【作者】 王永胜；

【导师】 杨文斌；

【作者基本信息】 中国林业科学研究院 ， 水土保持与荒漠化防治， 2014， 博士

【摘要】 库姆塔格沙漠东缘地理位置特殊，生态环境脆弱，是我国沙尘暴发生和发展的重要区域，同时历史文化名城敦煌位于其东侧，受到盛行西北风的影响，库姆塔格沙漠成为敦煌地区主要沙尘来源，而位于敦煌绿洲和库姆塔格沙漠之间的过渡带成为阻止沙尘侵害绿洲的天然屏障。因此通过对荒漠-绿洲过渡带的风沙活动特征以及典型风沙地貌的研究，对于完善区域风沙环境资料，揭示区域风沙地貌的形成具有重要的理论意义，同时也为敦煌地区防沙治沙工作提供理论参考。本文利用建立在库姆塔格沙漠东缘的国家林业局库姆塔格荒漠生态系统定位研究站实测数据，对库姆塔格沙漠东缘风沙活动特征以及“羽毛状沙丘”剖面特征进行研究，文章的主要结论如下：（1）库姆塔格沙漠东缘年平均风速在3.5m/s左右，风速主要分布在2m/s～5m/s之间，占全部风速的63.7%，起沙风（≥6m/s）约占全部风速的10%，风速随着高度的增加呈现幂函数方程V=aHb增加的趋，1970年以来平均风速有逐渐降低的趋势，起沙风主要发生在4～7月份，占全年起沙风的56.32%，起沙风在白天16～18（6%）时发生频率较高。（2）库姆塔格沙漠东缘荒漠绿洲过渡带白天多以西北风（NW）、北风（N）和东北风（NE）为主，夜间主要受到东南偏南风（SSE）控制。起沙风主要集中在西北偏西方向（WNW）和东北偏东方向（ENE），分布频率分别为22.62%和17.25%，起沙风风向昼夜变化不明显。（3）研究区输沙势主要集中在ENE和WNW方向上，输沙势分别为40.83VU和33.24VU，年合成输沙势（RDP）为54.73VU，合成输沙势方向为南方向（RDD为189°）。春季总输沙势（DP）和合成输沙势（RDP）最大，分别为71.68VU（其中四月份为43.31VU）和45VU（其中四月份为30.60VU）。（4）库姆塔格沙漠地区多风沙天气，年平均沙尘暴日数在6天以上，沙尘天气年内分布具有明显的季节特征，其中春季是沙尘天气的高发季节，其次为夏季，冬季和秋季发生沙尘天气日数相对较少；1950～2008年间，敦煌年沙尘暴发生日数、扬沙天气发生日数、浮尘天气发生日数均表现出逐渐减少的趋势。（5）24m高度范围内，沙尘水平通量随着高度的增加呈现幂函数递减的趋势，研究区1年内（2012年6月至2013年5月）通过1m（宽度）×24m（高度）断面的年总沙尘水平通量为1759kg，主要来自东北方向（NE）和西方向（W），分别占23.08%和19.97%，输沙量合成方向为S偏W1.36°，合成输沙量为465.47kg。（6）库姆塔格沙漠东缘荒漠绿洲过度带24m高度内收集的沙尘主要以细沙、极细沙和粉沙为主。沙粒的粒径级配随着高度的增加表现出明显的变化规律，在0～8m范围内，粉沙含量随着高度的增加呈现线性增加的趋势，细沙含量随着高度的增加表现出线性降低的趋势，当高度超过8m，各粒径沙粒比例变化不大。沙粒的偏度均为“正偏”，阶梯频率曲线为“单峰”曲线，沙粒分选系数随着高度的增加而增加。戈壁、沙丘迎风坡、沙丘丘顶、沙丘背风坡、林地和灌丛沙堆6种下垫面沙粒平均粒径在2.46～3.08φ之间，均以细沙（0.125～0.25mm）和极细沙（0.063～0.125mm）为主，因此不同下垫面均有提供沙物质的可能性。（7）库姆塔格沙漠东缘荒漠绿洲过渡带分布的灌丛、新月形沙丘链以及绿洲农田防护林具有显著的防风阻沙作用，荒漠绿洲过度带1m高处输沙量较荒漠地区降低了22.57%～48.54%，绿洲内1m高处输沙量较荒漠地区输沙量降低了89.64%～93.9%。（8）构成“羽毛状沙丘”羽轴的沙垄由首尾相连的“变形的”新月形沙丘构成，其走向为NE55°；新月形沙丘的平均高度为17.65m，西北翼角的平均长度为72m，均长于东南翼角。沙垄的纵断面（SW→NE）表现出明显的波动性，波长在50～100m之间，波高在10～25m之间。沙垄的平均宽度为127.69m，平均坡度为12.59°；西北坡平均坡长为71.74m，平均坡度为11.65°，东南坡平均坡长为59.05m，平均坡度为13.52°。“羽毛状”沙丘的“羽枝”部分是由地形平缓的穹状“大沙波”首尾相连构成，并未像遥感影像一样呈现出明暗相间的“羽毛状”图案。“大沙波”的平均宽度为641.34m，其纵断面相对平缓，2个“波峰”之间的距离在400m左右，“波峰”高度为1～3m，平均坡长为322.37m，平均坡度为1.28°，仅为沙垄的10%。更多还原

【Abstract】 The edge of eastern Kumtag Desert’ location is a special region withfragile ecologicalenvironment, where is an important area with the sandstorms occurrence and development inour country. The historical and cultural city of Dunhuang is located in the east of KumtagDesert, so Kumtag Desert becomes a main source of dust to Dunhuang, and the ecotone locatedbetween Dunhuang Oasis and Kumtag Desert becomes a natural barrier to prevent dustinvasion Oasis. Therefore, to study the wind and sand activity characteristics and typicalaeolian geomorphology in desert-oasis ecotone is meaningful for revealing the formation ofregional aeolian landforms. It also provides theoretical reference for desertification combatingin Dunhuang. In this study a statistical analysis on wind regimes in the eastern marginal zoneof the Kumtag Desert and characteristics of profiles of “feather-like dunes” was carried outduring the period from2012to2013. The principle features and findings are listed as follows:(1) The average wind velocity is3.5m/s in the eastern marginal zone of the KumtagDesert, the winds of2-5m/s account for63.7%of all winds, and the wind more than6m/saccounts for10%. Wind velocity increases with the height as a power function. The averagewind velocity has gradually decreased since the1970. Sand-moving wind in the study areaoccurs mainly in April to July and the frequency is56.32percent, and the frequency ofsand-moving wind during16:00to18:00was6percent.(2) This region is affected predominantly by NW and NNE winds during the daytime, andSSE winds during the night, there is a higher accumulated frequency of sand-moving windswith22.62percent in the WNW and17.25percent in the ENE. Finally, sand-moving windsdo not change significantly in daytime and nighttime.(3) There is a higher sand-transport potential in the ENE and WNW directions, and thesand-transport potential is40.83VU and33.24VU, resultant sand-transporting potential (RDP)54.73VU, resultant sand-transporting direction (RDD)189°S. There is a higher drift potential (DP) with71.68VU and sand-transporting potential (RDP) with45VU in the spring, and theRDPis43.31VU and the DP30.6VU in April.(4) The average annual sandstorm days have6days, and spring and summer are theseasons with more dust weather, the sandstorm days and jansa days and dust weather show adecreasing trend during1950to2008.(5) Horizontal aeolian dust flux decays with height in power exponentiation, the totalhorizontal aeolian dust flux through the transect with a height of24m and width of1m is1,759kg a year, of which23.08percent of the total horizontal aeolian dust flux comes from NEand19.97percent from W, and the resultant sand-transporting direction is181.36°S, theresultant sand-transporting465.47kg.(6) The dust is mainly composed of fine sand, very fine sand and silts at the height of0--24m in the eastern marginal zone of the Kumtag Desert. The particle size distribution curvecan be divided into2parts:0-8m is the lower part, where the percentage content of siltsincreased with height, but the percentage content of fine sand decreased with the increase ofheight;8-24m is the upper part, where the percentage content of silts and the percentagecontent of fine sand change little with height. The skewness of dust is “positively biased”,and the frequency curve “single peak curve”, the sorting coefficient of the dust increases withheight. The fine sand and very fine sand take a large proportion in different land surfaces, theaverage grain diameter is in the range from2.46φ to3.08φ in six surfaces, which all the sixsurfaces can supply dust to air potentially.(7) The shrubs and barchan dunes in the eastern marginal zone of the Kumtag Desertand the farmland shelterbelt in oasis have significant effects on wind-provention andsand-stabilization, the horizontal aeolian dust flux in transitional zone and in oasis are reducedby22.57percent to48.54percent than that in desert, and89.64percent to93.9percent,respectively.(8) The direction of “quill” of “feather-like dunes” is NE55°, and the “quill” composesof crescent dunes ridges with the average height of17.65m, whichthe average length of northwest wing is generally72m, longer than their southeast wing. Great fluctuation is foundfrom the profile of the “quill”: the wave length is50-100m, and the wave height10-25m.The average width and slop of the “quill” are127.69m and12.59°, respectively. The averagelength and slop of northwest slope were71.74m and11.65°, respectively. The average lengthand slop of southeast slope were50.09m and13.52°, respectively. The “plume” of “feather-likedunes” is composed of large dome-like sand dune waves, not a “feathery” pattern of light anddark hues as shown in remote sensing images. The average width of the large dome sand dunewaves is641.34m, with a relatively flat profile. The distance between two waves is about400m, and the wave height ranges in1-3m, the average slop length and average gradient are322.37m and1.28°, respectively.更多还原