黄土高原土壤侵蚀与地貌形态耦合分析

发布时间：2019-07-06 10:02

【摘要】：土壤侵蚀是黄土高原最严重的环境问题,影响因素主要分为自然因素和人为因素。自然因素包括气候、水文、地形、地貌等;人为因素则主要表现在人类活动对土壤侵蚀的影响,其中有积极和消极影响之分,例如退耕还林还草,水土保持措施实施等都有利于水土保持。本文系统深入地研究了黄土高原地区近50年气候水文变化状况及其对水土流失变化的影响,并重点提取分析黄土高原典型流域河网水系及地貌特征,通过建立侵蚀地貌综合指标(ETI),分析土壤侵蚀与地貌特征的耦合关系,从而进一步分析人类活动对土壤侵蚀的影响。通过本文的综合分析,取得的主要结果如下:(1)地貌特征因子在各流域间存在一定的空间差异性,这一空间差异性也是导致水土流失差异性的重要原因,为实现黄土高原地貌特征量化分析,本研究建立了地貌特征综合评价指标(ETI)。地貌特征综合指标与输沙量之间存在显著正相关关系(P0.05),即输沙量随地貌特征综合指标的增加而增加,说明地貌特征是影响黄土高原地区土壤侵蚀的重要自然因素,其通过控制下垫面情况来影响水土流失的发生与发展。同时,地貌特征综合指标与2000~2011年输沙变量之间的回归方程斜率高于其他输沙变量,说明在地貌特征综合指标相同的情况下,2000~2011年输沙变量将小于其他年份输沙变量,即输沙量显著减少,这一现象说明在降水、径流及地貌特征相对一致的条件下,存在其他非自然因素使得黄土高原地区输沙量自2000年之后显著降低,即黄土高原地区自2000年后人为因素对土壤侵蚀的影响逐渐显著。(2)1960-2011年间,径流和输沙量在1960~2011年间呈波动减少趋势,2000s与1960s相比,年径流量和输沙量分别减少30%-80%和60%-90%,其中输沙量减少趋势较为显著。黄土高原地区降水整体呈现波动减少趋势,各气象站年均降水量变异系数在18.13%-38.66%,因此降水量在时间上属于中等变异。在空间上,降水呈现由东南向西北逐渐减少的整体分布规律,但个别地区受地形影响存在空间突变。虽然降水与径流整体都呈现减少趋势,但在不同的区域存在着空间及时间上的差异性。同时对典型水文站点数据分析表明,各站点间降水与径流变化虽然存在差异性,但两者之间的变化趋势基本保持一致,这说明黄土高原地区降水量与径流量间存在相关关系。黄土高原地区径流量与输沙量之间存在极显著线性正相关关系,径流是影响输沙的关键因素,但不是唯一因素。(3)黄土高原地区植被盖度在1981~2009年间不断增加,尤其在2000年后,植被盖度迅速增长,覆盖面积不但扩大,植被覆盖强度也不断增加。在空间分布上,植被盖度由东南向西北呈减少趋势,自2000年后增加速率上升。对比输沙数据可以发现,各典型流域植被盖度增加量与输沙减少量之间存在显著负相关关系,因此输沙量随植被盖度的增加而减少;同时回归方程决定系数(R2=0.6),植被盖度变化是2000年后水土流失变化的主要成因。除植被盖度外,淤地坝建设是影响黄土高原地区水土流失变化的重要因素,黄土高原大量淤地坝建设也是其输沙量与径流量减少的关键原因,但淤地坝与输沙量之间的动态变化关系还有待进一步研究。
文内图片：

图片说明：黄土高原及典型流域概略图
[Abstract]:Soil erosion is the most serious environmental problem in the Loess Plateau, which is mainly divided into natural and human factors. The natural factors include climate, hydrology, topography, landforms, etc. The human factors mainly show the effects of human activities on soil erosion, including the positive and negative effects, such as the conversion of farmland to forests, the implementation of water and soil conservation measures, and so on. In this paper, the climatic and hydrological changes of the Loess Plateau in the near 50 years and its effect on the change of soil and water loss are studied in-depth, and the water system and the characteristics of the river network in the typical basin of the Loess Plateau are analyzed and analyzed, and the comprehensive index of erosion and physiognomy (ETI) is established. The coupling relation between soil erosion and geomorphic features is analyzed, and the effect of human activity on soil erosion is further analyzed. Through the comprehensive analysis of this paper, the main results are as follows: (1) There is a certain spatial difference between the physiognomy characteristic factor and each river basin, and the difference of the spatial difference is an important reason for the difference of soil and water loss, so as to realize the quantitative analysis of the landforms of the Loess Plateau. In this study, a comprehensive evaluation index (ETI) for geomorphologic features was established. There is a significant positive correlation between the comprehensive index of the physiognomy and the sediment concentration (P0.05), that is, the sediment concentration is increased with the increase of the comprehensive index of the feature of the landforms, and the characteristics of the geomorphic features are the important natural factors that affect the soil erosion in the Loess Plateau. It affects the occurrence and development of soil and water loss by controlling the condition of the underlying surface. At the same time, the slope of the regression equation between the comprehensive index of the physiognomy and the sediment variable between 2000 and 2011 is higher than that of other sediment transport variables. In the same condition as the comprehensive index of the physiognomy characteristics, the sediment transport variable of the year 2000 to 2011 will be less than that of the other year, that is, the sediment concentration is significantly reduced, This phenomenon shows that in the condition of relatively consistent precipitation, runoff and physiognomy characteristics, there are other non-natural factors, so that the sediment discharge in the Loess Plateau is significantly reduced since 2000, that is, the effect of human factors on soil erosion after 2000 in the Loess Plateau is becoming more and more obvious. (2) During the period from 1960 to 2011, the runoff and sediment concentration decreased from 1960 to 2011, and the annual runoff and sediment concentration decreased by 30% to 80% and 60% to 90%, respectively, in the period from 1960 to 2011. The average annual precipitation variation coefficient of each meteorological station is from 18.13% to 38.66%, so the precipitation is of medium variation in time. In the space, the precipitation presents an overall distribution pattern that is gradually reduced from the southeast to the northwest, but there is a spatial mutation in the area affected by the terrain. Although both precipitation and runoff show a tendency to decrease, there are differences in space and time in different regions. At the same time, the data analysis of the typical hydrological station shows that the variation of the precipitation and runoff in each station is basically consistent, which indicates that there is a correlation between the precipitation and the runoff in the Loess Plateau. There is a very significant linear positive correlation between the runoff and the sediment discharge in the Loess Plateau. The runoff is the key factor affecting the sediment transport, but it is not the only factor. (3) The cover degree of the vegetation in the Loess Plateau is increasing from 1981 to 2009, especially after 2000, the cover degree of the vegetation is growing rapidly, and the covering area is not only expanded, but the cover strength of the vegetation is also increasing. In the spatial distribution, the degree of vegetation cover decreases from the southeast to the northwest, increasing the rate since 2000. Compared with the data transmission data, it is found that there is a significant negative correlation between the increase of the vegetation cover degree and the reduction of the sediment transport, so the sediment discharge is reduced with the increase of the cover degree of the vegetation, and the regression equation is determined by the regression equation (R2 = 0.6). The change of vegetation cover degree is the main cause of the change of water and soil loss after 2000. In addition to the vegetation cover, the construction of the silt dam is an important factor to influence the change of soil and water loss in the Loess Plateau, and the construction of a large amount of silt in the Loess Plateau is the key reason for the reduction of the sediment discharge and the runoff, but the dynamic relationship between the silt and the sediment discharge is still to be studied further.
【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】：博士
【学位授予年份】：2016
【分类号】：S157

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