Mobile Dunes Research Articles

Preliminary reconstruction of the desert and sandy land distributions in China since the last interglacial period

The desert and sandy land are the products of arid climate. The spatial distribution of modern deserts and sandy land in China and their relation to climate show following characteristics: arid and hyper-arid desert zones, at isohyet of less than 200 mm, are dominated by mobile dunes; semi-arid steppe and arid desert steppe with the precipitation between 200–400 mm, are dominated by semi-fixed and fixed sand dunes; the precipitation of sub-humid forest grassland and humid forest zones with scattered fixed sand land is higher than 400 mm. With this as reference, in combination with considerable amount of paleoclimatic data in desert regions and adjacent regions, the distributions of desert and sandy land in China during the last interglacial period, the last glacial maximum (LGM), and the Holocene megathermal, were preliminarily reconstructed. The results compared with that of today show that the distribution of desert and sandy land in China was greatly dwindled during last interglacial period, and the mobile dune area was about two-thirds of that of today’s, but greatly expanded during LGM. However, the dwindling area of desert and sandy land in the Holocene megathermal was smaller than that in the last interglacial period. The forcing mechanism was mainly related to the changes of East Asian winter and summer monsoon, south-northward swing of the westerlies and the variations of the Qinghai-Tibet Plateau monsoon intensity caused by global climate changes during the cold and warm intervals since the last interglacial period.

Facilitative interactions on coastal dunes in response to seasonal weather fluctuations and benefactor size

:We analyzed spatial plant-plant associations (during three seasons: nortes, dry, and rainy) and performed a field experiment on seedling survival, in order to test whether the occurrence of facilitation varied in response to seasonal weather fluctuations and to benefactor size. In a mobile dune system (central Gulf of Mexico) we focused on the endemic early colonizer shrub Chamaecrista chamaecristoides and two late colonizer bunch grasses. Total shrub cover and density were highest during the rainy period. Density of adult Trachypogon plumosus, but not that of adult Schizachyrium scoparium, was higher beneath the canopy of the shrub. No seasonal variations in spatial associations were observed. Density of grass seedlings decreased during the nortes beneath and beyond the canopy of C. chamaecristoides. Fitness parameters of both grasses improved beneath the benefactor plants, while sand accretion decreased. The number of grass individuals benefiting from facilitation increased with shrub size except for the largest shrubs, which had a reduced density of grasses. Temperature on the sand surface was lowest beneath the larger shrubs. Our results highlight the importance of different life stages at which facilitation may occur together with a varying effect of benefactor size in the overall role of facilitation in structuring communities.

Wind tunnel simulation of aeolian sandy soil erodibility under human disturbance

Inappropriate anthropogenic activities such as overcultivation and overgrazing of steppe and excessive collection of fuelwood are largely responsible for current desertification in China. However, quantitative information concerning the impacts of human disturbance on soil erosion remains sparse. This study investigated aeolian sandy soil erodibility under human disturbance by wind tunnel simulation. The fixed aeolian sandy soils were taken from an artificial vegetation protective system on mobile dunes at the southeastern edge of the Tengger Desert. The results indicate that: (1) human disturbance such as cultivation can accelerate the erodibility of the fixed aeolian sandy soil. The ratio between total soil loss from the undisturbed soil and the cultivated soil is about 0.004; (2) surface vegetation and microbiotic crust are the main factors responsible for the natural wind erodibility of the fixed sandy soil. Wind erosion rate increases with decreasing percent of the vegetation and crust cover; (3) the grain size distribution shows a higher percentage of particles in the range >1.0 mm and a lower percentage in the range <0.05 mm for the cultivated sandy soil than for the undisturbed fixed sandy soil.

Response of three plant communities to trampling in a sand dune system in brittany (france).

Dunes that are protected because of their very rich and diverse plant communities are often exposed to excessive visitor pressure. The effects of trampling on the habitat must be known from a conservation viewpoint but also are important for management. To determine the response of plant assemblages to trampling by people, an experimental study was conducted on the state-owned dunes at Quiberon (Brittany, France). Indices of resistance and resilience were used to compare three typical plant communities belonging to the various landscape units: mobile dune, semifixed dune, and fixed dune. The strong contrasts between communities belonging to different successional stages reflect their ecological functioning. The mobile dune and semifixed dune with their low resistance contrasted with the fixed dune. Only the vegetation cover of the semifixed dune benefited from long-term trampling and had a very high resilience (134%). This response could be explained by a good balance of two opposite factors: soil compaction increasing soil stability and moisture content, and vegetation destruction. Because of their low resilience, trampling seems to be harmful for fixed dunes in the long term. The tourist pressure seems easier to integrate in to the mobile dunes and the semifixed dunes if periods of recovery are included in the management.

The blown sand disaster to the Tarim Desert Highway in Xinjiang, China

The Tarim Desert Highway in Xinjiang, China, the longest one in the world, has a length of 562 km, about 80% of which runs across, from north to south, the Taklimakan Desert. Obviously, the main problem of the road maintenance is the blown sand disaster. The research results showed: (1) the physical environment along the desert highway is characterized by strong winds, fine and loose ground materials, different dunes and so on, which provides the dynamical condition and material source for the formation of blown sand disaster to the road and its shelter system. Meanwhile, the trend and cross-section of the road and the structure of the shelter system, as damage objects, play important roles in the formation process of blown sand disaster; (2) the blown sand disaster to the shelter system is original from the intrusion of the drift sands and mobile dunes outside the shelter system, and the wind erosion and sand deposit caused by the air stream changes on the ground in the shelter system. The main damage object in the Tarim Desert Highway is the shelter system presently. The damage forms include wind erosion, sand burying and dune covering; and (3) the damaged length of the blocking sand fences is 83.7%, 88.4%, 72.4%, 72.8% and 40.3% and the damaged area of the straw checkerboard belts is 73.1%, 58.2%, 44.5%, 35.4% and 36.6%, in turn, in 5 different landform units from north to south, and, the disasters to fences and the straw checkerboard belts are 79.5% and 57.6% in the compound dunes while they are 64.6% and 37.7% in the interdunes

Strategies to combat desertification for the twenty-first century in China

SUMMARY During the past half century, China has experienced increasingly severe land degradation, soil erosion, and desert expansion. Desertification is affecting one third of China's total territory and the annual accelerating rate of desertification spread is as high as 2460 km2 in China. In 1996, China developed a National Action Programme to Combat Desertification (NAP), which is aimed to apply new legal measures and technical approaches to slow down desertification processes and achieve a long-term goal — control desertification and alleviate poverty through continuous efforts to fight against desertification, stabilize mobile dunes, revegetate degraded rangeland and control soil erosion in arid, semi-arid, and dry sub-humid areas. The long-term and integrated strategies of China's NAP result in encouragement of social participation, legal institutional guarantees, policy making, and establishment of demonstrations/pilot projects to combat desertification at both national and provincial level.

Photosynthetic Pathways, Life Forms, and Reproductive Types for Forage Species Along the Desertification Gradient on Hunshandake Desert, North China

Floristic compositions, life forms, reproductive types for forage species, and their responses to desertification in Hunshandake desert were studied. 164 species, in 30 families and 94 genera, were identified with C3 (137 species), C4 (25 species), and CAM (2 species) photosynthesis. Of the 25 C4 species, 76 % were grasses and Chenopodiaceae species (hereafter chenopods). This suggests that the C4 species mainly occurred in a few families in the desert region. The reduction of C3 species and the increase of C4 species with desertification indicated that C4 species might have higher tolerance to environmental stresses (e.g. dry and poor soil). Relatively more hemicrytophyte and therophyte forms in the desert are related to the local temperate climate and vegetation dynamics. Relatively greater proportions of C4/C3 and clonal species/sexual species at mobile dune showed that the C4 species and clonal species could make greater contribution to sand land restoration in the Hunshandake desert.

A Erosão Praial na Costa Atlântica Uruguaia

The Uruguayan Atlantic coast is wave dominated. It appears as a sequence of beaches built between rocky headlands showing all ranges of morphodynamic behaviors from reflective to dissipative. Several beaches are undergoing erosion. All of them coincide with urbanized areas. In most cases the causes have not been established yet but there is no doubt that human activities have contributed to such problems. This fact raises the question about the nature of the erosion process. Does location of beaches under erosion on urbanized areas prove the man-induced origin of it? This paper discusses the possible factors involved on the beach erosion process. Sediment inputs to the beaches are limited. The inner shelf is likely to be the main source as it is covered with sandy sediments and shows a low gradient relief. The most significant continental source are the gullies although this remains a controversial issue as sediments eroded from them are usually finer than beach sediments. Anyway, as minor as it might be, this input contributes positively to the beach sediment budget. Sediment losses occur mainly by the inland migration of dunes and human activities. The latter includes the occupation of the backshore and frontal dunes, the building of seawalls, revetments and other hard structures to protect the houses, and the fixation of mobile dunes by planting. Pinus and Eucalyptus forests. Possible natural causes for beach erosion include storm surges and concentration of wave energy due to wave refraction. The latter hypothesis arouse in this research from wave refraction diagrams that showed a strong influence of the shelf relief on wave climate.

Shifting-Sand Control in Central Tibet

The middle reaches of the Yarlung Zangbo, the Lhasa, and the Nianchu rivers form the center of politics, economy, and culture in the Tibetan Autonomous Region. Due to the fragility of the natural environment and overexploitation of land by the local people, desertification is becoming a serious problem in the valleys. Shifting sands cover an area of 578 km2 and have caused problems such as damage to farmland and grassland, traffic blockage and burying of water projects. This paper discusses strategies and techniques for combating shifting sands, including reformation of the agricultural structure, exploitation of new sources of energy, and combinations of mechanical and biotic measures. Using mechanical measures, straw barriers, and gravel layer covers, artificial vegetation can be established on the mobile sand dune by sowing and planting introduced species.

The role of European marram grass in dune stabilization and succession near Cape Agulhas, South Africa

The coastline near the southern tip of Africa is characterized by large mobile dunes that are driven along wide beaches by strong winds throughout the year. This results in the blockage of the river mouths causing severe flooding of the low-lying farmland of the Agulhas Plain during the rainy winter season. Large parts of the driftsands were stabilized with the European dune pioneer species Marram grass (Ammophila arenaria), which has proved highly invasive along the North American west coast. In order to establish the potential invasiveness ofA. arenaria in South African coastal dune systems and its role in the succession of a large stabilization area, studies were carried out on De Mond Nature Reverve. Using aerial photos, maps and planting records, the vegetation of sites of various ages were sampled. By means of this chronosequence of stands, there is clear evidence that succession takes place at De Mond. Four communities are distinguished, varying from recent plantings ofA. arenaria to mature dune thicket or dune fynbos (heath) vegetation. These relate to four different stages of succession,A. arenaria occurring in reduced abundance in the older communities. After 50 years, formerA. arenaria areas are usually covered by dense dune scrub and in some places even in asteraceous dune fynbos. Succession is most rapid in sheltered, moist dune slacks, butA. arenaria remains vigorous in conditions favourable for its growht, i.e. on exposed, steep dune slopes with strong sand movement.A. arenaria does not appear to spread unaidedly at De Mond and has been successfully used for temporary dune stabilization.

A study on micro-fungi in arid areas: Notes on soil saprotrophs and animal opportunistic pathogens

ABSTRACT Soil fungi were studied in three desert areas in Namibia with the aim of identifying saprotrophic microorganisms associated with animal communities as opportunistic pathogens. The extremely arid environment of the Naukluft Desert Park was found to be more selective for soil fungi, whereas the soils of Etosha Pan, with seasonal wet areas, and the mobile dunes of Sossousvlei, which absorb atmospheric moisture at night by virtue of their proximity to the sea, host saprotrophic microorganisms and potential and/or opportunistic pathogens.

Galium aparine L.

Galiun L., Section KOLGYDA Dumort. (Section Aparine Koch). An annual herb with prostrate or, more usually, scrambling-ascending diffusely branched stems 15-300cm, stout and hairy at the nodes, the four angles very rough with downwardly directed prickles. Leaves 12-60 x 3-8 mm, in whorls of 6-9, narrowly to widely oblanceolate or elliptical, mucronate, 1-veined, glabrous or with hooked bristles above, margins rough with backward-pointing prickles. Flowers 1.5 mm diameter in 2-5-flowered axillary cymes, their peduncles topped by a whorl of 4-8 bracts; hermaphrodite, sometimes male (andromonoecious). Calyx a minute annular ridge; corolla 1.5-1.7 mm in diameter, whitish, with four acute lobes. Stamens 4, exserted; styles 2, short, connate below; stigmas capitate. Two-seeded fruits with length of longest axis 3-5 mm (excluding setae), wider than the corolla, olive or purplish, covered with white hooked setae with tuberculate bases, their stalks divaricate. Mature fruit a dry mericarp with length of longest axis 2-3 mm, and a mean airdry mass of 9.65 mg ? 0.33 (10 samples of 100 from a hedgerow population). Salisbury (1974) reports the average mass of seed from shade-tolerant woodland and hedgerow plants as 3.7 mg, and Grime et al. (1988) record a mean seed mass of 7.25mg for a hedgerow population. Galiumn iparine is a highly variable species owing to a combination of phenotypic plasticity and genecological variation. The species has different responses to the environment corresponding to different environmentally conditioned life cycles [see VI (e)]; plasticity in the timing of seed germination, productivity, growth form, freezing tolerance, and the light and temperature dependence of photosynthesis enable G. apa7ine to establish itself in a wide variety of habitats. Potential variability concealed in the higher polyploid conditions, especially in the widespread hexaploids [see VI (d)], enabling them to respond to changing environmental conditions, is probably also the basis of their success. Among plants of G. apariine raised from seed collected from various sites in continental Europe, B6cher etal. (1955) distinguished at least five different climatic ecotypes or races that either may be discrete or more probably ranges of a large clinal variation: mediterranean, summer-annual (seed germinates in the spring) with accelerated development from Portugal; mediterranean, biennial from Spain; southern, winterto summer-annual from France; northern, rather late flowering winterto summerannual from Denmark and Poland; and northern, very late flowering winter-annual (seed germinates in autumn) from Denmark and Sweden. Ecotypes of G. aparine have been demonstrated by Berkefeld (1988), differing in shape of cotyledons, hairiness of stems, colour of stem edges and length of fruit spines in plants grown under uniform garden conditions from seed collected in several different habitats. In Britain, two discrete ecotypes of G. apa7i71e exist, one found in arable fields or open situations and the other growing in hedgerows (FroudWilliams 1985); the two ecotypes are very similar morphologically but differ markedly in seed dormancy and germination requirements [see VIII (d)]. Bain & Attridge (1988) provide evidence of genotypic differences in shade strategies between hedgerow and field populations [see VI (e)]. Two forms have been recognized, the rarer G. aparine f. interimediwan Bonnet, with smooth or tuberculate fruits without spiny hairs, and the common form G. apar-ine f. apari71e with spiny fruits (Moore 1975). Variants of G. spur-ium with setose fruits, apart from the flower characters and the diploid chromosome number, are often not easy to distinguish from G. caparine and have been described as G. spuritini ssp. infestlin (Hanf 1983). Galiuiml apariine is native on maritime shingle beaches, in primary tall-herb fen communities, and in primary alderwood in natural hydrarch successions, but is also a very variable cosmopolitan weed found in hedges, waste places, drained fen peat, on limestone scree, roadside verges, river and stream banks, and is a major arable weed, especially of cereal crops. *Abbreviated references are used for standard works, see Jolurnal of Ecology (1975), 63, 335-344. Nomenclature of vascular plants follows Florca Euri0opaea and Stace (1997) for British species.

Autecological traits ofHalimium halimifolium in contrasting habitats under a Mediterranean type climate—A review

Halimium halimifolium (L.) WILLK. is a woody Cistaceae species occurring locally in the Western Mediterranean. At the Doiiana National Park (S Atlantic coast of Spain), Halimium halimifolium is the main component of stable sand vegetation. It grows in a range of environmental conditions from flood-prone depressions to mobile dunes, but it is most abundant, and dominates the scrub composition on the slopes of fixed dune ridges with a water table depth of 2 to 4 m. The species exhibits not only morphological modifications (hairy leaves and twigs), but also structural and ecophysiological adaptations. The response of H. halimifolium to stress conditions (leaf water potential, leaf diffusion resistance, and plant growth) have been studied in the field, throughout an annual cycle in four populations growing in different environments, three dune types differing in soil moisture, and one dune slack. Results showed that plants from the hygrophytic area (MN) had the less negative water potentials, the lowest stomatal resistances and the biggest vegetative growth, together with the highest Leaf Area Index, canopy light extinction, the largest leaf area and the lowest sclerophyll index. Plants from the most xerophytic area (MB) had the lowest Leaf Area Index, the smallest leaf area and the highest sclerophyll index. Even though in dune slopes (MI) water table was shallower than in MB, plants in the latter had more negative water potentials and bigger vegetative growth. Water potential values only exhibited significant differences among the four populations at the end of the spring period and over the summer. These results are discussed in relation to the climatic conditions of the study period (3 years of a drought cycle). Plants from the mobile dune system showed features which were intermediate between MN and MI plants.

Responses of dune mosses to experimental burial by sand under natural and greenhouse conditions

Sand movement is a predominant feature of mobile coastal and lake-shoreline sand dunes. Plants growing in these environments are able to withstand and survive periods of burial by sand. Although mosses are important dune stabilizers in temperate dunes, there are few studies focused on their response to burial by sand. In this study we examined the effects of burial by sand on 11 moss species that grow naturally on Lake Huron sand dunes and occur in a gradient of habitats from the foredunes along the shore to forested areas. Artificial burial treatments (sand depth of 0, 1, 3, 5 and 7 cm) were imposed under greenhouse and field conditions. We measured final plant cover and calculated the speed of emergence and an interpretive index (tolerance index) to compare burial responses among species by calculating a burial ratio which standardized the initial size of each species. In the greenhouse, Ceratodon purpureus and Ditrichum flexicaule recorded the highest mean speeds of emergence and Dicranum scoparium, Plagiothecium laetum, Dicranum flagellare and Brachythecium sp. 1 the lowest. In the field the trends were similar although the speed of emergence was much slower. Three types of response to burial were evident in plant cover: neutral, inhibition and stimulation. Although all eleven studied species were able to emerge from the different depths of burial, we observed that species colonizing areas with high sand mobility and deposition (C. purpureus and D. flexicaule) were the most tolerant and emerged from depths of up to 35 times their height. Species growing inland, at the base of trees (Dicranum scoparium, Brachythecium sp. 2, Plagiomnium cuspidatum and Dicranum flagellare) showed the least tolerance of burial.

Sustainability of reclaimed desertified land in Ningxia, China

Desertification is a severe environmental problem in north-central China, where deserts are expanding at an estimated rate of 2100km2year−1. The Chinese government approved plans to control 6·66 million ha of desertified land in 10 years. Techniques used include planting of trees, shrubs and grasses; land enclosure; irrigation; extraction of buried soils; and stabilization of dunes with straw checkerboards. These efforts are co-ordinated by the Institute of Desert Research of Academia Sinica (IDRAS). Some of the pioneering work was carried out at Shapotou and Yanchi Research Stations in Ningxia Autonomous Region. Community action is one of the cornerstones of reclamation. In 1978 the Chinese government initiated the Shelterbelt Development Program to form a ‘Green Great Wall’ of 35 million ha of trees stretching 700km across northern China. At Shapotou, sand dunes irrigated with silt-laden water have developed 30cm of minero-organic topsoil in 25 years. Using a chronosequence of these reclaimed soils, chemical analysis showed progressive increases in nutrients. These reclaimed areas produce high yields of cereals, vegetables, grapes and deciduous fruits. Use of straw checkerboards and planting of indigenous shrubs have established a stabilized ecosystem on mobile dunes of the Tengger Desert. In the Shabianzi Region 74 families in a resettlement project have worked collectively on sand stabilization and steppe reclamation. Farmers levelled dunes and manually excavated buried soils. A chronosequence of land reclaimed and cultivated between 1983 and 1991 showed sustainable increases in soil nutrients. Soil fertility in these reclaimed desertified lands is sustainable but places high demands on resources. These and other examples show what is achievable, but, unfortunately, desertification rates exceed reclamation rates.

The vegetation of linear desert dunes in the north-western Negev, Israel

Summary In 1992 the flora and vegetation of an area of linear sand dunes at Nizzana, western Negev desert, Israel, was investigated. Seven different plant communities were found and a vegetation map of the research area was produced. The plant communities were distinguished by only the dominating perennial species. Nevertheless, the results of the study indicate, that also annual species may be suitable as a tool to distinguish between desert plant communities The results suggest, that the most important environmental factor determining patterns of plant distribution in the Nizzana research site is the structure and dynamics of the soil-surface. Vegetation cover was lowest in highly stable areas with hard surface crust or a high amount of fines in the soil (playas) and on the mobile dune tops. Highest plant cover was found at the dune bases and in areas which had been used for cultivation in former times. Mean species richness per unit area was lowest on the dune tops and highest in the interdune areas with more or less stable surface crust. Absolute number of species found was highest for the playas and lowest on the dune-tops. As most of the plant communities described for the research site are restricted to areas which are characterized by a certain surface stability it is discussed to regard some of the vegetation units as succession stages in a process of continuing stabilization of the dunes.

Arbuscular mycorrhizae in a tropical sand dune ecosystem on the Gulf of Mexico

Root samples of 37 species distributed on the beach and along a successional gradient (from mobile to stabilized areas) in a tropical sand dune system on the Gulf of Mexico showed that 97% of the species were mycorrhizal. The mycorrhizal inoculum potential of the sand from several dune areas was compared using two different bioassays. Firstly, the field rate of colonization by arbuscular mycorrhizal fungi of Chamaecrista chamaecristoides seedlings transplanted to random plots in the foredunes and in the mobile area was measured. The seedlings were harvested at intervals during 3 weeks to record mycorrhizal structures. In the mobile area, no mycorrhizal colonization was observed during the experiment. In the foredunes, hyphae and external mycelium were present in 40% of the seedlings as early as 8 days after transplanting. After 15 days, arbuscules and vesicles were observed in 60 and 20% of the seedlings, respectively, and after 21 days, 100, 46 and 20% of the seedlings showed hyphae, arbuscules and vesicles, respectively. Secondly, maize seedlings were transplanted to pots previously filled with sand from the foredunes, mobile dunes, grassland and a Dyphisa robinoides shrub area. After 1 month, the lowest mycorrhizal inoculum potential was recorded for the mobile dunes and the highest for the shrub area. As expected, mycorrhizal inoculum potential increased with dune stabilization.

Habitat associations of coastal wintering passerines

The species composition, relative abundance and vegetation community associations of a wintering passerine assemblage were studied on 7 sites in north Norfolk between 1989 and 1994. A total of 20 species was recorded including coastal specialists as well as habitat generalists; relative abundance varied greatly from Chaffinch and Great Tit with single records, to Twite and Skylark with many hundreds. Most species showed strong association with, and aversion to, particular vegetation community types, but the relationships with vegetation communities varied between species. The communities with the higher bird densities were Limonium, Suaeda vera and Suaeda/Salicornia saltmarshes. Amongst the least used vegetation communities were Halimione saltmarsh and mobile dunes. There was little evidence of any seasonal change in habitat associations. The findings are discussed both in terms of vegetation community availability in north Norfolk and in the wider context of coastal zone planning and the threats and opportunities open to wintering passerines by differing responses to sea-level rise in eastern England.

Coastal dunes: sensitive or not?

This paper introduces a classification of coastal dune systems into two main morphodynamic classes, namely retentive and transgressive dune systems. Retentive systems include coastal dune types where sand accumulation within vegetation is dominant over other processes. In this category we include such morphological types as hummock dunes, foredunes, and retention ridges, including sub-environments such as precipitation ridges that form the landward boundary of transgressive dunefields. Transgressive systems include those coastal dune types where sand transport is dominant over other processes, and the dunes are unvegetated and mobile. In this category we include such morphological types as parabolic dunes, reversing transverse dunes, barchans, seif dunes, transgressive sheet dunefields and headland-bypass dunefields. Components of the two main morphodynamic types of coastal dune systems range in sensitivity from sensitive to robust. Retentive dune systems, being vegetated, are sensitive and fragile. Mobile dunes that form the major component of transgressive dune systems are robust and resilient. This morphodynamic classification is particularly useful because the two types of dune systems have diametrically opposed sensitivities and hence different management requirements.

VERTICAL DISTRIBUTION OF WIND-BLOWN SAND FLUX IN THE SURFACE LAYER, TAKLAMAKAN DESERT, CENTRAL ASIA

The vertical distribution of the wind-blown sand flux in a 40-cm flow layer above the ground surface was investigated through laboratory wind-tunnel tests and field measurements on the mobile dune surface during sand storms in the Taklamakan Desert of China. Results show that vertical distribution of the horizontal mass flux of drifting sand is a discontinuous function of height. More than 90% of the total material is transported in the flow layer from the surface to 14 cm. From 2 to 4 cm above the surface, a distinct transition zone occurs wherein mixed transport by creep, saltation, and suspension becomes saltation and suspension. The flow layer from 14 to 15 cm represents a further transition from saltation to suspension, where the distribution curves of the transport rate against height converge. The basic natural exponential function cannot describe well the vertical distribution of the saltation mass flux in the Taklamakan Desert. As a function of height, saltation mass flux follows a function qsalt...