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In May 2008,the vegetation,terrain and landforms were investigated at a plot of 200 m x 50 m in a typical region of longitudinal sand dunes in the southern marginal zone of the Gurbantonggut Desert.At the plot 180 quadrats were selected for the observation,measurement and soil sampling.These soil samples were sampled from the surface layer(0～10 cm)and shallow layer(10～30 cm),and their moisture content values were measured. Under the support of geostatistical software,such as GS~+ and geostatistical model in ArcGis,this paper analyzes the spatial varying pattern of soil moisture content at the different positions of two longitudinal sand dunes in the study area.The results show that the semi-variance functional values of soil moisture content in the two layers can be well fitted as an exponential model.The variation ranges of surface layer and shallow layer of aeolian sandy soil are 37.8 m and 21.3 m,and the ratios of partial sill and sill[C/(C_0+C)]are 75.1%and 75.6%,respectively.These reveal that there is a high spatial autocorrelation in soil moisture between the surface layer and the shallow layer of aeolian sandy soil,and the spatial variation of the soil moisture content comes mainly from a structural difference. The results can objectively reflect the spatial structure pattern of soil moisture in the plot.The figure of Kriging interpolation shows that soil moisture content is correspondently increased with the height increase of terrain.The analyzed results show that the values of soil moisture content are in an order of crestwindward slopeleeward slopeinter-dune land in the surface layer(0～10 cm)of aeolian sandy soil,and an order of windward slopecrestleeward slopeinter-dune land in the shallow layer(1030 cm).

In the present research, the authors measured parameters of richness, cover and importance value of ephemeral and ephemeroid plants on south-north and east-west transects in the Gurbantunggut Desert in early spring, and investigated and analyzed the microhabitats, such as terrain, geomorphology, soil physical-chemical properties and crusts. By comparison, the regional differences in the ephemeral distribution in the desert were revealed. The species of ephemeral plants in the south and center are the richest and those in the west are the poorest in the desert. The cover of ephemeral plants in the mid-south is higher than that in the north, and that in the mid-east is higher than that in the west. The response of ephemeral plants to the spatial variation of the desert habitat forms the population-habitat gradient of ephemeral plants. The characteristics are: (1) In the habitat with higher terrain, coarser textured soil with poorer sorting and correspondingly higher organic matter and lower alkali-saline contents, Carex physoides and Eremopyrum orientale are the dominant ephemeral plants; (2) In the dry habitat with lower terrain, looser textured soil, some organic matter, alkali-saline soil, and developed crust, the ephemeral plants Alyssum linifolium and Erodium oxyrrhynchum are of characteristic of drought and alkali-saline tolerance; (3) In the habitat with lower terrain, some water and more alkali-saline soil, the ephemeral plants Neotorularia torulosa and Hypecoum parviflorum being of alkali-saline tolerance are mainly developed. However, most ephemerals are distributed in a habitat order of higher terrain, some organic, and less alkali-saline soil on the above-mentioned ephemeral population-habitat gradient. The spatial gradient of variation in desert microhabitats is small, and as a whole, the physiological character of mesophytism is represented by the desert ephemerals.

This paper reports a geomorphologic landscape investigation, vegetation survey and soil sampling at 14 sites across the Gurbantunggut Desert between 87°37′09″-88°24′04″E and 44°14′04″-45°41′52″N. The study encountered 8 species of low trees and shrubs, 5 of perennial herbs, 8 of annual plants and 48 of ephemeral and ephemeroid plants. These species of plants represent one-third of the species found in the Gurbantunggut Desert, and their communities make up a large proportion of desert vegetation with great landscape significance. In the investigation we found that the plant communities are accordingly succeeded with the spatial variation of macro-ecoenvironment. Using Principal Component Analysis (PCA) and Correlation Analysis (CA) we found that the micro-ecoenvironment heterogeneity of aeolian sandy soil’s physical and chemical properties such as soil nutrient, soil moisture, soil salt, pH etc. only impacted the diversity of herb synusia (PIEherb) of the desert, with a negative correlation. Meanwhile, the impact of microhabitat on the plant community pattern with an antagonistic interaction made vegetation’s eco-distribution in a temporary equilibrium.

Based on systematically monitoring plants on dune ridges in the southern part of the Gurbantunggut Desert in 2002, this paper, from the angle of dune stabilization by vegetation, describes the temporal and spatial distribution patterns of ephemeral plants on isolated sand dunes, analyses the natural invasion processes of ephemeral plants on human-disturbed sand surface and expounds the importance of ephemeral plants in stabilizing sand dune surface. A total of 45 plant species were identified in the study area, 29 of which are ephemeral plants. Ephemeral plants sprouted in early April and completed their life-circle within about two months. Just as aeolian sand activities came to the strongest stage from April to June in desert regions of northern Xinjiang, the total coverage of trees, shrubs and herbs of long vegetational period on most dune ridges was less than 10%, while the mean coverage of ephemeral plants reached 13.9% in April, 40.2% in May and 14.1% in June. Therefore ephemeral plants acted as the major contributor to dune surface stabilization in the Gurbantunggut Desert. Investigations of vegetation restoration on engineering-disturbed dune surface show that ephemeral plants first recolonized the disturbed dune surface.

The grain size and mineral composition analyses of 236 samples from nine different sub-deserts within the Jungger Basin of north-western China reveal that dune sands from that region may be derived by local reworking of the underlying sands. That the grain size characteristics and mineral compositions vary with different sub-deserts show the diversities of their sand sources. The similarities and differences in mineral assemblage, mineral dispersion, quartz/feldspar value and grain size distribution between the dune sands and their underlying sands in the same sub-desert indicate that dune sands have derived from underlying sands within the same sub-basin, but dune sands have also received minor contributions of sediment from areas outside the sub-deserts.