【作者】 胡良军；

【导师】 邵明安；

【作者基本信息】 西北农林科技大学 ， 土壤学， 2002， 博士

【摘要】 黄土高原地处半干旱半湿润向干旱荒漠的过渡地带，生态环境十分脆弱。水分是制约该区植被恢复和生长及生态重建的主要生态限制因子。研究黄土高原的水分生态环境问题，对于该区的植被恢复等生态环境建设工作具有十分重要的意义。 本研究针对黄土高原水分生态环境研究的现状及存在的问题，主要致力于下述四个方面的研究：(1)黄土高原的土壤水分背景；(2)黄土高原土壤水分状况的现实；(3)黄土高原水分的植被生产力；(4)基于GIS的黄土高原区域水分生态环境的空间格局。 经过两年多的野外实地调查、取样及室内分析，获得的主要研究结果如下： 1．对黄土高原地区气候—降水的区域分异及水资源状况进行了分析。黄土高原地区的区域降水状况及其水资源是决定该区土壤水分生态条件的前提。分析结果显示：(1)黄土高原地区的降水分布自东向西、自南向北逐渐减少，东南部可达900多毫米，西北部最低则仅约100毫米，表现出显著的大陆性气候特征；(2)由于地形等因素的影响，山地森林等局部地区小气候特征明显，降水量高于周围地区，结果形成降水的岛状镶嵌结构；(3)土壤水是黄土高原最重要的水资源之一，它是该区植被水分利用的重要资源。黄土高原的水资源利用程度高，供需矛盾突出；地下水资源赋存有限，不宜开发利用。 2．发展了“土壤水分背景”的概念，并以之为基础对其各个方面进行了研究，使之形成一个相对独立和完整的体系，主要包括黄土高原土壤水分的背景值、土壤水分背景的区域分异、坡面分异、镶嵌结构及其季节分异等：(1)由于植被生长发展、演替的基础阶段是天然草被群落，故认为黄土高原的土壤水分背景在概念上是特指该区天然草被群落下的土壤水分状况；(2)黄土高原的土壤水分背景值，根据植被地带的不同表现出自南向北逐渐降低的规律：森林地带3米以下土层水分背景值普遍稳定地高于12％，森林草原地带4米以下土层水分背景值稳定大于6％，且均随土层的加深水分含量逐渐增加，而草原带的土壤水分背景值自土表至底土层一直在4％～6％之间徘徊。在土壤水分背景值的垂向分异上，森林带3米以上土层、森林草原带4米以上土层，自上而下增加显著，上述深度以下土层其值则较稳定，而草原带的土壤水分背景值垂向变化不强烈；(3)黄土高原天然草被下土壤水分的百分含量与其有效水含量的区域分布有着相似的规律，即南高北低，同时具有与降水的区域分异相似的镶嵌结构；(4)黄土高原的土壤水分背景值受坡度、坡向、坡位等因素的影响显著，一般规律为缓坡大于陡坡，阴坡大于阳坡，坡脚、沟道大于沟坡和峁坡；(5)黄土高原的土壤水分背景表现出区域范围上的大镶嵌以及局部坡面尺度上的小镶嵌结构；(6)黄土高原的土壤水分背景值受降水的季节分配影响而表现出一定的季节分异，旱季失水，雨季有所恢复，恢复的程度则取决于季节降水量的多寡。 胡良军博士学位论文：黄土高原植被恢复的土壤水分生态环境一 3．分别植被类型、土地类型对黄土高原的土壤水分状况进行了研究，提出了土壤干化的判别标准，并就典型地区的土壤水分状况、土壤干化在黄土高原的分布、以及土壤水分的自然恢复与补偿等问题进行了探讨。结果表明：（l）人工植被，包括人工草被和人工林地的土壤水分状况，低于相应天然草被下的土壤水分状况；一些代表性人工草种如沙打旺、首淆等耗水强烈，其土壤水分含量接近萎蔫湿度水平；天然草被、灌丛（如柠条）对土壤水分的影响较乔木为低，影响的土壤深度较浅，而乔木对深层尤其是5米以下土层的土壤水分状况影响强烈。（2）梯田的土壤水分状况较好，在生长有沙打旺的条件下仍具有相当于天然草被下的土壤水分含量；滩地在生长首淆（3年生）的条件下有与该地天然草被下相当的土壤水分含量；涧地土壤水分优于相应的坡地；撂荒地土壤水分则优于该地天然草被下的土壤水分状况。 门）黄丘区典型地米脂的沟道横断面土壤水分数据显示，该区的土壤水分总体含量水平不高，稳定土壤水分含量保持在5～7％（萎蔫湿度为3．8％）；土壤水分含量在雨季前后仅反映在距地表 40厘米土层内的变化上，水分的季节性补偿十分有限。（4）提出“初始萎蔫湿度”的概念，并将其作为判别土壤干化发生的标准；以此为依据，计算并确定了中部黄土高原典型地区的土壤干化层发生分布情况。（5）黄土高原地区土壤水分的自然恢复主要发生在雨季，恢复的程度取决于年降水量的多寡，并且与所处的植被地带有关。恢复的程度自南向北逐渐减弱。 4．对黄土高原局部地区水分的植被生产力进行了研究，结合理论分析与黄土高原植被生产力的现实表现，提出并建立了该区水分的植被生产力模型。结果表明，黄土高原水分的植被生产力与水分的变率具有密切的关系，其次是生物学特性中年龄特性的影响。 5．利用GIS技术和地理综合的观点，在全面考虑各种影响因素的条件下，对黄土高原水分生态环境的区域空间格局进行了研究。提出以对不同植被的适生性作为黄土高原植被水分生态状况的反映指标。认为，影响并能够反映黄土高原土壤水?更多还原

【Abstract】 The Loess Plateau of China is located at a transitional area where the semi-humid climate is changing into the semi-arid and arid climate. This makes the eco-environment of the plateau very fragile. Because of both natural and man-induced causes, up to now, the Loess Plateau of China is being a colossal degraded eco-system. In such an area, water is the controlling factor which refrains the growth of vegetation and crop production. So, the study on the water eco-environment of the plateau is significant to vegetation recovery and eco-reconstruction.Based on the achievements of related previous studies on this issue and the unsolved problems, here, four aspects are concentrated in this dissertation for the issue. They are: (1) Background of the soil water environment of the plateau; (2) Reality of the soil water environment of the plateau; (3) Vegetation capacity of the soil water of the Plateau; and (4) Spatial differences study for the soil water eco-environment of the plateau using GIS.The objectives are approached both by field survey and lab analysis. The following results are obtained based on the field data and analyses:1. The spatial heterogeneity of climate and precipitation and the water resources in the Loess Plateau area are analyzed and discussed.The water eco-conditions are derived from the regional precipitation and the water resources of the plateau area. Results show that: (1) The precipitation of the Loess Plateau appears to descend spatially from east to west and from south to north. At the southeast, the maximum average annual precipitation can reach 950mm, and the minimum at the northwest is just 150mm. These reflect an obvious continental climate characteristic. (2) Parts of the area show apparent local climatic properties because of the influence of topography, landcover, and so on. Precipitation in mountainous and forest area is usually more affluent than in vicinity, this creates a typical mosaic structure of precipitation distribution like the islands. (3) Soil water is the most significant form of water resources, which is the only water for vegetation uptake. The utilization of surface water resources in areas of the Loess Plateau is in full extent, so the balance between supply and demand is a serious problem. However theuse of groundwater has rooms to be extended and the water-using efficiency is relatively low.2. The concept of soil water background is developed in this dissertation. Meanwhile, most aspects about this perspective are concerned, which include quantification of the soil water background of the plateau area, the regional spatial variation of soil water background and variation along the slope, mosaic structure and seasonal changes etc. The results show that: (1) For the fundamental circumstance for vegetation development is the original debilitated slope, so the perspective of soil water background specially for the Loess Plateau refers to the soil water conditions on the original slope. (2) The value of soil water background appears to be a descending trend from south to north based on the difference of vegetation zones. In the forest zone, soil moisture contents beneath 3m depth from the soil surface are more than 12% usually; in the forest-pasture zone, the values of soil moisture content beneath 4m depth underground are more than 6% and stable, and tend to be ascending while the depth increases; but the values in the dry pasture zone is lingering between 4% to 6% from the surface layer to sub-layers. Vertically, the values of the upper 3m soil layer in the forest zone and upper 4m soil layer in the forest-pasture zone increase dramatically with depth, and the soil moisture contents beneath the depths seem to be stable, but they vary a little bit along the profile in the pasture zone. (3) The distributions of both regional soil moisture and available soil water are similar, high in the south and low in the north, and have a mosaic structure similar to the regional precipitation distribution. (4) The soil moisture of the original slope is inf更多还原