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古尔班通古特沙漠沙丘坡面侧向流研究
刘昊
学位类型硕士
导师周宏飞
2015
学位授予单位中国科学院大学
学位授予地点北京
学位专业自然地理学
关键词沙丘 雪融水 土壤水分 坡面侧向流 入渗 降雨 古尔班通古特沙漠
摘要土壤水分是沙漠生态系统植被演替的的主要驱动因子。古尔班通古特沙漠的土壤水分主要来源于春季集中融化的冬季积雪和降雨。受植被、地形、下垫面等众多因素的影响,局地土壤水分空间分布差异显著,在沙丘坡脚存在水分富集现象。研究雪融水和降雨形成的沙丘坡面侧向流有助于深入理解降水转化过程、土壤水分再分配过程以及坡脚土壤水分富集的成因。对古尔班通古特沙漠沙丘坡面侧向流的定量研究前人未曾开展。 以古尔班通古特沙漠南缘典型树枝状沙丘为研究对象,通过在融雪期开展亮蓝示踪实验和土壤水分观测,确定雪融水在土壤中的运移路径,量化坡面侧向流。通过在研究区开展不同雨量和雨强的人工模拟降雨实验,确定降雨形成坡面侧向流的条件。主要研究结果如下: (1) 沙丘尺度上,积雪的空间分布均匀,均匀系数大于0.90,积雪空间分布并非沙丘土壤水分空间差异的成因。 (2) 雪融水在垂直入渗的同时,存在沿沙丘坡面方向的侧向流。2013年冬季累计积雪40 mm (雪水当量),侧向运移距离29.72~45.60 cm,侧向流流量1.08×10-3 m3/d。融雪期结束后,坡脚处43.97%的土壤水分来源于坡面侧向流补给。可见,雪融水侧向运移是坡脚土壤水分富集的重要原因。 (3) 研究区2003~2013年间最大自然降雨强度是14 mm/h,远小于裸露沙地平均土壤稳定入渗率(7.45 mm/min),自然条件下,降雨以垂直入渗为主,裸露沙丘坡面难易形成地表径流和沿坡向的壤中流。 (4) 人工强降雨模拟实验表明,在降雨后期,沙丘存在壤中侧向流,侧向流水量陡坡大于缓坡,土壤水分富集层深度陡坡大于缓坡,土壤水分富集区域位置陡坡比缓坡偏下。在雨强0.52 mm/min、雨量20.9 mm的情况下,陡坡和缓坡的侧向流对下部1 m深土壤剖面补给水量分别为8.68 mm和4.66 mm,分别占其土壤水分总储量补给的37.32%和32.63%。
其他摘要Water is the main driving factor to the vegetation succession in desert ecosystem. The soil moisture in Gurbantunggut Desert mainly comes from winter snow cover melting primarily in spring and rainfall. Many factors such as vegetation, topography, underlying surface conditions and so on, affect the soil moisture, which result in its spatial distribution variation in local areas and accumulation at the foot of sand dune. The study of lateral water flow deriving from snowmelt water and rainfall contributes to digest the process of rainfall conversion and soil moisture redistribution as well as the cause of soil moisture accumulation at the foot of sand dune further. Up to now, quantitative researches of lateral water flow in Gurbantunggut Desert have been largely neglected. At dendritic sand dune in south of Gurbantunggut Desert, we carried out continuous observation of dynamic variations of soil moisture and brilliant blue traced experiment during snow melting period or after rainfal for exploring the migration path of snowmelt water in soil layer and quantifing the lateral flow at the sametime. Meanwhile, through the simulated rainfall experiment of different rainfall amount and intensity, we analyzed the producing conditions of lateral water flow resulting from rainfall. The main results are as follows: (1) The uniformity coefficient (K) was greater than 0.9, which mean that spatial distributions of snow cover were homogeneous on sand dune scales. So the features of spatial distribution of snow cover weren’t the factors causing evident spatial variation in soil moisture of sand dune. (2) Snowmelt on the sand dune infiltrated vertically and migrated laterally. The lateral migration distance was in the range of 29.72~45.60 cm when the accumulation of snow cover is 40 mm (snow water equivalent). Snowmelt water amount of lateral flow was 1.08×10-3 m3/d. The contribution of soil water at the foot of sand dune derived from snowmelt lateral flow was 43.29%, indicating that snowmelt lateral migration was an important factor for the accumulation of soil water at the foot of sand dune. (3) Bare sandy land had an average soil infiltration rate of 7.45 mm/min, which is bigger than the strongest rainfall intensity (14 mm/h) during the period of 2003 - 2013 in this study region. It means that rainfall mostly infiltrated vertically under natural conditions, which result in less overland runoff and interflow along the slope direction of bare sandy dune. (4) The outcomes of simulated strong rainfall show that soil moisture migrated laterally apparently after rainfall. The depth of soil moisture accumulation layer on the gentle slope was greater than that on the steep slope. Meanwhile, the enrichment area of soil moisture was respectively located at middle and lower parts of slope. When rainfall intensity is 0.52 mm/min and rainfall amount is 0.52 mm/min, amounts of lateral water flow were 8.68 mm and 4.66 mm in 0~100 cm horizon, respectively, accounting for 37.32% and 32.63% of total soil water source in the lowland respectively.
学科领域自然地理学
语种中文
文献类型学位论文
条目标识符http://ir.xjlas.org/handle/365004/14637
专题研究系统_荒漠环境研究室
作者单位中科院新疆生态与地理研究所
推荐引用方式
GB/T 7714
刘昊. 古尔班通古特沙漠沙丘坡面侧向流研究[D]. 北京. 中国科学院大学,2015.
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