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1
Silvertooth, J. C., A. Galadima, and E. R. Norton. "Residual Soil Nitrogen Evaluations in Irrigated Desert Soils, 2003." College of Agriculture, University of Arizona (Tucson, AZ), 2004. http://hdl.handle.net/10150/198133.
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Field experiments aimed at investigating N fertilizer management in irrigated cotton production have been conducted for the past 16 seasons at three University of Arizona Agricultural Centers (Maricopa, MAC; Marana, MAR; and Safford, SAC). In 2003, residual N studies were conducted at two of these locations (MAC and MAR). The MAC and SAC experiments have been conducted each season since 1989 and the Marana site was initiated in 1994. Original purposes of the experiments were to test nitrogen (N) fertilization strategies and to validate and refine N fertilization recommendations for Upland (Gossypium hirsutum L.) and American Pima (G. barbadense L.) cotton. Each experiment has utilized N management tools such as pre-season soil tests for NO₃⁻-N, in-season plant tissue testing (petioles) for N fertility status, and crop monitoring to ascertain crop fruiting patterns and crop N needs. At each location, treatments varied from a conservative to a more aggressive approach of N management. Results at each location revealed a strong relationship between fruit retention levels and N needs of the crop. This pattern was further reflected in the final yield analysis as a response to the N fertilization regimes used. The higher, more aggressive N application regimes did not consistently benefit yields at any location. Generally, the more conservative, feedback approach to N management provided optimum yields at all locations. In 2001, a transition project evaluating residual N effects associated with each treatment regime was initiated with no N fertilizer applied. Therefore, all N taken-up by the crop was derived from residual soil N. In 2001, 2002, and even 2003 there were no significant differences among the original fertilizer N regimes in terms of residual soil NO₃⁻-N concentrations, crop growth, development, lint yield, or fiber properties. Lint yields were very uniform at each location in 1991 and averaged 1500, 1100, and 850 lbs. lint/acre for MAC, MAR, and SAC, respectively. In 2002, results were very similar and yields averaged 1473 and 1060 lbs. lint/acre for MAC and MAR locations respectively. The results for 2003 were similar to the results of the prior two years with yields at 1322 and 1237 lbs. lint/acre for MAC and MAR, respectively. Trends associated with residual fertilizer N effects are not evident at either location following three consecutive seasons of N fertilizer treatments.
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Silvertooth, J. C., A. Galadima, and E. R. Norton. "Residual Soil Nitrogen Evaluations in Irrigated Desert Soils, 2004." College of Agriculture, University of Arizona (Tucson, AZ), 2005. http://hdl.handle.net/10150/198175.
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Field experiments aimed at investigating N fertilizer management in irrigated cotton production have been conducted for the past 16 seasons at three Arizona locations on University of Arizona Agricultural Centers (Maricopa, MAC; Marana, MAR; and Safford, SAC). In 2004, residual N studies were conducted at two of these locations (MAC and MAR). The MAC and SAC experiments have been conducted each season since 1989 and the Marana site was initiated in 1994. The original purposes of the experiments were to test nitrogen (N) fertilization strategies and to validate and refine N fertilization recommendations for Upland (Gossypium hirsutum L.) and American Pima (G. barbadense L.) cotton. The experiments have each utilized N management tools such as pre-season soil tests for NO₃⁻-N, in-season plant tissue testing (petioles) for N fertility status, and crop monitoring to ascertain crop fruiting patterns and crop N needs. At each location, treatments varied from a conservative to a more aggressive approach of N management. Results at each location reveal a strong relationship between the crop fruit retention levels and N needs for the crop. This pattern was further reflected in final yield analysis as a response to the N fertilization regimes used. The higher, more aggressive N application regimes did not consistently increase yields at any location. Generally, the more conservative, feedback approach to N management provided optimum yields at all locations. In 2001, a transition project evaluating the residual N effects associated with each treatment regime was initiated and no fertilizer N was applied. Therefore, all N taken-up by the crop was derived from residual soil N. In 2001, 2002, 2003 and even 2004 there were no significant differences among the original fertilizer N regimes in terms of residual soil NO₃⁻-N concentrations, crop growth, development, lint yield, or fiber properties. The lint yields were very uniform at each location in 1991 and averaged 1500, 1100, and 850 lbs. lint/acre for MAC, MAR, and SAC, respectively. In 2002, results were very similar and yields averaged at 1473 and 1060 lbs. lint/acre for MAC and MAR locations respectively. The 2003 results were not different from the prior two years of results and yields averaged at 1322 and 1237 lbs. lint/acre for MAC and MAR respectively. In 2004, yields averaged 828 and 1075 lbs. lint/acre. Trends associated with residual fertilizer N effects are not evident at either location four seasons following N fertilizer applications.
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Silvertooth, J. C., A. Galadima, and E. R. Norton. "Residual Soil Nitrogen Evaluations in Irrigated Desert Soils, 2001." College of Agriculture, University of Arizona (Tucson, AZ), 2002. http://hdl.handle.net/10150/197713.
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Field experiments were conducted in Arizona in 2001 at three locations (Maricopa, Marana, and Safford). The Maricopa and Safford experiments have been conducted for14 consecutive seasons and the Marana site was initiated in 1994. The original purposes of the experiments were to test nitrogen (N) fertilization strategies and to validate and refine N fertilization recommendations for Upland (Gossypium hirsutum L.) and American Pima (G. barbadense L.) cotton. The experiments have each utilized N management tools such as pre-season soil tests for NO₃⁻-N, in-season plant tissue testing (petioles) for N fertility status, and crop monitoring to ascertain crop fruiting patterns and crop N needs. At each location, treatments varied from a conservative to a more aggressive approach of N management. Results at each location revealed a strong relationship between the crop fruit retention levels and N needs for the crop. This pattern was further reflected in final yield analysis as a response to the N fertilization regimes used. The higher, more aggressive, N application regimes did not benefit yields at any location. Generally, the more conservative, feedback approach to N management provided optimum yields at all locations. In 2001, a transition project evaluating the residual N effects associated with each treatment regime was initiated and no fertilizer N was applied. Therefore, all N taken-up by the crop was derived from residual soil N. In 2001 there were no significant differences among the original fertilizer N regimes in terms of residual soil NO₃⁻-N concentrations, crop growth, development, lint yield, or fiber properties. The lint yields were very uniform at each location and averaged 1500, 1100, and 850 lbs. lint/acre for Maricopa, Marana, and Safford, respectively.
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Silvertooth, J. C., A. Galadima, and E. R. Norton. "Residual Soil Nitrogen Evaluations in Irrigated Desert Soils, 2002." College of Agriculture, University of Arizona (Tucson, AZ), 2003. http://hdl.handle.net/10150/197911.
Full textAbstract:
Field experiments investigating N fertilizer management in irrigated cotton production have been conducted for the past 15 seasons at three Arizona locations on University of Arizona Agricultural Centers (Maricopa, MAC; Marana, MAR; and Safford, SAC). In 2002, residual N studies were conducted at two of these locations (MAC and MAR). The MAC and SAC experiments have been conducted each season since 1989 and the Marana site was initiated in 1994. The original purposes of the experiments were to test nitrogen (N) fertilization strategies and to validate and refine N fertilization recommendations for Upland (Gossypium hirsutum L.) and American Pima (G. barbadense L.) cotton. The experiments have each utilized N management tools such as pre-season soil tests for NO₃⁻-N, in-season plant tissue testing (petioles) for N fertility status, and crop monitoring to ascertain crop fruiting patterns and crop N needs. At each location, treatments varied from a conservative to a more aggressive approach of N management. Results at each location revealed a strong relationship between the crop fruit retention levels and N needs for the crop. This pattern was further reflected in final yield analysis as a response to the N fertilization regimes used. The higher, more aggressive N application regimes did not consistently benefit yields at any location. Generally, the more conservative, feedback approach to N management provided optimum yields at all locations. In 2001, a transition project evaluating the residual N effects associated with each treatment regime was initiated and no fertilizer N was applied. Therefore, all N taken-up by the crop was derived from residual soil N. In 2001, there were no significant differences among the original fertilizer N regimes in terms of residual soil NO₃⁻-N concentrations, crop growth, development, lint yield, or fiber properties. The lint yields were very uniform at each location and averaged 1500, 1100, and 850 lbs. lint/acre for MAC, MAR, and SAC, respectively. In 2002, results were very similar at the MAC and MAR locations. Trends associated with residual fertilizer N effects are not evident at either location just two seasons following N fertilizer applications.
5
Silvertooth, J. C., A. Galadima, and E. R. Norton. "Residual Soil Nitrogen Evaluations In Irrigated Desert Soils, 2005." College of Agriculture, University of Arizona (Tucson, AZ), 2006. http://hdl.handle.net/10150/198203.
Full textAbstract:
Field experiments aimed at investigating N fertilizer management in irrigated cotton production have been conducted for the past 16 seasons at three Arizona locations on University of Arizona Agricultural Centers (Maricopa, MAC; Marana, MAR; and Safford, SAC). In 2001-2005, residual N studies were conducted at two of these locations (MAC and MAR). The MAC and SAC experiments have been conducted each season since 1989 and the Marana site was initiated in 1994. The original purposes of the experiments were to test nitrogen (N) fertilization strategies and to validate and refine N fertilization recommendations for Upland (G. hirsutum L.) and American Pima (G. barbadense L.) cotton. The experiments have each utilized N management tools such as pre-season soil tests for NO₃⁻-N, in-season plant tissue testing (petioles) for N fertility status, and crop monitoring to ascertain crop fruiting patterns and crop N needs. At each location, treatments varied from a conservative to a more aggressive approach of N management. Results at each location revealed a strong relationship between the crop fruit retention levels and N needs for the crop. This pattern was further reflected in final yield analysis as a response to the N fertilization regimes used. The higher, more aggressive N application regimes did not consistently benefit yields at any location. Generally, the more conservative, feedback approach to N management provided optimum yields at all locations. In 2001, a transition project evaluating the residual N effects associated with each treatment regime was initiated and no N fertilizer was applied. Therefore, all N taken-up by the crop was assumed to be derived from residual soil N. However irrigation water analysis showed that NO₃⁻-N concentration levels added to the crop ranged from about 5-9 ppm. In 2001-2005 there were no significant differences among the original fertilizer N regimes in terms of residual soil NO₃⁻-N concentrations, crop growth, development, lint yield, or fiber properties. The lint yields were very uniform at each location and season. Trends associated with residual fertilizer N effects are not evident at either location for five seasons following N fertilizer applications.
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Hildreth, Jane N. "Investigation of lower Colorado River Valley desert soil mineral and nutrient content in relation to plant proximity and identity." CSUSB ScholarWorks, 1989. https://scholarworks.lib.csusb.edu/etd-project/518.
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Young, Kelly M. "Container Gardening In The Southwest Desert." College of Agriculture, University of Arizona (Tucson, AZ), 2016. http://hdl.handle.net/10150/625429.
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Van, de Water James Gordon 1963. "Physical and chemical processes affecting forced ventilation of benzene and p-xylene in a desert soil." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277044.
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The rate at which volatile organic compounds (VOCs) are removed from the vadose zone by forced ventilation may be reduced by slow micro-scale processes such as diffusion through intra-aggregate and pore water and slow reactions at sorption sites located at the soil-water interface. Column experiments using benzene and p-xylene were performed in order to simulate cleanup of VOC's in the vadose zone by forced ventilation. Analytical solutions of the one-dimensional advection-dispersion equation coupled to mass transfer equations were fitted to the data. Parameter estimates were used in order to determine time scales of diffusion through water, desorption from, and sorption to, soil organic matter. Lower limits for the time scales for these processes were calculated to be on the order of minutes. Results indicate that these micro-scale processes reduce the rate of removal on the laboratory scale but may have no effect on the field scale.
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Cable, Jessica Marie. "Precipitation Effects on Soil Carbon Cycling in the Sonoran Desert." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195358.
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Biological activity in desert soils is driven by water availability. The nature of individual precipitation events is critical to understanding soil moisture availability. Rain falls as discrete events (pulses) that vary in size and sequencing, resulting in soil "wet-dry cycles". Soil organisms are responsive to wet-dry cycles with rapid changes in activity. How soil activity is driven by changes in water content associated with individual pulses is poorly understood. The effects of precipitation on soil processes likely depend on ecosystem structure, which influences the soil environment. The goal of this dissertation was to determine how soil carbon cycling responds to precipitation in the context of ecosystem structure (plant composition, geomorphology) and climate.I used differences in stable carbon isotopic composition of soil organisms and plants to understand how positioning in the soil profile influences biological responses to different sized pulses. I evaluated how soil texture and grass species composition affect soil process response to rainfall in different seasons. I manipulated rainfall sequence to understand the interaction between closely spaced rainfall events of different sizes on soil processes. I evaluated the role of plant functional types in influencing soil microclimate and litter deposition and the response of soil processes to seasonal rainfall.Chamber measurements of soil and plant CO2 flux were used to understand their response to rainfall. I found that surface organisms are more responsive to small rainfall events due to the relationship between pulse size and infiltration. While soil texture and season of rainfall are important, the best predictor of the response of soil respiration to rainfall was initial activity levels. Grass species was not important. Grass roots and soil microbes differ in response to sequences of precipitation. Grasses responded less to subsequent large events if they were already 'activated' by a recent rainfall event. The effect of plant functional type was size dependent with differences occurring only with large shrubs. This work suggests that large scale simulations of soil carbon cycling in deserts should carefully consider wet-dry transitions in the context of plant functional type and initial soil condition in order to predict the responses to global change.
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Lawson, Peter Ward 1963. "Sorption of fulvic acid on aluminum oxide and desert soil." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/191989.
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Four batch and four column experiments were conducted to investigate the sorption of salicylic acid onto aluminum oxide. Nine column experiments were performed using fulvic acid as a sorbate, and aluminum oxide and a desert soil with a low fraction organic carbon (f(OC)) ( 0.009 percent) as sorbents. Batch experiments provided estimates of partition coefficient that were eight to ten times larger than column estimates. A two-site kinetic model was used to interpret the observed tailing of breakthrough curves. Kp estimates for fulvic acid on desert soil ranged from 3 to 23 cm³/g. The time scale of the desorption reaction is 12 days. The majority of the sorption sites appear to be kinetically controlled. Results suggest that recharge of untreated Central Arizona Project water through desert washes will remove only 10-15 percent of the fulvic acid present after two void volumes have infiltrated. This may eventually contaminate existing groundwater supplies with trihalomethane precursors.
11
Sanchez, C. A., and J. C. Silvertooth. "Evaluation of Soil Amendments for Lettuce Production in the Desert." College of Agriculture, University of Arizona (Tucson, AZ), 1997. http://hdl.handle.net/10150/221598.
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Two field studies were conducted during the 1993-1994 season to evaluate the response of lettuce to soil applied amendments. Treatments included gypsum, polymaleic acid (Spersal), and two acid products (N-phuric and Phos-phuric). Gypsum rates (0, 2240, and 4480 kg /ha) were the main plots and other soil amendments were subplot randomized within the mainplots. Overall, gypsum reduced early growth and vigor of lettuce. Gypsum had no effects on marketable yield and quality parameters in experiment 1, but the highest gypsum rate (4448 kg /ha) decreased marketable yield in experiment 2. There were no differences in plant stands due to subplot treatments. However, there were differences in earlygrowth and vigor. In experiment 1, both "N-phuric" and "Phos-phuric" increased early lettuce growth compared to the control. In experiment 2, Phos-phuric was superior to N-phuric. In experiment 1, the benefits of early growth and vigor to the "N-phuric" and "Phos-phuric" carried to harvest where marketable yield and quality were significantly increased. Spersal did not significantly effect yield and quality of lettuce in either experiment.
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Khalifa, Hamdy Elhoussainy Mohammed. "Modeling coupled heat and moisture flow within a bare desert soil." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/185882.
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Revegetation of semi-desert rangeland is dependent on rainfall, weather, and soil factors affecting seed germination and seedling establishment. To aid in predicting seed zone temperature and moisture following rainfall, a weather driven one-dimensional computer model was developed to simulate the simultaneous flow of heat and water within a bare semi-desert soil. The Newton-Raphson method was used to solve the surface energy budget equation for surface temperature. The coupled soil heat and water flow equations were then solved numerically using the weighted average finite-difference method to calculate the subsurface temperature (T(s)) and water content (θᵥ) profiles. Weather data and soil thermal and hydraulic properties were the only required inputs to the model. The model was tested using two data sets collected in the Altar Valley of Arizona during the summer rainy season of 1988. Data set 1, collected from calendar day (CD) 198 to 205, was used to calibrate the model. Calibration tests revealed that the model markedly underestimated T(s) when measured values exceeded 37°C. Underestimation of T(s) was found to be related to overestimation of latent heat flux. Therefore, the modelled latent heat flux was reduced as a linear function of air temperature (Tₐᵢᵣ) when Tₐᵢᵣ > 30°C. Also, soil thermal conductivity values predicted by the de Vries model had to be reduced 80% in order to achieve acceptable agreement between measured and modelled T(s). Data set 2, from CD 191 to 195, was then used to validate the calibrated (modified) model. Results obtained with data set 2 indicated that the modified model accurately simulated T(s) at 0.01 m depth even when the measured T(s) at that depth exceeded 50°C. Simulated T(s) values for the soil profile were generally within ± 3°C of the measured values. Results also showed good agreement between modelled and measured net radiation flux densities. In addition, the modified model predicted surface layer (0-0.03 m) moisture content remained wet enough for seed germination, i.e. θᵥ > 0.09 m³ m⁻³, about 24 to 36 hours longer than indicated by measured (resistance block) θᵥ values.
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Whitehead, Thomas William 1951. "Sorption and desorption of volatile alkyl halides in a desert soil." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/191936.
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A series of twelve laboratory column experiments were conducted to determine equilibrium partitioning coefficients (K ) and kinetic rate coefficients for sorption of four hydrophobic pollutants on a low organic carbon natural soil. K 's for trichloroethene (ICE), tetrachloroethene (PCE), 1,1,1-trichloroethane (TCA), and 1,1,2,2-tetrachloroethane (PCA), were 0.17, 0.44, 0.06, and 0.05, respectively; about as expected based on empirical carbon-based partitioning equations found in the literature. Tailing of the breakthrough curves could be accounted for with a two-site non-equilibrium solute transport model. Rates were fast compared to pore water velocities normally encountered in an alluvial aquifer, but kinetic effects were observed at pore water velocities likely to be encountered during pumping, such as for site cleanup. Desorption was faster than adsorption, with forward rates of about 10⁻⁴ to 10⁻⁵ s⁻¹ and reverse rates about 10⁻³ to 10⁻⁴ s⁻¹. The two-site model indicated that slower sites constituted roughly half the total number of sites.
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Galadima, A., and J. C. Silvertooth. "Mathematical Models of Potassium Release Kinetics for Sonoran Desert Soils of Arizona." College of Agriculture, University of Arizona (Tucson, AZ), 1998. http://hdl.handle.net/10150/210381.
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The objective of this study was to determine the potassium (K) release kinetics of clay samples from 10 agricultural representative soils of Arizona by successive extraction using Ca-saturated cation resin. A 1993 physical and chemical characterization of the soils revealed that all soils contain smectite-mica K bearing minerals. Four mathematical models (power function, Elovich, parabolic diffusion and first-order) were used to describe the nonexchangeable K release reaction involving 700-hr cumulative reaction time. Comparison of the models using the coefficient of determination (r²) and the standard error of the estimate (SE) indicated that the Elovich and the power function equations overall displayed the best fit. The first-order rate and for the most part, the parabolic diffusion equation did not describe the K release very well. The constants a and b for the Elovich and the power function equations, which represent the intercept and the release rate of the nonexchangeable K respectively, are at least in the order of magnitude as those found by others in several previous studies.
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Al-Taani, Ahmed A. "Non-biological fixation of atmospheric nitrogen to nitrate on titanium dioxide and desert soil surfaces." abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3339090.
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James, Jeremy Joseph. "Plant growth and physiological responses to soil resource heterogeneity in desert ecosystems /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
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Drees, Kevin Paul. "Quantitative analysis of soil microbial diversity in the hyperarid Atacama Desert, Chile." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/284318.
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The Atacama Desert of northern Chile is one of the most arid regions on Earth. The central plateau, between the coastal escarpment and the Andes, is devoid of vegetation and receives only millimeters of rain every few years. Though plants are absent in the soils of this desert, perhaps bacteria can survive, and even thrive, in these hyperarid conditions. This dissertation represents the first comprehensive study of bacterial diversity in the driest central latitudes (approximately 24°S) of the Atacama Desert. Study 1 covers the development of a soil DNA extraction method for the study of soil bacterial populations. This method was field tested in an ecology study in the Santa Catalina Mountains of southern Arizona. In Study 2, Atacama soils were sampled in two transects at approximately 24°S and 25°S. The first transect runs across the absolute (plantless) desert and through several narrow bands of sparse vegetation at high altitudes in the Andes. The second transect is within the well-developed fog zone near Paposo on the Pacific coastal escarpment, where an endemic plant community called lomas is established. Analysis of DGGE profiles of bacterial !6S rRNA genes extracted from these soils with Kruskal's Isotonic Multidimensional Scaling indicates that the bacterial populations cluster into several groups, including the low diversity populations of the core absolute desert, and the higher diversity high elevation Andean populations influenced by the vegetation of Andean biomes. Only one group clustered in the lomas; the rest of the profiles were unique, demonstrating the high diversity of bacterial populations within this diverse vegetation community. Soil 3107, which is within the absolute desert, clustered with the Andean bacterial populations. This soil lies within the transition zone between the low precipitation of the absolute desert (approximately 2.4 mm per year) and the higher precipitation of the high elevation Andes (approximately 47.1 mm per year). This Andean bacterial population may extend further into the absolute desert than the Andean vascular plants due to superior aridity tolerance. Alternatively, this bacterial population may be a relic from when the Andean vegetation advanced through this elevation in a wet period 3000 years ago.
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Al-Ateeqi, Sarah Salah. "Phytoremediation of oil-polluted desert soil in Kuwait using native plant species." Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5751/.
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As a result of damage caused during the First Gulf War in 1990-1991, the Kuwaiti environment suffered from drastic pollution caused by massive petroleum hydrocarbon contamination resulting from the destruction and burning of 700 oil wells across Kuwait. A range of types of polluted soils, including fresh oil lakes, dry oil lakes, and tarcretes, damaged desert wildlife. The idea of phytoremediaton using native plants was introduced and concluded that the native species Haloxylon salicornicum (Amaranthaceae) had potential as a phytoremediator. In the initial phase of this study a follow-up survey of clean and polluted sites in 7 areas in Kuwait was undertaken: Bahra, Sabah Alahmad protected area, Burgan oil field, Um Alaish oil field, Um Alrros Military Base, Sabriya oil field, and Um Ghadaier oil field where 41 plant species were found to be present. TWINSPAN classification of the dataset identified four assemblages of plant species, occurring in four ecologically-distinguishable habitat types (represented by 7 sample-groups produced by the classification procedure); one of them is mostly north of Kuwait where Sabah Alahmad protected area is and Bahra and Um Alaish oil fields and tends to be more in the oil damaged areas and characterized by the presence of the Haloxylon salicornicum; the other one is in both the north (Um Alaish oil field) and south of Kuwait (Burgan oil fields) and is characterized by the presence of both Cyperus conglomeratus and Rhanterium epapposum while the third and fourth assemblages can be mostly considered variant and characterized by the presence of Pennisitum divisum. These native species (former 3) were hence selected as the focus for subsequent investigation. The survival of Haloxylon salicornicum plants in weathered oil-polluted soils was experimentally investigated under greenhouse conditions, using a random block design with 4 replicates and 5 treatments: pots containing 100%, 75%, 50%, and 25% polluted soil, mixed with clean soil, and clean soil only as a control. The results indicated that the plants could grow successfully even in 100% oil-polluted soil. The experimental results also provided evidence that water applied to the surface (simulating rainfall) could reach the root system in all of the treatments (even for the 100% oil contamination treatment). Following on from the greenhouse study, a field trial was undertaken to examine the survival and growth of Haloxylon plants introduced into clean and oil-polluted soils (in and adjacent to a weathered dry oil lake) under field conditions. Three replicate two-year old iii (nursery-grown) Haloxylon plants were planted at each randomly-chosen location in the dry oil lake soil, and the design was repeated at 10 random locations in clean soil close to the lake boundary. The experiment was set up in two different locations (Bahra area in the north; and in Burgan oil field in the south of Kuwait). there was no significant difference in growth rates between plants in clean and polluted soil, in either area. The biomass data showed a significant difference in fresh weight between plants from clean and polluted soils, with those growing in clean soil having higher moisture content (possibly less woody than those from the polluted sites). However there was no significant difference in either fresh or dry biomass between the two experimental areas in the north and south. Data produced by analysis of amount of TPH in the polluted soils in both experimental areas showed some variability, but overall there was no significant difference between the two polluted areas, in terms of their weathered petroleum hydrocarbon content. Successful phytoremediation usually, if not always, is a function not only of phytoremediator plant physiology, but also the activity of the phytoremediator species associated rhizosphere microflora. In order to gain some insight into the hitherto unknown rhizosphere microflora of Haloxylon salicornicum plants, bacterial and fungal isolation procedures were carried out on samples taken from the roots of wild Haloxylon salicornicum plants, and from cultured plants growing in oil-contaminated soils in the greenhouse experiment, using media enriched with petroleum hydrocarbons to encourage the culture to survive in such conditions. Bacteria organisms found to be associated with the rhizosphere of wild Haloxylon are Streptomyces spp. and Inquilinus sp., while in 100% oil contaminated soil Rhodococcus manshanensis, Agrobacterium tumefaciens, Nocardia cyriacigeorgica, Gordonia lacunae / Gordonia terrae and Lysobacter spp., occurred. In the 50% oil contamination treatment soil, around the roots of Haloxylon plants contained Gordonia lacunae / Gordonia terrae and Agrobacterium tumefaciens and finally the clean soil Sphingopyxis spp. was present. Fungi found in the Haloxylon rhizosphere included organisms known to be associated with petroleum hydrocarbon degradation, including Penicillium spp. in wild Haloxylon (and also 50%, 100% and clean soil from the greenhouse trial), as well as Trichoderma asperellum in the clean soil. The conclusion is that Haloxylon salicornicum, together with its rhizosphere microflora it contain, offers high potential for use in phytoremediation operations designed to assist in the clean-up of oil polluted desert soils in Kuwait.
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Prellwitz, Joel S. "A CHARACTERIZATION OF HYPER-ARID NITRATE SOILS IN THE BAQUEDANO VALLEY OF THE ATACAMA DESERT, NORTHERN CHILE." Miami University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=miami1193748962.
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Jones, Mary Pletsch. "Evaluating Nutrient Availability in Low Fertility Soils With Resin Capsules and Conventional Soil Tests." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/3049.
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Commonly used soil analysis and resin capsule procedures are used to assess nutrient status in fertile soils, but their validity in semi-arid ecosystems is unknown. Three studies were performed to assess resin capsule effectiveness in semi-arid ecosystems. An incubation study was completed in which loamy sand and sandy clay loam soils were treated with rates of N, P, Fe and Zn. Each soil treatment was implanted with a resin capsule and incubated for 60 or 120 days. Resin capsules reflected NH4-N and P fertilizer at low rates in the loamy sand. NO3-N reflected rates in both soils, but did not reflect Fe or Zn application. Resin capsule NH4-N was a better indicator than KCl-extractable NH4-N, but resin capsule NO3-N was not as effective as water extraction, and resin capsule P was poor compared to NaHCO3-P. A second study was performed in glasshouse conditions using the incubation study soils. Soils were treated with rates of N, P and resin capsules were placed in pots. Pots were seeded with squirreltail grass (Elymus elymoides) and placed in a glasshouse. Resin capsules were removed at 120 days, soil samples taken, grass harvested and yield measured. Yield and total nutrient removal was correlated to resin NH4-N, marginally related to resin or soil NO3-N, and unrelated to resin P. Yield and total nutrient removal was correlated with application rates and resin NH4-N and NaHCO3-extracted P. The third field study, compared two sites with rates of N and P application were established on clay loam and sandy loam soils. Resin capsule and conventional soil tests for NO3-N, NH4-N and P were measured and plant nutrient status examined. Resin capsules were removed and replaced and soil samples taken every 90 days. Resins P was not related to P application or to plant tissue P but NaHCO3-extracted P was, while resin NO3-N, KCl-extracted NO3-N and NH4-N were correlated to N application and plant N. Soil test P was more effective in predicting P status and bioavailability than resin capsules. Resin NH4-N and NO3-N predicted N status and bioavailability, but soil tests were just as effective in semi-arid conditions.
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Roberts, Philip Andrew 1962. "The effects of system variables on soil-vapor extraction of benzene and p-xylene in an unsaturated desert soil." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/278316.
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Water-unsaturated column experiments using benzene and p-xylene were performed with a desert soil sample (fc = 0.001) to simulate the removal of volatile organic compounds (VOC) by soil-vapor extraction. Higher flow rates of air were found to facilitate quicker VOC removal but lower flow rates were more efficient. Initial concentrations had no effect on the rate of VOC removal. Sorption of both compounds by the solid phase at 18 and 10 percent wetness was similar to that reported for saturated systems. At these moisture contents, Kp the for benzene averaged 0.03 cm 3/g and that for p-xylene averaged 0.61 cm 3/g. At the driest soil condition, higher than predicted sorption of benzene (Kp = 0.12 cm3/g) is attributed to VOC sorption on dry mineral sites. Mechanisms that limited transport of both compounds are assumed to be intra-aggregate aqueous diffusion and desorption. (Abstract shortened with permission of author.)
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Bai, YanYing. "Distribution of soil temperature regimes and climate change in the Mojave Desert region." Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://proquest.umi.com/pqdweb?index=0&did=1957301331&SrchMode=2&sid=1&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1268844053&clientId=48051.
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Thesis (Ph. D.)--University of California, Riverside, 2009.Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 16, 2010). Includes bibliographical references. Also issued in print.
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Davis, James Hal 1956, and James Hal 1956 Davis. "Sorption and desorption of benzene and para-xylene on an unsaturated desert soil." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/291366.
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A series of bench-scale experiments was carried out to determine the rate and efficiency with which benzene and p-xylene, components of gasoline, could be removed from an unsaturated soil by air stripping. Glass columns, 30 cm in length, were packed with soil and wetted to volumetric moisture contents of 10 and 18 percent. Air saturated with one of the volatile organic compounds (VOCs) was used to load the column. Clean air was used to strip the contaminant from the soil. Benzene and p-xylene concentrations in the soil water and air were reduced four orders of magnitude after a few hours (2-8) of stripping. Benzene was removed faster than p-xylene. Air flow was the rate-limiting step early in the stripping, however slow desorption from the soil became rate-limiting as the stripping progressed. As moisture content increased the rate of removal of both contaminants decreased.
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Levi, Eva Marie, and Eva Marie Levi. "Foliar and Woody Litter Decomposition in a Shrub-Invaded Sonoran Desert Grassland." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/623065.
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Decomposition of organic matter is a critical component in global biogeochemical cycling. While decomposition rates have been robustly predicted for mesic systems, modeling decomposition dynamics in drylands has proven to be problematic, reflecting a need to account for processes that may be unique to dryland systems: low and spatially variable vegetation cover, high rates of soil movement, and high levels of radiant energy exposure at the soil surface. Recent empirical evidence suggests that the discrepancies between measured and predicted decomposition rates in drylands may be due to the greater influence of abiotic drivers, such as soil-litter mixing (SLM) and solar radiation, on plant litter decomposition relative to more mesic systems. UV-driven photodegradation may dominate until SLM reaches a threshold, at which point litter is shielded from radiation and microbial processes become predominant. The overarching goal of this dissertation was to examine the influence of SLM and solar radiation on decomposition of foliar and woody plant litter in a dryland ecosystem undergoing woody plant encroachment. A series of four complimentary experiments sought to quantify the effects of these abiotic drivers on decomposition in relation to variables such as vegetation patch type (e.g., beneath a shrub canopy, in a grass patch, on bare ground), radiant energy regime (e.g., full sun vs. shade), geomorphic surface (e.g., sandy, Holocene-age vs. clay-rich, Pleistocene-age soils), seasonality of litter fall (e.g., summer vs. winter), and litter quality (e.g., grass, shrub leaf, woody). Results indicate that interactions between SLM and photodegradation are complex and mediated by variations in ground cover which influence the local radiant energy environment and the movement of soil across the landscape by wind and water. Decomposition rates were significantly influenced by SLM, UV radiation, radiant energy regime, vegetation structure, and initial litter quality. While these results confirmed the importance of SLM and photodegradation as dryland decomposition drivers, they also reinforced the need for additional research to further clarify the relative importance of these processes under field conditions, particularly the interplay between UV radiation and SLM and their relative influence on biotic and abiotic decomposition processes. Given the changes in climate and vegetation projected for drylands, it is critical to further elucidate the influence of these processes on dryland biogeochemical cycling, as their effects may be magnified or dampened under future conditions. A deeper understanding of the processes driving biogeochemical cycling that may be unique to systems undergoing shifts in plant lifeform composition will allow us to better account for the fate of carbon in these globally important ecosystems.
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Neilson, Julia W., Katy Califf, Cesar Cardona, Audrey Copeland, Treuren Will van, Karen L. Josephson, Rob Knight, et al. "Significant Impacts of Increasing Aridity on the Arid Soil Microbiome." AMER SOC MICROBIOLOGY, 2017. http://hdl.handle.net/10150/625716.
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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 [r(s)] = >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 dominant in global soils. IMPORTANCE We identify key environmental and geochemical factors that shape the arid soil microbiome along aridity and vegetation gradients spanning over 300 km of the Atacama Desert, Chile. Decreasing average soil relative humidity and increasing temperature explain significant reductions in the diversity and connectivity of these desert soil microbial communities and lead to significant reductions in the abundance of key taxa typically associated with fertile soils. This finding is important because it suggests that predicted climate change-driven increases in aridity may compromise the capacity of the arid-soil microbiome to sustain necessary nutrient cycling and carbon sequestration functions as well as vegetative cover in desert ecosystems, which comprise one-third of the terrestrial biomes on Earth.
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Van, Brunt Jim. "Vegetative habitat analysis of proposed mine sites in the Mojave Desert: The first step towards revegetation of disturbed desert communities." CSUSB ScholarWorks, 1993. https://scholarworks.lib.csusb.edu/etd-project/663.
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Shepard, Christopher. "Soil Modulation of Ecosystem Response to Climate Forcing and Change Across the US Desert Southwest." Thesis, The University of Arizona, 2014. http://hdl.handle.net/10150/323416.
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The dryland ecosystems of the US Desert Southwest (SW) are dependent on soil moisture for aboveground productivity; the generation of soil moisture in the SW is dependent on both soil physical properties and climate forcing. This study is one of the first regional point-scale analyses that explores the role of soil physical properties in modulating aboveground vegetation dynamics in response to climate forcing in the SW. Soil texture accounted for significant differences in average aboveground primary productivity across the SW. However, soil texture could not account for differences in inter-annual aboveground productivity variation across the SW. Subsurface soil texture was tightly coupled with precipitation seasonality in accounting for differences in long-term average seasonal aboveground productivity in the Mojave and Sonoran Deserts. The results of this study indicate that the subsurface is a significant factor in modulating aboveground primary productivity, and needs to be included in future modeling exercises of dryland ecosystem response to climate forcing and change.
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Mexicano, Vargas Maria de Lourdes. "Remote Sensing Methods To Classify a Desert Wetland." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/232457.
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The Cienega de Santa Clara is a 5600 ha, anthropogenic wetland in the delta of the Colorado River in Mexico. It is the inadvertent creation of the disposal of brackish agricultural waste water from the U.S. into the intertidal zone of the river delta in Mexico, but has become an internationally important wetland for resident and migratory water birds. The marsh is dominated by Typha domengensis with Phragmites australis as a sub-dominant species in shallower marsh areas. The most important factor controlling vegetation density was fire. The second significant (P<0.01) factor controlling NDVI was flow rate of agricultural drain water from the U.S. into the marsh. Reduced summer flows in 2001 due to canal repairs, and in 2010 during the YDP test run, produced the two lowest NDVI values of the time series from 2000 to 2011 (P<0.05). Salinity is a further determinant of vegetation dynamics as determined by greenhouse experiments, but was nearly constant over the period 2000 to 2011, so it was not a significant variable in regression analyses. Evapotranspiration (ET) and other water balance components were measured in Cienega de Santa Clara; we used a remote sensing algorithm to estimate ET from meteorological data and Enhanced Vegetation Index values from the Moderate Resolution Imaging Spectrometer (MODIS) sensors on the Terra satellite. We used Landsat NDVI imagery from 1978-2011 to determine the area and intensity of vegetation and to estimate evapotranspiration (ET) to construct a water balance. Remote sensing data was supplemented with hydrological data, site surveys and literature citations. The vegetated area increased from 1978 to 1995 and has been constant at about 4200 ha since then. The dominant vegetation type is Typha domingensis (southern cattail), and peak summer NDVI since 1995 has been stable at 0.379 (SD = 0.016), about half of NDVI(max). About 30% of the inflow water is consumed in ET, with the remainder exiting the Cienega as outflow water, mainly during winter months when T. domingensis is dormant.
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McKeon, Casey Anne. "Phytoremediation of nitrate contaminated soil and groundwater by desert phreatophytes in Monument Valley, Arizona." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280436.
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The results of a study on phytoremediation of nitrate and ammonium contaminated soil and groundwater at the Monument Valley Uranium Mill Tailings Remedial Action (UMTRA) Project site are presented in this dissertation. The following is a summary of the findings: A phytoremediation plot was established to remediate soil nitrate and ammonium contamination at a former uranium ore-processing site. Atriplex canescens were planted and deficit irrigated, preventing recharge into the shallow aquifer. Initial soil concentration of nitrate-N was approximately 180 mg kg⁻¹ but decreased to only 80 mg kg⁻¹ after 41 months. A decrease in nitrate-N concentrations was observed throughout the 4.6 m soil profile, which was a unique observation. Ammonium-N concentrations remained at initial levels of approximately 180 mg kg⁻¹ and did not decline over the study period. Soluble salts decreased only 20% in the soil, which was attributable to nitrate loss. Residual soil nitrogen became enriched in ¹⁵N, indicating biological denitrification. Nitrate-N loss was 1,360 kg ha⁻¹yr⁻¹, which is approximately three times higher than agricultural soils. These findings may provide a low-cost method for soil nitrate remediation. A. canescens and Sarcobatus vermiculatus are native phreatophytic shrubs at the UMTRA Project site that were evaluated for their potential to remove nitrate from the shallow aquifer. Stable isotope signatures from plant stem water were similar to the groundwater isotope signatures, suggesting the plants are rooted in the plume. Currently only 7% of the plume area is vegetated, mainly due to heavy grazing. When protected from grazing, plants increased in cover by over 50% per year during a three-year period. Transplants of A. canescens that were protected from grazing and irrigated during the first summer after planting were rooted in the plume within three years, growing greater than 2-m in height. Based on these results, the nitrate plume could be removed within 13 years if grazing were restricted and vegetation were to be enhanced to 50% cover, whereas almost six decades would be required for remediation under current conditions. This study shows that phytoremediation may be an inexpensive and non-invasive means of nitrate remediation at this and other arid locations.
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Saum, Lindsey A. "Petroleum-Degrading Bacteria Community Response to Limiting Nutrients in Marine Sediment and Desert Soil." Thesis, University of California, Riverside, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10181504.
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Though humans have over a century of experience with catastrophic marine and terrestrial oil spills, response plans and cleanup techniques are still active areas of research and development. This work evaluated the oil degradation potential and changes in the microbial community following nutrient additions in polluted marine sediment and desert soil.
Biostimulation experiments on Alaskan beach sediment still contaminated by the Exxon Valdez tanker oil spill demonstrated that ambient air and hydrogen peroxide both serve as suitable sources of oxygen to stimulate aerobic microbial degradation of the oil. The addition of oxygen to the oil-contaminated sediment stimulated the growth of Proteobacteria, which made up 77-92% of the population in the presence of ambient oxygen and 76-88% with hydrogen peroxide. These experiments also revealed that sediment samples collected from a non-contaminated portion of the beach also contained a large fraction of microbial species that are known oil degraders. A phytoremediation experiment using mesquite trees in motor-oil-contaminated desert soil indicated that the use of compost as a soil amendment enhanced oil degradation, while biochar hindered degradation activity.
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McCarthy, Laura Elaine 1960. "Impact of military maneuvers on Mojave Desert surfaces: A multiscale analysis." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282131.
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Concern for environmental management of our natural resources is most often focused on the human impacts upon these resources. Minor stresses on surface materials in sensitive desert landscapes can greatly increase the rate and character of erosion. The National Training Center, Ft. Irwin, located in the middle of the Mojave Desert, California, provides a study area of intense off-road vehicle (ORV) activity spanning a 50-year period. This study documents a case of concentrated ORV activity on sensitive desert environments, and the resulting environmental impacts. Geomorphic surfaces from two study sites within the Ft. Irwin area were mapped from 1:28,400 scale black and white aerial photographs taken in 1947. Surface disruption attributed to military activity was then mapped for the same areas from 1993, 1:12,000, black and white aerial photographs. Several field checks were conducted to verify this mapping. Images created from SPOT panchromatic and Landsat Thematic Mapper (TM) multispectral data acquired during the spring of 1987 and 1993 were analyzed to assess both the extent of disrupted surfaces and the surface geomorphology discernable from satellite data. Classified and merged images were then created from these data and demonstrate the capabilities of satellite data to aid in the delineation of disrupted geomorphic surfaces. Correlations were also established between highly disrupted surfaces and soil surface conditions on selected geomorphic surfaces. Disruption maps produced from the air photos indicate that the amount of disrupted surfaces within the study sites grew from a combined total of 1.3 km² in 1947 to 33.4 km² by 1993. A combination of 6 bands of Landsat TM data with a seventh band of SPOT panchromatic data yielded a product that delineated broad geomorphic surfaces that closely correlate with those mapped from the aerial photography. An error matrix between these two products resulted in an overall accuracy of 83.36% and a Kappa Index of Agreement of 77.28%. A 15-class unsupervised classification of the SPOT panchromatic data produced the representation of the extent and levels of disruption present in the study areas that closely matched field observations. Field sampling of soil strength and clay/silt percentages on disturbed and undisturbed surfaces reveals that these arid land surfaces react to intense ORV activity by becoming more compact and exhibiting higher percentages of clays and silts.
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Rosenthal, Randi Helaine 1961. "The interaction of parent material and eolian debris on the formation of soils in the Silverbell Desert Biome of Arizona." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276628.
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The objective of this study was to determine whether the properties of four soils of the Silverbell Desert Biome could be attributed solely to the parent material or alternately reflect the nature of contributions, if any, from eolian dust. The Anklam, Lajitas and Chimenea soils, classified as fine-loamy, mixed, thermic Lithic Haplargids and the Greyeagle (coarse-loamy, mixed, thermic, Lithic Torriorthent) soil formed an andesite, basalt, granite and basalt, respectively. They occur on gently sloping, stable terrain in Pima County, Arizona. The four soils were studied through field descriptions, particle size analysis, mineralogical analyses of light and heavy sand fractions and clay mineral identification. The light mineral fraction of all four soils is directly affected by the parent material and is influenced much less, if at all by eolian activities due to the larger particle sizes. It is concluded that the genesis of soils was influenced by both the underlying rock and the input of eolian particulates. (Abstract shortened with permission of author.)
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Lalley, Jennifer S. "Lichen-dominated soil crusts in the hyper-arid Namib Desert : anthropogenic impacts and conservation implications." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417605.
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Adesioye, Fiyinfoluwa Adenike. "Structural and functional characterization of a novel acetyl xylan esterase from a desert soil metagenome." Thesis, University of Pretoria, 2017. http://hdl.handle.net/2263/65881.
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A Namib Desert soil hypolith metagenomic dataset was screened, in silico, for novel acetyl xylan esterase (AcXE) - encoding genes. AcXEs hydrolyse ester bonds to liberate acetic acid in acetylated polymeric xylan and xylooligosaccharides during bioconversion of lignocellulosic biomass for sustainable biofuel production. One of the identified genes (NaMet1) was synthesized, cloned and expressed to produce a ~36 kDa protein. This protein, NaM1, was confirmed to be functional and was purified and characterized. NaM1, a carbohydrate esterase (CE) 7 enzyme, was optimally active on para-nitrophenol acetate at pH 8.5 and 30 oC, and remained active in up to 5 M NaCl and 65% DMSO. The specific activity and catalytic efficiency were 488.9 Umg-1 and 3.26x106 M-1s-1, respectively. NaM1 deacetylated para-nitrophenol acetate and butyrate, 7-aminocephalosporanic acid and acetylated xylan. Most investigations of CE7 esterases have been carried out using structural information from thermostable members of this family and little is known about thermolabile members. A 2.03 Å crystal structure of native NaM1, the first CE structure of metagenomic origin to be submitted to the Protein data bank, was solved. The structure was compared with those of thermostable CE7 enzymes and used to study the thermal stability determinants of this enzyme family. This comparison showed strong structural conservation between both enzyme types and suggested that differences in several key residues, as well as, packing within the core, were responsible for thermal stability. Directed evolution (DE) of NaM1 yielded thermostable variants, including a variant with 10oC improved stability. Analyses of the kinetic and putative structural characteristics of selected variants in comparison with those of the wild-type provided insights to the role of residues influencing the thermal stability, substrate specificity and activity of NaM1. A single substitution was found to expand acyl moiety specificity and improve both thermal stability and activity of NaM1. Knowledge of key residues identified during NaM1 DE is useful for the future engineering of CE7 and ?/? hydrolase enzymes in order to improve catalytic turnover, substrate specificity and thermal stability.Thesis (PhD)--University of Pretoria, 2017.
Genetics
PhD
Unrestricted
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Fearnehough, William. "Spatial and temporal variations in soil and vegetation dynamics on stabilized desert dunes in Ningxia, China." Thesis, University of Wolverhampton, 1998. http://hdl.handle.net/2436/104425.
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MILLER, MARIBETH SCHLINKERT. "PHYSIOLOGICAL AND BIOCHEMICAL CHARACTERISTICS OF A FAST-GROWING STRAIN OF LUPINE RHIZOBIA ISOLATED FROM THE SONORAN DESERT (NITROGEN FIXATION, MEXICO)." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/188091.
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An effective, fast-growing strain of Rhizobium was isolated from a species of Lupinus native to the Sonoran desert near San Felipe, Baja, Mexico (generation time, 3.6 h). Bacteria isolated from the roots of lupines are normally slow growing, however, Lupine 43, is a fast grower, possesses multiple flagella and produces acid in a defined medium. In comparison to a slow-growing lupine strain, Nitragin 96A11, Lupine 43 has a low intrinsic resistance to antibiotics and is able to utilize a wide range of carbon and nitrogen sources. Field and incubator studies were conducted to determine if the adaptation of the characteristics of fast-growing strains enables this strain to survive under the desert conditions of the southwestern United States. In the field, where no moisture was added after initial inoculation, Lupine 43 survived in significantly higher numbers than 96A11 for the first two weeks of the low (19C) and the first month of the high (35C) temperature study. In a laboratory study, at a constant moisture level of 1/3 bar, differences in survival between the two strains were dependent on temperature, pH and soil texture.
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Buck, Rachel Lynn. "Importance of Placement Depth in Evaluating Soil Nitrogen, Phosphorus, and Sulfur Using Ion Exchange Resin Capsules in Semi-Arid, Low Fertility Soils." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/4293.
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Ion exchange resin capsules provide a possible alternative to conventional soil testing procedures. Previous studies with semi-arid, low fertility soils observed poor relationships with poorly mobile nutrients such as phosphorus (P). We propose that placement depth may improve those relationships. Our objective was to (1) determine if placement depth could improve resin capsule estimation of the bioavailability of nitrogen (N), P, and sulfur (S) and (2) to determine if resin capsules can effectively estimate S availability in semi-arid, low fertility soils. Field sites were established in Rush and Skull Valleys, Utah on loam and sandy loam soils, respectively. Fertilizer was surface applied as ammonium sulfate and triple superphosphate with six N, P and S treatments (0, 5.5, 11, 22, 44 and 88 kg ha-1 of N and P2O5 and 0, 7, 14, 28, 56 and 112 kg ha-1 of S). Thirty 4.0-m2 plots were established at each field location. Resin capsules were placed three per plot at 0–5, 5–10, and 10–15 cm deep in the soil and soil samples taken at respective depths. The capsules were removed and replaced after approximately 90 d. Final removal and soil sampling occurred approximately 240 d later. For the second study, fertilizer was surface applied as ammonium sulfate with six S treatments (0, 7, 14, 28, 56 and 112 kg ha-1 of S) with one resin capsule placed in each 4.0-m2 plot at a depth of 5 cm in the soil. Resin capsules were removed and replaced approximately every 90 d for a total of four samplings. Soil samples were taken with every resin capsules install and removal. In the first study, bicarbonate extractable P was significantly related to P application at all depths and times except the two lowest depths at the time of final sampling, and resin capsule P was only related to P application 398 days after application in the 0–5 and 5–10 cm depths. However, this is an improvement in estimates of bioavailability compared to a single placement depth. The 5–10 cm depth was the best for placement for determination of NH4-N, and resin capsules improved upon soil test estimates. For NO3-N, depth was not important, but resin capsules had a stronger relationship with N applied than the soil test 398 d after application. In addition, both resin capsules and the S soil test were related to S applied, but resin capsules were more able to pick up S cycling through the system. In the second study resin capsules and conventional soil tests were both effective in distinguishing between fertilizer rates, though only the conventional soil test was related to S applied at the last sampling (366 d after fertilizer application). Overall resin capsules were effective at reflecting application rates, and may be a good tool to estimate nutrient bioavailability. Correlation with plant uptake is required to determine if soil tests or resin capsules were a better estimate of bioavailable nutrients.
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Pillai, Suresh Divakaran. "Ecology and genetic stability of Tn5 mutants of bean rhizobia in Sonoran desert soils." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184823.
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Five transposon Tn5 mutants of bean rhizobia (Rhizobium leguminosarum b.v. phaseoli) and the wild type strain were used in ecological studies to evaluate the efficacy of transposon Tn5 as a phenotypic marker in rhizobia for ecological studies in two Sonoran desert soils. All mutants possessed chromosomal insertions of the transposable element. Survival of each mutant strain was compared to that of the wild type strain under non stress, moisture stress and temperature stress conditions in Pima silty clay loam and Brazil to sandy loam. The genetic stability of Tn5 in terms of transposition of the element within the chromosome and the Tn5 coded antibiotic resistant phenotype was determined in cells recovered throughout the survival period. Under non stress conditions, the viable Tn5 mutant population decreased in size. Two mutants showed significantly (p < 0.01) lower populations than the wild type at the end of 30 days in the silty clay loam. In the sandy loam, four of the five mutant populations were significantly lower than the wild type. Tn5 was genetically stable in both soils. Under moisture stress conditions, the decline of the Tn5 mutant and wild type populations corresponded to a decline in soil moisture content. The finer textured soil afforded more protection to the cells than the coarse textured soil. There were no indications of Tn5 instability under moisture stress. In both soils under temperature stress, sizes of all populations declined rapidly and after 12 days, the mutant cells when screened using the Tn5 coded markers were significantly less in numbers than the wild type indicating a loss of Tn5 coded antibiotic resistance phenotype. There were no significant differences in numbers between wild type and mutant cells when screened using only the intrinsic markers. DNA:DNA hybridizations confirmed that the lack of Tn5 coded antibiotic resistance phenotype was probably not due to a deletion or transposition of the element. Under non stress conditions Tn5 is a useful ecological marker, but each Tn5 mutant has to be evaluated independently under specific environmental conditions to determine the efficacy of Tn5 as an ecological marker.
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Agasanapura, Nagendra Basavaraju. "Analysis of adsorption & migration behaviour of contaminants in aqueous phase through the desert soil porous medium." abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1467738.
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Darby, Brian. "Influence of Altered Temperature and Precipitation on Desert Microfauna and Their Role in Mediating Soil Nutrient Availability." ScholarWorks @ UVM, 2008. http://scholarworks.uvm.edu/graddis/64.
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Arid-land deserts comprise up to 30% of global land surface area and experience degradation by anthropogenic land use demands. Sixteen of the 19 climate models used by the International Panel on Climate Change predict increased temperature and prolonged periods of drought for much of the arid southwest US. Soil microfauna consume organic-bound nitrogen and excrete soluble inorganic and dissolved organic nitrogen that is available for plant uptake or as substrate for microbial saprotrophs. However, the growth and activity of nematodes and protozoa is restricted to periods of adequate temperature and moisture. The objective of this dissertation research project is to determine the possible effects of predicted climate changes on cool desert soil nematodes and protozoa and their role in nitrogen cycling. Climate changes are predicted to affect nematodes more adversely than protozoa. Nematodes are thought to contribute more to nitrogen cycling through dissolved organics while protozoa are thought to contribute relatively more to nitrogen cycling through inorganic nitrogen. A shift in community composition favoring amoebae over nematodes could shift the relative balance of organic and inorganic pools of soil nitrogen. Soil microfauna are not readily observed in their soil habitat, so extraction and enumeration techniques are adapted and tested for the desert microfaunal communitites. Desert soil nematodes and protozoa participate in energy channels deriving from vascular and non-vascular primary producers as well as bacterial and fungal saprotrophs. Environmental conditions influence the prey that are available to nematodes and protozoa and, thus, indirectly affect the relative composition of microfaunal feeding groups. Environmental conditions also directly affect microfauna. Not only are nematodes affected more negatively by adverse abiotic stress than amoebae, many species of bacterivorous nematodes appear to be susceptible to unique combination of the major abiotic stresses experienced in the desert. Findings from a two-year field experiment treated with elevated temperature and summer precipitation are consistent with lab and field mesocosm experiments, but highlight the uncertainly inherent in predicting long-term trends with brief experiments. In comparison with temperature and precipitation, long-term elevated carbon-dioxide enrichment was not shown to affect the abundance of desert soil microfauna directly but did affect the distribution of protozoa and the composition of nematodes indirectly through altered plant water use patterns. Continued work is needed to devise experimental systems that quantify the relative role of microfaunal functional groups in nutrient cycling.
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Pianalto, Frederick Scott. "Estimating Sources of Valley Fever Pathogen Propagation in Southern Arizona: A Remote Sensing Approach." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/311322.
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Coccidioidomycosis (Valley Fever) is an environmentally-mediated respiratory disease caused by the inhalation of airborne spores from the fungi Coccidioides spp. The fungi reside in arid and semi-arid soils of the Americas. The disease has increased epidemically in Arizona and other areas within the last two decades. Despite this increase, the ecology of the fungi remains obscure, and environmental antecedents of the disease are largely unstudied. Two sources of soil disturbance, hypothesized to affect soil ecology and initiate spore dissemination, are investigated. Nocturnal desert rodents interact substantially with the soil substrate. Rodents are hypothesized to act as a reservoir of coccidioidomycosis, a mediator of soil properties, and a disseminator of fungal spores. Rodent distributions are poorly mapped for the study area. We build automated multi-linear regression models and decision tree models for ten rodent species using rodent trapping data from the Organ Pipe Cactus National Monument (ORPI) in southwest Arizona with a combination of surface temperature, a vegetation index and its texture, and a suite of topographic rasters. Surface temperature, derived from Landsat TM thermal images, is the most widely selected predictive variable in both automated methods. Construction-related soil disturbance (e.g. road construction, trenching, land stripping, and earthmoving) is a significant source of fugitive dust, which decreases air quality and may carry soil pathogens. Annual differencing of Landsat Thematic Mapper (TM) mid-infrared images is used to create change images, and thresholded change areas are associated with coordinates of local dust inspections. The output metric identifies source areas of soil disturbance, and it estimates the annual amount of dust-producing surface area for eastern Pima County spanning 1994 through 2009. Spatially explicit construction-related soil disturbance and rodent abundance data are compared with coccidioidomycosis incidence data using rank order correlation and regression methods. Construction-related soil disturbance correlates strongly with annual county-wide incidence. It also correlates with Tucson periphery incidence aggregated to zip codes. Abundance values for the desert pocket mouse (Chaetodipus penicillatus), derived from a soil-adjusted vegetation index, aspect (northing) and thermal radiance, correlate with total study period incidence aggregated to zip code.
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Lehmann, Sophie Butler. "Climatic and Tectonic Implications of a mid-Miocene Landscape: examination of the Tarapaca Pediplain, Atacama Desert, Chile." Miami University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=miami1375486991.
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Hirsch, Merilynn Carol. "Process_Based Management of Downy Brome in Salt Desert Shrublands: Assessing Pre- and Post-Rehabilitation Soil and Vegetation Attributes." DigitalCommons@USU, 2011. https://digitalcommons.usu.edu/etd/1032.
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A number of technical approaches had to be employed within the planner, namely, 1) translating expected reward into a probability of goal satisfaction criterion, 2) monitoring belief states with a Rao-Blackwellized particle, and 3) employing Rao-Blackwellized particles in the McLUG probabilistic conformant planning graph heuristic. POND-Hindsight is an action selection mechanism that evaluates each possible action by generating a number of lookahead samples (up to a xed horizon) that greedily select actions based on their heuristic value and samples the actions' observation; the average goal satisfaction probability of the end horizon belief states is used as the value of each action.
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McKellar, Trevor T., and Trevor T. McKellar. "Evaluating How Representative Simple Multiscalar Drought Indices Are of Modeled Soil Moisture Across the Desert Southwest United States." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/622900.
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Drought indices based on monthly precipitation and sometimes temperature are widely used due to their simple calculation with readily available climate data. The portrayal of drought through simple precipitation anomalies or water balances when accounting for temperature may not capture the potentially complex evolution of drought events due to the timing, intensity, and frequency of precipitation events at the daily scale. In this study, we present a new drought index that incorporates a deterministic soil model, HYDRUS-1D, and daily climate data to assess how representative simple drought indices are of soil moisture status in the Southwest. Specifically, we compare our drought index with two widely used drought indices: the Standardized Precipitation Index (SPI) and the Standardized Perception-Evapotranspiration Index (SPEI). Modeled soil moisture output was summed into monthly values for direct comparison between indices. SPI and SPEI proved to be representative of soil moisture status at shallow depths, correlating best at a two-month window. SPI correlated higher with our modeled drought index than SPEI in shallow settings across all study sites. Intense drought events were controlled by the magnitude and frequency of precipitation, with large events creating water surplus and then a slow decay in soil moisture until the next large event. Furthermore, heat map correlations indicate that monitoring drought at depth is dependent upon the previous years monsoon, with the best correlating window growing with distance from monsoon onset. Modeled soil moisture showed volumetric water content increased during monsoon season and remained high through the fall and into the winter months. Higher moisture content increased hydraulic conductivity, priming the soil profile for winter recharge. We believe that the addition of a soil physics based drought index greatly improves drought monitoring conditions for the southwest.
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Castrezana, Sergio Javier. "Patterns of Differentiation Among Allopatric Drosophila mettleri Populations." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1313%5F1%5Fm.pdf&type=application/pdf.
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Wilson, Thomas Bachman. "Nutrient dynamics and fire history in mesquite (Prosopis spp.)-dominated desert grasslands of the southwestern United States." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/279975.
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In desert grasslands of the southwestern United States, Prosopis velutina (mesquite), an N-fixing legume, has proliferated from historic drainage locations into more xeric grassland plains. This expansion is forming a more heterogenous soil nutrient topography in grasslands, N-pools are becoming localized under mesquite canopies, yet the rate and extent of this sequestration remains relatively unknown. Repeated prescribed burning has been used to control Prosopis distribution, but effects of fires on grassland soil nutrient distribution and aboveground plant biomass are also largely unknown. I examined recent research concerning P. velutina natural history, emphasizing characteristics that contribute to range expansion. I also evaluated Prosopis management practices---which include herbicide treatment, prescribed burning, grazing reduction, and mechanical removal---and management goals---which involve complete removal, no removal, and limited removal. Of these, limited removal is the most beneficial, using an herbicide application followed by periodic prescribed burning. In 1997 I established a study area at Fort Huachuca Military Reservation in southeastern Arizona, selecting two adjacent sites with similar soil composition and topography but different fire histories. I examined spatial and seasonal changes in composition and distribution of available soil N and litterfall. My results indicated these were more spatially and temporally heterogenous on sites with low fire frequency and high P. velutina stand development. In 1998 I selected nine sites at Fort Huachuca on two upland surfaces located < 1 km apart, with similar soil physical characteristics and fire frequencies ranging from 0 to 5 fires/decade. I evaluated relationships between fire frequency, soil nutrient status (pH, available P, organic C, total N, and available N), and aboveground plant biomass, including that of the non-native Eragrostis lehmanniana (Lehmann lovegrass). Soil pH and ammonium significantly decreased with increased fire frequency on one surface, and available P significantly decreased with increased fire frequency on the other surface. Available P and pH were significantly different between the 2 surfaces, but aboveground biomass was similar. Soil nutrient status and biomass were not related, suggesting plant-available soil nutrients may not control plant distribution or recovery following fire. E. lehmanniana biomass was negatively correlated with native grass and forb biomass, and tended to increase with increasing fire frequency. Surface litter and E. lehmanniana biomass were correlated, and may increase fire frequency, an important consideration when implementing grassland fire management practices.
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Holmes, Christopher Dale. "Effects of three global climate change factors on soil water and sap flow of Larrea tridentata in the Mojave Desert." abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1464439.
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Neilson, Julia Worsley. "Bacterial Diversity of the Atacama Desert, Chile: The Challenges of Characterizing the Community Dynamics of Extreme Oligotrophic Ecosystems." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/242364.
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This dissertation examines the bacterial diversity of hyperarid and arid regions of the Atacama Desert, Chile, as a first step towards understanding the global biogeochemical significance of arid-land microbial communities. The specific objectives were to characterize bacterial diversity and infer the possible metabolic potential of these bacterial communities, and to evaluate the influence of moisture exposure on community structure. In addition, the strengths and limitations of available tools for probing microbial diversity and activity in terrestrial ecosystems were characterized for their application to extreme oligotrophic communities. Preliminary PCR-DGGE analysis of a west-east elevational transect from the Pacific Ocean near Antofagasta to the western slopes of the central Andes indicated that bacterial communities along this transect belonged to two distinct community types: 1) hyperarid (700 - 2000 m) and 2) arid (2500 - 4500 m) communities that included both vegetated and unvegetated regions. Subsequent diversity analysis of these two regions revealed novel but distinct communities in both regions. A greater diversity was observed in the unvegetated arid regions than in the unvegetated hyperarid areas. The unvegetated arid sites were characterized by a bacterial community harboring a combination of radiotolerant and halotolerant heterotrophs as wells as diverse phylotypes closely related to chemolithoautotrophs. These rare phylotypes may be uniquely adapted to arid ecosystems. Molecular tools evaluated for community diversity analysis included PCR-DGGE, Sanger-clone and 454-pyrosequencing analysis of 16S rRNA gene libraries, and the use of reverse transcriptase quantitative PCR (RT-qPCR) for quantifying the impact of environmental variables on the metabolic activity of a specific organism. These techniques were evaluated using the ecosystems of the Atacama Desert as well as model ecosystems designed to address specific questions. Molecular tools are invaluable to the study of microbial ecology because they facilitate the study of fastidious organisms that are difficult or impossible to culture, but the analysis presented in this dissertation demonstrates that each of these methods has limitations and biases which must be acknowledged to avoid inaccurate conclusions from skewed results. The most complete picture of the taxonomic and functional profile of a microbial community is obtained by employing a combination of molecular techniques.
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Warren, Daniel Cram. "Transpiration and conductance responses of salt-desert vegetaion in the Owens Valley of California in relation to climate and soil moisture." Diss., The University of Arizona, 1991. http://ezproxy.library.arizona.edu/login?url=.
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Rech, Jason Arnold. "Late Quaternary paleohydrology and surficial processes of the Atacama Desert, Chile: Evidence from wetland deposits and stable isotopes of soil salts." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/279910.
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The origin of pedogenic salts in the Atacama Desert has long been debated. Possible salt sources include in situ weathering at the soil site, local sources such as aerosols from the adjacent Pacific Ocean or salt-encrusted playas, and extra-local atmospheric dust. To identify the origin of Ca and S in Atacama soil salts, we determined δ ³⁴S and ⁸⁷Sr/⁸⁶Sr values of soil gypsum/anhydrite and ⁸⁷Sr/⁸⁶Sr values of calcium carbonate along three east-west trending transects in the Atacama. Our results demonstrate the strong influence of marine aerosols on soil gypsum/anhydrite development in areas where marine fog penetrates inland. In areas where the Coastal Cordillera is >1200 m, however, coastal fog cannot penetrate inland and the contribution of marine aerosols to soils is greatly reduced. Salts in inland soils appear to originate from eolian redistribution of playa salts that are precipitated from evaporated ground water. This ground water has acquired its dissolved solids from water-rock interactions (both thermal and low-temperature) along flowpaths from recharge areas in the Andes. The spatial distribution of high-grade nitrate deposits appears to correspond with areas that receive the lowest fluxes of local dust, supporting arguments for an atmospheric source of nitrate. Ground water in the Atacama is derived from precipitation in the High Andes (>3500 m) that infiltrates soils and then flows down the Pacific slope of the Andes to feed aquifers within the hyperarid core of the Atacama Desert. At many locations, ground water surfaces and creates springs, marshes, and wetlands. In order to track late Quaternary fluctuations in ground-water recharge, paleowetland deposits at eight separate locations (between 18°-26°S) were mapped and dated. Over 200 AMS ¹⁴C dates on a variety of materials provide firm age control on these deposits. Replication of time-stratigraphic units from an assortment of hydrologic settings and varying distances from recharge areas in the Andes show that ground-water systems are responding to regional changes in climate and that response times are probably short (<1000 years). Results suggest that the wettest period represented by deposits was during the late Glacial/early Holocene (∼16-9.5 ka B.P.) and that a moderately wet period occurred during the mid-Holocene (8--3 ka B.P.). Major drops in Atacama water tables, due to regional drought, occurred between 9.5-8 and ∼3 ka B.P. The late Holocene was characterized by generally lower water tables than during the mid-Holocene and subject to more frequent water table drops. Fluctuations in tropical Pacific Sea Surface Temperatures, the Walker Circulation, and ENSO variability is thought to be the major control on precipitation over this region during the late Quaternary.