methods derived from plant landscape ecology, we measured the abundance and spatial distribution of cyanobacterial colonization on quartz stony pavement across environmental gradients of rainfall and temperature in the isolated Taklimakan and Qaidam Basin deserts of western China. Colonization within available habitat ranged from 0.37+/-0.16% to 12.6+/-1.8%, with cold dry desert sites exhibiting the lowest abundance. Variation between sites was most strongly correlated with moisture-related variables and was independent of substrate availability. Cyanobacterial communities were spatially aggregated at multiple scales in patterns distinct from the underlying rock pattern. Site-level differences in cyanobacterial spatial pattern (e.g. mean inter-patch distance) were linked with rainfall, whereas patchiness within sites was correlated with local geology (greater colonization frequency of large rocks) and biology (dispersal during rainfall). We suggest that cyanobacterial patchiness may also in part be self-organized - that is, an outcome of soil water-biological feedbacks. We propose that landscape ecology concepts and models linking desert vegetation, biological feedbacks and ecohydrological processes are applicable to microbial communities.

  10. Russian deserters of World War I

    Directory of Open Access Journals (Sweden)

    Os'kin Maksim

    2014-10-01

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

  11. Cross-biome metagenomic analyses of soil microbial communities and their functional attributes.

    Science.gov (United States)

    Fierer, Noah; Leff, Jonathan W; Adams, Byron J; Nielsen, Uffe N; Bates, Scott Thomas; Lauber, Christian L; Owens, Sarah; Gilbert, Jack A; Wall, Diana H; Caporaso, J Gregory

    2012-12-26

    For centuries ecologists have studied how the diversity and functional traits of plant and animal communities vary across biomes. In contrast, we have only just begun exploring similar questions for soil microbial communities despite soil microbes being the dominant engines of biogeochemical cycles and a major pool of living biomass in terrestrial ecosystems. We used metagenomic sequencing to compare the composition and functional attributes of 16 soil microbial communities collected from cold deserts, hot deserts, forests, grasslands, and tundra. Those communities found in plant-free cold desert soils typically had the lowest levels of functional diversity (diversity of protein-coding gene categories) and the lowest levels of phylogenetic and taxonomic diversity. Across all soils, functional beta diversity was strongly correlated with taxonomic and phylogenetic beta diversity; the desert microbial communities were clearly distinct from the nondesert communities regardless of the metric used. The desert communities had higher relative abundances of genes associated with osmoregulation and dormancy, but lower relative abundances of genes associated with nutrient cycling and the catabolism of plant-derived organic compounds. Antibiotic resistance genes were consistently threefold less abundant in the desert soils than in the nondesert soils, suggesting that abiotic conditions, not competitive interactions, are more important in shaping the desert microbial communities. As the most comprehensive survey of soil taxonomic, phylogenetic, and functional diversity to date, this study demonstrates that metagenomic approaches can be used to build a predictive understanding of how microbial diversity and function vary across terrestrial biomes.

  12. Desert Test Site Uniformity Analysis

    Science.gov (United States)

    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.

  13. Draft Genome Sequence of Streptomyces sp. Strain Wb2n-11, a Desert Isolate with Broad-Spectrum Antagonism against Soilborne Phytopathogens

    Energy Technology Data Exchange (ETDEWEB)

    Köberl, Martina; White, Richard A.; Erschen, Sabine; El-Arabi, Tarek F.; Jansson, Janet K.; Berg, Gabriele

    2015-08-06

    Streptomyces sp. strain Wb2n-11, isolated from native desert soil, exhibited broad-spectrum antagonism against plant pathogenic fungi, bacteria and nematodes. The 8.2 Mb draft genome reveals genes putatively responsible for its promising biocontrol activity and genes which enable the soil bacterium to directly interact beneficially with plants.

  14. Impacts of water and nitrogen addition on nitrogen recovery in Haloxylon ammodendron dominated desert ecosystems.

    Science.gov (United States)

    Cui, Xiaoqing; Yue, Ping; Gong, Yanming; Li, Kaihui; Tan, Dunyan; Goulding, Keith; Liu, Xuejun

    2017-12-01

    Desert ecosystems are likely to change in response to global climate change and nitrogen (N) deposition. The effects of increased precipitation and N deposition on plant growth and the N cycle largely depend on N allocation and N recovery efficiency in the plant-soil ecosystem, but there is limited research on this in desert ecosystems. Here we report results using double-labeled (15)NH4(15)NO3 (30 and 60kgNha(-1)yr(-1)) as a tracer under ambient (no additional water addition) and enhanced precipitation (60mm water addition) in a Haloxylon ammodendron dominated ecosystem in the Gurbantunggut Desert of Northwest China. Herbaceous plants were a significantly larger sink for added (15)N than the H. ammodendron trees, and N retention varied with water and N addition, relative to growing season precipitation. The retention of added (15)N varied within the components of H. ammodendron, with the stems retaining most, followed by the assimilation branches. Soil was the dominant sink for added (15)N, in which the topsoil and subsoil respond differently to water and N addition over the two-year period. Nitrogen relative recovery percentage in the whole ecosystem ranged from 43% to 61%, lower than average recovery rate in temperate forests; N tracer recovery percentage significantly increased with water addition but decreased with enhanced N deposition. Future N cycling in central Asian deserts will depend on changes in precipitation. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Albedo indicating land degradation around the Badain Jaran Desert for better land resources utilization.

    Science.gov (United States)

    Liu, Fengshan; Chen, Ying; Lu, Haiying; Shao, Hongbo

    2017-02-01

    Surface albedo is an easy access parameter in reflecting the status of both human disturbed soil and indirectly influenced area, whose characteristic is an important indicator in sustainable development under the background of global climate change. In this study, we employed meteorological data, MODIS 8-day BRDF/Albedo and LAI products from 2000 to 2014 to show the amelioration and mechanism around the Badain Jaran Desert. Results showed that the human-dominated afforestation activities significantly increased the leaf area index (LAI) in summer and autumn. Lower reflectance at visible band was sensed inside the desert compared with the ecozone and the lowest albedo at forested area. The contribution of soil and vegetation reflectance to surface albedo determined the linear sensitivity of albedo to LAI variation. Decreased albedo dominated the spatial-temporal pattern of the Badain Jaran Desert. This study suggested that surface albedo can be regarded as a useful index in indicating the change process and evaluating the sustainable development of biological management around the Badain Jaran Desert. Copyright © 2016. Published by Elsevier B.V.

  16. Influence of Disturbance on Soil Respiration in Biologically Crusted Soil during the Dry Season

    Directory of Open Access Journals (Sweden)

    Wei Feng

    2013-01-01

    Full Text Available Soil respiration (Rs is a major pathway for carbon cycling and is a complex process involving abiotic and biotic factors. Biological soil crusts (BSCs are a key biotic component of desert ecosystems worldwide. In desert ecosystems, soils are protected from surface disturbance by BSCs, but it is unknown whether Rs is affected by disturbance of this crust layer. We measured Rs in three types of disturbed and undisturbed crusted soils (algae, lichen, and moss, as well as bare land from April to August, 2010, in Mu Us desert, northwest China. Rs was similar among undisturbed soils but increased significantly in disturbed moss and algae crusted soils. The variation of Rs in undisturbed and disturbed soil was related to soil bulk density. Disturbance also led to changes in soil organic carbon and fine particles contents, including declines of 60–70% in surface soil C and N, relative to predisturbance values. Once BSCs were disturbed, Q10 increased. Our findings indicate that a loss of BSCs cover will lead to greater soil C loss through respiration. Given these results, understanding the disturbance sensitivity impact on Rs could be helpful to modify soil management practices which promote carbon sequestration.

  17. Deserts

    DEFF Research Database (Denmark)

    Graulund, Rune

    2016-01-01

    As many places around the world confront issues of globalization, migration and postcoloniality, travel writing has become a serious genre of study, reflecting some of the greatest concerns of our time. Encompassing forms as diverse as field journals, investigative reports, guidebooks, memoirs, c...

  18. Deserts

    DEFF Research Database (Denmark)

    Graulund, Rune

    2016-01-01

    geographies, and the relationship between travel writing and the social, ideological and occasionally fictional constructs through which we view the different regions of the world. Covering all of the major topics and debates, this is an essential overview of the field, which will also encourage new......As many places around the world confront issues of globalization, migration and postcoloniality, travel writing has become a serious genre of study, reflecting some of the greatest concerns of our time. Encompassing forms as diverse as field journals, investigative reports, guidebooks, memoirs......, comic sketches and lyrical reveries; travel writing is now a crucial focus for discussion across many subjects within the humanities and social sciences. An ideal starting point for beginners, but also offering new perspectives for those familiar with the field, The Routledge Companion to Travel Writing...

  19. 76 FR 50493 - Notice of Availability of the Record of Decision for the Desert Sunlight Holdings, LLC, Desert...

    Science.gov (United States)

    2011-08-15

    ... Bureau of Land Management Notice of Availability of the Record of Decision for the Desert Sunlight Holdings, LLC, Desert Sunlight Solar Farm (DSSF) and California Desert Conservation Area Plan Amendment... Amendment to the California Desert Conservation Area (CDCA) Plan, the applicable Resource Management Plan...

  20. Does a Nutritious Diet Cost More in Food Deserts?

    OpenAIRE

    Fan, Linlin; Baylis, Kathy; Gundersen, Craig; Ver Ploeg, Michele

    2015-01-01

    Food deserts and their potential effects on diet and nutrition have received much attention from policymakers. While some research has found correlations between food deserts and consumer outcomes, it is unclear whether food deserts truly affect consumption behavior. In this paper, we compare food prices in food deserts and non-food deserts to check whether lack of access is associated with higher food prices of a complete diet, which could constrain the consumption of healthy foods in food d...

  1. Microphytic crusts: 'topsoil' of the desert

    Science.gov (United States)

    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.

  2. Nutrient and water addition effects on day- and night-time conductance and transpiration in a C3 desert annual

    NARCIS (Netherlands)

    Ludwig, F.; Jewitt, R.A.; Donovan, L.A.

    2006-01-01

    Recent research has shown that many C3 plant species have significant stomatal opening and transpire water at night even in desert habitats. Day-time stomatal regulation is expected to maximize carbon gain and prevent runaway cavitation, but little is known about the effect of soil resource

  3. Potential for deserts to supply reliable renewable electric power

    Science.gov (United States)

    Labordena, Mercè; Lilliestam, Johan

    2015-04-01

    To avoid dangerous climate change, the electricity systems must be decarbonized by mid-century. The world has sufficient renewable electricity resources for complete power sector decarbonization, but an expansion of renewables poses several challenges for the electricity systems. First, wind and solar PV power are intermittent and supply-controlled, making it difficult to securely integrate this fluctuating generation into the power systems. Consequently, power sources that are both renewable and dispatchable, such as biomass, hydro and concentrating solar power (CSP), are particularly important. Second, renewable power has a low power density and needs vast areas of land, which is problematic both due to cost reasons and due to land-use conflicts, in particular with agriculture. Renewable and dispatchable technologies that can be built in sparsely inhabited regions or on land with low competition with agriculture would therefore be especially valuable; this land-use competition greatly limits the potential for hydro and biomass electricity. Deserts, however, are precisely such low-competition land, and are at the same time the most suited places for CSP generation, but this option would necessitate long transmission lines from remote places in the deserts to the demand centers such as big cities. We therefore study the potential for fleets of CSP plants in the large deserts of the world to produce reliable and reasonable-cost renewable electricity for regions with high and/or rapidly increasing electricity demand and with a desert within or close to its borders. The regions in focus here are the European Union, North Africa and the Middle East, China and Australia. We conduct the analysis in three steps. First, we identify the best solar generation areas in the selected deserts using geographic information systems (GIS), and applying restrictions to minimize impact on biodiversity, soils, human heath, and land-use and land-cover change. Second, we identify

  4. Spatial distribution of microbial communities associated with dune landform in the Gurbantunggut Desert, China.

    Science.gov (United States)

    Liu, Ruyin; Li, Ke; Zhang, Hongxun; Zhu, Junge; Joshi, DevRaj

    2014-11-01

    The microbial community compositions and potential ammonia oxidation in the topsoil at different positions of sand dune (stoss slope, crest, lee slope, and interdune) from the Gurbantunggut Desert, the largest semi-fixed desert in China, were investigated using several molecular methods. Actinobacteria and Proteobacteria (especially Alphaproteobacteria) were commonly the dominant taxa across all soil samples. Bacterial communities were similar in soils collected from the stoss slopes and interdunes (HC-BSCs, biological soil crusts with a high abundance of cyanobacteria), containing more abundant cyanobacterial populations (16.9-24.5%) than those (0.2-0.7% of Cyanobacteria) in the crests and lee slopes (LC-BSCs, biological soil crusts with a low abundance of cyanobacteria). The Cyanobacteria were mainly composed of Microcoleus spp., and quantitative PCR analysis revealed that 16S rRNA gene copy numbers of Cyanobacteria (especially genus Microcoleus) were at least two orders of magnitude higher in HC-BSCs than in LC-BSCs. Heterotrophic Geodermatophilus spp. frequently occurred in HC-BSCs (2.5-8.0%), whereas genera Arthrobacter, Bacillus, and Segetibacter were significantly abundant in LC-BSC communities. By comparison, the desert archaeal communities were less complex, and were dominated by Nitrososphaera spp. The amoA gene abundance of ammonia-oxidizing archaea (AOA) was higher than that of ammonia-oxidizing bacteria (AOB) in all soil samples, particularly in the interdunal soils (10(6)-10(8) archaeal amoA gene copies per gram dry soil), indicating that AOA possibly dominate the ammonia oxidation at the interdunes.

  5. Desert Dust and Monsoon Rain

    Science.gov (United States)

    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.

  6. Heavy metal distribution and bioaccumulation in Chihuahuan Desert Rough Harvester ant (Pogonomyrmex rugosus) populations

    Energy Technology Data Exchange (ETDEWEB)

    Del Toro, I., E-mail: ideltoro@nsm.umass.ed [Department of Organismic and Evolutionary Biology, University of Massachusetts at Amherst, 611 N. Pleasant Street Amherst, MA 01003 (United States); Floyd, K. [Environmental Science and Engineering, University of Texas at El Paso, 500 W. University Ave., El Paso, TX 79968 (United States); Gardea-Torresdey, J. [Department of Chemistry, University of Texas at El Paso, 500 W. University Ave., El Paso, TX 79968 (United States); Borrok, D. [Department of Geological Sciences, University of Texas at El Paso, 500 W. University Ave., El Paso, TX 79968 (United States)

    2010-05-15

    Heavy metal contamination can negatively impact arid ecosystems; however a thorough examination of bioaccumulation patterns has not been completed. We analyzed the distribution of As, Cd, Cu, Pb and Zn in soils, seeds and ant (Pogonomyrmex rugosus) populations of the Chihuahuan Desert near El Paso, TX, USA. Concentrations of As, Cd, Cu, and Pb in soils, seeds and ants declined as a function of distance from a now inactive Cu and Pb smelter and all five metals bioaccumulated in the granivorous ants. The average bioaccumulation factors for the metals from seeds to ants ranged from 1.04x (As) to 8.12x (Cd). The findings show bioaccumulation trends in linked trophic levels in an arid ecosystem and further investigation should focus on the impacts of heavy metal contamination at the community level. - Heavy metals bioaccumulate in desert ants.

  7. Thar`s gold in them thar notebooks: benefits of laboratory notebooks in the government archive

    Energy Technology Data Exchange (ETDEWEB)

    O`Canna, M.

    1996-01-01

    As Archive Coordinator for Sandia National Laboratories Corporate Archives, I am responsible for promoting the preservation and value of Sandia`s history. Today I will talk about one important part of Sandia`s historical record--the laboratory notebook. I will start with some brief background on Sandia National Laboratories, including the Laboratories` mission and an example of how the gold in one lab notebook helped to give a picture of Sandia`s early history. Next, I will talk about the use of notebooks at Sandia Labs, how they represent technology developed at Sandia, and include noteworthy examples of how patent information has been collected, used, and released to the public. Then, I will discuss how the National Competitiveness Technology Transfer Act of 1989 authorized technology transfer initiatives and the exclusive use of patented information, resulting in many golden opportunities for the national laboratories to work with private industry to further technology. I will briefly discuss laboratory notebook retention schedules and mention a new initiative to better utilize Laboratory notebooks. And, finally, I will summarize how the `gold` in laboratory notebooks in government archives are a reflection of the valuable and extensive research authorized and funded by the government to benefit the public.

  8. Desert Dust Satellite Retrieval Intercomparison

    Science.gov (United States)

    Carboni, E.; Thomas, G. E.; Sayer, A. M.; Siddans, R.; Poulsen, C. A.; Grainger, R. G.; Ahn, C.; Antoine, D.; Bevan, S.; Braak, R.; hide

    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. Diversity and Community Composition of Vertebrates in Desert River Habitats.

    Directory of Open Access Journals (Sweden)

    C L Free

    Full Text Available Animal species are seldom distributed evenly at either local or larger spatial scales, and instead tend to aggregate in sites that meet their resource requirements and maximise fitness. This tendency is likely to be especially marked in arid regions where species could be expected to concentrate at resource-rich oases. In this study, we first test the hypothesis that productive riparian sites in arid Australia support higher vertebrate diversity than other desert habitats, and then elucidate the habitats selected by different species. We addressed the first aim by examining the diversity and composition of vertebrate assemblages inhabiting the Field River and adjacent sand dunes in the Simpson Desert, western Queensland, over a period of two and a half years. The second aim was addressed by examining species composition in riparian and sand dune habitats in dry and wet years. Vertebrate species richness was estimated to be highest (54 species in the riverine habitats and lowest on the surrounding dune habitats (45 species. The riverine habitats had different species pools compared to the dune habitats. Several species, including the agamid Gowidon longirostris and tree frog Litoria rubella, inhabited the riverine habitats exclusively, while others such as the skinks Ctenotus ariadnae and C. dux were captured only in the dune habitats. The results suggest that, on a local scale, diversity is higher along riparian corridors and that riparian woodland is important for tree-dependent species. Further, the distribution of some species, such as Mus musculus, may be governed by environmental variables (e.g. soil moisture associated with riparian corridors that are not available in the surrounding desert environment. We conclude that inland river systems may be often of high conservation value, and that management should be initiated where possible to alleviate threats to their continued functioning.

  10. Tree water potentials supporting an explanation for the occurrence of Vachellia erioloba in the Namib Desert (Namibia)

    OpenAIRE

    Joachim H. A. Krug

    2017-01-01

    Background Site-vegetation relations of Vachellia erioloba, Faidherbia albida, Euclea pseudebenus and Tamarix usneoides in two contrasting locations in the Namib Desert (Namibia) were evaluated with the goal to relate soil water availability to the occurrence of trees under hyper-arid conditions. Methods Plant water potentials were measured using a pressure chamber in the field. Pre-dawn water potentials were assessed to reflect the soil water potential of the rhizosphere. Midday wa...

  11. Involvement of cytochrome P450 in host-plant utilization by Sonoran Desert Drosophila.

    OpenAIRE

    Frank, M. R.; Fogleman, J C

    1992-01-01

    The four Drosophila species endemic to the Sonoran Desert (Drosophila mettleri, Drosophila mojavensis, Drosophila nigrospiracula, and Drosophila pachea) utilize necrotic cactus tissue or soil soaked by rot exudate as breeding substrates. Each Drosophila species uses a different cactus species as its primary host. D. pachea is limited to senita cactus by a biochemical dependency on unusual sterols available only in that cactus. For the other Drosophila species, no such chemical dependencies ex...

  12. Positive Interactions between Desert Granivores: Localized Facilitation of Harvester Ants by Kangaroo Rats

    OpenAIRE

    Andrew J Edelman

    2012-01-01

    Facilitation, when one species enhances the environment or performance of another species, can be highly localized in space. While facilitation in plant communities has been intensely studied, the role of facilitation in shaping animal communities is less well understood. In the Chihuahuan Desert, both kangaroo rats and harvester ants depend on the abundant seeds of annual plants. Kangaroo rats, however, are hypothesized to facilitate harvester ants through soil disturbance and selective seed...

  13. Vegetation - Central Mojave Desert [ds166

    Data.gov (United States)

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

  14. Overview about polluted sites management by mining activities in coastal-desertic zones

    Science.gov (United States)

    Reyes, Arturo; Letelier, María Victoria; Arenas, Franko; Cuevas, Jacqueline; Fuentes, Bárbara

    2016-04-01

    In Chile the main mining operations as well as artisanal and small-scale mining (copper, gold and silver) are located in desert areas. A large number of abandoned polluted sites with heavy metals and metalloids (Hg, Pb, Cu, Sb, As) remain in coastal areas close to human centers. The aim of this work was to identify the best remediation alternatives considering the physic-chemical characteristics of the coastal-desertic soils. The concentrations of above mentioned pollutants as well as soil properties were determined. The results showed variable concentration of the pollutants, highest detected values were: Hg (46.5 mg kg-1), Pb (84.7 mg kg-1), Cu (283.0 mg kg-1), Sb (90 mg kg-1), As (2,691 mg kg-1). The soils characteristic were: high alkalinity with pH: 7.75-9.66, high electric conductivity (EC: 1.94-118 mScm-1), sodium adsorption ratio (SAR: 5.07-8.22) and low permeability of the soils. Coastal-desertic sites are potential sources of pollution for population, and for terrestrial and marine ecosystems. Exposure routes of pollution for the population include: primary, by incidental ingestion and inhalation of soil and dust and secondary, by the ingestion of marine sediments, sea food and seawater. Rehabilitation of coastal-desertic sites, by using techniques like soil washing in situ, chemical stabilization, or phytostabilization, is conditioned by physic-chemical properties of the soils. In these cases the recommendation for an appropriate management, remediation and use of the sites includes: 1) physic chemical characterization of the soils, 2) evaluation of environmental risk, 3) education of the population and 3) application of a remediation technology according to soil characteristic and the planned use of the sites. Acknowledgments: Funding for this study was supported by the Regional Council of Antofagasta under Project Estudio de ingeniería para la remediación de sitios abandonados con potencial presencia de contaminantes identificados en la comuna de

  15. Plant ecology of the Namib desert

    OpenAIRE

    P. Van Damme

    1991-01-01

    The Namib desert is reportedly the oldest desert in the world. It consists of a number of very distinct ecosystems, six of which are dealt with in this text. Among them are the sand dune, the dry river bed and the domed inselbergs vegetation. The importance of fog water absorption for the Namib flora is discussed. Two important and noteworthy endemic plant species, i.e. Welwitschia mirabilis and Acanthosicyos horrida are treated extensively, because of their great interest for plant physiolog...

  16. In vitro germination of desert rose varieties(

    OpenAIRE

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

    2015-01-01

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

  17. Evidence for direct water absorption by shallow-rooted desert plants in desert-oasis ecotone, Northwest China

    Science.gov (United States)

    Fang, Jing

    2014-05-01

    Besides the absorption by roots from the soil substrate, it has long been known that plants exhibit alternative water-absorption strategies, particularly in drought-prone environments. For many tropical epiphytic orchids, air moisture can be absorbed directly by aerial roots. Some conifers are also found to utilize air moisture by foliar absorption during the summer fog season. However, few studies have been carried out on the atmospheric water vapor absorption by shallow-rooted desert plants. We conducted experiments in desert-oasis ecotone and investigated the effects of dew absorbed by three kinds of shallow-rooted seedlings on net photosynthesis rate, as well as on other water relations variables. Three kinds of typical shallow-rooted desert species (Bassia dasyphylla, Salsola collina and Corispermum declinatum) have been chosen and potted. Each species were subjected to contrasting watering regimes (normal and deficient) and different air moisture conditions (having dew and having no dew) for 10 weeks. Net photosynthesis rate was measured on six occasions during the study. Other water relations variables (midday shoot water potential, relative water content, stomatal conductance) were also measured. Under the dew conditions, average net photosynthesis rate, shoot water potential, leaf relative water content and stomatal conductance increased, with greater responses observed for plants subjected to a deficient watering regime than for well-watered plants. These results indicated dew occurred in arid region could be utilized through foliar absorption by some shallow-rooted plants, and for the shallow-rooted plants, the presence of dew could significantly relieve the deficit of water in water-stressed regime.

  18. Threshold Velocity for Saltation Activity in the Taklimakan Desert

    Science.gov (United States)

    Yang, Xinghua; He, Qing; Matimin, Ali; Yang, Fan; Huo, Wen; Liu, Xinchun; Zhao, Tianliang; Shen, Shuanghe

    2017-08-01

    The threshold velocity is an indicator of a soil's susceptibility to saltation activity and is also an important parameter in dust emission models. In this study, the saltation activity, atmospheric conditions, and soil conditions were measured from 1 August 2008 to 31 July 2009 in the Taklimakan Desert, China. the threshold velocity was estimated using the Gaussian time fraction equivalence method. At 2 m height, the 1-min averaged threshold velocity varied between 3.5 and 10.9 m/s, with a mean of 5.9 m/s. Threshold velocities varying between 4.5 and 7.5 m/s accounted for about 91.4% of all measurements. The average threshold velocity displayed clear seasonal variations in the following sequence: winter (5.1 m/s) relations between daily mean threshold velocity and air temperature, specific humidity, and soil volumetric moisture content. High or moderate positive correlations were found between threshold velocity and air temperature, specific humidity, and soil volumetric moisture content (air temperature r = 0.75; specific humidity r = 0.59; and soil volumetric moisture content r = 0.55; sample size = 251). In the study area, the observed horizontal dust flux was 4198.0 kg/m during the whole period of observation, while the horizontal dust flux calculated using the threshold velocity from the regression equation was 4675.6 kg/m. The correlation coefficient between the calculated result and the observations was 0.91. These results indicate that atmospheric and soil conditions should not be neglected in parameterization schemes for threshold velocity.

  19. CONTEMPORARY CHANGES OF THE CLIMATIC CONDITIONS OF THE CASPIAN SEMI-DESERT LANDSCAPES OF THE EASTERN CISCAUCASIA

    Directory of Open Access Journals (Sweden)

    Z. V. Ataev

    2011-01-01

    Full Text Available The article analyzes the changes in the hydrothermal conditions within the pricaspian littoral plains accumulation and denudation-accumulative in places aeolian landscapes saltwort, saltwort-sagebrush deserts and semi-deserts in light chestnut soils based on data from weather stations "Makhachkala" for years 1945-2005.Tendencies of changes in temperature, precipitation, and hydrothermal coefficient and coefficient of moisture are shown. Tendency of modern fluctuations suggests that the climatic conditions of the last period contribute to the development of dry steppes and significant deviations from the conditions of the previous period do not occur.

  20. Bacterial diversity of Drass, cold desert in Western Himalaya, and its comparison with Antarctic and Arctic.

    Science.gov (United States)

    Gupta, Puja; Sangwan, Naseer; Lal, Rup; Vakhlu, Jyoti

    2015-08-01

    Drass is the coldest inhabited place in India and the second coldest, inhabited place in the world, after Siberia. Using the 16SrDNA amplicon pyrosequencing, bacterial diversity patterns were cataloged across the Drass cold desert. In order to identify the ecotype abundance across cold desert environment, bacterial diversity patterns of Drass were further compared with the bacterial diversity of two other cold deserts, i.e., Antarctic and Arctic. Acidobacteria, Proteobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria and Gemmatimonadetes were among the highly abundant taxonomic groups present across all the three cold deserts and were designated as the core phyla. However, Firmicutes, Nitrospirae, Armatimonadetes (former candidate division OP10), Planctomycetes, TM7, Chloroflexi, Deinococcus-Thermus, Tenericutes and candidate phyla WS3 were identified as rare phyla in Drass, Antarctic and Arctic samples. Differential abundance patterns were also computed across all the three samples, i.e., Acidobacteria (32.1 %) were dominant in Drass and Firmicutes (52.9 ± 17.6 %) and Proteobacteria (42 ± 1.3 %) were dominant in Antarctic and Arctic reference samples, respectively. Alpha diversity values Shannon's (H) and Simpson's (1-D) diversity indices were highest for Antarctic samples, whereas richness estimators (ACE and Chao1) were maximum for Drass soil suggesting greater species richness in bacterial communities in Drass than the Antarctic and Arctic samples.

  1. Hydrogeologic factors that influence ground water movement in the desert southwest United States

    Science.gov (United States)

    Chuang, Frank C.; McKee, Edwin H.; Howard, Keith A.

    2003-01-01

    A project to study ground-water and surface-water interactions in the desert southwestern United States was initiated in 2001 by the Tucson, Arizona office of the Water Resources Division, U.S. Geological Survey (USGS). One of the goals of the Southwest Ground-water Resources Project was to develop a regional synthesis that includes the use of available digital geologic data, which is growing rapidly due to the increasing use of Geographic Information Systems (GIS). Included in this report are the digital maps and databases of geologic information that should have a direct impact on the studies of ground-water flow and surface-water interaction. Ground-water flow is governed by many geologic factors or elements including rock and soil permeability, stratigraphy and structural features. These elements directly influence ground-water flow, which is key to understanding the possible inter-connectivity of aquifer systems in desert basins of the southwestern United States. We derive these elements from the evaluation of regional geology and localized studies of hydrogeologic basins. These elements can then be applied to other unstudied areas throughout the desert southwest. This report presents a regional perspective of the geologic elements controlling ground-water systems in the desert southwest that may eventually lead to greater focus on smaller sub-regions and ultimately, to individual ground-water basins.

  2. Linking Populus euphratica hydraulic redistribution to diversity assembly in the arid desert zone of Xinjiang, China.

    Directory of Open Access Journals (Sweden)

    Xiao-Dong Yang

    Full Text Available 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.

  3. Effects of Altered Temperature & Precipitation on Soil Bacterial & Microfaunal Communities as Mediated by Biological Soil Crusts

    Energy Technology Data Exchange (ETDEWEB)

    Neher, Deborah A. [University of Vermont

    2004-08-31

    With increased temperatures in our original pot study we observed a decline in lichen/moss crust cover and with that a decline in carbon and nitrogen fixation, and thus a probable decline of C and N input into crusts and soils. Soil bacteria and fauna were affected negatively by increased temperature in both light and dark crusts, and with movement from cool to hot and hot to hotter desert climates. Crust microbial biomass and relative abundance of diazotrophs was reduced greatly after one year, even in pots that were not moved from their original location, although no change in diazotroph community structure was observed. Populations of soil fauna moved from cool to hot deserts were affected more negatively than those moved from hot to hotter deserts.

  4. Impacts of feral horses on a desert environment

    Directory of Open Access Journals (Sweden)

    Hendrickson Larry E

    2009-11-01

    Full Text Available Abstract Background Free-ranging horses (Equus caballus in North America are considered to be feral animals since they are descendents of non-native domestic horses introduced to the continent. We conducted a study in a southern California desert to understand how feral horse movements and horse feces impacted this arid ecosystem. We evaluated five parameters susceptible to horse trampling: soil strength, vegetation cover, percent of nonnative vegetation, plant species diversity, and macroinvertebrate abundance. We also tested whether or not plant cover and species diversity were affected by the presence of horse feces. Results Horse trailing resulted in reduced vegetation cover, compacted soils, and in cases of intermediate intensity disturbance, increased plant species diversity. The presence of horse feces did not affect plant cover, but it did increase native plant diversity. Conclusion Adverse impacts, such as soil compaction and increased erosion potential, were limited to established horse trails. In contrast, increased native plant diversity near trails and feces could be viewed as positive outcomes. Extensive trailing can result in a surprisingly large impact area: we estimate that 25 km2 of trails in our study area.

  5. Significant Impacts of Increasing Aridity on the Arid Soil Microbiome.

    Science.gov (United States)

    Neilson, Julia W; Califf, Katy; Cardona, Cesar; Copeland, Audrey; van Treuren, Will; Josephson, Karen L; Knight, Rob; Gilbert, Jack A; Quade, Jay; Caporaso, J Gregory; Maier, Raina M

    2017-01-01

    Global deserts occupy one-third of the Earth's surface and contribute significantly to organic carbon storage, a process at risk in dryland ecosystems that are highly vulnerable to climate-driven ecosystem degradation. The forces controlling desert ecosystem degradation rates are poorly understood, particularly with respect to the relevance of the arid-soil microbiome. Here we document correlations between increasing aridity and soil bacterial and archaeal microbiome composition along arid to hyperarid transects traversing the Atacama Desert, Chile. A meta-analysis reveals that Atacama soil microbiomes exhibit a gradient in composition, are distinct from a broad cross-section of nondesert soils, and yet are similar to three deserts from different continents. Community richness and diversity were significantly positively correlated with soil relative humidity (SoilRH). Phylogenetic composition was strongly correlated with SoilRH, temperature, and electrical conductivity. The strongest and most significant correlations between SoilRH and phylum relative abundance were observed for Acidobacteria, Proteobacteria, Planctomycetes, Verrucomicrobia, and Euryarchaeota (Spearman's rank correlation [rs] = >0.81; false-discovery rate [q] = ≤0.005), characterized by 10- to 300-fold decreases in the relative abundance of each taxon. In addition, network analysis revealed a deterioration in the density of significant associations between taxa along the arid to hyperarid gradient, a pattern that may compromise the resilience of hyperarid communities because they lack properties associated with communities that are more integrated. In summary, results suggest that arid-soil microbiome stability is sensitive to aridity as demonstrated by decreased community connectivity associated with the transition from the arid class to the hyperarid class and the significant correlations observed between soilRH and both diversity and the relative abundances of key microbial phyla typically

  6. Desert Amplification in a Warming Climate

    Science.gov (United States)

    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

  7. Experimental Investigation of climate change effects on plant available water on rocky desert slopes

    Science.gov (United States)

    Kuhn, Nikolaus; Hikel, H.; Schwanghart, W.; Yair, Aaron

    2010-05-01

    Deserts and semi-deserts cover more than one-third of the global land surface, affecting about 49 million km2 with aridity. In many arid regions, slopes are characterized by sparse and patchy soil and vegetation cover, forming so called 'fertility islands'. The mosaic of soil and vegetation is dynamically interdependent, controlled by adaption of the ecosystem to limited and spatially as well as temporarily variable precipitation. Commonly, the role of the pattern of rocks and soil is considered to act as a natural water harvesting system. In an ideal system, the rocky area supplying water matches the soil's infiltration capacity for the given rainfall magnitude. This approach limits the assessment of plant water supply to the amount and intensity of rainfall events, i.e. the supply of water. In reality, the demand of water by the plants also requires consideration. Therefore, the volume of soil storing water is equally important to the ration of soil to rock. Soil volume determines the absolute amount of water stored in the soil and is thus indicative of the time period during which plants do not experience drought related stress between rainfall events. With climate change likely affecting the temporal pattern of rainfall events, a detailed understanding of soil-water interaction, including the storage capacity of patchy soils on rocky slopes, is required. The aim of the study is to examine the relationship between climate change and plant available water on patchy soils in the Negev desert. Thirteen micro-catchments near Sede Boqer were examined. For each micro-catchment, soil volume and distribution was estimated by laser scanning before and after soil excavation. Porosity was estimated by weighing the excavated soil. Before excavation, sprinkling experiments were conducted. Rainfall of 18mm/h was applied to an area of 1m2 each. The experiments lasted 25 to 40 minutes, until equilibrium runoff rates were achieved. Based on these data, rainfall required for soil

  8. Thermal characteristics of mountain desert terrain derived from thermal infrared multispectral scanner measurements

    Science.gov (United States)

    Astling, E. G.; Quattrochi, D. A.

    1989-01-01

    The spatial and temporal variability of mountain-desert territory thermal is examined with an airborne thermal infrared multispectral scanner (TIMS). The purpose of the study is to demonstrate that inhomogeneities of the surface temperatures in the area can be adequately large to influence mesoscale circulations and the turbulence characteristics of boundary-layer flow. Ground truth measurements are compared to the TIMS imagery, with focus placed on the thermal infrared sensitivity to wet and dry soils, terrain elevation, and soil type. The results indicate that variations in the thermal features are dependent on soil type and soil moisture, and that the dependence on surface radiative temperatures on terrain elevation is apparent in daytime measurements.

  9. Preface

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    coordinated programme towards the understand- ing of the ideological evolution of the Thar Desert in India. These groups discussed various aspects of such a study and a comprehensive programme of research entitled 'Quaternary Stratigraphy and Palaeoenvironmental History of the. Thar Desert' was submitted to the ...

  10. Journal of Earth System Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    pp 403-425 Special Section on: Quaternary History and Palaeoenvironmental Record of the Thar Desert in India. Palaeoenvironmental history of Bap-Malar and Kanod playas of western Rajasthan, Thar desert · B C Deotare M D Kajale S N Rajaguru S Kusumgar A J T Jull J D Donahue · More Details Abstract Fulltext PDF.

  11. Mycoflora associated with Hyoscyamus muticus growing under an extremely arid desert environment (Aswan region, Egypt).

    Science.gov (United States)

    El-Zayat, Soad A; Nassar, Mortada S M; El-Hissy, Farida T; Abdel-Motaal, Fatma F; Ito, Shin-ichi

    2008-04-01

    Hyoscyamus muticus L. (Egyptian henbane) is one of the desert medicinal plants of family Solanaceae. The plant produces pharmaceutically important compounds (tropane alkaloids) as secondary metabolites. In the present study, we describe mycoflora of H. muticus grown in four different locations in Egyptian southern desert (Aswan region): Aswan university campus, Wadi Allaqi down stream part, Aswan airport road, and Sahari city. Eighty-one species and two varieties belonging to 31 genera were isolated from soils surrounding H. muticus plants, the surface of the plants, and inside the plants as endophytic fungi. Aspergillus was the most common genus in all study areas. The highest number of genera and species of fungi were recorded in Aswan university campus followed by Aswan airport road. Fungal diversity analysis revealed that these two locations have higher fungal diversity compared to other two locations. A higher number of fungal species were isolated from rhizosphere soil and rhizoplane than from non-rhizosphere and other plant organs. Endophytic fungi were isolated from all plant parts of H. muticus. Communications between H. muticus plants and fungi under desert conditions both in rhizosphere and inside the plant are deduced.

  12. Mate desertion in response to female promiscuity in the socially ...

    African Journals Online (AJOL)

    It has therefore been predicted, but never observed in the field, that if the female of a monogamous male is promiscuous, he will desert her and attempt to breed with an alternative female. Here we report a case of such a mate desertion in the aardwolf Proteles cristatus. We suggest, however, that mate desertion should ...

  13. Condensation of water vapour on moss-dominated biological soil ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 123; Issue 2 ... Condensation; water vapour; desert ecosystem; moss; biological soil crust. Abstract. Characteristics of water vapour condensation, including the onset, duration, and amount of water vapour condensation on moss-dominated biological soil crust ...

  14. Heterogeneity of soil surface temperature induced by xerophytic ...

    Indian Academy of Sciences (India)

    Variation characteristics of the soil surface temperature induced by shrub canopy greatly affects the near- surface biological and biochemical processes in desert ecosystems. However, information regarding the effects of shrub upon the heterogeneity of soil surface temperature is scarce. Here we aimed to characterize.

  15. Heterogeneity of soil surface temperature induced by xerophytic ...

    Indian Academy of Sciences (India)

    Variation characteristics of the soil surface temperature induced by shrub canopy greatly affects the nearsurface biological and biochemical processes in desert ecosystems. However, information regarding the effects of shrub upon the heterogeneity of soil surface temperature is scarce. Here we aimed to characterize the ...

  16. Murzuk Sand Sea, Sahara Desert, Libya, Africa

    Science.gov (United States)

    1993-01-01

    This near vertical view of the Murzuk Sand Sea, Sahara Desert, Libya (22.5N, 13.0E) shows the very diverse landscape that is part of the great Sahara Desert of North Africa. The vast expanse of sand dunes known as the Murzuk sand Sea of Libya and the adjacent rock outcrops support little human habitation. In fact, the tiny village of Murzuk with its center pivot, swing arm irrigated agriculture complex is the only sign of life in the region.

  17. Desert Dust Properties, Modelling, and Monitoring

    Science.gov (United States)

    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.

  18. Consistency of dimensional distributions and refractive indices of desert dust measured over Lampedusa with IASI radiances

    Science.gov (United States)

    Liuzzi, Giuliano; Masiello, Guido; Serio, Carmine; Meloni, Daniela; Di Biagio, Claudia; Formenti, Paola

    2017-02-01

    In the context of the ChArMEx campaign, we present here some results concerning the quantitative comparison between simulated and observed radiances in the presence of atmospheric desert dust, between June and July 2013 in the southern Mediterranean Basin, in the air mass above the island of Lampedusa. In particular, comparisons have been performed between radiances as observed by the Infrared Atmospheric Sounder Interferometer (IASI) and those simulated using the σ-IASI-as radiative transfer model, which takes into account aerosol extinction effect through a set of fast parameterizations. Simulations have been carried out using different sets of input complex refractive indices, which take into account the parent soils of the aerosols. Their accuracy also relies on the quality of the characterization of desert dust microphysical properties, achieved through direct measurements in the ChArMEx experiment. On the one hand, the fact that the model can ingest such a variable input proves its feasibility. On the other hand, this work goes through a direct validation of different refractive index sets for desert dust in the thermal infrared, and pursues an assessment of the sensitivity of IASI data with respect to the dimensional distribution of desert dust particles. Results show a good consistency between calculations and observations, especially in the spectral interval 800-1000 cm-1; further, the comparison between calculations and observations suggests that further efforts are needed to better characterize desert dust optical properties in the shortwave (above 2000 cm-1). Whatever the case, we show that it is necessary to properly tune the refractive indices according to the geographical origin of the observed aerosol.

  19. African and Asian dust: from desert soils to coral reefs

    Science.gov (United States)

    Garrison, Virginia H.; Shinn, Eugene A.; Foreman, William T.; Griffin, Dale W.; Holmes, Charles W.; Kellogg, Christina A.; Majewski, Michael S.; Richardson, Laurie L.; Ritchie, Kim B.; Smith, Garriet W.

    2003-01-01

    Many hypotheses have been proposed to explain the decline of coral reefs throughout the world, but none adequately accounts for the lack of recovery of reefs or the wide geographical distribution of coral diseases. The processes driving the decline remain elusive. Hundreds of millions of tons of dust transported annually from Africa and Asia to the Americas may be adversely affecting coral reefs and other downwind ecosystems. Viable microorganisms, macro- and micronutrients, trace metals, and an array of organic contaminants carried in the dust air masses and deposited in the oceans and on land may play important roles in the complex changes occurring on coral reefs worldwide.

  20. Pre-treating Seed to Enhance Germination of Desert Shrubs

    Energy Technology Data Exchange (ETDEWEB)

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

    2002-06-01

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

  1. Actinobacterial Rare Biospheres and Dark Matter Revealed in Habitats of the Chilean Atacama Desert.

    Science.gov (United States)

    Idris, Hamidah; Goodfellow, Michael; Sanderson, Roy; Asenjo, Juan A; Bull, Alan T

    2017-08-21

    The Atacama Desert is the most extreme non-polar biome on Earth, the core region of which is considered to represent the dry limit for life and to be an analogue for Martian soils. This study focused on actinobacteria because they are keystone species in terrestrial ecosystems and are acknowledged as an unrivalled source of bioactive compounds. Metagenomic analyses of hyper-arid and extreme hyper-arid soils in this desert revealed a remarkable degree of actinobacterial 'dark matter', evidenced by a detected increase of 34% in families against those that are validly published. Rank-abundance analyses indicated that these soils were high-diversity habitats and that the great majority of designated 'rare' genera (up to 60% of all phylotypes) were always rare. These studies have enabled a core actinobacterial microbiome common to both habitats to be defined. The great majority of detected taxa have not been recovered by culture dependent methods, neither, with very few exceptions, has their functional ecology been explored. A microbial seed bank of this magnitude has significance not just for Atacama soil ecosystem resilience but represents an enormous untapped resource for biotechnology discovery programmes in an era where resistance to existing antibiotics is rapidly becoming a major threat to global health.

  2. Is the Taklimakan Desert Highway Shelterbelt Sustainable to Long-Term Drip Irrigation with High Saline Groundwater?

    Science.gov (United States)

    Zhang, Jianguo; Xu, Xinwen; Li, Shengyu; Zhao, Ying; Zhang, Afeng; Zhang, Tibin; Jiang, Rui

    2016-01-01

    Freshwater resources are scarce in desert regions. Highly saline groundwater of different salinity is being used to drip irrigate the Taklimakan Desert Highway Shelterbelt with a double-branch-pipe system controlling the irrigation cycles. In this study, to evaluate the dynamics of soil moisture and salinity under the current irrigation system, soil samples were collected to a 2-m depth in the shelterbelt planted for different years and irrigated with different groundwater salinities, and soil moisture and salinity were analyzed. The results showed that both depletion of soil moisture and increase of topsoil salinity occurred simultaneously during one irrigation cycle. Soil moisture decreased from 27.4% to 2.4% for a 15-day irrigation cycle and from 26.4% to 2.7% for a 10-day-cycle, respectively. Topsoil electrical conductivity (EC) increased from 0.64 to 3.32 dS/m and 0.70 to 3.99 dS/m for these two irrigation cycles. With increased shelterbelt age, profiled average soil moisture (0–200 cm) reduced from 12.8% (1-year) to 7.1% (10-year); however, soil moisture in 0–20-cm increased, while topsoil salinity decreased. In addition, irrigation salinity mainly affected soil salinity in the 0–20-cm range. We conclude that water supply with the double-branch-pipe is a feasible irrigation method for the Taklimakan Desert Highway Shelterbelt, and our findings provide a model for shelterbelt construction and sustainable management when using highly saline water for irrigation in analogous habitats. PMID:27711244

  3. Comparisons of diazotrophic communities in native and agricultural desert ecosystems reveal plants as important drivers in diversity.

    Science.gov (United States)

    Köberl, Martina; Erlacher, Armin; Ramadan, Elshahat M; El-Arabi, Tarek F; Müller, Henry; Bragina, Anastasia; Berg, Gabriele

    2016-02-01

    Diazotrophs provide the only biological source of fixed atmospheric nitrogen in the biosphere. Although they are the key player for plant-available nitrogen, less is known about their diversity and potential importance in arid ecosystems. We investigated the nitrogenase gene diversity in native and agricultural desert soil as well as within root-associated microbiota of medicinal plants grown in Egypt through the combination of nifH-specific qPCR, fingerprints, amplicon pyrosequencing and fluorescence in situ hybridization-confocal laser scanning microscopy. Although the diazotrophic microbiota were characterized by generally high abundances and diversity, statistically significant differences were found between both soils, the different microhabitats, and between the investigated plants (Matricaria chamomilla L., Calendula officinalis L. and Solanum distichum Schumach. and Thonn.). We observed a considerable community shift from desert to agriculturally used soil that demonstrated a higher abundance and diversity in the agro-ecosystem. The endorhiza was characterized by lower abundances and only a subset of species when compared to the rhizosphere. While the microbiomes of the Asteraceae were similar and dominated by potential root-nodulating rhizobia acquired primarily from soil, the perennial S. distichum generally formed associations with free-living nitrogen fixers. These results underline the importance of diazotrophs in desert ecosystems and additionally identify plants as important drivers in functional gene pool diversity. © FEMS 2015.

  4. Modeling the Variability of Canopy Resistance and Evapotranspiration over a Desert Steppe Site in Inner Mongolia, China

    Science.gov (United States)

    Zhang, G.; Zhou, G.; Chen, F.; Wang, Y.

    2012-12-01

    The land-atmospheric exchange of heat and water vapor in the transitional semi-arid region is often heterogeneous due to large spatial variability in physical and physiological properties (surface albedo, roughness length, vegetation fraction, canopy resistance, etc.). That significantly affects daytime development of boundary-layer structure and summer precipitation. This study analyzed the variability of canopy resistance, evapotranpiration, and associated driving environmental factors over a desert steppe site in Inner Mongolia, China, using eddy-flux and meteorological data collected from 2008 to 2010. Distinct seasonal and interannual variabilities in canopy resistance were identified within those three years. Based on the principal component regression method, the analysis of the relative contribution of five major environmental factors including soil water content, leaf-area index, photosynthetically active radiation, vapor pressure deficit, and air temperature to canopy resistance showed that canopy-resistance variation was most responsive to soil water content. This study revealed that the canopy resistance decreased exponentially with soil water content. Therefore, the linear soil moisture stress function in Jarvis scheme was replaced by this new exponential water-stress function for the desert steppe site and it produced better canopy resistance. With this modified Jarvis scheme, the Noah land surface model improved the simulation of latent heat flux over the desert steppe. This study indicated that there is a need to analyze the statistical distributions of canopy properties and to incorporate parameters more specific to the given land covers.

  5. Comparisons of diazotrophic communities in native and agricultural desert ecosystems reveal plants as important drivers in diversity

    Science.gov (United States)

    Köberl, Martina; Erlacher, Armin; Ramadan, Elshahat M.; El-Arabi, Tarek F.; Müller, Henry; Bragina, Anastasia; Berg, Gabriele

    2015-01-01

    Diazotrophs provide the only biological source of fixed atmospheric nitrogen in the biosphere. Although they are the key player for plant-available nitrogen, less is known about their diversity and potential importance in arid ecosystems. We investigated the nitrogenase gene diversity in native and agricultural desert soil as well as within root-associated microbiota of medicinal plants grown in Egypt through the combination of nifH-specific qPCR, fingerprints, amplicon pyrosequencing and fluorescence in situ hybridization–confocal laser scanning microscopy. Although the diazotrophic microbiota were characterized by generally high abundances and diversity, statistically significant differences were found between both soils, the different microhabitats, and between the investigated plants (Matricaria chamomilla L., Calendula officinalis L. and Solanum distichum Schumach. and Thonn.). We observed a considerable community shift from desert to agriculturally used soil that demonstrated a higher abundance and diversity in the agro-ecosystem. The endorhiza was characterized by lower abundances and only a subset of species when compared to the rhizosphere. While the microbiomes of the Asteraceae were similar and dominated by potential root-nodulating rhizobia acquired primarily from soil, the perennial S. distichum generally formed associations with free-living nitrogen fixers. These results underline the importance of diazotrophs in desert ecosystems and additionally identify plants as important drivers in functional gene pool diversity. PMID:26705571

  6. Transport of desert dust mixed with North African industrial pollutants in the subtropical Saharan Air Layer

    Directory of Open Access Journals (Sweden)

    S. Rodríguez

    2011-07-01

    Full Text Available An analysis of chemical composition data of particulate matter samples (TSP, PM10 and PM2.5 collected from 2002 to 2008 in the North Atlantic free troposphere at the Izaña Global Atmospheric Watch (GAW observatory (Tenerife, Canary Islands shows that desert dust is very frequently mixed with particulate pollutants in the Saharan Air Layer (SAL. The study of this data set with Median Concentrations At Receptor (MCAR plots allowed the identification of the potential source regions of the dust and particulate pollutants. Areas located at the south of the southern slope of the Atlas mountains emerge as the most frequent source of the soil desert dust advected to the northern edge of the SAL in summer. Industrial emissions occurring in Northern Algeria, Eastern Algeria, Tunisia and the Atlantic coast of Morocco appear as the most important source of the nitrate, ammonium and a fraction of sulphate (at least 60 % of the sulphate <10 μm transported from some regions observed in the SAL. These emissions are mostly linked to crude oil refineries, phosphate-based fertilizer industry and power plants. Although desert dust emissions appear as the most frequent source of the phosphorous observed in the SAL, high P concentrations are observed when the SAL is affected by emissions from open mines of phosphate and phosphate based fertilizer industry. The results also show that a significant fraction of the sulphate (up to 90 % of sulphate <10 μm transported from some regions observed in the SAL may be influenced by soil emissions of evaporite minerals in well defined regions where dry saline lakes (chotts are present. These interpretations of the MCAR plots are consistent with the results obtained with the Positive Matrix Factorization (PMF2 receptor modelling. The results of this study show that North African industrial pollutants may be mixed with desert dust and exported to the North Atlantic in the Saharan Air Layer.

  7. Integrating Army Aviation into the Combined Arms Team: Operational Art in Desert Shield and Desert Storm

    Science.gov (United States)

    2017-05-25

    Integrating Army Aviation into the Combined Arms Team: Operational Art in Desert Shield and Desert Storm A Monograph by MAJ Chris D. Hanna...ELEMENT NUMBER 6. AUTHOR(S) MAJ Chris D. Hanna 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S...18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE PERSON MAJ Chris D. Hanna a. REPORT b. ABSTRACT c. THIS PAGE 19b. PHONE NUMBER (include area

  8. Micromorphology of takyrs and the desert ``papyrus'' of Southwestern Turkmenia

    Science.gov (United States)

    Lebedeva-Verba, M. P.; Gerasimova, M. I.

    2010-11-01

    The perception of takyrs as clayey mineral soils extremely poor in humus and occurring in deserts was supported by micromorphological studies with the first ones being performed by I.I. Feofarova for the takyrs in Western Turkmenia. However, in the fundamental monograph of 1956, there were abundant data on the contribution of biota (primarily of algae and invertebrates) to the takyr formation. The importance of the biota was emphasized by N.I. Bazilevich, who was an active participant in terrain and analytical investigations of Western Turkmenia takyrs. The micromorphological analysis, along with the studies of the chemical and mineralogical properties of the algal takyr on the Kopet-Dag piedmont plain, made it possible to introduce some corrections to the concepts concerning the mechanisms of takyr development; the contribution of bluegreen algae, microorganisms, and zooplankton was shown to be prominent. The available information on the properties and ecology of blue-green algae enabled the authors to interpret both their own data and the micromorphological descriptions made by I.I. Feofarova in the 1950s. The uppermost subhorizons are proposed to be regarded as the soil miniprofiles, whose properties are strongly affected by the activity of aquatic and terrestrial microorganisms, rather than the sedimentation strata.

  9. Preventing desert locust plagues: optimizing management interventions

    NARCIS (Netherlands)

    Huis, van A.; Cressman, K.; Magor, J.I.

    2007-01-01

    Solitarious desert locusts, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae), inhabit the central, arid, and semi-arid parts of the species¿ invasion area in Africa, the Middle East, and South-West Asia. Their annual migration circuit takes them downwind to breed sequentially where winter,

  10. Liquid Water Restricts Habitability in Extreme Deserts.

    Science.gov (United States)

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

    2017-04-01

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

  11. Reclaiming freshwater sustainability in the Cadillac Desert

    Science.gov (United States)

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

    2010-01-01

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

  12. Reclaiming freshwater sustainability in the Cadillac Desert

    Science.gov (United States)

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

    2010-01-01

    Increasing human appropriation of freshwater resources presents a tangible limit to the sustainability of cities, agriculture, and ecosystems in the western United States. Marc Reisner tackles this theme in his 1986 classic Cadillac Desert: The American West and Its Disappearing Water. Reisner's analysis paints a portrait of region-wide hydrologic dysfunction in the western United States, suggesting that the storage capacity of reservoirs will be impaired by sediment infilling, croplands will be rendered infertile by salt, and water scarcity will pit growing desert cities against agribusiness in the face of dwindling water resources. Here we evaluate these claims using the best available data and scientific tools. Our analysis provides strong scientific support for many of Reisner's claims, except the notion that reservoir storage is imminently threatened by sediment. More broadly, we estimate that the equivalent of nearly 76% of streamflow in the Cadillac Desert region is currently appropriated by humans, and this figure could rise to nearly 86% under a doubling of the region's population. Thus, Reisner's incisive journalism led him to the same conclusions as those rendered by copious data, modern scientific tools, and the application of a more genuine scientific method. We close with a prospectus for reclaiming freshwater sustainability in the Cadillac Desert, including a suite of recommendations for reducing region-wide human appropriation of streamflow to a target level of 60%. PMID:21149727

  13. Abiotic drivers of Chihuahuan Desert plant communities

    Science.gov (United States)

    Laura Marie Ladwig

    2014-01-01

    Within grasslands, precipitation, fire, nitrogen (N) addition, and extreme temperatures influence community composition and ecosystem function. The differential influences of these abiotic factors on Chihuahuan Desert grassland communities was examined within the Sevilleta National Wildlife Refuge, located in central New Mexico, U.S.A. Although fire is a natural...

  14. Extrafloral nectar fuels ant life in deserts

    Science.gov (United States)

    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

  15. Endolithic microbial life in hot and cold deserts

    Science.gov (United States)

    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.

  16. Wood decay in desert riverine environments

    Science.gov (United States)

    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

  17. Geology and geochemistry of the Atacama Desert.

    Science.gov (United States)

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

    2018-02-14

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

  18. Dust Availability in Desert Terrains

    Science.gov (United States)

    1985-01-01

    Netivot AS 30 - 60 bc o60 - 86 Bbca 86 -100 2. Loossial Soil Alluvial - LL!e Seat-arid western Negev 0936 0840 A 0 - 40 Terrace (270) ID 40 - 77 8 77 -112...10YR8/4 Bbca 10 - 85 1.0 - 7.7 48.2 44.1 7.5YR4.6/4 7.6YR4/4 lbca 86 -100 1.8 - 0.9 46.0 44.1 7.BYR8/4 7.5YR4/4 Negev 0938 0840 A 0 - 40 0.4 - 63.6 29.8

  19. Soil micromorphogenesis and Early Holocene paleoclimate at the desert margin of Southern Arabia Micromorfoedafogénesis y paleoclima del Holoceno Inferior en el márgen desértico del sur de Arabia Micromorfogénese do solo e paleoclima inicial do Holoceno na margem deserta do Sul da Arábia

    Directory of Open Access Journals (Sweden)

    Peter Kühn

    2013-07-01

    Full Text Available The Ramlat as-Sab'atayn desert margin near Ma'rib, Yemen, displays well-preserved Early Holocene paleosols that are documented by micromorphological and pedological data. The buried soils, which are represented by Ahb horizons, indicate soil formation mostly before 8.3 cal ka BP. In contrast, sandy cover sediments without signs of pedogenesis appeared between 8.3 and 6.6 cal ka BP due to increasing aridity. Characteristic micromorphological features of the cover sediments are a single grain microstructure, crystallitic b-fabric, predominant occurrence of fresh sideromelane, and remnants of microlayers. Micromorphological pedogenic features in the buried Ah horizons include a subangular blocky microstructure, undifferentiated b-fabric as a result of enrichment of organic matter and decalcification, and the predominant occurrence of completely altered sideromelane. Most of these horizons appeared to be nearly completely decalcified so that in parts a stipple speckled b-fabric and neoformed clay coatings could be detected as a result of stronger weathering and soil formation. Pedogenic data provide important information about Holocene climate fluctuations, including the amount of precipitation, which was calculated on the basis of geochemical data from buried A, AB and B horizons. The buried paleosols represent moist climate conditions with precipitation ranging from 400 to 600 mm a-1.En los márgenes del desierto Ramlat as-Sab'atayn, cerca de Ma'rib (Yemen, se encuentran paleosuelos del Holoceno Inferior bien conservados que se documentan con datos micromorfológicos y edáficos. Los suelos enterrados, representados por horizontes Ahb, indican que se formaron mayoritariamente antes de hace 8,3 ka. Por el contrario, los sedimentos arenosos que los cubren sin rasgos de edafogénesis se depositaron posteriormente debido a una aridez creciente hasta hace 6,6 ka. Los rasgos micromorfológicos de los sedimentos arenosos están caracterizados por una

  20. Synthesis, Characterization, and Application of Superhydrophobic Sands in Desert Agriculture

    KAUST Repository

    Reihmer, Joel W.

    2017-04-01

    A sustainable supply of fresh water for the human population is a global concern. Intriguingly, about 70% of the total fresh water consumed in the world annually is claimed by agriculture alone; this fraction is even higher in the Middle East and North Africa (MENA) region, where natural regeneration of groundwater is the slowest. Thus, there is a serious need for innovative materials and technologies to enhance the efficiency water usage in agriculture. To this end, plastic mulches have been employed across the developed world to minimize evaporative loss of water from top-soils. While plastic mulches are inexpensive, they do require specialized farm machinery for installation and long processing times. On one hand, plastic mulches have proven to increase crop yields, but on the other their non-biodegradability poses serious environmental concerns. In response, development of low-cost bio-/photo-degradable artificial mulches remains an area of intense research. In this thesis, we report on a novel superhydrophobic material exploiting inexpensive simple components to reduce the amount of water required for irrigation in agriculture by suppressing evaporative losses from the top-soil. Our material consists of ordinary beach sand coated with < 20 nm thick layer of paraffin wax. We synthesized and extensively characterized our material and applied them as mulches for tomato and barley plants at the KAUST greenhouse. We found that when a ~5 mm thick layer of superhydrophobic sand was placed onto the top-soil in pots, it dramatically suppressed evaporative losses and significantly enhanced the yields. Our preliminary field-scale experiments with tomatoes and barley crops at the Hada Al Sham site corroborate these results. Our approach might find applications in desert agriculture and other fields and alleviate water stress in the MENA region.

  1. Grazing effects on surface energy fluxes in a desert steppe on the Mongolian Plateau.

    Science.gov (United States)

    Shao, Changliang; Chen, Jiquan; Li, Linghao; Dong, Gang; Han, Juanjuan; Abraha, Michael; John, Ranjeet

    2017-03-01

    Quantifying the surface energy fluxes of grazed and ungrazed steppes is essential to understand the roles of grasslands in local and global climate and in land use change. We used paired eddy-covariance towers to investigate the effects of grazing on energy balance (EB) components: net radiation (Rn ), latent heat (LE), sensible heat (H), and soil heat (G) fluxes on adjacent grazed and ungrazed areas in a desert steppe of the Mongolian Plateau for a two-year period (2010-2012). Near 95% of Rn was partitioned as LE and H, whereas the contributions of G and other components of the EB were 5% at an annual scale. H dominated the energy partitioning and shared ~50% of Rn . When comparing the grazed and the ungrazed desert steppe, there was remarkably lower Rn and a lower H, but higher G at the grazed site than at the ungrazed site. Both reduced available energy (Rn - G) and H indicated a "cooling effect" feedback onto the local climate through grazing. Grazing reduced the dry year LE but enhanced the wet year LE. Energy partitioning of LE/Rn was positively correlated with the canopy conductivity, leaf area index, and soil moisture. H/Rn was positively correlated with the vapor pressure deficit but negatively correlated with the soil moisture. Boosted regression tree results showed that LE/Rn was dominated by soil moisture in both years and at both sites, while grazing shifted the H/Rn domination from temperature to soil moisture in the wet year. Grazing not only caused an LE shift between the dry and the wet year, but also triggered a decrease in the H/Rn because of changes in vegetation and soil properties, indicating that the ungrazed area had a greater resistance while the grazed area had a greater sensitivity of EB components to the changing climate. © 2016 by the Ecological Society of America.

  2. Deriving Polarization Properties of Desert-Reflected Solar Spectra with PARASOL Data

    Science.gov (United States)

    Sun, Wenbo; Baize, Rosemary R.; Lukashin, Constantine

    2015-01-01

    Reflected solar radiation from desert is strongly polarized by sand particles. To date, there is no reliable desert surface reflection model to calculate desert reflection matrix. In this study, the PARASOL data are used to retrieve physical properties of desert. These physical properties are then used in the ADRTM to calculate polarization of desert-reflected light for the whole solar spectra.

  3. The spatial distribution and temporal variation of desert riparian forests and their influencing factors in the downstream Heihe River basin, China

    Science.gov (United States)

    Ding, Jingyi; Zhao, Wenwu; Daryanto, Stefani; Wang, Lixin; Fan, Hao; Feng, Qiang; Wang, Yaping

    2017-05-01

    Desert riparian forests are the main restored vegetation community in Heihe River basin. They provide critical habitats and a variety of ecosystem services in this arid environment. Since desert riparian forests are also sensitive to disturbance, examining the spatial distribution and temporal variation of these forests and their influencing factors is important to determine the limiting factors of vegetation recovery after long-term restoration. In this study, field experiment and remote sensing data were used to determine the spatial distribution and temporal variation of desert riparian forests and their relationship with the environmental factors. We classified five types of vegetation communities at different distances from the river channel. Community coverage and diversity formed a bimodal pattern, peaking at the distances of 1000 and 3000 m from the river channel. In general, the temporal normalized difference vegetation index (NDVI) trend from 2000 to 2014 was positive at different distances from the river channel, except for the region closest to the river bank (i.e. within 500 m from the river channel), which had been undergoing degradation since 2011. The spatial distribution of desert riparian forests was mainly influenced by the spatial heterogeneity of soil properties (e.g. soil moisture, bulk density and soil particle composition). Meanwhile, while the temporal variation of vegetation was affected by both the spatial heterogeneity of soil properties (e.g. soil moisture and soil particle composition) and to a lesser extent, the temporal variation of water availability (e.g. annual average and variability of groundwater, soil moisture and runoff). Since surface (0-30 cm) and deep (100-200 cm) soil moisture, bulk density and the annual average of soil moisture at 100 cm obtained from the remote sensing data were regarded as major determining factors of community distribution and temporal variation, conservation measures that protect the soil structure

  4. Contrasting water use pattern of introduced and native plants in an alpine desert ecosystem, Northeast Qinghai–Tibet Plateau, China

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Huawu, E-mail: wuhuawu416@163.com [State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875 (China); College of Resources Science and Technology, Beijing Normal University, Beijing 100875 (China); Li, Xiao-Yan, E-mail: xyli@bnu.edu.cn [State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875 (China); College of Resources Science and Technology, Beijing Normal University, Beijing 100875 (China); Jiang, Zhiyun; Chen, Huiying; Zhang, Cicheng; Xiao, Xiong [College of Resources Science and Technology, Beijing Normal University, Beijing 100875 (China)

    2016-01-15

    Plant water use patterns reflect the complex interactions between different functional types and environmental conditions in water-limited ecosystems. However, the mechanisms underlying the water use patterns of plants in the alpine desert of the Qinghai–Tibet Plateau remain poorly understood. This study investigated seasonal variations in the water sources of herbs (Carex moorcroftii, Astragalus adsurgens) and shrubs (Artemisia oxycephala, Hippophae rhamnoides) using stable oxygen-18 isotope methods. The results indicated that the native herbs (C. moorcroftii, A. adsurgens) and one of the shrubs (A. oxycephala) mainly relied on water from the shallow layer (0–30 cm) throughout the growing season, while the introduced shrub (H. rhamnoides) showed plasticity in switching between water from shallow and deep soil layers depending on soil water availability. All studied plants primarily depended on water from shallow soil layers early in the season. The differences of water use patterns between the introduced and native plants are closely linked with the range of active root zones when competing for water. Our findings will facilitate the mechanistic understanding of plant–soil–water relations in alpine desert ecosystems and provide information for screening introduced species for sand fixation. - Highlights: • Stable oxygen-18 in soil water experienced great evaporation enrichment. • H. rhamnoides experiences a flexible plasticity to switch between shallow and deep soil water. • Native plants mostly relied on shallow and middle soil water. • Water-use patterns by introduced-native plants are controlled by root characteristics.

  5. Abiotic processes are insufficient for fertile island development: A 10-year artificial shrub experiment in a desert grassland

    Science.gov (United States)

    Li, Junran; Gilhooly, William P.; Okin, Gregory S.; Blackwell, John

    2017-03-01

    The relative importance of biotic and abiotic processes in the development of "fertile islands" in dryland systems has rarely been investigated. Here we approached this question by using artificial shrubs, which exclude plant litter production and soil nutrient uptake, but retain the functions of trapping windblown material, funneling of stemflow, and differential rain splash. We conducted a vegetation manipulation study more than a decade ago in the desert grassland of southern New Mexico and subsequently revisited the site in 2012 and 2015. The results show that no notable soil mounds were observed under the artificial shrubs; however, soil texture under the artificial shrubs has gradually changed to resemble the patterns of soil particle-size distribution under natural shrubs. Our results highlight that with the exclusion of direct biotic additions, soils captured by shrub canopies are not necessarily fertile and thus do not themselves contribute to the development of fertile islands.

  6. Fungal endophytes in aboveground tissues of desert plants: infrequent in culture, but highly diverse and distinctive symbionts.

    Science.gov (United States)

    Massimo, Nicholas C; Nandi Devan, M M; Arendt, Kayla R; Wilch, Margaret H; Riddle, Jakob M; Furr, Susan H; Steen, Cole; U'Ren, Jana M; Sandberg, Dustin C; Arnold, A Elizabeth

    2015-07-01

    In hot deserts, plants cope with aridity, high temperatures, and nutrient-poor soils with morphological and biochemical adaptations that encompass intimate microbial symbioses. Whereas the root microbiomes of arid-land plants have received increasing attention, factors influencing assemblages of symbionts in aboveground tissues have not been evaluated for many woody plants that flourish in desert environments. We evaluated the diversity, host affiliations, and distributions of endophytic fungi associated with photosynthetic tissues of desert trees and shrubs, focusing on nonsucculent woody plants in the species-rich Sonoran Desert. To inform our strength of inference, we evaluated the effects of two different nutrient media, incubation temperatures, and collection seasons on the apparent structure of endophyte assemblages. Analysis of >22,000 tissue segments revealed that endophytes were isolated four times more frequently from photosynthetic stems than leaves. Isolation frequency was lower than expected given the latitude of the study region and varied among species a function of sampling site and abiotic factors. However, endophytes were very species-rich and phylogenetically diverse, consistent with less arid sites of a similar latitudinal position. Community composition differed among host species, but not as a function of tissue type, sampling site, sampling month, or exposure. Estimates of abundance, diversity, and composition were not influenced by isolation medium or incubation temperature. Phylogenetic analyses of the most commonly isolated genus (Preussia) revealed multiple evolutionary origins of desert-plant endophytism and little phylogenetic structure with regard to seasonality, tissue preference, or optimal temperatures and nutrients for growth in vitro. Together, these results provide insight into endophytic symbioses in desert-plant communities and can be used to optimize strategies for capturing endophyte biodiversity at regional scales.

  7. Metagenomic evidence for metabolism of trace atmospheric gases by high-elevation desert Actinobacteria

    Directory of Open Access Journals (Sweden)

    Ryan C Lynch

    2014-12-01

    Full Text Available Previous surveys of very dry Atacama Desert mineral soils have consistently revealed sparse communities of non-photosynthetic microbes. The functional nature of these microorganisms remains debatable given the harshness of the environment and low levels of biomass and diversity. The aim of this study was to gain an understanding of the phylogenetic community structure and metabolic potential of a low-diversity mineral soil metagenome that was collected from a high-elevation Atacama Desert volcano debris field. We pooled DNA extractions from over 15 grams of volcanic material, and using whole genome shotgun sequencing, observed only 75 - 78 total 16S rRNA gene OTUs3%. The phylogenetic structure of this community is significantly under dispersed, with actinobacterial lineages making up 97.9% - 98.6% of the 16S rRNA genes, suggesting a high degree of environmental selection. Due to this low diversity and uneven community composition, we assembled and analyzed the metabolic pathways of the most abundant genome, a Pseudonocardia sp. (56% - 72% of total 16S genes. Our assembly and binning efforts yielded almost 4.9 Mb of Pseudonocardia sp. contigs, which accounts for an estimated 99.3% of its non-repetitive genomic content. This genome contains a limited array of carbohydrate catabolic pathways, but encodes for CO2 fixation via the Calvin cycle. The genome also encodes complete pathways for the catabolism of various trace gases (H2, CO and several organic C1 compounds and the assimilation of ammonia and nitrate. We compared genomic content among related Pseudonocardia spp. and estimated rates of non-synonymous and synonymous nucleic acid substitutions between protein coding homologs. Collectively, these comparative analyses suggest that the community structure and various functional genes have undergone strong selection in the nutrient poor desert mineral soils and high-elevation atmospheric conditions.

  8. Namib Desert dune/interdune transects exhibit habitat-specific edaphic bacterial communities

    Science.gov (United States)

    Ronca, Sandra; Ramond, Jean-Baptiste; Jones, Brian E.; Seely, Mary; Cowan, Don A.

    2015-01-01

    The sand dunes and inter-dune zones of the hyper-arid central Namib Desert represent heterogeneous soil habitats. As little is known about their indigenous edaphic bacterial communities, we aimed to evaluate their diversity and factors of assembly and hypothesized that soil physicochemistry gradients would strongly shape dune/interdune communities. We sampled a total of 125 samples from 5 parallel dune/interdune transects and characterized 21 physico-chemical edaphic parameters coupled with 16S rRNA gene bacterial community fingerprinting using T-RFLP and 454 pyrosequencing. Multivariate analyses of T-RFLP data showed significantly different bacterial communities, related to physico-chemical gradients, in four distinct dune habitats: the dune top, slope, base and interdune zones. Pyrosequencing of 16S rRNA gene amplicon sets showed that each dune zone presented a unique phylogenetic profile, suggesting a high degree of environmental selection. The combined results strongly infer that habitat filtering is an important factor shaping Namib Desert dune bacterial communities, with habitat stability, soil texture and mineral and nutrient contents being the main environmental drivers of bacterial community structures. PMID:26388839

  9. Namib Desert dune/interdune transects exhibit habitat-specific edaphic bacterial communities

    Directory of Open Access Journals (Sweden)

    Sandra eRonca

    2015-09-01

    Full Text Available The sand dunes and inter-dune zones of the hyper-arid central Namib Desert represent heterogeneous soil habitats. As little is known about their indigenous edaphic bacterial communities, we aimed to evaluate their diversity and factors of assembly and hypothesized that soil physicochemistry gradients would strongly shape dune/interdune communities. We sampled a total of 125 samples from 5 parallel dune/interdune transects and characterized 21 physico-chemical edaphic parameters coupled with 16S rRNA gene bacterial community fingerprinting using T-RFLP and 454 pyrosequencing. Multivariate analyses of T-RFLP data showed significantly different bacterial communities, related to physico-chemical gradients, in four distinct dune habitats: the dune top, slope, base and interdune zones. Pyrosequencing of 16S rRNA gene amplicon sets showed that each dune zone presented a unique phylogenetic profile, suggesting a high degree of environmental selection. The combined results strongly infer that habitat filtering is an important factor shaping Namib Desert dune bacterial communities, with habitat stability, soil texture and mineral and nutrient contents being the main environmental drivers of bacterial community structures.

  10. Namib Desert dune/interdune transects exhibit habitat-specific edaphic bacterial communities.

    Science.gov (United States)

    Ronca, Sandra; Ramond, Jean-Baptiste; Jones, Brian E; Seely, Mary; Cowan, Don A

    2015-01-01

    The sand dunes and inter-dune zones of the hyper-arid central Namib Desert represent heterogeneous soil habitats. As little is known about their indigenous edaphic bacterial communities, we aimed to evaluate their diversity and factors of assembly and hypothesized that soil physicochemistry gradients would strongly shape dune/interdune communities. We sampled a total of 125 samples from 5 parallel dune/interdune transects and characterized 21 physico-chemical edaphic parameters coupled with 16S rRNA gene bacterial community fingerprinting using T-RFLP and 454 pyrosequencing. Multivariate analyses of T-RFLP data showed significantly different bacterial communities, related to physico-chemical gradients, in four distinct dune habitats: the dune top, slope, base and interdune zones. Pyrosequencing of 16S rRNA gene amplicon sets showed that each dune zone presented a unique phylogenetic profile, suggesting a high degree of environmental selection. The combined results strongly infer that habitat filtering is an important factor shaping Namib Desert dune bacterial communities, with habitat stability, soil texture and mineral and nutrient contents being the main environmental drivers of bacterial community structures.

  11. Biomass and nutrient allocation strategies in a desert ecosystem in the Hexi Corridor, northwest China.

    Science.gov (United States)

    Zhang, Ke; Su, YongZhong; Yang, Rong

    2017-07-01

    The allocation of biomass and nutrients in plants is a crucial factor in understanding the process of plant structures and dynamics to different environmental conditions. In this study, we present a comprehensive scaling analysis of data from a desert ecosystem to determine biomass and nutrient (carbon (C), nitrogen (N), and phosphorus (P)) allocation strategies of desert plants from 40 sites in the Hexi Corridor. We found that the biomass and levels of C, N, and P storage were higher in shoots than in roots. Roots biomass and nutrient storage were concentrated at a soil depth of 0-30 cm. Scaling relationships of biomass, C storage, and P storage between shoots and roots were isometric, but that of N storage was allometric. Results of a redundancy analysis (RDA) showed that soil nutrient densities were the primary factors influencing biomass and nutrient allocation, accounting for 94.5% of the explained proportion. However, mean annual precipitation was the primary factor influencing the roots biomass/shoots biomass (R/S) ratio. Furthermore, Pearson's correlations and regression analyses demonstrated that although the biomass and nutrients that associated with functional traits primarily depended on soil conditions, mean annual precipitation and mean annual temperature had greater effects on roots biomass and nutrient storage.

  12. Analysis of land cover change and its driving forces in a desert oasis landscape of southern Xinjiang, China

    Science.gov (United States)

    Amuti, T.; Luo, G.

    2014-07-01

    The combined effects of drought, warming and the changes in land cover have caused severe land degradation for several decades in the extremely arid desert oases of Southern Xinjiang, Northwest China. This study examined land cover changes during 1990-2008 to characterize and quantify the transformations in the typical oasis of Hotan. Land cover classifications of these images were performed based on the supervised classification scheme integrated with conventional vegetation and soil indexes. Change-detection techniques in remote sensing (RS) and a geographic information system (GIS) were applied to quantify temporal and spatial dynamics of land cover changes. The overall accuracies, Kappa coefficients, and average annual increase rate or decrease rate of land cover classes were calculated to assess classification results and changing rate of land cover. The analysis revealed that major trends of the land cover changes were the notable growth of the oasis and the reduction of the desert-oasis ecotone, which led to accelerated soil salinization and plant deterioration within the oasis. These changes were mainly attributed to the intensified human activities. The results indicated that the newly created agricultural land along the margins of the Hotan oasis could result in more potential areas of land degradation. If no effective measures are taken against the deterioration of the oasis environment, soil erosion caused by land cover change may proceed. The trend of desert moving further inward and the shrinking of the ecotone may lead to potential risks to the eco-environment of the Hotan oasis over the next decades.

  13. Himalayan Mountain Range, Taklimakan Desert, China

    Science.gov (United States)

    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.

  14. Anthropocene changes in desert area: Sensitivity to climate model predictions

    Science.gov (United States)

    Mahowald, N.

    2007-12-01

    Changes in desert area due to humans have important implications from a local, regional to global level. Here we focus on the latter in order to better understand estimated changes in desert dust aerosols and the associated iron deposition into oceans. Using 17 model simulations from the World Climate Research Programme's Coupled Model Intercomparison Project phase 3 multi-model dataset and the BIOME4 equilibrium vegetation model we estimate changes in desert dust source areas due to climate change and carbon dioxide fertilization. If we assume no carbon dioxide fertilization, the mean of the model predictions is that desert areas expand from the 1880s to the 2080s, due to increased aridity. If we allow for carbon dioxide fertilization, the desert areas become smaller. Thus better understanding carbon dioxide fertilization is important for predicting desert response to climate. There is substantial spread in the model simulation predictions for regional and global averages.

  15. CAMEL REARING IN CHOLISTAN DESERT OF PAKISTAN

    Directory of Open Access Journals (Sweden)

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

    2009-05-01

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

  16. The Palm Desert renewable [hydrogen] transportation system

    Energy Technology Data Exchange (ETDEWEB)

    Chamberlin, C.E.; Lehman, P. [Humboldt State Univ., Arcata, CA (United States). Schatz Energy Research Center

    1998-08-01

    This paper describes the Schatz Energy Research Center (SERC) progress on the Palm Desert Renewable Hydrogen Transportation System Project for the period June 1997 through May 1998. The project began in March 1996. The goal of the Palm Desert Project is to develop a clean and sustainable transportation system for a community. The project demonstrates the practical utility of hydrogen as a transportation fuel and the proton exchange membrane (PEM) fuel cell as a vehicle power system. The project includes designing and building 4 fuel cell powered vehicles, a solar hydrogen generating and refueling station, and a fuel cell vehicle diagnostic center. Over this last year, SERC has built a fuel cell powered neighborhood electric vehicle and delivered it to the City of Palm Desert. The design of the hydrogen refueling station is near completion and it is anticipated that construction will be complete in the fall of 1998. The vehicles are currently being refueled at a temporary refueling station. The diagnostic center is being designed and maintenance procedures as well as computer diagnostic programs for the fuel cell vehicles are being developed. City employees are driving the vehicles daily and monitoring data are being collected. The drivers are pleased with the performance of the vehicles.

  17. Contraction of the Gobi Desert, 2000–2012

    OpenAIRE

    Troy Sternberg; Henri Rueff; Nick Middleton

    2015-01-01

    Deserts are critical environments because they cover 41% of the world’s land surface and are home to 2 billion residents. As highly dynamic biomes desert expansion and contraction is influenced by climate and anthropogenic factors with variability being a key part of the desertification debate across dryland regions. Evaluating a major world desert, the Gobi in East Asia, with high resolution satellite data and the meteorologically-derived Aridity Index from 2000 to 2012 identified a r...

  18. Risk assessment of desert pollution on composite high voltage insulators

    OpenAIRE

    El-Shahat, Mohammed; Anis, Hussein

    2014-01-01

    Transmission lines located in the desert are subjected to desert climate, one of whose features is sandstorms. With long accumulation of sand and with the advent of moisture from rain, ambient humidity and dew, a conductive layer forms and the subsequent leakage current may lead to surface discharge, which may shorten the insulator life or lead to flashover thus interrupting the power supply. Strategically erected power lines in the Egyptian Sinai desert are typically subject to such a risk, ...

  19. Late Quaternary faulting in the Sevier Desert driven by magmatism

    OpenAIRE

    Stahl, T.; Niemi, N. A.

    2017-01-01

    Seismic hazard in continental rifts varies as a function of strain accommodation by tectonic or magmatic processes. The nature of faulting in the Sevier Desert, located in eastern Basin and Range of central Utah, and how this faulting relates to the Sevier Desert Detachment low-angle normal fault, have been debated for nearly four decades. Here, we show that the geodetic signal of extension across the eastern Sevier Desert is best explained by magma-assisted rifting associated with Plio-Pleis...

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

    National Research Council Canada - National Science Library

    Wang, Guohua; Zhao, Wenzhi

    2015-01-01

    Eight groundwater observation wells were installed along the river plain, where the landscapes varied from floodplain, to oasis farmland, to desert-oasis ecotone to desert, in a typical desert-oasis...

  1. Extremely arid soils of the Ili Depression in Kazakhstan

    Science.gov (United States)

    Lebedeva, M. P.; Gerasimova, M. I.; Golovanov, D. L.; Yamnova, I. A.

    2015-01-01

    On the basis of macro- and micromorphological and analytical studies of extremely arid soils of the Ili Depression in Kazakhstan, a comparative analysis of pedogenetic processes shaping these soils on piedmont plains of different ages and heights is performed. The types of soil horizons and their combinations are analyzed in the context opf modern Russian and international soil classification systems. The genesis of extremely arid soils is controlled by the climatic conditions and by their geomorphic position on alluvial fans of piedmont plains. The following processes are diagnosed in these soils: soil crusting with vesicular porosity, the development of desert pavements with rock varnish, rubification, surface salinization, and iron depletion around the pores. It is suggested that the initial factor-based name (extremely arid) of these soils can be replaced by the name vesicular-crusty soils with the corresponding AKL diagnostic horizon, which is more consistent with the principles of substantive-genetic classification systems. In order to determine the classification position of these soils in terms of the new Russian soil classification system, new diagnostic horizons—AKL and CS—have to be introduced in this system. According to the WRB classification, the studied soils belong to the group of Gypsisols; the soil with strong salinization fits the criteria of the group of Solonchaks. A qualifier [yermic] is to be added to reflect the development of desert pavement and vesicular layer under extreme arid conditions.

  2. Fine-scale analysis reveals cryptic landscape genetic structure in desert tortoises.

    Directory of Open Access Journals (Sweden)

    Emily K Latch

    Full Text Available Characterizing the effects of landscape features on genetic variation is essential for understanding how landscapes shape patterns of gene flow and spatial genetic structure of populations. Most landscape genetics studies have focused on patterns of gene flow at a regional scale. However, the genetic structure of populations at a local scale may be influenced by a unique suite of landscape variables that have little bearing on connectivity patterns observed at broader spatial scales. We investigated fine-scale spatial patterns of genetic variation and gene flow in relation to features of the landscape in desert tortoise (Gopherus agassizii, using 859 tortoises genotyped at 16 microsatellite loci with associated data on geographic location, sex, elevation, slope, and soil type, and spatial relationship to putative barriers (power lines, roads. We used spatially explicit and non-explicit Bayesian clustering algorithms to partition the sample into discrete clusters, and characterize the relationships between genetic distance and ecological variables to identify factors with the greatest influence on gene flow at a local scale. Desert tortoises exhibit weak genetic structure at a local scale, and we identified two subpopulations across the study area. Although genetic differentiation between the subpopulations was low, our landscape genetic analysis identified both natural (slope and anthropogenic (roads landscape variables that have significantly influenced gene flow within this local population. We show that desert tortoise movements at a local scale are influenced by features of the landscape, and that these features are different than those that influence gene flow at larger scales. Our findings are important for desert tortoise conservation and management, particularly in light of recent translocation efforts in the region. More generally, our results indicate that recent landscape changes can affect gene flow at a local scale and that their

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

    Science.gov (United States)

    Mao, Xuesong; Wang, Fuchun; Wang, Binggang

    2011-07-01

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

  4. Contraction of the Gobi Desert, 2000-2012

    National Research Council Canada - National Science Library

    Troy Sternberg; Henri Rueff; Nick Middleton

    2015-01-01

    .... As highly dynamic biomes desert expansion and contraction is influenced by climate and anthropogenic factors with variability being a key part of the desertification debate across dryland regions...

  5. A drought resistance-promoting microbiome is selected by root system under desert farming.

    Directory of Open Access Journals (Sweden)

    Ramona Marasco

    Full Text Available BACKGROUND: Traditional agro-systems in arid areas are a bulwark for preserving soil stability and fertility, in the sight of "reverse desertification". Nevertheless, the impact of desert farming practices on the diversity and abundance of the plant associated microbiome is poorly characterized, including its functional role in supporting plant development under drought stress. METHODOLOGY/PRINCIPAL FINDINGS: We assessed the structure of the microbiome associated to the drought-sensitive pepper plant (Capsicum annuum L. cultivated in a traditional Egyptian farm, focusing on microbe contribution to a crucial ecosystem service, i.e. plant growth under water deficit. The root system was dissected by sampling root/soil with a different degree of association to the plant: the endosphere, the rhizosphere and the root surrounding soil that were compared to the uncultivated soil. Bacterial community structure and diversity, determined by using Denaturing Gradient Gel Electrophoresis, differed according to the microhabitat, indicating a selective pressure determined by the plant activity. Similarly, culturable bacteria genera showed different distribution in the three root system fractions. Bacillus spp. (68% of the isolates were mainly recovered from the endosphere, while rhizosphere and the root surrounding soil fractions were dominated by Klebsiella spp. (61% and 44% respectively. Most of the isolates (95% presented in vitro multiple plant growth promoting (PGP activities and stress resistance capabilities, but their distribution was different among the root system fractions analyzed, with enhanced abilities for Bacillus and the rhizobacteria strains. We show that the C. annuum rhizosphere under desert farming enriched populations of PGP bacteria capable of enhancing plant photosynthetic activity and biomass synthesis (up to 40% under drought stress. CONCLUSIONS/SIGNIFICANCE: Crop cultivation provides critical ecosystem services in arid lands with the

  6. A drought resistance-promoting microbiome is selected by root system under desert farming.

    Science.gov (United States)

    Marasco, Ramona; Rolli, Eleonora; Ettoumi, Besma; Vigani, Gianpiero; Mapelli, Francesca; Borin, Sara; Abou-Hadid, Ayman F; El-Behairy, Usama A; Sorlini, Claudia; Cherif, Ameur; Zocchi, Graziano; Daffonchio, Daniele

    2012-01-01

    Traditional agro-systems in arid areas are a bulwark for preserving soil stability and fertility, in the sight of "reverse desertification". Nevertheless, the impact of desert farming practices on the diversity and abundance of the plant associated microbiome is poorly characterized, including its functional role in supporting plant development under drought stress. We assessed the structure of the microbiome associated to the drought-sensitive pepper plant (Capsicum annuum L.) cultivated in a traditional Egyptian farm, focusing on microbe contribution to a crucial ecosystem service, i.e. plant growth under water deficit. The root system was dissected by sampling root/soil with a different degree of association to the plant: the endosphere, the rhizosphere and the root surrounding soil that were compared to the uncultivated soil. Bacterial community structure and diversity, determined by using Denaturing Gradient Gel Electrophoresis, differed according to the microhabitat, indicating a selective pressure determined by the plant activity. Similarly, culturable bacteria genera showed different distribution in the three root system fractions. Bacillus spp. (68% of the isolates) were mainly recovered from the endosphere, while rhizosphere and the root surrounding soil fractions were dominated by Klebsiella spp. (61% and 44% respectively). Most of the isolates (95%) presented in vitro multiple plant growth promoting (PGP) activities and stress resistance capabilities, but their distribution was different among the root system fractions analyzed, with enhanced abilities for Bacillus and the rhizobacteria strains. We show that the C. annuum rhizosphere under desert farming enriched populations of PGP bacteria capable of enhancing plant photosynthetic activity and biomass synthesis (up to 40%) under drought stress. Crop cultivation provides critical ecosystem services in arid lands with the plant root system acting as a "resource island" able to attract and select

  7. A Drought Resistance-Promoting Microbiome Is Selected by Root System under Desert Farming

    Science.gov (United States)

    Marasco, Ramona; Rolli, Eleonora; Ettoumi, Besma; Vigani, Gianpiero; Mapelli, Francesca; Borin, Sara; Abou-Hadid, Ayman F.; El-Behairy, Usama A.; Sorlini, Claudia; Cherif, Ameur; Zocchi, Graziano; Daffonchio, Daniele

    2012-01-01

    Background Traditional agro-systems in arid areas are a bulwark for preserving soil stability and fertility, in the sight of “reverse desertification”. Nevertheless, the impact of desert farming practices on the diversity and abundance of the plant associated microbiome is poorly characterized, including its functional role in supporting plant development under drought stress. Methodology/Principal Findings We assessed the structure of the microbiome associated to the drought-sensitive pepper plant (Capsicum annuum L.) cultivated in a traditional Egyptian farm, focusing on microbe contribution to a crucial ecosystem service, i.e. plant growth under water deficit. The root system was dissected by sampling root/soil with a different degree of association to the plant: the endosphere, the rhizosphere and the root surrounding soil that were compared to the uncultivated soil. Bacterial community structure and diversity, determined by using Denaturing Gradient Gel Electrophoresis, differed according to the microhabitat, indicating a selective pressure determined by the plant activity. Similarly, culturable bacteria genera showed different distribution in the three root system fractions. Bacillus spp. (68% of the isolates) were mainly recovered from the endosphere, while rhizosphere and the root surrounding soil fractions were dominated by Klebsiella spp. (61% and 44% respectively). Most of the isolates (95%) presented in vitro multiple plant growth promoting (PGP) activities and stress resistance capabilities, but their distribution was different among the root system fractions analyzed, with enhanced abilities for Bacillus and the rhizobacteria strains. We show that the C. annuum rhizosphere under desert farming enriched populations of PGP bacteria capable of enhancing plant photosynthetic activity and biomass synthesis (up to 40%) under drought stress. Conclusions/Significance Crop cultivation provides critical ecosystem services in arid lands with the plant root

  8. Biosolids Effects in Chihuahuan Desert Rangelands: A Ten-Year Study

    Directory of Open Access Journals (Sweden)

    David B. Wester

    2011-01-01

    Full Text Available Arid and semiarid rangelands are suitable for responsible biosolids application. Topical application is critical to avoid soil and vegetation disturbance. Surface-applied biosolids have long-lasting effects in these ecosystems. We conducted a 10-year research program investigating effects of biosolids applied at rates from 0 to 90 dry Mg ha−1 on soil water infiltration; runoff and leachate water quality; soil erosion; forage production and quality; seedling establishment; plant physiological responses; nitrogen dynamics; biosolids decomposition; and grazing animal behavior and management. Biosolids increased soil water infiltration and reduced erosion. Effects on soil water quality were observed only at the highest application rates. Biosolids increased soil nitrate-nitrogen. Biosolids increased forage production and improved forage quality. Biosolids increased leaf area of grasses; photosynthetic rates were not necessarily increased by biosolids. Biosolids effects on plant establishment are expected only under moderately favorable conditions. Over an 82-mo exposure period, total organic carbon, nitrogen, and total and available phosphorus decreased and inorganic matter increased. Grazing animals spent more time grazing, ruminating, and resting in biosolids-treated areas; positive effects on average daily gain were observed during periods of higher rainfall. Our results suggest that annual biosolids application rates of up to 18 Mg ha−1 are appropriate for desert rangelands.

  9. Assessing an exotic plant surveying program in the Mojave Desert, Clark County, Nevada, USA.

    Science.gov (United States)

    Abella, Scott R; Spencer, Jessica E; Hoines, Joshua; Nazarchyk, Carrie

    2009-04-01

    Exotic species can threaten native ecosystems and reduce services that ecosystems provide to humans. Early detection of incipient populations of exotic species is a key step in containing exotics before explosive population growth and corresponding impacts occur. We report the results of the first three years of an exotic plant early detection and treatment program conducted along more than 3,000 km of transportation corridors within an area >1.5 million ha in the Mojave Desert, USA. Incipient populations of 43 exotic plant species were mapped using global positioning and geographic information systems. Brassica tournefortii (Sahara mustard) infested the most soil types (47% of 256) surveyed in the study area, while Nicotiana glauca (tree tobacco) and others currently occupy less than 5% of soil types. Malcolmia africana (African mustard) was disproportionately detected on gypsum soils, occurring on 59% of gypsum soil types compared to 27% of all surveyed soils. Gypsum soils constitute unique rare plant habitat in this region, and by conventional wisdom were not previously considered prone to invasion. While this program has provided an initial assessment of the landscape-scale distribution of exotic species along transportation corridors, evaluations of both the survey methods and the effectiveness of treating incipient populations are needed. An exotic plant information system most useful to resource mangers will likely include integrating planning oriented coarse-scale surveys, more detailed monitoring of targeted locations, and research on species life histories, community invasibility, and treatment effectiveness.

  10. The influence of organic-containing soil dust on ice nucleation and cloud properties

    Science.gov (United States)

    Hummel, Matthias; Grini, Alf; Berntsen, Terje K.; Ekman, Annica

    2017-04-01

    Natural mineral dust from desert regions is known to be the most important contributor to atmospheric ice-nucleating particles (INP) which induce heterogeneous ice nucleation in mixed-phase clouds. Its ability to nucleate ice effectively is shown by various laboratory (Hoose and Möhler 2012) and field results (DeMott et al. 2015) and its abundance in ice crystal residuals has also been shown (Cziczo et al. 2013). Thus it is an important player when representing mixed-phase clouds in climate models. MODIS satellite data indicate that 1 /4 of the global dust emission originates from semi-arid areas rather than from arid deserts (Ginoux et al. 2012). Here, organic components can mix with minerals within the soil and get into the atmosphere. These so-called 'soil dust' particles are ice-nucleating active at high sub-zero temperatures, i.e. at higher temperatures than pure desert dust (Steinke et al. 2016). In this study, soil dust is incorporated into the Norwegian Earth System Model (NorESM, Bentsen et al. 2013) and applied to a modified ice nucleation parameterization (Steinke et al. 2016). Its influence on the cloud ice phase is evaluated by comparing a control run, where only pure desert dust is considered, and a sensitivity experiment, where a fraction of the dust emissions are classified as soil dust. Both simulations are nudged to ERA-interim meteorology and they have the same loading of dust emissions. NorESM gives a lower annual soil dust emission flux compared to Ginoux et al. (2012), but the desert dust flux is similar to the MODIS-retrieved data. Although soil dust concentrations are much lower than desert dust, the NorESM simulations indicate that the annual INP concentrations from soil dust are on average lower by a just a factor of 4 than INP concentrations from pure desert dust. The highest soil dust INP concentrations occur at a lower height than for desert dust, i.e at warmer temperatures inside mixed-phase clouds. Furthermore, soil dust INP

  11. Participatory action research as a tool in solving desert vernacular architecture problems in the Western Desert of Egypt

    OpenAIRE

    Dabaieh, Marwa

    2013-01-01

    Vernacular architecture is suffering all over the world and Egypt is one of the countries where the desert vernacular is facing a great risk of disappearance. The aim of the research is to introduce a methodological approach applying participatory action research (PAR) as a tool to help save the future of the currently deteriorating desert vernacular architecture. The aim was to help prevent further loss of desert vernacular architecture knowledge and to encourage vernacular know-how in becom...

  12. Are Wildlife Detector Dogs or People Better at Finding Desert Tortoises (Gopherus Agassizii)?

    National Research Council Canada - National Science Library

    Nussear, Kenneth E; Esque, Todd C; Heaton, Jill S; Cablk, Mary E; Drake, Kristina K; Valentin, Cindee; Yee, Julie L; Medica, Philip A

    2008-01-01

    .... Recent studies highlight the effectiveness of trained detector dogs to locate wildlife during field surveys, including Desert Tortoises in a semi-natural setting. Desert Tortoises (Gopherus agassizii...

  13. Desert Cyanobacteria under simulated space and Martian conditions

    Science.gov (United States)

    Billi, D.; Ghelardini, P.; Onofri, S.; Cockell, C. S.; Rabbow, E.; Horneck, G.

    2008-09-01

    The environment in space and on planets such as Mars, can be lethal to living organisms and high levels of tolerance to desiccation, cold and radiation are needed for survival: rock-inhabiting cyanobacteria belonging to the genus Chroococcidiopsis can fulfil these requirements [1]. These cyanobacteria constantly appear in the most extreme and dry habitats on Earth, including the McMurdo Dry Valleys (Antarctica) and the Atacama Desert (Chile), which are considered the closest terrestrial analogs of two Mars environmental extremes: cold and aridity. In their natural environment, these cyanobacteria occupy the last refuges for life inside porous rocks or at the stone-soil interfaces, where they survive in a dry, dormant state for prolonged periods. How desert strains of Chroococcidiopsis can dry without dying is only partially understood, even though experimental evidences support the existence of an interplay between mechanisms to avoid (or limit) DNA damage and repair it: i) desert strains of Chroococcidiopsis mend genome fragmentation induced by ionizing radiation [2]; ii) desiccation-survivors protect their genome from complete fragmentation; iii) in the dry state they show a survival to an unattenuated Martian UV flux greater than that of Bacillus subtilis spores [3], and even though they die following atmospheric entry after having orbited the Earth for 16 days [4], they survive to simulated shock pressures up to 10 GPa [5]. Recently additional experiments were carried out at the German Aerospace Center (DLR) of Cologne (Germany) in order to identify suitable biomarkers to investigate the survival of Chroococcidiopsis cells present in lichen-dominated communities, in view of their direct and long term space exposition on the International Space Station (ISS) in the framework of the LIchens and Fungi Experiments (LIFE, EXPOSEEuTEF, ESA). Multilayers of dried cells of strains CCMEE 134 (Beacon Valley, Antarctica), and CCMEE 123 (costal desert, Chile ), shielded by

  14. Comparison of remote sensing indices for monitoring of desert cienegas

    Science.gov (United States)

    Wilson, Natalie R; Norman, Laura M.; Villarreal, Miguel; Gass, Leila; Tiller, Ron; Salywon, Andrew

    2016-01-01

    This research considers the applicability of different vegetation indices at 30 m resolution for mapping and monitoring desert wetland (cienega) health and spatial extent through time at Cienega Creek in southeastern Arizona, USA. Multiple stressors including the risk of decadal-scale drought, the effects of current and predicted global warming, and continued anthropogenic pressures threaten aquatic habitats in the southwest and cienegas are recognized as important sites for conservation and restoration efforts. However, cienegas present a challenge to satellite-imagery based analysis due to their small size and mixed surface cover of open water, exposed soils, and vegetation. We created time series of five well-known vegetation indices using annual Landsat Thematic Mapper (TM) images retrieved during the April–June dry season, from 1984 to 2011 to map landscape-level distribution of wetlands and monitor the temporal dynamics of individual sites. Indices included the Normalized Difference Vegetation Index (NDVI), the Soil-Adjusted Vegetation Index (SAVI), the Normalized Difference Water Index (NDWI), and the Normalized Difference Infrared Index (NDII). One topographic index, the Topographic Wetness Index (TWI), was analyzed to examine the utility of topography in mapping distribution of cienegas. Our results indicate that the NDII, calculated using Landsat TM band 5, outperforms the other indices at differentiating cienegas from riparian and upland sites, and was the best means to analyze change. As such, it offers a critical baseline for future studies that seek to extend the analysis of cienegas to other regions and time scales, and has broader applicability to the remote sensing of wetland features in arid landscapes.

  15. There's Iron in Them Thar Hills: A Geologic Look at the Aristarchus Plateau as a Potential Landing Site for Human Lunar Return

    Science.gov (United States)

    Coombs, Cassandra R.; McKay, David S.

    1997-01-01

    Lunar pyroclastic deposits are unique among lunar soils. Composed of very fine grained glass beads rich in Fe, Ti and Mg they yield unique spectral signatures. From the spectra two major classes and five subclasses of lunar dark mantling deposits have been identified. Recent work by me and others has shown that the larger regional deposits are more numerous, extensive, thicker, and widely distributed than previously thought, leading us to suggest that they would make ideal resource feedstock for future lunar surface activities. Returned sample studies and the recently collected Galileo and Clementine data also corroborate these findings. Recent planning for return to the Moon indicates that large cost savings can result from using locally produced oxygen, and recent JSC laboratory results indicate that iron-rich pyroclastic dark mantling deposits may be the richest oxygen resource on the Moon. My earlier work demonstrated that instead of using regolith, bulk lunar pyroclastic deposits are better suited for beneficiation as they are thick (lO's m's), unconsolidated, fine-grained deposits. In addition, the lack of rocks and boulders and the typically flat to gently rolling terrain will facilitate their mining and processing. In preparation for the Human Lunar Return (HLR) I have characterized the Aristarchus Plateau (24 deg. N 52 deg. W) as a potential landing site for an in-situ resource utilization (ISRU) demonstration. The geologic diversity and large volume of Fe-rich pyroclastic material present at the Aristarchus site make it an ideal target for extracting O2, H2 and halogens. This paper (1) describes the current understanding of the geology of Aristarchus plateau; (2) describes the resource potential of the Aristarchus plateau; and (3) presents several candidate landing sites on the plateau for future lunar activities.

  16. Extremely high UV-C radiation resistant microorganisms from desert environments with different manganese concentrations.

    Science.gov (United States)

    Paulino-Lima, Ivan Glaucio; Fujishima, Kosuke; Navarrete, Jesica Urbina; Galante, Douglas; Rodrigues, Fabio; Azua-Bustos, Armando; Rothschild, Lynn Justine

    2016-10-01

    Desiccation resistance and a high intracellular Mn/Fe ratio contribute to ionizing radiation resistance of Deinococcus radiodurans. We hypothesized that this was a general phenomenon and thus developed a strategy to search for highly radiation-resistant organisms based on their natural environment. While desiccation is a typical feature of deserts, the correlation between radiation resistance and the intracellular Mn/Fe ratio of indigenous microorganisms or the Mn/Fe ratio of the environment, has not yet been described. UV-C radiation is highly damaging to biomolecules including DNA. It was used in this study as a selective tool because of its relevance to early life on earth, high altitude aerobiology and the search for life beyond Earth. Surface soil samples were collected from the Sonoran Desert, Arizona (USA), from the Atacama Desert in Chile and from a manganese mine in northern Argentina. Microbial isolates were selected after exposure to UV-C irradiation and growth. The isolates comprised 28 genera grouped within six phyla, which we ranked according to their resistance to UV-C irradiation. Survival curves were performed for the most resistant isolates and correlated with their intracellular Mn/Fe ratio, which was determined by ICP-MS. Five percent of the isolates were highly resistant, including one more resistant than D. radiodurans, a bacterium generally considered the most radiation-resistant organism, thus used as a model for radiation resistance studies. No correlation was observed between the occurrence of resistant microorganisms and the Mn/Fe ratio in the soil samples. However, all resistant isolates showed an intracellular Mn/Fe ratio much higher than the sensitive isolates. Our findings could represent a new front in efforts to harness mechanisms of UV-C radiation resistance from extreme environments. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Characterization of Morphology, Volatile Profiles, and Molecular Markers in Edible Desert Truffles from the Negev Desert.

    Science.gov (United States)

    Kamle, Madhu; Bar, Einat; Lewinsohn, Dalia; Shavit, Elinoar; Roth-Bejerano, Nurit; Kagan-Zur, Varda; Barak, Ze'ev; Guy, Ofer; Zaady, Eli; Lewinsohn, Efraim; Sitrit, Yaron

    2017-03-28

    Desert truffles are mycorrhizal, hypogeous fungi considered a delicacy. On the basis of morphological characters, we identified three desert truffle species that grow in the same habitat in the Negev desert. These include Picoa lefebvrei (Pat.), Tirmania nivea (Desf.) Trappe, and Terfezia boudieri (Chatain), all associated with Helianthemum sessiliflorum. Their taxonomy was confirmed by PCR-RFLP. The main volatiles of fruit bodies of T. boudieri and T. nivea were 1-octen-3-ol and hexanal; however, volatiles of the latter species further included branched-chain amino acid derivatives such as 2-methylbutanal and 3-methylbutanal, phenylalanine derivatives such as benzaldehyde and benzenacetaldehyde, and methionine derivatives such as methional and dimethyl disulfide. The least aromatic truffle, P. lefebvrei, contained low levels of 1-octen-3-ol as the main volatile. Axenic mycelia cultures of T. boudieri displayed a simpler volatile profile compared to its fruit bodies. This work highlights differences in the volatile profiles of desert truffles and could hence be of interest for selecting and cultivating genotypes with the most likable aroma.

  18. Hydration status and diurnal trophic interactions shape microbial community function in desert biocrusts

    Science.gov (United States)

    Kim, Minsu; Or, Dani

    2017-12-01

    Biological soil crusts (biocrusts) are self-organised thin assemblies of microbes, lichens, and mosses that are ubiquitous in arid regions and serve as important ecological and biogeochemical hotspots. Biocrust ecological function is intricately shaped by strong gradients of water, light, oxygen, and dynamics in the abundance and spatial organisation of the microbial community within a few millimetres of the soil surface. We report a mechanistic model that links the biophysical and chemical processes that shape the functioning of biocrust representative microbial communities that interact trophically and respond dynamically to cycles of hydration, light, and temperature. The model captures key features of carbon and nitrogen cycling within biocrusts, such as microbial activity and distribution (during early stages of biocrust establishment) under diurnal cycles and the associated dynamics of biogeochemical fluxes at different hydration conditions. The study offers new insights into the highly dynamic and localised processes performed by microbial communities within thin desert biocrusts.

  19. Baseline studies in the desert ecosystem at East Mesa Geothermal Test Site, Imperial Valley, California

    Energy Technology Data Exchange (ETDEWEB)

    Romney, E.M.; Wallace, A.; Lunt, O.R.; Ackerman, T.A.; Kinnear, J.E.

    1977-09-01

    Baseline data reported herein for soil, vegetation, and small mammal components of the East Mesa desert ecosystem represent a collection period from October 1975 to September 1977. Inasmuch as changes in salt balance from geothermal brine sources are of potential impact upon the ecosystem, considerable analytical effort was given to the determination of element constituents in soil, plant, and animal samples. A preliminary synthesis of data was done to investigate the heterogeneity of element constituents among the sampled population and to summarize results. Findings indicate that periodic sampling and chemical analysis of vegetation around an industrialized geothermal energy source is probably the best way to monitor the surrounding ecosystem for assuring containment of any resource pollutants.

  20. Surface vitrification caused by natural fires in Late Pleistocene wetlands of the Atacama Desert

    Science.gov (United States)

    Roperch, Pierrick; Gattacceca, Jérôme; Valenzuela, Millarca; Devouard, Bertrand; Lorand, Jean-Pierre; Arriagada, Cesar; Rochette, Pierre; Latorre, Claudio; Beck, Pierre

    2017-07-01

    We describe extended occurrences of unusual silicate glass surface layers from the Atacama Desert (Chile). These glasses, found near the town of Pica at four localities separated by up to 70 km, are neither fulgurites, nor volcanic glasses, nor metallurgical slags related to anthropic activity, but show close similarities to other glasses that have been previously attributed to large airbursts created by meteoroids entering the Earth's atmosphere. The glasses are restricted to specific Late Pleistocene terrains: paleo-wetlands and soils rich in organic matter with SiO2-rich plant remains, salts and carbonates. 14C dating and paleomagnetic data indicate that the glasses were formed during at least two distinct periods. This rules out the hypothesis of a single large airburst as the cause of surface melting. Instead, burning of organic-rich soils in dried-out grassy wetlands during climate oscillations between wet and dry periods can account for the formation of the Pica glasses. Large oases did indeed form in the hyperarid Atacama Desert due to elevated groundwater tables and increased surface discharge during the Central Andean Pluvial Event (roughly coeval with the Mystery interval and Younger Dryas). Finally, we discuss the implications of our results for the other surface glasses previously attributed to extraterrestrial events.

  1. The Desert and the Sown Project in Northern Jordan

    DEFF Research Database (Denmark)

    Kerner, Susanne

    2014-01-01

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

  2. The politics of accessing desert land in Jordan

    NARCIS (Netherlands)

    Naber, Al Majd; Molle, Francois

    2016-01-01

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

  3. Forager abundance and dietary relationships in a Namib Desert ant ...

    African Journals Online (AJOL)

    Forager abundance and dietary relationships in a Namib Desert ant community. A.C. Marsh. Abstract. Thirteen ant species coexist on a barren gravel plain habitat in the central Namib Desert. Numerical density of foragers of all species fluctuated considerably over a 17-month period. Peaks in abundance correlated to ...

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

    Science.gov (United States)

    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

  5. Pastoralist rock art in the Black Desert of Jordan

    NARCIS (Netherlands)

    Brusgaard, N.O.

    2015-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Binggang Wang

    2011-06-01

    Full Text Available 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.

  7. Food Deserts and Overweight Schoolchildren: Evidence from Pennsylvania

    Science.gov (United States)

    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…

  8. The Palm Desert Renewable Hydrogen Transportation System

    Energy Technology Data Exchange (ETDEWEB)

    Lehman, P. [Humboldt State Univ., Arcata, CA (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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. Pioneer unmanned air vehicle accomplishments during Operation Desert Storm

    Science.gov (United States)

    Christner, James H.

    1991-12-01

    This paper will describe the accomplishments and lessons learned of the Pioneer Unmanned Air Vehicle (UAV) during Operations Desert Shield and Desert Storm. The Pioneer UAV has been deployed with three branches of the U.S. military (USA, USN, and USMC) for the past four years. Although the system has compiled over 6,000 flight hours, the recent conflict in the Gulf is the first opportunity to demonstrate its true value in a combat scenario. In a relatively short time (42 days), 307 flights and 1,011 flight hours were completed on Operation Desert Storm. This, coupled with the accuracy of various weapons systems that Pioneer observed/cued for, resulted in timely target engagements. This paper will chronicle the Pioneer deployment and accomplishments on Operations Desert Shield and Desert Storm. Various employment methods, tactics, doctrine, and lessons learned will be presented.

  12. Constructing a Symbolic Desert: Place and Identity in Contemporary Israel

    Directory of Open Access Journals (Sweden)

    Shavit, Ze'ev

    2014-04-01

    Full Text Available The paper focuses on images of the Negev desert in Israel among the Jewish population of Israel, presented in marketing websites of tourism and leisure resorts. The analysis of the data, focused on verbal and visual images of desert, shows a significant change in the symbolic construction of the desert compared to the first decades of Israeli statehood: from a desert conceived in light of national ideology and its imperatives, to one who’s images highlight consumerism and individual preferences, fantasies and desires. This change in the symbolic construction of the desert is treated as a part of some major changes in Jewish-Israeli collective identity thus pointing towards the link between two social processes: place-making and identity-work.

  13. Molecular and Isotopic Signs of Life and Climate in the Hyperarid Atacama Desert

    Science.gov (United States)

    Finstad, K. M.; Tuite, M. L., Jr.; Williford, K. H.; Amundson, R.

    2015-12-01

    The hyperarid region of the Atacama Desert is considered one of the driest places on earth. Geomorphological studies suggest that this area has maintained a near-continuous hyperarid climate for at least the past 2 million years. Water-limited biological and geochemical processes have created a unique landscape with many similarities to Mars. While precipitation is rare in the Atacama Desert, coastal fog occurs regularly and microbial communities capable of utilizing fog and dew water are able to persist. Within this region, we found soils with lichen-dominated biological soil crusts living in association with physical sulfate crusts on the soil surface. Due to their high tolerance of desiccation and ability to utilize fog water, biologic soil crusts are able to exist in this hyperarid environment. We chose two sites ~30 km apart along a fog frequency transect which showed visible differences in the degree of biological coverage to study how shifts in fog water availability affect the biogeochemical processes occurring. Our previous radiocarbon dating and δ13C analysis of soil carbonates here indicates that soil in both locations has been accreting for over 15,000 years and confirmed that biological activity and rates of C cycling are greater at the higher fog frequency site. This study expands on that work to characterize the isotopic imprint of extreme aridity and evaporative processes in this environment, examining both organic and inorganic materials. A standard fatty acid extraction method was used and we were able to detect fatty acids in all soils analyzed, even those over 15,000 years old. Compound specific isotope analysis of these fatty acids clearly showed an enrichment of 2H at the drier site, with ~ 25 per mil difference between the surface samples. Similarly, analysis of δ18O of soil carbonates show ~10 per mil enrichment of 18O at the drier site. We attribute these differences to a prolonged and consistently greater evaporative stress at the

  14. Dune-scale distribution pattern of herbaceous plants and their relationship with environmental factors in a saline-alkali desert in Central Asia.

    Science.gov (United States)

    Tao, Ye; Wu, Gan-Lin; Zhang, Yuan-Ming

    2017-01-15

    Sand dunes are the main landforms in modern deserts worldwide. As an important type of desert vegetation, herbaceous plants have long been acknowledged for their important ecological functions. We focus on the dune-scale distribution pattern of herbaceous plants and their relationship with the environment. During the early summer of 2010, the herbaceous plant density, coverage, aboveground biomass and eighteen environmental factors were surveyed from 214 plots (5m×5m) across two linear sand dunes (220m×110m) located in the Gurbantunggut Desert, China, a typical saline-alkali desert in Central Asia. Data were analyzed using univariate, ordination, and geostatistical techniques. Three vegetation variables represent a significant clumped distribution (Pdunes. The ranges (lag distance) of density (32.2m) and coverage (33.5m) were close to the average width (31.4m) of the transects. The biomass range (74.1m) was almost equal to the average width (75m) of the sand dunes. Pearson's correlation analysis and nonmetric multidimensional scaling analysis consistently demonstrated that the distributions of herbs on sand dunes were dominantly influenced by sand dune topography (slope position, convexity, and relative height), soil nutrients (total nitrogen and phosphorus) and deep-rooted shrubbery (Ephedra distachya). Compared to large, mobile and steep sand dunes, low, fixed and gentle sand dunes contribute to herbaceous plant abundance and distribution as well as the stability maintenance of the whole desert ecosystem. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Fractal scaling of particle size distribution and relationships with topsoil properties affected by biological soil crusts.

    Science.gov (United States)

    Gao, Guang-Lei; Ding, Guo-Dong; Wu, Bin; Zhang, Yu-Qing; Qin, Shu-Gao; Zhao, Yuan-Yuan; Bao, Yan-Feng; Liu, Yun-Dong; Wan, Li; Deng, Ji-Feng

    2014-01-01

    Biological soil crusts are common components of desert ecosystem; they cover ground surface and interact with topsoil that contribute to desertification control and degraded land restoration in arid and semiarid regions. To distinguish the changes in topsoil affected by biological soil crusts, we compared topsoil properties across three types of successional biological soil crusts (algae, lichens, and mosses crust), as well as the referenced sandland in the Mu Us Desert, Northern China. Relationships between fractal dimensions of soil particle size distribution and selected soil properties were discussed as well. The results indicated that biological soil crusts had significant positive effects on soil physical structure (Pproperties (R(2) = 0.494∼0.955, Pproperties that additionally implies desertification. This study will be essential to provide a firm basis for future policy-making on optimal solutions regarding desertification control and assessment, as well as degraded ecosystem restoration in arid and semiarid regions.

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

    Energy Technology Data Exchange (ETDEWEB)

    Paul D. Greger and Philip A. Medica

    2009-01-01

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

  17. Spatial variation in hydraulic redistribution by the desert shrub, Sarcobatus vermiculatus, at multiple scales

    Science.gov (United States)

    Richards, J. H.; Donovan, L. A.

    2012-12-01

    Passive water movement through roots from moist to dry soils, i.e. hydraulic redistribution, can be important for plant water status, vegetation water use, nutrient acquisition and cycling, and competition/facilitation among plant species. Although hydraulic redistribution is known from many species and habitats, little is known about how it varies at multiple spatial scales across species ranges. In the Mono Basin, California ecosystem we documented variation in hydraulic redistribution by the desert halophytic shrub, Sarcobatus vermiculatus, at three spatial scales: landscape, shrub-island versus interspace, and depth. Hydraulic redistribution varied among sites across the landscape. It was most prevalent at a low salinity site with deep groundwater (9.4 m), but of lower magnitude at more saline sites with shallower groundwater. At the low salinity site, infiltration from snowmelt, the predominant precipitation input, was confined to interspaces between shrub islands. Shrub-island soils remained very dry after snowmelt, even in a year with high total snow accumulation. Shrub-island soils, however, had substantial net increases in Ψsoil during week- to month-long periods in the early part of the growing season, concomitant with self-irrigated root growth into these dry soils, as documented with mini-rhizotrons. The source of this root-system-transported water was both moist interspace soils and moist deep soil layers. Wetting up of otherwise dry shrub-island soils is likely essential for nutrient mineralization and acquisition from trapped litter, making hydraulic redistribution an important driver of landscape-scale biogeochemical cycles in these saline basins. In addition, hydraulic redistribution buffered spatial variation in water availability among sites, depths, depth to groundwater, and for plants with different root distributions, such that plant Ψpredawn and Ψmidday differed little across the landscape. Multi-scale variation in hydraulic redistribution

  18. Morphological characterization of mycorrhizae formed between three Terfezia species (desert truffles) and several Cistaceae and Aleppo pine.

    Science.gov (United States)

    Zitouni-Haouar, Fatima El-Houaria; Fortas, Zohra; Chevalier, Gerard

    2014-07-01

    Six Cistaceae species, Helianthemum ledifolium, Helianthemum lippii, Fumana procumbens, Cistus albidus, Cistus incanus, Cistus salvifolius, and Pinus halepensis (Aleppo pine) were inoculated with three mycorrhizal desert truffles, Terfezia leptoderma, Terfezia boudieri, and Terfezia claveryi under greenhouse conditions, on soil originating from desert truffle natural habitat in Algeria. The syntheses have led to the formation of typical endomycorrhizae in annual Cistaceae (H. ledifolium) and perennial ones (H. lippii and F. procumbens) and an ectomycorrhiza with a less developed sheath in Cistus species and Aleppo pine. These results demonstrate the plasticity of Terfezia species to form different mycorrhizal types. The formation of an endomycorrhiza with H. ledifolium and F. procumbens and a sheathing ectomycorrhiza with P. halepensis inoculated by T. leptoderma in in vivo culture conditions was obtained for the first time.

  19. Tree water potentials supporting an explanation for the occurrence of Vachellia erioloba in the Namib Desert (Namibia

    Directory of Open Access Journals (Sweden)

    Joachim H. A. Krug

    2017-09-01

    Full Text Available Background Site-vegetation relations of Vachellia erioloba, Faidherbia albida, Euclea pseudebenus and Tamarix usneoides in two contrasting locations in the Namib Desert (Namibia were evaluated with the goal to relate soil water availability to the occurrence of trees under hyper-arid conditions. Methods Plant water potentials were measured using a pressure chamber in the field. Pre-dawn water potentials were assessed to reflect the soil water potential of the rhizosphere. Midday water potentials were measured to assess the strongest negative water potential applied by the sample trees. Results Pre-dawn water potentials and midday water potentials indicated access to soil water in the rhizosphere and by this, provide an explanation for an occurrence of V. erioloba within the extreme environmental conditions of sand dunes in the Namib Desert. Diurnal ranges seem to reflect more and less suitable stands, in terms of soil water availability, within the sampling sites. While the impact of the ephemeral Kuiseb river on soil water availability was assessed through the four species’ plant-internal water relations, comparable pre-dawn water potentials of V. erioloba at both sites indicate soil water availability also in the dunes of Namibrand. The extreme midday water potentials of the dune plants possibly show the upper limit of tolerance for V. erioloba. Conclusions The preliminary data provide an explanation of the occurrence and distribution of the investigated species in beds of ephemeral rivers and on dunes under the hyper-arid climatic conditions of the Namib Desert and qualify suitability within the assessed sites. Understanding the plant-physiological processes and assessing the plant-internal water potential provides a valuable tool to evaluate soil water availability within the rhizosphere and to describe an adaptation potential of investigated species. The comparability of pre-dawn water potentials at both sites indicates unexpected soil

  20. A review of pedogenic zonation in well-drained soils of the Southern Circumpolar Region

    Science.gov (United States)

    Bockheim, James G.; Ugolini, Fiorenzo C.

    1990-07-01

    The concept of zonality is used to link well-drained mineral soils and processes along a bioclimatic gradient extending from ca. 48° to 87° S, including southernmost Chile, the subantarctic islands, and maritime and continental Antarctica. The following environmental factors decline along this gradient: mean annual temperature and precipitation and the type and number of plant species. Six pedological zones (along with representative soils) are identified along the gradient: (1) Subantarctic Forest Zone (Podzol?), (2) Subantarctic Low Tundra zone, (3) Subantarctic High Tundra Zone (Subantarctic Brown soil, without permafrost), (4) Antarctic Sub-Polar Desert Zone (Subantarctic Brown soil, with permafrost), (5) Antarctic Polar Desert Zone (Red Ahumisol), and (6) Cold Desert Zone (Ahumisol). Zonal mineral soils in the Subantarctic Forest and Low Tundra Zones are rare, because large amounts of precipitation (>-2500 mm) and cool summers have led to thick accumulation of peat. Whereas the processes of rubification, melanization, and peat accumulation decline in relative magnitude southward, the processes of salinization and desert pavement formation increase in relative importance along this bioclimatic gradient. Carbonation and pervection (silt and clay migration) are maximized in the Subantarctic Tundra and Antarctic Polar Desert Zones. Because of the limited amount of land between 40° and 65° S and the presence of the Antarctic Convergence, comparable pedogenic zones occur at lower latitudes in the Southern than in the Northern Circumpolar Region.

  1. Actinomycetes in the rhizosphere of semidesert soils of Mongolia

    Science.gov (United States)

    Norovsuren, Zh.; Zenova, G. M.; Mosina, L. V.

    2007-04-01

    The population density of actinomycetes in the desert-steppe soil, rhizosphere, and the above-ground parts of plants varies from tens to hundreds of thousands of colony-forming units (CFU) per gram of substrate. The actinomycetal complexes of the brown desert-steppe soil without plant roots are more diverse in their taxonomic composition than the actinomycetal complexes in the rhizosphere and the aboveground parts of plants. Additionally to representatives of the Streptomyces and Micromonospora genera, actinomycetes from the Nocardia, Saccharopolyspora, Thermomonospora, and Actinomadura genera were identified in the soil. The population density of actinomycetes in the rhizosphere and in the soil reached hundreds of thousand CFU/g; it considerably exceeded the population density of actinomycetes in the aboveground parts of plants. The maximum population density of actinomycetes was determined in the rhizosphere of Asparagus gobicus, Salsola pestifera, and Cleistogenes songorica.

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

    NARCIS (Netherlands)

    Offer, Z.Y.; Goossens, D.

    2001-01-01

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

  3. Intermediate complex morphophysiological dormancy in seeds of the cold desert sand dune geophyte Eremurus anisopterus (Xanthorrhoeaceae; Liliaceae s.l.).

    Science.gov (United States)

    Mamut, Jannathan; Tan, Dun Yan; Baskin, Carol C; Baskin, Jerry M

    2014-10-01

    Little is known about morphological (MD) or morphophysiological (MPD) dormancy in cold desert species and in particular those in Liliaceae sensu lato, an important floristic element in the cold deserts of Central Asia with underdeveloped embyos. The primary aim of this study was to determine if seeds of the cold desert liliaceous perennial ephemeral Eremurus anisopterus has MD or MPD, and, if it is MPD, then at what level. Embryo growth and germination was monitored in seeds subjected to natural and simulated natural temperature regimes and the effects of after-ripening and GA3 on dormancy break were tested. In addition, the temperature requirements for embryo growth and dormancy break were investigated. At the time of seed dispersal in summer, the embryo length:seed length (E:S) ratio was 0·73, but it increased to 0·87 before germination. Fresh seeds did not germinate during 1 month of incubation in either light or darkness over a range of temperatures. Thus, seeds have MPD, and, after >12 weeks incubation at 5/2 °C, both embryo growth and germination occurred, showing that they have a complex level of MPD. Since both after-ripening and GA3 increase the germination percentage, seeds have intermediate complex MPD. Embryos in after-ripened seeds of E. anisopterus can grow at low temperatures in late autumn, but if the soil is dry in autumn then growth is delayed until snowmelt wets the soil in early spring. The ecological advantage of embryo growth phenology is that seeds can germinate at a time (spring) when sand moisture conditions in the desert are suitable for seedling establishment. © The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  4. Intermediate complex morphophysiological dormancy in seeds of the cold desert sand dune geophyte Eremurus anisopterus (Xanthorrhoeaceae; Liliaceae s.l.)

    Science.gov (United States)

    Mamut, Jannathan; Tan, Dun Yan; Baskin, Carol C.; Baskin, Jerry M.

    2014-01-01

    Background and Aims Little is known about morphological (MD) or morphophysiological (MPD) dormancy in cold desert species and in particular those in Liliaceae sensu lato, an important floristic element in the cold deserts of Central Asia with underdeveloped embyos. The primary aim of this study was to determine if seeds of the cold desert liliaceous perennial ephemeral Eremurus anisopterus has MD or MPD, and, if it is MPD, then at what level. Methods Embryo growth and germination was monitored in seeds subjected to natural and simulated natural temperature regimes and the effects of after-ripening and GA3 on dormancy break were tested. In addition, the temperature requirements for embryo growth and dormancy break were investigated. Key Results At the time of seed dispersal in summer, the embryo length:seed length (E:S) ratio was 0·73, but it increased to 0·87 before germination. Fresh seeds did not germinate during 1 month of incubation in either light or darkness over a range of temperatures. Thus, seeds have MPD, and, after >12 weeks incubation at 5/2 °C, both embryo growth and germination occurred, showing that they have a complex level of MPD. Since both after-ripening and GA3 increase the germination percentage, seeds have intermediate complex MPD. Conclusions Embryos in after-ripened seeds of E. anisopterus can grow at low temperatures in late autumn, but if the soil is dry in autumn then growth is delayed until snowmelt wets the soil in early spring. The ecological advantage of embryo growth phenology is that seeds can germinate at a time (spring) when sand moisture conditions in the desert are suitable for seedling establishment. PMID:25180288

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-11-30

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

  6. Desert dust outbreaks and respiratory morbidity in Athens, Greece.

    Science.gov (United States)

    Trianti, Stavroula-Myrto; Samoli, Evangelia; Rodopoulou, Sophia; Katsouyanni, Klea; Papiris, Spyros A; Karakatsani, Anna

    2017-07-01

    Ambient particulate matter (PM) has an adverse effect on respiratory morbidity. Desert dust outbreaks contribute to increased PM levels but the toxicity of desert dust mixed with anthropogenic pollutants needs clarification. We identified 132 days with desert dust episodes and 177 matched days by day of the week, season, temperature and humidity between 2001 and 2006 in Athens, Greece. We collected data on regulated pollutants and daily emergency outpatient visits and admissions for respiratory causes. We applied Poisson regression models adjusting for confounding effects of seasonality, meteorology, holidays and influenza epidemics. We evaluated the sensitivity of our results to co-pollutant exposures and effect modification by age and sex. A 10 μg/m3 increase in PM10 concentration was associated with 1.95% (95% confidence interval (CI): 0.02%, 3.91%) increase in respiratory emergency room visits. No significant interaction with desert dust episodes was observed. Compared with non-dust days, there was a 47% (95% CI: 29%, 68%) increase in visits in dust days not adjusting for PM10. Desert dust days were associated with higher numbers of emergency room visits for asthma, chronic obstructive pulmonary disease and respiratory infections with increases of 38%, 57% and 60%, respectively (p desert dust days and were further confounded by co-pollutants. Desert dust episode days are associated with higher respiratory emergency room visits and hospital admissions. This effect is insufficiently explained by increased PM10 levels.

  7. Evolution and Functional Classification of Vertebrate Gene Deserts

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Science.gov (United States)

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

    2011-01-01

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

  9. Soil formation in the Tsauchab Valley, Namibia

    Science.gov (United States)

    Eden, Marie; Bens, Oliver; Ramisch, Arne; Schwindt, Daniel; Völkel, Jörg

    2016-04-01

    The BMBF-funded project GeoArchives (Spaces) investigates soils and sediments in Southern Africa. A focus area lies on the Tsauchab Valley (Namibia), South of the Naukluft mountain range (24°26'40'' S, 16°10'40'' E). On a gently sloping alluvial fan facing East towards the river, the surface is characterized by a desert pavement covering soils used as farmland. The landscape units were mapped and the area at the lower slope of a hill was divided into three units: a rinsing surface and a gravel plain, separated by a channel. On these surfaces soil profiles were excavated. Profile description followed the German system (Bodenkundliche Kartieranleitung KA 5) and disturbed samples were taken at various depths and analysed in the lab. Undisturbed soil cores with a volume of 100 cm³ were taken just below the surface at a depth of ~1-6 cm. Lab analyses included texture and gravel content, colour, pH, electrical conductivity, carbonates, CNS, cation exchange capacity, pedogenic oxides, main and trace elements (XRF), and clay mineral distribution (XRD). Undisturbed samples were used to determine soil water retention curve, air permeability and bulk density. The profiles revealed moderately developed cambic soils rich in clay minerals and with total carbon contents ranging up to 1.8 %, bearing shrubs and after episodic rainfall a dense grass vegetation. Their genesis is discussed and interpreted in the context of the landscape and climate history of this semi-desert environment.

  10. Properties of Desert Sand and CMAS Glass

    Science.gov (United States)

    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.

  11. In vitro germination of desert rose varieties(

    Directory of Open Access Journals (Sweden)

    Tatiane Lemos Varella

    2015-08-01

    Full Text Available The drought stress resistance is a characteristic of the desert rose and its estimable beauty flowers, which gave it great relevance in the ornamental market. However, the desert rose production and germination is hampered by possible sterility of their male and female flowers and frequent problems in pollination, so the tissue culture is a promising alternative to the propagation of these plants. This study aimed to evaluate the effect of gibberellic acid on four commercial varieties of desert rose (Adenium obesum cultivated in vitro. The seeds of the varieties ‘Orange Pallet’, ‘Carnation violet’, ‘Diamond ring’ and ‘Vermiliont’ were sterilized and inoculated on Water + Agar (T0, medium MS (T1, ½ MS (T2, MS + 0.25 mg L-1 GA3 (T3, MS + 0.5 mg L-1 GA3 (T4, ½ MS + 0.25 mg L-1 GA3 (T5, ½ MS 0.5 mg L-1 GA3 (T6. The seeds germination of A. obesum was initiated on the fourth day of cultivation and on the tenth day was possible to observe the expansion of the cotyledons and leaf expansion with subsequent development of early secondary root. The ‘Orange pallet’ variety germinated 100% of seeds on water + agar and MS ½ + 0.5 mg L-1 of GA3. For ‘Diamond Ring’ and ‘Carnation violet’ the highest rate of germination occurred in treatments MS ½; 0.25 mg L-1 GA3; MS + 0.5 mg L-1 GA3 MS ½ + 0.5 mg L-1 GA3 averaging 80% and 70%, respectively. For ‘Vermiliont’ the best response was in MS and MS ½ + 0.5 mg L-1 GA3 ranging between 70-90% germinated embryos. It was registered different malformations in all treatments like absence of roots and apexes during seedling development. The concentrations of GA3 did not affect significantly the seed germination.

  12. How to identify food deserts in Amazonian cities?

    OpenAIRE

    Davies, Gemma; Frausin Bustamante, Gina Giovanna; Parry, Luke Thomas Wyn

    2016-01-01

    Food deserts are areas without affordable access to healthy foods. This paper explores whether food deserts are present within urban areas of the Brazilian Amazon. The availability and price of a variety of food products was surveyed in a total of 304 shops, across 3 cities in 2015. Least-cost distances were calculated to estimate travel distance to access products, with map overlay used to help identify areas with poor access to a variety of healthy food - these were defined as food deserts.

  13. Multi-scale forcing and the formation of subtropical desert and monsoon

    Directory of Open Access Journals (Sweden)

    G. X. Wu

    2009-09-01

    parts of their respective continents, and orography-induced ascent is separated from ascent due to continental-scale forcing. Accordingly, the deserts and monsoon climate over these continents are not as strongly developed as those over the Eurasian Continent. A new mechanism of positive feedback between diabatic heating and vorticity generation, which occurs via meridional transfer of heat and planetary vorticity, is proposed as a means of explaining the formation of subtropical desert and monsoon. Strong low-level longwave radiative cooling over eastern parts of oceans and strong surface sensible heating on western parts of continents generate negative vorticity that is balanced by positive planetary vorticity advection from high latitudes. The equatorward flow generated over eastern parts of oceans produces cold sea-surface temperature and stable stratification, leading in turn to the formation of low stratus clouds and the maintenance of strong in situ longwave radiative cooling. The equatorward flow over western parts of continents carries cold, dry air, thereby enhancing local sensible heating as well as moisture release from the underlying soil. These factors result in a dry desert climate. Over the eastern parts of continents, condensation heating generates positive vorticity in the lower troposphere, which is balanced by negative planetary vorticity advection of the meridional flow from low latitudes. The flow brings warm and moist air, thereby enhancing local convective instability and condensation heating associated with rainfall. These factors produce a wet monsoonal climate. Overall, our results demonstrate that subtropical desert and monsoon coexist as a consequence of multi-scale forcing along the subtropics.

  14. Multi-scale forcing and the formation of subtropical desert and monsoon

    Directory of Open Access Journals (Sweden)

    G. X. Wu

    2009-09-01

    located over the western parts of their respective continents, and orography-induced ascent is separated from ascent due to continental-scale forcing. Accordingly, the deserts and monsoon climate over these continents are not as strongly developed as those over the Eurasian Continent.

    A new mechanism of positive feedback between diabatic heating and vorticity generation, which occurs via meridional transfer of heat and planetary vorticity, is proposed as a means of explaining the formation of subtropical desert and monsoon. Strong low-level longwave radiative cooling over eastern parts of oceans and strong surface sensible heating on western parts of continents generate negative vorticity that is balanced by positive planetary vorticity advection from high latitudes. The equatorward flow generated over eastern parts of oceans produces cold sea-surface temperature and stable stratification, leading in turn to the formation of low stratus clouds and the maintenance of strong in situ longwave radiative cooling. The equatorward flow over western parts of continents carries cold, dry air, thereby enhancing local sensible heating as well as moisture release from the underlying soil. These factors result in a dry desert climate. Over the eastern parts of continents, condensation heating generates positive vorticity in the lower troposphere, which is balanced by negative planetary vorticity advection of the meridional flow from low latitudes. The flow brings warm and moist air, thereby enhancing local convective instability and condensation heating associated with rainfall. These factors produce a wet monsoonal climate. Overall, our results demonstrate that subtropical desert and monsoon coexist as a consequence of multi-scale forcing along the subtropics.

  15. Desert dust contribution to PM10 loads in Italy: Methods and recommendations addressing the relevant European Commission Guidelines in support to the Air Quality Directive 2008/50

    Science.gov (United States)

    Barnaba, Francesca; Bolignano, Andrea; Di Liberto, Luca; Morelli, Matteo; Lucarelli, Franco; Nava, Silvia; Perrino, Cinzia; Canepari, Silvia; Basart, Sara; Costabile, Francesca; Dionisi, Davide; Ciampichetti, Spartaco; Sozzi, Roberto; Gobbi, Gian Paolo

    2017-07-01

    In 2011 the European Commission (EC) released specific 'Guidelines' describing the methods to quantify and subtract the contribution of natural sources from the PM10 values regulated by the European Air Quality Directive (2008/50/EC). This work investigates the applicability to Italy of the EC-Methodology suggested for desert-dust, describes main limitations encountered and proposes specific modifications embedded within a 'revised-Methodology' to extend/improve its use. The revised-Methodology capabilities are evaluated using original, chemically-resolved mineral-dust mass concentration measurements, showing better performances in predicting timing and absolute values of the desert-dust contribution to the daily-PM10 with respect to the current EC-approach. The revised-Methodology is then translated into an automatic (user-independent) tool tailored to the expected final-users. This tool is applied over Central Italy across a 3-year long period (2012-2014), and over the whole Italian country for a calendar year (2012). The derived results confirm and extend to Italian regions never addressed before some previously observed features of the desert-dust impact over the country, such as a clear latitudinal dependence of the desert-dust impact on the yearly average PM10 (from more than 5 μg/m3 to less than 0.5 μg/m3, going from south to north Italy). The modifications introduced within the revised-Methodology also suggest a non-negligible role of desert-dust resuspension in areas characterized by both high traffic levels and soil sealing (urban areas and along the major Italian routes). In the Rome area, such an effect is found to add a contribution of about 2 μg/m3 (i.e., of 20%) to the mean desert-dust load per dust day (about 10 μg/m3). At the national level, this effect contributes increasing the total number of desert-dust-driven exceedances of the PM10 daily limit value even in the northern regions, where the desert-dust impact on the PM10 yearly average is

  16. Microbial ecology and biogeochemistry of continental Antarctic soils

    Directory of Open Access Journals (Sweden)

    Don A Cowan

    2014-04-01

    Full Text Available The Antarctica Dry Valleys are regarded as the coldest hyperarid desert system on Earth. While a wide variety of environmental stressors including very low minimum temperatures, frequent freeze-thaw cycles and low water availability impose severe limitations to life, suitable niches for abundant microbial colonization exist. Antarctic desert soils contain much higher levels of microbial diversity than previously thought. Edaphic niches, including cryptic and refuge habitats, microbial mats and permafrost soils all harbour microbial communities which drive key biogeochemical cycling processes. For example, lithobionts (hypoliths and endoliths possess a genetic capacity for nitrogen and carbon cycling, polymer degradation and other system processes. Nitrogen fixation rates of hypoliths, as assessed through acetylene reduction assays, suggest that these communities are a significant input source for nitrogen into these oligotrophic soils. Here we review aspects of microbial diversity in Antarctic soils with an emphasis on functionality and capacity. We assess current knowledge regarding adaptations to Antarctic soil environments and highlight the current threats to Antarctic desert soil communities.

  17. Actinobacteria from arid and desert habitats: diversity and biological activity

    Directory of Open Access Journals (Sweden)

    Joachim eWink

    2016-01-01

    Full Text Available Abstract The lack of new antibiotics in the pharmaceutical pipeline guides more and more researchers to leave the classical isolation procedures and to look in special niches and ecosystems. Bioprospecting of extremophilic Actinobacteria through mining untapped strains and avoiding resiolation of known biomolecules is among the most promising strategies for this purpose. With this approach, members of acidtolerant, alkalitolerant, psychrotolerant, thermotolerant, halotolerant and xerotolerant Actinobacteria have been obtained from respective habitats. Among these, little survey exists on the diversity of Actinobacteria in arid areas, which are often adapted to relatively high temperatures, salt concentrations, and radiation. Therefore, arid and desert habitats are special ecosystems which can be recruited for the isolation of uncommon Actinobacteria with new metabolic capability.At the time of this writing, members of Streptomyces, Micromonospora, Saccharothrix, Streptosporangium, Cellulomonas, Amycolatopsis, Geodermatophilus, Lechevalieria, Nocardia and Actinomadura are reported from arid habitats. However, metagenomic data present dominant members of the communities in desiccating condition of areas with limited water availability that are not yet isolated. Furthermore, significant diverse types of polyketide synthase (PKS and nonribosomal peptide synthetase (NRPS genes are detected in xerophilic and xerotolerant Actinobacteria and some bioactive compounds are reported from them. Rather than pharmaceutically active metabolites, molecules with protection activity against drying such as Ectoin and Hydroxyectoin with potential application in industry and agriculture have also been identified from xerophilic Actinobacteria. In addition, numerous biologically active small molecules are expected to be discovered from arid adapted Actinobacteria in the future. In the current survey, the diversity and biotechnological potential of Actinobacteria

  18. 2-\tAllred B.W., and Snyder K.A. 2008. Ecophysiological responses of Chihuahuan desert grasses to fire. Journal of Arid Environments, 72 (11:1989-1996. 3-\tBento-Gonçalves A., Vieira A., Úbeda X., and Martin D. 2012. Fire and soils: Key concepts and recent

    Directory of Open Access Journals (Sweden)

    H. Taefi

    2017-06-01

    Full Text Available Introduction: Amongst different habitats, fire is an ecological factor and determinant that affects many physico-chemical soil factors. In addition, among natural disturbances, fire plays an important role in plant diversity conservation and in some areas around the world, the presence of some plant species depends on natural fire. The extension of fire influences on soil is related to the fire severity. In fact, fire severity encompasses of two characteristics: extension and time of burning. On the other hand, fire extension and burning time are affected by humidity, air temperature, wind speed, topographical characteristics. Despite high frequency of fire in natural habitats and high level of fire effectiveness on soil parameters, study of fire impacts on soil characteristics were rarely reported in Iran. In addition, most previous studies were conducted in forest habitats, ignoring the severity of fire on soil. Materials and Methods: In order to investigate the effect of fire severity on some soil physico-chemical characteristics, Yeylagh Dasht area (rangeland habitats was selected in southern-east of national Golestan Park with three different plant covers, viz. grass, shrub and cushion. Many fires occurring have been reported in this park in each year. For the current study, we tried to select the habitats in which the fire was occurred at least one year before. A control area without burning with similar ecological parameters was also selected adjacent to the burnt area. in fact unburnt area was isolated by a road from burnt area, unable to extend the fire into unburnt area due to the road. Fire had been occurred in the burnt area in September, 2014. Soil samples with 15 replications in burnt area and 15 replications in unburnt were collected within a depth of 0-5 cm and then transported to the soil laboratory to measure some qualitative soil characteristics i.e. soil organic matter (SOM, particulate organic matter (POM, total nitrogen (TN

  19. Desert ants learn vibration and magnetic landmarks.

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    Cornelia Buehlmann

    Full Text Available 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.

  20. Ethnomycological survey of traditional usage and indigenous knowledge on desert truffles among the native Sahara Desert people of Algeria.

    Science.gov (United States)

    Bradai, Lyès; Neffar, Souad; Amrani, Khaled; Bissati, Samia; Chenchouni, Haroun

    2015-03-13

    Desert truffles are edible hypogeous fungi, highly appreciated by the inhabitants of hot-desert settlements. Native Saharan people use truffles for food, promoting tourism, increasing fertility, and treatment of eye diseases and fatigue. This study consists of a cross-sectional survey focusing on the knowledge, use and ethnomycological practices of desert truffles among the native people of the Algerian Northern Sahara. The study was conducted through direct interviews with 60 truffle-hunters in the regions of Ouargla and Ghardaia. Three species were harvested and consumed by the surveyed subjects: Terfezia claveryi was the most appreciated and most expensive species, followed by Terfezia areanaria moderately preferred, then Tirmania nivea the least appreciated and least expensive. Among the 60 interviewees, 90% rely on the abundance of symbiotic plants (Helianthemum lippii) to harvest truffles, 65% begin harvesting from mid-February to March, after rains of the autumn (38%) and winter (36%), particularly in the Wadi beds (37%) and Daya landscapes (32%). Interviewees harvested truffles mainly for home consumption; however 26.7% sell any harvest surplus, and of those only 15% generate significant revenue from this source, and 73% considered the sale of desert truffles to have low financial value. Desert truffles are used in traditional medicine, especially against eye infections (22%), weakness (19%) and to promote male fertility (19%). In the case of desert truffles for consumption, the surveyed population preferred to prepare the truffles with couscous and meat, or in porridge. Respondents used price as the main criterion for deciding whether to purchase desert truffles. The surveyed trufflers use the knowledge passed from one generation to the next to help ensure a good harvest of truffles during each foray into the desert. Our findings highlight the various uses of truffles in the Sahara Desert, and how these relate to the lifestyle of local people. Copyright

  1. Canopy Transpiration and Stomatal Responses to Prolonged Drought by a Dominant Desert Species in Central Asia

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    Daxing Gu

    2017-06-01

    Full Text Available In arid and semiarid lands, canopy transpiration and its dynamics depend largely on stomatal sensitivity to drought. In this study, the sap flow of a dominant species, Haloxylon ammodendron growing in Central Asian deserts, was monitored using Granier-type sensors, from which the canopy stomatal conductance was derived. The responses of canopy transpiration and stomatal conductance to environmental variables during the second half of the growing season, when annual prolonged drought occurred, was analyzed for four continuous years, from 2013 to 2016. A soil water content (SWC of 3% was identified as the lower soil water threshold for this species, below which the plant lost the ability for stomatal regulation on water loss and suffered the risk of mortality. Above this threshold, the sensitivity of canopy transpiration to vapor pressure deficit, VPD (K, was linearly correlated with SWC, which mainly resulted from different stomatal behaviors at varying drought intensities. Stomatal sensitivity to VPD (m/Gsref increased linearly with soil moisture deficit, inducing a shift from more anisohydric to a more isohydric stomatal behavior. The flexibility of stomatal behavior regarding soil drought was one key element facilitating the survival of H. ammodendron in such an extreme dry environment.

  2. Area integrated emission of biogenic nitric oxide by Lagrangian dispersion modeling (LASAT): Milan oasis, Taklimakan desert (Xinjiang, PR China)

    Science.gov (United States)

    Badawy, M.; Wu, Z.; Behrendt, T.; Fechner, A. D.; Meixner, F. X.; Andreae, M. O.; Mamtimin, B.

    2012-04-01

    Today's knowledge of soil biogenic NO emission rates from arid and hyper-arid land is based on a total of about 20 experimental studies. Nevertheless, biogenic NO emissions even from non-managed arid and hyper-arid soils are significant and may range between 1-10 ng m-2 s-1 (in terms of nitrogen, if conditions for soil NO production are favourable (optimum soil moisture, high soil temperatures). Irrigated and fertilized oases, ranging about 3000 km long around the great Central Asian Taklimakan desert form the backbone of the agricultural output (80% of the Chinese cotton production) of the Xinjiang Uygur Autonomous Region (NW-China). Recent and future development of farmland and intensification of agriculture will definitely impact the regional soil NO emission and consequently the budget of nitrogen oxides and ozone. Up to today, only a few studies have preliminarily addressed soil biogenic NO emissions from the Taklimakan desert. In our contribution, we will focus on the quantification of the area integrated NO emission from the Milan oasis located on the most southern fringe of the Takalimkan desert (39.26° N, 88.91° E). At a first step, the 3D distribution of ambient NO concentration is calculated using a state-of-the-art commercially available dispersion model (LASAT 3.2, Lagrange Simulation of Aerosol-Transport). Performing the dispersion simulation, transport and turbulent diffusion are simulated for a group of representative "simulation particles" by means of a stochastic process (Lagrange simulation). Surface sources (individual cotton fields, Jujube orchards) are known: their geographical location as well as their areal extent, their stage of vegetation growth as well as irrigation and fertilization events and amounts, soil temperatures and soil water contents. This information is used to up-scale our results of field specific potential net NO emission, which has been parameterized in terms of soil temperature, soil water content, and soil nutrient

  3. The Impact of Solar Arrays on Arid Soil Hydrology: Some Numerical Simulations

    Science.gov (United States)

    Luo, Y.; Berli, M.; Koonce, J.; Shillito, R.; Dijkema, J.; Ghezzehei, T. A.; Yu, Z.

    2016-12-01

    Hot deserts are prime locations for solar energy generation but also recognized as particularly fragile environments. Minimizing the impact of facility-scale solar installations on desert environments is therefore of increasing concern. This study focuses on the impact of photovoltaic solar arrays on the water balance of arid soil underneath the array. The goal was to explore whether concentrated rainwater infiltration along the solar panel drip lines would lead to deeper infiltration and an increase in soil water storage in the long term. A two-dimensional HYDRUS model was developed to simulate rainwater infiltration into the soil within a photovoltaic solar array. Results indicate that rainwater infiltrates deeper below the drip lines compared to the areas between solar panels but only for coarse textured soil. Finer-textured soils redistribute soil moisture horizontally and the concentrating effect of solar panels on rainwater infiltration appears to be small.

  4. Sulfate and nitrate in Asian dust particles observed in desert, coastal and marine air

    Science.gov (United States)

    Zhang, D.; Wu, F.; Junji, C.

    2016-12-01

    Sulfate and nitrate in dust particles are believed to be two key species which can largely alter the physical and chemical properties of the particles in the atmosphere, in particular under humid conditions. Their occurrence in the particles has usually been considered to be the consequence of particles' aging during their long-distance travel in the air although they are present in some crustal minerals. Our observations at two deserts in China during dust episodes revealed that there were soil-derived sulfate and background-like nitrate in atmospheric dust samples. Sulfate in dust samples was proportional to samples' mass and comprised at steady mass percentages in differently sized samples. In contrast, nitrate concentration was approximately stable and independent from dust loading. Our observations at inland and coastal areas of China during dust episodes revealed that sulfate and nitrate were hardly produced on the surface of dust particles that were originated from the deserts areas in northwestern China. This is because the dust particles were in the postfrontal air, where the temperature was low and the relative humidity was small due to the adiabatic properties of the air mass. There are a number studies reporting that sulfate and nitrate had been efficiently produced on mineral particles in inland areas of China. However, those mineral particles were more likely from the local areas rather than from the desert areas. Our observations in the coastal areas of Japan, which is located in the downstream areas of the Asian continent and surrounded by sea areas revealed that dust particles appearing there frequently contained sulfate and nitrate, indicating sulfate and nitrate had been efficiently produced on the surface of the particles when the particles traveled in the marine air between China and Japan.

  5. Cyanobacteria and cyanotoxins are present in drinking water impoundments and groundwater wells in desert environments.

    Science.gov (United States)

    Chatziefthimiou, Aspassia D; Metcalf, James S; Glover, W Broc; Banack, Sandra A; Dargham, Soha R; Richer, Renee A

    2016-05-01

    Desert environments and drylands experience a drastic scarcity of water resources. To alleviate dependence on freshwater for drinking water needs, countries have invested in infrastructure development of desalination plants. Collectively, the countries of the Arabian Gulf produce 45% of the world's desalinated water, which is stored in dams, mega-reservoirs and secondary house water tanks to secure drinking water beyond daily needs. Improper storage practices of drinking water in impoundments concomitant with increased temperatures and light penetration may promote the growth of cyanobacteria and accumulation of cyanotoxins. To shed light on this previously unexplored research area in desert environments, we examined drinking and irrigation water of urban and rural environments to determine whether cyanobacteria and cyanotoxins are present, and what are the storage and transportation practices as well as the environmental parameters that best predict their presence. Cyanobacteria were present in 80% of the urban and 33% of the rural water impoundments. Neurotoxins BMAA, DAB and anatoxin-a(S) were not detected in any of the water samples, although they have been found to accumulate in the desert soils, which suggests a bioaccumulation potential if they are leached into the aquifer. A toxic BMAA isomer, AEG, was found in 91.7% of rural but none of the urban water samples and correlated with water-truck transportation, light exposure and chloride ions. The hepatotoxic cyanotoxin microcystin-LR was present in the majority of all sampled impoundments, surpassing the WHO provisional guideline of 1 μg/l in 30% of the urban water tanks. Finally, we discuss possible management strategies to improve storage and transportation practices in order to minimize exposure to cyanobacteria and cyanotoxins, and actions to promote sustainable use of limited water resources. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. C