【作者】 李亮；

【导师】 王焰新； 许天福；

【作者基本信息】 中国地质大学 ， 地下水科学与工程， 2013， 博士

【摘要】 中国西北内陆干旱地区生态地质环境极其脆弱,干旱区的天然植被系统是生态地质环境系统中的重要组成部分。敦煌盆地位于河西走廊西段,是我国典型的内陆干旱地区。近几十年来,敦煌盆地以地下水资源为中的生态地质环境问题日益突出,尤其是天然植被系统和湿地退化严重,区内天然植被系统已经严重影响河西走廊乃至我国西北的生态安全,其天然植被系统的生态恢复已经成为“引哈济党”工程的首要目标。论文以敦煌盆地为研究区,对敦煌盆地浅地表层0-100cm内的土壤含盐量、含水量、有机质和地下水盐赋存特征进行分析研究,并利用遥感技术定量反演植被覆盖度和植物群落分布特征,深入开展了地下水-土壤-植被之间的相互关系研究,确定了地下水对天然植被格局的控制作用及其表现形态。通过研究地下水系统对天然植被系统生长的影响,以期为敦煌盆地的生态环境保护、植被恢复提供科学支撑,也为“引哈济党”工程提供有效的科学支撑,并为内陆干旱区依赖地下水天然植被生态系统的研究提供思路。本论文通过以上研究,得到如下结论：(1)利用2010年Rapideye影像,基于宏观尺度对敦煌盆地的天然植被信息进行提取,并采用归一化植被指数(NDVI),提取分类出芦苇群落、骆驼刺群落、红柳群落、胡杨林群落、盐穗木群落、白刺群落、黑枸杞群落分布的空间位置以及他们平均植被覆盖度分别为：13.1%、8.6%、8.2%、4.2%、3.8%、3.4%、2.8%。(2)研究区浅地表土壤盐渍化空间分布特征研究。通过分析5个不同深度梯度环境下(0-20cm、20-40cm、40-60cm、60-80cm和80-100cm)土壤盐渍化(含盐量、有机质、含水量.K+、Na+、ca2+、Mg2+、cl-、SO42-、NO3-)的垂直和水平分布特征,确定了土壤盐渍化的类型及其空间分布特征：工作区盐分表现出比较强烈的表聚性,土壤含盐量按其含量大小呈自上而下递减的垂直分异规律：有机质含量最高层位在20-40cm,研究区东湖和北湖大部分地区有机质含量低；含水量由高到低分别为40-60cm、60-80cm、80-100cm、20-40cm和0-20cm,在0-60cm深度下,含水量随着深度的增加而增加的趋势,在60-80cm内土壤含水量基本保持不变。(3)研究区土壤盐渍化类型划分：依据土壤Cl-/SO42-当量比值结果,显示5个不同深度下的土壤盐渍化主要类型以氯化物、氯化物-硫酸盐和硫酸盐-氯化物为主。氯化物含量自上而下逐渐减小,表现出很强的表聚性；硫酸盐呈自上而下增多的趋势；氯化物-硫酸盐基本保持不变和硫酸盐-氯化物有自上而下增加的趋势,表现出强底聚性。此外,土壤含盐量主成分分析结果显示,研究区土壤盐盐渍化主要是以Na2SO4和NaCl为主。(4)研究区不同深度下土壤含盐量、有机质与盐基离子相关性分析表明：不同深度下土壤含盐量与Cl-、Na+、SO42有较高的正相关性；在深度为80-100cm时,土壤含盐量与Cl-、SO42-、Ca2+、K+和Na+(P<0.01)呈现较好相关性；0-20cm内有机质与含盐量、C1-和Na+(P<0.01)有着较好相关性；.在深度为0-60cm时,C1-.与5042-、Na+之间都具有较好正相关性；深度为60-100cm时,主要以C1-与S042-为主。(5)研究区不同深度下土壤含盐量与天然植被覆盖度的响应关系：在0-80cm深度下的植被覆盖度随着土壤含盐量的增加均有减小的趋势,其中0-40cm内对天然植被覆盖度的影响比较大；有机质在0-20cm、20-40cm、40-60cm、60-80cm范围内随着有机质的增高植被覆盖度呈现出降低的趋势,说明有机质与天然植被覆盖度的关系非常弱且呈现一定的负相关性。(6)不同土壤盐渍化类型下土壤含盐量与植被盖度关系：按照CI/SO42-比值范围分三类,硫酸盐型、硫酸盐-氯化物型和氯化物-硫酸盐型、氯化物型下平均植被覆盖度分别为10.4%、9.7%和7.1%,在硫酸盐类型随着盐度的增加植被覆盖度呈现出减小的趋势,而在硫酸盐-氯化物型和氯化物-硫酸盐型、氯化物型下植被覆盖度与盐度没有明显趋势。(7)不同土壤盐渍化类型下地下水潜水埋深与植被盖度的关系：在硫酸盐型地区、氯化物-硫酸盐类型地区、氯化物型地区三类不同的盐渍化地区适宜植被生长的最大地下水潜水埋深分别是1.82m、2.17m和3.3m,超过这个潜水埋深植被生长明显受到抑制,说明不同盐渍化类型下,相同地下水潜水埋深,对天然植被生长影响存在着差异。(8)不同土壤盐渍化类型下TDS与植被覆盖度的关系：天然植被覆盖度和TDS有很好的对应关系,适宜植被发育的土壤盐渍化类型顺序为硫酸盐地区>硫酸盐-氯化物地区>氯化物地区；当TDS大于10g/L时,任何土壤盐渍化类型下的植被覆盖度都有明显降低的趋势。(9)土壤含水量与植被覆盖度的关系：土壤含水量对植被覆盖度的关系表现为先增大后减小的规律,对植物生长影响的深度在0-60cm表现突出,且当土壤含水量达到25%左右,植被覆盖度达到最高值,之后随着含水量的增大,植被覆盖度迅速降低。(10)植物群落分布与地下水补、径、排关系研究：不同地下水补径排条件下,植被群落分布特征明显,具体表现为：一是植物在地下水排泄到地表之前植物对其进行吸收利用,主要是从潜水面或毛细上升带内直接吸收利用地下水而存在的耐干旱植物；二是在地下水排泄到地表之后对其进行利用的喜水性植物。(11)地下水对天然植被格局的控制作用研究：依据天然植物对地下水的依赖程度、天然植物对地下水的利用方式和地下水的排泄方式把敦煌盆地地下水作用的天然植被系统划分为3种类型。分别为：(1)非地下水作用的植被系统；(2)地下水部分作用的植被系统；(3)地下水作用的植被系统,并根据每个GEDs进行了区域的划分和植被面积统计。(12)地下水流系统对天然植被群落格局具有宏观的控制影响,其地下水补给区、径流区和排泄区发育着不同的优势植被群落。而在排泄区的地下水位埋深、土壤含盐量和含水量等对局部植被群落局部格局的演化起着非常重要的作用。更多还原

【Abstract】 The system of natural vegetation in arid areas is an important part of ecological and geological environment system; especially it is fragile in region ecological and geological environment of the northwest of China. For recent decades, ecological geological environment problems in relation to groundwater resource had been increasingly prominent happened in the areas of natural vegetation system and wetland degradation. As a typical inland arid area of the Hexi corridor, Dunhuang basin has been seriously affected by degradation of natural vegetation system. And the natural ecological restoration of vegetation system has become a primary goal by the engineering of guide water from Ha er teng river into the Dang river.The thesis focused on the relationship the groundwater and soil-vegetation and to determine the groundwater effect on the control of natural vegetation structure and its expression form by means of analyzing the surface of0-100cm different depth of soil salinity, soil water content, organic matter and the occurrence features of groundwater and salt, also through using remote sensing quantitative inversion of the distribution characteristics of vegetation coverage and plant community in Dunhuang basin. It would provide scientific support for ecological environment protection, vegetation restoration and guide water from Ha’erteng river into the Dang River through studying the influence of the groundwater system of natural vegetation growth, as well would offer scientific mind for research of dependent groundwater ecosystems.This paper get the following conclusions through the above-mentioned-research:(1) Using Rapideye images technology of the normalized difference vegetation index (NDVI) has extracted the natural vegetation information about the reed community, alhagi community, Philippine community, lam wood community in iminqak community, salt, white communities, and the spatial location of black Chinese wolfberry community distribution and their average vegetation coverage is respectively:13.1%,8.6%,8.2%,4.2%,8.2%,3.4%and2.8%, respectively, based on a large scale in the dunhuang basin in2010. (2)The research of surface of soil salinization, the distribution characteristics and salinization type. Through analying the vertical and horizontal distribution characteristics of five different depth (0-20cm、20-40cm、40-60cm、60-80cm and80-100cm) and soil salinization (soil salinity, K+, Na+, Ca2+, Mg2+, Cl-, SO42-, NO3-) to determine the type of soil salinization in the study area and its spatial distribution features, to clarify the workspace salt has a relatively strong cohesion and also certify the soil salinity decrease size is top-down according to its content of the rule of vertical differentiation. Area of soil organic matter content is low and the highest value in20-40cm, high organic content areas are mainly distributed in the Mamitu of west lake to Yumen pass, and most of east lake and north lake have low organic content in the study area. Characteristics of soil water content distribution in the study area:the average depth of soil water content from high to low is (40-60cm,60-80cm,80-100cm,20-40cm,0-20cm), water content has increased with the increase of depth from0to60cm deep.(3)The classification of soil salinization in the study area:the types of salinization are main of chloride, chloride-sulfate and sulfate-chloride by the Cl-/SO42-equivalent weight in the study area. The performances are the chloride content from top to bottom gradually decreases, and showed a strong surface concentration, the sulfate showed a trend of increased from top to bottom, the chloride basic remains the same, the sulfate and sulfate-chloride has a tendency to increase from top to bottom, and showed a strong bottom concentration. In addition, the soil salt salinization results of under the different depth of soil salinity of the principal component analysis show that the study area is the main NaCl and Na2SO4.(4)The correlation analysis of soil base cation and soil salinity under different depth in study area:the soil base cations of Cl-, Na+and SO42-have higher positive correlation with the soil salinity. It shows that the organic content and soil salinity has certain relevance in the0-20cm and it becomes weaken with the increase of depth. There have well positive correlation about Cl-, SO42-,Na+from0to60cm, while there has low relationship Cl-and SO42-in the60-100cm.(5)The soil salinity and the vegetation fraction have a certain relationship under different depth of the study area. The vegetation fraction decrease with the soil salinity increase in the0-80cm, especially in the0-40cm has a significant impact on natural vegetation. The vegetation fraction increase with decrease of organic content that shows the relationship between organic matter and natural vegetation fraction.(6)The research of relationship between the soil salinity and vegetation fraction under type of different soil salinization according to the Cl-/SO42-equivalent weight ratio shows average vegetation fraction of the sulfate, sulfate-chloride and chloride-sulfate, chloride were10.4%,9.7%and7.1%. The general trend is salinity increase with the decrease of vegetation fraction within the sulfate area but there is no clearly trend in the sulfate-chloride, chloride-sulfate and chloride area.(7)The research of relationship between the groundwater buried depth and vegetation fraction under type of different soil salinization according to the Cl-/SO42-equivalent weight ratio shows the different groundwater buried depth has various impact on the natural vegetation growth. The suitable for natural vegetation growth groundwater buried depth are1.82m,2.17m and3.3m in the sulfate area, chloride-sulfate area, chloride area.(8)The research of relationship between the TDS and the vegetation fraction in different type of salinization indicate that the natural vegetation fraction and TDS has a good corresponding relation. It suitable for vegetation development order for sulfate> sulfate-chloride> chloride. When the TDS is greater than10g/L, the natural vegetation fraction has the trend of decrease.(9)The research of relationship between the soil water content and the vegetation fraction shows the vegetation fraction increase first and then decrease with increase the soil water content in0-100cm and the soil water content affect on the natural plant growth in0-60cm. When the soil water content is25%the vegetation fraction up to the highest value, but when the soil water content continue increase the vegetation fraction rapidly reduced.(10)Study on the relationship between the plant community’s distribution and groundwater recharge, runoff and discharge shows the plant communities distribution different under different conditions of groundwater. The drought resistance plant absorbs the water from the phreatic surface or the capillary rise. And the hydrophile plant uses the water after the groundwater reach to surface.(11)The study on groundwater effect on the control of natural vegetation structure come up with three vegetation systems are the effect by groundwater system of natural vegetation, part of the groundwater system of natural vegetation and non-groundwater system of natural vegetation according to extent of natural plant dependence on groundwater, the natural vegetation use of groundwater and the way of groundwater discharge, also according to each characteristic of GDEs divide the area and calculate the vegetation area in the Dunhuang basin.(12) Groundwater flow system has a macro control influence on natural vegetation community pattern. There have different vegetation community in the groundwater recharge area, runoff area, and drainage area. And buried depth of underground water level, the soil salt content and water content play a very important role to the evolution of the local vegetation pattern, in the drainage area.更多还原