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题名: 华北土石山区坡面和流域森林生态水文特征研究
作者: 王晓学
学位类别: 博士
答辩日期: 2015-05
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 李叙勇
关键词: 森林水文过程 ; 地表产流 ; 密云水库 ; SWAT模型 ; 结构方程模型,forest hydrological process ; surface runoff ; Miyun Reservoir ; SWAT ; structural equation model
其他题名: Study of forest ecohydrological characteristics in plot and watershed scales in mountainous regions of north China
学位专业: 生态学
中文摘要:       维持森林生态系统功能的良好发挥是区域经济社会可持续发展的重要基础。森林水源涵养功能是森林提供的一项重要生态系统功能。本研究以华北土石山区森林生态 系统为对象,从坡面尺度上分析降雨特征和森林相关特征对地表产流的影响机制,然后在流域尺度上构建SWAT模型,情景模拟森林覆盖率变化对水量平衡各组分 的影响,分析土地利用类型对河道径流中几个水化学指标季节变化的影响,并以此提出坡面和流域尺度上森林水源涵养定量评价的关注重点。最后,根据坡面和流域 尺度森林水源涵养特征及其关键生态水文过程,提出了基于元胞自动机的森林水文动态定量评价模型理论框架。本研究得出以下主要结论:
      1)提出半干旱地区日尺度林地土壤水分模型
      构建了半干旱林地日尺度土壤水分动态模型,该模型能够较好的反映林地土壤水分收支特征。与将降雨作为土壤水分的收入项相比,将穿透雨作为输入项能显著提高 模型模拟结果。模型参数的敏感性分析表明,不同目标函数的参数敏感度信息反映了该模型参数具有较强的物理意义。
      2)定量评价坡面尺度地表产流的主要影响因素及其作用机制
      在半干旱地区降雨特征是影响地表产流的最主要因素,但其作用大小受到森林生态系统相关特征的影响。穿透雨对坡面径流的作用受到其他森林生态系统特征,如林 下枯落物量和前期土壤含水量等因素影响。林下枯落物层通过影响径流流速来影响径流形成时间及大小。前期土壤含水量对坡面产流的影响较小。
      3)流域尺度森林生态系统调节水量和净化水质功能分析
       土地利用类型转换对水量平衡各组分的影响并不是线性关系,土地利用变化对径流及各组分较其他水分通量影响明显。森林覆盖率下降较森林覆盖率增加对径流及其 各组分的影响明显,特别在非汛期更显著。半干旱地区森林具有调节水量的功能,但流域总产水量会显著减少。对典型站点的监测数据分析发现,不同土地利用在不 同季节表现出对污染物的源、汇特征,主要跟气象条件及污染物赋存形态有关。
      4)提出基于元胞自动机的森林水文动态定量评价模型框架
      模型模拟是定量评价森林水文动态过程的重要途径。基于坡面尺度不同影响因素对地表产流的作用机制以及流域尺度森林水源涵养的特征,提出基于元胞自动机的森 林水源涵养量模型,将森林水文响应单元网格化作为元胞空间的基本单元,将元胞单元对不同降雨事件的响应分为不产生径流和产生径流两种情况,通过对蒸散发、 邻域元胞间水量传输、深层渗漏等制定转换规则,模拟森林在不同尺度上的水源涵养动态特征。
英文摘要:        Forest water conservation as an important ecosystem function has caused a rising interests in the scientific community in recent years. However, there were still some arguments in several aspects regarding the forest water conservation function. First the connotation of the forest water conservationhasn’t been clearly defined. Secondlyto scale up the estimation for the forest water conservation from plot scales to larger scales such as watershed or regional scales is challenging. Many quantification methods have been developed, but their suitability, performance, advantages and disadvantages are unknown. These argumentive issues have greatly limited the research and management in forest water conservation.
      1) We revised a simple parametric water balance model to simulating soil moisture conditions in different forest types (natural secondary forest, evergreenneedleleaf and deciduous/coniferous plantation forest) in semiarid regions of southwestern Beijing, China. Model calibration and validation were performed using a dataset comprising averaged soil moisture content measured at depths of 0–75 cm in the growing seasons of 2006, 2007, and 2010. The models performed reasonably well in simulating the patterns and magnitudes of daily average soil moisture content in the upper 75 cm soil layer in all three forest types. Using different parameters in the model did not significantly alter the results and the model structure exhibited a relatively small amount of uncertainty. Sensitivity analysis revealed that four parameters played important roles in rainfall infiltration, deep percolation and evaporative processes. In addition, differences in soil moisture flux among forest types suggested that both annual evapotranspiration in deciduous/coniferous forest plantations and infiltration in deciduous broad-leaved forest were greater than those in other forestlands; in addition, deep percolation in all three forestlands was low.
      2) The effects of rainfall features (amount, duration, intensity, and interval), forest ecosystem characteristics (canopy structure, litter mass, and soil moisture) on runoff in hillslope scale, indicated that rainfall features were the main factors controlling runoff. Rainfall intensity was a significant determinant of runoff via the indirect throughfall pathway for low-intensity events, while rainfall amount was the principal control factor determining runoff in high-intensity events. Rainfall interval had weak negative effects on runoff. Results also showed that the importance of throughfall in runoff was mediated by other forest ecosystem characteristics, including litter mass and antecedent soil moisture. Litter mass had a negative effect on runoff, mainly via reducing surface runoff velocity in low-intensity events. The SEM results showed that the antecedent soil moisture had very low or no significant effects on runoff in the three types of forests. Our findings proposed a holistic approach to analyze the relationships between runoff and its factors, and provide explicit quantitative evidence of the interactions among forest ecosystem characteristics and rainfall features controlling runoff at the hillslope scale.
      3) The effects of land use change on the components of the water balance is not a linear relationship, in which runoff and its component have more sensitive than other water flux components. The effects of forest cover decreased have more rapidly response than the forest cover increased, especially more pronounced in dry season. The forest in semiarid regions have the capbility of cuting flood in rainny seasons and increasing the river discharge in dry seasons, but the total water yield in catchments will be significantly reduced. Typical sites for monitoring data analysis show that different land use in different seasons may be the pollutant or sinks sources, which was related with the weather conditions and the forms of major pollutants.
      4) We apply the basic theories of cellular automata to developing a new modeling method for quantifying forest conservation. In the model, we integrate the hydrological characteristics of rainfall redistribution by canopy, water retention of litter and water conservation of soil. We define a cell as an elementary spatial unit that is rasterized from a hydrologic response unit, with every cell interior having relatively consistent characteristics of the vegetation, soil and terrain attributes. A cell neighborhood is defined as the Moore type. The range of quantitative change of water is measured in continuous real numbers. The water quantity in each cell is affected by neighboring cells and status of the previous time step. Based on the response characteristics of the underlying surfaces on different rainfall intensity and duration, we classify the cellular responses to different rainfall events with two scenarios: generation of runoff and without generation. We set transformation rules of forest hydrological processes, including evapotranspiration, intercellular water transmission and deep seepage. We also consider hydrological processes with both horizontal and vertical directions. Taking main factors affecting forest water conservation and its spatial heterogeneity into consideration, the model overcomes the defects of most traditional methods which focus on one dimension.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/34516
Appears in Collections:城市与区域生态国家重点实验室_学位论文

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Recommended Citation:
王晓学. 华北土石山区坡面和流域森林生态水文特征研究[D]. 北京. 中国科学院研究生院. 2015.
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