柴达木盆地沙丘移动的空间分异及对形态参数的响应

Spatial regionalization and response to morphological parameters of dune migration in the Qaidam Basin of China

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Google Earth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(R2=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。

Desertification and dune migration are two serious forms of land degradation,resulting in the destruction of grassland and farmland ecosystems.Sandstorm activities occur more frequently in the Tibetan Plateau of western China in recent years,particularly with the expansion of desertification.The Qaidam Basin is the largest intermountain basin located in the northwestern portion of the Tibetan Plateau.This basin is usually considered to be'the region of Earth most similar to Mars',providing for a sound reference for the study of Mars aeolian geomorphology.However,it is still lacking the understanding of dune migration in the Qaidam Basin.Taking the transverse dunes(such as barchan dune)as the research objects,this study aims to clarify the spatial regionalization and response to morphological parameters of dune migration in the Qaidam Basin.Geo Eye,Quick bird and World View satellite images were utilized to measure morphological parameters and migration using the Google Earth software.The main results were listed as follows:1)The average migration rate of dunes was between 0 and 23.53 m/a in the study area,with an average of 4.66 m/a,more than half of which was the medium speed(53.73%).The migration direction of the dune was between 53.52°and 150.06°,with an average of 104.13°,indicating a better agreement with the main wind direction.The average speed of dune migration slowed down spatially from northwest to southeast,but there was no obvious trend.Specifically,the fastest migration was found in the middle(5.22 m/a),followed by the northwest(4.84 m/a),the north(3.49 m/a),the southwest(3.35 m/a),and the southeast(3.27 m/a).The migration direction changed with the direction of the mountain range.2)The migration of the dune was much slower as the volume of dune increased in the same environment.There was a very significant(P<0.01)exponential negative correlation between the migration speeds and morphological parameters of dune,such as the length of windward slope(R^(2)=0.716),length of lee slope(R^(2)=0.705),height(R^(2)=0.705),width(R^(2)=0.988),perimeter(R^(2)=0.986),basal area(R^(2)=0.955),whereas,a very significant(P<0.01)linear negative correlation with the coefficient of dune shape(R^(2)=0.438),and a significant(P<0.05)positive linear correlation with the length-width ratio(R2=0.130).Therefore,more attention can be paid to the dune width in future studies using remote sensing images.3)The dune migration was much slower as the wind velocity decreased and the precipitation increased in the whole basin.Furthermore,the dune moved slowly under the great vegetation coverage in the southeastern basin.4)Dense rivers blocked the dune migration and protected Golmud City,but the dune migration still posed great threats to the whole ecosystem.This finding can make a great contribution to the accurate understanding of sandstorm activities for regional town planning and protection in the national ecological security shelter zone on the Tibetan Plateau of western China.