Science.gov

Sample records for aridic regimes

  1. Impacts of altered precipitation regimes on soil communities and biogeochemistry in arid and semi-arid ecosystems.

    PubMed

    Nielsen, Uffe N; Ball, Becky A

    2015-04-01

    Altered precipitation patterns resulting from climate change will have particularly significant consequences in water-limited ecosystems, such as arid to semi-arid ecosystems, where discontinuous inputs of water control biological processes. Given that these ecosystems cover more than a third of Earth's terrestrial surface, it is important to understand how they respond to such alterations. Altered water availability may impact both aboveground and belowground communities and the interactions between these, with potential impacts on ecosystem functioning; however, most studies to date have focused exclusively on vegetation responses to altered precipitation regimes. To synthesize our understanding of potential climate change impacts on dryland ecosystems, we present here a review of current literature that reports the effects of precipitation events and altered precipitation regimes on belowground biota and biogeochemical cycling. Increased precipitation generally increases microbial biomass and fungal:bacterial ratio. Few studies report responses to reduced precipitation but the effects likely counter those of increased precipitation. Altered precipitation regimes have also been found to alter microbial community composition but broader generalizations are difficult to make. Changes in event size and frequency influences invertebrate activity and density with cascading impacts on the soil food web, which will likely impact carbon and nutrient pools. The long-term implications for biogeochemical cycling are inconclusive but several studies suggest that increased aridity may cause decoupling of carbon and nutrient cycling. We propose a new conceptual framework that incorporates hierarchical biotic responses to individual precipitation events more explicitly, including moderation of microbial activity and biomass by invertebrate grazing, and use this framework to make some predictions on impacts of altered precipitation regimes in terms of event size and frequency as

  2. The influence of agricultural management on soil's CO2 regime in semi-arid and arid regions

    NASA Astrophysics Data System (ADS)

    Eshel, G.; Lifshithz, D.; Sternberg, M.; Ben-Dor, E.; Bonfile, D. J.; Arad, B.; Mingelgrin, U.; Fine, P.; Levy, G. J.

    2008-12-01

    Two of the more important parameters which may help us better evaluate the impact of agricultural practices on the global carbon cycle are the in-situ soil pCO2 profile and the corresponding CO2 fluxes to the atmosphere. In an ongoing study, we monitored the pCO2 to a depth of 5 m in two adjacent irrigated Avocado orchards in the coastal plain of Israel (semi-arid region), and to a depth of 2 m in a semi- arid rain-fed and a arid rain-fed wheat fields in southern Israel. The soil pCO2 profiles and CO2 fluxes measurements were supplemented by measurements of soil moisture and temperature. The results showed differences in the CO2 profiles (both in the depth of the highest concentration and its absolute values) and the CO2 fluxes between the orchards and the wheat fields as well as along the year. In the irrigated Avocado orchards pCO2 values were in the range of 1.5 kPa at a depth of 0.5 m up to 8 kPa at depths of 3-5 m (even though Avocado trees are characterized by shallow roots). Such levels could affect reactions (e.g., enhancement of inorganic carbon dissolution) that may take place in the soil and some of its chemical properties (e.g., pH). As expected, soil pCO2 was affected by soil moisture and temperature, and the distance from the trees. Maximum soil respiration was observed during the summer when the orchards are under irrigation. In the wheat fields pCO2 level ranged from 0.2- 0.6 kPa at a depth of 0.2 m to 0.2-1 kPa at depths of 1-1.5 m (in arid and semiarid respectively). These pCO2 levels were much lower than those obtained in the irrigated orchards and seemed to depend on the wheat growing cycle (high concentration were noted at depth of 1-1.5 m close to the end of grain filling) and precipitation gradient (arid vs. semiarid). Since CO2 fluxes are directly affected by the pCO2 profile and soil moister and temperature the CO2 fluxes from the wheat fields were much lower (0.02- 0.2 ml min-1 m-2) compared to those obtained from the Avocado orchards (2

  3. Evidence of Urban-Induced Precipitation Variability in Arid Climate Regimes

    NASA Technical Reports Server (NTRS)

    Shepherd, J. Marshall

    2005-01-01

    -urban (1900-1950) Phoenix. The study hypothesis that a complex interaction between the city landscape, irrigated lands, and nearby mountains have created preferred regions for rainfall development. The study also provides early evidence that rapidly urbanizing parts of the arid Middle East may also be experiencing different precipitation regimes in response to urbanization and irrigation.

  4. Influence of Precipitation Regime on Microbial Decomposition Patterns in Semi-Arid Ecosystems

    NASA Astrophysics Data System (ADS)

    Feris, K. P.; Jilek, C.; Huber, D. P.; Reinhardt, K.; deGraaff, M.; Lohse, K.; Germino, M.

    2011-12-01

    In water-limited semi-arid sagebrush steppe ecosystems predicted changes in climate may manifest as a shift from historically winter/snow-dominated precipitation regimes to one dominated by spring rains. In these ecosystems soil microorganisms play a vital role in linking the effects of water availability and plant productivity to biogeochemical cycling. Patterns of soil microbial catalyzed organic matter decomposition patters (i.e. patterns of extracellular enzyme activity (EEA)) are thought to depend upon the quantity and quality of soil organic matter (SOM), pH, and mean annual precipitation (Sinsabaugh, 2008), and less on the timing and magnitude of precipitation. However, sagebrush-steppe plant communities respond strongly to changes in the timing and magnitude of precipitation, and preliminary findings by our group suggest that corresponding changes in SOM quantity, quality, N-cycle dynamics, and soil structure are occurring. Therefore, we hypothesized: 1) Shifts in the timing and magnitude of precipitation would indirectly affect soil microbial decomposition patterns via responses in the plant community structure; and 2) Changes in precipitation patterns can directly affect soil microbial community structure and function, in effect uncoupling the interaction between plant community structure and soil community structure. We tested our hypotheses by determining the influence of experimentally manipulated timing and magnitude of precipitation on soil microbial EEA using standard flourometric assays in soils sampled under plant canopies and plant interspaces. We assessed this response in a mature (18 + years) ecohydrologic field experiment in eastern Idaho that annually imitates three possible post climatic-shift precipitation regimes (Ambient (AMB): no additional precipitation, ~200mm annually; Summer (SUMM): 200mm provisioned at 50mm bi-weekly starting in June; and Fall/Spring (F/S): 200mm provisioned over 1-2 weeks in October or April) (n=3). Within plant

  5. Observed variability of drought and aridity and its impact on the hydrological regime in the Barlad catchment (Romania)

    NASA Astrophysics Data System (ADS)

    Borcan, Mihaela; Cheval, Sorin; Chendes, Viorel

    2015-04-01

    The drought is a complex phenomenon with slow manifestation which engages, depending on its duration and intensity, a number of different components of the climatic, hydrologic, pedologic systems. This paper investigates the relationships between drought and aridity on one hand and hydrological regime, on the other hand, in Bârlad river basin, in the eastern part of Romania. Recent studies have revealed that both meteorological and hydrological drought events have a significant frequency and magnitude in the area, so that an important impact on the hydrological regime is likely to occur. For the next decades, climate change scenarios estimate increasing temperatures and relatively low decreasing of precipitation. Therefore, eventual changes in the aridity characteristics can be expected, and they might have a considerable impact on the water supply or agriculture in the Bârlad catchment. The analysis covers the period 1961-2013 and it is based on monthly data from meteorological and hydrological stations. Seasonal indices were calculated for characterising the drought (SPI, SFI, PDSI, PHDI) and aridity (UNEP, de Martonne, Pinna), while their temporal variability was further investigated in relations with specific hydrological parameters (monthly discharge time series). The spatial distribution of the selected indices was analysed in the same context using co-variables integrated in a GIS framework. The results show that the hydrological drought is influenced and determined mostly by the meteorological drought. The highest variability between the aridity indices has been identified for the summer season, where the time lag between the hydrological response to the meteorological impulse is up to 2 months. The work has been financed by the research project Changes in climate extremes and associated impact in hydrological events in Romania (CLIMHYDEX), Cod PN II-ID-2011-2-0073, sponsored by the National Authority for Scientific Research.

  6. The influence of conservation tillage methods on soil water regimes in semi-arid southern Zimbabwe

    NASA Astrophysics Data System (ADS)

    Mupangwa, W.; Twomlow, S.; Walker, S.

    Planting basins and ripper tillage practices are major components of the recently introduced conservation agriculture package that is being extensively promoted for smallholder farming in Zimbabwe. Besides preparing land for crop planting, these two technologies also help in collecting and using rainwater more efficiently in semi-arid areas. The basin tillage is being targeted for households with limited or no access to draught animals while ripping is meant for smallholder farmers with some draught animal power. Trials were established at four farms in Gwanda and Insiza in southern Zimbabwe to determine soil water contributions and runoff water losses from plots under four different tillage treatments. The tillage treatments were hand-dug planting basins, ripping, conventional spring and double ploughing using animal-drawn implements. The initial intention was to measure soil water changes and runoff losses from cropped plots under the four tillage practices. However, due to total crop failure, only soil water and runoff were measured from bare plots between December 2006 and April 2007. Runoff losses were highest under conventional ploughing. Planting basins retained most of the rainwater that fell during each rainfall event. The amount of rainfall received at each farm significantly influenced the volume of runoff water measured. Runoff water volume increased with increase in the amount of rainfall received at each farm. Soil water content was consistently higher under basin tillage than the other three tillage treatments. Significant differences in soil water content were observed across the farms according to soil types from sand to loamy sand. The basin tillage method gives a better control of water losses from the farmers’ fields. The planting basin tillage method has a greater potential for providing soil water to crops than ripper, double and single conventional ploughing practices.

  7. Greenhouse gas emissions from cotton field under different irrigation methods and fertilization regimes in arid northwestern China.

    PubMed

    Wu, Jie; Guo, Wei; Feng, Jinfei; Li, Lanhai; Yang, Haishui; Wang, Xiaohua; Bian, Xinmin

    2014-01-01

    Drip irrigation is broadly extended in order to save water in the arid cotton production region of China. Biochar is thought to be a useful soil amendment to reduce greenhouse gas (GHG) emissions. Here, a field study was conducted to compare the emissions of nitrous oxide (N2O) and methane (CH4) under different irrigation methods (drip irrigation (D) and furrow irrigation (F)) and fertilization regimes (conventional fertilization (C) and conventional fertilization + biochar (B)) during the cotton growth season. The accumulated N2O emissions were significantly lower with FB, DC, and DB than with FC by 28.8%, 36.1%, and 37.6%, while accumulated CH4 uptake was 264.5%, 226.7%, and 154.2% higher with DC, DB, and FC than that with FB, respectively. Irrigation methods showed a significant effect on total global warming potential (GWP) and yield-scaled GWP (P < 0.01). DC and DB showed higher cotton yield, water use efficiency (WUE), and lower yield-scaled GWP, as compared with FC and FB. This suggests that in northwestern China mulched-drip irrigation should be a better approach to increase cotton yield with depressed GHG. In addition, biochar addition increased CH4 emissions while it decreased N2O emissions. PMID:25133229

  8. Greenhouse Gas Emissions from Cotton Field under Different Irrigation Methods and Fertilization Regimes in Arid Northwestern China

    PubMed Central

    Guo, Wei; Feng, Jinfei; Li, Lanhai; Yang, Haishui; Wang, Xiaohua; Bian, Xinmin

    2014-01-01

    Drip irrigation is broadly extended in order to save water in the arid cotton production region of China. Biochar is thought to be a useful soil amendment to reduce greenhouse gas (GHG) emissions. Here, a field study was conducted to compare the emissions of nitrous oxide (N2O) and methane (CH4) under different irrigation methods (drip irrigation (D) and furrow irrigation (F)) and fertilization regimes (conventional fertilization (C) and conventional fertilization + biochar (B)) during the cotton growth season. The accumulated N2O emissions were significantly lower with FB, DC, and DB than with FC by 28.8%, 36.1%, and 37.6%, while accumulated CH4 uptake was 264.5%, 226.7%, and 154.2% higher with DC, DB, and FC than that with FB, respectively. Irrigation methods showed a significant effect on total global warming potential (GWP) and yield-scaled GWP (P < 0.01). DC and DB showed higher cotton yield, water use efficiency (WUE), and lower yield-scaled GWP, as compared with FC and FB. This suggests that in northwestern China mulched-drip irrigation should be a better approach to increase cotton yield with depressed GHG. In addition, biochar addition increased CH4 emissions while it decreased N2O emissions. PMID:25133229

  9. Simulation and classification of the impacts of projected climate change on flow regimes in the arid Hexi Corridor of Northwest China

    NASA Astrophysics Data System (ADS)

    Zhang, Yongyong; Fu, Guobin; Sun, Boyang; Zhang, Shifeng; Men, Baohui

    2015-08-01

    Traditional assessment approaches of climate change on flow regimes usually focus on flow magnitude and cannot capture the overall variation of flow regimes (e.g., variability, frequency, duration, timing, and rating). The Hexi Corridor, which is a typical arid and semiarid region in Northwest China, was selected as the study area. Streamflows were simulated by an integrated water system model in a historical period (1985-2005) and three future periods (2030s, 2050s, and 2070s). Twenty-nine global climate models were picked from the Coupled Model Intercomparison Project Phase 5 based on projection performance, and the high (RCP85) and intermediate (RCP45) ranges of Representative Concentration Pathways were selected for future scenario analysis. All the streamflows were characterized in detail by flow regime metrics, including the magnitude, variability, and frequency of the overall flow events. The regional impacts of climate change were assessed and clustered into several similar spatial patterns. Results showed that the projected climate change would sensibly increase the magnitudes of average and low flows (75th percentile), as well as the frequencies of low and high flows (25th percentile), but decrease the flow variability. By contrast, it would not sensibly change the magnitude of high-flow events. The flow regime variations of all scenarios and periods were clustered into three robust classes (highly, moderately, and slightly impacted classes) in the entire region. The flow regimes would be highly and moderately impacted in the middle stream and downstream with large-sized and semidesert catchments but slightly impacted in the upper and middle streams with small-sized and montane vegetation catchments. The impacted classes will sensibly vary at most stations in different future periods because of the spatial differences of climate change. This study would provide scientific support to implement the integrated adaptive water resource management for climate

  10. Experimental Manipulation of Soil Moisture Regime Impacts Soil Microbial Community Abundance, Diversity, and Function in a Semi-Arid Sagebrush Steppe

    NASA Astrophysics Data System (ADS)

    Sorensen, P. O.; Feris, K. P.; Germino, M. J.

    2010-12-01

    Rising global temperatures are predicted to alter regional climate regimes, including the spatial and temporal distribution of precipitation. In water-limited (e.g. arid and semi-arid) ecosystems annual precipitation is low and shows a high degree of variability. In these environments, soil microbes occupy a pivotal seat coupling the effects of water availability and plant productivity to biogeochemical cycling and ecosystem function. Using a long running ecological field experiment (>15 years) sited in Idaho’s sagebrush steppe, effects of experimentally manipulated precipitation regime on microbial diversity, abundance, and terrestrial carbon cycling are being explored. Soils were sampled in January (winter) of 2009. Replicate cores collected at 15-20cm and 95-100cm, were taken from field plots planted with native vegetation under three different precipitation amendments; Ambient, Summer (+200mm in June), or Fall/Spring (+200mm in April or October). Bacterial and Fungal community structure was analyzed by high-resolution 454 pyrosequencing. Edaphic properties (soil moisture, pH, total C, total N, organic C, inorganic N, ortho P) were measured and used as factors for general linear modeling of Bacterial and Fungal community structure against field treatments. Labile soil carbon pools were measured as C mineralization rates by gas chromatography using long term soil incubations. Pyrosequencing analysis of soil Bacterial communities has revealed greater Bacterial community abundance and diversity across all treatments relative to Archaeal and Fungal communities. General linear modeling of sequences obtained from 454 pyrosequencing showed significant interactions of phyla-level Bacterial and Fungal abundance with experimental precipitation regime and depth of sampling. Edaphic properties such as soil moisture and pH also showed significant interactions with phyla-level Bacterial and Fungal abundance. Long-term soil incubation studies revealed treatment effects on

  11. Differences in macroinvertebrate community structure in streams and rivers with different hydrologic regimes in the semi-arid Colorado Plateau

    USGS Publications Warehouse

    Miller, Matthew P.; Brasher, Anne M.D.

    2011-01-01

    Aquatic macroinvertebrates are sensitive to changes in their chemical and physical environment, and as such, serve as excellent indicators of overall ecosystem health. Moreover, temporal and spatial differences in macroinvertebrate community structure can be used to investigate broad issues in aquatic science, such as the hypothesis that changes in climate are likely to have disproportionately large effects on small, intermittent stream ecosystems. We quantified macroinvertebrate community structure and abiotic conditions at ten stream sites with different dominant hydrologic regimes in the Colorado Plateau, ranging from small, intermittent desert streams to large perennial mountain rivers. Considerable differences were observed in community structure between sites with differing hydrologic regimes. Quantitative results of non-metric multidimensional scaling (NMDS) ordination and Spearman rank correlations between physical habitat and macroinvertebrate resemblance matrices indicate that discharge, geomorphic channel unit type (% pools vs. % riffles), percent of substrate composed of sand, and velocity were the subset of measured habitat variables that best explained the differences in macroinvertebrate community structure among sites. Of the 134 taxa identified, nine taxa explained 95 % of the variability in community structure between sites. These results add to a growing base of knowledge regarding the functioning of lotic ecosystems in the Colorado Plateau, and provide timely information on anticipated changes in the structure and function of aquatic ecosystems in response to predicted future environmental conditions.

  12. Nutritional and ecological evaluation of dairy farming systems based on concentrate feeding regimes in semi-arid environments of Jordan

    PubMed Central

    Alqaisi, Othman; Hemme, Torsten; Hagemann, Martin; Susenbeth, Andreas

    2013-01-01

    The objective of this study was to evaluate the nutritional and ecological aspects of feeding systems practiced under semi-arid environments in Jordan. Nine dairy farms representing the different dairy farming systems were selected for this study. Feed samples (n = 58), fecal samples (n = 108), and milk samples (n = 78) were collected from the farms and analysed for chemical composition. Feed samples were also analysed for metabolisable energy (ME) contents and in vitro organic matter digestibility according to Hohenheim-Feed-Test. Furthermore, fecal nitrogen concentration was determined to estimate in vivo organic matter digestibility. ME and nutrient intakes were calculated based on the farmer’s estimate of dry matter intake and the analysed composition of the feed ingredients. ME and nutrient intakes were compared to recommended standard values for adequate supply of ME, utilizable crude protein, rumen undegradable crude protein (RUCP), phosphorus (P), and calcium (Ca). Technology Impact Policy Impact Calculation model complemented with a partial life cycle assessment model was used to estimate greenhouse gas emissions of milk production at farm gate. The model predicts CH4, N2O and CO2 gases emitted either directly or indirectly. Average daily energy corrected milk yield (ECM) was 19 kg and ranged between 11 and 27 kg. The mean of ME intake of all farms was 184 MJ/d with a range between 115 and 225 MJ/d. Intake of RUCP was lower than the standard requirements in six farms ranging between 19 and 137 g/d, was higher (32 and 93 g/d) in two farms, and matched the requirements in one farm. P intake was higher than the requirements in all farms (mean oversupply = 19 g/d) and ranged between 3 and 30 g/d. Ca intake was significantly below the requirements in small scale farms. Milk nitrogen efficiency N-eff (milk N/intake N) varied between 19% and 28% and was mainly driven by the level of milk yield. Total CO2 equivalent (CO2 equ) emission ranged

  13. Radial growth of Tamarix ramosissima responds to changes in the water regime in an extremely arid region of northwestern China

    NASA Astrophysics Data System (ADS)

    Xiao, Shengchun; Xiao, Honglang

    2007-11-01

    The response of radial growth of tamarisk ( Tamarix ramosissima) growing on the shore of West-Juyan Lake, on the Heihe River in northwestern China, to changes in the lake’s water regime was studied using tree-ring chronologies, principal components (PC) analysis, and classical correlation analysis. The first PC accounted for 53.3% of the total variance and reflected a common growth response at different sites. Correlation analysis indicated that fluctuations in the lake’s water level during the growing season (May August) was primarily responsible for variations in the radial growth of tamarisk and explained more of the variance at low-lying sites than at higher sites. The second PC accounted for 30.7% of the total variance and revealed distinct differences in growth response between low-lying sites and those on higher ground. Total annual precipitation played an important role in radial growth of tamarisk at the higher sites. The spatial pattern in the tree-ring chronologies for different sites was performed in the temporal pattern of the tree-ring chronology at the same site. Other factors such as microtopography, soil salinity, sand activity, and browsing by herbivores also affected the radial growth of tamarisk. The diversity in responses to the maximum water table depth for tamarisk in the study area appears to have been caused by local variations in precipitation, which can compensate to some degree for the inability of a plant’s roots to reach the water table.

  14. Use of the subsurface thermal regime as a groundwater-flow tracer in the semi-arid western Nile Delta, Egypt

    NASA Astrophysics Data System (ADS)

    Salem, Zenhom E.; Bayumy, Dina A.

    2016-02-01

    Temperature profiles from 25 boreholes were used to understand the spatial and vertical groundwater flow systems in the Western Nile Delta region of Egypt, as a case study of a semi-arid region. The study area is located between the Nile River and Wadi El Natrun. The recharge areas, which are located in the northeastern and the northwestern parts of the study area, have low subsurface temperatures. The discharge areas, which are located in the western (Wadi El Natrun) and southern (Moghra aquifer) parts of the study area, have higher subsurface temperatures. In the deeper zones, the effects of faults and the recharge area in the northeastern direction disappear at 80 m below sea level. For that depth, one main recharge and one main discharge area are recognized. The recharge area is located to the north in the Quaternary aquifer, and the discharge area is located to the south in the Miocene aquifer. Two-dimensional groundwater-flow and heat-transport models reveal that the sealing faults are the major factor disturbing the regional subsurface thermal regime in the study area. Besides the main recharge and discharge areas, the low permeability of the faults creates local discharge areas in its up-throw side and local recharge areas in its down-throw side. The estimated average linear groundwater velocity in the recharge area is 0.9 mm/day to the eastern direction and 14 mm/day to the northwest. The average linear groundwater discharge velocities range from 0.4 to 0.9 mm/day in the southern part.

  15. Use of the subsurface thermal regime as a groundwater-flow tracer in the semi-arid western Nile Delta, Egypt

    NASA Astrophysics Data System (ADS)

    Salem, Zenhom E.; Bayumy, Dina A.

    2016-06-01

    Temperature profiles from 25 boreholes were used to understand the spatial and vertical groundwater flow systems in the Western Nile Delta region of Egypt, as a case study of a semi-arid region. The study area is located between the Nile River and Wadi El Natrun. The recharge areas, which are located in the northeastern and the northwestern parts of the study area, have low subsurface temperatures. The discharge areas, which are located in the western (Wadi El Natrun) and southern (Moghra aquifer) parts of the study area, have higher subsurface temperatures. In the deeper zones, the effects of faults and the recharge area in the northeastern direction disappear at 80 m below sea level. For that depth, one main recharge and one main discharge area are recognized. The recharge area is located to the north in the Quaternary aquifer, and the discharge area is located to the south in the Miocene aquifer. Two-dimensional groundwater-flow and heat-transport models reveal that the sealing faults are the major factor disturbing the regional subsurface thermal regime in the study area. Besides the main recharge and discharge areas, the low permeability of the faults creates local discharge areas in its up-throw side and local recharge areas in its down-throw side. The estimated average linear groundwater velocity in the recharge area is 0.9 mm/day to the eastern direction and 14 mm/day to the northwest. The average linear groundwater discharge velocities range from 0.4 to 0.9 mm/day in the southern part.

  16. Inter-species comparisons in Water use with Different water Irrigation Regimes in a Semi-arid area of Korea-Mongolia Greenbelt Plantation

    NASA Astrophysics Data System (ADS)

    Cho, S.; Ser-Oddamba, B.; Batkhuu, N. O.; Kim, H. S.

    2014-12-01

    As an effort to mitigate desertification and to restore desert areas in Mongolia, Korea-Mongolia Green Belt was established to develop a 3000 ha plantation in 2006. Two native tree species, Populus sibirica and Ulmus pumila L., have been planted under different irrigation regimes (control, control+2L, control +4L and control +8L) since 2008. To investigate the responses of different tree species to different treatment and the effect of plantation on water balance, intensive field experiments have been carried out in 2013-2014 in Mongolia. The objectives of our study are 1) to investigate whether different irrigation regimes changed the physiological characteristics of tree species, 2) to quantify transpirations and water balance under different irrigation regimes, and 3) to compare the water-use-efficiencies among species and irrigation regimes. We used Granier type thermal dissipation sensor, portable photosynthesis analyzer (Li-Cor 6400) and species and site specific allometric equations for transpiration, photosynthetic characteristics and net primary production, respectively. Our preliminary results show that the transpiration rates of P. sibirica increased with the increase of irrigation amount. For examples, the average water consumption of P. sibirica was 1.87kg/tree under control+2L irrigation and 2.97kg/tree at controal+4L irrigation. However, the transpiration rates of U. pumila were not different among different irrigation regimes; the average transpiration of U. pumila at control+2L was 1.1kg/tree compared to 0.89kg/tree at control+4L. But, photosynthetic characteristic showed similar results, which no apparent response under high irrigation regimes. The water use and carbon assimilation of P. sibirica responded to the water irrigation, however, U. pumila did not show any significant response to added water. Our results show different species respond differently to irrigation regimes, and this would lead to different effects on water balance. Therefore

  17. Effects of three nematode anthelmintic treatment regimes on flock performance of sheep and goats under extensive management in semi-arid Kenya.

    PubMed

    Gatongi, P M; Scott, M E; Ranjan, S; Gathuma, J M; Munyua, W K; Cheruiyot, H; Prichard, R K

    1997-03-01

    A study was undertaken in a semi-arid area of Kenya between August 1991 and June 1993 to evaluate the effects of anthelmintic treatment using ivermectin before or during the rains, on performance of mixed sheep and goat flocks, in comparison with an untreated flock. Performance parameters measured included age and weight of dams at first parturition, parturition intervals, body weights of dams and offspring, and birth weights, growth rates, and mortality rates of offspring. Among these parameters, birth weights and growth rates of offspring were found to be significantly improved by the treatment administered before the rains compared with the other two treatments. Mortality was lower in lambs and kids with high birth weights. Treatment, either before or during the rains, significantly reduced the faecal egg output and improved body weight, packed cell volume and flock fertility. Liveweight was confirmed to be a better measure of sexual maturity than age. It was further shown that lambs and kids, born of dams at their first lambing or kidding, experienced higher mortality rates than lambs and kids born of dams in their second and subsequent parturitions. Overall, treatment with ivermectin before the onset of rains was equal to or better, in terms of the performance parameters measured, than treatment during the rains, whilst treatment compared with no treatment increased performance in almost all of the parameters measured. PMID:9106954

  18. From hydrodynamic to hydrological modelling: Investigating long-term hydrological regimes of key wetlands in the Macquarie Marshes, a semi-arid lowland floodplain in Australia

    NASA Astrophysics Data System (ADS)

    Wen, Li; Macdonald, Rohan; Morrison, Tim; Hameed, Tahir; Saintilan, Neil; Ling, Joanne

    2013-09-01

    The Macquarie Marshes is an intermittently flooded wetland complex covering nearly 200,000 ha. It is one of the largest semi-permanent wetland systems in the Murray-Darling Basin, Australia, and portions of the Marshes are listed as internationally important under the Ramsar Convention. Previous studies indicate that the Marshes have undergone accelerated ecological degradation since the 1980s. The ecological degradation is documented in declining biodiversity, encroaching of terrestrial species, colonisation of exotic species, and deterioration of floodplain forests. There is strong evidence that reduction in river flows is the principal cause of the decrease in ecological values. Although the streams are relatively well gauged and modelled, the lack of hydrological records within the Marshes hampers any attempts to quantitatively investigate the relationship between hydrological variation and ecosystem integrity. To enable a better understanding of the long-term hydrological variations within the key wetland systems, and in particular, to investigate the impacts of the different water management policies (e.g. environmental water) on wetlands, a river system model including the main wetland systems was needed. The morphological complex nature of the Marshes means that the approximation of hydrological regimes within wetlands using stream hydrographs would have been difficult and inaccurate. In this study, we built a coupled 1D/2D MIKE FLOOD floodplain hydrodynamic model based on a 1 m DEM derived from a LiDAR survey. Hydrological characteristics of key constituent wetlands such as the correlation between water level and inundation area, relationships between stream and wetlands and among wetlands were estimated using time series extracted from hydrodynamic simulations. These relationships were then introduced into the existing river hydrological model (IQQM) to represent the wetlands. The model was used in this study to simulate the daily behaviours of inflow

  19. Understanding the link between aridity and hydrological extremes: Lessons from hyper-arid climates

    NASA Astrophysics Data System (ADS)

    Molini, Annalisa

    2016-04-01

    Precipitation over arid and hyper-arid regions represents "per se" an extreme event, often resulting in surface-hydrologic impacts comparatively more catastrophic than in temperate climates. The spatio-temporal distribution of precipitation through arid climates is in fact characterized by intense and short-lived patterns and intimately related to the local availability of water and energy. However - given the scarcity of data and the limited number of research contributions analyzing rain extremes in hyper arid environments - is still an open question whether rainfall sporadically falling on hyper-arid regions, and in particular its convective component, presents peculiar features connected with the endemically water-limited regime of these regions. If so, understanding the link between aridity and rainfall variability could turn out a precious tool to investigate not only the climate of arid regions but also more global trends of precipitation under global warming and aridification. In this contribution we analyze the connection between rainfall variability, its temporal scaling laws and aridity in a climatological prospective. Through a wide dataset of precipitation time series covering most Continental US (CONUS) we explore the local dependence of classic intermittency measures on aridity, finding evidence of a well-defined variability patterns across a wide range of water-limited climates. We also explore the connection between different intermittency features of arid climates as contrasted with "wet" regions and briefly discuss the links between clustering, water-availability thresholds and hydro-climatic extremes. Our findings provide a framework to better understand the link between intermittency, rainfall scaling and climate in water-limited regions of the world, with possible extension to global aridification studies.

  20. Waste biorefinery in arid/semi-arid regions.

    PubMed

    Bastidas-Oyanedel, Juan-Rodrigo; Fang, Chuanji; Almardeai, Saleha; Javid, Usama; Yousuf, Ahasa; Schmidt, Jens Ejbye

    2016-09-01

    The utilization of waste biorefineries in arid/semi-arid regions is advisable due to the reduced sustainable resources in arid/semi-arid regions, e.g. fresh water and biomass. This review focuses on biomass residues available in arid/semi-arid regions, palm trees residues, seawater biomass based residues (coastal arid/semi-arid regions), and the organic fraction of municipal solid waste. The present review aims to describe and discuss the availability of these waste biomasses, their conversion to value chemicals by waste biorefinery processes. For the case of seawater biomass based residues it was reviewed and advise the use of seawater in the biorefinery processes, in order to decrease the use of fresh water. PMID:27072789

  1. Preliminary assessment of aridity conditions in the Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Andrade, C.; Corte-Real, J. A.

    2016-06-01

    Aridity is one of the key elements characterizing the climate of a region, having a severe impact on human activities. Aiming at assessing aridity conditions in the Iberian Peninsula, the spatial distribution of the UNEP aridity index is analyzed during the period 1901-2012. Gridded precipitation and potential evapotranspiration datasets are used on a monthly basis. Results show that the southern half of Iberia is particularly vulnerable to water stress and hence to desertification processes. In particular, the UNEP aridity index reveals an increase and northward extension of the semi-arid regime in the Iberian Peninsula between 1901 and 2012. More than 50% of the north and western territory have experienced humid/sub-humid conditions, while the other regions underwent semi-arid settings. Results also reveal that climate was subjected to spatial and temporal variabilities with an overall statistically significant (at a 95% confidence level) trend to aridification in the south-easternmost and central regions. The remaining territory of the Iberian Peninsula does not reveal statistically significant trends.

  2. Regime change?

    SciTech Connect

    Pilat, Joseph F.; Budlong-Sylvester, K. W.

    2004-01-01

    Following the 1998 nuclear tests in South Asia and later reinforced by revelations about North Korean and Iraqi nuclear activities, there has been growing concern about increasing proliferation dangers. At the same time, the prospects of radiological/nuclear terrorism are seen to be rising - since 9/11, concern over a proliferation/terrorism nexus has never been higher. In the face of this growing danger, there are urgent calls for stronger measures to strengthen the current international nuclear nonproliferation regime, including recommendations to place civilian processing of weapon-useable material under multinational control. As well, there are calls for entirely new tools, including military options. As proliferation and terrorism concerns grow, the regime is under pressure and there is a temptation to consider fundamental changes to the regime. In this context, this paper will address the following: Do we need to change the regime centered on the Treaty on the Nonproliferation of Nuclear Weapons (NPT) and the International Atomic Energy Agency (IAEA)? What improvements could ensure it will be the foundation for the proliferation resistance and physical protection needed if nuclear power grows? What will make it a viable centerpiece of future nonproliferation and counterterrorism approaches?

  3. GLDAS Land Surface Models based Aridity Indices

    NASA Astrophysics Data System (ADS)

    Pande, S.; Ghazanfari, S.

    2011-12-01

    Identification of dryland areas is crucial to guide policy aimed at intervening in water stressed areas and addressing its perennial livelihood or food insecurity. Aridity indices based on spatially relative soil moisture conditions such as NCEP aridity index allow cross comparison of dry conditions between sites. NCEP aridity index is based on the ratio of annual precipitation (supply) to annual potential evaporation (demand). Such an index ignores subannual scale competition between evaporation and drainage functions well as rainfall and temperature regimes. This determines partitioning of annual supply of precipitation into two competing (but met) evaporation and runoff demands. We here introduce aridity indices based on these additional considerations by using soil moisture time series for the past 3 decades from three Land Surface Models (LSM) models and compare it with NCEP index. We analyze global monthly soil moisture time series (385 months) at 1 x 1 degree spatial resolution as modeled by three GLDAS LSMs - VIC, MOSAIC and NOAH. The first eigen vector from Empirical Orthogonal Function (EOF) analysis, as it is the most dominant spatial template of global soil moisture conditions, is extracted. Frequency of nonexceedences of this dominant soil moisture mode for a location by other locations is calculated and is used as our proposed aridity index. An area is indexed drier (relative to other areas in the world) if its frequency of nonexceedence is lower. The EOF analysis reveals that their first eigen vector explains approximately 32%, 43% and 47% of variance explained by first 385 eigen vectors for VIC, MOSAIC and NOAH respectively. The temporal coefficients associated with it for all three LSMS show seasonality with a jump in trend around the year 1999 for NOAH and MOSAIC. The VIC aridity index displays a pattern most closely resembling that of NCEP though all LSM based indices isolate dominant dryland areas. However, all three LSMs identify some parts of

  4. Deserts and Arid Lands

    NASA Astrophysics Data System (ADS)

    Brown, Glen F.

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

  5. Investigations on the Aridity Paradox

    NASA Astrophysics Data System (ADS)

    Donohue, R. J.; Roderick, M. L.

    2014-12-01

    How global aridity might change in the immediate future is an important question. Several recent analyses have concluded that aridity will, in general, increase over land primarily because of increasing vapour pressure deficit. Taken at face value that result is difficult to understand because a warmer world is also anticipated to be a moister world. For example, at the global scale, climate model projections are for increasing rainfall and runoff. In this presentation we investigate this seeming paradox. We find that the previous analyses have not accounted for the biological impacts of elevated CO2 and when that is incorporated, the climate model projections are for a modest reduction in meteorological and hydrologic aridity and for larger reductions in biological aridity.

  6. Adapting to extreme climates: raising animals in hot and arid ecosystems in Australia

    NASA Astrophysics Data System (ADS)

    Seo, S. Niggol

    2015-05-01

    This paper provides an analysis of adaptation to extreme climate changes using the Australian animal husbandry data. The paper finds that farmers have adapted to a hot and arid climate regime through animal husbandry. The number of sheep vastly increases into arid ecosystems while the number of beef cattle does not decline in high temperatures. In the future climate system in which Australia becomes hotter and more arid, we predict that farmers will increase by large percentages the numbers of beef cattle and/or sheep owned in order to adapt to a highly unfavorable climate condition, especially into the arid ecosystems. This paper shows how humanity has adapted to climate extremes taking into account changing ecosystems.

  7. Aridity Modulates N Availability in Arid and Semiarid Mediterranean Grasslands

    PubMed Central

    Delgado-Baquerizo, Manuel; Maestre, Fernando T.; Gallardo, Antonio; Quero, José L.; Ochoa, Victoria; García-Gómez, Miguel; Escolar, Cristina; García-Palacios, Pablo; Berdugo, Miguel; Valencia, Enrique; Gozalo, Beatriz; Noumi, Zouhaier; Derak, Mchich; Wallenstein, Matthew D.

    2013-01-01

    While much is known about the factors that control each component of the terrestrial nitrogen (N) cycle, it is less clear how these factors affect total N availability, the sum of organic and inorganic forms potentially available to microorganisms and plants. This is particularly true for N-poor ecosystems such as drylands, which are highly sensitive to climate change and desertification processes that can lead to the loss of soil nutrients such as N. We evaluated how different climatic, abiotic, plant and nutrient related factors correlate with N availability in semiarid Stipa tenacissima grasslands along a broad aridity gradient from Spain to Tunisia. Aridity had the strongest relationship with N availability, suggesting the importance of abiotic controls on the N cycle in drylands. Aridity appeared to modulate the effects of pH, plant cover and organic C (OC) on N availability. Our results suggest that N transformation rates, which are largely driven by variations in soil moisture, are not the direct drivers of N availability in the studied grasslands. Rather, the strong relationship between aridity and N availability could be driven by indirect effects that operate over long time scales (decades to millennia), including both biotic (e.g. plant cover) and abiotic (e.g. soil OC and pH). If these factors are in fact more important than short-term effects of precipitation on N transformation rates, then we might expect to observe a lagged decrease in N availability in response to increasing aridity. Nevertheless, our results suggest that the increase in aridity predicted with ongoing climate change will reduce N availability in the Mediterranean basin, impacting plant nutrient uptake and net primary production in semiarid grasslands throughout this region. PMID:23565170

  8. Integrated Modeling and Ecological Valuation: Applications in the Semi Arid Southwest 1912

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A Conservation of freshwater systems is critical in the semi-arid Southwest where groundwater and flood regimes strongly influence the abundance, composition, and structure of riparian (streamside) vegetation. At the same time these systems are in high demand for competing human use. To address thi...

  9. Problems and Prospects of SWAT Model Application on an Arid/Semi-Arid Watershed in Arizona

    EPA Science Inventory

    In arid/semi-arid regions, precipitation mainly occurs during two periods: long-duration, low-intensity rainfall in winter; and short-duration, high-intensity rainfall in summer. Watersheds in arid/semi-arid regions often release water almost immediately after a storm due to spa...

  10. Calibration of the ARID robot

    NASA Technical Reports Server (NTRS)

    Doty, Keith L

    1992-01-01

    The author has formulated a new, general model for specifying the kinematic properties of serial manipulators. The new model kinematic parameters do not suffer discontinuities when nominally parallel adjacent axes deviate from exact parallelism. From this new theory the author develops a first-order, lumped-parameter, calibration-model for the ARID manipulator. Next, the author develops a calibration methodology for the ARID based on visual and acoustic sensing. A sensor platform, consisting of a camera and four sonars attached to the ARID end frame, performs calibration measurements. A calibration measurement consists of processing one visual frame of an accurately placed calibration image and recording four acoustic range measurements. A minimum of two measurement protocols determine the kinematics calibration-model of the ARID for a particular region: assuming the joint displacements are accurately measured, the calibration surface is planar, and the kinematic parameters do not vary rapidly in the region. No theoretical or practical limitations appear to contra-indicate the feasibility of the calibration method developed here.

  11. Stability measures in arid ecosystems

    NASA Astrophysics Data System (ADS)

    Nosshi, M. I.; Brunsell, N. A.; Koerner, S.

    2015-12-01

    Stability, the capacity of ecosystems to persist in the face of change, has proven its relevance as a fundamental component of ecological theory. Here, we would like to explore meaningful and quantifiable metrics to define stability, with a focus on highly variable arid and semi-arid savanna ecosystems. Recognizing the importance of a characteristic timescale to any definition of stability, our metrics will be focused scales from annual to multi-annual, capturing different aspects of stability. Our three measures of stability, in increasing order of temporal scale, are: (1) Ecosystem resistance, quantified as the degree to which the system maintains its mean state in response to a perturbation (drought), based on inter-annual variability in Normalized Difference Vegetation Index (NDVI). (2) An optimization approach, relevant to arid systems with pulse dynamics, that models vegetation structure and function based on a trade off between the ability to respond to resource availability and avoid stress. (3) Community resilience, measured as species turnover rate (β diversity). Understanding the nature of stability in structurally-diverse arid ecosystems, which are highly variable, yields theoretical insight which has practical implications.

  12. Patterns of ant (Hymenoptera: Formicidae) richness and relative abundance along an aridity gradient in Western Venezuela.

    PubMed

    Pérez-Sánchez, A J; Lattke, J E; Viloria, A L

    2013-04-01

    In xeric ecosystems, ant diversity response to aridity varies with rainfall magnitude and gradient extension. At a local scale and with low precipitation regimes, increased aridity leads to a reduction of species richness and an increased relative abundance for some ant species. In order to test this pattern in tropical environments, ant richness and relative abundance variation were evaluated along 35 km of an aridity gradient in the Araya Peninsula, state of Sucre, Venezuela. Three sampling stations comprising five transects each were set up. Pitfall traps and direct collecting from vegetation were assessed per transect. Overall, 52 species, 23 genera, and 7 subfamilies of ants were recorded in the peninsula. The total number of species and genera recorded by both sampling stations and transects decreased linearly with increasing aridity. Total relative abundance was highest in the most arid portion of the peninsula, with Crematogaster rochai (Forel) and Camponotus conspicuus zonatus (Emery) (Hymenoptera: Formicidae) being the numerically dominant species. Spatial and multivariate analyses revealed significant changes in ant composition every 11 km of distance, and showed a decrease of ant diversity with the increase of harsh conditions in the gradient. Here, we discuss how local geographic and topographic features of Araya originate the aridity gradient and so affect the microhabitat conditions for the ant fauna. PMID:23949745

  13. Precipitation and nitrogen interactions in arid ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arid and semi-arid ecosystems are among the most impoverished terrestrial systems in terms of water and nitrogen (N) availability. Productivity (NPP) is generally low, soil N pools are small and N loss through percolation is assumed to be negligible. Increased water availability can stimulate both N...

  14. RIVERBANK FILTRATION EFFECTIVENESS IN AN ARID ENVIRONMENT

    EPA Science Inventory

    This experiment is a field test of bank filtration at a site where water level and salinity vary on an annual basis, as they do in many arid and semi-arid streams. No other studies of bank filtration have been performed in this kind of setting. Along the border with Mexico, shall...

  15. Kinematic analysis of the ARID manipulator

    NASA Technical Reports Server (NTRS)

    Doty, Keith L

    1992-01-01

    The kinematic structure of the ARID manipulator lends itself to simple forward and inverse kinematics analysis. The purpose of this paper is to fully document and verify an existing analysis. The symbolic software package MATHEMATICA was used to produce and verify the equations presented here. In the analysis to follow, the standard Devenit-Hartenberg kinematic parameters of the ARID were employed.

  16. Climate change and potential reversal of regime shifts in desrt ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Globally, regime shifts from grasslands to shrublands (i.e., desertification) in arid and semiarid ecosystems are thought to be irreversible, similar to state changes in other ecosystems. The consequences of desertification, including loss of soil and nutrients to wind and water erosion, reductions ...

  17. ARID relative calibration experimental data and analysis

    NASA Technical Reports Server (NTRS)

    Doty, Keith L

    1992-01-01

    Several experiments measure the orientation error of the ARID end-frame as well as linear displacements in the Orbiter's y- and z-axes. In each experiment the position of the ARID on the trolley is fixed and the manipulator extends and retracts along the Orbiter's y-axis. A sensor platform consisting of four sonars arranged in a '+' pattern measures the platform pitch about the Orbiter's y-axis (angle b) and yaw about the Orbiter's x-axis (angle alpha). Corroborating measurements of the yaw error were performed using a carpenter's level to keep the platform perpendicular to the gravity vector at each ARID pose being measured.

  18. Arid3b Is Critical for B Lymphocyte Development

    PubMed Central

    Kurkewich, Jeffrey L.; Klopfenstein, Nathan; Hallas, William M.; Wood, Christian; Sattler, Rachel A.; Das, Chhaya; Tucker, Haley; Dahl, Richard; Cowden Dahl, Karen D.

    2016-01-01

    Arid3a and Arid3b belong to a subfamily of ARID (AT-rich interaction domain) transcription factors. The Arid family is involved in regulating chromatin accessibility, proliferation, and differentiation. Arid3a and Arid3b are closely related and share a unique REKLES domain that mediates their homo- and hetero-multimerization. Arid3a was originally isolated as a B cell transcription factor binding to the AT rich matrix attachment regions (MARS) of the immunoglobulin heavy chain intronic enhancer. Deletion of Arid3a results in a highly penetrant embryonic lethality with severe defects in erythropoiesis and hematopoietic stem cells (HSCs). The few surviving Arid3a-/- (<1%) animals have decreased HSCs and early progenitors in the bone marrow, but all mature lineages are normally represented in the bone marrow and periphery except for B cells. Arid3b-/- animals die around E7.5 precluding examination of hematopoietic development. So it is unclear whether the phenotype of Arid3a loss on hematopoiesis is dependent or independent of Arid3b. In this study we circumvented this limitation by also examining hematopoiesis in mice with a conditional allele of Arid3b. Bone marrow lacking Arid3b shows decreased common lymphoid progenitors (CLPs) and downstream B cell populations while the T cell and myeloid lineages are unchanged, reminiscent of the adult hematopoietic defect in Arid3a mice. Unlike Arid3a-/- mice, HSC populations are unperturbed in Arid3b-/- mice. This study demonstrates that HSC development is independent of Arid3b, whereas B cell development requires both Arid3a and Arid3b transcription factors. PMID:27537840

  19. Arid3b Is Critical for B Lymphocyte Development.

    PubMed

    Kurkewich, Jeffrey L; Klopfenstein, Nathan; Hallas, William M; Wood, Christian; Sattler, Rachel A; Das, Chhaya; Tucker, Haley; Dahl, Richard; Cowden Dahl, Karen D

    2016-01-01

    Arid3a and Arid3b belong to a subfamily of ARID (AT-rich interaction domain) transcription factors. The Arid family is involved in regulating chromatin accessibility, proliferation, and differentiation. Arid3a and Arid3b are closely related and share a unique REKLES domain that mediates their homo- and hetero-multimerization. Arid3a was originally isolated as a B cell transcription factor binding to the AT rich matrix attachment regions (MARS) of the immunoglobulin heavy chain intronic enhancer. Deletion of Arid3a results in a highly penetrant embryonic lethality with severe defects in erythropoiesis and hematopoietic stem cells (HSCs). The few surviving Arid3a-/- (<1%) animals have decreased HSCs and early progenitors in the bone marrow, but all mature lineages are normally represented in the bone marrow and periphery except for B cells. Arid3b-/- animals die around E7.5 precluding examination of hematopoietic development. So it is unclear whether the phenotype of Arid3a loss on hematopoiesis is dependent or independent of Arid3b. In this study we circumvented this limitation by also examining hematopoiesis in mice with a conditional allele of Arid3b. Bone marrow lacking Arid3b shows decreased common lymphoid progenitors (CLPs) and downstream B cell populations while the T cell and myeloid lineages are unchanged, reminiscent of the adult hematopoietic defect in Arid3a mice. Unlike Arid3a-/- mice, HSC populations are unperturbed in Arid3b-/- mice. This study demonstrates that HSC development is independent of Arid3b, whereas B cell development requires both Arid3a and Arid3b transcription factors. PMID:27537840

  20. Photodegradation Pathways in Arid Ecosystems

    NASA Astrophysics Data System (ADS)

    King, J. Y.; Lin, Y.; Adair, E. C.; Brandt, L.; Carbone, M. S.

    2013-12-01

    Recent interest in improving our understanding of decomposition patterns in arid and semi-arid ecosystems and under potentially drier future conditions has led to a flurry of research related to abiotic degradation processes. Oxidation of organic matter by solar radiation (photodegradation) is one abiotic degradation process that contributes significantly to litter decomposition rates. Our meta-analysis results show that increasing solar radiation exposure corresponds to an average increase of 23% in litter mass loss rate with large variation among studies associated primarily with environmental and litter chemistry characteristics. Laboratory studies demonstrate that photodegradation results in CO2 emissions. Indirect estimates suggest that photodegradation could account for as much as 60% of ecosystem CO2 emissions from dry ecosystems, but these CO2 fluxes have not been measured in intact ecosystems. The current data suggest that photodegradation is important, not only for understanding decomposition patterns, but also for modeling organic matter turnover and ecosystem C cycling. However, the mechanisms by which photodegradation operates, along with their environmental and litter chemistry controls, are still poorly understood. Photodegradation can directly influence decomposition rates and ecosystem CO2 flux via photochemical mineralization. It can also indirectly influence biotic decomposition rates by facilitating microbial degradation through breakdown of more recalcitrant compounds into simpler substrates or by suppressing microbial activity directly. All of these pathways influence the decomposition process, but the relative importance of each is uncertain. Furthermore, a specific suite of controls regulates each of these pathways (e.g., environmental conditions such as temperature and relative humidity; physical environment such as canopy architecture and contact with soil; and litter chemistry characteristics such as lignin and cellulose content), and

  1. Arctic circulation regimes.

    PubMed

    Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L

    2015-10-13

    Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability. PMID:26347536

  2. Arctic circulation regimes

    PubMed Central

    Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L.

    2015-01-01

    Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability. PMID:26347536

  3. Water sources accessed by arid zone riparian trees in highly saline environments, Australia.

    PubMed

    Costelloe, Justin F; Payne, Emily; Woodrow, Ian E; Irvine, Elizabeth C; Western, Andrew W; Leaney, Fred W

    2008-05-01

    The flow regimes of arid zone rivers are often highly variable, and shallow groundwater in the alluvial aquifers can be very saline, thus constraining the availability and quality of the major water sources available to riparian trees-soil water, shallow groundwater and stream water. We have identified water sources and strategies used by riparian trees in more highly saline and arid conditions than previously studied for riparian trees of arid zone rivers. Our research focused on the riparian species Eucalyptus coolabah, one of the major riparian trees of ephemeral arid zone rivers in Australia. The water sources available to this riparian tree were examined using delta(18)O isotope data from xylem, soil water, groundwater and surface water. Additionally, soil chloride and matric potential data were used to infer zones of water availability for root uptake. Despite the saline conditions, the trees used a mixture of soil water and groundwater sources, but they did not use surface water directly. The study identified three strategies used to cope with typically high groundwater and soil water salinities. Firstly, the trees preferentially grow in zones of most frequent flushing by infiltrating streamflow, such as the bank-tops of channels. Secondly, the trees limit water use by having low transpiration rates. Thirdly, the trees are able to extract water at very low osmotic potentials, with water uptake continuing at chloride concentrations of at least 20,000-30,000 mg L(-1). PMID:18270743

  4. Identification of Chromatin Remodeling Genes Arid4a and Arid4b as Leukemia Suppressor Genes

    PubMed Central

    Wu, Mei-Yi; Eldin, Karen W.

    2008-01-01

    Background Leukemia evolves through a multistep process from premalignancy to malignancy. Epigenetic alterations, including histone modifications, have been proposed to play an important role in tumorigenesis. The involvement of two chromatin remodeling genes, retinoblastoma-binding protein 1 (Rbbp1/Arid4a) and Rbbp1-like 1 (Rbbp1l1/Arid4b), in leukemogenesis was not characterized. Methods The leukemic phenotype of mice deficient for Arid4a with or without haploinsufficiency for Arid4b was investigated by serially monitoring complete blood counts together with microscopic histologic analysis and flow cytometric analysis of bone marrow and spleen from the Arid4a−/− mice or Arid4a−/−Arid4b+/− mice. Regulation in bone marrow cells of downstream genes important for normal hematopoiesis was analyzed by reverse transcription–polymerase chain reaction. Genotypic effects on histone modifications were examined by western blotting and immunofluorescence analysis. All statistical tests were two-sided. Results Young (2–5 months old) Arid4a-deficient mice had ineffective blood cell production in all hematopoietic lineages. Beyond 5 months of age, the Arid4a−/− mice manifested monocytosis, accompanied by severe anemia and thrombocytopenia. These sick Arid4a−/− mice showed bone marrow failure with myelofibrosis associated with splenomegaly and hepatomegaly. Five of 42 Arid4a−/− mice and 10 of 12 Arid4a−/−Arid4b+/− mice progressed to acute myeloid leukemia (AML) and had rapid further increases of leukocyte counts. Expression of Hox genes (Hoxb3, Hoxb5, Hoxb6, and Hoxb8) was decreased in Arid4a-deficient bone marrow cells with or without Arid4b haploinsufficiency, and FoxP3 expression was reduced in Arid4a−/−Arid4b+/− bone marrow. Increases of histone trimethylation of H3K4, H3K9, and H4K20 (fold increases in trimethylation = 32, 95% confidence interval [CI] = 27 to 32; 45, 95% CI = 41 to 49; and 2.2, 95% CI = 1.7 to 2.7, respectively) were

  5. Regimes of Helium Burning

    SciTech Connect

    Timmes, F. X.; Niemeyer, J. C.

    2000-07-10

    The burning regimes encountered by laminar deflagrations and Zeldovich von Neumann Doering [ZND] detonations propagating through helium-rich compositions in the presence of buoyancy-driven turbulence are analyzed. Particular attention is given to models of X-ray bursts that start with a thermonuclear runaway on the surface of a neutron star and to the thin-shell helium instability of intermediate-mass stars. In the X-ray burst case, turbulent deflagrations propagating in the lateral or radial direction encounter a transition from the distributed regime to the flamelet regime at a density of {approx}108 g cm-3. In the radial direction, the purely laminar deflagration width is larger than the pressure scale height for densities smaller than {approx}106 g cm-3. Self-sustained laminar deflagrations traveling in the radial direction cannot exist below this density. Similarly, the planar ZND detonation width becomes larger than the pressure scale height at {approx}107 g cm-3, suggesting that steady state, self-sustained detonations cannot come into existence in the radial direction. In the thin helium shell case, turbulent deflagrations traveling in the lateral or radial direction encounter the distributed regime at densities below {approx}107 g cm-3 and the flamelet regime at larger densities. In the radial direction, the purely laminar deflagration width is larger than the pressure scale height for densities smaller than {approx}104 g cm-3, indicating that steady state laminar deflagrations cannot form below this density. The planar ZND detonation width becomes larger than the pressure scale height at {approx}5x10{sup 4} g cm-3, suggesting that steady state, self-sustained detonations cannot come into existence in the radial direction. (c) 2000 The American Astronomical Society.

  6. Identifying Groundwater Recharge in Arid Regions

    NASA Astrophysics Data System (ADS)

    Thomas, B. F.; Famiglietti, J. S.

    2015-12-01

    Recharge epodicity in arid regions provides a method to estimate annual groundwater recharge given a relationship expressed as the recharge to precipitation ratio. Traditionally, in-situ observations are required to identify aquifer recharge events, while more advanced approaches such as the water-table fluctuation method or the episodic master recession method are necessary to delineate the recharge event. Our study uses the Gravity Recovery and Climate Experiment (GRACE) observations to estimate monthly changes in groundwater storage which are attributed to the combination of groundwater abstraction and episodic recharge in the arid southwestern United States. Our results illustrate the ability of remote sensing technologies to identify episodic groundwater recharge in arid regions which can be used within sustainable groundwater management frameworks to effectively manage groundwater resources.

  7. Seasonality of soil moisture mediates responses of ecosystem phenology to elevated CO2 and warming in a semi-arid grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Concurrent changes in temperature, atmospheric CO2, and precipitation regimes are altering ecosystems globally, and may be especially important in water-limited ecosystems. Such ecosystems include the semi-arid grasslands of western North America which provide critical ecosystem services, including ...

  8. ARID3B Directly Regulates Ovarian Cancer Promoting Genes

    PubMed Central

    Bobbs, Alexander; Gellerman, Katrina; Hallas, William Morgan; Joseph, Stancy; Yang, Chao; Kurkewich, Jeffrey; Cowden Dahl, Karen D.

    2015-01-01

    The DNA-binding protein AT-Rich Interactive Domain 3B (ARID3B) is elevated in ovarian cancer and increases tumor growth in a xenograft model of ovarian cancer. However, relatively little is known about ARID3B's function. In this study we perform the first genome wide screen for ARID3B direct target genes and ARID3B regulated pathways. We identified and confirmed numerous ARID3B target genes by chromatin immunoprecipitation (ChIP) followed by microarray and quantitative RT-PCR. Using motif-finding algorithms, we characterized a binding site for ARID3B, which is similar to the previously known site for the ARID3B paralogue ARID3A. Functionality of this predicted site was demonstrated by ChIP analysis. We next demonstrated that ARID3B induces expression of its targets in ovarian cancer cell lines. We validated that ARID3B binds to an epidermal growth factor receptor (EGFR) enhancer and increases mRNA expression. ARID3B also binds to the promoter of Wnt5A and its receptor FZD5. FZD5 is highly expressed in ovarian cancer cell lines, and is upregulated by exogenous ARID3B. Both ARID3B and FZD5 expression increase adhesion to extracellular matrix (ECM) components including collagen IV, fibronectin and vitronectin. ARID3B-increased adhesion to collagens II and IV require FZD5. This study directly demonstrates that ARID3B binds target genes in a sequence-specific manner, resulting in increased gene expression. Furthermore, our data indicate that ARID3B regulation of direct target genes in the Wnt pathway promotes adhesion of ovarian cancer cells. PMID:26121572

  9. Dynamic Treatment Regimes

    PubMed Central

    Chakraborty, Bibhas; Murphy, Susan A.

    2014-01-01

    A dynamic treatment regime consists of a sequence of decision rules, one per stage of intervention, that dictate how to individualize treatments to patients based on evolving treatment and covariate history. These regimes are particularly useful for managing chronic disorders, and fit well into the larger paradigm of personalized medicine. They provide one way to operationalize a clinical decision support system. Statistics plays a key role in the construction of evidence-based dynamic treatment regimes – informing best study design as well as efficient estimation and valid inference. Due to the many novel methodological challenges it offers, this area has been growing in popularity among statisticians in recent years. In this article, we review the key developments in this exciting field of research. In particular, we discuss the sequential multiple assignment randomized trial designs, estimation techniques like Q-learning and marginal structural models, and several inference techniques designed to address the associated non-standard asymptotics. We reference software, whenever available. We also outline some important future directions. PMID:25401119

  10. Pulse driven productivity in semi-arid lands

    NASA Astrophysics Data System (ADS)

    Bennett, A. C.; Collins, S. L.; Maurer, G. E.; Ruhi, A.; Litvak, M. E.

    2015-12-01

    carbon fluxes is in the size and sensitivity of both photosynthetic and respiratory responses. Understanding how these natural systems respond to rain is important for estimating future carbon storage capacity under altered precipitation regimes and assessing the potential contribution of arid and semi-arid ecosystems to the global carbon budget.

  11. Ecotoxicology of organisms adapted to life in temporary freshwater ponds in arid and semi-arid regions.

    PubMed

    Lahr, J

    1997-01-01

    Hot arid and semi-arid zones are characterized by an abundance of temporary ponds. Most of these depend on rain for their existence. These habitats are distinguished by fluctuating and unpredictable changes in their hydrological regime and of physical and chemical conditions.They contain a uniquely-adapted fauna that copes in different ways with changing and often extreme temperatures, oxygen levels, pH, salinity and turbidity. A classification is presented of the most distinctive adaptations,the various tactics that organisms apply to survive dry periods. The main strategies are dormancy (escape in time) and dispersal (escape in space). These adaptations may affect the impact of toxicants on individuals, populations and communities of temporary ponds. The physiological adaptations of species found in temporary ponds are likely to alter the sensitivity to pollutants of characteristic species. Results from laboratory experiments,for example, suggest that fairy shrimp (Branchiopoda, Anostraca) may react differently to heavy metals and pesticides as the standard test species Daphnia. Life history strategies influence recovery rates of populations after exposure to acutely toxic substances such as pesticides. It is also suggested that slow growth and decreased reproductive capacity of organisms caused by toxicants may, in ephemeral ponds, result in the failure of annual recruitment. Whether assemblages of organisms in temporary ponds are generally more vulnerable or more resilient than those in permanent waters or temperate regions could not be determined conclusively with the limited data available. Ecological concepts for studying the habitat and the development of risk assessment methods for temporary ponds are briefly discussed. PMID:9002434

  12. Satellite observation of aerosol - cloud interactions over semi-arid and arid land regions

    NASA Astrophysics Data System (ADS)

    Klüser, L.; Holzer-Popp, T.

    2012-04-01

    Satellite observations from three different sources are used to study the interactions between aerosol and ice clouds in five semi-arid and arid land regions over Africa and Asia, reaching from the South-African Kalahari to the Taklimakan and Gobi in Mongolia. (1) Six years of Aqua MODIS cloud and aerosol observations (including "Deep Blue" retrievals) which contain a qualitative separation into coarse and fine mode aerosol are analysed. (2) Five years of APOLLO cloud observations and SYNAER aerosol retrievals which allow discriminating between mineral dust and soot dominated cases from AATSR and SCIAMACHY on ENVISAT are exploited. (3) Moreover IASI provides one year of ice cloud and mineral dust observations over land retrieved with a newly developed method based on singular vector decomposition. Cloud top temperature observations are used to asses the state of convection and to statistically re-project observation distributions of cloud properties to background conditions. Then the difference between observation density distributions of background and re-projected aerosol-contaminated samples can be evaluated. By such way of analysis the influence of different cloud development stages, which also manifest in seasonal cycles of cloud properties, can be minimised. The analysis of the various observation density distributions shows that liquid water and ice effective radius is mainly decreased for increased total aerosol content for both aerosol types, biomass burning aerosols and mineral dust, separately. Two different modes of aerosol impacts on cloud optical depth can be shown. Optical depth is mainly increased, directly following the theory of the so-called "Twomey effect". In the West African Sahel a decrease of cloud water path (for both liquid water and ice) under the influence of absorbing aerosols results also in decreased optical depth. As at the same time the cloud fraction does not decrease under aerosol influence, the statistical decrease of mean

  13. Elementary and Secondary Education in Arid Lands.

    ERIC Educational Resources Information Center

    Wilson, Herbert B.

    The basic point to be considered in establishing a curriculum for elementary and secondary schools in the arid areas of the world is relevancy. Usually, the educational system of an area reflects the dominant culture of the political power in control. However, the educational system of the dominant culture might not be relevant to the people of…

  14. Applying animal behavior to arid rangeland mangement

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Livestock production is one of many demands placed on today’s arid rangelands. Therefore, understanding plant and animal biology and their effects on biotic and abiotic landscape components is fundamental if rangelands are to remain ecologically sustainable. One limiting factor to accomplishing posi...

  15. Aridity and decomposition processes in complex landscapes

    NASA Astrophysics Data System (ADS)

    Ossola, Alessandro; Nyman, Petter

    2015-04-01

    Decomposition of organic matter is a key biogeochemical process contributing to nutrient cycles, carbon fluxes and soil development. The activity of decomposers depends on microclimate, with temperature and rainfall being major drivers. In complex terrain the fine-scale variation in microclimate (and hence water availability) as a result of slope orientation is caused by differences in incoming radiation and surface temperature. Aridity, measured as the long-term balance between net radiation and rainfall, is a metric that can be used to represent variations in water availability within the landscape. Since aridity metrics can be obtained at fine spatial scales, they could theoretically be used to investigate how decomposition processes vary across complex landscapes. In this study, four research sites were selected in tall open sclerophyll forest along a aridity gradient (Budyko dryness index ranging from 1.56 -2.22) where microclimate, litter moisture and soil moisture were monitored continuously for one year. Litter bags were packed to estimate decomposition rates (k) using leaves of a tree species not present in the study area (Eucalyptus globulus) in order to avoid home-field advantage effects. Litter mass loss was measured to assess the activity of macro-decomposers (6mm litter bag mesh size), meso-decomposers (1 mm mesh), microbes above-ground (0.2 mm mesh) and microbes below-ground (2 cm depth, 0.2 mm mesh). Four replicates for each set of bags were installed at each site and bags were collected at 1, 2, 4, 7 and 12 months since installation. We first tested whether differences in microclimate due to slope orientation have significant effects on decomposition processes. Then the dryness index was related to decomposition rates to evaluate if small-scale variation in decomposition can be predicted using readily available information on rainfall and radiation. Decomposition rates (k), calculated fitting single pool negative exponential models, generally

  16. Contribution of Afforestation Practices to Changing Hydrology in Arid and Semi-arid Regions

    NASA Astrophysics Data System (ADS)

    Xie, X.; Meng, S.; Li, J.

    2014-12-01

    Arid and semi-arid regions are generally susceptible to land degeneration due to limited precipitation and high potential evapotranspiration (ET). Afforestation has been assumed to be a feasible strategy to conserve water and to improve ecological environment. For example, the Northern China, as a typical arid and semi-arid region has experienced large-scale and long-term afforestation practices since the early 1980s. The land cover has been altered to some degree as tree planting with increasing greenness. However, the effectiveness of afforestation might not be as expected due to the interference of climate change. In this study, we attempted to quantify the contribution of afforestation practices to the hydrological system in the Northern China. A macro-scale hydrological model, i.e., the Variable Infiltration Capacity (VIC), was employed to simulate ET, soil moisture and runoff for the period 1959 - 2009. Fractional simulation scenarios were designed regarding different conditions of land cover and climate changes. The results indicate that the land cover has minor impact on the variability of hydrological variables at regional scale, comparing with the climate change. Particularly, the decreasing precipitation plays a dominant role in shaping the trends of ET, soil moisture and runoff. The findings have significant implications for the implementation of the afforestation practices and for the management of water resources in arid and semi-arid regions.

  17. Aridity under conditions of increased CO2

    NASA Astrophysics Data System (ADS)

    Greve, Peter; Roderick, Micheal L.; Seneviratne, Sonia I.

    2016-04-01

    A string of recent of studies led to the wide-held assumption that aridity will increase under conditions of increasing atmospheric CO2 concentrations and associated global warming. Such results generally build upon analyses of changes in the 'aridity index' (the ratio of potential evaporation to precipitation) and can be described as a direct thermodynamic effect on atmospheric water demand due to increasing temperatures. However, there is widespread evidence that contradicts the 'warmer is more arid' interpretation, leading to the 'global aridity paradox' (Roderick et al. 2015, WRR). Here we provide a comprehensive assessment of modeled changes in a broad set of dryness metrics (primarily based on a range of measures of water availability) over a large range of realistic atmospheric CO2 concentrations. We use an ensemble of simulations from of state-of-the-art climate models to analyse both equilibrium climate experiments and transient historical simulations and future projections. Our results show that dryness is, under conditions of increasing atmospheric CO2 concentrations and related global warming, generally decreasing at global scales. At regional scales we do, however, identify areas that undergo changes towards drier conditions, located primarily in subtropical climate regions and the Amazon Basin. Nonetheless, the majority of regions, especially in tropical and mid- to northern high latitudes areas, display wetting conditions in a warming world. Our results contradict previous findings and highlight the need to comprehensively assess all aspects of changes in hydroclimatological conditions at the land surface. Roderick, M. L., P. Greve, and G. D. Farquhar (2015), On the assessment of aridity with changes in atmospheric CO2, Water Resour. Res., 51, 5450-5463

  18. Global semi-arid climate change over last 60 years

    NASA Astrophysics Data System (ADS)

    Huang, Jianping; Ji, Mingxia; Xie, Yongkun; Wang, Shanshan; He, Yongli; Ran, Jinjiang

    2016-02-01

    This study analyzes areal changes and regional climate variations in global semi-arid regions over 61 years (1948-2008) and investigates the dynamics of global semi-arid climate change. The results reveal that the largest expansion of drylands has occurred in semi-arid regions since the early 1960s. This expansion of semi-arid regions accounts for more than half of the total dryland expansion. The area of semi-arid regions in the most recent 15 years studied (1990-2004) is 7 % larger than that during the first 15 years (1948-1962) of the study period; this expansion totaled 0.4 × 106 and 1.2 × 106 km2 within the American continents and in the Eastern Hemisphere, respectively. Although semi-arid expansion occurred in both regions, the shifting patterns of the expansion are different. Across the American continents, the newly formed semi-arid regions developed from arid regions, in which the climate became wetter. Conversely, in the continental Eastern Hemisphere, semi-arid regions replaced sub-humid/humid regions, in which the climate became drier. The climate change in drying semi-arid regions over East Asia is primarily dominated by a weakened East Asian summer monsoon, while the wetting of semi-arid regions over North America is primarily controlled by enhanced westerlies.

  19. Dead Sea Water Sources during Periods of Extreme Aridity: Insights from U Isotopes

    NASA Astrophysics Data System (ADS)

    Olson, J. M.; Kiro, Y.; Goldstein, S. L.

    2015-12-01

    The Dead Sea is a hypersaline lake whose watershed spans the Mediterranean and Saharan-Arabian climate systems. Between 2010 and 2011, the ICDP-Dead Sea Deep Drilling Project recovered a sediment core that records ~200 ka of climate history in the region. The last interglacial (MIS 5e) included periods of extreme aridity in this region. This study aimed to characterize water sources into the lake during such critically dry periods. Geochemical analyses of aragonite, detritus, and halite samples waere carried out though a halite-rich interval during MIS 5e that represents a large drop in lake level, when discharge was less than half of modern levels. Uranium isotope activity ratios indicate a completely different hydrological regime during the driest periods in the Dead Sea, which is reflected by a major decrease of 234U/238U from 1.5, typical to the modern day and glacial high-stands of the lake, to ~1 . The decrease toward secular equilibrium happened gradually through the arid interval. Possible explanations include more southern sources coming into the lake, more flood events, addition dissolution of old salt (i.e. in secular equilibrium) by saline springs, and possibly shutdown of the Jordan River during extremely arid conditions. Further research will yield important information to prepare for future warming in the Middle East, a region where water access and droughts greatly affect socio-economic and political stability.

  20. Determining erosion and sedimentation chronology on semi-arid catchments using radioisotopes.

    NASA Astrophysics Data System (ADS)

    Polyakov, Viktor; Nichols, Mary; Nearing, Mark

    2015-04-01

    Semi-arid environment is defined by high magnitude, low frequency rainfalls that produce highly variable soil erosion rates. This study attempted to establish erosion dynamic of past 70 years on three small semi-arid catchments with history of grazing and vegetation change. Activity of Cs-137 and excess Pb-210 from 18 cores collected from sedimentation ponds were measured using gamma spectrometer. The sediment was dated using constant initial concentration (CIC) and constant rate of supply (CRS) models. These estimates were compared with direct measurement of aggradation from historic topographic surveys. Sedimentation in the ponds ranged between 3.1 and 5.4 cm/year and the long term average erosion rates on catchments varied between 0.8 and 1.4 t/ha/year. The distribution of excess Pb-210 in the cores was better described by CRS model. Estimated erosion rates were in agreement with those established by other methods for similar catchments in the region. Past variation in sedimentation rates were identified and correlated with recorded history of grazing, vegetation management, and anthropogenic disturbance. Cs-137 and Pb-210 methods are suitable for use in arid environment and can complement each other to increase reliability of sedimentation rate estimates under highly variable hydrologic regimes.

  1. Anomalous trend in soil evaporation in semi-arid, snow-dominated watersheds

    NASA Astrophysics Data System (ADS)

    Wang, R.; Kumar, M.

    2012-12-01

    Soil evaporation in arid and semi-arid regions is generally "moisture-limited". Evaporation in such regions shows an increasing trend with increase in magnitude of annual precipitation. This paper explores the trend in soil evaporation in a snow-dominated, semi-arid Reynolds Mountain East (RME) watershed by using a series of scenario experiments based on a linked snow melt and accumulation model with an integrated hydrology model. The results suggest that for the same hydrogeologic properties and meteorological conditions in the watershed, while the trend of annual soil evaporation with increasing annual rain shows an expected monotonic increase, the annual soil evaporation initially increases and then subsequently decreases with increasing annual precipitation for snow-dominated regimes. To further evaluate the controls on the existence of anomalous trends of evaporation, changes in the trend due to watershed characteristics such as watershed hydraulic conductivity, vegetation cover, and snowfall area fraction is systematically studied. The results show that the anomalous trend persists in a wide range of conditions, although the considered factors have significant influence both on the magnitude of the annual evaporation and the location of the inflection point in the trend curve. If validated, the results highlight the crucial role that snow accumulation and melt play on annual evaporation and water budget.

  2. Heterogeneous aquifer system modelisation under semi-arid climate

    NASA Astrophysics Data System (ADS)

    Drias, Tarek; Toubal, Ahmed Cherif

    2010-05-01

    The studied zone is a part of the Mellegne's (North-East of Algeria) under pound, this zone is characterised by its semi-arid climate. The water bearing system is formed by the plio-quaternairy alluviums resting on a marley substratuim of age Eocene. The geostatiscitcs approach of the hydrodynamics parameters (Hydrolic load, transmisivity) allowed the study of their spatial distrubution (casting) by the method of Krigeage by blocks and the identification of zones with water-bearing potentialities. In this respect, the zone of Ain Chabro which, is situated in the South of the plain shows the best values of the transmisivity...... The use of a bidimensinnel model in the differences ended in the permanent regime allowed us to establish the global balence sheet (overall assessment) of the tablecloth and to refine the transmisivity field. These would vary more exactley between 10-4 to 10-2 m²/s. The method associating the probability appraoch of Krigeage to that determining the model has facilited the wedging of the model and clarified the inflitration value. Keys words: hydrodynamics, geostatiscitcs, Modeling, Chabro, Tébessa.

  3. Water Through Life, A New Technique for Mapping Shallow Water Tables in Arid and Semi-Arid Climates using Color Infrared Aerial Photographs

    NASA Astrophysics Data System (ADS)

    Fielding, G.

    2003-04-01

    usefulness of the technique becomes greatly enhanced. By extending the analysis from 2D to 3D, the technique evolves from being a powerful descriptive tool for mapping the lateral extent of shallow groundwater into a very powerful predictive tool that can aid in unlocking the dynamics of shallow aquifers and groundwater flow regimes within basins in arid and semi-arid climates.

  4. Guatemalan forest synthesis after Pleistocene aridity

    PubMed Central

    Leyden, Barbara W.

    1984-01-01

    Sediments from two lakes in the Peten Department, Guatemala, provide palynological evidence from Central America of late Pleistocene aridity and subsequent synthesis of mesic forests. Late Glacial vegetation consisted of marsh, savanna, and juniper scrub. An early Holocene temperate forest preceded a mesic tropical forest with Brosimum (ramon). Thus “primeval” rain forests of Guatemala are no older than 10,000 to 11,000 years and are considerably younger in the Peten due to Mayan disturbances. Among dated Neotropical sites, the Peten has the most mesic vegetation yet shown to have supplanted xeric vegetation present during the Pleistocene. The arid late Glacial-humid early Holocene transition appears to have been pantropical in the lowlands. The Peten was not a Pleistocene refugium for mesophytic taxa, as has been suggested. Thus genesis of extant rain forests in northern Central America and southern Mexico remains unexplained. Images PMID:16593498

  5. VOCs in Arid soils: Technology summary

    SciTech Connect

    Not Available

    1994-02-01

    The Volatile Organic Compounds In Arid Soils Integrated Demonstration (VOC-Arid ID) focuses on technologies to clean up volatile organic compounds and associated contaminants in soil and groundwater at arid sites. The initial host site is the 200 West Area at DOE`s Hanford site in southeastern Washington state. The primary VOC contaminant is carbon tetrachloride, in association with heavy metals and radionuclides. An estimated 580--920 metric tons of carbon tetrachloride were disposed of between 1955 and 1973, resulting in extensive soil and groundwater contamination. The VOC-Arid ID schedule has been divided into three phases of implementation. The phased approach provides for: rapid transfer of technologies to the Environmental Restoration (EM-40) programs once demonstrated; logical progression in the complexity of demonstrations based on improved understanding of the VOC problem; and leveraging of the host site EM-40 activities to reduce the overall cost of the demonstrations. During FY92 and FY93, the primary technology demonstrations within the ID were leveraged with an ongoing expedited response action at the Hanford 200 West Area, which is directed at vapor extraction of VOCs from the vadose (unsaturated) zone. Demonstration efforts are underway in the areas of subsurface characterization including: drilling and access improvements, off-gas and borehole monitoring of vadose zone VOC concentrations to aid in soil vapor extraction performance evaluation, and treatment of VOC-contaminated off-gas. These current demonstration efforts constitute Phase 1 of the ID and, because of the ongoing vadose zone ERA, can result in immediate transfer of successful technologies to EM-40.

  6. Resource pulses, species interactions, and diversity maintenance in arid and semi-arid environments.

    PubMed

    Chesson, Peter; Gebauer, Renate L E; Schwinning, Susan; Huntly, Nancy; Wiegand, Kerstin; Ernest, Morgan S K; Sher, Anna; Novoplansky, Ariel; Weltzin, Jake F

    2004-10-01

    Arid environments are characterized by limited and variable rainfall that supplies resources in pulses. Resource pulsing is a special form of environmental variation, and the general theory of coexistence in variable environments suggests specific mechanisms by which rainfall variability might contribute to the maintenance of high species diversity in arid ecosystems. In this review, we discuss physiological, morphological, and life-history traits that facilitate plant survival and growth in strongly water-limited variable environments, outlining how species differences in these traits may promote diversity. Our analysis emphasizes that the variability of pulsed environments does not reduce the importance of species interactions in structuring communities, but instead provides axes of ecological differentiation between species that facilitate their coexistence. Pulses of rainfall also influence higher trophic levels and entire food webs. Better understanding of how rainfall affects the diversity, species composition, and dynamics of arid environments can contribute to solving environmental problems stemming from land use and global climate change. PMID:15069635

  7. Arid sites stakeholder participation in evaluating innovative technologies: VOC-Arid Site Integrated Demonstration

    SciTech Connect

    Peterson, T.S.; McCabe, G.H.; Brockbank, B.R.

    1995-05-01

    Developing and deploying innovative environmental cleanup technologies is an important goal for the U.S. Department of Energy (DOE), which faces challenging remediation problems at contaminated sites throughout the United States. Achieving meaningful, constructive stakeholder involvement in cleanup programs, with the aim of ultimate acceptance of remediation decisions, is critical to meeting those challenges. DOE`s Office of Technology Development sponsors research and demonstration of new technologies, including, in the past, the Volatile Organic Compounds Arid Site Integrated Demonstration (VOC-Arid ID), hosted at the Hanford Site in Washington State. The purpose of the VOC-Arid ID has been to develop and demonstrate new technologies for remediating carbon tetrachloride and other VOC contamination in soils and ground water. In October 1994 the VOC-Arid ID became a part of the Contaminant Plume Containment and Remediation Focus Area (Plume Focus Area). The VOC Arid ID`s purpose of involving stakeholders in evaluating innovative technologies will now be carried on in the Plume Focus Area in cooperation with Site Technology Coordination Groups and Site Specific Advisory Boards. DOE`s goal is to demonstrate promising technologies once and deploy those that are successful across the DOE complex. Achieving that goal requires that the technologies be acceptable to the groups and individuals with a stake in DOE facility cleanup. Such stakeholders include groups and individuals with an interest in cleanup, including regulatory agencies, Native American tribes, environmental and civic interest groups, public officials, environmental technology users, and private citizens. This report documents the results of the stakeholder involvement program, which is an integral part of the VOC-Arid ID.

  8. A quantitative comparison of Soil Development in four climatic regimes

    USGS Publications Warehouse

    Harden, J.W.; Taylor, E.M.

    1983-01-01

    A new quantitative Soil Development Index based on field data has been applied to chronosequences formed under different climatic regimes. The four soil chronosequences, developed primarily on sandy deposits, have some numeric age control and are located in xeric-inland (Merced, Calif.), xeric-coastal (Ventura, Calif.), aridic (Las Cruces, N. Mex.), and udic (Susquehanna Valley, Pa.) soil-moisture regimes. To quantify field properties, points are assigned for developmental increases in soil properties in comparison to the parent material. Currently ten soil-field properties are quantified and normalized for each horizon in a given chronosequence, including two new properties for carbonate-rich soils in addition to the eight properties previously defined. When individual properties or the combined indexes are plotted as a function of numeric age, rates of soil development can be compared in different climates. The results demonstrate that (1) the Soil Development Index can be applied to very different soil types, (2) many field properties develop systematically in different climatic regimes, (3) certain properties appear to have similar rates of development in different climates, and (4) the Profile Index that combines different field properties increases significantly with age and appears to develop at similar rates in different climates. The Soil Development Index can serve as a preliminary guide to soil age where other age control is lacking and can be used to correlate deposits of different geographical and climatic regions. ?? 1983.

  9. Examination Regimes and Student Achievement

    ERIC Educational Resources Information Center

    Cosentino de Cohen, Clemencia

    2010-01-01

    Examination regimes at the end of secondary school vary greatly intra- and cross-nationally, and in recent years have undergone important reforms often geared towards increasing student achievement. This research presents a comparative analysis of the relationship between examination regimes and student achievement in the OECD. Using a micro…

  10. Problems and Prospects of SWAT Model Application on an Arid/Semi-arid Watershed in Arizona

    EPA Science Inventory

    Hydrological characteristics in the semi-arid southwest create unique challenges to watershed modelers. Streamflow in these regions is largely dependent on seasonal, short term, and high intensity rainfall events. The objectives of this study are: 1) to analyze the unique hydrolo...

  11. Problems and Prospects of Swat Model Application on an Arid/Semi-Arid Watershed in Arizona

    EPA Science Inventory

    Hydrological characteristics in the semi-arid southwest create unique challenges to watershed modellers. Streamflow in these regions is largely dependent on seasonal, short term, and high intensity rainfall events. The objectives of this study are: 1) to analyze the unique hydrol...

  12. Use of composts in revegetating arid lands

    SciTech Connect

    Brandt, C.A.; Hendrickson, P.L.

    1991-09-01

    Compost has been suggested as a soil amendment for arid lands at the US Department of Energy's Hanford Site in southeastern Washington State. The operating contractor of the site, Westinghouse Hanford Company, requested that the Pacific Northwest Laboratory conduct a literature review to compile additional information on the use of compost amendments and their benefits. This report provides background information on the factors needed for plant growth and the consequences of severe soil disturbance. This report also discussed the characteristics of composts relative to other amendments and how they each affect plant growth. Finally,regulatory requirements that could affect land application of sludge-based compost on the Hanford Site are reviewed.

  13. Watershed Management in Arid Zones: A Prototype Short Course.

    ERIC Educational Resources Information Center

    Thames, John L., Ed.; Fischer, John N., Ed.

    Presented is information recommended for inclusion in a short course to help extend knowledge of water resource development and research techniques in arid and semi-arid regions. Information is particularly intended for applicability in developing nations. Included are considerations of livestock grazing, use of hydrologic data, vegetation…

  14. Demographic processes limiting seedling recruitment in arid grassland restoration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seeding is commonly used in plant community restoration to overcome recruitment limitations. In arid systems, seeding is a particularly important management tool because plant community recovery following disturbance is slow and often inhibited by invasive species. While important in arid systems,...

  15. Remote sensing of threshold conditions in an arid ecosystem

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Land management in the arid southwestern USA increasingly addresses thresholds in response to recent concepts adopted by private and public lands agencies and conservation organizations. Vegetation in arid rangelands typically presents as distinctive mosaics of vegetation patches, which persist in d...

  16. Uses of tree legumes in semi-arid regions

    SciTech Connect

    Felker, P.

    1980-01-01

    Uses of tree legumes in semi-arid and arid regions are reviewed. This review is divided into sections according to the following general use categories: fuels; human food; livestock food; to increase yields of crops grown beneath their canopies;and control of desertification. (MHR)

  17. Herbivore-plant interactions and desertification in arid lands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arid lands around the world have experienced or are currently experiencing degradation that is known as desertification. Animal-plant interactions that have an effect on desertification are among the most important function of animals in arid ecosystems. Desertification has been defined as land de...

  18. Food Production in Arid Regions as Related to Salinity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arid and semi arid regions of the world are generally associated with high population density and lower than average per capita incomes and living standards. These regions are vulnerable to food shortages due to current, unsustainable use of fresh water for irrigation and soil salinization. This pa...

  19. Sediment source determination using fallout Cesium-137 in arid rangelands.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sediment source identification in arid rangelands is necessary to understanding rangeland conditions and developing management practices to improve rangeland health and reduce sediment load to streams. The purpose of this research was to use Cesium-137 to identify sources of sediments in an arid ran...

  20. Optimizing conjunctive use of surface water and groundwater for irrigation in arid and semi-arid areas: an integrated modeling approach

    NASA Astrophysics Data System (ADS)

    Wu, Xin; Wu, Bin; Zheng, Yi; Tian, Yong; Liu, Jie; Zheng, Chunmiao

    2015-04-01

    In arid and semi-arid agricultural areas, groundwater (GW) is an important water source of irrigation, in addition to surface water (SW). Groundwater pumping would significantly alter the regional hydrological regime, and therefore complicate the water resources management process. This study explored how to optimize the conjunctive use of SW and GW for agricultural irrigation at a basin scale, based on integrated SW-GW modeling and global optimization methods. The improved GSFLOW model was applied to the Heihe River Basin, the second largest inland river basin in China. Two surrogate-based global optimization approaches were implemented and compared, including the well-established DYCORS algorithm and a new approach we proposed named as SOIM, which takes radial basis function (RBF) and support vector machine (SVM) as the surrogate model, respectively. Both temporal and spatial optimizations were performed, aiming at maximizing saturated storage change of midstream part conditioned on non-reduction of irrigation demand, constrained by certain annual discharge for the downstream part. Several scenarios for different irrigation demand and discharge flow are designed. The main study results include the following. First, the integrated modeling not only provides sufficient flexibility to formulation of optimization problems, but also makes the optimization results more physically interpretable and managerially meaningful. Second, the surrogate-based optimization approach was proved to be effective and efficient for the complex, time-consuming modeling, and is quite promising for decision-making. Third, the strong and complicated SW-GW interactions in the study area allow significant water resources conservation, even if neither irrigation demand nor discharge for the downstream part decreases. Under the optimal strategy, considerable part of surface water division is replaced by 'Stream leakage-Pump' process to avoid non-beneficial evaporation via canals. Spatially

  1. Mountains and arid climates of middle latitudes

    SciTech Connect

    Manabe, S.; Broccoli, A.J. )

    1990-01-12

    Simulations from a global climate model with and without orography have been used to investigate the role of mountains in maintaining extensive arid climates in middle latitudes of the Northern hemisphere. Dry climates similar to those observed were simulated over central Asia and western interior North America in the experiment with mountains, whereas relatively moist climates were simulated in these areas in the absence of orography. The experiments suggest that these interior regions are dry because general subsidence and relatively infrequent storm development occur upstream of orographically induced stationary wave troughs. Downstream of these troughs, precipitation-bearing storms develop frequently in association with strong jet streams. In contrast, both atmospheric circulation and precipitation were more zonally symmetric in the experiment without mountains. In addition, orography reduces the moisture transport into the continental interiors from nearby oceanic sources. The relative soil wetness of these regions in the experiment without mountains is consistent with paleoclimatic evidence of less aridity during the late Tertiary, before substantial uplift of the Rocky Mountains and Tibetan Plateau is believed to have occurred.

  2. Determine the optimum spectral reflectance of juniper and pistachio in arid and semi-arid region

    NASA Astrophysics Data System (ADS)

    Fadaei, Hadi; Suzuki, Rikie

    2012-11-01

    Arid and semi-arid areas of northeast Iran cover about 3.4 million ha are populated by two main tree species, the broadleaf Pistacia vera. L (pistachio) and the conifer Juniperus excelsa ssp. polycarpos (Persian juniper). Natural stands of pistachio in Iran are not only environmentally important but genetically essential as seed sources for pistachio production in orchards. In this study, we estimated the optimum spectral reflectance of juniper forests and natural pistachio stands using remote sensing to help in the sustainable management and production of pistachio in Iran. In this research spectral reflectance are able to specify of multispectral from Advanced Land Observing Satellite (ALOS) that provided by JAXA. These data included PRISM is a panchromatic radiometer with a 2.5 m spatial resolution at nadir, has one band with a wavelength of 0.52-0.77 μm and AVNIR-2 is a visible and near infrared radiometer for observing land and coastal zones with a 10 m spatial resolution at nadir, has four multispectral bands: blue (0.42-0.50 μm), green (0.52-0.60 μm), red (0.61-0.69 μm), and near infrared (0.76-0.89 μm). Total ratio vegetation index (TRVI) of optimum spectral reflectance of juniper and pistachio have been evaluated. The result of TRVI for Pistachio and juniper were (R2= 0.71 and 0.55). I hope this research can provide decision of managers to helping sustainable management for arid and semi-arid regions in Iran.

  3. Ecotonal Control on Vadose-Zone Fluxes in Arid Regions Over Very Long Time Scales

    NASA Astrophysics Data System (ADS)

    Phillips, F. M.; Walvoord, M. A.; Sandvig, R.

    2003-12-01

    Recent studies indicate that vegetation plays an important role in regulating recharge in semiarid and arid basins over very long time scales. Several lines of evidence from desert floor environments in the southwestern United States suggest that vegetation has established essentially permanent upward hydraulic gradients, effectively precluding diffuse recharge since the transition from woodland to xeric scrub in the early Holocene. However, less xeric vegetation (such as the pygmy piñon and juniper forest) may support significant diffuse recharge. We show comparative water potential and porewater chemistry profiles collected from various vegetation communities in the Chihuahuan Desert of west Texas. The modeled soil water (vapor and liquid) flux regimes illustrate a conversion from substantial downward fluxes under the mixed woodland to upward fluxes under grassland and xeric scrub. Model results also indicated a trend in increasing drying front propagation depth from the grassland to recently-encroached xeric scrub to well-established xeric scrub. Drying fronts are the result of upward soil water fluxes initiated up to 16 thousand years ago in the xeric scrub community. In contrast, the nearby woodland community supports active, and likely episodic, recharge on the order of 5 to 15 mm yr-1. The mechanism by which some vegetation takes up essentially all seasonally available moisture within the root zone, preventing downward soil water fluxes for periods of thousands of years, but adjacent vegetation communities regularly permit downward fluxes, remains to be determined. Nevertheless, these results suggest that understanding the relation between vegetation community and vadose-zone hydrological processes may be the most profitable avenue toward quantifying diffuse groundwater recharge. We hypothesize that vegetation type may be a reasonable proxy for estimating recharge in semiarid and arid basins. Ongoing research is intended to test the hypothesis of ecotonal

  4. Carbon isotopic evidence for increased aridity in northwestern Australia through the Quaternary

    NASA Astrophysics Data System (ADS)

    Pack, Sean M.; Miller, Gifford H.; Fogel, Marilyn L.; Spooner, Nigel A.

    2003-03-01

    Carbon isotopic records of bulk soil organic matter from two independent sedimentary sequences in the Lake Gregory region record vegetation change from monsoonal NW Australia. A broad isotopic enrichment of ˜16% through a 9-m-thick sedimentary sequence in the main basin is interpreted to indicate a shift from C 3 to C 4 plant dominance. A second isotopic record from a 4-m-thick sequence recovered southwest of the modern lakes corroborates this conclusion. Optically stimulated luminescence (OSL) dates of an eolian sand ( depth=60 cm) and fluvial sand ( depth=330 cm) from the 9-m sequence are 27.6±1.4 and 122.4±9.5 ka, respectively, indicating that the entire record is likely to span several hundred thousand years. C 4 plants dominate only after 120 ka. Conversion of C 3 woodland to C 4 grassland requires a decrease in total precipitation and increased seasonality of precipitation, reflecting a long-term trend toward a more arid and monsoon-dominated climate regime in NW Australia. The rapid shift from mixed C 3/C 4 to dominantly C 4 vegetation after 120 ka may reflect an acceleration of landscape change in the Late Quaternary. Other Australian records that indicate increased continental aridity in the Late Quaternary support the Lake Gregory evidence. However, neither of the Lake Gregory isotopic records mimics the global oxygen isotope record, suggesting that temperature has not played a significant role in forcing vegetation change in this region.

  5. Impacts of inundation and drought on eukaryote biodiversity in semi-arid floodplain soils.

    PubMed

    Baldwin, Darren S; Colloff, Matthew J; Rees, Gavin N; Chariton, Anthony A; Watson, Garth O; Court, Leon N; Hartley, Diana M; Morgan, Matthew J; King, Andrew J; Wilson, Jessica S; Hodda, Michael; Hardy, Christopher M

    2013-03-01

    Floodplain ecosystems are characterized by alternating wet and dry phases and periodic inundation defines their ecological character. Climate change, river regulation and the construction of levees have substantially altered natural flooding and drying regimes worldwide with uncertain effects on key biotic groups. In southern Australia, we hypothesized that soil eukaryotic communities in climate change affected areas of a semi-arid floodplain would transition towards comprising mainly dry-soil specialist species with increasing drought severity. Here, we used 18S rRNA amplicon pyrosequencing to measure the eukaryote community composition in soils that had been depleted of water to varying degrees to confirm that reproducible transitional changes occur in eukaryotic biodiversity on this floodplain. Interflood community structures (3 years post-flood) were dominated by persistent rather than either aquatic or dry-specialist organisms. Only 2% of taxa were unique to dry locations by 8 years post-flood, and 10% were restricted to wet locations (inundated a year to 2 weeks post-flood). Almost half (48%) of the total soil biota were detected in both these environments. The discovery of a large suite of organisms able to survive nearly a decade of drought, and up to a year submerged supports the concept of inherent resilience of Australian semi-arid floodplain soil communities under increasing pressure from climatic induced changes in water availability. PMID:23379967

  6. Nuclear-waste isolation in the unsaturated zone of arid regions

    SciTech Connect

    Wollenberg, H.A.; Wang, J.S.Y.; Korbin, G.

    1982-05-01

    The vadose zone in arid regions is considered as a possible environment for geologic isolation of nuclear waste. There are several topographic and lithologic combinations in the vadose zone of arid regions that may lend themselves to waste isolation considerations. In some cases, topographic highs such as mesas and interbasin ranges - comprised of several rock types, may contain essentially dry or partially saturated conditions favorable for isolation. The adjacent basins, especially in the far western and southwestern US, may have no surface or subsurface hydrologic connections with systems ultimately leading to the ocean. Some rock types may have the favorable characteristics of very low permeability and contain appropriate minerals for the strong chemical retardation of radionuclides. Environments exhibiting these hydrologic and geochemical attributes are the areas underlain by tuffaceous rocks, relatively common in the Basin and Range geomorphic province. Adjacent valley areas, where tuffaceous debris makes up a significant component of valley fill alluvium, may also contain thick zones of unsaturated material, and as such also lend themselves to strong consideration as respository environments. This paper summarizes the aspects of nuclear waste isolation in unsaturated regimes in alluvial-filled valleys and tuffaceous rocks of the Basin and Range province.

  7. Simulating Water Flow and Heat Transfer in Arid Soil Using Weighing Lysimeter Data

    NASA Astrophysics Data System (ADS)

    Dijkema, Jelle; Koonce, Jeremy; Ghezzehei, Teamrat; Berli, Markus; van der Ploeg, Martine; (Rien) van Genuchten, Martinus

    2015-04-01

    Deserts cover about one third of the Earth's land surface. Rather little though is known about the physics of desert soils and their implications for the ecology and hydrology of arid environments. The recently constructed weighing lysimeters located in Boulder City, Nevada, were designed to improve our understanding of the physical processes and properties of arid soils at the meter scale. In this study, we developed a HYDRUS-1D model to simulate water infiltration, hydraulic redistribution, and heat transfer for one of the lysimeters. HYDRUS-1D solves the coupled equations for water flow and heat transfer in variably saturated soil. Soil hydraulic and thermal properties were initialized based on prior knowledge and characterizations of the lysimeter soil. Soil hydraulic and thermal parameters were further refined by inverse simulation using a subset of the soil water content, water potential and temperature measurements at various depths. The model was validated using a separate portion of the soil moisture and temperature data set that was not used for calibration. The calibrated model provides a tool to virtually test future experiments in the lysimeters such as changes in the irrigation regime or the incorporation of plants. The model will also help to assess the impact of the placement of physical structures (such as solar panels) on the water and heat balance of desert soils.

  8. The origin of high-nitrate ground waters in the Australian arid zone

    NASA Astrophysics Data System (ADS)

    Barnes, C. J.; Jacobson, G.; Smith, G. D.

    1992-08-01

    Nitrate concentrations beyond the drinking-water limit of 10 mg1 -1 NO 3-N, are common in Australian arid-zone ground waters and are often associated with otherwise potable waters. In some aquifers nitrate-N concentrations of up to 80 mg1 -1 have been found, and this is a severe constraint on water supply development for small settlements. Water-bore data indicate a correlation of high-nitrate ground waters with shallow unconfined aquifers. Aguifer hydrochemistry indicats that these ground waters were emplaced by episodic Holocene recharge events in an otherwise arid climate regime. Nitrate has been flushed through the unsaturated zone which apparently lacks denitrification activity. The nitrate originates by near-surface biological fixation and contributing organisms include cyanobacteria in soil crusts and bacteria in termite mounds with the highest soil nitrate concentrations found in the outer skin of termite mounds. Bacteria associated with the termites appear to fix nitrogen, which eventually appears in an inorganic form, principally as ammonia. Nitrate is produced by bacterial oxidation of the ammonia, and is leached to the outside of the termite mound by capillary action. Diffuse recharge from extreme rainfall events then flushes this nitrate to the water table.

  9. Cloud regimes as phase transitions

    NASA Astrophysics Data System (ADS)

    Stechmann, Samuel N.; Hottovy, Scott

    2016-06-01

    Clouds are repeatedly identified as a leading source of uncertainty in future climate predictions. Of particular importance are stratocumulus clouds, which can appear as either (i) closed cells that reflect solar radiation back to space or (ii) open cells that allow solar radiation to reach the Earth's surface. Here we show that these clouds regimes -- open versus closed cells -- fit the paradigm of a phase transition. In addition, this paradigm characterizes pockets of open cells as the interface between the open- and closed-cell regimes, and it identifies shallow cumulus clouds as a regime of higher variability. This behavior can be understood using an idealized model for the dynamics of atmospheric water as a stochastic diffusion process. With this new conceptual viewpoint, ideas from statistical mechanics could potentially be used for understanding uncertainties related to clouds in the climate system and climate predictions.

  10. Nitrogen cycling: water use efficiency interactions in semi-arid ecosystems in relation to management of tree legumes (Prosopis)

    SciTech Connect

    Felker, P.; Clark, P.R.; Osborn, J.; Cannell, G.H.

    1980-04-01

    Plant productivity in semi-arid ecosystems is often limited by soil fertility as much as it is by moisture availability. A quantitative assessment of nitrogen limitations on water use efficiency has been made after careful review of plant water use efficiency data at high and low soil fertilities and after careful review of nitrogen inputs to semi arid ecosystems in the form of: blue-green algae-lichen crusts; non-symbiotic nitrogen fixers; rainfall; and tree legumes. This analysis indicates that plant productivity in semi-arid regions may be 10 fold more limited by nitrogen than moisture availability. Forage yields of non-nitrogen fixing trees and shrubs could be greatly increased by interplanting with drought adapted nitrogen fixers such as Prosopis and Acacia. Calculations based on water use efficiencies of annual legumes and nitrogen fixation values of tree legumes predict that well managed, spaced, and cared for orchards of specially selected Prosopis could produce 4000 Kgha/sup -1/ yr/sup -1/ of 13% protein pods at 500 mm annual rainfall with only light fertilization with phosphate, potassium and sulfur. Field measurements of pod yields for 25 selections of 3 year old Prosopis grown under managed orchard conditions in southern California are presented. Spacing regimes and harvesting techniques for Prosopis are proposed to facilitate pod production.

  11. Spatial and temporal diversity and abundance of ammonia oxidizers in semi-arid and arid soils: indications for a differential seasonal effect on archaeal and bacterial ammonia oxidizers.

    PubMed

    Sher, Yonatan; Zaady, Eli; Nejidat, Ali

    2013-12-01

    Besides water, nitrogen is the limiting factor for biomass production in arid ecosystems. Global climatic changes are exacerbating aridity levels, and the response of nitrogen-transforming microorganisms to these changes is not clear yet. Using semi-arid and arid ecosystems as surrogates for conditions of increased aridity, we investigated the activity, abundance, and diversity of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in arid and semi-arid soils. Ammonia oxidation potentials were higher during the winter in both sites than in the summer, and higher nitrate concentrations were measured in the arid soil than in the semi-arid soil. Denaturing gradient gel electrophoresis (DGGE) patterns of AOB 16S rRNA gene fragments were similar for the arid and semi-arid soils with no seasonal variations. In contrast, the DGGE patterns of the AOA amoA gene fragments differed between the sites and a soil transfer experiment suggested that these differences are possibly associated with soil type. AOB numbers were higher during the winter than in the summer, while AOA numbers were higher during the summer. The results indicate the resistance of AOB and AOA community structure to arid conditions, albeit with seasonal variations in their abundance. Together, the results suggest the resilience of nitrification activity to increased aridity level. PMID:23855990

  12. Quantifying the thermal heat requirement of Brassica in assessing biophysical parameters under semi-arid microenvironments

    NASA Astrophysics Data System (ADS)

    Adak, Tarun; Chakravarty, N. V. K.

    2010-07-01

    Evaluation of the thermal heat requirement of Brassica spp. across agro-ecological regions is required in order to understand the further effects of climate change. Spatio-temporal changes in hydrothermal regimes are likely to affect the physiological growth pattern of the crop, which in turn will affect economic yields and crop quality. Such information is helpful in developing crop simulation models to describe the differential thermal regimes that prevail at different phenophases of the crop. Thus, the current lack of quantitative information on the thermal heat requirement of Brassica crops under debranched microenvironments prompted the present study, which set out to examine the response of biophysical parameters [leaf area index (LAI), dry biomass production, seed yield and oil content] to modified microenvironments. Following 2 years of field experiments on Typic Ustocrepts soils under semi-arid climatic conditions, it was concluded that the Brassica crop is significantly responsive to microenvironment modification. A highly significant and curvilinear relationship was observed between LAI and dry biomass production with accumulated heat units, with thermal accumulation explaining ≥80% of the variation in LAI and dry biomass production. It was further observed that the economic seed yield and oil content, which are a function of the prevailing weather conditions, were significantly responsive to the heat units accumulated from sowing to 50% physiological maturity. Linear regression analysis showed that growing degree days (GDD) could indicate 60-70% variation in seed yield and oil content, probably because of the significant response to differential thermal microenvironments. The present study illustrates the statistically strong and significant response of biophysical parameters of Brassica spp. to microenvironment modification in semi-arid regions of northern India.

  13. Native, Arid Green Design: Strategies to Combat Urban Heat Island Effect

    NASA Astrophysics Data System (ADS)

    Tepler, S. K.; Pavao-Zuckerman, M.; Livingston, M.; Smith, S. E.; Stoltz, R.

    2010-12-01

    The heat island effect has one of the greatest impacts on the biogeochemistry of urban microclimates. As cities grow hotter from climate change and increased energy consumption, the effect on urban ecosystem function will likely intensify. One strategy for ameliorating local elevated temperatures is to use green design to alter energy balances and reduce energy demands for cooling. In arid environments, however, little is known about how to balance needs for energy reduction with water costs associated with green roof installations in cities. We are conducting a pilot study to investigate strategies to implement green roofs in arid cities that are environmentally ‘responsible’ with respect to water consumption. In this study we ask, (a) is green roof technology appropriate for a desert city, (b) if native plants and environmentally responsible watering regimes are used, will ecosystem services we seek from green roofs be supported, and (c) would such an installation meet building code requirements. Small-plot model green roofs are constructed on the campus of Biosphere 2, near Oracle, AZ. The study design crosses two artificial soil types (a heavy and light mix made of different proportions of sand, organic materials, and a lightweight porous material [SOILMatrixTM], two irrigation regimes (ambient and drip irrigated), and three plant species (succulent: Hesparaloe parviflora; shrub: Calliandra eriophylla; grass: Cathestecum erectum) in initial tests. To address the questions we are posing, we compare energy balance of the plots, water status and health of the plants, and soil water contents. EPA MIST models indicate that plant cover has the potential to reduce average temperatures by 4 to 8°C, resulting in energy savings of 3 - 6% kWhr/ft2. In preliminary tests we found that the dry weights of our environmentally accurate rocky soil mixes were well under 40 lbs per sq. ft., the building code limit. Preliminary results from the first season of data collection

  14. Arid Lands--A Study in Ecological Disaster

    ERIC Educational Resources Information Center

    Eckholm, Erik

    1977-01-01

    Reports that over-grazing and unsound agricultural practices are increasing the world-wide amount of uninhabitable land. Cites some practices which have been used to successfully reclaim arid land areas. (CP)

  15. Aridity changes in the Tibetan Plateau in a warming climate

    SciTech Connect

    Gao, Yanhong; Li, Xia; Leung, Lai-Yung R.; Chen, Deliang; Xu, Jianwei

    2015-03-10

    Desertification in the Tibetan Plateau (TP) has drawn increasing attention in the recent decades. It has been postulated as a consequence of climate aridity due to the observed warming. This study quantifies the aridity changes in the TP and attributes the changes to different climatic factors. Using the ratio of P/PET (precipitation to potential evapotranspiration) as an aridity index to indicate changes in dryness and wetness in a given area, P/PET was calculated using observed records at 83 stations in the TP, with PET calculated using the Penman–Monteith (PM) algorithm. Spatial and temporal changes of P/PET in 1979-2011 are analyzed. Results show that stations located in the arid and semi-arid northwestern TP are becoming significantly wetter and stations in the semi-humid southeastern TP are becoming drier, though not significantly, in the recent three decades. The aridity change patterns are significantly correlated with precipitation, sunshine duration and diurnal temperature range changes at confidence level of 99.9% from two-tail t-test. Temporal correlations also confirm the significant correlation between aridity changes with the three variables, with precipitation being the most dominant driver of P/PET changes at interannual time scale. PET changes are insignificant but negatively correlated with P/PET in the cold season. In the warm season, however, correlation between PET changes and P/PET changes are significant at confidence level of 99.9% when the cryosphere melts near the surface. Significant correlation between wind speed changes and aridity changes occurs in limited locations and months. Consistency in the climatology pattern and linear trends in surface air temperature and precipitation calculated using station data, gridded data, and nearest grid-to-stations for the TP average and across sub-basins indicate the robustness of the trends despite the large spatial heterogeneity in the TP that challenge climate monitoring.

  16. Aridity changes in the Tibetan Plateau in a warming climate

    DOE PAGESBeta

    Gao, Yanhong; Li, Xia; Leung, Lai-Yung R.; Chen, Deliang; Xu, Jianwei

    2015-03-10

    Desertification in the Tibetan Plateau (TP) has drawn increasing attention in the recent decades. It has been postulated as a consequence of climate aridity due to the observed warming. This study quantifies the aridity changes in the TP and attributes the changes to different climatic factors. Using the ratio of P/PET (precipitation to potential evapotranspiration) as an aridity index to indicate changes in dryness and wetness in a given area, P/PET was calculated using observed records at 83 stations in the TP, with PET calculated using the Penman–Monteith (PM) algorithm. Spatial and temporal changes of P/PET in 1979-2011 are analyzed.more » Results show that stations located in the arid and semi-arid northwestern TP are becoming significantly wetter and stations in the semi-humid southeastern TP are becoming drier, though not significantly, in the recent three decades. The aridity change patterns are significantly correlated with precipitation, sunshine duration and diurnal temperature range changes at confidence level of 99.9% from two-tail t-test. Temporal correlations also confirm the significant correlation between aridity changes with the three variables, with precipitation being the most dominant driver of P/PET changes at interannual time scale. PET changes are insignificant but negatively correlated with P/PET in the cold season. In the warm season, however, correlation between PET changes and P/PET changes are significant at confidence level of 99.9% when the cryosphere melts near the surface. Significant correlation between wind speed changes and aridity changes occurs in limited locations and months. Consistency in the climatology pattern and linear trends in surface air temperature and precipitation calculated using station data, gridded data, and nearest grid-to-stations for the TP average and across sub-basins indicate the robustness of the trends despite the large spatial heterogeneity in the TP that challenge climate monitoring.« less

  17. Investigating Satellite Microwave observations of Precipitation in Different Climate Regimes

    NASA Astrophysics Data System (ADS)

    Wang, N.; Ferraro, R. R.

    2013-12-01

    Microwave satellite remote sensing of precipitation over land is a challenging problem due to the highly variable land surface emissivity, which, if not properly accounted for, can be much greater than the precipitation signal itself, especially in light rain/snow conditions. Additionally, surfaces such as arid land, deserts and snow cover have brightness temperature characteristics similar to precipitation Ongoing work by GPM microwave radiometer team is constructing databases through a variety of means, however, there is much uncertainty as to what is the optimal information needed for the wide array of sensors in the GPM constellation, including examination of regional conditions. The original data sets will focus on stratification by emissivity class, surface temperature and total perceptible water. We'll perform sensitivity studies to determine the potential role of ancillary data (e.g., land surface temperature, snow cover/water equivalent, etc.) to improve precipitation estimation over land in different climate regimes, including rain and snow. In other words, what information outside of the radiances can help describe the background and subsequent departures from it that are active precipitating regions? It is likely that this information will be a function of the various precipitation regimes. Statistical methods such as Principal Component Analysis (PCA) will be utilized in this task. Databases from a variety of sources are being constructed. They include existing satellite microwave measurements of precipitating and non-precipitating conditions, ground radar precipitation rate estimates, surface emissivity climatology from satellites, surface temperature and TPW from NWP reanalysis. Results from the analysis of these databases with respect to the microwave precipitation sensitivity to the variety of environmental conditions in different climate regimes will be discussed.

  18. Spatiotemporal trends in mean temperatures and aridity index over Rwanda

    NASA Astrophysics Data System (ADS)

    Muhire, I.; Ahmed, F.

    2016-01-01

    This study aims at quantifying the trends in mean temperatures and aridity index over Rwanda for the period of 1961-1992, based on analysis of climatic data (temperatures, precipitations, and potential evapotranspiration). The analysis of magnitude and significance of trends in temperatures and aridity index show the degree of climate change and mark the level of vulnerability to extreme events (e.g., droughts) in different areas of the country. The study reveals that mean temperatures increased in most parts of the country, with a significant increase observed in the eastern lowlands and in the southwestern parts. The highlands located in the northwest and the Congo-Nile crest showed a nonsignificant increase in mean temperatures. Aridity index increased only in March, April, October, and November, corresponding with the rainy seasons. The remaining months of the year showed a decreasing trend. At an annual resolution, the highlands and the western region showed a rise in aridity index with a decreasing pattern over the eastern lowlands and the central plateau. Generally, the highlands presented a nonsignificant increase in mean temperatures and aridity index especially during the rainy seasons. The eastern lowlands showed a significant increase in mean temperatures and decreasing trends in aridity index. Therefore, these areas are bound to experience more droughts, leading to reduced water and consequent decline in agricultural production. On the other hand, the north highlands and southwest region will continue to be more productive.

  19. Flow regime change in an Endorheic basin in Southern Ethiopia

    NASA Astrophysics Data System (ADS)

    Worku, F. F.; Werner, M.; Wright, N.; van der Zaag, P.; Demissie, S.

    2014-01-01

    Endorheic basins, often found in semi-arid and arid climates, are particularly sensitive to changes in climatological fluxes such as precipitation, evaporation and runoff, resulting in variability of river flows as well as of water levels in end-point lakes that are often present. In this paper we apply the Indicators of Hydrological Alteration (IHA) to characterise change to the natural flow regime of the Omo-Ghibe basin in Southern Ethiopia. This endorheic basin is considered relatively pristine, with the basin being the main source of flow to Lake Turkana, the end-point lake in the East-African rift valley. The water level in Lake Turkana shows significant fluctuation, but an increasing trend can be observed over the past 20 yr. The reasons are currently not well understood. Of the five groups of metrics in the IHA, only those related to magnitude were found to show significant trends, with the main trend being the increase of flow during the dry season. This trend was not reflected in climatological drivers such as rainfall, evaporation, and temperature (which shows an increasing trend), but rather is attributed to the substantial changes in Land Use and Land Cover (LULC) in the basin. The impact on the basin hydrology is apparent mainly in the more humid part of the basin. The significant shift from forest and woodland to grassland and cropland results in a decrease of actual evaporation and subsequent increase in (dry season) runoff. The long term trend of the increasing levels in lake Turkana are related to these trends in dry season flows, while shorter term fluctuations of the lake levels are attributed primarily to anomalies in consecutive wet and dry season rainfall.

  20. Flow regime change in an endorheic basin in southern Ethiopia

    NASA Astrophysics Data System (ADS)

    Worku, F. F.; Werner, M.; Wright, N.; van der Zaag, P.; Demissie, S. S.

    2014-09-01

    Endorheic basins, often found in semi-arid and arid climates, are particularly sensitive to variation in fluxes such as precipitation, evaporation and runoff, resulting in variability of river flows as well as of water levels in end-point lakes that are often present. In this paper we apply the indicators of hydrological alteration (IHA) to characterise change to the natural flow regime of the Omo-Ghibe Basin in southern Ethiopia. Little water resource infrastructure has been developed in the basin to date, and it is considered pristine. The basin is endorheic and is the main source of flow to Lake Turkana in the East African Rift Valley. The water level in Lake Turkana shows significant fluctuation, but increase of its level can be observed over the past 20 years. The reasons are currently not well understood. Of the five groups of hydrological characteristics in the IHA (magnitude, timing, duration, frequency and variability), only those related to magnitude were found to show significant trends, with the main trend being the increase of flow during the dry season. This trend was not reflected in climatological drivers such as rainfall, evaporation and temperature (which shows a positive trend), but rather is attributed to the substantial changes in land use and land cover in the basin. The change in the basin hydrology is apparent mainly in the more humid part of the basin. The significant shift from forest and woodland to grassland and cropland results in a decrease of actual evaporation and subsequent increase in (dry season) runoff. The long-term trend of the increasing levels in Lake Turkana are related to these trends in dry season flows, while shorter-term fluctuations of the lake levels are attributed primarily to anomalies in consecutive wet and dry season rainfall.

  1. Arid Lands Ecology Facility management plan

    SciTech Connect

    1993-02-01

    The Arid Lands Ecology (ALE) facility is a 312-sq-km tract of land that lies on the western side of the Hanford Site in southcentral Washington. The US Atomic Energy Commission officially set aside this land area in 1967 to preserve shrub-steppe habitat and vegetation. The ALE facility is managed by Pacific Northwest Laboratory (PNL) for the US Department of Energy (DOE) for ecological research and education purposes. In 1971, the ALE facility was designated the Rattlesnake Hills Research Natural Area (RNA) as a result of an interagency federal cooperative agreement, and remains the largest RNA in Washington. it is also one of the few remaining large tracts of shrub-steppe vegetation in the state retaining a predominant preeuropean settlement character. This management plan provides policy and implementation methods for management of the ALE facilities consistent with both US Department of Energy Headquarters and the Richland Field Office decision (US Congress 1977) to designate and manage ALE lands as an RNA and as a component of the DOE National Environmental Research Park System.

  2. Late glacial aridity in southern Rocky Mountains

    SciTech Connect

    Davis, O.K.; Pitblado, B.L.

    1995-09-01

    While the slopes of the present-day Colorado Rocky Mountains are characterized by large stands of subalpine and montane conifers, the Rockies of the late glacial looked dramatically different. Specifically, pollen records suggest that during the late glacial, Artemisia and Gramineae predominated throughout the mountains of Colorado. At some point between 11,000 and 10,000 B.P., however, both Artemisia and grasses underwent a dramatic decline, which can be identified in virtually every pollen diagram produced for Colorado mountain sites, including Como Lake (Sangre de Cristo Mountains), Copley Lake and Splains; Gulch (near Crested Butte), Molas Lake (San Juan Mountains), and Redrock Lake (Boulder County). Moreover, the same pattern seems to hold for pollen spectra derived for areas adjacent to Colorado, including at sites in the Chuska Mountains of New Mexico and in eastern Wyoming. The implications of this consistent finding are compelling. The closest modem analogues to the Artemisia- and Gramineae-dominated late-glacial Colorado Rockies are found in the relatively arid northern Great Basin, which suggests that annual precipitation was much lower in the late-glacial southern Rocky Mountains than it was throughout the Holocene.

  3. Keeping Sediment and Nutrients out of Streams in Arid/Semi-Arid Regions: Application of Low Impact Development/Green Infrastructure Practices

    NASA Astrophysics Data System (ADS)

    Yongping, Yuan

    2015-04-01

    Climatic and hydrological characteristics in the arid/semi-arid areas create unique challenges to soil, water and biodiversity conservation. These areas are environmentally sensitive, but very valuable for the ecosystems services they provide to society. Some of these areas are experiencing the fastest urbanization and now face multiple water resource challenges. Low Impact Development (LID)/Green Infrastructure (GI) practices are increasingly popular for reducing stormwater and nonpoint source pollution in many regions around the world. However, streamflow in the arid/semi-arid regions is largely dependent on seasonal, short term, and high intensity rainfall events. LID has not been very common in the arid/semi-arid regions due to a lack of performance evaluation, as well as the perception that LID may not be very useful for regions with little annual precipitation. This study focused on investigating the hydrologic and pollutant removal performance of LID/GI systems in arid/semi-arid climates. Ten types of practices were found in use in the Western/Southwestern U.S.: rainwater harvest systems, detention ponds, retention ponds, bioretention, media filters, porous pavements, vegetated swales/buffer/strips, green roofs, infiltration trenches, and integrated LIDs. This study compared the performance of these practices in terms of their effectiveness at pollutant removal and cost-effectiveness. This analysis provides insight into the future implementation of LID/GI in the arid/semi-arid areas. Key words: LID/GI, arid/semi-arid, effectiveness of pollutant removal, cost-effectiveness analysis

  4. Comprehensive assessment of projected changes in water availability and aridity

    NASA Astrophysics Data System (ADS)

    Greve, Peter; Seneviratne, Sonia I.

    2015-04-01

    Substantial changes in the hydrological cycle are projected for the 21st century, with potential major impacts, particularly at regional scale. However, the projections are subject to major uncertainties and the metrics generally used to assess such changes do not fully account for the hydroclimatological characteristics of the land surface. In this context, the 'dry gets drier, wet gets wetter' paradigm is often used as a simplifying summary. However, recent studies have challenged the validity of the paradigm both for observations (Greve et al., 2014) and projections (Roderick et al., 2014), especially casting doubt on applying the widely used P-E (precipitation - evapotranspiration) metric over global land surfaces. Here we show in a comprehensive assessment that projected changes in mean annual P-E are generally not significant in most land areas, with the exception of the northern high latitudes where significant changes towards wetter conditions are found. We further show that the combination of decreasing P and increasing atmospheric demand (potential evapotranspiration, Ep) leads to a significant increase in aridity in many subtropical and neighbouring regions, thus confirming the paradigm for some dry regions, but invalidating it for the relative large fraction of the affected area which is currently in a humid or transitional climate regime. Combining both metrics (P-E and P-E_p) we conclude that the 'dry gets drier, wet gets wetter' paradigm is generally not confirmed for projected changes in most land areas (despite notable exceptions in the high latitudes and subtropics), because of a lack of robustness of the projected changes in some regions (tropics) and because humid to transitional regions are shifting to drier conditions, i.e. not following the paradigm. References Greve, P., Orlowsky, B., Mueller, B., Sheffield, J., Reichstein, M., & Seneviratne, S. I. Global assessment of trends in wetting and drying over land. Nature Geosci. 7, 716-721 (2014

  5. A Sediment Budget for a Semi-arid Reservoir

    NASA Astrophysics Data System (ADS)

    Rathburn, S. L.; Finley, J. B.; Smith, S. R.

    2002-12-01

    Sediment accumulation within reservoirs poses a continued threat to reservoir storage capacity and decreases the operating efficiency and expected life of a dam. Numerous small irrigation reservoirs built during the last century in the semi-arid western U.S. are undergoing siltation at rates that make active sediment management plans imperative. Managers of Halligan Reservoir on the North Fork Cache la Poudre River in northern Colorado are incorporating a sediment budget into sediment management practices. Data collection for the sediment budget began during the spring 2002 snowmelt. Sediment and water discharge were measured upstream of the reservoir during the months April-June, with the same measurements collected downstream from the reservoir during the fall draw-down in early September. Because of the abnormally low snowpack during Spring 2002, peak discharge upstream never exceeded 1.5 m3/s (one order of magnitude lower than during an average year) over the course of the field measurements, and maximum suspended and bedload transport rates were 9.7E-07 and 0.17 metric tons/day, respectively. As such, the delivery of sediment into Halligan Reservoir during 2002 was severely limited. Fall releases of sediment have historically been used to regain storage capacity in the reservoir. Suspended sediment transport rates downstream from the dam, measured during a two-day step-down in September, were significantly higher than inflow rates measured in the spring. An important control on sediment influx into the reservoir is beaver dam storage. One beaver dam within the upstream study reach currently stores 3.6 m3 of fine-grained sediment behind the beaver dam. Bathymetric surveys of the sediment accumulation within Halligan Reservoir indicate that maximum accumulation occurs near the dam, up to thicknesses of 4.5 m. Similar measurements will be repeated during the spring 2003 snowmelt to further quantify the sediment flux into and out of the reservoir over a range of

  6. Predicted performance of clay-barrier landfill covers in arid and semi-arid environments.

    PubMed

    Sadek, S; Ghanimeh, S; El-Fadel, M

    2007-01-01

    Conventional landfill cover systems for municipal solid waste include low-permeability compacted clay barriers to minimize infiltration into the landfilled waste. Such layers are vulnerable in climates where arid to semi-arid conditions prevail, whereby the clay cover tends to desiccate and crack, resulting in drastically higher infiltration, i.e., lower cover efficiency. To date, this phenomenon, which has been reported in field observations, has not been adequately assessed. In this paper, the performance of a cover system solely relying on a clay barrier was simulated using a numerical finite element formulation to capture changes in the clay layer and the corresponding modified hydraulic characteristics. The cover system was guided by USEPA Subtitle-D minimum requirements and consisted of a clay layer underlying a protective vegetated soil. The intrinsic characteristics of the clay barrier and vegetative soil cover, including their saturated hydraulic conductivities and their soil-water characteristic curves, were varied as warranted to simulate intact or "cracked" conditions as determined through the numerical analyses within the proposed methodology. The results indicate that the levels of percolation through the compromised or cracked cover were up to two times greater than those obtained for intact covers, starting with an intact clay hydraulic conductivity of 10(-5)cm/s. PMID:16987648

  7. Non-isothermal water flow in the vadose zone of arid and semi-arid environments

    NASA Astrophysics Data System (ADS)

    Mallants, Dirk; Gerke, Kirill; Cook, Peter

    2013-04-01

    In desert environments thermally-driven vapour flow can be an important component of the total water flux in soils. As such, vapour flow can have considerable impact on recharge estimation, with small errors in soil water flow rates resulting in relatively larger errors in the recharge estimates since recharge is a very small fraction of rainfall. The additional effects of vegetation and temperature contributions may also impact soil water movement and thus calculated recharge rates in arid and semi-arid vadose zones. Currently most methods for estimating large-scale recharge rates do not consider these various processes, which adds an unknown degree of uncertainty to recharge estimation. The HYDRUS-1D numerical simulator was used to simulate coupled isothermal liquid, isothermal vapour, non-isothermal liquid and vapour flow, and heat flow in deep variably saturated vadose zones. The considered climatic conditions are characteristic of central Australia with approximate mean annual precipitation and potential evapotranspiration rates of 300 and 3000 mm, respectively. A time series of 130 years of daily climate data provides the upper boundary conditions. Groundwater recharge under highly erratic rainfall conditions is hypothesized to be primarily episodic and linked to flood events which may be significant only once every few years. The combined effect of vegetation and temperature on water flow and soil water redistribution is discussed for both vegetated and bare soils.

  8. The emerging climate change regime

    SciTech Connect

    Bodansky, D.M.

    1995-11-01

    The emerging climate change regime--with the UN Framework Convention on Climate Change (FCCC) at its core--reflects the substantial uncertainties, high stakes and complicated politics of the greenhouse warming issue. The regime represents a hedging strategy. On the one hand, it treats climate change as a potentially serious problem, and in response, creates a long-term, evolutionary process to encourage further research, promote national planning, increase public awareness, and help create a sense of community among states. But it requires very little by way of substantive--and potentially costly--mitigation or adaptation measures. Although the FCCC parties have agreed to negotiate additional commitments, substantial progress is unlikely without further developments in science, technology, and public opinion. The FCCC encourages such developments, and is capable of evolution and growth, should the political will to take stronger international action emerge. 120 refs., 3 tabs.

  9. Optics in the Relativistic Regime

    NASA Astrophysics Data System (ADS)

    Tajima, Toshiki

    2012-06-01

    Optics has extended the frontier of low energy physics. Here we present the progress in the opposite direction of relativistic intensity regime of optics. With intense and large energy laser, particles may be accelerated to high energies via laser wakefield acceleration (Tajima and Dawson, 1979) over a compact distance orders of magnitude shorter than the RF approach. We should be able to accelerate electrons (over 30m) and ions (over cm) toward TeV with an existing kJ laser. We can check Lorentz invariance in the ultrarelativistic regime. Further, laser allows us to explore the presence of weakly coupling fields such as Dark Matter and Dark Energy with an unprecedented sensitivity. We call this emerging capability as the Laser Particle Physics Paradigm (LP^3).

  10. Demystifying optimal dynamic treatment regimes.

    PubMed

    Moodie, Erica E M; Richardson, Thomas S; Stephens, David A

    2007-06-01

    A dynamic regime is a function that takes treatment and covariate history and baseline covariates as inputs and returns a decision to be made. Murphy (2003, Journal of the Royal Statistical Society, Series B 65, 331-366) and Robins (2004, Proceedings of the Second Seattle Symposium on Biostatistics, 189-326) have proposed models and developed semiparametric methods for making inference about the optimal regime in a multi-interval trial that provide clear advantages over traditional parametric approaches. We show that Murphy's model is a special case of Robins's and that the methods are closely related but not equivalent. Interesting features of the methods are highlighted using the Multicenter AIDS Cohort Study and through simulation. PMID:17688497

  11. Hall effect in hopping regime

    NASA Astrophysics Data System (ADS)

    Avdonin, A.; Skupiński, P.; Grasza, K.

    2016-02-01

    A simple description of the Hall effect in the hopping regime of conductivity in semiconductors is presented. Expressions for the Hall coefficient and Hall mobility are derived by considering averaged equilibrium electron transport in a single triangle of localization sites in a magnetic field. Dependence of the Hall coefficient is analyzed in a wide range of temperature and magnetic field values. Our theoretical result is applied to our experimental data on temperature dependence of Hall effect and Hall mobility in ZnO.

  12. The International Climate Change Regime

    NASA Astrophysics Data System (ADS)

    Yamin, Farhana; Depledge, Joanna

    2005-01-01

    Aimed at the increasing number of policy-makers, stakeholders, researchers, and other professionals working on climate change, this volume presents a detailed description and analysis of the international regime established in 1992 to combat the threat of global climate change. It provides a comprehensive accessible guide to a high-profile area of international law and politics, covering not only the obligations and rights of countries, but ongoing climate negotiations as well.

  13. Shallow Horizontal GCHP Effectiveness in Arid Climate Soils

    NASA Astrophysics Data System (ADS)

    North, Timothy James

    Ground coupled heat pumps (GCHPs) have been used successfully in many environments to improve the heating and cooling efficiency of both small and large scale buildings. In arid climate regions, such as the Phoenix, Arizona metropolitan area, where the air condi-tioning load is dominated by cooling in the summer, GCHPs are difficult to install and operate. This is because the nature of soils in arid climate regions, in that they are both dry and hot, renders them particularly ineffective at dissipating heat. The first part of this thesis addresses applying the SVHeat finite element modeling soft-ware to create a model of a GCHP system. Using real-world data from a prototype solar-water heating system coupled with a ground-source heat exchanger installed in Menlo Park, California, a relatively accurate model was created to represent a novel GCHP panel system installed in a shallow vertical trench. A sensitivity analysis was performed to evaluate the accuracy of the calibrated model. The second part of the thesis involved adapting the calibrated model to represent an ap-proximation of soil conditions in arid climate regions, using a range of thermal properties for dry soils. The effectiveness of the GCHP in the arid climate region model was then evaluated by comparing the thermal flux from the panel into the subsurface profile to that of the prototype GCHP. It was shown that soils in arid climate regions are particularly inefficient at heat dissipation, but that it is highly dependent on the thermal conductivity inputted into the model. This demonstrates the importance of proper site characterization in arid climate regions. Finally, several soil improvement methods were researched to evaluate their potential for use in improving the effectiveness of shallow horizontal GCHP systems in arid climate regions.

  14. Merging of Rhine flow regimes

    NASA Astrophysics Data System (ADS)

    Boessenkool, Berry; Bronstert, Axel; Bürger, Gerd

    2016-04-01

    The Rhine flow regime is changing: (a) in the alpine nival regime, snow melt floods occur earlier in the year and (b) in the pluvial middle-Rhine regime, rainfall induced flood magnitudes rise. The seasonality of each is currently separated in time, but it is conceivable that this may shift due to climate change. If extremes of both flood types coincide, this would create a new type of hydrologic extreme with disastrous consequences. Quantifying the probability for a future overlap of pluvial and nival floods is therefore of high relevance to society and particularly to reinsurance companies. In order to investigate possible changes in magnitude and timing of flood types, we are developing a chain of physical models for spatio-temporal combination of flood probabilities. As input, we aim to use stochastically downscaled temperature and rainfall extremes from climate model weather projections. Preliminary research shows a six-week forward-shift of peak discharge at the nival gauge Maxau in the past century. The aim of presenting our early-stage work as a poster is to induce an exchange of ideas with fellow scientists in close research disciplines.

  15. Nebkha patterns in semi-arid environments

    NASA Astrophysics Data System (ADS)

    Nield, J. M.; Gillies, J. A.; Nickling, W. G.

    2014-12-01

    In semi-arid supply-limited, environments, nehbka dunes typically form through ecogeomorphic feedbacks. The size, shape and orientation of these dunes are controlled by the interactions between vegetation growth and aeolian sedimentations processes. Once established, these dune patterns modify sediment transport and often form streets of bare surfaces between dune corridors. We examine typical dune and vegetation patterns that form with varying amounts of sediment availability and nebkha maturity at Jornada in the Chihuahuan Desert, New Mexico, USA using terrestrial laser scanning (TLS) to separate the plant and sand elements. Manual and automated TLS shrub height extractions compare well at all sites (p = 0.48-0.94) enabling the quantification of both solid and plant roughness element components in three dimensions. We find that there is a switch in orientation of the dune elements with respect to dominant wind direction from perpendicular to parallel as the landscape develops from an incipient to mature configuration and mesquite-nebkha streets are enhanced. As the nebkha dunes develop the surface coverage of bare sand increases and dune surfaces exceed the size of their companion shrubs. Roughness density also increases at the mature dune site. Individual shrub orientations remain similar at each site, but nebkhas typically host multiple shrub crowns at the mature site. Over a two year period up to 20 cm of erosion was measured on the upwind faces of the mature nebkha dunes, in agreement with the dominant annual wind direction. However, deposition patterns were more diffuse and influenced by the vegetation patterns. This study highlights the importance of ecogeomorphic interactions in shaping nebkha landscape patterns.

  16. Breddin's graph for tectonic regimes

    NASA Astrophysics Data System (ADS)

    Célérier, Bernard; Séranne, Michel

    2001-05-01

    A simple graphical method is proposed to infer the tectonic regime from a fault and slip data set. An abacus is overlaid on a plot of the rake versus strike of the data. This yields the horizontal principal stress directions and a constraint on the stress tensor aspect ratio, in a manner similar to Breddin's graph for two-dimensional strain analysis. The main requirement is that one of the principal stress directions is close to the vertical. This method is illustrated on monophase synthetic and natural data, but is also expected to help sort out multiphase data sets.

  17. Ireland unveils new license regime

    SciTech Connect

    Not Available

    1992-11-23

    Ireland has unveiled new terns designed to integrate the licensing regime for oil and gas exploration and development. They apply to new exploration and development authorizations and replace the exclusive offshore licensing terns introduced in 1975. Holders of existing licenses are still subject to the 1975 terms but can choose the new terns under appropriate circumstances. Frontier exploration licenses are currently available to complement the standard and deepwater exploration licenses in use. Rental fees are now spread evenly over the duration of the license, thereby eliminating large upfront payments. Lease extensions also have been introduced to enable operators to judge commerciality of a discovery beyond the set license period.

  18. Water Presence in an Arid and Semi-arid River: Pattern, causes, mechanisms and change

    NASA Astrophysics Data System (ADS)

    Meixner, T.; Soto, C. D.; Ajami, H.; Turner, D.; Richter, H.; Dominguez, F.

    2012-12-01

    The presence or absence of water in a stream is among the most fundamental hydrologic variables, particularly for arid and semi-arid rivers. The perennial or intermittent nature of a specific stream location is strongly tied to the biotic diversity and ecosystem services provided by a specific stream reach. Wet dry mapping has been conducted on several Arizona rivers over the last several years. The mapping has been most extensive in time and space along the San Pedro River where the effort has been led by the Bureau of Land Management and the Nature Conservancy. Analysis of the available 13 years of data reveals a number of critical aspects about how a river's wetness changes with climatic and geomorphic conditions. First, the pattern displays power law scaling across space for all completed surveys. Second, using a logistic regression approach the following variables were found to be important in predicting the wet/dry status of a given stream location: surface topography , depth to bedrock, mean daily streamflow in May, change in depth to bedrock, channel sinuosity, and flood plain width. The model is able to correctly predict 80.1 to 86.7% of the wet/dry locations in the river when 52.8% (31.5% wet and 21.3% dry) of its wet/dry status was constant during calibration. Importantly but unsurprisingly the logistic model indicates that hydrologic state combined with subsurface capacity to transmit flow and fluvial structure are important variables in determining the wet/dry status of specific river locations. Using groundwater models as well as climate scenarios for future conditions we are able to estimate how both the extent and the spatial pattern of stream wetness will change under future climate scenarios.

  19. Integrated Water Resources Planning and Management in Arid/Semi-arid Regions: Data, Modeling, and Assessment

    NASA Astrophysics Data System (ADS)

    Gupta, H.; Liu, Y.; Wagener, T.; Durcik, M.; Duffy, C.; Springer, E.

    2005-12-01

    Water resources in arid and semi-arid regions are highly sensitive to climate variability and change. As the demand for water continues to increase due to economic and population growth, planning and management of available water resources under climate uncertainties becomes increasingly critical in order to achieve basin-scale water sustainability (i.e., to ensure a long-term balance between supply and demand of water).The tremendous complexity of the interactions between the natural hydrologic system and the human environment means that modeling is the only available mechanism for properly integrating new knowledge into the decision-making process. Basin-scale integrated models have the potential to allow us to study the feedback processes between the physical and human systems (including institutional, engineering, and behavioral components); and an integrated assessment of the potential second- and higher-order effects of political and management decisions can aid in the selection of a rational water-resources policy. Data and information, especially hydrological and water-use data, are critical to the integrated modeling and assessment for water resources management of any region. To this end we are in the process of developing a multi-resolution integrated modeling and assessment framework for the south-western USA, which can be used to generate simulations of the probable effects of human actions while taking into account the uncertainties brought about by future climatic variability and change. Data are being collected (including the development of a hydro-geospatial database) and used in support of the modeling and assessment activities. This paper will present a blueprint of the modeling framework, describe achievements so far and discuss the science questions which still require answers with a particular emphasis on issues related to dry regions.

  20. Actinobacteria from Arid and Desert Habitats: Diversity and Biological Activity

    PubMed Central

    Mohammadipanah, Fatemeh; Wink, Joachim

    2016-01-01

    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 non-ribosomal 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 obtained from arid ecosystems

  1. Quantification of the aridity process in South-Western Romania.

    PubMed

    Peptenatu, Daniel; Sîrodoev, Igor; Pravalie, Remus

    2013-01-01

    The report released by the Intergovernmental Committee for Climate Change indicates that Romania ranks among the top seven countries in Europe that would be strongly impacted by aridity in the next few years, with climate changes consisting in a rise of average annual temperatures by as much as 5°C. The research work was conducted in the South of the Oltenia South-Western Development Region, where more than 700,000 hectares of farmland is impacted by aridification, more than 100,000 hectares among them impacted by aridity. Research methodology encompassed the analysis of average annual temperatures over the time span data was available for, at three weather stations, an analysis of average annual precipitations, an analysis of the piezometric data, the evolution of land use as a result of the expansion of the aridity process. The assessment of the aridity process also involved taking into consideration the state of the vegetation by means of the normalized difference vegetation index (NDVI), used to assess the quality of the vegetal stratum, an important element in the complex analysis of the territory. The aridity process is an effect of global warming, and, based on the results of this study, the post-1990 escalation of its effects was brought about by socio-economic factors. The destruction of the irrigation systems and protective forest belts because of the uncertain situation of land ownership are the main factors that contributed to amplification of the effects of aridity on the efficiency of agricultural systems that nowadays are exposed to very high risks. PMID:24499565

  2. The biogeophysical effect of large-scale afforestation in semi-arid regions

    NASA Astrophysics Data System (ADS)

    Yosef, Gil; Avissar, Roni; Walko, Robert; Medvigy, David; Yakir, Dan

    2015-04-01

    Forestation in the semi-arid region can significantly influence the surface energy budget and, in turn, the local atmospheric circulations. Such effects could be particularly important in regions under the influence of monsoon regimes, such as the Sahel and North Australia. In these regions, summer solar heating leads first to migration of the equatorial through and the tropical convergence zones (ITCZ) and to the monsoon rain. And second, to a meridional surface temperature gradient that generates low-level easterly jet that acts as a barrier to the penetration of the precipitation into the semi arid areas. In this study we tested the hypothesis that large-scale afforestation in these semi-regions can result in changes in local and regional atmospheric circulation and, consequently, in the precipitation and potential changes in land cover and land use. The GCM OLAM was used to performing high-resolution simulations (50km horizontal grid scale and 50 vertical layers) of afforestation scenarios in the Sahel and North Australia. These areas (Sahel 2.6 E6 km2 and North Australia 2.1 E6 km2) were afforested with a mature pine forest, using the extensive data form the long-term semi-arid Yatir forest in Israel as a reference forest for surface parameterization. The regional effect of the afforestation was analyzed for the following parameters; Surface energy budget, temperature, Easterly jet stream location and intensity, above forest atmospheric instability, water recycling and precipitation. Afforestation in the Sahel resulted in large increase of the surface net radiation (45 W m-2), mainly as a result of decrease in albedo (43 W m-2), decrease of incoming short wave radiation (21 W m-2) and increase of downward long wave radiation (13 W m-2) due to higher clouds cover, and decrease in long wave upward radiation (10 W m-2), as a result of the lower surface temperature. Increasing soil moisture because of the new forest is expressed into higher evapotranspiration, i

  3. Fundamentals of Glacial-Interglacial Variability in Tropical Pangaean Aridity during the Late Paleozoic

    NASA Astrophysics Data System (ADS)

    Heavens, N. G.; Mahowald, N. M.; Soreghan, G. S.; Soreghan, M. J.

    2011-12-01

    explore the sensitivity of precipitation and evaporation in tropical Pangaea to climate forcings, such as orbital variability, changes in greenhouse gas levels, changes in sea level, and the extent of Gondwanan glaciation. The results of the simulations support general glacial aridity in equatorial Pangaea. Under eccentric orbital conditions, the precipitation regime over equatorial Pangaea and elsewhere in the Pangaean tropics would have been strongly affected by monsoonal precipitation variability forced by the precession cycle. Resulting pluvials and droughts controlled dust source variability in tropical Pangaea. Therefore, cyclical dust sedimentation away from the Equator would have been strongly in phase with precession cycles modulated by the eccentricity cycles. Moreover, under conditions either of full ice sheet retreat or of retreat to a stable state much like the current East Antarctic ice sheet, the amplitude of sedimentary cycles in northern Pangaea would have intensified. Thus, the spectral characteristics of tropical Pangaean dust deposits should provide low-latitude insight into the amplitude of high-latitude climate variability.

  4. Discharge estimation in arid areas with the help of optical satellite data

    NASA Astrophysics Data System (ADS)

    Mett, M.; Aufleger, M.

    2009-04-01

    The MENA region is facing severe water scarcity. Overexploitation of groundwater resources leads to an ongoing drawdown of the water tables, salinisation and desertification of vast areas. To make matters worse enormous birth-rates, economic growth and refugees from conflict areas let the need for water explode. In the context of climate change this situation will even worsen and armed conflicts are within the bounds of possibility. To ease water scarcity many innovative techniques like artificial groundwater recharge are being developed or already state of the art. But missing hydrological information (for instance discharge data) often prevents design and efficient operation of such measures. Especially in poor countries hydrological measuring devices like gage stations are often missing, in a bad status or professionals of the water sector are absent. This leads to the paradox situation that in many arid regions water resources are indeed available but they cannot be utilised because they are not known. Nowadays different approaches are being designed to obtain hydrological information from perennial river systems with the help of satellite techniques. Mostly they are based on hydraulic parameters like river dimensions, roughness and water levels which can be derived from satellite data. By using conventional flow formulas and additional field investigations the discharge can be estimated. Another methodology derived information about maximum flow depth and flow width from optical sensors of high resolution to calculate discharge of the rivers whilst the flood. Attempts to derive discharge information from structural components of the river and fluviomorphologic changes due to changing flow regimes are in the focus of recent research. One attempt used Synthetic Aperture Radar (SAR) data to estimate discharge in braided river systems. Other attempts used airborne SAR imagery to obtain information about sinuosity and total river width of perennial braided river

  5. ENVIRONMENTAL MONITORING AND ASSESSMENT PROGRAM: EMAP ARID COLORADO PLATEAU PILOT STUDY - 1992 IMPLEMENTATION PLAN

    EPA Science Inventory

    The 1992 Colorado Plateau Indicator Pilot Study, the first field activity for the EMAP-Arid group, is designed to evaluate several indicators of arid ecosystem condition for continued development and implementation for monitoring. his Implementation Plan describes the conceptual ...

  6. Groundwater hydrochemistry evolution in cyclone driven hydrological regimes, NW Australia

    NASA Astrophysics Data System (ADS)

    Skrzypek, G.; Dogramaci, S.; Grierson, P.

    2013-12-01

    Groundwater reserves supply the water needs of many arid regions around the world. Aquifer recharge in these regions is primarily depended on the amount and distribution of rainfall, coupled with exceedingly high rates of evaporation and interactions with both local and regional geomorphology and geology. In semi-arid northwest Australia, the majority of rainfall is delivered by large but infrequent cyclonic events and relatively more frequent but low intensity frontal systems. Changes to rainfall patterns due to global climate change may impact hydrological regimes, recharge rates and groundwater hydrochemistry. These changes may significantly restrict freshwater resources in the future. Between 2008 and 2012, we analysed >400 groundwater, surface and rainwater samples for stable isotope composition (δ2H and δ18O) and major ion chemistry. We then developed conceptual geochemical models of groundwater evolution for the Hamersley Basin (>100,000 km2) and a salt inventory for the Fortescue Marsh (the largest wetland in NW Australia) [1,2]. Fresh groundwater from the alluvium (-8.02 × 0.83‰) and fractured aquifers (-8.22 × 0.70‰) were hydrochemically similar and characterised by a very narrow range of δ18O [1]. In contrast, δ18O of saline and brine groundwater (TDS >10 g L-1) varies in wide range from +2.5 to -7.2‰ [2]. Most of the fresh and brackish groundwater reflects modern recharge and is evaporated by <20% prior to recharge. In contrast, highly saline and brine groundwater reflects mixing between modern rainfall, brackish water and older deep groundwater. The Fortescue Marsh primarily acts as a terminal basin for surface water from the upper Fortescue River catchment [2]. The stable isotope composition of the deep brine groundwater under the Marsh suggests a complex evolution, which cannot be explained by evaporation under current climatic conditions. The observed salinity and δ18O values may result from progressive evaporation from highly saline

  7. New crops for arid lands. [Jojoba; Buffalo gourd; Bladderpod; Gumweed

    SciTech Connect

    Hinman, C.W.

    1984-09-28

    Five plants are described that could be grown commercially under arid conditions. Once the most valuable component has been obtained from each plant (rubber from guayule; seed oil from jojoba, buffalo gourd, and bladderpod; and resin from gumweed), the remaining material holds potential for useful products as well as fuel. It is difficult to realize the full potential of arid land plants, however, because of the complexities of developing the necessary agricultural and industrial infrastructure simultaneously. To do so, multicompany efforts or cooperative efforts between government and the private sector will be required.

  8. Different regimes of dynamic wetting

    NASA Astrophysics Data System (ADS)

    Gustav, Amberg; Wang, Jiayu; Do-Quang, Minh; Shiomi, Junichiro; Physiochemical fluid mechanics Team; Maruyama-Chiashi Laboratory Team

    2014-11-01

    Dynamic wetting, as observed when a droplet contacts a dry solid surface, is important in various engineering processes, such as printing, coating, and lubrication. Our overall aim is to investigate if and how the detailed properties of the solid surface influence the dynamics of wetting. Here we discuss how surface roughness influences the initial dynamic spreading of a partially wetting droplet by studying the spreading on a solid substrate patterned with microstructures just a few micrometers in size. This is complemented by matching numerical simulations. We present a parameter map, based on the properties of the liquid and the solid surface, which identifies qualitatively different spreading regimes, where the spreading speed is limited by either the liquid viscosity, the surface properties, or the liquid inertia. The peculiarities of the different spreading regimes are studied by detailed numerical simulations, in conjuction with experiments. This work was financially supported in part by, the Japan Society for the Promotion of Science (J.W. and J.S) and Swedish Governmental Agency for Innovation Systems (M.D.-Q. and G.A).

  9. Adaptation in Collaborative Governance Regimes

    NASA Astrophysics Data System (ADS)

    Emerson, Kirk; Gerlak, Andrea K.

    2014-10-01

    Adaptation and the adaptive capacity of human and environmental systems have been of central concern to natural and social science scholars, many of whom characterize and promote the need for collaborative cross-boundary systems that are seen as flexible and adaptive by definition. Researchers who study collaborative governance systems in the public administration, planning and policy literature have paid less attention to adaptive capacity specifically and institutional adaptation in general. This paper bridges the two literatures and finds four common dimensions of capacity, including structural arrangements, leadership, knowledge and learning, and resources. In this paper, we focus on institutional adaptation in the context of collaborative governance regimes and try to clarify and distinguish collaborative capacity from adaptive capacity and their contributions to adaptive action. We posit further that collaborative capacities generate associated adaptive capacities thereby enabling institutional adaptation within collaborative governance regimes. We develop these distinctions and linkages between collaborative and adaptive capacities with the help of an illustrative case study in watershed management within the National Estuary Program.

  10. A surfactant film spreading regime

    SciTech Connect

    Nikishov, V.I.

    1984-06-01

    Interest has recently increased in the study of the mechanisms whereby oil spills spread over sea and ocean surfaces. In the later stages of this process, when the petroleum film thickness becomes sufficiently small, the main forces determining the growth of its horizontal dimensions are surface tension and viscosity. In this case the flow characteristics do not depend on total quantity of spreading substance nor its surface concentration distribution. However, in the final stages of the spreading process the film becomes so thin that it is necessary to consider the effect of surface concentration distribution of the material on the process. Similar problems occur in the study of the spreading of a surfactant in the case where the total quantity of material is small and the surface tension regime sets in quickly. Therefore, the author examines here the spreading of a film in a regime wherein it is necessary to consider the total quantity of surfactant present, initially located on the surface of a viscous incompressible liquid.

  11. Adaptation in collaborative governance regimes.

    PubMed

    Emerson, Kirk; Gerlak, Andrea K

    2014-10-01

    Adaptation and the adaptive capacity of human and environmental systems have been of central concern to natural and social science scholars, many of whom characterize and promote the need for collaborative cross-boundary systems that are seen as flexible and adaptive by definition. Researchers who study collaborative governance systems in the public administration, planning and policy literature have paid less attention to adaptive capacity specifically and institutional adaptation in general. This paper bridges the two literatures and finds four common dimensions of capacity, including structural arrangements, leadership, knowledge and learning, and resources. In this paper, we focus on institutional adaptation in the context of collaborative governance regimes and try to clarify and distinguish collaborative capacity from adaptive capacity and their contributions to adaptive action. We posit further that collaborative capacities generate associated adaptive capacities thereby enabling institutional adaptation within collaborative governance regimes. We develop these distinctions and linkages between collaborative and adaptive capacities with the help of an illustrative case study in watershed management within the National Estuary Program. PMID:25073764

  12. a Proposed New Vegetation Index, the Total Ratio Vegetation Index (trvi), for Arid and Semi-Arid Regions

    NASA Astrophysics Data System (ADS)

    Fadaei, H.; Suzuki, R.; Sakai, T.; Torii, K.

    2012-07-01

    Vegetation indices that provide important key to predict amount vegetation in forest such as percentage vegetation cover, aboveground biomass, and leaf-area index. Arid and semi-arid areas are not exempt of this rule. Arid and semi-arid areas of northeast Iran cover about 3.4 million ha and are populated by two main tree species, the broadleaf Pistacia vera (pistachio) and the conifer Juniperus excelsa ssp. polycarpos (Persian juniper). Natural stands of pistachio in Iran are not only environmentally important but also genetically essential as seed sources for pistachio production in orchards. We investigated the relationships between tree density and vegetation indices in the arid and semi-arid regions in the northeast of Iran by analysing Advanced Land Observing Satellite (ALOS) data PRISM is a panchromatic radiometer with a 2.5 m spatial resolution at nadir, and has one band with a wavelength of 0.52-0.77 μm (JAXA EORC). AVNIR-2 is a visible and near infrared radiometer for observing land and coastal zones with a 10 m spatial resolution at nadir, and has four multispectral bands: blue (0.42-0.50 μm), green (0.52-0.60 μm), red (0.61-0.69 μm), and near infrared (0.76-0.89 μm) (JAXA EORC). In this study, we estimated various vegetation indices using maximum filtering algorithm (5×5) and examined. This study carried out of juniper forests and natural pistachio stand using Advanced Land Observing Satellite (ALOS) and field inventories. Have been compared linear regression model of vegetation indices and proposed new vegetation index for arid and semi-arid regions. Also, we estimated the densities of juniper forests and natural pistachio stands using remote sensing to help in the sustainable management and production of pistachio in Iran. We present a new vegetation index for arid and semi-arid regions with sparse forest cover, the Total Ratio Vegetation Index (TRVI), and we investigate the relationship of the new index to tree density by analysing data from the

  13. Anomalous trend in soil evaporation in semi-arid, snow-dominated watersheds

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil evaporation in arid and semi-arid regions 1 is generally “moisture-limited”. Evaporation in such regions shows an increasing trend with increase in magnitude of annual precipitation. This paper explores the trend in soil evaporation in a snow dominated, semi-arid Reynolds Mountain East (RME) wa...

  14. Individual based, long term monitoring of acacia trees in hyper arid zone: Integration of a field survey and a remote sensing approach

    NASA Astrophysics Data System (ADS)

    Isaacson, Sivan; Blumberg, Dan G.; Ginat, Hanan; Shalmon, Benny

    2013-04-01

    Vegetation in hyper arid zones is very sparse as is. Monitoring vegetation changes in hyper arid zones is important because any reduction in the vegetation cover in these areas can lead to a considerable reduction in the carrying capacity of the ecological system. This study focuses on the impact of climate fluctuations on the acacia population in the southern Arava valley, Israel. The period of this survey includes a sequence of dry years with no flashfloods in most of the plots that ended in two years with vast floods. Arid zone acacia trees play a significant role in the desert ecosystem by moderating the extreme environmental conditions including radiation, temperature, humidity and precipitation. The trees also provide nutrients for the desert dwellers. Therefore, acacia trees in arid zones are considered to be `keystone species', because they have major influence over both plants and animal species, i.e., biodiversity. Long term monitoring of the acacia tree population in this area can provide insights into long term impacts of climate fluctuations on ecosystems in arid zones. Since 2000, a continuous yearly based survey on the three species of acacia population in seven different plots is conducted in the southern Arava (established by Shalmon, ecologist of the Israel nature and parks authority). The seven plots representing different ecosystems and hydrological regimes. A yearly based population monitoring enabled us to determine the mortality and recruitment rate of the acacia populations as well as growing rates of individual trees. This survey provides a unique database of the acacia population dynamics during a sequence of dry years that ended in a vast flood event during the winter of 2010. A lack of quantitative, nondestructive methods to estimate and monitor stress status of the acacia trees, led us to integrate remote sensing tools (ground and air-based) along with conventional field measurements in order to develop a long term monitoring of acacia

  15. Urban-Induced Rainfall Anomalies in an Arid Regime: Evidence from a 108-Year Data Record and Satellite Measurements

    NASA Technical Reports Server (NTRS)

    Shepherd, J. Marshall

    2004-01-01

    The study employs a 108-year precipitation data record to identify statistically significant anomalies in rainfall downwind of the Phoenix urban region. The analysis reveals that during the monsoon season locations northeastern suburbs and exurbs of the Phoenix metropolitan area have experienced statistically significant increases in mean precipitation of 12 to 14 percent from a pre-urban (1895-1949) to post-urban (1950-2003) period. Mean and median post-urban precipitation totals in the anomaly region are significantly greater, in the statistical sense, than regions west of the city and in nearby mountainous regions of similar or greater topography. Further analysis of satellite-based rainfall totals for the summer of 2003 also reveal the existence of the anomaly region during a severe drought period. The anomaly can not simply be attributed to maximum topographic relief and is hypothesize to be related to urban-topographic interactions.

  16. Defining near-surface groundwater flow regimes in the semi-arid glaciated plains of North America.

    PubMed

    Hendry, M Jim; Barbour, S Lee; Schmeling, Erin E

    2016-06-01

    The dominant transport mechanisms controlling the migration of contaminants in geologic media are advection and molecular diffusion. To date, defining which transport mechanism dominates in saturated, non-lithified sediments has been difficult. Here, we illustrate the value of using detailed profiles of the conservative stable isotope values of water (δ(2)H and δ(18)O) to identify the dominant processes of contaminant transport (i.e. diffusion- or advection-dominated transport) in near-surface, non-lithified, saturated sediments of the Interior Plains of North America (IPNA). The approach presented uses detailed δ(18)O analyses of glacial till, glaciolacustrine clay, and fluvial sand core samples taken to depths of 11-50 m below ground at 22 sites across the IPNA to show whether transport in the fractured and oxidized sediments is dominated by advection or diffusion. Diffusion is by far the dominant transport mechanism in fine-textured lacustrine and glacial till sediments, but lateral advection dominates transport in sand-rich sediments and some oxidized, fine-textured lacustrine and glacial till sediments. The approach presented has a number of applications, including identifying dominant transport mechanisms in geomedia and potential protective barriers for underlying aquifers or surface waters, constraining groundwater transport models, and selecting optimum locations for monitoring wells. These findings should be applicable to most glaciated regions of the world that are composed of similar hydrogeologic units (i.e. low K clay till layers overlain by higher K coarse-textured aquifers or weathered clay till layers) and may also be applicable to non-glaciated regions exhibiting similar hydrogeologic characteristics. PMID:26606976

  17. Using magnetic susceptibility to discriminate between soil moisture regimes in selected loess and loess-like soils in northern Iran

    NASA Astrophysics Data System (ADS)

    Valaee, Morteza; Ayoubi, Shamsollah; Khormali, Farhad; Lu, Sheng Gao; Karimzadeh, Hamid Reza

    2016-04-01

    This study used discriminant analysis to determine the efficacy of magnetic measures for discriminating between four soil moisture regimes in northern Iran. The study area was located on loess deposits and loess-like soils containing similar parent material. Four soil moisture regimes including aridic, xeric, udic, and aquic were selected. A total of 25 soil profiles were drug from each regime and composite soil samples were collected within the moisture control section. A set of magnetic measures including magnetic susceptibility at low (χlf) and high (χhf) frequencies, frequency-dependent magnetic susceptibility (χfd), saturation isothermal remnant magnetization (SIRM), and isothermal remnant magnetization (IRM100 mT, IRM 20 mT) were measured in the laboratory. Dithionite citrate bicarbonate (Fed) and acid oxalate (Feo) contents of all soil samples were also determined. The lowest and highest χlf and χhf were observed in aquic and udic moisture regimes, respectively. A similar trend was obtained for Fed and Fed-Feo. The significant positive correlation between Fed and SIRM (r = 0.60; P < 0.01) suggested the formation of stable single domains (SSD) due to pedogenic processes. The results of discriminant analysis indicated that a combination of magnetic measures could successfully discriminate between the selected moisture regimes in the study area (average accuracy = 80%). It can thus be concluded that magnetic measures could be applied as a powerful indicator for differentiation of soil moisture regimes in the study area.

  18. Ecosystem services to and from North American arid grasslands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arid grasslands throughout North America are characterized by low and variable precipitation, nutrient-poor soils, and high spatial and temporal variability in plant production. These grasslands have provided a variety of goods and services, with the provisioning of food and fiber dominating through...

  19. Evaporation as the transport mechanism of metals in arid regions.

    PubMed

    Lima, Ana T; Safar, Zeinab; Loch, J P Gustav

    2014-09-01

    Soils of arid regions are exposed to drought and drastic temperature oscillations throughout the year. Transport mechanisms in these soils are therefore very different from the ones in temperate regions, where rain dictates the fate of most elements in soils. Due to the low rainfall and high evaporation rates in arid regions, groundwater quality is not threatened and all soil contamination issues tend to be overlooked. But if soil contamination happens, where do contaminants go? This study tests the hypothesis of upward metal movement in soils when evaporation is the main transport mechanism. Laboratory evaporation tests were carried out with heavy metal spiked Saudi soil, using circulation of air as the driving force (Fig. 1). Main results show that loamy soil retains heavy metals quite well while evaporation drives heavy metals to the surface of a sandy soil. Evaporation transports heavy metals upward in sandy soils of arid regions, making them accumulate at the soil surface. Sand being the dominating type of soil in arid regions, soils can then be a potential source of contaminated aerosols and atmospheric pollution - a transboundary problem. Some other repercussions for this problem are foreseen, such as the public ingestion or inhalation of dust. PMID:24997976

  20. Documentation of Arid Land Soilscapes in Southwestern Europe

    NASA Astrophysics Data System (ADS)

    José Ibáñez, Juan; Pérez-Gómez, Rufino; Oyonarte, Cecilio; Brevik, Eric C.

    2016-04-01

    There have been no studies to date that have proven the existence of soil assemblages typical of arid lands in Europe. This study was carried out in Almería province, a representative territory of the SE part of the Iberian Peninsula which is the driest part of Europe, to determine if soils characteristic of arid lands were present. The study made use of mathematical tools previously developed in biodiversity and pedodiversity analysis, such as richness, entropy indices, abundance distribution models, diversity-area relationships and nested subset analysis to analyse the spatial distribution of soils. The study demonstrated that the soil types or pedotaxa are typical of mountainous arid lands. Shallow and weakly developed soils (e.g. Leptosols, Regosols, Arenosols), Calcisols, Gypsisols and Solonchaks cover most of the study area, and pedodiversity analysis demonstrates that the pedotaxa spatial patterns follow the same regularities as in other areas, environments and scales. In view of the fact that the class of landscapes identified in this study are unique in Europe, the Tarbernas desert and other arid lands sites of the study area merit preservation as part of the European geological, geomorphological, and pedological heritage.

  1. Extremely arid soils of the Ili Depression in Kazakhstan

    NASA Astrophysics Data System (ADS)

    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. A GIS MODEL OF SOIL PROCESSES FOR ARID LAND MANAGEMENT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is a growing need at the state and federal management agency levels to make decisions based on ecological processes across the landscape. Arid and semiarid lands around the world are thought to be best understood in terms of their soil resources. One soil process that influences water infilt...

  3. Problems of Adult Education in Less Developed Arid Regions.

    ERIC Educational Resources Information Center

    Behravesh, Z.

    Today adult education is recognized as one of the most important factors in bringing about social and economic development. However, there are some problems which serve as impediments to adult education in the less developed arid regions. These problems include: (1) entrusting adult education to agents who may not have the necessary…

  4. Sediments in Semi-arid Wetlands: US Southern High Plains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Playas are ephemeral wetlands on the semi-arid U.S. Southern High Plains that serve as runoff catchment basins and are thought to be focal points of Ogallala aquifer recharge. Sediments in playas alter biodiversity and hydroperiods. The purpose of this study was to evaluate the effects of outerbas...

  5. ARID1A Is Essential for Endometrial Function during Early Pregnancy

    PubMed Central

    Wang, Zhong; Lydon, John P.; Khatri, Shikha; Hawkins, Shannon M.; Leach, Richard E.; Fazleabas, Asgerally T.; Young, Steven L.; Lessey, Bruce A.; Ku, Bon Jeong; Jeong, Jae-Wook

    2015-01-01

    AT-rich interactive domain 1A gene (ARID1A) loss is a frequent event in endometriosis-associated ovarian carcinomas. Endometriosis is a disease in which tissue that normally grows inside the uterus grows outside the uterus, and 50% of women with endometriosis are infertile. ARID1A protein levels were significantly lower in the eutopic endometrium of women with endometriosis compared to women without endometriosis. However, an understanding of the physiological effects of ARID1A loss remains quite poor, and the function of Arid1a in the female reproductive tract has remained elusive. In order to understand the role of Arid1a in the uterus, we have generated mice with conditional ablation of Arid1a in the PGR positive cells (Pgr cre/+ Arid1a f/f; Arid1a d/d). Ovarian function and uterine development of Arid1a d/d mice were normal. However, Arid1a d/d mice were sterile due to defective embryo implantation and decidualization. The epithelial proliferation was significantly increased in Arid1a d/d mice compared to control mice. Enhanced epithelial estrogen activity and reduced epithelial PGR expression, which impedes maturation of the receptive uterus, was observed in Arid1a d/d mice at the peri-implantation period. The microarray analysis revealed that ARID1A represses the genes related to cell cycle and DNA replication. We showed that ARID1A positively regulates Klf15 expression with PGR to inhibit epithelial proliferation at peri-implantation. Our results suggest that Arid1a has a critical role in modulating epithelial proliferation which is a critical requisite for fertility. This finding provides a new signaling pathway for steroid hormone regulation in female reproductive biology and furthers our understanding of the molecular mechanisms that underlie dysregulation of hormonal signaling in human reproductive disorders such as endometriosis. PMID:26378916

  6. Evidence for extreme floods in arid subtropical northwest Australia during the Little Ice Age chronozone (CE 1400-1850)

    NASA Astrophysics Data System (ADS)

    Rouillard, A.; Skrzypek, G.; Turney, C.; Dogramaci, S.; Hua, Q.; Zawadzki, A.; Reeves, J.; Greenwood, P.; O'Donnell, A. J.; Grierson, P. F.

    2016-07-01

    Here we report a ∼2000-year sediment sequence from the Fortescue Marsh (Martuyitha) in the eastern Pilbara region, which we have used to investigate changing hydroclimatic conditions in the arid subtropics of northwest Australia. The Pilbara is located at the intersection of the tropical Indian and Pacific Oceans and its modern rainfall regime is strongly influenced by tropical cyclones, the Intertropical Convergence Zone (ITCZ) and the Indo-Pacific Warm Pool. We identified four distinct periods within the record. The most recent period (P1: CE ∼1990-present) reveals hydroclimatic conditions over recent decades that are the most persistently wet of potentially the last ∼2000 years. During the previous centuries (P2: ∼CE 1600-1990), the Fortescue Marsh was overall drier but likely punctuated by a number of extreme floods, which are defined here as extraordinary, strongly episodic floods in drylands generated by rainfall events of high volume and intensity. The occurrence of extreme floods during this period, which encompasses the Little Ice Age (LIA; CE 1400-1850), is coherent with other southern tropical datasets along the ITCZ over the last 2000 years, suggesting synchronous hydroclimatic changes across the region. This extreme flood period was preceded by several hundred years (P3: ∼CE 700-1600) of less vigorous but more regular flows. The earliest period of the sediment record (P4: ∼CE 100-700) was the most arid, with sedimentary and preservation processes driven by prolonged drought. Our results highlight the importance of developing paleoclimate records from the tropical and sub-tropical arid zone, providing a long-term baseline of hydrological conditions in areas with limited historical observations.

  7. Loess is the accumulation of dust, not evidence for aridity

    NASA Astrophysics Data System (ADS)

    Zech, Roland

    2013-04-01

    Loess-paleosol sequences (LPS) are valuable terrestrial archives for Quaternary climate and environmental changes. The famous sections on the Chinese Loess Plateau, for example, document the alternation of warm and humid interglacials (paleosols) and cold and more arid glacials (loess). This, at least partly, reflects the weakening of the monsoonal circulation during glacials and has led to the notion that loess in general documents more arid conditions. Paleosols, on the other hand, are often interpreted to document more humid conditions. We studied the LPS Crvenka in the Carpathian Basin, southeast Europe, which spans the full last glacial cycle, and obtained results that do not fit the above concept: (i) The analysis of plant-derived long-chain n-alkanes indicates the presence of deciduous trees and shrubs during glacials, i.e. sufficient precipitation for tree growth, whereas tree-less grass steppes seem to have prevailed during the Eemian, the last interglacial. (ii) Compound-specific deuterium analyses on the alkanes show only little changes on glacial-interglacial timescale. When compared with the isotopic enrichment of the Mediterranean Sea during the last glacial, this likely documents a combination of increased rainfall, reduced evapo-transpiration and reduced temperatures. (iii) Novel lipid biomarkers derived from soil bacteria (GDGTs, glycerol dialkyl glycerol tetraethers) also indicate humid glacials (BIT index close to 1) and more arid interglacials (BIT<0.8). Our results are in good agreement with modelling studies suggesting a southward shift of the westerlies during glacials, and aridization in the Mediterranean area in response to man-made global warming. More importantly, they remind us of an important fact: Loess is the accumulation of dust, but not (necessarily) evidence for aridity. Pedogenesis may simply not have been able to keep pace with high glacial dust accumulation rates related to intense glacial, periglacial and fluvial activity

  8. Arid land plants: promising new tools for economic development and basic research

    SciTech Connect

    Felker, P.

    1980-01-01

    An overview is presented of arid land plant development stressing products and plant physiological and ecological concepts unique to arid land plants. Integration of new arid land crops into polyculture management systems is suggested utilizing specialized plant functions, e.g., drought resistance, resistance to salinity, ability to fix nitrogen, frost tolerance and capability to produce a cash crop. Impacts on arid land plant productivity on political systems of developing countries are discussed and recommendations are presented for overcoming institutional constraints facing arid land plant development. (MHR)

  9. Damage caused to the environment by reforestation policies in arid and semi-arid areas of China.

    PubMed

    Cao, Shixiong; Tian, Tao; Chen, Li; Dong, Xiaobin; Yu, Xinxiao; Wang, Guosheng

    2010-06-01

    Traditional approaches to ecosystem restoration have considered afforestation to be an important tool. To alleviate land degradation in China, the Chinese government has therefore invested huge amounts of money in planting trees. However, the results of more than half a century of large-scale afforestation in arid and semi-arid China have shown that when the trees are not adapted to the local environment, the policy does not improve the environment, and may instead increase environmental degradation. When precipitation is lower than potential evaporation, surface soil moisture typically cannot sustain forest vegetation, and shrubs or steppe species replace the forest to form a sustainable natural ecosystem that exists in a stable equilibrium with the available water supply. The climate of much of northwestern China appears to be unsuitable for afforestation owing to the extremely low rainfall. Although some small-scale or short-term afforestation efforts have succeeded in this region, many of the resulting forests have died or degraded over longer periods, so policymakers must understand that these small-scale or short-term results do not support an inflexible policy of large-scale afforestation throughout arid and semi-arid northwestern China. Rather than focusing solely on afforestation, it would be more effective to attempt to recreate natural ecosystems that are better adapted to local environments and that thus provide a better chance of sustainable, long-term rehabilitation. PMID:20799677

  10. MULTI-SCALE CONTROLS ON AND CONSEQUENCES OF AEOLIAN PROCESSES IN LANDSCAPE CHANGE IN ARID AND SEMI-ARID ENVIRONMENTS

    EPA Science Inventory

    This paper reviews the controls on aeolian processes and their consequences at plant-interspace, patch-landscape, and regional-global scales. Based on this review, we define the requirements for a cross-scale model of wind erosion in structurally complex arid and semiarid ecosyst...

  11. Spatial pattern of nitrogen isotopes as an indicator of ecosystem responses to rainfall in semi-arid and arid grasslands

    NASA Astrophysics Data System (ADS)

    WANG, C.; Bai, E.; Liu, D.; Fang, T. Y.; Jiang, P.; Han, G. X.

    2013-12-01

    Nitrogen (N) is an essential element for plant growth, however, whether it is a limiting factor of plant growth in water-limited areas is still not clear. Here we examined spatial variations of plant and soil stable N isotopes along a 3200 km precipitation gradient and proposed a conceptual model to explain ecosystem responses to increasing precipitation in arid and semi-arid grasslands in China. Soil δ15N increased with increasing MAP in areas with MAP < 200 mm, but decreased in areas with 200 mm < MAP < 500 mm. Variations of foliar δ15N, soil total N, and soil C: N provided further evidence of a threshold at MAP = 200 mm for precipitation effects. Results indicated that soil microbes can be activated by precipitation even when MAP < 200 mm while plant N uptake can only be activated when MAP > 200 mm. In areas with MAP < 200 mm, productivity was limited by water, but not nitrogen, although soil N is low. This study provides fundamental inputs for future process-based modeling of nutrient cycling in arid and semi-arid areas. If future climate change leads to drier climate in dryland, the uncoupled plant and microbial response may cause more N losses and higher ecosystem vulnerability. 3 Soil organic carbon (Soil C, a), total nitrogen (Soil N, b), C/N (c) and δ15N (d) of study sites along a MAP gradient. Relationship between MAP and foliar δ15N (a) and root δ15N (b).

  12. Impacts of climate change on nutrient cycling in semi-arid and arid ecosystems

    SciTech Connect

    Belnap, J.

    1995-09-01

    Effective precipitation is a major factor in determining nutrient pathways in different ecosystems. Soil flora and fauna play a critical role in nutrient cycles of all ecosystems. Temperature, timing, and amounts of precipitation affect population composition, activity levels, biomass, and recovery rates from disturbance. Changes in these variables can result in very different inputs and outputs for different nutrients. As a result, areas with less effective precipitation have very different nutrient cycles than more mesic zones. Climate change, therefore, can profoundly affect the nutrient cycles of ecosystems. Nitrogen cycles may be especially sensitive to changes in temperature and to timing and amounts of precipitation. Rainfall contains varying amounts of nitrogen compounds. Changes in amounts of rainfall will change amounts of nitrogen available to these systems. Because rainfall is limited in semi-arid and regions, these systems tend to be more dependent on microbial populations for nitrogen input. Consequently, understanding the effects of climate change on these organisms is critical in understanding the overall effect on ecosystems.

  13. Agave: a biofuel feedstock for arid and semi-arid environments

    SciTech Connect

    Gross, Stephen; Martin, Jeffrey; Simpson, June; Wang, Zhong; Visel, Axel

    2011-05-31

    Efficient production of plant-based, lignocellulosic biofuels relies upon continued improvement of existing biofuel feedstock species, as well as the introduction of newfeedstocks capable of growing on marginal lands to avoid conflicts with existing food production and minimize use of water and nitrogen resources. To this end, specieswithin the plant genus Agave have recently been proposed as new biofuel feedstocks. Many Agave species are adapted to hot and arid environments generally unsuitable forfood production, yet have biomass productivity rates comparable to other second-generation biofuel feedstocks such as switchgrass and Miscanthus. Agavesachieve remarkable heat tolerance and water use efficiency in part through a Crassulacean Acid Metabolism (CAM) mode of photosynthesis, but the genes andregulatory pathways enabling CAM and thermotolerance in agaves remain poorly understood. We seek to accelerate the development of agave as a new biofuelfeedstock through genomic approaches using massively-parallel sequencing technologies. First, we plan to sequence the transcriptome of A. tequilana to provide adatabase of protein-coding genes to the agave research community. Second, we will compare transcriptome-wide gene expression of agaves under different environmentalconditions in order to understand genetic pathways controlling CAM, water use efficiency, and thermotolerance. Finally, we aim to compare the transcriptome of A.tequilana with that of other Agave species to gain further insight into molecular mechanisms underlying traits desirable for biofuel feedstocks. These genomicapproaches will provide sequence and gene expression information critical to the breeding and domestication of Agave species suitable for biofuel production.

  14. Hepatocyte-Specific Arid1a Deficiency Initiates Mouse Steatohepatitis and Hepatocellular Carcinoma

    PubMed Central

    Liu, Xiao-Yan; Hu, Tao-Tao; Fan, Zu-Sen; Han, Ze-Guang

    2015-01-01

    ARID1A, encoding a subunit of chromatin remodeling SWI/SNF complexes, has recently been considered as a new type of tumor suppressor gene for its somatic mutations frequently found in various human tumors, including hepatocellular carcinoma (HCC). However, the role and mechanism of inactivated ARID1A mutations in tumorigenesis remain unclear. To investigate the role of ARID1A inactivation in HCC pathogenesis, we generated hepatocyte-specific Arid1a knockout (Arid1aLKO) mice by crossing mice carrying loxP-flanked Arid1a exon 8 alleles (Arid1af/f) with albumin promoter-Cre transgenic mice. Significantly, the hepatocyte-specific Arid1a deficiency results in mouse steatohepatitis and HCC development. In Arid1aLKO mice, we found that innate immune cells, including F4/80+ macrophages and CD11c+ neutrophil cells, infiltrate into the liver parenchyma, accompanied by the increased tumor necrosis factor (TNF)-α and interleukin (IL)-6, and activation of STAT3 and NF-κB pathways. In conclusion, hepatocyte-specific Arid1a deficiency could lead to mouse steatohepatitis and HCC development. This study provides an alternative mechanism by which Arid1a deficiency contributes to HCC tumorigenesis. PMID:26569409

  15. Propagation Regime of Iron Dust Flames

    NASA Technical Reports Server (NTRS)

    Tang, Francois-David; Goroshin, Samuel; Higgins, Andrew J.

    2012-01-01

    A flame propagating through an iron-dust mixture can propagate in two asymptotic regimes. When the characteristic time of heat transfer between particles is much smaller than the characteristic time of particle combustion, the flame propagates in the continuum regime where the heat released by reacting particles can be modelled as a space-averaged function. In contrast, when the characteristic time of heat transfer is much larger than the particle reaction time, the flame can no longer be treated as a continuum due to dominating effects associated with the discrete nature of the particle reaction. The discrete regime is characterized by weak dependence of the flame speed on the oxygen concentration compared to the continuum regime. The discrete regime is observed in flames propagating through an iron dust cloud within a gas mixture containing xenon, while the continuum regime is obtained when xenon is substituted with helium.

  16. Discriminatory Proofreading Regimes in Nonequilibrium Systems

    NASA Astrophysics Data System (ADS)

    Murugan, Arvind; Huse, David A.; Leibler, Stanislas

    2014-04-01

    We use ideas from kinetic proofreading, an error-correcting mechanism in biology, to identify new kinetic regimes in nonequilibrium systems. These regimes are defined by the sensitivity of the occupancy of a state of the system to a change in its energy. In biological contexts, higher sensitivity corresponds to stronger discrimination between molecular substrates with different energetics competing in the same reaction. We study this discriminatory ability in systems with discrete states that are connected by a general network of transitions. We find multiple regimes of different discriminatory ability when the energy of a given state of the network is varied. Interestingly, the occupancy of the state can even increase with its energy, corresponding to an "antiproofreading" regime. The number and properties of such discriminatory regimes are limited by the topology of the network. Finally, we find that discriminatory regimes can be changed without modifying any "hard-wired" structural aspects of the system but rather by simply changing external chemical potentials.

  17. On unstable periodic regime of small HAWT

    NASA Astrophysics Data System (ADS)

    Dosaev, Marat Z.; Klimina, Liubov A.; Selyutskiy, Yury D.; Tsai, Mi-Ching; Yang, Hong-Tzer

    2012-11-01

    Dynamics of a small HAWT is studied. The closed mathematical model involving phenomenological description of both aerodynamic load upon turbine blades and permanent magnet electric generator is developed, in order to take into account the inductive reactance of the electric circuit. A series of experiments is performed in the subsonic wind tunnel of the LMSU Institute of Mechanics that allowed verifying the model and identifying its parameters. Parameters of dynamic model are identified, such as the coefficient of electromechanical interaction, the active internal resistance of generator, the circuit reactance. Parametric analysis of steady regimes is performed. The model prediction that HAWT operating dynamic system has two stable steady regimes (high speed regime and low speed one) is confirmed by experiments. Transient regimes are registered depending on parameters of the system, which allows estimating the unstable steady regime. The characteristics of the unstable regime are experimentally determined. Obtained results are used for estimation of aerodynamic moment acting on HAWT blades.

  18. Evaluating abiotic influences on soil salinity of inland managed wetlands and agricultural croplands in a semi-arid environment

    USGS Publications Warehouse

    Fowler, D.; King, Sammy L.; Weindorf, David C.

    2014-01-01

    Agriculture and moist-soil management are important management techniques used on wildlife refuges to provide adequate energy for migrant waterbirds. In semi-arid systems, the accumulation of soluble salts throughout the soil profile can limit total production of wetland plants and agronomic crops and thus jeopardize meeting waterbird energy needs. This study evaluates the effect of distinct hydrologic regimes associated with moist-soil management and agricultural production on salt accumulation in a semi-arid floodplain. We hypothesized that the frequency of flooding and quantity of floodwater in a moist-soil management hydroperiod results in a less saline soil profile compared to profiles under traditional agricultural management. Findings showed that agricultural croplands differed (p-value < 0.001, df = 9) in quantities of total soluble salts (TSS) compared to moist-soil impoundments and contained greater concentrations (TSS range = 1,160-1,750 (mg kg-1)) at depth greater than 55 cm below the surface of the profile, while moist-soil impoundments contained lower concentrations (TSS range = 307-531 (mg kg-1)) at the same depths. Increased salts in agricultural may be attributed to the lack of leaching afforded by smaller summer irrigations while larger periodic flooding events in winter and summer flood irrigations in moist-soil impoundments may serve as leaching events.

  19. Disconnected runoff contributing areas: Evidence provided by ancient watershed management systems in arid north-eastern Marmarica (NW-Egypt)

    NASA Astrophysics Data System (ADS)

    Vetter, T.; Rieger, A.-K.; Nicolay, A.

    2014-05-01

    This study presents the importance of disconnectivity in dryland area runoff demonstrated by manmade water harvesting structures dated to Greco-Roman times. Located on the coastal strip of some 20 km width along the Mediterranean coast of modern northwestern Egypt covering the north-eastern part of the region known in antiquity as Marmarica, the area receives winterly rainfalls of up to 140 mm. Further south, precipitation decreases quickly and desert conditions become more pronounced. Bedrocks are predominantly calcareous, soils are loamy, stony, calcareous, and shallow, except in relief sinks with sedimentary deposits. The land rises from the coast up to 230 m a.s.l. on the Marmarica Plateau in a sequence of zonal northsloping plains and scarps the northern parts of which are dissected and drained by wadis. Agriculturally suitable areas comprise some 9% of the coastal zone and adjacent tablelands. Overland flow controls the discharge dynamics and is the main source of wadi runoff and hence agricultural water supply. The land use pattern is scattered because cropping areas depend mainly on suitability of soils and the generation of runoff harvest, which are closely interrelated because of the arid water and sediment regime. The patchiness of runoff generation increases further south where aridity is higher and topography inhibits greater drainage patterns. The abundance of cisterns, many of them originally Greco-Roman, is strong evidence that tableland overland flows occur and are frequently disconnected from larger drainage systems.

  20. Genetic Divergence among Regions Containing the Vulnerable Great Desert Skink (Liopholis kintorei) in the Australian Arid Zone.

    PubMed

    Dennison, Siobhan; McAlpin, Steve; Chapple, David G; Stow, Adam J

    2015-01-01

    Knowledge of genetic structure and patterns of connectivity is valuable for implementation of effective conservation management. The arid zone of Australia contains a rich biodiversity, however this has come under threat due to activities such as altered fire regimes, grazing and the introduction of feral herbivores and predators. Suitable habitats for many species can be separated by vast distances, and despite an apparent lack of current geographical barriers to dispersal, habitat specialisation, which is exhibited by many desert species, may limit connectivity throughout this expansive region. We characterised the genetic structure and differentiation of the great desert skink (Liopholis kintorei), which has a patchy, but widespread distribution in the western region of the Australian arid zone. As a species of cultural importance to local Aboriginal groups and nationally listed as Vulnerable, it is a conservation priority for numerous land managers in central Australia. Analysis of mitochondrial ND4 sequence data and ten nuclear microsatellite loci across six sampling localities through the distribution of L. kintorei revealed considerable differentiation among sites, with mitochondrial FST and microsatellite F'ST ranging from 0.047-0.938 and 0.257-0.440, respectively. The extent of differentiation suggests three main regions that should be managed separately, in particular the southeastern locality of Uluru. Current genetic delineation of these regions should be maintained if future intervention such as translocation or captive breeding is to be undertaken. PMID:26061141

  1. Genetic Divergence among Regions Containing the Vulnerable Great Desert Skink (Liopholis kintorei) in the Australian Arid Zone

    PubMed Central

    Dennison, Siobhan; McAlpin, Steve; Chapple, David G.; Stow, Adam J.

    2015-01-01

    Knowledge of genetic structure and patterns of connectivity is valuable for implementation of effective conservation management. The arid zone of Australia contains a rich biodiversity, however this has come under threat due to activities such as altered fire regimes, grazing and the introduction of feral herbivores and predators. Suitable habitats for many species can be separated by vast distances, and despite an apparent lack of current geographical barriers to dispersal, habitat specialisation, which is exhibited by many desert species, may limit connectivity throughout this expansive region. We characterised the genetic structure and differentiation of the great desert skink (Liopholis kintorei), which has a patchy, but widespread distribution in the western region of the Australian arid zone. As a species of cultural importance to local Aboriginal groups and nationally listed as Vulnerable, it is a conservation priority for numerous land managers in central Australia. Analysis of mitochondrial ND4 sequence data and ten nuclear microsatellite loci across six sampling localities through the distribution of L. kintorei revealed considerable differentiation among sites, with mitochondrial FST and microsatellite F′ST ranging from 0.047-0.938 and 0.257-0.440, respectively. The extent of differentiation suggests three main regions that should be managed separately, in particular the southeastern locality of Uluru. Current genetic delineation of these regions should be maintained if future intervention such as translocation or captive breeding is to be undertaken. PMID:26061141

  2. Functional traits drive the contribution of solar radiation to leaf litter decomposition among multiple arid-zone species

    PubMed Central

    Pan, Xu; Song, Yao-Bin; Liu, Guo-Fang; Hu, Yu-Kun; Ye, Xue-Hua; Cornwell, William K.; Prinzing, Andreas; Dong, Ming; Cornelissen, Johannes H.C.

    2015-01-01

    In arid zones, strong solar radiation has important consequences for ecosystem processes. To better understand carbon and nutrient dynamics, it is important to know the contribution of solar radiation to leaf litter decomposition of different arid-zone species. Here we investigated: (1) whether such contribution varies among plant species at given irradiance regime, (2) whether interspecific variation in such contribution correlates with interspecific variation in the decomposition rate under shade; and (3) whether this correlation can be explained by leaf traits. We conducted a factorial experiment to determine the effects of solar radiation and environmental moisture for the mass loss and the decomposition constant k-values of 13 species litters collected in Northern China. The contribution of solar radiation to leaf litter decomposition varied significantly among species. Solar radiation accelerated decomposition in particular in the species that already decompose quickly under shade. Functional traits, notably specific leaf area, might predict the interspecific variation in that contribution. Our results provide the first empirical evidence for how the effect of solar radiation on decomposition varies among multiple species. Thus, the effect of solar radiation on the carbon flux between biosphere and atmosphere may depend on the species composition of the vegetation. PMID:26282711

  3. Functional traits drive the contribution of solar radiation to leaf litter decomposition among multiple arid-zone species.

    PubMed

    Pan, Xu; Song, Yao-Bin; Liu, Guo-Fang; Hu, Yu-Kun; Ye, Xue-Hua; Cornwell, William K; Prinzing, Andreas; Dong, Ming; Cornelissen, Johannes H C

    2015-01-01

    In arid zones, strong solar radiation has important consequences for ecosystem processes. To better understand carbon and nutrient dynamics, it is important to know the contribution of solar radiation to leaf litter decomposition of different arid-zone species. Here we investigated: (1) whether such contribution varies among plant species at given irradiance regime, (2) whether interspecific variation in such contribution correlates with interspecific variation in the decomposition rate under shade; and (3) whether this correlation can be explained by leaf traits. We conducted a factorial experiment to determine the effects of solar radiation and environmental moisture for the mass loss and the decomposition constant k-values of 13 species litters collected in Northern China. The contribution of solar radiation to leaf litter decomposition varied significantly among species. Solar radiation accelerated decomposition in particular in the species that already decompose quickly under shade. Functional traits, notably specific leaf area, might predict the interspecific variation in that contribution. Our results provide the first empirical evidence for how the effect of solar radiation on decomposition varies among multiple species. Thus, the effect of solar radiation on the carbon flux between biosphere and atmosphere may depend on the species composition of the vegetation. PMID:26282711

  4. Spatiotemporal variation of river temperature as a predictor of groundwater/surface-water interactions in an arid watershed in China

    NASA Astrophysics Data System (ADS)

    Yao, Yingying; Huang, Xiang; Liu, Jie; Zheng, Chunmiao; He, Xiaobo; Liu, Chuankun

    2015-08-01

    Interactions between groundwater and surface water in arid regions are complex, and recharge-discharge processes are often influenced by the hydrological regime, climate and geology. Traditional methods such as hydraulic gradient measuring by piezometers, differential discharge gauging and conservative tracer experiments, are often inadequate to capture the spatial and temporal variation of exchange rates. In this study, the distribution and the size of the overall groundwater inflow zone (GIZ) and the hyporheic inflow zone (HIZ) in the middle Heihe River Basin, northwest China, are characterized, and the relative inflow flux is estimated by high-resolution temperature measurements. Distributed temperature sensing (DTS) was used to measure the mixing temperatures of a 5-km reach of streambed with a spatial resolution of 0.5 m. The sampling interval was 0.25 m, and the temporal interval was 15 and 10 min at Pingchuan and Banqiao experimental sites, respectively. Two separate measurement periods in Pingchuan (Ping1, Ping2) captured different meteorological and stream-flow conditions. The results show that the number and the size range of the individual HIZs are greater than those of GIZs. Groundwater upwelling (GIZ) causes a larger decrease in river-water temperature with less inflow flux compared with the HIZ. The distribution pattern of HIZs and GIZs is influenced by the hydrodynamics of the river and the hydraulic permeability of the riverbed. High-resolution temperature variation based on DTS is an effective predictor of distributed inflows from groundwater upwelling and hyporheic exchange in an arid region.

  5. Global patterns and environmental controls of perchlorate and nitrate co-occurrence in arid and semi-arid environments

    NASA Astrophysics Data System (ADS)

    Jackson, W. Andrew; Böhlke, J. K.; Andraski, Brian J.; Fahlquist, Lynne; Bexfield, Laura; Eckardt, Frank D.; Gates, John B.; Davila, Alfonso F.; McKay, Christopher P.; Rao, Balaji; Sevanthi, Ritesh; Rajagopalan, Srinath; Estrada, Nubia; Sturchio, Neil; Hatzinger, Paul B.; Anderson, Todd A.; Orris, Greta; Betancourt, Julio; Stonestrom, David; Latorre, Claudio; Li, Yanhe; Harvey, Gregory J.

    2015-09-01

    Natural perchlorate (ClO4-) is of increasing interest due to its wide-spread occurrence on Earth and Mars, yet little information exists on the relative abundance of ClO4- compared to other major anions, its stability, or long-term variations in production that may impact the observed distributions. Our objectives were to evaluate the occurrence and fate of ClO4- in groundwater and soils/caliche in arid and semi-arid environments (southwestern United States, southern Africa, United Arab Emirates, China, Antarctica, and Chile) and the relationship of ClO4- to the more well-studied atmospherically deposited anions NO3- and Cl- as a means to understand the prevalent processes that affect the accumulation of these species over various time scales. ClO4- is globally distributed in soil and groundwater in arid and semi-arid regions on Earth at concentrations ranging from 10-1 to 106 μg/kg. Generally, the ClO4- concentration in these regions increases with aridity index, but also depends on the duration of arid conditions. In many arid and semi-arid areas, NO3- and ClO4- co-occur at molar ratios (NO3-/ClO4-) that vary between ∼104 and 105. We hypothesize that atmospheric deposition ratios are largely preserved in hyper-arid areas that support little or no biological activity (e.g. plants or bacteria), but can be altered in areas with more active biological processes including N2 fixation, N mineralization, nitrification, denitrification, and microbial ClO4- reduction, as indicated in part by NO3- isotope data. In contrast, much larger ranges of Cl-/ClO4- and Cl-/NO3- ratios indicate Cl- varies independently from both ClO4- and NO3-. The general lack of correlation between Cl- and ClO4- or NO3- implies that Cl- is not a good indicator of co-deposition and should be used with care when interpreting oxyanion cycling in arid systems. The Atacama Desert appears to be unique compared to all other terrestrial locations having a NO3-/ClO4- molar ratio ∼103. The relative

  6. ARID1A Deficiency Impairs the DNA Damage Checkpoint and Sensitizes Cells to PARP Inhibitors

    PubMed Central

    Shen, Jianfeng; Peng, Yang; Wei, Leizhen; Zhang, Wei; Yang, Lin; Lan, Li; Kapoor, Prabodh; Ju, Zhenlin; Mo, Qianxing; Shih, Ie-Ming; Uray, Ivan P.; Wu, Xiangwei; Brown, Powel H.; Shen, Xuetong; Mills, Gordon B.; Peng, Guang

    2015-01-01

    ARID1A, a chromatin remodeler of the SWI/SNF family, is a recently identified tumor suppressor that is mutated in a broad spectrum of human cancers. Thus, it is of fundamental clinical importance to understand its molecular functions and determine whether ARID1A deficiency can be exploited therapeutically. In this manuscript, we report a key function of ARID1A in regulating the DNA damage checkpoint. ARID1A is recruited to DNA double strand breaks (DSBs) via its interaction with the upstream DNA damage checkpoint kinase ATR. At the molecular level, ARID1A facilitates efficient processing of DSB to single strand ends, and sustains DNA damage signaling. Importantly, ARID1A deficiency sensitizes cancer cells to PARP inhibitors in vitro and in vivo providing a potential therapeutic strategy for patients with ARID1A-mutant tumors. PMID:26069190

  7. Modeling the Surface Water-Groundwater Interaction in Arid and Semi-Arid Regions Impacted by Agricultural Activities

    NASA Astrophysics Data System (ADS)

    Tian, Y.; Wu, B.; Zheng, Y.

    2013-12-01

    In many semi-arid and arid regions, interaction between surface water and groundwater plays an important role in the eco-hydrological system. The interaction is often complicated by agricultural activities such as surface water diversion, groundwater pumping, and irrigation. In existing surface water-groundwater integrated models, simulation of the interaction is often simplified, which could introduce significant simulation uncertainty under certain circumstance. In this study, GSFLOW, a USGS model coupling PRMS and MODFLOW, was improved to better characterize the surface water-groundwater interaction. The practices of water diversion from rivers, groundwater pumping and irrigation are explicitly simulated. In addition, the original kinematic wave routing method was replaced by a dynamic wave routing method. The improved model was then applied in Zhangye Basin (the midstream part of Heihe River Baisn), China, where the famous 'Silk Road' came through. It is a typical semi-arid region of the western China, with extensive agriculture in its oasis. The model was established and calibrated using the data in 2000-2008. A series of numerical experiments were conducted to evaluate the effect of those improvements. It has been demonstrated that with the improvements, the observed streamflow and groundwater level were better reproduced by the model. The improvements have a significant impact on the simulation of multiple fluxes associated with the interaction, such as groundwater discharge, riverbed seepage, infiltration, etc. Human activities were proved to be key elements of the water cycle in the study area. The study results have important implications to the water resources modeling and management in semi-arid and arid basins.

  8. Multistability of synchronous regimes in rotator ensembles.

    PubMed

    Kryukov, A K; Petrov, V S; Osipov, G V; Kurths, J

    2015-12-01

    We study collective dynamics in rotator ensembles and focus on the multistability of synchronous regimes in a chain of coupled rotators. We provide a detailed analysis of the number of coexisting regimes and estimate in particular, the synchronization boundary for different types of individual frequency distribution. The number of wave-based regimes coexisting for the same parameters and its dependence on the chain length are estimated. We give an analytical estimation for the synchronization frequency of the in-phase regime for a uniform individual frequency distribution. PMID:26723160

  9. Mid-Holocene erosive episodes in tufa deposits from Trabaque Canyon, central Spain, as a result of abrupt arid climate transitions

    NASA Astrophysics Data System (ADS)

    Domínguez-Villar, David; Vázquez-Navarro, Juan A.; Carrasco, Rosa M.

    2012-08-01

    During the Holocene a series of tufa sediments were deposited from a karstic spring along the Trabaque Canyon, central Spain. A long-term lowering of the water table caused the location of the spring to be displaced from the upper sector of the canyon during the early Holocene to the lower sector in the late Holocene. This progressive shift was in response to decreased precipitation in the region. The depositional environments and their geomorphologic relationships were characterized. Thus, five morphosedimentary units (MSUs) were identified within the Holocene tufa deposits. Erosive episodes were recognized between MSUs and, as most of the MSUs partially overlap, the older ones are perched in relation to the younger ones. The chronology of the MSUs is based on 14C dates, and stable isotopes and total organic carbon content provided environmental information during the period of tufa sedimentation. The successive dissection episodes in the Trabaque Canyon tufa deposits took place during transitioning climate conditions from the relatively wet early Holocene to the more arid late Holocene. During this transitional period in the mid-Holocene, wet phases alternated with more arid conditions, causing the largest hydrological regime gradients in the Holocene. Thus, the four erosive episodes causing tufa dissection in Trabaque during the Holocene are interpreted as the result of abrupt transitional periods towards arid conditions.

  10. Aridity changes over the Tibetan Plateau in recent three decades

    NASA Astrophysics Data System (ADS)

    Xia, L.; Gao, Y.

    2015-12-01

    The Tibetan Plateau (TP) is the highest and widest plateau in the world and it plays an important role in Asian and global climate and climate impacts. The ecosystems over the TP are rather fragile. Studies show the terrestrial changes in the TP in recent decades including desertification (Dong et al. 2012; Gao et al. 2014, 2015a, 2015b; Li et al. submitted; Gao et al. submitted). Arid climate plays a vital role in the presence of desertication. Aridity, as defined by the shortage of moisture, is a climatic phenomenon that is based on average climatic conditions over a region. Numerous indices have been proposed to quantify the degree of dryness of a climate at a given location. Ratio of precipitation and potential evapotranspiration (P/PET) describing the degree of moisture deficiency at a given location is worldwide used. In this study, P/PET was calculated to explore the aridity changes over the TP (Gao et al. 2015a). PET in 1979-2011 was calculated using the Penman-Monteith formulation based on the observed meteorological records at 83 China Meteorological Administration (CMA) stations in the TP. And the dominate factors on P/PET change are analyzed. The results indicate that stations located in the northwestern TP are becoming wetter and half of the stations in the eastern TP are becoming drier in recent three decades. The change patterns of precipitation, sunshine duration and diurnal temperature range have great influences on aridity change pattern especially precipitation. Precipitation is the dominant factors that affect aridity change on TP. How the aridity will change in the future under the warming has drawn great attention given the importance of the TP in the water resources in the Asia. GCMs output from CMIP5 could do the projection but with spread biases. Dynamic downscaling (DDM) could somehow reduce the local biases of the GCMs (Gao et al. 2011, 2015c). P/PET projections will be calculated through the bias corrected GCMs and DDM outputs.

  11. Climate warming threatens semi-arid forests in Inner Asia

    NASA Astrophysics Data System (ADS)

    WU, X.

    2015-12-01

    A line of evidences reveal an increasing tree growth decline and tree mortality mainly attributable to climate warming and the warming-mediated changes in drought and other processes in many parts of world tropical, temperate and boreal forests. However, the growth responses to climate change of the widely distributed semi-arid forests are unclear. Here, we synthetically investigate the tree growth patterns during past decades and its interannual response to climate variations in Inner Asia combining the ground truth field survey and samplings, remote sensing observations and climate data. We identified a pervasive tree growth decline since mid-1990s in semi-arid forests in Inner Asia. The widely observed tree growth decline is dominantly attributable to warming-induced water stress during pre- and early growing season. Tree growth of semi-arid forests in Inner Asia is particularly susceptible to spring warming and has been suffering a prolonged growth limitation in recent decades due to spring warming-mediated water conditions. Additionally, we identified a much slower growth rate in younger trees and a lack of tree regeneration in these semi-arid forests. The widely observed forest growth reduction and lack of tree regeneration over semi-arid forests in Inner Asia could predictably exert great effects on forest structure, regionally/globally biophysical and biochemical processes and the feedbacks between biosphere and atmosphere. Notably, further increases in forest stress and tree mortality could be reasonably expected, especially in context of the increase frequency and severity of high temperature and heat waves and changes in forest disturbances, potentially driving the eventual regional loss of current semi-arid forests. Given the potential risks of climate induced forest dieback, increased management attention to adaptation options for enhancing forest resistance and resilience to projected climate stress can be expected. However, the functionally realistic

  12. Climate Warming Threatens Semi-arid Forests in Inner Asia

    NASA Astrophysics Data System (ADS)

    WU, X.; Liu, H.; Qi, Z.; Li, X.

    2014-12-01

    A line of evidences reveal an increasing tree growth decline and tree mortality mainly attributable to climate warming and the warming-mediated changes in drought and other processes (such as fire and insect dynamics) in many parts of world tropical, temperate and boreal forests. However, the growth responses to climate change of the widely distributed semi-arid forests are unclear. Here, we synthetically investigate the tree growth patterns during past decades and its interannual response to climate variations in Inner Asia combining the ground truth field survey and samplings, remote sensing observations and climate data. We identified a pervasive tree growth decline since mid-1990s in semi-arid forests in Inner Asia. The widely observed tree growth decline is dominantly attributable to warming-induced water stress during pre- and early growing season. Tree growth of semi-arid forests in Inner Asia is particularly susceptible to spring warming and has been suffering a prolonged growth limitation in recent decades due to spring warming-mediated water conditions. Additionally, we identified a much slower growth rate in younger trees and a lack of tree regeneration in these semi-arid forests. The widely observed forest growth reduction and lack of tree regeneration over semi-arid forests in Inner Asia could predictably exert great effects on forest structure, regionally/globally biophysical and biochemical processes and the feedbacks between biosphere and atmosphere. Notably, further increases in forest stress and tree mortality could be reasonably expected, especially in context of the increase frequency and severity of high temperature and heat waves and changes in forest disturbances, potentially driving the eventual regional loss of current semi-arid forests. Given the potential risks of climate induced forest dieback, increased management attention to adaptation options for enhancing forest resistance and resilience to projected climate stress can be expected

  13. Analysis of principal parameters of forest fires and identification of desertification process in semi-arid land in Algeria

    NASA Astrophysics Data System (ADS)

    Zegrar, Ahmed

    2013-10-01

    In semi arid land in Algeria the ecosystem of steppe presents a different vegetal formation, generally used for pasture, and the forest are in most time composed by species like Aleppo pine sparse. And seen climatic unfavourable conditions in zone and impact of forest fires; we notes deterioration of physical environment particularly, deterioration of natural forest. This deterioration of forests provokes an unbalance of environment witch provokes a process of deterioration advanced in the ultimate stadium is desertification. The specific regeneration of plants are influenced greatly by the regime of fire (season of fire, intensity, interval), who leads to the recuperation of the vegetation of meadow- fire, but in the most case there are unfavourable climatic conditions. In this survey we used satellite data for detection of zones with risk of forest fire and their influenced parameters witch permit generally a desertification process. A thematic detailed analysis of forests ecosystems well attended, some processing on the satellite data (2003) allowed us to identify and classifying the forests in there opinion components flowers. We identified ampleness of fire on this zone also. The parameters slope, the proximity to the road and the forests formations and fire regime were studied in the goal of determining the zones to risk of fire drill. A crossing of information in a geographic information system according to a very determined logic allowed us to classify the zones in degree of risk of fire. These results compared with image data (2011) permit to conclude that in semi arid land the forest ecosystem after fire becomes steppe courses permitting installation of process of desertification.

  14. Development and use of bioenergy feedstocks for semi-arid and arid lands.

    PubMed

    Cushman, John C; Davis, Sarah C; Yang, Xiaohan; Borland, Anne M

    2015-07-01

    Global climate change is predicted to increase heat, drought, and soil-drying conditions, and thereby increase crop sensitivity to water vapour pressure deficit, resulting in productivity losses. Increasing competition between agricultural freshwater use and municipal or industrial uses suggest that crops with greater heat and drought durability and greater water-use efficiency will be crucial for sustainable biomass production systems in the future. Agave (Agavaceae) and Opuntia (Cactaceae) represent highly water-use efficient bioenergy crops that could diversify bioenergy feedstock supply yet preserve or expand feedstock production into semi-arid, abandoned, or degraded agricultural lands, and reclaim drylands. Agave and Opuntia are crassulacean acid metabolism species that can achieve high water-use efficiencies and grow in water-limited areas with insufficient precipitation to support traditional C3 or C4 bioenergy crops. Both Agave and Opuntia have the potential to produce above-ground biomass rivalling that of C3 and C4 crops under optimal growing conditions. The low lignin and high amorphous cellulose contents of Agave and Opuntia lignocellulosic biomass will be less recalcitrant to deconstruction than traditional feedstocks, as confirmed by pretreatments that improve saccharification of Agave. Refined environmental productivity indices and geographical information systems modelling have provided estimates of Agave and Opuntia biomass productivity and terrestrial sequestration of atmospheric CO2; however, the accuracy of such modelling efforts can be improved through the expansion of field trials in diverse geographical settings. Lastly, life cycle analysis indicates that Agave would have productivity, life cycle energy, and greenhouse gas balances comparable or superior to those of traditional bioenergy feedstocks, but would be far more water-use efficient. PMID:25873672

  15. Multi-metric calibration of hydrological model to capture overall flow regimes

    NASA Astrophysics Data System (ADS)

    Zhang, Yongyong; Shao, Quanxi; Zhang, Shifeng; Zhai, Xiaoyan; She, Dunxian

    2016-08-01

    Flow regimes (e.g., magnitude, frequency, variation, duration, timing and rating of change) play a critical role in water supply and flood control, environmental processes, as well as biodiversity and life history patterns in the aquatic ecosystem. The traditional flow magnitude-oriented calibration of hydrological model was usually inadequate to well capture all the characteristics of observed flow regimes. In this study, we simulated multiple flow regime metrics simultaneously by coupling a distributed hydrological model with an equally weighted multi-objective optimization algorithm. Two headwater watersheds in the arid Hexi Corridor were selected for the case study. Sixteen metrics were selected as optimization objectives, which could represent the major characteristics of flow regimes. Model performance was compared with that of the single objective calibration. Results showed that most metrics were better simulated by the multi-objective approach than those of the single objective calibration, especially the low and high flow magnitudes, frequency and variation, duration, maximum flow timing and rating. However, the model performance of middle flow magnitude was not significantly improved because this metric was usually well captured by single objective calibration. The timing of minimum flow was poorly predicted by both the multi-metric and single calibrations due to the uncertainties in model structure and input data. The sensitive parameter values of the hydrological model changed remarkably and the simulated hydrological processes by the multi-metric calibration became more reliable, because more flow characteristics were considered. The study is expected to provide more detailed flow information by hydrological simulation for the integrated water resources management, and to improve the simulation performances of overall flow regimes.

  16. A Framework Predicting Water Availability in a Rapidly Growing, Semi-Arid Region under Future Climate Change

    NASA Astrophysics Data System (ADS)

    Han, B.; Benner, S. G.; Glenn, N. F.; Lindquist, E.; Dahal, K. R.; Bolte, J.; Vache, K. B.; Flores, A. N.

    2014-12-01

    Climate change can lead to dramatic variations in hydrologic regime, affecting both surface water and groundwater supply. This effect is most significant in populated semi-arid regions where water availability are highly sensitive to climate-induced outcomes. However, predicting water availability at regional scales, while resolving some of the key internal variability and structure in semi-arid regions is difficult due to the highly non-linearity relationship between rainfall and runoff. In this study, we describe the development of a modeling framework to evaluate future water availability that captures elements of the coupled response of the biophysical system to climate change and human systems. The framework is built under the Envision multi-agent simulation tool, characterizing the spatial patterns of water demand in the semi-arid Treasure Valley area of Southwest Idaho - a rapidly developing socio-ecological system where urban growth is displacing agricultural production. The semi-conceptual HBV model, a population growth and allocation model (Target), a vegetation state and transition model (SSTM), and a statistically based fire disturbance model (SpatialAllocator) are integrated to simulate hydrology, population and land use. Six alternative scenarios are composed by combining two climate change scenarios (RCP4.5 and RCP8.5) with three population growth and allocation scenarios (Status Quo, Managed Growth, and Unconstrained Growth). Five-year calibration and validation performances are assessed with Nash-Sutcliffe efficiency. Irrigation activities are simulated using local water rights. Results show that in all scenarios, annual mean stream flow decreases as the projected rainfall increases because the projected warmer climate also enhances water losses to evapotranspiration. Seasonal maximum stream flow tends to occur earlier than in current conditions due to the earlier peak of snow melting. The aridity index and water deficit generally increase in the

  17. Hydrodynamic caracterisation of an heterogeneous aquifer system under semi-arid climate

    NASA Astrophysics Data System (ADS)

    Drias, T.; Toubal, A. Ch

    2009-04-01

    The studied zone is a part of the Mellegne's (North-East of Algeria) under pound, this zone is characterised by its semi-arid climate. The water bearing system is formed by the plio-quaternairy alluviums resting on a marley substratuim of age Eocene. The geostatiscitcs approach of the hydrodynamics parameters (Hydrolic load, transmisivity) allowed the study of their spatial distrubution (casting) by the method of Krigeage by blocks and the identification of zones with water-bearing potentialities. In this respect, the zone of Ain Chabro which, is situated in the South of the plain shows the best values of the transmisivity...... The use of a bidimensinnel model in the differences ended in the permanent regime allowed us to establish the global balence sheet (overall assessment) of the tablecloth and to refine the transmisivity field. These would vary more exactley between 10-4 to 10-2 m²/s. The method associating the probability appraoch of Krigeage to that determining the model has facilited the wedging of the model and clarified the inflitration value. Keys words: hydrodynamics, geostatiscitcs, Modeling, Chabro, Tébessa.

  18. CARBON AND NITROGEN STORAGE IN SOIL AND LITTER OF SOUTHERN CALIFORNIAN SEMI-ARID SHRUBLANDS

    PubMed Central

    Vourlitis, George L.; Zorba, Gypsi; Pasquini, Sarah C.; Mustard, Robert

    2009-01-01

    Semi-arid shrublands of southern California, including chaparral and coastal sage, are found in widely varying elevation and microclimatic regimes and are subjected to disturbance such as fire and atmospheric N deposition that have the capacity to alter soil and litter C and N storage. Here we present a case study where soil and litter C and N were measured over 19 months in post-fire chaparral and mature coastal sage stands to assess whether differences in soil and litter C and N between these diverse shrublands could be attributed to differences in elevation, stand age, rainfall, and/or estimated N deposition exposure. Our results indicate that atmospheric N deposition exposure, either alone or in conjunction with other environmental variables (elevation, rainfall, and/or stand age), was the most frequent predictor of the spatial pattern in the soil and litter N and C variables observed. These results are consistent with those reported for high-elevation coniferous forests arrayed along an N deposition gradient in southern California, suggesting that N deposition may affect the soil N and C storage of semiarid shrublands and woodlands in a qualitatively similar manner. PMID:21654933

  19. High Contribution of Gallery Forests to Local Evaporation in Semi-Arid Burkina Faso

    NASA Astrophysics Data System (ADS)

    Ceperley, N. C.; Mande, T.; Tyler, S. W.; Van De Giesen, N.; Rinaldo, A.; Parlange, M. B.

    2014-12-01

    Management of the hydrologic cycle is critical to the primary livelihood of a large part of semi-arid West Africa's primary livelihood, rain-fed farming. We use flux measurements from an eddy-covariance station coupled with a dense network of small wireless meteorological stations to examine the relationship between land surface properties (albedo, soil moisture, and roughness) and evapotranspiration in a small (3.5 km2) catchment in Burkina Faso, West Africa. The catchment is a matrix of savanna and agricultural land maintained under various regimes, providing a comparison of multiple land use types of Sudanian Wooded Savanna including a canyon gallery forest, agroforestry parklands, occasionally grazed semi-open savanna, a semi-closed wooded slope, fallow fields, rice paddies, and ephemeral wetlands. By filtering out times when dry air was entrained, we demonstrate the small control of soil moisture and vegetation on the evaporative fraction, which was not initially visible. Additionally we document the high contribution of the gallery forest to the the catchment evaporation, despite its small size. These small meteorological stations could be paired with currently available satellite data to calculate evaporation over a much larger area, even when eddy-covariance equipment is not available. These findings reinforce local cultural beliefs of the importance of gallery forests for climate regulation and may provide tools to key local decision makers, rural farmers.

  20. Capacitance densitometer for flow regime identification

    DOEpatents

    Shipp, Jr., Roy L.

    1978-01-01

    This invention relates to a capacitance densitometer for determining the flow regime of a two-phase flow system. A two-element capacitance densitometer is used in conjunction with a conventional single-beam gamma densitometer to unambiguously identify the prevailing flow regime and the average density of a flowing fluid.

  1. Regimes of DNA confined in a nanochannel

    NASA Astrophysics Data System (ADS)

    Dai, Liang; Doyle, Patrick

    2014-03-01

    Scaling regimes for polymers confined to tubular channels are well established when the channel cross-sectional dimension is either very small (Odjik regime) or large (classic de Gennes regime) relative to the polymer Kuhn length. In the literature, there is no clear consensus regarding the intermediate region and if subregimes even exist to connect these two classic bounding regimes. The confluence of emerging single DNA mapping technologies and a resurged interest in the fundamental properties of confined polymers has led to extensive research in this area using DNA as a model system. Due to the DNA molecule's properties and limitations of nanofabrication, most experiments are performed in this intermediate regime with channel dimensions of a few Kuhn lengths. Here we use simulations and theory to reconcile conflicting theories and show that there are indeed extended de Gennes, partial alignment and hairpin regimes located between the two classic regimes. Simulations results for both chain extension and free energy support the existence of these regimes. This research was supported by the National Research Foundation Singapore through the Singapore MIT Alliance for Research and Technology's research program in BioSystems and Micromechanics, the National Science Foundation (CBET-1335938).

  2. FISHER INFORMATION AND ECOSYSTEM REGIME CHANGES

    EPA Science Inventory

    Following Fisher’s work, we propose two different expressions for the Fisher Information along with Shannon Information as a means of detecting and assessing shifts between alternative ecosystem regimes. Regime shifts are a consequence of bifurcations in the dynamics of an ecosys...

  3. Cattle and pastoralism: survival and production in arid lands

    SciTech Connect

    Western, D.; Finch, V.

    1986-03-01

    Traditional subsistence pastoralists in East Africa tend to keep large herds, milk cattle in preference to eating them, and subject them to long foraging treks. Such practices are widely considered ill-suited to arid lands and are believed to arise because cattle are raised more for social prestige than food production. Whether this is true can only be judged by considering the responses of cattle to arid zones and, given the herder's goals and options, his management practices. In considering these factors, we show that indigenous East African cattle demonstrate energy-sparing capabilities during drought. Pastoralists can therefore herd cattle at great distances from water at little more cost than animals on the normal maintenance diet and watered more frequently. The physiological response of cattle to drought, the ecological constraints imposed by livestock and wildlife competition, and the energetic efficiency of mixed milk and meat pastoralism explain why herders traditionally select their characteristic management practices.

  4. Mitigating Climate Change in the Arid Lands of Namibia

    NASA Astrophysics Data System (ADS)

    Schneider, Martin B.; Sorensen, Marten

    2014-05-01

    Mitigating Climate Change in the Arid Lands of Namibia Namibia is the most arid country south of the Sahara, with scarce rainfall and perennial rivers only at its borders, > 80% of the area relies solely on groundwater. This has had devastating economic effects limiting opportunities for sustainable rural livelihoods that keep the population majority living below the World Bank poverty line (IFAD, 2013). A primary example of climatic variability which affects agrarian productivity is increased bush encroachment of Namibia's arid grazing land. The result has been a severe biodiversity loss, increased desertification and diminished water-use efficiency and underground water tables. Given these factors, Namibia's arid lands provide a unique opportunity to assess and test innovative / appropriate adaptation and mitigation strategies. Working toward sustainable management, restoration, and maintenance of balanced, resilient arid ecosystems in Namibia will also be a means to support and expand economic sectors incl. opportunities for job creation and potentially provide a model for similar arid regions. Main vegetation zones are: desert (46%), savannah (37%), and dry woodlands and forests (17%), i.e. < 2% is arable. Also, government protected areas cover 13.8% of the land surface. Current climate models suggest that Namibia faces serious risks, e.g. increased temperatures, hyper-arid conditions, and more frequent and extreme weather events (Pamaccafrica, 2013). The Namibian government, civil society organizations, and the scientific community attempt to address these risks and a certain level of institutional and human capacities are already in place. However, overall climate variability appears significantly higher than current plans and policies take into account. To improve livelihoods, reduce poverty, and food insecurity for rural Namibians in marginal/hyper-arid lands through sustainable climate change adaptation these objectives will be implemented: 1. Identify

  5. Mitigating Climate Change in the Arid Lands of Namibia

    NASA Astrophysics Data System (ADS)

    Schneider, Martin B.; Sorensen, Marten

    2014-05-01

    Mitigating Climate Change in the Arid Lands of Namibia Namibia is the most arid country south of the Sahara, with scarce rainfall and perennial rivers only at its borders, > 80% of the area relies solely on groundwater. This has had devastating economic effects limiting opportunities for sustainable rural livelihoods that keep the population majority living below the World Bank poverty line (IFAD, 2013). A primary example of climatic variability which affects agrarian productivity is increased bush encroachment of Namibia's arid grazing land. The result has been a severe biodiversity loss, increased desertification and diminished water-use efficiency and underground water tables. Given these factors, Namibia's arid lands provide a unique opportunity to assess and test innovative / appropriate adaptation and mitigation strategies. Working toward sustainable management, restoration, and maintenance of balanced, resilient arid ecosystems in Namibia will also be a means to support and expand economic sectors incl. opportunities for job creation and potentially provide a model for similar arid regions. Main vegetation zones are: desert (46%), savannah (37%), and dry woodlands and forests (17%), i.e. < 2% is arable. Also, government protected areas cover 13.8% of the land surface. Current climate models suggest that Namibia faces serious risks, e.g. increased temperatures, hyper-arid conditions, and more frequent and extreme weather events (Pamaccafrica, 2013). The Namibian government, civil society organizations, and the scientific community attempt to address these risks and a certain level of institutional and human capacities are already in place. However, overall climate variability appears significantly higher than current plans and policies take into account. To improve livelihoods, reduce poverty, and food insecurity for rural Namibians in marginal/hyper-arid lands through sustainable climate change adaptation these objectives will be implemented: 1. Identify

  6. Keeping Sediment and Nutrients out of Streams in Arid/Semi-Arid United States: Application of Low Impact Development/Green Infrastructure Practices

    EPA Science Inventory

    Climatic and hydrological characteristics in the arid/semi-arid areas create unique challenges to soil, water and biodiversity conservation. These areas are environmentally sensitive, but very valuable for the ecosystems services they provide to society. Some of these areas are...

  7. Estimating large-scale evapotranspiration in arid and semi-arid systems: A multi-site study linking MODIS and Ameriflux data

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A common goal for water resource managers is to ensure long-term water sustainability for increasing human populations in the arid and semi-arid southwestern United States. In these areas, estimating evapotranspiration (ET) at watershed or river-reach scales is critical in determining an amount of w...

  8. Green Infrastructure Management Techniques in Arid and Semi-arid Regions: Software Implementation and Demonstration using the AGWA/KINEROS2 Watershed Model

    EPA Science Inventory

    Increasing urban development in the arid and semi-arid regions of the southwestern United States has led to greater demand for water in a region with limited water resources and has fundamentally altered the hydrologic response of developed watersheds. Green Infrastructure (GI) p...

  9. Representing Green Infrastructure Management Techniques in Arid and Semi-arid Regions: Software Implementation and Demonstration using the AGWA/KINEROS2 Watershed Model

    EPA Science Inventory

    Increasing urban development in the arid and semi-arid regions of the southwestern United States has led to greater demand for water from a region of limited water resources which has fundamentally altered the hydrologic response of developed watersheds. Green Infrastructure (GI)...

  10. Blowout regimes of plasma wakefield acceleration.

    PubMed

    Lotov, K V

    2004-04-01

    A wide region of beam parameters is numerically scanned and the dependence of wakefield properties on the beam length and current is clarified for the blowout regime of beam-plasma interaction. The main regimes of the plasma response are found, which qualitatively differ in the plasma behavior. To characterize the efficiency of the energy exchange between the beam and the plasma, the energy flux through the comoving window is introduced. Scalings of the energy flux for the linear plasma response and the main blowout regimes are studied. The most efficient energy transfer occurs in the so-called "strong beam" regime of interaction. For this regime, analytical approximations for various aspects of the plasma response are obtained. PMID:15169104

  11. Discrete fluorescent saturation regimes in multilevel systems

    NASA Technical Reports Server (NTRS)

    Kastner, S. O.; Bhatia, A. K.

    1988-01-01

    Using models of multilevel atoms, the fluorescent process was examined for the ratio of the photooxidation rate, Pij, to the collisional oxidation rate, Cij, in the pumped resonance transition i-j. It is shown that, in the full range of the parameter Pij/Cij, there exist three distinct regimes (I, II, and III) which may be usefully exploited. These regimes are defined, respectively, by the following conditions: Pij/Cij smaller than about 1; Pij/Cij much greater than 1 and Pij much lower than Cki; and Pij/Cij much greater than 1 and Pij much higher than Cki, where Cki is the collisional rate populating the source level i. The only regime which is characterized by the sensitivity of fluorescent-fluorescent line intensity ratios to Pij is regime I. If regime III is reached, even fluorescent-nonfluorescent line ratios become independent of Pij. The analysis is applied to the resonant photoexcitation of a carbonlike ion.

  12. Arid land characterisation with EO-1 Hyperion hyperspectral data

    NASA Astrophysics Data System (ADS)

    Jafari, R.; Lewis, M. M.

    2012-10-01

    The low spectral resolution of multispectral satellite imagery limits its capability for extracting information in arid environments with sparse vegetation cover. The higher spectral resolution of hyperspectral imagery may improve discrimination of different vegetation types, even with low cover. The aim of this study was to evaluate the potential of Earth Observing 1 (EO-1) Hyperion hyperspectral data to discriminate arid landscape components in the southern rangelands of South Australia. Hyperion imagery was analysed with spectral mixture analysis to discriminate spectrally distinct land cover components. Five distinct end-members were extracted: two associated with vegetation cover and the remaining three associated with different soils and surface gravel and stone. The end-members were characterised with field spectra collected by ASD Fieldspec Pro spectrometer. To confirm the identity of the end-members we also investigated relationships between their abundance and field cover data collected at 54 sample sites using a step-point technique. One vegetation end-member was significantly correlated with Cottonbush (Maireanaaphylla) vegetation cover (R2 = 0.89) that was distributed as patches throughout the study area. The second vegetation end-member mapped green and grey-green perennial shrubs (e.g. Mulga, Acacia aneura) and was significantly correlated with total vegetation cover (R2 = 0.68). The soil and surface gravel and stone were not significantly correlated with the field estimates of these physical components. Despite the high spectral resolution of the Hyperion scene, spectral mixture analysis was unable to identify more than five meaningful spectral end-members in this arid environment. This may be the result of low vegetation cover of the region (28%), the lack of spectral contrast in arid vegetation types, and the ground resolution of Hyperion (900 m2) that reduced the ability to identify spectrally pure end-members to represent different land cover

  13. Snowpack regimes of the Western United States

    NASA Astrophysics Data System (ADS)

    Trujillo, Ernesto; Molotch, Noah P.

    2014-07-01

    Snow accumulation and melt patterns play a significant role in the water, energy, carbon, and nutrient cycles in the montane environments of the Western United States. Recent studies have illustrated that changes in the snow/rainfall apportionments and snow accumulation and melt patterns may occur as a consequence of changes in climate in the region. In order to understand how these changes may affect the snow regimes of the region, the current characteristics of the snow accumulation and melt patterns must be identified. Here we characterize the snow water equivalent (SWE) curve formed by the daily SWE values at 766 snow pillow stations in the Western United States, focusing on several metrics of the yearly SWE curves and the relationships between the different metrics. The metrics are the initial snow accumulation and snow disappearance dates, the peak snow accumulation and date of peak, the length of the snow accumulation season, the length of the snowmelt season, and the snow accumulation and snowmelt slopes. Three snow regimes emerge from these results: a maritime, an intermountain, and a continental regime. The maritime regime is characterized by higher maximum snow accumulations reaching 300 cm and shorter accumulation periods of less than 220 days. Conversely, the continental regime is characterized by lower maximum accumulations below 200 cm and longer accumulation periods reaching over 260 days. The intermountain regime lies in between. The regions that show the characteristics of the maritime regime include the Cascade Mountains, the Klamath Mountains, and the Sierra Nevada Mountains. The intermountain regime includes the Eastern Cascades slopes and foothills, the Blue Mountains, Northern and Central basins and ranges, the Columbia Mountains/Northern Rockies, the Idaho Batholith, and the Canadian Rockies. Lastly, the continental regime includes the Middle and Southern Rockies, and the Wasatch and Uinta Mountains. The implications of snow regime

  14. Environmental physiology of a small marsupial inhabiting arid floodplains.

    PubMed

    Warnecke, L; Cooper, C E; Geiser, F; Withers, P C

    2010-09-01

    Giles' planigale (Planigale gilesi) is among the smallest extant marsupials and inhabits deep soil cracks in arid floodplains. We examined whether its physiology shows specific adaptations to its extreme habitat. Metabolic rate, body temperature, evaporative water loss and thermal conductance were measured for eight planigales (average mass 9 g) exposed to four different ambient temperatures ranging from 10 degrees C to 32 degrees C. Water economy and respiratory variables were measured for the first time in this species. All of these standard physiological variables conformed to allometrically-predicted values for a marsupial. All variables were significantly affected by ambient temperature, except tidal volume and dry thermal conductance. Metabolic rate increased substantially at low ambient temperatures, as required to maintain a relatively constant body temperature of about 32-34 degrees C. This increased oxygen demand was accommodated by increased ventilation rather than increased oxygen extraction. Planigales had a comparatively high point of relative water economy of 19.1 degrees C, consistent with their small body size and arid habitat. Torpor reduced energy expenditure by 79% and evaporative water loss by 62%. Our study suggests that torpor use, along with behavioural adaptations, suffice for P. gilesi to live underground in arid habitats without further physiological adaptations. PMID:20451650

  15. Chromate Reduction and Retention Processes within Arid Subsurface Environments

    SciTech Connect

    Ginder-Vogel,M.; Borch, T.; Mayes, M.; Jardine, P.; Fendorf, S.

    2005-01-01

    Chromate is a widespread contaminant that has deleterious impacts on human health, the mobility and toxicity of which are diminished by reduction to Cr(III). While biological and chemical reduction reactions of Cr(VI) are well resolved, reduction within natural sediments, particularly of arid environments, remains poorly described. Here, we examine chromate reduction within arid sediments from the Hanford, WA site, where Fe(III) (hydr)oxide and carbonate coatings limit mineral reactivity. Chromium(VI) reduction by Hanford sediments is negligible unless pretreated with acid; acidic pretreatment of packed mineral beds having a Cr(VI) feed solution results in Cr(III) associating with the minerals antigorite and lizardite in addition to magnetite and Fe(II)-bearing clay minerals. Highly alkaline conditions (pH > 14), representative of conditions near high-level nuclear waste tanks, result in Fe(II) dissolution and concurrent Cr(VI) reduction. Additionally, Cr(III) and Cr(VI) are found associated with portlandite, suggesting a secondary mechanism for chromium retention at high pH. Thus, mineral reactivity is limited within this arid environment and appreciable reduction of Cr(VI) is restricted to highly alkaline conditions resulting near leaking radioactive waste disposal tanks.

  16. Mutations in ARID2 are associated with intellectual disabilities.

    PubMed

    Shang, Linshan; Cho, Megan T; Retterer, Kyle; Folk, Leandra; Humberson, Jennifer; Rohena, Luis; Sidhu, Alpa; Saliganan, Sheila; Iglesias, Alejandro; Vitazka, Patrik; Juusola, Jane; O'Donnell-Luria, Anne H; Shen, Yufeng; Chung, Wendy K

    2015-10-01

    The etiology of intellectual disabilities (ID) remains unknown for the majority of patients. Due to reduced reproductive fitness in many individuals with ID, de novo mutations account for a significant portion of severe ID. The ATP-dependent SWI/SNF chromatin modifier has been linked with neurodevelopmental disorders including ID and autism. ARID2 is an intrinsic component of polybromo-associated BAF (PBAF), the SWI/SNF subcomplex. In this study, we used clinical whole exome sequencing (WES) in proband-parent-trios to identify the etiology of ID. We identified four independent, novel, loss of function variants in ARID2 gene in four patients, three of which were confirmed to be de novo. The patients all have ID and share other clinical characteristics including attention deficit hyperactivity disorder, short stature, dysmorphic facial features, and Wormian bones. All four novel variants are predicted to lead to a premature termination with the loss of the two conservative zinc finger motifs. This is the first report of mutations in ARID2 associated with developmental delay and ID. PMID:26238514

  17. Chromate reduction and retention processes within arid subsurface environments.

    PubMed

    Ginder-Vogel, Matthew; Borch, Thomas; Mayes, Melanie A; Jardine, Phillip M; Fendorf, Scott

    2005-10-15

    Chromate is a widespread contaminantthat has deleterious impacts on human health, the mobility and toxicity of which are diminished by reduction to Cr(III). While biological and chemical reduction reactions of Cr(VI) are well resolved, reduction within natural sediments, particularly of arid environments, remains poorly described. Here, we examine chromate reduction within arid sediments from the Hanford, WA site, where Fe(III) (hydr)oxide and carbonate coatings limit mineral reactivity. Chromium(VI) reduction by Hanford sediments is negligible unless pretreated with acid; acidic pretreatment of packed mineral beds having a Cr(VI) feed solution results in Cr(III) associating with the minerals antigorite and lizardite in addition to magnetite and Fe(II)-bearing clay minerals. Highly alkaline conditions (pH > 14), representative of conditions near high-level nuclearwaste tanks, result in Fe(II) dissolution and concurrent Cr(VI) reduction. Additionally, Cr(III) and Cr(VI) are found associated with portlandite, suggesting a secondary mechanism for chromium retention at high pH. Thus, mineral reactivity is limited within this arid environment and appreciable reduction of Cr(VI) is restricted to highly alkaline conditions resulting near leaking radioactive waste disposal tanks. PMID:16295844

  18. Frame Shift/warp Compensation for the ARID Robot System

    NASA Technical Reports Server (NTRS)

    Latino, Carl D.

    1991-01-01

    The Automatic Radiator Inspection Device (ARID) is a system aimed at automating the tedious task of inspecting orbiter radiator panels. The ARID must have the ability to aim a camera accurately at the desired inspection points, which are in the order of 13,000. The ideal inspection points are known; however, the panel may be relocated due to inaccurate parking and warpage. A method of determining the mathematical description of a translated as well as a warped surface by accurate measurement of only a few points on this surface is developed here. The method uses a linear warp model whose effect is superimposed on the rigid body translation. Due to the angles involved, small angle approximations are possible, which greatly reduces the computational complexity. Given an accurate linear warp model, all the desired translation and warp parameters can be obtained by knowledge of the ideal locations of four fiducial points and the corresponding measurements of these points on the actual radiator surface. The method uses three of the fiducials to define a plane and the fourth to define the warp. Given this information, it is possible to determine a transformation that will enable the ARID system to translate any desired inspection point on the ideal surface to its corresponding value on the actual surface.

  19. Rock glaciers and the sediment dynamics in arid mountain belts

    NASA Astrophysics Data System (ADS)

    Blöthe, Jan Henrik; Höser, Thorsten; Rosenwinkel, Swenja; Korup, Oliver

    2016-04-01

    Rock glaciers are common periglacial features in highest elevations of semiarid to arid mountain ranges. Rock glaciers predominate in realms where precipitation values fall below thresholds that allow for ice glacier formation, then even outranging ice glaciers in size and number. The influence of ice glaciers on high-mountain's sediment dynamics is manifold: ice-glacier-driven erosion produces large amounts of clastic material; ice glaciers act as a conveyor belt for sediments, delivering material from their source regions to their terminus; ice glaciers entering trunk valleys form efficient dams that interrupt sediment delivery. While these mechanisms have been addressed in numerous earlier studies, the role of rock glaciers for the sediment dynamics of arid mountain belts remains elusive. We address this shortcoming by analysing a rock glacier inventory that we compiled for the Himalaya-Karakoram ranges and the Tien Shan ranges in Central Asia. Our inventory comprises more than 1000 specimen, a large number of which form dams of large trunk rivers and minor tributaries, disconnecting the sediment fluxes from upstream. In certain regions that are nearly devoid of ice-glaciers, like the Gamugah surface of NW Pakistan, rock glaciers of >10^4-m length occupy valley bottoms entirely, constituting the only mode of transport for sediments produced in headwaters. In conclusion, we call for a better understanding of the role that rock glaciers take in the sediment dynamics of arid mountain belts.

  20. Characteristics of the volatile organic compounds -- Arid Integrated Demonstration Site

    SciTech Connect

    Last, G.V.; Lenhard, R.J.; Bjornstad, B.N.; Evans, J.C.; Roberson, K.R.; Spane, F.A.; Amonette, J.E.; Rockhold, M.L.

    1991-10-01

    The Volatile Organic Compounds -- Arid Integrated Demonstration Program (VOC-Arid ID) is targeted at demonstration and testing of technologies for the evaluation and cleanup of volatile organic compounds and associated contaminants at arid DOE sites. The initial demonstration site is an area of carbon tetrachloride (CCl{sub 4}) contamination located near the center of the Hanford Site. The movement of CCl{sub 4} and other volatile organic contaminants in the subsurface is very complex. The problem at the Hanford Site is further complicated by the concurrent discharge of other waste constituents including acids, lard oil, organic phosphates, and transuranic radionuclides. In addition, the subsurface environment is very complex, with large spatial variabilities in hydraulic properties. A thorough understanding of the problem is essential to the selection of appropriate containment, retrieval, and/or in situ remedial technologies. The effectiveness of remedial technologies depends on knowing where the contaminants are, how they are held up in a given physical and chemical subsurface environment; and knowing the physical, chemical, and microbiological changes that are induced by the various remedial technologies.

  1. Eco-Physiological Responses of Dominant Species to Watering in a Natural Grassland Community on the Semi-Arid Loess Plateau of China.

    PubMed

    Niu, Furong; Duan, Dongping; Chen, Ji; Xiong, Peifeng; Zhang, He; Wang, Zhi; Xu, Bingcheng

    2016-01-01

    Altered precipitation regimes significantly affect ecosystem structure and function in arid and semi-arid regions. In order to investigate effects of precipitation changes on natural grassland community in the semi-arid Loess Plateau, the current research examined eco-physiological characteristics of two co-dominant species (i.e., Bothriochloa ischaemum and Lespedeza davurica) and community composition following two watering instances (i.e., precipitation pulses, July and August, 2011, respectively) in a natural grassland community. Results showed that the photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO2 concentration rapidly increased on the first to third day following watering in both species, and both months. Under watering treatments, the maximum net photosynthetic rates appeared on the second to third day after watering, which increased 30-80% in B. ischaemum and 40-50% in L. davurica compared with non-watering treatments, respectively. Leaf water use efficiency kept stable or initially decreased in both species under watering treatments. Watering in July produced more promoting effects on grass photosynthesis than in August, particularly in B. ischaemum. Community above-ground biomass at the end of the growing season increased after watering, although no significant changes in species diversity were observed. Our results indicated that timing and magnitude of watering could significantly affect plant eco-physiological processes, and there were species-specific responses in B. ischaemum and L. davurica. Pulsed watering increased community productivity, while did not significantly alter community composition after one growing season. The outcomes of this study highlight eco-physiological traits in dominant species may playing important roles in reshaping community composition under altered precipitation regimes. PMID:27242864

  2. Eco-Physiological Responses of Dominant Species to Watering in a Natural Grassland Community on the Semi-Arid Loess Plateau of China

    PubMed Central

    Niu, Furong; Duan, Dongping; Chen, Ji; Xiong, Peifeng; Zhang, He; Wang, Zhi; Xu, Bingcheng

    2016-01-01

    Altered precipitation regimes significantly affect ecosystem structure and function in arid and semi-arid regions. In order to investigate effects of precipitation changes on natural grassland community in the semi-arid Loess Plateau, the current research examined eco-physiological characteristics of two co-dominant species (i.e., Bothriochloa ischaemum and Lespedeza davurica) and community composition following two watering instances (i.e., precipitation pulses, July and August, 2011, respectively) in a natural grassland community. Results showed that the photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO2 concentration rapidly increased on the first to third day following watering in both species, and both months. Under watering treatments, the maximum net photosynthetic rates appeared on the second to third day after watering, which increased 30–80% in B. ischaemum and 40–50% in L. davurica compared with non-watering treatments, respectively. Leaf water use efficiency kept stable or initially decreased in both species under watering treatments. Watering in July produced more promoting effects on grass photosynthesis than in August, particularly in B. ischaemum. Community above-ground biomass at the end of the growing season increased after watering, although no significant changes in species diversity were observed. Our results indicated that timing and magnitude of watering could significantly affect plant eco-physiological processes, and there were species-specific responses in B. ischaemum and L. davurica. Pulsed watering increased community productivity, while did not significantly alter community composition after one growing season. The outcomes of this study highlight eco-physiological traits in dominant species may playing important roles in reshaping community composition under altered precipitation regimes. PMID:27242864

  3. Soil stabilization by biological soil crusts in arid Tunisia

    NASA Astrophysics Data System (ADS)

    Guidez, Sabine; Couté, Alain; Bardat, Jacques

    2015-04-01

    As part of the fight against desertification (LCD) in arid Tunisia, we have been able to highlight the important role played by biological soil crusts (BSC) in soil stabilization. The identification of the major species of cyanobacteria, lichens and bryophytes, their adaptation and terrestrial colonization strategies in this high climatic constraints area through their morpho-anatomical criteria have been set. In addition to their biological composition, their internal arrangement (i.e. texture and microstructure) reflects the structural stability of BSC against erosion. Precisely, the aggregative power of cyanobacteria and their ways of moving inside a soil, the capacity of mosses to grow through the sediments and lichens ability to bind at particles on surface, thus stabilizing the substrate have been demonstrated. Then, the three biological components ability to capture soil particles has been widely illustrated, proving the major environmental contribution of BSC in arid areas biological crusts formation, providing that soils will experience an increase of organic matter and fine particles rates subsequently gaining faster and better stability. Although the thickness and the morphology of crusts are related to the cover rates of these different biological components, the water properties of the latter, studied at the environmental SEM, illustrate their important role in altering the water cycle. Thus, the mixed crusts, i.e. with good presence of three biological components, cause the highest runoff rates by their ability to retain the water and spread on the surface. In spite of a swelling coefficient in presence of water higher than cryptogams, the cyanobacterial crusts located in newly stabilized areas of our studied region, remain finally insufficiently dense to impact surface hydrology. But, we showed after all that the cyanobacteria, pioneer species, have a certain environmental role. The lichen crusts cause a increased runoff because the lichens have a

  4. Evolution of the rainfall regime in the United Arab Emirates

    NASA Astrophysics Data System (ADS)

    Ouarda, T. B. M. J.; Charron, C.; Niranjan Kumar, K.; Marpu, P. R.; Ghedira, H.; Molini, A.; Khayal, I.

    2014-06-01

    Arid and semiarid climates occupy more than 1/4 of the land surface of our planet, and are characterized by a strongly intermittent hydrologic regime, posing a major threat to the development of these regions. Despite this fact, a limited number of studies have focused on the climatic dynamics of precipitation in desert environments, assuming the rainfall input - and their temporal trends - as marginal compared with the evaporative component. Rainfall series at four meteorological stations in the United Arab Emirates (UAE) were analyzed for assessment of trends and detection of change points. The considered variables were total annual, seasonal and monthly rainfall; annual, seasonal and monthly maximum rainfall; and the number of rainy days per year, season and month. For the assessment of the significance of trends, the modified Mann-Kendall test and Theil-Sen’s test were applied. Results show that most annual series present decreasing trends, although not statistically significant at the 5% level. The analysis of monthly time series reveals strong decreasing trends mainly occurring in February and March. Many trends for these months are statistically significant at the 10% level and some trends are significant at the 5% level. These two months account for most of the total annual rainfall in the UAE. To investigate the presence of sudden changes in rainfall time-series, the cumulative sum method and a Bayesian multiple change point detection procedure were applied to annual rainfall series. Results indicate that a change point happened around 1999 at all stations. Analyses were performed to evaluate the evolution of characteristics before and after 1999. Student’s t-test and Levene’s test were applied to determine if a change in the mean and/or in the variance occurred at the change point. Results show that a decreasing shift in the mean has occurred in the total annual rainfall and the number of rainy days at all four stations, and that the variance has

  5. Abrupt climate-independent fire regime changes

    USGS Publications Warehouse

    Pausas, Juli G.; Keeley, Jon E.

    2014-01-01

    Wildfires have played a determining role in distribution, composition and structure of many ecosystems worldwide and climatic changes are widely considered to be a major driver of future fire regime changes. However, forecasting future climatic change induced impacts on fire regimes will require a clearer understanding of other drivers of abrupt fire regime changes. Here, we focus on evidence from different environmental and temporal settings of fire regimes changes that are not directly attributed to climatic changes. We review key cases of these abrupt fire regime changes at different spatial and temporal scales, including those directly driven (i) by fauna, (ii) by invasive plant species, and (iii) by socio-economic and policy changes. All these drivers might generate non-linear effects of landscape changes in fuel structure; that is, they generate fuel changes that can cross thresholds of landscape continuity, and thus drastically change fire activity. Although climatic changes might contribute to some of these changes, there are also many instances that are not primarily linked to climatic shifts. Understanding the mechanism driving fire regime changes should contribute to our ability to better assess future fire regimes.

  6. Relationships between primary production and crop yields in semi-arid and arid irrigated agro-ecosystems

    NASA Astrophysics Data System (ADS)

    Jaafar, H. H.; Ahmad, F. A.

    2015-04-01

    In semi-arid areas within the MENA region, food security problems are the main problematic imposed. Remote sensing can be a promising too early diagnose food shortages and further prevent the population from famine risks. This study is aimed at examining the possibility of forecasting yield before harvest from remotely sensed MODIS-derived Enhanced Vegetation Index (EVI), Net photosynthesis (net PSN), and Gross Primary Production (GPP) in semi-arid and arid irrigated agro-ecosystems within the conflict affected country of Syria. Relationships between summer yield and remotely sensed indices were derived and analyzed. Simple regression spatially-based models were developed to predict summer crop production. The validation of these models was tested during conflict years. A significant correlation (p<0.05) was found between summer crop yield and EVI, GPP and net PSN. Results indicate the efficiency of remotely sensed-based models in predicting summer yield, mostly for cotton yields and vegetables. Cumulative summer EVI-based model can predict summer crop yield during crisis period, with deviation less than 20% where vegetables are the major yield. This approach prompts to an early assessment of food shortages and lead to a real time management and decision making, especially in periods of crisis such as wars and drought.

  7. Identification and functional characterization of a novel bipartite nuclear localization sequence in ARID1A.

    PubMed

    Bateman, Nicholas W; Shoji, Yutaka; Conrads, Kelly A; Stroop, Kevin D; Hamilton, Chad A; Darcy, Kathleen M; Maxwell, George L; Risinger, John I; Conrads, Thomas P

    2016-01-01

    AT-rich interactive domain-containing protein 1A (ARID1A) is a recently identified nuclear tumor suppressor frequently altered in solid tumor malignancies. We have identified a bipartite-like nuclear localization sequence (NLS) that contributes to nuclear import of ARID1A not previously described. We functionally confirm activity using GFP constructs fused with wild-type or mutant NLS sequences. We further show that cyto-nuclear localized, bipartite NLS mutant ARID1A exhibits greater stability than nuclear-localized, wild-type ARID1A. Identification of this undescribed functional NLS within ARID1A contributes vital insights to rationalize the impact of ARID1A missense mutations observed in patient tumors. PMID:26614907

  8. VOC-Arid Integrated Demonstration guide to preparation of demonstration documents

    SciTech Connect

    Jensen, E.J.; Brouns, T.M.; Koegler, K.J.; McCabe, G.H.; Morris, F.A.

    1994-06-01

    This guide has been prepared by Demonstration Operations of the Volatile Organic Compound-Arid Integrated Demonstration (VOC-Arid ID). Its purpose is to describe demonstration documents, designate responsibilities for these documents, and guide the Principal Investigator (PI) and others in their preparation. The main emphasis of this guide is to describe the documentation required of the PI. However, it does cover some of the responsibilities of other members of the VOC-Arid ID team. The VOC-Arid ID is one of several US Department of Energy (DOE) integrated demonstrations designed to support the demonstration of emerging environmental management and restoration technologies. The principal objective of the VOC-Arid ID is to identify, develop, and demonstrate new and innovative technologies for environmental restoration at arid or semiarid sites containing volatile organic compounds with or without associated contamination (e.g., radionuclides and metals).

  9. Spatiotemporal analysis and trends of aridity of Iberian Peninsula (1960-2010)

    NASA Astrophysics Data System (ADS)

    Paniagua, Luis L.; García, Abelardo; Moral, Francisco J.; Rebollo, Francisco J.

    2016-04-01

    In this study the aridity of the Iberian Peninsula was analysed, taking into account 45 stations in Spain and Portugal from 1960 to 2010. The De Martonne Index was considered. The goal of this study was to explore the spatial distribution and to determine monotonic trends and shift changes in annual aridity by using the Mann-Kendall test and the Seńs estimator. The spatially interpolated maps of the aridity indice were generated using the ordinary kriging algorithm in a geographic information system (GIS) environment. A great variability for Martonne Index was found, gathering from semiarid climates to extremely humid, although the former being the dominant type. 41 temporal series showed decreasing tendencies, 15 of them significant, belonging to all climate types, which indicates a increase in aridity during the research period. A shift in the aridity tendency has been observed around 1979, and a period of greater aridity started since.

  10. New Technologies to Reclaim Arid Lands User's Manual

    SciTech Connect

    W. K. Ostler

    2002-10-01

    Approximately 70 percent of all U.S. military training lands are located in arid and semi-arid areas. Training activities in such areas frequently adversely affect vegetation, damaging plants and reducing the resilience of vegetation to recover once disturbed. Fugitive dust resulting from a loss of vegetation creates additional problems for human health, increasing accidents due to decreased visibility, and increasing maintenance costs for roads, vehicles, and equipment. Under conventional technologies to mitigate these impacts, it is estimated that up to 35 percent of revegetation projects in arid areas will fail due to unpredictable natural environmental conditions, such as drought, and reclamation techniques that were inadequate to restore vegetative cover in a timely and cost-effective manner. New reclamation and restoration techniques are needed in desert ranges to help mitigate the adverse effects of military training and other activities to arid-land environments. In 1999, a cooperative effort between the U.S. Department of Energy (DOE), the US. Department of Defense (DoD), and selected university scientists was undertaken to focus on mitigating military impacts in arid lands. As arid lands are impacted due to DoD and DOE activities, biological and soil resources are gradually lost and the habitat is altered. A conceptual model of that change in habitat quality is described for varying levels of disturbance in the Mojave Desert. As the habitat quality degrades and more biological and physical resources are lost from training areas, greater costs are required to return the land to sustainable levels. The purpose of this manual is to assist land managers in recognizing thresholds associated with habitat degradation and provide reclamation planning and techniques that can reduce the costs of mitigation for these impacted lands to ensure sustainable use of these lands. The importance of reclamation planning is described in this manual with suggestions about

  11. Discharge estimation in arid areas with the help of optical satellite data

    NASA Astrophysics Data System (ADS)

    Mett, M.; Aufleger, M.

    2009-04-01

    The MENA region is facing severe water scarcity. Overexploitation of groundwater resources leads to an ongoing drawdown of the water tables, salinisation and desertification of vast areas. To make matters worse enormous birth-rates, economic growth and refugees from conflict areas let the need for water explode. In the context of climate change this situation will even worsen and armed conflicts are within the bounds of possibility. To ease water scarcity many innovative techniques like artificial groundwater recharge are being developed or already state of the art. But missing hydrological information (for instance discharge data) often prevents design and efficient operation of such measures. Especially in poor countries hydrological measuring devices like gage stations are often missing, in a bad status or professionals of the water sector are absent. This leads to the paradox situation that in many arid regions water resources are indeed available but they cannot be utilised because they are not known. Nowadays different approaches are being designed to obtain hydrological information from perennial river systems with the help of satellite techniques. Mostly they are based on hydraulic parameters like river dimensions, roughness and water levels which can be derived from satellite data. By using conventional flow formulas and additional field investigations the discharge can be estimated. Another methodology derived information about maximum flow depth and flow width from optical sensors of high resolution to calculate discharge of the rivers whilst the flood. Attempts to derive discharge information from structural components of the river and fluviomorphologic changes due to changing flow regimes are in the focus of recent research. One attempt used Synthetic Aperture Radar (SAR) data to estimate discharge in braided river systems. Other attempts used airborne SAR imagery to obtain information about sinuosity and total river width of perennial braided river

  12. ARID1A immunohistochemistry improves outcome prediction in invasive urothelial carcinoma of urinary bladder.

    PubMed

    Faraj, Sheila F; Chaux, Alcides; Gonzalez-Roibon, Nilda; Munari, Enrico; Ellis, Carla; Driscoll, Tina; Schoenberg, Mark P; Bivalacqua, Trinity J; Shih, Ie-Ming; Netto, George J

    2014-11-01

    AT-rich interactive domain 1A (ARID1A) is tumor suppressor gene that interacts with BRG1 adenosine triphosphatase to form a SWI/SNF chromatin remodeling protein complex. Inactivation of ARID1A has been described in several neoplasms, including epithelial ovarian and endometrial carcinomas, and has been correlated with prognosis. In the current study, ARID1A expression in urothelial carcinoma (UC) of the bladder and its association with clinicopathological parameters and outcome are addressed. Five tissue microarrays were constructed from 136 cystectomy specimens performed for UC at our institution. Nuclear ARID1A staining was evaluated using immunohistochemistry. An H-score was calculated as the sum of the products of intensity (0-3) multiplied by extent of expression (0%-100%). Average H-score per case was used for statistical analysis. ARID1A expression was categorized in low and high using Youden index to define the cut point. ARID1A expression significantly increased from normal to noninvasive UC to invasive UC. For both tumor progression and cancer death, Youden index yielded an H-score of 288 as the optimal cut point for ARID1A expression. Low ARID1A expression showed a tendency for lower risk of tumor progression and cancer mortality. Adding ARID1A expression to pathologic features offers a better model for predicting outcome than pathologic features alone. Low ARID1A expression was more frequently seen in earlier stage disease. There was a tendency for low ARID1A expression to predict better outcome. More importantly, the findings indicate that adding ARID1A expression to pathologic features increases the goodness of fit of the predictive model. PMID:25175170

  13. Various ARID1A expression patterns and their clinical significance in gastric cancers.

    PubMed

    Kim, Young-Bae; Ham, In-Hye; Hur, Hoon; Lee, Dakeun

    2016-03-01

    AT-rich interactive domain 1A (ARID1A) is frequently mutated in gastric cancers, and loss of ARID1A expression is considered a poor prognostic factor in various cancers. However, in practice, ARID1A shows various expression patterns, and our understanding of its significance is limited. We performed immunohistochemistry for ARID1A, MLH1, and pS6 using whole tissue blocks of 350 gastric cancers and classified the ARID1A expression as follows: retained (63.7%), reduced (17.7%), complete loss (14.9%), and partial loss (3.7%). Complete/partial loss was more common in poorly differentiated histology (P < .001), and reduced or complete loss of ARID1A was frequent in cases with MLH1 loss (P < .001). The ARID1A-reduced group showed only slightly inferior disease-free survival (DFS; P = .254) and overall survival (OS; P = .377) compared to those of the ARID1A-retained group, whereas the group with complete loss showed significantly worse DFS (hazard ratio [HR], 1.732; P = .015) and OS (HR, 1.751; P = .013). Worse DFS (HR, 2.672; P = .005) and OS (HR, 2.531; P = .002) were also noted in the group with partial loss. High expression of pS6 was observed more frequently in groups showing altered ARID1A expression patterns (P < .001). In conclusion, reduced ARID1A expression is not a major prognostic determinant, although it may lead to AKT pathway activation. Tumor cells lacking ARID1A expression may influence the prognosis even if they constitute only a small proportion of the tumor sample. Our data provide an enhanced roadmap for understanding ARID1A with implications for future research and therapeutics. PMID:26826411

  14. Epigenetic synthetic lethality in ovarian clear cell carcinoma: EZH2 and ARID1A mutations

    PubMed Central

    Bitler, Benjamin G; Aird, Katherine M; Zhang, Rugang

    2016-01-01

    The components of the Switch/Sucrose non-fermentable (SWI/SNF) complex are mutated in approximately 20% of human cancers. The A/T-rich interacting domain 1A (ARID1A) subunit has one of the highest mutation rates. Most notably, ARID1A is mutated in over 50% of ovarian clear cell carcinomas (OCCCs). We reported that inhibition of enhancer of zeste homology 2 (EZH2) is synthetically lethal in ARID1A-mutated OCCC. PMID:27308548

  15. Spatial distribution and comparison of aridity indices in Extremadura, southwestern Spain

    NASA Astrophysics Data System (ADS)

    Moral, Francisco J.; Rebollo, Francisco J.; Paniagua, Luis L.; García-Martín, Abelardo; Honorio, Fulgencio

    2015-09-01

    In semi-arid lands with warm climates, aridity is a real hazard, with the threat of desertification because of greater precipitation variability and prolonged droughts. Aridity indices can be used to identify areas prone to desertification. The present study aimed to analyse the spatial distribution of aridity in Extremadura, southwestern Spain, using three indices: the De Martonne aridity index (I DM), the Pinna combinative index (I P), and the Food and Agriculture Organization (FAO) aridity index (I F). Temperature, precipitation, and evapotranspiration data from 90 weather stations located throughout Extremadura and 27 along boundaries with at least 30-year length (within the 1980-2011 period) were used to compute each index at each station. The statistical properties of each aridity index were assessed, and later, they were mapped by means of an integrated geographic information system (GIS) and a multivariate geostatistical (regression-kriging) algorithm in which exhaustive secondary information on elevation was incorporated. Annual and seasonal I DM and I F, and annual I P-kriged maps were generated. According to annual I DM, the semi-arid and Mediterranean conditions are predominant in the region, covering about 70 % of the territory, while about 94 % of the areas are classified as dry and semi-dry Mediterranean based on annual I P and about 86 % are classified as semi-arid and dry categories based on annual I F. The most vulnerable to aridity are the natural regions located to the west, the south, and the southeast of Extremadura, especially during summer, when arid conditions are found across the region. Although the three aridity indices were highly correlated, displaying similar spatial patterns, I DM was preferred because it can better discriminate different climate conditions in Extremadura.

  16. Epigenetic synthetic lethality in ovarian clear cell carcinoma: EZH2 and ARID1A mutations.

    PubMed

    Bitler, Benjamin G; Aird, Katherine M; Zhang, Rugang

    2016-01-01

    The components of the Switch/Sucrose non-fermentable (SWI/SNF) complex are mutated in approximately 20% of human cancers. The A/T-rich interacting domain 1A (ARID1A) subunit has one of the highest mutation rates. Most notably, ARID1A is mutated in over 50% of ovarian clear cell carcinomas (OCCCs). We reported that inhibition of enhancer of zeste homology 2 (EZH2) is synthetically lethal in ARID1A-mutated OCCC. PMID:27308548

  17. Estimation of soil moisture-thermal infrared emissivity relation in arid and semi-arid environments using satellite observations

    NASA Astrophysics Data System (ADS)

    Grazia Blasi, Maria; Masiello, Guido; Serio, Carmine; Venafra, Sara; Liuzzi, Giuliano; Dini, Luigi

    2016-04-01

    The retrieval of surface parameters is very important for various aspects concerning the climatological and meteorological context. At this purpose surface emissivity represents one of the most important parameters useful for di fferent applications such as the estimation of climate changes and land cover features. It is known that thermal infrared (TIR) emissivity is aff ected by soil moisture, but there are very few works in literature on this issue. This study is aimed to analyze and fi nd a relation between satellite soil moisture data and TIR emissivity focusing on arid and semi-arid environments. These two parameters, together with the land surface temperature, are fundamental for a better understanding of the physical phenomena implied in the soil-atmosphere interactions and the surface energy balance. They are also important in several fi elds of study, such as climatology, meteorology, hydrology and agriculture. In particular, there are several studies stating a correlation between soil moisture and the emissivity at 8-9 μ m in desertic soils, which corresponds to the quartz Reststrahlen, a feature which is typical of sandy soils. We investigated several areas characterized by arid or semi-arid environments, focusing our attention on the Dahra desert (Senegal), and on the Negev desert (Israel). For the Dahra desert we considered both in situ, provided by the International Soil Moisture Network, and satellite soil moisture data, from ASCAT and AMSR-E sensors, for the whole year 2011. In the case of the Negev desert soil moisture data are derived from ASCAT observations and we computed a soil moisture index from a temporal series of SAR data acquired by the Cosmo-SkyMed constellation covering a period of six months, from June 2015 to November 2015. For both cases soil moisture data were related to the retrieved TIR emissivity from the geostationary satellite SEVIRI in three di erent spectral channels, at 8.7 μm, 10.8 μ m and 12 μ m. A Kalman lter

  18. Are faults preferential flow paths through semiarid and arid vadose zones?

    NASA Astrophysics Data System (ADS)

    Sigda, John M.; Wilson, John L.

    2003-08-01

    Numerous faults crosscut the poorly lithified, basin-fill sands found in New Mexico's Rio Grande rift and in other extensional regimes. The deformational processes that created these faults sharply reduced both fault porosity and fault saturated hydraulic conductivity by altering grains and pores, particularly in structures referred to as deformation bands. The resulting pore distribution changes, which create barriers to saturated flow, should enhance fault unsaturated flow relative to parent sand under the relatively dry conditions of the semiarid southwest. We report the first measurements of unsaturated hydraulic properties for undisturbed fault materials, using samples from a small-displacement normal fault and parent sands in the Bosque del Apache Wildlife Refuge, central New Mexico. Fault samples were taken from a narrow zone of deformation bands. The unsaturated flow apparatus (UFA) centrifuge system was used to measure both relative permeability and moisture retention curves. We compared these relations and fitted hydraulic conductivity-matric potential models to test whether the fault has significantly different unsaturated hydraulic properties than its parent sand. Saturated conductivity is 3 orders of magnitude less in the fault than the undeformed sand. As matric potential decreases from 0 to -200 cm, unsaturated conductivity decreases roughly 1 order of magnitude in the fault but 5-6 orders of magnitude in undeformed sands. Fault conductivity is greater by 2-6 orders of magnitude at matric potentials between -200 and -1000 cm, which are typical potentials for semiarid and arid vadose zones. Fault deformation bands have much higher air-entry matric potential values than parent sands and remain close to saturation well after the parent sands have begun to approach residual moisture content. Under steady state, one-dimensional, gravity-driven flow conditions, moisture transport and solute advection is 102-106 times larger in the fault material than

  19. Modeling the Hydrological Response to Climate Change in an Arid Inland River Basin

    NASA Astrophysics Data System (ADS)

    Zheng, C.; Zhang, A.; Tian, Y.; Zheng, Y.; Liu, J.

    2014-12-01

    Located deep in the hinterlands of Eurasia, the Heihe River Basin (HRB) is an arid inland river basin in northwest China where the hydrologic regime responds sensitively to climate change. From the headwater region to terminal lakes, the HRB can be roughly divided into three sections, i.e., the upstream Qilian Mountains, the midstream oases and the downstream Gobi Desert. Runoff generated in the upstream mountainous terrains, dominated by climate variations, is the critical water resource for the whole river basin. With increasing intensification of climate change, there is an urgent need to understand future changes of water resources and water-related disasters to support regional water management. This study investigates the potential impact of climate change on hydrologic processes in the upper HRB for the future period of 2021~2150. Downscaled temperature and precipitation projections from six General Circulation Models under two emission scenarios (RCP4.5 and RCP8.5) are adopted to drive a commonly used flow model, Soil Water Assessment Tool (SWAT), for the upper HRB. The impacts of climate change on the total runoff and its components are quantified based on the future climate scenario analysis and the results of SWAT simulation. To understand how the climate change affects the availability and distribution of water resources in the middle and lower HRB where irrigated agriculture and ecosystem conservation compete for water resources, runoffs from the upper HRB are used as the boundary conditions for an integrated groundwater-surface water model based on the USGS GSFLOW for the middle and lower HRB. The integrated model assimilated multiple types of data including groundwater levels at monitoring wells, streamflow at gaging stations, and evapotranspiration (ET) derived from remote sensing data. The calibrated model was able to adequately reproduce the observed hydrological variables. The integrated model was then used to assess the potential response of the

  20. Targeting EZH2 methyltransferase activity in ARID1A mutated cancer cells is synthetic lethal

    PubMed Central

    Biter, Benjamin G.; Aird, Katherine M.; Garipov, Azat; Li, Hua; Amatangelo, Michael; Kossenkov, Andrew V.; Schultz, David C.; Liu, Qin; Shih, Ie-Ming; Conejo-Garcia, Jose R.; Speicher, David W.; Zhang, Rugang

    2015-01-01

    ARID1A, a chromatin remodeler, shows one of the highest mutation rates across many cancer types. Notably, ARID1A is mutated in over 50% of ovarian clear cell carcinomas, which currently has no effective therapy. To date, clinically applicable targeted cancer therapy based on ARID1A mutational status has not been described. Here we show that inhibition of the EZH2 methyltransferase acts in a synthetic lethal manner in ARID1A mutated ovarian cancer cells. ARID1A mutational status correlates with response to the EZH2 inhibitor. We identified PIK3IP1 as a direct ARID1A/EZH2 target, which is upregulated by EZH2 inhibition and contributes to the observed synthetic lethality by inhibiting PI3K/AKT signaling. Significantly, EZH2 inhibition causes regression of ARID1A mutated ovarian tumors in vivo. Together, these data demonstrate for the first time a synthetic lethality between ARID1A mutation and EZH2 inhibition. They indicate that pharmacological inhibition of EZH2 represents a novel treatment strategy for ARID1A mutated cancers. PMID:25686104

  1. Androgen Receptor Coactivator ARID4B Is Required for the Function of Sertoli Cells in Spermatogenesis.

    PubMed

    Wu, Ray-Chang; Zeng, Yang; Pan, I-Wen; Wu, Mei-Yi

    2015-09-01

    Defects in spermatogenesis, a process that produces spermatozoa inside seminiferous tubules of the testis, result in male infertility. Spermatogenic progression is highly dependent on a microenvironment provided by Sertoli cells, the only somatic cells and epithelium of seminiferous tubules. However, genes that regulate such an important activity of Sertoli cells are poorly understood. Here, we found that AT-rich interactive domain 4B (ARID4B), is essential for the function of Sertoli cells to regulate spermatogenesis. Specifically, we generated Sertoli cell-specific Arid4b knockout (Arid4bSCKO) mice, and showed that the Arid4bSCKO male mice were completely infertile with impaired testis development and significantly reduced testis size. Importantly, severe structural defects accompanied by loss of germ cells and Sertoli cell-only phenotype were found in many seminiferous tubules of the Arid4bSCKO testes. In addition, maturation of Sertoli cells was significantly delayed in the Arid4bSCKO mice, associated with delayed onset of spermatogenesis. Spermatogenic progression was also defective, showing an arrest at the round spermatid stage in the Arid4bSCKO testes. Interestingly, we showed that ARID4B functions as a "coactivator" of androgen receptor and is required for optimal transcriptional activation of reproductive homeobox 5, an androgen receptor target gene specifically expressed in Sertoli cells and critical for spermatogenesis. Together, our study identified ARID4B to be a key regulator of Sertoli cell function important for male germ cell development. PMID:26258622

  2. Earth Regime Network Evolution Study (ERNESt)

    NASA Technical Reports Server (NTRS)

    Menrad, Bob

    2016-01-01

    Speaker and Presenter at the Lincoln Laboratory Communications Workshop on April 5, 2016 at the Massachusetts Institute of Technology Lincoln Laboratory in Lexington, MA. A visual presentation titled Earth Regimes Network Evolution Study (ERNESt).

  3. Westerly jet stream and past millennium climate change in Arid Central Asia simulated by COSMO-CLM model

    NASA Astrophysics Data System (ADS)

    Fallah, Bijan; Sodoudi, Sahar; Cubasch, Ulrich

    2016-05-01

    This study tackles one of the most debated questions around the evolution of Central Asian climate: the "Puzzle" of moisture changes in Arid Central Asia (ACA) throughout the past millennium. A state-of-the-art Regional Climate Model (RCM) is subsequently employed to investigate four different 31-year time slices of extreme dry and wet spells, chosen according to changes in the driving data, in order to analyse the spatio-temporal evolution of the moisture variability in two different climatological epochs: Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). There is a clear regime behavior and bimodality in the westerly Jet phase space throughout the past millennium in ACA. The results indicate that the regime changes during LIA show a moist ACA and a dry East China. During the MCA, the Kazakhstan region shows a stronger response to the westerly jet equatorward shift than during the LIA. The out-of-phase pattern of moisture changes between India and ACA exists during both the LIA and the MCA. However, the pattern is more pronounced during the LIA.

  4. Electron transport fluxes in potato plateau regime

    SciTech Connect

    Shaing, K.C.; Hazeltine, R.D.

    1997-12-01

    Electron transport fluxes in the potato plateau regime are calculated from the solutions of the drift kinetic equation and fluid equations. It is found that the bootstrap current density remains finite in the region close to the magnetic axis, although it decreases with increasing collision frequency. This finite amount of the bootstrap current in the relatively collisional regime is important in modeling tokamak startup with 100{percent} bootstrap current. {copyright} {ital 1997 American Institute of Physics.}

  5. Molecular motors in conservative and dissipative regimes

    NASA Astrophysics Data System (ADS)

    Perez-Carrasco, R.; Sancho, J. M.

    2011-10-01

    We present a theoretical study of a rotatory molecular motor under a conservative torque regime. We show that conservative and dissipative regimes present a different observable phenomenology. Our approach starts with a preliminary deterministic calculation of the motor cycle, which is complemented with stochastic simulations of a Langevin equation under a flashing ratchet potential. Finally, by using parameter values obtained from independent experimental information, our theoretical predictions are compared with experimental data of the F1-ATPase motor of the Bacillus PS3.

  6. Altered stream-flow regimes and invasive plant species: The Tamarix case

    USGS Publications Warehouse

    Stromberg, J.C.; Lite, S.J.; Marler, R.; Paradzick, C.; Shafroth, P.B.; Shorrock, D.; White, J.M.; White, M.S.

    2007-01-01

    Aim: To test the hypothesis that anthropogenic alteration of stream-flow regimes is a key driver of compositional shifts from native to introduced riparian plant species. Location: The arid south-western United States; 24 river reaches in the Gila and Lower Colorado drainage basins of Arizona. Methods: We compared the abundance of three dominant woody riparian taxa (native Populus fremontii and Salix gooddingii, and introduced Tamarix) between river reaches that varied in stream-flow permanence (perennial vs. intermittent), presence or absence of an upstream flow-regulating dam, and presence or absence of municipal effluent as a stream water source. Results: Populus and Salix were the dominant pioneer trees along the reaches with perennial flow and a natural flood regime. In contrast, Tamarix had high abundance (patch area and basal area) along reaches with intermittent stream flows (caused by natural and cultural factors), as well as those with dam-regulated flows. Main conclusions: Stream-flow regimes are strong determinants of riparian vegetation structure, and hydrological alterations can drive dominance shifts to introduced species that have an adaptive suite of traits. Deep alluvial groundwater on intermittent rivers favours the deep-rooted, stress-adapted Tamarix over the shallower-rooted and more competitive Populus and Salix. On flow-regulated rivers, shifts in flood timing favour the reproductively opportunistic Tamarix over Populus and Salix, both of which have narrow germination windows. The prevailing hydrological conditions thus favour a new dominant pioneer species in the riparian corridors of the American Southwest. These results reaffirm the importance of reinstating stream-flow regimes (inclusive of groundwater flows) for re-establishing the native pioneer trees as the dominant forest type. ?? 2007 The Authors Journal compilation ?? 2007 Blackwell Publishing Ltd.

  7. Regime Diagrams for K-Theory Dispersion

    NASA Astrophysics Data System (ADS)

    Smith, Ronald B.

    2011-06-01

    In atmospheric dispersion, the "non-Gaussian" effects of gravitational settling, the vertical gradient in diffusivity and the surface deposition do not enter uniformly but rather break up parameter space into several discrete regimes. Here, we describe regime diagrams that are constructed for K-theory dispersion of effluent from a surface line source in unsheared inhomogeneous turbulence, using a previously derived Fourier-Hankel method. This K-theory formulation differs from the traditional one by keeping a non-zero diffusivity at the ground. This change allows for turbulent exchange between the canopy and the atmosphere and allows new natural length scales to emerge. The axes on the regime diagrams are non-dimensional distance defined as the ratio of downwind distance to the characteristic length scale for each effect. For each value of the ratio of settling speed to the K gradient, two to four regimes are found. Concentration formulae are given for each regime. The regime diagrams allow real dispersion problems to be categorized and the validity of end-state concentration formulae to be judged.

  8. Biometeorology and animal protein production: the case of arid lands

    NASA Astrophysics Data System (ADS)

    Yousef, M. K.

    1991-09-01

    To meet the food demands of the ever-increasing world population, man's only major future land bank is the arid lands. However, their exploitation has been limited and constitutes a major challenge to many scientific disciplines. Under the present conditions of hunger and/or malnutrition, a large-scale expansion in food production is not to be expected. Hence, it is imperative that in any development programme for arid lands, malnutrition, in general, and a deficiency of animal proteins, in particular, should be considered. Major advancements have been made, but much remains to be learned and implemented. Improvement of native farm animals should be the first step in increasing the availability of animal proteins. This may be achieved by an educational programme to enhance management, housing, food intake, etc. Then a breeding programme selecting for high productivity can be pursued. After eliciting the maximum return from the present livestock, attention should be directed to domesticating wild ungulates and/or introducing highly productive temperature-zone breeds for upgrading the local animals. Additionally, new potential and unconventional sources of animal proteins must be explored. Aquaculture, in particular, has the potential of producing large quantities of lowercost protein-rich food. Available evidence in arid regions of the developed countries, i.e. USA and Australia, promises favourable results in our efforts toward increasing the production of animal protein. By innovative methods and long-term planning, such successes can be adapted and transferred to other regions of the world, with the aim of gradually lessening the present state of malnutrition and hunger.

  9. Understanding Hydrologic Processes in Semi-Arid Cold Climates

    NASA Astrophysics Data System (ADS)

    Barber, M. E.; Beutel, M.; Lamb, B.; Watts, R.

    2004-12-01

    Water shortages destabilize economies and ecosystems. These shortages are caused by complex interactions between climate variability, ecosystem processes, and increased demand from human activities. In the semi-arid region of the northwestern U.S., water availability during drought periods has already reached crisis levels and the problems are expected to intensify as the effects of global climate change and population growth continue to alter the supply and demand patterns. Many of the problems are critical to this region because hydropower, agriculture, navigation, fish and wildlife survival, water supply, tourism, environmental protection, and water-based recreation are vital to state economies and our way of life. In order to assess the spatial and temporal nature of hydrologic responses, consistent and comprehensive long-term data sets are needed. In response to these needs, we would like to propose the Spokane River drainage basin as a long-term hydrologic observatory. The Spokane River basin is located in eastern Washington and northern Idaho and is a tributary of the Columbia River. The watershed consists of several major surface water tributaries as well as natural and man-made lakes and reservoirs. With headwaters beginning in the Rocky Mountains, the drainage area is approximately 6,640 mi2. In addition to providing an excellent study area for examining many conventional water resource problems, the Spokane River watershed also presents a unique opportunity for investigating many of the hydrologic processes found in semi-arid cold climates. Snowfall in the watershed varies spatially between 35 inches near the mouth of the basin to over 112 inches at the headwaters. These varied hydrologic uses provide a unique opportunity to address many common challenges faced by water resource professionals. This broad array of issues encompasses science, engineering, agriculture, social sciences, economics, fisheries, and a host of other disciplines. In addition

  10. Improved Climate Risk Simulations for Rice in Arid Environments

    PubMed Central

    van Oort, Pepijn A. J.; de Vries, Michiel E.; Yoshida, Hiroe; Saito, Kazuki

    2015-01-01

    We integrated recent research on cardinal temperatures for phenology and early leaf growth, spikelet formation, early morning flowering, transpirational cooling, and heat- and cold-induced sterility into an existing to crop growth model ORYZA2000. We compared for an arid environment observed potential yields with yields simulated with default ORYZA2000, with modified subversions of ORYZA2000 and with ORYZA_S, a model developed for the region of interest in the 1990s. Rice variety ‘IR64’ was sown monthly 15-times in a row in two locations in Senegal. The Senegal River Valley is located in the Sahel, near the Sahara desert with extreme temperatures during day and night. The existing subroutines underestimated cold stress and overestimated heat stress. Forcing the model to use observed spikelet number and phenology and replacing the existing heat and cold subroutines improved accuracy of yield simulation from EF = −0.32 to EF =0.70 (EF is modelling efficiency). The main causes of improved accuracy were that the new model subversions take into account transpirational cooling (which is high in arid environments) and early morning flowering for heat sterility, and minimum rather than average temperature for cold sterility. Simulations were less accurate when also spikelet number and phenology were simulated. Model efficiency was 0.14 with new heat and cold routines and improved to 0.48 when using new cardinal temperatures for phenology and early leaf growth. The new adapted subversion of ORYZA2000 offers a powerful analytic tool for climate change impact assessment and cropping calendar optimisation in arid regions. PMID:25774909

  11. Meaningful traits for grouping plant species across arid ecosystems.

    PubMed

    Bär Lamas, Marlene Ivonne; Carrera, A L; Bertiller, M B

    2016-05-01

    Grouping species may provide some degree of simplification to understand the ecological function of plants on key ecosystem processes. We asked whether groups of plant species based on morpho-chemical traits associated with plant persistence and stress/disturbance resistance reflect dominant plant growth forms in arid ecosystems. We selected twelve sites across an aridity gradient in northern Patagonia. At each site, we identified modal size plants of each dominant species and assessed specific leaf area (SLA), plant height, seed mass, N and soluble phenol concentration in green and senesced leaves at each plant. Plant species were grouped according with plant growth forms (perennial grasses, evergreen shrubs and deciduous shrubs) and plant morphological and/or chemical traits using cluster analysis. We calculated mean values of each plant trait for each species group and plant growth form. Plant growth forms significantly differed among them in most of the morpho-chemical traits. Evergreen shrubs were tall plants with the highest seed mass and soluble phenols in leaves, deciduous shrubs were also tall plants with high SLA and the highest N in leaves, and perennial grasses were short plants with high SLA and low concentration of N and soluble phenols in leaves. Grouping species by the combination of morpho-chemical traits yielded 4 groups in which species from one growth form prevailed. These species groups differed in soluble phenol concentration in senesced leaves and plant height. These traits were highly correlated. We concluded that (1) plant height is a relevant synthetic variable, (2) growth forms adequately summarize ecological strategies of species in arid ecosystems, and (3) the inclusion of plant morphological and chemical traits related to defenses against environmental stresses and herbivory enhanced the potential of species grouping, particularly within shrubby growth forms. PMID:26897637

  12. Method to detect environmental change for an arid land

    NASA Astrophysics Data System (ADS)

    Ito, A.; Miyamoto, J.; Tsuchiya, K.; Ishiyama, T.

    A method to detect natural environmental change for an arid land is developed based on 17 bands Visible NIR SWIR and Thermal IR ASTER Advanced SpaceborneThermal Emission and Reflection radiometer aboard Terra and in situ ground truth survey in Taklimakan Desert The method first extracts an area of macroscopic change then detailed or microscopic changes are detected Although the procedure is described in two steps the actual precessing is performed automatically and nearly simultaneously The method is named as ECD Environmental Change Automatic Discrimination model method for the sake of convenience

  13. ARID1A alteration in aggressive urothelial carcinoma and variants of urothelial carcinoma.

    PubMed

    Li, Jianhong; Lu, Shaolei; Lombardo, Kara; Monahan, Rene; Amin, Ali

    2016-09-01

    ARID1A mutation leads to loss of the products of this tumor-suppressor gene. Studies demonstrated ARID1A mutation in 20% of stage IV urothelial carcinomas (UCs) with worse prognosis. The expression of ARID1A in aggressive variants of UC is not studied properly. From 2000 to 2015, 81 variants of UC (29 micropapillary, 33 sarcomatoid, 31 small cell, 2 nested, and 3 plasmacytoid variants) were identified in the archives of Rhode Island Hospital. Immunohistochemistry for anti-ARID1A antibody (Sigma-Aldrich, St Louis, MO) was performed. The staining pattern was semiquantitatively scored, and results were analyzed by Fisher exact test (2 tailed) on contingency tables, survival curve, and log-rank test. Patients were predominantly male (78%) with mean age of 67.9 years. The plasmacytoid variant group occurred in younger ages (mean: 54 years). Half of the specimens contained concurrent conventional UCs. Normal urothelium invariably exhibited strong ARID1A nuclear staining. There was no difference in expression between upper and lower tracts. ARID1A expression was lower in the variants compared with conventional UCs (P<.0001). In micropapillary UCs, an inverse correlation between stage and ARID1A expression was noted, with significant correlation between ARID1A expression and overall survival (P=.0221). Sarcomatoid UCs and small cell CCs showed lower ARID1A expression compared with UCs that was not statistically significant, and neither showed any significant correlation with stage or overall survival. ARID1A expression is significantly decreased in higher stages of UC and its aggressive variants; therefore, ARID1A mutation appears to play an important role in the prognosis of UC and its aggressive variants. This finding may have therapeutic implications. PMID:27137986

  14. A holistic view of marine regime shifts

    PubMed Central

    Conversi, Alessandra; Dakos, Vasilis; Gårdmark, Anna; Ling, Scott; Folke, Carl; Mumby, Peter J.; Greene, Charles; Edwards, Martin; Blenckner, Thorsten; Casini, Michele; Pershing, Andrew; Möllmann, Christian

    2015-01-01

    Understanding marine regime shifts is important not only for ecology but also for developing marine management that assures the provision of ecosystem services to humanity. While regime shift theory is well developed, there is still no common understanding on drivers, mechanisms and characteristic of abrupt changes in real marine ecosystems. Based on contributions to the present theme issue, we highlight some general issues that need to be overcome for developing a more comprehensive understanding of marine ecosystem regime shifts. We find a great divide between benthic reef and pelagic ocean systems in how regime shift theory is linked to observed abrupt changes. Furthermore, we suggest that the long-lasting discussion on the prevalence of top-down trophic or bottom-up physical drivers in inducing regime shifts may be overcome by taking into consideration the synergistic interactions of multiple stressors, and the special characteristics of different ecosystem types. We present a framework for the holistic investigation of marine regime shifts that considers multiple exogenous drivers that interact with endogenous mechanisms to cause abrupt, catastrophic change. This framework takes into account the time-delayed synergies of these stressors, which erode the resilience of the ecosystem and eventually enable the crossing of ecological thresholds. Finally, considering that increased pressures in the marine environment are predicted by the current climate change assessments, in order to avoid major losses of ecosystem services, we suggest that marine management approaches should incorporate knowledge on environmental thresholds and develop tools that consider regime shift dynamics and characteristics. This grand challenge can only be achieved through a holistic view of marine ecosystem dynamics as evidenced by this theme issue.

  15. Greenland Meltwater and Arctic Circulation Regimes

    NASA Astrophysics Data System (ADS)

    Dukhovskoy, D. S.; Proshutinsky, A. Y.; Timmermans, M. L.; Myers, P. G.; Platov, G.

    2015-12-01

    Between 1948 and 1996, wind-driven components of ice drift and surface ocean currents experienced a well-pronounced decadal variability alternating between anticyclonic and cyclonic circulation regimes. During cyclonic regimes, low sea level atmospheric pressure dominated over the Arctic Ocean driving sea ice and the upper ocean clockwise; the Arctic atmosphere was relatively warm and humid and freshwater flux from the Arctic Ocean toward the sub-Arctic seas was intensified. During anticylonic circulation regimes, high sea level pressure dominated over the Arctic driving sea ice and ocean counter-clockwise; the atmosphere was cold and dry and the freshwater flux from the Arctic to the sub-Arctic seas was reduced. Since 1997, however, the Arctic system has been dominated by an anticyclonic circulation regime with a set of environmental parameters that are atypical for these regimes. Of essential importance is to discern the causes and consequences of the apparent break-down in the natural decadal variability of the Arctic climate system, and specifically: Why has the well-pronounced decadal variability observed in the 20th century been replaced by relatively weak interannual changes under anticyclonic circulation regime conditions in the 21st century? We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from Greenland impact environmental conditions and interrupt their decadal variability. In order to test this hypothesis, numerical experiments with several FAMOS (Forum for Arctic Modeling & Observational Synthesis) ice-ocean coupled models have been conducted. In these experiments, Greenland melt freshwater is tracked by passive tracers being constantly released along the Greenland coast. Propagation pathways and time scales of Greenland meltwater within the sub-Arctic seas are discussed.

  16. Identifying natural flow regimes using fish communities

    NASA Astrophysics Data System (ADS)

    Chang, Fi-John; Tsai, Wen-Ping; Wu, Tzu-Ching; Chen, Hung-kwai; Herricks, Edwin E.

    2011-10-01

    SummaryModern water resources management has adopted natural flow regimes as reasonable targets for river restoration and conservation. The characterization of a natural flow regime begins with the development of hydrologic statistics from flow records. However, little guidance exists for defining the period of record needed for regime determination. In Taiwan, the Taiwan Eco-hydrological Indicator System (TEIS), a group of hydrologic statistics selected for fisheries relevance, is being used to evaluate ecological flows. The TEIS consists of a group of hydrologic statistics selected to characterize the relationships between flow and the life history of indigenous species. Using the TEIS and biosurvey data for Taiwan, this paper identifies the length of hydrologic record sufficient for natural flow regime characterization. To define the ecological hydrology of fish communities, this study connected hydrologic statistics to fish communities by using methods to define antecedent conditions that influence existing community composition. A moving average method was applied to TEIS statistics to reflect the effects of antecedent flow condition and a point-biserial correlation method was used to relate fisheries collections with TEIS statistics. The resulting fish species-TEIS (FISH-TEIS) hydrologic statistics matrix takes full advantage of historical flows and fisheries data. The analysis indicates that, in the watersheds analyzed, averaging TEIS statistics for the present year and 3 years prior to the sampling date, termed MA(4), is sufficient to develop a natural flow regime. This result suggests that flow regimes based on hydrologic statistics for the period of record can be replaced by regimes developed for sampled fish communities.

  17. Aerosol radiative effects over global arid and semi-arid regions based on MODIS Deep Blue satellite observations

    NASA Astrophysics Data System (ADS)

    Hatzianastassiou, Nikolaos; Papadimas, Christos D.; Gkikas, Antonis; Matsoukas, Christos; Sayer, Andrew M.; Hsu, N. Christina; Vardavas, Ilias

    2014-05-01

    Aerosols are a key parameter for several atmospheric processes related to weather and climate of our planet. Specifically, the aerosol impact on Earth's climate is exerted and quantified through their radiative effects, which are induced by their direct, indirect and semi-direct interactions with radiation, in particular at short wavelengths (solar). It is acknowledged that the uncertainty of present and future climate assessments is mainly associated with aerosols and that a better understanding of their physico-chemical, optical and radiative effects is needed. The contribution of satellites to this aim is important as a complementary tool to climate and radiative transfer models, as well as to surface measurements, since space observations of aerosol properties offer an extended spatial coverage. However, such satellite based aerosol properties and associated model radiation computations have suffered from unavailability over highly reflecting surfaces, namely polar and desert areas. This is also the case for MODIS which, onboard the Terra and Aqua satellites, has been providing high quality aerosol data since 2000 and 2002, respectively. These data, more specifically the aerosol optical depth (AOD) which is the most important optical property used in radiative and climate models, are considered to be of best quality. In order to address this problem, the MODIS Deep Blue (DB) algorithm has been developed which enables the retrieval of AOD above arid and semi-arid areas of the globe, including the major deserts. In the present study we make use of the FORTH detailed spectral radiative transfer model (RTM) with MODIS DB AOD data, supplemented with single scattering albedo (SSA) and asymmetry parameter (AP) aerosol data from the Global Aerosol DataSet (GADS) to estimate the aerosol DREs over the arid and semi-arid regions of the globe. The RTM is run using surface and atmospheric data from the ISCCP-D2 dataset and the NCEP global reanalysis project and computes the

  18. Evaluating the impacts of drought stress on arid and semi-arid ecosystems in Northeast Asia using satellite imagery data

    NASA Astrophysics Data System (ADS)

    Do, N.; Kang, S.; Choi, G.

    2010-12-01

    Drought stress on vegetation growth can lead alteration in function and structure of ecosystem. Severe drought in arid and semi-arid area may result in reduction of vegetation productivity or biomass as well as alteration of species composition of ecosystem. Previous studies have commonly used precipitation data to assess the effect of water stress on dryland ecosystems. However, soil moisture would be better water-related environmental variable than precipitation because it affects stomata behavior. The remote sensing data derived from satellite imagery are useful to monitor ecological processes such as vegetation production and its response to soil moisture in broad regions. For instance, the GIMMS AVHRR Normalized Difference Vegetation Index (NDVI) data as well as soil moisture data detected by Special Sensor Microwave Imager (SSM/I) soil moisture data have potentials to examine the associations between water stress and vegetation productivity across entire Northeast Asia. The productivity index (i.e. accumulated, maximum, mean NDVI) derived from NDVI may have considerable uncertainty to represent vegetation productivity. Hence, we tested whether the productivity index can be surrogate of vegetation productivity from MODIS cloud-corrected annual GPP. As well, soil moisture from SSM/I lacks credibility in areas where vegetation is dense. We confined our study areas where significant correlation between precipitation record and SSM/I soil moisture occurred. The purposes of this study are (1) to examine the spatial and temporal patterns of soil moisture and productivity indices in arid and semi-arid regions of Northeast Asia from 1987 to 2006, and (2) to investigate how the drylands productivity responded to inter-annual soil moisture variability, and (3) to examine how the drylands productivity was sensitive to the change of soil moisture. Finally, (4) it was evaluated the spatial and inter-annual patterns of drought stress in the Northeast Asia drylands (i

  19. Significance of Overland Flow in Sustaining Water Resources of Arid and Semi-Arid Rivers - Water Quantity and Quality Implications

    NASA Astrophysics Data System (ADS)

    Meixner, T.; Hogan, J. F.; Brooks, P. D.; Oelsner, G. P.; Soto-López, C. D.; Baillie, M. N.; Simpson, S. C.

    2007-12-01

    Overland flow is known to be a dominant runoff generation mechanism in arid and semiarid river systems. Despite its prevalence, little is known about the impact of overland flow on the quantity and quality of water in arid and semi-arid rivers and riparian systems. Several studies along the San Pedro and Rio Grande Rivers in the Southwest United States have documented the importance of ephemeral overland flows to the quantity and quality of river water in the stream and near stream zones. First, studies on both rivers have documented the importance of flood flows in providing a significant source of water to near stream aquifers. On the San Pedro River studies have shown that ~50% of baseflow water originates from summer Monsoon floods with a stronger influence on losing versus gaining river reaches. In the Rio Grande, stable isotope data indicate that nearly 100% of the increase in discharge during a Monsoon flood event can be attributed to ephemeral overland flow with approximately 40% of this flood pulse in the Rio Grande lost to the shallow alluvial aquifer. Second, nutrient studies on both rivers demonstrate that reconnecting the river with its uplands during flood events causes a dramatic increase in nutrient concentrations and fundamentally alters near and in-stream biogeochemical conditions and processes by providing a large pulse of allochthonous nutrients and organic matter. Despite the large nutrient influx with flood events the sustained impact on nutrient composition is limited; with upwelling zones, possibly reworking particulate organic matter, having more influence than water source on in-stream nutrient concentrations. Furthermore the influence of flood events attenuates significantly over a period of months with the influence of flood events diminishing from 40% of river flow to 20% in a period of just 6 months.

  20. Understanding sources of uncertainty in flash-flood forecasting for semi-arid regions 1913

    Technology Transfer Automated Retrieval System (TEKTRAN)

    About one-third of the earth’s landsurface is located in arid or semi-arid regions, often in areas suffering severely from the negative impacts of desertification and population pressure. Reliable hydrological forecasts across spatial and temporal scales are crucial in order to achieve water securit...

  1. Woody plants modulate the temporal dynamics of soil moisture in a semi-arid mesquite savanna

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In arid and semi-arid ecosystems (drylands), soil moisture abundance limits biological activity and mediates the effects of anthropogenic global change factors such as atmospheric CO2 increases and climate warming. Moreover, climate variability and human activities are interacting to increase the ab...

  2. Evaporative loss from the interrow of irrigated crops in a semi-arid agricultural area

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil evaporation plays an important role in the water balance of irrigated crops, especially in arid and semi-arid regions. Irrigation scheduling may affect the fraction of evaporative loss (E) from the total evapotranspiration (ET), and thus affect the water use efficiency. During the second intens...

  3. Comparison of turbulent statistics and spectra at two heights over a semi-arid grassland surface

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding the turbulent exchange of mass and energy from a surface remains essential to appropriate characterization and quantification of the components of surface energy balance. This is particularly true for arid and semi-arid regions that often contain surfaces that are highly heterogeneous...

  4. The contribution of vegetation cover and bare soil to pixel reflectance in an arid ecosystem

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The heterogeneity of vegetation and soils in arid and semi-arid environments complicates the analysis of medium spatial resolution remotely sensed imagery. A single pixel may contain several different types of vegetation, as well as a sizeable proportion of bare soil. We have used linear mixture mod...

  5. Influence of halophyte plantings in arid regions on local atmospheric structure

    NASA Astrophysics Data System (ADS)

    Pielke, R. A.; Lee, T. J.; Glenn, E. P.; Avissar, R.

    1993-06-01

    The practicality of modifying climate in arid regions through irrigation has up to now been constrained by the availability of fresh water with which to grow crops. The present results suggest a new paradigm: the use of salt water to grow halophyte crops and modify local climate along coastal deserts and other arid regions where saline water supplies are available.

  6. Learning Flow Regimes from Snapshot Data

    NASA Astrophysics Data System (ADS)

    Hemati, Maziar

    2015-11-01

    Fluid flow regimes are often categorized based on the qualitative patterns observed by visual inspection of the flow field. For example, bluff body wakes are traditionally classified based on the number and groupings of vortices shed per cycle (e.g., 2S, 2P, P+S), as seen in snapshots of the vorticity field. Subsequently, the existence and nature of these identified flow regimes can be explained through dynamical analyses of the fluid mechanics. Unfortunately, due to the need for manual inspection, the approach described above can be impractical for studies that seek to learn flow regimes from large volumes of numerical and/or experimental snapshot data. Here, we appeal to established techniques from machine learning and data-driven dynamical systems analysis to automate the task of learning flow regimes from snapshot data. Moreover, by appealing to the dynamical structure of the fluid flow, this approach also offers the potential to reveal flow regimes that may be overlooked by visual inspection alone. Here, we will introduce the methodology and demonstrate its capabilities and limitations in the context of several model flows.

  7. Dynamic treatment regimes: technical challenges and applications

    PubMed Central

    Lizotte, Daniel J.; Qian, Min; Pelham, William E.; Murphy, Susan A.

    2014-01-01

    Dynamic treatment regimes are of growing interest across the clinical sciences because these regimes provide one way to operationalize and thus inform sequential personalized clinical decision making. Formally, a dynamic treatment regime is a sequence of decision rules, one per stage of clinical intervention. Each decision rule maps up-to-date patient information to a recommended treatment. We briefly review a variety of approaches for using data to construct the decision rules. We then review a critical inferential challenge that results from nonregularity, which often arises in this area. In particular, nonregularity arises in inference for parameters in the optimal dynamic treatment regime; the asymptotic, limiting, distribution of estimators are sensitive to local perturbations. We propose and evaluate a locally consistent Adaptive Confidence Interval (ACI) for the parameters of the optimal dynamic treatment regime. We use data from the Adaptive Pharmacological and Behavioral Treatments for Children with ADHD Trial as an illustrative example. We conclude by highlighting and discussing emerging theoretical problems in this area. PMID:25356091

  8. Feasibility of groundwater recharge dam projects in arid environments

    NASA Astrophysics Data System (ADS)

    Jaafar, H. H.

    2014-05-01

    A new method for determining feasibility and prioritizing investments for agricultural and domestic recharge dams in arid regions is developed and presented. The method is based on identifying the factors affecting the decision making process and evaluating these factors, followed by determining the indices in a GIS-aided environment. Evaluated parameters include results from field surveys and site visits, land cover and soils data, precipitation data, runoff data and modeling, number of beneficiaries, domestic irrigation demand, reservoir objectives, demography, reservoirs yield and reliability, dam structures, construction costs, and operation and maintenance costs. Results of a case study on more than eighty proposed dams indicate that assessment of reliability, annualized cost/demand satisfied and yield is crucial prior to investment decision making in arid areas. Irrigation demand is the major influencing parameter on yield and reliability of recharge dams, even when only 3 months of the demand were included. Reliability of the proposed reservoirs as related to their standardized size and net inflow was found to increase with increasing yield. High priority dams were less than 4% of the total, and less priority dams amounted to 23%, with the remaining found to be not feasible. The results of this methodology and its application has proved effective in guiding stakeholders for defining most favorable sites for preliminary and detailed design studies and commissioning.

  9. An Evaluation of Unsaturated Flow Models in an Arid Climate

    SciTech Connect

    Dixon, J.

    1999-12-01

    The objective of this study was to evaluate the effectiveness of two unsaturated flow models in arid regions. The area selected for the study was the Area 5 Radioactive Waste Management Site (RWMS) at the Nevada Test Site in Nye County, Nevada. The two models selected for this evaluation were HYDRUS-1D [Simunek et al., 1998] and the SHAW model [Flerchinger and Saxton, 1989]. Approximately 5 years of soil-water and atmospheric data collected from an instrumented weighing lysimeter site near the RWMS were used for building the models with actual initial and boundary conditions representative of the site. Physical processes affecting the site and model performance were explored. Model performance was based on a detailed sensitivity analysis and ultimately on storage comparisons. During the process of developing descriptive model input, procedures for converting hydraulic parameters for each model were explored. In addition, the compilation of atmospheric data collected at the site became a useful tool for developing predictive functions for future studies. The final model results were used to evaluate the capacities of the HYDRUS and SHAW models for predicting soil-moisture movement and variable surface phenomena for bare soil conditions in the arid vadose zone. The development of calibrated models along with the atmospheric and soil data collected at the site provide useful information for predicting future site performance at the RWMS.

  10. Arid land monitoring using Landsat albedo difference images

    USGS Publications Warehouse

    Robinove, Charles J.; Chavez, Pat S., Jr.; Gehring, Dale G.; Holmgren, Ralph

    1981-01-01

    The Landsat albedo, or percentage of incoming radiation reflected from the ground in the wavelength range of 0.5 [mu]m to 1.1 [mu]m, is calculated from an equation using the Landsat digital brightness values and solar irradiance values, and correcting for atmospheric scattering, multispectral scanner calibration, and sun angle. The albedo calculated for each pixel is used to create an albedo image, whose grey scale is proportional to the albedo. Differencing sequential registered images and mapping selected values of the difference is used to create quantitative maps of increased or decreased albedo values of the terrain. All maps and other output products are in black and white rather than color, thus making the method quite economical. Decreases of albedo in arid regions may indicate improvement of land quality; increases may indicate degradation. Tests of the albedo difference mapping method in the Desert Experimental Range in southwestern Utah (a cold desert with little long-term terrain change) for a four-year period show that mapped changes can be correlated with erosion from flash floods, increased or decreased soil moisture, and increases or decreases in the density of desert vegetation, both perennial shrubs and annual plants. All terrain changes identified in this test were related to variations in precipitation. Although further tests of this method in hot deserts showing severe "desertification" are needed, the method is nevertheless recommended for experimental use in monitoring terrain change in other arid and semiarid regions of the world.