新疆策勒不同类型流动和半流动沙丘运移规律

通过对新疆策勒流动沙丘地、半流动沙丘地、砾质戈壁不同类型流动沙丘进行观测,研究了不同下垫面不同类型流动沙丘年运移速度、方向及其规律,为沙丘运移规律及保护绿洲生态安全提供理论依据。结果表明:沙漠—绿洲过渡带流动和半流动沙丘年平均前移距离为4.76~12.92m,半流动沙丘比流动沙丘前移速度明显减小,沙丘移动方向为东南东(99.82°—115.48°)。砾质戈壁2 m高新月形流动沙丘年移动距离为9.37 m,年移动方向为东南东(105.1°)。0.9m高盾状沙丘年运移距离19.15m,移动方向为东南东(93.77°),流动沙丘移动方向与年合成输沙势方向东南东(108°)基本一致,沙丘高度与运移速度呈二次函数反比关系。如果不采取有效的防沙措施,流动沙丘将会对策勒绿洲产生潜在的入侵威胁。     

别里库姆沙漠胡杨与胡杨回涡沙丘形态特征间的关系

为了探究影响胡杨(Populus euphratica)回涡沙丘发育的主导树木因子和影响胡杨生长的沙丘因子,以别里库姆沙漠为研究区,采用无人机航拍与影像解译法获取胡杨与胡杨回涡沙丘的形态参数,并结合相关统计分析法从定量角度对胡杨与胡杨回涡沙丘的形态特征间的关系进行分析。结果表明:(1)胡杨回涡沙丘以胡杨为中心,整体形状类似"n"形。胡杨形态参数的大小与胡杨回涡沙丘形态参数的大小基本保持一致。(2)胡杨的形态特征与胡杨回涡沙丘的形态特征具有显著的相关关系,胡杨的生长和胡杨回涡沙丘的发育之间存在协同变化趋势。(3)胡杨株高和冠幅是影响胡杨回涡沙丘的主导树木因子,影响胡杨的主导沙丘因子分别是沙丘表面积、体积、周长、丘体长度。     

Causes of Sandstorm Disaster and Strategies against Desertification——A Case Study of Hexi Corridor in Northwest China

This case study outlines the problems faced by the peoples of the Hexi Corridor. These problems are serious and urgent, and are representative of those faced by other communities right across western China. The root causes are outlined and some remedies are suggested. The practical measures proposed under China's National Action Plan to Combat Desertification are described and discussed.     

The sand dunes and their vegetation along the Mediterranean coast of France. Their likely response to climatic change

The Golfe du Lion is mainly bordered by low and narrow sand dunes. Since about four decades, 1/3 of its shoreline has been receding, while 1/3 has been prograding and another 1/3 is stable. Several types of dunes may be described mainly depending on storms, high wind frequencies and sand grain size. Vegetation on dune system is distributed along a primary gradient according to sand stability and soil development, and a secondary gradient along slope of dune according to a seasonal cycle of fresh and salt phreatic water level.Global changes in climate may influence these geomorphological and biological structures mainly through:- Winter minimum temperatures changing the distribution of several plant species, especially in the middle part of the Golfe du Lion.- Frequent high storms which cause damages to the front of the dune systems and disrupt the shore. Changes in dune ecosystems will be cyclic so these tendencies will be obvious only upon a long term period.     

青藏高原爬坡沙丘地表沉积物特征分析——以柴达木盆地托拉海河为例

为了阐明青藏高原爬坡沙丘的物源及沉积学意义并揭示其形成机理,对托拉海河爬坡沙丘进行断面采样,分析爬坡沙丘不同地形部位的粒度与地球化学元素特征。结果表明,托拉海河爬坡沙丘地表沉积物的粒度组成总体以极细砂、细砂、中砂为主,粒度特征表现出明显的风成特点;不同地形部位,粒度特征呈现不同的递变规律,自河床到迎风坡顶粒径变粗,分选变好,迎风坡顶到背风坡,粒径粗细混杂,分选变差。沉积物地球化学元素组成以Si、Al、Ca为主,和上陆壳(UCC)相比,除Co、As、CaO、SiO2以外,其余元素都有一定的亏损,不同部位化学元素分布具有一定相似性,且常量氧化物之间有较好的相关性,表明其具有相似的沉积环境。A-CN-K图解及CIA值揭示了托拉海河爬坡沙丘地表沉积物化学风化处于较低程度,大部分化学元素没有显著的风化或迁移,整体属于早期去Na、Ca的阶段;A-CNK-FM图则表明整个断面Fe、Mg元素在空间分布上存在一定的差异,Fe、Mg流失主要是差异风力风选的结果。从化学风化指标来看,不同地形部位风化程度不同,河床风化程度最弱,山地迎风坡的风化程度最强;河床与河流阶地的物源呈现多样性,而迎风坡和背风坡物源较为单一,可能是古沙翻新和就地起沙。因此,初步认为托拉海河爬坡沙丘的形成经历了两个阶段:一是古沙丘形成阶段;二是现代爬坡沙丘形成阶段。在不同空间尺度上,托拉海河爬坡沙丘地表沉积物的理化特征差异与风动力和水动力的差异有关,反映出沉积物对风、水交互作用的响应。     

不同类型白刺沙丘土壤理化性状与微生物相关性研究

利用民勤荒漠绿洲过渡带不同类型白刺沙丘的土壤微生物、土壤理化性状及二者之间的相关性进行研究,旨在探讨白刺沙丘的成土过程,为绿洲生态建设提供基础数据,结果表明,1)固定、半固定和流动沙丘粘粒、粉粒、细砂粒、粗砂粒含量差异较大;土壤养分含量与土壤粘粒、粉粒、细砂粒等细沙物质含量呈正相关性,与粗砂粒含量呈负相关性,表现为土壤养分含量随土壤颗粒的增大,相关性减弱。2)土壤微生物类群数量在半固定沙丘明显高于固定沙丘和流动沙丘。3)过渡带土壤均处于偏碱性状态,有机质、全氮、全磷、全钾、水解氮、速效钾、速效磷和CaCO₃含量随沙丘发育年代的增加逐渐增加。4)不同年代沙丘中土壤微生物和土壤理化因子均具较好的相关性,尤其是细菌和放线菌与pH值呈显著的负相关关系,土壤有机质含量与三大菌群数量都表现出显著的正相关关系。     

Abiotic conditions and plant cover differentially affect microbial biomass and community composition on dune gradients

Dune systems are characterized by strong gradients of physical stress, with blowing sand and salt spray decreasing with distance from the ocean, and soil nutrients increasing. In this study we ask how soil microbial community composition and biomass change along transects away from the ocean, and whether these changes are regulated by abiotic stress or by resource availability. We collected bulk soil from under three plant species representative of the dune front, back, and flat: Ammophila breviligulata, Rosa rugosa, and Myrica pensylvanica. The biomass and composition of microbial communities were examined using phospholipid fatty acid (PLFA) analysis under patches of dominant vegetation, and in paired bare plots. We found that microbial biomass was strongly correlated with soil C, and thus the presence of vegetation. Community composition, on the other hand, varied with abiotic stresses, especially soil salinity. These variables in turn depended on distance from the shore, and were ameliorated in some cases by vegetation. These findings demonstrate that biomass and community composition are influenced by different environmental variables. Thus, relationships between biomass and composition are unlikely to be readily predicted on the basis of a single resource.     

临策铁路防沙明洞对新月形沙丘沙物质粒度特征的影响分异

本文通过临策铁路防沙明洞影响区内外新月形沙丘各部位粒度特征参数的对比研究,探明了防沙明洞对新月形沙丘粒度特征的影响分异规律。研究表明:(1)防沙明洞改变了影响区内新月形沙丘的自然风场结构,地表沙物质呈现粗粒化、粒径均匀程度提高、粒径分布集中的特点。(2)防沙明洞上风向沙丘各个部位沙物质粗粒化程度均高于下风向沙丘,上风向沙丘迎风坡、下风向沙丘背风坡粒度变化最显著。(3)防沙明洞上风向沙丘运动状态受冬季风控制,风蚀作用强于堆积作用,而下风向沙丘运动状态受夏季风控制,堆积作用强于风蚀作用。     

Mathematical and statistical modeling of morphometric and planar parameters of barchans in Pashoeyeh Erg in the west of Lut Desert,Iran

Barchan dunes are among the most common accumulative phenomena made by wind erosion, which are usually formed in regions where the prevailing wind direction is almost constant throughout the year and there is not enough sand to completely cover the land surface. Barchans are among the most common windy landscapes in Pashoueyeh Erg in the west of Lut Desert, Iran. This study aims to elaborate on morphological properties of barchans in this region using mathematical and statistical models. The results of these methods are very important in investigating barchan shapes and identifying their behavior. Barchan shapes were mathematically modeled by simulating them in the coordinate system through nonlinear parabolic equations, so that two separate equations were calculated for barchan windward and slip-face parabolas. The type and intensity of relationships between barchan morphology and mathematical parameters were determined by the statistical modeling. The results indicated that the existing relationships followed the power correlation with the maximum coefficient of determination and minimum error of estimate. Combining the above two methods is a powerful basis for stimulating barchans in virtual and laboratory environments. The most important result of this study is to convert the mathematical and statistical models of barchan morphology to each other. Focal length is one of the most important parameters of barchan parabolas, suggesting different states of barchans in comparison with each other. As the barchan's focal length decreases, its opening becomes narrower, and the divergence of the barchan's horns reduces. Barchans with longer focal length have greater width, dimensions, and volume. In general, identifying and estimating the morphometric and planar parameters of barchans is effective in how they move, how much they move, and how they behave in the environment. These cases play an important role in the management of desert areas.     

内蒙古多伦农牧交错区固定沙丘植被群落特征分析

研究固定沙丘丘顶和丘间地土壤含水量、物种优势度、物种多样性与相似性。结果表明,丘顶和丘间地土壤含水量的差异较大,后者的土壤含水量明显高于前者,在丘顶和丘间地不仅植物种类和数量存在差异,而且优势种的序列亦发生较大变化,其中丘顶的主要优势种为黄柳和褐沙蒿,丘间则为羊柴和白沙蒿。群落中物种多样性与相似性指数表明,丘顶和丘间地植物群落生态因子的差异不仅对群落内优势种和从属种的分布格局产生较大影响,而且也导致群落结构和功能发生较大变化。