Deserts In Northwestern China Research Articles

Characterization of the Transcriptome of the Xerophyte Ammopiptanthus mongolicus Leaves under Drought Stress by 454 Pyrosequencing.

Background Ammopiptanthus mongolicus (Maxim. Ex Kom.) Cheng f., an endangered ancient legume species, endemic to the Gobi desert in north-western China. As the only evergreen broadleaf shrub in this area, A. mongolicus plays an important role in the region’s ecological-environmental stability. Despite the strong potential of A. mongolicus in providing new insights on drought tolerance, sequence information on the species in public databases remains scarce. To both learn about the role of gene expression in drought stress tolerance in A. mongolicus and to expand genomic resources for the species, transcriptome sequencing of stress-treated A. mongolicus plants was performed.ResultsUsing 454 pyrosequencing technology, 8,480 and 7,474 contigs were generated after de novo assembly of RNA sequences from leaves of untreated and drought-treated plants, respectively. After clustering using TGICL and CAP3 programs, a combined assembly of all reads produced a total of 11,357 putative unique transcripts (PUTs). Functional annotation and classification of the transcripts were conducted by aligning the 11,357 PUTs against the public protein databases and nucleotide database (Nt). Between control and drought-treated plants, 1,620 differentially expressed genes (DEGs) were identified, of which 1,106 were up-regulated and 514 were down-regulated. The differential expression of twenty candidate genes in metabolic pathways and transcription factors families related to stress-response were confirmed by quantitative real-time PCR. Representatives of several large gene families, such as WRKY and P5CS, were identified and verified in A. mongolicus for the first time.ConclusionsThe additional transcriptome resources, gene expression profiles, functional annotations, and candidate genes provide a more comprehensive understanding of the stress response pathways in xeric-adapted plant species such as A. mongolicus.

Heterologous expression of the dehydrin-like protein gene AmCIP from Ammopiptanthus mongolicus enhances viability of Escherichia coli and tobacco under cold stress

Ammopiptanthus mongolicus is the only evergreen broadleaf shrub endemic to the Alashan Desert in northwestern China. The plants can survive temperatures of −30 °C or less in winter. A dehydrin-like protein gene, AmCIP, cloned from a cold-acclimated A. mongolicus seedling was transformed into E. coli. The transgenic strains exhibited enhanced freezing tolerance compared with non-transformed host cells. The recombinant AmCIP remained soluble pre- and post-boiling for 10 min, and protected activity of lactate dehydrogenase during two freeze–thaw cycles more effectively than bovine serum albumin, a protein with a proven cryoprotective effect. Expression of AmCIP in transgenic tobacco increased cold tolerance during seed germination and seedling growth. The YFP-AmCIP fusion protein was localized in the cytoplasm and nucleus in onion inner epidermal cells, indicating that AmCIP might function both in the cytoplasm and nucleus.

Genetic diversity and structure of Libanotis buchtormensis (Fisch.) DC. in disjunct populations along the bilateral sides of deserts in northwestern China

Libanotis buchtormensis (Fisch.) DC. is a medicinal species exhibiting a disjunct distribution along the bilateral sides of deserts in northwestern China. The desert belt, as a phytogeography boundry, might play a key role in restricting gene flow of the species along the region. To determine the genetic pattern and evaluate the effect of the deserts barrier on the divergence of L. buchtormensis, inter-simple sequence repeat (ISSR) markers were used to investigate the genetic diversity and population structure of 19 populations separated by deserts in northwestern China. Ten selected primers generated 125 (90.58 %) polymorphic bands. Low level of genetic diversity (average h = 0.110) was detected at the population level, while higher diversity was detected at the species level (h = 0.298). Unrooted neighbor-joining distance-based phenogram, Bayesian clustering, and principle coordinate analysis revealed that the 19 populations well clustered into three distinct clades corresponding to their geographical origins. The analysis of molecular variance uncovered that a large component of the genetic differentiation was among populations (68.5 %). Genetic distances showed a significant correlation with geographic distances (r = 0.76, P < 0.001), demonstrating a strong geographical pattern of genetic differentiation. In general, the desert zone can be regarded as a geographical barrier to the disjunct distribution pattern of L. buchtormensis. This study provides basic genetic information of L. buchtormensis in China and sheds lights on the protection of some excessively damaged populations.

Development of a nondestructive method for sexing live adult Sternoplax souvorowiana (Coleoptera: Tenebrionidae).

The darkling beetle, Sternoplax souvorowiana (Reitter) (Coleoptera: Tenebrionidae), is flightless and lives in the Guerbantonggut desert in northwestern China. Its special eggshell structure, day-active habit, large body size, short life cycle, and ease of rearing under laboratory conditions make it an excellent model for advanced studies on desert adaptation. Determining the sex of this beetle is usually complicated by the lack of a discreet, externally visible gender-specific character. To date, dissection has been used for sex identification in this species, whereas a nondestructive means is needed for further studies of sexual dimorphism. Here, a new method based on the difference of the pigmentation pattern on the eighth tergite of each sex is described and illustrated. This method can be quickly learned, is nondestructive, is 100% accurate, and is fast enough for most applications in both the field and the laboratory. Experienced users in our laboratory routinely sex 8–10 beetles per minute.

Nitrogen control of &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C enrichment in heterotrophic organs relative to leaves in a landscape-building desert plant species

Abstract. A longstanding puzzle in isotope studies of C3 plant species is that heterotrophic plant organs (e.g., stems, roots, seeds, and fruits) tend to be enriched in 13C compared to the autotrophic organ (leaves) that provides them with photosynthate. Our inability to explain this puzzle suggests key deficiencies in understanding post-photosynthetic metabolic processes. It also limits the effectiveness of applications of stable carbon isotope analyses in a variety of scientific disciplines ranging from plant physiology to global carbon cycle studies. To gain insight into this puzzle, we excavated whole plant architectures of Nitraria tangutorum Bobrov, a C3 species that has an exceptional capability of fixing sands and building sand dunes, in two deserts in northwestern China. We systematically and simultaneously measured carbon isotope ratios and nitrogen and phosphorous contents of different parts of the excavated plants. We also determined the seasonal variations in leaf carbon isotope ratios on nearby intact plants of N. tangutorum. We found, for the first time, that higher nitrogen contents in heterotrophic organs were significantly correlated with increased heterotrophic 13C enrichment compared to leaves. However, phosphorous contents had no effect on the enrichment. In addition, new leaves had carbon isotope ratios similar to roots but were progressively depleted in 13C as they matured. We concluded that a nitrogen-mediated process, hypothesized to be the refixation of respiratory CO2 by phosphoenolpyruvate (PEP) carboxylase, was responsible for the differences in 13C enrichment among different heterotrophic organs, while processes such as fractionating foliar metabolism and preferentially loading into phloem of 13C-enriched sugars may contribute to the overall autotrophic–heterotrophic difference in carbon isotope compositions.

Ground-dwelling arthropod community response to native grassland conversion in a temperate desert of northwestern China

Oases are common in desert regions of northwestern China and are major sites for human settlement. The implementation of oasis conservation planning has led to afforestation with appropriate shrubs and trees in the native grasslands surrounding inhabited oases. However, little is known about how this Land use change from native grassland to shrub and tree plantations influences the composition of ground-dwelling arthropod communities and the performance of their different trophic groups. To address this, we measured activity density, taxon richness, and relative abundance of four different ground arthropod trophic groups (spiders, beetle predators, beetle herbivores, and beetle detritivores) and several environmental variables affecting arthropod distributions (vegetation cover, ground temperature, soil moisture, soil properties, and leaf litter) along an experimentally established land use change gradient of a mature shrub (Haloxylon ammodendron) planation, a mature poplar (Populus gansuensis) plantation and a mature pine (Pinus sylvestris) plantation, as well as a native grassland from which all cultivated systems were converted. We found that converted shrub plantation had much lower activity density of predatory, herbivorous, and detritivorous beetles; similar activity density of spiders; and similar taxa richness of all four trophic groups relative to the native grassland. However, converted forest plantations regardless of tree species had much higher activity density of spiders, lower activity density of the three beetle groups, much higher richness of predatory beetles, and lower richness of herbivorous and detritivorous beetles. We also found a change in the composition of the ground arthropod community that was largely driven by changes in ground temperature and leaf litter mass. We conclude that conversion of native grassland to shrub and tree plantations can significantly affect ground-dwelling arthropod communities, reducing the activity of ground-dwelling beetle assemblages while increasing that of ground-dwelling spider assemblages. These findings are important for conserving native arthropod diversity in desert ecosystems.

Ephemeral plants mediate responses of ecosystem carbon exchange to increased precipitation in a temperate desert

The ecological consequences of increased precipitation on ecosystem carbon (C) exchange are gaining increasing concern, especially in the context of ongoing climate change in temperate deserts. In this study, a field manipulative experiment was conducted to assess the effects of increased precipitation and nitrogen (N) addition on net ecosystem C exchange (NEE) in a temperate desert in northwestern China during two years with contrasting precipitation patterns (2011 and 2012). Increased precipitation decreased ecosystem C release by nearly 50% in the wet year of 2011, whereas ecosystem C release was increased in the dry year of 2012 because of the disproportional stimulation of gross ecosystem productivity (GEP) and ecosystem respiration (ER) by increased precipitation. N addition had no impact on NEE because of the slight responses of both GEP and ER to N addition. During the wet year, most of the precipitation occurred during the growing season of ephemeral plants, which profoundly stimulated plant growth and led to a higher response of GEP than ER to increased precipitation. As a result, positive effects of increased precipitation on NEE occurred in this year. During the dry year, the majority of the precipitation fell post the ephemeral growing season and only a small increase in herb biomass was observed. However, the response of ER to increased precipitation was larger than that of GEP, leading to a more negative NEE in 2012, as compared to 2011. C release was thus stimulated by increased precipitation in 2012. Irrespective of precipitation treatment, N addition weakly decreased C release because of the negligible stimulation of GEP and ER, as well as the slight response of ephemeral biomass. The responses of NEE to increased precipitation showed no difference between interplant spaces and beneath the dominant shrubs because of the similar responses of plant growth, GEP and ER between sites. Overall, this study shows that the responses of NEE to projected increasing precipitation depend on the coupling of precipitation timing and plant growing season.

Feasibility of EPS-producing bacterial inoculation to speed up the sand aggregation in the Gurbantunggut Desert, Northwestern China.

Exopolymers are known to be useful in improving sand aggregation and the development of biological soil crusts (BSCs). A facultative bacterium KLBB0001 was isolated from BSCs in the Gurbantunggut Desert in northwestern China. With the strong effective production of extracellular polymeric substances (EPS), this strain exhibits a multifunctional role for sand stabilization and maintenance of water under laboratory conditions. Practical testing of the feasibility of its inoculation to speed up BSC recovery in the field was also conducted in this experiment. This strain stimulated the heterotrophic community assembly in the topsoil layer (0-2 cm) before the commencement of autotrophic cyanobacteria, while also significantly increasing the number of bacteria, actinomycetes, and content of total phosphorus, available nitrogen, and available phosphorus. However, the low nitrogenase activity (NA) (0.57 µmol/h) that was observed caused us to doubt the previous identification as Azotobacter Beijerinck that was based on physiological and biochemical properties. A phylogenetic analysis based on 16S rRNA gene sequences revealed that this strain was a member of the genus Paenibacillus. It exhibited the closest phylogenetic affinity and highest sequence similarity to the strain Paenibacillus mucilaginosus VKPM B-7519 (sequence similarity 99.698%), which is well known as a typical silicate-weathering bacteria that releases lots of nutritional ions from minerals and the soil. Because P. mucilaginosus can excrete carbonic anhydrase (CA) to capture atmospheric CO2 through hydration of CO2 , it is possible that KLBB0001 might use a similar strategy for heterotrophs in the BSCs to sequester CO2 from the air. Because of its potential role in the reestablishment of the BSC ecosystem due to its ability to improve water relations, sand stabilization, and chemical erosion, EPS-producing bacterial inoculation was concluded to be a suitable and effective treatment for BSC recovery, especially in environments with limited water and nutrients.

Two kinds of persistent soil seed banks in an amphi-basicarpic cold-desert annual

AbstractSeveral studies have compared seed banks of the different morphs of heteromorphic species, but none of them was on an amphi-basicarpic species. Our primary aim was to compare the relative ability of aerial and basal diaspores of an amphi-basicarpic species to form a seed bank. We compared the seed-bank dynamics of basal and aerial diaspores of three populations of the cold-desert annualCeratocarpus arenariusgrowing in the Junggar Desert in north-western China. A 2.5-year experimental garden study compared germination phenology and retention of viability in basal (a) and aerial (c and f) morphs. Aerial morphs formed a modified Thompson and Grime type III seed bank (small proportion of seeds carried over to next year) and the basal morph a modified type IV seed bank (large proportion of seeds carried over to next year). Seeds germinated only in spring, and cumulative germination percentages were f&gt;c&gt;a (year 1), f = c&gt;a (year 2) and f = c = a (year 3). The relationship between length of germination period, retention of viability during burial and relative ability to form a persistent seed bank was basal morph &gt; aerial morphs. The results of this seed-bank study onC. arenariusare in full agreement with those published previously on seed dispersal and dormancy in this species. Thus, strong additional support is provided for a high risk–low risk germination strategy in this cold-desert annual.

Diurnal variations of chlorophyll fluorescence and CO2 exchange of biological soil crusts in different successional stages in the Gurbantunggut Desert of northwestern China

AbstractBiological soil crusts (BSCs) formed by different combinations of photosynthetic algae, cyanobacteria, lichens and mosses are well‐developed in the Gurbantunggut Desert of northwestern China. To investigate the different responses of BSCs to environmental factors, the diurnal variations of chlorophyll fluorescence and CO2 exchange of BSCs in different successional stages were measured following artificial rehydration in the field. Results showed that the maximum potential quantum efficiency of PSII (Fv/Fm), the actual PSII efficiency (ΦPSII) and the relative rate of electron transport as well as net photosynthesis of the different successional BSCs varied similarly and changed markedly with diurnal fluctuations in light and temperature. Further analyses indicated that CO2 exchange and photosynthetic pigment content of chlorophyll (Chl) a, Chl b and carotenoids increased with the developmental level of BSCs, from cyanobacterial crust to lichen crust to moss crust. The differences in responses of BSCs to environmental factors and photosynthetic pigment content may be partially attributed to differences in species composition and morphological characteristics of the various BSCs. Overall, moss crust is better adapted to a wide range of irradiance and higher temperatures than lichen and cyanobacterial crusts. Therefore, BSCs in a later successional stage are expected to play a more important role in desertification control than those of the earlier stages.

Temporal dynamics of soil oxidative enzyme activity across a simulated gradient of nitrogen deposition in the Gurbantunggut Desert, Northwestern China

Increasing nitrogen (N) deposition has been reported to result in positive, negative, and neutral impacts on soil oxidative enzyme activities, which are associated with lignin degradation. The oxidative enzyme activities are usually high and stable in desert ecosystems. Therefore, the exploration of how these enzymes respond to N addition is critical to evaluate the carbon transformation in desert ecosystems. We present the seasonal variations in oxidative enzyme activity and their responses to simulated N deposition in the topsoil (0–5cm) and in subsoil (5–10cm) of the Gurbantunggut Desert in Northwestern China. Polyphenol oxidase (PPO) and peroxidase activity exhibited clear seasonal variations over the 2-year study, with relatively higher values in spring than in the other seasons. The seasonal changes in oxidative enzyme activity were mainly driven by the seasonal patterns in soil moisture and temperature. Shifts in pH, organic carbon, and electrical conductivity were not closely correlated with the seasonal changes in oxidative enzyme activity. In general, PPO and peroxidase activity responded minimally to low N addition (0.5–3gNm−2yr−1), but the activity decreased in response to high N addition (6–24gNm−2yr−1). Although higher organic carbon concentrations were observed in the topsoil than in the subsoil, few significant differences in PPO and peroxidase activity and in their sensitivity to N addition were observed between the two layers. These results suggest that the carbon transformation related to oxidative enzyme activity is regulated by the seasonal patterns of soil moisture, soil temperature, and the N concentration in desert soil.

Phylogeography and conservation genetics of the relic Gymnocarpos przewalskii (Caryophyllaceae) restricted to northwestern China

Gymnocarpos przewalskii is restricted mainly to the arid desert areas of northwestern China, and is listed as a rare and endangered species of second conservation priority in the China Red Data Book. A phylogeographic study was conducted using two chloroplast regions (psbA–trnH and ycf6–psbM), together with various population genetic analyses, to examine genetic variation, population structure, and evolutionary history of the species. In all, 25 haplotypes were detected, 14 of which were found in the northwestern Tarim Basin of southern Xinjiang Autonomous Region. G. przewalskii showed high levels of total genetic diversity (h T = 0.849) and average gene diversity within populations (h S = 0.350). A higher N ST than G ST (P < 0.001) indicated significant phylogeographic structure across the species range. Nested clade phylogeographic analysis (NCPA) suggested that genetic structure in G. przewalskii has been heavily affected by past fragmentation, which likely resulted from aridity and the expansion of desert in northwestern China during the Quaternary. Mismatch analyses were consistent with NCPA in additionally suggesting contiguous range expansion for populations in the northern Tarim Basin and the Yumen region of Gansu Province, which may have occurred during a less arid interval. Human disturbance was identified as the greatest current threat to the species.

Draft Genome Sequence of Mesorhizobium alhagi CCNWXJ12-2T, a Novel Salt-Resistant Species Isolated from the Desert of Northwestern China

Mesorhizobium alhagi strain CCNWXJ12-2(T) is a novel species of soil-dwelling, nitrogen-fixing bacteria that can form symbiotic root nodules with Alhagi sparsifolia. Moreover, the strain has high resistance to salt and alkali. Here we report the draft genome sequence of Mesorhizobium alhagi strain CCNWXJ12-2(T). A large number of osmotic regulation-related genes have been identified.

Niche Separation of Two Sympatric Owls in the Desert of Northwestern China

Abstract The diets of Little Owls (Athene noctua) and Long-eared Owls (Asio otus) have been studied extensively, although seldom in desert habitats where they coexist. We compared diets of these two species near the Minqin Desert Experimental Research Station in northwestern China. Diets differed significantly by frequency: Little Owls fed mainly on mammals (56%) and beetles (42%), and Long-eared Owls fed almost exclusively on mammals (97%). Dietary overlap was 0.62. Diets differed significantly in four dimensions: prey size, feeding time, feeding habitat, and prey mass, and the overlaps for these dimensions were less than 0.74. However, at the generic level for mammals, the difference was not significant, and dietary overlap was 0.97, indicating that they fed on similar mammal assemblages. The overlap for presumed feeding time and habitat was almost complete for mammals. However, owls consumed mammals of different size; overlap of mammal size was 0.74. Our results indicate that although the roost sites o...

Effects of inoculated Microcoleus vaginatus on the structure and function of biological soil crusts of desert

Microcoleus vaginatus Gom., the dominant species in biological soil crusts (BSCs) in desert regions, plays a significant role in maintaining the BSC structure and function. The BSC quality is commonly assessed by the chlorophyll a content, thickness, and compressive strength. Here, we have studied the effect of different proportions of M. vaginatus, collected from the Gurbantunggut Desert in northwestern China, on the BSC structure and function under laboratory conditions. We found that when M. vaginatus was absent in the BSC, the BSC coverage, quantified by the percentage of BSC area to total land surface area, was low with a chlorophyll a content of 4.77 x 10(-2) mg g(-1) dry soil, a thickness of 0.86 mm, and a compressive strength of 12.21 Pa. By increasing the percentage of M. vaginatus in the BSC, the BSC coverage, chlorophyll a content, crust thickness, and compressive strength all significantly increased (P < 0.01). The maximum chlorophyll a content (13.12 mg g(-1)dry soil), the highest crust thickness, and the compressive strength (1.48 mm and 36.60 Pa, respectively) occurred when the percentage of inoculated M. vaginatus reached 80% with a complex network of filaments under scanning electron microscope. The BSC quality indicated by the above variables, however, declined when the BSC was composed of pure M. vaginatus (monoculture). In addition, we found that secretion of filaments and polymer, which stick sands together in the BSC, increased remarkably with the increase of the dominant species until the percentage of M. vaginatus reached 80%. Our results suggest that not only the dominant species but also the accompanying taxa are critical for maintaining the structure and functions of the BSC and thus the stability of the BSC ecosystems.

Bright dust devil tracks on Earth: Implications for their formation on Mars

We report on the first observations of bright dust devil tracks (BDDTs) on Earth, observed in the Turpan depression desert in northwestern China, where raindrop impacts on sand surfaces form aggregates of sand, silt and clay resulting in rough surface textures, which are destroyed by passages of dust devils leading to smooth surface textures within the tracks. The differences in photometric properties between the track and outside the tracks cause the albedo differences leading to the formation of BDDTs and similar processes might lead to BDDTs on Mars in areas with thick dust covers.

First in‐situ analysis of dust devil tracks on Earth and their comparison with tracks on Mars

In this study we report about the first in‐situ analysis of terrestrial dust devil tracks (DDTs) observed in the Turpan depression desert in northwestern China. Passages of active dust devils remove a thin layer of fine grained material (&lt; ∼63 μm), cleaning the upper surface of coarse sands (0.5–1 mm). This erosional process changes the photometric properties of the upper surface causing the albedo differences within the track to the surroundings. Measurements imply that a removal of an equivalent layer thickness of ∼2 μm is sufficient to form the dark dust devil tracks. Our terrestrial results are in agreement with the mechanism proposed by Greeley et al. (2005) for the formation of DDTs on Mars.

Anthropogenic air pollution observed near dust source regions in northwestern China during springtime 2008

Trace gases and aerosols were measured in Zhangye (39.082°N, 100.276°E, 1460 m a.s.l.), a rural site near the Gobi deserts in northwestern China during spring 2008. Primary trace gases (CO: 265 ppb; SO2: 3.4 ppb; NOy*: 4.2 ppb; hereafter results given as means of hourly data) in the area were lower than in eastern China, but still indicative of marked anthropogenic emissions. Sizable aerosol mass concentration (153 μg/m3) and light scattering (159 Mm−1 at 500 nm) were largely attributable to dust emissions, and aerosol light absorption (10.3 Mm−1 at 500 nm) was dominated by anthropogenic pollution. Distinct diurnal variations in meteorology and pollution were induced by the local valley terrain. Strong daytime northwest valley wind cleaned out pollution and was replaced by southeast mountain wind that allowed pollutants to build up overnight. In the afternoon, aerosols had single scattering albedo (SSA, 500 nm) of 0.95 and were mainly of supermicron particles, presumably dust, while at night smaller particles and SSA of 0.89–0.91 were related to pollution. The diverse local emission sources were characterized: the CO/SO2, CO/NOy, NOy/SO2 (by moles), and BC/CO (by mass) ratios for small point sources such as factories were 24.6–54.2, 25.8–35.9, 0.79–1.31, and 4.1–6.1 × 10−3, respectively, compared to the corresponding inventory ratios of 43.7–71.9, 23.7–25.7, 1.84–2.79, and 3.4–4.0 × 10−3 for the industrial sector in the area. The mixing between dust and pollution can be ubiquitous in this region. During a dust storm shown as an example, pollutants were observed to mix with dust, causing discernible changes in both SSA and aerosol size distribution. Further interaction between dust and pollutants during transport may modify the properties of dust particles that are critical for their large‐scale impact on radiation, clouds, and global biogeochemical cycles.

Aeolian deposits at the southeastern margin of the Tengger Desert (China): Implications for surface wind strength in the Asian dust source area over the past 20,000 years

Independent dust provenance data play an important role in understanding changes in the atmospheric dust loading over geological time. Major elemental compositions and grain-size characteristics of the aeolian deposits (Xiangshan (XS) section) at the southeastern margin of the Tengger Desert in northwestern China demonstrate that the deposits are an intermediate product of the transportation of aeolian materials from the dust source area (deserts) to the dust depositional regions (Chinese Loess Plateau) that were likely formed by dust storm processes. The > 40 μm and 63–178 μm fractions and the ratio of SiO 2/TiO 2 of the XS section were used as proxies to reconstruct the surface wind regime over the last 20 kyr. The results show that the surface winds were much stronger and fluctuate acutely from 19.1 to 11.4 kyr. The winds gradually attenuated after the beginning of the Holocene and reached a minimum between 4.0 and 3.5 kyr BP. A sharp increase in surface winds occurred after 2.5 kyr BP. The surface winds in the Asian dust source area are largely consistent with the changes in winter monsoon strength documented by the Chinese loess deposits. Also, the stronger surface winds from 19.1 to 11.4 kyr coincide with the high mineral dust concentration determined from the Greenland ice core, except for the period of Bölling–Allerød (B/A), when the atmospheric dust may have been washed out by enhanced global hydrological cycles although dust was still emitted from source areas. This suggests that the stronger surface winds in dust source areas can enhance the atmospheric dust loadings during the late glacial. The weakening surface wind regime during the Holocene may have greatly contributed to the decrease in dust concentration of the remote dust records. The paleo-environmental changes in the study area since 42.5 kyr BP are broadly in agreement with other adjacent records. However, the possible warm and humid spell of 42.5–19.1 kyr BP still requires verification.

An elevated large-scale dust veil from the Taklimakan Desert: Intercontinental transport and three-dimensional structure as captured by CALIPSO and regional and global models

Abstract. An intense dust storm occurred during 19–20 May 2007 over the Taklimakan Desert in northwestern China. Over the following days, the space-borne lidar CALIOP tracked an optically thin, highly elevated, horizontally extensive dust veil that was transported intercontinentally over eastern Asia, the Pacific Ocean, North America, and the Atlantic Ocean. A global aerosol transport model (SPRINTARS) simulated the dust veil quite well and provided a three-dimensional view of the intercontinental dust transport. The SPRINTARS simulation revealed that the dust veil traveled at 4–10 km altitudes with a thickness of 1–4 km along the isentropic surface between 310 and 340 K. The transport speed was about 1500 km/day. The estimated dust amount exported to the Pacific was 30.8 Gg, of which 65% was deposited in the Pacific and 18% was transported to the North Atlantic. These results imply that dust veils can fertilize open oceans, add to background dust, and affect the radiative budget at high altitudes through scattering and absorption. The injection mechanism that lifts dust particles into the free atmosphere is important for understanding the formation of the dust veil and subsequent long-range transport. We used a regional dust transport model (RC4) to analyze the dust emission and injection over the source region. The RC4 analysis revealed that strong northeasterly surface winds associated with low pressures invaded the Taklimakan Desert through the eastern corridor. These winds then formed strong upslope wind along the high, steep mountainsides of the Tibetan Plateau and blew large amounts of dust into the air. The updraft lifted the dust particles farther into the upper troposphere (about 9 km above mean sea level, MSL), where westerlies are generally present. The unusual terrain surrounding the Taklimakan Desert played a key role in the injection of dust to the upper troposphere to form the dust veil.