| 题名 | 黄土高原深层土壤水分对植被恢复的响应研究 |
| 作者 | 杨磊 |
| 学位类别 | 博士后 |
| 答辩日期 | 2014-06 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 傅伯杰，陈利顶 |
| 关键词 | 黄土高原 土壤水分 植被恢复 空间变异 Loess Plateau soil moisture vegetation restoration spatial variation |
| 其他题名 | Response of deep soil moisture to vegetation restoration in the Loess Plateau, China |
| 学位专业 | 环境科学与工程 |
| 中文摘要 | 干旱和半干旱地区植被和水分的相互作用关系及其时空变异是目前生态水文学领域的研究热点和前沿。土壤水分是陆地生态系统中多个生态过程的重要纽带，尤其在我国黄土高原，深层土壤水分是人工植被维持生长的重要水分来源，也是维系这一地区生态系统健康与可持续性的关键。自1999 年以来大规模开展的植被恢复显著改变了这一区域的地表覆盖特征，也改变了一系列的生态水文过程。探讨深层土壤水分对植被恢复的响应，阐明植被与深层土壤水分相互作用的空间分异及其时序特征，是深入揭示生态系统—水文过程相互作用机理的重要内容，也是黄土高原生态系统恢复和植被建设合理布局的前提和基础。 为探讨大规模人工植被恢复对深层土壤水分的影响，本研究选取了位于典型半干旱黄土丘陵区的甘肃定西龙滩流域为研究区，以坡面和小流域为重点研究尺度，在对土壤水分进行定位监测和系统采样的基础上，采用经典统计、典范对应分析、GIS 分析等方法，探讨了坡面尺度植被和地形耦合作用下的浅层和深层土壤水分空间分异规律，造林和农耕小流域土壤水分的对比研究，以及流域尺度土壤水分时间稳定性的空间分异特征，取得以下主要结论： （1）在同种人工植被覆盖条件下，坡面尺度浅层土壤水分的空间分异主要受地形驱动，与地形湿度指数显著正相关，呈现出自上而下逐渐增加的空间分布规律。而深层土壤水分含量沿着坡面自上而下逐渐降低，其空间分异特征与浅层水分截然相反，深层土壤水分与地形湿度指数和地上植被生长状况呈显著负相关。研究发现地上植被生长状况在坡面自上而下逐渐增加，导致其对深层土壤水分的消耗出现坡面分异，在地形和植被的耦合作用下，使得浅层和深层土壤水分空间分异规律有所不同。人工植被的耗水特征使得地形对深层土壤水分空间变异的影响有所改变，深层土壤水分更倾向于受植被生长的影响。 （2）土地利用是深层土壤水分的关键影响因素，农地在整个土壤剖面均具有较高的水分含量，而人工植被深层土壤水分含量普遍较低，且不同人工植被类型之间并无显著性差异。对比造林和农耕小流域，发现流域深层土壤水分状况及其空间变异特征与土地利用紧密相关，土地利用类型、结构及其空间格局是流域尺度深层土壤水分空间变异的决定因素。复杂的土地利用结构具有较高的深层土壤水分空间异质性，而进行大规模人工植被恢复以后，深层土壤水分则会呈现出较高的空间均质性。 （3）流域土壤水分定位监测表明，不同深度土壤水分受环境因子的影响不同，人工植被土壤水分在降雨入渗深度以下没有明显的季节动态和年际变化，具有较高的时间稳定性，且随着土层深度的增加而增加。土地利用是流域尺度土壤水分时间稳定性差异的主要影响因素，其次为坡度和土壤质地。不同水文年深层土壤水分的对比研究表明长期人工植被恢复以后，深层土壤水分没有明显的年际变化，深层土壤水分可能难以为人工植被的生长提供有效的水分来源。 |
| 英文摘要 | The interaction between vegetation and soil moisture and its spatial-temporal variations at different scales in the arid and semi-arid areas is focused in current studies in Ecohydrology. Soil moisture plays a critical role in many surface prcesses in terrestrial ecosystems. Characterizing soil moisture variations across a range of spatial and temporal scale is important for both theoretical and practical applications. This is especially true in the Loess Plateau of China. The soil water stored in deep soil layers is an important water source for introduced vegetation, and becomes a critical component in local ecosystem. The drought and high water consumption by introduced vegetation are the key limitations for sustainable vegetation restoration in the Loess Plateau. The large-scale implementation of “Grain-for-Green” Project was initiated by the central government in 1999. This large-scale vegetation restoration has changed the land cover and the associated hydrological processes, for example, deep soil desiccation. The aim of this study was to explore the response of deep soil moisture to vegetation restoration, and identifiy the interactions between vegetation and deep soil moisture acorss a range of spatial and temporal scales. The identification of the interactions between vegetation restoration and deep soil moisture is an important issue for the ecological restoration in the Loess Plateau, and can support more effective restoration policies in arid and semi-arid regions. The Longtan watershed was selected in this study to identify the interactions of large-scale vegetation restoration and deep soil water. The Longtan watershed is located in the western Loess Plateau. The hillslope and watershed scale were focused in this study. The soil moisture in the depth of 0-2 m was monitored during 2009-2013 by using FDR and deep soil moisture in the depth of 0-8 m was observed during 2010-2013 by gravimetric approach. The methods of statistical analysis, canonical correspondence analysis (CCA), and spatial analysis in GIS were used to explore the relationship between soil moisture and vegetation attributes, topographical factors, soil properties, and other environmental factors. The driving force between shallow and deep soil moisture on hillsloep scale was compared, the deep soil mosituer condition and its spatial pattern was compared between two differnet small watersheds with different land use pattern, and temporal dynamics of deep soil moisture at the watershed scale were explored. The major conclusions is this study are: (1) Soil moisture in the shallow soil layers increased from the upper positions to the bottom positions at the hillslopes covered with introduced vegetation. However,the spatial variations of deep-layer soil moisture was different with that of shallow soil layers. The soil moisture content in depth below 2 m was decreasing from upper positions to bottom positions. Correlation analysis indicated that the topographic wetness index was positively correlated with soil moisture near the surface (0-1 m),but negatively correlated with soil moisture at depths below 2 m; and the clear negative relationship was found between biomass and soil moisture content in deep layers. Experimental sites with relatively high biomass usually had lower deep soil moisture content. Soil moisture in shallow layers was more likely to be affected by topographic factors at the hillslope scale. However, comparisons of soil moisture at different slope positions indicated that the effect of topographic factors on the spatial variability of deep soil moisture was altered, mainly because plants with different biomasses may differ in their consumption of soil water and thus cause greater spatial variations in deep soil moisture. The introduced vegetation has altered the spatial pattern of deep soil moisture influenced by topographic factors at the hillslope scale, and the biomass has a determining role in the spatial variation of deep-layer soil moisture content. (2) Profile characteristics and spatial pattern of deep soil moisture showed that the introduced vegetation drastically decreased deep soil moisture when compared with farmland and native grassland. The farmland had the highest soil moisture content, and the lands covered with introduced vegetation had the lowest deep soil moisture content. No significant differences in deep soil moisture were found between different introduced vegetation types. The analysis of differences in soil moisture contente for different land use patterns indicated that land use had significant influence on deep soil moisture spatial variability. Land use structure determined the soil moisture condition and its spatial variation. Watershed with complex land use pattern ususlaly had relatively higher spatial heterogeneity of deep soil mosisture, and watershed with simple land use pattern usually had higher spatial homogeneity of deep soil moisture. Vegetation restoration with introduced plants diminished the spatial heterogeneity of deep soil moisture on watershed scale. The improvement of land use management should be used to improve the water management and maintain the sustainability of vegetation restoration. (3) The long-term soil moisture observation indicated that soil moisture below the depth of rainfall infiltration had no obvious temporal variations between different seasons or years. The soil moisture was temporal stable in the deep soil layers, and the temporal stability incrased with increasing soil depth. Deep-layer soil moisture was not vared with rainfall fluctuation and root water uptake. The land use played a determining role in the deep soil moisture content and the spatial variation of temporal stability at the watershed scale. The slope gradient and soil sand content had relatively smaller influence on the spatial variation of temporal stability in soil moisture content. The deep soil moisture content in introduced vegetation had no significant changes between different observating years (2010 and 2013). This indicated that the deep soil layer may provide no water source for plant growth after years of vegetation restoration. |
| 公开日期 | 2015-06-16 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/13474]  |
| 专题 | 生态环境研究中心_城市与区域生态国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 杨磊. 黄土高原深层土壤水分对植被恢复的响应研究[D]. 北京. 中国科学院研究生院. 2014. |
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