Drought Variability and Land Degradation in Semiarid Regions: Assessment Using Remote Sensing Data and Drought Indices (1982–2011

Directory of Open Access Journals (Sweden)

Sergio M. Vicente-Serrano

2015-04-01

Full Text Available We analyzed potential land degradation processes in semiarid regions worldwide using long time series of remote sensing images and the Normalized Difference Vegetation Index (NDVI for the period 1981 to 2011. The objectives of the study were to identify semiarid regions showing a marked decrease in potential vegetation activity, indicative of the occurrence of land degradation processes, and to assess the possible influence of the observed drought trends quantified using the Standardized Precipitation Evapotranspiration Index (SPEI. We found that the NDVI values recorded during the period of maximum vegetation activity (NDVImax predominantly showed a positive evolution in the majority of the semiarid regions assessed, but NDVImax was highly correlated with drought variability, and the trends of drought events influenced trends in NDVImax at the global scale. The semiarid regions that showed most increase in NDVImax (the Sahel, northern Australia, South Africa were characterized by a clear positive trend in the SPEI values, indicative of conditions of greater humidity and lesser drought conditions. While changes in drought severity may be an important driver of NDVI trends and land degradation processes in semiarid regions worldwide, drought did not apparently explain some of the observed changes in NDVImax. This reflects the complexity of vegetation activity processes in the world’s semiarid regions, and the difficulty of defining a universal response to drought in these regions, where a number of factors (natural and anthropogenic may also affect on land degradation.

Drought Variability and Land Degradation in Semiarid Regions: Assessment Using Remote Sensing Data and Drought Indices (1982–2011)

KAUST Repository

Vicente-Serrano, Sergio

2015-04-14

We analyzed potential land degradation processes in semiarid regions worldwide using long time series of remote sensing images and the Normalized Difference Vegetation Index (NDVI) for the period 1981 to 2011. The objectives of the study were to identify semiarid regions showing a marked decrease in potential vegetation activity, indicative of the occurrence of land degradation processes, and to assess the possible influence of the observed drought trends quantified using the Standardized Precipitation Evapotranspiration Index (SPEI). We found that the NDVI values recorded during the period of maximum vegetation activity (NDVImax) predominantly showed a positive evolution in the majority of the semiarid regions assessed, but NDVImax was highly correlated with drought variability, and the trends of drought events influenced trends in NDVImax at the global scale. The semiarid regions that showed most increase in NDVImax (the Sahel, northern Australia, South Africa) were characterized by a clear positive trend in the SPEI values, indicative of conditions of greater humidity and lesser drought conditions. While changes in drought severity may be an important driver of NDVI trends and land degradation processes in semiarid regions worldwide, drought did not apparently explain some of the observed changes in NDVImax. This reflects the complexity of vegetation activity processes in the world’s semiarid regions, and the difficulty of defining a universal response to drought in these regions, where a number of factors (natural and anthropogenic) may also affect on land degradation.

Drought Variability and Land Degradation in Semiarid Regions: Assessment Using Remote Sensing Data and Drought Indices (1982–2011)

KAUST Repository

Vicente-Serrano, Sergio; Cabello, Daniel; Tomá s-Burguera, Miquel; Martí n-Herná ndez, Natalia; Beguerí a, Santiago; Azorin-Molina, Cesar; Kenawy, Ahmed

2015-01-01

We analyzed potential land degradation processes in semiarid regions worldwide using long time series of remote sensing images and the Normalized Difference Vegetation Index (NDVI) for the period 1981 to 2011. The objectives of the study were to identify semiarid regions showing a marked decrease in potential vegetation activity, indicative of the occurrence of land degradation processes, and to assess the possible influence of the observed drought trends quantified using the Standardized Precipitation Evapotranspiration Index (SPEI). We found that the NDVI values recorded during the period of maximum vegetation activity (NDVImax) predominantly showed a positive evolution in the majority of the semiarid regions assessed, but NDVImax was highly correlated with drought variability, and the trends of drought events influenced trends in NDVImax at the global scale. The semiarid regions that showed most increase in NDVImax (the Sahel, northern Australia, South Africa) were characterized by a clear positive trend in the SPEI values, indicative of conditions of greater humidity and lesser drought conditions. While changes in drought severity may be an important driver of NDVI trends and land degradation processes in semiarid regions worldwide, drought did not apparently explain some of the observed changes in NDVImax. This reflects the complexity of vegetation activity processes in the world’s semiarid regions, and the difficulty of defining a universal response to drought in these regions, where a number of factors (natural and anthropogenic) may also affect on land degradation.

State Transitions in Semiarid Landscapes

Science.gov (United States)

Phillips, J. D.

2012-04-01

The U.S. Department of Agriculture has developed a large number of state-and-transition models (STM) to predict and interpret changes in vegetation communities in drylands of the southwestern U.S. These are represented as box-and-arrow models indicating potential changes in response to various combinations of management practices and environmental forcings. Analysis of the 320 STMs developed for areas within the state of Texas reveals two important aspects of environmental change in semiarid environments. First, the STMs are highly local—they are specific to very particular combinations of landform, soil, and climate. This is consistent with the perfect landscape concept in geomorphology, which emphasizes the irreducible importance of geographically and historically contingent local factors in addition to universal laws or principles in determining the state or condition of landscapes. Second, analysis of the STMs using algebraic graph theory shows that a majority of them have structures that tend to amplify effects of change and disturbances. In many cases the STMs represent a form of self-organization characterized by the potential of divergent behavior rather than convergence toward a dominant pattern or outcome. These results indicate that geomorphic, hydrologic, and ecological responses to climate and land use change are likely to be highly variable and idiosyncratic, both within and between semiarid landscapes of Texas.

Nuclear applications for the management of aquifers in the semi-arid region

International Nuclear Information System (INIS)

Simoes Filho, Fernando Lamego

2005-01-01

The semi-arid region of the Northeast of Brazil is characterized by a lack of superficial waters due to the low pluviometric precipitation and high evaporation rates. In addition to this, the precipitation events are irregular in time causing long periods of dryness or flooding with catastrophic consequences. Owing to adverse climatic conditions with recurrent droughts, intense pressure is being put on the use of groundwater resources. Groundwater occurrence on its turn depends on a series of geological and climatological characteristics that are very variable in the region. Because of this situation, groundwater is of strategical importance and represents a vital factor to its socioeconomic development. However, there is still insufficient knowledge of the basic aquifers characteristics leading to an over exploitation of the water resources. It is not surprising that, amongst other reasons, this situation contributes to the fact that areas with the lowest human development pattern are located in the semi-arid region of Brazil. Given the nature of hydrological problems that need to be addressed in semi-arid regions, nuclear/isotope techniques are increasingly recognized as indispensable tools for water resources assessment and development. However, information arising from these techniques has to cope with other hydrological methods in an integrated manner. The general objective was prospect nuclear technologies as tools for aquifer management, promoting sustainable use of groundwater in the semi-arid region. (author)

Assessing Ecosystem Model Performance in Semiarid Systems

Science.gov (United States)

Thomas, A.; Dietze, M.; Scott, R. L.; Biederman, J. A.

2017-12-01

In ecosystem process modelling, comparing outputs to benchmark datasets observed in the field is an important way to validate models, allowing the modelling community to track model performance over time and compare models at specific sites. Multi-model comparison projects as well as models themselves have largely been focused on temperate forests and similar biomes. Semiarid regions, on the other hand, are underrepresented in land surface and ecosystem modelling efforts, and yet will be disproportionately impacted by disturbances such as climate change due to their sensitivity to changes in the water balance. Benchmarking models at semiarid sites is an important step in assessing and improving models' suitability for predicting the impact of disturbance on semiarid ecosystems. In this study, several ecosystem models were compared at a semiarid grassland in southwestern Arizona using PEcAn, or the Predictive Ecosystem Analyzer, an open-source eco-informatics toolbox ideal for creating the repeatable model workflows necessary for benchmarking. Models included SIPNET, DALEC, JULES, ED2, GDAY, LPJ-GUESS, MAESPA, CLM, CABLE, and FATES. Comparison between model output and benchmarks such as net ecosystem exchange (NEE) tended to produce high root mean square error and low correlation coefficients, reflecting poor simulation of seasonality and the tendency for models to create much higher carbon sources than observed. These results indicate that ecosystem models do not currently adequately represent semiarid ecosystem processes.

Plastic-Film Mulching for Enhanced Water-Use Efficiency and Economic Returns from Maize Fields in Semiarid China

OpenAIRE

Zhang, Peng; Wei, Ting; Cai, Tie; Ali, Shahzad; Han, Qingfang; Ren, Xiaolong; Jia, Zhikuan

2017-01-01

Film mulch has gradually been popularized to increase water availability to crops for improving and stabilizing agricultural production in the semiarid areas of Northwest China. To find more sustainable and economic film mulch methods for alleviating drought stress in semiarid region, it is necessary to test optimum planting methods in same cultivation conditions. A field experiment was conducted during 2013 and 2014 to evaluate the effects of different plastic film mulch methods on soil wate...

Electron Conditioning of Technical Aluminium Surfaces: Effect on the Secondary Electron Yield

Energy Technology Data Exchange (ETDEWEB)

Le Pimpec, F.

2004-12-13

The effect of electron conditioning on commercially aluminium alloys 1100 and 6063 were investigated. Contrary to the assumption that electron conditioning, if performed long enough, can reduce and stabilize the SEY to low values (< 1.3, value of many pure elements [1] ), the SEY of aluminium did not go lower than 1.8. In fact, it reincreases with continued electron exposure dose.

Nitrogen symbiotically fixed by cowpea and gliricidia in traditional and agroforestry systems under semiarid conditions

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Júlio César Rodrigues Martins

2015-02-01

Full Text Available The objective of this work was to estimate the amounts of N fixed by cowpea in a traditional system and by cowpea and gliricidia in an agroforestry system in the Brazilian Northeast semiarid. The experiment was carried out in a randomized complete block design, in a split-plot arrangement, with four replicates, in the semiarid region of the state of Paraíba, Brazil. Plots consisted of agroforestry and traditional systems (no trees, and split-plots of the three crops planted between the tree rows in the agroforestry system. To estimate N fixation, plant samples were collected in the fourth growth cycle of the perennial species and in the fourth planting cycle of the annual species. In the agroforestry system with buffel grass and prickly-pear cactus, gliricidia plants symbiotically fix high proportions of N (>50% and contribute with higher N amounts (40 kg ha-1 in leaves than in the traditional system (11 kg ha-1 in grain and 18 kg ha-1 in straw. In the agroforestry system with maize and cowpea, gliricidia plants do not fix nitrogen, and N input is limited to the fixation by cowpea (2.7 kg ha-1, which is lower than in the traditional system due to its lower biomass production.

Simulated Optimum Sowing Date for Forage Pearl Millet Cultivars in Multilocation Trials in Brazilian Semi-Arid Region.

Science.gov (United States)

Santos, Rafael D; Boote, Kenneth J; Sollenberger, Lynn E; Neves, Andre L A; Pereira, Luiz G R; Scherer, Carolina B; Gonçalves, Lucio C

2017-01-01

Forage production is primarily limited by weather conditions under dryland production systems in Brazilian semi-arid regions, therefore sowing at the appropriate time is critical. The objectives of this study were to evaluate the CSM-CERES-Pearl Millet model from the DSSAT software suite for its ability to simulate growth, development, and forage accumulation of pearl millet [ Pennisetum glaucum (L.) R.] at three Brazilian semi-arid locations, and to use the model to study the impact of different sowing dates on pearl millet performance for forage. Four pearl millet cultivars were grown during the 2011 rainy season in field experiments conducted at three Brazilian semi-arid locations, under rainfed conditions. The genetic coefficients of the four pearl millet cultivars were calibrated for the model, and the model performance was evaluated with experimental data. The model was run for 14 sowing dates using long-term historical weather data from three locations, to determine the optimum sowing window. Results showed that performance of the model was satisfactory as indicated by accurate simulation of crop phenology and forage accumulation against measured data. The optimum sowing window varied among locations depending on rainfall patterns, although showing the same trend for cultivars within the site. The best sowing windows were from 15 April to 15 May for the Bom Conselho location; 12 April to 02 May for Nossa Senhora da Gloria; and 17 April to 25 May for Sao Bento do Una. The model can be used as a tool to evaluate the effect of sowing date on forage pearl millet performance in Brazilian semi-arid conditions.

Sediment delivery ratio in a small semi-arid watershed under conditions of low connectivity

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Julio Cesar Neves dos Santos

Full Text Available ABSTRACT The semi-arid region in the northeast of Brazil is characterised by rains of high intensity and short duration, with the processes of erosion being aggravated by an inappropriate land-use model. In this region, the lack of measured data for runoff and sediment yield increases the need to apply hydro-sedimentological models in estimating erosion, requiring knowledge of the actual sediment delivery ratio for the region. The aim of this study therefore, was to map soil erosion, making use of the Universal Soil Loss Equation (USLE, in the Iguatu Experimental Watershed (IEW. The mean annual sediment delivery ratio (SDR, and the SDR for individual events, was calculated from hydro-sedimentological measurements, contributing to an understanding of the processes of sediment propagation in the Brazilian semi-arid region, allowing identification of areas susceptible to water erosion. The IEW has an area of 16.74 km2 and is equipped with sensors for the continuous measurement of rainfall, flow and sediment yield. The mean annual SDR for the IEW was 0.37%. The SDR for individual rainfall events ranged from 0.08 to 1.67%, with an average of 0.68%. Among the main variables that influence the SDR for individual events is the magnitude of rainfall depth and antecedent soil moisture that can be better represented by the total antecedent precipitation of the previous 15 days. According to maps of soil loss, only 6.27% of the watershed presented losses beyond tolerable limits.

Hypogeous fungi from Southern Spanish semi-arid lands

NARCIS (Netherlands)

Honrubia, M.; Cano, A.; Molina-Niñirola, C.

1992-01-01

Six hypogeous fungi of Ascomycotina and Basidiomycotina have been studied from semiarid zones in Southern Spain. Melanogaster variegatus (Vitt.) Tul. is recorded for the first time from Spain. Picoa juniperi Vitt. and Terfezia claveryi Chat. are revealed as the most frequent species in semi-arid

AGROECOLOGY AND CLIMATE CHANGE IN THE SEMIARID TROPICS

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Guillermo Gamarra-Rojas

2017-04-01

Full Text Available This article makes a theoretical and, to a certain extent, propositional reflection on the conceptions, assumptions and evidences of climate change in the tropics, with emphasis on the Brazilian semiarid region. The contributions of agriculture to climate change are presented and the impacts of climate change on family agriculture in the semiarid region are analyzed. Evidence of mitigation and adaptation in agroecological systems of the semiarid region is presented and an outline of an agenda of the sector based on the commitments assumed by the country and the needs of mitigation and adaptation is provided.

Pathways to Resilience in Semi-Arid Economies (PRISE)

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

rlarbey

PRISE Goal. This research will support the emergence of equitable, climate resilient economic development in semi-arid lands through research excellence and ... change in semi-arid areas, and how is the private sector adapting? 4. How do ... Role. Individual. Contact email. Lead Principal Investigator. Dr Tom Mitchell.

Short communication. Effect of deficit irrigation on curly lettuce grown under semiarid conditions

Energy Technology Data Exchange (ETDEWEB)

Kuslu, Y.; Dursun, A.; Sahin, U.; Kiziloglu, F. M.; Turan, M.

2008-07-01

Field experiments were conducted to characterize the effects of deficit irrigation on curly lettuce (Lactuca sativa var. Crispa cv. Bohemia) evapotranspiration, water use efficiency, marketable yield, yield components and mineral contents. The experiments were performed under semiarid climatic conditions in Erzurum province (east of Turkey) in the summer periods of 2005 and 2006. Irrigation water levels were selected to be 100% of usable soil water in full irrigation treatment (control) (T-100) and 80%, 60%, 40% and 20% of usable soil water in deficit irrigation treatments (T-80, T-60, T-40 and T- 20, respectively). Average seasonal evapotranspiration was 232 mm in T-100 and 121 mm in T-20. Average marketable yield was 39.49 Mg ha{sup -}1 in T-100 and 14.57 Mg ha{sup -}1 in T-20. A linear relationship (y=0.23x-13.97; R{sup 2}0.94) was found between seasonal evapotranspiration (x) and marketable plant yield (y). According to the regression equation, the yield response factor (k{sub y}) was found to be 1.39, and the coefficient of determination 0.91. Average water use efficiency was 168.88 kg ha{sup -}1 mm{sup -}1 in T-100 and 117.39 kg ha{sup -}1 mm{sup -}1 in T-20. The lowest plant length, width, steam diameter, leaf number, macro and micro element content values were obtained for T-20 in both years. (Author) 21 refs.

Agroecological and Social Transformations for Coexistence with Semi-Aridity in Brazil

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Aldrin M. Pérez-Marin

2017-06-01

Full Text Available This article explores whether a shift in development paradigm resulted in coexistence with semi-aridity for residents of the Semi-Arid region of Brazil (SAB. If so, which strategies contributed and which conditions facilitated it? We conducted a comparative analysis of the transformations that occurred in 10 territories of the SAB during two time periods: PI (1973–2001 when “development” policies almost exclusively aimed to “combat drought and its effects”; and PII (2002–2016 when a concept of coexistence with semi-aridity informed policy making. Our study from the 10 territories of the SAB show significant changes between PI and PII. On average, there was a substantial improvement in Access to Water Infrastructure (+33%∆, Diversification of Production Systems (Animals +36%∆; Crops +61%∆, Management of Common Pool Resources (+45%∆, Involvement in Spaces of Political Organizing (+24%∆, and Access to Public Programs (+29%∆. As such, “coexistence” went from concept to action as a consequence of structural, agroecological, social, and management transformations in combination with a strengthening of mechanisms for community reciprocity. These were characterized by (a the creation of resource reserves for use during times of drought; (b the efficient use of available natural resources; and (c enhanced articulation between diverse actors.

Sustainable semiarid dryland production in relation to tillage effects on Hydrology: 1983-2013

Science.gov (United States)

Semiarid dryland crop yields with no-till, NT, residue management are often greater than stubble-mulch tillage, SM, as a result of improved soil conditions or water conservation, but knowledge of long-term tillage effects on the comprehensive field hydrology and sustained crop production is needed. ...

Water conservation in semiarid dryland agriculture

International Nuclear Information System (INIS)

Willis, W.O.

1980-01-01

Factors affecting water conservation in semiarid dryland regions are discussed. Because precipitation is the only source of water for plant growth in most semiarid regions, a good understanding of precipitation patterns (quantity, distribution, and their probable frequency) is needed for each dryland area. The various dryland practices, e.g. tillage, cultivars, residue management, fertility, erosion control, and grazing, must be considered as integral parts of an entire system to develop best management practices and to gain most efficient water conservation for food and fiber production. (author)

Beyond the desertification narrative: a framework for agricultural drought in semi-arid East Africa

NARCIS (Netherlands)

Slegers, M.F.W.; Stroosnijder, L.

2008-01-01

In the 20th century, much research was done on desertification. Desertification developed into a complex and vague construct that means land degradation under specific conditions. Projects focusing on land degradation in semiarid East Africa have met with limited success because farmers prioritize

Soil tillage and water infiltration in semi-arid Morocco: the role fo surface and sub-surface soil conditions

NARCIS (Netherlands)

Dimanche, P.H.; Hoogmoed, W.B.

2002-01-01

Production of cereals in a dryland farming system forms an important part of agricultural production in Morocco. Yield levels on the Saïs Plateau between Meknès and Fez in the semi-arid zone, however, remain low possibly because of sub-optimum water use due to inefficient tillage systems. A study

An Overview of Biodegradation of LNAPLs in Coastal (Semi)-arid Environment.

KAUST Repository

Yadav, Brijesh Kumar

2011-02-22

Contamination of soil and water due to the release of light non-aqueous phase liquids (LNAPLs) is a ubiquitous problem. The problem is more severe in arid and semi-arid coastal regions where most of the petroleum production and related refinery industries are located. Biological treatment of these organic contaminated resources is receiving increasing interests and where applicable, can serve as a cost-effective remediation alternative. The success of bioremediation greatly depends on the prevailing environmental variables, and their remediation favoring customization requires a sound understanding of their integrated behavior on fate and transport of LNAPLs under site-specific conditions. The arid and semi-arid coastal sites are characterized by specific environmental extremes; primarily, varying low and high temperatures, high salinity, water table dynamics, and fluctuating soil moisture content. An understanding of the behavior of these environmental variables on biological interactions with LNAPLs would be helpful in customizing the bioremediation for restoring problematic sites in these regions. Therefore, this paper reviews the microbial degradation of LNAPLs in soil-water, considering the influences of prevailing environmental parameters of arid and semi-arid coastal regions. First, the mechanism of biodegradation of LNAPLs is discussed briefly, followed by a summary of popular kinetic models used by researchers for describing the degradation rate of these hydrocarbons. Next, the impact of soil moisture content, water table dynamics, and soil-water temperature on the fate and transport of LNAPLs are discussed, including an overview of the studies conducted so far. Finally, based on the reviewed information, a general conclusion is presented with recommendations for future research subjects on optimizing the bioremediation technique in the field under the aforesaid environmental conditions. The present review will be useful to better understand the

Influence of rootstocks on growth, yield, fruit quality and leaf mineral element contents of pear cv. 'Santa Maria' in semi-arid conditions

Directory of Open Access Journals (Sweden)

Ali Ikinci

2014-01-01

Full Text Available BACKGROUND: Rootstocks play an essential role to determining orchard performance of fruit trees. Pyrus communisand Cydonia oblonga are widely used rootstocks for European pear cultivars. The lack of rootstocks adapted to different soil conditions and different grafted cultivars is widely acknowledged in pear culture. Cydonia rootstocks (clonal and Pyrus rootstocks (seedling or clonal have their advantages and disadvantages. In each case, site-specific environmental characteristics, specific cultivar response and production objectives must be considered before choosing the best rootstock. In this study, the influence of three Quince (BA 29, Quince A = MA, Quince C = MC and a local European pear seedling rootstocks on the scion yield, some fruit quality characteristics and leaf macro (N, P, K, Ca and Mg and micro element (Fe, Zn, Cu, Mn and B content of 'Santa Maria' pear (Pyrus communis L. were investigated. RESULTS: Trees on seedling rootstock had the highest annual yield, highest cumulative yield (kg tree−1, largest trunk cross-sectional area (TCSA, lowest yield efficiency and lowest cumulative yield (ton ha−1 in the 10th year after planting. The rootstocks had no significant effect on average fruit weight and fruit volume. Significantly higher fruit firmness was obtained on BA 29 and Quince A. The effect of rootstocks on the mineral element accumulation (N, K, Ca, Mg, Fe, Zn, Cu, Mn and B was significant. Leaf analysis showed that rootstocks used had different mineral uptake efficiencies throughout the early season. CONCLUSION: The results showed that the rootstocks strongly affected fruit yield, fruit quality and leaf mineral element uptake of 'Santa Maria' pear cultivar. Pear seedling and BA 29 rootstock found to be more prominent in terms of several characteristics for 'Santa Maria' pear cultivar that is grown in highly calcareous soil in semi-arid climate conditions. We determined the highest N, P (although insignificant, K, Ca, Mg, Fe

Effect of high ambient temperature on behavior of sheep under semi-arid tropical environment.

Science.gov (United States)

De, Kalyan; Kumar, Davendra; Saxena, Vijay Kumar; Thirumurugan, Palanisamy; Naqvi, Syed Mohammed Khursheed

2017-07-01

High environmental temperature is a major constraint in sheep production under semi-arid tropical environment. Behavior is the earliest indicator of animal's adaptation and responses to the environmental alteration. Therefore, the objective of this study was to assess the effects of high ambient temperature on the behavior of sheep under a semi-arid tropical environment. The experiment was conducted for 6 weeks on 16 Malpura cross (Garole × Malpura × Malpura (GMM)) rams. The rams were divided equally into two groups, designated as C and T. The rams of C were kept in comfortable environmental conditions served as control. The rams of T were exposed to a different temperature at different hours of the day in a climatic chamber, to simulate a high environmental temperature of summer in semi-arid tropic. The behavioral observations were taken by direct instantaneous observation at 15-min intervals for each animal individually. The feeding, ruminating, standing, and lying behaviors were recorded twice a week from morning (0800 hours) to afternoon (1700 hours) for 6 weeks. Exposure of rams to high temperature (T) significantly (P behavior of sheep which is directed to circumvent the effect of the stressor.

Effect of high ambient temperature on behavior of sheep under semi-arid tropical environment

Science.gov (United States)

De, Kalyan; Kumar, Davendra; Saxena, Vijay Kumar; Thirumurugan, Palanisamy; Naqvi, Syed Mohammed Khursheed

2017-07-01

High environmental temperature is a major constraint in sheep production under semi-arid tropical environment. Behavior is the earliest indicator of animal's adaptation and responses to the environmental alteration. Therefore, the objective of this study was to assess the effects of high ambient temperature on the behavior of sheep under a semi-arid tropical environment. The experiment was conducted for 6 weeks on 16 Malpura cross (Garole × Malpura × Malpura (GMM)) rams. The rams were divided equally into two groups, designated as C and T. The rams of C were kept in comfortable environmental conditions served as control. The rams of T were exposed to a different temperature at different hours of the day in a climatic chamber, to simulate a high environmental temperature of summer in semi-arid tropic. The behavioral observations were taken by direct instantaneous observation at 15-min intervals for each animal individually. The feeding, ruminating, standing, and lying behaviors were recorded twice a week from morning (0800 hours) to afternoon (1700 hours) for 6 weeks. Exposure of rams to high temperature (T) significantly ( P animals of T spent significantly ( P behavior of sheep which is directed to circumvent the effect of the stressor.

Water Resources Management. Coexistence and Conflict in Semiarid Brazil

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Thiago Ferreira Dias

2016-01-01

Full Text Available The paper analyzes water management in the Brazilian semiarid region with emphasis on aspects of coexistence and conflicts over access in rural areas. Experiences of social coexistence in semiarid technologies from the joint to the Brazilian semiarid (ASA and water conflicts from cases of irrigated areas in the states of Ceará and Rio Grande do Norte are explained. For this purpose, we used a qualitative approach through the use of primary and secondary data. The cases provide concrete actions that articulate civil society and the State in favor of the common good. The results indicate that the policy articulated by the ASA there is a governance process in which there are links between the forums of civil society and the interfaces in the planning and implementation of public policies in building public agenda that can bridge the gap between planning, deployment, management and improvement of this policy. In the second case the policy is implemented exclusion and allocation of those communities, placing them on the margins of development, scrapping its links with the territory. The water is not seen from the perspective of the common good and the communities are perceived as an obstacle to “development”. Finally, it outlines themselves from the cases under study, with the idea that limiting access to water in the semiarid region, reflects the precarious welfare and perpetuation of relations of dependency, paternalism and clientelism high proportion of the population rural Brazilian semiarid.

Arbuscular mycorrhizal fungi in Mimosa tenuiflora (Willd. Poir from Brazilian semi-arid

Directory of Open Access Journals (Sweden)

Tancredo Augusto Feitosa de Souza

2016-06-01

Full Text Available Abstract Many plant species from Brazilian semi-arid present arbuscular mycorrhizal fungi (AMF in their rhizosphere. These microorganisms play a key role in the establishment, growth, survival of plants and protection against drought, pathogenic fungi and nematodes. This study presents a quantitative analysis of the AMF species associated with Mimosa tenuiflora, an important native plant of the Caatinga flora. AMF diversity, spore abundance and root colonization were estimated in seven sampling locations in the Ceará and Paraíba States, during September of 2012. There were significant differences in soil properties, spore abundance, percentage of root colonization, and AMF diversity among sites. Altogether, 18 AMF species were identified, and spores of the genera Acaulospora, Claroideoglomus, Dentiscutata, Entrophospora, Funneliformis, Gigaspora, Glomus, Racocetra, Rhizoglomus and Scutellospora were observed. AMF species diversity and their spore abundance found in M. tenuiflora rhizosphere shown that this native plant species is an important host plant to AMF communities from Brazilian semi-arid region. We concluded that: (a during the dry period and in semi-arid conditions, there is a high spore production in M. tenuiflora root zone; and (b soil properties, as soil pH and available phosphorous, affect AMF species diversity, thus constituting key factors for the similarity/dissimilarity of AMF communities in the M. tenuiflora root zone among sites.

Conditions for formation of electron pairs in a metal

Energy Technology Data Exchange (ETDEWEB)

Shekhtman, A.Z., E-mail: shekhtmanalexander@gmail.com

2015-04-15

Highlights: • A new approach has been developed for consideration of electron pairing in metals. • Binding energy of a single pair induced by electron-phonon interaction is very small. • A new mechanism for electron pairing in metals has been considered. • Conditions for feasibility of the mechanism give conditions for electron pairing. • The mechanism gives wide opportunities to study new conditions for electron pairing. - Abstract: In an isotropic model of the electron system of metal that is presented by the Fröhlich’s initial Hamiltonian, in the approximation of a weak electron–phonon interaction at T = 0, first time, we show that the ground state of the system is the state with pairing correlations of electrons (the pair correlations of occupied electron states). In contrast to the BCS approach, the initial point in our approach is not electron pairing but is the maximum reduction of the energy of the considered system due to virtual processes of the electron–phonon interaction and to the exchange effect for the indirect electron–electron interaction (which is induced by certain phonon modes separately from others). In contrast to the BCS approach, we take into account the portion of the energy of the electron system that is connected with the above exchange effect. In the BCS approach, the corresponding portion is missed, and its role is prescribed to the portion that does not relate to the electron pairing. We show that expectation values of the above Hamiltonian for different wave functions for two interacting electrons above the Fermi sea of the non-interacting system (with interaction between the electrons that is induced by different phonon modes separately from others) are minimum for a certain structure of these functions and simultaneously for phonon modes that can induce the transitions of the interacting electrons between electron states in which they are (without violation of the Pauli exclusion principle and at everything else

Impacts of urbanization on nitrogen cycling and aerosol, surface and groundwater transport in semi-arid regions

Science.gov (United States)

Lohse, K. A.; Gallo, E.; Carlson, M.; Riha, K. M.; Brooks, P. D.; McIntosh, J. C.; Sorooshian, A.; Michalski, G. M.; Meixner, T.

2011-12-01

Semi-arid regions are experiencing disproportionate increases in human population and land transformation worldwide, taxing limited water resources and altering nitrogen (N) biogeochemistry. How the redistribution of water and N by urbanization affects semi-arid ecosystems and downstream water quality (e.g. drinking water) is unclear. Understanding these interactions and their feedbacks will be critical for developing science-based management strategies to sustain these limited resources. This is especially true in the US where some of the fastest growing urban areas are in semi-arid ecosystems, where N and water cycles are accelerated, and intimately coupled, and where runoff from urban ecosystems is actively managed to augment a limited water supply to the growing human population. Here we synthesize several ongoing studies from the Tucson Basin in Arizona and examine how increasing urban land cover is altering rainfall-runoff relationships, groundwater recharge, water quality, and long range transport of atmospheric N. Studies across 5 catchments varying in impervious land cover showed that only the least impervious catchment responded to antecedent moisture conditions while hydrologic responses were not statistically related to antecedent rainfall conditions at more impervious sites. Regression models indicated that rainfall depth, imperviousness, and their combined effect control discharge and runoff ratios (p channel characteristics and infrastructure controlled runoff chemistry. Groundwater studies showed nonpoint source contamination of CFCs and associated nitrate in areas of rapid recharge along ephemeral channels. Aerosol measurements indicate that both long-range transport of N and N emissions from Tucson are being transported and deposited at high elevation in areas that recharge regional groundwater. Combined, our findings suggest that urbanization in semi-arid regions results in tradeoffs in the redistribution of water and N that have important

Microbial Community Activity And Plant Biomass Are Insensitive To Passive Warming In A Semiarid Ecosystem

Science.gov (United States)

Espinosa, N. J.; Fehmi, J. S.; Rasmussen, C.; Gallery, R. E.

2017-12-01

microbial community activity in semiarid ecosystems are complex and are potentially regulated more by pulse events than small changes in conditions such as a warmer environment.

Spatial patterns and natural recruitment of native shrubs in a semi-arid sandy land.

Science.gov (United States)

Wu, Bo; Yang, Hongxiao

2013-01-01

Passive restoration depending on native shrubs is an attractive approach for restoring desertified landscapes in semi-arid sandy regions. We sought to understand the relationships between spatial patterns of native shrubs and their survival ability in sandy environments. Furthermore, we applied our results to better understand whether passive restoration is feasible for desertified landscapes in semi-arid sandy regions. The study was conducted in the semi-arid Mu Us sandy land of northern China with the native shrub Artemisia ordosica. We analyzed population structures and patterns of A. ordosica at the edges and centers of land patches where sand was stabilized by A. ordosica-dominated vegetation. Saplings were more aggregated than adults, and both were more aggregated at the patch edges than at the patch centers. At the patch edges, spatial association of the saplings with the adults was mostly positive at distances 0.3-6.6 m, and turned from positive to neutral, and even negative, at other distances. At the patch centers, the saplings were spaced almost randomly around the adults, and their distances from the adults did not seem to affect their locations. A greater number of A. ordosica individuals emerged at the patch edges than at the patch centers. Such patterns may have resulted from their integrative adjustment to specific conditions of soil water supply and sand drift intensity. These findings suggest that in semi-arid sandy regions, native shrubs that are well-adapted to local environments may serve as low-cost and competent ecological engineers that can promote the passive restoration of surrounding patches of mobile sandy land.

Assessing groundwater storage changes using remote sensing-based evapotranspiration and precipitation at a large semiarid basin scale

NARCIS (Netherlands)

Gokmen, M.; Vekerdy, Z.; Lubczynski, M.; Timmermans, J.; Batelaan, Okke; Verhoef, W.

2013-01-01

A method is presented that uses remote sensing (RS)-based evapotranspiration (ET) and precipitation estimates with improved accuracies under semiarid conditions to quantify a spatially distributed water balance, for analyzing groundwater storage changes due to supplementary water uses. The method is

Predicting germination in semi-arid wildland seedbeds II. Field validation of wet thermal-time models

Science.gov (United States)

Jennifer K. Rawlins; Bruce A. Roundy; Dennis Eggett; Nathan. Cline

2011-01-01

Accurate prediction of germination for species used for semi-arid land revegetation would support selection of plant materials for specific climatic conditions and sites. Wet thermal-time models predict germination time by summing progress toward germination subpopulation percentages as a function of temperature across intermittent wet periods or within singular wet...

Diurnal regulation of photosynthesis in Jatropha curcas under drought during summer in a semi-arid region

International Nuclear Information System (INIS)

Tominaga, Jun; Inafuku, Sayuri; Coetzee, Tidimalo; Kawamitsu, Yoshinobu

2014-01-01

The diurnal photosynthetic responses to drought in Jatropha curcas have not been well assessed under field conditions in harsh semi-arid habitats. To illustrate this, diurnal changes in chlorophyll fluorescence and gas exchange rates were measured in field-grown Jatropha with or without a short (13 days) water recovery treatment under drought conditions during hot summer in a semi-arid. Sensitive stomatal closure coordinated with a drying atmosphere strictly limited a net CO 2 assimilation rate with a predominant morning peak, eventually turning negative during the day. Even though the risk of excess excitation energy which potentially causes photodamage increased with the extremely low capacity for CO 2 fixation, Jatropha preserved the integrity of PSII. Quantitative analysis of quenching partitioning revealed that regulated thermal energy dissipation accounted a large fraction of both instantaneous and daily absorbed energy by up to 80 and 72%, respectively, under the drought condition. Water recovery treatment more than doubled daily CO 2 uptake via mitigating diurnal stomatal closure. The regulated thermal dissipation flexibly adjusted PSII quantum efficiency to capacity of CO 2 fixation. In addition, downregulation of PSII quantum efficiency via sustained regulated thermal dissipation was observed and thought to be an additional photoprotective function. It is clear that Jatropha strongly rely upon the regulated thermal dissipation under drought condition, which must be critically important for this strict water conserving species, especially under a climate with high solar radiation loads as is seen in semi-arid regions. - Highlights: • Diurnal gas exchange and the fate of absorbed energy were assessed in Jatropha. • The dynamic stomatal closure was the predominant restriction under water stress. • The PSII integrity was preserved even under severe water stress. • The regulated thermal dissipation accounted by up to 72% of daily absorbed energy. �

Moisture ingress into electronics enclosures under isothermal conditions

DEFF Research Database (Denmark)

Staliulionis, Zygimantas; Jabbaribehnam, Mirmasoud; Hattel, Jesper Henri

2016-01-01

loads are still not understood well by design engineers, therefore this field has become one of the bottlenecks in the electronics system design. The objective of this paper is to model moisture ingress into an electronics enclosure under isothermal conditions. The moisture diffusion model is based......The number of electronics used in outdoor environment is constantly growing. The humidity causes about 19 % of all electronics failures and, especially, moisture increases these problems due to the ongoing process of miniaturization and lower power consumption of electronic components. Moisture...

Initiation of soil formation in weathered sulfidic Cu-Pb-Zn tailings under subtropical and semi-arid climatic conditions.

Science.gov (United States)

You, Fang; Dalal, Ram; Huang, Longbin

2018-08-01

Field evidence has been scarce about soil (or technosol) formation and direct phytostabilization of base metal mine tailings under field conditions. The present study evaluated key attributes of soil formation in weathered and neutral Cu-Pb-Zn tailings subject to organic amendment (WC: woodchips) and colonization of pioneer native plant species (mixed native woody and grass plant species) in a 2.5-year field trial under subtropical and semi-arid climatic conditions. Key soil indicators of engineered soil formation process were characterized, including organic carbon fractions, aggregation, microbial community and key enzymatic activities. The majority (64-87%) of the OC was stabilized in microaggregate or organo-mineral complexes in the amended tailings. The levels of OC and water soluble OC were elevated by 2-3 folds across the treatments, with the highest level in the treatment of WC and plant colonization (WC+P). Specifically, the WC+P treatment increased the proportion of water stable macroaggregates. Plants further contributed to the N rich organic matter in the tailings, favouring organo-mineral interactions and organic stabilization. Besides, the plants played a major role in boosting microbial biomass and activities in the treated tailings. WC and plants enhanced the contents of organic carbon (OC) associated with aggregates (e.g., physically protected OC), formation of water-stable aggregates (e.g., micro and macroaggregates), chemical buffering capacity (e.g., cation exchange capacity). Microbial community and enzymatic activities were also stimulated in the amended tailings. The present results showed that the formation of functional technosol was initiated in the eco-engineered and weathered Cu-Pb-Zn tailings under field conditions for direct phytostabilization. Copyright © 2018 Elsevier Ltd. All rights reserved.

Long-term forest resilience to climate change indicated by mortality, regeneration, and growth in semiarid southern Siberia.

Science.gov (United States)

Xu, Chongyang; Liu, Hongyan; Anenkhonov, Oleg A; Korolyuk, Andrey Yu; Sandanov, Denis V; Balsanova, Larisa D; Naidanov, Bulat B; Wu, Xiuchen

2017-06-01

Several studies have documented that regional climate warming and the resulting increase in drought stress have triggered increased tree mortality in semiarid forests with unavoidable impacts on regional and global carbon sequestration. Although climate warming is projected to continue into the future, studies examining long-term resilience of semiarid forests against climate change are limited. In this study, long-term forest resilience was defined as the capacity of forest recruitment to compensate for losses from mortality. We observed an obvious change in long-term forest resilience along a local aridity gradient by reconstructing tree growth trend and disturbance history and investigating postdisturbance regeneration in semiarid forests in southern Siberia. In our study, with increased severity of local aridity, forests became vulnerable to drought stress, and regeneration first accelerated and then ceased. Radial growth of trees during 1900-2012 was also relatively stable on the moderately arid site. Furthermore, we found that smaller forest patches always have relatively weaker resilience under the same climatic conditions. Our results imply a relatively higher resilience in arid timberline forest patches than in continuous forests; however, further climate warming and increased drought could possibly cause the disappearance of small forest patches around the arid tree line. This study sheds light on climate change adaptation and provides insight into managing vulnerable semiarid forests. © 2016 John Wiley & Sons Ltd.

Isotope and radiation techniques for efficient water and fertilizer use in semi-arid regions

International Nuclear Information System (INIS)

1986-04-01

The Joint FAO/IAEA Division carried out a coordinated research programme, which was concerned with the efficiency of water and fertilizer uses in semi-arid farming systems. The present publication is a summary of the individual contributions from Belgium, Chile, Ivory Coast, Cyprus, France, India, Israel, Romania, Senegal, Sri Lanka and the United States of America, over the period 1978-1984. Water and fertilizer uptake by crops are dynamic processes affected by several factors of the soil-plant-atmosphere system. The neutron moisture meters were used not only to measure soil water contents but also to understand water dynamics under field conditions. Nitrogen is the most limiting nutrient in many semi-arid regions, and as its absorption is very much related to water dynamics in the soil, experiments using N-15 labelled fertilizer were carried out, which are presented in this report

EFFECT OF SEASON ON SERUM COPPER AND ZINC CONCENTRATIONS IN CROSSBRED GOATS HAVING DIFFERENT REPRODUCTIVE STATUS UNDER SEMIARID RANGELAND CONDITIONS IN SOUTHERN MEXICO STATE

Directory of Open Access Journals (Sweden)

José Fernando Vázquez-Armijo

2010-10-01

Full Text Available The effect of season (rainy: RS, and dry: DS and reproductive status on copper (Cu and zinc (Zn concentrations in blood serum of crossbred goats (BW= 36.01 ± 1.59 kg were studied under semiarid rangeland conditions in Southern Mexico State. Blood samples from 80 crossbred goats were taken each season (RS and DS. The goats were clustered into 10 different groups considering their reproductive status. Concentrations of Cu and Zn in serum were assayed using atomic absorption. Data were analyzed using a general linear model procedure for a completely randomized design and differences among means were examined using a Tukey test. Blood serum concentrations of Cu and Zn were affected by reproductive status and season (P

Hydrological Response of Semi-arid Degraded Catchments in Tigray, Northern Ethiopia

Science.gov (United States)

Teka, Daniel; Van Wesemael, Bas; Vanacker, Veerle; Hallet, Vincent

2013-04-01

To address water scarcity in the arid and semi-arid part of developing countries, accurate estimation of surface runoff is an essential task. In semi-arid catchments runoff data are scarce and therefore runoff estimation using hydrological models becomes an alternative. This research was initiated in order to characterize runoff response of semi-arid catchments in Tigray, North Ethiopia to evaluate SCS-CN for various catchments. Ten sub-catchments were selected in different river basins and rainfall and runoff were measured with automatic hydro-monitoring equipments for 2-3 years. The Curve Number was estimated for each Hydrological Response Unit (HRU) in the sub-catchments and runoff was modeled using the SCS-CN method at λ = 0.05 and λ = 0.20. The result showed a significant difference between the two abstraction ratios (P =0.05, df = 1, n= 132) and reasonable good result was obtained for predicted runoff at λ = 0.05 (NSE = -0.69; PBIAS = 18.1%). When using the CN values from literature runoff was overestimated compared to the measured value (e= -11.53). This research showed the importance of using measured runoff data to characterize semi-arid catchments and accurately estimate the scarce water resource. Key words: Hydrological response, rainfall-runoff, degraded environments, semi-arid, Ethiopia, Tigray

Efficiency of water and fertilizer use in semi-arid regions

International Nuclear Information System (INIS)

1976-01-01

The proceedings contain 14 papers considering problems on soil and soil water, irrigation, and the use of fertilizers in semi-arid zones. Research projects in these fields are discussed and results obtained so far are reported (tables and diagrams on the behaviour of water and fertilizers in soils). The use of radioisotope techniques is mentioned briefly. Finally, some future ''first priority'' research areas are identified and recommendations for further research programs are given. These programs aim at reducing the hazards of crop failure and at increasing production under dry farming conditions

Endemic shrubs in temperate arid and semiarid regions of northern China and their potentials for rangeland restoration.

Science.gov (United States)

Chu, Jianmin; Yang, Hongxiao; Lu, Qi; Zhang, Xiaoyan

2015-06-03

Some endemic shrubs in arid and semiarid ecosystems are in danger of extinction, and yet they can play useful roles in maintaining or restoring these ecosystems, thus practical efforts are needed to conserve them. The shrubs Amygdalus pedunculata Pall., Amygdalus mongolica (Maxim.) Ricker and Ammopiptanthus mongolicus (Maxim. ex Kom.) Cheng f. are endemic species in arid and semiarid regions of northern China, where rangeland desertification is pronounced due to chronic overgrazing. In this study, we tested the hypothesis that these endemic shrubs have developed adaptations to arid and semiarid environments and could play critical roles as nurse species to initiate the process of rangeland recovery. Based on careful vegetation surveys, we analysed the niches of these species in relation to precipitation, temperature and habitats. All sampling plots were categorized by these endemics and sorted by the non-metric multidimensional scaling method. Species ratios of each life form and species co-occurrence rates with the endemics were also evaluated. Annual average temperature and annual precipitation were found to be the key factors determining vegetation diversity and distributions. Amygdalus pedunculata prefers low hills and sandy land in temperate semiarid regions. Amygdalus mongolica prefers gravel deserts of temperate semiarid regions. Ammopiptanthus mongolicus prefers sandy land of temperate arid regions. Communities of A. pedunculata have the highest diversity and the largest ratios of long-lived grass species, whereas those of A. mongolicus have the lowest diversity but the largest ratios of shrub species. Communities of A. mongolica are a transition between the first two community types. These findings demonstrate that our focal endemic shrubs have evolved adaptations to arid and semiarid conditions, thus they can be nurse plants to stabilize sand ground for vegetation restoration. We suggest that land managers begin using these shrub species to restore

Rapid warming accelerates tree growth decline in semi-arid forests of Inner Asia.

Science.gov (United States)

Liu, Hongyan; Park Williams, A; Allen, Craig D; Guo, Dali; Wu, Xiuchen; Anenkhonov, Oleg A; Liang, Eryuan; Sandanov, Denis V; Yin, Yi; Qi, Zhaohuan; Badmaeva, Natalya K

2013-08-01

Forests around the world are subject to risk of high rates of tree growth decline and increased tree mortality from combinations of climate warming and drought, notably in semi-arid settings. Here, we assess how climate warming has affected tree growth in one of the world's most extensive zones of semi-arid forests, in Inner Asia, a region where lack of data limits our understanding of how climate change may impact forests. We show that pervasive tree growth declines since 1994 in Inner Asia have been confined to semi-arid forests, where growing season water stress has been rising due to warming-induced increases in atmospheric moisture demand. A causal link between increasing drought and declining growth at semi-arid sites is corroborated by correlation analyses comparing annual climate data to records of tree-ring widths. These ring-width records tend to be substantially more sensitive to drought variability at semi-arid sites than at semi-humid sites. Fire occurrence and insect/pathogen attacks have increased in tandem with the most recent (2007-2009) documented episode of tree mortality. If warming in Inner Asia continues, further increases in forest stress and tree mortality could be expected, potentially driving the eventual regional loss of current semi-arid forests. © 2013 John Wiley & Sons Ltd.

The importance of considering rainfall partitioning in afforestation initiatives in semiarid climates: A comparison of common planted tree species in Tehran, Iran

International Nuclear Information System (INIS)

Sadeghi, Seyed Mohammad Moein; Attarod, Pedram; Van Stan, John Toland; Pypker, Thomas Grant

2016-01-01

As plantations become increasingly important sources of wood and fiber in arid/semiarid places, they have also become increasingly criticized for their hydrological impacts. An examination and comparison of gross rainfall (GR) partitioning across commonly-planted tree species (Pinus eldarica, Cupressus arizonica, Robinia pseudoacacia, and Fraxinus rotundifolia) in semiarid regions has great value for watershed and forest managers interested in managing canopy hydrological processes for societal benefit. Therefore, we performed a field study examining GR partitioning into throughfall (TF), stemflow (SF), and rainfall interception (I) for these species in the semiarid Chitgar Forest Park, Tehran, Iran. An advantage to our study is that we explore the effects of forest structural differences in plantation forests experiencing similar climatic factors and storm conditions. As such, variability in GR partitioning due to different meteorological conditions is minimized, allowing comparison of structural attributes across plantations. Our results show that commonly-selected afforestation species experiencing the same climate produced differing stand structures that differentially partition GR into TF, SF, and I. P. eldarica might be the best of the four species to plant if the primary goal of afforestation is to limit erosion and stormwater runoff as it intercepted more rainfall than other species. However, the high SF generation from F. rotundifolia, and low GR necessary to initiate SF, could maximize retention of water in the soils since SF has been shown to infiltrate along root pathways and access groundwater. A consideration of GR partitioning should be considered when selecting a species for afforestation/reforestation in water-limited ecosystems. - Highlights: • Measured rain partitioning of four most common species used in semiarid afforestation • Species rain partitioning differences are important in a water management. • Recommendations provided to guide

The importance of considering rainfall partitioning in afforestation initiatives in semiarid climates: A comparison of common planted tree species in Tehran, Iran

Energy Technology Data Exchange (ETDEWEB)

Sadeghi, Seyed Mohammad Moein, E-mail: moeinsadeghi@ut.ac.ir [Department of Forestry and Forest Economics, University of Tehran (Iran, Islamic Republic of); Attarod, Pedram [Department of Forestry and Forest Economics, University of Tehran (Iran, Islamic Republic of); Van Stan, John Toland [Department of Geology and Geography, Georgia Southern University, Statesboro, Georgia (United States); Pypker, Thomas Grant [Department of Natural Resource Sciences, Faculty of Science, Thompson Rivers University, Kamloops (Canada)

2016-10-15

As plantations become increasingly important sources of wood and fiber in arid/semiarid places, they have also become increasingly criticized for their hydrological impacts. An examination and comparison of gross rainfall (GR) partitioning across commonly-planted tree species (Pinus eldarica, Cupressus arizonica, Robinia pseudoacacia, and Fraxinus rotundifolia) in semiarid regions has great value for watershed and forest managers interested in managing canopy hydrological processes for societal benefit. Therefore, we performed a field study examining GR partitioning into throughfall (TF), stemflow (SF), and rainfall interception (I) for these species in the semiarid Chitgar Forest Park, Tehran, Iran. An advantage to our study is that we explore the effects of forest structural differences in plantation forests experiencing similar climatic factors and storm conditions. As such, variability in GR partitioning due to different meteorological conditions is minimized, allowing comparison of structural attributes across plantations. Our results show that commonly-selected afforestation species experiencing the same climate produced differing stand structures that differentially partition GR into TF, SF, and I. P. eldarica might be the best of the four species to plant if the primary goal of afforestation is to limit erosion and stormwater runoff as it intercepted more rainfall than other species. However, the high SF generation from F. rotundifolia, and low GR necessary to initiate SF, could maximize retention of water in the soils since SF has been shown to infiltrate along root pathways and access groundwater. A consideration of GR partitioning should be considered when selecting a species for afforestation/reforestation in water-limited ecosystems. - Highlights: • Measured rain partitioning of four most common species used in semiarid afforestation • Species rain partitioning differences are important in a water management. • Recommendations provided to guide

Selection of the optimum condition for electron capture detector operation

International Nuclear Information System (INIS)

Lasa, J.; Korus, A.

1974-01-01

A method of determination of the optimal work conditions for the electron capture detector is presented in the paper. Physical phenomena which occur in the detector, as well as the energetic dependence of the electron attachment process are taken into consideration. The influence of the kind of carrier gas, temperature, and the parameters of the supplied voltage in both direct and pulse methods on average values of electron energy is described. Dependence of the sensitivity of the electron capture detector on the carrier gas and the polarizing voltage is illustrated for the Model DNW-300 electron capture detector produced in Poland. Practical indications for selecting optimal conditions of electron capture detector operation are given at the end of the paper. (author)

Avaluation of the adaptability of dairy goats with help of thermographic precision in the semiarid brazilian

Directory of Open Access Journals (Sweden)

Elisângela Maria Nunes da Silva

2014-06-01

Full Text Available ABSTRACT. Silva E.M.N., Souza B.B., Silva G.A., Alcântara M.D.B., Cunha M.G.G. & Marques B.A.A. [Avaluation of the adaptability of dairy goats with help of thermographic precision in the semiarid brazilian.] Avaliação da adaptabilidade de caprinos leiteiros com auxílio da precisão termográfica no semiárido brasileiro. Revista Brasileira de Medicina Veterinaria, 36(2:231-237, 2014. Programa de Pós-Graduação em Medicina Veterinária, Universidade Federal de Campina Grande, Rodovia Patos-Teixeira, Km 01, Jatobá, Patos, PB 58708-110, Brasil. E-mail: elisangelamns@yahoo.com.br The present study aimed to evaluate the adaptability of dairy goats with help of thermographic precision in the semiarid brazilian. Thirty-six female goats were used in the study, mean age 2.5 years old and mean weight of 45 kg, all of them pure-bred, lactating and not pregnant, distributed in a completely randomized design, in a factorial outline 2 x 2; two genotypes (Anglo Nubian and Alpine vs two shifts (morning and afternoon with 18 repetitions. Analysis of variance showed that the shift had significant effect (P0.05. Also, there was no significant interaction between breed and shift. Regarding the parameters: respiratory rate (RR and surface temperature of the muzzle of cinnamon there was significant effect of breed and shift and significant interaction between breed and shift (P<0.05. Positive correlations between physiological parameters and room temperature and negative correlation between thermal gradients and more parameters. The Anglo Nubian breed had become more adapted to the semi-arid environmental conditions representing a good alternative for breeding programs. The Alpine breed increased respiratory effort required to dissipate heat and maintain homeothermy, proving to be more demanding regarding system creation and management in the semi-arid climatic conditions.

Sediment budgets and source determinations using fallout Cesium-137 in a semiarid rangeland watershed, Arizona, USA

International Nuclear Information System (INIS)

Ritchie, Jerry C.; Nearing, Mark A.; Rhoton, Fred E.

2009-01-01

Analysis of soil redistribution and sediment sources in semiarid and arid watersheds provides information for implementing management practices to improve rangeland conditions and reduce sediment loads to streams. The purpose of this research was to develop sediment budgets and identify potential sediment sources using 137 Cs and other soil properties in a series of small semiarid subwatersheds on the USDA ARS Walnut Gulch Experimental Watershed near Tombstone, Arizona, USA. Soils were sampled in a grid pattern on two small subwatersheds and along transects associated with soils and geomorphology on six larger subwatersheds. Soil samples were analyzed for 137 Cs and selected physical and chemical properties (i.e., bulk density, rocks, particle size, soil organic carbon). Suspended sediment samples collected at measuring flume sites on the Walnut Gulch Experimental Watershed were also analyzed for these properties. Soil redistribution measured using 137 Cs inventories for a small shrub-dominated subwatershed and a small grass-dominated subwatershed found eroding areas in these subwatersheds were losing -5.6 and -3.2 t ha -1 yr -1 , respectively; however, a sediment budget for each of these subwatersheds, including depositional areas, found net soil loss to be -4.3 t ha -1 yr -1 from the shrub-dominated subwatershed and -0.1 t ha -1 yr -1 from the grass-dominated subwatershed. Generally, the suspended sediment collected at the flumes of the six other subwatersheds was enriched in silt and clay. Using a mixing model to determine sediment source indicated that shrub-dominated subwatersheds were contributing most of the suspended sediment that was measured at the outlet flume of the Walnut Gulch Experimental Watershed. The two methodologies (sediment budgets and sediment source analyses) indicate that shrub-dominated systems provide more suspended sediment to the stream systems. The sediment budget studies also suggest that sediment yields measured at the outlet of a

Regional integrated modelling of climate change impacts on natural resources and resource usage in semi-arid Norhteast Brazil

NARCIS (Netherlands)

Krol, Martinus S.; Bronstert, Axel

2007-01-01

Semi-arid regions are characterised by a high vulnerability of natural resources to climate change, pronounced climatic variability and often by water scarcity and related social stress. The analysis of the dynamics of natural conditions and the assessment of possible strategies to cope with

Influence of Soil Moisture on Litter Respiration in the Semiarid Loess Plateau

Science.gov (United States)

Zhang, Yanjun; Guo, Shengli; Liu, Qingfang; Jiang, Jishao

2014-01-01

Understanding the response mechanisms of litter respiration to soil moisture in water-limited semi-arid regions is of vital importance to better understanding the interplay between ecological processes and the local carbon cycle. In situ soil respiration was monitored during 2010–2012 under various conditions (normal litter, no litter, and double litter treatments) in a 30-year-old artificial black locust plantation (Robinia pseudoacacia L.) on the Loess Plateau. Litter respiration with normal and double litter treatments exhibited similar seasonal variation, with the maximum value obtained in summer (0.57 and 1.51 μmol m−2 s−1 under normal and double litter conditions, respectively) and the minimum in spring (0.27 and 0.69 μmol m−2 s−1 under normal and double litter conditions, respectively). On average, annual cumulative litter respiration was 115 and 300 g C m−2 y−1 under normal and double litter conditions, respectively. Using a soil temperature of 17°C as the critical point, the relationship between litter respiration and soil moisture was found to follow quadratic functions well, whereas the determination coefficient was much greater at high soil temperature than at low soil temperature (33–35% vs. 22–24%). Litter respiration was significantly higher in 2010 and 2012 than in 2011 under both normal litter (132–165 g C m−2 y−1 vs. 48 g C m−2 y−1) and double litter (389–418 g C m−2 y−1 vs. 93 g C m−2 y−1) conditions. Such significant interannual variations were largely ascribed to the differences in summer rainfall. Our study demonstrates that, apart from soil temperature, moisture also has significant influence on litter respiration in semi-arid regions. PMID:25474633

Composition and fate of mine- and smelter-derived particles in soils of humid subtropical and hot semi-arid areas

Energy Technology Data Exchange (ETDEWEB)

Ettler, Vojtěch, E-mail: ettler@natur.cuni.cz [Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University in Prague, Albertov 6, 128 43 Praha 2 (Czech Republic); Johan, Zdenek [BRGM, Avenue Claude Guillemin, 45082 Orléans Cedex 2 (France); Kříbek, Bohdan; Veselovský, František [Czech Geological Survey, Geologická 6, 152 00 Praha 5 (Czech Republic); Mihaljevič, Martin [Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University in Prague, Albertov 6, 128 43 Praha 2 (Czech Republic); Vaněk, Aleš; Penížek, Vít [Department of Soil Science and Soil Protection, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Praha 6 (Czech Republic); Majer, Vladimír [Czech Geological Survey, Geologická 6, 152 00 Praha 5 (Czech Republic); Sracek, Ondra [Department of Geology, Faculty of Science, Palacký University in Olomouc, 17. listopadu 12, 771 46 Olomouc (Czech Republic); Mapani, Ben; Kamona, Fred [Department of Geology, Faculty of Science, University of Namibia, Private Bag 13301, Windhoek (Namibia); Nyambe, Imasiku [University of Zambia, School of Mines, P. O. Box 32 379, Lusaka (Zambia)

2016-09-01

We studied the heavy mineral fraction, separated from mining- and smelter-affected topsoils, from both a humid subtropical area (Mufulira, Zambian Copperbelt) and a hot semi-arid area (Tsumeb, Namibia). High concentrations of metal(loid)s were detected in the studied soils: up to 1450 mg As kg{sup −1}, 8980 mg Cu kg{sup −1}, 4640 mg Pb kg{sup −1}, 2620 mg Zn kg{sup −1}. A combination of X-ray diffraction analysis (XRD), scanning electron microscopy (SEM/EDS), and electron probe microanalysis (EPMA) helped to identify the phases forming individual metal(loid)-bearing particles. Whereas spherical particles originate from the smelting and flue gas cleaning processes, angular particles have either geogenic origins or they are windblown from the mining operations and mine waste disposal sites. Sulphides from ores and mine tailings often exhibit weathering rims in contrast to smelter-derived high-temperature sulphides (chalcocite [Cu{sub 2}S], digenite [Cu{sub 9}S{sub 5}], covellite [CuS], non-stoichiometric quenched Cu–Fe–S phases). Soils from humid subtropical areas exhibit higher available concentrations of metal(loids), and higher frequencies of weathering features (especially for copper-bearing oxides such as delafossite [Cu{sup 1+} Fe{sup 3+} O{sub 2}]) are observed. In contrast, metal(loid)s are efficiently retained in semi-arid soils, where a high proportion of non-weathered smelter slag particles and low-solubility Ca–Cu–Pb arsenates occur. Our results indicate that compared to semi-arid areas (where inorganic contaminants were rather immobile in soils despite their high concentrations) a higher potential risk exists for agriculture in mine- and smelter-affected humid subtropical areas (where metal(loid) contaminants can be highly available for the uptake by crops). - Highlights: • Mining- and smelter-derived particles identified in subtropical and semi-arid soils • Sulphides, oxides, and metal-bearing arsenates most frequently encountered �

Insolation driven biomagnetic response to Holocene Warm Period in semi-arid East Asia

OpenAIRE

Liu, S.; Deng, Chenglong; Xiao, Jule; Li, Jinhua; Paterson, Greig; Chang, Liao; Yi, Liang; Qin, Huafeng; Pan, Yongxin; Zhu, Rixiang

2015-01-01

The Holocene Warm Period (HWP) provides valuable insights into the climate system and biotic responses to environmental variability and thus serves as an excellent analogue for future global climate changes. Here we document, for the first time, that warm and wet HWP conditions were highly favourable for magnetofossil proliferation in the semi-arid Asian interior. The pronounced increase of magnetofossil concentrations at ~9.8 ka and decrease at ~5.9 ka in Dali Lake coincided respectively wit...

Influence of rainfall on the trophic status of a brazilian semiarid reservoir - doi: 10.4025/actascibiolsci.v35i4.18261

Directory of Open Access Journals (Sweden)

Francisco Ítalo Barbosa Chaves

2013-07-01

Full Text Available This study evaluated the trophic conditions of the reservoir located in the urban perimeter of the town General Sampaio, semiarid region of the Ceará State, Brazil and its relationship with seasonal variation in rainfall between 2010 and 2011. It was obtained data for Secchi disk transparency, total phosphorus, and chlorophyll a to calculate the Trophic State Index (TSI, as well as rainfall data. The Trophic State Index (TSI proposed by Carlson (1977 and modified by Toledo Junior (1990 was used to test the influence of the seasonal variation in rainfall on hydrological variables and on trophic conditions of the reservoir in 2010 and 2011. There was seasonal variability in variables analyzed between climatic periods (rainy and dry and trophic conditions determined through the trophic index indicated conditions ranging from oligotrophic to eutrophic during the two years analyzed in this reservoir. Under these circumstances, one may conclude that the trophic status is related to seasonal fluctuations in the hydrology of the system controlled by rainfall, which is a common feature of semiarid regions.

Assessment of the performance of water harvesting systems in semi-arid regions

Science.gov (United States)

Lasage, Ralph

2016-04-01

Water harvesting is widely practiced and has the potential to improve water availability for domestic and agricultural use in semi-arid regions. New funds are becoming available to stimulate the implementation of water harvesting projects, for meeting the Sustainable Development Goals and to help communities to adapt to climate change. For this, it is important to understand which factors determine the success of water harvesting techniques under different conditions. For this, we review the literature, including information on the crop yield impacts of water harvesting projects in semi-arid Africa and Asia. Results show that large water harvesting structures (> 500 m3) are less expensive than small structures, when taking into account investment costs, storage capacity and lifetimes. We also find that water harvesting improves crop yields significantly, and that the relative impact of water harvesting on crop yields is largest in low rainfall years. We also see that the governance, technical knowledge and initial investment are more demanding for the larger structures than for smaller structures, which may affect their spontaneous adoption and long term sustainability when managed by local communities. To support the selection of appropriate techniques, we present a decision framework based on case specific characteristics. This framework can also be used when reporting and evaluating the performance of water harvesting techniques, which is up to now quite limited in peer reviewed literature. Based on Bouma, J., Hegde, S.E., Lasage, R., (2016). Assessing the returns to water harvesting: A meta-analysis. Agricultural Water Management 163, 100-109. Lasage, R., Verburg P.H., (2015). Evaluation of small scale water harvesting techniques for semi-arid environments. Journal of Arid Environments 118, 48-57.

Peach response to water deficit in a semi-arid region

Science.gov (United States)

Paltineanu, C.; Septar, L.; Moale, C.; Nicolae, S.; Nicola, C.

2013-09-01

During three years a deficit irrigation experiment was performed on peach response under the semi-arid conditions of south-eastern Romania. Three sprinkler-irrigated treatments were investigated: fully irrigated, deficit irrigation treatment, and non-irrigated control treatment. Soil water content ranged between 60 and 76% of the plant available soil water capacity in fully irrigated, between 40 and 62% in deficit irrigation treatment, and between 30 and 45% in control. There were significant differences in fruit yield between the treatments. Irrigation water use efficiency was maximum in deficit irrigation treatment. Fruit yield correlated significantly with irrigation application. Total dry matter content, total solids content and titrable acidity of fruit were significantly different in the irrigated treatments vs. the control. Significant correlation coefficients were found between some fruit chemical components. For the possible future global warming conditions, when water use becomes increasingly restrictive, deficit irrigation will be a reasonable solution for water conservation in regions with similar soil and climate conditions.

Effect of complementary irrigation on yield components and alternate bearing of a traditional olive orchard in semi-arid conditions

Directory of Open Access Journals (Sweden)

Enrico M. Lodolini

2016-06-01

Full Text Available Traditional olive orchards are usually not irrigated in the Mediterranean basin, but at those latitudes, the yearly rainfall is frequently insufficient to support equilibrated vegetative growth and high fruit and oil production. This three-year field study investigated the effect of complementary irrigation on olive tree vegetative growth, fruit and oil yield during a biennial alternate bearing cycle in a traditional grove under semi-arid conditions. Adult olive trees (Olea europaea L. cv. Nabali Baladi were subjected to complementary irrigation in 2011 and 2012 ('on' and 'off' years, respectively with 6, 10, 15 or 20 m3 of water per tree per season, which corresponded to 14.2%, 23.8%, 35.7% and 47.6% of the whole seasonal evapotranspiration (42 m3 of water per year, respectively. Rain-fed trees were used as control. In 2013, no complementary irrigation was supplied, and any residual effects on the yield components were determined. Results showed that none of the irrigation regimes affected vegetative growth, or olive fruit size (mesocarp and endocarp, as fresh and dry weights. The fruit and oil yield per tree increased compared to the rain-fed conditions only when the threshold of 15 m3 was exceeded, thus inducing a higher crop load compared to the rain-fed control during the 'off' and even further during the 'on' year. No residual effects were registered in 2013. The study showed that complementary irrigation of at least 35% of the seasonal water requirement can produce remarkable positive effects on fruit yield especially during 'on' bearing years.

Boundary Condition Effects on Hillslope Form and Soil Development Along a Climatic Gradient From Semiarid to Hyperarid in Northern Chile

Science.gov (United States)

Owen, J. J.; Dietrich, W. E.; Nishiizumi, K.; Bellugi, D.; Amundson, R.

2008-12-01

Modeling the development of hillslopes using mass balance equations has generated many testable hypotheses related to morphology, process rates, and soil properties, however it is only relatively recently that techniques for constraining these models (such as cosmogenic radionuclides) have become commonplace. As such, many hypotheses related to the effects of boundary conditions or climate on process rates and soil properties have been left untested. We selected pairs of hillslopes along a precipitation gradient in northern Chile (24°-30° S) which were either bounded by actively eroding (bedrock-bedded) channels or by stable or aggradational landforms (pediments, colluvial aprons, valley bottoms). For each hillslope we measured soil properties, atmospheric deposition rates, and bedrock denudation rates. We observe significant changes in soil properties with climate: there is a shift from thick, weathered soils in the semiarid south, to the near absence of soil in the arid middle, to salt-rich soils in the hyperarid north. Coincident with these are dramatic changes in the types and rates of processes acting on the soils. We found relatively quick, biotically-driven soil formation and transport in the south, and very slow, salt-driven processes in the north. Additionally, we observe systematic differences between hillslopes of different boundary condition within the same climate zone, such as thicker soils, gentler slopes, and slower erosion rates on hillslopes with a non-eroding boundary versus an eroding boundary. These support general predictions based on hillslope soil mass balance equations and geomorphic transport laws. Using parameters derived from our field data, we attempt to use a mass balance model of hillslope development to explore the effect of changing boundary conditions and/or shifting climate.

Alternate furrow irrigation of four fresh-market tomato cultivars under semi-arid condition of Ethiopia – Part II: Physiological response

Directory of Open Access Journals (Sweden)

Ashinie Bogale

2016-11-01

Full Text Available Understanding the variation in physiological response to deficit irrigation together with better knowledge on physiological characteristics of different genotypes that contribute to drought adaptation mechanisms would be helpful in transferring different irrigation technologies to farmers. A field experiment was carried to investigate the physiological response of four tomato cultivars (Fetan, Chali, Cochoro and ARP Tomato d2 to moderate water deficit induced by alternate furrow irrigation (AFI and deficit irrigation (DI under semi-arid condition of Ethiopia during 2013 and 2014. The study also aimed at identifying physiological attributes to the fruit yield of tomato under different deficit irrigation techniques. A factorial combination of irrigation treatments and cultivar were arranged in a complete randomized design with three replicates. Results showed that stomatal conductance (g_s was significantly reduced while photosynthetic performance measured as chlorophyll fluorescence (Fv’/Fm’, relative water content (RWC and leaf ash content remained unaffected under deficit irrigations. Significant differences among cultivars were found for water use efficiency (WUE, g_s, chlorophyll content (Chl_SPAD, normal difference vegetation index (NDVI, leaf ash content and fruit growth rate. However, cultivar differences in WUE were more accounted for by the regulation of g_s, therefore, g_s could be useful for breeders for screening large numbers of genotypes with higher WUE under deficit irrigation condition. The study result also demonstrated that cultivar with traits that contribute to achieve higher yields under deficit irrigation strategies has the potential to increase WUE.

The challenges of rehabilitating denuded patches of a semi-arid environment in Kenya

NARCIS (Netherlands)

Mganga, K.Z.; Nyangito, M.M.; Musimba, N.K.R.; Nyariki, D.M.; Mwangombe, A.W.; Ekaya, W.N.; Muiri, W.M.; Clavel, D.; Francis, J.; Kaufmann, Von R.; Verhagen, J.

2010-01-01

Land degradation is a major problem in the semi-arid environments of Sub-Saharan Africa. Fighting land degradation is essential to ensure the sustainable and long-term productivity of the habited semiarid lands. In Kenya, grass reseeding technology has been used to combat land degradation. However,

Composition and fate of mine- and smelter-derived particulates in soils from humid subtropical and semiarid areas

Science.gov (United States)

Ettler, Vojtech; Kribek, Bohdan; Mihaljevic, Martin; Vanek, Ales; Penizek, Vit; Sracek, Ondra; Mapani, Ben; Kamona, Fred; Nyambe, Imasiku

2017-04-01

Soils in the vicinity of non-ferrous metal smelters are often highly polluted by inorganic contaminants released from particulate emissions, which undergo weathering processes and release contaminants when deposited in soils. We studied the heavy mineral fraction, separated from mining- and smelter-affected topsoils, from both a humid subtropical area in the Zambian Copperbelt and a hot semi-arid area in the northern Namibia. High concentrations of metal(loid)s were detected in the studied soils: up to 1450 ppm As, 8980 ppm Cu, 4640 ppm Pb, 2620 ppm Zn. A combination of X-ray diffraction analysis (XRD), scanning electron microscopy (SEM/EDS), and electron probe microanalysis (EPMA) helped to identify the phases forming individual metal(loid)-bearing particles. Whereas spherical particles originate from the smelting and flue gas cleaning processes, angular particles either have geogenic origins or they are windblown from the mining operations and mine waste disposal sites. Sulphides from ores and mine tailings often exhibit weathering rims in contrast to smelter-derived high-temperature sulphides (chalcocite [Cu2S], digenite [Cu9S5], covellite [CuS], non-stoichiometric quenched Cu-Fe-S phases). Soils from humid subtropical areas exhibit higher available concentrations of metal(loids), and higher frequencies of weathering features (especially for copper-bearing oxides such as delafossite [CuFeO2]) are observed. In contrast, metal(loid)s are efficiently retained in semi-arid soils, where a high proportion of non-weathered smelter slag particles and low-solubility Ca-Cu-Pb arsenates occur. Our results indicate that compared to semi-arid areas (where inorganic contaminants were rather immobile in soils despite their high concentrations) a higher potential risk exists for agriculture in mine- and smelter-affected humid subtropical areas (where metal(loid) contaminants can be highly available for the uptake by crops). This study was supported by the Czech Science

Enhanced precipitation promotes decomposition and soil C stabilization in semiarid ecosystems, but seasonal timing of wetting matters

Science.gov (United States)

Campos, Xochi; Germino, Matthew; de Graaff, Marie-Anne

2017-01-01

AimsChanging precipitation regimes in semiarid ecosystems will affect the balance of soil carbon (C) input and release, but the net effect on soil C storage is unclear. We asked how changes in the amount and timing of precipitation affect litter decomposition, and soil C stabilization in semiarid ecosystems.MethodsThe study took place at a long-term (18 years) ecohydrology experiment located in Idaho. Precipitation treatments consisted of a doubling of annual precipitation (+200 mm) added either in the cold-dormant season or in the growing season. Experimental plots were planted with big sagebrush (Artemisia tridentata), or with crested wheatgrass (Agropyron cristatum). We quantified decomposition of sagebrush leaf litter, and we assessed organic soil C (SOC) in aggregates, and silt and clay fractions.ResultsWe found that: (1) increased precipitation applied in the growing season consistently enhanced decomposition rates relative to the ambient treatment, and (2) precipitation applied in the dormant season enhanced soil C stabilization.ConclusionsThese data indicate that prolonged increases in precipitation can promote soil C storage in semiarid ecosystems, but only if these increases happen at times of the year when conditions allow for precipitation to promote plant C inputs rates to soil.

Humidity Buildup in Electronic Enclosures Exposed to Constant Conditions

DEFF Research Database (Denmark)

Conseil, Helene; Staliulionis, Zygimantas; Jellesen, Morten Stendahl

2017-01-01

Electronic components and devices are exposed to a wide variety of climatic conditions, therefore the protection of electronic devices from humidity is becoming a critical factor in the system design. The ingress of moisture into typical electronic enclosures has been studied with defined paramet....... The moisture buildup inside the enclosure has been simulated using an equivalent RC circuit consisting of variables like controlled resistors and capacitors to describe the diffusivity, permeability, and storage in polymers....

Soil fertility dynamics in a semiarid basin: impact of scale level in weighing the effect of the landscape variables

International Nuclear Information System (INIS)

Ruiz-Navarro, A.; Barbera, G. G.; Albaladejo, J.

2009-01-01

Arid and semi-arid Mediterranean soils are particularly sensitive to degradation processes, and soil fertility could play important role in restoration/conservation practices. Our objective was to study the relationships between soil and landscape at different scales in order to understand the main drivers of soil fertility on a semiarid catchment. A stratified sampling plan was carried out to take soil and landscape representative variability. Multivariate statistic techniques were used to elucidate the relationship between both. The results showed that soil fertility are positively related with density of vegetation and topographical conditions favourable to soil moisture at small scale, while negatively with topographical factors that contributed erosion dynamic on ero debility lithologies at medium and large scale. (Author) 8 refs.

Insolation driven biomagnetic response to the Holocene Warm Period in semi-arid East Asia

OpenAIRE

Liu, Suzhen; Deng, Chenglong; Xiao, Jule; Li, Jinhua; Paterson, Greig A.; Chang, Liao; Yi, Liang; Qin, Huafeng; Pan, Yongxin; Zhu, Rixiang

2015-01-01

The Holocene Warm Period (HWP) provides valuable insights into the climate system and biotic responses to environmental variability and thus serves as an excellent analogue for future global climate changes. Here we document, for the first time, that warm and wet HWP conditions were highly favourable for magnetofossil proliferation in the semi-arid Asian interior. The pronounced increase of magnetofossil concentrations at ~9.8?ka and decrease at ~5.9?ka in Dali Lake coincided respectively wit...

Simulations for Making On-farm Decisions in Relation to ENSO in Semi-arid Areas, South Africa

Science.gov (United States)

Tesfuhuney, W. A.; Crespo, O. O.; Walker, S. S.; Steyn, S. A.

2017-12-01

The study was employed to investigate and improve on-farm decision making on planting dates and fertilization by relating simulated yield and seasonal outlook information. The Agricultural Production Systems SIMulator model (APSIM) was used to explore ENSO/SOI effects for small-scale farmers to represent weather conditions and soil forms of semi-arid areas of Bothaville, Bethlehem and Bloemfontein regions in South Africa. The relationships of rainfall and SOI anomalies indicate a positive correlation, signifies ENSO/SOI as seasonal outlooks for study areas. Model evaluation results showed higher degree of bias (RMSEs/RMSE value of 0.88-0.98). The D-index of agreement in the range 0.61-0.71 indicate the ability of the APSIM-Maize model is an adequate tool in evaluating relative changes in maize yield in relation to various management practices and seasonal variations. During rainy, La Niño years (SOI > +5), highest simulated yields were found for Bethlehem in November with addition of 100 - 150 kg ha-1 N fertilization and up to 50 kg ha-1 for both Bothaville and Bloemfontein. With respect to various levels of fertilization, the dry El Niño years (SOI risk for dryland farming in semi-arid regions. Key word: Semi-arid; APSIM; SOI; El Niño / La Niña; On-farm Decisions

Moisture ingress into electronics enclosures under isothermal conditions

International Nuclear Information System (INIS)

Staliulionis, Ž.; Jabbari, M.; Hattel, J. H.

2016-01-01

The number of electronics used in outdoor environment is constantly growing. The humidity causes about 19 % of all electronics failures and, especially, moisture increases these problems due to the ongoing process of miniaturization and lower power consumption of electronic components. Moisture loads are still not understood well by design engineers, therefore this field has become one of the bottlenecks in the electronics system design. The objective of this paper is to model moisture ingress into an electronics enclosure under isothermal conditions. The moisture diffusion model is based on a 1D quasi-steady state (QSS) approximation for Fick’s second law. This QSS approach is also described with an electrical analogy which gives a fast tool in modelling of the moisture response. The same QSS method is applied to ambient water vapour variations. The obtained results are compared to an analytical solution and very good agreement is found.

Soil carbon and nitrogen stocks in traditional agricultural and agroforestry systems in the semiarid region of Brazil

Directory of Open Access Journals (Sweden)

José Augusto Amorim Silva do Sacramento

2013-06-01

Full Text Available In the semiarid region of Brazil, inadequate management of cropping systems and low plant biomass production can contribute to reduce soil carbon (C and nitrogen (N stocks; therefore, management systems that preserve C and N must be adopted. This study aimed to evaluate the changes in soil C and N stocks that were promoted by agroforestry (agrosilvopastoral and silvopastoral and traditional agricultural systems (slash-and-burn clearing and cultivation for two and three years and to compare these systems with the natural Caatinga vegetation after 13 years of cultivation. The experiment was carried out on a typical Ortic Chromic Luvisol in the municipality of Sobral, Ceará, Brazil. Soil samples were collected (layers 0-6, 6-12, 12-20, 20-40 and 40-60 cm with four replications. The plain, convex and concave landforms in each study situation were analyzed, and the total organic C, total N and densities of the soil samples were assessed. The silvopastoral system promoted the greatest long-term reductions in C and N stocks, while the agrosilvopastoral system promoted the smallest losses and therefore represents a sustainable alternative for soil C and N sequestration in these semiarid conditions. The traditional agricultural system produced reductions of 58.87 and 9.57 Mg ha-1 in the organic C and total N stocks, respectively, which suggests that this system is inadequate for these semiarid conditions. The organic C stocks were largest in the concave landform in the agrosilvopastoral system and in the plain landform in the silvopastoral system, while the total N values were highest in the concave landform in the native, agrosilvopastoral and silvopastoral systems.

Differential nitrogen cycling in semiarid sub-shrubs with contrasting leaf habit.

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Sara Palacio

Full Text Available Nitrogen (N is, after water, the most limiting resource in semiarid ecosystems. However, knowledge on the N cycling ability of semiarid woody plants is still very rudimentary. This study analyzed the seasonal change in the N concentrations and pools of the leaves and woody organs of two species of semiarid sub-shrubs with contrasting leaf habit. The ability of both species to uptake, remobilize and recycle N, plus the main storage organ for N during summer drought were evaluated. We combined an observational approach in the field with experimental (15N labelling of adult individuals grown in sand culture. Seasonal patterns of N concentrations were different between species and organs and foliar N concentrations of the summer deciduous Lepidium subulatum were almost double those of the evergreen Linum suffruticosum. L. subulatum up took ca. 60% more external N than the evergreen and it also had a higher N resorption efficiency and proficiency. Contrastingly, L. suffruticosum relied more on internal N remobilization for shoot growth. Differently to temperate species, the evergreen stored N preferentially in the main stem and old trunks, while the summer deciduous stored it in the foliage and young stems. The higher ability of L. subulatum to uptake external N can be related to its ability to perform opportunistic growth and exploit the sporadic pulses of N typical of semiarid ecosystems. Such ability may also explain its high foliar N concentrations and its preferential storage of N in leaves and young stems. Finally, L. suffruticosum had a lower ability to recycle N during leaf senescence. These strategies contrast with those of evergreen and deciduous species from temperate and boreal areas, highlighting the need of further studies on semiarid and arid plants.

Organic amendments as restoration techniques in degraded arid and semiarid systems: A review

Science.gov (United States)

Hueso-González, Paloma; Muñoz-Rojas, Miriam

2017-04-01

There is an increasing concern at the global scale about interrelated environmental problems such as soil degradation, desertification, erosion, and climate change impacts (Hueso-Gonzalez et al., 2014). Indiscriminate use of agro-chemicals, excessive and deep tillage, excessive irrigation, among many others factors, have largely contributed to soil degradation, particularly in arid and semi-arid areas (Lal, 2008). Soil is an essential non-renewable resource with extremely slow formation and regeneration potential (Muñoz-Rojas et al., 2016a and c, Martínez-Murillo et al., 2016). The decline in organic matter content of many soils is becoming a major cause of soil degradation, particularly in dryland regions (Muñoz-Rojas et al., 2016b) where low soil fertility cannot maintain sustainable production in many cases (Hueso-González et al., 2015). The use of soil organic amendments is a common practice in agricultural management and land restoration that can help to improve physical and chemical soil properties, soil structure, temperature and humidity conditions, as well as nutrient contents which are essential for plant growth (Guerrero et al., 2001). Under degraded conditions, several studies have shown their benefits for improving soil physical, chemical and biological properties (Jordan et al., 2010 and 2011). However, there are many research gaps in the knowledge of the effects of climatic conditions on their application, as well as the adequate types of amendment and doses and decomposition rates, (Hueso-Gonzalez,2016). All these factors are crucial for the success in their application. Here, we review long-term experiments worldwide studying the benefits associated with the application of organic materials, particularly, in restoration of arid and semiarid ecosystems together with the possible threats and risks that can result from their use. We will specifically adress: (1) type of amended and benefits arising from their use, (2) application methods and more

Effect of complementary irrigation on yield components and alternate bearing of a traditional olive orchard in semi-arid conditions

Energy Technology Data Exchange (ETDEWEB)

Lodolini, E.M.; Polverigiani, S.; Ali, S.; Mutawea, M.; Qutub, M.; Pierini, F.; Neri, D.

2016-11-01

Traditional olive orchards are usually not irrigated in the Mediterranean basin, but at those latitudes, the yearly rainfall is frequently insufficient to support equilibrated vegetative growth and high fruit and oil production. This three-year field study investigated the effect of complementary irrigation on olive tree vegetative growth, fruit and oil yield during a biennial alternate bearing cycle in a traditional grove under semi-arid conditions. Adult olive trees (Olea europaea L. cv. Nabali Baladi) were subjected to complementary irrigation in 2011 and 2012 ('on' and 'off' years, respectively) with 6, 10, 15 or 20 m3 of water per tree per season, which corresponded to 14.2%, 23.8%, 35.7% and 47.6% of the whole seasonal evapotranspiration (42 m3 of water per year), respectively. Rain-fed trees were used as control. In 2013, no complementary irrigation was supplied, and any residual effects on the yield components were determined. Results showed that none of the irrigation regimes affected vegetative growth, or olive fruit size (mesocarp and endocarp), as fresh and dry weights. The fruit and oil yield per tree increased compared to the rain-fed conditions only when the threshold of 15 m3 was exceeded, thus inducing a higher crop load compared to the rain-fed control during the 'off' and even further during the 'on' year. No residual effects were registered in 2013. The study showed that complementary irrigation of at least 35% of the seasonal water requirement can produce remarkable positive effects on fruit yield especially during 'on' bearing years. (Author)

Insert Maranhao in O cial Semi-Arid Geography: A Requirement of Social Justice in the Brazilian Northeast

Directory of Open Access Journals (Sweden)

José de Jesus Sousa Lemos

2016-07-01

Full Text Available The study attempts to show that the Brazilian semi-arid region is a region too needy. Even the Interior Ministry considering that there are municipalities only in the semiarid in eight of the Northeastern States excluding Maranhão, but incorporating municipalities in the state of Minas Gerais, the study also seeks to show that at least fteen municipalities of Maranhão has semiarid features and these municipalities have some of the largest pockets of poverty in this Brazilian ecosystem. In order to achieve its objectives the study uses data collected by the State University of Maranhão, the Demographic Census of IBGE 2010 and the GDP of the municipalities published by the IBGE in 2012. They use the estimated drought indices in a previous study of the State University of Maranhão to the Maranhão municipalities supposed to possess technical characteristics of semiarid region. Social indicators are estimated suchas education exclusion, income, running water, sanitation and garbage collection to all municipalities. The results showed that the average GDP of the semi-arid districts are much smaller than that of other municipalities in the Northeast. The ratio between the highest and the lowest GDP per capita in the semiarid region is 38.4. The iliteracy rates are high in all of them. Very high is also deprivation of access to piped water, sanitation and garbage collection also. e evidence of this study allow us to conclude that, in general, municipalities with technical characteristics of semi-arid in Maranhao State has economic, social and environmental indicators worse than the average of other municipalities already recognized in the Brazilian semiarid region.

The simulation of naturally ventilated residential buildings in semi-arid regions

Energy Technology Data Exchange (ETDEWEB)

Ghiabaklou, Z.; Ballinger, J.A.; Prasad, D.K. [New South Wales Univ., Kensington, NSW (Australia). Solar Architecture Research Unit

1995-12-31

The most important consideration in hot arid and semi-arid zones is to reduce the internal day temperature and to maintain the interior spaces of buildings in a comfortable condition. An important contributor to errors in the thermal analysis of naturally ventilated buildings is inaccurate airflow predictions. These predictions are important for designers in regions where most buildings are naturally ventilated. Passive cooling by day and night natural ventilation in a single story residential building in Wagga Wagga, a semi-arid location in New South Wales has been compared and analyzed theoretically. A modified version of the computer simulation program CHEETAH, has been used to consider a building with continuous natural ventilation to simulate indoor air temperature. The aim of the study was to investigate the thermal behaviour of the building with continuous ventilation (24 hour/day) and the same building with only night time ventilation. Using night time ventilation in high mass buildings in such a climate, leads to a considerable decrease in room air temperature. Simulation results showed that increasing the effective area of windows is effective only when the wind blows. Using a steady averaged air change per hour can also cause a reduction in room air temperatures which results in different temperatures than the actual air changes per hour. (author). 3 figs., 4 refs.

Effects of Seasonal Land Surface Conditions on Hydrometeorological Dynamics in South-western North America

Science.gov (United States)

2015-09-21

rain gauges to measure precipitation , and 1 internal mini-flume to measure runoff . 9 Fig. 8. Processed fluxes measured at the two eddy...SECURITY CLASSIFICATION OF: Arid and semiarid landscapes in regions with seasonal precipitation experience dramatic changes that alter land surface...semiarid landscapes in regions with seasonal precipitation experience dramatic changes that alter land surface conditions, including soil moisture

Introducing Pathways to Resilience in Semi-Arid Economies (PRISE ...

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

rlarbey

Equitable, climate resilient economic development in semi-arid .... manufacturing or services (apart from health, insurance and tourism). Further research ... evaluated, particularly economic impact assessments of adaptation both on existing.

Cereals for the semi-arid tropics

International Nuclear Information System (INIS)

De Wet, J.M.J.

1989-01-01

The region of semi-arid tropics is the most famine prone area of the world. This region with nearly one billion people extends across some 20 million square kilometres. Major domesticated cereals adapted to semi-arid regions are sorghum (Sorghum bicolor (L.) Moench), foxtail millet (Setaria italica (L.) P. Beauv.) and pearl millet (Pennisetum glaucum (L.) R. Br.). Several minor cereals are grown as speciality crops, or harvested in the wild in times of severe drought and scarcity. Important in the African Sahel are the fonios Digitaria iburua Stapf, D. exilis (Kapist) Stapf and Brachiaria deflexa (Schumach). C.E. Hubbard. These species are aggressive colonizers and are commonly encouraged as weeds in cultivated fields. Sown genotypes differ from their close wild relatives primarily in the lack of efficient natural seed dispersal. The fonios lend themselves to rapid domestication. Several wild cereals extend well beyond the limits of agriculture into the Sahara. Commonly harvested are the perennial Stipagrostis pungens and Panicum turgidum, and the annual Cenchrus biflorus (kram-kram). Kram-kram yields well under extreme heat and drought stress, and holds promise as a domesticated cereal. Sauwi millet (Panicum sonorum) is promising cereal in arid northwestern Mexico. (author). 31 refs

Soil-atmosphere trace gas exchange in semiarid and arid zones.

Science.gov (United States)

Galbally, Ian E; Kirstine, Wayne V; Meyer, C P Mick; Wang, Ying Ping

2008-01-01

A review is presented on trace gas exchange of CH4, CO, N2O, and NOx arising from agriculture and natural sources in the world's semiarid and arid zones due to soil processes. These gases are important contributors to the radiative forcing and the chemistry of the atmosphere. Quantitative information is summarized from the available studies. Between 5 and 40% of the global soil-atmosphere exchange for these gases (CH4, CO, N2O, and NOx) may occur in semiarid and arid zones, but for each of these gases there are fewer than a dozen studies to support the individual estimates, and these are from a limited number of locations. Significant differences in the biophysical and chemical processes controlling these trace gas exchanges are identified through the comparison of semiarid and arid zones with the moist temperate or wet/dry savanna land regions. Therefore, there is a poorly quantified understanding of the contribution of these regions to the global trace gas cycles and atmospheric chemistry. More importantly, there is a poor understanding of the feedback between these exchanges, global change, and regional land use and air pollution issues. A set of research issues is presented.

Utility of the end-of-season nitrate test for nitrogen sufficiency of irrigated maize under Mediterranean semi-arid conditions

Energy Technology Data Exchange (ETDEWEB)

Isla, R.; Salmeron, M.; Cavero, J.; Yagüe, M.R.; Quilez, D.

2015-07-01

Calibration of decision tools to improve N fertilizer management is critical to increase its adoption by maize (Zea mays L.) growers. The objective of this study was to establish nitrate and total nitrogen concentrations in the basal maize stalks (BMS) at harvest to separate maize fields among three N availability categories (N-deficient, N-optimum, and N-excess) under Mediterranean irrigated semiarid conditions. We analysed data from 26 irrigated maize trials conducted between 2001 and 2012. Trials included treatments receiving different N fertilizer rates and sources (mineral and organic), irrigation systems (flood, sprinkler) and soil types. The critical nitrate concentration in BMS to identify N-deficient plots (CNCL) is affected by the irrigation system. The CNCL was lower under sprinkler irrigation (708 mg NO{sub 3}{sup -}–N/kg) than under flood irrigation (2205 mg NO{sub 3}{sup -}–N/kg), and the later presented a higher degree of uncertainty compared to sprinkler irrigated systems. The results showed the difficulty to identify the N-deficient plots with the BMS test and the higher sensibility of nitrate-N than total-N concentration in BMS to separate N-deficient from N-optimal plots. Under sprinkler irrigation, nitrate in BMS>1500 mg NO{sub 3}{sup -}–N/kg had a 85% probability of having received an excess of N. Considering economic net returns to N fertilization, the range of nitrate concentration in BMS that maximized profit under sprinkler-irrigated conditions was established between 1100 and 1700 mg NO3-–N/kg. Results suggest that BMS test can be useful in detecting plots with an excess of N but considering irrigation efficiency is crucial for stablishing successful CNC thresholds. (Author)

Rainwater harvesting in arid and semi-arid zones

NARCIS (Netherlands)

Boers, T.M.

1994-01-01

In arid and semi-arid regions, the scarcity of water can be alleviated by rainwater harvesting, which is defined as a method of inducing, collecting, storing, and conserving local surface runoff for agriculture. Rainwater harvesting can be applied with different

Soil moisture and its role in growth-climate relationships across an aridity gradient in semiarid Pinus halepensis forests.

Science.gov (United States)

Manrique-Alba, Àngela; Ruiz-Yanetti, Samantha; Moutahir, Hassane; Novak, Klemen; De Luis, Martin; Bellot, Juan

2017-01-01

In Mediterranean areas with limited availability of water, an accurate knowledge of growth response to hydrological variables could contribute to improving management and stability of forest resources. The main goal of this study is to assess the temporal dynamic of soil moisture to better understand the water-growth relationship of Pinus halepensis forests in semiarid areas. The estimates of modelled soil moisture and measured tree growth were used at four sites dominated by afforested Pinus halepensis Mill. in south-eastern Spain with 300 to 609mm mean annual precipitation. Firstly, dendrochronological samples were extracted and the widths of annual tree rings were measured to compute basal area increments (BAI). Secondly, soil moisture was estimated over 20 hydrological years (1992-2012) by means of the HYDROBAL ecohydrological model. Finally, the tree growth was linked, to mean monthly and seasonal temperature, precipitation and soil moisture. Results depict the effect of soil moisture on growth (BAI) and explain 69-73% of the variance in semiarid forests, but only 51% in the subhumid forests. This highlights the fact that that soil moisture is a suitable and promising variable to explain growth variations of afforested Pinus halepensis in semiarid conditions and useful for guiding adaptation plans to respond pro-actively to water-related global challenges. Copyright © 2016 Elsevier B.V. All rights reserved.

Spatial variation in the structure and composition of the herbaceous community in a semiarid region of northeastern Brazil

Directory of Open Access Journals (Sweden)

KA. Silva

Full Text Available In the arid and semiarid environments of the world, microhabitats serve as models for the structure of vegetation communities. The goal of this study was to identify differences in the structures of the herbaceous communities growing on a crystalline substrate and those growing on a sedimentary substrate in a semiarid region of northeastern Brazil. One hundred 1 × 1 m plots were established in each area for quantitative sampling, with 69 species recorded in the crystalline area and 76 in the sedimentary area. The average plant density was higher in the sedimentary area, and average diameters and heights were greater in the crystalline area. The families and species with a high Importance Value Index (IVI and a high Mixed Ecological Value Index (MEVI differed between the areas. Of the species with high densities, only four were found in both areas. Shannon-Weiner diversity index values in the crystalline (2.96 nats/ind.-1 and sedimentary (2.89 nats/ind.-1 areas were similar. Evenness values on both substrates were also similar (0.72 and 0.71 in the crystalline and sedimentary areas, respectively. This study shows that variations in plant establishment conditions between crystalline and sedimentary areas in a semiarid region of northeastern Brazil should be considered as structure-modeling factors for the herbaceous community.

A generalized electron energy probability function for inductively coupled plasmas under conditions of nonlocal electron kinetics

Science.gov (United States)

Mouchtouris, S.; Kokkoris, G.

2018-01-01

A generalized equation for the electron energy probability function (EEPF) of inductively coupled Ar plasmas is proposed under conditions of nonlocal electron kinetics and diffusive cooling. The proposed equation describes the local EEPF in a discharge and the independent variable is the kinetic energy of electrons. The EEPF consists of a bulk and a depleted tail part and incorporates the effect of the plasma potential, Vp, and pressure. Due to diffusive cooling, the break point of the EEPF is eVp. The pressure alters the shape of the bulk and the slope of the tail part. The parameters of the proposed EEPF are extracted by fitting to measure EEPFs (at one point in the reactor) at different pressures. By coupling the proposed EEPF with a hybrid plasma model, measurements in the gaseous electronics conference reference reactor concerning (a) the electron density and temperature and the plasma potential, either spatially resolved or at different pressure (10-50 mTorr) and power, and (b) the ion current density of the electrode, are well reproduced. The effect of the choice of the EEPF on the results is investigated by a comparison to an EEPF coming from the Boltzmann equation (local electron kinetics approach) and to a Maxwellian EEPF. The accuracy of the results and the fact that the proposed EEPF is predefined renders its use a reliable alternative with a low computational cost compared to stochastic electron kinetic models at low pressure conditions, which can be extended to other gases and/or different electron heating mechanisms.

Body condition scores at calving and their association with dairy cow performance and health in semiarid environment under two cooling systems

Directory of Open Access Journals (Sweden)

Mohamed A.B. Mandour

2015-02-01

Full Text Available Under tropical environments cow’s body condition at calving may influence productivity and health performance. Therefore, the current research evaluated the impact of body condition score (BCS at calving on milk production traits and health problems of primiparous and multiparous cows raised under two cooling systems in semi-arid environment. Milk yield parameters and health disorders data at different parities were obtained from 1700 Holstein cows, which were managed under Korral Kool (KKC and fan (FC cooling systems in Saudi Arabia. The results revealed that KKC system induced high level of milk production improvement (305TM, days in milk, daily milk yield (P<0.05 compared to FC, especially in multiparous cows. There was an advantage of the high BCS group under KKC system over the FC system for peak yield and period. Cows from both cooling systems having moderate BCS outdid the other groups for total milk yield. Low BCS primiparous cows reared under KKC system were the most to suffer from stillbirth (18%, and calving ease (26.1% in winter, while high BCS were the most to be treated for mastitis (8.5% in summer. On the other hand, spring calved multiparous cows raised under FC system suffered more from lameness (21.57% - high BCS and milk fever (4.4% - moderate BCS. Further, cows having moderate BCS kept under KKC system had the highest incidence of lameness (62.2%, and abomasum displacement (4.4%. In conclusion, achieving correct BCS at calving and cooling system is important to avoid calving subsequent lactation performance and metabolic disease losses.

Elevation Control on Vegetation Organization in a Semiarid Ecosystem in Central New Mexico

Science.gov (United States)

Nudurupati, S. S.; Istanbulluoglu, E.; Adams, J. M.; Hobley, D. E. J.; Gasparini, N. M.; Tucker, G. E.; Hutton, E. W. H.

2015-12-01

Many semiarid and desert ecosystems are characterized by patchy and dynamic vegetation. Topography plays a commanding role on vegetation patterns. It is observed that plant biomes and biodiversity vary systematically with slope and aspect, from shrublands in low desert elevations, to mixed grass/shrublands in mid elevations, and forests at high elevations. In this study, we investigate the role of elevation dependent climatology on vegetation organization in a semiarid New Mexico catchment where elevation and hillslope aspect play a defining role on plant types. An ecohydrologic cellular automaton model developed within Landlab (component based modeling framework) is used. The model couples local vegetation dynamics (that simulate biomass production based on local soil moisture and potential evapotranspiration) and plant establishment and mortality based on competition for resources and space. This model is driven by elevation dependent rainfall pulses and solar radiation. The domain is initialized with randomly assigned plant types and the model parameters that couple plant response with soil moisture are systematically changed. Climate perturbation experiments are conducted to examine spatial vegetation organization and associated timescales. Model results reproduce elevation and aspect controls on observed vegetation patterns indicating that this model captures necessary and sufficient conditions that explain these observed ecohydrological patterns.

Large-scale hydrological modelling in the semi-arid north-east of Brazil

Energy Technology Data Exchange (ETDEWEB)

Guentner, A

2002-09-01

Semi-arid areas are characterized by small water resources. An increasing water demand due to population growth and economic development as well as a possible decreasing water availability in the course of climate change may aggravate water scarcity in future in these areas. The quantitative assessment of the water resources is a prerequisite for the development of sustainable measures of water management. For this task, hydrological models within a dynamic integrated framework are indispensable tools. The main objective of this study is to develop a hydrological model for the quantification of water availability over a large geographic domain of semi-arid environments. The study area is the Federal State of Ceara in the semi-arid north-east of Brazil. Surface water from reservoirs provides the largest part of water supply. The area has recurrently been affected by droughts which caused serious economic losses and social impacts like migration from the rural regions. (orig.)

Uses of tree legumes in semi-arid regions

Energy Technology Data Exchange (ETDEWEB)

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)

Semiarid ethnoagroforestry management: Tajos in the Sierra Gorda, Guanajuato, Mexico.

Science.gov (United States)

Hoogesteger van Dijk, Vincent M; Casas, Alejandro; Moreno-Calles, Ana Isabel

2017-06-12

The semi-arid environments harbor nearly 40% of biodiversity, and half of indigenous cultures of Mexico. Thousands of communities settled in these areas depend on agriculture and using wild biodiversity for their subsistence. Water, soil, and biodiversity management strategies are therefore crucial for people's life. The tajos, from Sierra Gorda, are important, poorly studied, biocultural systems established in narrow, arid alluvial valleys. The systems are constructed with stone-walls for capturing sediments, gradually creating fertile soils in terraces suitable for agriculture in places where it would not be possible. We analyzed biocultural, ecological, economic and technological relevance of the artificial oasis-like tajos, hypothesizing their high capacity for maintaining agricultural and wild biodiversity while providing resources to people. We conducted our research in three sections of the Mezquital-Xichú River, in three communities of Guanajuato, Mexico. Agroforestry management practices were documented through semi-structured and in-depth qualitative interviews. Vegetation composition of local forests and that maintained in tajos was sampled and compared. Tajos harbor high agrobiodiversity, including native varieties of maize and beans, seven secondary crops, 47 native and 25 introduced perennial plant species. Perennial plants cover on average 26.8% of the total surface of plots. Tajos provide nearly 70% of the products required by households' subsistence and are part of their cultural identity. Tajos are heritage of TEK and land management forms of pre-Columbian Mexican and Mediterranean agricultural techniques, adapting and integrating modern agricultural practices. Tajos are valuable biocultural systems adapted to local semiarid conditions and sources of technology for similar areas of the World.

Antecedent Moisture and Biological Inertia as Predictors of Plant and Ecosystem Productivity in Arid and Semiarid Systems

Science.gov (United States)

Ogle, K.

2011-12-01

Many plant and ecosystem processes in arid and semiarid systems may be affected by antecedent environmental conditions (e.g., precipitation patterns, soil water availability, temperature) that integrate over past days, weeks, months, seasons, or years. However, the importance of such antecedent exogenous effects relative to conditions occurring at the time of the observed process is relatively unexplored. Even less is known about the potential importance of antecedent endogenous effects that describe the influence of past ecosystem states on the current ecosystem state; e.g., how is current ecosystem productivity related to past productivity patterns? We hypothesize that incorporation of antecedent exogenous and endogenous factors can improve our predictive understanding of many plant and ecosystem processes, especially in arid and semiarid ecosystems. Furthermore, the common approach to quantifying the effects of antecedent (exogenous) variables relies on arbitrary, deterministic definitions of antecedent variables that (1) may not accurately describe the role of antecedent conditions and (2) ignore uncertainty associated with applying deterministic definitions. In this study, we employ a stochastic framework for (1) computing the antecedent variables that estimates the relative importance of conditions experienced each time unit into the past, also providing insight into potential lag responses, and (2) estimating the effect of antecedent factors on the response variable of interest. We employ this approach to explore the potential roles of antecedent exogenous and endogenous influences in three settings that illustrate the: (1) importance of antecedent precipitation for net primary productivity in the shortgrass steppe in northern Colorado, (2) dependency of tree growth on antecedent precipitation and past growth states for pinyon growing in western Colorado, and (3) influence of antecedent soil water and prior root status on observed root growth in the Mojave

Patchiness in semi-arid dwarf shrublands: evidence from satellite ...

African Journals Online (AJOL)

... Plants; Remote sensing; Rhigozum obovatum Burch; Satellite-derived vegetation indices; Woody species; patchiness; semi-arid; dwarf shrubland; shrublands; co2; assimilation; karoo; south africa; ndvi; satellite imagery; geochemical mound; rhigozum obovatum; eriocephalus ericoides; pentzia incana; vegetation; botany

Analysis and evaluation of tillage on an alfisol in a semi-arid tropical region of India

NARCIS (Netherlands)

Klaij, M.C.

1983-01-01

Tillage field experiments were conducted on Alfisols in a semi-arid tropical environment in India. The research was conducted within the framework of the Farming Systems Research Program of the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT).

To put the

MONITORING CANOPY AND AIR TEMPERATURE OF DOMINANT VEGETATION IN TROPICAL SEMI-ARID USING BIOCLIMATIC MODEL

Directory of Open Access Journals (Sweden)

Josiclêda Domiciano Galvíncio

2016-10-01

Full Text Available Typical vegetation of arid environments consist of few dominant species highly threatened by climate change. Jurema preta (Mimosa tenuiflora (Willd. Poiret is one of these successful species that now is dominant in extensive semiarid areas in the world. The development of a simple bioclimatic model using climate change scenarios based on optimistic and pessimistic predictions of the Intergovernmental Panel on Climate Change (IPCC shown as a simple tool to predict possible responses of dominant species under dry land conditions and low functional biodiversity. The simple bioclimatic model proved satisfactory in creating climate change scenarios and impacts on the canopy temperature of Jurema preta in semiarid Brazil. The bioclimatic model was efficient to obtain spatially relevant estimations of air temperature from determinations of the surface temperature using satellite images. The model determined that the average difference of 5oC between the air temperature and the leaf temperature for Jurema preta, and an increase of 3oC in air temperature, promote an increase of 2oC in leaf temperature. It lead to disturbances in vital physiological mechanisms in the leaf, mainly the photosynthesis and efficient use of water.

Hydrologic feasibility of artificial forestation in the semi-arid Loess Plateau of China

Science.gov (United States)

Jin, T. T.; Fu, B. J.; Liu, G. H.; Wang, Z.

2011-08-01

Hydrologic viability, in terms of moisture availability, is fundamental to ecosystem sustainability in arid and semi-arid regions. In this study, we examine the spatial distribution and after-planting variations of soil moisture content (SMC) in black locust tree (Robinia pseudoacacia L.) plantings in the Loess Plateau of China at a regional scale. Thirty sites (5 to 45 yr old) were selected, spanning an area of 300 km by 190 km in the northern region of the Shaanxi Province. The SMC was measured to a depth of 100 cm at intervals of 10 cm. Geographical, topographic and vegetation information was recorded, and soil organic matter was evaluated. The results show that, at the regional scale, SMC spatial variability was most highly correlated with rainfall. The negative relationship between the SMC at a depth of 20-50 cm and the stand age was stronger than at other depths, although this relationship was not significant at a 5 % level. Watershed analysis shows that the after-planting SMC variation differed depending upon precipitation. The SMC of plantings in areas receiving sufficient precipitation (e.g., mean annual precipitation (MAP) of 617 mm) may increase with stand age due to improvements in soil water-holding capacity and water-retention abilities after planting. For areas experiencing water shortages (e.g., MAP = 509 mm), evapotranspiration may cause planting soils to dry within the first 20 yr of growth. It is expected that, as arid and semi-arid plantings age, evapotranspiration will decrease, and the soil profile may gradually recover. In extremely dry areas (e.g., MAP = 352 mm), the variation in after-planting SMC with stand age was found to be negligible. The MAP can be used as an index to divide the study area into different ecological regions. Afforestation may sequentially exert positive, negative and negligible effects on SMCs with a decrease in the MAP. Therefore, future restoration measures should correspond to the local climate conditions, and the

Electrochemical migration in electronics: effect of contamination and bias conditions

DEFF Research Database (Denmark)

Verdingovas, Vadimas; Jellesen, Morten Stendahl; Ambat, Rajan

A number of reliability issues are caused by mechanisms different from the conventional corrosion due to specific aspects of the printed circuit board assembly (PCBA). The size of the components and the distance between them, combinations of dissimilar metals, voltage and temperature gradients...... – all together influence susceptibility of electronic PCBA to corrosion. When electronics is operating under humid conditions, the cleanliness of the PCBA becomes essential, since corrosion related failures in electronics can occur at extremely low levels of moisture and contamination. A synergetic...... effect of the aspects mentioned above makes it challenging to predict the lifetime of electronic device. The aim of this work is to investigate corrosion influencing factors, which at a later stage improve capabilities of predicting the functioning and herewith reliability of electronics under certain...

Preface paper to the Semi-Arid Land-Surface-Atmosphere (SALSA) Program special issue

Science.gov (United States)

Goodrich, D.C.; Chehbouni, A.; Goff, B.; MacNish, B.; Maddock, T.; Moran, S.; Shuttleworth, W.J.; Williams, D.G.; Watts, C.; Hipps, L.H.; Cooper, D.I.; Schieldge, J.; Kerr, Y.H.; Arias, H.; Kirkland, M.; Carlos, R.; Cayrol, P.; Kepner, W.; Jones, B.; Avissar, R.; Begue, A.; Bonnefond, J.-M.; Boulet, G.; Branan, B.; Brunel, J.P.; Chen, L.C.; Clarke, T.; Davis, M.R.; DeBruin, H.; Dedieu, G.; Elguero, E.; Eichinger, W.E.; Everitt, J.; Garatuza-Payan, J.; Gempko, V.L.; Gupta, H.; Harlow, C.; Hartogensis, O.; Helfert, M.; Holifield, C.; Hymer, D.; Kahle, A.; Keefer, T.; Krishnamoorthy, S.; Lhomme, J.-P.; Lagouarde, J.-P.; Lo, Seen D.; Luquet, D.; Marsett, R.; Monteny, B.; Ni, W.; Nouvellon, Y.; Pinker, R.; Peters, C.; Pool, D.; Qi, J.; Rambal, S.; Rodriguez, J.; Santiago, F.; Sano, E.; Schaeffer, S.M.; Schulte, M.; Scott, R.; Shao, X.; Snyder, K.A.; Sorooshian, S.; Unkrich, C.L.; Whitaker, M.; Yucel, I.

2000-01-01

The Semi-Arid Land-Surface-Atmosphere Program (SALSA) is a multi-agency, multi-national research effort that seeks to evaluate the consequences of natural and human-induced environmental change in semi-arid regions. The ultimate goal of SALSA is to advance scientific understanding of the semi-arid portion of the hydrosphere-biosphere interface in order to provide reliable information for environmental decision making. SALSA approaches this goal through a program of long-term, integrated observations, process research, modeling, assessment, and information management that is sustained by cooperation among scientists and information users. In this preface to the SALSA special issue, general program background information and the critical nature of semi-arid regions is presented. A brief description of the Upper San Pedro River Basin, the initial location for focused SALSA research follows. Several overarching research objectives under which much of the interdisciplinary research contained in the special issue was undertaken are discussed. Principal methods, primary research sites and data collection used by numerous investigators during 1997-1999 are then presented. Scientists from about 20 US, five European (four French and one Dutch), and three Mexican agencies and institutions have collaborated closely to make the research leading to this special issue a reality. The SALSA Program has served as a model of interagency cooperation by breaking new ground in the approach to large scale interdisciplinary science with relatively limited resources.

Mechanisms, timing and quantities of recharge to groundwater in semi-arid and tropical regions

International Nuclear Information System (INIS)

Edmunds, W.M.

2001-01-01

Groundwater being exploited in many and and semi-arid regions at the present day was recharged during former humid episodes of the Pleistocene or Holocene and, in contrast, the amounts derived from modem recharge are small generally small and variable. Geochemical and isotopic techniques provide the most effective way to calculate modem recharge and to investigate recharge history, since physically- based water-balance methods are generally inapplicable in semiarid regions. Examples from Africa (Senegal, Niger, Nigeria, Sudan as well as Cyprus) show that direct recharge rates may vary from zero to around 40% of mean rainfall, dependent primarily on the soil depth and the lithology. Spatial variability presents a real problem in any recharge investigation but results from Senegal show that unsaturated zone profiles may be extrapolated using the chemistry of shallow groundwater. Unsaturated-zone studies show that there are limiting conditions to direct recharge through soil, but that present day replenishment of aquifers takes place via wadis and channels. In the Butana area of central Sudan the regional groundwater was also recharged during a mid-Holocene wet phase and is now in decline. The only current recharge sources, which can be recognised distinctly using stable isotopes, are Nile baseflow and ephemeral wadi floods. (author)

YIELD OF COMMON FIG FERTIGATED WITH BOVINE BIOFERTILIZER IN THE SEMIARID REGION OF CEARÁ

Directory of Open Access Journals (Sweden)

FRANCISCO LIMEIRA DA SILVA

2016-01-01

Full Text Available The objective was to evaluate the productivity of the fig tree the organic fertirrigation cattle under different environmental conditions in Ceará semiarid region. The experiment was conducted in the experimental area of the Teaching Unit, Research and Extension, the IFCE, North Lemon Tree, EC. The experimental design was a randomized complete block design with split plots, with four replications and three plants per plot. The plots consisted of three rooms (full sun - PS; trellis - LT and greenhouse - EST, the subplots, the concentrations of bovine biofertilizer diluted in water in the following concentrations: T0 (0% of biofertilizer + 100% water; T1 (20% biofertilizer 80 +% water; T2 (40% biofertilizer + 60% water, T3 (60% biofertiliante + 40% water and subsubplot, the production cycles. The variables were evaluated: average fruit weight, fruit diameter, number of fruits per plant and yield. The cultivation environments (greenhouse and trellis promote better performance on average mass and diameter of the fruit compared to plants grown in full sun during the production cycles of the fig crop grown in Ceará semiarid region. The bovine biofertilizer in the concentration of 60% promoted the highest mass, diameter, number of fruits per plant and the fig crop yield.

Climatic growing conditions of Jatropha curcas L.

Energy Technology Data Exchange (ETDEWEB)

Maes, W.H.; Achten, W.M.J.; Muys, B. [Katholieke Universiteit Leuven, Division Forest, Nature and Landscape, Celestijnenlaan 200 E Box 2411, BE-3001 Leuven (Belgium); Trabucco, A. [Katholieke Universiteit Leuven, Division Forest, Nature and Landscape, Celestijnenlaan 200 E Box 2411, BE-3001 Leuven (Belgium); International Water Management Institute (IWMI), P.O. Box 2075, Colombo (Sri Lanka)

2009-10-15

The massive investment in new jatropha plantations worldwide is not sufficiently based on a profound scientific knowledge of its ecology. In this article, we define the climatic conditions in its area of natural distribution by combining the locations of herbarium specimens with corresponding climatic information, and compare these conditions with those in 83 jatropha plantations worldwide. Most specimens (87%) were found in tropical savannah and monsoon climates (A{sub m}, A{sub w}) and in temperate climates without dry season and with hot summer (C{sub fa}), while very few were found in semi-arid (B{sub S}) and none in arid climates (B{sub W}). Ninety-five percent of the specimens grew in areas with a mean annual rainfall above 944 mm year{sup -1} and an average minimum temperature of the coldest month (T{sub min}) above 10.5 C. The mean annual temperature range was 19.3-27.2 C. The climatic conditions at the plantations were different from those of the natural distribution specimens for all studied climatic variables, except average maximum temperature in the warmest month. Roughly 40% of the plantations were situated in regions with a drier climate than in 95% of the area of the herbarium specimens, and 28% of the plantations were situated in areas with T{sub min} below 10.5 C. The observed precipitation preferences indicate that jatropha is not common in regions with arid and semi-arid climates. Plantations in arid and semi-arid areas hold the risk of low productivity or irrigation requirement. Plantations in regions with frost risk hold the risk of damage due to frost. (author)

Woody plants in agro-ecosystems of semi-arid regions

NARCIS (Netherlands)

Breman, H.; Kessler, J.J.

1995-01-01

A quantitative analysis of the role of woody plants in semi-arid regions, focusing on the Sahel and Sudan zones in West-Africa, is given for the assessment of their benefits in agro-sylvopastoral land-use systems with productive and sustainability objectives.

Development and water requirements of cowpea under climate change conditions in the Brazilian semi-arid region

Directory of Open Access Journals (Sweden)

Edmilson G. Cavalcante Junior

Full Text Available ABSTRACT This study aimed to determine the impacts that climate change may cause on the development and evapotranspiration of cowpea, in semi-arid climate region of Northeast Brazil. The study was conducted in the municipalities of Apodi, Ipanguaçu and Mossoró, in the state of Rio Grande do Norte. In order to evaluate the influence of climate change on crop water consumption, changes in air temperature and relative humidity were simulated using the PRECIS climate model. Two scenarios of emissions were evaluated based on the report of the Intergovernmental Panel on Climate Change: a pessimistic named A2 and an optimistic B2. The duration of the crop cycle showed an average reduction of 14 and 23 days for the optimistic and pessimistic scenarios, respectively. Temperatures will be well above the limit tolerated by crop, which could have a negative impact on its development and yield. There will be a decrease in total evapotranspiration of 4.8%, considering the optimistic scenario, and 8.7% in the pessimistic scenario.

New Possibilities for High-Resolution, Large-Scale Ecosystem Assessment of the World's Semi-Arid Regions

Science.gov (United States)

Burney, J. A.; Goldblatt, R.

2016-12-01

Understanding drivers of land use change - and in particular, levels of ecosystem degradation - in semi-arid regions is of critical importance because these agroecosystems (1) are home to the world's poorest populations, almost all of whom depend on agriculture for their livelihoods, (2) play a critical role in the global carbon and climate cycles, and (3) have in many cases seen dramatic changes in temperature and precipitation, relative to global averages, over the past several decades. However, assessing ecosystem health (or, conversely, degradation) presents a difficult measurement problem. Established methods are very labor intensive and rest on detailed questionnaires and field assessments. High-resolution satellite imagery has a unique role semi-arid ecosystem assessment in that it can be used for rapid (or repeated) and very simple measurements of tree and shrub density, an excellent overall indicator for dryland ecosystem health. Because trees and large shrubs are more sparse in semi-arid regions, sub-meter resolution imagery in conjunction with automated image analysis can be used to assess density differences at high spatial resolution without expensive and time-consuming ground-truthing. This could be used down to the farm level, for example, to better assess the larger-scale ecosystem impacts of different management practices, to assess compliance with REDD+ carbon offset protocols, or to evaluate implementation of conservation goals. Here we present results comparing spatial and spectral remote sensing methods for semi-arid ecosystem assessment across new data sources, using the Brazilian Sertão as an example, and the implications for large-scale use in semi-arid ecosystem science.

Water conservation for semi-arid rangelands

International Nuclear Information System (INIS)

Willis, W.O.

1983-01-01

Water deficiency is most often the cause for low forage production on rangelands in semi-arid and arid regions. Water conservation methods have been developed but additional research is needed to develop the best management practices for various climatic regions. Poor management is another major cause of low rangeland production. Better management, including the application of research findings, depends on attitudes, policies, adaptability of findings, resources for implementation and a good understanding of the governing biotic and abiotic factors. (author)

Relation between parameters of self-sustaining magnetically confined electron cloud and external conditions

International Nuclear Information System (INIS)

Yu Qingchang

1991-01-01

On the basis of the fluid theory of the axisymmetrical self-sustaining magnetically confined electron clouds an approximate analytical method is developed. By means of this method the relations between the parameters of this type of electron cloud and external conditions are studied. The parameters include electron density, electron temperature, drift angular frequency of electrons, radius of the electron cloud and electric potential at the centre of the electron cloud. They depend on the voltage, magnetic induction, pressure, electromagnetic field distribution in the confinement device and parameters of electron-atom collisions

Modelling hydrologic and hydrodynamic processes in basins with large semi-arid wetlands

Science.gov (United States)

Fleischmann, Ayan; Siqueira, Vinícius; Paris, Adrien; Collischonn, Walter; Paiva, Rodrigo; Pontes, Paulo; Crétaux, Jean-François; Bergé-Nguyen, Muriel; Biancamaria, Sylvain; Gosset, Marielle; Calmant, Stephane; Tanimoun, Bachir

2018-06-01

Hydrological and hydrodynamic models are core tools for simulation of large basins and complex river systems associated to wetlands. Recent studies have pointed towards the importance of online coupling strategies, representing feedbacks between floodplain inundation and vertical hydrology. Especially across semi-arid regions, soil-floodplain interactions can be strong. In this study, we included a two-way coupling scheme in a large scale hydrological-hydrodynamic model (MGB) and tested different model structures, in order to assess which processes are important to be simulated in large semi-arid wetlands and how these processes interact with water budget components. To demonstrate benefits from this coupling over a validation case, the model was applied to the Upper Niger River basin encompassing the Niger Inner Delta, a vast semi-arid wetland in the Sahel Desert. Simulation was carried out from 1999 to 2014 with daily TMPA 3B42 precipitation as forcing, using both in-situ and remotely sensed data for calibration and validation. Model outputs were in good agreement with discharge and water levels at stations both upstream and downstream of the Inner Delta (Nash-Sutcliffe Efficiency (NSE) >0.6 for most gauges), as well as for flooded areas within the Delta region (NSE = 0.6; r = 0.85). Model estimates of annual water losses across the Delta varied between 20.1 and 30.6 km3/yr, while annual evapotranspiration ranged between 760 mm/yr and 1130 mm/yr. Evaluation of model structure indicated that representation of both floodplain channels hydrodynamics (storage, bifurcations, lateral connections) and vertical hydrological processes (floodplain water infiltration into soil column; evapotranspiration from soil and vegetation and evaporation of open water) are necessary to correctly simulate flood wave attenuation and evapotranspiration along the basin. Two-way coupled models are necessary to better understand processes in large semi-arid wetlands. Finally, such coupled

Is annual recharge coefficient a valid concept in arid and semi-arid regions?

Directory of Open Access Journals (Sweden)

Y. Cheng

2017-10-01

Full Text Available Deep soil recharge (DSR (at depth greater than 200 cm is an important part of water circulation in arid and semi-arid regions. Quantitative monitoring of DSR is of great importance to assess water resources and to study water balance in arid and semi-arid regions. This study used a typical bare land on the eastern margin of Mu Us Sandy Land in the Ordos Basin of China as an example to illustrate a new lysimeter method of measuring DSR to examine if the annual recharge coefficient is valid or not in the study site, where the annual recharge efficient is the ratio of annual DSR over annual total precipitation. Positioning monitoring was done on precipitation and DSR measurements underneath mobile sand dunes from 2013 to 2015 in the study area. Results showed that use of an annual recharge coefficient for estimating DSR in bare sand land in arid and semi-arid regions is questionable and could lead to considerable errors. It appeared that DSR in those regions was influenced by precipitation pattern and was closely correlated with spontaneous strong precipitation events (with precipitation greater than 10 mm other than the total precipitation. This study showed that as much as 42 % of precipitation in a single strong precipitation event can be transformed into DSR. During the observation period, the maximum annual DSR could make up 24.33 % of the annual precipitation. This study provided a reliable method of estimating DSR in sandy areas of arid and semi-arid regions, which is valuable for managing groundwater resources and ecological restoration in those regions. It also provided strong evidence that the annual recharge coefficient was invalid for calculating DSR in arid and semi-arid regions. This study shows that DSR is closely related to the strong precipitation events, rather than to the average annual precipitation, as well as the precipitation patterns.

In-situ transmission electron microscopy growth of nanoparticles under extreme conditions

International Nuclear Information System (INIS)

Luce, F. P.; Azevedo, G. de M.; Baptista, D. L.; Zawislak, F. C.; Oliviero, E.; Fichtner, P. F. P.

2016-01-01

The formation and time resolved behavior of individual Pb nanoparticles embedded in silica have been studied by in-situ transmission electron microscopy observations at high temperatures (400–1100 °C) and under 200 keV electron irradiation. It is shown that under such extreme conditions, nanoparticles can migrate at long distances presenting a Brownian-like behavior and eventually coalesce. The particle migration phenomenon is discussed considering the influence of the thermal energy and the electron irradiation effects on the atomic diffusion process which is shown to control particle migration. These results and comparison with ex-situ experiments tackle the stability and the microstructure evolution of nanoparticles systems under extreme conditions. It elucidates on the effects of energetic particle irradiation-annealing treatments either as a tool or as a detrimental issue that could hamper their long-term applications in radiation-harsh environments such as in space or nuclear sectors

Will water scarcity in semiarid regions limit hydraulic fracturing of shale plays?

International Nuclear Information System (INIS)

Scanlon, Bridget R; Reedy, Robert C; Philippe Nicot, Jean

2014-01-01

There is increasing concern about water constraints limiting oil and gas production using hydraulic fracturing (HF) in shale plays, particularly in semiarid regions and during droughts. Here we evaluate HF vulnerability by comparing HF water demand with supply in the semiarid Texas Eagle Ford play, the largest shale oil producer globally. Current HF water demand (18 billion gallons, bgal; 68 billion liters, bL in 2013) equates to ∼16% of total water consumption in the play area. Projected HF water demand of ∼330 bgal with ∼62 000 additional wells over the next 20 years equates to ∼10% of historic groundwater depletion from regional irrigation. Estimated potential freshwater supplies include ∼1000 bgal over 20 yr from recharge and ∼10 000 bgal from aquifer storage, with land-owner lease agreements often stipulating purchase of freshwater. However, pumpage has resulted in excessive drawdown locally with estimated declines of ∼100–200 ft in ∼6% of the western play area since HF began in 2009–2013. Non-freshwater sources include initial flowback water, which is ≤5% of HF water demand, limiting reuse/recycling. Operators report shifting to brackish groundwater with estimated groundwater storage of 80 000 bgal. Comparison with other semiarid plays indicates increasing brackish groundwater and produced water use in the Permian Basin and large surface water inputs from the Missouri River in the Bakken play. The variety of water sources in semiarid regions, with projected HF water demand representing ∼3% of fresh and ∼1% of brackish water storage in the Eagle Ford footprint indicates that, with appropriate management, water availability should not physically limit future shale energy production. (letter)

Water requirement and use by Jatropha curcas in a semi-arid tropical location

International Nuclear Information System (INIS)

Kesava Rao, A.V.R.; Wani, Suhas P.; Singh, Piara; Srinivas, K.; Srinivasa Rao, Ch.

2012-01-01

Increasing emphasis on biofuel to meet the growing energy demand while reducing emissions of greenhouse gases, Jatropha curcas has attracted the attention of researchers, policy makers and industries as a good candidate for biodiesel. It is a non-edible oil crop, drought tolerant and could be grown on degraded lands in the tropics without competing for lands currently used for food production. J. curcas being a wild plant, much about its water requirement and production potential of promising clones in different agroclimatic conditions is not known. Water use assessment of J. curcas plantations in the semi-arid tropical location at ICRISAT, Patancheru indicated that crop evapotranspiration of J. curcas under no moisture stress varied from 1410 to 1538 mm per year during 2006–2009. Under field conditions the crop evapotranspiration varied from 614 to 930 mm depending on the atmospheric demand, rainfall and crop phenological stage. Patterns of soil-water depletion indicated that with growing plant age from two to five years, depth of soil-water extraction increased from 100 to 150 cm by fifth year. Monthly water use of Jatropha varied from 10–20 (leaf shedding period) to 140 mm depending on water availability and environmental demand. This study indicated that J. curcas has a good drought tolerance mechanism, however under favorable soil moisture conditions Jatropha could use large amounts of water for luxurious growth and high yield. These findings highlight the need to carefully identify suitable niche areas for Jatropha cultivation and assess the implications of large J. curcas plantations on water availability and use under different agroecosystems, particularly so in water scarce regions such as semi-arid and arid regions in the tropics. -- Highlights: ► Jatropha ET varied from 1410 to 1538 mm in optimal and 614 to 930 mm in field conditions. ► Depth of soil-water extraction increased from 100 to 150 cm by fifth year of age. ► Jatropha yields varied

Differential Impact of Passive versus Active Irrigation on Urban Forests in Semiarid Regions

Science.gov (United States)

Luketich, A. M.; Papuga, S. A.; Crimmins, M.

2017-12-01

The network of trees within a city provides a variety of ecosystem services such as flood mitigation and reduced heat island effects. To maintain these `urban forests' in semiarid cities, the use of scarce water resources for irrigation is often necessary. Rainwater harvesting has been widely adopted in Tucson, AZ as a sustainable water source for trees, but the effects of passive water harvesting versus active irrigation on tree canopy productivity and microclimate is largely unquantified. We hypothesize that regardless of whether trees are passively or actively irrigated, deep soil moisture will be elevated compared to natural conditions; however, we expect that increased deep soil moisture conditions will be more frequent using active irrigation. Additionally, we hypothesize that similar to natural settings, urban trees will need access deep soil moisture for transpiration. Therefore, we expect that actively irrigated trees will have more periods of transpiration than passively irrigated trees and that this will result in elevated and sustained phenological activity. We also expect that this difference will translate to more ecosystem services for a longer portion of the year in actively irrigated urban forests. Here, we compare key ecohydrological indicators of passive and active irrigation systems at two sites in Tucson, AZ. Our measurements include soil moisture, transpiration, air temperature, soil temperature, below- and within- canopy temperatures, and canopy phenology. Our first year of results suggest there are differences in transpiration, canopy greening and microclimate between the two irrigation techniques and that the magnitude of these differences are highly seasonal. This research can help to improve understanding of the practices and function of green infrastructure in semiarid cities and inform models that attempt to aggregate the influence of these urban forests for understanding watershed management strategies.

Predicting the future impact of droughts on ungulate populations in arid and semi-arid environments.

Directory of Open Access Journals (Sweden)

Clare Duncan

Full Text Available Droughts can have a severe impact on the dynamics of animal populations, particularly in semi-arid and arid environments where herbivore populations are strongly limited by resource availability. Increased drought intensity under projected climate change scenarios can be expected to reduce the viability of such populations, yet this impact has seldom been quantified. In this study, we aim to fill this gap and assess how the predicted worsening of droughts over the 21(st century is likely to impact the population dynamics of twelve ungulate species occurring in arid and semi-arid habitats. Our results provide support to the hypotheses that more sedentary, grazing and mixed feeding species will be put at high risk from future increases in drought intensity, suggesting that management intervention under these conditions should be targeted towards species possessing these traits. Predictive population models for all sedentary, grazing or mixed feeding species in our study show that their probability of extinction dramatically increases under future emissions scenarios, and that this extinction risk is greater for smaller populations than larger ones. Our study highlights the importance of quantifying the current and future impacts of increasing extreme natural events on populations and species in order to improve our ability to mitigate predicted biodiversity loss under climate change.

Conditions for electron runaway under leader breakdown of long gaps

International Nuclear Information System (INIS)

Ul'yanov, K. N.

2008-01-01

An original hydrodynamic model in which inelastic collisions in the equations of motion and energy balance play a decisive role is developed and applied to simulate electron avalanches in strong electric fields. The mean energy and drift velocity of electrons, as well as the ionization coefficient and electric field in a wide range of mean electron energies, are determined for helium and xenon. A criterion is derived for the runaway of the average electron in discharges with ionization multiplication. It is shown that runaway can take place at any value of E/p, provided that the momentum mean free path exceeds the gap length. The voltage corresponding to electron runaway is found for helium, xenon, and air as a function of the electric field, the electron mean energy, and the parameter pd. Conditions for the formation of a precursor in electronegative gases are analyzed. It is shown that the presence of a precursor with a high electric conductance is necessary for the formation of a new leader step. The voltage and time ranges corresponding to efficient electron runaway and X-ray generation during leader breakdown in air are determined

First record of Chantransia macrospora Wood, 1887 (Batrachospermales, Rhodophyta in semi-arid northeastern Brazil

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Janiele França Vasconcelos

2014-12-01

Full Text Available This study presents the first record of Chantransia macrospora in the state of Rio Grande do Norte, in the semi-arid region of northeastern Brazil. Analyses of periphytic algae revealed C. macrospora individuals associated in particular with shells of Melanoides tuberculatus, a non-native species, suggesting that C. macrospora have been introduced into systems associated with the gastropods. In this context, new records of C. macrospora are still expected for the Brazilian semi-arid region in the next years.

Soil Microbial Activity Responses to Fire in a Semi-arid Savannah Ecosystem Pre- and Post-Monsoon Season

Science.gov (United States)

Jimenez, J. R.; Raub, H. D.; Jong, E. L.; Muscarella, C. R.; Smith, W. K.; Gallery, R. E.

2017-12-01

Extracellular enzyme activities (EEA) of soil microorganisms can act as important proxies for nutrient limitation and turnover in soil and provide insight into the biochemical requirements of microbes in terrestrial ecosystems. In semi-arid ecosystems, microbial activity is influenced by topography, disturbances such as fire, and seasonality from monsoon rains. Previous studies from forest ecosystems show that microbial communities shift to similar compositions after severe fires despite different initial conditions. In semi-arid ecosystems with high spatial heterogeniety, we ask does fire lead to patch intensification or patch homogenization and how do monsoon rains influence the successional trajectories of microbial responses? We analyzed microbial activity and soil biogeochemistry throughout the monsoon season in paired burned and unburned sites in the Santa Rita Experimental Range, AZ. Surface soil (5cm) from bare-ground patches, bole, canopy drip line, and nearby grass patches for 5 mesquite trees per site allowed tests of spatiotemporal responses to fire and monsoon rain. Microbial activity was low during the pre-monsoon season and did not differ between the burned and unburned sites. We found greater activity near mesquite trees that reflects soil water and nutrient availability. Fire increased soil alkalinity, though soils near mesquite trees were less affected. Soil water content was significantly higher in the burned sites post-monsoon, potentially reflecting greater hydrophobicity of burned soils. Considering the effects of fire in these semi-arid ecosystems is especially important in the context of the projected changing climate regime in this region. Assessing microbial community recovery pre-, during, and post-monsoon is important for testing predictions about whether successional pathways post-fire lead to recovery or novel trajectories of communities and ecosystem function.

INTEGRATION OF SATELLITE RAINFALL DATA AND CURVE NUMBER METHOD FOR RUNOFF ESTIMATION UNDER SEMI-ARID WADI SYSTEM

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E. O. Adam

2017-11-01

Full Text Available The arid and semi-arid catchments in dry lands in general require a special effective management as the scarcity of resources and information which is needed to leverage studies and investigations is the common characteristic. Hydrology is one of the most important elements in the management of resources. Deep understanding of hydrological responses is the key towards better planning and land management. Surface runoff quantification of such ungauged semi-arid catchments considered among the important challenges. A 7586 km2 catchment under investigation is located in semi-arid region in central Sudan where mean annual rainfall is around 250 mm and represent the ultimate source for water supply. The objective is to parameterize hydrological characteristics of the catchment and estimate surface runoff using suitable methods and hydrological models that suit the nature of such ungauged catchments with scarce geospatial information. In order to produce spatial runoff estimations, satellite rainfall was used. Remote sensing and GIS were incorporated in the investigations and the generation of landcover and soil information. Five days rainfall event (50.2 mm was used for the SCS CN model which is considered the suitable for this catchment, as SCS curve number (CN method is widely used for estimating infiltration characteristics depending on the landcover and soil property. Runoff depths of 3.6, 15.7 and 29.7 mm were estimated for the three different Antecedent Moisture Conditions (AMC-I, AMC-II and AMC-III. The estimated runoff depths of AMCII and AMCIII indicate the possibility of having small artificial surface reservoirs that could provide water for domestic and small household agricultural use.

Integrated modelling of climate, water, soil, agricultural and socio-economic processes: A general introduction of the methodology and some exemplary results from the semi-arid north-east of Brazil

NARCIS (Netherlands)

Krol, Martinus S.; Jaeger, Annekathrin; Bronstert, Axel; Güntner, Andreas

2006-01-01

Many semi-arid regions are characterised by water scarcity and vulnerability of natural resources, pronounced climatic variability and social stress. Integrated studies including climatology, hydrology, and socio-economic studies are required both for analysing the dynamic natural conditions and to

Microbial inoculants and organic amendment improves the establishment of autochtonous shrub species and microbial activity recovery in a semiarid soil

Science.gov (United States)

Mengual, Carmen; Schoebitz, Mauricio; Azcon, Rosario; Torres, Pilar; Caravaca, Fuensanta; Roldan, Antonio

2014-05-01

The re-establishment of autochthonous shrub species is an essential strategy for recovering degraded soils under semiarid Mediterranean conditions. A field assay was carried out to determine the combined effects of the inoculation with native rhizobacteria (B. megaterium, Enterobacter sp, B. thuringiensis and Bacillus sp) and the addition of composted sugar beet (SB) residue on physicochemical soil properties and Lavandula dentata L. establishment. One year after planting, Bacillus sp. and B. megaterium+SB were the most effective treatments for increasing shoot dry biomass (by 5-fold with respect to control) and Enterobacter sp+SB was the most effective treatments for increasing dry root biomass. All the treatments evaluated significantly increased the foliar nutrient content (NPK) compared to control values (except B. thuringiensis+SB). The organic amendment had significantly increased available phosphorus content in rhizosphere soil by 29% respect to the control. Enterobacter sp combined with sugar beet residue improved total N content in soil (by 46% respect to the control) as well as microbiological and biochemical properties. The selection of the most efficient rhizobacteria strains and their combined effect with organic residue seems to be a critical point that drives the effectiveness of using these biotechnological tools for the revegetation and rehabilitation of degraded soils under semiarid conditions.

Optimising post-mining soil conditions to maximise restoration success in a biodiverse semiarid environment

Science.gov (United States)

Muñoz-Rojas, Miriam; Erickson, Todd; Merritt, David; Dixon, Kingsley

2014-05-01

The original topsoil of mine degraded areas is frequently lost or damaged, which together with the absence of soil forming materials is a major constraint for seed germination and establishment in post-mining restoration. Thus, management of the available topsoil and the use of alternative growth media are critical to improve restoration areas disturbed through mining. Here we are developing laboratory and field trials to define the optimal range for physical and chemical properties of potentially suitable natural and 're-made' soil substrates and growth medium for 20 selected native plant species from the mining intensive Pilbara region of Western Australia. In this semiarid area, water is a limiting factor for seedling establishment, which is compounded by the lack of organic matter of post-disturbance soils. Therefore, particular attention is given to indicators of soil biological activity such as soil respiration, and hydrological soil properties such as water holding capacity, infiltration, hydraulic conductivity and soil water repellence. This research is part of a broader multi-study approach, the Restoration Seedbank Initiative project, a partnership between The University of Western Australia, BHP Billiton Iron Ore, and Kings Park and Botanic Garden to develop the science and underpinning knowledge to achieve biodiverse restoration in the Pilbara region, where land areas disturbed by mining exceed 40,000 ha. Achieving restoration success is critical as the Pilbara region is an ancient landscape with diverse geology and high levels of regional and local endemism in plants and animals.

Modelling annual evapotranspiration in a semi-arid, African savanna ...

African Journals Online (AJOL)

Accurately measuring evapotranspiration (ET) is essential if we are to derive reasonable estimates of production and water use for semi-arid savannas. Estimates of ET are also important in defining the health of an ecosystem and the quantity of water used by the vegetation when preparing a catchment-scale water balance.

Adaptation at Scale in Semi-Arid Regions | IDRC - International ...

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

People living in Africa and South Asia's semi-arid regions face challenges that hinder their economic growth and development. This project seeks to find proactive, longer-term approaches to climate change adaptation in these vulnerable regions, while helping locals manage existing risks. Short-term focus must shift. So far ...

Determining Dry Matter Degradability of Some Semi-Arid Browse ...

African Journals Online (AJOL)

acer

ABSTRACT: The in vitro gas production of some semi-arid browse species were evaluated. The relationship between in ... between in vitro gas measured on incubation of browse leaves and that calculated from SCFA allows the prediction of SCFA from ... with concentrate feed (40% corn, 10% wheat offal, 10% palm kernel ...

Paclobutrazol biodegradation in unsaturated soil in the Semi-Arid ...

African Journals Online (AJOL)

Paclobutrazol (PBZ) is a plant growth regulator, increasing flowe ring and yield that is widely used in mango cultivation in the semi-arid northeastern Brazil. PBZ remains active in the soil for several years. However, it can severely affect the growth and development of subsequent crops, mainly by reducing vegetative vigor.

Biodigestor for validation of the productive system self-sustainable in the Brazil semi-arid; Biodigestor para validacao de sistema produtivo auto-sustentavel no semi-arido

Energy Technology Data Exchange (ETDEWEB)

Carvalho, Paulo C.M. [Universidade Federal do Ceara (UFCE), Fortaleza, CE (Brazil). Dept. de Engenharia Eletrica; Silveira Neto, Jose W; Diniz, Magilce M.N. [Instituto Joazeiro de Desenvolvimento Sustentavel, Fortaleza, CE (Brazil); Canafistula, Francisco J.F. [Universidade Federal do Ceara (UFCE), Fortaleza, CE (Brazil). Dept. de Engenharia Agricola

2004-07-01

The present paper shows the first phase of a project about the use of digester adapted to the conditions of the semi-arid areas of the Brazilian Northeast region. The project aims to analyze the technical, economical, financial and environmental viability of a production system based on the use of digesters. (author)

PRODUCTION AND DISTRIBUTION OF Jatropha curcas BIOMASS IN THE BRAZILIAN SEMIARID

Directory of Open Access Journals (Sweden)

Marcos Antônio Drumond

2016-03-01

Full Text Available In order to assess production and distribution of biomass shoots of different genotypes of Jatropha curcas under irrigation in the semiarid region of Pernambuco, Brazil, an experiment was established in Gabriela Farm, in the municipality of Santa Maria da Boa Vista-PE. The experimental design was randomized blocks with ten treatments (genotypes of Jatropha curcas, and three replications in row plots of six plants, with a single border and spacing of 3.0 x 2.0 m. Plants were fertilized with 150 g of NPK (06:24:12 at planting time, and a topdressing with 150 g.planta-1 NPK (10:10:10 applied at six and twelve months of age. The plants were irrigated weekly using a dripping system with an average water application of 20 l.plant-1 during the dry period of the region. At 24 months of age, the overall height of the plants, the average diameter of bifurcations at 1.30m from the soil level and the number of bifurcations at 0.5 m of height were evaluated. Twenty six fruit/ seed harvests were done weekly. Fruits were harvested ripe, before falling on the ground, for seven months. To determine dry biomass, the plants were cut at 0.30 m from soil level. The genotypes showed high agronomic uniformity, except for the variable number of bifurcations, where the genotype 1701 was superior to the genotypes 1501, 1602, 1703 and 1601. Biomass production of genotypes in irrigated conditions in the semiarid region is high and the distribution of biomass followed the decreasing order: root>fruit>thick branches>leaves>bark>thin branches.

Impact of bee pollinators on seed set and yield of Vicia villosa spp. dasycarpa (Leguminosae grown under semiarid conditions

Directory of Open Access Journals (Sweden)

Shahera Zaitoun

2010-01-01

Full Text Available A field experiment was conducted during 2005/2006 at Jordan University of Science and Technology campus (32°30” N, 35°59” E, Irbid, Jordan, to study the role of bee visitors on seed set and production of Vicia villosa spp. dasycarpa grown under semiarid conditions. Two treatments were imposed on Vicia villosa plants before flowering: 1 Plants were covered in cages (control or 2 Plants were left uncovered to permit bee visiting. The results of this experiment showed that V. villosa flowers were very attractive to worker honeybees as well as to few numbers of wild bees. The most frequent visitor species were A. mellifera and Anthophora albigena of family Apidae. V. villosa flowers attracted most of the bee visitors in the early hours of the day. The duration of their visit on the flowers also peaked early in the day and decreased toward the end of the day. The percentage of pod set of the un-covered plants averaged 14% out of the total florets on the plants, which was significantly higher than the covered plants (2%. These results indicated that the percentage of flower abscission was high and averaged more than 86%. Plant covering significantly reduced seed yield by reducing seed and pod number per plant and seed number per pod, but had no effect on individual seed weight. In conclusion, preventing bees from visiting during flowering of V. villosa spp. dasycarpa decreased seed set, seed yield and yield components. Further studies are needed to understand the high flower abscission and failure of seed set in this species.

Hydrological modeling in semi-arid region using HEC-HMS model ...

African Journals Online (AJOL)

The purpose of this study is to simulate rainfall-runoff in the semi-arid region of ... the frequency storm is used for the meteorological model, the SCS curve number is ... SCS unit hydrograph method have been applied to simulate the runoff rate.

Amphibian and reptile biodiversity in the semi-arid region of the municipality of Nopala de Villagrán, Hidalgo, Mexico

OpenAIRE

Roth-Monzón, Andrea J.; Mendoza-Hernández, Andrés Alberto; Flores-Villela, Oscar

2018-01-01

Current global changes are putting both biodiversity and the processes that depend on it at risk. This is especially true for semi-arid regions and the flagship groups that inhabit them, such as amphibians and reptiles. Semi-arid regions are often thought to have lower biodiversity and thus have been overlooked, resulting in the underestimation of their biological richness. Therefore, the aim of this study was to conduct an inventory of amphibians and reptiles in the semi-arid municipality of...

A numerical investigation of the effect of ambient conditions on natural convection cooling of electronics

DEFF Research Database (Denmark)

Shojaee Nasirabadi, Parizad; Hattel, Jesper Henri

2017-01-01

Thermal management is a serious concern in electronic industry. It is important to understand the effects of ambient conditions on cooling of electronics. In this work, the effect of ambient conditions on the thermophysical properties of humid air is estimated in five cities (Copenhagen, Mashhad...

Pollen-mediated gene flow in wheat (Triticum aestivum L.) in a semiarid field environment in Spain.

Science.gov (United States)

Loureiro, Iñigo; Escorial, María-Concepción; González, Águeda; Chueca, María-Cristina

2012-12-01

Transgenic wheat (Triticum aestivum L.) varieties are being developed and field-tested in various countries. Concerns regarding gene flow from genetically modified (GM) crops to non-GM crops have stimulated research to estimate outcrossing in wheat prior to the release and commercialization of any transgenic cultivars. The aim is to ensure that coexistence of all types of wheat with GM wheat is feasible in accordance with current regulations. The present study describes the result of a field experiment under the semi-arid climate conditions of Madrid, Spain, at two locations ("La Canaleja" and "El Encin" experimental stations) in Madrid over a 3-year period, from 2005 to 2007. The experimental design consisted of a 50 × 50 m wheat pollen source sown with wheat cultivars resistant to the herbicide chlortoluron ('Deganit' and 'Castan' respectively) and three susceptible receptor cultivars ('Abental', 'Altria' and 'Recital') sown in replicated 1 × 1 m plots at different distances (0, 1, 3, 5, 10, 20, 40, 80 and 100 m) and four directions. Outcrossing rates were measured as a percentage of herbicide-resistant hybrids using an herbicide-screening assay. Outcrossing was greatest near the pollen source, averaging 0.029% at 0 m distance at "La Canaleja" and 0.337% at "El Encin", both below the 0.9% European Union regulated threshold, although a maximum outcrossing rate of 3.5% was detected in one recipient plot. These percentages declined rapidly as the distance increased, but hybrids were detected at different rates at distances of up to 100 m, the maximum distance of the experiment. Environmental conditions, as drought in 2004-2005 and 2005-2006, may have influenced the extent of outcrossing. These assays carried out in wheat under semi-arid conditions in Europe provide a more complete assessment of pollen-mediated gene flow in this crop.

Controlled cooling of an electronic system based on projected conditions

Science.gov (United States)

David, Milnes P.; Iyengar, Madhusudan K.; Schmidt, Roger R.

2015-08-18

Energy efficient control of a cooling system cooling an electronic system is provided based, in part, on projected conditions. The control includes automatically determining an adjusted control setting(s) for an adjustable cooling component(s) of the cooling system. The automatically determining is based, at least in part, on projected power consumed by the electronic system at a future time and projected temperature at the future time of a heat sink to which heat extracted is rejected. The automatically determining operates to reduce power consumption of the cooling system and/or the electronic system while ensuring that at least one targeted temperature associated with the cooling system or the electronic system is within a desired range. The automatically determining may be based, at least in part, on an experimentally obtained model(s) relating the targeted temperature and power consumption of the adjustable cooling component(s) of the cooling system.

Evaluating water controls on vegetation growth in the semi-arid sahel using field and earth observation data

DEFF Research Database (Denmark)

Abdi, Abdulhakim M.; Boke-Olen, Niklas; Tenenbaum, David E.

2017-01-01

Water loss is a crucial factor for vegetation in the semi-arid Sahel region of Africa. Global satellite-driven estimates of plant CO2 uptake (gross primary productivity, GPP) have been found to not accurately account for Sahelian conditions, particularly the impact of canopy water stress. Here, we...... identify the main biophysical limitations that induce canopy water stress in Sahelian vegetation and evaluate the relationships between field data and Earth observation-derived spectral products for up-scaling GPP. We find that plant-available water and vapor pressure deficit together control the GPP...

Vertical and temporal variation in phytoplankton assemblages correlated with environmental conditions in the Mundaú reservoir, semi-arid northeastern Brazil.

Science.gov (United States)

Lira, G A S T; Moura, A N; Vilar, M C P; Cordeiro-Araújo, M K; Bittencourt-Oliveira, M C

2014-08-01

The goal of this study was to analyse the vertical structure of the phytoplankton community at the Mundaú reservoir, located in the semi-arid region of northeastern Brazil, and to correlate it to environmental conditions over two distinct seasons, dry and rainy. Samples were collected bimonthly at eight depths in the dry and rainy season for analyses of the physical and chemical variables of the water, as well as density, abundance, dominance, species diversity index and equitability of the community. Analysis of variance (ANOVA-two way) was used to analyse the vertical and seasonal differences, and Canonical Correspondence Analysis (CCA) was used to assess associations between phytoplankton and environmental variables Cylindrospermopsis raciborskii (Woloszynska) Seenaya and Subba Raju was the only dominant species and Geitlerinema amphibium (C. Agardh) Anagnostidis, Merismopedia punctata Meyen and Synedra rumpens Kützing. Others six taxa were abundant in at least one of the samples. Distinct vertical distribution patterns were observed for the abundant taxa between depths and seasons. The cyanobacteria, with the exception of C. raciborskii, showed similar seasonal patterns, with higher densities in the dry season. The CCA showed a strong correlation between the density of the phytoplanktonic species and abiotic variables. The vertical changes in abundant taxa revealed distinct patterns regulated by the variation in the environmental factors that were directly linked to seasonality, with the success of one or more species being dependent on their life strategies and ecological needs. The present study restates the importance of environmental and seasonal factors for phytoplankton composition and distribution in a freshwater tropical reservoir through a vertical gradient.

Carbon and water dynamics of a bioenergy crop (Cynara cardunculus L. under different meteorological conditions in a semi-arid region

Directory of Open Access Journals (Sweden)

Gianfranco Rana

2017-12-01

Full Text Available To evaluate the environmental adaptability of cultivated cardoon (Cynara cardunculus L. its water use efficiency [(WUE – ratio between net ecosystem exchange (NEE and evapotranspiration (ET] was analysed. The crop was cultivated in South Italy and WUE was evaluated at different time scales during two seasons: wet and dry. Even if the crop development is similar in the two seasons, plants delay their development in the presence of drought, showing, in this way, an improvement in their adaptability. Seasonal WUE in the dry season is greater than in the wet one by +11.2%, and this is also confirmed at monthly and daily scale. Hourly analysis around the full development phase shows that WUE is greater during the wet season than during the dry one, this being explainable when considering the impact of the drivers [(photosynthetically active radiation (PAR, vapour pressure deficit (VPD, and air temperature (Tair] on CO2 and H2O exchanges by stomatal regulation. The saturation values of NEE in function of PAR (threshold 2.5 MJ m–2h–1 and VPD (threshold 10 hPa are greater during the wet season than the dry one. Furthermore, also the linear relationships between ET and PAR and VPD showed higher slopes in the wet season than in the dry one. Drought causes reduction in both photosynthesis and evapotranspiration by stomatal regulation, however, the photosynthesis process is surely more sensitive to water stress than the crop transpiration, thus demonstrating the good adaptability of this crop to scarce water availability of semi-arid conditions.

Linking Bayesian and agent-based models to simulate complex social-ecological systems in semi-arid regions

Directory of Open Access Journals (Sweden)

Aloah J Pope

2015-08-01

Full Text Available Interdependencies of ecologic, hydrologic, and social systems challenge traditional approaches to natural resource management in semi-arid regions. As a complex social-ecological system, water demands in the Sonoran Desert from agricultural and urban users often conflicts with water needs for its ecologically-significant riparian corridors. To explore this system, we developed an agent-based model to simulate complex feedbacks between human decisions and environmental conditions in the Rio Sonora Watershed. Cognitive mapping in conjunction with stakeholder participation produced a Bayesian model of conditional probabilities of local human decision-making processes resulting to changes in water demand. Probabilities created in the Bayesian model were incorporated into the agent-based model, so that each agent had a unique probability to make a positive decision based on its perceived environment at each point in time and space. By using a Bayesian approach, uncertainty in the human decision-making process could be incorporated. The spatially-explicit agent-based model simulated changes in depth-to-groundwater by well pumping based on an agent’s water demand. Changes in depth-to-groundwater feedback to influence agent behavior, as well as determine unique vegetation classes within the riparian corridor. Each vegetation class then provides varying stakeholder-defined quality values of ecosystem services. Using this modeling approach allowed us to examine effects on both the ecological and social system of semi-arid riparian corridors under various scenarios. The insight provided by the model contributes to understanding how specific interventions may alter the complex social-ecological system in the future.

Estimation of alluvial recharge in the semiarid

OpenAIRE

Andrade,Tafnes S.; Montenegro,Suzana M. G. L.; Montenegro,Abelardo A. de A.; Rodrigues,Diogo F. B.

2014-01-01

In areas where there is irrigated agriculture, the recuperation of water reserves in alluvial aquifers may occur preferentially due to precipitation. Recharging can be evaluated from variation information of water depth measured in piezometers or observation wells. Thus, the aim of this research is to study the recharge in the alluvial aquifer formed by the Mimoso temporary stream in the semiarid region of Pernambuco (PE), Brazil, using the method of the fluctuation of the water level. This s...

Air pollution measurements in a semi-arid zone, using neutron activation analysis

Energy Technology Data Exchange (ETDEWEB)

Shani, G; Cohen, D [Ben-Gurion Univ. of the Negev, Beersheba (Israel). Dept. of Nuclear Engineering

1977-12-01

Neutron activation analysis was used for measurement of air pollution in a semi-arid zone. After a careful selection of the air filter, air samples were filtered in the city of Beer-Sheva in the south of Israel. The sampling took place over a period of 2 months with each sampling period lasting 2 days. The samples were irradiated in a thermal neutron flux of the order of 10/sup 13/ n/cm/sup 2/ sec for 1 h and the gamma spectrum was measured several times. The concentration of elements was concluded from the measured gamma spectrum. Several conclusions were obtained by combining the weather conditions with the measurement results. The air pollution can be divided into several sources: dust of a certain origin containing Fe, Co, Cr, Sc, Th and Na (probably from the Dead Sea area), other dust sources containing Sb, Eu, and Hf, and urban pollution due to industry and transportation-Br, Hg. The air pollution has its maxima and minima according to weather or industrial conditions. The pollution requires 4 days to clear out. Other relations to weather conditions were also found.

Air pollution measurements in a semi-arid zone, using neutron activation analysis

International Nuclear Information System (INIS)

Shani, G.; Cohen, D.

1977-01-01

Neutron activation analysis was used for measurement of air pollution in a semi-arid zone. After a careful selection of the air filter, air samples were filtered in the city of Beer-Sheva in the south of Israel. The sampling took place over a period of 2 months with each sampling period lasting 2 days. The samples were irradiated in a thermal neutron flux of the order of 10 13 n/cm 2 sec for 1 h and the gamma spectrum was measured several times. The concentration of elements was concluded from the measured gamma spectrum. Several conclusions were obtained by combining the weather conditions with the measurement results. The air pollution can be divided into several sources: dust of a certain origin containing Fe, Co, Cr, Sc, Th and Na (probably from the Dead Sea area), other dust sources containing Sb, Eu, and Hf, and urban pollution due to industry and transportation-Br, Hg. The air pollution has its maxima and minima according to weather or industrial conditions. The pollution requires 4 days to clear out. Other relations to weather conditions were also found. (Auth.)

Modelling hydrological connectivity in semi-arid flat areas: effect of the flow accumulation algorithm on the spatial pattern

Science.gov (United States)

López-Vicente, Manuel; Álvarez, Sara

2017-04-01

Much of the water and sediment fluxes in semi-arid landscapes are found to be concentrated in localized pathways. Identifying the location of these pathways is important for management and restoration. This task becomes more complicated in flat areas, such as alluvial terraces, where geomorphic features of concentrated overland flow (rills and ephemeral gullies) are scarce or inexistent. Field identification of sediment delivery pathways as well as depositional areas is also difficult and challenged. The concept of hydrological connectivity (HC) helps us to express the complexity of landscape non-linear responses to rainfall inputs. One of the unsolved issues in overland flow modelling studies is the choice of the right flow accumulation algorithm (FAA). There is an abundant literature on runoff generation under semi-arid conditions, and relating HC and land use management and changes. However, we found a scientific gap in the literature focussed on modelling of HC in flat areas under semi-arid conditions. This study aims to fill in this gap by modelling HC in alluvial terraces (28 ha) in NE Spain under semi-arid conditions (342 mm / year), mainly devoted to rain-fed cereal fields, by using eight FAA. For this purpose, we applied a modified version of the Borselli's index of runoff and sediment connectivity (IC). The study area includes seven fields on flat alluvial terraces, three fields on a gentle slope, small patches of scrubland, and twelve grass buffer strips that are located between each set of fields. Gentle and flat areas (S drone (model eBee by senseFly Ltd.). In order to minimize the effect of the vegetation on the photogrammetry restitution technique, pictures were taken in early spring, before the growth of the cereals. Then, several DEMs were generated independently. For this study, we chose the DEM at 0.5 x 0.5 m of spatial resolution. Before running the IC model, the continuity of the flow path lines throughout the landscape was ensured by removing

A Review of the Condition Monitoring of Capacitors in Power Electronic Converters

DEFF Research Database (Denmark)

Soliman, Hammam Abdelaal Hammam; Wang, Huai; Blaabjerg, Frede

2015-01-01

Capacitor is one of the reliability critical components in power electronic systems. In the last two decades, many efforts in the academic research have been devoted to the condition monitoring of capacitors to estimate their health status. Industry applications demand more reliable power...... electronics products with preventive maintenance. Nevertheless, most of the developed capacitor condition monitoring technologies are rarely adopted by industry due to the complexity, increased cost and other relevant issues. An overview of the prior-art research in this area is therefore needed to justify....... Therefore, this paper firstly classifies the capacitor condition monitoring methods into three categories, then the respective technology evolution from 1993 to 2015 is summarized. Remarks on the state-of-the-art research and the future opportunities targeting for practical industry applications are given....

A Review of the Condition Monitoring of Capacitors in Power Electronic Converters

DEFF Research Database (Denmark)

Soliman, Hammam Abdelaal Hammam; Wang, Huai; Blaabjerg, Frede

2016-01-01

Capacitors are one type of reliability-critical components in power electronic systems. In the last two decades, many efforts in academic research have been devoted to the condition monitoring of capacitors to estimate their health status. Industry applications are demanding more reliable power...... electronics products with preventive maintenance. Nevertheless, most of the developed capacitor condition monitoring technologies are rarely adopted by industry due to the complexity, increased cost, and other relevant issues. An overview of the prior-art research in this area is therefore needed to justify......, this paper first classifies the capacitor condition monitoring methods into three categories, then the respective technology evolution in the last two decades is summarized. Finally, the state-of-the-art research and the future opportunities targeting for industry applications are given....

Response of transpiration to rain pulses for two tree species in a semiarid plantation

Science.gov (United States)

Chen, Lixin; Zhang, Zhiqiang; Zeppel, Melanie; Liu, Caifeng; Guo, Junting; Zhu, Jinzhao; Zhang, Xuepei; Zhang, Jianjun; Zha, Tonggang

2014-09-01

Responses of transpiration ( E c) to rain pulses are presented for two semiarid tree species in a stand of Pinus tabulaeformis and Robinia pseudoacacia. Our objectives are to investigate (1) the environmental control over the stand transpiration after rainfall by analyzing the effect of vapor pressure deficit (VPD), soil water condition, and rainfall on the post-rainfall E c development and recovery rate, and (2) the species responses to rain pulses and implications on vegetation coverage under a changing rainfall regime. Results showed that the sensitivity of canopy conductance ( G c) to VPD varied under different incident radiation and soil water conditions, and the two species exhibited the same hydraulic control (-d G c/dlnVPD to G cref ratio) over transpiration. Strengthened physiological control and low sapwood area of the stand contributed to low E c. VPD after rainfall significantly influenced the magnitude and time series of post-rainfall stand E c. The fluctuation of post-rainfall VPD in comparison with the pre-rainfall influenced the E c recovery. Further, the stand E c was significantly related to monthly rainfall, but the recovery was independent of the rainfall event size. E c enhanced with cumulative soil moisture change (ΔVWC) within each dry-wet cycle, yet still was limited in large rainfall months. The two species had different response patterns of post-rainfall E c recovery. E c recovery of P. tabulaeformis was influenced by the pre- and post-rainfall VPD differences and the duration of rainless interval. R. pseudoacacia showed a larger immediate post-rainfall E c increase than P. tabulaeformis did. We, therefore, concluded that concentrated rainfall events do not trigger significant increase of transpiration unless large events penetrate the deep soil and the species differences of E c in response to pulses of rain may shape the composition of semiarid woodlands under future rainfall regimes.

Using NDVI to measure precipitation in semi-arid landscapes

Science.gov (United States)

Birtwhistle, Amy N.; Laituri, Melinda; Bledsoe, Brian; Friedman, Jonathan M.

2016-01-01

Measuring precipitation in semi-arid landscapes is important for understanding the processes related to rainfall and run-off; however, measuring precipitation accurately can often be challenging especially within remote regions where precipitation instruments are scarce. Typically, rain-gauges are sparsely distributed and research comparing rain-gauge and RADAR precipitation estimates reveal that RADAR data are often misleading, especially for monsoon season convective storms. This study investigates an alternative way to map the spatial and temporal variation of precipitation inputs along ephemeral stream channels using Normalized Difference Vegetation Index (NDVI) derived from Landsat Thematic Mapper imagery. NDVI values from 26 years of pre- and post-monsoon season Landsat imagery were derived across Yuma Proving Ground (YPG), a region covering 3,367 km2 of semiarid landscapes in southwestern Arizona, USA. The change in NDVI from a pre-to post-monsoon season image along ephemeral stream channels explained 73% of the variance in annual monsoonal precipitation totals from a nearby rain-gauge. In addition, large seasonal changes in NDVI along channels were useful in determining when and where flow events have occurred.

Biomass and biomass water use efficiency in oilseed crop (Brassica juncea L.) under semi-arid microenvironments

International Nuclear Information System (INIS)

Adak, Tarun; Kumar, Gopal; Chakravarty, N.V.K.; Katiyar, R.K.; Deshmukh, P.S.; Joshi, H.C.

2013-01-01

Biomass production in arid and semi-arid regions requires a special attention owing to spatiotemporal scarcity of irrigation water wherein improved water use efficiency (WUE) of the crop is targeted. Under field conditions, the crop undergoes dynamic changes in near ground or within-canopy microenvironments. This changed microclimatic condition may have an impact on phenological response of the oilseed crop which in turn would affect biomass productivity, economic seed yield and water use efficiency of the crop. Henceforth, quantification of biomass production and its WUE of oilseed Brassica crop is essentially required owing to have better understanding of the crop water requirement under the era of climate change. Following a 2 years field experiment, it was revealed that the changes in leaf area index were explained by about 68–74%. The best fit polynomial third order regression analysis indicated >93% prediction in biomass production as a function of time factor. Improved biomass partitioning into economic sinks was also observed. Small scale change in near ground microenvironment may reduce the prediction of biomass variability to the extent of 3%. The mean ET variations were observed as 2.4, 1.5 and 3.2 mm day −1 during the critical phenological stages. Mean seed yield, biomass WUE and seed yield WUE ranged between 2.71 and 2.87 Mg ha −1 , 11.4 and 13.1 g m −2 mm −1 and 19.3 and 22.9 kg ha −1 mm −1 respectively. Variations in both biomass and seed yield water use efficiencies due to small scale change in near ground microclimates were revealed. -- Highlights: ► Assessing biomass productivity and its water use efficiency under arid and semi-arid regions is important. ► Under field conditions, the crop undergoes dynamic changes in near ground or within-canopy microenvironments. ► We have estimated changes in seasonal ET, within-canopy micrometeorological dynamics. ► Biomass productivity, partitioning and water use efficiencies were

The use of soil quality indicators to assess soil functionality in restored semi-arid ecosystems

Science.gov (United States)

Muñoz-Rojas, Miriam; Erickson, Todd E.; Dixon, Kingsley W.; Merritt, David J.

2016-04-01

. Soil microbial activity was measured with the 1-day CO2 test, a cost-effective and rapid method to determine soil microbial respiration rate based on the measurement of the CO2 burst produced after moistening dry soil (Muñoz-Rojas et al., 2016). Soil microbial abundance of specific groups was measured by phospholipid fatty acid analysis. Results and discussion We showed that in addition to organic C and C:N ratio, biological indicators (microbial diversity and activity in particular), are the most sensitive indicators to detect differences among reconstructed soils and analogue undisturbed soils in semi-arid areas. The 1-day CO2 test is an alternative cost- and time-effective method to measure microbial activity and assess soil functionality of restored soils. Our results also showed a positive effect of vegetation on reconstructed soils and a recovery of soil functionality in waste material to levels similar to topsoil once vegetation is established, although soil quality levels are still far from those in undisturbed native soils four years post-restoration. Soil functionality is critical in the restoration process, particularly in semi-arid areas, and the methods used here could be effectively applied in a broad range of restoration projects in arid and semi-arid environments. References Costantini EAC, Branquinho C, Nunes A, Schwilch G, Stavi I, Valdecantos A and Zucca C (2015) Soil indicators to assess the effectiveness of restoration strategies in dryland ecosystems. Solid Earth Discussions 7:3645-3687. James JJ, Sheley RL, EricksonT, Rollins KS, Taylor MH, Dixon KW (2013) A systems approach to restoring degraded drylands. Journal of Applied Ecology 50:730-739. Muñoz-Rojas M., Erickson T, Merritt D, Dixon K (2014) Optimising post-mining soil conditions to maximise restoration success in a biodiverse semiarid environment. Geophysical Research. Abstracts Vol. 16, EGU2014-2069-1, EGU General Assembly. Muñoz-Rojas M, Erickson T, Merritt D, Dixon K (2015) Applying

Evaluating rainwater harvesting systems in arid and semi-arid regions

NARCIS (Netherlands)

Ammar, Adham Ali

2017-01-01

Rainwater harvesting (RWH) is an ancient traditional technology practised in many parts of the world, especially in arid and semi-arid regions (ASARs). ASARs represent 40% of the earth’s land surface and are characterised by low average annual rainfall and uneven temporal and spatial

Coupled flow and salinity transport modelling in semi-arid environments

DEFF Research Database (Denmark)

Bauer-Gottwein, Peter; Held, R.J.; Zimmermann, S.

2006-01-01

Numerical groundwater modelling is used as the base for sound aquifer system analysis and water resources assessment. In many cases, particularly in semi-arid and arid regions, groundwater flow is intricately linked to salinity transport. A case in point is the Shashe River Valley in Botswana. A ...

Crop Upgrading Strategies and Modelling for Rainfed Cereals in a Semi-Arid Climate—A Review

Directory of Open Access Journals (Sweden)

Festo Richard Silungwe

2018-03-01

Full Text Available Spatiotemporal rainfall variability and low soil fertility are the primary crop production challenges facing poor farmers in semi-arid environments. However, there are few solutions for addressing these challenges. The literature provides several crop upgrading strategies (UPS for improving crop yields, and biophysical models are used to simulate these strategies. However, the suitability of UPS is limited by systemization of their areas of application and the need to cope with the challenges faced by poor farmers. In this study, we reviewed 187 papers from peer-reviewed journals, conferences and reports that discuss UPS suitable for cereals and biophysical models used to assist in the selection of UPS in semi-arid areas. We found that four UPS were the most suitable, namely tied ridges, microdose fertilization, varying sowing dates, and field scattering. The DSSAT, APSIM and AquaCrop models adequately simulate these UPS. This work provides a systemization of crop UPS and models in semi-arid areas that can be applied by scientists and planners.

Evaporation studies on Themeda triandra under field conditions: a ...

African Journals Online (AJOL)

In the semi-arid regions of South Africa, the efficiency of water use by natural grazing plants is important and can be used to evaluate the production potentially of comparative grasses. Hydraulic non-floating lysimeters were designed and tested under field conditions and indicated that with accurate calibration for ...

Financial costs of ecologically nonsustainable farming practices in a semiarid system

CSIR Research Space (South Africa)

Herling, MC

2009-11-01

Full Text Available Nonsustainable ostrich farming practices have degraded large areas of the Little Karoo, a semiarid region in South Africa. The Little Karoo lies within the Succulent Karoo biome, a recognized biodiversity hotspot. A financial feasibility analysis...

Spatial distribution of overland flow and sediment yield in semi-arid rangelands

International Nuclear Information System (INIS)

Sarah, P.; Lavee, H.

2009-01-01

Feedbacks and mutual links exist among soil, vegetation and water; they enable co-evolution of these features within eco-geomorphic systems, These relations are fragile, especially in semi-arid areas where grazing is the main land use. The simples subdivision of the surface of many semi-arid rangelands is into a two-component mosaic pattern comprising shrub patches interspersed with open spaces, with the former acting s skinks for water and other resources, and the latter as sources. However close observations in areas under grazing in the northern Negev region of Israel suggested that the spatial patterns of surface components is more complicated, and that the open space between shrubs consists of two components: herbaceous areas, separated by trampling routes that support no vegetation. (Author)

The linkage between household water consumption and rainfall in the semi-arid region of East Nusa Tenggara, Indonesia

Science.gov (United States)

Messakh, J. J.; Moy, D. L.; Mojo, D.; Maliti, Y.

2018-01-01

Several studies have shown that the amount of water consumption by communities will depend on the factors of water consumption patterns that are influenced by social, cultural, economic and local climate conditions. Research on the linkage between rainfall and household water consumption in semi-arid areas of Indonesia has never been done. This study has been conducted on 17 regions in NTT, and case study has taken samples in one town and one village. The research used survey and documentation method. The results show that the average amount of household water consumption in semi-arid region of East Nusa Tenggara is 107 liters / person / day. Statistical test results using Pearson correlation found r = -0.194 and sig = 0.448. This means that there is a negative correlation between rainfall and household water consumption. The greater the rainfall the smaller the consumption of water, or the smaller the rainfall the greater the consumption of water, but the linkage is not significant. Research shows that the amount of household water consumption will be influenced by many interrelated factors and none of the most dominant factors, including the size of the rainfall that occurs in a region.

Antecedent conditions influence soil respiration differences in shrub and grass patches

Science.gov (United States)

Quantifying the response of soil respiration to past environmental conditions is critical for predicting how future climate and vegetation change will impact ecosystem carbon balance. Increased shrub dominance in semiarid grasslands has potentially large effects on soil carbon cycling. The goal of t...

Arid and semiarid land stewardship: A 10-year review of accomplishments and contributions of the lnternational Arid Lands Consortium

Science.gov (United States)

Peter F. Ffolliott; Jeffrey O. Dawson; James T. Fisher; Itshack Moshe; Darrell W. DeBoers; Timothy. E. Fulbright; John Tracy; Abdullah Al Musa; Carter Johnson; Jim P. M. Chamie

2001-01-01

The International Arid Lands Consortium (IALC) was established in 1990 to promote research, education, and training activities related to the development, management, and restoration or reclamation of arid and semiarid lands worldwide. The IALC, a leading international organization, supports ecological sustainability and development of arid and semiarid lands. Building...

Semi-arid vegetation response to antecedent climate and water balance windows

Science.gov (United States)

Thoma, David P.; Munson, Seth M.; Irvine, Kathryn M.; Witwicki, Dana L.; Bunting, Erin

2016-01-01

Questions Can we improve understanding of vegetation response to water availability on monthly time scales in semi-arid environments using remote sensing methods? What climatic or water balance variables and antecedent windows of time associated with these variables best relate to the condition of vegetation? Can we develop credible near-term forecasts from climate data that can be used to prepare for future climate change effects on vegetation? Location Semi-arid grasslands in Capitol Reef National Park, Utah, USA. Methods We built vegetation response models by relating the normalized difference vegetation index (NDVI) from MODIS imagery in Mar–Nov 2000–2013 to antecedent climate and water balance variables preceding the monthly NDVI observations. We compared how climate and water balance variables explained vegetation greenness and then used a multi-model ensemble of climate and water balance models to forecast monthly NDVI for three holdout years. Results Water balance variables explained vegetation greenness to a greater degree than climate variables for most growing season months. Seasonally important variables included measures of antecedent water input and storage in spring, switching to indicators of drought, input or use in summer, followed by antecedent moisture availability in autumn. In spite of similar climates, there was evidence the grazed grassland showed a response to drying conditions 1 mo sooner than the ungrazed grassland. Lead times were generally short early in the growing season and antecedent window durations increased from 3 mo early in the growing season to 1 yr or more as the growing season progressed. Forecast accuracy for three holdout years using a multi-model ensemble of climate and water balance variables outperformed forecasts made with a naïve NDVI climatology. Conclusions We determined the influence of climate and water balance on vegetation at a fine temporal scale, which presents an opportunity to forecast vegetation

Homogenization of the soil surface following fire in semiarid grasslands

Science.gov (United States)

Carleton S. White

2011-01-01

Semiarid grasslands accumulate soil beneath plant "islands" that are raised above bare interspaces. This fine-scale variation in microtopographic relief is plant-induced and is increased with shrub establishment. Research found that fire-induced water repellency enhanced local-scale soil erosion that reduced variation in microtopographic relief, suggesting...

First record of Chantransia macrospora Wood, 1887 (Batrachospermales, Rhodophyta in semi-arid northeastern Brazil

Directory of Open Access Journals (Sweden)

Janiele França Vasconcelos

2014-08-01

Full Text Available http://dx.doi.org/10.5007/2175-7925.2014v27n4p129 This study presents the first record of Chantransia macrospora in the state of Rio Grande do Norte, in the semi-arid region of northeastern Brazil. Analyses of periphytic algae revealed C. macrospora individuals associated in particular with shells of Melanoides tuberculatus, a non-native species, suggesting that C. macrospora have been introduced into systems associated with the gastropods. In this context, new records of C. macrospora are still expected for the Brazilian semi-arid region in the next years.

Effect of nitrogen on partitioning and yield in grain sorghum under differing environmental conditions in the semi-arid tropics

International Nuclear Information System (INIS)

Muchow, R.C.

1990-01-01

The effect of nitrogen (N) supply on the relative contributions of pre- and post-anthesis net above-ground biomass accumulation and N uptake to grain-yield and grain N concentration was examined in four contrasting environments in semi-arid tropical Australia. The four environments had different radiation and temperature regimes, and varying levels of water deficit. The grain-yield achieved under high N supply ranged from 156 to 621 g m −2 (on an oven-dry basis). In all but the lowest-yielding environment, there was substantial biomass accumulation during grain-filling and it increased with N application. Only in the lowest-yielding environment was there substantial mobilization of pre-anthesis biomass to grain. Biomass mobilization was not affected by N application. Nitrogen uptake during grain-filling was unresponsive to N application, and was small relative to total N uptake during the life-cycle. Mobilization of pre-anthesis N to the grain was much more significant. In all but the lowest-yielding environment, N mobilization increased with N application. Grain-yield under variable N supply and differing environmental conditions was not dependent on the proportions of pre- and post-anthesis growth. However, grain-yield was proportional to biomass at maturity over the entire yield range in this study and variability in biomass accounted for 95% of the variance in grain-yield. Similarly, grain N concentration was not related to the proportions of pre- and post-anthesis N uptake, but variability in total N uptake accounted for 92% of the variance in grain N accumulation. Consequently, there was no differential effect of N supply or environmental factors on yield physiology that could not be explained by their effect on biomass and N uptake. (author)

Fun in the Sun: Effects of Solar Radiation on Carbon Cycling in Semiarid Ecosystems of South America

Science.gov (United States)

Austin, A.; Berenstecher, P.; Méndez, M. S.; Ballare, C. L.

2016-12-01

Plant litter decomposition is an essential process in the first stages of carbon turnover in terrestrial ecosystems, and together with soil microbial biomass, provide the principal inputs of carbon for the formation of soil organic matter. Photodegradation, the photochemical mineralization of organic matter due to exposure to solar radiation, has been recently identified as a mechanism for previously unexplained high rates of litter mass loss in arid and semiarid ecosystems. Nevertheless, the indirect effects of photodegradation and wavelength dependence on biotic stimulation or inhibition of carbon turnover have been debated in recent studies. In controlled conditions of a two-phase experiment, we demonstrated that in a wide range of plant species, previous exposure to solar radiation, and visible light in particular, enhanced subsequent biotic degradation of leaf litter. Field studies in Patagonian woodland ecosystems confirm the importance of biotic facilitation on litter decomposition, which appears to have larger stimulatory effects than those observed in controlled conditions. Litter decomposition of previously exposed grass litter decomposed more than two times faster than unexposed litter in a one year field experiment, while strong seasonal effects of direct photodegradation and biotic facilitation of solar radiation were observed in a second experiment with changes in solar irradiance using attenuation filters. The generalized positive effect of solar radiation exposure on subsequent microbial activity appears to be mediated by increased accessibility to cell wall polysaccharides, which is consistent in both field and controlled condition experiments. These results suggests that photodegradation is quantitatively important in determining rates of mass loss and nutrient release through its impacts on biotic decomposition, which has implications for the potential alterations in carbon turnover in semiarid ecosystems to predicted climate or land-use change.

Geochemical Weathering Increases Lead Bioaccessibility in Semi-Arid Mine Tailings

Science.gov (United States)

Hayes, Sarah M.; Webb, Sam M.; Bargar, John R.; O'Day, Peggy A.; Maier, Raina M.; Chorover, Jon

2012-01-01

Mine tailings can host elevated concentrations of toxic metal(loid)s that represent a significant hazard to surrounding communities and ecosystems. Eolian transport, capable of translocating small (micrometer-sized) particles, can be the dominant mechanism of toxic metal dispersion in arid or semi-arid landscapes. Human exposure to metals can then occur via direct inhalation or ingestion of particulates. The fact that measured doses of total lead (Pb) in geomedia correlate poorly with blood Pb levels highlights a need to better resolve the precise distribution of molecularly-speciated metal-bearing phases in the complex particle mixtures. Species distribution controls bioaccessibility, thereby directly impacting health risk. This study seeks to correlate Pb-containing particle size and mineral composition with lability and bioaccessibility in mine tailings subjected to weathering in a semi-arid environment. We employed X-ray absorption spectroscopy (XAS) and X-ray fluorescence (XRF), coupled with sequential chemical extractions, to study Pb speciation in tailings from the semi-arid Arizona Klondyke State Superfund Site. Representative samples ranging in pH from 2.6 to 5.4 were selected for in-depth study of Pb solid-phase speciation. The principle lead-bearing phase was plumbojarosite (PbFe6(SO4)4(OH)12), but anglesite (PbSO4) and iron oxide-sorbed Pb were also observed. Anglesite, the most bioavailable mineral species of lead identified in this study, was enriched in surficial tailings samples, where Pb concentrations in the clay size fraction were 2–3 times higher by mass relative to bulk. A mobile and bioaccessible Pb phase accumulates in surficial tailings, with a corresponding increase in risk of human exposure to atmospheric particles. PMID:22553941

Climate change in semi-arid Malawi: Perceptions, adaptation strategies and water governance

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Miriam K. Joshua

2016-04-01

Full Text Available Climate change and variability are a threat to sustainable agricultural production in semi-arid areas of Malawi. Overdependence on subsistence rain-fed agriculture in these areas calls for the identification of sustainable adaptation strategies. A study was therefore conducted in Chikwawa, a semi-arid district in southern Malawi, to: (1 assess community’s perception of a changing climate against empirical evidence, (2 determine their local adaptive measures, (3 evaluate the potential of irrigated agriculture as an adaptive measure in household food security and (4 challenges over access to available water resources. The study employed focus group discussions and key informant interviews to assess people’s perceptions of climate change and variability and their desired interventions. To validate the people’s perceptions, rainfall and temperature data for the period 1960–2010 were analysed. A participatory complete randomised experimental design in both rain-fed and dry season–irrigated conditions was conducted to assess a maize cropping system that would improve adaptation. The study established persistent declining yields from rain-fed production in part because of perennial rainfall failure. In response, the community has shifted its focus to irrigation as an adaptation strategy, which has in turn triggered water conflicts in the community over the control of the resource. Water legislation however fails to adequately provide for rules governing sharing of water resources between various stakeholders. This article therefore recommends development of an appropriate institutional framework that forms a strong basis for equitable distribution of water for irrigation in areas most vulnerable to extreme climate events – including droughts and floods. Keywords: Food Security; Climate Change and Variability; Rainfall Variability; Irrigation; Water Resources; Governance Crisis

BVOCs emission in a semi-arid grassland under climate warming and nitrogen deposition

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H. J. Wang

2012-04-01

Full Text Available Biogenic volatile organic compounds (BVOCs profoundly affect atmospheric chemistry and ecosystem functioning. BVOCs emission and their responses to global change are still unclear in grasslands, which cover one quarter of the Earth's land surface and are currently undergoing the largest changes. Over two growing seasons, we conducted a field experiment in a semi-arid grassland (Inner Mongolia, China to examine the emission and the responses of BVOCs emissions to warming and nitrogen deposition. The natural emission rate (NER of monoterpene (dominant BVOCs here is 107 ± 16 μg m⁻² h⁻¹ in drought 2007, and 266 ± 53 μg m⁻² h⁻¹ in wet 2008, respectively. Warming decreased the standard emission factor (SEF by 24% in 2007, while it increased by 43% in 2008. The exacerbated soil moisture loss caused by warming in dry season might be responsible for the decrease of SEF in 2007. A possible threshold of soil moisture (8.2% (v/v, which controls the direction of warming effects on monoterpene emission, existed in the semiarid grassland. Nitrogen deposition decreased the coverage of Artemisia frigida and hence reduced the NER by 24% across the two growing seasons. These results suggest that the grasslands dominated by the extended Artemisia frigida are an important source for BVOCs, while the responses of their emissions to global changes are more uncertain since they depend on multifactorial in-situ conditions.

Vertical and temporal variation in phytoplankton assemblages correlated with environmental conditions in the Mundaú reservoir, semi-arid northeastern Brazil

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GAST LIRA

Full Text Available The goal of this study was to analyse the vertical structure of the phytoplankton community at the Mundaú reservoir, located in the semi-arid region of northeastern Brazil, and to correlate it to environmental conditions over two distinct seasons, dry and rainy. Samples were collected bimonthly at eight depths in the dry and rainy season for analyses of the physical and chemical variables of the water, as well as density, abundance, dominance, species diversity index and equitability of the community. Analysis of variance (ANOVA-two way was used to analyse the vertical and seasonal differences, and Canonical Correspondence Analysis (CCA was used to assess associations between phytoplankton and environmental variables Cylindrospermopsis raciborskii (Woloszynska Seenaya and Subba Raju was the only dominant species and Geitlerinema amphibium (C. Agardh Anagnostidis, Merismopedia punctata Meyen and Synedra rumpens Kützing. Others six taxa were abundant in at least one of the samples. Distinct vertical distribution patterns were observed for the abundant taxa between depths and seasons. The cyanobacteria, with the exception of C. raciborskii, showed similar seasonal patterns, with higher densities in the dry season. The CCA showed a strong correlation between the density of the phytoplanktonic species and abiotic variables. The vertical changes in abundant taxa revealed distinct patterns regulated by the variation in the environmental factors that were directly linked to seasonality, with the success of one or more species being dependent on their life strategies and ecological needs. The present study restates the importance of environmental and seasonal factors for phytoplankton composition and distribution in a freshwater tropical reservoir through a vertical gradient.

Beekeeping technology adoption in arid and semi-arid lands of ...

African Journals Online (AJOL)

This study was conducted in Kibwezi Sub-County, south eastern Kenya. This is a typical semiarid area and beekeeping is a major economic activity. Although various beekeeping technologies have been available in the study area for many decades, information on the effect of these technologies on the production levels of ...

REPRODUCTIVE ADAPTATIONS OF THE GREEN IGUANA ON A SEMIARID ISLAND

NARCIS (Netherlands)

LICHTENBELT, WDV; ALBERS, KB

1993-01-01

Reproductive cycle and clutch size were studied in the green iguana (Iguana iguana) on the semiarid Caribbean island of Curacao. The reproductive cycle is correlated with seasonality in rainfall. Mating is in the first half of the dry season, egg laying in the second part of the dry season, and

Amphibian and reptile biodiversity in the semi-arid region of the municipality of Nopala de Villagrán, Hidalgo, Mexico.

Science.gov (United States)

Roth-Monzón, Andrea J; Mendoza-Hernández, Andrés Alberto; Flores-Villela, Oscar

2018-01-01

Current global changes are putting both biodiversity and the processes that depend on it at risk. This is especially true for semi-arid regions and the flagship groups that inhabit them, such as amphibians and reptiles. Semi-arid regions are often thought to have lower biodiversity and thus have been overlooked, resulting in the underestimation of their biological richness. Therefore, the aim of this study was to conduct an inventory of amphibians and reptiles in the semi-arid municipality of Nopala de Villagrán, Mexico, and analyze its biodiversity in relation to the seasons, vegetation and microhabitat. During a year of fieldwork, we found 24 species in the area, most of them of low abundance, and one of which was recorded for the first time for the state of Hidalgo. We documented five amphibian species and 19 reptile species. We also found that observed species richness was higher in the rainy season and in xeric scrub vegetation, although only the season differences were significant according to rarefaction curves. Our findings highlight the importance of seasonality and vegetation type for the species that inhabit this semi-arid region. This study broadens our understanding of the importance of semi-arid regions and, by extension, that of other areas with similar characteristics.

Amphibian and reptile biodiversity in the semi-arid region of the municipality of Nopala de Villagrán, Hidalgo, Mexico

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Andrea J. Roth-Monzón

2018-01-01

Full Text Available Current global changes are putting both biodiversity and the processes that depend on it at risk. This is especially true for semi-arid regions and the flagship groups that inhabit them, such as amphibians and reptiles. Semi-arid regions are often thought to have lower biodiversity and thus have been overlooked, resulting in the underestimation of their biological richness. Therefore, the aim of this study was to conduct an inventory of amphibians and reptiles in the semi-arid municipality of Nopala de Villagrán, Mexico, and analyze its biodiversity in relation to the seasons, vegetation and microhabitat. During a year of fieldwork, we found 24 species in the area, most of them of low abundance, and one of which was recorded for the first time for the state of Hidalgo. We documented five amphibian species and 19 reptile species. We also found that observed species richness was higher in the rainy season and in xeric scrub vegetation, although only the season differences were significant according to rarefaction curves. Our findings highlight the importance of seasonality and vegetation type for the species that inhabit this semi-arid region. This study broadens our understanding of the importance of semi-arid regions and, by extension, that of other areas with similar characteristics.

Amphibian and reptile biodiversity in the semi-arid region of the municipality of Nopala de Villagrán, Hidalgo, Mexico

Science.gov (United States)

Mendoza-Hernández, Andrés Alberto; Flores-Villela, Oscar

2018-01-01

Current global changes are putting both biodiversity and the processes that depend on it at risk. This is especially true for semi-arid regions and the flagship groups that inhabit them, such as amphibians and reptiles. Semi-arid regions are often thought to have lower biodiversity and thus have been overlooked, resulting in the underestimation of their biological richness. Therefore, the aim of this study was to conduct an inventory of amphibians and reptiles in the semi-arid municipality of Nopala de Villagrán, Mexico, and analyze its biodiversity in relation to the seasons, vegetation and microhabitat. During a year of fieldwork, we found 24 species in the area, most of them of low abundance, and one of which was recorded for the first time for the state of Hidalgo. We documented five amphibian species and 19 reptile species. We also found that observed species richness was higher in the rainy season and in xeric scrub vegetation, although only the season differences were significant according to rarefaction curves. Our findings highlight the importance of seasonality and vegetation type for the species that inhabit this semi-arid region. This study broadens our understanding of the importance of semi-arid regions and, by extension, that of other areas with similar characteristics. PMID:29312825

Surficial weathering of iron sulfide mine tailings under semi-arid climate.

Science.gov (United States)

Hayes, Sarah M; Root, Robert A; Perdrial, Nicolas; Maier, Raina; Chorover, Jon

2014-09-15

Mine wastes introduce anthropogenic weathering profiles to the critical zone that often remain unvegetated for decades after mining cessation. As such, they are vulnerable to wind and water dispersion of particulate matter to adjacent ecosystems and residential communities. In sulfide-rich ore tailings, propagation to depth of the oxidative weathering front controls the depth-variation in speciation of major and trace elements. Despite the prevalence of surficial mine waste deposits in arid regions of the globe, few prior studies have been conducted to resolve the near-surface profile of sulfide ore tailings weathered under semi-arid climate. We investigated relations between gossan oxidative reaction-front propagation and the molecular speciation of iron and sulfur in tailings subjected to weathering under semi-arid climate at an EPA Superfund Site in semi-arid central Arizona (USA). Here we report a multi-method data set combining wet chemical and synchrotron-based X-ray diffraction (XRD) and X-ray absorption near-edge spectroscopy (XANES) methods to resolve the tight coupling of iron (Fe) and sulfur (S) geochemical changes in the top 2 m of tailings. Despite nearly invariant Fe and S concentration with depth (130-140 and 100-120 g kg -1 , respectively), a sharp redox gradient and distinct morphological change was observed within the top 0.5 m, associated with a progressive oxidative alteration of ferrous sulfides to (oxyhydr)oxides and (hydroxy)sulfates. Transformation is nearly complete in surficial samples. Trends in molecular-scale alteration were co-located with a decrease in pH from 7.3 to 2.3, and shifts in Fe and S lability as measured via chemical extraction. Initial weathering products, ferrihydrite and gypsum, transform to schwertmannite, then jarosite-group minerals with an accompanying decrease in pH. Interestingly, thermodynamically stable phases such as goethite and hematite were not detected in any samples, but ferrihydrite was observed even in

IMPACT OF ZOOTECHNICAL PARAMETERS ON CELL QUALITY OF CATTLE MILK (SEMI-ARID COSTAL TUNISIA

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R. HAJ MBAREK

2015-09-01

Full Text Available The work was realized on a sample of 50 cattle herds, conducted in aboveground, in a coastal area of the semi-arid Tunisia, by using investigation related to cows and their breeding and milking conditions as well as despoliation in milk control data. Analysis of the data relating to the parameters of udder conformation and cow cleanliness revealed that “Udder depth” settings “Udder cleanliness” have been shown to affect the ICC and are considered factors risk of bovine mastitis. The study of breeding and milking conditions highlight some significant factors on changes on the variation of cell counts and the probability of the spread of mastitis, especially the "No disinfection of teat." The level of housing, the analysis revealed that the use of a litter reduced to half the average of ICC which proved highly related to the cleanliness of both the sleeping area as the udder.

Insolation driven biomagnetic response to the Holocene Warm Period in semi-arid East Asia

Science.gov (United States)

Liu, Suzhen; Deng, Chenglong; Xiao, Jule; Li, Jinhua; Paterson, Greig A.; Chang, Liao; Yi, Liang; Qin, Huafeng; Pan, Yongxin; Zhu, Rixiang

2015-01-01

The Holocene Warm Period (HWP) provides valuable insights into the climate system and biotic responses to environmental variability and thus serves as an excellent analogue for future global climate changes. Here we document, for the first time, that warm and wet HWP conditions were highly favourable for magnetofossil proliferation in the semi-arid Asian interior. The pronounced increase of magnetofossil concentrations at ~9.8 ka and decrease at ~5.9 ka in Dali Lake coincided respectively with the onset and termination of the HWP, and are respectively linked to increased nutrient supply due to postglacial warming and poor nutrition due to drying at ~6 ka in the Asian interior. The two-stage transition at ~7.7 ka correlates well with increased organic carbon in middle HWP and suggests that improved climate conditions, leading to high quality nutrient influx, fostered magnetofossil proliferation. Our findings represent an excellent lake record in which magnetofossil abundance is, through nutrient availability, controlled by insolation driven climate changes.

Field and experimental symptomless infections support wandering donkeys as healthy carriers of Trypanosoma vivax in the Brazilian Semiarid, a region of outbreaks of high mortality in cattle and sheep.

Science.gov (United States)

Rodrigues, Carla M F; Batista, Jael S; Lima, Joseney M; Freitas, Francisco J C; Barros, Isabella O; Garcia, Herakles A; Rodrigues, Adriana C; Camargo, Erney P; Teixeira, Marta M G

2015-10-28

The Brazilian Semiarid is the home of the largest herd of donkeys in South America and of outbreaks of Trypanosoma vivax infection of high mortality in dairy cattle and sheep. For a comprehensive understanding of the underlying mechanisms of these outbreaks and epidemiological role of donkeys, we surveyed for T. vivax in wandering donkeys and follow the experimental infection of donkeys and sheep with a highly virulent isolate from the Semiarid. Blood samples from 180 randomly selected wandering donkeys from the Brazilian Semiarid region were employed for PCV and parasitemia assessments and tested using the T. vivax-specific TviCATL-PCR assay. PCR-amplifed Cathepsin L (CATL) sequences were employed for genotyping and phylogenetic analysis. Four wandering donkeys were experimentally infected with a T. vivax isolate obtained during an outbreak of high mortality in the Semiarid; the control group consisted of two non-inoculated donkeys. We detected T. vivax in 30 of 180 wandering donkeys (16.6 %) using TviCATL-PCR. The prevalence was higher during the dry (15.5 %) than the wet season (1.1 %) and more females (23.1 %) than males (8.9 %) were infected. All the PCR-positive donkeys lacked patent parasitemia and showed normal values of body condition score (BCS) and packed cell volume (PCV). To evaluate the probable tolerance of donkeys to T. vivax, we inoculated five donkeys with a highly virulent isolate (TviBrRp) from the Semiarid. All inoculated donkeys became PCR-positive, but their parasitemia was always subpatent. A control goat inoculated with TviBrRp showed increasing parasitemia concurrently with fever, declining PCV, tachycardia, mucous membrane pallor, enlarged lymph nodes and anorexia. None of these signs were observed in donkeys. However, T. vivax from wandering donkeys shared identical or highly similar genotypes (identified by Cathepsin L sequences) with isolates from cattle and sheep outbreaks of acute disease in the Semiarid. This is the first

Evaporative Cooler Use Influences Temporal Indoor Relative Humidity but Not Dust Mite Allergen Levels in Homes in a Semi-Arid Climate.

Science.gov (United States)

Johnston, James D; Tuttle, Steven C; Nelson, Morgan C; Bradshaw, Rebecca K; Hoybjerg, Taylor G; Johnson, Julene B; Kruman, Bryce A; Orton, Taylor S; Cook, Ryan B; Eggett, Dennis L; Weber, K Scott

2016-01-01

Concerns about energy consumption and climate change make residential evaporative coolers a popular alternative to central air conditioning in arid and semi-arid climates. However, evaporative coolers have been shown to significantly increase indoor relative humidity and dust mite allergen levels in some studies, while showing no association in other studies. Improved measurement of temporal fluctuations in indoor relative humidity may help identify factors that promote mite growth in homes in dry climates. Dust samples and continuous indoor relative humidity measurements were collected from homes with central air conditioning and homes with evaporative coolers in Utah. Samples were collected over two seasons, winter/spring (Jan-Apr) and summer (July-Sept), 2014. Dust samples were analyzed for Der p 1 and Der f 1 using a two-site monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA) analysis. Housing characteristics including age of home, occupant density, and age of mattresses, furniture, and carpeting were also measured. Positive Der p 1 or Der f 1 samples were found in 25.0% of the homes and there was no difference in mean allergen levels by type of air conditioning. Indoor relative humidity was significantly higher in homes with evaporative coolers compared to those with central air conditioning during the summer. Homes with evaporative coolers also spent significantly more time during summer above 55.0% and 65.0% relative humidity compared to central air homes, but not above 75.0%. Findings from this study suggest that increased humidity from evaporative coolers may not be sufficient to exceed the critical equilibrium humidity or maintain humidity excursions for sufficient duration in relatively larger single-family homes in semi-arid climates to support mite growth and reproduction.

Soil quality improvement for crop production in semi-arid West Africa

NARCIS (Netherlands)

Ouédraogo, E.

2004-01-01

Soil quality maintenance and crop production improvement in semi-arid West Africa require appropriate cropping technologies, which are ecologically sound and economically viable. Thus, on-farm and on-station experiments have been carried out on the central plateau and in the south of Burkina Faso

Dynamics in carbon exchange fluxes for a grazed semi-arid savanna ecosystem in West Africa

DEFF Research Database (Denmark)

Tagesson, Torbern; Fensholt, Rasmus; Cropley, Ford

2015-01-01

variable in scaling carbon fluxes from ground observations using earth observation data. The net ecosystem exchange of carbon dioxide (NEE) 2010-2013 was measured using the eddy covariance technique at a grazed semi-arid savanna site in Senegal, West Africa. Night-time NEE was not related to temperature......-arid savanna sites; half-hourly GPP and Reco peaked at -43μmol CO2m-2s-1 and 20μmol CO2m-2s-1, and daily GPP and Reco peaked at -15gCm-2 and 12gCm-2, respectively. Possible explanations for the high CO2 fluxes are a high fraction of C4 species, alleviated water stress conditions, and a strong grazing pressure...

Soil Chemistry after Irrigation with Treated Wastewater in Semiarid Climate

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Pedro Carlos Pacheco de Oliveira

2016-01-01

Full Text Available ABSTRACT Soil irrigation using treated wastewater in the Brazilian semiarid region is a promising practice as this area currently faces water scarcity and pollution of water resources by domestic sewage. The aim of this study was to evaluate the use of treated wastewater in drip irrigation and its effect on the chemistry of soil cultivated with squash (Cucurbita maxima Duch. Coroa IAC and to verify whether there was an increase in soil salinity under a semiarid climate. The experiment was conducted for 123 days on a farm close to the sewage treatment plant, in a randomized block design with five treatments and four replications. The treatments consisted of two irrigation water depths (100 and 150 % of the evapotranspiration, two applications of gypsum to attenuate wastewater sodicity (0 and 5.51 g per plant, and a control treatment with no application of wastewater or gypsum. During the experiment, treated wastewater and soil gravitational water, at a depth of 0.40 m, were collected for measurement of Na+, K+, Ca2+, Mg2+, NO−3, NH4+, Cl− , alkalinity, electrical conductivity, pH and sodium adsorption ratio. At the end of the experiment, soil samples were collected at depths of 0.00-0.10, 0.10-0.20, and 0.20-0.40 m; and pH, total N, organic C, exchangeable cations and electrical conductivity of the saturation extract (CEs were analyzed. Besides an increase in pH and a reduction in total N, the irrigation with wastewater reduces soil salinity of the naturally salt-rich soils of the semiarid climate. It also led to soil sodification, in spite of the added gypsum, which indicates that irrigation with wastewater might require the addition of greater quantities of gypsum to prevent physical degradation of the soil.

Catchment management in semi-arid area of central South Africa ...

African Journals Online (AJOL)

This accentuates the need for wise decisions by catchment management agencies (CMAs), especially in water-scarce semi-arid areas. ... A financial analysis also showed that gross margin of option, expressed as R/ m3 of rainwater utilised, was estimated to be between 0.0234 to 0.0254 under Option 1 and 0.0354 for ...

Iron and sulfur geochemistry in semi-arid mangrove soils (Ceará, Brazil) in relation to seasonal changes and shrimp farming effluents.

Science.gov (United States)

Nóbrega, G N; Ferreira, T O; Romero, R E; Marques, A G B; Otero, X L

2013-09-01

Iron and sulfur are key elements in the biogeochemistry of estuarine soils, in which Fe and sulfate reduction (SR) pathways are important for organic matter decomposition. In the semi-arid coast of NE Brazil, mangroves are characterized by large seasonal variations in weather and the presence of numerous shrimp farms. The objective was to determine the impacts of shrimp farm effluents on iron and sulfur geochemistry in mangrove soils under the semi-arid climate of NE Brazil. A seasonal study was made of two mangrove forest soils (SF, a mangrove forest that directly receives wastewater from shrimp ponds and CS, a control site). Pyrite Fe, oxyhydroxides Fe, acid volatile sulfide, degree of pyritization (DOP), pH, Eh, total organic carbon (TOC) and total S were determined. There was a clear decrease in pyritic Fe and DOP in the SF soils, which may be related to the anaerobic oxidation of pyrite coupled with nitrate reduction, or to the dominance of denitrification over SR. Lower TOC contents in the SF site suggest that below ground decomposition increased in response to eutrophication. The seasonal variations led to important changes in the semi-arid mangrove soils. During the dry period, both soils experienced oxidizing conditions with remarkable loss of reduced and oxidized forms of Fe, which may have important environmental implications as Fe is biolimiting for marine primary production. The data show that both factors (seasonal weather variations and shrimp effluents) play important roles in the geochemical processes that occur in these soils and, thus, may affect their functioning and maintenance.

Nitrogen deposition alters nitrogen cycling and reduces soil carbon content in low-productivity semiarid Mediterranean ecosystems

International Nuclear Information System (INIS)

Ochoa-Hueso, Raúl; Maestre, Fernando T.; Ríos, Asunción de los; Valea, Sergio; Theobald, Mark R.; Vivanco, Marta G.; Manrique, Esteban; Bowker, Mathew A.

2013-01-01

Anthropogenic N deposition poses a threat to European Mediterranean ecosystems. We combined data from an extant N deposition gradient (4.3–7.3 kg N ha −1 yr −1 ) from semiarid areas of Spain and a field experiment in central Spain to evaluate N deposition effects on soil fertility, function and cyanobacteria community. Soil organic N did not increase along the extant gradient. Nitrogen fixation decreased along existing and experimental N deposition gradients, a result possibly related to compositional shifts in soil cyanobacteria community. Net ammonification and nitrification (which dominated N-mineralization) were reduced and increased, respectively, by N fertilization, suggesting alterations in the N cycle. Soil organic C content, C:N ratios and the activity of β-glucosidase decreased along the extant gradient in most locations. Our results suggest that semiarid soils in low-productivity sites are unable to store additional N inputs, and that are also unable to mitigate increasing C emissions when experiencing increased N deposition. -- Highlights: •Soil organic N does not increase along the extant N deposition gradient. •Reduced N fixation is related to compositional shifts in soil cyanobacteria community. •Nitrogen cycling is altered by simulated N deposition. •Soil organic C content decrease along the extant N deposition gradient. •Semiarid soils are unable to mitigate CO 2 emissions after increased N deposition. -- N deposition alters N cycling and reduces soil C content in semiarid Mediterranean ecosystems

Vegetation monitoring on semi-arid grasslands unglazed by domestic livestock

Science.gov (United States)

Linda Kennedy; Dan Robinett

2013-01-01

The Research Ranch is an 8000-acre sanctuary and research facility in the semi-arid grasslands of southeastern Arizona, USA. Cattle were removed from the property in 1968 to provide a reference area by which various land uses, such as grazing and exurbanization, could be evaluated. Vegetation transects were established in 2000 and 2003 on several ecological sites in...

Human health risk assessment of lead from mining activities at semi-arid locations in the context of total lead exposure.

Science.gov (United States)

Zheng, Jiajia; Huynh, Trang; Gasparon, Massimo; Ng, Jack; Noller, Barry

2013-12-01

Lead from historical mining and mineral processing activities may pose potential human health risks if materials with high concentrations of bioavailable lead minerals are released to the environment. Since the Joint Expert Committee on Food Additives of Food and Agriculture Organization/World Health Organization withdrew the Provisional Tolerable Weekly Intake of lead in 2011, an alternative method was required for lead exposure assessment. This study evaluated the potential lead hazard to young children (0-7 years) from a historical mining location at a semi-arid area using the U.S. EPA Integrated Exposure Uptake Biokinetic (IEUBK) Model, with selected site-specific input data. This study assessed lead exposure via the inhalation pathway for children living in a location affected by lead mining activities and with specific reference to semi-arid conditions and made comparison with the ingestion pathway by using the physiologically based extraction test for gastro-intestinal simulation. Sensitivity analysis for major IEUBK input parameters was conducted. Three groups of input parameters were classified according to the results of predicted blood concentrations. The modelled lead absorption attributed to the inhalation route was lower than 2 % (mean ± SE, 0.9 % ± 0.1 %) of all lead intake routes and was demonstrated as a less significant exposure pathway to children's blood, compared with ingestion. Whilst dermal exposure was negligible, diet and ingestion of soil and dust were the dominant parameters in terms of children's blood lead prediction. The exposure assessment identified the changing role of dietary intake when house lead loadings varied. Recommendations were also made to conduct comprehensive site-specific human health risk assessment in future studies of lead exposure under a semi-arid climate.

Consistency between Sweat Rate and Wet Bulb Globe Temperature for the Assessment of Heat Stress of People Working Outdoor in Arid and Semi-arid Regions

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Hamidreza Heidari

2018-01-01

Full Text Available Background: Heat stress is common among workers in arid and semi-arid areas. In order to take every preventive measure to protect exposed workers against heat-related disorders, it is crucial to choose an appropriate index that accurately relates environmental parameters to physiological responses. Objective: To investigate the consistency between 2 heat stress and strain indices, ie, sweat rate and wet bulb globe temperature (WBGT, for the assessment of heat stress of people working outdoor in arid and semi-arid regions in Iran. Methods: During spring and summer, 136 randomly selected outdoor workers were enrolled in this study. Using a defined protocol, the sweat rate of these workers was measured 3 times a day. Simultaneously, the environmental parameters including WBGT index were recorded for each working station. Results: The level of agreement between sweat rate and WBGT was poor (κ<0.2. Based on sweat rate, no case exceeding the reference value was observed during the study. WBGT overestimated the heat stress in outdoor workers compared to sweat rate. Conclusion: It seems that the sweat rate standards may need some modifications related to real condition of work in arid and semi-arid regions in Iran. Moreover, it seems that judging workers solely based on monitoring their sweat rate in such regions, can probably result in underestimation of heat stress.

Effect of Residue Nitrogen Concentration and Time Duration on Carbon Mineralization Rate of Alfalfa Residues in Regions with Different Climatic Conditions

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saeid shafiei

2017-08-01

Full Text Available Introduction Various factors like climatic conditions, vegetation, soil properties, topography, time, plant residue quality and crop management strategies affect the decomposition rate of organic carbon (OC and its residence time in soil. Plant residue management concerns nutrients recycling, carbon recycling in ecosystems and the increasing CO2 concentration in the atmosphere. Plant residue decomposition is a fundamental process in recycling of organic matter and elements in most ecosystems. Soil management, particularly plant residue management, changes soil organic matter both qualitatively and quantitatively. Soil respiration and carbon loss are affected by soil temperature, soil moisture, air temperature, solar radiation and precipitation. In natural agro-ecosystems, residue contains different concentrations of nitrogen. It is important to understand the rate and processes involved in plant residue decomposition, as these residues continue to be added to the soil under different weather conditions, especially in arid and semi-arid climates. Material and methods Organic carbon mineralization of alfalfa residue with different nitrogen concentrations was assessed in different climatic conditions using split-plot experiments over time and the effects of climate was determined using composite analysis. The climatic conditions were classified as warm-arid (Jiroft, temperate arid (Narab and cold semi-arid (Sardouiyeh using cluster analysis and the nitrogen (N concentrations of alfalfa residue were low, medium and high. The alfalfa residue incubated for four different time periods (2, 4, 6 and 8 months. The dynamics of organic carbon in different regions measured using litter bags (20×10 cm containing 20 g alfalfa residue of 2-10 mm length which were placed on the soil surface. Results and discussion The results of this study showed that in a warm-arid (Jiroft, carbon loss and the carbon decomposition rate constant were low in a cold semi-arid

Performance of sorghum cultivars for biomass quality and biomethane yield grown in semi-arid area of Pakistan.

Science.gov (United States)

Hassan, Muhammad Umair; Chattha, Muhammad Umer; Mahmood, Athar; Sahi, Shahbaz Talib

2018-05-01

Biomass is a promising renewable energy source and its significance is escalating in the context of climate change and depletion of fossil foils. This study was conducted for two consecutive years 2016 and 2017, using five sorghum cultivars, i.e., JS-263, Jawar-2011, Hagari, JS-2002, and YS-2016, in order to determine the best cultivars in terms of dry matter yield, chemical composition, and biomethane yield grown under semi-arid conditions in Pakistan. The results revealed that sorghum cultivars responded differently in terms of growth, biomass yield, chemical composition, and methane yield. Cultivars Jawar-2011 produced maximum leaf area index, leaf area duration, crop growth rate, plant height, and leaves per plant, however, they were comparable with Sorghum-2016, whereas cultivar JS-2002 performed poorly among the tested cultivars. Similarly, cultivar Jawar-2011 produced maximum dry matter yield (16.37 t ha -1 ) similar to that of YS-2016, further cultivar JS-2002 performed poorly and gave lower dry matter yield (12.87 t ha -1 ). The maximum protein concentration (10.95), neutral detergent fibers (61.20), and lignin contents (5.55) found in Jawar-2011 were comparable with those in YS-2016, while the lowest neutral detergent fiber and lignin contents were found in JS-2002. Although JS-2002 produced the highest specific methane yield per kilogram of volatile solids, it was overcompensated by Jawar-2011 owing to higher dry matter yield per hectare. These results suggested that cultivar Jawar-2011 can be grown successfully in semi-arid conditions of Pakistan in order to get good biomass yield along with higher methane yield.

Semi-arid development: competitiveness factors in biodiesel productive chain

OpenAIRE

Breno Barros Telles do Carmo; Dmontier Pinheiro Aragão; Heráclito Lopes Jaguaribe Pontes; Bruno Magalhães Ribeiro; Marcos Ronaldo Albertin

2009-01-01

The new global market competitiveness considerer the competition between productive chains (PC) or supply chains, not just between enterprises. In this case, it can be observed collaboration and cooperation enterprises that dispute with others productives chain. The PC competitiveness can be impaired if is subject by inhibitors factors, that can impairer the performance. This paper analyses these competitiveness factors inhibitors in biodiesel productive chain (CPB) in semi-arid area: exporte...

Soil moisture prediction to support management in semiarid wetlands during drying episodes

NARCIS (Netherlands)

Aguilera, Héctor; Moreno, Luis; Wesseling, Jan G.; Jiménez-Hernández, María E.; Castaño, Silvino

2016-01-01

Wetlands supported by groundwater in semiarid regions are extremely vulnerable to the impacts of droughts, particularly anthropized systems. During drying periods, soil water content arises as the controlling factor for environmental and ecological disturbances such as the spread of invasive

Mucorales from the semiarid of Pernambuco, Brazil.

Science.gov (United States)

de Azevedo Santiago, André Luiz Cabral Monteiro; Dos Santos, Paulo Jorge Parreira; Maia, Leonor Costa

2013-01-01

Nineteen taxa of Mucorales, belonging to Absidia, Apophysomyces, Cunninghamella, Fennellomyces, Lichtheimia, Mucor, Mycotypha, Rhizopus and Syncephalastrum were isolated from 36 composite soil samples in three semiarid areas in the State of Pernambuco (Triunfo, Cabrobó and Belém de São Francisco), Northeast Brazil, which are characterized by Caatinga vegetation. Triunfo is preserved, whereas Cabroró and Belém de São Francisco are experiencing low and severe desertification processes, respectively. Mucorales were isolated in Petri dishes in triplicate from 5 mg samples of soil placed on the surface of wheat germ agar plus chloramphenicol and Cercobin [Dimethyl 4,49-(103 phenylene) bis (3-thioallophanate)] medium. The plates were left on a bench at room temperature (28 ± 2 °C) for 72 h of alternating dark and light periods. Absidia cylindrospora presented the highest amount of CFU/g of soil, followed by L. hyalospora, C. phaeospora and C. echinulata var. echinulata. The latter, and R. microsporus var. microsporus, presented the highest frequencies of occurrence. Soils from Triunfo showed higher diversity of Mucorales than the samples from the other areas, although without differing statistically in relation to species richness. The communities of Mucorales from the degraded areas were more similar, while that from the preserved area was quite different. Most of the identified specimens have been commonly isolated from soil in other Brazilian regions, which indicates that they are not endemic of the semiarid. Eleven taxa are registered for the first time in this ecosystem, while F. heterothallicus is reported for the first time in Brazil.

Mucorales from the semiarid of Pernambuco, Brazil

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André Luiz Cabral Monteiro de Azevedo Santiago

2013-01-01

Full Text Available Nineteen taxa of Mucorales, belonging to Absidi, Apophysomyces, Cunninghamella, Fennellomyces, Lichtheimi, Mucor, Mycotypha, Rhizopus and Syncephalastrum were isolated from 36 composite soil samples in three semiarid areas in the State of Pernambuco (Triunfo, Cabrobó and Belém de São Francisco, Northeast Brazil, which are characterized by Caatinga vegetation. Triunfo is preserved, whereas Cabroró and Belém de São Francisco are experiencing low and severe desertification processes, respectively. Mucorales were isolated in Petri dishes in triplicate from 5 mg samples of soil placed on the surface of wheat germ agar plus chloramphenicol and Cercobin [Dimethyl 4,49-(103 phenylene bis (3-thioallophanate] medium. The plates were left on a bench at room temperature (28 ± 2 ºC for 72 h of alternating dark and light periods. Absidia cylindrospora presented the highest amount of CFU/g of soil, followed by L. hyalospor, C. phaeospora and C. echinulata var. echinulata. The latter, and R. microsporus var. microsporus, presented the highest frequencies of occurrence. Soils from Triunfo showed higher diversity of Mucorales than the samples from the other areas, although without differing statistically in relation to species richness. The communities of Mucorales from the degraded areas were more similar, while that from the preserved area was quite different. Most of the identified specimens have been commonly isolated from soil in other Brazilian regions, which indicates that they are not endemic of the semiarid. Eleven taxa are registered for the first time in this ecosystem, while F. heterothallicus is reported for the first time in Brazil.

The electron localization as the information content of the conditional pair density

Energy Technology Data Exchange (ETDEWEB)

Urbina, Andres S.; Torres, F. Javier [Universidad San Francisco de Quito (USFQ), Grupo de Química Computacional y Teórica (QCT-USFQ), Departamento de Química e Ingeniería Química, Diego de Robles y Via Interoceanica, Quito 17-1200-841 (Ecuador); Universidad San Francisco de Quito (USFQ), Instituto de Simulación Computacional (ISC-USFQ), Diego de Robles y Via Interoceanica, Quito 17-1200-841 (Ecuador); Rincon, Luis, E-mail: lrincon@usfq.edu.ec, E-mail: lrincon@ula.ve [Universidad San Francisco de Quito (USFQ), Grupo de Química Computacional y Teórica (QCT-USFQ), Departamento de Química e Ingeniería Química, Diego de Robles y Via Interoceanica, Quito 17-1200-841 (Ecuador); Universidad San Francisco de Quito (USFQ), Instituto de Simulación Computacional (ISC-USFQ), Diego de Robles y Via Interoceanica, Quito 17-1200-841 (Ecuador); Departamento de Química, Facultad de Ciencias, Universidad de Los Andes (ULA), La Hechicera, Mérida-5101 (Venezuela, Bolivarian Republic of)

2016-06-28

In the present work, the information gained by an electron for “knowing” about the position of another electron with the same spin is calculated using the Kullback-Leibler divergence (D{sub KL}) between the same-spin conditional pair probability density and the marginal probability. D{sub KL} is proposed as an electron localization measurement, based on the observation that regions of the space with high information gain can be associated with strong correlated localized electrons. Taking into consideration the scaling of D{sub KL} with the number of σ-spin electrons of a system (N{sup σ}), the quantity χ = (N{sup σ} − 1) D{sub KL}f{sub cut} is introduced as a general descriptor that allows the quantification of the electron localization in the space. f{sub cut} is defined such that it goes smoothly to zero for negligible densities. χ is computed for a selection of atomic and molecular systems in order to test its capability to determine the region in space where electrons are localized. As a general conclusion, χ is able to explain the electron structure of molecules on the basis of chemical grounds with a high degree of success and to produce a clear differentiation of the localization of electrons that can be traced to the fluctuation in the average number of electrons in these regions.

Coprophilous Mucorales (ex Zygomycota from three areas in the semi-arid of Pernambuco, Brazil

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Carlos Alberto Fragoso de Souza

Full Text Available Abstract Mucorales comprises fungi commonly isolated as saprobes from soil, dung, stored grains and plants. Although these fungi have been studied in several countries, there are relatively a few reports of them in semi-arid areas. Therefore, the aims of the present study were to assess and compare the Mucorales communities in dung from different species and breeds of herbivores in the semi-arid of Pernambuco, based on the frequency of occurrence and species richness of these fungi. Samples of dung collected in the cities of Arcoverde, Serra Talhada and Sertânia were incubated in moist chambers in triplicate. Altogether, 24 taxa of Mucorales distributed in the genera Absidia, Circinella, Cunninghamella, Lichtheimia, Mucor, Pilobolus, Rhizopus and Syncephalastrum were identified. The highest species richness was found in sheep excrement. Mucor circinelloides f. griseo-cyanus was the most common taxon, followed by M. ramosissimus. The similarity of the composition of Mucorales species was greatest between the excrements of Guzerá and Sindi breeds (bovine. All mucoralean species isolated are being cited for the first time from animal dung found in Caatinga and a new species of Mucor was recorded. An identification key for species of Mucorales from dung in the semi-arid region of Brazil is provided.

Characterisation of rainfall at a semi-arid ecotope in the Limpopo ...

African Journals Online (AJOL)

Detailed knowledge of rainfall regime is an important prerequisite for agricultural planning. Despite the importance of rain-fed agriculture to food security in the semi-arid regions of South Africa, studies to understand the spatial and temporal variability of rainfall are not widely documented. Twenty-three years (1983 to 2005) ...

Electronic apex locator: A comprehensive literature review — Part II: Effect of different clinical and technical conditions on electronic apex locator′s accuracy

Directory of Open Access Journals (Sweden)

Hamid Razavian

2014-01-01

Full Text Available Introduction: To investigate the effects of different clinical and technical conditions on the accuracy of electronic apex locators (EALs. Materials and Methods: "Tooth apex," "dental instrument," "odontometry," "electronic medical," and "electronic apex locator" were searched as primary identifiers via Medline/PubMed, Cochrane library, and Scopus data base up to 30 July 2013. Original articles that fulfilled the inclusion criteria were selected and reviewed. Results: Out of 402 relevant studies, 183 were selected based on the inclusion criteria. In this part, 75 studies are presented. Pulp vitality conditions and root resorption, types of files and irrigating materials do not affect an EAL′s accuracy; however, the file size and foramen diameter can affect its accuracy. Conclusions: Various clinical conditions such as the file size and foramen diameter may affect EALs′ accuracy. However, more randomized clinical trials are needed for definitive conclusion.

Arbuscular mycorrhizal fungi in a semi-arid, limestone mining-impacted area of Brazil

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Thaís Teixeira-Rios

2013-12-01

Full Text Available The main goal of this study was to determine the diversity and activity of arbuscular mycorrhizal fungi (AMF in an area degraded by limestone mining within the semi-arid region of Brazil known as the caatinga (shrublands. Near a limestone quarry, we selected two areas of caatinga (preserved and degraded for study. The number of glomerospores did not differ significantly between the two areas. There was a trend toward the most probable number of infective propagules being higher in the degraded area. Twenty AMF taxa were identified in the two sampled areas, species richness, diversity and evenness being higher in the preserved area. Two species of Racocetra represent new records for the semi-arid region of Brazil. Glomerospore production and AMF species richness were unaffected by mining activity in the study area.

Adaptation to the degradation of natural resources in the semiarid area of Mexico

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José Luis Gonzalez Barrios

2010-12-01

Full Text Available Hydrology and soil research in the semiarid zone of Mexico highlight an erosion process that is worsened by climate and land use changes. Scientific results have inspired a successful adaptation program with an environmental and socioeconomic scope. The Hydrological Environmental Services Programm.e (PSAH, in Spanish pays local workers to build soil and water conservation infrastructure in areas with the potential to provide hydrological environmental services. The programme’s results are still under assessment, but some qualitative results may be already identified: soil and water retention, plant cover recovery, permanence of local people in their comm.unities, and social welfare, among others. The PSAH as a strategy should be echoed in other places of Mexico in order to replicate their benefits on the physical and human environments of the semiarid zone.

Extensive Green Roof Species and Soilless Media Evaluations in Semi-arid Colorado

Science.gov (United States)

In the high elevation, semi-arid climate of Colorado, green roofs have not been scientifically tested. This research examined alternative plant species, soilless media blends and plant interactions on an existing, modular-extensive (shallow, 10 cm deep) green roof in Denver, Colo...

Effects of fishing technique on assessing species composition in aquatic systems in semi-arid Brazil

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ESF Medeiros

Full Text Available In most ecological field research, appropriate sampling is critical for the understanding of processes underlying fish populations and communities, and is even more important in heterogeneous environments such as the aquatic systems of the semi-arid region of Brazil. This study intends to make a contribution to the development of sampling programs and gear selection in aquatic systems of semi-arid Brazil by evaluating the effects of different fishing techniques on the assessment of richness and composition of the fish fauna in selected aquatic environments. Six sites were selected to represent typical artificial (reservoirs and natural (intermittent streams environments and four different types of sampling gear were applied to each site during four occasions. The present study shows that when selecting sampling techniques to be used in aquatic systems in semi-arid Brazil, one must consider the objectives of the study, e.g. ecological or taxonomic, in order to decide on inclusion of rare species in the sampling population. Also, the effect of the sampling gear on natural abundances of fish must be considered given that some sampling techniques are highly detrimental to fish population numbers.

GIS-Based KW-GIUH hydrological model of semiarid catchments: The case of Faria Catchment, Palestine

International Nuclear Information System (INIS)

Shadeed, S.; Shaheen, H.; Jayyousi, A.

2007-01-01

Among the most basic challenges of hydrology are the quantitative understanding of the processes of runoff generation and prediction of flow hydrographs. Traditional techniques have been widely applied for the estimation of runoff hydrographs of gauged catchments using historical rainfall-runoff data and unit hydrographs. Such procedures are questioned as to their reliability and their application to ungauged, arid and semiarid catchments. To overcome such difficulties, the use of physically based rainfall-runoff process of Faria Catchment using the lately developed KW-GIUH. Faria catchment, located in the northeastern part of the West Bank, Palestine, is characterized as a semiarid region with annual rainfall depths ranging on average from 150 to 640 mm at both ends of the catchment. The Geographical Information System (GIS) techniques were used to shape the geomorphological features of the catchment. A GIS based KW-GIUH hydrological model was used to stimulate the rainfall-runoff process in the three sub-catchments of Faria, namely: Al-Badan, Al-Faria and Al-Malaqi. The simulated runoff hydrographs proved that the GIS-based KW-GIUH model is applicable to semiarid regions and can be used to estimate the unit hydrographs in the West Bank catchments. (author)

Nitrogen flows and balances as affected by water and nutrient management in a sorghum cropping system of semi-arid Burkina Faso

NARCIS (Netherlands)

Zougmoré, R.; Mando, A.; Stroosnijder, L.; Guillobez, S.

2004-01-01

Efficient use of external inputs and water conservation are a prerequisite of sustainable agricultural productivity in semiarid West Africa. A field experiment was carried out during 3 years (2000–2002) at Saria in semiarid Burkina Faso (800 mm of annual rainfall, PET of 2000 mm per year) to assess

Water balance of two earthen landfill caps in a semi-arid climate

International Nuclear Information System (INIS)

Khire, M.V.; Benson, C.H.; Bosscher, P.J.

1997-01-01

Water balance data are presented that were obtained from two earthen cap test sections located in a semi-arid region. The test sections were constructed on a municipal solid waste landfill in East Wenatchee, Washington, USA. One test section represents a traditional resistive barrier, and is constructed with a compacted silty clay barrier 60 cm thick and a vegetated silty clay surface layer 15 cm thick. The other test section represents a capillary barrier and has a sand layer 75 cm thick overlain by a 15-cm-thick vegetated surface layer of silt. Extensive hydrological and meteorological data have been collected since November 1992. Unsaturated hydraulic properties of soils, hydrologic parameters, and vegetation have been extensively characterized. Results of the study show that capillary barriers can be effective caps in semi-arid and arid regions. They are also cheaper to construct and can perform better than traditional resistive barriers

Environmental and socioeconomic benefits and limitations of water harvesting techniques in semiarid regions

Science.gov (United States)

Díaz-Pereira, Elvira; Asunción Romero-Díaz, María; de Vente, Joris

2016-04-01

Under climate change, sustainable management of soil and water resources is increasingly important, especially in rainfed agroecosystems of semiarid environments. Water harvesting refers to a range of techniques for the collection and management of flood or rainwater for domestic and agricultural use and for water retention in natural ecosystems. Water harvesting represents a good example of sustainable management of water resources that contribute to water and food security. However, there are often environmental and socioeconomic constraints for implementation of water harvesting techniques, so each condition asks for a specific solution. Here we aim to highlight the environmental and socioeconomic benefits, requirements and limitations of different water harvesting techniques and to characterize their implications for provisioning, regulating, supporting, and cultural ecosystem services. We reviewed 62 water harvesting techniques for semiarid regions extracted from the WOCAT (World Overview of Conservation Approaches and Technologies) database. We discuss aspects related to: i) human and environmental characteristics, ii) cost-benefit ratio during implementation and maintenance phases, iii) socioeconomic and environmental impacts at local and regional scales, and, iv) impacts on ecosystem services. Our review reveals that water harvesting represents very diverse methods of collecting and managing floodwaters and surface runoff. We grouped techniques as 'floodwater harvesting', 'macro-catchment water harvesting', 'micro-catchment water harvesting', and 'rooftop and courtyard' water harvesting. Almost half of all technologies originates from traditional knowledge. The implementation of water harvesting is generally positive on the short-term, to very positive on the long-term, while its maintenance is very positive at short and long-term. However, perception depends on the type of water harvesting and local conditions. Most relevant socioeconomic benefits from

Multidimensional Quantum Mechanical Modeling of Electron Transfer and Electronic Coherence in Plant Cryptochromes: The Role of Initial Bath Conditions.

Science.gov (United States)

Mendive-Tapia, David; Mangaud, Etienne; Firmino, Thiago; de la Lande, Aurélien; Desouter-Lecomte, Michèle; Meyer, Hans-Dieter; Gatti, Fabien

2018-01-11

A multidimensional quantum mechanical protocol is used to describe the photoinduced electron transfer and electronic coherence in plant cryptochromes without any semiempirical, e.g., experimentally obtained, parameters. Starting from a two-level spin-boson Hamiltonian we look at the effect that the initial photoinduced nuclear bath distribution has on an intermediate step of this biological electron transfer cascade for two idealized cases. The first assumes a slow equilibration of the nuclear bath with respect to the previous electron transfer step that leads to an ultrafast decay with little temperature dependence; while the second assumes a prior fast bath equilibration on the donor potential energy surface leading to a much slower decay, which contrarily displays a high temperature dependence and a better agreement with previous theoretical and experimental results. Beyond Marcus and semiclassical pictures these results unravel the strong impact that the presence or not of equilibrium initial conditions has on the electronic population and coherence dynamics at the quantum dynamics level in this and conceivably in other biological electron transfer cascades.

Management of nutrients and water in rainfed arid and semi-arid areas. Proceedings of a consultants meeting

International Nuclear Information System (INIS)

1998-07-01

Sustainable food security is needed for the arid and semi-arid regions of the tropical, subtropical and warm-temperate climatic zones. In these regions the supply of locally grown food is unreliable because much of it is produced in conditions of highly variable rainfall. Even in favourable seasons, these regions re becoming increasingly dependent on imported food. The IAEA's involvement in field studies on soil-water use dates back several years. A five year Co-ordinated Research Project on ''The Use of Nuclear and Related Techniques in Assessment of Irrigation Schedules of Field Crops to Increase Effective Use of Water in Irrigation Projects''. That project, completed in 1995, laid a solid foundation for future research. Because of a scarcity of water in many developing countries and increasing needs for sustainable food security in the face of increasing populations and lack of funds for irrigation schemes of significant dimension, research must focus on improved management of (i) the modest quantities of fertilizers that are available to farmers, (ii) the natural resources that are available to farmers for increasing soil organic matter content, and (iii) rain water. The Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture held a Consultants Meeting on Management of Nutrients and Water in Rainfed Arid and Semi-Arid Areas for Increasing Crop Production, 26-29 May 1997

Evaporative Cooler Use Influences Temporal Indoor Relative Humidity but Not Dust Mite Allergen Levels in Homes in a Semi-Arid Climate.

Directory of Open Access Journals (Sweden)

James D Johnston

Full Text Available Concerns about energy consumption and climate change make residential evaporative coolers a popular alternative to central air conditioning in arid and semi-arid climates. However, evaporative coolers have been shown to significantly increase indoor relative humidity and dust mite allergen levels in some studies, while showing no association in other studies. Improved measurement of temporal fluctuations in indoor relative humidity may help identify factors that promote mite growth in homes in dry climates. Dust samples and continuous indoor relative humidity measurements were collected from homes with central air conditioning and homes with evaporative coolers in Utah. Samples were collected over two seasons, winter/spring (Jan-Apr and summer (July-Sept, 2014. Dust samples were analyzed for Der p 1 and Der f 1 using a two-site monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA analysis. Housing characteristics including age of home, occupant density, and age of mattresses, furniture, and carpeting were also measured. Positive Der p 1 or Der f 1 samples were found in 25.0% of the homes and there was no difference in mean allergen levels by type of air conditioning. Indoor relative humidity was significantly higher in homes with evaporative coolers compared to those with central air conditioning during the summer. Homes with evaporative coolers also spent significantly more time during summer above 55.0% and 65.0% relative humidity compared to central air homes, but not above 75.0%. Findings from this study suggest that increased humidity from evaporative coolers may not be sufficient to exceed the critical equilibrium humidity or maintain humidity excursions for sufficient duration in relatively larger single-family homes in semi-arid climates to support mite growth and reproduction.

A zoological catalogue of hunted reptiles in the semiarid region of Brazil

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Nóbrega Alves Rômulo

2012-07-01

Full Text Available Abstract The variety of interactions between human cultures and herpetofauna is the subject matter of Ethnoherpetology, a subdivision of Ethnozoology. In the semi-arid region of Brazil, many reptiles interact with human communities because of their utility or because of the risks they represent. These interactions have obvious implications for the conservation of reptiles from this region.In this context, ethnoherpetology studies are crucial because they serve as subsidies for guiding strategies for the handling and conservation of reptiles. This paper presents ethnozoological and taxonomic informations of hunted reptiles in the semiarid region of Brazil and analyse the implications on conservation that are related to the interactions between people and reptiles in this region. Taxonomic keys to identifying recorded reptiles are provided. Records of humans interacting with 38 reptile species that belong to 31 genuses and 16 families have been found. The groups with the largest numbers of recorded species were snakes (18 species, and this group was followed in number by lizards (13, chelonians (4, and crocodilians (3. The reptiles that were recorded may be used for the following purposes: medicinal purposes (24 species, food (13 species, ornamental or decorative purposes (11 species, in magical/religious practices (10 species, and as pets (10 species. Some species (n = 16 may have multiple uses. Furthermore, more than half of the species (n = 19 are commonly killed because they are considered potentially dangerous. Strategies for conserving the reptiles of the Brazilian semi-arid region must reconcile and integrate human and conservation needs.

A zoological catalogue of hunted reptiles in the semiarid region of Brazil.

Science.gov (United States)

Nóbrega Alves, Rômulo Romeu; Pereira Filho, Gentil Alves; Silva Vieira, Kleber; Silva Souto, Wedson Medeiros; Mendonça, Lívia Emanuelle Tavares; Montenegro, Paulofernandoguedespereira; Almeida, Waltécio de Oliveira; Silva Vieira, Washington Luiz

2012-07-30

The variety of interactions between human cultures and herpetofauna is the subject matter of Ethnoherpetology, a subdivision of Ethnozoology. In the semi-arid region of Brazil, many reptiles interact with human communities because of their utility or because of the risks they represent. These interactions have obvious implications for the conservation of reptiles from this region. In this context, ethnoherpetology studies are crucial because they serve as subsidies for guiding strategies for the handling and conservation of reptiles. This paper presents ethnozoological and taxonomic informations of hunted reptiles in the semiarid region of Brazil and analyse the implications on conservation that are related to the interactions between people and reptiles in this region. Taxonomic keys to identifying recorded reptiles are provided. Records of humans interacting with 38 reptile species that belong to 31 genuses and 16 families have been found. The groups with the largest numbers of recorded species were snakes (18 species), and this group was followed in number by lizards (13), chelonians (4), and crocodilians (3). The reptiles that were recorded may be used for the following purposes: medicinal purposes (24 species), food (13 species), ornamental or decorative purposes (11 species), in magical/religious practices (10 species), and as pets (10 species). Some species (n = 16) may have multiple uses. Furthermore, more than half of the species (n = 19) are commonly killed because they are considered potentially dangerous. Strategies for conserving the reptiles of the Brazilian semi-arid region must reconcile and integrate human and conservation needs.

Biomass and cellulosic ethanol production of forage sorghum under limited water conditions

Science.gov (United States)

A two year field study was conducted to evaluate biofuel production potential of two forage sorghum cultivars differing in brown midrib trait under non-irrigated and deficit irrigation conditions in the semiarid Southern High Plains of the U.S. Cultivar SP1990 (non-bmr = conventional cell wall comp...

Energetics of the green iguana (Iguana iguana) in a semi-arid environment

NARCIS (Netherlands)

van Marken Lichtenbelt, Wouter David

1991-01-01

Energy budgets in the herbivorous green iguana (Iguana Iguana) were studied from April 1985-October 1988 in a strongly seasonal environment on the semi-arid island Curacao (Netherlands Antilles) under the auspices of the CARMABI Foundation in cooperation with the State University of Groningen (The

Conditional Dispersive Readout of a CMOS Single-Electron Memory Cell

Science.gov (United States)

Schaal, S.; Barraud, S.; Morton, J. J. L.; Gonzalez-Zalba, M. F.

2018-05-01

Quantum computers require interfaces with classical electronics for efficient qubit control, measurement, and fast data processing. Fabricating the qubit and the classical control layer using the same technology is appealing because it will facilitate the integration process, improving feedback speeds and offering potential solutions to wiring and layout challenges. Integrating classical and quantum devices monolithically, using complementary metal-oxide-semiconductor (CMOS) processes, enables the processor to profit from the most mature industrial technology for the fabrication of large-scale circuits. We demonstrate a CMOS single-electron memory cell composed of a single quantum dot and a transistor that locks charge on the quantum-dot gate. The single-electron memory cell is conditionally read out by gate-based dispersive sensing using a lumped-element L C resonator. The control field-effect transistor (FET) and quantum dot are fabricated on the same chip using fully depleted silicon-on-insulator technology. We obtain a charge sensitivity of δ q =95 ×10-6e Hz-1 /2 when the quantum-dot readout is enabled by the control FET, comparable to results without the control FET. Additionally, we observe a single-electron retention time on the order of a second when storing a single-electron charge on the quantum dot at millikelvin temperatures. These results demonstrate first steps towards time-based multiplexing of gate-based dispersive readout in CMOS quantum devices opening the path for the development of an all-silicon quantum-classical processor.

Contamination of semiarid potiguar reservoirs by harmful bacteria

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Ermeton Duarte do Nascimento

2016-04-01

Full Text Available Water contamination in the semi-arid section of Northeast Brazil is a current concern for the country’s researchers, since this region is considered one of the poorest in Brazil and the water in these locations is a primary vehicle for disease transmission. We collected physical and chemical data as well as water samples from four semiarid potiguar reservoirs during the dry and rainy seasons of 2013 and 2014. These samples were prepared in a laboratory at the Federal University of Rio Grande do Norte (UFRN and their physical, chemical and microbiological characteristics were evaluated. The procedures of microbial isolation and identification followed the Standard Methods for Examinations of Water and Wastewater. Then Vitek II system (Bio-Merieux® was used to identify the microbial specimens and we calculated the frequency of specimens’ occurrence. Altogether, 168 bacteria were isolated and identified; 97% were Gram-negative and only 3% were Gram-positive. Within the Gram negatives, 73.2% were identified as belonging to the Enterobacteriaceae family and, in general terms, the most constant genera in the water reservoirs were Vibrio and Aeromonas. Among the Enterobacteriaceae family, the species Escherichia coli, Enterobacter cloacae complex and Klebsiella pneumoniae were the most frequent. There was no statistical difference between the number or morphotype groups found in the periods, p=0.255 and p=0.237, respectively. The analyzed data indicate possible contamination of these water reservoirs by human and/or animal fecal material.

Seasonal characterization of CDOM for lakes in semiarid regions of Northeast China using excitation-emission matrix fluorescence and parallel factor analysis (EEM-PARAFAC)

Science.gov (United States)

Zhao, Ying; Song, Kaishan; Wen, Zhidan; Li, Lin; Zang, Shuying; Shao, Tiantian; Li, Sijia; Du, Jia

2016-03-01

The seasonal characteristics of fluorescent components in chromophoric dissolved organic matter (CDOM) for lakes in the semiarid region of Northeast China were examined by excitation-emission matrix (EEM) spectra and parallel factor analysis (PARAFAC). Two humic-like (C1 and C2) and protein-like (C3 and C4) components were identified using PARAFAC. The average fluorescence intensity of the four components differed under seasonal variation from June and August 2013 to February and April 2014. Components 1 and 2 exhibited a strong linear correlation (R2 = 0.628). Significantly positive linear relationships between CDOM absorption coefficients a(254) (R2 = 0.72, 0.46, p DOC). However, almost no obvious correlation was found between salinity and EEM-PARAFAC-extracted components except for C3 (R2 = 0.469). Results from this investigation demonstrate that the EEM-PARAFAC technique can be used to evaluate the seasonal dynamics of CDOM fluorescent components for inland waters in the semiarid regions of Northeast China, and to quantify CDOM components for other waters with similar environmental conditions.

Aspect-related Vegetation Differences Amplify Soil Moisture Variability in Semiarid Landscapes

Science.gov (United States)

Yetemen, O.; Srivastava, A.; Kumari, N.; Saco, P. M.

2017-12-01

Soil moisture variability (SMV) in semiarid landscapes is affected by vegetation, soil texture, climate, aspect, and topography. The heterogeneity in vegetation cover that results from the effects of microclimate, terrain attributes (slope gradient, aspect, drainage area etc.), soil properties, and spatial variability in precipitation have been reported to act as the dominant factors modulating SMV in semiarid ecosystems. However, the role of hillslope aspect in SMV, though reported in many field studies, has not received the same degree of attention probably due to the lack of extensive large datasets. Numerical simulations can then be used to elucidate the contribution of aspect-driven vegetation patterns to this variability. In this work, we perform a sensitivity analysis to study on variables driving SMV using the CHILD landscape evolution model equipped with a spatially-distributed solar-radiation component that couples vegetation dynamics and surface hydrology. To explore how aspect-driven vegetation heterogeneity contributes to the SMV, CHILD was run using a range of parameters selected to reflect different scenarios (from uniform to heterogeneous vegetation cover). Throughout the simulations, the spatial distribution of soil moisture and vegetation cover are computed to estimate the corresponding coefficients of variation. Under the uniform spatial precipitation forcing and uniform soil properties, the factors affecting the spatial distribution of solar insolation are found to play a key role in the SMV through the emergence of aspect-driven vegetation patterns. Hence, factors such as catchment gradient, aspect, and latitude, define water stress and vegetation growth, and in turn affect the available soil moisture content. Interestingly, changes in soil properties (porosity, root depth, and pore-size distribution) over the domain are not as effective as the other factors. These findings show that the factors associated to aspect-related vegetation

Karst characterization in a semi-arid region using gravity, seismic, and resistivity geophysical techniques.

Energy Technology Data Exchange (ETDEWEB)

Barnhart, Kevin Scott

2013-10-01

We proposed to customize emerging in situ geophysical monitoring technology to generate time-series data during sporadic rain events in a semi-arid region. Electrodes were to be connected to wireless \

Cattle grazing in semiarid forestlands: Habitat selection during periods of drought

Science.gov (United States)

C. L. Roever; T. DelCurto; M. Rowland; M. Vavra; M. Wisdom

2015-01-01

Climate change models are predicting increased frequency and severity of droughts in arid and semiarid environments, and these areas are responsible for much of the world’s livestock production. Because cattle (Bos Taurus) grazing can impact the abundance, distribution, and ecological function of native plant and animal communities, it is important...

Leaf green-up in a semi-arid African savanna - separating tree and grass responses to environmental cues

CSIR Research Space (South Africa)

Archibald, S

2007-01-01

Full Text Available -arid African savanna - 583 Journal of Vegetation Science 18: 583-594, 2007 © IAVS; Opulus Press Uppsala. Leaf green-up in a semi-arid African savanna – separating tree and grass responses to environmental cues Archibald, S.1* & Scholes, R.J.1,2 1Natural... to identify tree and grass green-up dates in a semi-arid savanna system, and are there predictable environmental cues for green-up for each life form? Location: Acacia nigrescens/Combretum apiculatum savanna, Kruger National Park, South Africa (25° S, 31...

Effects of temperature on embryonic and larval development and growth in the natterjack toad (Bufo calamita in a semi-arid zone

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Sanuy, D.

2008-06-01

Full Text Available Temperature affects the duration of embryonic and larval periods in amphibians. Plasticity in time to metamorphosis is especially important in amphibian populations of Mediterranean semi-arid zones where temperatures are high and precipitation is low, increasing the rate of pond desiccation. In order to test the influence of water temperature on the larval development and growth of the natterjack toad (Bufo calamita, we collected two spawns in a semi¿arid zone at Balaguer (Lleida, NE Iberian peninsula. Approximately 50 (+/-10 eggs (stage 14-16 were raised in the lab at different temperature conditions: 10, 15, 20, 22.5 and 25ºC with 12:12 photoperiod. The results show a lengthening of development time with decreasing temperatures and a better survival performance of B. calamita to high temperatures. However, mean size at metamorphosis was not different across treatments, thus, suggesting that this population of B. calamita requires a minimum size to complete the metamorphosis. This study is the first approach to examine the effects that climatic factors have on the growth and development of B. calamita in semi-arid zones.

Dew measurement and estimation of rain-fed jujube (Zizyphus jujube Mill) in a semi-arid loess hilly region of China

Institute of Scientific and Technical Information of China (English)

WANG Xing; GAO Zhiyong; WANG Youke; Wang Zhi; JIN Shanshan

2017-01-01

Dew is an important water source for plants in arid and semi-arid regions.However,information on dew is scarce in such regions.In this study,we explored dew formation,amount,and duration of rain-fed jujube (Zi（w）phus jujube Mill) trees in a semi-arid loess hilly region of China (i.e.,Mizhi County).The data included dew intensity and duration,relative humidity,temperature,and wind speed measured from 26 July to 23 October,2012 and from 24 June to 17 October,2013 using a micro-climate system (including dielectric leaf wetness sensors,VP-3 Relative Humidity/Temperature Sensor,High Resolution Rain Gauge,and Davis Cup Anemometer).The results show that atmospheric conditions of relative humidity of ＞78％ and dew point temperature of 1℃C-3℃C are significantly favorable to dew formation.Compared with the rainfall,dew was characterized by high frequency,strong stability,and long duration.Furthermore,heavy dew accounted for a large proportion of the total amount.The empirical models (i.e.,relative humidity model (RH model) and dew point depression model (DPD model)) for daily dew duration estimation performed well at 15-rain intervals,with low errors ranging between 1.29 and 1.60 h,respectively.But it should be noted that the models should be calibrated firstly by determining the optimal thresholds of relatively humidity for RH model and dew point depression for DPD model.For rain-fed jujube trees in the semi-arid loess hilly regions of China,the optimal threshold of relative humidity was 78％,and the optimal upper and lower thresholds of dew point depression were 1℃C and 5℃C,respectively.The study further demonstrates that dew is an important water resource that cannot be ignored for rain-fed jujube trees and may affect water balance at regional scales.

Wind and water erosion control on semiarid lands

International Nuclear Information System (INIS)

Siddoway, F.H.

1980-01-01

Commercial crop production on semiarid lands is difficult because insufficient water is often present to manage the system effectively. Erosion control presents the major management problem. The factors contributing to wind erosion and their interaction have been quantified into a wind erosion equation. The control of wind erosion through agronomic alteration of the various factors is discussed. The quantification and control of water erosion is also discussed with respect to the Universal Soil Loss Equation. Radioisotopes tracers have been used in conjunction with these erosion equations to measure soil losses. (author)

Competing effects of groundwater withdrawals and climate change on water availability in semi-arid India

Science.gov (United States)

Sishodia, R. P.; Shukla, S.

2017-12-01

India, a global leader in groundwater use (250 km3/yr), is experiencing groundwater depletion. There has been a 130-fold increase in number of irrigation wells since 1960. Anticipated future increase in groundwater demand is likely to exacerbate the water availability in the semi-arid regions of India. Depending on the direction of change, future climate change may either worsen or enhance the water availability. This study uses an integrated hydrologic modeling approach (MIKE SHE MIKE 11) to compare and combine the effects of future (2040-2069) increased groundwater withdrawals and climate change on surface and groundwater flows and availability for an agricultural watershed in semi-arid south India. Modeling results showed that increased groundwater withdrawals in the future resulted in reduced surface flows (25%) and increased frequency and duration (90 days/yr) of well drying. In contrast, projected future increase in rainfall (7-43%) under the changed climate showed increased groundwater recharge (15-67%) and surface flows (9-155%). Modeling results suggest that the positive effects of climate change may enhance the water availability in this semi-arid region of India. However, in combination with increased withdrawals, climate change was shown to increase the well drying and reduce the water availability especially during dry years. A combination of management options such as flood to drip conversion, energy subsidy reductions and water storage can support increased groundwater irrigated area in the future while mitigating the well drying. A cost-benefit analysis showed that dispersed water storage and flood to drip conversion can be highly cost-effective in this semi-arid region. The study results suggest that the government and management policies need to be focused towards an integrated management of demand and supply to create a sustainable food-water-energy nexus in the region.

Produced water irrigation changes the soil mesofauna community in a semiarid agroecosystem.

Science.gov (United States)

Ferreira, Raimundo Nonato Costa; Weber, Olmar Baller; Crisóstomo, Lindbergue Araujo

2015-08-01

The scarcity of water in semiarid regions requires alternative sources for irrigation to improve agricultural production. Here, we aimed to evaluate the effects of produced water from oil exploration on the structure of soil mesofauna during the dry and rainy seasons in irrigated sunflower and castor bean fields in a Brazilian semiarid region. Three irrigation treatments were applied on plots cultivated with castor beans and sunflowers: produced water treated by filtration (filtrated) or treated by reverse osmosis (reverse osmosis) and groundwater. The mesofauna under the biofuel crops was collected and identified during the dry and rainy seasons. Although the abundance and richness of the total fauna did not differ between seasons in sunflower plots, the community was altered. In castor beans, the abundance, richness, and community of mesofauna observed in plots irrigated with produced water differed from the groundwater treatment. Irrigation with produced water promotes important changes in soil fauna community that justify their assessment for the maintenance and monitoring of agroecosystems.

Effects of rainfall on bird reproduction in a semi-arid Neotropical region

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Liana Monique Paiva Cavalcanti

Full Text Available ABSTRACT In semi-arid ecosystems, birds commonly use rainfall as a reliable environmental cue to adjust the timing and strength of their reproductive activity. Here we evaluate this hypothesis for a community of birds in the Caatinga (the semi-arid region of northeastern Brazil, using brood patch information and nest abundance. Sampling occurred every 14 days between September 2012 and August 2013 (brood patch, and every three or four days during the reproductive period (nests. Abundance of brood patches and nests were correlated, and all brood patches were recorded between March and July (4.5 to 5.0 months. We recorded three peaks of brood patch abundance: the first 28 days after the first rains, the second 14 days after the second rainfall peak, and the third synchronously with the third rainy period. These results indicate that intra-annual variation in local rainfall has the potential to account for variations in the timing and intensity of reproduction in the studied birds.

Hylleraas-like functions with the correct cusp conditions: K-shell electrons for the neutral atoms

Energy Technology Data Exchange (ETDEWEB)

Rodriguez, K.V. [Universidad Nacional del Sur, 8000 Bahia Blanca and Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina)], E-mail: krodri@criba.edu.ar; Gasaneo, G. [Universidad Nacional del Sur, 8000 Bahia Blanca and Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina); Mitnik, D.M.; Miraglia, J.E. [Instituto de Astronomia y Fisica del Espacio and Universidad de Buenos Aires (Argentina)

2007-10-15

We present simple correlated wavefunctions for the two K-shell electrons of neutral atoms. A variational method was chosen to calculate the mean energy of the ground state, in which the electrons are subject to a local Hartree potential representing the presence of the outer shell electrons. The functions are constructed in terms of exponential and power series, where special care has been taken in order to fulfill the exact behavior at the electron-electron and electron-nucleus coalescence points (Kato cusp conditions). Global properties, such as the energies and virial coefficients, as well as local properties, such as spatial mean values, are also analyzed.

1 Title page Title: Groundwater quality in a semi-arid region of India ...

Indian Academy of Sciences (India)

64

Groundwater quality in a semi-arid region of India - suitability for drinking, ... concentration ranges from 0.1 to 4.4 mg/L and 39% of the total samples measured ..... on identifying local priorities and implementing proper management is very.

Climate-vegetation relationship: adaptations of jarillal community to the semiarid climate. Lihué Calel National Park, province of La Pampa, Argentina

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Valeria Soledad Duval

2015-12-01

Full Text Available The study of vegetation from the Geography perspective focuses on the analysis of the spatial distribution and on the factors affecting it. One of these factors is the climate, which determines the characteristics of the vegetation and, on a larger scale, of the communities. The aim of this paper is to analyze the climate-vegetation relationship by studying adaptations of the jarillal community regarding the semiarid climate in the Lihué Calel National Park, Argentina. Therefore, this contribution is concerned with the knowledge of the characteristics of the environment in order to understand how vegetation responds to certain phenomena, so management of protected areas will be more suitable. Lihué Calel National Park is a national protected area located in the south-center of La Pampa province, Argentina. According to Cabrera (1976 the area belongs to the floristic province of “monte” and the climate is warm and dry. In the interest to achieve the goals of this paper, Thornthwaite and Mather´s water balance was done. The data was collected from a weather station that belongs to the national park, for the period 1995-2010. Emberger›s pluviothermic coefficient, Lang´s rainfall index, De Martonne´s aridity index and Currey´s continentality index were analyzed. In addition, ten stands or plots of vegetation were placed to determine the floristic composition and the vegetation physiognomy. Then, plants species were identified as individuals and their adaptive responses were also analyzed. In conclusion, the survey verified that semi-arid climate conditions determine the morphology and the appearance of jarillal. Climate analysis shows that for the period 1995-2010 the average annual temperature is 16.2° C and reveals that thermal summers and winters are well differentiated. Large water deficit is defined, because water balance indicates that the evapotranspiration exceeds precipitation during every month of the year. According to

Coprophilous Mucorales (ex Zygomycota) from three areas in the semi-arid of Pernambuco, Brazil.

Science.gov (United States)

Souza, Carlos Alberto Fragoso de; Lima, Diogo Xavier; Gurgel, Luciana M S; Santiago, André Luiz Cabral Monteiro de Azevedo

Mucorales comprises fungi commonly isolated as saprobes from soil, dung, stored grains and plants. Although these fungi have been studied in several countries, there are relatively a few reports of them in semi-arid areas. Therefore, the aims of the present study were to assess and compare the Mucorales communities in dung from different species and breeds of herbivores in the semi-arid of Pernambuco, based on the frequency of occurrence and species richness of these fungi. Samples of dung collected in the cities of Arcoverde, Serra Talhada and Sertânia were incubated in moist chambers in triplicate. Altogether, 24 taxa of Mucorales distributed in the genera Absidia, Circinella, Cunninghamella, Lichtheimia, Mucor, Pilobolus, Rhizopus and Syncephalastrum were identified. The highest species richness was found in sheep excrement. Mucor circinelloides f. griseo-cyanus was the most common taxon, followed by M. ramosissimus. The similarity of the composition of Mucorales species was greatest between the excrements of Guzerá and Sindi breeds (bovine). All mucoralean species isolated are being cited for the first time from animal dung found in Caatinga and a new species of Mucor was recorded. An identification key for species of Mucorales from dung in the semi-arid region of Brazil is provided. Copyright © 2016 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

Use of carbon isotope analysis to understand semi-arid erosion dynamics and long-term semi-arid land degradation.

Science.gov (United States)

Turnbull, Laura; Brazier, Richard E; Wainwright, John; Dixon, Liz; Bol, Roland

2008-06-01

Many semi-arid areas worldwide are becoming degraded, in the form of C(4) grasslands being replaced by C(3) shrublands, which causes an increase in surface runoff and erosion, and altered nutrient cycling, which may affect global biogeochemical cycling. The prevention or control of vegetation transitions is hindered by a lack of understanding of their temporal and spatial dynamics, particularly in terms of interactions between biotic and abiotic processes. This research investigates (1) the effects of soil erosion on the delta(13)C values of soil organic matter (SOM) throughout the soil profile and its implications for reconstructing vegetation change using carbon-isotope analysis and (2) the spatial properties of erosion over a grass-shrub transition to increase understanding of biotic-abiotic interactions by using delta(13)C signals of eroded material as a sediment tracer. Results demonstrate that the soils over grass-shrub transitions are not in steady state. A complex interplay of factors determines the input of SOM to the surface horizon of the soil and its subsequent retention and turnover through the soil profile. A positive correlation between event runoff and delta(13)C signatures of eroded sediment was found in all plots. This indicates that the delta(13)C signatures of eroded sediment may provide a means of distinguishing between changes in erosion dynamics over runoff events of different magnitudes and over different vegetation types. The development of this technique using delta(13)C signatures of eroded sediment provides a new means of furthering existing understanding of erosion dynamics over vegetation transitions. This is critical in terms of understanding biotic-abiotic feedbacks and the evolution of areas subject to vegetation change in semi-arid environments. John Wiley & Sons, Ltd

An overview of nitrate sources and operating processes in arid and semiarid aquifer systems.

Science.gov (United States)

Gutiérrez, Mélida; Biagioni, Richard N; Alarcón-Herrera, Maria Teresa; Rivas-Lucero, Bertha A

2018-05-15

Nitrate concentration in most aquifers in arid and semi-arid areas has increased in the past several decades as a result of human activities. Under the predominantly oxic conditions of these aquifers, denitrification is inhibited, allowing nitrate, a soluble and stable form of nitrogen (N), to accumulate. Because of its close association with municipal and agricultural wastes, nitrate is commonly used as an indicator of anthropogenic contamination. Aquifers affected by agricultural waste may contain salts from irrigation returns and herbicides in addition to nitrates. Preventing leakage from soil to deeper parts of the aquifer is thus a priority in the sustainable management of aquifers in arid and semiarid areas. Studies report a wide range of nitrate concentrations distributed non-uniformly within the aquifer, with roughly 40% and 20% of sampled wells exceeding 50mg/L nitrate in shallow and deep parts of the aquifer respectively. In aquifers at risk of becoming contaminated, nitrate isotopes (δ 15 N, δ 18 O, Δ 17 O) can be used to identify the source of nitrogen as mineral or organic fertilizer, sewage, or atmospheric deposition. A variety of mathematical models (crop, hydrological, geochemical, or a combination of them) have been successful in identifying best practices that minimize N leakage without negatively affecting crop yield. In addition, field research in crop management, e.g., conservation agriculture, has yielded promising results in determining the adequate dosage and time of application of fertilizers to reduce N losses. Examples of key dryland aquifers impacted by nitrate are discussed, and some of the most pressing challenges to achieve sustainability are presented. Copyright © 2017 Elsevier B.V. All rights reserved.

Seedling survival of Handroanthus impetiginosus (Mart ex DC Mattos in a semi-arid environment through modified germination speed and post-germination desiccation tolerance

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J. R. Martins

Full Text Available Abstract Uniform rapid seed germination generally forms a great risk for the plant population if subsequent intermittent precipitation causes desiccation and seedling death. Handroanthus impetiginosus can be found commonly in a wide range of biomes within Brazil including those that are semi-arid. Germination and early growth was studied to understand how germinated seeds survive under these stringent conditions. Accessions were sampled from four seasonally dry biomes in Brazil. Precipitation at the start of the rainy season in the Caatinga, a semi-arid biome, is less predictable and the number of successive dry days per dry interval in the first four months of the rainy season was higher than in the other studied biomes. Plants from the Caatinga produced thicker seeds and this trait concurred with slow germination and stronger osmotic inhibition of germination across the accessions, forming a stress avoidance mechanism in the Caatinga. Post-germination desiccation tolerance was high in the Caatinga accession, could be re-induced in accessions from biomes with more regular precipitation (Cerrado and transition zone, but remained poor in the Cerradão accession; thus forming a stress tolerance mechanism. Production of adventitious roots ascertained survival of all tested individuals from all four locations, even if protruded radicles did not survive desiccation, forming an additional stress tolerance mechanism. A sequence of stress avoidance and stress tolerance mechanisms in seeds and germinated seeds was associated with precipitation patterns in different biomes. These mechanisms purportedly allow rapid seedling establishment when conditions are suitable and enable survival of the young seedling when conditions are adverse.

Estimation of groundwater recharge via deuterium labelling in the semi-arid Cuvelai-Etosha Basin, Namibia.

Science.gov (United States)

Beyer, Matthias; Gaj, Marcel; Hamutoko, Josefina Tulimeveva; Koeniger, Paul; Wanke, Heike; Himmelsbach, Thomas

2015-01-01

The stable water isotope deuterium ((2)H) was applied as an artificial tracer ((2)H2O) in order to estimate groundwater recharge through the unsaturated zone and describe soil water movement in a semi-arid region of northern central Namibia. A particular focus of this study was to assess the spatiotemporal persistence of the tracer when applied in the field on a small scale under extreme climatic conditions and to propose a method to obtain estimates of recharge in data-scarce regions. At two natural sites that differ in vegetation cover, soil and geology, 500 ml of a 70% (2)H2O solution was irrigated onto water saturated plots. The displacement of the (2)H peak was analyzed 1 and 10 days after an artificial rain event of 20 mm as well as after the rainy season. Results show that it is possible to apply the peak displacement method for the estimation of groundwater recharge rates in semi-arid environments via deuterium labelling. Potential recharge for the rainy season 2013/2014 was calculated as 45 mm a(-1) at 5.6 m depth and 40 mm a(-1) at 0.9 m depth at the two studied sites, respectively. Under saturated conditions, the artificial rain events moved 2.1 and 0.5 m downwards, respectively. The tracer at the deep sand site (site 1) was found after the rainy season at 5.6 m depth, corresponding to a displacement of 3.2 m. This equals in an average travel velocity of 2.8 cm d(-1) during the rainy season at the first site. At the second location, the tracer peak was discovered at 0.9 m depth; displacement was found to be only 0.4 m equalling an average movement of 0.2 cm d(-1) through the unsaturated zone due to an underlying calcrete formation. Tracer recovery after one rainy season was found to be as low as 3.6% at site 1 and 1.9% at site 2. With an in situ measuring technique, a three-dimensional distribution of (2)H after the rainy season could be measured and visualized. This study comprises the first application of the peak displacement method using a

Insights from a network of long-term measurements of biosphere-atmospheric exchanges of water vapor and carbon dioxide in a water-limited semiarid region

Science.gov (United States)

Scott, Russell; Biederman, Joel

2017-04-01

Around one-third of Earth's land surface is classified as semiarid, and carbon dioxide exchange in these regions has been shown to be an important regulator of both the trend and interannual variability of the terrestrial carbon sink. Fifteen years ago, when we began making measurements of biosphere-atmospheric exchanges of energy, water vapor, and carbon dioxide using eddy covariance in southern Arizona USA, there was paucity of semiarid observations in flux networks like AmeriFlux and EuroFlux. We started by establishing riparian sites across a woody plant encroachment gradient to quantify the productivity and consumptive plant water use along a iconic and ecologically important desert river. Soon thereafter, we added semiarid grassland, shrubland, and savanna sites that do not have access to groundwater in order to better understand how water limitation and changes in vegetation structure affect ecosystem productivity. Here, we highlight the value of multiyear, multisite flux data for addressing regional to global scale problems associated with groundwater pumping, land cover change, drought, and climate change. For the riparian sites, we find that ecosystem water availability is altered by vegetation structure such that ecosystems with more deeply rooted trees have higher productivity but at a cost of greater groundwater use. For the non-riparian sites, precipitation strongly controls ecosystem water availability and the resultant productivity, but differences in ecosystem structure impact water use efficiency due to the partitioning of evapotranspiration into its component sources. Also, the productivity at sites with more grass, and less woody, plants responds more quickly to precipitation fluctuations including long-term drought conditions. In semiarid regions, variability in water and carbon fluxes is much larger than in more mesic climes. Across our riparian and non-riparian sites, access to more stable groundwater reserves reduces variability in water and

Use of the tritium thermonuclear peak in the deep unsaturated zone for quantitative estimate of aquifer recharge under semi-arid conditions: first application in Sahel

International Nuclear Information System (INIS)

Cheikh Becaye Gaye; Aranyossy, J.F.

1992-01-01

The location of the bomb tritium signal at 20 and 12 m depth in the unsaturated sand dunes in the semi-arid part of North Senegal leads to a qualitative estimate of the effective infiltration of 22 and 26 mm.yr -1 . These figures correspond respectively to 6.5 and 8% of the total precipitation since 1963. Tritium content distribution in interstitial water is modelled by convolution of the analytical solution of the dispersion equation. Best fitting of the complete 12 m depth tritium peak is obtained with a dispersion coefficient of 0.03 m 2 .yr -1

Thermoregulatory responses and blood parameters of locally adapted ewes under natural weather conditions of Brazilian semiarid region

Directory of Open Access Journals (Sweden)

Wirton Peixoto Costa

2015-12-01

Full Text Available The effect of the natural weather conditions on respiratory rate, rectal temperature and hematologic parameters such as glucose, total cholesterol, triacylglycerol, total protein, albumin, globulin, red blood cells, microhematocrit, mean corpuscular volume, serum triiodothyronine (T3 and thyroxine (T4 levels was evaluated in red (RMN and white (WMN coat colored Morada Nova ewes, of different class of body condition score (CBCS, during the dry (from july to december and wet (from january to june seasons, which exhibited different (P<0.05 air temperature, relative humidity and radiant thermal load averages. Tukey’s test was used and the difference considered was to P<0.05. Significant greater averages of respiratory rate were observed in the dry period compared to the rainy period (42.26±8.96 and 36.89±8.20 breaths min-1, respectively, mainly in the RMN (45.54±8.23 breaths min-1 compared with the WMN (39.27±8.57 breaths min-1. No differences were observed in rectal temperature measurements between the dry and the wet periods (38.59±0.58 and 38.60±0.56 oC, respectively, but the WMN had higher values than the RMN (38.77±0.54 and 38.40±0.54 oC, respectively. The glucose and total cholesterol were higher in the wet season, with no variation due to breed variety and CBCS. The triacylglycerol did not change between breed varieties and seasons. The albumin was similar between varieties and in different seasons, being different in CBCS. Total protein and globulin serum were higher during the wet season, but total protein was higher and globulin was lower in better CBCS. T3 and T4 levels were higher in the rainy season (0.25±0.07 and 6.74±11.37 ?g dL-1, for T3 and T4, respectively than in the dry season (0.18±0.08 and 6.31±1.64 ?g dL-1, for T3 and T4, respectively. The red blood cells showed no difference, but microhematocrit was higher in WMN and in the better CBCS and mean corpuscular volume was higher in the dry season. The concentration

Energetics of the green iguana (Iguana iguana) in a semi-arid environment

OpenAIRE

van Marken Lichtenbelt, Wouter David

1991-01-01

Energy budgets in the herbivorous green iguana (Iguana Iguana) were studied from April 1985-October 1988 in a strongly seasonal environment on the semi-arid island Curacao (Netherlands Antilles) under the auspices of the CARMABI Foundation in cooperation with the State University of Groningen (The Netherlands). ... Zie: Summary

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

Science.gov (United States)

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

Channel response in a semiarid stream to removal of tamarisk and Russian olive

Science.gov (United States)

Jaeger, Kristin L.; Wohl, Ellen

2011-02-01

We report observed short-term (3 years) channel adjustment in an incised, semiarid stream to the removal of invasive plants, tamarisk (Tamarix spp.) and Russian olive (Elaeagnus angustifolia) by (1) removing the above-ground portion of the plant (cut-stump method) and (2) removing the entire plant (whole-plant method). The stream flows through Canyon de Chelly National Monument in Arizona, USA., draining an ˜1500 km2 catchment. Average channel width is 13 m; average thalweg depth is 2-3 m, although channel banks exceed 8 m locally. Channels adjusted primarily through widening, with significantly larger changes occurring in whole-plant removal reaches; however, neither plant removal method elicited large-scale bank destabilization, and the channels remained entrenched. Particular site conditions limiting large-scale destabilization include the absence of sufficient streamflow magnitudes, the presence of clay layers at the bank toe, the remaining presence of native vegetation, and the entrenched morphology. Our findings serve as a cautionary note regarding the temporal and spatial variability in channel response to invasive plant removal and underscore the importance of considering site-specific conditions in future restoration projects that include invasive plant removal.

Plasma conditions for non-Maxwellian electron distributions in high current discharges and laser-produced plasmas

International Nuclear Information System (INIS)

Whitney, K.G.; Pulsifer, P.E.

1993-01-01

Results from the standard quasilinear theory of ion-acoustic and Langmuir plasma microturbulence are incorporated into the kinetic theory of the electron distribution function. The theory is then applied to high current discharges and laser-produced plasmas, where either the current flow or the nonlinear laser-light absorption acts, respectively, as the energy source for the microturbulence. More specifically, the theory is applied to a selenium plasma, whose charge state is determined under conditions of collisional-radiative equilibrium, and plasma conditions are found under which microturbulence strongly influences the electron kinetics. In selenium, we show that this influence extends over a wide range of plasma conditions. For ion-acoustic turbulence, a criterion is derived, analogous to one previously obtained for laser heated plasmas, that predicts when Ohmic heating dominates over electron-electron collisions. This dominance leads to the generation of electron distributions with reduced high-energy tails relative to a Maxwellian distribution of the same temperature. Ion-acoustic turbulence lowers the current requirements needed to generate these distributions. When the laser heating criterion is rederived with ion-acoustic turbulence included in the theory, a similar reduction in the laser intensity needed to produce non-Maxwellian distributions is found. Thus we show that ion-acoustic turbulence uniformly (i.e., by the same numerical factor) reduces the electrical and heat conductivities, as well as the current (squared) and laser intensity levels needed to drive the plasma into non-Maxwellian states

Turbulent fluxes in atmospheric boundary layer of a semi-arid region of N-E Brazil

International Nuclear Information System (INIS)

Patel, S. R.; De Fatima Correia, M.; Da Silva, E. M.; Costa, A. M. N.

2004-01-01

The preliminary results of the Experiment 'Experimento de Microfisica de Nuvens-EmfiN' (Experiment of microphysics of clouds) conducted by Universidade Estatual de Ceara-UECE at Fortaleza, a semi-arid region of N-E Brazil, are presented. The mean kinematic fluxes of sensible heat and water vapor of the surface boundary layer are estimated by the thermodynamic energy and water vapor conservation equations; and by the Monin-Obukhov similarity theory. The results of the two methods are in good agreement. It is shown that in the absence of sophisticated fast-response turbulence instrumentation and wind data the conservations equations methods are better option for estimation of heat and water vapor fluxes. Further they are useful to study the turbulent fluxes in inhomogeneous condition in time like early morning and late evening boundary layer transitions

A missing piece of the puzzle in climate change hotspots: Near-surface turbulent interactions controlling ET-soil moisture coupling in semiarid areas

Science.gov (United States)

Haghighi, Erfan; Gianotti, Daniel J.; Rigden, Angela J.; Salvucci, Guido D.; Kirchner, James W.; Entekhabi, Dara

2017-04-01

Being located in the transitional zone between dry and wet climate areas, semiarid ecosystems (and their associated ecohydrological processes) play a critical role in controlling climate change and global warming. Land evapotranspiration (ET), which is a central process in the climate system and a nexus of the water, energy and carbon cycles, typically accounts for up to 95% of the water budget in semiarid areas. Thus, the manner in which ET is partitioned into soil evaporation and plant transpiration in these settings is of practical importance for water and carbon cycling and their feedbacks to the climate system. ET (and its partitioning) in these regions is primarily controlled by surface soil moisture which varies episodically under stochastic precipitation inputs. Important as the ET-soil moisture relationship is, it remains empirical, and physical mechanisms governing its nature and dynamics are underexplored. Thus, the objective of this study is twofold: (1) to provide observational evidence for the influence of surface cover conditions on ET-soil moisture coupling in semiarid regions using soil moisture data from NASA's SMAP satellite mission combined with independent observationally based ET estimates, and (2) to develop a relatively simple mechanistic modeling platform improving our physical understanding of interactions between micro and macroscale processes controlling ET and its partitioning in partially vegetated areas. To this end, we invoked concepts from recent progress in mechanistic modeling of turbulent energy flux exchange in bluff-rough regions, and developed a physically based ET model that explicitly accounts for how vegetation-induced turbulence in the near-surface region influences soil drying and thus ET rates and dynamics. Model predictions revealed nonlinearities in the strength of the ET-soil moisture relationship (i.e., ∂ET/∂θ) as vegetation cover fraction increases, accounted for by the nonlinearity of surface

Integrated water and nutrient management for sorghum production in semi-arid Burkina Faso

NARCIS (Netherlands)

Zougmoré, R.

2003-01-01

Loss of water and nutrients through runoff are major agriculture problems for inherent poor fertile soils in semiarid West Africa. The intensification of crop production requires an integration of soil, water and nutrient management that is locally acceptable and beneficial for smallholder farmers.

Semi-arid Northeast Brazil: integrated modelling of regional development and global change impacts

NARCIS (Netherlands)

Krol, Martinus S.; Fuhr, Dagmar; Döring, Andreas; Unruh, Jon D.; Krol, Maarten S.; Kliot, Nurit

2004-01-01

Societies in semi-arid areas in developing regions are amongst those most vulnerable to climate variability and potentially most vulnerable to climate change. The vulnerability to climate variability emerges from a combination of the level of availability of natural resources and the human

Local conditions for the Pauli potential in order to yield self-consistent electron densities exhibiting proper atomic shell structure

Energy Technology Data Exchange (ETDEWEB)

Finzel, Kati, E-mail: kati.finzel@liu.se [Linköpings University, IFM Department of Physics, 58183 Linköping (Sweden)

2016-01-21

The local conditions for the Pauli potential that are necessary in order to yield self-consistent electron densities from orbital-free calculations are investigated for approximations that are expressed with the help of a local position variable. It is shown that those local conditions also apply when the Pauli potential is given in terms of the electron density. An explicit formula for the Ne atom is given, preserving the local conditions during the iterative procedure. The resulting orbital-free electron density exhibits proper shell structure behavior and is in close agreement with the Kohn-Sham electron density. This study demonstrates that it is possible to obtain self-consistent orbital-free electron densities with proper atomic shell structure from simple one-point approximations for the Pauli potential at local density level.

78 FR 11555 - Special Conditions: Embraer S.A., Model EMB-550 Airplane; Design Roll Maneuver for Electronic...

Science.gov (United States)

2013-02-19

... Law 92-574, the ``Noise Control Act of 1972.'' The FAA issues special conditions, as defined in 14 CFR...; Design Roll Maneuver for Electronic Flight Controls AGENCY: Federal Aviation Administration (FAA), DOT... design roll maneuver for electronic flight controls, specifically an electronic flight control system...

77 FR 70384 - Special Conditions: Embraer S.A., Model EMB-550 Airplane; Design Roll Maneuver for Electronic...

Science.gov (United States)

2012-11-26

... Law 92-574, the ``Noise Control Act of 1972.'' The FAA issues special conditions, as defined in 14 CFR... Maneuver for Electronic Flight Controls AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice... design roll maneuver for electronic flight controls, specifically an electronic flight control system...

Photodouble ionization differential cross sections for D2 with various electron energy sharing conditions

International Nuclear Information System (INIS)

Seccombe, D.P.; Collins, S.A.; Reddish, T.J.; Selles, P.; Malegat, L.; Huetz, A.; Kazansky, A.K.

2002-01-01

The mutual angular distributions of the two ejected electrons following direct photodouble ionization have been measured for D 2 at an excess energy (E) of 25 eV using linearly polarized light. These (γ, 2e) 'triple' differential cross sections (TDCSs) were obtained for asymmetric electron energy conditions with energy sharing ratios (R=E 2 /E 1 ) of R=24, 11.5, 4 and 2.57. In all cases the 'reference' electron (energy = E 1 ) was oriented along the direction of the electric field vector (ε) and detected in coincidence with a second electron (energy = E 2 ) coplanar with ε and the photon beam direction (kγ). For comparison, helium TDCSs were obtained for the same E and R values under nearly identical spectrometer conditions. These show very good agreement with the results of hyperspherical-R-matrix with semi-classical outgoing waves calculations, thus providing even more confidence in the D 2 TDCSs where there is as yet no accurate ab initio theory. The similarities and differences between the experimental results associated with the two targets are qualitatively discussed in terms of Feagin's model (Feagin J M 1998 J. Phys. B: At. Mol. Opt. Phys. 31 L729). (author)

Ground-water recharge in the arid and semiarid southwestern United States

Science.gov (United States)

Stonestrom, David A.; Constantz, Jim; Ferré, Ty P.A.; Leake, Stanley A.

2007-01-01

areas, and distinct modes of recharge in the Colorado Plateau and Basin and Range subregions.The chapters in this professional paper present (first) an overview of climatic and hydrogeologic framework (chapter A), followed by a regional analysis of ground-water recharge across the entire study area (chapter B). These are followed by an overview of site-specific case studies representing different subareas of the geographically diverse arid and semiarid southwestern United States (chapter C); the case studies themselves follow in chapters D–K. The regional analysis includes detailed hydrologic modeling within the framework of a high-resolution geographic-information system (GIS). Results from the regional analysis are used to explore both the distribution of ground-water recharge for mean climatic conditions as well as the influence of two climatic patterns—the El Niño-Southern Oscillation and Pacific Decadal Oscillation—that impart a high degree of variability to the hydrologic cycle. Individual case studies employ a variety of geophysical and geochemical techniques to investigate recharge processes and relate the processes to local geologic and climatic conditions. All of the case studies made use of naturally occurring tracers to quantify recharge. Thermal and geophysical techniques that were developed in the course of the studies are presented in appendices.The quantification of ground-water recharge in arid settings is inherently difficult due to the generally low amount of recharge, its spatially and temporally spotty nature, and the absence of techniques for directly measuring fluxes entering the saturated zone from the unsaturated zone. Deep water tables in arid alluvial basins correspond to thick unsaturated zones that produce up to millennial time lags between changes in hydrologic conditions at the land surface and subsequent changes in recharge to underlying ground water. Recent advances in physical, chemical, isotopic, and modeling techniques have

Sandy soil plantation in semi-arid zones by polyacrylamide gel conditioner prepared by ionizing radiation. Part of a coordinated programme on radiation modified polymers for biomedical and biochemical applications

International Nuclear Information System (INIS)

Azzam, R.A.I.

1983-07-01

Polyacrylamide gel prepared by ionizing radiation was found to be capable of furnishing adequate conditions for sandy-soil plantation in semi-arid zones. The gel can be tailored for any soil texture under various climatic conditions. The sand-gel combination maintains three cycles of complete destruction and reformation without significant changes in erosion index. Water holding capacity and retention at different suctions in treated sand are increased. This increases water use efficiency. Fertilizers use efficiency is also increased to almost three times that of fertile clayey soil

Soil Respiration in Semiarid Temperate Grasslands under Various Land Management.

Directory of Open Access Journals (Sweden)

Zhen Wang

Full Text Available Soil respiration, a major component of the global carbon cycle, is significantly influenced by land management practices. Grasslands are potentially a major sink for carbon, but can also be a source. Here, we investigated the potential effect of land management (grazing, clipping, and ungrazed enclosures on soil respiration in the semiarid grassland of northern China. Our results showed the mean soil respiration was significantly higher under enclosures (2.17 μmol.m(-2.s(-1 and clipping (2.06 μmol.m(-2.s(-1 than under grazing (1.65 μmol.m-(2.s(-1 over the three growing seasons. The high rates of soil respiration under enclosure and clipping were associated with the higher belowground net primary productivity (BNPP. Our analyses indicated that soil respiration was primarily related to BNPP under grazing, to soil water content under clipping. Using structural equation models, we found that soil water content, aboveground net primary productivity (ANPP and BNPP regulated soil respiration, with soil water content as the predominant factor. Our findings highlight that management-induced changes in abiotic (soil temperature and soil water content and biotic (ANPP and BNPP factors regulate soil respiration in the semiarid temperate grassland of northern China.

Pythiosis in dogs in the semiarid region of Northeast Brazil

Directory of Open Access Journals (Sweden)

Maria T.S. Frade

Full Text Available ABSTRACT: We describe the epidemiological, clinical and pathological features of five cases of pythiosis in dogs in northeast semiarid. The disease occurred in dogs with age between one and three years, females and males of different breeds. The dogs were created in urban areas, but were occasionally taken to the countryside and then had contact with wetlands. The main clinical signs were weight loss, vomiting, diarrhea and tenesmus. Macroscopically there were intestinal wall thickening with irregular firm masses with yellowish granular areas interspersed with a whitish tissue, involving the duodenum, colon and rectum, extending to the lymph nodes and pancreas, and the vagina and liver. In the skin there were areas of alopecia and irregular ulcerations, some containing small cavitations with serosanguineous secretion. Microscopically there were pyogranulomatous inflammation and in one case also there were eosinophilic necrosis associated with negative images tubuliformes by hematoxylin and eosin, strongly stained by GMS and weakly by PAS. Hyphae were strongly marked by immunohistochemistry with polyclonal anti-Pythium insidiosum. The disease occurs sporadically in dogs in the semiarid Northeast, however should be included in the differential diagnosis of chronic diseases and proliferative aspect of the gastrointestinal system, and front skin lesions of difficult treatment.

LEGUMINOUS COVER CROPS FOR BANANA PLANTATIONS IN SEMI-ARID REGIONS

Directory of Open Access Journals (Sweden)

MATEUS AUGUSTO LIMA QUARESMA

2017-01-01

Full Text Available High temperatures and low rainfall characterize the Brazilian semiarid regions. This regional climate demands the adoption of practices that increase the efficiency and sustainability of local farming. This study aimed to assess the ability of two perennial herbaceous leguminous species, calopo and tropical kudzu, to provide permanent soil cover in banana plantations in Jequitinhonha Valley, northeast Minas Gerais state, Brazil. To this end, we evaluated the differences of calopo and tropical kudzu in soil cover capacity and the amount of senescent phytomass deposited on the soil surface, nutrient content in senescent phytomass, as well as their effects on temperature and soil moisture, compared with bare soil in two experimental sites. The results showed that, compared with tropical kudzu, calopo had a higher soil cover capacity and was more effective at increasing organic material and nutrients in the soil owing to the relatively higher amount of senescent phytomass deposited on the soil surface. However, both calopo and tropical kudzu reduced soil temperature and increase soil moisture compared with bare soil. Overall, we concluded that these species can deposit high levels of senescence in the soil, providing several benefits to the cultivation system of banana plants in the semiarid regions.

Soil Respiration in Semiarid Temperate Grasslands under Various Land Management.

Science.gov (United States)

Wang, Zhen; Ji, Lei; Hou, Xiangyang; Schellenberg, Michael P

2016-01-01

Soil respiration, a major component of the global carbon cycle, is significantly influenced by land management practices. Grasslands are potentially a major sink for carbon, but can also be a source. Here, we investigated the potential effect of land management (grazing, clipping, and ungrazed enclosures) on soil respiration in the semiarid grassland of northern China. Our results showed the mean soil respiration was significantly higher under enclosures (2.17 μmol.m(-2).s(-1)) and clipping (2.06 μmol.m(-2).s(-1)) than under grazing (1.65 μmol.m-(2).s(-1)) over the three growing seasons. The high rates of soil respiration under enclosure and clipping were associated with the higher belowground net primary productivity (BNPP). Our analyses indicated that soil respiration was primarily related to BNPP under grazing, to soil water content under clipping. Using structural equation models, we found that soil water content, aboveground net primary productivity (ANPP) and BNPP regulated soil respiration, with soil water content as the predominant factor. Our findings highlight that management-induced changes in abiotic (soil temperature and soil water content) and biotic (ANPP and BNPP) factors regulate soil respiration in the semiarid temperate grassland of northern China.

Soil water retention as affected by tillage and residue management in semiarid Spain

NARCIS (Netherlands)

Bescansa, P.; Imaz, M.J.; Virto, I.; Enrique, A.; Hoogmoed, W.B.

2006-01-01

Conservation tillage preserves soil water and this has been the main reason for its rapid dissemination in rainfed agriculture in semiarid climates. We determined the effects of conservation versus conventional tillage on available soil water capacity (AWC) and related properties at the end of 5

Jatropha curcasand Ricinus communisdisplay contrasting photosynthetic mechanisms in response to environmental conditions

Directory of Open Access Journals (Sweden)

Milton Costa Lima Neto

2015-06-01

Full Text Available Higher plants display different adaptive strategies in photosynthesis to cope with abiotic stress. In this study, photosynthetic mechanisms and water relationships displayed byJatropha curcasL. (physic nuts andRicinus communisL. (castor bean, in response to variations in environmental conditions, were assessed.R. communis showed higher CO2 assimilation, stomatal and mesophyll conductance thanJ. curcas as light intensity and intercellular CO2 pressure increased. On the other hand,R. communis was less effective in stomatal control in response to adverse environmental factors such as high temperature, water deficit and vapor pressure deficit, indicating lower water use efficiency. Conversely,J. curcas exhibited higher photosynthetic efficiency (gas exchange and photochemistry and water use efficiency under these adverse environmental conditions.R. communisdisplayed higher potential photosynthesis, but exhibited a lowerin vivo Rubisco carboxylation rate (Vcmax and maximum electron transport rate (Jmax. During the course of a typical day, in a semiarid environment, with high irradiation, high temperature and high vapor pressure deficit, but exposed to well-watered conditions, the two studied species presented similar photosynthesis. Losing potential photosynthesis, but maintaining favorable water status and increasing non-photochemical quenching to avoid photoinhibition, are important acclimation mechanisms developed byJ. curcas to cope with dry and hot conditions. We suggest thatJ. curcas is more tolerant to hot and dry environments thanR. communis but the latter species displays higher photosynthetic efficiency under well-watered and non-stressful conditions.

Potential Use of Organic- and Hard-Rock Mine Wastes on Aided Phytostabilization of Large-Scale Mine Tailings under Semiarid Mediterranean Climatic Conditions: Short-Term Field Study

Directory of Open Access Journals (Sweden)

Claudia Santibañez

2012-01-01

Full Text Available The study evaluated the efficacy of organic- and hard-rock mine waste type materials on aided phytostabilization of Cu mine tailings under semiarid Mediterranean conditions in order to promote integrated waste management practices at local levels and to rehabilitate large-scale (from 300 to 3,000 ha postoperative tailings storage facilities (TSFs. A field trial with 13 treatments was established on a TSF to test the efficacy of six waste-type locally available amendments (grape and olive residues, biosolids, goat manure, sediments from irrigation canals, and rubble from Cu-oxide lixiviation piles during early phases of site rehabilitation. Results showed that, even though an interesting range of waste-type materials were tested, biosolids (100 t ha-1 dry weight, d.w. and grape residues (200 t ha-1 d.w., either alone or mixed, were the most suitable organic amendments when incorporated into tailings to a depth of 20 cm. Incorporation of both rubble from Cu-oxide lixiviation piles and goat manure into upper tailings also had effective results. All these treatments improved chemical and microbiological properties of tailings and lead to a significant increase in plant yield after three years from trial establishment. Longer-term evaluations are, however required to evaluate self sustainability of created systems without further incorporation of amendments.

Land degradation assessment by geo-spatially modeling different soil erodibility equations in a semi-arid catchment.

Science.gov (United States)

Saygın, Selen Deviren; Basaran, Mustafa; Ozcan, Ali Ugur; Dolarslan, Melda; Timur, Ozgur Burhan; Yilman, F Ebru; Erpul, Gunay

2011-09-01

Land degradation by soil erosion is one of the most serious problems and environmental issues in many ecosystems of arid and semi-arid regions. Especially, the disturbed areas have greater soil detachability and transportability capacity. Evaluation of land degradation in terms of soil erodibility, by using geostatistical modeling, is vital to protect and reclaim susceptible areas. Soil erodibility, described as the ability of soils to resist erosion, can be measured either directly under natural or simulated rainfall conditions, or indirectly estimated by empirical regression models. This study compares three empirical equations used to determine the soil erodibility factor of revised universal soil loss equation prediction technology based on their geospatial performances in the semi-arid catchment of the Saraykoy II Irrigation Dam located in Cankiri, Turkey. A total of 311 geo-referenced soil samples were collected with irregular intervals from the top soil layer (0-10 cm). Geostatistical analysis was performed with the point values of each equation to determine its spatial pattern. Results showed that equations that used soil organic matter in combination with the soil particle size better agreed with the variations in land use and topography of the catchment than the one using only the particle size distribution. It is recommended that the equations which dynamically integrate soil intrinsic properties with land use, topography, and its influences on the local microclimates, could be successfully used to geospatially determine sites highly susceptible to water erosion, and therefore, to select the agricultural and bio-engineering control measures needed.

Observing Semi-Arid Ecoclimates across Mountain Gradients in the Great Basin, USA

Science.gov (United States)

Strachan, Scotty

Observation of climate and ecohydrological variables in mountain systems is a necessary (if challenging) endeavor for modern society. Water resources are often intimately tied to mountains, and high elevation environments are frequently home to unique landscapes and biota with limited geographical distributions. This is especially true in the temperate and semi-arid mountains of the western United States, and specifically the Great Basin. Stark contrasts in annual water balance and ecological populations are visible across steep elevational gradients in the region; and yet the bulk of our historical knowledge of climate and related processes comes from lowland observations. Interpolative models that strive to estimate conditions in mountains using existing datasets are often found to be inaccurate, making future projections of mountain climate and ecosystem response suspect. This study details the results of high-resolution topographically-diverse ecohydrological monitoring, and describes the character and seasonality of basic climatic variables such as temperature and precipitation as well as their impact on soil moisture and vegetation during the 2012-2015 drought sequence. Relationships of topography (elevation/aspect) to daily and seasonal temperatures are shown. Tests of the PRISM temperature model are performed at the large watershed scale, revealing magnitudes, modes, and potential sources of bias that could dramatically affect derivative scientific conclusions. A new method of precipitation phase partitioning to detect and quantify frozen precipitation on a sub-daily basis is described. Character of precipitation from sub-daily to annual scales is quantified across all major Great Basin vegetation/elevation zones, and the relationship of elevation to precipitation phase, intensity, and amount is explored. Water-stress responses of Great Basin conifers including Pinus flexilis, Pinus longaeva, and Pinus ponderosa are directly observed, showing potential

Long term impact of organic amendments on forest soil properties under semiarid Mediterranean climatic conditions

Science.gov (United States)

Hueso González, Paloma; Francisco Martinez Murillo, Juan; Damian Ruiz Sinoga, Jose

2017-04-01

M, Zorzona BG, Caravaca F.: Soil microbial biomass and activity under different agricultural management systems in a semiarid Mediterranean agroecosystem. Soil and Tillage Research 109: 110-115, 2010. DOI: 10.1016/j.still.2010.05.005 Hueso-González, P., Martínez-Murillo, J.F., and Ruiz Sinoga., J.D.: The impact of organic amendments on forest soil properties under Mediterranean climatic conditions, Land Degradation and Development, 25, 604-612, 2014. Hueso-González, P., Martínez-Murillo, J.F., and Ruiz Sinoga., J.D.: Effects of topsoil treatments on afforestation in a dry-Mediterranean climate (Southern Spain), Solid Earth, 7, 1479-1489, 2016. Hueso-González, P., Ruíz Sinoga, J.D., Martínez-Murillo, J.F., and Lavee, H.: Overland flow generation mechanisms affected by topsoil treatment: Application to soil conservation, Geomorphology, 228, 796-804, 2015. Martínez-Murillo, J.F., Hueso-González, P., Ruiz-Sinoga, J.D., Lavee, H.: Short-Experimental fire effects in soil and water losses in southern of Spain. Land Degradation and Development, 27, 1513-1522, 2016. Parras-Alcántara L, Díaz-Jaimes L, Lozano-García B.: Organic farming affects C and N in soils under olive groves in Mediterranean areas. Land Degradation & Development, 2013. DOI: 10.1002/ldr.2231.

Changes in semi-arid plant species associations along a livestock grazing gradient.

Directory of Open Access Journals (Sweden)

Hugo Saiz

Full Text Available In semi-arid ecosystems, vegetation is heterogeneously distributed, with plant species often associating in patches. These associations between species are not constant, but depend on the particular response of each species to environmental factors. Here, we investigated how plant species associations change in response to livestock grazing in a semi-arid ecosystem, Cabo de Gata-Níjar Natural Park in South East Spain. We established linear point-intercept transects at four sites with different grazing intensity, and recorded all species at each point. We investigated plant associations by comparing the number of times that each pair of species occurred at the same spatial point (co-occurrences, with the expected number of times based on species abundances. We also assessed associations for each shrub and grass species by considering all their pairs of associations and for the whole plant community by considering all pairs of associations on each site. At all sites, the plant community had a negative pattern of association, with fewer co-occurrences than expected. Negative association in the plant community increased at maximum grazing intensity. Most species associated as expected, particularly grass species, and positive associations were most important at intermediate grazing intensities. No species changed its type of association along the grazing gradient. We conclude that in the present plant community, grazing-resistant species compete among themselves and segregate in space. Some shrub species act as refuges for grazing-sensitive species that benefit from being spatially associated with shrub species, particularly at intermediate grazing intensities where positive associations were highest. At high grazing intensity, these shrubs can no longer persist and positive associations decrease due to the disappearance of refuges. Spatial associations between plant species and their response to grazing help identify the factors that organize

Linking the spatial patterns of organisms and abiotic factors to ecosystem function and management: insights from semi-arid environments

Directory of Open Access Journals (Sweden)

F. T. Maestre

2006-12-01

Full Text Available Numerous theoretical and modeling studies have demonstrated the ecological significance of the spatial patterning of organisms on ecosystem functioning and dynamics. However, there is a paucity of empirical evidence that quantitatively shows how changes in the spatial patterns of the organisms forming biotic communities are directly related to ecosystem structure and functioning. In this article, I review a series of experiments and observational studies conducted in semi-arid environments from Spain (degraded calcareous shrubland, steppes dominated by Stipa tenacissima, and gypsum shrublands to: 1 evaluate whether the spatial patterns of the dominant biotic elements in the community are linked to ecosystem structure and functioning, and 2 test if these patterns, and those of abiotic factors, can be used to improve ecosystem restoration. In the semiarid steppes we found a significant positive relationship between the spatial pattern of the perennial plant community and: i the water status of S. tenacissima and ii perennial species richness and diversity. Experimental plantings conducted in these steppes showed that S. tenacissima facilitated the establishment of shrub seedlings, albeit the magnitude and direction of this effect was dependent on rainfall conditions during the first yr after planting. In the gypsum shrubland, a significant, direct relationship between the spatial pattern of the biological soil crusts and surrogates of ecosystem functioning (soil bulk density and respiration was found. In a degraded shrubland with very low vegetation cover, the survival of an introduced population of the shrub Pistacia lentiscus showed marked spatial patterns, which were related to the spatial patterns of soil properties such as soil compaction and sand content. These results provide empirical evidence on the importance of spatial patterns for maintaining ecosystem structure and functioning in semi-arid ecosystems

Phytostabilization of semiarid soils residually contaminated with trace elements using by-products: Sustainability and risks

Energy Technology Data Exchange (ETDEWEB)

Perez-de-Mora, Alfredo, E-mail: perezdemora@gmail.com [Instituto de Recursos Naturales y Agrobiologia de Sevilla (IRNAS), CSIC, PO Box 1052, 41080 Sevilla (Spain); Madejon, Paula; Burgos, Pilar; Cabrera, Francisco [Instituto de Recursos Naturales y Agrobiologia de Sevilla (IRNAS), CSIC, PO Box 1052, 41080 Sevilla (Spain); Lepp, Nicholas W. [35, Victoria Road, Formby, Liverpool L37 7DH (United Kingdom); Madejon, Engracia [Instituto de Recursos Naturales y Agrobiologia de Sevilla (IRNAS), CSIC, PO Box 1052, 41080 Sevilla (Spain)

2011-10-15

We investigated the efficiency of various by-products (sugarbeet lime, biosolid compost and leonardite), based on single or repeated applications to field plots, on the establishment of a vegetation cover compatible with a stabilization strategy on a multi-element (As, Cd, Cu, Pb and Zn) contaminated soil 4-6 years after initial amendment applications. Results indicate that the need for re-treatment is amendment- and element-dependent; in some cases, a single application may reduce trace element concentrations in above-ground biomass and enhance the establishment of a healthy vegetation cover. Amendment performance as evaluated by % cover, biomass and number of colonizing taxa differs; however, changes in plant community composition are not necessarily amendment-specific. Although the translocation of trace elements to the plant biotic compartment is greater in re-vegetated areas, overall loss of trace elements due to soil erosion and plant uptake is usually smaller compared to that in bare soil. - Highlights: > By-products enhance vegetation dynamics in contaminated semiarid soils. > Depending on the situation single or repeated incorporations may be required. > The structure of the plant community established is not amendment-dependent. > Phytostabilization reduces overall loss of trace elements in semiarid soils. - Phytostabilization using by-products as amendments is a suitable approach for long-term immobilization of various trace elements in semiarid contaminated soils.

Phytostabilization of semiarid soils residually contaminated with trace elements using by-products: Sustainability and risks

International Nuclear Information System (INIS)

Perez-de-Mora, Alfredo; Madejon, Paula; Burgos, Pilar; Cabrera, Francisco; Lepp, Nicholas W.; Madejon, Engracia

2011-01-01

We investigated the efficiency of various by-products (sugarbeet lime, biosolid compost and leonardite), based on single or repeated applications to field plots, on the establishment of a vegetation cover compatible with a stabilization strategy on a multi-element (As, Cd, Cu, Pb and Zn) contaminated soil 4-6 years after initial amendment applications. Results indicate that the need for re-treatment is amendment- and element-dependent; in some cases, a single application may reduce trace element concentrations in above-ground biomass and enhance the establishment of a healthy vegetation cover. Amendment performance as evaluated by % cover, biomass and number of colonizing taxa differs; however, changes in plant community composition are not necessarily amendment-specific. Although the translocation of trace elements to the plant biotic compartment is greater in re-vegetated areas, overall loss of trace elements due to soil erosion and plant uptake is usually smaller compared to that in bare soil. - Highlights: → By-products enhance vegetation dynamics in contaminated semiarid soils. → Depending on the situation single or repeated incorporations may be required. → The structure of the plant community established is not amendment-dependent. → Phytostabilization reduces overall loss of trace elements in semiarid soils. - Phytostabilization using by-products as amendments is a suitable approach for long-term immobilization of various trace elements in semiarid contaminated soils.

Arbuscular mycorrhizal fungi regulate soil respiration and its response to precipitation change in a semiarid steppe.

Science.gov (United States)

Zhang, Bingwei; Li, Shan; Chen, Shiping; Ren, Tingting; Yang, Zhiqiang; Zhao, Hanlin; Liang, Yu; Han, Xingguo

2016-01-28

Arbuscular mycorrhizal fungi (AMF) are critical links in plant-soil continuum and play a critical role in soil carbon cycles. Soil respiration, one of the largest carbon fluxes in global carbon cycle, is sensitive to precipitation change in semiarid ecosystems. In this study, a field experiment with fungicide application and water addition was conducted during 2010-2013 in a semiarid steppe in Inner Mongolia, China, and soil respiration was continuously measured to investigate the influences of AMF on soil respiration under different precipitation regimes. Results showed that soil respiration was promoted by water addition treatment especially during drought seasons, which induced a nonlinear response of soil respiration to precipitation change. Fungicide application suppressed AMF root colonization without impacts on soil microbes. AMF suppression treatment accelerated soil respiration with 2.7, 28.5 and 37.6 g C m(-2) across three seasons, which were mainly caused by the enhanced heterotrophic component. A steeper response of soil respiration rate to precipitation was found under fungicide application treatments, suggesting a greater dampening effect of AMF on soil carbon release as water availability increased. Our study highlighted the importance of AMF on soil carbon stabilization and sequestration in semiarid steppe ecosystems especially during wet seasons.

Arbuscular mycorrhizal fungi regulate soil respiration and its response to precipitation change in a semiarid steppe

Science.gov (United States)

Zhang, Bingwei; Li, Shan; Chen, Shiping; Ren, Tingting; Yang, Zhiqiang; Zhao, Hanlin; Liang, Yu; Han, Xingguo

2016-01-01

Arbuscular mycorrhizal fungi (AMF) are critical links in plant-soil continuum and play a critical role in soil carbon cycles. Soil respiration, one of the largest carbon fluxes in global carbon cycle, is sensitive to precipitation change in semiarid ecosystems. In this study, a field experiment with fungicide application and water addition was conducted during 2010-2013 in a semiarid steppe in Inner Mongolia, China, and soil respiration was continuously measured to investigate the influences of AMF on soil respiration under different precipitation regimes. Results showed that soil respiration was promoted by water addition treatment especially during drought seasons, which induced a nonlinear response of soil respiration to precipitation change. Fungicide application suppressed AMF root colonization without impacts on soil microbes. AMF suppression treatment accelerated soil respiration with 2.7, 28.5 and 37.6 g C m-2 across three seasons, which were mainly caused by the enhanced heterotrophic component. A steeper response of soil respiration rate to precipitation was found under fungicide application treatments, suggesting a greater dampening effect of AMF on soil carbon release as water availability increased. Our study highlighted the importance of AMF on soil carbon stabilization and sequestration in semiarid steppe ecosystems especially during wet seasons.

CMIP5 land surface models systematically underestimate inter-annual variability of net ecosystem exchange in semi-arid southwestern North America.

Science.gov (United States)

MacBean, N.; Scott, R. L.; Biederman, J. A.; Vuichard, N.; Hudson, A.; Barnes, M.; Fox, A. M.; Smith, W. K.; Peylin, P. P.; Maignan, F.; Moore, D. J.

2017-12-01

Recent studies based on analysis of atmospheric CO2 inversions, satellite data and terrestrial biosphere model simulations have suggested that semi-arid ecosystems play a dominant role in the interannual variability and long-term trend in the global carbon sink. These studies have largely cited the response of vegetation activity to changing moisture availability as the primary mechanism of variability. However, some land surface models (LSMs) used in these studies have performed poorly in comparison to satellite-based observations of vegetation dynamics in semi-arid regions. Further analysis is therefore needed to ensure semi-arid carbon cycle processes are well represented in global scale LSMs before we can fully establish their contribution to the global carbon cycle. In this study, we evaluated annual net ecosystem exchange (NEE) simulated by CMIP5 land surface models using observations from 20 Ameriflux sites across semi-arid southwestern North America. We found that CMIP5 models systematically underestimate the magnitude and sign of NEE inter-annual variability; therefore, the true role of semi-arid regions in the global carbon cycle may be even more important than previously thought. To diagnose the factors responsible for this bias, we used the ORCHIDEE LSM to test different climate forcing data, prescribed vegetation fractions and model structures. Climate and prescribed vegetation do contribute to uncertainty in annual NEE simulations, but the bias is primarily caused by incorrect timing and magnitude of peak gross carbon fluxes. Modifications to the hydrology scheme improved simulations of soil moisture in comparison to data. This in turn improved the seasonal cycle of carbon uptake due to a more realistic limitation on photosynthesis during water stress. However, the peak fluxes are still too low, and phenology is poorly represented for desert shrubs and grasses. We provide suggestions on model developments needed to tackle these issues in the future.

Spectral mixture analysis (SMA and change vector analysis (CVA methods for monitoring and mapping land degradation/desertification in arid and semiarid areas (Sudan, using Landsat imagery

Directory of Open Access Journals (Sweden)

Abdelrahim A.M. Salih

2017-04-01

Full Text Available The severe Sahel catastrophe in 1968–1974 as well as repeated famines and food shortage that have hit many African countries during the 1970s have highlighted the need for further research concerning land degradation and environmental monitoring in arid and semi-arid areas. Land degradation, and desertification processes in arid and semi-arid environment were increased in the last four decades, especially in the developing countries like Sudan. To test to what extent remote sensing and geographical information science (GIS methodologies and techniques could be used for monitoring changes in arid and semi-arid regions and environment, these methodologies have long been suggested as a time and cost-efficient method. In this frame, spectral Mixture Analysis (SMA, Object-based oriented classification (Segmentation, and Change Vector Analysis are recently much recommended as a most suitable method for monitoring and mapping land cover changes in arid and semi-arid environment. Therefor the aim of this study is to use these methods and techniques for environmental monitoring with emphasis on desertification and to find model that can describe and map the status and rate of desertification processes and land cover changes in semi-arid areas in White Nile State (Sudan by using multi-temporal imagery of the Landsat satellite TM (1987, TM (2000, and ETM+ (2014 respectively. The paper also discusses and evaluates the efficiency of the adapted methodologies in monitoring the land degradation processes and changes in the arid and semi-arid regions.

Untangling the biological contributions to soil stability in semiarid shrublands

Science.gov (United States)

Chaudhary, V. Bala; Bowker, Matthew A.; O'Dell, Thomas E.; Grace, James B.; Redman, Andrea E.; Rillig, Matthias C.; Johnson, Nancy C.

2009-01-01

Communities of plants, biological soil crusts (BSCs), and arbuscular mycorrhizal (AM) fungi are known to influence soil stability individually, but their relative contributions, interactions, and combined effects are not well understood, particularly in arid and semiarid ecosystems. In a landscape-scale field study we quantified plant, BSC, and AM fungal communities at 216 locations along a gradient of soil stability levels in southern Utah, USA. We used multivariate modeling to examine the relative influences of plants, BSCs, and AM fungi on surface and subsurface stability in a semiarid shrubland landscape. Models were found to be congruent with the data and explained 35% of the variation in surface stability and 54% of the variation in subsurface stability. The results support several tentative conclusions. While BSCs, plants, and AM fungi all contribute to surface stability, only plants and AM fungi contribute to subsurface stability. In both surface and subsurface models, the strongest contributions to soil stability are made by biological components of the system. Biological soil crust cover was found to have the strongest direct effect on surface soil stability (0.60; controlling for other factors). Surprisingly, AM fungi appeared to influence surface soil stability (0.37), even though they are not generally considered to exist in the top few millimeters of the soil. In the subsurface model, plant cover appeared to have the strongest direct influence on soil stability (0.42); in both models, results indicate that plant cover influences soil stability both directly (controlling for other factors) and indirectly through influences on other organisms. Soil organic matter was not found to have a direct contribution to surface or subsurface stability in this system. The relative influence of AM fungi on soil stability in these semiarid shrublands was similar to that reported for a mesic tallgrass prairie. Estimates of effects that BSCs, plants, and AM fungi have

Geoecohydrological mechanisms couple soil and leaf water dynamics and facilitate species coexistence in shallow soils of a tropical semiarid mixed forest.

Science.gov (United States)

Rodríguez-Robles, Ulises; Arredondo, J Tulio; Huber-Sannwald, Elisabeth; Vargas, Rodrigo

2015-07-01

Trees growing on shallow rocky soils must have exceptional adaptations when underlying weathered bedrock has no deep fractures for water storage. Under semiarid conditions, hydrology of shallow soils is expected to decouple from plant hydrology, as soils dry out as a result of rapid evaporation and competition for water increases between coexisting tree species. Gas exchange and plant-water relations were monitored for 15 months for Pinus cembroides and Quercus potosina tree species in a tropical semiarid forest growing on c. 20-cm-deep soils over impermeable volcanic bedrock. Soil and leaf water potential maintained a relatively constant offset throughout the year in spite of high intra-annual fluctuations reaching up to 5 MPa. Thus, hydrology of shallow soils did not decouple from hydrology of trees even in the driest period. A combination of redistribution mechanisms of water stored in weathered bedrock and hypodermic flow accessible to oak provided the source of water supply to shallow soils, where most of the actively growing roots occurred. This study demonstrates a unique geoecohydrological mechanism that maintains a tightly coupled hydrology between shallow rocky soils and trees, as well as species coexistence in this mixed forest, where oak facilitates water access to pine. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

An AES Study of the Room Temperature Surface Conditioning of Technological Metal Surfaces by Electron Irradiation

CERN Document Server

Scheuerlein, C; Taborelli, M; Brown, A; Baker, M A

2002-01-01

The modifications to technological copper and niobium surfaces induced by 2.5 keV electron irradiation have been investigated in the context of the conditioning process occurring in particle accelerator ultra high vacuum systems. Changes in the elemental surface composition have been found using Scanning Auger Microscopy (SAM) by monitoring the carbon, oxygen and metal Auger peak intensities as a function of electron irradiation in the dose range 10-6 to 10-2 C mm-2. The surface analysis results are compared with electron dose dependent secondary electron and electron stimulated desorption yield measurements. Initially the electron irradiation causes a surface cleaning through electron stimulated desorption, in particular of hydrogen. During this period both the electron stimulated desorption and secondary electron yield decrease as a function of electron dose. When the electron dose exceeds 10-4 C mm-2 electron stimulated desorption yields are reduced by several orders of magnitude and the electron beam indu...

THE EFFECT OF INTRODUCED FORAGE LEGUMES ON IMPROVEMENT OF SOIL FERTILITY IN NATURAL PASTURES OF SEMI-ARID RANGELANDS OF KAJIADO DISTRICT, KENYA

Directory of Open Access Journals (Sweden)

Peter N Macharia

2010-11-01

Full Text Available A two phase study was carried out from 2002 to 2005 in the semi-arid rangelands of Kajiado District, Kenya to determine the effect of introduced forage legumes on soil fertility improvement of natural pastures. During legume evaluation phase, Neonotonia wightii (Glycine, Macroptilium atropurpureum (Siratro, Lablab purpureus cv. Rongai (Dolichos, Mucuna pruriens (Velvet bean and Stylosanthes scabra var. Seca (Stylo were screened for adaptability and growth performance under the semi-arid conditions for two years. Results of soil analysis showed there were significant increases in soil pH (4.92 to 5.36, organic carbon (1.17 to 2.57% , nitrogen (0.17 to 0.22% and potassium (1.23 to 1.68 me% probably due to the large amounts of organic residues produced by the legumes (particularly Glycine, Siratro and Stylo which are perennials. The calcium content decreased significantly from 7.97 to 4.50 me% (which was attributed to plant uptake while the decrease of phosphorus was not significant. During the second phase of study for 1½ years Glycine, Siratro and Stylo were integrated into natural pastures. The results showed that only the soil pH significantly increased from 5.23 to 5.31 while all the other nutrients decreased results, which were attributed to production of less organic residues by the legumes compared to the residues produced during the legume evaluation phase. The study concluded that Glycine, Siratro and Stylo were capable of improving the soil fertility of semi-arid natural pastures only if the respective dry matter production was 10.31, 7.81 and 3.52 tha-1, amounts which were able to produce large amounts of organic residues. Â

Application of factor analysis and electrical resistivity to understand groundwater contributions to coastal embayments in semi-arid and hypersaline coastal settings

Energy Technology Data Exchange (ETDEWEB)

Bighash, Paniz, E-mail: Bighash.p@gmail.com; Murgulet, Dorina

2015-11-01

Groundwater contributions and sources of salinity to Oso Bay in south Texas were investigated using multivariate statistical analysis of geochemical data and multitemporal electrical resistivity tomography surveys. Both analysis of geochemical data and subsurface imaging techniques identified two commonalities for the investigated system: 1) hypersaline water occurs near the groundwater/surface water interface during wet conditions creating reverse hydraulic gradients due to density effects. The development and downward movement of these fluids as continuous plumes deflect fresher groundwater discharge downward and laterally away from the surface; and 2) more pronounced upwelling of fresher groundwater occurs during drought periods when density inversions are more defined and are expected to overcome dispersion and diffusion processes and create sufficiently large-enough unstable gradients that induce density-difference convection. Salinity mass-balance models derived from time-difference resistivity tomograph and in-situ salinity data reaffirm these findings indicating that groundwater upwelling is more prominent during dry to wet conditions in 2013 (~ 545.5 m{sup 3}/d) and is less pronounced during wet to dry conditions in 2012 (~ 262.7 m{sup 3}/d) for the 224 m{sup 2} area surveyed. Findings show that the highly saline nature of water in this area and changes in salinity regimes can be attributed to a combination of factors, namely: surface outflows, evapoconcentration, recirculation of hypersaline groundwaters, and potential trapped oil field brines. Increased drought conditions will likely exacerbate the rate at which salinity levels are increasing in bays and estuaries in semi-arid regions where both hypersaline groundwater discharge and high evaporation rates occur simultaneously. - Highlights: • Study of salinity regimes in relation to groundwater in a coastal semiarid setting • Factor analysis defined dominant factors influencing water quality

Application of factor analysis and electrical resistivity to understand groundwater contributions to coastal embayments in semi-arid and hypersaline coastal settings

International Nuclear Information System (INIS)

Bighash, Paniz; Murgulet, Dorina

2015-01-01

Groundwater contributions and sources of salinity to Oso Bay in south Texas were investigated using multivariate statistical analysis of geochemical data and multitemporal electrical resistivity tomography surveys. Both analysis of geochemical data and subsurface imaging techniques identified two commonalities for the investigated system: 1) hypersaline water occurs near the groundwater/surface water interface during wet conditions creating reverse hydraulic gradients due to density effects. The development and downward movement of these fluids as continuous plumes deflect fresher groundwater discharge downward and laterally away from the surface; and 2) more pronounced upwelling of fresher groundwater occurs during drought periods when density inversions are more defined and are expected to overcome dispersion and diffusion processes and create sufficiently large-enough unstable gradients that induce density-difference convection. Salinity mass-balance models derived from time-difference resistivity tomograph and in-situ salinity data reaffirm these findings indicating that groundwater upwelling is more prominent during dry to wet conditions in 2013 (~ 545.5 m 3 /d) and is less pronounced during wet to dry conditions in 2012 (~ 262.7 m 3 /d) for the 224 m 2 area surveyed. Findings show that the highly saline nature of water in this area and changes in salinity regimes can be attributed to a combination of factors, namely: surface outflows, evapoconcentration, recirculation of hypersaline groundwaters, and potential trapped oil field brines. Increased drought conditions will likely exacerbate the rate at which salinity levels are increasing in bays and estuaries in semi-arid regions where both hypersaline groundwater discharge and high evaporation rates occur simultaneously. - Highlights: • Study of salinity regimes in relation to groundwater in a coastal semiarid setting • Factor analysis defined dominant factors influencing water quality variations. �

Development of D-region electron and ion densities under various auroral conditions during the Energy Budget Campaign (EBC)

International Nuclear Information System (INIS)

Brekke, A.; Holt, O.; Friedrich, M.; Hansen, T.; Stauning, P.; Thrane, E.V.

1985-01-01

D-region electron density profiles and time variations were obtained during the Energy Budget Campaign 1980 by a partial reflection radar at Ramfjordmoen, Tromso, located between the rocket ranges at Andoya and Kiruna. The observations were made under various geophysical conditions which are illustrated by riometer observations. The partial reflection measurements indicate that the rockets were launched into a relatively stable D-region on two occasions, while it was somewhat more disturbed on the third. A comparison between the electron density profiles derived by the partial reflection technique and rocket borne probes and Faraday rotation experiments does indicate fair agreement during the quiet conditions, but relatively large discrepancies during disturbed conditions. Simultaneously derived electron density profiles, by use of the Faraday technique, and ion density profiles, by gridded electrostatic spheres mounted on the rocket payload, have made it possible to estimate the negative ion to electron density ratio lambda versus height. These values of lambda are within the range of model calculations. (author)

Chemical and Physical Weathering of Granites in a Semi-Arid Savanna

Science.gov (United States)

Khomo, L.; Hartshorn, A.; Chadwick, O.; Kurtz, A.; Heimsath, A.; Rogers, K.

2005-12-01

The catena concept describes soil properties on hillslopes and implies a hydrological mass redistribution process that has been applied differently in different parts of the Earth. In tectonically active regions, it is mostly used to describe the redistribution of mass by overland flow leading to thickening soil mantles downslope. This application is somewhat different from its initial and still popular usage in tectonically inactive areas of Africa, where it defines long-term soil property differentiation along hillslopes as controlled by internal soil hydrology as opposed to overland flow. Many ecologists have found the "African" catena concept to be useful as an organizing principal for savanna studies, but there has been little recent research on catenas per se in Africa. Elsewhere however, there is a growing body of research that places the concept ever more strongly into a landscape evolution context. Here, we apply these new approaches to catenas in a South African savanna underlain by a heterogeneous suite of Basement granites straddling a gradient in effective precipitation. We constrain the weathering extent of hilly terrains formed on these oldrocks by calculating element losses with solid-phase mass-balance calculations augmented by cosmogenic (26Al/10Be) derived rates of landscape denudation. We test the efficacy of Ti, Zr and Nb as immobile elements to benchmark chemical losses and gains in these semi-arid weathering environments. We also trace and quantify the abundance of the host minerals for these elements (Ti = rutile and ilmenite, Nb = columbite and Zr = zircon and baddleyite) in a variety of rocks in the basement complex. This analysis provides the boundary conditions for assigning immobile elements to parent materials required for the mass balance calculations. We calculate total denudation using the cosmogenic isotopes and then partition it into chemical and physical loss vectors using the mass balance calculations for representative

Basic regulatory principles of Escherichia coli's electron transport chain for varying oxygen conditions

NARCIS (Netherlands)

Henkel, S.G.; Ter Beek, A.S.; Steinsiek, S.; Stagge, S.; Bettenbrock, K.; Teixeira De Mattos, M.J.; Sauter, T.; Sawodny, O.; Ederer, M.

2014-01-01

For adaptation between anaerobic, micro-aerobic and aerobic conditions Escherichia coli's metabolism and in particular its electron transport chain (ETC) is highly regulated. Although it is known that the global transcriptional regulators FNR and ArcA are involved in oxygen response it is unclear

Interband optical absorption in the Wannier-Stark ladder under the electron-LO-phonon resonance condition

International Nuclear Information System (INIS)

Govorov, A.O.

1993-08-01

Interband optical absorption in the Wannier-Stark ladder in the presence of the electron-LO-phonon resonance is investigated theoretically. The electron-LO-phonon resonance occurs when the energy spacing between adjacent Stark-ladder levels coincides with the LO-phonon energy. We propose a model describing the polaron effect in a superlattice. Calculations show that the absorption line shape is strongly modified due to the polaron effect under the electron-LO-phonon resonance condition. We consider optical phenomena in a normal magnetic field that leads to enhancement of polaron effects. (author). 17 refs, 5 figs

Growth and yield performance of Jerusalem artichoke clones in a semiarid region of China

NARCIS (Netherlands)

Liu, Z.X.; Spiertz, J.H.J.; Sha, J.; Xue, S.; Xie, G.H.

2012-01-01

This study investigated biomass yield and growth characteristics of 26 Jerusalem artichoke (Helianthus tuberosus L.) clones and assessed it as a bioenergy crop for a semiarid region of the Loess Plateau in China. Genotype, year, and genotype ´ year interaction contributed to differences in crop

Testing for thresholds in a semiarid grassland: The influence of prairie dogs and plague

Science.gov (United States)

State and transition models for semiarid grasslands in the Great Plains of North America suggest that the presence of herbivorous black-tailed prairie dogs (Cynomys ludovicianus) on a site (1) creates a vegetation state characterized by increased dominance of annual forbs and unpalatable bunchgrasse...

Polyacrylamide molecular weight and phosphogypsum effects on infiltration and erosion in semi-arid soils

Science.gov (United States)

Seal formation at the surface of semi-arid soils during rainstorms reduces soil infiltration rate (IR) and causes runoff and erosion. Surface application of dry anionic polyacrylamide (PAM) with high molecular weight (MW) has been found to be effective in stabilizing soil aggregates, and decreasing ...

Integrated Scenarios of Regional Development in Two Semi-Arid States of North-Eastern Brazil

NARCIS (Netherlands)

Döll, Petra; Krol, Martinus S.

2002-01-01

Scenario analysis of the future is an important tool for supporting sustainability-oriented regional planning. To assist regional planning in two federal states in semi-arid North-eastern Brazil, Ceará and Piauí, we developed integrated qualitative¿quantitative scenarios that show potential

Rainfall-interception-evaporation-runoff relationships in a semi-arid catchment, northern Limpopo basin, Zimbabwe

NARCIS (Netherlands)

Love, D.; Uhlenbrook, S.; Corzo Perez, G.; Twomlow, S.; Zaag, van der P.

2010-01-01

Characterizing the response of a catchment to rainfall, in terms of the production of runoff vs the interception, transpiration and evaporation of water, is the first important step in understanding water resource availability in a catchment. This is particularly important in small semi-arid

Basic regulatory principles of Escherichia coli's electron transport chain for varying oxygen conditions.

Science.gov (United States)

Henkel, Sebastian G; Ter Beek, Alexander; Steinsiek, Sonja; Stagge, Stefan; Bettenbrock, Katja; de Mattos, M Joost Teixeira; Sauter, Thomas; Sawodny, Oliver; Ederer, Michael

2014-01-01

For adaptation between anaerobic, micro-aerobic and aerobic conditions Escherichia coli's metabolism and in particular its electron transport chain (ETC) is highly regulated. Although it is known that the global transcriptional regulators FNR and ArcA are involved in oxygen response it is unclear how they interplay in the regulation of ETC enzymes under micro-aerobic chemostat conditions. Also, there are diverse results which and how quinones (oxidised/reduced, ubiquinone/other quinones) are controlling the ArcBA two-component system. In the following a mathematical model of the E. coli ETC linked to basic modules for substrate uptake, fermentation product excretion and biomass formation is introduced. The kinetic modelling focusses on regulatory principles of the ETC for varying oxygen conditions in glucose-limited continuous cultures. The model is based on the balance of electron donation (glucose) and acceptance (oxygen or other acceptors). Also, it is able to account for different chemostat conditions due to changed substrate concentrations and dilution rates. The parameter identification process is divided into an estimation and a validation step based on previously published and new experimental data. The model shows that experimentally observed, qualitatively different behaviour of the ubiquinone redox state and the ArcA activity profile in the micro-aerobic range for different experimental conditions can emerge from a single network structure. The network structure features a strong feed-forward effect from the FNR regulatory system to the ArcBA regulatory system via a common control of the dehydrogenases of the ETC. The model supports the hypothesis that ubiquinone but not ubiquinol plays a key role in determining the activity of ArcBA in a glucose-limited chemostat at micro-aerobic conditions.

Effect of storage conditions on graft of polypropylene non-woven fabric induced by electron beam

Energy Technology Data Exchange (ETDEWEB)

Lee, Jin Young; Jeun, Joon Pyo; Kang, Phil Hyun [Radiation Research Dvision for Industry and Environment, Korea Atomic Energy Research Institute, Jeongeup(Korea, Republic of)

2015-05-15

In this study, we fabricated effect of storage conditions on graft of polypropylene (PP) non-woven fabric induced by electron beam. The electron beam irradiations on PP non-woven fabric were carried out over a range of irradiation doses from 25 to 100 kGy to make free radicals on fabric surface. The radical measurement was established by electron spin resonance (ESR) for confirming the changes of the alkyl radical and peroxy radical according to effect of storage time, storage temperature and atmosphere. It was observed that the free radicals were increased with irradiation dose and decreased with storage time due to the continuous oxidation. However, the radical extinction was significantly delayed due to reduced mobility of radicals at extremely low temperature. The degree of graft based on the analysis of ESR was investigated. The conditions of graft reaction were set at a temperature: 60 degrees Celcius, reaction time: 6 hours and styrene monomer concentration: 20 wt%.

Spatiotemporal soil and saprolite moisture dynamics across a semi-arid woody plant gradient

Science.gov (United States)

Woody plant cover has increased 10-fold over the last 140+ years in many parts of the semi-arid western USA. Woody plant cover can alter the timing and amount of plant available moisture in the soil and saprolite. To assess spatiotemporal subsurface moisture dynamics over two water years in a snow-d...

Microbial Anaerobic Ammonium Oxidation Under Iron Reducing Conditions, Alternative Electron Acceptors

Science.gov (United States)

Ruiz-Urigüen, M.; Jaffe, P. R.

2015-12-01

Autotrophic Acidimicrobiaceae-bacterium named A6 (A6), part of the Actinobacteria phylum have been linked to anaerobic ammonium (NH4+) oxidation under iron reducing conditions. These organisms obtain their energy by oxidizing NH4+ and transferring the electrons to a terminal electron acceptor (TEA). Under environmental conditions, the TEAs are iron oxides [Fe(III)], which are reduced to Fe(II), this process is known as Feammox. Our studies indicate that alternative forms of TEAs can be used by A6, e.g. iron rich clays (i.e. nontronite) and electrodes in bioelectrochemical systems such as Microbial Electrolysis Cells (MECs), which can sustain NH4+removal and A6 biomass production. Our results show that nontronite can support Feammox and promote bacterial cell production. A6 biomass increased from 4.7 x 104 to 3.9 x 105 cells/ml in 10 days. Incubations of A6 in nontronite resulted in up to 10 times more NH4+ removal and 3 times more biomass production than when ferrihydrite is used as the Fe(III) source. Additionally, Fe in nontronite can be reoxidized by aeration and A6 can reutilize it; however, Fe is still finite in the clay. In contrast, in MECs, A6 harvest electrons from NH4+ and use an anode as an unlimited TEA, as a result current is produced. We operated multiple MECs in parallel using a single external power source, as described by Call & Logan (2011). MECs were run with an applied voltage of 0.7V and different growing mediums always containing initial 5mM NH4+. Results show that current production is favored when anthraquinone-2,6-disulfonate (AQDS), an electron shuttled, is present in the medium as it facilitates the transfer of electrons from the bacterial cell to the anode. Additionally, A6 biomass increased from 1 x 104 to 9.77 x 105cells/ml in 14 days of operation. Due to Acidimicrobiaceae-bacterium A6's ability to use various TEAs, MECs represent an alternative, iron-free form, for optimized biomass production of A6 and its application in NH4

Polarization reversal of electron cyclotron wave due to radial boundary condition

International Nuclear Information System (INIS)

Takahashi, K.; Kaneko, T.; Hatakeyama, R.

2004-01-01

The electron cyclotron wave is an important plasma wave in the fields of basic plasma physics and nuclear fusion. Propagation and absorption of electromagnetic waves with electron cyclotron resonance (ECR) frequency are experimentally and theoretically investigated for the case of inhomogeneously magnetized plasma column with peripheral vacuum layer, when a left-hand polarized wave (LHPW) is selectively launched. The polarization reversal from the LHPW to the right-hand polarized wave is found to occur near the ECR point. As a result, it is clarified that the LHPW, which has been considered not to be absorbed at the ECR point, is absorbed near the ECR point. The phenomena can be explained by taking into account the effects of the radial boundary conditions. In addition, it is found that the polarization reversal point can be adjusted by the external parameters, for example, plasma radius. (authors)

Bottom-up control of consumers leads to top-down indirect facilitation of invasive annual herbs in semiarid Chile.

Science.gov (United States)

Madrigal, Jaime; Kelt, Douglas A; Meserve, Peter L; Gutierrez, Julio R; Squeo, Francisco A

2011-02-01

The abundance of exotic plants is thought to be limited by competition with resident species (including plants and generalist herbivores). In contrast, observations in semiarid Chile suggest that a native generalist rodent, the degu (Octodon degus), may be facilitating the expansion of exotic annual plants. We tested this hypothesis with a 20-year data set from a World Biosphere Reserve in mediterranean Chile. In this semiarid environment, rainfall varies annually and dramatically influences cover by both native and exotic annual plants; degu population density affects the composition and cover of exotic and native annual plants. In low-rainfall years, cover of both native and exotic herbs is extremely low. Higher levels of precipitation result in proportional increases in cover of all annual plants (exotic and native species), leading in turn to increases in degu population densities, at which point they impact native herbs in proportion to their greater cover, indirectly favoring the expansion of exotic plants. We propose that bottom-up control of consumers at our site results in top-down indirect facilitation of invasive annual herbs, and that this pattern may be general to other semiarid ecosystems.

High Spatial Resolution Visual Band Imagery Outperforms Medium Resolution Spectral Imagery for Ecosystem Assessment in the Semi-Arid Brazilian Sertão

Directory of Open Access Journals (Sweden)

Ran Goldblatt

2017-12-01

Full Text Available Semi-arid ecosystems play a key role in global agricultural production, seasonal carbon cycle dynamics, and longer-run climate change. Because semi-arid landscapes are heterogeneous and often sparsely vegetated, repeated and large-scale ecosystem assessments of these regions have to date been impossible. Here, we assess the potential of high-spatial resolution visible band imagery for semi-arid ecosystem mapping. We use WorldView satellite imagery at 0.3–0.5 m resolution to develop a reference data set of nearly 10,000 labeled examples of three classes—trees, shrubs/grasses, and bare land—across 1000 km 2 of the semi-arid Sertão region of northeast Brazil. Using Google Earth Engine, we show that classification with low-spectral but high-spatial resolution input (WorldView outperforms classification with the full spectral information available from Landsat 30 m resolution imagery as input. Classification with high spatial resolution input improves detection of sparse vegetation and distinction between trees and seasonal shrubs and grasses, two features which are lost at coarser spatial (but higher spectral resolution input. Our total tree cover estimates for the study area disagree with recent estimates using other methods that may underestimate treecover because they confuse trees with seasonal vegetation (shrubs and grasses. This distinction is important for monitoring seasonal and long-run carbon cycle and ecosystem health. Our results suggest that newer remote sensing products that promise high frequency global coverage at high spatial but lower spectral resolution may offer new possibilities for direct monitoring of the world’s semi-arid ecosystems, and we provide methods that could be scaled to do so.

Modeling mechanisms of vegetation change due to fire in a semi-arid ecosystem

Science.gov (United States)

White, J.D.; Gutzwiller, K.J.; Barrow, W.C.; Randall, L.J.; Swint, P.

2008-01-01

Vegetation growth and community composition in semi-arid environments is determined by water availability and carbon assimilation mechanisms specific to different plant types. Disturbance also impacts vegetation productivity and composition dependent on area affected, intensity, and frequency factors. In this study, a new spatially explicit ecosystem model is presented for the purpose of simulating vegetation cover type changes associated with fire disturbance in the northern Chihuahuan Desert region. The model is called the Landscape and Fire Simulator (LAFS) and represents physiological activity of six functional plant types incorporating site climate, fire, and seed dispersal routines for individual grid cells. We applied this model for Big Bend National Park, Texas, by assessing the impact of wildfire on the trajectory of vegetation communities over time. The model was initialized and calibrated based on landcover maps derived from Landsat-5 Thematic Mapper data acquired in 1986 and 1999 coupled with plant biomass measurements collected in the field during 2000. Initial vegetation cover change analysis from satellite data showed shrub encroachment during this time period that was captured in the simulated results. A synthetic 50-year climate record was derived from historical meteorological data to assess system response based on initial landcover conditions. This simulation showed that shrublands increased to the detriment of grass and yucca-ocotillo vegetation cover types indicating an ecosystem-level trajectory for shrub encroachment. Our analysis of simulated fires also showed that fires significantly reduced site biomass components including leaf area, stem, and seed biomass in this semi-arid ecosystem. In contrast to other landscape simulation models, this new model incorporates detailed physiological responses of functional plant types that will allow us to simulated the impact of increased atmospheric CO2 occurring with climate change coupled with fire

An automated microlysimeter to study dew formation and evaporation in arid and semiarid regions

NARCIS (Netherlands)

Heusinkveld, B.G.; Berkowicz, S.M.; Jacobs, A.F.G.; Holtslag, A.A.M.; Hillen, W.C.A.M.

2006-01-01

The development of a simple and low-cost portable weighing microlysimeter that makes use of a load cell for automated recording and for studying daily dew formation, rate of accumulation, and subsequent evaporation in arid or semiarid regions during rainless seasons is presented. The sampling cup is

Agroforestry parkland species diversity : uses and management in semi-arid West-Africa (Burkina Faso)

NARCIS (Netherlands)

Nikiema, A.

2005-01-01

Agroforestry parkland in semi-arid West Africa is a rural land use system, which allows farmers to grow annual crops in combination with useful trees. In addition to cereals, tree products such as vegetables, fruits, vegetable oil, firewood, fodder, and medicines are obtained from the parklands.

Understanding hydrological variability for improved water management in the Semi-Arid Karkheh basin, Iran

NARCIS (Netherlands)

Masih, I.

2011-01-01

This study provides a hydrology based assessment of (surface) water resources and its continuum of variability and change at different spatio-temporal scales in the semi-arid Karkheh Basin, Iran, where water is scarce, competition among users is high and massive water resources development is under

Soil quality improvement for crop production in semi-arid West Africa

OpenAIRE

Ouédraogo, E.

2004-01-01

Soil quality maintenance and crop production improvement in semi-arid West Africa require appropriate cropping technologies, which are ecologically sound and economically viable. Thus, on-farm and on-station experiments have been carried out on the central plateau and in the south of Burkina Faso The results show that adoption of improved soil fertility technologies such as composting by farmers is determined by soil fertility status, access to the market and social reasons. Organic amendment...

Prescribed fire, soil inorganic nitrogen dynamics, and plant responses in a semiarid grassland

Science.gov (United States)

David J. Augustine; Paul Brewer; Dana M. Blumenthal; Justin D. Derner; Joseph C. von Fischer

2014-01-01

In arid and semiarid ecosystems, fire can potentially affect ecosystem dynamics through changes in soil moisture, temperature, and nitrogen cycling, as well as through direct effects on plant meristem mortality. We examined effects of annual and triennial prescribed fires conducted in early spring on soil moisture, temperature, and N, plant growth, and plant N content...

Evaluation of methods for delineating riparian zones in a semi-arid montane watershed

Science.gov (United States)

Jessica A. Salo; David M. Theobald; Thomas C. Brown

2016-01-01

Riparian zones in semi-arid, mountainous regions provide a disproportionate amount of the available wildlife habitat and ecosystem services. Despite their importance, there is little guidance on the best way to map riparian zones for broad spatial extents (e.g., large watersheds) when detailed maps from field data or high-resolution imagery and terrain data...

Identifying plant traits: a key aspect for suitable species selection in ecological restoration of semiarid slopes

Science.gov (United States)

Bochet, Esther; García-Fayos, Patricio

2017-04-01

In the context of ecological restoration, one of the greatest challenges for practitioners and scientists is to select suitable species for revegetation purposes. In semiarid environments where restoration projects often fail, little attention has been paid so far to the contribution of plant traits to species success. The objective of this study was to (1) identify plant traits associated with species success on four roadside situations along an erosion-productivity gradient, and (2) to provide an ecological framework for selecting suitable species on the basis of their morphological and functional traits, applied to semiarid environments. We analyzed the association of 10 different plant traits with species success of 296 species surveyed on the four roadside situations in a semiarid region (Valencia, Spain). Plant traits included general plant traits (longevity, woodiness) and more specific root-, seed- and leaf-related traits (root type, sprouting ability, seed mucilage, seed mass, seed susceptibility to removal, specific leaf area and leaf dry matter content). All of them were selected according to the prevailing limiting ecogeomorphological processes acting along the erosion-productivity gradient. We observed strong shifts along the erosion-productivity gradient in the traits associated to species success. At the harshest end of the gradient, the most intensely eroded and driest one, species success was mainly associated to seed resistance to removal by runoff and to resistance to drought. At the opposite end of the gradient, the most productive one, species success was associated to a competitive-ruderal plant strategy (herbaceous successful species with high specific leaf area and low leaf dry matter content). Our study provides an ecologically-based approach for selecting suitable native species on the basis or their morphological and functional traits and supports a differential trait-based selection of species as regards roadslope type and aspect. In

Infiltration and planting pits for improved water management and maize yield in semi-arid Zimbabwe

NARCIS (Netherlands)

Nyakudya, I.W.; Stroosnijder, L.; Nyagumbo, I.

2014-01-01

Realising that rainwater harvesting (RWH) improves crop productivity, smallholder farmers in semi-arid Zimbabwe modified contour ridges traditionally used for rainwater management by digging infiltration pits inside contour ridge channels in order to retain more water in crop fields. However,

Runoff controlling factors in various sized catchments in a semi-arid Mediterranean environment in Spain

NARCIS (Netherlands)

Wit, A.M.W. de

2001-01-01

Understanding land degradation in a semi-arid Mediterranean environment is very difficult because of the contributing factors: precipitation, infiltration vegetation cover and discontinuity of flow and the temporal and spatial levels of resolution at which these factors are acting. Therefore it

Recovery of rangelands : the functioning of soil seed banks in a semi-arid African savanna

NARCIS (Netherlands)

Tessema, Z.K.

2011-01-01

Rangelands in Africa provide important forage resources for herbivores; particularly perennial grasses provide grazing for domestic and wild herbivores. However, semi-arid African rangelands experience severe vegetation and soil degradation due to heavy grazing, causing negative impacts

Selective geochemistry of iron in mangrove soils in a semiarid tropical climate: effects of the burrowing activity of the crabs Ucides cordatus and Uca maracoani

Science.gov (United States)

Araújo, J. M. C.; Otero, X. L.; Marques, A. G. B.; Nóbrega, G. N.; Silva, J. R. F.; Ferreira, T. O.

2012-08-01

Bioturbation by crabs may affect processes associated with organic matter decomposition in mangrove soils. This study examines how two crabs ( Uca maracoani and Ucides cordatus), which are of substantial ecological and economic importance in semiarid coastal areas of Brazil, affect biogeochemical processes in mangrove soils. For this purpose, the physicochemical and geochemical parameters of the soils at different sites were analyzed. The redox potential was always positive at bioturbated sites (+12 to +218 mV), indicating more oxidizing conditions conducive to the oxidation of pyrite and precipitation of oxyhydroxides. In contrast, anoxic conditions prevailed at the control site (Eh mangrove soils, being capable of enhancing organic matter decomposition and also shifting the dominant pathway of organic matter degradation.

Double-wall IFR cell for conditioning intense relativistic electron beams

International Nuclear Information System (INIS)

Myers, M.C.; Meger, R.A.; Murphy, D.P.; Fernsler, R.F.; Hubbard, R.F.; Slinker, S.P.; Weidman, D.J.

1994-01-01

An intense relativistic electron beam (IREB) injected into neutral gas in the high pressure regime characteristically propagates in a self-pinched mode but is susceptible to the resistive hose instability. Typically, beam are conditioned for propagation experiments by reducing the perturbations that may excite resistive hose and by adjusting the emittance profile of the beam such that the convective growth of the instability is decreased. The former has been achieved by applying an anharmonic focusing force as the beam is transported through a conducting tube or cell. The latter has been effectively demonstrated by passing the beam through an ion focus regime (IFR) cell which imposes a head to tail beam emittance variations. However, since the physical parameters of the two types of cells are different, conflicts arise when the cells are coupled sequentially. The double-wall IFR cell described here eliminates these interface difficulties by providing the necessary conditions properties in a single cell. The physics and design of the cell will be introduced and parameter variations explored. The conditioning and propagation measurements will be presented and the results of the experiment will be discussed in relation to theory and simulation

Advancements in Hydrology and Erosion Process Understanding and Post-Fire Hydrologic and Erosion Model Development for Semi-Arid Landscapes

Science.gov (United States)

Williams, C. Jason; Pierson, Frederick B.; Al-Hamdan, Osama Z.; Robichaud, Peter R.; Nearing, Mark A.; Hernandez, Mariano; Weltz, Mark A.; Spaeth, Kenneth E.; Goodrich, David C.

2017-04-01

Fire activity continues to increase in semi-arid regions around the globe. Private and governmental land management entities are challenged with predicting and mitigating post-fire hydrologic and erosion responses on these landscapes. For more than a decade, a team of scientists with the US Department of Agriculture has collaborated on extensive post-fire hydrologic field research and the application of field research to development of post-fire hydrology and erosion predictive technologies. Experiments funded through this research investigated the impacts of fire on vegetation and soils and the effects of these fire-induced changes on infiltration, runoff generation, erodibility, and soil erosion processes. The distribution of study sites spans diverse topography across grassland, shrubland, and woodland landscapes throughout the western United States. Knowledge gleaned from the extensive field experiments was applied to develop and enhance physically-based models for hillslope- to watershed-scale runoff and erosion prediction. Our field research and subsequent data syntheses have identified key knowledge gaps and challenges regarding post-fire hydrology and erosion modeling. Our presentation details some consistent trends across a diverse domain and varying landscape conditions based on our extensive field campaigns. We demonstrate how field data have advanced our understanding of post-fire hydrology and erosion for semi-arid landscapes and highlight remaining key knowledge gaps. Lastly, we briefly show how our well-replicated experimental methodologies have contributed to advancements in hydrologic and erosion model development for the post-fire environment.

Surficial weathering of iron sulfide mine tailings under semi-arid climate

Science.gov (United States)

Hayes, Sarah M.; Root, Robert A.; Perdrial, Nicolas; Maier, Raina M.; Chorover, Jon

2014-09-01

Mine wastes introduce anthropogenic weathering profiles to the critical zone that often remain unvegetated for decades after mining cessation. As such, they are vulnerable to wind and water dispersion of particulate matter to adjacent ecosystems and residential communities. In sulfide-rich ore tailings, propagation to depth of the oxidative weathering front controls the depth-variation in speciation of major and trace elements. Despite the prevalence of surficial mine waste deposits in arid regions of the globe, few prior studies have been conducted to resolve the near-surface profile of sulfide ore tailings weathered under semi-arid climate. We investigated relations between gossan oxidative reaction-front propagation and the molecular speciation of iron and sulfur in tailings subjected to weathering in a semi-arid climate at an EPA Superfund Site in central Arizona (USA). Here we report a multi-method data set combining wet chemical and synchrotron-based X-ray diffraction (XRD) and X-ray absorption near-edge spectroscopy (XANES) methods to resolve the tight coupling of iron (Fe) and sulfur (S) geochemical changes in the top 2 m of tailings. Despite nearly invariant Fe and S concentration with depth (130-140 and 100-120 g kg-1, respectively), a sharp redox gradient and distinct morphological change was observed within the top 0.5 m, associated with a progressive oxidative alteration of ferrous sulfides to (oxyhydr)oxides and (hydroxy)sulfates. Transformation is nearly complete in surficial samples. Trends in molecular-scale alteration were co-located with a decrease in pH from 7.3 to 2.3, and shifts in Fe and S lability as measured via chemical extraction. Initial weathering products, ferrihydrite and gypsum, transform to schwertmannite, then jarosite-group minerals with an accompanying decrease in pH. Interestingly, thermodynamically stable phases such as goethite and hematite were not detected in any samples, but ferrihydrite was observed even in samples with

Monitoring the variations of evapotranspiration due to land use/cover change in a semiarid shrubland

Science.gov (United States)

Gong, Tingting; Lei, Huimin; Yang, Dawen; Jiao, Yang; Yang, Hanbo

2017-02-01

Evapotranspiration (ET) is an important process in the hydrological cycle, and vegetation change is a primary factor that affects ET. In this study, we analyzed the annual and inter-annual characteristics of ET using continuous observation data from eddy covariance (EC) measurement over 4 years (1 July 2011 to 30 June 2015) in a semiarid shrubland of Mu Us Sandy Land, China. The Normalized Difference Vegetation Index (NDVI) was demonstrated as the predominant factor that influences the seasonal variations in ET. Additionally, during the land degradation and vegetation rehabilitation processes, ET and normalized ET both increased due to the integrated effects of the changes in vegetation type, topography, and soil surface characteristics. This study could improve our understanding of the effects of land use/cover change on ET in the fragile ecosystem of semiarid regions and provide a scientific reference for the sustainable management of regional land and water resources.

Yield and quality responses of drip-irrigated spinach to different irrigation quantities in a semi-arid region with a high altitude

Directory of Open Access Journals (Sweden)

Yasemin KUSLU

2016-09-01

Full Text Available The effect of different irrigation quantities on the growth, marketable yield, crop quality (antioxidant activity, mineral and total phenolic content and irrigation water use efficiency (IWUE of spinach grown in a semi-arid region of high altitude (1795 m a.s.l. was determined. Plants were irrigated with three different irrigation quantities which determined considering 100 (I1, 85 (I2 and 70% (I3 of the evaporation obtained from a Class A pan. Irrigation quantities in the I1, I2 and I3 treatments as two years average were 290, 264.3 and 238.6 mm, respectively. The I1 treatment provided the highest growth, marketable yield (28.06 t*ha-1 and IWUE (9.7 kg*m-3. However, mineral and total phenolic content and antioxidant activity in the leaves of spinach were significantly higher under lower water application conditions. The I2 treatment resulted with the highest antioxidant activity and content of N, K, Mg, Na, Fe, Cu and total phenolics. As a result of the study, I1 treatment in spinach production could be suitable for water sufficient regions due to higher yield and IWUE. However, I2 treatment may be more appropriate for water scarce semi-arid regions of high altitude for obtaining higher minerals and antioxidant activity.

Assessing anthropogenic impacts on limited water resources under semi-arid conditions: three-dimensional transient regional modelling in Jordan

Science.gov (United States)

Rödiger, Tino; Magri, Fabien; Geyer, Stefan; Morandage, Shehan Tharaka; Ali Subah, H. E.; Alraggad, Marwan; Siebert, Christian

2017-11-01

Both increasing aridity and population growth strongly stress freshwater resources in semi-arid areas such as Jordan. The country's second largest governorate, Irbid, with over 1 million inhabitants, is already suffering from an annual water deficit of 25 million cubic meters (MCM). The population is expected to double within the next 20 years. Even without the large number of refugees from Syria, the deficit will likely increase to more then 50 MCM per year by 2035 The Governorate's exclusive resource is groundwater, abstracted by the extensive Al Arab and Kufr Asad well fields. This study presents the first three-dimensional transient regional groundwater flow model of the entire Wadi al Arab to answer important questions regarding the dynamic quality and availability of water within the catchment. Emphasis is given to the calculation and validation of the dynamic groundwater recharge, derived from a multi-proxy approach, including (1) a hydrological model covering a 30-years dataset, (2) groundwater level measurements and (3) information about springs. The model enables evaluation of the impact of abstraction on the flow regime and the groundwater budget of the resource. Sensitivity analyses of controlling parameters indicate that intense abstraction in the southern part of the Wadi al Arab system can result in critical water-level drops of 10 m at a distance of 16 km from the production wells. Moreover, modelling results suggest that observed head fluctuations are strongly controlled by anthropogenic abstraction rather than variable recharge rates due to climate changes.

Inter-annual Variability of Evapotranspiration in a Semi-arid Oak-savanna Ecosystem: Measured and Modeled Buffering to Precipitation Changes

Science.gov (United States)

Raz-Yaseef, N.; Sonnentag, O.; Kobayashi, H.; Baldocchi, D. D.

2010-12-01

Precipitation (P) is the primary control on vegetation dynamics and productivity, implying that climate induced disturbances in frequency and timing of P are intimately coupled with fluxes of carbon, water and energy. Future climate change is expected to increase extreme rainfall events as well as droughts, suggesting linked vegetation changes to an unknown extent. Semi-arid climates experience large inter-annual variability (IAV) in P, creating natural conditions adequate to study how year-to-year changes in P affect atmosphere-biosphere fluxes. We used a 10-year flux database collected at a semi-arid savanna site in order to: (1) define IAV in P by means of frequency and timing; (2) investigate how changes in P affect the ecohydrology of the forest and its partitioning into the main vapor fluxes, and (3) evaluate model capability to predict IAV of carbon and water fluxes above and below the canopy. This is based on the perception that the capability of process-oriented models to construct the deviation, and not the average, is important in order to correctly predict ecosystem sensitivity to climate change. Our research site was a low density and low LAI (0.8) semi-arid (P=523±180 mm yr-1) savanna site, combined of oaks and grass, and located at Tonzi ranch, California. Measurements of carbon and water fluxes above and below the tree canopy using eddy covariance and supplementary measurements have been made since 2001. Measured fluxes were compared to modeled based on two bio-meteorological process-oriented ecosystem models: BEPS and 3D-CAONAK. Our results show that IAV in P was large, and standard deviation (STD) was 38% of the average. Accordingly, the wet soil period (measured volumetric water content > 8%) varied between 156 days in dry years to 301 days in wet years. IAV of the vapor fluxes were lower than that of P (STD was 17% for the trees and 23% for the floor components), suggesting on ecosystem buffering to changes in P. The timing of grass green up

Do Red Edge and Texture Attributes from High-Resolution Satellite Data Improve Wood Volume Estimation in a Semi-Arid Mountainous Region?

DEFF Research Database (Denmark)

Schumacher, Paul; Mislimshoeva, Bunafsha; Brenning, Alexander

2016-01-01

to overcome this issue. However, clear recommendations on the suitability of specific proxies to provide accurate biomass information in semi-arid to arid environments are still lacking. This study contributes to the understanding of using multispectral high-resolution satellite data (RapidEye), specifically...... red edge and texture attributes, to estimate wood volume in semi-arid ecosystems characterized by scarce vegetation. LASSO (Least Absolute Shrinkage and Selection Operator) and random forest were used as predictive models relating in situ-measured aboveground standing wood volume to satellite data...

Contour hedgerows and grass strips in erosion and runoff control in semi-arid Kenya

NARCIS (Netherlands)

Kinama, J.M.; Stigter, C.J.; Ong, C.K.; Ng'ang'a, J.K.; Gichuki, F.N.

2007-01-01

Most early alley cropping studies in semi-arid Kenya were on fairly flat land while there is an increase in cultivated sloping land. The effectiveness of aging contour hedgerows and grass strips for erosion control on an about 15% slope of an Alfisol was compared. The five treatments were Senna

Effects of irrigation and plastic mulch on soil properties on semi-arid abandoned fields

NARCIS (Netherlands)

van der Meulen, E.S.; Nol, L.; Cammeraat, L.H.

2006-01-01

The Guadalentín Basin in Spain is one of the driest areas of Europe and has problems with high evaporation rates, and high risks of desertification exist including soil quality loss and soil erosion. Farmers in this semi-arid region use polyethylene covers on their irrigated croplands to reduce

Plastic-Film Mulching for Enhanced Water-Use Efficiency and Economic Returns from Maize Fields in Semiarid China.

Science.gov (United States)

Zhang, Peng; Wei, Ting; Cai, Tie; Ali, Shahzad; Han, Qingfang; Ren, Xiaolong; Jia, Zhikuan

2017-01-01

Film mulch has gradually been popularized to increase water availability to crops for improving and stabilizing agricultural production in the semiarid areas of Northwest China. To find more sustainable and economic film mulch methods for alleviating drought stress in semiarid region, it is necessary to test optimum planting methods in same cultivation conditions. A field experiment was conducted during 2013 and 2014 to evaluate the effects of different plastic film mulch methods on soil water, soil temperature, water use efficiency (WUE), yield and revenue. The treatments included: (i) the control, conventional flat planting without plastic film mulch (CK); (ii) flat planting with maize rows (60 cm spacing) on plastic film mulch (70 cm wide); (iii) furrow planting of maize (60 cm spacing), separated by consecutive plastic film-mulched ridges (each 50 cm wide and 15 cm tall); (iv) furrow planting of maize (60 cm spacing), separated by alternating large and small plastic film-mulched ridges (large ridges: 70 cm wide and 15 cm tall, small ridges 50 cm wide and 10 cm tall); and (v) furrow-flat planting of maize (60 cm spacing) with a large plastic film-mulched ridge (60 cm wide and 15 cm tall) alternating with a flat without plastic film-mulched space (60 cm wide). Topsoil temperature (5-25 cm) was significantly ( p plastic film mulch than the control (CK), and resulted in greater soil water storage (0-200 cm) up to 40 days after planting. Maize grain yield and WUE were significantly ( p < 0.05) higher with the furrow planting methods (consecutive film-mulched ridges and alternating film-mulched ridges) than the check in both years. Maize yield was, on average, 29% ( p < 0.05) greater and 28% ( p < 0.05) greater with these furrow planting methods, while the average WUE increased by 22.8% ( p < 0.05) with consecutive film-mulched ridges and 21.1% ( p < 0.05) with alternating film-mulched ridges. The 2-year average net income increased by 1559, 528, and 350 Chinese Yuan

Time-resolved Shielded-Pickup Measurements and Modeling of Beam Conditioning Effects on Electron Cloud Buildup at CesrTA

CERN Document Server

Crittenden, J A; Liu, X; Palmer, M A; Santos, S; Sikora, J P; Kato, S; Calatroni, S; Rumolo, G

2012-01-01

The Cornell Electron Storage Ring Test Accelerator program includes investigations into electron cloud buildup in vacuum chambers with various coatings. Two 1.1-mlong sections located symmetrically in the east and west arc regions are equipped with BPM-like pickup detectors shielded against the direct beam-induced signal. They detect cloud electrons migrating through an 18-mm-diameter pattern of 0.76 mm-diameter holes in the top of the chamber. A digitizing oscilloscope is used to record the signals, providing time-resolved information on cloud development. We present new measurements of the effect of beam conditioning on a newly-installed amorphous carbon coated chamber, as well as on an extensively conditioned chamber with a diamond-like carbon coating. The ECLOUD modeling code is used to quantify the sensitivity of these measurements to model parameters, differentiating between photoelectron and secondary-electron production processes.

Soil fertility management strategies and practices by smallholder farmers in semi-arid areas of Zimbabwe

NARCIS (Netherlands)

Mapfumo, P.; Giller, K.E.

2001-01-01

Indigenous soil fertility management strategies in semi-arid Communal Areas of Zimbabwe have largely been driven by an extensive use of resources. The shrinking of common property resources (CPRs) due to expansion of cultivated lands, the general loss of productivity in natural ecosystems (e.g.,

The current bioenergy production potential of semi-arid and arid regions in sub-Saharan Africa

NARCIS (Netherlands)

Wicke, B.; Smeets, E.M.W.; Watson, H.; Faaij, A.P.C.

2011-01-01

This article assesses the current technical and economic potential of three bioenergy production systems (cassava ethanol, jatropha oil and fuelwood) in semi-arid and arid regions of eight sub-Saharan African countries. The results indicate that the availability of land for energy production ranges

Water use efficiency and functional traits of a semiarid shrubland

Science.gov (United States)

Perez-Priego, Oscar; Lopez-Ballesteros, Ana; Sánchez-Cañete, Enrique P.; Serrano-Ortiz, Penélope; Carrara, Arnaud; Palomares-Palacio, Agustí; Oyonarte, Cecilio; Domingo, Francisco; Kowalski, Andrew S.

2013-04-01

In semiarid climates, water is the fundamental factor determining ecosystem productivity and thereby the capacity for carbon sequestration. Increased water use efficiency (WUE), the ratio of carbon dioxide assimilation (canopy photosynthesis, Pc) to water transpired (canopy evaporation, Ec), is assumed to be an adaptive strategy for sclerophyll shrublands to improve productivity and stress resistance in water-limited environments. However, the real complexity of WUE lies in its dependence on both plant physiological traits (e.g. stomatal resistance, photosynthetic capacity, leaf chemical composition, structure) and on environmental conditions (e.g. atmospheric CO2 concentration, vapour pressure deficit, temperature, light, soil water availability). We used a transient-state closed canopy-chamber to characterise CO2 and water vapour exchanges at the whole plant scale under different environmental conditions and phenological stages. Diurnal and seasonal variations in Pc, Ec and WUE were explained by both physiological and environmental variables. All species showed symmetric patterns in both Pc and Ec when not water limited, but asymmetry during summer drought when leaf water potential was low. During drought, grasses (Festuca sp.) showed a marked decline in functioning (Pc and Ec), whereas shrubs (Genista sp., Hormathophylla sp.) maintained spring-like assimilation rates all morning until stomatal controls shut down gas exchanges. While grasses showed the highest WUE when not water limited, their near senescence during summer drought yielded the lowest WUE. Shrubs showed reduced WUE under moderate drought stress, in contradiction to the assumptions made in global ecosystem models. The importance of the appropriate time-scale for calculating WUE (daily versus hourly), together with water use strategies and ecological functions of individual species, will be further discussed.

The Soil-Land use System in a Sand Spit Area in the Semi-Arid ...

African Journals Online (AJOL)

The Soil-Land use System in a Sand Spit Area in the Semi-Arid Coastal Savanna Region of Ghana – Development, Sustainability and Threats. ... The investigation comprises soil profile descriptions and analyses on the dominant soil type on the sand spit, measurement of electrical conductivity of well water and in the soil, ...

Vulnerability Assessment of the Livelihoods in Tanzania’s Semi-Arid Agro-Ecological Zone under Climate Change Scenarios

Directory of Open Access Journals (Sweden)

Msafiri Y. Mkonda

2018-04-01

Full Text Available Despite the established literature on the vulnerability to climate change in various parts of Tanzania, it is worthwhile to assess the extent of this vulnerability of the peoples’ livelihoods and predict its future outcome. This is particularly important in the vulnerable ecosystems, that is, the semi-arid zones of Tanzania where the people’s livelihoods are highly attached to the declining local condition. The present study aims to assess the livelihoods vulnerability in Kongwa District, the semi-arid zone of Central Tanzania. In doing so, a wide range of methods were employed during data collection and analyses including surveys, informative interviews, discussions and observation. The study sampled 400 (≤10% respondents during a survey. The Mann-Kendall Test with SPSS V20, Microsoft Excel and Theme content techniques were used for data analyses. The results indicate that climate stress has adversely impacted the quality of soil, vegetation, crop yields and intensified environmental degradation. Since most people depend upon the mentioned affected aspects, it is expected that also the level of livelihood vulnerability has elevated. Further, this situation has greatly contributed to increased poverty and thus, propagates the “tragedy of the common” to the available environmental resources. As a response to increased vulnerability, some farmers have abandoned thousands of hectares of agricultural farms that seemed to be less productive. Despite this, slight measures have been taken by both the government and other key stakeholders to limit vulnerability. The findings of this study provide a theoretical and practical basis for coordinating a sustainable man-environment relationship, ensuring the sustainability of the environment which is the major source of peoples’ livelihoods.

Use of fertilizer nitrogen by wheat in semiarid region of the pampa, Argentina

International Nuclear Information System (INIS)

Lazzari, M.A.; Laurent, G.C.

1984-01-01

The efficiency of nitrogen utilization by wheat (Buck Pucara cultivar) in semiarid region of the Argentina Pampas is studied. A single-treatment-fertility-experimet is used, and in this method all treatments, as far as the plant, soil or environment are concerned, are identical. The only difference is the occurrence of the 15 N label within a given subtreatment. (M.A.C.) [pt

Hydrological Processes Simulation at Plot Scale Using The Smap Model In The Semiarid | Simulação de processos hidrológicos na escala de lotes usando o modelo Smap em semi-árido

Directory of Open Access Journals (Sweden)

Iug Lopes

2017-06-01

Full Text Available Vegetation cover plays an important role on overland flow generation and erosion, directly impacting infiltration and soil water storage. The objective of this study was to investigate hydrological processes and soil moisture dynamics through conceptual modelling in intensively monitored experimental plots under natural rainfall with different soil cover conditions, in the Brazilian semiarid. Soil moisture was monthly monitored using a CPN 503 DR Neutron Probe device. Calibration curves previously defined were adopted for moisture assessment. Four experimental soil cover treatment were established: Cactus “Palma” barriers (PB; mulching (MC; Bare soil (BS and natural vegetation cover (NC. Nash-Sutcliffe (ENS coefficient and PBIAS index were adopted to assess hydrological processes analysis. The SMAP model successfully predicted the flow and humidity of the experimental plots for the natural cover and Mulching coverage, with a global ENS index of over 0.877. Scenarios of changes in soil cover have dramatically affected the modeling of water resources in the plots. The present study was important to improve the understanding and distinct hydrological processes relevance under different cover conditions in experimental plots in the semiarid.

Alternative states of a semiarid grassland ecosystem: implications for ecosystem services

Science.gov (United States)

Miller, Mark E.; Belote, R. Travis; Bowker, Matthew A.; Garman, Steven L.

2011-01-01

Ecosystems can shift between alternative states characterized by persistent differences in structure, function, and capacity to provide ecosystem services valued by society. We examined empirical evidence for alternative states in a semiarid grassland ecosystem where topographic complexity and contrasting management regimes have led to spatial variations in levels of livestock grazing. Using an inventory data set, we found that plots (n = 72) cluster into three groups corresponding to generalized alternative states identified in an a priori conceptual model. One cluster (biocrust) is notable for high coverage of a biological soil crust functional group in addition to vascular plants. Another (grass-bare) lacks biological crust but retains perennial grasses at levels similar to the biocrust cluster. A third (annualized-bare) is dominated by invasive annual plants. Occurrence of grass-bare and annualized-bare conditions in areas where livestock have been excluded for over 30 years demonstrates the persistence of these states. Significant differences among all three clusters were found for percent bare ground, percent total live cover, and functional group richness. Using data for vegetation structure and soil erodibility, we also found large among-cluster differences in average levels of dust emissions predicted by a wind-erosion model. Predicted emissions were highest for the annualized-bare cluster and lowest for the biocrust cluster, which was characterized by zero or minimal emissions even under conditions of extreme wind. Results illustrate potential trade-offs among ecosystem services including livestock production, soil retention, carbon storage, and biodiversity conservation. Improved understanding of these trade-offs may assist ecosystem managers when evaluating alternative management strategies.

Water scarcity under scenarios for global climate change and regional development in semiarid Northeastern Brazil

NARCIS (Netherlands)

de Araújo, José Carlos; Döll, Petra; Güntner, Andreas; Krol, Martinus S.; Rodrigues Abreu, Cláudia Beghini; Hauschild, Maike; Mendiondo, Eduardo Mario

2004-01-01

The State of Ceará, located in semiarid Northeastern Brazil, suffers under irregularly recurring droughts that go along with water scarcity. Structural policies to control and reduce water scarcity, as water supply and demand management, should be seen as long-term planning, and thus have to

Thermal boundary conditions for electrons in a weakly ionized gas near a catalytic wall

International Nuclear Information System (INIS)

Chekmarev, I.

1981-01-01

A technique of matched asymptotic expansions is used to examine the derivation of hydrodynamic transport equations for the external region of a weakly ionized multitemperature gas near an absorbing and conducting wall. An approximate moment solution is constructed for the Knudsen boundary layer. The conditions for the matching of the external and internal expansions lead to a new form of the hydrodynamic boundary conditions, from which the singular behavior of the energy equation for electrons near the wall has been eliminated

The Impact of Green Water Management Strategies on Household-Level Agricultural Water Productivity in a Semi-Arid Region: A Survey-based Assessment

Directory of Open Access Journals (Sweden)

Afton Clarke-Sather

2017-12-01

Full Text Available This study evaluates the effect of policies that encourage farmers to shift to crops with higher water productivity (CWP on the farm-level CWP of agricultural systems in a semi-arid region of western China. We combine survey results of farmers’ historical cropping decisions from a 2010 survey with estimates of CWP from agronomic experiments analogous to actual cultivation practices in the region to model CWP at the farm level and understand changes driven by shifting crops. Policies designed to replace subsistence agricultural systems with two cash crops; potatoes and maize; resulted in an increase in the CWP of semi-arid agricultural systems of approximately 30% between the years 1990–2010. This change was driven by shifting to crops that have a peak water demand that occurs in the portions of the growing season with the highest rainfall. The results of this article illustrate the potential of shifts in cropping patterns to increase the CWP of agricultural systems in semi-arid regions.

Empirical model for the electron density peak height disturbance in response to solar wind conditions

Science.gov (United States)

Blanch, E.; Altadill, D.

2009-04-01

Geomagnetic storms disturb the quiet behaviour of the ionosphere, its electron density and the electron density peak height, hmF2. Many works have been done to predict the variations of the electron density but few efforts have been dedicated to predict the variations the hmF2 under disturbed helio-geomagnetic conditions. We present the results of the analyses of the F2 layer peak height disturbances occurred during intense geomagnetic storms for one solar cycle. The results systematically show a significant peak height increase about 2 hours after the beginning of the main phase of the geomagnetic storm, independently of both the local time position of the station at the onset of the storm and the intensity of the storm. An additional uplift is observed in the post sunset sector. The duration of the uplift and the height increase are dependent of the intensity of the geomagnetic storm, the season and the local time position of the station at the onset of the storm. An empirical model has been developed to predict the electron density peak height disturbances in response to solar wind conditions and local time which can be used for nowcasting and forecasting the hmF2 disturbances for the middle latitude ionosphere. This being an important output for EURIPOS project operational purposes.

Transfer of 137Cs in Zea mays and Phaseolus vulgaris in a semi-arid ecosystem

International Nuclear Information System (INIS)

Cervantes, M.L.; Segovia, N.; Gaso P, M.I.; Palacios, J.C.

1999-01-01

With the objective to analyse the transference of 137 Cs from soil to plants, it is realized a study in maize and bean plants in the Radioactive Waste Storage Center (CADER). This site is located in a semi-arid region with a characteristic vegetation of a sub humid temperature zone. So those plants maize and beans were cultivated in four zones near CADER during a four years period. The obtained results for 1991 to 1994 for 137 Cs in soil samples for those zones showed an evident contamination in zone 1, due to a rupture of an industrial source. In 1994 the effect of decontamination was evident since the values of specific activity found in roots were around magnitude lesser than found in 1992. In spite of exhaustive studies have been reported about the transference factors for 137 Cs in different agricultural foods, relatively few of them have paid attention to the interactions between cereals and leguminous associated in semiarid ecosystems. (Author)

Carbon storage capacity of semi-arid grassland soils and sequestration potentials in northern China.

Science.gov (United States)

Wiesmeier, Martin; Munro, Sam; Barthold, Frauke; Steffens, Markus; Schad, Peter; Kögel-Knabner, Ingrid

2015-10-01

Organic carbon (OC) sequestration in degraded semi-arid environments by improved soil management is assumed to contribute substantially to climate change mitigation. However, information about the soil organic carbon (SOC) sequestration potential in steppe soils and their current saturation status remains unknown. In this study, we estimated the OC storage capacity of semi-arid grassland soils on the basis of remote, natural steppe fragments in northern China. Based on the maximum OC saturation of silt and clay particles soils (grazing land, arable land, eroded areas) were estimated. The analysis of natural grassland soils revealed a strong linear regression between the proportion of the fine fraction and its OC content, confirming the importance of silt and clay particles for OC stabilization in steppe soils. This relationship was similar to derived regressions in temperate and tropical soils but on a lower level, probably due to a lower C input and different clay mineralogy. In relation to the estimated OC storage capacity, degraded steppe soils showed a high OC saturation of 78-85% despite massive SOC losses due to unsustainable land use. As a result, the potential of degraded grassland soils to sequester additional OC was generally low. This can be related to a relatively high contribution of labile SOC, which is preferentially lost in the course of soil degradation. Moreover, wind erosion leads to substantial loss of silt and clay particles and consequently results in a direct loss of the ability to stabilize additional OC. Our findings indicate that the SOC loss in semi-arid environments induced by intensive land use is largely irreversible. Observed SOC increases after improved land management mainly result in an accumulation of labile SOC prone to land use/climate changes and therefore cannot be regarded as contribution to long-term OC sequestration. © 2015 John Wiley & Sons Ltd.

Atomic and electronic structure transformations of silver nanoparticles under rapid cooling conditions

OpenAIRE

Lobato, I.; Rojas, J.; Landauro, C. V.; Torres, J.

2008-01-01

The structural evolution and dynamics of silver nanodrops Ag${}_{2896}$ (4.4 nm in diameter) during rapid cooling conditions has been studied by means of molecular dynamics simulations and electronic density of state calculations. The interaction of silver atoms is modeled by a tight-binding semiempirical interatomic potential proposed by Cleri and Rosato. The pair correlation functions and the pair analysis technique is applied to reveal the structural transition in the process of solidifica...

Conditioning of mealybug (Hemiptera: Pseudococcidae) by Scanning Electron Microscopy

International Nuclear Information System (INIS)

Palma-Jimenez, Melissa; Blanco-Meneses, Monica

2015-01-01

The cleaning and correct observation of the mealybug specimens was determined by the conditioning methodology. The research was done in the Laboratorio del Centro de Investigacion en Estructuras Microscopicas (CIEMIC) of the Universidad de Costa Rica during the year 2012. A gradual improvement for the observation of the ultrastructures through the Scanning Electron Microscope was evidenced by the implementation of four types of methodologies. Each process was described in detail. The incorporation of 10% xylene (in some cases have been viable using ethanol at 95-100% ) was allowed to remove the wax from the body of the insect, to avoid this the collapse and to observe specific ultrastructures of the individual, they were the best results. The methodology used has reduced the time and costs in future taxonomic research of mealybug. (author) [es

The experimental electron mean-free-path in Si under typical (S)TEM conditions

International Nuclear Information System (INIS)

Potapov, P.L.

2014-01-01

The electron mean-free-path in Si was measured by EELS using the test structure with the certified dimensions as a calibration standard. In a good agreement with the previous CBED measurements, the mean-free-path is 150 nm for 200 keV and 179 nm for 300 keV energy of primary electrons at large collection angles. These values are accurately predicted by the model of Iakoubovskii et al. while the model of Malis et al. incorporated in common microscopy software underestimates the mean-free-path by 15% at least. Correspondingly, the thickness of TEM samples reported in many studies of the Si-based materials last decades might be noticeably underestimated. - Highlights: • The electron inelastic mean-free-path in Si is measured for the typical (S)TEM conditions. • These reference values allow for accurate determination of the lamella thickness by EELS. • The theoretical model by Malis et al. underestimates the mean-free-path values

Ecology and functional roles of biological soil crusts in semi-arid ecosystems of Spain

Science.gov (United States)

Maestre, Fernando T.; Bowker, Matthew A.; Cantón, Yolanda; Castillo-Monroy, Andrea P.; Cortina, Jordi; Escolar, Cristina; Escudero, Adrián; Lázaro, Roberto; Martínez, Isabel

2015-01-01

Biological soil crusts (BSCs), composed of lichens, cyanobacteria, mosses, liverworts and microorganisms, are key biotic components of arid and semi-arid ecosystems worldwide. Despite they are widespread in Spain, these organisms have been historically understudied in this country. This trend is beginning to change as a recent wave of research has been identifying BSCs as a model ecological system. Many studies and research projects carried out in Spain have explored the role of BSCs on water, carbon and nitrogen fluxes, the interactions between BSCs and vascular plants, their dynamics after disturbances, and their response to global change, among other topics. In this article we review the growing body of research on BSCs available from semi-arid areas of Spain, highlighting its importance for increasing our knowledge on this group of organisms. We also discuss how it is breaking new ground in emerging research areas on the ecology of BSCs, and how it can be use to guide management and restoration efforts. Finally, we provide directions for future research on the ecology of BSCs in Spain and abroad. PMID:25908884

Functional group, biomass, and climate change effects on ecological drought in semiarid grasslands

Science.gov (United States)

Wilson, Scott D.; Schlaepfer, Daniel R.; Bradford, John B.; Lauenroth, William K.; Duniway, Michael C.; Hall, Sonia A.; Jamiyansharav, Khishigbayar; Jia, Gensuo; Lkhagva, Ariuntsetseg; Munson, Seth M.; Pyke, David A.; Tietjen, Britta

2018-01-01

Water relations in plant communities are influenced both by contrasting functional groups (grasses, shrubs) and by climate change via complex effects on interception, uptake and transpiration. We modelled the effects of functional group replacement and biomass increase, both of which can be outcomes of invasion and vegetation management, and climate change on ecological drought (soil water potential below which photosynthesis stops) in 340 semiarid grassland sites over 30‐year periods. Relative to control vegetation (climate and site‐determined mixes of functional groups), the frequency and duration of drought were increased by shrubs and decreased by annual grasses. The rankings of shrubs, control vegetation, and annual grasses in terms of drought effects were generally consistent in current and future climates, suggesting that current differences among functional groups on drought effects predict future differences. Climate change accompanied by experimentally‐increased biomass (i.e. the effects of invasions that increase community biomass, or management that increases productivity through fertilization or respite from grazing) increased drought frequency and duration, and advanced drought onset. Our results suggest that the replacement of perennial temperate semiarid grasslands by shrubs, or increased biomass, can increase ecological drought both in current and future climates.

Cost/benefit analysis of biomass energy supply options for rural smallholders in the semi-arid eastern part of Shinyanga Region in Tanzania

Energy Technology Data Exchange (ETDEWEB)

Wiskerke, W.T.; Dornburg, V.; Faaij, A.P.C. [Department of Science, Technology and Society, Utrecht University, Heidelberglaan 2, 3584 CS, Utrecht (Netherlands); Rubanza, C.D.K. [Tanzania Forestry Research Institute (TAFORI)/National Forest Resource Management and Agroforestry Centre (NACRAF), P.O. Box 1257, Shinyanga (Tanzania); Malimbwi, R.E. [Faculty of Forestry and Natural Resources, Sokoine University, P.O. Box 3010, Morogoro (Tanzania)

2010-01-15

This study analyzes the economic feasibility of sustainable smallholder bio-energy production under semi-arid conditions. The eastern part of Shinyanga region in Tanzania was chosen as a case study area. Three different sustainable biomass energy supply systems were compared by means of cost/benefit analysis: a small-scale forestation project for carbon sequestration, a short rotation woodlot and a Jatropha plantation, thereby using the produced Jatropha oil as a substitute for fuelwood or diesel. Rotational woodlots are most profitable with a Net Present Value of up to US${sub 2007} 1165/ha, a return on labour of up to US${sub 2007} 6.69/man-day and a fuelwood production cost of US${sub 2007} 0.53/GJ, compared to a local market price of US${sub 2007} 1.95/GJ. With a production cost of US${sub 2007} 19.60/GJ, Jatropha oil is too expensive to be used as an alternative for fuelwood. Instead it can be utilized economically as a diesel substitute, at an observed diesel cost of US${sub 2007} 1.49/l. The mean annual biomass increment (MAI) in semi-arid East Shinyanga is too low to collect sufficient benefits from trading forestation carbon credits under the Clean Development Mechanism (CDM) to cover the costs of forestation and forest management. (author)

Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes

Science.gov (United States)

Poon, Patrick K.; Kinoshita, Alicia M.

2018-04-01

In recent years climate change and other anthropogenic factors have contributed to increased wildfire frequency and size in western United States forests. This research focuses on the evaluation of spatial and temporal changes in evapotranspiration (ET) following the 2011 Las Conchas Fire in New Mexico (USA) using the Operational Simplified Surface Energy Balance Model (SSEBop ET). Evapotranspiration is coupled with soil burn severity and analyzed for 16 watersheds for water years 2001-2014. An average annual decrease of 120 mm of ET is observed within the regions affected by the Las Conchas Fire, and conifers were converted to grassland a year after the fire. On average, the post-fire annual ET in high, moderate, and low burn severity is lower than pre-fire ET by approximately 103-352 mm, 97-304 mm, and 91-268 mm, respectively. The ratio of post-fire evapotranspiration to precipitation (ET/P) is statistically different from pre-fire conditions (α = 0.05) in nine of the watersheds. The largest decrease in ET is approximately 13-57 mm per month and is most prominent during the summer (April to September). The observed decrease in ET contributes to our understanding of changes in water yield following wildfires, which is of interest for accurately modeling and predicting hydrologic processes in semi-arid landscapes.

Association analysis of resistance to cereal cyst nematodes (Heterodera avenae) and root lesion nematodes (Pratylenchus neglectus and P. thornei) in CIMMYT advanced spring wheat lines for semi-arid conditions.

Science.gov (United States)

Dababat, Abdelfattah A; Ferney, Gomez-Becerra Hugo; Erginbas-Orakci, Gul; Dreisigacker, Susanne; Imren, Mustafa; Toktay, Halil; Elekcioglu, Halil I; Mekete, Tesfamariam; Nicol, Julie M; Ansari, Omid; Ogbonnaya, Francis

2016-12-01

To identify loci linked to nematode resistance genes, a total of 126 of CIMMYT advanced spring wheat lines adapted to semi-arid conditions were screened for resistance to Heterodera avenae , Pratylenchus neglectus , and P. thornei , of which 107 lines were genotyped with 1,310 DArT. Association of DArT markers with nematode response was analyzed using the general linear model. Results showed that 11 markers were associated with resistance to H. avenae (pathotype Ha21), 25 markers with resistance to P. neglectus , and 9 significant markers were identified to be linked with resistance to P. thornei . In this work we confirmed that chromosome 4A (~90-105 cM) can be a source of resistance to P. thornei as has been recently reported. Other significant markers were also identified on chromosomal regions where no resistant genes have been reported for both nematodes species. These novel QTL were mapped to chromosomes 5A, 6A, and 7A for H. avenae ; on chromosomes 1A, 1B, 3A, 3B, 6B, 7AS, and 7D for P. neglectus ; and on chromosomes 1D, 2A, and 5B for P. thornei and represent potentially new loci linked to resistance that may be useful for selecting parents and deploying resistance into elite germplasm adapted to regions where nematodes are causing problem.

Economic Feasibility of Underwater Adduction of Rivers for Metropolises in Semiarid Coastal Environments: Case Studies

Directory of Open Access Journals (Sweden)

Daniel Albiero

2018-02-01

Full Text Available The supply of raw water to the inhabitants of metropolises is not a trivial problem, and involves many challenges, both in terms of the quantity and quality of this water. When these metropolises are located in semiarid regions, this challenge takes on enormous proportions, and in many situations, there are no sustainable solutions, especially in times of global climate change. One hypothesis to try to mitigate this problem in coastal cities is the underwater adduction of rivers. The objective of this paper was to make the abstraction of drinking water in the mouths of great rivers near semi-arid regions. This water would be led by a pipeline below the water level and would follow the route of the seacoast, where the energy to move the water would be supplied by an axial hydraulic pump embedded in the pipeline by water-cooled electric motors driven by the energy generated from offshore wind turbines. Estimates have been made for the four metropolises in semi-arid regions: Fortaleza-Brazil, Dalian-China, Tel Aviv-Israel, and Gaza-Palestine, where it was possible to calculate economic viability through the Present Worth Value, the internal rate of return, and payback. The results indicated that Fortaleza had economic viability under restrictions. Dalian proved the ideal result. Tel Aviv and Gaza both had great economic viability, but only if Egypt agreed to supply water from the Nile. This paper proved that the management of the water supply for human consumption through the underwater adduction of rivers could be achieved with real clearance for any deficits in the volume of water that due to global climate change are becoming more frequent.

Exploiting machine learning algorithms for tree species classification in a semiarid woodland using RapidEye image

CSIR Research Space (South Africa)

Adelabu, S

2013-11-01

Full Text Available in semiarid environments. In this study, we examined the suitability of 5-band RapidEye satellite data for the classification of five tree species in mopane woodland of Botswana using machine leaning algorithms with limited training samples. We performed...

Study on Applicability of Conceptual Hydrological Models for Flood Forecasting in Humid, Semi-Humid Semi-Arid and Arid Basins in China

Directory of Open Access Journals (Sweden)

Guangyuan Kan

2017-09-01

Full Text Available Flood simulation and forecasting in various types of watersheds is a hot issue in hydrology. Conceptual hydrological models have been widely applied to flood forecasting for decades. With the development of economy, modern China faces with severe flood disasters in all types of watersheds include humid, semi-humid semi-arid and arid watersheds. However, conceptual model-based flood forecasting in semi-humid semi-arid and arid regions is still challenging. To investigate the applicability of conceptual hydrological models for flood forecasting in the above mentioned regions, three typical conceptual models, include Xinanjiang (XAJ, mix runoff generation (MIX and northern Shannxi (NS, are applied to 3 humid, 3 semi-humid semi-arid, and 3 arid watersheds. The rainfall-runoff data of the 9 watersheds are analyzed based on statistical analysis and information theory, and the model performances are compared and analyzed based on boxplots and scatter plots. It is observed the complexity of drier watershed data is higher than that of the wetter watersheds. This indicates the flood forecasting is harder in drier watersheds. Simulation results indicate all models perform satisfactorily in humid watersheds and only NS model is applicable in arid watersheds. Model with consideration of saturation excess runoff generation (XAJ and MIX perform better than the infiltration excess-based NS model in semi-humid semi-arid watersheds. It is concluded more accurate mix runoff generation theory, more stable and efficient numerical solution of infiltration equation and rainfall data with higher spatial-temporal resolution are main obstacles for conceptual model-based flood simulation and forecasting.

Ethno-ornithology and conservation of wild birds in the semi-arid Caatinga of northeastern Brazil

Science.gov (United States)

2013-01-01

The utilization of birds as pets has been recognized as one of the principal threats to global avifauna. Most of the information about the use and sale of birds as pets has been limited to areas of high biodiversity and whose impacts of anthropic actions have been widely broadcast internationally, for example for the Amazon Forest and forest remnants of Southeast Asia. The Caatinga predominates in the semi-arid region of Brazil, and is one of the semi-arid biomes with the greatest biological diversity in the world, where 511 species of birds exist. Many of these birds are used as pets, a common practice in the region, which has important conservationist implications but has been little studied. Therefore, the aim of the present study was to detail aspects of the use of birds as pets in a locality in the semi-arid region of Northeast Brazil. Information on the use of avifauna was obtained through interviews and visits to the homes of 78 wild bird keepers. A total of 41 species of birds were recorded, mostly of the families Emberizidae (n = 9 species), Columbidae (n = 7 species), Icteridae (n = 6 species) and Psittacidae (n = 3 species). The birds that were most often recorded were Paroaria dominicana (n = 79 especimens), Sporophila albogularis (n = 67), Aratinga cactorum (n = 49), Sporophila lineola (n = 36), Sicalis flaveola (n = 29) and Sporophila nigricollis (n = 27). The use of wild birds in the area studied, as an example of what occurs in other places in the semi-arid Northeast, demonstrates that such activities persist in the region, in spite of being illegal, and have been happening in clandestine or semi-clandestine manner. No statistically significant correlation were found between socioeconomic factors and keeping birds as pets reflects the cultural importance of this practice of rearing wild birds for pets in the region, which is widespread among the local population, independent of socioeconomic factors. Obviously

The extreme condition analyzing for NEMPI shielding of electronic system in high-intensity pulsed radiation diagnosing

International Nuclear Information System (INIS)

Cheng Xiaolei; Liu Fang; Ouyang Xiaoping

2012-01-01

The difficulty for estimating the NEMPI (electromagnetic pulsed interference caused by the nuclear reaction) on the electronic system in high-intensity pulsed radiation diagnosing is analyzed in this article. To solve the difficulty, a method called 'Extreme Condition Analyzing' is presented for estimating the NEMPI conservatively and reliably. Through an extreme condition hypothesizing which could be described as 'Entire Coupling of Electric Field Energy', the E max (maximum electric field intensity which could be endured by the electronic system in the high-intensity pulsed radiation) could be figured out without any other information of the EMP caused by the nuclear reaction. Then a feasibility inspection is introduced, to confirm that the EMPI shielding request according to E max is not too extreme to be achieved. (authors)

Species diversity and drivers of arbuscular mycorrhizal fungal communities in a semi-arid mountain in China

Directory of Open Access Journals (Sweden)

He Zhao

2017-12-01

Full Text Available Arbuscular mycorrhizal fungi (AMF play an essential role in complex ecosystems. However, the species diversity and composition of AMF communities remain unclear in semi-arid mountains. Further, it is not well understood if the characteristics of AMF community assemblies differ for different habitat types, e.g., agricultural arable land, artificial forest land, natural grassland, and bush/wood land. Here, using the high-throughput technology by Illumina sequencing on the MiSeq platform, we explored the species diversity and composition of soil AMF communities among different habitat types in a semi-arid mountain (Taihang Mountain, Mid-western region of China. Then, we analyzed the effect of nutrient composition and soil texture on AMF community assembly. Our results showed that members of the Glomus genera were predominated in all soil types. The distance-based redundancy analysis indicated that the content of water, available phosphorus, and available potassium were the most crucial geochemical factors that significantly affected AMF communities (p < 0.05. The analysis of the soil texture confirmed that AMF diversity was negatively correlated with soil clay content. The comparison of AMF diversity among the various habitat types revealed that the artificial forest land had the lowest AMF diversity in comparison with other land types. Our findings suggest that there were differences in species diversity and composition of soil AMF communities among different habitat types. These findings shed new light on the characteristics of community structure and drivers of community assembly in AMF in semi-arid mountains, and point to the potential importance of different habitat types on AMF communities.

Modeling water scarcity and droughts for policy adaptation to climate change in arid and semiarid regions

Science.gov (United States)

Kahil, Mohamed Taher; Dinar, Ariel; Albiac, Jose

2015-03-01

Growing water extractions combined with emerging demands for environment protection increase competition for scarce water resources worldwide, especially in arid and semiarid regions. In those regions, climate change is projected to exacerbate water scarcity and increase the recurrence and intensity of droughts. These circumstances call for methodologies that can support the design of sustainable water management. This paper presents a hydro-economic model that links a reduced form hydrological component, with economic and environmental components. The model is applied to an arid and semiarid basin in Southeastern Spain to analyze the effects of droughts and to assess alternative adaptation policies. Results indicate that drought events have large impacts on social welfare, with the main adjustments sustained by irrigation and the environment. The water market policy seems to be a suitable option to overcome the negative economic effects of droughts, although the environmental effects may weaken its advantages for society. The environmental water market policy, where water is acquired for the environment, is an appealing policy to reap the private benefits of markets while protecting ecosystems. The current water management approach in Spain, based on stakeholders' cooperation, achieves almost the same economic outcomes and better environmental outcomes compared to a pure water market. These findings call for a reconsideration of the current management in arid and semiarid basins around the world. The paper illustrates the potential of hydro-economic modeling for integrating the multiple dimensions of water resources, becoming a valuable tool in the advancement of sustainable water management policies.

Index of Relative Importance of the Dietary Proportions of Sloth Bear (Melursus ursinus in Semi-Arid Region

Directory of Open Access Journals (Sweden)

Tana P. MEWADA

2015-09-01

Full Text Available Characterisations of the Sloth bear (Melursus ursinus diet during three distinguished seasons (monsoon, winter and summer in the semi-arid region of western India was under study. Diet was estimated using scat analysis, based on the calculation of Index of Relative Importance (IRI in order to determine the contribution of different food items in the Sloth bear diet. Sloth bears were observed to feed on a wide variety of prey items. They are specialized on insect prey, particularly termites or ants, and are considered as myrmecophagous. The myrmecophagousis character was confirmed by the highest score of insect part (IRI = 21.37 from the samples (n = 566, which was followed by Diospyros melanoxylon (IRI Score 13.51, Ficus spp. (IRI score 12.69 and Cassia fistula (IRI Score 10.13. Sloth bear dietary proportions varied among the three seasons under the study interval. Data suggested that the Sloth bear is essentially behaving as an omnivore, having similar diet (in terms of high incidence of wild fruits and insects with the bears inhabiting semi-arid regions. The opportunistic and generalist strategy of selecting diet ingredients has probably helped the species to survive in semi-arid habitat across the North Gujarat.

Characterising root density of peach trees in a semi-arid Chernozem to increase plant density

Science.gov (United States)

Paltineanu, Cristian; Septar, Leinar; Gavat, Corina; Chitu, Emil; Oprita, Alexandru; Moale, Cristina; Calciu, Irina; Vizitiu, Olga; Lamureanu, Gheorghe

2016-01-01

The available information on root system in fully mature peach orchards in semi-arid regions is insufficient. This paper presents a study on the root system density in an irrigated peach orchard from Dobrogea, Romania, using the trench technique. The old orchard has clean cultivation in inter-row and in-row. The objectives of the study were to: test the hypothesis that the roots of fully mature peach trees occupy the whole soil volume; find out if root repulsive effect of adjacent plants occurred for the rootstocks and soil conditions; find relationships between root system and soil properties and analyse soil state trend. Some soil physical properties were significantly deteriorated in inter-row versus in-row, mainly due to soil compaction induced by technological traffic. Density of total roots was higher in-row than inter-row, but the differences were not significant. Root density decreased more intensely with soil depth than with distance from tree trunks. Root density correlated with some soil properties. No repulsive effect of the roots of adjacent peach trees was noted. The decrease of root density with distance from trunk can be used in optimising tree arrangement. The conclusions could also be used in countries with similar growth conditions.

Stand structure modulates the long-term vulnerability of Pinus halepensis to climatic drought in a semiarid Mediterranean ecosystem.

Science.gov (United States)

Moreno-Gutiérrez, Cristina; Battipaglia, Giovanna; Cherubini, Paolo; Saurer, Matthias; Nicolás, Emilio; Contreras, Sergio; Querejeta, José Ignacio

2012-06-01

We investigated whether stand structure modulates the long-term physiological performance and growth of Pinus halepensis Mill. in a semiarid Mediterranean ecosystem. Tree radial growth and carbon and oxygen stable isotope composition of latewood (δ(13)C(LW) and δ(18)O(LW), respectively) from 1967 to 2007 were measured in P. halepensis trees from two sharply contrasting stand types: open woodlands with widely scattered trees versus dense afforested stands. In both stand types, tree radial growth, δ(13)C(LW) and δ(18)O(LW) were strongly correlated with annual rainfall, thus indicating that tree performance in this semiarid environment is largely determined by inter-annual changes in water availability. However, trees in dense afforested stands showed consistently higher δ(18)O(LW) and similar δ(13)C(LW) values compared with those in neighbouring open woodlands, indicating lower stomatal conductance and photosynthesis rates in the former, but little difference in water use efficiency between stand types. Trees in dense afforested stands were more water stressed and showed lower radial growth, overall suggesting greater vulnerability to drought and climate aridification compared with trees in open woodlands. In this semiarid ecosystem, the negative impacts of intense inter-tree competition for water on P. halepensis performance clearly outweigh potential benefits derived from enhanced infiltration and reduced run-off losses in dense afforested stands. © 2011 Blackwell Publishing Ltd.

The carbon balance pivot point of southwestern U.S. semiarid ecosystems: Insights from the 21st century drought

Science.gov (United States)

Scott, Russell L.; Biederman, Joel A.; Hamerlynck, Erik P.; Barron-Gafford, Greg A.

2015-12-01

Global-scale studies indicate that semiarid regions strongly regulate the terrestrial carbon sink. However, we lack understanding of how climatic shifts, such as decadal drought, impact carbon sequestration across the wide range of structural diversity in semiarid ecosystems. Therefore, we used eddy covariance measurements to quantify how net ecosystem production of carbon dioxide (NEP) differed with relative grass and woody plant abundance over the last decade of drought in four Southwest U.S. ecosystems. We identified a precipitation "pivot point" in the carbon balance for each ecosystem where annual NEP switched from negative to positive. Ecosystems with grass had pivot points closer to the drought period precipitation than the predrought average, making them more likely to be carbon sinks (and a grass-free shrubland, a carbon source) during the current drought. One reason for this is that the grassland located closest to the shrubland supported higher leaf area and photosynthesis at the same water availability. Higher leaf area was associated with a greater proportion of evapotranspiration being transpiration (T/ET), and therefore with higher ecosystem water use efficiency (gross ecosystem photosynthesis/ET). Our findings strongly show that water availability is a primary driver of both gross and net semiarid productivity and illustrate that structural differences may contribute to the speed at which ecosystem carbon cycling adjusts to climatic shifts.

Leaf anatomy of six species of Heliotropiaceae Schrad. from the Brazilian semi-arid region

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Elisabeth Emília Augusta Dantas Tölke

2015-09-01

Full Text Available The family Heliotropiaceae has more than 450 species, mainly distributed in the tropics and subtropics. In Brazil, it is represented by the genera Euploca Nutt., Heliotropium L., Myriopus Small and Tournefortia L. The aim of this study was to describe the leaf anatomy of six species of Heliotropiaceae recorded in the semi-arid region of Brazil: E. polyphylla (Lehm. J.I.M. Melo & Semir, E. procumbens (Mill. Diane & Hilger, H. angiospermum Murray, H. curassavicum L., M. rubicundus (Salzm. ex DC. Luebert and M. salzmannii (DC. Diane & Hilger. Besides contributing to the knowledge of the anatomy of the representatives of the family in the Caatinga (Brazilian savannah, we also sought to determine and highlight the anatomical features adaptive to the region and to identify features with potential diagnostic value. Leaf structures were analyzed by light microscopy and scanning electron microscopy. Additional tests were also carried out to detect starch and total lipids. The morphological variation and the distribution of trichomes were the most relevant features for species diagnosis. The distribution of stomata in M. salzmannii and H. angiospermum differed from that described in other papers, which demonstrates the anatomical plasticity of these species. This is the first report describing the leaf blade of M. rubicundus.

Salinization mechanisms in semi-arid regions

International Nuclear Information System (INIS)

Santiago, M.M.F.

1984-01-01

During a period of three years the basins of the Pereira de Miranda and Caxitore dams, located in the crystalline rock area of Ceara, Brazil, were studied in order to determine the mechanisms of salinization of their waters. Isotope methods ( 18 O/ 16 O) and hidrochemistry (determination of the of the maior ions) were applied to surface, underground and rain water in this study. An isotope model was designed and applied to the determination of evaporation and percolation of dams in semi-arid zones during the dry season. The results are compared to those from a conventional chemical model. As causes of salinization of the water in the dams, the contributions of the rain itself and the lixiviation of the soil are quantified. An interaction between the dams and the underground water is imperceptible. The salinization of the underground water is attributed to recharge of the aquifer with rain water from the surface runoff followed by evaporation of the water rising, due to capilarity, in a one-directional flow to the surface. (Author) [pt

Should we plant trees to offset greenhouse gas emissions in semi-arid environments?

Science.gov (United States)

Pataki, D. E.; Pincetl, S.; Gillespie, T. W.; Li, W.; McCarthy, H. R.; Saatchi, S.; Saphores, J.

2008-12-01

Urban tree planting programs have been gaining popularity in the United States. Urban trees have been associated with a variety of environmental benefits, including improvements in air quality, mitigation of urban heat island effects, reductions in stormwater runoff, and more recently, carbon sequestration. There are also other potential aesthetic and economic benefits of urban forests, which have been shown to affect real estate values. However, there may also be significant economic and environmental costs of planting and maintaining trees in urban areas, particularly in semi-arid environments where trees are not native and require irrigation and fertilization. We are conducting an analysis of the Million Tree Initiative in the city of Los Angeles, which has committed to a major tree planting program. Los Angeles currently has a low tree canopy cover relative to other cities, particularly in its low income neighborhoods. We are evaluating the decision-making processes associated with the new tree planting program, its perceived benefits, and its actual benefits based on measurements of plant and ecosystem processes such as transpiration, photosynthesis, and water use efficiency; remote sensing analyses of tree cover and surface temperature; and economic analyses. We have found great variability in the interpretation of the program by its various participants, but also significant institutional learning as the program has evolved. Our datasets have challenged some of the common assumptions of the program, for example, the assumption that native species use less water than imported species and are therefore more environmentally beneficial in terms of water resources. We have also found significant impacts of the urban forest on air temperature, which may reduce energy use during the summer due to reductions in air conditioning. This is likely to be a larger effect of urban trees on greenhouse gas emissions than direct carbon sequestration alone, which is a very

Socio-economic effect on socially-deprived communities of developing drinking water quality problems in arid and semi-arid area of central Rajasthan

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I. Husain

2014-09-01

Full Text Available Rajasthan is well known for its Great Thar desert. Central Rajasthan has an arid to semi-arid environment. The area faces either scarcity of water or poor quality of drinking water. In some areas water is transported 2 km or more, which uses time, energy and money. Rich people have their own sources, which is restricted for use by others. Such conditions are affecting socially-deprived communities, both socially and economically. Groundwater is a major source of drinking water due to the unavailability of surface water. There is a lack of groundwater quality knowledge in the community and the data available is hard to understand by consumers. The CCME Water Quality Index is a tool to simplify the water quality report by rating the water on quality standards. It provides meaningful summaries of overall water quality and trends, which is accessible to non-technical lay people. In the present study the objective is to examine the groundwater quality of six districts (Ajmer, Bhilwara, Pali, Rajasamand, Nagaur and Jodhpur, centrally located in Rajasthan, with arid and semi-arid conditions. CCME WQI is also evaluated to produce quality data in a form to be understood by the community. A total of 4369 groundwater sources in 1680 villages from six districts (76 546 km2 were collected and examined. Results are outlined in the Bureau of Indian Standards (BIS: 10500, 2012 and 2952 sources are unsafe for drinking. According to CCME WQI groundwater of 93 villages is poor, 343 villages are marginal, and 369 villages are fair in quality. Toxicological studies of unsafe drinking water and their remedial measures are also discussed. A tentative correlation between prevailing water-borne diseases and quality parameter has also been shown

Carbon dioxide emissions from semi-arid soils amended with biochar alone or combined with mineral and organic fertilizers.

Science.gov (United States)

Fernández, José M; Nieto, M Aurora; López-de-Sá, Esther G; Gascó, Gabriel; Méndez, Ana; Plaza, César

2014-06-01

Semi-arid soils cover a significant area of Earth's land surface and typically contain large amounts of inorganic C. Determining the effects of biochar additions on CO2 emissions from semi-arid soils is therefore essential for evaluating the potential of biochar as a climate change mitigation strategy. Here, we measured the CO2 that evolved from semi-arid calcareous soils amended with biochar at rates of 0 and 20tha(-1) in a full factorial combination with three different fertilizers (mineral fertilizer, municipal solid waste compost, and sewage sludge) applied at four rates (equivalent to 0, 75, 150, and 225kg potentially available Nha(-1)) during 182 days of aerobic incubation. A double exponential model, which describes cumulative CO2 emissions from two active soil C compartments with different turnover rates (one relatively stable and the other more labile), was found to fit very well all the experimental datasets. In general, the organic fertilizers increased the size and decomposition rate of the stable and labile soil C pools. In contrast, biochar addition had no effects on any of the double exponential model parameters and did not interact with the effects ascribed to the type and rate of fertilizer. After 182 days of incubation, soil organic and microbial biomass C contents tended to increase with increasing the application rates of organic fertilizer, especially of compost, whereas increasing the rate of mineral fertilizer tended to suppress microbial biomass. Biochar was found to increase both organic and inorganic C contents in soil and not to interact with the effects of type and rate of fertilizer on C fractions. As a whole, our results suggest that the use of biochar as enhancer of semi-arid soils, either alone or combined with mineral and organic fertilizers, is unlikely to increase abiotic and biotic soil CO2 emissions. Copyright © 2014 Elsevier B.V. All rights reserved.

Response of deep soil moisture to land use and afforestation in the semi-arid Loess Plateau, China

Science.gov (United States)

Yang, Lei; Wei, Wei; Chen, Liding; Mo, Baoru

2012-12-01

SummarySoil moisture is an effective water source for plant growth in the semi-arid Loess Plateau of China. Characterizing the response of deep soil moisture to land use and afforestation is important for the sustainability of vegetation restoration in this region. In this paper, the dynamics of soil moisture were quantified to evaluate the effect of land use on soil moisture at a depth of 2 m. Specifically, the gravimetric soil moisture content was measured in the soil layer between 0 and 8 m for five land use types in the Longtan catchment of the western Loess Plateau. The land use types included traditional farmland, native grassland, and lands converted from traditional farmland (pasture grassland, shrubland and forestland). Results indicate that the deep soil moisture content decreased more than 35% after land use conversion, and a soil moisture deficit appeared in all types of land with introduced vegetation. The introduced vegetation decreased the soil moisture content to levels lower than the reference value representing no human impact in the entire 0-8 m soil profile. No significant differences appeared between different land use types and introduced vegetation covers, especially in deeper soil layers, regardless of which plant species were introduced. High planting density was found to be the main reason for the severe deficit of soil moisture. Landscape management activities such as tillage activities, micro-topography reconstruction, and fallowed farmland affected soil moisture in both shallow and deep soil layers. Tillage and micro-topography reconstruction can be used as effective countermeasures to reduce the soil moisture deficit due to their ability to increase soil moisture content. For sustainable vegetation restoration in a vulnerable semi-arid region, the plant density should be optimized with local soil moisture conditions and appropriate landscape management practices.

Blood gas and electrolyte values of (Capra hircus Canindé breed goats raised in the northeastern semiarid

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Talyta Lins Nunes

2014-09-01

Full Text Available ABSTRACT. Nunes T.L., Oliveira M.G.C., Paiva A.L.C., Bezerra T.C.G., Barrêto Júnior R.A. & Paula V.V. [Blood gas and electrolyte values of (Capra hircus Canindé breed goats raised in the northeastern semiarid.] Valores hemogasométricos de caprinos (Capra hircus da raça Canindé criados no semiárido nordestino. Revista Brasileira de Medicina Veterinária, 36(3:255-260, 2014. Departamento de Ciências Animais, Universidade Federal Rural do Semi-Árido, BR 110, Km 47, Bairro Presidente Costa e Silva, Mossoró, RN 59625-900, Brasil. E-mail: talyta_lins@hotmail.com Canindé goat breed is native of northeastern Brazil and is in danger of extinction. The objective of this research was to determine blood gas and electrolytes values in Canindé goat breed reared in the state of Rio Grande do Norte, establishing baseline data for the breed in the semi-arid conditions. Blood samples from 83 clinically healthy animals were collected and distributed in four groups: Group I comprised of 32 pregnant females, Group II, 29 non-pregnant, Group III, 10 males, and group IV consisted of 12 pups. The blood sample was submitted for blood gas analysis, determining the concentration of sodium, potassium, chloride, total carbon dioxide, pH, carbon dioxide partial pressure, sodium bicarbonate, excess base, and anion gap. Data with normal distribution were analyzed by ANOVA and Tukey test; those which did not have a normal distribution were analyzed by Kruskal-Wallis, Mann-Whitney and Spearman. The results were expressed as mean and standard deviation. The values obtained were similar to those found in other studies with different goat and sheep breeds, and thus may serve as reference for the Canindé breed. The data suggest an influence of age, sex and reproductive status in the variables analyzed.

'If only it would rain': Farmers' perceptions of rainfall and drought in semi-arid central Tanzania

NARCIS (Netherlands)

Slegers, M.F.W.

2008-01-01

Farmers in semi-arid East Africa prioritize drought as their major productivity-reducing problem, while scientists identify soil degradation as a major threat. The question that needs to be addressed is how farmers perceive drought. Insight into farmers¿ perceptions of drought could be the missing

Adaptive livelihood strategies employed by farmers to close the food gap in semi-arid south eastern Zimbabwe

NARCIS (Netherlands)

Murungweni, C.; Wijk, van M.T.; Giller, K.E.; Andersson, J.A.; Smaling, E.M.A.

2014-01-01

Rural households in semi-arid areas of southern Africa are confronted with numerous hazards that threaten the household food base. The new wildlife policy of establishing transfrontier conservation areas aims to increase conservation of wildlife resources while improving local livelihoods. This

Topsoil moisture mapping using geostatistical techniques under different Mediterranean climatic conditions.

Science.gov (United States)

Martínez-Murillo, J F; Hueso-González, P; Ruiz-Sinoga, J D

2017-10-01

Soil mapping has been considered as an important factor in the widening of Soil Science and giving response to many different environmental questions. Geostatistical techniques, through kriging and co-kriging techniques, have made possible to improve the understanding of eco-geomorphologic variables, e.g., soil moisture. This study is focused on mapping of topsoil moisture using geostatistical techniques under different Mediterranean climatic conditions (humid, dry and semiarid) in three small watersheds and considering topography and soil properties as key factors. A Digital Elevation Model (DEM) with a resolution of 1×1m was derived from a topographical survey as well as soils were sampled to analyzed soil properties controlling topsoil moisture, which was measured during 4-years. Afterwards, some topography attributes were derived from the DEM, the soil properties analyzed in laboratory, and the topsoil moisture was modeled for the entire watersheds applying three geostatistical techniques: i) ordinary kriging; ii) co-kriging considering as co-variate topography attributes; and iii) co-kriging ta considering as co-variates topography attributes and gravel content. The results indicated topsoil moisture was more accurately mapped in the dry and semiarid watersheds when co-kriging procedure was performed. The study is a contribution to improve the efficiency and accuracy of studies about the Mediterranean eco-geomorphologic system and soil hydrology in field conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

Monte Carlo study of electron relaxation in graphene with spin polarized, degenerate electron gas in presence of electron-electron scattering

Science.gov (United States)

Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek

2017-12-01

The Monte Carlo simulation method is applied to study the relaxation of excited electrons in monolayer graphene. The presence of spin polarized background electrons population, with density corresponding to highly degenerate conditions is assumed. Formulas of electron-electron scattering rates, which properly account for electrons presence in two energetically degenerate, inequivalent valleys in this material are presented. The electron relaxation process can be divided into two phases: thermalization and cooling, which can be clearly distinguished when examining the standard deviation of electron energy distribution. The influence of the exchange effect in interactions between electrons with parallel spins is shown to be important only in transient conditions, especially during the thermalization phase.

Development of conditioned taste aversion to Mascagnia rigida in goats

OpenAIRE

Barbosa,Raquel Ribeiro; Silva,Idalécio Pacífico da; Soto-Blanco,Benito

2008-01-01

The aim of this study was to determine whether goats could be averted from consuming Mascagnia rigida, a toxic plant found in the semiarid region of northeastern Brazil. Fourteen male goats not previously familiarized to M. rigida were randomly allocated to two treatment groups: control (treated with 5.5mL water orally by a drenching gun) and lithium group (treated with 100mg LiCl/kg body weight orally by a drenching gun). For conditioning, goats were allowed to feed on M. rigida leaves for 1...

Application of 13C and 15N stable isotope probing to characterize RDX degrading microbial communities under different electron-accepting conditions

International Nuclear Information System (INIS)

Cho, Kun-Ching; Lee, Do Gyun; Fuller, Mark E.; Hatzinger, Paul B.; Condee, Charles W.; Chu, Kung-Hui

2015-01-01

Highlights: • SIP characterized RDX-degrading communities under different e-accepting conditions. • Dominant RDX degradation pathways differed under different e-accepting conditions. • More complete detoxification of RDX occurred under methanogenic and sulfate-reducing conditions than under manganese(IV) and iron(III)-reducing conditions. - Abstract: This study identified microorganisms capable of using the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) or its metabolites as carbon and/or nitrogen sources under different electron-accepting conditions using 13 C and 15 N stable isotope probing (SIP). Mesocosms were constructed using groundwater and aquifer solids from an RDX-contaminated aquifer. The mesocosms received succinate as a carbon source and one of four electron acceptors (nitrate, manganese(IV), iron(III), or sulfate) or no additional electron acceptor (to stimulate methanogenesis). When RDX degradation was observed, subsamples from each mesocosm were removed and amended with 13 C 3 - or ring- 15 N 3 -, nitro- 15 N 3 -, or fully-labeled 15 N 6 -RDX, followed by additional incubation and isolation of labeled nucleic acids. A total of fifteen 16S rRNA sequences, clustering in α- and γ-Proteobacteria, Clostridia, and Actinobacteria, were detected in the 13 C-DNA fractions. A total of twenty seven sequences were derived from different 15 N-DNA fractions, with the sequences clustered in α- and γ-Proteobacteria, and Clostridia. Interestingly, sequences identified as Desulfosporosinus sp. (in the Clostridia) were not only observed to incorporate the labeled 13 C or 15 N from labeled RDX, but also were detected under each of the different electron-accepting conditions. The data suggest that 13 C- and 15 N-SIP can be used to characterize microbial communities involved in RDX biodegradation, and that the dominant pathway of RDX biodegradation may differ under different electron-accepting conditions

A geochemical and isotopic approach to recharge evaluation in semi-arid zones. Past and present

International Nuclear Information System (INIS)

Edmunds, W.M.; Walton, N.R.G.

1980-01-01

The magnitude of any recharge to aquifers in semi-arid and arid zones is the principal uncertainty in estimating a water balance. Recent studies in Cyprus and Libyan Arab Jamahiriya are currently being used to demonstrate the application of geochemical and isotopic techniques, to the determination of both current and palaeo-recharge. In Cyprus, solute profiles of the unsaturated zone have been interpreted to provide estimates of the direct recharge component using a steady-state, mass-balance approach; results from the chloride profiles compare well with recharge estimates using tritium. In addition, it is found that some solute peaks, notably for specific electrical conductance, give a reasonably accurate record of the rainfall history during the period 1950-1975. The solute profile method is relatively unsophisticated and could be more widely applied to recharge estimation in other semi-arid areas of the world. In Libya, a clear distinction can be made using the combined isotopic, hydrological and geochemical results between regional groundwaters recharged to the upper, unconfined aquifer of the Sirte Basin before 13,000 years BP and younger waters recharged locally during the period 5000-7800 years BP. A well-defined fresh-water channel, superimposed upon the regional water quality pattern, can be traced within the aquifer for some 130 km and represents direct evidence of recharge during the Holocene. Some shallow groundwaters of similar composition to the fresh-water channel are also considered to represent recent, if intermittent, recharge which took place during historical times. It is concluded that geochemical and isotopic studies of both the unsaturated zone and of shallow groundwaters in semi-arid regions, can be used to determine not only the present-day direct recharge component, but also a recharge chronology of immediate historic times, which may be important in the estimation of long-term water resources. (author)

Land cover controls on summer discharge and runoff solution chemistry of semi-arid urban catchments

Science.gov (United States)

Gallo, Erika L.; Brooks, Paul D.; Lohse, Kathleen A.; McLain, Jean E. T.

2013-04-01

SummaryRecharge of urban runoff to groundwater as a stormwater management practice has gained importance in semi-arid regions where water resources are scarce and urban centers are growing. Despite this trend, the importance of land cover in controlling semi-arid catchment runoff quantity and quality remains unclear. Here we address the question: How do land cover characteristics control the amount and quality of storm runoff in semi-arid urban catchments? We monitored summertime runoff quantity and quality from five catchments dominated by distinct urban land uses: low, medium, and high density residential, mixed use, and commercial. Increasing urban land cover increased runoff duration and the likelihood that a rainfall event would result in runoff, but did not increase the time to peak discharge of episodic runoff. The effect of urban land cover on hydrologic responses was tightly coupled to the magnitude of rainfall. At distinct rainfall thresholds, roads, percent impervious cover and the stormwater drainage network controlled runoff frequency, runoff depth and runoff ratios. Contrary to initial expectations, runoff quality did not vary in repose to impervious cover or land use. We identified four major mechanisms controlling runoff quality: (1) variable solute sourcing due to land use heterogeneity and above ground catchment connectivity; (2) the spatial extent of pervious and biogeochemically active areas; (3) the efficiency of overland flow and runoff mobilization; and (4) solute flushing and dilution. Our study highlights the importance of the stormwater drainage systems characteristics in controlling urban runoff quantity and quality; and suggests that enhanced wetting and in-stream processes may control solute sourcing and retention. Finally, we suggest that the characteristics of the stormwater drainage system should be integrated into stormwater management approaches.

Agronomic performance of onion hybrids in Baraúna, in the semi-arid region of Brazil

Directory of Open Access Journals (Sweden)

Renato Leandro Costa Nunes

Full Text Available In the Brazilian state of Rio Grande do Norte, the significant planting of onions is relatively recent, with producers seeking alternative ways to reduce losses. As a result, it was aimed to evaluate the agronomic performance of onion hybrids in the town of Baraúna in the semi-arid region of Rio Grande do Norte. The experimental design was of randomised blocks with six replications. Treatments consisted of eight hybrids (Cronus F1, Predilata F1, Serena F1, Fortaleza F1, Mata Hari, Luana, Lambada, Don Victor and a control cultivar (IPA 11. The following were evaluated: average plant height; average number of leaves; diameter of the pseudostem; productivity; average bulb weight; rate of survival; leaf-waxiness; cultivar cycle; commercial classification of the bulbs. The Serena F1 and Mata Hari cultivars are recommended for the northeast semi-arid region due to high productivity, early cycle and better bulb classification. The use of these cultivars may help, in the short term, to change cultivation of the onion in the state of Rio Grande do Norte.

Groundwater recharge in irrigated semi-arid areas: quantitative hydrological modelling and sensitivity analysis

Science.gov (United States)

Jiménez-Martínez, Joaquín; Candela, Lucila; Molinero, Jorge; Tamoh, Karim

2010-12-01

For semi-arid regions, methods of assessing aquifer recharge usually consider the potential evapotranspiration. Actual evapotranspiration rates can be below potential rates for long periods of time, even in irrigated systems. Accurate estimations of aquifer recharge in semi-arid areas under irrigated agriculture are essential for sustainable water-resources management. A method to estimate aquifer recharge from irrigated farmland has been tested. The water-balance-modelling approach was based on VisualBALAN v. 2.0, a computer code that simulates water balance in the soil, vadose zone and aquifer. The study was carried out in the Campo de Cartagena (SE Spain) in the period 1999-2008 for three different groups of crops: annual row crops (lettuce and melon), perennial vegetables (artichoke) and fruit trees (citrus). Computed mean-annual-recharge values (from irrigation+precipitation) during the study period were 397 mm for annual row crops, 201 mm for perennial vegetables and 194 mm for fruit trees: 31.4, 20.7 and 20.5% of the total applied water, respectively. The effects of rainfall events on the final recharge were clearly observed, due to the continuously high water content in soil which facilitated the infiltration process. A sensitivity analysis to assess the reliability and uncertainty of recharge estimations was carried out.

Shifts of growing-season precipitation peaks decrease soil respiration in a semiarid grassland.

Science.gov (United States)

Ru, Jingyi; Zhou, Yaqiong; Hui, Dafeng; Zheng, Mengmei; Wan, Shiqiang

2018-03-01

Changing precipitation regimes could have profound influences on carbon (C) cycle in the biosphere. However, how soil C release from terrestrial ecosystems responds to changing seasonal distribution of precipitation remains unclear. A field experiment was conducted for 4 years (2013-2016) to examine the effects of altered precipitation distributions in the growing season on soil respiration in a temperate steppe in the Mongolian Plateau. Over the 4 years, both advanced and delayed precipitation peaks suppressed soil respiration, and the reductions mainly occurred in August. The decreased soil respiration could be primarily attributable to water stress and subsequently limited plant growth (community cover and belowground net primary productivity) and soil microbial activities in the middle growing season, suggesting that precipitation amount in the middle growing season is more important than that in the early, late, or whole growing seasons in regulating soil C release in grasslands. The observations of the additive effects of advanced and delayed precipitation peaks indicate semiarid grasslands will release less C through soil respiratory processes under the projected seasonal redistribution of precipitation in the future. Our findings highlight the potential role of intra-annual redistribution of precipitation in regulating ecosystem C cycling in arid and semiarid regions. © 2017 John Wiley & Sons Ltd.

Climate change mitigation by carbon stock - the case of semi-arid West Africa

Science.gov (United States)

Lykke, A. M.; Barfod, A. S.; Tinggaard Svendsen, G.; Greve, M.; Svenning, J.-C.

2009-11-01

Semi-arid West Africa has not been integrated into the afforestation/reforestation (AR) carbon market. Most projects implemented under the Clean Development Mechanism (CDM) have focused on carbon emission reductions from industry and energy consumption, whereas only few (only one in West Africa) have been certified for AR carbon sequestration. A proposed mechanism, Reducing Emissions from Deforestation and Degradation (REDD) to be discussed under COP15 aims to reduce emissions by conserving already existing forests. REDD has high potential for carbon stocking at low costs, but focuses primarily on rain forest countries and excludes semi-arid West Africa from the preliminary setup. African savannas have potential to store carbon in the present situation with degrading ecosystems and relatively low revenues from crops and cattle, especially if it is possible to combine carbon stocking with promotion of secondary crops such as food resources and traditional medicines harvested on a sustainable basis. Methods for modelling and mapping of potential carbon biomass are being developed, but are still in a preliminary state. Although economic benefits from the sale of carbon credits are likely to be limited, carbon stocking is an interesting option if additional benefits are considered such as improved food security and protection of biodiversity.

Climate change mitigation by carbon stock - the case of semi-arid West Africa

International Nuclear Information System (INIS)

Lykke, A M; Barfod, A S; Greve, M; Svenning, J-C; Svendsen, G Tinggaard

2009-01-01

Semi-arid West Africa has not been integrated into the afforestation/reforestation (AR) carbon market. Most projects implemented under the Clean Development Mechanism (CDM) have focused on carbon emission reductions from industry and energy consumption, whereas only few (only one in West Africa) have been certified for AR carbon sequestration. A proposed mechanism, Reducing Emissions from Deforestation and Degradation (REDD) to be discussed under COP15 aims to reduce emissions by conserving already existing forests. REDD has high potential for carbon stocking at low costs, but focuses primarily on rain forest countries and excludes semi-arid West Africa from the preliminary setup. African savannas have potential to store carbon in the present situation with degrading ecosystems and relatively low revenues from crops and cattle, especially if it is possible to combine carbon stocking with promotion of secondary crops such as food resources and traditional medicines harvested on a sustainable basis. Methods for modelling and mapping of potential carbon biomass are being developed, but are still in a preliminary state. Although economic benefits from the sale of carbon credits are likely to be limited, carbon stocking is an interesting option if additional benefits are considered such as improved food security and protection of biodiversity.

Genetic improvement of Nellore cattle in the semi-arid region of northeastern Brazil

Directory of Open Access Journals (Sweden)

Ana Carla Borges Barbosa

2015-08-01

Full Text Available The semi-arid region of Brazil represents approximately 57% of the northeastern territory. The main economic activity in this region is agriculture and livestock, in most cases, using traditional technologies. However, there is little published information currently available on cattle-raising in this part of Brazil. The objective of this study was to estimate genetic parameters and trends for productive and reproductive traits of Nellore cattle raised in semi-arid region of northeastern Brazil. Data were collected on weight-adjusted at 205 (W205, 365 (W365 and 550 (W550 days of life, age at first calving (AFC, calving interval (CI and scrotal circumference (SC at 550 days of life of cattle born between 1965 and 2011. Estimates of covariance and variance were obtained through univariate analysis using a Gibbs sampler. The estimated coefficients of heritability (mode were 0.27 (W205, 0.36 (W365 and 0.39 (W550, 0.37 (SC, 0.22 (AFC and 0.03 (CI. Little or no gain from selection is apparent in the genetic trend analysis over the 45 years of the study. However, environmental improvement has allowed phenotypic progress in growth traits and age at first age calving.

Seasonality of Fruit-Feeding Butterflies (Lepidoptera, Nymphalidae) in a Brazilian Semiarid Area

OpenAIRE

Nobre, Carlos Eduardo Beserra; Iannuzzi, Luciana; Schlindwein, Clemens

2012-01-01

A survey of 6,000 trap/hours using fruit-bait traps was conducted, in order to characterize the community of fruit-feeding butterflies and their seasonal variation in a semiarid area of NE Brazil, which exhibits a highly seasonal rainfall regime. The community was composed of 15 species, the four most abundant comprising more than 80% of the total individuals. In the first sampling month, 80% of the species had already been recorded. A strong positive correlation was found between butterfly a...

Low-energy-electron interactions with DNA: approaching cellular conditions with atmospheric experiments

International Nuclear Information System (INIS)

Alizadeh, E.; Sanche, L.

2014-01-01

A novel technique has been developed to investigate low energy electron (LEE)-DNA interactions in the presence of small biomolecules (e.g., N 2 , O 2 , H 2 O) found near DNA in the cell nucleus, in order to simulate cellular conditions. In this technique, LEEs are emitted from a metallic surface exposed by soft X-rays and interact with DNA thin films at standard ambient temperature and pressure (SATP). Whereas atmospheric N 2 had little effect on the yields of LEE-induced single and double strand breaks, both O 2 and H 2 O considerably modified and increased such damage. The highest yields were obtained when DNA is embedded in a combined O 2 and H 2 O atmosphere. In this case, the amount of additional double strand breaks was supper-additive. The effect of modifying the chemical and physical stability of DNA by platinum-based chemotherapeutic agents (Pt-drugs) including cisplatin, carboplatin and oxaliplatin was also investigated with this technique. The results obtained provide information on the role played by subexcitation-energy electrons and dissociative electron attachment in the radiosensitization of DNA by Pt-drugs, which is an important step to unravel the mechanisms of radiosensitization of these agents in chemo-radiation cancer therapy. (authors)

Low-energy-electron interactions with DNA: approaching cellular conditions with atmospheric experiments

Science.gov (United States)

Alizadeh, Elahe; Sanche, Léon

2014-04-01

A novel technique has been developed to investigate low energy electron (LEE)-DNA interactions in the presence of small biomolecules (e.g., N2, O2, H2O) found near DNA in the cell nucleus, in order to simulate cellular conditions. In this technique, LEEs are emitted from a metallic surface exposed by soft X-rays and interact with DNA thin films at standard ambient temperature and pressure (SATP). Whereas atmospheric N2 had little effect on the yields of LEE-induced single and double strand breaks, both O2 and H2O considerably modified and increased such damage. The highest yields were obtained when DNA is embedded in a combined O2 and H2O atmosphere. In this case, the amount of additional double strand breaks was supper-additive. The effect of modifying the chemical and physical stability of DNA by platinum-based chemotherapeutic agents (Pt-drugs) including cisplatin, carboplatin and oxaliplatin was also investigated with this technique. The results obtained provide information on the role played by subexcitation-energy electrons and dissociative electron attachment in the radiosensitization of DNA by Pt-drugs, which is an important step to unravel the mechanisms of radiosensitisation of these agents in chemoradiation cancer therapy.

Spatio-temporal dynamics of arbuscular mycorrhizal fungi associated with glomalin-related soil protein and soil enzymes in different managed semiarid steppes.

Science.gov (United States)

Wang, Qi; Bao, Yuying; Liu, Xiaowei; Du, Guoxin

2014-10-01

Temporal and spatial patterns of arbuscular mycorrhizal fungi (AMF) and glomalin and soil enzyme activities were investigated in different managed semiarid steppes located in Inner Mongolia, North China. Soils were sampled in a depth up to 30 cm from non-grazed, overgrazed, and naturally restored steppes from June to September. Roots of Leymus chinense (Trin.) Tzvel. and Stipagrandis P. Smirn. were also collected over the same period. Results showed that overgrazing significantly decreased the total mycorrhizal colonization of S. grandis; total colonization of L. chinensis roots was not significantly different in the three managed steppes. Nineteen AMF species belonging to six genera were isolated. Funneliformis and Glomus were dominant genera in all three steppes. Spore density and species richness were mainly influenced by an interaction between plant growth stage and management system (P soil depth. AMF species richness was significantly positively correlated with soil acid phosphatase activity, alkaline phosphatase activity, and two Bradford-reactive soil protein (BRSP) fractions (P soil glomalin and phosphatase activity in different managed semiarid steppes. Based on these observations, AMF communities could be useful indicators for evaluating soil quality and function of semiarid grassland ecosystems.

Effect on stone lines on soil chemical characteristics under continuous sorghum cropping in semiarid Burkina Faso

NARCIS (Netherlands)

Zougmore, R.; Gnankambary, Z.; Guillobez, L.S.; Stroosnijder, L.

2002-01-01

In the semiarid Sahel, farmers commonly lay stone lines in fields to disperse runoff. This study was conducted in northern Burkina Faso to assess the chemical fertility of soil under a permanent, non-fertilised sorghum crop, which is the main production system in this area, 5 years after laying

Reduction of tree cover in West African woodlands and promotion in semi-arid farmlands

Science.gov (United States)

Brandt, Martin; Rasmussen, Kjeld; Hiernaux, Pierre; Herrmann, Stefanie; Tucker, Compton J.; Tong, Xiaoye; Tian, Feng; Mertz, Ole; Kergoat, Laurent; Mbow, Cheikh; David, John L.; Melocik, Katherine A.; Dendoncker, Morgane; Vincke, Caroline; Fensholt, Rasmus

2018-05-01

Woody vegetation in farmland acts as a carbon sink and provides ecosystem services for local people, but no macroscale assessments of the impact of management and climate on woody cover exist for drylands. Here we make use of very high spatial resolution satellite imagery to derive wall-to-wall woody cover patterns in tropical West African drylands. Our study reveals that mean woody cover in farmlands along all semi-arid and sub-humid rainfall zones is 16%, on average only 6% lower than in savannahs. In semi-arid Sahel, farmland management promotes woody cover around villages (11%), while neighbouring savannahs had on average less woody cover. However, farmlands in sub-humid zones have a greatly reduced woody cover (21%) as compared with savannahs (33%). In the region as a whole, rainfall, terrain and soil are the most important (80%) determinants of woody cover, while management factors play a smaller (20%) role. We conclude that agricultural expansion causes a considerable reduction of trees in woodlands, but observations in Sahel indicate that villagers safeguard trees on nearby farmlands which contradicts simplistic ideas of a high negative correlation between population density and woody cover.

Development of spatial heterogeneity in vegetation and soil properties after land abandonment in a semi-arid ecosystem

NARCIS (Netherlands)

Lesschen, J.P.; Cammeraat, L.H.; Kooijman, A.M.; van Wesemael, B.

2008-01-01

To mitigate erosion on abandoned fields in semi-arid ecosystems, it is important to understand how vegetation and soil properties and patterns develop after land abandonment. Our objective was to investigate the development of spatial heterogeneity in vegetation and soil properties after land

Drivers of inter-annual variability in Net Ecosystem Exchange in a semi-arid savanna ecosystem, South Africa

CSIR Research Space (South Africa)

Archibald, SA

2009-01-01

Full Text Available and filling gaps in eddy-covariance data in semi-arid systems were developed. Net ecosystem exchange (NEE) in these systems occurs as pulses associated with rainfall events, a pattern not well-represented in current standard gap-filling procedures developed...

An AES Study of the Room Temperature Surface Conditioning of Technological Metal Surfaces by Electron Irradiation

OpenAIRE

Scheuerlein, C; Hilleret, Noël; Taborelli, M; Brown, A; Baker, M A

2002-01-01

The modifications to technological copper and niobium surfaces induced by 2.5 keV electron irradiation have been investigated in the context of the conditioning process occurring in particle accelerator ultra high vacuum systems. Changes in the elemental surface composition have been found using Scanning Auger Microscopy (SAM) by monitoring the carbon, oxygen and metal Auger peak intensities as a function of electron irradiation in the dose range 10-6 to 10-2 C mm-2. The surface analysis resu...

Germination patterns of a suite of semiarid grassland forbs from central New Mexico

Science.gov (United States)

Rosemary L. Pendleton; Burton K. Pendleton

2014-01-01

We examined the germination response of 21 forb species collected from semiarid grasslands of central New Mexico. After-ripened seeds were subjected to 1 of 3 treatments: 1) no treatment; 2) a 3-wk stratification at 5 °C (cold-moist treatment); or 3) a 3-wk warm-moist treatment at 30 °C. All seeds were incubated under an alternating 10/20 °C temperature regime for 6 wk...

Antibacterial, Antioxidant, and Anticholinesterase Activities of Plant Seed Extracts from Brazilian Semiarid Region

OpenAIRE

Davi Felipe Farias; Terezinha Maria Souza; Martônio Ponte Viana; Bruno Marques Soares; Arcelina Pacheco Cunha; Ilka Maria Vasconcelos; Nágila Maria Pontes Silva Ricardo; Paulo Michel Pinheiro Ferreira; Vânia Maria Maciel Melo; Ana Fontenele Urano Carvalho

2013-01-01

The antimicrobial, antioxidant, and anticholinesterase activities of ethanolic seed extracts of twenty-one plant species from Brazilian semiarid region were investigated. The extracts were tested for antimicrobial activity against six bacteria strains and three yeasts. Six extracts presented activity against the Gram (−) organism Salmonella choleraesuis and the Gram (+) organisms Staphylococcus aureus and Bacillus subtilis. The MIC values ranged from 4.96 to 37.32 mg/mL. The Triplaris gardner...

Edaphic factors controlling summer (rainy season) greenhouse gas emissions (CO_2 and CH_4) from semiarid mangrove soils (NE-Brazil)

International Nuclear Information System (INIS)

Nóbrega, Gabriel N.; Ferreira, Tiago O.; Siqueira Neto, M.; Queiroz, Hermano M.; Artur, Adriana G.; Mendonça, Eduardo De S.; Silva, Ebenezer De O.

2016-01-01

The soil attributes controlling the CO_2, and CH_4 emissions were assessed in semiarid mangrove soils (NE-Brazil) under different anthropogenic activities. Soil samples were collected from different mangroves under different anthropogenic impacts, e.g., shrimp farming (Jaguaribe River); urban wastes (Cocó River) and a control site (Timonha River). The sites were characterized according to the sand content; physicochemical parameters (Eh and pH); total organic C; soil C stock (SCS) and equivalent SCS (SCS_E_Q_V); total P and N; dissolved organic C (DOC); and the degree of pyritization (DOP). The CO_2 and CH_4 fluxes from the soils were assessed using static closed chambers. Higher DOC and SCS and the lowest DOP promote greater CO_2 emission. The CH_4 flux was only observed at Jaguaribe which presented higher DOP, compared to that found in mangroves from humid tropical climates. Semiarid mangrove soils cannot be characterized as important greenhouse gas sources, compared to humid tropical mangroves. - Highlights: • GHG emission was associated with different soil characteristics. • Highest CO_2 emissions were found in mangroves with larger dissolved C and lower DOP. • Less CH_4 flux was due to low DOP in semiarid mangrove soils.

Spectroscopic surrogates of soil organic matter resilience in crusted semiarid Mediterranean ecosystems

Science.gov (United States)

Miralles Mellado, Isabel; Almendros, Gonzalo; Ortega, Raúl; Cantón, Yolanda; Poveda, Francisco; van Wesemael, Bas

2016-04-01

Arid and semiarid ecosystems represent nearly a third of the Earth's total land surface. In these ecosystems, there is a critical balance between C sequestration and biodegradation that could easily be altered due to human disturbance or global change. These ecosystems are widely characterized by the presence of biological soil crusts (BSCs) which play the most important role in the C-cycle in arid and semiarid areas. Consequently, soil organic matter (SOM) characteristics of crusted soil could readily reflect important information on the resilience of SOM in response to any global temperature increase or to inappropriate soil management practices. In this research, representative BSCs and underlying soils were studied in two different semiarid ecosystems in Southern Spain, i.e., Amoladeras (located in Cabo de Gata Natural Park), and El Cautivo (located in Tabernas desert). Chemical fractionation and characterization of the SOM in BSCs and underlying soils were carried out in order to assess not only the total amount of organic C sequestered but mainly the quality of humic-type organic fractions. After isolating the major organic fractions (particulate fraction, humic acid-like (HA), alkali-extracted fulvic acid (FA) and H3PO4-FAs), the macromolecular, HA fraction was purified and studied by derivative visible spectroscopy and resolution-enhanced infrared (IR) spectroscopy. Our results show differences in the structural characteristics of the HA-type substances, interpreted as progressive stages of diagenetic transformation of biomacromolecules. Amoladeras showed higher SOM content, and higher values of HA and HA/FA ratio than El Cautivo, with lower SOM content in BSCs and underlying soils. The latter site accumulates SOM consisting mainly of comparatively less recalcitrant organic fractions with small molecular sizes (H3PO4-FAs and FAs). Moreover HAs in samples from Amoladeras showed higher condensation and aromaticity (higher E4, lower E4/E6 ratio), pointing to

Prolonged limitation of tree growth due to warmer spring in semi-arid mountain forests of Tianshan, northwest China

International Nuclear Information System (INIS)

Wu Xiuchen; Liu Hongyan; Wang Yufu; Deng Minghua

2013-01-01

Based on radial tree growth measurements in nine plots of area 625 m 2 (369 trees in total) and climate data, we explored the possibly changing effects of climate on regional tree growth in the temperate continental semi-arid mountain forests in the Tianshan Mountains in northwest China during 1933–2005. Tree growth in our study region is generally limited by the soil water content of pre- and early growing season (February–July). Remarkably, moving correlation functions identified a clear temporal change in the relationship between tree growth and mean April temperature. Tree growth showed a significant (p < 0.05) and negative relationship to mean April temperature since approximately the beginning of the 1970s, which indicated that the semi-arid mountain forests are suffering a prolonged growth limitation in recent years accompanying spring warming. This prolonged limitation of tree growth was attributed to the effects of soil water limitation in early spring (March–April) caused by the rapid spring warming. Warming-induced prolonged drought stress contributes, to a large part, to the marked reduction of regional basal area increment (BAI) in recent years and a much slower growth rate in young trees. Our results highlight that the increasing water limitation induced by spring warming on tree growth most likely aggravated the marked reduction in tree growth. This work provides a better understanding of the effects of spring warming on tree growth in temperate continental semi-arid forests. (letter)

Evaluating Impacts of Land Use/Land Cover Change on Water Resources in Semiarid Regions

Science.gov (United States)

Scanlon, B. R.; Faunt, C. C.; Pool, D. R.; Reedy, R. C.

2017-12-01

Land use/land cover (LU/LC) changes play an integral role in water resources by controlling the partitioning of water at the land surface. Here we evaluate impacts of changing LU/LC on water resources in response to climate variation and change and land use change related to agriculture using data from semiarid regions in the southwestern U.S. Land cover changes in response to climate can amplify or dampen climate impacts on water resources. Changes from wet Pleistocene to much drier Holocene climate resulted in expansion of perennial vegetation, amplifying climate change impacts on water resources by reducing groundwater recharge as shown in soil profiles in the southwestern U.S.. In contrast, vegetation response to climate extremes, including droughts and floods, dampen impacts of these extremes on water resources, as shown by water budget monitoring in the Mojave Desert. Agriculture often involves changes from native perennial vegetation to annual crops increasing groundwater recharge in many semiarid regions. Irrigation based on conjunctive use of surface water and groundwater increases water resource availability, as shown in the Central Valley of California and in southern Arizona. Surface water irrigation in these regions is enhanced by water transported from more humid settings through extensive pipelines. These projects have reversed long-term declining groundwater trends in some regions. While irrigation design has often focused on increased efficiency, "more crop per drop", optimal water resource management may benefit more from inefficient (e.g. flood irrigation) surface-water irrigation combined with efficient (e.g. subsurface drip) irrigation to maximize groundwater recharge, as seen in parts of the Central Valley. Flood irrigation of perennial crops, such as almonds and vineyards, during winter is being considered in the Central Valley to enhance groundwater recharge. Managed aquifer recharge can be considered a special case of conjunctive use of

Small-Scale Farming in Semi-Arid Areas: Livelihood Dynamics between 1997 and 2010 in Laikipia, Kenya

Science.gov (United States)

Ulrich, Anne; Speranza, Chinwe Ifejika; Roden, Paul; Kiteme, Boniface; Wiesmann, Urs; Nusser, Marcus

2012-01-01

The rural population of semi-arid lands in Kenya face multiple challenges that result from population growth, poor markets, land use and climatic changes. In particular, subsistence oriented farmers face various risks and opportunities in their attempt to secure their livelihoods. This paper presents an analysis on how livelihood assets and…

Effect of combined water and nutrient management on runoff and sorghum yield in semi-arid Burkina Faso

NARCIS (Netherlands)

Zougmoré, R.; Mando, A.; Ringersma, J.; Stroosnijder, L.

2003-01-01

In the semiarid regions of sub-Saharan Africa, fertilizer recovery and nutrient release from organic sources are often moisture limited. Moreover, in these regions runoff brings about large nutrient losses from fertilizer or organic inputs. This study was conducted in the north sudanian climate zone

Evaluation of soil and water conservation measures in a semi-arid river basin in Tunisia using SWAT

Science.gov (United States)

The Merguellil catchment (Central Tunisia) is a typical Mediterranean semi-arid basin which suffers from regular water shortage aggravated by current droughts. During the recent decades the continuous construction of small and large dams and Soil and Water Conservation Works (i.e. Contour ridges) ha...

Divergent Effects of Nitrogen Addition on Soil Respiration in a Semiarid Grassland

OpenAIRE

Cheng Zhu; Yiping Ma; Honghui Wu; Tao Sun; Kimberly J. La Pierre; Zewei Sun; Qiang Yu

2016-01-01

Nitrogen (N) deposition has been steadily increasing for decades, with consequences for soil respiration. However, we have a limited understanding of how soil respiration responds to N availability. Here, we investigated the soil respiration responses to low and high levels of N addition (0.4?mol N m?2 yr?1 vs 1.6?mol N m?2 yr?1) over a two-year period in a semiarid Leymus chinensis grassland in Inner Mongolia, China. Our results show that low-level N addition increased soil respiration, plan...

77 FR 57039 - Special Conditions: Embraer S.A., Model EMB-550 Airplane; Electronic Flight Control System...

Science.gov (United States)

2012-09-17

... Flight Control System: Control Surface Awareness and Mode Annunciation AGENCY: Federal Aviation... a fly-by-wire electronic flight control system and no direct coupling from the flightdeck controller... nuisance alerting. This special condition also addresses flight control system mode annunciation. It...

Qualitative soil moisture assessment in semi-arid Africa - the role of experience and training on inter-rater reliability

Science.gov (United States)

Rinderer, M.; Komakech, H. C.; Müller, D.; Wiesenberg, G. L. B.; Seibert, J.

2015-08-01

Soil and water management is particularly relevant in semi-arid regions to enhance agricultural productivity. During periods of water scarcity, soil moisture differences are important indicators of the soil water deficit and are traditionally used for allocating water resources among farmers of a village community. Here we present a simple, inexpensive soil wetness classification scheme based on qualitative indicators which one can see or touch on the soil surface. It incorporates the local farmers' knowledge on the best soil moisture conditions for seeding and brick making in the semi-arid environment of the study site near Arusha, Tanzania. The scheme was tested twice in 2014 with farmers, students and experts (April: 40 persons, June: 25 persons) for inter-rater reliability, bias of individuals and functional relation between qualitative and quantitative soil moisture values. During the test in April farmers assigned the same wetness class in 46 % of all cases, while students and experts agreed on about 60 % of all cases. Students who had been trained in how to apply the method gained higher inter-rater reliability than their colleagues with only a basic introduction. When repeating the test in June, participants were given improved instructions, organized in small subgroups, which resulted in a higher inter-rater reliability among farmers. In 66 % of all classifications, farmers assigned the same wetness class and the spread of class assignments was smaller. This study demonstrates that a wetness classification scheme based on qualitative indicators is a robust tool and can be applied successfully regardless of experience in crop growing and education level when an in-depth introduction and training is provided. The use of a simple and clear layout of the assessment form is important for reliable wetness class assignments.

Qualitative soil moisture assessment in semi-arid Africa: the role of experience and training on inter-rater reliability

Science.gov (United States)

Rinderer, M.; Komakech, H.; Müller, D.; Seibert, J.

2015-03-01

Soil and water management is particularly relevant in semi-arid regions to enhance agricultural productivity. During periods of water scarcity soil moisture differences are important indicators of the soil water deficit and are traditionally used for allocating water resources among farmers of a village community. Here we present a simple, inexpensive soil wetness classification scheme based on qualitative indicators which one can see or touch on the soil surface. It incorporates the local farmers' knowledge on the best soil moisture conditions for seeding and brick making in the semi-arid environment of the study site near Arusha, Tanzania. The scheme was tested twice in 2014 with farmers, students and experts (April: 40 persons, June: 25 persons) for inter-rater reliability, bias of individuals and functional relation between qualitative and quantitative soil moisture values. During the test in April farmers assigned the same wetness class in 46% of all cases while students and experts agreed in about 60% of all cases. Students who had been trained in how to apply the method gained higher inter-rater reliability than their colleagues with only a basic introduction. When repeating the test in June, participants were given improved instructions, organized in small sub-groups, which resulted in a higher inter-rater reliability among farmers. In 66% of all classifications farmers assigned the same wetness class and the spread of class assignments was smaller. This study demonstrates that a wetness classification scheme based on qualitative indicators is a robust tool and can be applied successfully regardless of experience in crop growing and education level when an in-depth introduction and training is provided. The use of a simple and clear layout of the assessment form is important for reliable wetness class assignments.

Influence of Experimental Conditions on Electronic Tongue Results—Case of Valsartan Minitablets Dissolution

Directory of Open Access Journals (Sweden)

Małgorzata Wesoły

2016-08-01

Full Text Available A potentiometric electronic tongue was applied to study the release of valsartan from pharmaceutical formulations, i.e., minitablets uncoated and coated with Eudragit E. Special attention was paid to evaluate the influence of medium temperature and composition, as well as to compare the performances of the sensor arrays working in various hydrodynamic conditions. The drug dissolution profiles registered with the ion-sensitive electrodes were compared with standard dissolution tests performed with USP Apparatus 2 (paddle. Moreover, the signal changes of all sensors were processed by principal component analysis to visualize the release modifications, related to the presence of the coating agent. Finally, the importance and influence of the experimental conditions on the results obtained using potentiometric sensor arrays were discussed.

Exploring the strategies for households to adapt to climate-change in arid and semiarid East Africa

NARCIS (Netherlands)

Ng'ang'a, Stanley K.

2018-01-01

In this thesis I set out to investigate how households cope and adapt to climate change in the context of arid and semi-arid areas of East Africa. This research fits well in the wider literature on the relationship between climate change and variability and household responses in term of coping

Effects of feral free-roaming horses on semi-arid rangeland ecosystems: an example from the sagebrush steppe

Science.gov (United States)

Feral horses (Equus caballus) are viewed as a symbol of freedom and power; however, they are also a largely unmanaged, non-native grazer in North America, South America, and Australia. Information on their influence on vegetation and soil characteristics in semi-arid rangelands has been limited by ...

Water-scarcity patterns : spatiotemporal interdependencies between water use and water availability in a semi-arid river basin

NARCIS (Netherlands)

van Oel, P.R.

2009-01-01

This thesis addresses the interdependencies between water use and water availability and describes a model that has been developed to improve understanding of the processes that drive changes and variations in the spatial and temporal distribution of water resources in a semi-arid river basin. These

Leachate generation from landfill in a semi-arid climate: A qualitative and quantitative study from Sousse, Tunisia.

Science.gov (United States)

Frikha, Youssef; Fellner, Johann; Zairi, Moncef

2017-09-01

Despite initiatives for enhanced recycling and waste utilization, landfill still represents the dominant disposal path for municipal solid waste (MSW). The environmental impacts of landfills depend on several factors, including waste composition, technical barriers, landfill operation and climatic conditions. A profound evaluation of all factors and their impact is necessary in order to evaluate the environmental hazards emanating from landfills. The present paper investigates a sanitary landfill located in a semi-arid climate (Tunisia) and highlights major differences in quantitative and qualitative leachate characteristics compared to landfills situated in moderate climates. Besides the qualitative analysis of leachate samples, a quantitative analysis including the simulation of leachate generation (using the HELP model) has been conducted. The results of the analysis indicate a high load of salts (Cl, Na, inorganic nitrogen) in the leachate compared to other landfills. Furthermore the simulations with HELP model highlight that a major part of the leachate generated originates form the water content of waste.

Estimation of surface roughness in a semiarid region from C-band ERS-1 synthetic aperture radar data

Directory of Open Access Journals (Sweden)

E. E. Sano

1999-12-01

Full Text Available In this study, we investigated the feasibility of using the C-band European Remote Sensing Satellite (ERS-1 synthetic aperture radar (SAR data to estimate surface soil roughness in a semiarid rangeland. Radar backscattering coefficients were extracted from a dry and a wet season SAR image and were compared with 47 in situ soil roughness measurements obtained in the rocky soils of the Walnut Gulch Experimental Watershed, southeastern Arizona, USA. Both the dry and the wet season SAR data showed exponential relationships with root mean square (RMS height measurements. The dry C-band ERS-1 SAR data were strongly correlated (R² = 0.80, while the wet season SAR data have somewhat higher secondary variation (R² = 0.59. This lower correlation was probably provoked by the stronger influence of soil moisture, which may not be negligible in the wet season SAR data. We concluded that the single configuration C-band SAR data is useful to estimate surface roughness of rocky soils in a semiarid rangeland.

Experimental and theoretical study of electronic structure of aluminum in extreme conditions with X-ray absorption spectroscopy

International Nuclear Information System (INIS)

Festa, Floriane

2013-01-01

Matter in extreme conditions belongs to Warm Dense Matter regime which lays between dense plasma regime and condensed matter. This regime is still not well known, indeed it is very complex to generate such plasma in the laboratory to get experimental data and validate models. The goal of this thesis is to study electronic structure of aluminum in extreme conditions with X-ray absorption spectroscopy. Experimentally aluminum has reached high densities and high temperatures, up to now unexplored. An X-ray source has also been generated to probe highly compressed aluminum. Two spectrometers have recorded aluminum absorption spectra and aluminum density and temperature conditions have been deduced thanks to optical diagnostics. Experimental spectra have been compared to ab initio spectra, calculated in the same conditions. The theoretical goal was to validate the calculation method in high densities and high temperatures regime with the study of K-edge absorption modifications. We also used absorption spectra to study the metal-non metal transition which takes place at low density (density ≤ solid density). This transition could be study with electronic structure modifications of the system. (author) [fr

Changes in zinc speciation with mine tailings acidification in a semi-arid weathering environment

OpenAIRE

Hayes, Sarah M.; O’Day, Peggy A.; Webb, Sam M.; Maier, Raina M.; Chorover, Jon

2011-01-01

High concentrations of residual metal contaminants in mine tailings can be transported easily by wind and water, particularly when tailings remain unvegetated for decades following mining cessation, as is the case in semi-arid landscapes. Understanding the speciation and mobility of contaminant metal(loid)s, particularly in surficial tailings, is essential to controlling their phytotoxicities and to revegetating impacted sites. In prior work, we showed that surficial tailings samples from the...

Nanoscale Electronic Conditioning for Improvement of Nanowire Light-Emitting-Diode Efficiency.

Science.gov (United States)

May, Brelon J; Belz, Matthew R; Ahamed, Arshad; Sarwar, A T M G; Selcu, Camelia M; Myers, Roberto C

2018-04-24

Commercial III-Nitride LEDs and lasers spanning visible and ultraviolet wavelengths are based on epitaxial films. Alternatively, nanowire-based III-Nitride optoelectronics offer the advantage of strain compliance and high crystalline quality growth on a variety of inexpensive substrates. However, nanowire LEDs exhibit an inherent property distribution, resulting in uneven current spreading through macroscopic devices that consist of millions of individual nanowire diodes connected in parallel. Despite being electrically connected, only a small fraction of nanowires, sometimes current in the ensemble devices. Burn-in electronic conditioning is performed by applying a short-term overload voltage; the nanoshorts experience very high current density, sufficient to render them open circuits, thereby forcing a new current path through more nanowire LEDs in an ensemble device. Current-voltage measurements of individual nanowires are acquired using conductive atomic force microscopy to observe the removal of nanoshorts using burn-in. In macroscopic devices, this results in a 33× increase in peak EL and reduced leakage current. Burn-in conditioning of nanowire ensembles therefore provides a straightforward method to mitigate nonuniformities inherent to nanowire devices.

Cyclic electron flow provides acclimatory plasticity for the photosynthetic machinery under various environmental conditions and developmental stages

Directory of Open Access Journals (Sweden)

Marjaana eSuorsa

2015-09-01

Full Text Available Photosynthetic electron flow operates in two modes, linear and cyclic. In cyclic electron flow (CEF, electrons are recycled around photosystem I. As a result, a transthylakoid proton gradient (ΔpH is generated, leading to the production of ATP without concomitant production of NADPH, thus increasing the ATP/NADPH ratio within the chloroplast. At least two routes for CEF exist: a PGR5-PGRL1–and a chloroplast NDH-like complex mediated pathway. This review focuses on recent findings concerning the characteristics of both CEF routes in higher plants, with special emphasis paid on the crucial role of CEF in under challenging environmental conditions and developmental stages.

Leaf anatomy of six species of Heliotropiaceae Schrad. from the Brazilian semi-arid region

Directory of Open Access Journals (Sweden)

Elisabeth Tölke

2015-06-01

Full Text Available http://dx.doi.org/10.5007/2175-7925.2015v28n3p1 The family Heliotropiaceae has more than 450 species, mainly distributed in the tropics and subtropics. In Brazil, it is represented by the genera Euploca Nutt., Heliotropium L., Myriopus Small and Tournefortia L. The aim of this study was to describe the leaf anatomy of six species of Heliotropiaceae recorded in the semi-arid region of Brazil: E. polyphylla (Lehm. J.I.M. Melo & Semir, E. procumbens (Mill. Diane & Hilger, H. angiospermum Murray, H. curassavicum L., M. rubicundus (Salzm. ex DC. Luebert and M. salzmannii (DC. Diane & Hilger. Besides contributing to the knowledge of the anatomy of the representatives of the family in the Caatinga (Brazilian savannah, we also sought to determine and highlight the anatomical features adaptive to the region and to identify features with potential diagnostic value. Leaf structures were analyzed by light microscopy and scanning electron microscopy. Additional tests were also carried out to detect starch and total lipids. The morphological variation and the distribution of trichomes were the most relevant features for species diagnosis. The distribution of stomata in M. salzmannii and H. angiospermum differed from that described in other papers, which demonstrates the anatomical plasticity of these species. This is the first report describing the leaf blade of M. rubicundus.

Effects of plant cover on properties of rhizosphere and inter-plant soil in a semiarid valley, SW China

NARCIS (Netherlands)

Qu, Laiye; Huang, Yuanyuan; Ma, Keming; Zhang, Yuxin; Biere, A.

2016-01-01

Plant establishment is widely recognized as an effective way to prevent soil erosion in arid and semiarid ecosystems. Artemisia gmelinii, a pioneering species in many degraded ecosystems in China, is effective in improving soil properties and controlling runoff and soil loss, but mechanisms

Development of corrective measures and site stabilization technologies for shallow land burial facilities at semiarid sites

International Nuclear Information System (INIS)

Nyhan, J.W.; Abeele, W.V.

1986-01-01

The overall purpose of the corrective measures task performed for the National Low-Level Waste Management Program has been to develop and test methods that can be used to correct any actual or anticipated problems with new and existing shallow land burial (SLB) sites in a semiarid environment. These field tests have not only evaluated remedial actions, but have also investigated phenomena suspected of being a possible problem at semiarid SLB sites. The approach we have taken in developing remedial action and site closure technologies for low-level waste sites is to recognize that physical and biological processes affecting site integrity are interdependent, and therefore, cannot be treated as separate problems. The field experiments performed for this task were to identify, evaluate, and model erosion control technologies, field test second generation biointrusion barriers, determine by field experiments the extent of upward radionuclide migration due to moisture cycling, and measure the effects of subsidence on remedial action of other system components. Progress made in each of these research areas is described

Effects of repeated burning on woody vegetation structure and composition in a semi-arid southern African savanna

NARCIS (Netherlands)

Gandiwa, E.

2011-01-01

The objective of this study was to investigate the effects of repeated dry season annual hot fires on woody plants in a semiarid southern African savanna in Zimbabwe. Parts of the National University of Science and Technology (NUST) research fields in Bulawayo, Zimbabwe have been burnt annually in

Electron temperature gradient mode instability and stationary vortices with elliptic and circular boundary conditions in non-Maxwellian plasmas

Energy Technology Data Exchange (ETDEWEB)

Haque, Q. [Theoretical Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); Zakir, U. [Department of Physics, University of Peshawar, Khyber Pakhtun Khwa 25000 (Pakistan); Department of Physics, University of Malakand, Khyber Pakhtun Khwa 18800 (Pakistan); Qamar, A. [Department of Physics, University of Peshawar, Khyber Pakhtun Khwa 25000 (Pakistan)

2015-12-15

Linear and nonlinear dynamics of electron temperature gradient mode along with parallel electron dynamics is investigated by considering hydrodynamic electrons and non-Maxwellian ions. It is noticed that the growth rate of η{sub e}-mode driven linear instability decreases by increasing the value of spectral index and increases by reducing the ion/electron temperature ratio along the magnetic field lines. The eigen mode dispersion relation is also found in the ballooning mode limit. Stationary solutions in the form of dipolar vortices are obtained for both circular and elliptic boundary conditions. It is shown that the dynamics of both circular and elliptic vortices changes with the inclusion of inhomogeneity and non-Maxwellian effects.

Electron temperature gradient mode instability and stationary vortices with elliptic and circular boundary conditions in non-Maxwellian plasmas

Science.gov (United States)

Haque, Q.; Zakir, U.; Qamar, A.

2015-12-01

Linear and nonlinear dynamics of electron temperature gradient mode along with parallel electron dynamics is investigated by considering hydrodynamic electrons and non-Maxwellian ions. It is noticed that the growth rate of ηe-mode driven linear instability decreases by increasing the value of spectral index and increases by reducing the ion/electron temperature ratio along the magnetic field lines. The eigen mode dispersion relation is also found in the ballooning mode limit. Stationary solutions in the form of dipolar vortices are obtained for both circular and elliptic boundary conditions. It is shown that the dynamics of both circular and elliptic vortices changes with the inclusion of inhomogeneity and non-Maxwellian effects.

Impact of Climate Change on Rain-fed Farming and Response Solutions in Semiarid Area of Northwest China

Directory of Open Access Journals (Sweden)

WANG Hong-li

2015-12-01

Full Text Available The impact of climate change on the agriculture production in semi-arid areas of Northwest, the major drought-resistant technology, the mechanism of increasing grain production were analyzed to explore technical solutions to retort the future climate change, future development of rainfed agriculture, and provide reference for food security. The results showed that the impact of future climate change on crop growth had main three aspects: Firstly, higher temperatures resulted in lower crop yield and quality decline; Secondly, changes in precipitation and precipitation patterns resulted in drought/flooding problems; Thirdly, meteorological disasters caused by extreme weather lead to fluctuations of food production. To adapt or mitigate these adverse effects, increase use efficiency of limited rainfall, optimize soil structure, improve soil fertility, enhance withstanding environmental change ability of crop-soil system, mitigate the impact of future climate change on food production in semi-arid region of Northwest China, the mainly solutions were: (1 Covering gathered precipitation, improve the ability to accumulate soil moisture, change the distribution of soil moisture, regulate the migration and improve the infiltration of precipitation, thus “adjusting water” to adapt to precipitation changes; (2 Optimizing soil structure, physical and chemical properties by soil fertilization, thus “regulating soil” to improve the ability of crop-soil system against to environmental changes, in order to stabilize productivity of rainfed agriculture; (3 Integrate “adjusting water” and “regulating soil” technology, forming technical system of “coordination of water and soil” to comprehensively response to future climate change, mitigate the adverse impact of future climate change on food production in semi-arid region of Northwest, China.

Epidemiology of Eimeria infections in sheep raised extensively in a semiarid region of Brazil

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Luiz Eduardo Barreto de Souza

Full Text Available Abstract The aim of this study was to identify and determine the prevalence of Eimeria species affecting sheep raised extensively in a semiarid region of Brazil. Fecal samples of native sheep were collected during the rainy and dry seasons. The degree of infection was determined by counting oocysts per gram (OPG of feces, and the morphometric method was used for species identification. Oocysts were found in all the properties assessed, in which 68.3% of the animals were infected. The prevalence of oocysts was influenced by the season and animal category (P<0.05. It was higher during the rainy season than the dry season (80.2% vs. 55.8% and highest in young animals than the adults animals (68.2% vs. 39.6%. The OPG was lower during the dry season (1,269 ± 312 vs. 4,400 ± 1,122. Ten species were found; of these, E. ovinoidalis, E. granulosa, E. faurei, and E. crandallis were the most frequent. E. ovinoidalis and E. crandallis were found in all properties, with their prevalences being 19.4% and 13.6% respectively. The high prevalence of pathogenic species shows that eimeriosis is a risk for animals raised extensively in the semiarid region.

Seasonal and Interannual Variation in Energy Balance in the Semiarid Grassland Area of China

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Qun’ou Jiang

2015-01-01

Full Text Available Near surface energy budget changes have been proved to be induced by the land cover conversion through changing the surface physical properties, which can further impact the regional climate change. This study applies the DLS model to simulate the land cover under the business as usual (BAU scenario and then analyses the seasonal and interannual variation of energy balance in the semiarid grassland area of China based on the simulated land cover with the Weather Research and Forecasting (WRF model. The results indicate that the grassland will show a growing trend under the BAU scenario. Downward long wave radiation and downward short wave radiation will all have small-scale increase with time going by, while the surface net radiation will decrease from 2030 to 2050. However, there is obvious seasonal variation. Summer has the highest downward long wave radiation and downward short wave radiation, followed by spring and autumn. The lowest are in winter. As for the net surface radiation, there is obvious decrease in southeast of study area due to returning cropland to grassland. Those research conclusions can offer valuable information for the land use planning and relieving the effects of land cover change on climate change at the semiarid grassland area.

Groundwater Diffuse Recharge and its Response to Climate Changes in Semi-Arid Northwestern China

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Lin Deng

2015-01-01

Full Text Available Understanding the processes and rates of groundwater recharge in arid and semi-arid areas is crucial for utilizing and managing groundwater resources sustainably. We obtained three chloride profiles of the unsaturated-zone in the desert/loess transition zone of northwestern China and reconstructed the groundwater recharge variations over the last 11, 21, and 37 years, respectively, using the generalized chloride mass balance (GCMB method. The average recharge rates were 43.7, 43.5, and 45.1 mm yr-1, respectively, which are similar to those evaluated by the chloride mass balance (CMB or GCMB methods in other semi-arid regions. The results indicate that the annual recharge rates were not in complete linear proportion to the corresponding annual precipitations, although both exhibited descending tendencies on the whole. Comparisons between the daily precipitation aggregate at different intensity and recharge rates reveal that the occurrence of relatively heavy daily precipitation per year may contribute to such nonlinearity between annual precipitation and recharge. The possible influences of vegetation cover alterations following precipitation change cannot be excluded as well. The approximately negative correlation between the average annual recharge and temperature suggests that changes in temperature have had significant influences on recharge.

Meteorological conditions associated to high sublimation amounts in semiarid high-elevation Andes decrease the performance of empirical melt models

Science.gov (United States)

Ayala, Alvaro; Pellicciotti, Francesca; MacDonell, Shelley; McPhee, James; Burlando, Paolo

2015-04-01

Empirical melt (EM) models are often preferred to surface energy balance (SEB) models to calculate melt amounts of snow and ice in hydrological modelling of high-elevation catchments. The most common reasons to support this decision are that, in comparison to SEB models, EM models require lower levels of meteorological data, complexity and computational costs. However, EM models assume that melt can be characterized by means of a few index variables only, and their results strongly depend on the transferability in space and time of the calibrated empirical parameters. In addition, they are intrinsically limited in accounting for specific process components, the complexity of which cannot be easily reconciled with the empirical nature of the model. As an example of an EM model, in this study we use the Enhanced Temperature Index (ETI) model, which calculates melt amounts using air temperature and the shortwave radiation balance as index variables. We evaluate the performance of the ETI model on dry high-elevation sites where sublimation amounts - that are not explicitly accounted for the EM model - represent a relevant percentage of total ablation (1.1 to 8.7%). We analyse a data set of four Automatic Weather Stations (AWS), which were collected during the ablation season 2013-14, at elevations between 3466 and 4775 m asl, on the glaciers El Tapado, San Francisco, Bello and El Yeso, which are located in the semiarid Andes of central Chile. We complement our analysis using data from past studies in Juncal Norte Glacier (Chile) and Haut Glacier d'Arolla (Switzerland), during the ablation seasons 2008-09 and 2006, respectively. We use the results of a SEB model, applied to each study site, along the entire season, to calibrate the ETI model. The ETI model was not designed to calculate sublimation amounts, however, results show that their ability is low also to simulate melt amounts at sites where sublimation represents larger percentages of total ablation. In fact, we

Prosopis laevigata and Mimosa biuncifera (Leguminosae, jointly influence plant diversity and soil fertility of a Mexican semiarid ecosystem

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Rosalva García-Sánchez

2012-03-01

Full Text Available Prosopis laevigata and Mimosa biuncifera are frequently found in arid and semiarid shrublands, but scarce information is available about their influence on plant community structure and soil fertility. We compared plant community structure, diversity and soil nutrients of three semiarid shrubland sites located in Mezquital Valley, Mexico. These sites differ in their dominant species: Site 1 (Bingu P. laevigata, Site 2 (González M. biuncifera, and Site 3 (Rincón with the presence of both legumes. The results showed that the plant community with P. laevigata and M. biuncifera (Site 3 had more cover, taller plants and higher plant diversity than sites with only one legume (Site 1 and Site 2. Soil organic matter (SOM, soil organic carbon (SOC, total nitrogen (TN, phosphorus-Olsen (P and C mineralization were higher in the soil under the canopy of both legumes than in bare soil. In contrast, soil cation concentrations were lower under the canopy of P. laevigata, but not for M. biuncifera. In addition, the density of arbuscular mycorrhizal fungi spores was higher within the soil under the canopy of M. biuncifera than in the soil under the canopy of P. laevigata. Thus, resource islands (RI created by P. laevigata increased the amounts of SOC, TN and P when compared with the RI of M. biuncifera. This study provided evidences about the importance of species identity in order to expand the niche availability for the establishment of other plants, and highlights that P. laevigata and M. biuncifera jointly influencing plant colonization within semiarid ecosystems

PRODUCERS’ PERCEPTION OF GEOGRAPHICAL INDICATIONS AS A PRODUCT DIVERSIFICATION TOOL FOR AGRIFOOD PRODUCTS IN SEMI-ARID REGIONS OF KENYA

Directory of Open Access Journals (Sweden)

Fredah Wangui Maina

2018-04-01

Full Text Available The study assessed producers’ awareness and perceptions of territorial-based qualities and the economic potential of two potential origin-based geographical indications in two semi-arid counties in Kenya. Protection of the origin products as geographical indications is presented as an option for ecosystem approach in managing fragile semi-arid regions while providing producers economic incentives and social inclusion; key components of green growth. Factor analysis was conducted on Likert scale perception questions administered to producers of goats (Baringo and mangoes (Makueni. The producers were aware of the uniqueness of their products and its geographical source. The resultant factors reveal the importance of public policies, institutions, market access and public sector actors as important to producers’ perception of the success of protecting their products as geographical indications. Clustering revealed producer heterogeneity in their perceptions of protecting their respective products as geographical indications. The constitution of the clusters was significantly different based on the number of years the producers had practiced farming in the region, their awareness of the uniqueness of their goats, income received from goat production and institutional factors. Enhanced collective action for both goats and mangoes in the semi-arid regions would ensure collective reputation in the product presented to the market. The producers’ perceptions emphasise geographical indications as a marketing tool rather than an environmental tool, agreeing with Principle 4 of the ecosystem approach on managing ecosystem in an economic context.

Modeling gross primary production in semi-arid Inner Mongolia using MODIS imagery and eddy covariance data

Science.gov (United States)

Ranjeet John; Jiquan Chen; Asko Noormets; Xiangming Xiao; Jianye Xu; Nan Lu; Shiping Chen

2013-01-01

We evaluate the modelling of carbon fluxes from eddy covariance (EC) tower observations in different water-limited land-cover/land-use (LCLU) and biome types in semi-arid Inner Mongolia, China. The vegetation photosynthesis model (VPM) and modified VPM (MVPM), driven by the enhanced vegetation index (EVI) and land-surface water index (LSWI), which were derived from the...

Tailoring conservation agriculture technologies to West Africa semi-arid zones: Building on traditional local practices for soil restoration

NARCIS (Netherlands)

Lahmar, R.; Bationo, B.A.; Lamso, N.D.; Guéro, Y.; Tittonell, P.A.

2012-01-01

Low inherent fertility of tropical soils and degradation, nutrient deficiency and water stress are the key factors that hamper rainfed agriculture in semi-arid West Africa. Conservation Agriculture (CA) is currently promoted in the region as a technology to reduce soil degradation, mitigate the

Overlap in nitrogen sources and redistribution of nitrogen between trees and grasses in a semi-arid savanna

NARCIS (Netherlands)

Priyadarshini, K.V.R.; Prins, H.H.T.; Bie, de S.; Heitkonig, I.M.A.; Woodborne, S.; Gort, G.; Kirkman, K.; Fry, B.; Kroon, de H.

2014-01-01

A key question in savanna ecology is how trees and grasses coexist under N limitation. We used N stable isotopes and N content to study N source partitioning across seasons from trees and associated grasses in a semi-arid savanna. We also used 15N tracer additions to investigate possible

Probing the local, electronic and magnetic structure of matter under extreme conditions of temperature and pressure

DEFF Research Database (Denmark)

Torchio, R.; Boccato, S.; Cerantola, V.

2016-01-01

In this paper we present recent achievements in the field of investigation of the local, electronic and magnetic structure of the matter under extreme conditions of pressure and temperature. These results were obtained thanks to the coupling of a compact laser heating system to the energy-dispersive...

Evaluation of semiarid grassland degradation in North China from multiple perspectives

Science.gov (United States)

Han, D.; Wang, G.; Xue, B. L.; Xu, X.

2017-12-01

There has been increasing interest in grassland ecosystem degradation resulting from intensive human activity and climate change, especially in arid and semiarid regions. Species composition, grassland desertification, and aboveground biomass (AGB) are used as indicators of grassland degradation in this study. We comprehensively analyzed variations in these three indicators in semiarid grassland in North China, on multiple time scales, based on MODIS products and field sampling datasets. Since 1984, species composition has become simpler and species indicative of grassland degradation, such as Potentilla acaulis and Artemisia frigida, have become dominant. These changes indicate that serious grassland degradation has occurred since 1984. Grassland degradation was also analyzed on shorter time scales. Analyses of interannual variations during 2005-2015 showed that desertification decreased and average AGB in the growth season increased over the study area, indicating that grassland was recovering. Analyses of spatial variations showed that the position of slightly desertified grassland shifted and formed a band in the west, where the lowest AGB in the growth season was recorded but tendency ratio of AGB increased from 2005 to 2015. Climatic factors had critical effects on grassland degradation, as identified by the three indicators on different time scales. The simpler species composition resulted from the increase in average temperature and decrease in average precipitation over the past 30 years. For nearly a decade, an increase in precipitation and decreases in temperature and potential evapotranspiration reduced desertification and increased AGB in the growth season overall. Consequently, there has distinct difference in grassland degradation between analysis results on above two time scales, indicating multiple perspectives should be considered to accurately assess the state and characteristics of grassland degradation.

Probability of detecting perchlorate under natural conditions in deep groundwater in California and the Southwestern United States

Science.gov (United States)

Fram, Miranda S.; Belitz, Kenneth

2011-01-01

We use data from 1626 groundwater samples collected in California, primarily from public drinking water supply wells, to investigate the distribution of perchlorate in deep groundwater under natural conditions. The wells were sampled for the California Groundwater Ambient Monitoring and Assessment Priority Basin Project. We develop a logistic regression model for predicting probabilities of detecting perchlorate at concentrations greater than multiple threshold concentrations as a function of climate (represented by an aridity index) and potential anthropogenic contributions of perchlorate (quantified as an anthropogenic score, AS). AS is a composite categorical variable including terms for nitrate, pesticides, and volatile organic compounds. Incorporating water-quality parameters in AS permits identification of perturbation of natural occurrence patterns by flushing of natural perchlorate salts from unsaturated zones by irrigation recharge as well as addition of perchlorate from industrial and agricultural sources. The data and model results indicate low concentrations (0.1-0.5 μg/L) of perchlorate occur under natural conditions in groundwater across a wide range of climates, beyond the arid to semiarid climates in which they mostly have been previously reported. The probability of detecting perchlorate at concentrations greater than 0.1 μg/L under natural conditions ranges from 50-70% in semiarid to arid regions of California and the Southwestern United States to 5-15% in the wettest regions sampled (the Northern California coast). The probability of concentrations above 1 μg/L under natural conditions is low (generally <3%).

Screening of efficient arbuscular mycorrhizal fungi for Azadirachta indica under nursery condition: a step towards afforestation of semi-arid region of western India

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K. Banerjee

2013-01-01

Full Text Available To optimize nursery practices for efficient plant production procedures and to keep up to the ever growing demand of seedlings, identification of the most suitable species of arbuscular mycorrhizal fungi (AMF, specific for a given tree species, is clearly a necessary task. Sixty days old seedlings of Neem (Azadirachta indica A. Juss raised in root trainers were inoculated with six species of AMF and a mixed inoculum (consortia and kept in green house. Performances of the treatments on this tree species were evaluated in terms of growth parameters like plant height shoot collar diameter, biomass and phosphorous uptake capabilities. Significant and varied increase in the growth parameters and phosphorous uptake was observed for most of the AMF species against control. Consortia culture was found to be the best suited AMF treatment for A.indica, while Glomus intraradices and Glomus mosseae were the best performing single species cultures. It is the first time in the state of Gujarat that a wide variety of AMF species, isolated from the typical semi-arid region of western India, were tested for the best growth performance with one of the most important tree species for the concerned region.

Concerns about irrigation efficiency as an adaptation measure to cope with droughts and climate change in semi-arid basins

Science.gov (United States)

Vicuna, S.; Henriquez, L.; Melo, O.

2016-12-01

As expected in the late 1960s, the Paloma reservoir was built in the Limari basin in the semi-arid region in central Chile with the premise that climate conditions of the past, including the recurrence of dry and wet periods, were going to repeat in the future. That was in fact the case for almost 30 years after the reservoir was built. During this period water supplies from the reservoir were reliable and irrigation efficiency was improved with the result of irrigated land in the basin increasing four times especially with high value-permanent-water-consumption crops (fruits, orchards). Since 2003, during a mega-drought that has affected large proportions of central Chile, inflows to the Paloma reservoir have never again equaled or surpassed average historic flows. The refill of the reservoir, an event that happened every 3-4 years has not occurred in the last 13 years. And the capacity of the basin to accommodate to such a drastic reduction in water availability is no longer present because of the already large "efficient" and permanent use of water. The results in terms of agriculture losses and runoff at the outlet of the basin have been dramatic. Some 400 kms. south of the Limari basin, with higher precipitation levels but still in the semi-arid region in Chile is located the Maipo basin home to the 6 million people city of Santiago and around 250,000 has of irrigated land. Irrigation efficiency is also improving in this basin with savings being used mostly to supply drinking water supply shortages via transfer of water rights. Considering costly infrastructure alternatives, adaptation to climate change projections in this basin will likely extend the improvements in irrigation efficiency most likely affecting downstream environmental uses and reducing overall resilience of the basin to cope with droughts.

Tree Morphologic Plasticity Explains Deviation from Metabolic Scaling Theory in Semi-Arid Conifer Forests, Southwestern USA.

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Tyson L Swetnam

Full Text Available A significant concern about Metabolic Scaling Theory (MST in real forests relates to consistent differences between the values of power law scaling exponents of tree primary size measures used to estimate mass and those predicted by MST. Here we consider why observed scaling exponents for diameter and height relationships deviate from MST predictions across three semi-arid conifer forests in relation to: (1 tree condition and physical form, (2 the level of inter-tree competition (e.g. open vs closed stand structure, (3 increasing tree age, and (4 differences in site productivity. Scaling exponent values derived from non-linear least-squares regression for trees in excellent condition (n = 381 were above the MST prediction at the 95% confidence level, while the exponent for trees in good condition were no different than MST (n = 926. Trees that were in fair or poor condition, characterized as diseased, leaning, or sparsely crowned had exponent values below MST predictions (n = 2,058, as did recently dead standing trees (n = 375. Exponent value of the mean-tree model that disregarded tree condition (n = 3,740 was consistent with other studies that reject MST scaling. Ostensibly, as stand density and competition increase trees exhibited greater morphological plasticity whereby the majority had characteristically fair or poor growth forms. Fitting by least-squares regression biases the mean-tree model scaling exponent toward values that are below MST idealized predictions. For 368 trees from Arizona with known establishment dates, increasing age had no significant impact on expected scaling. We further suggest height to diameter ratios below MST relate to vertical truncation caused by limitation in plant water availability. Even with environmentally imposed height limitation, proportionality between height and diameter scaling exponents were consistent with the predictions of MST.

Tree Morphologic Plasticity Explains Deviation from Metabolic Scaling Theory in Semi-Arid Conifer Forests, Southwestern USA.

Science.gov (United States)

Swetnam, Tyson L; O'Connor, Christopher D; Lynch, Ann M

2016-01-01

A significant concern about Metabolic Scaling Theory (MST) in real forests relates to consistent differences between the values of power law scaling exponents of tree primary size measures used to estimate mass and those predicted by MST. Here we consider why observed scaling exponents for diameter and height relationships deviate from MST predictions across three semi-arid conifer forests in relation to: (1) tree condition and physical form, (2) the level of inter-tree competition (e.g. open vs closed stand structure), (3) increasing tree age, and (4) differences in site productivity. Scaling exponent values derived from non-linear least-squares regression for trees in excellent condition (n = 381) were above the MST prediction at the 95% confidence level, while the exponent for trees in good condition were no different than MST (n = 926). Trees that were in fair or poor condition, characterized as diseased, leaning, or sparsely crowned had exponent values below MST predictions (n = 2,058), as did recently dead standing trees (n = 375). Exponent value of the mean-tree model that disregarded tree condition (n = 3,740) was consistent with other studies that reject MST scaling. Ostensibly, as stand density and competition increase trees exhibited greater morphological plasticity whereby the majority had characteristically fair or poor growth forms. Fitting by least-squares regression biases the mean-tree model scaling exponent toward values that are below MST idealized predictions. For 368 trees from Arizona with known establishment dates, increasing age had no significant impact on expected scaling. We further suggest height to diameter ratios below MST relate to vertical truncation caused by limitation in plant water availability. Even with environmentally imposed height limitation, proportionality between height and diameter scaling exponents were consistent with the predictions of MST.

Strategic Framework for Sustainable Management of Drainage Systems in Semi-Arid Cities: An Iraqi Case Study

Directory of Open Access Journals (Sweden)

Mohammed Nanekely

2016-09-01

Full Text Available For the purpose of this paper, Erbil city, located in the northern part of Iraq, has been chosen as a representative case study for a large number of cities, particularly in semi-arid areas, lacking sustainable drainage systems (SuDS. The study assesses (a the role of SuDS as a measure in areas with a water shortage; (b water scarcity in decision-making processes; (c the lack of legislation to implement SuDS; (d the adverse effects of climate change on the urban drainage system; and (e the effects of an increased population on SuDS implementation. An integrated methodology that incorporates a self-administrated questionnaire, workshops, face-to-face communication and interviews, as well as electronic media interactions, were used to achieve the objectives. A generic platform that consists of thirteen pillars, supporting the short to long-term national policies and strategies towards a sustainable urban drainage system, has been developed. Results showed that environmental laws need to be introduced. Findings also indicate that a growing population, which is partly due to an increase of internally displaced people, is a major challenge to an early application of SuDS, due to a rise in land demand and a lack of financial resources.

Ignition conditions relaxation for central hot-spot ignition with an ion-electron non-equilibrium model

Science.gov (United States)

Fan, Zhengfeng; Liu, Jie

2016-10-01

We present an ion-electron non-equilibrium model, in which the hot-spot ion temperature is higher than its electron temperature so that the hot-spot nuclear reactions are enhanced while energy leaks are considerably reduced. Theoretical analysis shows that the ignition region would be significantly enlarged in the hot-spot rhoR-T space as compared with the commonly used equilibrium model. Simulations show that shocks could be utilized to create and maintain non-equilibrium conditions within the hot spot, and the hot-spot rhoR requirement is remarkably reduced for achieving self-heating. In NIF high-foot implosions, it is observed that the x-ray enhancement factors are less than unity, which is not self-consistent and is caused by assuming Te =Ti. And from this non-consistency, we could infer that ion-electron non-equilibrium exists in the high-foot implosions and the ion temperature could be 9% larger than the equilibrium temperature.

Evaluation of high-energy electron detectors for probing the inner magnetosphere under high-counting condition

International Nuclear Information System (INIS)

Tamada, Yukihiro; Takashima, Takeshi; Mitani, Takefumi; Miyake, Wataru

2013-01-01

An ERG (Energization and Radiation in Geospace) satellite will be launched to study the acceleration processes of energetic particles in the radiation belt surrounding the earth. It is very important to reveal the acceleration process of high-energy particles for both science and the application to space weather forecast. Drastic increases of high-energy electrons in the radiation belt is sometimes observed during a geomagnetic storm. When a large magnetic storm occurs, energetic electron count rates may exceed flux limits expected in the nominal design and large number of incident electrons leading to detection loss. The purpose of this study is to demonstrate that the count rate range of a single detection on board ERG satellite can be expanded by means of reading circuit operations to decrease an area of detection. In our ground experiment, we also found an unexpected result that count peaks shift to the higher energy side under high counting conditions. (author)

Electron/electron acoustic instability

International Nuclear Information System (INIS)

Gary, S.P.

1987-01-01

The electron acoustic wave becomes a normal mode of an unmagnetized collisionless plasma in the presence of two electron components with similar densities, but strongly disparate temperatures. The characteristic frequency of this mode is the plasma frequency of the cooler electron component. If these two electron components have a relative drift speed several times the thermal speed of the cooler component, the electron/electron acoustic instability may arise. This paper describes the parametric dependences of the threshold drift speed and maximum growth rate of this instability, and compares these with the same properties of the electron/ion acoustic instability. Under the condition of zero current, the electron/ion acoustic instability typically has the lower threshold drift speed, so that observation of the electron/electron acoustic instability is a strong indication of the presence of an electrical current in the plasma

Rainfed agriculture in a semi-arid tropical climate : aspects of land- and watermanagement for red soils in India

NARCIS (Netherlands)

Huibers, F.P.

1985-01-01

Rainfed agriculture is defined as the production of field crops that completely depend on the local precipitation for their water supply. Although in the semi-arid tropics the mean annual precipitation might seem to be sufficient to grow (adapted) crops, its variability over the years and

Runoff and sorghum performance as affected by the spacing of stone lines in the semi-arid Sahelian zone

NARCIS (Netherlands)

Zougmore, R.; Guillobez, S.; Kambou, N.F.; Son, G.

2000-01-01

Crop yields are primarily water-limited in dryland production systems in semiarid regions. This study was conducted in a catchment located in the 'plateau central' of Burkina Faso to assess the impact of the space between stone lines on runoff and crop performance. The experimental design consisted

Water management can reinforce plant competition in salt-affected semi-arid wetlands

Science.gov (United States)

Coletti, Janaine Z.; Vogwill, Ryan; Hipsey, Matthew R.

2017-09-01

The diversity of vegetation in semi-arid, ephemeral wetlands is determined by niche availability and species competition, both of which are influenced by changes in water availability and salinity. Here, we hypothesise that ignoring physiological differences and competition between species when managing wetland hydrologic regimes can lead to a decrease in vegetation diversity, even when the overall wetland carrying capacity is improved. Using an ecohydrological model capable of resolving water-vegetation-salt feedbacks, we investigate why water surface and groundwater management interventions to combat vegetation decline have been more beneficial to Casuarina obesa than to Melaleuca strobophylla, the co-dominant tree species in Lake Toolibin, a salt-affected wetland in Western Australia. The simulations reveal that in trying to reduce the negative effect of salinity, the management interventions have created an environment favouring C. obesa by intensifying the climate-induced trend that the wetland has been experiencing of lower water availability and higher root-zone salinity. By testing alternative scenarios, we show that interventions that improve M. strobophylla biomass are possible by promoting hydrologic conditions that are less specific to the niche requirements of C. obesa. Modelling uncertainties were explored via a Markov Chain Monte Carlo (MCMC) algorithm. Overall, the study demonstrates the importance of including species differentiation and competition in ecohydrological models that form the basis for wetland management.

Edaphic factors controlling summer (rainy season) greenhouse gas emissions (CO{sub 2} and CH{sub 4}) from semiarid mangrove soils (NE-Brazil)

Energy Technology Data Exchange (ETDEWEB)

Nóbrega, Gabriel N. [Departamento de Ciência do Solo, Escola Superior de Agricultura Luiz de Queiroz, ESALQ/USP, Av.Pádua Dias 11, Piracicaba, São Paulo 13.418-260 (Brazil); Ferreira, Tiago O., E-mail: toferreira@usp.br [Departamento de Ciência do Solo, Escola Superior de Agricultura Luiz de Queiroz, ESALQ/USP, Av.Pádua Dias 11, Piracicaba, São Paulo 13.418-260 (Brazil); Siqueira Neto, M. [Laboratório de Biogeoquímica Ambiental, Centro de Energia Nuclear na Agricultura, CENA/USP, Av. Centenário 303, Piracicaba, São Paulo 13.400-970 (Brazil); Queiroz, Hermano M.; Artur, Adriana G. [Departamento de Ciências do Solo, Universidade Federal do Ceará, UFC, Av. Mister Hull 2977, Campus do Pici, Fortaleza, Ceará 60.440-554 (Brazil); Mendonça, Eduardo De S. [Departamento de Produção Vegetal, Universidade Federal do Espírito Santo, UFES, Alto Universitário s/n, Alegre, Espírito Santo 29.500-000 (Brazil); Silva, Ebenezer De O. [Empresa Brasileira de Pesquisa Agropecuária, Centro Nacional de Pesquisa de Agroindústria Tropical, Pós Colheita, Dra. Sara Mesquita Street, 2270, Planalto Pici, Fortaleza, Ceará 60.511-110 (Brazil); and others

2016-01-15

The soil attributes controlling the CO{sub 2}, and CH{sub 4} emissions were assessed in semiarid mangrove soils (NE-Brazil) under different anthropogenic activities. Soil samples were collected from different mangroves under different anthropogenic impacts, e.g., shrimp farming (Jaguaribe River); urban wastes (Cocó River) and a control site (Timonha River). The sites were characterized according to the sand content; physicochemical parameters (Eh and pH); total organic C; soil C stock (SCS) and equivalent SCS (SCS{sub EQV}); total P and N; dissolved organic C (DOC); and the degree of pyritization (DOP). The CO{sub 2} and CH{sub 4} fluxes from the soils were assessed using static closed chambers. Higher DOC and SCS and the lowest DOP promote greater CO{sub 2} emission. The CH{sub 4} flux was only observed at Jaguaribe which presented higher DOP, compared to that found in mangroves from humid tropical climates. Semiarid mangrove soils cannot be characterized as important greenhouse gas sources, compared to humid tropical mangroves. - Highlights: • GHG emission was associated with different soil characteristics. • Highest CO{sub 2} emissions were found in mangroves with larger dissolved C and lower DOP. • Less CH{sub 4} flux was due to low DOP in semiarid mangrove soils.

Food Insecurity and Not Dietary Diversity Is a Predictor of Nutrition Status in Children within Semiarid Agro-Ecological Zones in Eastern Kenya

Directory of Open Access Journals (Sweden)

Zipporah N. Bukania

2014-01-01

Full Text Available Machakos and Makueni counties in Kenya are associated with historical land degradation, climate change, and food insecurity. Both counties lie in lower midland (LM lower humidity to semiarid (LM4, and semiarid (LM5 agroecological zones (AEZ. We assessed food security, dietary diversity, and nutritional status of children and women. Materials and Methods. A total of 277 woman-child pairs aged 15–46 years and 6–36 months respectively, were recruited from farmer households. Food security and dietary diversity were assessed using standard tools. Weight and height, or length in children, were used for computation of nutritional status. Findings. No significant difference (P>0.05 was observed in food security and dietary diversity score (DDS between LM4 and LM5. Stunting, wasting, and underweight levels among children in LM4 and LM5 were comparable as were BMI scores among women. However, significant associations (P=0.023 were found between severe food insecurity and nutritional status of children but not of their caregivers. Stunting was significantly higher in older children (>2 years and among children whose caregivers were older. Conclusion. Differences in AEZ may not affect dietary diversity and nutritional status of farmer households. Consequently use of DDS may lead to underestimation of food insecurity in semiarid settings.

[Effect of Biochar on Soil Greenhouse Gas Emissions in Semi-arid Region].

Science.gov (United States)

Guo, Yan-liang; Wang, Dan-dan; Zheng, Ji-yong; Zhao, Shi-wei; Zhang, Xing-chang

2015-09-01

This study aimed to investigate the effects of biochar addition on the emission of greenhouse gases from farmland soil in semi-arid region. Through an in-situ experiments, the influence of sawdust biochar(J) and locust tree skin biochar (H) at three doses (1%, 3%, and 5% of quality percentage) on C2, CH4 and N2O emissions were studied within the six months in the south of Ningxiaprovince. The results indicated that soil CO2 emission flux was slightly increased with the addition doses for both biochars, and the averaged CO2 emission flux for sawdust and locust tree skin biochar was enhanced by 1. 89% and 3. 34% compared to the control, but the difference between treatments was not statistically significant. The soil CH4 emission was decreased with the increasing of biochar doses, by 1. 17%, 2. 55%, 4. 32% for J1, J3, J5 and 2. 35%, 5. 83%, 7. 32% for H1, H3, H5, respectively. However, the difference was statistically significant only for J5, H3 and H5 treatments (P effect on soil N2O emission. Our study indicated that the biochar has no significant influence on soil CO2 and N2O emissions within six months in semi-arid region and can significantly influence soil CH4 emissions (P < 0. 05). As for biochar type, the locust tree skin biochar is significantly better than the sawdust biochar in terms of restraining CH4 emission(P = 0. 048).

Metal(loid) allocation and nutrient retranslocation in Pinus halepensis trees growing on semiarid mine tailings

Energy Technology Data Exchange (ETDEWEB)

Parraga-Aguado, Isabel, E-mail: isabel.parraga@upct.es [Universidad Politecnica de Cartagena, Departamento de Ciencia y Tecnología Agraria Paseo Alfonso XIII, Cartagena 48. 30203 (Spain); Querejeta, Jose-Ignacio [Water and Soil Conservation Department, Centro de Edafología y Biología Aplicada del Segura CEBAS-CSIC Campus Universitario de Espinardo, PO Box 164, Espinardo-Murcia ES-30100 (Spain); González-Alcaraz, María Nazaret; Conesa, Hector M. [Universidad Politecnica de Cartagena, Departamento de Ciencia y Tecnología Agraria Paseo Alfonso XIII, Cartagena 48. 30203 (Spain)

2014-07-01

The goal of this study was to evaluate internal metal(loid) cycling and the risk of metal(loid) accumulation in litter from Pinus halepensis trees growing at a mine tailing disposal site in semiarid Southeast Spain. Internal nutrient retranslocation was also evaluated in order to gain insight into the ability of pine trees to cope with the low-fertility soil conditions at the tailings. We measured metal(loid) concentrations in the foliage (young and old needles), woody stems and fresh leaf litter of pine trees growing on tailings. The nutrient status and stable isotope composition of pine foliage (δ{sup 13}C, δ{sup 15}N, δ{sup 18}O as indicators of photosynthesis and water use efficiency) were also analyzed. Tailing soil properties in vegetation patches and in adjacent bare soil patches were characterized as well. Significant amounts of metal(loid)s such us Cd, Cu, Pb and Sb were immobilized in the woody stems of Pinus halepensis trees growing on tailings. Leaf litterfall showed high concentrations of As, Cd, Sb, Pb and Zn, which thereby return to the soil. However, water extractable metal(loid) concentrations in tailing soils were similar between vegetation patches (mineral soil under the litter layer) and bare soil patches. The pines growing on mine tailings showed very low foliar P concentrations in all leaf age classes, which suggests severe P deficiency. Young (current year) needles showed lower accumulation of metal(loid)s, higher nutrient concentrations (P and K), and higher water use efficiency (as indicated by and δ{sup 13}C and δ{sup 18}O data) than older needles. Substantial nutrient resorption occurred before leaf litterfall, with 46% retranslocation efficiency for P and 89% for K. In conclusion, phytostabilization of semiarid mine tailings with Pinus halepensis is feasible but would require careful monitoring of the trace elements released from litterfall, in order to assess the long term risk of metal(loid) transfer to the food chain

Metal(loid) allocation and nutrient retranslocation in Pinus halepensis trees growing on semiarid mine tailings

International Nuclear Information System (INIS)

Parraga-Aguado, Isabel; Querejeta, Jose-Ignacio; González-Alcaraz, María Nazaret; Conesa, Hector M.

2014-01-01

The goal of this study was to evaluate internal metal(loid) cycling and the risk of metal(loid) accumulation in litter from Pinus halepensis trees growing at a mine tailing disposal site in semiarid Southeast Spain. Internal nutrient retranslocation was also evaluated in order to gain insight into the ability of pine trees to cope with the low-fertility soil conditions at the tailings. We measured metal(loid) concentrations in the foliage (young and old needles), woody stems and fresh leaf litter of pine trees growing on tailings. The nutrient status and stable isotope composition of pine foliage (δ 13 C, δ 15 N, δ 18 O as indicators of photosynthesis and water use efficiency) were also analyzed. Tailing soil properties in vegetation patches and in adjacent bare soil patches were characterized as well. Significant amounts of metal(loid)s such us Cd, Cu, Pb and Sb were immobilized in the woody stems of Pinus halepensis trees growing on tailings. Leaf litterfall showed high concentrations of As, Cd, Sb, Pb and Zn, which thereby return to the soil. However, water extractable metal(loid) concentrations in tailing soils were similar between vegetation patches (mineral soil under the litter layer) and bare soil patches. The pines growing on mine tailings showed very low foliar P concentrations in all leaf age classes, which suggests severe P deficiency. Young (current year) needles showed lower accumulation of metal(loid)s, higher nutrient concentrations (P and K), and higher water use efficiency (as indicated by and δ 13 C and δ 18 O data) than older needles. Substantial nutrient resorption occurred before leaf litterfall, with 46% retranslocation efficiency for P and 89% for K. In conclusion, phytostabilization of semiarid mine tailings with Pinus halepensis is feasible but would require careful monitoring of the trace elements released from litterfall, in order to assess the long term risk of metal(loid) transfer to the food chain. - Highlights: • Significant

Energy balance in rainfed herbaceous crops in a semiarid environment for a 15-year experiment. 1. Impact of farming systems

Science.gov (United States)

Moreno, M. M.; Moreno, C.; Lacasta, C.; Tarquis, A. M.; Meco, R.

2012-04-01

During the last years, agricultural practices have led to increase yields by means of the massive consumption on non-renewable fossil energy. However, the viability of a production system does not depend solely on crop yield, but also on its efficiency in the use of available resources. This work is part of a larger study assessing the effects of three farming systems (conventional, conservation with zero tillage, and organic) and four barley-based crop rotations (barley monoculture and in rotation with vetch, sunflower and fallow) on the energy balance of crop production under the semi-arid conditions over a 15 year period. However, the present work is focused on the farming system effect, so crop rotations and years are averaged. Experiments were conducted at "La Higueruela" Experimental Farm (4°26' W, 40°04' N, altitude 450 m) (Spanish National Research Council, Santa Olalla, Toledo, central Spain). The climate is semi-arid Mediterranean, with an average seasonal rainfall of 480 mm irregularly distributed and a 4-month summer drought period. Conventional farming included the use of moldboard plow for tillage, chemical fertilizers and herbicides. Conservation farming was developed with zero tillage, direct sowing and chemical fertilizers and herbicides. Organic farming included the use of cultivator and no chemical fertilizers or herbicides. The energy balance method used required the identification and quantification of all the inputs and outputs implied, and the conversion to energy values by corresponding coefficients. The parameters considered were (i) energy inputs (EI) (diesel, machines, fertilizers, herbicides, seeds) (ii) energy outputs (EO) (energy in the harvested biomass), (iii) net energy produced (NE) (EI - EO), (iv) the energy output/input ratio (O/I), and (v) energy productivity (EP) (Crop yield/EI). EI was 3.0 and 3.5 times higher in conservation (10.4 GJ ha-1 year-1) and conventional (11.7 GJ ha-1 year-1) than in organic farming (3.41 GJ ha-1

Agroforestry parkland species diversity : uses and management in semi-arid West-Africa (Burkina Faso)

OpenAIRE

Nikiema, A.

2005-01-01

Agroforestry parkland in semi-arid West Africa is a rural land use system, which allows farmers to grow annual crops in combination with useful trees. In addition to cereals, tree products such as vegetables, fruits, vegetable oil, firewood, fodder, and medicines are obtained from the parklands. However the multiple function of the parkland system can only be fulfilled if parkland species diversity is adequately managed.This thesis is focused on assessing the woody species diversity in the pa...

Organic amendments and mulches influence the quality of restored mine soils and plant cover in semiarid regions.

Science.gov (United States)

Luna Ramos, Lourdes; Miralles, Isabel; Contreras, Sergio; Lázaro-Suau, Roberto; Solé-Benet, Albert

2017-04-01

An experimental restoration was designed in a calcareous quarry in Sierra de Gádor, SE Spain, with the aim of determining useful semiarid restoration techniques. The factors tested were: a) organic amendments (sewage sludge, compost and no amendment), b) mulches (gravel, woodchip and no mulch), and c) three native species (Macrochloa tenacissima, Anthyllis terniflora and Anthyllis cytisoides). Nine combinations of organic amendments and mulches were established in plots of 15 x 5 m and 75 plants were planted in each plot. Plant survival and growth were measured at months 6, 24, 36 and 48 after planting. Moreover, the possible relationships between soil quality indicators (physico-chemical and microbiological properties, aggregate stability and infiltration rate) and changes in the planted vegetation caused by restoration treatments were explored. This study demonstrated that opencast mine revegetation with native species (M. tenacissima, A. terniflora and A. cytisoides) was successful in the boundary between arid and semiarid climate in only four years, compared to previous soil restoration treatment. The response of plant species was different, showing their own physiological mechanisms. M. tenacissima presented the highest survival rates although the two Anthyllis species had the highest growth rates. Despite organic amendments had not a positive effect on plant survival, these treatments increased plant growth. In particular, the improvement on chemical, microbiological and physical soil properties induced by sewage sludge and especially compost treatment, enhanced plant growth. However, changes induced by mulches on the physico-chemical soil properties did not provided clear evidences, either positive or negative, in plant establishment. Thus, the addition of organic matter from organic residues and revegetation with native species can improve the restoration success in SE Spain and perhaps similar regions worldwide under arid-semiarid climate.

Comparing soil carbon loss through respiration and leaching under extreme precipitation events in arid and semiarid grasslands

Science.gov (United States)

Liu, Ting; Wang, Liang; Feng, Xiaojuan; Zhang, Jinbo; Ma, Tian; Wang, Xin; Liu, Zongguang

2018-03-01

Respiration and leaching are two main processes responsible for soil carbon loss. While the former has received considerable research attention, studies examining leaching processes are limited, especially in semiarid grasslands due to low precipitation. Climate change may increase the extreme precipitation event (EPE) frequency in arid and semiarid regions, potentially enhancing soil carbon loss through leaching and respiration. Here we incubated soil columns of three typical grassland soils from Inner Mongolia and the Qinghai-Tibetan Plateau and examined the effect of simulated EPEs on soil carbon loss through respiration and leaching. EPEs induced a transient increase in CO2 release through soil respiration, equivalent to 32 and 72 % of the net ecosystem productivity (NEP) in the temperate grasslands (Xilinhot and Keqi) and 7 % of NEP in the alpine grasslands (Gangcha). By comparison, leaching loss of soil carbon accounted for 290, 120, and 15 % of NEP at the corresponding sites, respectively, with dissolved inorganic carbon (DIC, biogenic DIC + lithogenic DIC) as the main form of carbon loss in the alkaline soils. Moreover, DIC loss increased with recurring EPEs in the soil with the highest pH due to an elevated contribution of dissolved CO2 from organic carbon degradation (indicated by DIC-δ13C). These results highlight the fact that leaching loss of soil carbon (particularly in the form of DIC) is important in the regional carbon budget of arid and semiarid grasslands and also imply that SOC mineralization in alkaline soils might be underestimated if only measured as CO2 emission from soils into the atmosphere. With a projected increase in EPEs under climate change, soil carbon leaching processes and the influencing factors warrant a better understanding and should be incorporated into soil carbon models when estimating carbon balance in grassland ecosystems.

Comparing soil carbon loss through respiration and leaching under extreme precipitation events in arid and semiarid grasslands

Directory of Open Access Journals (Sweden)

T. Liu

2018-03-01

Full Text Available Respiration and leaching are two main processes responsible for soil carbon loss. While the former has received considerable research attention, studies examining leaching processes are limited, especially in semiarid grasslands due to low precipitation. Climate change may increase the extreme precipitation event (EPE frequency in arid and semiarid regions, potentially enhancing soil carbon loss through leaching and respiration. Here we incubated soil columns of three typical grassland soils from Inner Mongolia and the Qinghai–Tibetan Plateau and examined the effect of simulated EPEs on soil carbon loss through respiration and leaching. EPEs induced a transient increase in CO2 release through soil respiration, equivalent to 32 and 72 % of the net ecosystem productivity (NEP in the temperate grasslands (Xilinhot and Keqi and 7 % of NEP in the alpine grasslands (Gangcha. By comparison, leaching loss of soil carbon accounted for 290, 120, and 15 % of NEP at the corresponding sites, respectively, with dissolved inorganic carbon (DIC, biogenic DIC + lithogenic DIC as the main form of carbon loss in the alkaline soils. Moreover, DIC loss increased with recurring EPEs in the soil with the highest pH due to an elevated contribution of dissolved CO2 from organic carbon degradation (indicated by DIC-δ13C. These results highlight the fact that leaching loss of soil carbon (particularly in the form of DIC is important in the regional carbon budget of arid and semiarid grasslands and also imply that SOC mineralization in alkaline soils might be underestimated if only measured as CO2 emission from soils into the atmosphere. With a projected increase in EPEs under climate change, soil carbon leaching processes and the influencing factors warrant a better understanding and should be incorporated into soil carbon models when estimating carbon balance in grassland ecosystems.

Conserving the Brazilian semiarid (Caatinga) biome under climate change

DEFF Research Database (Denmark)

Oliveira, Guilherme de; Bastos Araujo, Miguel; Rangel, Thiago Fernado

2012-01-01

to assess changes in climate suitability across individual species ranges, ensemble forecasting was used based on seven bioclimatic envelope models, three atmosphere–ocean general circulation models, and two greenhouse emission gas scenarios for 2020, 2050, and 2080. We found that most species will gain...... additional threats to the biome’s biodiversity. Here, we ask if the remnants of natural vegetation in Caatinga biome, where endemic terrestrial vertebrate species occur, are likely to retain more climatic suitability under climate change scenarios than other less pristine areas of the biome. In order......The Caatinga is a semiarid biome of the northeast of Brazil with only 1 % of its territory currently conserved. The biome’s biodiversity is highly threatened due to exposure to land conversion for agricultural and cattle ranch. Climate forecasts predict increases in aridity, which could pose...

Soil nutrient and sediment loss as affected by erosion barriers and nutrient source in semi-arid Burkina Faso

NARCIS (Netherlands)

Zougmore, R.; Mando, A.; Stroosnijder, L.

2009-01-01

In semi-arid Sahel, soil erosion by water is one major factor accounting for negative nutrient balances in agricultural systems. A field experiment was conducted on a Ferric Lixisol in Burkina Faso to assess the effects of soil and water conservation barriers (stone rows or grass strips of

Simply obtained global radiation, soil temperature and soil moisture in an alley cropping system in semi-arid Kenya

NARCIS (Netherlands)

Mungai, D.N.; Stigter, C.J.; Coulson, C.L.; Ng'ang'a, J.K.

2000-01-01

Global radiation, soil temperature and soil moisture data were obtained from a 4-6 year old Cassia siamea/maize (CM) alley cropping (or hedgerow intercropping) system, at a semi-arid site at Machakos, Kenya, in the late eighties. With the growing need to explore and manage variations in

Study Bioprospecting of Medicinal Plant Extracts of the Semiarid Northeast: Contribution to the Control of Oral Microorganisms

Directory of Open Access Journals (Sweden)

Maria Suênia P. Silva

2012-01-01

Full Text Available Dental pathologies can be caused by plaque-forming bacteria and yeast, which reside in the oral cavity. The bacteria growing in dental plaque, a naturally occurring biofilm, display increased resistance to antimicrobial agents. The objective was the evaluation of a preclinical assay of medicinal plants of the semiarid region from the northeast against oral pathogenic microorganism, aiming at bioprospecting a new product. The selection of plant material for this study was based on the ethnobotanical data on the traditional use of plants from the semiarid region. The thirty extracts were subjected to the determination of antibiofilm activity against gram-positive, gram-negative bacteria and yeast. The hydroalcoholic extract which showed positive antibiofilm activity against most of the microorganisms tested in agar diffusion assay was further tested for the determination of minimum inhibitory concentration (MIC and Bioassay with Artemia salina. Plant samples tested in this study exhibited good antibiofilm activity for the treatment of oral problems. The Schinopsis brasiliensis showed greater activity for Pseudomonas aeruginosa and Staphylococcus aureus, but toxicity against Artemia salina.

Multi-gauge Calibration for modeling the Semi-Arid Santa Cruz Watershed in Arizona-Mexico Border Area Using SWAT

Science.gov (United States)

Niraula, Rewati; Norman, Laura A.; Meixner, Thomas; Callegary, James B.

2012-01-01

In most watershed-modeling studies, flow is calibrated at one monitoring site, usually at the watershed outlet. Like many arid and semi-arid watersheds, the main reach of the Santa Cruz watershed, located on the Arizona-Mexico border, is discontinuous for most of the year except during large flood events, and therefore the flow characteristics at the outlet do not represent the entire watershed. Calibration is required at multiple locations along the Santa Cruz River to improve model reliability. The objective of this study was to best portray surface water flow in this semiarid watershed and evaluate the effect of multi-gage calibration on flow predictions. In this study, the Soil and Water Assessment Tool (SWAT) was calibrated at seven monitoring stations, which improved model performance and increased the reliability of flow, in the Santa Cruz watershed. The most sensitive parameters to affect flow were found to be curve number (CN2), soil evaporation and compensation coefficient (ESCO), threshold water depth in shallow aquifer for return flow to occur (GWQMN), base flow alpha factor (Alpha_Bf), and effective hydraulic conductivity of the soil layer (Ch_K2). In comparison, when the model was established with a single calibration at the watershed outlet, flow predictions at other monitoring gages were inaccurate. This study emphasizes the importance of multi-gage calibration to develop a reliable watershed model in arid and semiarid environments. The developed model, with further calibration of water quality parameters will be an integral part of the Santa Cruz Watershed Ecosystem Portfolio Model (SCWEPM), an online decision support tool, to assess the impacts of climate change and urban growth in the Santa Cruz watershed.

Envisioning Adaptive Strategies to Change: Participatory Scenarios for Agropastoral Semiarid Systems in Nicaragua

Directory of Open Access Journals (Sweden)

Federica Ravera

2011-03-01

Full Text Available Historically, the semiarid social-ecological systems of the dry Central American corridor have proven resilient to pressures. However, in the last century, these systems have experienced huge environmental and socioeconomic changes that have increased the vulnerability of local livelihoods to shocks. New approaches are needed to capture complex, uncertain, cross-scale and nonlinear relationships among drivers of change and vulnerability. Therefore, to tackle this challenge, we have applied a participatory and interdisciplinary methodological framework of vulnerability assessment to a case study in northern Nicaragua. We triangulated a range of information and data from participatory and scientific research to explore historical and current drivers of changes that affect the system's components and indicators of vulnerability, represented in a 3-dimensional space in terms of ecological resilience, the socioeconomic ability of individuals to adapt to change, and an institutional capacity to buffer and respond to crisis. A projection of climatic changes combined with a participatory scenario analysis helped, then, to heuristically analyze tendencies of vulnerability in the future and to explore what policy options might enhance the system's adaptive capacity to face new pressures. Our work primarily contributes to an empirical understanding of key factors that influence vulnerability and learning about local strategies to adapt to change in semiarid agropastoral systems in Central America. We also make a methodological contribution by testing the use of a multidimensional vulnerability framework as a way of stimulating discussion among researchers, local stakeholders, and policy makers.

Corrosion in Electronics

DEFF Research Database (Denmark)

Ambat, Rajan; Gudla, Helene Virginie Conseil; Verdingovas, Vadimas

2017-01-01

Electronic control units, power modules, and consumer electronics are used today in a wide variety of varying climatic conditions. Varying external climatic conditions of temperature and humidity can cause an uncontrolled local climate inside the device enclosure. Uncontrolled humidity together...... and high density packing combined with the use of several materials, which can undergo electrochemical corrosion in the presence of water film formed due to humidity exposure and bias conditions on the PCBA surface. This article provides a short review of the corrosion reliability issues of electronics due...... to the use of electronics under varying humidity conditions. Important PCBA aspects, which are fundamental to the corrosion cell formation under humid conditions, are discussed. Effect of hygroscopic residues from the process and service and their role in assisting water film build up and corrosion...

Hybrid concentrated solar power (CSP)–biomass plants in a semiarid region: A strategy for CSP deployment in Brazil

International Nuclear Information System (INIS)

Soria, Rafael; Portugal-Pereira, Joana; Szklo, Alexandre; Milani, Rodrigo; Schaeffer, Roberto

2015-01-01

The production of electricity using concentrated solar power (CSP) technology is not yet possible in Brazil due to the technology’s high capital costs and the lack of a local industry. However, this study introduces a low-cost approach to CSP in Brazil by describing and simulating the operation of hybrid CSP plants that use sustainably managed biomass in Brazil’s semiarid northeast. Biomass hybridisation of a CSP plant with a solar multiple (SM) of 1.2 and a biomass fill fraction (BFF) of 30% can generate electricity at 110 USD/MWh. The high direct normal irradiation (DNI) and the availability of local low-cost biomass in Brazil’s semiarid northeast suggest the possibility of developing a CSP industry capable of supplying low-cost components under a national program framework, with the co-benefits of local job and income generation. For example, the deployment of 10 CSP plants of 30 MWe each would generate 760 direct and indirect jobs during the 24 months of plant construction and approximately 2100 annual jobs associated with the operation and maintenance (O&M) of the generating units. These 10 new units would generate additional local income on the order of USD 57 million. - Highlights: • CSP plant with supplementary biomass hybridisation is a strategic option for Brazil. • DNI and biomass availability in Brazil's semiarid can foster local CSP industry. • LCOE of CSP would cost 11 cent USD/kWh becoming competitive at solar auctions. • Co-benefits of local job and income generation due to CSP in Brazil are high.

Atomic and electronic structure transformations of silver nanoparticles under rapid cooling conditions.

Science.gov (United States)

Lobato, I; Rojas, J; Landauro, C V; Torres, J

2009-02-04

The structural evolution and dynamics of silver nanodrops Ag(2869) (4.4 nm in diameter) under rapid cooling conditions have been studied by means of molecular dynamics simulations and electronic density of state calculations. The interaction of silver atoms is modelled by a tight-binding semiempirical interatomic potential proposed by Cleri and Rosato. The pair correlation functions and the pair analysis technique are used to reveal the structural transition in the process of solidification. It is shown that Ag nanoparticles evolve into different nanostructures under different cooling processes. At a cooling rate of 1.5625 × 10(13) K s(-1) the nanoparticles preserve an amorphous-like structure containing a large amount of 1551 and 1541 pairs which correspond to icosahedral symmetry. For a lower cooling rate (1.5625 × 10(12) K s(-1)), the nanoparticles transform into a crystal-like structure consisting mainly of 1421 and 1422 pairs which correspond to the face centred cubic and hexagonal close packed structures, respectively. The variations of the electronic density of states for the differently cooled nanoparticles are small, but in correspondence with the structural changes.

Pyrite as a proxy for the identification of former coastal lagoons in semiarid NE Brazil

Science.gov (United States)

Ferreira, Tiago O.; Nóbrega, Gabriel N.; Albuquerque, Antonia G. B. M.; Sartor, Lucas R.; Gomes, Irlene S.; Artur, Adriana G.; Otero, Xosé L.

2015-10-01

This work aimed to test the suitability of pyrite (FeS2) as a proxy for reconstructing past marine environmental conditions along the semiarid coast of Brazil. Morphological description combined with physicochemical analyses including Fe partitioning were conducted for soil depth profiles (30 and 60 cm depths) at three sites in two contrasting lagoons of the state of Ceará: a suspected former lagoon that would have been transformed into a freshwater "lake" at a site vegetated by Juncus effusus (site P1), and another lagoon with connection to the sea at sites vegetated by J. effusus (site P2) or Portulaca oleracea (site P3). Soil samples were collected in September 2010. Site P3 had more reducing conditions, reaching Eh values of -132 mV in the surface layer (0-10 cm), whereas minimum values for the P1 and P2 sites were +219 and +85 mV, respectively. Lower pyritic Fe values were found at site P1, with a degree of pyritization (DOP) ranging from 10 to 13%. At sites P2 and P3, DOP ranged from 9 to 67% and from 55 to 72%, respectively. These results are consistent with an interruption of tidal channels by eolian dune migration inducing strong changes in the hydrodynamics and physicochemical characteristics (lower salinity, oxidizing conditions) of these sites, causing the dieback of suspected former mangroves and a succession to freshwater marshes with an intermediate salt marsh stage. Together with other physicochemical signatures, pyrite can evidently serve as a useful proxy in tracking environmental changes in such ecotones, with implications for coastal management.

Thermalization of secondary electrons under AMSGEMP conditions

International Nuclear Information System (INIS)

Bloomberg, H.W.; Pine, V.W.

1984-01-01

A Monte Carlo algorithm is used to determine the time behavior of source secondary electrons for ranges of the electric field to pressure ratio E/p of interest in AMSGEMP. The algorithm contains a very detailed cross section set describing electron interactions with the background gas. The authors show that the delay in the attainment of the peak time independent ionization frequency (or ionization coefficient) may result in negligible ionization over times of interest. In any case the behavior is shown to behave much differently than in examples where limited cross section sets, common in currently employed predictive codes, are employed. In particular, the importance of momentum transfer is indicated. A critique of the scaling implications of the phenomena is made

Effect of Planting Date on Reducing Growth Period of Spring Safflower Cultivars in Tabriz Cold and Semi-arid Climate

Directory of Open Access Journals (Sweden)

B Pasban Eslam

2018-02-01

Full Text Available Introduction Safflower is a plant adaptable to areas with limited rainfall during winter and spring and dry air at flowering, seed filling and maturity stages, and tolerant to water deficit. The positive correlation coefficient observed between safflower seed yield with precipitation and low air temperature during seed germination to flowering and flowering to seed maturity. Furthermore, precipitation and low temperature during flowering to seed maturity significantly increased seed oil percentage. Therefore, it seems that, by adjusting the planting time can be adapted phenological stages of plant with appropriate weather conditions. The aims of this research were study the possibility reducing the growth period of safflower spring varieties with maintaining performance through delay in planting time, evaluate seed and oil yields at different planting times, and identify the best varieties for cold and semi-arid areas. Materials and Methods The experiment was conducted at the East Azarbaijan Agriculture and Natural Resources Research Center (46°2¢E, 37°58¢N, 1347 m a.s.l. during 2014-2015 growing season. According to Koppen climatic classification system, the area climate is semi-arid and cold. This study was carried out as factorial experiment based on randomized complete block design with three replications. Treatments were four planting dates (30 March, 9, 19 and 29 April and three safflower spring cultivars (Sina, Soffeh and Goldasht. Plant spacing between rows was 24 cm and final plant density was 70 plant per m2. Each plot consisted of 6 rows in 5 meters. Plants were harvested on the 11th and 14th of August in the first and second years of experiment, respectively. At the harvest time, in order to control boarder effects, plants from the sides of each plot were removed. Measured traits were plant height, capitulum diameter, seed yield, capitula number per plant, seed number per capitulum and 1000-seed weight. Ten plants in each plot

Use of Electronic Health Records and Administrative Data for Public Health Surveillance of Eye Health and Vision-Related Conditions

Science.gov (United States)

Elliott, Amanda; Davidson, Arthur; Lum, Flora; Chiang, Michael; Saaddine, Jinan B; Zhang, Xinzhi; Crews, John E.; Chou, Chiu-Fang

2014-01-01

Purpose To discuss the current trend toward greater use of electronic health records and how these records could enhance public health surveillance of eye health and vision-related conditions. Methods We describe three currently available sources of electronic health data (Kaiser Permanente, the Veterans Health Administration, and the Centers for Medicare & Medicaid Services) and how these sources can contribute to a comprehensive vision and eye health surveillance system. Results Each of the three sources of electronic health data can contribute meaningfully to a comprehensive vision and eye health surveillance system, but none currently provide all the information required. The use of electronic health records for vision and eye health surveillance has both advantages and disadvantages. Conclusions Electronic health records may provide additional information needed to create a comprehensive vision and eye health surveillance system. Recommendations for incorporating electronic health records into such a system are presented. PMID:23158225

Chemical profile of size-fractionated soils collected in a semiarid industrial area of Argentina

Science.gov (United States)

Morales Del Mastro, Anabella; Pereyra, Marcelo; Londonio, Agustín; Pereyra, Victoria; Rebagliati, Raúl Jiménez; Dawidowski, Laura; Gómez, Darío; Smichowski, Patricia

2014-12-01

A study was undertaken to assess the chemical profile of soil collected in Bahía Blanca (Argentina). In this industrial city, semiarid soils are affected by different industrial and agricultural activities, the presence of a saltpeter extraction facility, traffic and increasing urbanization. Sixteen soil samples (superficial and sub-superficial) were collected. Samples were sieved in two fractions (A plasma optical emission spectrometry (ICP OES). Anions (Cl-, F-, SO42-) and cations (K+, Na+ and NH4+) were determined by high performance liquid chromatography (HPLC) after an aqueous extraction. As expected, crustal elements namely, Al, Ca, Fe, Mg and Ti exhibited the highest concentrations. Mean elemental concentration ranged from Na+ ≅ SO42- > K+ > NO3-. Three indicators, namely, (i) coefficient of variation, (ii) coefficient of divergence and (iii) ratio of elemental concentration with respect to Ca were used to assess chemical, spatial and inter-profile variability. Chloride > Ca > Na+ > Mo > SO42-, dominated the variability indicating that these are key chemical markers for future assessment of crustal contribution to airborne particles in the area. The ratios Xi/Ca allowed discriminating the soil of the semi-arid region surrounding Bahía Blanca. The chemical profiles obtained in this study, particularly those of topsoil, will be a key input to characterize soil resuspension and its contribution to airborne particulate matter in a forthcoming receptor model analysis.

Voluntary cooperation in the provision of a semi-public good : Community-based soil and water conservation in semi-arid India

NARCIS (Netherlands)

Bouma, J.A.

2008-01-01

This dissertation analyses the question whether households in India’s semi-arid tropics can be expected to voluntarily maintain semi-public investments in soil and water conservation. Increasingly, public investment programs decentralise project planning, implementation and management to local

Improving satellite-based post-fire evapotranspiration estimates in semi-arid regions

Science.gov (United States)

Poon, P.; Kinoshita, A. M.

2017-12-01

Climate change and anthropogenic factors contribute to the increased frequency, duration, and size of wildfires, which can alter ecosystem and hydrological processes. The loss of vegetation canopy and ground cover reduces interception and alters evapotranspiration (ET) dynamics in riparian areas, which can impact rainfall-runoff partitioning. Previous research evaluated the spatial and temporal trends of ET based on burn severity and observed an annual decrease of 120 mm on average for three years after fire. Building upon these results, this research focuses on the Coyote Fire in San Diego, California (USA), which burned a total of 76 km2 in 2003 to calibrate and improve satellite-based ET estimates in semi-arid regions affected by wildfire. The current work utilizes satellite-based products and techniques such as the Google Earth Engine Application programming interface (API). Various ET models (ie. Operational Simplified Surface Energy Balance Model (SSEBop)) are compared to the latent heat flux from two AmeriFlux eddy covariance towers, Sky Oaks Young (US-SO3), and Old Stand (US-SO2), from 2000 - 2015. The Old Stand tower has a low burn severity and the Young Stand tower has a moderate to high burn severity. Both towers are used to validate spatial ET estimates. Furthermore, variables and indices, such as Enhanced Vegetation Index (EVI), Normalized Difference Moisture Index (NDMI), and the Normalized Burn Ratio (NBR) are utilized to evaluate satellite-based ET through a multivariate statistical analysis at both sites. This point-scale study will able to improve ET estimates in spatially diverse regions. Results from this research will contribute to the development of a post-wildfire ET model for semi-arid regions. Accurate estimates of post-fire ET will provide a better representation of vegetation and hydrologic recovery, which can be used to improve hydrologic models and predictions.

Changes in Trace Gas Nitrogen Emissions as a Response to Ecosystem Type Conversion in a Semi-Arid Climate.

Science.gov (United States)

Andrews, H.; Eberwein, J. R.; Jenerette, D.

2016-12-01

As humans continue to introduce exotic plants and to alter climate and fire regimes in semi-arid ecosystems, many plant communities have begun to shift from perennial forbs and shrubs to annual grasses with different functional traits. Shifts in plant types are also associated with shifts in microclimate, microbial activity, and litter inputs, all of which contribute to the efficiency of nitrogen processing and the magnitude of trace gas emissions (NOx and N2O), which are increasingly important fluxes in water-limited systems. Here, we explored how changes in plant litter impact trace gas emissions, asking the question: How does conversion from a native shrubland to exotic grassland ecosystem alter NOx and N2O fluxes in a semi-arid climate? We posed two hypotheses to explain the impacts of different types of litter on soils disturbed by exotic grasses and those that were still considered shrublands: 1.) Soils that have undergone conversion by exotic grasses release higher amounts of NOx and N2O than do those of unconverted shrublands, due to disruptions of native plant and soil processes by exotic grasses, and 2.) Because litter of exotic grasses has lower C:N than that of shrubs, litter inputs from exotic grasses will increase NOx and N2O emissions from soils more than will litter inputs from shrubs. As a preliminary study, we experimentally wetted mesocosms in a laboratory incubation containing converted and unconverted soils that had been mixed with no litter or either exotic grass or coastal sage scrub (CSS) litter. We measured N2O fluxes from mesocosms over a 48-hour period. 24 hours after wetting, samples with grass litter produced higher amounts of N2O than those with CSS litter; similarly, converted soils produced higher amounts of N2O than unconverted soils. These two effects combined resulted in exotic grassland conditions (converted soils with exotic grass litter) producing 10 times the amount of N2O as those containing native shrubland conditions

Cell inactivation studies on yeast cells under euoxic and hypoxic condition using electron beam from microtron accelerator

International Nuclear Information System (INIS)

Praveen Joseph; Santhosh Acharya; Ganesh Sanjeev; Narayana, Y.; Bhat, N.N.

2011-01-01

In the case of sparsely ionizing radiation such as electron, the dose rate and the pattern of energy deposition of the radiation are the important physical factors which can affect the amount of damage in living cells. In the present study, the differences in the cell survival efficiency and dose rate effect in diploid yeast strains Saccharomyces cerevisiae X2180 and Saccharomyces cerevisiae D7 under euoxic and hypoxic condition have been quantified. Irradiation was carried out using 8 MeV pulsed electron beam from Microtron accelerator. The dose per pulse and pulse width of the beam used was 0.6 Gy and 2.3 μs, respectively, which correspond to an instantaneous dose rate of 2.6 x 10 5 Gy s -1 . For survival studies doses were delivered at a rate of 50 pulses per second (an average dose rate of 1,800 Gy s -1 ). Fricke and alanine dosimeters were used to measure the dose delivered to the sample. A significant difference in the dose response has been observed under euoxic and hypoxic condition. Dose rate effect has been studied by changing the pulse repetition rate of the Microtron and the dose rate used was from 180 to 1800 Gy min -1 . A significant dose rate effect was observed under euoxic condition for Saccharomyces cerevisiae X2180 but the same was absent under hypoxic condition. The dose rate effect was absent for Saccharomyces cerevisiae D7 under both irradiation condition. The survival curves are found to be sigmoidal in shape under both condition but with a wider shoulder under hypoxic condition. The D 0 value and the Oxygen Enhancement Ratio (OER) at that point have been derived. (author)

Detecting changes in riparian habitat conditions based on patterns of greenness change: a case study from the upper San Pedro River Basin, USA

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K. Bruce Jones; Curtis E. Edmonds; E. Terrance Slonecker; James D. Wickham; Anne C. Neale; Timothy G. Wade; Kurt H. Riitters; William G. Kepner

2008-01-01

Healthy riparian ecosystems in arid and semi-arid regions exhibit shifting patterns of vegetation in response to periodic flooding. Their conditions also depend upon the amount of grazing and other human uses. Taking advantage of these system properties, we developed and tested an approach that utilizes historical Landsat data to track changes in the patterns...

Photosystem II cycle activity and alternative electron transport in the diatom Phaeodactylum tricornutum under dynamic light conditions and nitrogen limitation.

Science.gov (United States)

Wagner, Heiko; Jakob, Torsten; Lavaud, Johann; Wilhelm, Christian

2016-05-01

Alternative electron sinks are an important regulatory mechanism to dissipate excessively absorbed light energy particularly under fast changing dynamic light conditions. In diatoms, the cyclic electron transport (CET) around Photosystem II (PS II) is an alternative electron transport pathway (AET) that contributes to avoidance of overexcitation under high light illumination. The combination of nitrogen limitation and high-intensity irradiance regularly occurs under natural conditions and is expected to force the imbalance between light absorption and the metabolic use of light energy. The present study demonstrates that under N limitation, the amount of AET and the activity of CETPSII in the diatom Phaeodactylum tricornutum were increased. Thereby, the activity of CETPSII was linearly correlated with the amount of AET rates. It is concluded that CETPSII significantly contributes to AET in P. tricornutum. Surprisingly, CETPSII was found to be activated already at the end of the dark period under N-limited conditions. This coincided with a significantly increased degree of reduction of the plastoquinone (PQ) pool. The analysis of the macromolecular composition of cells of P. tricornutum under N-limited conditions revealed a carbon allocation in favor of carbohydrates during the light period and their degradation during the dark phase. A possible linkage between the activity of CETPSII and degree of reduction of the PQ pool on the one side and the macromolecular changes on the other is discussed.

Versatile 0.5 TW electron beam facility for power conditioning studies of large rare-gas/halide lasers

International Nuclear Information System (INIS)

Ramirez, J.J.

1980-01-01

Rare-gas/halide lasers which are being developed for Inertial Confinement Fusion will require large area, low impedance electron beam drivers. A wide range of electron beam parameters are being considered for future systems in an effort to optimize the overall system design. A number of power conditioning issues must be investigated in order to obtain a better understanding of the various trade-offs involved in making such optimizations. The RAYITO electron beam accelerator is being designed and built at Sandia National Laboratories and will be used for such investigations. It will be capable of operating in either a 2 or 4 ohm configuration at 1 MV, 50 ns or 0.8 MV, 200 ns. Design details for RAYITO are presented in this paper. Experiments planned for this facility are also discussed

Annual variation of 7Be soil inventory in a semiarid region of central Argentina

International Nuclear Information System (INIS)

Lohaiza, F.; Velasco, H.; Juri Ayub, J.; Rizzotto, M.; Di Gregorio, D.E.; Huck, H.; Valladares, D.L.

2014-01-01

Reliable information on environmental radionuclides atmospheric entrance, and their distribution along the soil profile, is a necessary condition for using these soil and sediment tracers to investigate key environmental processes. To address this need, 7 Be content in rainwater and the wet deposition in a semiarid region at San Luis Province, Argentina, were studied. Following these researches, in the same region, we have assessed the 7 Be content along a soil profile, during 2.5 years from September 2009 to January 2012. As expected, the specific activity values in soil samples in the wet period (November–April) were higher than in the dry period (May–October). During the investigated period (2009 – beginning 2012) and for all sampled points, the maximum value of the 7 Be specific activity (Bq kg −1 ) was measured at the surface level. A typical decreasing exponential function of 7 Be areal activity (Bq m −2 ) with soil mass depth (kg m −2 ) was found and the key distribution parameters were determined for each month. The minimum value of areal activity was 51 Bq m −2 in August, and the maximum was 438 Bq m −2 in February. The relaxation mass depth ranges from 2.9 kg m −2 in March to 1.3 kg m −2 in August. 7 Be wet deposition can explain in a very significant proportion the 7 Be inventory in soil. During the period of winds in the region (September and October), the 7 Be content in soil was greater than the expected contribution from wet deposition, situation that is compatible with a higher relative contribution of dry deposition at this period of the year. - Highlights: • The 7 Be content along the soil profile in a semiarid region of Argentina was assessed. • The 7 Be areal activity on soil shows an exponentially decreasing distribution with mass depth. • The relaxation mass depth ranging from 2.9 kg m −2 to 1.3 kg m −2 in wet and dry period respectively. • A simple model is used to determine the 7 Be content in soil from the 7

Cyanobacterial blooms in stratified and destratified eutrophic reservoirs in semi-arid region of Brazil.

Science.gov (United States)

Dantas, Enio W; Moura, Ariadne N; Bittencourt-Oliveira, Maria do Carmo

2011-12-01

This study investigated the dynamics of cyanobacteria in two deep, eutrophic reservoirs in a semi-arid region of Brazil during periods of stratification and destratification. Four collections were carried out at each reservoir at two depths at three-month intervals. The following abiotic variables were analyzed: water temperature, dissolved oxygen, pH, turbidity, water transparency, total phosphorus, total dissolved phosphorus, orthophosphate and total nitrogen. Phytoplankton density was quantified for the determination of the biomass of cyanobacteria. The data were analyzed using CCA. Higher mean phytoplankton biomass values (29.8 mm(3).L(-1)) occurred in the period of thermal stratification. A greater similarity in the phytoplankton communities also occurred in this period and was related to the development of cyanobacteria, mainly Cylindrospermopsis raciborskii (>3.9 mm(3).L(-1)). During the period of thermal destratification, this species co-dominated the environment with Planktothrix agardhii, Geitlerinema amphibium, Microcystis aeruginosa and Merismopedia tenuissima, as well as with diatoms and phytoflagellates. Environmental instability and competition among algae hindered the establishment of blooms more during the mixture period than during the stratification period. Thermal changes in the water column caused by climatologic events altered other physiochemical conditions of the water, leading to changes in the composition and biomass of the cyanobacterial community in tropical reservoirs.

The semi-Arid integrated model (SIM), a regional integrated model assessing water availability, vulnerability, of ecossytems and society in NE-Brazil

NARCIS (Netherlands)

Krol, Martinus S.; Jaeger, A.; Bronstert, A.; Krywkow, Jorg

2001-01-01

Northeastern Brazil, an example of vulnerable semi-arid regions on the earth, is characterised by water scarcity and vulnerability of natural resources, pronounced climatic variability and social stress situations. Integrated studies involving hydrology, ecology, meteorology, climatology, pedology,

Human-Induced Vegetation Degradation in a Semi-Arid Rangeland

Science.gov (United States)

Jackson, Hasan

Current assessments of anthropogenic land degradation and its impact on vegetation at regional scales are prone to large uncertainties due to the lack of an objective, transferable, spatially and temporally explicit measure of land degradation. These uncertainties have resulted in contradictory estimates of degradation extent and severity and the role of human activities. The uncertainties limit the ability to assess the effects on the biophysical environment and effectiveness of past, current, and future policies of land use. The overall objective of the dissertation is to assess degradation in a semi-arid region at a regional scale where the process of anthropogenic land degradation is evident. Net primary productivity (NPP) is used as the primary indicator to measure degradation. It is hypothesized that land degradation resulting from human factors on the landscape irreversibly reduces NPP below the potential set by environmental conditions. It is also hypothesized that resulting reductions in NPP are distinguishable from natural, spatial and temporal, variability in NPP. The specific goals of the dissertation are to (1) identify the extent and severity of degradation using productivity as the primary surrogate, (2) compare the degradation of productivity to other known mechanisms of degradation, and (3) relate the expression of degradation to components of vegetation and varying environmental conditions. This dissertation employed the Local NPP Scaling (LNS) approach to identify patterns of anthropogenic degradation of NPP in the Burdekin Dry Tropics (BDT) region of Queensland (14 million hectares), Australia from 2000 to 2013. The method started with land classification based on the environmental factors presumed to control NPP to group pixels having similar potential NPP. Then, satellite remotely sensing data were used to compare actual NPP with its potential. The difference, in units of mass of carbon fixed in NPP per unit area per monitoring interval and

Evaluation of Three Evaporation Estimation Techniques In A Semi-Arid Region (Omar El Mukhtar Reservoir Sluge, Libya- As a case Study

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Lubna s. Ben Taher

2017-02-01

Full Text Available In many semi-arid countries in the world like Libya, drinking water supply is dependent on reservoirs water storage. Since the evaporation rate is very high in semi-arid countries, estimates and forecasts of reservoir evaporation rate can be useful in the management of major water source. Many researchers have been investigating the suitability of estimates evaporation rates methods in many climatic settings, infrequently of which were in an arid setting. This paper presents the modeling results of evaporation from Omar El Mukhtar Reservoir, Libya. Three techniques namely (artificial neural networks (ANN, Multiple linear regression (MLR and response surface methods (RSM were developed, to assess the estimation of monthly evaporation records from 2001 to 2009; their relative performance were compared using the coefficient of determination(E, mean absolute percentage error (MAPE%, and 95% confidence interval. The key variables used to develop and validate the models were: monthly (precipitation Rf., average temperature Temp., relative humidity Rh., sunshine hours Sh., atmospheric pressure Pa. and wind speed Ws.. The encouraging results approved that the models with more inputs generally had better accuracies and the ANN model performed superior to the other models in predicting monthly Evp with high E=0.86 and low MAPE%= 13.9 and the predicted mean within the range of observed 95CI%. In summary, it is revealed in this study that the ANN and RSM models are appropriate for predicting Evp using climatic inputs in semi-arid climate.

Estimation of Spatial Trends in LAI in Heterogeneous Semi-arid Ecosystems using Full Waveform Lidar

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Glenn, N. F.; Ilangakoon, N.; Spaete, L.; Dashti, H.

2017-12-01

Leaf area index (LAI) is a key structural trait that is defined by the plant functional type (PFT) and controlled by prevailing climate- and human-driven ecosystem stresses. Estimates of LAI using remote sensing techniques are limited by the uncertainties of vegetation inter and intra-gap fraction estimates; this is especially the case in sparse, low stature vegetated ecosystems. Small footprint full waveform lidar digitizes the total amount of return energy with the direction information as a near continuous waveform at a high vertical resolution (1 ns). Thus waveform lidar provides additional data matrices to capture vegetation gaps as well as PFTs that can be used to constrain the uncertainties of LAI estimates. In this study, we calculated a radiometrically calibrated full waveform parameter called backscatter cross section, along with other data matrices from the waveform to estimate vegetation gaps across plots (10 m x 10 m) in a semi-arid ecosystem in the western US. The LAI was then estimated using empirical relationships with directional gap fraction. Full waveform-derived gap fraction based LAI showed a high correlation with field observed shrub LAI (R2 = 0.66, RMSE = 0.24) compared to discrete return lidar based LAI (R2 = 0.01, RMSE = 0.5). The data matrices derived from full waveform lidar classified a number of deciduous and evergreen tree species, shrub species, and bare ground with an overall accuracy of 89% at 10 m. A similar analysis was performed at 1m with overall accuracy of 80%. The next step is to use these relationships to map the PFTs LAI at 10 m spatial scale across the larger study regions. The results show the exciting potential of full waveform lidar to identify plant functional types and LAI in low-stature vegetation dominated semi-arid ecosystems, an ecosystem in which many other remote sensing techniques fail. These results can be used to assess ecosystem state, habitat suitability as well as to constrain model uncertainties in

Land Surface Model and Particle Swarm Optimization Algorithm Based on the Model-Optimization Method for Improving Soil Moisture Simulation in a Semi-Arid Region.

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Yang, Qidong; Zuo, Hongchao; Li, Weidong

2016-01-01

Improving the capability of land-surface process models to simulate soil moisture assists in better understanding the atmosphere-land interaction. In semi-arid regions, due to limited near-surface observational data and large errors in large-scale parameters obtained by the remote sensing method, there exist uncertainties in land surface parameters, which can cause large offsets between the simulated results of land-surface process models and the observational data for the soil moisture. In this study, observational data from the Semi-Arid Climate Observatory and Laboratory (SACOL) station in the semi-arid loess plateau of China were divided into three datasets: summer, autumn, and summer-autumn. By combing the particle swarm optimization (PSO) algorithm and the land-surface process model SHAW (Simultaneous Heat and Water), the soil and vegetation parameters that are related to the soil moisture but difficult to obtain by observations are optimized using three datasets. On this basis, the SHAW model was run with the optimized parameters to simulate the characteristics of the land-surface process in the semi-arid loess plateau. Simultaneously, the default SHAW model was run with the same atmospheric forcing as a comparison test. Simulation results revealed the following: parameters optimized by the particle swarm optimization algorithm in all simulation tests improved simulations of the soil moisture and latent heat flux; differences between simulated results and observational data are clearly reduced, but simulation tests involving the adoption of optimized parameters cannot simultaneously improve the simulation results for the net radiation, sensible heat flux, and soil temperature. Optimized soil and vegetation parameters based on different datasets have the same order of magnitude but are not identical; soil parameters only vary to a small degree, but the variation range of vegetation parameters is large.

Effects of irrigation and plastic mulch on soil properties on semi-arid abandoned fields

OpenAIRE

van der Meulen, E.S.; Nol, L.; Cammeraat, L.H.

2006-01-01

The Guadalentín Basin in Spain is one of the driest areas of Europe and has problems with high evaporation rates, and high risks of desertification exist including soil quality loss and soil erosion. Farmers in this semi-arid region use polyethylene covers on their irrigated croplands to reduce evaporation in order to enhance crop yield. When farmers abandon the acres, they leave the plastic covers on the fields. Up to now research has been concentrating on the effects of plastic covers on cr...

Traditional uses of medicinal animals in the semi-arid region of northeastern Brazil

Directory of Open Access Journals (Sweden)

Alves Rômulo Romeu Nóbrega

2012-10-01

Full Text Available Abstract The present work presents an inventory of the traditional medicinal uses of animals in the municipality of Bom Sucesso in Paraíba State (PB in the semiarid northeastern region of Brazil. Information was obtained through the use of semi-structured interviews with 50 people who use zootherapeutic products. A total of 25 animal species used for medicinal purposes were identified (18 vertebrates and seven invertebrates distributed among five taxonomic categories; the groups with the largest numbers of citations were: mammals (8 citations, insects (7, and reptiles (5. The most cited animal species were: Tubinambis merianae “teju” lizards (44 citations; Apis mellifera Italian honeybees (318 citations; Gallus gallus chickens (31 citations; Ovis aries sheep (31 citations; Crotalus durissus rattlesnakes (14 citations; Boa constrictor (12 citations; and Bos taurus cattle (12 citations. A significant number of illnesses and conditions treated with animal-based medicines were cited, and the category with the greatest number of citations was “problems affecting the respiratory system”. Our results suggest that the use of zootherapeutics in the region is persistent, and that knowledge about these curative practices is an integral part of the regional culture. As such, studies concerning the uses of zootherapeutics are important windows to understanding human/environmental/cultural interactions and a pathway to conciliating regional cultures with efforts to conserve the native fauna.

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

Science.gov (United States)

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

Mapping Ecological Processes and Ecosystem Services for Prioritizing Restoration Efforts in a Semi-arid Mediterranean River Basin

Science.gov (United States)

Trabucchi, Mattia; O'Farrell, Patrick J.; Notivol, Eduardo; Comín, Francisco A.

2014-06-01

Semi-arid Mediterranean regions are highly susceptible to desertification processes which can reduce the benefits that people obtain from healthy ecosystems and thus threaten human wellbeing. The European Union Biodiversity Strategy to 2020 recognizes the need to incorporate ecosystem services into land-use management, conservation, and restoration actions. The inclusion of ecosystem services into restoration actions and plans is an emerging area of research, and there are few documented approaches and guidelines on how to undertake such an exercise. This paper responds to this need, and we demonstrate an approach for identifying both key ecosystem services provisioning areas and the spatial relationship between ecological processes and services. A degraded semi-arid Mediterranean river basin in north east Spain was used as a case study area. We show that the quantification and mapping of services are the first step required for both optimizing and targeting of specific local areas for restoration. Additionally, we provide guidelines for restoration planning at a watershed scale; establishing priorities for improving the delivery of ecosystem services at this scale; and prioritizing the sub-watersheds for restoration based on their potential for delivering a combination of key ecosystem services for the entire basin.

[Sowing date of corn in semiarid region of Jilin Province, Northeast China in adapting to climate change].

Science.gov (United States)

Jin, Ying-Hua; Zhou, Dao-Wei; Qin, Li-Jie

2012-10-01

Under the background of global climate change, the climate in semiarid region of west Jilin Province changed greatly, producing a profound impact on the corn production in this region. In this study, the corn seeds were under three treatments (accelerating germination at 10 and 25 degrees C, and dry seeds), and a field experiment with early sowing and traditional sowing was conducted in 2008 to investigate the effects of early sowing these seeds on the seedling emergence, growth, and yield, and compare the effects of early sowing and traditional sowing dates on the corn production and yield. In 1961-2010, the first day of the growth season of corn in semiarid region of west Jilin Province was advanced, the air temperature increased significantly, and the precipitation displayed a decreasing trend. At present, the corn sowing date in this region could be advanced to 11th, April. Accelerating germination at 10 degrees C, directly sowing dry seeds, and bed-irrigation sowing all benefited the seedling emergence and cold resistance of early-sown seeds, and the corn plant height and leaf area under early sowing were significantly higher, with the yield increased by 35% - 48%, compared with those under traditional sowing.

Mapping ecological processes and ecosystem services for prioritizing restoration efforts in a semi-arid Mediterranean river basin.

Science.gov (United States)

Trabucchi, Mattia; O'Farrell, Patrick J; Notivol, Eduardo; Comín, Francisco A

2014-06-01

Semi-arid Mediterranean regions are highly susceptible to desertification processes which can reduce the benefits that people obtain from healthy ecosystems and thus threaten human wellbeing. The European Union Biodiversity Strategy to 2020 recognizes the need to incorporate ecosystem services into land-use management, conservation, and restoration actions. The inclusion of ecosystem services into restoration actions and plans is an emerging area of research, and there are few documented approaches and guidelines on how to undertake such an exercise. This paper responds to this need, and we demonstrate an approach for identifying both key ecosystem services provisioning areas and the spatial relationship between ecological processes and services. A degraded semi-arid Mediterranean river basin in north east Spain was used as a case study area. We show that the quantification and mapping of services are the first step required for both optimizing and targeting of specific local areas for restoration. Additionally, we provide guidelines for restoration planning at a watershed scale; establishing priorities for improving the delivery of ecosystem services at this scale; and prioritizing the sub-watersheds for restoration based on their potential for delivering a combination of key ecosystem services for the entire basin.

Rainwater harvesting to enhance water productivity of rainfed agriculture in the semi-arid Zimbabwe

Science.gov (United States)

Kahinda, Jean-marc Mwenge; Rockström, Johan; Taigbenu, Akpofure E.; Dimes, John

Zimbabwe’s poor are predominantly located in the semi-arid regions and rely on rainfed agriculture for their subsistence. Decline in productivity, scarcity of arable land, irrigation expansion limitations, erratic rainfall and frequent dry spells, among others cause food scarcity. The challenge faced by small-scale farmers is to enhance water productivity of rainfed agriculture by mitigating intra-seasonal dry spells (ISDS) through the adoption of new technologies such as rainwater harvesting (RWH). The paper analyses the agro-hydrological functions of RWH and assesses its impacts (at field scale) on the crop yield gap as well as the Transpirational Water Productivity ( WPT). The survey in six districts of the semi-arid Zimbabwe suggests that three parameters (water source, primary use and storage capacity) can help differentiate storage-type-RWH systems from “conventional dams”. The Agricultural Production Simulator Model (APSIM) was used to simulate seven different treatments (Control, RWH, Manure, Manure + RWH, Inorganic Nitrogen and Inorganic Nitrogen + RWH) for 30 years on alfisol deep sand, assuming no fertiliser carry over effect from season to season. The combined use of inorganic fertiliser and RWH is the only treatment that closes the yield gap. Supplemental irrigation alone not only reduces the risks of complete crop failure (from 20% down to 7% on average) for all the treatments but also enhances WPT (from 1.75 kg m -3 up to 2.3 kg m -3 on average) by mitigating ISDS.

Collisional Damping of Electron Bernstein Waves and its Mitigation by Evaporated Lithium Conditioning in Spherical-Tokamak Plasmas

International Nuclear Information System (INIS)

Diem, S. J.; Caughman, J. B.; Taylor, G.; Efthimion, P. C.; Kugel, H.; LeBlanc, B. P.; Phillips, C. K.; Preinhaelter, J.; Urban, J.; Sabbagh, S. A.

2009-01-01

The first experimental verification of electron Bernstein wave (EBW) collisional damping, and its mitigation by evaporated Li conditioning, in an overdense spherical-tokamak plasma has been observed in the National Spherical Torus Experiment (NSTX). Initial measurements of EBW emission, coupled from NSTX plasmas via double-mode conversion to O-mode waves, exhibited <10% transmission efficiencies. Simulations show 80% of the EBW energy is dissipated by collisions in the edge plasma. Li conditioning reduced the edge collision frequency by a factor of 3 and increased the fundamental EBW transmission to 60%.

Rainwater harvesting to alleviate water scarcity in dry conditions: A case study in Faria Catchment, Palestine

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Sameer Shadeed

2010-06-01

Full Text Available In arid and semi-arid regions, the availability of adequate water of appropriate quality has become a limiting factor for development. This paper aims to evaluate the potential for rainwater harvesting in the arid to semi-arid Faria Catchment, in the West Bank, Palestine. Under current conditions, the supply-demand gap is increasing due to the increasing water demands of a growing population with hydrologically limited and uncertain supplies. By 2015, the gap is estimated to reach 4.5 × 106 m3. This study used the process-oriented and physically-based TRAIN-ZIN model to evaluate two different rainwater harvesting techniques during two rainfall events. The analysis shows that there is a theoretical potential for harvesting an additional 4 × 106 m3 of surface water over the entire catchment. Thus, it is essential to manage the potential available surface water supplies in the catchment to save water for dry periods when the supply-demand gap is comparatively high. Then a valuable contribution to bridging the supply-demand gap can be made.

Electron distribution function in electron-beam-excited plasmas

International Nuclear Information System (INIS)

Brau, C.A.

1976-01-01

In monatomic plasmas excited by high-intensity relativistic electron beams, the electron secondary distribution function is dominated by elastic electron-electron collisions at low electron energies and by inelastic electron-atom collisions at high electron energies (above the excitation threshold). Under these conditions, the total rate of excitation by inelastic collisions is limited by the rate at which electron-electron collisions relax the distribution function in the neighborhood of the excitation threshold. To describe this effect quantitatively, an approximate analytic solution of the electron Boltzmann equation is obtained, including both electron-electron and inelastic collisions. The result provides a simple formula for the total rate of excitation

A Tool for the Evaluation of Irrigation Water Quality in the Arid and Semi-Arid Regions

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Lucia Bortolini

2018-02-01

Full Text Available In the Mediterranean arid and semi-arid regions, large amounts of low quality waters could be used for crop irrigation, but the adoption of articulated classifications with too rigid quality limits can often reduce the recoverable quantities of water and make the monitoring of water quality too much expensive. Therefore, an evaluation of irrigation water quality based on only a few crucial parameters, which consider the crop species to be irrigated and the type of irrigation system and management adopted, can be an easy and flexible method for maximizing the reuse of wastewater and low-quality water for agricultural purposes. In this view, an irrigation water quality tool (IWQT was developed to support farmers of arid and semi-arid regions on evaluating the use of low quality water for crop irrigation. The most significant and cheapest parameters of irrigation water quality were identified and clustered in three quality classes according to their effects on crop yield and soil fertility (agronomic quality indicators, human health (hygiene and health quality indicators, and irrigation systems (management quality indicators. According to IWQT parameters, a tool reporting a series of recommendations, including water treatment types, was implemented to guide farmers on the use of low quality irrigation water.

Influence of hydraulic and geomorphologic components of a semi-arid watershed on depleted-uranium transport

International Nuclear Information System (INIS)

Becker, N.M.

1991-01-01

Investigations were undertaken to determine the fate and transport of depleted uranium away from high explosive firing sites at Los Alamos National Laboratory in north-central New Mexico. Investigations concentrated on a small, semi-arid watershed which drains 5 firing sites. Sampling for uranium in spring/summer/fall runoff, snowmelt runoff, in fallout, and in soil and in sediments revealed that surface water is the main transport mechanism. Although the watershed is less than 8 km 2 , flow discontinuity was observed between the divide and the outlet; flow discontinuity occurs in semi-arid and arid watersheds, but was unexpected at this scale. This region, termed a discharge sink, is an area where all flow infiltrates and all sediment, including uranium, deposits during nearly all flow events; it is estimated that the discharge sink has provided the locale for uranium detention during the last 23 years. Mass balance calculations indicate that over 90% of uranium expended still remains at or nearby the firing sites. Leaching experiments determined that uranium can rapidly dissolve from the solid phase. It is postulated that precipitation and runoff which percolate vertically through uranium-contaminated soil and sediment are capable of transporting uranium in the dissolved phase to deeper strata. This may be the key transport mechanism which moves uranium out of the watershed

Book title: Exotic brome grasses in arid and semi-arid ecosystems of the western US: causes, consequences, and management implications

Science.gov (United States)

Exotic invasive annual grass research and management in arid and semiarid ecosystems of the western US have historically focused on the outcome of efforts to reduce weed abundance. Given the current impact of invasive annual grasses and their continued spread in this region, we assessed components ...

The Non-Equilibrium Statistical Distribution Function for Electrons and Holes in Semiconductor Heterostructures in Steady-State Conditions

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Krzysztof Jόzwikowska

2015-06-01

Full Text Available The main goal of this work is to determine a statistical non-equilibrium distribution function for the electron and holes in semiconductor heterostructures in steady-state conditions. Based on the postulates of local equilibrium, as well as on the integral form of the weighted Gyarmati’s variational principle in the force representation, using an alternative method, we have derived general expressions, which have the form of the Fermi–Dirac distribution function with four additional components. The physical interpretation of these components has been carried out in this paper. Some numerical results of a non-equilibrium distribution function for an electron in HgCdTe structures are also presented.

Thrips collected in watermelon crops in the semiarid of Rio Grande do Norte, Brazil

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Ewerton Marinho Costa

2015-04-01

Full Text Available The aim of this research was to report the occurrence of two species of thrips in watermelon crops in the semiarid region of Rio Grande do Norte, Brazil. From August to September 2011, we performed weekly sampling of thrips in a commercial watermelon production area with 10,000m2, using 20 Moericke traps. We captured a total of 431 thrips, belonging to Frankliniella schultzei (Trybom (Thripidae and Haplothrips gowdeyi (Franklin (Phlaeothripidae. This is the first report of H. gowdeyi in watermelon crops in Brazil

Edaphic factors controlling summer (rainy season) greenhouse gas emissions (CO2 and CH4) from semiarid mangrove soils (NE-Brazil).

Science.gov (United States)

Nóbrega, Gabriel N; Ferreira, Tiago O; Siqueira Neto, M; Queiroz, Hermano M; Artur, Adriana G; Mendonça, Eduardo De S; Silva, Ebenezer De O; Otero, Xosé L

2016-01-15

The soil attributes controlling the CO2, and CH4 emissions were assessed in semiarid mangrove soils (NE-Brazil) under different anthropogenic activities. Soil samples were collected from different mangroves under different anthropogenic impacts, e.g., shrimp farming (Jaguaribe River); urban wastes (Cocó River) and a control site (Timonha River). The sites were characterized according to the sand content; physicochemical parameters (Eh and pH); total organic C; soil C stock (SCS) and equivalent SCS (SCSEQV); total P and N; dissolved organic C (DOC); and the degree of pyritization (DOP). The CO2 and CH4 fluxes from the soils were assessed using static closed chambers. Higher DOC and SCS and the lowest DOP promote greater CO2 emission. The CH4 flux was only observed at Jaguaribe which presented higher DOP, compared to that found in mangroves from humid tropical climates. Semiarid mangrove soils cannot be characterized as important greenhouse gas sources, compared to humid tropical mangroves.

Time-dependent plasma behavior triggered by a pulsed electron gun under conditions of beam-plasma-discharge

International Nuclear Information System (INIS)

Szuszczewicz, E.P.; Lin, C.S.

1982-01-01

This chapter reports on experiments whose purpose was to simulate spaceborne applications of energetic electron guns while exploring the ''in situ'' diagnostics of time-dependent beam-plasma behavior under pulsed electron gun conditions. Beam-plasma-discharge (BPD), the BPD afterglow that exists after gun-pulse termination, and the plasma decay process are considered. It is concluded that there is a rapid enhancement in plasma density as the gas turns on; that during the pulse-ON time a quasi-steady-state BPD can be maintained with characteristics identical with its dc counterpart; that in the period immediately following gun-pulse termination the plasma loss process is dominated by cross-field radial diffusion; and that the afterglow plasma is within + or -10% of being an isodensity contour

Analysis of energy fluxes and vegetation-atmosphere parameters in irrigated and natural ecosystems of semi-arid Brazil

Science.gov (United States)

Teixeira, A. H. de Castro; Bastiaanssen, W. G. M.; Ahmad, M. D.; Moura, M. S. B.; Bos, M. G.

2008-11-01

SummaryKnowledge on evapotranspiration is essential in quantifying water use depletion and to allocate scarce water resources to competing uses. Despite that an extensive literature describes the theoretical mechanisms of turbulent water vapour transport above and within crop canopies fewer studies have examined land surface parameters within composite landscapes of irrigated crops and semi-arid natural vegetation. Aiming to improve parameterizations of the radiation and energy balance in irrigated crops and natural vegetation, micro-climatic measurements were carried out on irrigated land (vineyards and mango orchard) and natural vegetation (caatinga) in the semi-arid zone of the São Francisco River basin (Brazil) from 2002 to 2005. The fractions of 24 h incident solar radiation available for net radiation were 46%, 55%, 51% and 53%, for wine grape, table grape, mango orchard and caatinga, respectively. Daily evaporative fractions of the net available energy used as latent heat flux ( λE) were 0.80, 0.88, 0.75 and 0.33 respectively. The daylight values of bulk surface resistances ( rs) averaged 128 s m -1, 73 s m -1, 133 s m -1 and 1940 s m -1 for wine grape, table grape, mango orchard and caatinga, respectively. Simplified parameterizations on roughness and evaporation resistances were performed. It could be concluded that net radiation can be estimated by means of a linear expression with incident global solar radiation depending on the type of vegetation. The variability of aerodynamic resistance ( ra) could be mainly explained by the friction velocity ( u ∗) which on turn depends on the surface roughness length for momentum transport ( z 0m). The experimental data showed that for sparse canopies z 0m being 9% of the mean vegetation height is a doable operational rule for the semi-arid region of São Francisco River basin. The seasonal values of rs for irrigated crops were highly correlated with water vapour pressure deficit. The availability of analytical

Temperature profile in apricot tree canopies under the soil and climate conditions of the Romanian Black Sea Coast

Science.gov (United States)

Paltineanu, Cristian; Septar, Leinar; Chitu, Emil

2016-03-01

The paper describes the temperature profiles determined by thermal imagery in apricot tree canopies under the semi-arid conditions of the Black Sea Coast in a chernozem of Dobrogea Region, Romania. The study analyzes the thermal vertical profile of apricot orchards for three representative cultivars during summertime. Measurements were done when the soil water content (SWC) was at field capacity (FC) within the rooting depth, after intense sprinkler irrigation applications. Canopy temperature was measured during clear sky days at three heights for both sides of the apricot trees, sunlit (south), and shaded (north). For the SWC studied, i.e., FC, canopy height did not induce a significant difference between the temperature of apricot tree leaves (Tc) and the ambient air temperature (Ta) within the entire vertical tree profile, and temperature measurements by thermal imagery can therefore be taken at any height on the tree crown leaves. Differences between sunlit and shaded sides of the canopy were significant. Because of these differences for Tc-Ta among the apricot tree cultivars studied, lower base lines (LBLs) should be determined for each cultivar separately. The use of thermal imagery technique under the conditions of semi-arid coastal areas with low range of vapor pressure deficit could be useful in irrigation scheduling of apricot trees. The paper discusses the implications of the data obtained in the experiment under the conditions of the coastal area of the Black Sea, Romania, and neighboring countries with similar climate, such as Bulgaria and Turkey.

Seedbed preparation influence on morphometric characteristics of perennial grasses of a semi-arid rangeland in Kenya

OpenAIRE

Opiyo, Francis EO; Ekaya, Wellington N; Nyariki, Dickson M; Mureithi, Stephen Mwangi

2011-01-01

Semi-arid rangelands in Kenya are an important source of forage for both domestic and wild animals. However, indigenous perennial grasses notably Cenchrus ciliaris (African foxtail grass), Eragrostis superba (Maasai love grass) and Enteropogon macrostachyus (Bush rye grass) are disappearing at an alarming rate. Efforts to re-introduce them through restoration programs have often yielded little success. This can partly be attributed to failure of topsoil to capture and store scarce water to me...

Analysis of the potentiality haying of native forage species in semiarid region

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Enoque de Sousa Leão

2017-10-01

Full Text Available The objective of this study was to evaluate the potential hay production from Spiny Amaranth (Amaranthus spinosus, Hairy Woodrose (Merremia aegyptia, Malva (Sida galheirensis, Mucuna (Mucuna pruriens and Ervanço (Froelichia humboldtiana, native forage species of the semiarid region of Brazil by observing morphological components of the plant, such as the dehydration curve, crude protein loss (CPL curve, chemical composition of plant and hay and hay degradability in situ. There were differences (P < 0.05 among species on leaf, stem and inflorescence quantification with Ervanço, Hairy Woodrose, and Mucuna having a greater number of leaves. There was a linearly increasing response for the dehydration curve of the five forage plants species. Mucuna forage had the greatest hay point at 800 g kg-1 dried matter (DM after 11.8 hours and Woodrose had a lower dehydration efficiency, which required 25 hours of sun exposure. There was no difference in CPL. Mucuna had the lowest crude protein (CP, neutral detergent fiber (NDF and acid detergent fiber (ADF content, 8.4, 67.7 and 73.8 g kg DM-1 in hay in relation to the plant, respectively. Ervanço, Spiny Amaranth, Hairy Woodrose and Malva hay had more of soluble fraction “a” of DM of 31.0, 26.2, 22.1 and 9.7 g kg-1 DM than Mucuna, respectively. Spiny Amaranth and Malva hay had values of 335.4 and 193.2 g kg-1 DM of fraction “b” more than Ervanço hay, respectively. For fraction “a’’ of CP, Spiny Amaranth and Hairy Woodrose hay obtained 312.6 and 227.4 g kg-1 CP more than that observed for Malva, respectively. Mucuna had better hay potential among the forage studied in the semiarid region of Brazil.

Vegetation-induced turbulence influencing evapotranspiration-soil moisture coupling: Implications for semiarid regions

Science.gov (United States)

Haghighi, E.; Kirchner, J. W.; Entekhabi, D.

2016-12-01

The relationship between soil moisture and evapotranspiration (ET) fluxes is an important component of land-atmosphere interactions controlling hydrology-climate feedback processes. Important as this relationship is, it remains empirical and physical mechanisms governing its dynamics are insufficiently studied. This is particularly of importance for semiarid regions (currently comprising about half of the Earth's land surface) where the shallow surface soil layer is the primary source of ET and direct evaporation from bare soil is likely a large component of the total flux. Hence, ET-soil moisture coupling in these regions is hypothesized to be strongly influenced by soil evaporation and associated mechanisms. Motivated by recent progress in mechanistic modeling of localized heat and mass exchange rates from bare soil surfaces covered by cylindrical bluff-body elements, we developed a physically based ET model explicitly incorporating coupled impacts of soil moisture and vegetation-induced turbulence in the near-surface region. Model predictions of ET and its partitioning were in good agreement with measured data and suggest that the strength and nature of ET-soil moisture interactions in sparsely vegetated areas are strongly influenced by aerodynamic (rather than radiative) forcing namely wind speed and near-surface turbulence generation as a function of vegetation type and cover fraction. The results demonstrated that the relationship between ET and soil moisture varies from a nonlinear function (the dual regime behavior) to a single moisture-limited regime (linear relationship) by increasing wind velocity and enhancing turbulence generation in the near-surface region (small-scale woody vegetation species of low cover fraction). Potential benefits of this study for improving accuracy and predictive capabilities of remote sensing techniques when applied to semiarid environments will also be discussed.