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Geochemical background is the basis of anomaly evaluation in mineral exploration and environmental investigation. However, the background value obtained from secondary media is inevitably affected by weathering, transportation, and sorting, which leads to secondary depletion or enrichment of chemical elements. This problem can be avoided by the geochemical mapping of the exposed crust. In this paper, more than 38,000 samples of rocks data were collected, and an original method was presented for the first time to produce the cobalt geochemical map of exposed crust across the whole of China. Using a geological map grid of 1:200,000 as the basic calculation unit, the area and content of rock types in each unit were calculated, and then the grid was assigned using the area-weighted average method. Based on this, an geochemical contour map was drawn in ArcGIS. The results show that the median of the exposed crust is 9.74 mg/kg, which is lower than that of the whole crust and soils. This value is explained by the vertical heterogeneity of the crust and the secondary enrichment, respectively. Co anomalies and anomalous centers of exposed crust are distributed in southwest, north, and northwest China, where they are primarily related to Permian Emeishan Large Igneous Province (ELIP), Pacific plate, and the big mantle wedge (BMW), Archean metamorphic basic rocks, and ophiolite belts. [ABSTRACT FROM AUTHOR]

In north-west China, extensive areas of gravel desert exist, whose surface properties have an important effect on the wind-erosion threshold friction velocity u ∗ t . In this study, we use four models and field observations of gravel mass fraction, soil physical crust, and soil clay content to assess the effect of gravel-surface properties on the value of u ∗ t . Results show that gravel coverage in north-west China ranges between 0.07 and 1.00 (with a mean of 0.67), and about 81% of the sites investigated are covered by soil physical crust. Clay content is 2.4% on average in the study region, less than 2% in 52.1% of that region, and between 2 and 4% in the remaining study regions. The four regions where clay content is greater than the mean include the western Alxa Plain, the alluvial fan of the western Alxa Plain, the northern Alxa Plain, and the Hexi Corridor. In the study region, the value of u ∗ t ranges between 0.12 and 0.78 m s−1 (with a mean of 0.45 m s−1). Soil moisture, gravel coverage, and soil physical crust all affect the magnitude of u ∗ t . A principal component analysis indicates that the soil crust contributes of about 62% of the u ∗ t variations, soil moisture 25%, and surface roughness 9%. A variance analysis shows clear spatial differences in the magnitude of u ∗ t in north-west China due to the spatial variations in gravel land-surface properties. [ABSTRACT FROM AUTHOR]

Soil sealing (loss of soil resources due to extensive land covering for the purpose of house building, road construction etc.) and subsequent soil landscape pattern changes constitute typical environmental problems in many places worldwide. Previous studies concentrated on soil sealing in urbanized regions, whereas rural areas have not been given sufficient attention. Accordingly, this paper studies soil landscape pattern dynamics (i.e., landscape pattern changes in response to rural anthropogenic activities) in the Tiaoxi watershed (Zhejiang province, eastern China), in which surface sealing is by far the predominant component of human forcing with respect to environmental change. A novel approach of quantifying the impacts of rural anthropogenic activities on soil resources is presented. Specifically, quantitative relationships were derived between five soil landscape pattern metrics (patch density, edge density, shape index, Shannon’s diversity index and aggregation index) and three rural anthropogenic activity indicators (anthropogenic activity intensity, distance to towns, and distance to roads) at two landscape block scales (3 and 5 km) between 1985 and 2010. The results showed that the Tiaoxi watershed experienced extensive rural settlement expansion and high rates of soil sealing. Soil landscapes became more fragmented, more irregular, more isolated, and less diverse. Relationships between soil landscape pattern changes and rural anthropogenic activities differed with the scale (spatial and temporal) and variable considered. In particular, the anthropogenic activity intensity was found to be the most important indicator explaining social development intensity, whereas the other two proximity indicators had a significant impact at certain temporal interval. In combination with scale effects, spatial dependency (correlation) was shown to play a key role that should be carefully taken into consideration in any relevant environmental study. Overall, the findings of this work suggest that soil sealing can be a critical human forcing issue with considerable consequences deserving serious attention by the experts, the public and the government alike. [ABSTRACT FROM AUTHOR]

Highlights: [•] Biological soil crusts significantly increased soil enzyme activities. [•] Moss crusts had greater soil enzyme activities than cyanobacteria–lichen crusts. [•] The elapsed time since sand dune stabilization correlated positively with soil enzyme activity. [•] Soil enzyme activities under crusts varied with soil depth and season. [Copyright &y& Elsevier]

Plant interactions greatly affect plant community structure. Dryland ecosystems are characterized by low amounts of unpredictable precipitation as well as by often having biological soil crusts (BSCs) on the soil surface. In dryland plant communities, plants interact mostly as they compete for water resources, and the direction and intensity of plant interaction varies as a function of the temporal fluctuation in water availability. Since BSCs influence water redistribution to some extent, a greenhouse experiment was conducted to test the hypothesis that the intensity and direction of plant interactions in a dryland plant community can be modified by BSCs. In the experiment, 14 combinations of four plant species (Artemisia ordosica, Artemisia sphaerocephala, Chloris virgata and Setaria viridis) were subjected to three levels of coverage of BSCs and three levels of water supply. The results show that: 1) BSCs affected plant interaction intensity for the four plant species: a 100% coverage of BSCs significantly reduced the intensity of competition between neighboring plants, while it was highest with a 50% coverage of BSCs in combination with the target species of A. sphaerocephala and C. virgata; 2) effects of the coverage of BSCs on plant interactions were modified by water regime when the target species were C. virgata and S. viridis; 3) plant interactions were species-specific. In conclusion, the percent coverage of BSCs affected plant interactions, and the effects were species-specific and could be modified by water regimes. Further studies should focus on effects of the coverage of BSCs on plant-soil hydrological processes. [ABSTRACT FROM AUTHOR]

The importance of cyanobacterial polysaccharides of biological soil crusts in sand surface stabilization and soil nutrient retention has been long acknowledged. However, the role of cyanobacterial polysaccharides as a source of nutrition to vascular plants in crusted areas is ignored. In this study, the chemical composition of the polysaccharide synthesized by Phormidium tenue and the effects of its presence on seed germination and seedling metabolism of the shrub Caragana korshinskii were investigated. The crude polysaccharide synthesized by P. tenue was composed of 15 % protein and 58 % carbohydrate and showed the presence of 12 different types of monosaccharides. The addition of the polysaccharide significantly ( P < 0.05) increased seed germination and metabolic activity of the seedling of the shrub C. korshinskii. The optimal concentration for vigor index, root length, root vigor, and total N and P contents was 10 mg/L polysaccharide; for the germination rate, nitrate reductase activity, carbohydrate content, chlorophyll, and Mg content, the optimal was 60 mg/L polysaccharide, while for K and Ca contents, photosynthetic efficiency and superoxide dismutase activity was 120 mg/L. The presence of the polysaccharide increased seed germination rate, ion uptake, and photosynthetic activity by affecting the electron transport chain and decreased oxidative damage by eliminating reactive oxygen species in C. korshinskii, thus promoting shrub performance in crusted desert areas. [ABSTRACT FROM AUTHOR]

Abstract: Biological soil crusts (BSCs) play an important role in the dune fixation and maintaining soil biota in arid desert systems. Free-living soil nematode communities could be used as significant bioindicators to reflect soil recover regime after sand burial. However, the relationship between BSCs and nematodes is rarely known. To examine the effects of BSCs on soil nematodes, 72 soil samples under cyanobacteria–lichen and moss crusts were collected to analyse nematode communities in the different aged vegetated areas at the southeastern edge of the Tengger Desert. Our results showed the colonization and development of BSCs significantly enhanced nematode diversity. Nematode abundances, generic richness, H′, MI, EI and SI were greater under crusts than those under noncrust. In particular, nematode abundances, generic richness, H′, MI, EI and SI were positively correlated with crust ages. The differences in nematode communities were also dependent upon crust types. Nematode abundances and generic richness under moss crusts were higher than those under cyanobacteria–lichen crusts. This can be contributed to the present and succession of BSCs that increased thickness of topsoil after dunes have been stabilized, namely, creating suitable habitats and providing an essential food source for nematodes. [Copyright &y& Elsevier]

The article presents a study of the structure of weathering crusts in the Russian Upper Amur region. Weathering crust composition was analyzed in three types of objects from the Dzhalta ore cluster of Stanovoi, Russia, namely sulfide copper-nickel ores, rocks in fault zones, and pyroxenite dikes barren of visible sulfide mineralization. Hand specimen sampling of the drill core suggests that copper and nickel contents are as high as six and 1%, respectively. Weathering crust composition includes green unconsolidated material with montmorillonite and an admixture of comparatively decomposed feldspar and pyroxene crystals and goethite. The study suggests that the composition of weathering crusts is variable across the region depending on the source rock composition.

Abstract: Biological soil crusts are receiving increasing attention due to their potentially positive effects on desert ecosystems. Artificial propagation of crusts is one way to restore degraded desert soils. However, little is known about their effectiveness on overland flow or water infiltration. Consequently, a study was done on soils of the Loess Plateau of China that had crusts propagated on different slopes. The results show that: (1) it is feasible to artificially grow moss-dominated biological soil crusts (moss crusts) in laboratory; when inoculated by sprinkling crushed fragments of stems and leaves of natural moss crusts they will cover the soil surface almost completely after about 10 months; (2) the artificially propagated moss crusts significantly increase infiltration consequently decreasing overland flow and this increase in infiltration is positively correlated to the soil coverage extent; (3) overland flow results increased by slope in moss-protected and bare soils, consequently the action of moss crusts is particularly important for protecting steep slopes; (4) the start time of runoff process is delayed by moss crusts, and the soil water redistribution process is also greatly affected. These results may be useful for helping to control desertification on the Loess Plateau of China or similar regions. [Copyright &y& Elsevier]

Abstract: Biological soil crusts are important cover in arid desert landscapes, yet their importance as habitats to secondary producers such as ants is relatively unknown. This study was conducted to determine if the presence and development of biological soil crusts on dune surfaces stabilized by revegetation facilitates ant establishment and survival. We measured topsoil properties and crustal features during different successional stages, which were characterized by cyanobacteria and algae, lichens, and mosses, respectively. The species richness and abundance (nest density) of ants were closely associated with silt content, soil organic matter, nitrogen and soil moisture, as well as topsoil temperature. However, ant nest distribution was largely dependent on the biomass and thickness of crusts and topsoil. These findings provide evidence that the recovery or development of biological soil crusts on dune surfaces in the Tengger Desert could favor and maintain higher ant species diversity. Therefore, the disturbance of crusts would result in a reduction of ant species richness and abundance in desert systems. [ABSTRACT FROM AUTHOR]

Abstract  Biological soil crusts (BSC), most notably lichen crusts, develop and diversify in the Gurbantunggut Desert, the largest fixed and semi-fixed desert in China. Four different successional stages of BSC, including bare sand, microalgal crusts, lichen crusts, and moss crusts, were selected to determine successional changes in microalgal species composition and biomass and formation of BSC. A 10 × 10-m observation plot was established in an interdune region of the Gurbantunggut Desert and data were collected over an 8-year study period. The main results were: (1) different successional stages of BSC significantly affected the content of soil organic C and total and available N but not the total and available P and K content of soil; (2) composition of microalgal communities differed among the four successional stages; (3) significant differences in microalgal biomass were observed among the four successional stages; (4) bare sand was mainly uncompacted sand gains; (5) filamentous cyanobacteria, particularly Microcoleus vaginatus, were the dominant species in the early phase of crust succession. The presence of fungal mycelium and moss rhizoids prevented water and wind erosion. [ABSTRACT FROM AUTHOR]

A viscous region with deformable boundaries is used to model simultaneous crustal flow and lithospheric coupling in northern Tibet. This model suggests that (1) the deformation of northern Tibet is different from that of southern Tibet because of structural differences between the regions; (2) the viscosity contrast between the crust and the mantle lithosphere is relatively small beneath northern Tibet; and (3) crustal flow is compatible with crust-mantle coupling under these conditions. [ABSTRACT FROM AUTHOR]

Analyzes the crustal structure of Tibet, China as derived from project INDEPTH wide-angle seismic data. Purpose of the wide-angle seismic measurements; Indications of the crustal thickness beneath the INDEPTH III profile; Factors affecting seismic refraction.

Biogenic Soil Crusts (BSCs) are critical components of desert ecosystems, significantly modifying the surfaces they occupy. Climate variability has significant effects on desert ecosystems, but little is known about the effects of climate variability on BSCs. In addition, BSCs' effects are absent in most Earth system model. Thus, studying BSCs interactions with climate variability and including the effect of BSCs in climate models is important.This study consist of two elements. First, we detect and map BSCs on the Gurbantunggut Desert in China. The satellite remote sensing data can be used. We get merged surface reflectance data from Landsat and MODIS. BSC Index (BSCI) is then calculated using the retrieved surface reflectance. Based on a BSC model, the range of BSCI is determined for the study area. Information of the typical spectral reflectance of BSCs is taken from literature. The BSCI is calculated for a 10 year period (2008-2017). The spatial-temporal variability of BSC on different time scales, including intra-annual, inter-annual and inter-decadal, is analyzed. Second, to explore how climate affects BSCs community distribution, we consider the effects of environmental climate conditions using ERA5 datasets. We bring together the spatial-temporal distribution of climate variables (e.g. temperature, total precipitation) and BSCs to analyze the response of BSCs to climate variability. [ABSTRACT FROM AUTHOR]