延河流域土地利用景观格局变化对径流输沙的影响

发布时间：2018-02-16 05:34

本文关键词： 延河流域土地利用景观格局水沙变化恢复阶段　出处：《中国科学院研究生院（教育部水土保持与生态环境研究中心）》2015年硕士论文　论文类型：学位论文

【摘要】：退耕还林(草)政策在黄土高原地区实施已逾20载,流域内土地利用景观格局和径流泥沙发生显著变化,针对这一现象,本论文以延河流域为研究区,基于甘谷驿水文站的长期实测水沙数据(1970-2010),结合四期遥感影像资料(1978年、1990年、2000年、2010年),采用GIS、RS和野外人工模拟降雨等技术手段,运用景观生态学、数理统计和定性定量相结合的分析方法。在流域尺度上,对延河流域的土地利用景观格局和径流泥沙变化特征进行分析总结,并建立景观格局指数和径流泥沙指标之间的关系;同时,在坡面尺度上,研究不同恢复阶段的人工刺槐林地、人工柠条林地和自然恢复草地的坡面产流产沙特征及减流减沙效益,为解释流域尺度上土地利用景观格局变化对径流泥沙的影响提供理论基础。研究取得的主要结论如下:(1)经过多年的生态建设和流域综合治理,尤其是退耕还林(草)工程的实施,延河流域的土地利用景观格局发生了显著变化。在斑块水平上,耕地和草地的破碎度较高,斑块形状也较复杂,林地、建设用地和水域斑块分布趋于集中化,破碎度较小,形状较为简单;在景观水平上,以耕地为主导的土地利用景观格局已不复存在,而以林地和草地为主导的新的土地利用景观格局正在形成,景观格局大致经历了“耕地主导-相对平衡-林草主导”的变化过程,向集中化和简单化的方向发展,由于林草植被的减蚀作用,以林草为主导的景观格局有利于生态环境的改善。(2)延河近40年的水沙量均呈下降趋势,输沙量的下降幅度高于径流量,Mann-Kendall趋势检验表明,2005年为水沙发生突变的年份。其变化过程大致经历了三个阶段,1970-1986年为水沙波动期,1987-1996年为丰水丰沙期,1997-2010年为枯水枯沙期。造成这种变化的主要原因不是降雨,而与流域内植被恢复引起土地利用的阶段性变化有关。(3)在流域尺度上,以耕林草为主导的土地利用景观格局与水沙变化关系密切。在景观类型水平上,延河流域耕地斑块的分离度指数、林地斑块的连通度和草地斑块的斑块个数对流域的径流过程影响较大,耕地斑块的边缘密度、林地斑块的斑块所占景观面积比、草地斑块的散布与并列指数与流域的输沙过程关系密切。回归方程表明林地和草地斑块的面积越大和连通性越高,分布越集中;耕地受人类活动的扰动越弱,分布越分散,则流域内的水土流失程度越弱,反之则越强。在景观水平上,延河流域景观格局的斑块个数、平均斑块面积、多样性指数和聚集度指数共同影响着流域的径流和输沙过程。回归方程表明景观的破碎化程度越弱,多样性越丰富,分布越集中,流域的径流输沙量越小。(4)在坡面尺度上,植被恢复年限是影响延河流域自然恢复草地、人工柠条林地和人工刺槐林地产流产沙的一个重要因素。同一植被恢复方式,在不同恢复阶段的径流率和产沙强度变化规律各不相同。随恢复年限的增加,自然恢复草地和人工柠条林地的径流率和产沙强度都减小,而人工刺槐林地则表现出径流率差异不显著,产沙强度增大,主要是由于人工刺槐林地的郁闭度较高和树木高度增加所致。各恢复阶段的累积径流量(QW)、累积产沙量(QS)和降雨历时之间均存在较好的二次函数关系,而累计产沙量和累计产流量之间的相互关系可通过幂函数来反应。(5)对于不同恢复阶段的自然恢复草地、人工柠条林地和人工刺槐林地,其减沙效益均大于减流效益,这也很好的解释了流域尺度上泥沙减少幅度大于径流的问题。人工刺槐林地的减流减沙效益最为突出,处在一个很高的水平,具有蓄水减沙的水土保持功效,自然恢复草地和人工柠条林地的减水减沙效益都随恢复年限的增加而增加,具有直接拦沙的水土保持功效。同时,处在恢复初期(0~8年)的自然恢复草地和人工柠条林地,生态功能仍然比较脆弱,以及恢复后期(16年以上)的人工刺槐林地,如果地表植被遭到破坏,仍然是暴雨条件下产沙的主要来源之一,因此,在植被恢复重建过程中,要做好封育、禁牧等保护措施。
[Abstract]:Returning farmland to forest (grass) policy has been implemented for more than 20 years in the Loess Plateau area, the land use landscape pattern and runoff sediment change significantly in response to this phenomenon, this thesis in Yanhe River Basin as the study area, Gangu Yi long term hydrological and sediment data station based on (1970-2010), combined with the remote sensing image data four (1978, 1990, 2000, 2010), by GIS, RS and field artificial rainfall simulation technique, using landscape ecology, analysis method of combining mathematical statistics and qualitative and quantitative. In the basin scale, the landscape pattern and the variation of runoff and sediment characteristics of land use along the river basin are analyzed and summarized, and the establishment of relations between landscape pattern index and runoff sediment index; at the same time, in the slope scale, study the different recovery stages of Robinia pseudoacacia plantation, Artificial Caragana forest and natural grassland restoration runoff in Saudi Arabia Sign and runoff and sediment reduction benefits, provide a theoretical basis for the effect of the change of the landscape patterns of land interpretation on basin scale on the runoff and sediment. The main conclusions are as follows: (1) after years of comprehensive management and ecological construction of river basin, especially in returning farmland to forest (grass) the implementation of the project, changed the landscape pattern of land use in Yanhe River Basin. At patch level, arable land and grassland fragmentation is high, the patch shape is more complex, woodland, centralized land and water were more construction, fragmentation, simple shapes; at the landscape level, the farmland landscape pattern of land use is no longer dominated there, in the woodland and grassland dominated the new land use landscape pattern is formed, the landscape pattern has experienced the change process of cultivated land dominant relative balance - grass, leading to centralization and simplification The direction of development, due to erosion of vegetation, the forest grass is dominant landscape pattern is conducive to the improvement of the ecological environment. (2) water sediment in nearly 40 years showed a downward trend, the decline rate is higher than sediment runoff, Mann-Kendall trend test showed that in 2005 for the water and sediment mutation year. The change process has experienced three stages, 1970-1986 years for a period of 1987-1996 years for the fluctuation of water and sand, wet wet period, 1997-2010 years of withered water and sediment. The main reason for this change is not the rainfall, and watershed vegetation restoration caused by land use changes. (3) in the. The basin scale, the close relationship between landscape pattern and land use change of water and sand to plow grass dominated. At the level of landscape types, cultivated land in Yanhe River Basin separation index, patch number convection connectivity and grassland patches of woodland patches The runoff process area affected farmland patch edge density, patches of woodland patches for landscape area ratio, the relationship between sediment process and river basin interspersion and juxtaposition index of grassland patches closely. Regression equation indicated that the woodland and grassland patch area more and more high connectivity, the distribution is more concentrated; the disturbance of human activities the weaker by the arable land, the distribution is more dispersed, the degree of soil erosion in the watershed is weak, whereas the more strong. At the landscape level, the number of patches of Yanhe River watershed landscape pattern, average patch area, diversity index and aggregation index affect the watershed runoff and sediment process. The regression equation shows that the fragmentation the degree of landscape diversity is weaker, more rich, more concentrated distribution, basin runoff and sediment transport amount is smaller. (4) in the slope scale, vegetation restoration years Grassland Natural Restoration effect of Yanhe River Basin, Artificial Caragana forest and people One of the important factors in industrial locust runoff and sediment. In the same way to restore vegetation, variation of runoff and sediment of different restoration stages are different. With the increase of the strength of the recovery period, runoff rate of natural grasslands and Artificial Caragana forest and sediment yield intensity decreased, and the performance of Robinia pseudoacacia plantation the runoff rate had no significant difference, sediment yield intensity increased, mainly due to the high degree of Robinia pseudoacacia plantation canopy and tree height increased. The recovery phase of the cumulative runoff (QW), cumulative sediment yield and rainfall duration (QS) are in quadratic function relationship better, and the relationship between the cumulative sediment yield and cumulative runoff to reaction by power function. (5) for different recovery stages of natural restoration of grassland, woodland and Artificial Caragana microphylla Robinia pseudoacacia plantation, the benefits of sediment reduction were greater than the current reducing efficiency, this is also a good solution The release of basin scale sediment reduction is greater than the runoff. Locust woodland runoff and sediment reduction benefits are most prominent, at a very high level, has the functions of water storage and sediment reduction of soil and water conservation, water and natural restoration of grassland and Artificial Caragana Plantation is increased with the increase of time of sediment reduction efficiency that has a direct effect on Soil and water conservation of sediment. At the same time, in the early stage of restoration (0~8) restoration of natural grassland and Artificial Caragana forest, ecological function is still weak, and the recovery period (16 years) of Robinia pseudoacacia plantation, if the destruction of surface vegetation, is still one of the main sources of sediment, heavy rain conditions therefore, in the vegetation restoration process, to do a good job of fencing, grazing and other protective measures.

【学位授予单位】：中国科学院研究生院（教育部水土保持与生态环境研究中心）
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P901;S157

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