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Desert Areas (desert + area)

Distribution by Scientific Domains

Engineering	42%
Earth and Environmental Science	28%

Selected Abstracts

Evaluation of a wind erosion model in a desert area of northern Asia by eddy covariance

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 13 2009
Gerardo Fratini
Abstract For the first time, vertical fluxes of mineral dust measured by Eddy Covariance in two desert sites of Northern Asia have been used to test the performances of a wind erosion model in the field. Soil parameters required by the model were obtained through field and laboratory determinations. Model predictions and direct measurements have been compared. The main finding was that the direction of the horizontal wind relative to the orientation of nebkhas played a crucial role in determining the emission of particles in one of the investigated sites. Being unable to simulate such interaction, the model generally overestimated the actual emission. It provided, instead, reliable predictions (r2 = 0·87) when the wind direction was suitable in detaching loose erodible elements placed on nebkhas thanks to their normal orientation. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Sap flow of Artemisia ordosica and the influence of environmental factors in a revegetated desert area: Tengger Desert, China

HYDROLOGICAL PROCESSES, Issue 10 2010
Huang Lei
Abstract Artemisia ordosica is considered as an excellent sand-fixing plant in revegetated desert areas, which plays a pertinent role in stabilizing the mobile dunes and sustaining the desert ecosystems. Stem sap flows of about 10-year-old Artemisia ordosica plants were monitored continuously with heat balance method for the entire growing season in order to understand the water requirement and the effects of environmental factors on its transpiration and growth. Environment factors such as solar radiation, air temperatures, relative humidity, wind speed and precipitation were measured by the eddy covariance. Diurnal and seasonal variations of sap flow rate with different stem diameters and their correlation with meteorological factors and reference evapotranspiration were analysed. At the daily time scale, there was a significantly linear relationship between sap flow rate and reference evapotranspiration with a correlation coefficient of R2 = 0·6368. But at the hourly time scale, the relationship of measured sap flow rate and calculated reference evapotranspiration (ET0) was affected by the precipitation. A small precipitation would increase the sap flow and the ET0; however, when the precipitation is large, the sap flow and ET0 decrease. Leaf area index had a coincident variation with soil water content; both were determined by the precipitation, and meteorological factors were the most significant factors that affected the sap flow of Artemisia ordosica in the following order: solar radiation > vapour pressure deficit > relative humidity > air temperature > wind speed. The close correlation between daily sap flow rate and meteorological factors in the whole growing season would provide us an accurate estimation of the transpiration of Artemisia ordosica and rational water-carrying capacity of sand dunes in the revegetated desert areas. Copyright © 2010 John Wiley & Sons, Ltd. [source]

The role of the mineral component in surface stabilization processes of a disturbed desert sandy surface

LAND DEGRADATION AND DEVELOPMENT, Issue 4 2002
A. Yair
Abstract The stabilization of sandy and loamy surfaces in semiarid and arid areas by topsoil crusts protecting the soil against wind or runoff erosion is well known. Destruction of such crusts, often by overgrazing, can enhance erosion and desertification. Crust recovery does not depend purely on biotic components of the crust and vegetation. Mineral components in the initial surface stabilization process are often overlooked. The present study focuses on the relative importance of the biotic and mineral components in the process of topsoil crust recovery in a sandy desert area located in the northwestern Negev Desert of Israel. Observations of the initial crust and of the disturbed surface, in the field and under the scanning electron microscope, showed that the mineral components of the crust recovered more quickly than its biotic elements. The implications for the rehabilitation of the disturbed ecosystem are discussed. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Artificial Recharge Through a Thick, Heterogeneous Unsaturated Zone

GROUND WATER, Issue 3 2008
John A. Izbicki
Thick, heterogeneous unsaturated zones away from large streams in desert areas have not previously been considered suitable for artificial recharge from ponds. To test the potential for recharge in these settings, 1.3 × 106 m3 of water was infiltrated through a 0.36-ha pond along Oro Grande Wash near Victorville, California, between October 2002 and January 2006. The pond overlies a regional pumping depression 117 m below land surface and is located where thickness and permeability of unsaturated deposits allowed infiltration and saturated alluvial deposits were sufficiently permeable to allow recovery of water. Because large changes in water levels caused by nearby pumping would obscure arrival of water at the water table, downward movement of water was measured using sensors in the unsaturated zone. The downward rate of water movement was initially as high as 6 m/d and decreased with depth to 0.07 m/d; the initial time to reach the water table was 3 years. After the unsaturated zone was wetted, water reached the water table in 1 year. Soluble salts and nitrate moved readily with the infiltrated water, whereas arsenic and chromium were less mobile. Numerical simulations done using the computer program TOUGH2 duplicated the downward rate of water movement, accumulation of water on perched zones, and its arrival at the water table. Assuming 10 × 106 m3 of recharge annually for 20 years, a regional ground water flow model predicted water level rises of 30 m beneath the ponds, and rises exceeding 3 m in most wells serving the nearby urban area. [source]

Sap flow of Artemisia ordosica and the influence of environmental factors in a revegetated desert area: Tengger Desert, China

Environmental factors and survival strategies of annual plant species in the Negev Desert, Israel

PLANT SPECIES BIOLOGY, Issue 2 2000
Yitzchak Gutterman
Abstract Several environmental factors have pronounced influences on the complementary sets of survival strategies, at different stages of the plant life cycle, of some of the most common annual plants in the Negev Desert, Israel. Plasticity of seed germination may spread germination over time and thus reduce the risk to species survival. This plasticity may be affected by day length during seed development and maturation and by position of seeds on mother plants. Post-seed maturation dry storage temperatures may affect the duration of after-ripening. The tiny, dust-like seeds produced by some plants that are dispersed by wind after maturation may escape massive seed predation and remain in large seed banks in the soil. Seeds of other species are protected in lignified structures in aerial seed banks on dead, dry, lignified mother plants. Seed dispersal strategies from these aerial seed banks by rain may also prevent massive seed collection by animals. The ,cautious' or ,opportunistic' germination strategy and seedling drought tolerance may increase seedling survival in many of the plant species under the unpredictable amounts and distribution of rain in these desert areas. Factors such as amount of rain, temperature, relative humidity, time of the beginning of soil wetting (day or night), seed size and history and the depth of seeds in the soil may affect germination percentages. Day length and soil water content during plant development may have a pronounced influence on plant age at first flowering, seed yield and plant life span. [source]

Settlement history in the eastern Rub al-Khali: Preliminary Report of the Dubai Desert Survey (2006,2007)

ARABIAN ARCHAEOLOGY AND EPIGRAPHY, Issue 1 2009
Jesse Casana
Regional archaeological survey in desert areas of Dubai, U.A.E., has identified numerous archaeological sites in this rapidly changing landscape. Subsurface geophysical surveys have been undertaken in concert with surface collection and test excavation to document the extent and chronology of each site. Contrary to expectations that deserts were permanently abandoned following the end of the mid-Holocene pluvial phase around 4000 BC, two sites, Al-Ashoosh and Saruq al-Hadid, show evidence of substantial occupation during the late third and early first millennia respectively. These findings suggest that the Rub al-Khali supported human settlement much later than is generally thought, challenging traditional understandings of the region's cultural and environmental histories. [source]