The Sources of Moisture in the Sand Dunes – The Example of the Western Sahara Dune Field

Abstract Climatic and meteorological conditions may limit the aeolian transport within barchans. An explanation of that issue was the main goal of the investigation held in Western Sahara dune fields located around Tarfaya and Laâyoune. Particular attention was paid to the factors causing the moisture content rising of the sand dune surface layer, which could influence the wind threshold shear velocity in the aeolian transport. The wetted surface layer of sand, when receiving moisture from precipitation or suspensions, reduces the aeolian transport, even in case of wind velocity above 4-5 m s-1. Fog and dew condensation does not affect the moisture of deeper sand layers, what occurs after rainfall.

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Studies of the Dry Surface Layer in a Sand Dune Field

Journal of Agricultural Meteorology ◽

10.2480/agrmet.42.113 ◽

1986 ◽

Vol 42 (2) ◽

pp. 113-118 ◽

Cited By ~ 4

Author(s):

Tetsuo KOBAYASHI ◽

Akiyoshi MATSUDA ◽

Makio KAMICHIKA ◽

Tomoaki SATO

Keyword(s):

Surface Layer ◽

Sand Dune ◽

Dune Field

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Geomorphological characteristics of the sand-dune field of the central Kyparissiakos Gulf

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.17056 ◽

2007 ◽

Vol 40 (4) ◽

pp. 1530 ◽

Cited By ~ 2

Author(s):

Th. Karamousalis ◽

S. Poulos ◽

H. Maroukian ◽

G. Ghionis

Keyword(s):

Sand Dune ◽

Sand Dunes ◽

Fine Sand ◽

Middle Part ◽

Alluvial Fan ◽

Last Glacial Period ◽

Dune Field ◽

Natural Processes ◽

Dune Ridge ◽

The Last Glacial

Sand dunes are sensitive coastal landforms closely related to the evolution (and/or stability) of the beach zone. The present work refers to the central part of the dune field that lies along the middle part of the shoreline of the Kyparissiakos Gulf. The scope of the present investigation is to reveal the geomorphological and sedimentological characteristics of the sand dune field in association with the natural processes contributing to their formation. On the basis of our findings, the dune field of the central Kyparissiakos Gulf consists of four dune ridges, with heights >4.0 m. Their extent indicates the availability of large quantities of sand and the existence of a rather stable wind field. They consist of well sorted medium to fine sand. The alluvial fan of the Zachareiko torrential river has covered the dune field in the area of its mouth and buried the oldest 4th dune ridge to its south. The development of the dune field is estimated to have taken place during the last 3-4 thousand years subsequently to the completion of the rapid sea level rise at the end of the last glacial period.

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Population differentiation of the Stellaria longipes complex within Saskatchewan's Athabasca sand dunes

Canadian Journal of Botany ◽

10.1139/b87-235 ◽

1987 ◽

Vol 65 (8) ◽

pp. 1726-1732 ◽

Cited By ~ 9

Author(s):

S. Ellen Macdonald ◽

C. C. Chinnappa ◽

David M. Reid ◽

Brett G. Purdy

Keyword(s):

Selection Pressure ◽

Sand Dune ◽

Reproductive Output ◽

Sand Dunes ◽

Common Garden ◽

Fine Sand ◽

Morphological Characters ◽

Genetic Isolation ◽

Dune Field ◽

Reciprocal Transplants

Stellaria arenicola, a recent derivative within the S. longipes complex, is an endemic of the Athabasca sand dunes. Analysis of 11 morphological characters on 40 genets showed that both the endemic and parental (S. longipes) species are present within the Thomson Bay dune field and that the two forms are distinct. Individuals of S. arenicola were distinguished by only a few characters, typically, large yellow capsules with reflexed teeth and yellowish leaf and stem pigmentation. The endemic also exhibited a higher sexual reproductive output. Many characteristics of vegetative morphology showed plasticity in both species, but the two remained distinct when grown in a common garden. On the sand dunes S. longipes is restricted to beach dunes bordering Lake Athabasca while S. arenicola is predominant on the active dune field inland. The two dune systems represented environmentally distinct microhabitats. The active inner dunes were characterized by an unstable, fine sand substrate and intense insolation. Field reciprocal transplants showed S. longipes was selected against in the inner dune habitat, while S. arenicola performed relatively well on the beach. Stellaria arenicola possibly arose in the active sand dune habitat as a result of selection pressure and genetic isolation.

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Studies of the dry surface layer in a sand dune field. (2). Effects of soil temperature gradients on the water content profiles in the dry surface layer.

Journal of Agricultural Meteorology ◽

10.2480/agrmet.43.121 ◽

1987 ◽

Vol 43 (2) ◽

pp. 121-126

Author(s):

Tetsuo KOBAYASHI ◽

Akiyoshi MATSUDA ◽

Makio KAMICHIKA

Keyword(s):

Surface Layer ◽

Soil Temperature ◽

Water Content ◽

Sand Dune ◽

Temperature Gradients ◽

Dune Field

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Numerical simulation of wind field and sand flux in crescentic sand dunes

Scientific Reports ◽

10.1038/s41598-021-84509-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Huiwen Zhang ◽

Zhen Wu ◽

Jing Hu ◽

Zhiping Zhang ◽

Bin Xiao ◽

...

Keyword(s):

Wind Velocity ◽

Wind Field ◽

Sand Dune ◽

Eddy Currents ◽

Sand Dunes ◽

Turbulent Intensity ◽

Leeward Side ◽

Wind Flow ◽

Simulation Results ◽

Sand Flux

AbstractSand flux is the key factor to determine the migration of sand dunes and the erosion to the surrounding environment. There are crescent-shaped sand dunes of various scales in the desert, and there are significant differences in spatial wind field and sand flux among them. However, due to the difficulty of monitoring, it is difficult to continuously observe the spatial wind field and sand flux around the larger crescentic dunes. On the basis of the Reynolds-Average Navier–Stokes (RA-NS) equation and the stress and sand flux model, the distribution of wind field and sand flux of a circular dune with a height of 4.2 m and a length of about 100 m during the four evolutionary periods of the evolution into a crescentic dune was simulated in this study. By comparing with the measured results, we verified that the closer to the leeward side, the more the simulated values of the velocity in wind field and sand flux were in line with the measured results. In order to further analyze the influence of the height of dune and other relevant parameters on sand flux, we simulated the influence on wind field and sand flux by changing the air viscosity and wind velocity of upper boundary. We found that the air viscosity mainly affected the amount of deposited sand on the leeward side of sand dune, while the increase of wind velocity would undoubtedly increase the sand flux of the whole sand dune. In addition, the simulation results also showed that the influence of changes in height of dune on the turbulent intensity of leeward side was very significant, and the turbulent intensity increased with the height of dune. The height changes of tall dunes gradually affected the transport of sand caused by wind flow behind the leeward side because that the rotation of the wind flow would form new vortexes at the large pores behind the leeward side, which would increase the turbulent energy in space and thus would increase the distance of migration of the lifting sand. While the low sand dunes could not form extra small vortexes at the bottom of the leeward side, so the wind velocity was small and the eddy currents behind the leeward side were more stable. The simulation results indicated that wind velocity was not the only reason for increasing the amount of sand flux, and the fluctuation of wind flow caused by turbulence could also stimulate the movement of sand particles on the ground.

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PREDICTION OF WIND-DRIVEN TRANSPORT RATE

Coastal Engineering Proceedings ◽

10.9753/icce.v20.117 ◽

1986 ◽

Vol 1 (20) ◽

pp. 117

Author(s):

D.H. Swart

Keyword(s):

Sand Dune ◽

Management Strategies ◽

Transport Rate ◽

Sand Transport ◽

Aeolian Transport ◽

Dune Field ◽

Best Estimate ◽

Effective Manner ◽

Sand Movement ◽

The Subject

The rate of wind-driven sand movement in a dune field is an important parameter needed to establish management strategies for sand dune fields. Until recently not much attention has been given in engineering circles to the possible effect of wind-blown sand transport. However, there is a wealth of literature on the subject which goes back as far as 1936. A study of literature reveals that there are at least 16 formulae for the prediction of the aeolian transport rates which are readily available. This paper describes a technique which utilizes these 16 formulae in the most effective manner for predicting the best estimate of the potential wind-blown transport rate. Restrictions on the applicability of the method are discussed and fields for further research are recommended.

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Barley seed storage under controlled conditions

Genetičnì resursi roslin (Plant Genetic Resources) ◽

10.36814/pgr.2019.25.11 ◽

2019 ◽

pp. 140-150 ◽

Cited By ~ 1

Author(s):

O. A. Zadorozhna ◽

T. P. Shyianova ◽

M.Yu. Skorokhodov

Keyword(s):

Hordeum Vulgare ◽

Moisture Content ◽

Spring Barley ◽

Seed Storage ◽

Growing Season ◽

Storage Conditions ◽

Meteorological Conditions ◽

Hordeum Vulgare L ◽

The Relationship ◽

And Storage

Seed longevity of 76 spring barley gene pool samples (Hordeum vulgare L. subsp. distichon, convar. distichon: 56 nutans Schubl., two deficience (Steud.) Koern., two erectum Rode ex Shuebl., two medicum Koern.; convar. nudum (L.) A.Trof.: one nudum L. та subsp. vulgare: convar. vulgare: nine pallidum Ser., three rikotense Regel.; convar. coeleste (L.) A.Trof.: one coeleste (L.) A.Trof.) from 26 countries, 11 years and four places of reproduction was analyzed. Seeds with 5–8% moisture content were stored in chamber with unregulated and 4oC temperature. The possibility of seed storage under these conditions for at least 10 years without significant changes in germination has been established. The importance of meteorological conditions in the formation and ripening of seeds for their longevity is confirmed. The relationship between the decrease of barley seeds longevity and storage conditions, amount of rainfall, temperature regime during the growing season of plants is discussed.

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Seedling desiccation tolerance of Leymus racemosus (Poaceae) (wild rye), a perennial sand-dune grass inhabiting the Junggar Basin of Xinjiang, China

Seed Science Research ◽

10.1079/ssr2004172 ◽

2004 ◽

Vol 14 (2) ◽

pp. 233-239 ◽

Cited By ~ 6

Author(s):

Zhenying Huang ◽

Yitzchak Gutterman

Keyword(s):

Desiccation Tolerance ◽

Sand Dune ◽

Sand Dunes ◽

Perennial Grass ◽

Junggar Basin ◽

Seedling Development ◽

Ecological Implications ◽

Leymus Racemosus ◽

Seedling Desiccation Tolerance ◽

Dune Grass

Leymus Racemosus, The Mammoth Wild Rye, Is A Rhizomatous Perennial Grass, Mainly Distributed In The Moving Or Semi-Stabilized Sand Dunes In Deserts Of The Junggar Basin In Xinjiang, China. The Revival Ability Of The Young Seedling After Periods Of Desiccation Can Be Influenced By Several Factors: (1) The Stage Of Seedling Development – The Later The Stage At Dehydration, The Longer The Root Length And The Lower Is The Percentage Of Seedlings That Survive; (2) The Length Of The Period Of Desiccation – The Longer The Period That The Seedlings Are Under Desiccation, The Lower Is The Percentage Of Seedlings That Survive; (3) Endosperm Size – The Smaller The Proportion Of Endosperm That Remains In The Caryopses, The Lower Is The Percentage Of Seedlings That Revive, Determined By (A) The Stage Of Seedling Development, And (B) The Proportion Of The Endosperm That Is Removed By Cutting; And (4) Caryopsis Size – The Larger The Polymorphic Caryopses, The Higher Is The Percentage Of Young Seedlings That Revive From Periods Of Desiccation. The Physiological And Ecological Implications Of L. Racemosus Seedling Desiccation Tolerance Are That Under Extreme Desert And Unpredictable Environmental Conditions, The Chances Of Seedling Establishment Are Increased.

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