Interdune Lowlands Research Articles

Vegetation pattern in shell ridge island in China’s Yellow River Delta

In general, coastal habitat conditions are extremely harsh, with the ecological equilibrium inextricably related to the plant community. Understanding the natural vegetation features of a coastal zone with little human disturbance could provide a reference for future vegetation restoration and ecosystem maintenance services. In this study, the vegetation patterns of Wangzi Shell Ridge Island in the Yellow River Delta were investigated. A total of 35 taxa of vascular plants were documented, representing 15 families and 33 genera (of which most were mono-specific). Surveys identified only one to eight taxa in each plot. From sea to land, the vegetation showed a typical zonal distribution pattern. There was a correlation between the landform and important factors that influenced the plants including soil factors and distance from the sea. Thus, the taxa distribution and vegetation had a significant correlation with landform. The dune crest, backdune and interdune lowlands were areas with weak storm surges and were the important locations for the taxa to be become established. Plants along the high-tide line formed important defenses from large waves and high winds. The significant protection provided a suitable living environment for many organisms with high medicinal value. Special attention and protection could be provided to this area by reducing the use of the beach road and enclosing the complete section from sea to land with a protective fence. In addition, vegetation protection and restoration on Shell Ridge Island would aid in the formulation and implementation of reintroduction strategies for similar vegetation in similar habitats.

Stable oxygen isotopes reveal distinct water use patterns of two Haloxylon species in the Gurbantonggut Desert

Haloxylon ammodendron and Haloxylon persicum are the dominant species in the Gurbantonggut Desert, China, with the former grows at inter-dune lowland and the later grows at the sand dune. This study aims to investigate the dynamics of water usage of the two species and their responses to the soil water fluctuations resulting from summer precipitation. Oxygen isotope ratios (δ 18O) were measured for xylem water, soil water in different soil layers (0–300 cm), precipitation water and groundwater. Four potential water sources were identified: shallow (0–40 cm), middle (40–100 cm) and deep soil water (100–300 cm), as well as groundwater. The water sources used by the two species were calculated using the IsoSource model. When the upper soil water was abundant in early spring, H. ammodendron mainly used shallow soil water while H. persicum mainly used middle soil water; when the upper soil water was depleted in summer, H. ammodendron mainly used groundwater while H. persicum mainly used deep soil water. Both species were conservative in using shallow soil water following the relatively large summer precipitations. The two Haloxylon species had distinct water use patterns during the growing season, which reflects their adaptations to their specific habitats in this water-limited desert environment. Large precipitations in dry summer hardly altered their water use patterns, which mean that these species are rather conservative in water use strategy.

Effects of different restoration measures and sand dune topography on short- and long-term vegetation restoration in northeast China

Our study investigated the effects of different restoration measures and sand dune topography on vegetation restoration in the Horqin Sandy Land, China. We conducted a vegetation survey at different topographic positions on sand dunes at four different types of restoration sites (i.e., grazing-exclusion, shrub-planting, pine-planting, and poplar-planting sites) with restoration periods of ≤35 years and two control sites (i.e., shifting sand dunes and fixed sand dunes). We found a restoration trajectory, starting from shifting sand dunes and aligning all the sites in chronological order. Five restoration phases were identified by distinct species composition in the trajectory. The planting of trees progressed vegetation restoration faster than livestock exclusion and the planting of shrubs. The planting of trees restored shifting sand dunes to the same level of fixed sand dunes after 25 years. Thirty-five years may restore shifting sand dunes to a near-stable state characterized by Cleistogenes squarrosa. We found sequential turnover in species composition along the upward topographic gradient throughout the restoration trajectory, indicating that vegetation restoration on sand dunes is promoted by a process where diaspores establish and spread upward from interdune lowland. Our study provides ecological foundations and suggestions for developing and implementing practical restoration programs in the sand dune area.

Species composition and diversity, and carbon stock in a dune ecosystem in the Horqin Sandy Land of northern China

In this study, we determined carbon allocation and carbon stocks in the plant-soil system of different dune ecosystems in northeastern China. We quantified the species composition, above- and below-ground biomasses, and carbon stocks of three dune types (i.e. active dunes, semi-stabilized dunes and stabilized dunes) and their corresponding inter-dune lowlands (i.e. interdune lowlands of active dunes, interdune lowlands of semi-stabilized dunes and interdune lowlands of stabilized dunes) in the Horqin Sandy Land. The results showed that the succession series on interdune lowlands of the Horqin Sandy Land confirmed differences in species composition of the various dune types. Aboveground carbon (AGC) on the interdune lowlands of semi-stabilized dunes (33.04 g C/m2) was greater (P<0.05) than that on the interdune lowlands of active dunes (10.73 g C/m2). At the same time, the different dune types did not show any significant differences (P>0.05) in belowground plant carbon (BGC). However, the percentage of plant BGC in interdune lowlands of active dunes (81.5%) was significantly higher (P<0.05) than that in the interdune lowlands of semi-stabilized dunes (58.9%). The predominant carbon pool in the study dune ecosystem was in the soil. It accounted for 95% to 99% of total carbon storage. Soil organic carbon (SOC) was at least 55% greater (P<0.05) in the interdunes than in the dunes. Stabilized dunes showed at least a 37% greater (P<0.05) SOC content than active dunes up to a 1-m soil depth. Meanwhile, SOC content of interdune lowlands of semi-stabilized dunes was greater (P<0.05) than that of interdune lowlands of active dunes only up to a 20-cm soil depth. The dune ecosystem showed a great potential to store carbon when interdune lowlands of active dunes were conversed to interdune lowlands of semi-stabilized dunes, which stored up to twice as much carbon per unit volume as interdune lowlands of active dunes.

Effects of Sand-Stabilization on Plant Abundance of Interdune Lowlands in the Active Sand Dune Fields

Sand-stabilization may exert enormous effects on plant abundance in interdune lowlands in the active sand dune fields. We investigated the plant abundance of 11 interdune lowlands in stabilized and active dunes, respectively, and analyzed the relationship of plant abundance and lowland area. 1) With the enlargement of lowland area, plant abundance of interdune lowlands in stabilized and active dune increased following logarithmic and power functions, respectively. When the area was the same, abundance of stabilized dunes was more than that of active dunes. 2) With the increasing of lowland area in stabilized and active dunes, psammophytes plant abundance relative to the overall plant abundance decreased exponentially. When the area was the same, the percentage in lowlands of active dunes was more than that of stabilized dunes. We concluded that the practice of sand-stabilization could improve plant abundance in interdune lowlands, however, which is at the cost of loss of psammophytes.

Effects of Sand Dune Stabilization on Plant Diversity of Interdune Lowlands in the Semi-Arid Sand Dune Fieds

Considering each interdune lowland as a self-contained unit, we investigated species composition of 15 interdune lowlands in stabilized and active dunes, respectively, and identified the relationship of species richness and lowland area. The results showed that 1) with the enlargement of lowland area, the overall species richness of interdune lowlands in stabilized and active dunes increased logarithmically. When the area was the same, richness of stabilized dunes was more than that of active dunes. 2) with the increasing of lowland area in stabilized and active dunes, psammophytes richness relative to the overall species richness decreased logarithmically. When the area was the same, the percentage in lowlands of active dunes was more than that of stabilized dunes. Therefore, We concluded that dune stabilization, on one hand, raises species richness and on the other, leads to the loss of endemic or rare psammophytes in interdune lowlands.

What makes Haloxylon persicum grow on sand dunes while H. ammodendron grows on interdune lowlands: a proof from reciprocal transplant experiments

Determining the mechanisms underlying the spatial distribution of plant species is one of the central themes in biogeography and ecology. However, we are still far from gaining a full understanding of the autecological processes needed to unravel species distribution patterns. In the current study, by comparing seedling recruitment, seedling morphological performance and biomass allocation of two Haloxylon species, we try to identify the causes of the dune/interdune distribution pattern of these two species. Our results show the soil on the dune had less nutrients but was less saline than that of the interdune; with prolonged summer drought, soil water availability was lower on the dune than on the interdune. Both species had higher densities of seedlings at every stage of recruitment in their native habitat than the adjacent habitat. The contrasting different adaptation to nutrients, salinity and soil water conditions in the seedling recruitment stage strongly determined the distribution patterns of the two species on the dune/interdune. Haloxylon persicum on the dunes had lower total dry biomass, shoot and root dry biomass, but allocated a higher percentage of its biomass to roots and possessed a higher specific root length and specific root area by phenotypic traits specialization than that of Haloxylon ammodendron on the interdune. All of these allowed H. persicum to be more adapted to water stress and nutrient shortage. The differences in morphology and allocation facilitated the ability of these two species to persist in their own environments.

Effects of Soil Moisture on Vegetation Invasion into Active Dune Areas

Soil moisture and soil seed bank are primary dependent factors during the vegetation natural regenerations in semi-arid sand areas. But the binary correlation analysis between seedling density and soil seed bank density as well soil moisture in transition zones between the windword slope of active dune and interdune lowland indicated that the correlation between seedling density and soil seed bank density was not significant (P&gt;0.05) in the plant growing season; but the one between seedling density and soil moisture was significant and positive (P&lt;0.05). The conclusions revealed that soil moisture was a primary dependent factor during seedling emergence and establishment in the transition zone

Patterns of Species Diversity across Scales and along the Slope on the Ecotone between the Active Sand Dune and the Inter-Dune Lowland in Horqin Sandy Land, China

To better understand the succession process of vegetation restoration from the active sand dune to the inter-dune lowland, species diversity which refers to species richness and abundance across scales and along the slope were studies in Horqin Sandy Land, China. A 0.25 ha square sampling plot, which sampled on the ecotone, was divided into five grain sizes and equal distance intervals along the slope from the top to the bottom. The results showed that both species abundance and richness increased as the grain sizes increased and along the slope, but the decreasing CV values indicated that species diversity gradually vary from heterogeneity to relatively homogeneity. In conclusion, species abundance and richness showed asynchronous changes and their relationship are more closely across scales than along the slope. Except that, more studies on the biotic and abiotic factors interaction concerning the vegetation patterns of sand dune ecosystems should be conducted. These could not only improve our understanding the mechanisms of vegetation invasion and succession, but also be beneficial for vegetation management and biodiversity conservation in semi-arid sand dune ecosystems.

Non-linear effect of habitat fragmentation on plant diversity: Evidence from a sand dune field in a desertified grassland in northeastern China

Although a large number of empirical studies have documented the effect of habitat fragmentation on plant diversity, we are far from being able to draw effective conclusions due to a lack of a proper reference point and a large range of patch size. This study aims to test the hypothesis that the effect of habitat fragmentation on plant diversity is non-linear, i.e. there is a shift in the effect of habitat fragmentation on plant diversity from positive to negative (or from negative to positive) with intensifying fragmentation. A sand dune field in a desertified grassland in eastern Inner Mongolia, China, was used as the study site. Eighteen fragmented plots (inter-dune lowlands in the sand dune) and 14 continuous plots (different sizes of grassland) were selected. Plant diversity was estimated by species richness, functional groups and rare species. Logarithmic, power and exponential functions were used to analyze the relationship of species richness, frequency and abundance and plot area. There was a shift from positive to negative in the relationship between habitat fragmentation and species richness with the intensifying fragmentation. The number of plant functional groups increased due to habitat fragmentation, and different functional groups showed distinct responses to the degree of fragmentation. The effect of habitat fragmentation on rare species richness is non-linear, and the effect of habitat fragmentation on rare species population is negative. Our results indicate: (1) thresholds should be taken into consideration when drawing up plant diversity conservation plans; and (2) a single large reserve and several small reserves have different implications in plant diversity conservation.

Dew variability in three habitats of a sand dune transect in a desert oasis ecotone, Northwestern China

Dew, as a supplementary water source, may have an important ecological role in arid and semi-arid regions. During August and September of 2007 and 2008, measurements were taken to investigate the dew accumulation and evaporation patterns in the very early morning hours, in three different habitats (dunetop, footslope, and interdune lowland) of a fixed sand dune in Northwest China. Dew quantities were measured using the cloth-plate method. The results indicated that there was a positive correlation between dew amounts and relative humidity, but a negative correlation between dew amounts and mean temperature. Clear mornings were characterized by higher dew amounts and longer dew duration, whereas less dew was recorded during cloudy and especially windy mornings. Dew continued to condense even after sunrise, although a shorter warming time after dawn is also of vital importance in dew formation. The higher average maximum dew quantities (0.06mm) and longer average dew duration (2.3h) occurred in the interdune lowland; the lower and shorter average dew amounts (0.048mm) and duration (1.9h) were obtained at the dune top. The footslope habitat exhibited intermediate values. Clearly, the differences in dew deposition can be partially attributed to the distinguishing characteristics of the microhabitats. The present study highlighted the impacts of these characteristics on near-ground dew condensation accumulation and evaporation in a fixed sand dune and may facilitate evaluation of the role of dew in arid and semi-arid environments. Copyright (c) 2012 John Wiley & Sons, Ltd.

Spatial heterogeneity of plant species on the windward slope of active sand dunes in a semi-arid region of China

Species richness and abundance are two important species diversity variables that have attracted particular attention because of their significance in determining present and future species composition conditions. This paper aims to explain the qualitative and quantitative relationships between species diversity pattern and grain size (i.e. size of the sampling unit), and species diversity pattern and sampling area, and to analyze species diversity variability on active sand dunes in the Horqin Sandy Land, northeastern Inner Mongolia, China. A 50 m×50 m sampling plot was selected on the windward slope, where the dominant species was annual herb Agriophyllum squarrosum. Species composition and abundance at five grain sizes were recorded, and the species-area curves were produced for thirteen grain sizes. The range of values for species abundance tended to increase with increasing grain size in the study area, whereas, generally, species richness did not follow this rule because of poor species richness on the windward slope of active sand dunes. However, the homogeneity of species richness increased significantly. With the increase in sampling area, species abundance increased linearly, but richness increased logarithmically. Furthermore, variograms showed that species diversity on the windward slope of active sand dunes was weakly anisotropic and the distribution pattern was random, according to the Moran Coefficient. The results also showed that species richness was low, with a random distribution pattern. This conflicts with the results of previous studies that showed spatial aggregation in lower richness in a sampling area within a community and inferred that the physical processes play a more important role in species diversity than distribution pattern on active sand dunes. Further research into different diversity patterns and mechanisms between active sand dunes and interdune lowlands should be conducted to better understand biodiversity conservation in sand dune fields.

The Relationship Between Shrub Growth and Stoichiometry Characteristics of C.davazamcii and the Stability of Soil Substrates

The community characteristics and leaf C,N and P stoichiometry of Caragana davazamcii Sancz in the semi-mobile dune area,semi-fixed dune area and inter-dune lowland in the Mu Us sandy land were studied.The soil substrates of different habitats as well as the relationship between plants characteristics and soil conditions were studied.We found three major results:(1)The soil substrates of different habitats showed significant differences,i.e.the semi-mobile dune area had relatively poor and loose soil while the semi-fixed dune area and inter-dune lowland had relatively compact soil.(2)Length of current branches,weight of dry current branches,weight of dry leaves and leaf dry matter content were negatively correlated with the soil compaction,while leaf N:P ratio and leaf C:P ratio were positively correlated with the soil compaction.There was no significant relationship between leaf C:N ratio and soil compaction.(3)The crown,density and coverage of C.davazamcii Sancz from different habitats showed significant differences,which might be caused by the differences of soil compaction.In one word,soil compaction influenced the growth status of C.davazamcii Sancz,not only by affecting the above ground biomass and length of current branches,but also affecting the leaf C,N and P stoichiometry and the efficiency of nutrient contents of leaf.

Aerial seed bank in Artemisia species: how it responds to sand mobility

Aerial seed bank has been found in the arid dune ecosystem. However, the relationship of aerial seed bank to sand mobility intensity is unknown. The adaptation of aerial seed bank to sand mobility was analyzed in four Artemisia species dominating at different habitats in northeastern Inner Mongolia, China. The four species, Artemisia gmelinii,A. frigida,A. halodendron and A. wudanica, are an interdune lowland, stabilized dune, semi-stabilized dune and active dune species, respectively. Seed (achene and capitulum) persistence on the parent plants, the supplement for the soil seed bank, the maintenance of seed viability, and the effect of burial depth on seedling emergence of these four species were studied. Dispersal delay differed interspecifically responding to sand mobility intensity: maximal dispersal was in the following May after maturation for A. wudanica, in the following April after maturation for A. halodendron, and in November of the year of seed maturation for A. frigida and A. gmelinii. The maximal supplement to the soil seed bank for A. wudanica and A. halodendron occurred in the following May and March, respectively. The viability of achenes in aerial seed bank of A. wudanica and A. halodendron maintained at 79.5 and 79.6% until the following May after maturation. This study indicated that aerial seed bank in the sand dune ecosystem functions to postpone seed dispersal until the end of windy season and the start of growing season, and therefore is a mechanism for psammophyte to adapt to sand mobility.

Formation of Ulan Buh desert and its environmental changes during the Holocene

Extensive investigations and studies on topography, sedimentary and chronology show new evidence for the formation and evolution of the Ulan Buh desert during early Holocene. Evidence on clay-sand strata and plant roots under interdune lowlands, lake shorelines covered by plenty of Corbicula largillierti and large amounts of dry salt lakes in the central region of the desert prove that many megalakes existed in the hinterland of Ulan Buh desert. Several OSL samples collected from Aeolian sands overlying lacustrine sediments in profiles around Jilantai Salt Lake and interdune lowlands in the southern Ulan Buh desert suggest that the desert began around 7 ka B.P.. The formation of Ulan Buh desert may have resulted from the shrinking of Jilantai megalakes and sands blown from exposed loose sediments.

Plant distribution at the mobile dune scale and its relevance to soil properties and topographic features

A survey was conducted in an 11-year recovery mobile dune (RMD11) and a 20-year recovery mobile dune (RMD20), in Horqin Sandy Land, Northern China, to determine plant distribution at the mobile dune scale and its relevance to soil properties and topographic features. The results showed that (1) vegetation cover and species number increased from dune top to bottom in the restoration process of mobile dune; (2) the average value of soil organic C, total N, pH, relative height of sampling site, very fine sand content and soil water contents (40−60 and 60−80 cm) of RMD11 were less than that of RMD20, respectively, and there were significant differences (P < 0.05) between the two dunes; (3) soil resources were redistributed by shrub restoration and relative height of sampling site on dune. The distribution of sand pioneer plant, Agriophyllum squarrosum, was positively related to the relative height of sampling site and soil water content, while that of other herbaceous plants was positively related to soil nutrients in the restoration process of mobile dune. These results suggest that at mobile dune scale, plant distributions are determined by a combination of soil properties and topographic feature. Much effort should be made to preserve the interdune lowland and to improve the level of soil nutrients on mobile dune.

Species richness and vegetation pattern in interdune lowlands of an active dune field in Inner Mongolia, China

Vegetation pattern in lowlands between active sand dunes has rarely been studied, but it may play an important role in maintaining the biodiversity. This paper aims to quantify relationships between lowland area and species richness, composition and vegetation distribution and to provide suggestions on biodiversity conservation in the active dune field. Considering each interdune lowland as a self-contained unit, we investigated species composition and vegetation pattern in 25 interdune lowlands (ranging from 0.06 ha to 9.5 ha) of an active sand dune field. Our results showed that species richness increased with lowland area following a power function. The richness of psammophytes relative to the overall species richness decreased with lowland area logarithmically, but increase in lowland area did not lead to significant decrease in psammophyte’s richness. With decrease of lowland area, frequency of psammophytes logarithmically increased, but that of nonpsammophytes logarithmically decreased. When the lowland area was about 2 ha, frequency of the psammophytes was equal to that of the nonpsammophytes (limnocryptophyte-meadow species and steppe species). Furthermore, a consistent pattern of vegetation differentiation along the direction of dune advancement occurred for lowlands larger than 1 ha: a psammophyte zone near the foot of leeward slope, a limnocryptophyte-meadow species zone in the central part of interdune lowland, and then followed by a psammophyte zone towards the foot of the windward slope. We concluded that lowland size is an important determinant of species diversity and vegetation pattern, and thus has implications for biodiversity conservation in sand dune fields.

RELATIONSHIP BETWEEN PLANT COMMUNITY AND SOIL ON THE INTER_DUNE LOWLAND IN THE MIDDLE OF OTINGDAG SAND LAND

Aims Vegetation and soil surveys were conducted in the summer of 2004 to study the relationship between vegetation types and soil of inter-dune lowland of Otindag sand land. Of 102 vegetation samples collected, 99 were herb-dominated, the others shrub-dominated. We analyzed soils for total nitrogen, soil organic matter, soluble sodium, soluble potassium and pH. Vegetation samples were classified based on species composition and species functional groups. We used detrended canonical correspondence analysis (DCCA) to determine the main environmental factors related to the distribution of plant communities. Methods The 102 samples were classified into twenty-eight groups dominated by Artemisia annua, A. intramongolica, Bromus ircutensis, Chenopodium acuminatum, A. sieversiana, Oxytropis gracilima, Setaria viridis, A. scoparia, A. frigida, Carex duriuscula, Cleistogenes squarrosa, Agropyron cristatum, Stipa krylovii, Leymus chinensis, L. secalinus, Bromus inermis, Saussurea amara, Potentilla tanacetifolia, Achnatherum splendens, Iris lactea, Salix microstachya, Phragmites australis, Calamagrostis epigejos, Potentilla anserine, Halerpestes ruthenica, Puccinellia tenuiflora, Scirpus tabernaemontani and Suaeda glauca. Importunt findings The Artemisia annua, A. intramongolica, Bromus ircutensis, Chenopodium acuminatum, A. sieversiana, Oxytropis gracilima, Setaria viridis and A. scoparia associations are mostly distributed on sites often covered by quicksand. The level of the groundwater is low, the lixivium of the soil is neutral and the average soluble K+, Na+, total nitrogen and organic matter are low. Artemisia frigida, Cleistogenes squarrosa, Agropyron cristatum, Stipa krylovii, Potentilla tanacetifolia, Leymus secalinus, Carex duriuscula and L. chinensis associations are rooted mostly in stable sand, where soil water, organic matter and total nitrogen are high. Bromus inermis, Saussurea amara, Puccinellia tenuiflora, Phragmites australis and Potentilla anserine associations grow in wet sites, where organic matter and total nitrogen are relatively high. Achnatherum splendens, Iris lacteal, Calamagrostis epigejos, Salix microstachya and Halerpestes ruthenica associations are on saline sites that have high groundwater and alkalinity. The Suaeda glauca association occurs in a highly saline lake, where water and salinity levels are very high. The Scirpus tabernaemontani association occurs in a marsh. The first DCCA axis denoted gradients in ground water level (GWL) and factors related to ground water level such as pH, soluble sodium and soluble potassium. The second axis reflected gradients of total nitrogen and soil organic matter. The third axis reflected a pH gradient. Ground water level, pH, soluble sodium, soluble potassium, total nitrogen and soil organic matter significantly correlated with the distribution of plant communities.

Structure, Pattern and Mechanisms of Formation of Seed Banks in Sand Dune Systems in Northeastern Inner Mongolia, China

A comparison of structure and pattern of the soil seed bank was made between active and stabilized sand dunes in northeastern Inner Mongolia, China. The objective of this paper was to determine the significance of seed bank in vegetation restoration of sand dunes. The results showed that (1) average seed density decreased from stabilized sand dune to interdune lowland of stabilized sand dune, to interdune lowland of active sand dune, and to active sand dune; (2) horizontally, along the transect from interdune lowland to ecotone and to sand dune top, a ‘V’ shaped pattern was presented in the active dune system, and a reverse ‘V’ shaped pattern in the stabilized sand dune system; (3) vertically, the proportion (accounting for the total seeds) of seeds found in 0–20 mm soil profile decreased from stabilized sand dune to interdune lowland of stabilized sand dune, to interdune lowland of active sand dune, and to active sand dune. The same order was also found in 20–50 mm and 50–100 mm soil profiles; (4) the Sokal and Sneath similarity indices in the species-composition between soil seed bank and above-ground vegetation were ranked as: the stabilized sand dune (24%) > the interdune lowland of active sand dune (21%) > the interdune lowland of stabilized sand dune (18%) > the active sand dune (5%); and (5) vegetation restoration of active sand dunes depends on the dispersal of seeds from nearby plant communities on the interdune lowlands. Much effort must be made to preserve the lowlands, as lowlands are the most important seed reservoir in the active sand dune field.

Ecological and environmental explanation of microbiotic crusts on sand dune scales in the Gurbantonggut Desert, Xinjiang

Abstract Results obtained from the field investigation and the analysis in laboratory show that many species of microbiotic crusts of lichens, mosses and algae develop extensively in the Gurbantonggut Desert, Xinjiang. The formation, species and distribution are closely related to the environmental conditions at the different positions of sand dunes. The animalcule crusts develop mainly on the mobile or semi-mobile sand surface of dune tops, the alga crusts develop mainly at the upper to middle parts of dune slopes, the lichen crusts develop at middle and lower parts of dune slopes, and the moss crusts are mainly distributed at the lower part of dune slopes and the interdune low-lands. The species, thickness and developing degree of microbiotic crusts increase from the upper part to the middle and lower parts of dune slopes and the interdune lowlands, and an obvious contrast between the microbiotic crusts and the different species of plant communities forms. The development and differentiation of microbio...