Influence of salinity and moisture on the threshold shear velocity of saline sand in the Qarhan Desert,Qaidam Basin of China: A wind tunnel experiment

Determination of the threshold shear velocity is essential for predicting sand transport, dust release and desertification. In this study, a wind tunnel experiment was conducted to evaluate the influence of salinity and moisture on the threshold shear velocity of saline sand. Saline sand samples (mean particle size of 164.50-186.08 μm and the total silt, clay and salt content of 0.80%-8.25%) were collected from three saline sand dunes (one barchan dune and two linear dunes) in the Qarhan Desert, Qaidam Basin of China. Original saline sand samples were placed in two experimental trays for wet and dry processing to simulate deliquescence and desiccation, respectively. Surface moisture content ranging from 0.30% to 1.90% was generated by the steam method so that the saline sand can absorb water in a saturated water vapor environment. The motion of sand particles was determined by the observers with a solid laser. The laser sheet (0.80 cm thick), which was emitted by the solid laser, horizontally covered the sand surface and was bound to the sand. Results show that the cohesion of saline sand results from a combination of salt and water. The threshold shear velocity increases exponentially with the increase in crust thickness for the linear sand dunes. There is a positive linear correlation between the original moisture content and relative threshold shear velocity. The threshold shear velocity of dewatered sand is greater than that of wet sand with the same original moisture content. Our results will provide valuable information about the sand transport of highly saline soil in the desert.     

Monitoring desertification processes in Mongolian Plateau using MODIS tasseled cap transformation and TGSI time series

Most remote sensing studies assess the desertification using vegetation monitoring method. But it has the insufficient precision of vegetation monitoring for the limited vegetation cover of the desertification region. Therefore, it offers an alternative approach for the desertification research to assess sand dune and sandy land change using remote sensing in the desertification region. In this study, the indices derived from the well-known tasseled cap transformation(TCT), tasseled cap angle(TCA),disturbance index(DI), process indicator(PI), and topsoil grain size index(TGSI) were integrated to monitor and assess the desertification at the thirteen study sites including sand dunes and sandy lands distributed in the Mongolian Plateau(MP) from 2000 to 2015. A decision tree was used to classify the desertification on a regional scale. The average overall accuracy of 2000, 2005, 2010 and 2015 desertification classification was higher than 90%. Results from this study indicated that integration of the advantages of TCA, DI and TGSI could better assess the desertification. During the last 16 years, Badain Jaran Desert, Tengger Desert, and Ulan Buh Desert showed a relative stabilization. Otindag Sandy Land and the deserts of Khar Nuur, Ereen Nuur, Tsagan Nuur, Khongoryn Els, Hobq, and Mu Us showed a slow increasing of desertification, whereas Bayan Gobi, Horqin and Hulun Buir sandy lands showed a slow decreasing of desertification. Compared with the other 11 sites, the fine sand dunes occupied the majority of the Tengger Desert, and the coarse sandy land occupied the majority of the Horqin Sandy Land. Our findings on a three or four years' periodical fluctuated changes in the desertification may possibly reflect changing precipitation and soil moisture in the MP. Further work to link the TCA, DI,TGSI, and PI values with the desertification characteristics is recommended to set the thresholds and improve the assessment accuracy with field investigation.     

6种灌木不同器官生物量及其碳、氮含量的分配特征

通过研究晋北地区草地黄刺玫、沙棘、荆条、酸枣、绣线菊和柠条等6种常见灌木的叶片、新生枝、老龄枝生物量及其碳、氮含量的分配特征,旨在为草地准确估算草地植物碳、氮循环提供依据。结果表明:黄刺玫的地上生物量最大,是酸枣的7倍。沙棘叶片生物量占地上生物量的比例最大;黄刺玫新生枝生物量占地上生物量的比例最大;柠条老龄枝生物量占地上生物量的比例最大。黄刺玫、沙棘和荆条的地上部分各器官生物量分配特征相似,由高到低表现为叶片、老龄枝、新生枝;绣线菊、酸枣和柠条的地上部分各器官生物量分配特征相似,由高到低表现为老龄枝、叶片、新生枝。6种灌木地上部分各器官碳含量差异不显著,氮含量分布由高到低为叶片、新生枝、老龄枝。     

灌木抗旱机理研究

从灌木生长性状、形态结构、细胞质膜透性、光合、渗透调节(可溶性糖、脯氨酸、甜菜碱和无机离子)、ABA和LEA蛋白变化及其与灌木抗旱性的关系方面,综述了灌木抗旱机理研究.     

基于文献计量的荒漠灌丛研究现状及热点分析

以中国期刊全文数据库(CNKI)和Web of science数据库中与荒漠灌丛有关的文献为国内和国际文献基础数据源,利用Origin 2019按年份统计发文量、论文增长率和文献共被引次数,通过Bibexcel将筛选出的高频关键词生成共词矩阵,利用Ucinet和Netdraw等软件得出高频关键词共现网络化可视图.利用S...     

基于无人机技术黄河沿岸沙丘移动速度监测及影响因素分析

为更便捷地监测乌兰布和沙漠黄河沿岸沙丘移动速度并解析其影响因素,该研究以乌兰布和沙漠沿黄段沙丘为研究对象,应用无人机航拍技术开展沿岸沙丘的季节性地貌过程和影响因素研究。结果表明:1)研究区沙丘年移动速率1.08～2.27 m/a,多年平均输沙势为78.82 VU,年合成输沙势为25.92 VU,处于低风能环境,8～12 m/s等级风输沙势是年输沙势的主要部分,约占73.24%。方向变率(合成输沙势(Resultant Drift Potential,RDP)与输沙势(Drift Potential,DP)的比值)RDP/DP保持在0.30～0.46之间,属于中等变率。合成输沙方向RDD为57.83°～107.39°,与沙丘移动方向较为一致,西风组占全年输沙势的52.09%,是沙丘年移动的主要驱动力。2)沙丘移动速率具有明显的季节特征,整体呈现春季移动速率快,冬末-春初次之,秋季与秋末-冬末相近,夏季移动速率最慢。其中,秋末-冬末、春季和秋季输沙势DP 8.48～20.49 VU,合成输沙势方向在90.02°～95.54°之间,RDP/DP值均在0.3～0.8之间,属于中等变率,西风组作用显著,这与年合成输沙方向及沙丘走向较为一致;冬末-春初和春末-夏季分别受东北风(NE)和南风组(SSE、S、SSW)作用,沙丘通过形态变化适应风向,移动速度降缓。季节输沙势主要集中在8～10m/s风速等级,约占整个季节输沙势的40.76%～56.93%。3)综合各季节和年际输沙势与沙丘移动距离呈线性正相关,拟合方程为y=1.02+0.006 62x(R~2=0.339,F=5.616,P=0.045),方程总体显著,输沙势可以表征该地区沙丘移动距离。基于无人机监测的沙丘运动研究综合显示,风况是该地区影响该地区沙丘移动的主要动力,其中西风组8 m/s以上风速是研究区沙丘移动的主要驱动力。风向变率和合成输沙势方向与沙丘移动方向一致时沙丘移动则快,不一致时则缓;无人机可在较大尺度上为沙丘移动提供更为便捷的监测服务,研究结果可为同类地区沙丘移动的无人机监测提供参考依据。     

柴达木盆地沙丘移动的空间分异及对形态参数的响应

研究沙丘移动规律与空间分异特征有助于准确了解风沙活动的危害程度,为区域城镇规划和青藏高原国家生态安全屏障保护与建设提供参考。该研究基于GoogleEarth软件测量横向沙丘的形态参数与移动速度,分析了移动速度与方向的空间分异特征,以及移动速度对形态参数的响应。结果表明,1)柴达木盆地内沙丘移动速度介于0～23.53 m/a之间,平均4.66 m/a,以中速(1～5 m/a)为主(53.73%),中部移动最快(5.22±4.27 m/a),东南部最慢(3.27±3.08 m/a),移动方向与主风向一致;2)沙丘移动速度与宽度的相关性最好(R~2=0.988),以后的研究中需多关注沙丘宽度这一参数;3)从柴达木盆地整体看,降水量越大、风速越低,沙丘移动越慢;从局部看,植被覆盖度越大,沙丘移动越慢;4)密集的河流可阻挡沙丘移动,保护格尔木市区,但不能消除沙丘移动的威胁。     

围封对流动沙丘表层土壤有机碳、全氮和活性有机碳的影响

以流动沙丘为对照,研究不同围封年限(14年和26年)下科尔沁退化沙质草地表层(0-15cm)土壤有机碳、全氮及活性有机碳的变化。结果表明:流动沙丘围封显著提高了土壤有机碳(SOC)、全氮(TN)、轻组有机碳(LFOC)和微生物量碳(MBC)含量,14年和26年围封样地SOC、TN、LFOC和MBC含量均随围封年限的增加而增加,且0-5cm层增幅高于5-15cm层。14年和26年围封样地土壤碳氮比显著高于流动沙丘,但2个围封样地之间差异不显著。流动沙丘围封也显著增加了表层SOC、TN、LFOC和MBC储量,0-15cm土层SOC、TN、LFOC和MBC储量均表现为26年围封地>14年围封地>流动沙丘。相关分析表明,LFOC、MBC均与SOC存在极显著正相关关系,说明LFOC和MBC均可作为衡量土壤有机碳变化的敏感指标。     

黄河乌兰布和沙漠段沿岸风沙流结构与沙丘移动规律

为明确黄河乌兰布和沙漠段沿岸的风沙活动及沙丘移动特征,该文以黄河乌兰布和沙漠段沿岸的流动沙丘为研究对象,采用野外观测与实验室分析相结合的方法对沿岸沙丘的起沙风况、沙物质组成、风沙流结构及沙丘移动规律进行初步的定量研究。结果表明:起沙风的主风为西南—西风,集中于3-5月份,且5～6m/s风占起沙风的50.26%;沙物质粒径以细砂(0.1～0.25mm)为主,沿黄段沙丘粒径极细砂以下(≤0.1mm)的沙物质粒径组成比沙漠腹地减少8.92%;距地60cm高度范围内,81.75%的沙物质在0～10cm高的气层中通过。在沙丘的不同部位上,相对输沙量与高程之间有着良好的幂函数关系;沙丘向前移动的距离为8.19m/a,主要发生在3-5月份。该研究结果可为合理计算入黄风积沙量及完善黄河沿岸综合防护体系提供科学依据。     

东祁连山不同高寒灌丛草地土壤抗蚀性研究

为探讨祁连山东段不同高寒灌丛草地的土壤抗蚀性特征,采用野外调查和室内试验的方式,对东祁连山金露梅、柳、杜鹃3类高寒灌丛草地的土壤抗蚀性特征及其影响因素进行了研究。结果表明:不同灌丛草地土壤水稳性团聚体主要以0.5mm的大粒径水稳性团聚体为主,土壤团聚结构破坏率表现为:柳灌丛草地杜鹃灌丛草地金露梅灌丛草地;土壤水稳性指数依次为:杜鹃灌丛草地(97.1%)柳灌丛草地(96.9%)金露梅灌丛草地(95.8%);土壤抗蚀指数表现为:杜鹃灌丛草地最大(95.0%),金露梅灌丛草地最小(92.9%)。总体上,杜鹃灌丛草地的土壤抗蚀性最强,金露梅灌丛草地的土壤抗蚀性最差。通过灰色关联度法,对0.5mm的机械团聚体含量、0.25mm的机械团聚体含量、0.25mm的水稳性团聚体含量、0.5mm的水稳性团聚体含量、土壤结构破坏率、水稳性团聚体平均质量直径、有机质、土壤崩解率、土壤水稳性指数、土壤抗蚀指数10个土壤抗蚀性指标进行评价分析认为,影响高寒灌丛草地土壤抗蚀性最主要的因素是水稳性指数、0.25mm水稳团聚体和水稳性团聚体平均质量直径。