نتایج جستجو برای: dune sand
تعداد نتایج: 29993 فیلتر نتایج به سال:
Deserts are one of the major landforms on the Earth. While deserts occupy about one-fifth of Earth’s land surface, they have been studied to a much lesser extent. All over the world, desert landforms are expanding ever rapidly and more and more human settlements are finding place in desert regions for habitation. Thus, quantifying and monitoring dunes becomes more relevant from a managerial per...
Coastal sand dunes are extremely dynamic ecosystems, characterized by stark ecological succession gradients. Dune stabilization is mainly attributed to plant growth, but the establishment and survival of dune-inhabiting vegetation is closely linked to soil microorganisms and to the ecological functions they fulfill. Fungi are particularly important in this context, as some interact intimately w...
ion, afforestation, urbanisation (Grootjans et al. 1998; Martinez et al., 2004; Provoost 106 et al., 2011), nitrogen deposition (Jones et al., 2004; Plassmann et al., 2008; Sival and 107 Strijkstra-Kalk, 1999) and from grass and scrub encroachment or exotic species invasion 108 (Martinez et al., 2004). In addition, changes in evapotranspiration due to vegetation change or 109 management will af...
Apollo-Soyuz photographs of the Monte Desert in southeastern San Juan, Argentina, were used for a reconnaissance survey of large-scale desert landforms. The Apollo-Soyuz color photographs were helpful in distinguishing lineaments and probable faults, drainage patterns, rock types, and soil-tonal variations. These photographs were especially useful in studying the distribution of sand deposits a...
Saharo-Arabian deserts includes large expanses of sand dunes called ergs. These dunes are formed and constantly reshaped by prevailing winds. In this paper, we use backscatter (σo) measurements observed at various azimuth angles from SeaWinds scatterometer (QSCAT) and ERS scatterometer (ESCAT) to determine the σo azimuthal modulation over the sand dunes. A second order harmonic equation is used...
We apply a model for sand dunes to calculate formation of dunes on Mars under the present Martian atmospheric conditions. We find that different dune shapes as those imaged by Mars Global Surveyor could have been formed by the action of sand-moving winds occurring on today's Mars. Our calculations show, however, that Martian dunes could be only formed due to the higher efficiency of Martian win...
Seasonal periodicity of seed germination and its relationship to seasonal changes in temperature and soil moisture have been well studied in seeds of species with physiological dormancy. However, relatively little information is available on the role of these environmental factors in controlling germination of seeds with physical dormancy (PY). Our primary aim was to determine if seeds of the c...
Kashan Erg is one of the most important sand dunes complexes in Iran. Due to erosive winds, always, Erg's marginal areas are faced to the transition of moving sands. So, in this research, the sand dune activity was investigated by Lancaster index. In this line, Erg's morphology map was prepared using aerial photographic, Google earth software and field observations. Then, maps of iso...
Sand dunes are found in a wide variety of shapes in deserts and coasts, and also on the planet Mars. The basic mechanisms of dune formation could be incorporated into a continuum saltation model, which successfully reproduced the shape of the barchan dunes and has been also applied to calculate interaction of barchans in a field. We have recently extended our dune model to investigate other dun...
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