In developing countermeasures to reduce the negative effects of strong dust events, the fundamental relationship between surface conditions and sand transport remains problematic. We conducted field observations and wind tunnel experiments to examine the effect on sand transport efficiency of actual frontal area when using flexible roughness elements (artificial grass) and rigid roughness elements (tufts of stiff wire). In the field observations, the sand trap ratio approached a limit as the frontal area of artificial grass, measured as the Actual Frontal Area Index (AFAI), approached 25%, equivalent to a vegetation cover of 20%. The wind tunnel experiments showed that the height of deposited sediment decreased downwind with both roughness elements, due to their reduction of both shear velocity and sand transport rates. The sediment flux decreased as the AFAI increased, and the rigid roughness element trapped more sand particles than the flexible one except at higher wind speeds and lower AFAI values. The sand trapping efficiency was greater for rigid roughness elements than for flexible ones, probably due to their high aerodynamic resistance, and thus wire tufts were more effective for trapping sand than artificial grass at higher AFAI values.

The big desert of Algeria is characterized by a hot and dry climate in summer, cold and dry in winter. In these reinforced concrete construction parts assuredly there was much disappointment to provide a healthy and comfortable indoor climate in buildings. To improve thermal comfort in a building and save energy, it is necessary to implement special performance materials, providing good thermal insulation. In this study we care to about producing clay bricks with good mechanical and thermal properties to reduce energy consumption and increase thermal comfort in the home. The objective of this research is to prepare clay bricks and examine afterwards with some mechanical and thermal tests. We have made some prototypes tested by these bricks who gave good thermal and mechanical properties in order to try to use them in the field of construction. We made the percentage of sand set at 30% and that of the fiber from 0% to3% by weight. The results of these tests showed that the increase in% of fiber is beneficial to the improvement of the thermal properties with acceptable mechanical strength. At14:00h, a remarkable temperature difference compared to the control performed in industrial prototype brick was obtained. (c) 2017 The Authors. Published by Elsevier Ltd.

The cement materials, such as concrete and conventional mortar present very little resistance to traction and cracking, these hydraulic materials which induces large withdrawals on materials and cracks in structures. The hot dry environments such as: the Saharan regions of Algeria, Indeed, concrete structures in these regions are very fragile, and present high shrinkage. Strengthening of these materials by fibers can provide technical solutions for improving the mechanical performance. The aim of this study is firstly, to reduce the shrinkage of conventional concrete with its reinforcement with date palm fibers. In fact, Algeria has an extraordinary resources in natural fibers ( from Palm, Abaca, Hemp) but without valorization in practical areas, especially in building materials. Secondly, to model the shrinkage behavior of concrete was reinforced by date palm fibers. In the literature, several models for still fiber concrete were founded but few are offers for natural fiber concretes. To do so, a still fiber concretes model of YOUNG - CHERN was used. According to the results, a reduction of shrinkage with reinforcement by date palm fibers was showed. A good ability of molding of shrinkage of date palm reinforced concrete with YOUNG - CHERN Modified model was obtained. In fact, a good correlation between experimental data and the model data was recorded.

The CGS3a from the Chagelebulu locates southeast of China's Badain Jaran Desert. This area includes 5.5 sedimentary cycles that consist of lacustrine facies and eolian dune sands or loess during the OIS3a. Based on analyses of contents of Rb and Sr and ratios of Rb/Sr in the CGS3a, along with particle Mz (Phi) and sigma, the values of contents of Rb and Sr and ratios of Rb/Sr in the dune sands or loess are lower than those in the lacustrine facies, showing 5.5 fluctuations, which are similar to the sedimentary cycles in the CGS3a segment. Therefore, the CGS3a segment reveals 5.5 warm-wet and cold-arid climate cycles that are controlled by the East Asian winter and summer monsoons in the OIS3a. This trend suggests climate changes at the millennium scale in the East Asian monsoon in the desert areas of China during the OIS3a period. Among those changes, the cold periods correspond well to the Heinrich Events, and warm periods are consistent with the Dansgaard-Oeschger events in the Greenland ice-core project. The millennium-scale climate variation in the East Asian monsoon is the actual regional response to the global climate variations during the OIS3a period.

The red sand dunes appear along the south east, -west coast of Tamil Nadu, India between the latitudes and longitudes of 8 degrees 07'56N to 8 degrees 22'11N; 77 degrees 19'84E to 77 degrees 53'40E. The dune sands from this region were studied through magnetic methods such as magnetic susceptibility measurements and acquisition of isothermal remanent magnetization, geochemistry and X-ray diffraction methods. Optically stimulated luminescence (OSL) dating method was used to constrain the chronology of deposits. Three sections were excavated up to 5-9.5 m with one inland deposit (TPV) and two near coastal sections (THOP and MUT). The magnetic parameters show both significant contribution of hematite structures and indicate the presence of multi-domain magnetite or mixed mineral contents of magnetite and anti-ferromagnetic minerals in the sample. The occurrence of magnetite in THOP and TPV sections is possibly due to the marine sediments transported by sturdy onshore winds. In XRD data, correlation analysis indicated TPV and MUT sections have a similar type of deposition and THOP did not show any positive correlation with TPV and MUT and even with its own deposition. In comparison with geochemistry data, chi variation and OSL dates, it was shown that the sample MUT21 (200 cm) with an OSL age of 14 +/- 2 ka indicated deposition during the humid interval and at similar to 17 +/- 2 to similar to 19 +/- 2 ka MUT61 (600 cm) depicts the dry period of deposition.

Strategies to promote dense, deep root systems are important for the efficient use of water and nitrogen fertilisers in subtropical loamy sandy soil. This study assessed the effect of interactions between irrigation method (drip and furrow), irrigation level (full and reduced), and nitrogen fertiliser type (quick release and slow-release) on root growth of maize (Zea mays L.) and the associated effect on grain yield, aboveground biomass and leaf area index. Factorial field experiments on semi-arid loamy sandy soil in Mozambique was carried out in four cropping periods (two in the hot-wet season, two in the cold-dry season). The response to the management factors at three growing stages of coarse (>= 0.7 mm diameter) and fine (<0.7 mm diameter) root density (RD) (two cropping periods) and maximum rooting depth (four cropping periods) were measured in situ by modified profile wall method. The interactions between management factors did not explain the variation in maize RD or maximum rooting depth. However, seasonal variation between the cropping periods affected the distribution of coarse RD. Drip irrigation gave 33-153% higher coarse RD and 26-55% higher fine RD than furrow irrigation in deeper layers (16-64 cm), whereas furrow irrigation gave 21-40% higher coarse RD than drip at a shallow depth (0-16 cm). Irrigation level had little effect on RD, whereas slow-release fertilisation resulted in overall higher RD, aboveground biomass and grain yield than quick-release fertilisation in the cold-dry season. RD or maximum rooting depth showed few significant correlations with grain yield, biomass and leaf area index, respectively, but higher RD generally tended to result in higher yield. Overall, drip irrigation combined with reduced irrigation and slow-release N fertiliser appeared to be the most promising strategy to promote maize rooting and increase yield, especially in the cold-dry season. (C) 2016 Elsevier B.V. All rights reserved.

The native environment in northwestern China is characterized by a loose surface, gullies, a dry climate and serious soil erosion. The purpose of this study was to reveal the effects of the subsidence of a coal mine on plant diversity and community structure. For this purpose, six sample plots were surveyed at the Daliuta coal mine based on different subsidence times. The species richness and importance value as well as a diversity indexes were applied. The results indicate that species richness varied across study sites. Coal mine subsidence had little effect on plant diversity and community structure. The number of species increased in subsided sites in loam soils, especially in the number of unique perennial herbs, but there were no differences in sandy soils. There was less biomass in the subsidence sites than in the control sites after several years of subsidence. The community structure did not change in general, but on some loam soils constructive species changed in response to coal mine subsidence. Surface subsidence induced by coal mining can be characterized as an intermediate disturbance to plant communities in northwestern China.

Most developed lands in arid and semi-arid areas of Algeria rest on a highly mineralized phreatic aquifer, the level of which is close (0-1.5 m) to the ground surface. Such a superficial water table, combined with the existence of highly severe climatic conditions, have enhanced the process of evaporation from the water table, which largely contributes to the salinization of soils and the degradation of the environment. The present study on the evaporation process of the phreatic aquifer in the Ouargla region shows that evaporation decreases the further the water table is from the ground surface. The study shows that evaporation of the water table reaches its maximum and is equal to the rate of evaporation of the aquifer at 0-0.6 m from the ground surface and its minimum rate when it is below 1.7 m. For better development of land and improved agricultural production, it is necessary to know the critical depth of the water table for which evaporation is low and therefore there is a low deposit of salts in sandy soils in the arid Ouargla region.

Peanut (Arachis hypogaea L.) is an important grain legume whose yield is often limited by water deficits because it is commonly grown in regions with intermittent rainfall and on sandy soils with low water-holding capacity. Annual peanut yield loss due to drought worldwide has been estimated at US$520 million (Sharma and Lavanya 2002). To increase yields, it is essential to develop genotypes that can sustain growth and yield when subjected to water deficit (Sinclair and Vadez 2012). The two plant traits, which are the topic of this book, have been identified in peanut to result in conservative use of water and allow sustained growth during drought: (1) earlier closure of stomata in the soil drying cycle resulting in decreased daily transpiration rate and (2) limited-transpiration rate (TRlim) under high atmospheric vapor pressure deficit (VPD) (Devi et al. 2009, 2010).

The paper deals with evaluation of the lodgepole pine research provenance plot in the pine site conditions in Trebon (Southern Bohemia, Czech Republic) at the age of 34 years. Based on the evaluation of specific quantitative and qualitative traits (height, DBH, stem volume, tree stock, mortality, defoliation, stem form and height of stem forking, branch thickness, and bark type), provenances were assessed in terms of their production capacity and utilization on extremely dry sandy soils. The lowest defoliation (20-25 %) has been recorded in the case of provenances No. 2089 Manzanita, No. 2235 Calling Lake and No. 1902 Mile 86, most others did not exceed a level of 50 %, but four provenances had a high needle loss (71-79 %). From the volume production point of view, the provenance No. 2089 Manzanita (P. c. subsp. contorta) from the Oregon coast and No. 2091 Mount Hood (P. c. subsp. latifolia) from Oregon Cascades, demonstrated their high production ability. The best-growing provenance No. 2089 Manzanita corresponds through its growth characteristics to the fourth relative site class of domestic Scots pine, which confirms that proper selection can find suitable provenances that can fulfill the production function even in poor and dry site conditions.