Analyzing the differences of brackish-water in the Badain Lake by geophysical exploration method

BadainJ aran Desert of Inner Mongolia is arid and rainless all the year around,with much more evaporation than rainfall.But the special groundwater recharge mechanism contributes to the generation of several lakes of different sizes that have never not dried up for years,among which there are many freshwater lakes.As the research object in this paper,East Badain Lake and West Badain Lake in the southeast of the desert,which are less than 50m away from each other,show the considerable difference in mineralization.In fact,one is a freshwater lake,but the other is a brackish-water lake.Considering the underground aquifer structure of BadainJ aran Desert and the special formation structure the particularity of the stratigraphic structure around Badain Lake,the author uses AMT(audio magneto telluric)method and ultra-high density resistivity method to analyze the difference in mineralization of East Badain Lake and West Badain Lake from the perspective of geophysical prospecting methods.     

成水滴灌下塔里木沙漠公路防护林土壤盐分分布特征分析

对塔里木沙漠公路防护林地进行实地取样分析,研究咸水滴灌条件下土壤盐分变化规律及其离子分布特征.试验采用5个矿化度水平的咸水灌溉处理:29.70(1号井),25.90(2号井),20.99(8号井),16.95(14号井)和5.75 g·L-1(18号井).试验结果表明:咸水滴灌对土壤盐分含量和离子组成有显著影响,土壤积盐程度随灌溉水矿化度的增大而加剧,土壤盐分组成以C1-、Na+和SO42-为主;不同盐分离子在土壤剖面上的分布特征不同,C1-、Na+、Mg2+和SO42-四种离子的分布较一致,在垂直滴头向下方向浓度最低,远离滴头径向浓度逐渐增大,Ca外和HCO3-在剖面上的分布存在明显的不一致性,在水平方向上远离滴头HCO3-离子浓度向上层聚集,Ca2+则表现为向下层淋溶.研究结果对极端干旱区高矿化度咸水的合理开发利用及防护林的可持续发展具有理论意义和应用价值.     

塔克拉玛干沙漠腹地春、夏季CO_2通量特征

利用世界上唯一深入流动沙漠腹地200 km以上的塔克拉玛干沙漠塔中站所采集的2011年4月、7月的气象资料,分析了塔克拉玛干沙漠腹地春、夏季CO2通量的变化特征及影响因素。结果表明:塔克拉玛干沙漠腹地CO2通量表现为白昼地表吸收CO2,夜间地表排放CO2,且地表吸收强度明显大于地表排放;塔克拉玛干沙漠腹地春、夏季CO2平均净吸收速率分别为0.93μmol·m2·s-1和0.82μmol·m2·s-1;CO2通量受大气稳定性影响较大,稳定大气条件利于沙漠地表CO2的释放,不稳定大气条件有利于沙漠地表CO2的吸收;此外,地表温度、土壤湿度、风速均与CO2通量呈不同程度的负相关关系。     

Advance agriculture in the desert: the Israeli case story

The Israeli Desert constitutes 60% of the country's total area. Regional annual precipitation is 100–200 mm and evaporation reaches 2,500 mm. Traditional desert agriculture of rain fed wheat and sheep, goat and camels grazing is common. Despite the harsh climate conditions, advance agriculture is concentrated in foci where water resources exist. Desert agriculture takes advantage of the winter(October–April) due to a mild climate season for growing vegetables, flowers, herbs and fruit which are mostly exported to European countries. The key factor is the sustainable management of the local natural resources. The regional research and development(RD) system is generating adequate local knowledge and technologies. The most important key factor is developing water resources, and using irrigation saving water systems such as drip irrigation. Technologies of protected agriculture such as greenhouses and plastic tunnels are used. The unfit desert soil is substitute by sand and artificial growing media. For gaining market purposes, introduction of botanical species was implemented for various flowers and vegetable varieties, avocado, pitaya, and jojoba. Controlled drip irrigation and drainage helps to solve salinity problems. Integrated Pest Management(IPM) is used to overcome plant protection issues. Advance raising of milking cows was developed by using reduction heat stress methods. Tilapia are raised in open ponds and greenhouse ponds, and ostriches adapted to desert conditions were introduced. On the southern Judean hills where precipitation is 250 mm, through soil conservation and rain harvesting, significant afforestation is changing the desert scenery. The human factor on this process such as farmers, agricultural extension agents and research scientists is the leading factor.     

Geochemical characteristics of Holocene aeolian deposits and their environmental significance in the Mu Us Desert,northern China

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.     

Characteristics of turbulence over the semi-fixed desert area north of Xinjiang,China

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 I_u > I_v > I_w. The normalized standard deviation of the wind velocity components (σ_u, σ_v and σ_w) 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.     

The Cosmolian program for simulating aeolian dynamics and its application to central Australia

The wide spatial coverage of sand dunes in continental interiors makes the understanding of their activity and accumulation history valuable for palaeoenvironmental reconstructions and the interpretation of landscape evolution. Nevertheless, the study of aeolian landscape development at the million-year timescale is hampered by the complex interaction of factors determining dune migration and the inherently self-destructive nature of their chronostratigraphy, thus limiting the applicability of traditional dating methods. This study presents a standalone program that simulates aeolian transport based on luminescence-derived chronologies coupled with numerical modelling of the accumulation of cosmogenic nuclides. This integrative approach to modelling the history of aeolian landforms reveals phases of emergence of aeolian sand into the landscape, and provides a data-based scheme that facilitates the morphodynamical study of aeolian processes over multiple timescales and up to several millions of years. The application of the program for reanalysing previously reported data from the Australian Simpson Desert reveals multiple pulses of sand dispersion into central Australia at 3.8–3.4, 2.9–2.5 and 1.5–1 Ma, corresponding to pronounced changes in climatic conditions and landscape deformation events. The synchronicity of the results with the established environmental framework that would promote the production and aeolian distribution of sand exemplifies the applicability of process-based modelling in constructing a timeframe of key landscape evolution events in arid environments by studying aeolian deposits. The dependence of the parameters used to determine environmental settings on sand transportation patterns additionally makes the program a powerful tool to further investigate the triggers and mechanisms of aeolian processes.     

The role of fire on soil mounds and surface roughness in the Mojave Desert

A fundamental question in arid land management centers on understanding the long‐term effects of fire on desert ecosystems. To assess the effects of fire on surface topography, soil roughness, and vegetation, we used terrestrial (ground‐based) LiDAR to quantify the differences between burned and unburned surfaces by creating a series of high‐resolution vegetation structure and bare‐earth surface models for six sample plots in the Grand Canyon‐Parashant National Monument, Arizona. We find that 11 years following prescribed burns, mound volumes, plant heights, and soil‐surface roughness were significantly lower on burned relative to unburned plots. Results also suggest a linkage between vegetation and soil mounds, either through accretion or erosion mechanisms such as wind and/or water erosion. The biogeomorphic implications of fire‐induced changes are significant. Reduced plant cover and altered soil surfaces from fire likely influence seed residence times, inhibit seed germination and plant establishment, and affect other ecohydrological processes. Published in 2012. This article is a US Government work and is in the public domain in the USA.     

巴丹吉林沙漠与腾格里沙漠连接带沙丘移动规律北大核心CSCD

巴丹吉林沙漠与腾格里沙漠分别为中国面积第二、第三大流动性沙漠,对两大沙漠连接带新月形沙丘的动态监测可以揭示该地区沙丘形成演化规律,为沙漠连接带风沙地貌发育研究提供科学支撑。通过Google Earth高清历史影像对巴丹吉林沙漠与腾格里沙漠连接带的新月形沙丘带进行监测,分析了两大沙漠交界处沙丘的移动速率和形态变化。结果表明:巴丹吉林沙漠与腾格里沙漠连接带沙丘移动速率范围5.88-19.55 m·a^(-1),平均移动速率10.03 m·a^(-1);移动方向范围109°-135°,平均移动方向122°。风况为沙丘移动提供动力条件,合成输沙方向与沙丘移动方向吻合。受NW、WNW方向输沙影响,新月形沙丘南翼在移动速率增加的同时长度不断伸长,显著区别于北翼。沙丘移动受控于沙丘本身形态,沙丘各形态参数(迎风坡长度、高度、宽度、周长、底面积)与移动速率呈现显著负相关关系(P<0.01)。植被覆盖以及沙丘密度的差异导致了研究区沙丘移动速率的差异。沙丘移动前后,形态参数变化具有复杂性,而沙源丰富度差异以及丘间地灌丛沙包对沙丘形态的改变,是沙丘形态变化复杂性的主要原因。两大沙漠连接带年输沙通量170-521 t·m^(-1),均值为301 t·m^(-1)。     

风化及其它类荒漠漆表面层对高光谱分辨率遥感的影响（一）

由地表风化产生的表面覆被层的矿物质，其质地或与它的基岩矿物相似，或十分不同，虽然这类表面层的厚度仅有几微米到几毫米，但它们却完全控制了地面的反射光谱。与此相似，有些由风吹送的尘埃、胶结物或其它附着物在表面形成的外层也是影响遥感反射光谱的重要因素。这种由胶结物形成的表层往往是深色（甚至黑色）的，因为它们通常出现在干旱区，故常称为“荒漠漆”（“ｄｅｓｅｒｔｖａｒｎｉｓｈ”）。尽管这些暗色对我们的眼睛并无特别之处，但这类表面层（通常为粘土）在短波红外区（ＳＷＩＲ）具有低反射率的吸收特征，并能据此推断它们的矿物成分。因此，为了要在遥感图象和地面的实际“地质状况”之间建立联系，必须对裸露岩石表面特征具有良好的了解。由于不可能在野外总能找到“新鲜”的岩石表面，因此，人们必需能将“岩石内部”物质的光谱和它“上、下表面”的光谱区分开。本部分以美国加里福尼亚东部Ｗｈｉｔｅ－Ｉｎｙｏ山区高海拔地区早古生代白云质碳酸盐的风化表面为例，研究其岩石表面风化特征与海拔高度的关系。