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     

Chao LI  Zhibao DONG  Shuyan YIN 《干旱区科学》2019,11(5):674-684

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.  相似文献   

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

LIU Qingsheng  LIU Gaohuan  HUANG Chong 《干旱区科学》2018,10(1):12-26

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.  相似文献   

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   总被引：1，自引：1，他引：0  

李锦荣  王健  王茹  郭建英  罗祥英  李映坤  崔万新 《农业工程学报》2021,37(19):57-64

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。  相似文献   

柴达木盆地沙丘移动的空间分异及对形态参数的响应     

李建军  焦菊英  曹雪  白雷超  陈同德  严晰芹  祁泓锟 《农业工程学报》2021,37(7):309-314

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。  相似文献   

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   总被引：1，自引：0，他引：1  

尚雯  李玉强  韩娟娟  赵学勇  张铜会  罗永清  王少昆 《水土保持学报》2012,26(6):147-152

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。  相似文献   

黄河乌兰布和沙漠段沿岸风沙流结构与沙丘移动规律   总被引：7，自引：4，他引：7  

何京丽  郭建英  邢恩德  崔崴  李锦荣 《农业工程学报》2012,28(17):71-77

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。  相似文献   

Spatial pattern and heterogeneity of soil properties in sand dunes under grazing and restoration in Horqin Sandy Land, Northern China   总被引：2，自引：0，他引：2  

Xiaoan Zuo  Halin Zhao  Xueyong Zhao  Tonghui Zhang  Yirui Guo  Shaokun Wang  Sam Drake 《Soil & Tillage Research》2008,99(2):202-212

Applying a combination of classical and geostatistical methods, we identified soil properties and their spatial variation in a 5-year grazed sand dune (GSD5) and a 20-year recovered sand dune (RSD20) in Horqin Sandy Land, northern China. The paper assesses the effect of grazing, topography and vegetation restoration on spatial heterogeneity of soil properties. The results showed that soil organic carbon, total nitrogen, very fine sand (0.1–0.05 mm) content and their coefficients of variation were lower in GSD5 than in RSD20, while soil water contents (0–20 cm and 20–40 cm depths) were higher in GSD5 than in RSD20. Geostatistical analysis revealed that the spatial structured variance accounted for the largest proportion of total sample variance in soil properties at the measured scale under grazing and restoration. The spatial autocorrelation ranges were 66.30 m for soil organic carbon and 50.80 m for total nitrogen in GSD5 less than those in RSD20 (70.00 m and 76.10 m, respectively), while the spatial autocorrelation ranges of soil particle size fractions and soil water contents in RSD20 were less than those in GSD5. Kriging-interpolated maps also showed that the heterogeneity of soil organic carbon and total nitrogen and their degree of patch fragmentation were higher in GSD5 than in RSD20. These results suggested that continuous grazing resulted in an increase in spatial variability of soil nutrient and a decrease in spatial variability of soil particle size fractions and soil water content. Soil organic carbon and total nitrogen of sand dunes are associated closely with soil particle size fractions, relative height of sampling site and vegetation cover. Spatial patterns of soil properties are most strongly related to grazing, topography and plant-induced heterogeneity in sand dune ecosystems prone to wind erosion.  相似文献   

Spatio-temporal variation of soil moisture in a fixed dune at the southern edge of the Gurbantunggut Desert in Xinjiang,China     

Hai ZHU 《干旱区科学》2019,11(5):685-700

Soil moisture is critical for vegetation growth in deserts. However, detailed dataregarding the soil moisture distribution in space and time in the Gurbantunggut Desert have not yet been reported. In this study, we conducted a series ofinsitu observation experiments in a fixed sand dune at the southern edge of the GurbantunggutDesert from February 2014 to October 2016, to explore the spatio-temporal variation of soil moisture content, investigate the impact of Haloxylonammodendron (C. A. Mey.) Bungeon soil moisture content in its root zone, and examine the factors influencing the soil moisture spatial pattern. One-way analysis of variance,least significant difference testsand correlation analysis were used to analyze the data. The results revealed that the soil moisture content exhibited annual periodicity and the temporal variation of soil moisture content throughout a year could be divided into three periods, namely, a moisture-gaining period, a moisture-losing period and a moisture-stable period.According to the temporal and spatial variability, the 0-400 cm soil profile could be divided into two layers: an active layer with moderate variability and a stable layer with weak variability.The temporal variability was larger than the spatial variability in the active layer,and the mean profile soil moisture content at different slope positions displayed the trend of decreasing with increasing relative heightand mainly followed the order of interdunearea>westand east slopes>slope top.The mean profile soil moisture content in the root zone of dead H. ammodendronindividuals was significantly higher than that in the root zones of adult and young individuals, while the soil moisture content in the root zone of adult individuals was slightly higher than that in the root zone of young individuals with no significant difference.The spatial pattern of soil moisture was attributable to the combined effects of snowfall, vegetation and soil texture, whereas the effects of rainfall and evaporation were not significant. The findings may offer a foundation for the management of sandy soil moisture and vegetation restoration in arid areas.  相似文献   

高寒草原不同种草方式对流动沙丘植被恢复的影响     

李银科  唐进年  王祺  袁宏波  杨雪梅  何芳兰 《水土保持通报》2021,41(1):22-28

[目的]研究种草方式对流动沙丘植被恢复效果的影响,为高寒草原沙化土地治理提供技术支持.[方法]在甘肃省玛曲县流动沙丘,设置不同播种方式、不同草种和不同种草模式试验,分析不同种草方式对植被恢复的影响.[结果]撒播和条播对植被恢复无显著影响.总体上草种对植被恢复影响不大,流动沙丘植被恢复中只需种植垂穗披碱草(Elymus ...  相似文献   

乌兰布和沙漠流动沙丘不同部位水分动态研究   总被引：5，自引：3，他引：5  

叶冬梅  秦佳琪  韩胜利  田有亮  郭连生 《干旱区研究》2005,22(3):367-370

通过对乌兰布和沙漠流动沙丘的不同部位沙土含水量的测定研究，结果表明：（1）乌兰布和沙漠流动沙丘3个不同部位的水分垂直变化趋势是一致的，0～60cm含水量变化幅度大，60～100cm变化幅度小，含水量最大值出现在20～60CITI，降雨主要影响60cm以上的沙土水分；（2）3种部位在时间变化上都表现为4～5月含水量最小，从6月开始含水量升高；（3）迎风坡含水量较其他部位大0．65％～0．9％，较背风坡大1．8％～2．5％，其他部位较背风坡大1％～1．7％，且3种地貌部位20～60cm处较80cm和100cm处有较大差异，同时迎风坡的变化幅度最大。  相似文献