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This paper addresses the surface and Holocene aeolian deposits in the southeastern Mu Us Desert, N. China, systematically analysing the evolution of the geochemical characteristics of aeolian sand-palaeosol sequences and their environmental significance. Our results indicate that the geochemical components of the Holocene aeolian deposits and surface deposits had the similar material sources, sediment transport and deposition processes in the study region, which were dominated by SiO2, Al2O3, and Na2O. In the weathering process of the Jinjie (JJ) profile, the Na, K, and Si presented the slight leaching and migration in general, while the other elements were relatively accumulated. The Holocene aeolian deposits and surface deposits incurred weaker geochemical weathering under cold and dry conditions and were only weakly leached, which implies a relatively arid environment in the Holocene epoch and the modern era. The weathering degree was controlled by the regional temperature and precipitation, and was probably more sensitive to the precipitation changes. In the sedimentary profile, the geochemical parameters and migration of elements demonstrated that there have been several alternating warm-wet and cold-dry intervals in the Mu Us Desert in the Holocene epoch; there were relatively warm and wet conditions prior to 4.6 ka, and it has been cold and dry since then. Six millennial-scale dry events were recorded during the Holocene, which were not only accordant with the history of palaeoclimatic changes in the different latitudes and archives of the Northern Hemisphere, but also correspond to the millennial-scale variation of cosmic radiation and solar activity during that period. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In arid northwestern China, as many inland areas around the world with arid or semi‐arid climate, inland river flow recharges groundwater; vegetation pattern depends on the water table, which characterizes the landscapes of oasis, transition zone and desert, within different distances from an inland river. The water table conditions play an important role in water and land management—a high water table causes salinization within the oasis while a low water table causes desertification around the oasis. This study applies a theoretical‐empirical method to calculating critical groundwater depths including the depth of critical groundwater level causing salinization (DCGS) and the depth of critical groundwater level causing desertification (DCGD); the calculations are validated with field observations in the Luocheng Irrigation District located in the middle reach of the Heihe River, an inland river of the northwestern China. Specifically, the calculated DCGS is 1.29 m for the case study area and the range of water table depth at the locations with saline soil is 0.5‐1.2 m. The calculated DCGD for three vegetation communities, Nitraria tangutorum + Glycyrrhiza uralensis Fisch community, Tamarix chinensis + Phragmites australis community, and Alhagi sparsifolia + Phragmites communis, are 8.26, 11.26, and 13.26 m, respectively, basically within an observed range of 6.0‐13.0 m in the study area. The critical depths can be used to design an engineering approach to control water tables and mitigate salinization and desertification problem for ecosystem restoration in the study region. Article impact statement: This paper quantifies threshold water tables for ecological restoration in an inland area in arid northwestern China underlying the threats of salinization and desertification. A theoretical‐empirical method is used for the quantification, which is validated by extensive field measurements. Although a theoretical equation proposed by Laplace et al. (cited in Rui 2004) is available for calculating the lifting height of capillary water, the key component of the critical water table depths, it is difficult to apply the equation for the calculation in real‐world problems due to the challenges in estimating some parameters in the equation. We develop some new empirical relationships in a case study area in northweastern China to estimate the soil characteristics function with porosity, which enables the real‐world application of the equation to calculate the lifting height of capillary water. The critical water table depths can be used to design an engineering approach to control water tables and mitigate salinization and desertification problem for ecosystem restoration in a region with arid or semi‐arid climate. [ABSTRACT FROM AUTHOR]

Humans influence desert ecosystem structure and function by transforming native vegetation into agricultural and non‐agricultural land. However, how different land uses in desert grasslands affect soil phosphorus (P) fractions with varying lability by creating distinct soil physicochemical and microbial properties remains poorly understood. To address this question, a field study was conducted in the arid region of northwestern China, where sites were selected for having an area containing natural desert grassland and three adjacent differently managed land uses converted from desert grassland: 28‐year‐old rainfed shrub (Haloxylon ammodendron) plantation, 35‐year‐old irrigated tree (Populus gansuensis) plantation, and 33‐ to 40‐year‐old irrigated and fertilized croplands. We collected data from four land‐use types for concentrations of soil inorganic and organic P (Pi and Po) fractions of decreasing lability (labile P: resin‐ and NaHCO3‐extractable P; moderately labile P: NaOH‐extractable P; recalcitrant P: HCl‐extractable P and residual P) and edaphic variables as predictors. The relative contributions of individual predictors to variation in P fractions were evaluated using a boosted regression tree analysis. We found significant increases in (1) all P fractions in croplands (77%–418%), with the largest increase in resin‐P; (2) all P fractions except resin‐P in tree plantations (52%–367%), with the largest increase in labile Po; and (3) NaHCO3‐P and HCl‐Pi in shrub plantations (14%–134%), with the largest increase in labile Pi, compared with natural desert grasslands. Edaphic properties dominantly controlled the changes of different P fractions, explaining 51%–93% of the variation in P fractions, but the dominant influential factors differed across P fractions. We conclude that different land uses in desert grassland soil resulted in significant differences in the fractional composition and availability of soil P by affecting edaphic properties differently, informing that soil P cycling can be regulated by altering land‐use types and management levels. Highlights: Assessing the impact of different land uses in desert grasslands on soil P fractions.Different land‐use types showed distinct patterns of soil P dynamics and availability.Soil P responses to land‐use changes were mainly mediated by edaphic properties.The importance of edaphic factors in regulating P dynamics differed among P fractions.Soil P cycling can be regulated by altering land‐use types and management levels. [ABSTRACT FROM AUTHOR]

Granule ripples are widespread on Earth and are a fundamental component of dryland sedimentary systems, but the relationship between their wavelength and surface particle size is unclear; in addition, their sedimentary bedding and granule ripple development are incompletely understood. In this study, we examined the relationship between granule ripple development, morphology, and the surface grain‐size distribution. We measured the morphology and particle‐size distribution of granule ripples in China's Kumtagh Desert, and found an exponential relationship between ripple wavelength and average crest particle size, which contradicts previous results. We hypothesize the ripples resulted from creep of coarse particles caused by saltation impacts, accompanied by decreasing bed elevation, leading to crest migration and increased crest height. The size composition and wind regime determined the movement mode of particles, which controlled ripple development and size, but dry–wet and freeze–thaw cycles also contributed. We established a new conceptual model for the development of large granule ripples. Sand ripples and small granule ripples develop similarly, but large ripples did not form from merger of smaller ripples. We report for the first time that particles between 2.3 and 4.7 mm in diameter were missing in the ripple crests (confirmed in wind tunnel experiments). This gap affects the particle movement mode. Since the threshold wind speed for particle saltation at 4.7 mm approaches the regional maximum wind speed, quantifying the missing particles may permit prediction of regional maximum wind speeds, and has practical significance for identifying wind conditions elsewhere, including the surface of Mars. Plain Language Summary: Granule ripple landforms develop under strong winds. Understanding their dynamics and characteristics better would reveal how near‐surface wind and sediment characteristics control sediment transport and the development and evolution of Aeolian landforms. We investigated granule ripple morphological characteristics and their range of particle sizes in China's Kumtagh Desert. We found a new relationship between particle size and ripple wavelength, and demonstrated that the largest ripples didn't form from merger of smaller ripples. Our results reveal a new conceptual model for large granule ripple development. We report for the first time that particle sizes from 2.3 to 4.7 mm were missing in the ripple crests (confirmed in a wind tunnel). The particles larger than 4.7 mm can only roll along the surface, whereas particles smaller than 2.3 mm can both roll and jump. The size gap represents a transition between the two movement modes. The particle movement mode is determined by the particle size and wind regime, which control granule ripple development and size, but dry–wet and freeze–thaw cycles also contributed. This phenomenon was missed in previous research, but may let us predict regional maximum wind speeds without needing to monitor these speeds in the field. Key Points: We found a new quantitative relationship between granule‐ripple wavelength and crest particle sizeOur results represent a new conceptual model for large granule ripple developmentParticles of a certain size were missing from the ripple crests, and this provides a new method for quantifying maximum wind speeds [ABSTRACT FROM AUTHOR]

In recent years, numerous meteorites have been collected in desert areas in northern and western China. We describe the environment of some deserts in this region, and the petrological and mineralogical characteristics of 49 of the recovered ordinary chondrites. They consist of 14 H chondrites, 33 L chondrites, and 2 LL chondrites. Of the 300 desert meteorites with approved names from deserts in China, there have been 287 ordinary chondrites, six iron meteorites, one CO3 chondrite, one diogenite, one ureilite, one brachinite, one eucrite, and one EL7 chondrite. Forty‐two dense meteorite collection areas (DCAs) have been defined, mainly located in northern and western China. The meteorites collected are mainly from the Kumtag DCA, followed by the Alatage Mountain, Loulan Yizhi, Hami, and Lop Nur DCAs. After tentative pairing of the meteorites, we estimate that the ordinary chondrites account for 72% of the desert meteorites collected in China, with 63 H chondrites, 133 L chondrites, and 20 LL chondrites. This dominance of L chondrites contrasts with other deserts, which may result from the insufficient collection or bias in pairing of ordinary chondrites. The mass distribution of meteorites from different DCAs in China is consistent with that from DCAs in Africa. Based on the available information and the meteorite flux model proposed by previous studies, we suggest that the time over which meteorites have been accumulated in the southern Hami DCA might be >10 kyr. Therefore, the southern Hami region is currently the most suitable area for meteorite collection in China. [ABSTRACT FROM AUTHOR]

Haloxylon ammodendron, an excellent tree species for sand fixation and afforestation in the desert areas of western China, is threatened by climate change and anthropogenic activities. The suitable habitat of this species is shrinking at a remarkable rate, although conservation measures have been implemented. Cistanche deserticola is an entirely parasitic herb that occurs in deserts, is a source of "desert ginseng" worldwide, and has extremely high medicinal value. Little is known about using niche models to simulate habitat suitability and evaluate important environmental variables related to parasitic species. In this study, we modeled the current suitable habitat of H. ammodendron and C. deserticola by MaxEnt based on occurrence record data of the distributions of these two species in China. We grouped H. ammodendron and C. deserticola into three groups according to the characteristics of parasitic species and modeled them with environmental factors. The results showed that bioclimate was the most important environmental parameter affecting the H. ammodendron and C. deserticola distribution. Precipitations, such as annual precipitation, precipitation seasonality, and precipitation in the driest quarter, were identified as the most critical parameters. The slope, diurnal temperature range, water vapor pressure, ground‐frost frequency, and solar radiation also substantially contributed to the distribution of the two species. The proportions of the most suitable areas for Groups 1, 2, and 3 were 1.2%, 1.3%, and 1.7%, respectively, in China. When combined with cultural geography, five hot spot conservation areas were determined within the distribution of H. ammodendron and C. deserticola. The comprehensive analysis indicated that by using MaxEnt to model the suitable habitat of parasitic species, we further improved the accuracy of the prediction and coupled the error of the distribution of a single species. This study provides a useful reference for the protection of H. ammodendron forests and the management of C. deserticola plantations. [ABSTRACT FROM AUTHOR]

As the largest fixed and semi‐fixed desert in China, the Gurbantünggüt Desert undergoes a long period of snow cover in the winter and the rapid growth of ephemeral plants in the spring, presenting obvious seasonal changes in the underlying desert surface type, which can lead to variation in the turbulence of the near‐surface boundary layer turbulence over the desert. In this study, gradient tower data and eddy covariance data from 2017 were analysed to investigate the turbulence characteristics of the different surface boundary layers in the hinterland of the Gurbantünggüt Desert. The results indicate that stable atmospheric conditions in the desert occur exclusively during the early morning and at night in the desert, and the onset and duration of this stable state varies seasonally. Two regimes of intermittent turbulence occur during the night, a weak turbulent regime that occurs when the wind speed is less than the threshold and a strong turbulent regime when the wind speed exceeds the threshold, and different wind speed thresholds were observed at each level. These parameters follow a seasonal pattern of summer (July) > spring (April) > autumn (October) > winter (January) in terms of magnitude. The mean turbulence intensities of the along‐wind, cross‐wind and vertical wind are 0.5, 0.47 and 0.14, respectively, with Iu > Iv > Iw. The normalized standard deviation of the wind velocity components (σu, σv and σw) generally satisfies a 1/3 power‐law relation. Our results show that the night‐time turbulence regime classification for the Gurbantünggüt Desert strongly depends on meteorological and orographic features, and the intermittent turbulent events have the non‐stationarity of the flow in common. The results can contribute to the study of land surface processes, climate change and desertification in inland arid desert areas. [ABSTRACT FROM AUTHOR]

Our study investigated the characteristics of Phragmites australis (Gramineae) silicon (Si) accumulation, and the response relationship between P. australis Si accumulation and groundwater depth changes. Plants were dug out and taken back to the laboratory for Si accumulation analysis, and a supplementary survey of P. australis Si accumulation was conducted among different groundwater depths. Result showed that Si absorbed and accumulated by P. australis mainly came from the soil and the Si accumulation differed significantly in tissues and growth stages, and the total Si accumulations (withering stage) of P. australis in sand dune (SD), desert steppe (DT), interdune lowland (IL), saline meadow (SM), and wetland (W) habitats were 7.09%, 6.77%, 5.72%, 7.73%, and 8.12%, respectively. More importantly, P. australis Si accumulation was almost equal to the total accumulation of nitrogen, phosphorus, and potassium, and even higher than of the total accumulation of calcium, magnesium, and sulfur. P. australis Si accumulation (withering stage) reduced first from SD to DT habitat, and then increased remarkably from DT to W habitat with a significant increase of −23.95% and 41.96%, respectively. P. australis Si accumulation positively responds to the groundwater depths, and the relationship was an increasing linear function of one variable. Our findings suggested that accumulating Si might be one of the effective strategies for P. australis to adapt to adverse habitats, and the Si‐rich characteristic of P. australis was likely to lay a solid theoretical foundation for exploring effective measures to restore and reconstruct the degraded ecosystems in desert oasis areas. [ABSTRACT FROM AUTHOR]

The climate history of the Alxa desert of northwestern China must be sought both in recent instrumental records (dating from 1960) and in high‐resolution proxy data. Climate proxies are scarce in desert areas; however, long‐lived desert shrubs can offer one such proxy. We have used shrub‐ring data from Zygophyllum xanthoxylum, collected in the central Alxa desert, to reconstruct the Self‐calibrating Palmer Drought Severity Index (scPDSI) for the period 1880–2015. The data covers the May–July growth season. When we compared the history constructed from the shrub‐ring data with the instrumental data collected 1960–2015, we found that the reconstructed history explained 41% of the variance in scPDSI data (40% after adjusting for loss of degrees of freedom). The reconstructed history shows that this region has experienced six persistent droughts and four seasons wetter than usual during the period under study. Of note is a severe drought event in 1920s that affected much of northern China (as noted in contemporary documents). The droughts and wet seasons identified in our reconstruction are consistent with reports from other researchers who have studied the climate history or the region. Our study suggests that it is feasible to reconstruct climate history using shrub‐ring data from long‐lived desert shrubs. [ABSTRACT FROM AUTHOR]

Knowledge of the biomass allometry and partitioning is essential for understanding shrub adaptive strategies to degraded habitats as well as for estimating organic carbon storage. We studied biomass accumulation, allocation patterns, and allometric models of Salsola passerina shrub in the Alxa Desert steppe, Northwestern China. We measured aboveground and belowground biomass accumulation across different ages (0–50 years) by destructive sampling. The biomass allocation patterns between aboveground biomass, leaves, branches, and roots were studied by fitting allometric functions for both pooled and age‐classed data. Allometric biomass models were developed by regressing on single‐input variable of basal diameter, crown area, height, and age alone or on the pairwise variables of above four parameters. Biomass accumulation increased with age, aboveground components represented 86–89% of the total biomass, root to shoot biomass ratios increased with shrub age. Allometry patterns of S. passerina were relatively constant, and the growth rate of root was faster than that of aboveground components. Allometric models with two‐input variables were obviously better than single variable models. Crown area and basal diameter were the best predictors for biomass of S. passerina shrub. [ABSTRACT FROM AUTHOR]

Sand dune systems in the arid region of north‐western China are maintained by sand‐stabilizing vegetation, which provides critical ecosystem services. Limited knowledge of soil moisture recharge in these systems hinders sand stabilization efforts. To increase the understanding of soil moisture response to rainfall, we analysed soil water transport in the desert vadose zone of sand dunes and dune slacks following four natural rainfall events during the growing season of 2017. Rainfall was dominated by small rain events (<5.0 mm), accounting for 58% of total rainfall events. Soil moisture at 5–25 cm depth in dune slacks was significantly higher and more variable to 60 cm depth than in sand dunes. Soil moisture at 5 cm depth was replenished with rainfall amounts of <5 mm in dune slacks, but not in sand dunes. When rainfall amount reached 20 mm, soil moisture in dune slack and in sand dune increased, but was much higher in dune slack than in sand dune at depth of 5 cm; after the rain, soil moisture remained at a relatively high level in dune slack but not in sand dune. This was possible because dune slacks had higher silt contents and root biomass, which played a key role in improving soil water holding capacity or accelerating rainfall infiltration at 0–25 cm depth. Overall, the rainfall‐driven hydrological regime coupled with soil physical factors regulated spatial and temporal variability of soil moisture in a sand dune system. [ABSTRACT FROM AUTHOR]

Soil microbial communities respond significantly to long‐term agricultural development in desert areas. Because soil microbial communities are distinct in various deserts at different eco‐climate regions, their response patterns to agricultural development are diverse at a local scale. However, whether the different response patterns had some commonalities across various types of deserts at a larger spatial scale remained unclear. To address this question, historical soil samples, collected in different years from pairwise long‐term experimental plots (desert and farmland) at five field stations of the Chinese Ecosystem Research Network across northern China, were analyzed through high‐throughput sequencing approach. Here, we found that soil bacterial communities were sharply different between deserts and agricultural lands. Contrasting to desert soils with higher relative abundances of Actinobacteria and Firmicutes, agricultural soils harbored higher relative abundances of Proteobacteria, Acidobacteria, and Planctomycetes and exhibited higher bacterial α‐diversity with less variation. More importantly, higher community similarities were found in agricultural lands for each station and all stations, suggesting that soil microbiotic homogenization occurred at both local and regional scales after long‐term agricultural development in desert areas. Further analyses revealed that the homogenization was due to the loss of desert‐endemic species and the range expansion of generalist species, which might result from the introduction of crops combined with agricultural practices. The soil microbiotic homogenization associated with the loss of endemic species should be paid special attention to because this might imply the decrease in ecological resilience to perturbations and might lead to rapid desertification in desert margin areas. [ABSTRACT FROM AUTHOR]

Plants generally adopt different reproductive strategies to adapt to their environments and increase their fitness. Here, we studied the effects of enclosure cultivation on the reproductive allocation of a wheatgrass species Agropyron mongolicum in the Desert steppes of Northern China. The results showed that: (a) after enclosure cultivation, the height, clump width, coverage, and clump biomass of A. mongolicum significantly increased by 78.96% (p =.040), 63.50% (p =.013), 50.89% (p =.032), and 205.38% (p =.022), respectively, whereas density did not show a significant change (p =.330). (b) Enclosure cultivation significantly affected the biomass of A. mongolicum. Compared with cultivation outside the fence, root, leaf, and spike biomass of A. mongolicum inside the fence significantly increased by 183.52% (p =.020), 334.09% (p =.011), and 381.25% (p =.005), respectively. In addition, root biomass was the highest among the components (38.53 and 13.59 g inside and outside the fence, respectively) and spike biomass was the lowest (6.16 and 1.28 g inside and outside the fence, respectively). (c) Enclosure cultivation affected elemental nutrient allocation and the caloric values of various components of A. mongolicum, and the caloric values are positively correlated with carbon, nitrogen, and phosphorus contents. Enclosure cultivation significantly reduced carbon, nitrogen, and phosphorus in the roots, as well as nitrogen and phosphorus in the spikes, but significantly increased nitrogen in the spikes by 9.78%. The caloric values of A. mongolicum inside and outside the fence in decreasing order were as follows: spikes > leaves > stems > roots. Comparison of cultivation effects between inside and outside the fence showed that the caloric values of the spikes and roots significantly increased by 0.92% and 1.60%, respectively, whereas those of the leaves significantly decreased by 0.70%. Our results demonstrate that the reproductive allocation of elemental nutrients and caloric values in nonreproductive and reproductive organs are plastic to arid environments. [ABSTRACT FROM AUTHOR]

Aim: Dryland ecosystems are exceedingly sensitive to climate change. Desertification induced by both climate changes and human activities seriously threatens dryland vegetation. However, the impact of climate change on distribution of dryland plant species has not been well documented. Here, we studied the potential distribution of four representative dryland plant species (Haloxylon ammodendron, Anabasis aphylla, Calligonum mongolicum, and Populus euphratica) under current and future climate scenarios in a temperate desert region, aiming to improve our understanding of the responses of dryland plant species to climate change and provide guidance for dryland conservation and afforestation. Location: Junggar Basin, a large desert region in northwestern China. Methods: Occurrence data of the studied species were collected from an extensive field investigation of 2,516 sampling sites in the Junggar Basin. Ensemble species distribution models using 10 algorithms were developed and used to predict the potential distribution of each studied species under current and future climate scenarios. Result: Haloxylon ammodendron and A. aphylla were likely to lose most of their current suitable habitats under future climate scenarios, while C. mongolicum and P. euphratica were likely to expand their ranges or remain relatively stationary. Variable importance evaluation showed that the most important climate variables influencing species distribution differed across the studied species. These results may be explained by the different ecophysiological characteristics and adaptation strategies to the environment of the four studied species. Main conclusions: We explored the responses of the representative dryland plant species to climate change in the Junggar Basin in northwestern China. The different changes in suitability of different species imply that policymakers may need to reconsider the selection and combination of the afforestation species used in this area. This study can provide valuable reference for the management and conservation of dryland ecosystems under future climate change scenarios. [ABSTRACT FROM AUTHOR]

Barchan dunes are common on Earth, Mars and Titan. Previous studies have shown that their formation, migration and evolution are influenced by the wind regime and other factors, but details vary among regions. Understanding barchan morphology and migration will both improve our understanding of dune geomorphology and provide a basis for describing the environmental conditions that affect the formation and development of these dunes on Earth and other planets. Here, we provide detailed measurements of barchan dune migration in China's Quruq Desert, in the lower reaches of the Tarim River. We monitored their migration direction and rate, and their morphological changes during migration, by comparing Google Earth images acquired in 2003 and 2014. The dunes migrated west‐southwest, close to the local resultant drift direction. The migration rate averaged 8.9 to 32.1 m year−1, with obvious spatial variation. In addition to the wind regime, the migration rate depended on dune morphology, density and vegetation cover; the rate was negatively related to dune height, density and vegetation cover, but positively linearly related to the length/width ratio (LU/W) and to the decrease in this ratio from 2003 to 2014. We found correlations among the dune morphometric parameters, but the relationships were weaker than in previous research. Due to the complexity of the factors that affect the processes that underlie sand dune development and migration, the morphological changes during dune migration were also complex. Our measurements suggest that the aeolian environment played a dominant role in dune migration and its spatial variation in the Quruq Desert. These results will support efforts to control dune migration in the western Quruq Desert and improve our understanding of dune morphodynamics. © 2019 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Understanding how grazing activity drives plant community structure or the distribution of specific species in a community remains a major challenge in community ecology. The patchiness or spatial aggregation of specific species can be quantified by analyzing their relative coordinates in the community. Using variance and geostatistical analysis methods, we examined the quantitative characteristics and spatial distribution of Stipa breviflora in a desert steppe in northern China under four different grazing intensities (no grazing, NG, light grazing, LG, moderate grazing, MG, and heavy grazing, HG) at three small spatial scales (10 × 10 cm, 20 × 20 cm, 25 × 25 cm). We found that grazing significantly increased cover, density, and proportion in standing crop of S. breviflora, but decreased height. The spatial distribution of S. breviflora was strongly dependent upon the sampling unit and grazing intensity. The patchiness of S. breviflora reduced with sampling scale, and spatial distribution of S. breviflora was mainly determined by structural factors. The intact clusters of S. breviflora were more fragmented with increasing grazing intensity and offspring clusters spread out from the center of the parent plant. These findings suggest that spatial aggregation can enhance the ability of S. breviflora to tolerate grazing and that smaller isolated clusters are beneficial to the survival of this dominant species under heavy grazing. [ABSTRACT FROM AUTHOR]

Biological soil crusts (BSCs) are common and play critical roles in semi-arid and arid ecosystems. Bacteria, as an important community in BSCs, play critical roles in biochemical processes. However, how bacterial diversity and community change in different successional stages of BSCs is still unknown. We used 454 pyrosequencing of 16S rRNA to investigate the bacterial composition and community, and the relationships between bacterial composition and environmental factors were also explored. In different successional stages of BSCs, the number of bacteria operational taxonomic units (OTUs) detected in each sample ranged from 2572 to 3157. Proteobacteria, Cyanobacteria, Bacteroidetes were dominant in BSCs, followed by Firmicutes, Acidobacteria, and Actinobacteria. At the successional stages of BSCs, bacterial communities, OTU composition and their relative abundance notably differentiated, and Cyanobacteria, especially Microcoleus vaginatus, dominated algal crust and lichen crust, and were the main C-fixing bacteria in BSCs. Proteobacteria and Bacteroidetes increased with the development of BSCs. OTUs related to Planomicrobium Chinese, Desulfobulbus sp., Desulfomicrobium sp., Arthrobacter sp., and Ahhaerbacter sp. showed higher relative abundance in bare sand than other successional stages of BSCs, while relative abundance of Sphingomonas sp. Niastella sp., Pedobacter, Candidatus solobacter, and Streptophyta increased with the development of BSCs. In successional stages of BSCs, bacterial OTUs composition demonstrated strong correlations with soil nutrients, soil salts, and soil enzymes. Additionally, variation of bacterial composition led to different ecological function. In bare sand, some species were related with mineral metabolism or promoting plant growth, and in algal crust and lichen crust, C-fixing bacteria increased and accumulated C to the desert soil. In later developed stage of BSCs, bacteria related with decomposition of organic matter, such as Sphingomonas sp. Niastella sp., Pedobacter, and Candidatus solobacter increased. Therefore, bacterial community composition and their key ecological roles shifted to the development of BSCs. [ABSTRACT FROM AUTHOR]

Wind is the primary control on the formation of aeolian geomorphology. In this study, we combined wind regime data from automated weather stations in the western and southwestern Tengger Desert of the Inner Mongolia region in China with remote-sensing data to analyse the relationship between the wind energy environment and aeolian geomorphology. Tengger Desert is one of the main dust storm sources in northwestern China. Therefore, efforts aimed at controlling desertification and dust storm require a deeper understanding of the processes that govern the formation and subsequent evolution of dunes in this area. Wind speed was largest in the northwest (3.3 m/s in the Xiqu station) and smallest in the southeast (1.2 m/s in the Haizitan station). Potential sand transport was also largest in the northwest (195 in the Jiahe station) and smallest in the southeast (33 in the Tumen station). The sand-driving wind (5.92 m/s) directions were from the NW and SE quadrant across the study area, at >76% of all sand-driving wind, reaching 99% in the Tumen station. The sand-driving wind in the NW quadrant reached >48%, and in the SE quadrant, >12% of all sand-driving wind in all stations. In the study area, sand dunes included crescent, dune networks, transverse, and coppice dunes. Dune crest directions had similar trends from upwind to downwind, at 133° in the middle region, and 124° in the southwestern region. Mean dune spacing changed with dune patterns; the maximum spacing for crescent dunes was 147 m, for dune networks 118 m, and for transverse dunes it was 77 m. The mean crest length was 124m (maximum) for crescent dunes in the northwest, 121m for transverse dunes, and 84m for dune networks. However, because of gullies in the southern region, the mean crest length was only 58m (least) for the crescent dunes in that area. The defect density ranged from 0.007 to 0.014. The spatial differences in dune patterns reflected the evolution of the dune field, where older dunes had been formed upwind and younger downwind. [ABSTRACT FROM AUTHOR]