【作者】 李燕；

【导师】 卢玉东；

【作者基本信息】 长安大学 ， 地下水科学与工程， 2013， 硕士

【摘要】 乌兰布和沙漠深居西北内陆，降水稀少，蒸发量大，而沙漠覆盖的吉兰泰湖盆区地下水资源较为丰富，水位埋深浅，地下水成为梭梭、白刺、沙冬青等沙生灌木半灌木林补充水分的主要途径。浅层地下水通过毛细带向上以水、汽形式补给土壤水，这种垂向水分循环维系着水分、盐分、热量均衡以及植被的生态平衡。恶劣的自然地理条件，加之吉兰泰盐化工业、查哈尔滩等绿洲农业超量开采地下水，造成了沙漠区地下水位持续下降，水质恶化和土壤盐渍化加剧，沙生植被出现大面积衰退死亡。土壤水和地下水转换关系及水文地质环境的变化对沙生植被的结构、演变的影响，成为该地区水文生态研究的核心和关键。围绕上述科学问题，本文通过文献查阅、资料收集、野外调查及室内试验相结合的方法，开展了乌兰布和沙漠地下水与土壤水间水汽热耦合运移规律及植被生态学意义研究。主要获得以下成果：（1）沙漠地下水浅埋区土壤垂直剖面分为4个区：根区、水分传输区、毛细饱和区、潜水层。其中，0~80cm根区土壤含水量变化频繁，变化幅度剧烈，在40~60cm出现土壤湿层，其水分主要来源于浅层地下水。浅层地下水与土壤水间相互转化具有年内周期性变化规律，可分为：地下水补给期，土壤水缓慢补给期，土壤水消耗-补给期。（2）近地表土壤温度和土壤含水量存在明显的日变化规律，随深度增加日变化幅度逐渐减小，其中以地表0cm变化最为剧烈，深层土壤温度和含水量无明显日变化，且各层之间基本稳定。土壤温度年变化曲线随深度增加振幅减小，出现一种“右倾”现象。（3）昼夜间，土壤温度垂直分布曲线放热型与受热型交替循环，对水汽运移产生一定的影响。温度梯度是浅层土壤水汽运移的主控因素，在温度梯度作用下，水汽往温度低的界面运移，引起浅层土壤含水量的变化。深层土壤水汽运移量相对液态水运移量甚微。运用HYDRUS-1D软件对土壤温度和含水率的计算值与实测值进行初步对比。（4）选择地下水埋深、风沙土毛细上升高度、土壤含水率、地下水埋深年变幅、地下水矿化度、土壤含盐量评价指标体系，应用基于GIS模糊综合评判法将研究区梭梭生态适宜性可划分为适宜区、较适宜区、较不适宜区、不适宜区，其中，适宜区面积为1924.71km2，占总面积的21.0%，主要分布在吉兰泰镇西侧及沃布多格至查干温都日格以南地区；较适宜区面积为1725.86km2，占总面积的18.8%，主要分布在好来宝—和平—苏海呼都格一线附近丘间洼地及平沙地；较不适宜区面积为1897.23km2，占总面积的20.7%，主要分布在贺兰山、狼山及巴彦乌拉山山前地带；不适宜区面积为3623.01km2，占总面积的39.5%，主要在研究区中部及以南吉兰泰至巴彦树贵洪积扇中、后缘及高大沙山。更多还原

【Abstract】 Ulan Buh desert situated the northwest island has scarce rainfall, large evaporation, butthe lower Jartai lake-basin area in the desert has abundant groundwater resources with shallowgroundwater level, so the groundwater becomes the main way to provide water for shrub-halfshrub vegetation in this area, such as Haloxylon,Nitraria, Ammopiptanthus. Shallowgroundwater upward supply soil water through capillary by the forms of liquid and vapor, thisvertical water cycle sustains the balance of water, salt and heat and the ecological balance ofvegetation.Harsh natural and geographical conditions, combined with the over-exploitation ofgroundwater by Jartai salt industry and Chahal beach oasis agriculture etc, caused thegroundwater level continue to decline, water quality deteriorate, soil salination intensify, largerecession death of desert vegetation appear. The influence on the structure and evolution ofdesert vegetation by transformation between soil water and groundwater and change ofhydro-geological environment become the core and key of the hydro-ecological research inthe region. Around these scientific issues, combining the ways of literature review, datacollection, field investigation and laboratory test, we carry out the research of the coupledwater-vapor-heat migration between groundwater and soil water and vegetation ecologicalsignificance of Ulan Buh desert. We obtained the following main achievements:(1) Soil vertical section is divided into four zones in shallow groundwater area of desert:the root zone, moisture transport zone, capillary saturation zone, phreatic water layer. Soilwater changes frequently with severe range in0~80cm root zone, soil wet layer appear in40~60cm layer, its water mainly comes from shallow groundwater. Shallow groundwater andsoil water interact with each other. The mutual conversion between shallow groundwater andsoil water has a cyclical variation with year and can be divided into three stages: thegroundwater recharge, soil water slow consumption, soil water consumption-recharge.(2) The diurnal variation of the temperature and the water content of near-surface isobvious，and the amplitude of diurnal variation decreases with depth, of which the change isthe most dramatic on surface (0cm), deep soil temperature and soil water content has noobvious diurnal variation, and difference is basically stable between the layers. The amplitudeof annual variation curve of soil temperature decreases with depth, presenting a "rightdeviation" phenomenon.(3) within one day, the vertical distribution of soil temperature curve circulates betweenheat-release and heat-acception, which produces a certain effect on moisture migration. Temperature gradient is the main controlling factor of shallow soil moisture migration. Underthe action of temperature gradient, water vapor transport toward interface with lowtemperature, which caused the change of shallow soil water content. Deep soil water-vapormigration flux is relatively little compared with liquid water flux. HYDRUS-1D software wasused to make a primary comparison between the calculated values and measured values aboutsoil temperature and water content.(4) We select the assessment index system including groundwater depth, height ofcapillary rise of sand soil, soil water content, the annual range of groundwater depth,groundwater salinity, soil salinity, apply the fuzzy comprehensive judgement based on GIS,the Haloxylon-oriented vegetation ecological suitability was divided into suitable area,relatively suitable area, less suitable area and unsuitable area. The suitable area is about1924.71km2, accounting for21.0%of the total area, mainly distributes in the west of Jartaiand the south area from Wobbe to ZhGanwen. The relatively suitable area is about1725.86km2, accounting for18.8%of the total area, mainly distributes in the inter-dune bottomlandand flat dunes near the line of Haolaibao-Heping-Suhai. The less suitable area is about1897.23km2, accounting for20.7%of the total area, mainly distributes in the piedmont ofHelan Mountain, Lang Mont, Byan ula Mountain. The unsuitable area is about3623.01km2,accounting for39.5%, mainly distributes in the middle and rear edge of diluvial fan and bigsand hill from Jartai to Byan Shugui on the central and south of study area.更多还原