Taklimakan Desert In China Research Articles

Depth-dependent responses of soil bacterial communities to salinity in an arid region

Soil salinization adversely affects soil fertility and plant growth in arid region worldwide. However, as the drivers of nutrient cycling, the response of microbial communities to soil salinization is poorly understood. This study characterized bacterial communities in different soil layers along a natural salinity gradient in the Karayulgun River Basin, located northwest of the Taklimakan desert in China, using the 16S rRNA Miseq-sequencing technique. The results revealed a significant filtering effect of salinity on the bacterial community in the topsoil. Only the α-diversity (Shannon index) in the topsoil (0–10 cm) significantly decreased with increasing salinity levels, and community dissimilarity in the topsoil was enhanced with increasing salinity, while there was no significant relationship in the subsoil. BugBase predictions revealed that aerobic, facultatively anaerobic, gram-positive, and stress-tolerant bacterial phenotypes in the topsoil was negatively related to salinity. The average degree and number of modules of the bacterial co-occurrence network in the topsoil were lower under higher salinity levels, which contrasted with the trends in the subsoil, suggesting an unstable bacterial network in the topsoil caused by higher salinity. The average path length among bacterial species increased in both soil layers under high salinity conditions. Plant diversity and available nitrogen were the main drivers affecting community composition in the topsoil, while available potassium largely shaped community composition in the subsoil. This study provides solid evidence that bacterial communities adapt to salinity through the adjustment of microbial composition based on soil depth. This information will contribute to the sustainable management of drylands and improved predictions and responses to changes in ecosystems caused by climate change.

The Transport Path and Vertical Structure of Dust Storms in East Asia and the Impacts on Cities in Northern China

Dust storm disasters have emerged as a significant environmental challenge in East Asia. However, relying on a single monitoring method to track dust storms presents limitations and can be variable. Therefore, it is necessary to use a combination of ground and remote sensing monitoring methods to explore the source and impact range of dust storms in order to fully characterize them. To achieve this, we examined the sources and impact ranges of dust storms in East Asia from 1980 to 2020 using both ground station data and remote sensing data. In addition, we focused on three specific dust storm events in the region. Our results indicate that the central source areas of dust storms are located in southern Mongolia and the Taklamakan Desert in China. Dust storms are mainly transported and spread in the northwestern region, while they are relatively rare in the southeastern region. The HYSPLIT model simulations reveal that the primary source directions of dust storms in East Asia are northwest, west, and north, the region involved includes Kazakhstan, southern Mongolia, and the Taklimakan Desert in China. The vertical structure of the dust storm layer depends on the source of the dust storm and the intensity of the dust storm event. Dust grain stratification probably occurs due to differences in dust storm sources, grain size, and regularity. These findings demonstrate that a combination of ground-based and remote sensing monitoring methods is an effective approach to fully characterize dust storms and can provide more comprehensive information for dust storm studies.

Validation of FY-4A Temperature Profiles by Radiosonde Observations in Taklimakan Desert in China

The atmospheric temperature profiles (ATPs) retrieved through the geostationary Interferometric Infrared Sounder (GIIRS) onboard the FY-4A satellite (GIIRS/FY-4A) can effectively fill the gap of the scarce conventional sounding data in the Taklimakan Desert (TD), the second largest desert in the world, with an area of 330,000 square kilometers. In this study, we take the experimental radiosonde observations (RAOB) from one RAOB station in the hinterland of TD and seven conventional radiosondes in the oasis region around the desert as the true values and analyze the bias distribution characteristics of GIIRS/FY-4A ATPs with quality control (QC) flags 0 or 1 for this region. In addition, a bias comparison is made with GIIRS/FY-4A ATPs, and the fifth generation ECMWF atmospheric reanalysis of the global climate (ERA5) ATPs. The results show that (1) Missing measurements in GIIRS/FY-4A ATPs are the most frequent in the near-surface layer, accounting for more than 80% of all the retrieved grid points. The averaged total proportion of GIIRS/FY-4A ATPs with QC marks 0 or 1 is about 33.06%. (2) The root mean square error (RMSE) of GIIRS/FY-4A ATPs is less than 3 K, smaller than that of ERA5 ATPs. The RMSE of ERA5 ATPs can exceed 10 K in the desert hinterland. The absolute mean biases of GIIRS/FY-4A ATPs and ERA5 ATPs are, respectively, smaller than 3 K and 2 K, the former being slightly larger. The correlation coefficients of GIIRS/FY-4A ATPs with ERA5 ATPs and RAOB ATPs are higher than 0.98 and 0.99, respectively, and the correlation between GIIRS/FY-4A ATPs and RAOB ATPs is inferior to the latter. (3) The overall atmospheric temperature retrieved by GIIRS/FY-4A is 0.08 K higher than the temperature of RAOB, on average, while the overall temperature from ERA5 is 0.13 K lower than that of RAOB, indicating that the temperature profile obtained by integrating GIIRS/FY-4A ATPs and ERA5 ATPs may be much closer to RAOB ATPs. (4) The probability density of the GIIRS/FY-4A ATP biases in the TD region generally follows the Gaussian distribution so that it can be effectively assimilated in the 3-D variational assimilation modules. The probability density distribution characteristics of the GIIRS/FY-4A ATP biases in the desert hinterland and oasis are not much different. However, due to the fusion analysis of the relatively rich multi-source conventional observation data from the oasis stations, the probability density of ERA5 ATPs biases at the oasis stations is nearer to Gaussian distribution than that of the GIIRS/FY-4A ATPs. In the desert hinterland, where conventional observation is not enough, the probability density distributions of the ATPs biases from ERA5 and GIIRS/FY-4A are alike. Therefore, the GIIRS FY4A can contribute to a more accurate estimation of ERA5 ATPs in the TD region.

Estimation of Atmospheric PM10 Concentration in China Using an Interpretable Deep Learning Model and Top‐of‐the‐Atmosphere Reflectance Data From China’s New Generation Geostationary Meteorological Satellite, FY‐4A

AbstractThe rapid urbanization in China and the long‐range transport dust (LRTD) from arid and semi‐arid areas has resulted in an increase of PM10 concentration. In this study, an interpretable deep learning model [deep forest (DF)] with FY‐4A top‐of‐the‐atmosphere reflectance (TOAR) data were used to obtain the hourly PM10 in China. The optimal hourly average R2 of 10‐fold cross validation can achieve 0.85 (13:00 Beijing time); The R2 (RMSE, μg/m³) of the daily, monthly, and annual averages were 0.82 (24.16), 0.97 (6.53), and 0.99 (2.30), respectively. Using TOAR data, the DF model performed better than other machine learning models. The feature importance of the TOAR‐PM10 model showed that TOAR and meteorological elements both contributed significantly to the model. In spring, the PM10 in northern China was greater than that in southern China, which may be related to the LRTD. Excluding the dust weather periods, the areas with high PM10 values in China were mainly in cities and their suburbs, where were correlated with human activities. During a dust weather process, LRTD increased PM10 in northern China by 80.4%. During a mixture haze and dust weather process, the PM10 increased by 130.2% in northern China, of which LRTD led to an increase of 73.7%. The sources (from the Taklimakan Desert in China) and transmission paths of these two LRTD processes were similar. The contribution of LRTD to PM10 was related to dust intensity and meteorological conditions. The results showed that LRTD and local pollution to PM10 was both important in haze periods.

Damage by wind-blown sand and its control measures along the Taklimakan Desert Highway in China

Desertification is one of the most serious environmental problems in the world, especially in the arid desert regions. Combating desertification, therefore, is an urgent task on a regional or even global scale. The Taklimakan Desert in China is the second largest mobile desert in the world and has been called the “Dead Sea” due to few organisms can exist in such a harsh environment. The Taklimakan Desert Highway, the longest desert highway (a total length of 446 km) across the mobile desert in the world, was built in the 1990s within the Taklimakan Desert. It has an important strategic significance regarding oil and gas resources exploration and plays a vital role in the socio-economic development of southern Xinjiang, China. However, wind-blow sand seriously damages the smoothness of the desert highway and, in this case, mechanical sand control system (including sand barrier fences and straw checkerboards) was used early in the life of the desert highway to protect the road. Unfortunately, more than 70% of the sand barrier fences and straw checkerboards have lost their functions, and the desert highway has often been buried and frequently blocked since 1999. To solve this problem, a long artificial shelterbelt with the length of 437 km was built along the desert highway since 2000. However, some potential problems still exist for the sustainable development of the desert highway, such as water shortage, strong sandstorms, extreme environmental characteristics and large maintenance costs. The study aims to provide an overview of the damages caused by wind-blown sand and the effects of sand control measures along the Taklimakan Desert Highway. Ultimately, we provide some suggestions for the biological sand control system to ensure the sustainable development of the Taklimakan Desert Highway, such as screening drought-resistant species to reduce the irrigation requirement and ensure the sound development of groundwater, screening halophytes to restore vegetation in the case of soil salinization, and planting cash crops, such as Cistanche, Wolfberry, Apocynum and other cash crops to decrease the high cost of maintenance on highways and shelterbelts.

Unmanned Aerial Vehicle Observations of the Vertical Distribution of Particulate Matter in the Surface Layer of the Taklimakan Desert in China

Field observations made with unmanned aerial vehicles of the particulate matter (PM) concentration from the ground to a height of 500 m were conducted at Xiaotang and Tazhong in the Taklimakan Desert (TD), China, from 7 to 15 November 2019. The vertical structures of the PM concentrations were studied. Pulsed lidar observations showed that dust aerosols in the TD can reach heights of 4 km. Within 500 m above the ground, the PM1.0, PM2.5, and PM10 concentrations were <100, <201, and <764 µg∙m−3, respectively, in the TD. On days containing sand-blowing periods (e.g., at 18:00 on 11 November), the PM1.0, PM2.5, and PM10 concentrations were 10–17.7 times higher than on clear days. The northern margin of the TD (Xiaotang) was dominated by fine particles, while the hinterland (Tazhong) was dominated by coarse particles, because there was sparse vegetation around Xiaotang and the surface was sand and clay, while there was no vegetation around Tazhong and the surface was sand. During floating dust periods, the boundary layer was dominated by fine particles. The average PM1.0/PM2.5 ratios were 0.25–0.65 and 0.40–0.80 at Tazhong and Xiaotang, respectively, while, during sand blowing periods, these ratios were 0.40–0.55 and 0.40–0.45, respectively. The critical condition in the atmospheric boundary layer for PM concentration was revealed with the enhanced momentum flux and sensible heat flux up to 0.52 kg∙m−1∙s−2, 0.69 m∙s−1, and 6.7 W∙m2, respectively, and the low mixed layer was high in the lower atmosphere.

Detection of New Dust Sources in Central/East Asia and Their Impact on Simulations of a Severe Sand and Dust Storm

AbstractInformation regarding dust concentrations and size distributions is very important for determining air quality and aerosol–radiation–cloud interactions. Only by using a correct erosion database can the sectional dust emission scheme resolve detailed size distributions and determine where and how dust will be emitted. In this paper, the bias and reasons for dust emission in China Meteorological Administration Unified Atmospheric Chemistry Environment–Dust, an operational dust forecasting model, are analyzed using a heavy sand and dust storm episode. We used 18 years of routine sand and dust storm phenomena recorded at meteorological stations to retrieve and update the desertification details in the MBA sectional dust emission scheme adopted in China Meteorological Administration Unified Atmospheric Chemistry Environment–Dust. New desertification details include decreased erodibility in the area adjacent to Uzbekistan, Turkmenistan, and southern Kazakhstan, where Kyzylkum, Karakum, and Aralkum are located in central Asia, and in the Chinese deserts of Onqin Daga, Mu Us, and Gurbantungut. New desertification also results in increased erodibility in northern Mongolia. Comparisons show that the new desertification database decreases overestimation of dust emission in central Asia, including western Mongolia. It improves the underestimation of dust emission in northern Mongolia and the Gobi desert in southeast Mongolia, and the Taklimakan desert in China. Consequently, it corrects the overestimated dust cloud in the source area and in areas impacted by dust transportation. The timing, quantitative mass concentrations, and dust size distributions determined here are all more reasonable and rational than those of the original case.

Phylogeography and ecological niche modeling unravel the evolutionary history of the Yarkand hare, Lepus yarkandensis (Mammalia: Leporidae), through the Quaternary

BackgroundThe Taklimakan Desert in China is characterized by unique geological and historical dynamics and endemic flora and fauna, but the influence of historical climate oscillations on the evolutionary history of endemic animals is poorly understood. Lepus yarkandensis is an oases-dependent Near Threatened species that lives in fragmented oasis habitats in the Taklimakan Desert, China. We investigated the geological and climatic impacts on its geographical differentiation, demographic history and influence of Pleistocene glacial-interglacial cycles on the evolutionary history of L. yarkandensis. Further, studied the impact of climatic oscillation based modification on phylogeography, distribution and diversification pattern of Yarkand hare by using Cytb (1140 bp), MGF (592 bp) and SPTBN1 (619 bp) markers. Ecological niche modeling (ENM) revealed the evolutionary history of this species in response to climate change during the Quaternary. Paleodistribution modeling was used to identify putative refugia and estimate their historical distributions.ResultsBoth historical demographic analyses and climatic niche modeling revealed strong effects of glacial climate changes, suggesting recurrent range contractions and expansions. The EBSP results indicated clear population expansion of L. yarkandensis since the Pleistocene. In the “early Pleistocene”, the demographic expansion continued from 0.83 MYA to the last glacial period. The ENM analysis supported a wide distribution of Lepus yarkandensis at high altitudes during the last interglacial (LIG) period. During the last glacial maximum (LGM), the suitable climate was reduced and restricted to the western part of the Taklimakan Desert.ConclusionsInland aridification, oasis evolution and river flow played major roles in the population differentiation and demographic history of Yarkand hares. Historically, the large, continuous oases in the Taklimakan Desert contained a viable and unique population of L. yarkandensis. The fragmented desert environment might have caused low gene flow between individuals or groups, thus leading to predominant genetic differentiation. The Pleistocene climatic cycles triggered the diversification and expansion of this species during cold and warm periods, respectively, leading to multiple colonization events within the Taklimakan Desert. These events might be due to the expansion of the Taklimakan Desert during the Middle Pleistocene. Yarkand hare previously occupied vast areas at low and intermediate altitudes in Xinjiang, Gansu, Shanxi, Henan and Shaanxi Provinces in China. The past aridification, climate change-induced oasis modifications, changes in river volumes and flow directions, and human activities all affected the population demography and phylogeography of the Yarkand hare.

Characterization of a novel class A carbapenemase PAD-1 from Paramesorhizobium desertii A-3-ET, a strain highly resistant to \u03b2-lactam antibiotics

Although clinical antibiotic-resistant bacteria have attracted tremendous attention in the microbiology community, the resistant bacteria that persist in natural environments have been overlooked for a longtime. We previously proposed a new species Paramesorhizobium desertii, isolated from the soil of the Taklimakan Desert in China that is highly resistant to most β-lactam antibiotics. To identify potential β-lactamase(s) in this bacteria, we first confirmed the carbapenemase activity in the freeze–thawed supernatant of a P. desertii A-3-ET culture using the modified Hodge assay. We then identified a novel chromosome-encoded carbapenemase (PAD-1) in strain A-3-ET, using a shotgun proteomic analysis of the supernatant and genomic information. The bioinformatics analysis indicated that PAD-1 is a class A carbapenemase. Subsequent enzyme kinetic assays with purified PAD-1 confirmed its carbapenemase activity, which is similar to that of clinically significant class A carbapenemases, including BKC-1 and KPC-2. Because the location in which A-3-ET was isolated is not affected by human activity, PAD-1 is unlikely to be associated with the selection pressures exerted by modern antibiotics. This study confirmed the diversity of antibiotic-resistant determinants in the environmental resistome.

Genetic structure of Salsola junatovii (Chenopodiaceae) in the northern edge of the Taklimakan desert and conservational implications

Salsola junatovii Botsch. (Chenopodiaceae), a desert shrub endemic to the northern edge of the Taklimakan desert in China, is listed as an endangered species because of its narrow habitat requirements and a decline in numbers of individuals. In order to provide information on conservation strategies, we investigated the genetic patterns and evolutionary history of this species. Two cpDNA spacers, (psbA-trnH and psbK-psbI), and the nrITS sequence were employed in 116 individuals from 15 populations across the whole range of the species. A total of 7 haplotypes and 12 ribotypes were detected. Based on separate BEAST analyses, we suggest that intraspecific differentiation of S. junatovii occurred at 2.284–0.264 Ma for cpDNA haplotypes, and 1.304–0.1 Ma for nrITS ribotypes, both in the Pleistocene. Only mismatch analysis and neutrality tests for nrITS sequences over all populations were indicative of demographic expansion. Inconsistency between results from chloroplast and nuclear sequences was detected, apparently due to a stronger seed-mediated gene flow among populations than pollen-mediated flow under the severe desert conditions. Based on genetic structure results, one population, KMS, with the highest number of unique genotypes, should be a conservation priority; another nine populations containing unique genotypes were suggested for ex situ conservation.

Nondimensional Wind and Temperature Profiles in the Atmospheric Surface Layer over the Hinterland of the Taklimakan Desert in China

Observed turbulent fluxes, wind, and temperature profiles at Tazhong station over the hinterland of the Taklimakan Desert in China have been analyzed to evaluate empirical parameters used in the profile functions of desert surface layer. The von Kármán constant derived from our observations is about 0.396 in near-neutral stratification, which is in good agreement with many other studies for different underlying surface. In our analysis, the turbulent Prandtl number is about 0.75 in near-neutral conditions. For unstable range, the nondimensional wind and temperature profile functions are best fitted by the exponents of −1/4 and −1/2, respectively. The linear relations still hold for stable stratification in this extremely arid desert. However, the parameters used in their profile functions need to be revised to be applicable for desert surfaces.

Variation Characteristics of Water Content in Two Typical Eremophytes under Drought Stress in the Drift Desert Hinterland

To reveal relationship between water content of plant tissue and soil moisture in the hinterland of Taklimakan desert in China's southern Xinjiang, Haloxylon ammodendron and Nitraria sibirica were selected, and the water potential and content in the tissues of two plants under drought stress were determined. The results were shown that: (1) water potential in the morning and the water content in the tissues of Haloxylon ammodendron and Nitraria sibirica decreased with the decline of soil moisture content. (2) When the soil water stress appeared, the water potential values of Haloxylon ammodendron and Nitraria sibirica were -4.47 MPa and -5.88 MPa, respectively. (3) The lower limits of soil moisture contents that were suitable for the growth of Haloxylon ammodendron and Nitraria sibirica were 2.50% and 3.00%, respectively.

Asian dust height and infrared optical depth retrievals over land from hyperspectral longwave infrared radiances

The dust top height and infrared optical depth over land are retrieved from the Atmospheric Infrared Sounder (AIRS) longwave infrared measurements by using a one‐dimensional‐variation retrieval algorithm for different Asian dust storms. By combining particle size measurements from a 10‐year ground observation data set from the Dunhuang Skynet station located to the east of the Taklimakan Desert in China and the Optical Properties of Aerosols and Clouds data set of optical properties, the mineral dust scattering and absorption coefficients are obtained and then used to compute brightness temperatures with RTTOV 9.3. The retrieved dust thermal infrared optical depths are compared with the Ozone Monitoring Instrument and Moderate Resolution Imaging Spectroradiometer (MODIS) products. The retrieved dust top heights are compared against the extinction backscatter profiles obtained from the Cloud‐Aerosol Lidar with Orthogonal Polarization lidar. Infrared optical depths from AIRS correlate favorably with visible optical depths from MODIS, and dust top heights agree reasonably with lidar observations for the single‐layered dust storms over the Taklimakan Desert.

Dew formation and its long-term trend in a desert riparian forest ecosystem on the eastern edge of the Taklimakan Desert in China

Summary Dewfall can be a substantial water resource crucial for maintaining water balance in desert ecosystems such as the hyper-arid zone of the Taklimakan Desert in China. However, little is known about the formation, quantitative characteristics, and factors influencing dewfall in this region. This study elucidates dew formation and its long-term trend in this region using observational data, including flux, meteorological, and soil water content data obtained using the Eddy covariance system and those recorded by a weather station in the area. The results are as follows: (1) Dew forms in the Populus forest, with nighttime dewfall duration being about 2 h. The average daily dewfall amount during the observation period (June 4–October 24, 2011) was 0.12 mm. The number of dewfall days was 104 days (73% of total days), and the cumulative dewfall amount was 12.87 mm. (2) The dewfall days and amounts on the canopy and soil surfaces were 86 days and 8.64 mm, and 38 days and 4.23 mm, respectively. The top soil can absorb more water vapor than condensed dew. (3) At different time scales (half-hour, day, and half-year), obvious variations in dewfall duration, dewfall amounts, and meteorological factors occurred. (4) Over the past 51 years, changes in the number of dewfall days during the summer (June–October) exhibited a trend similar to that of changes in total dewfall amount during the same period. The average dewfall amount during the summer half-year was 17.2 mm, which is about 64% of the summer half-year rainfall and 50% of the annual rainfall. In particular, the total dewfall amount was higher than the annual rainfall amount during the one-fifth of the past 51 years. The study proved dewfall is one of important water resources in the arid Taklimakan Desert region, and it also significantly influenced the water balance.

A Dissipative Hydrological Model for the Hotan Oasis (DHMHO)

Various hydrological models have been designed to simulate moisture transformation in the water-cycle system between atmospheric water, surface water, soil water and groundwater. But few have been designed specially for oases in arid desert areas where the ecology and the environment are vulnerable because of unwise water-land resources utilization. In order to analyze the moisture transformation in the Hotan Oasis in the Taklimakan Desert in China, and hence to provide scientific references for the rational exploitation and allocation of the limited water-land resources, for the purpose of ensuring that the vulnerable ecology and environment there can be gradually improved and the social economy there can develop sustainably, a dissipative hydrological model for the Hotan Oasis (DHMHO) was developed. It was an outcome of years of systematic study on the moisture transformation in arid areas and on the water–land conditions in the Hotan Oasis. Based on statistics, DHMHO introduces two empirical equations whereby we dynamically calibrated model parameters with monthly data from year 1971 to 1995. Then the calibrated parameters were used to model the moisture movement from 1996 to 2003 and thereafter rationality check and error analysis were conducted. The error analysis results show that the absolute relative errors between simulated and observed groundwater depth values are almost (11 of 12 points) within 20%, and those in annual watershed outflow simulation are mostly (six of eight points) within 20% with an average annual Nash–Sutcliffe Efficiency Coefficient (NSEC) of 0.80. With DHMHO and IPCC assessment, we also simulated the moisture transformation and dissipation in the Hotan Oasis from the year 2011 to 2020. Results show details of the water resources in the Hotan Oasis in the next decade and hence are expected to provide scientific references for establishing rational exploitation and allocation policies on the local water–land resources in the future.

Observation of transformation of calcite to gypsum in mineral aerosols by Ca K-edge X-ray absorption near-edge structure (XANES)

Calcium K-edge XANES was employed for the speciation of Ca in mineral aerosols collected by an Andersen-type air sampler in Aksu, close to the Taklimakan Desert in China. The sampling was conducted in April 2002 when dust events occurred. Additionally, the sample collected in January 2002 was studied for comparison purposes as well. It was found that the XANES spectra of mineral aerosols can be well simulated by those of calcite and gypsum, which can provide the ratio of gypsum to calcite (or total Ca minerals) in the samples. Moreover, we measured the XANES in both the fluorescence (FL) and conversion electron/He-ion yield (CEY) modes, which are bulk and surface-sensitive analysis, respectively. Based on the XANES data, several conclusions were deduced in this study: (1) the similarity of spectra recorded in the two modes in April suggests that the gypsum fraction (∼10%) in the period reflects the ratio of gypsum to the total Ca minerals in the source area without a significant effect of the formation of the secondary gypsum produced at the surface of the mineral aerosols; (2) a larger gypsum fraction detected in the CEY mode than in the FL mode in January reveals that gypsum is mainly found at the particle surfaces, suggesting that the gypsum in this period was mainly produced secondarily by the reaction of calcite with the acidic SO x species (=SO 2, sulfuric acid, and acidic sulfate salts) during the transport; (3) considering the neutralization of acidic SO x species by calcite in mineral aerosols, the Ca speciation data obtained here may be explained by (i) the large supply of mineral aerosols including calcite in April as well as (ii) the large anthropogenic emission of SO 2 generally found in winter in China (which is in January).

Analysis of root fractal characteristics in remote areas of the Taklimakan desert, China

Fractal geometry is a potential new approach to analyze the root architecture, which may offer improved ways to quantify and summarize root system complexity as well as yield ecological and physiological insights into the functional relevance of specific architectural patterns. Fractal analysis is a sensitive measure of root branching intensity and fractal dimension expresses the “space filling” properties of a structure. The objective of this study was to find out the fractal characteristics of root systems in a remote area of the Taklimakan desert in China. The entire root system of two naturally occurring species were excavated and exposed with shovels in 2007. The species were Tamarix taklamakanensis and Calligonum roborovskii. A one-factorial ANOVA with species as factor showed statistically a highly significant difference in fractal dimensions, indicating differences in their pattern of root branching. There was no relationship between root diameter and two parameters of fractal root models α and q, representing general characteristics of root systems, for either species (α: the ratio of the sum of root cross-sectional areas after a branching to the cross-sectional area before root division; q: the distribution of the cross-sectional areas after branching). We have found significant linear relationships between the diameter after branching and root length and biomass respectively, because of the self-similarity of root branching. Branching rules are the same for roots of all sizes and lengths. Root biomass for the root systems of entire trees can be estimated by measuring the diameter of each root at the base of the trunk or the diameter after branching. We have shown that the diameter of each root at the base of the trunk and the diameter after branching are effective indices that can be measured easily in order to estimate the root lengths, biomass and other parameters of root architecture.

Impact of fine-dust air burden on the mass balance of a high mountain glacier: a case study of the Chongce ice cap, west Kunlun Shan, China

AbstractThe coherent variations of annual snow accumulation rate and dust deposition over 60 years are recorded in an ice core drilled at 6530 ma.s.l. on the Chongce ice cap, located in the west Kunlun Shan, south of the Taklimakan desert in China. These records were investigated in the context both of the dust transport pathways from the source region and of climatic changes in this arid environment. The factors relating the dust transport from the source to sink area were taken into account to ascertain the integration of these factors on the precipitation-forming process at high elevations. Results indicate that: (1) dust is predominant among aerosols in precipitation at high altitude; (2) the dust aerosol population may be more instrumental than the vapor supply in the formation of precipitation at such altitudes; (3) compared to low-elevation glaciers, snow accumulation on high mountain glaciers seems to be more sensitive to changes in the concentration of air-burden dust particulates, which are closely related to the climatic variations around the desert region; and (4) under the current climate conditions surrounding the desert region, the decreasing trend in snow accumulation, in concert with the decrease in dust deposition that has occurred over the past several decades, might continue. This effect on snow accumulation at high altitudes may explain one of the elements potentially responsible for the longer-term glacial variation, i.e. the glacial retreat that has lasted for decades in central Asia.

Ground surface features of the Taklimakan Desert

In an attempt to utilize satellite data to obtain land surface features of Taklimakan Desert in China, in situ measurements of spectral reflectance of the land surface is made the portable spectro radiometer in the spectral range of 400 ∼ 2500 nm. The analyses of the data show following features. (1) The difference in spectral reflectance of different soils is comparatively small. (2) There is a tendency that spectral reflectance of soils increases with increases of wavelength, for example, the average reflectance of the sands in the periphery areas of Taklimakan Desert is 21 and 38% in visible and near infrared spectra respectively. (3) It is found that reflectance of the soils decreases with increase of moisture content. The large decrease is recognized in 1450 and 1950 nm spectra, water absorption bands. This fact suggests that the monitoring of soil moisture is possible by measuring the radiance at these spectra, thus Landsat TM Bands 5 and 7 will be effective for monitoring soil moisture content.