摘要
微地形和次降雨是坡面尺度土壤水分状况与侵蚀强度的重要影响因素。为阐明其对坡面土壤水分空间分布及其变异性的影响,采用高密度布点方法,结合经典统计学,研究了陕北黄土区坡面尺度微地形和次降雨对0—5 m土壤水分数量与空间分布特征的影响。结果表明:(1)次降雨(降雨量为88.6 mm)对土壤水分的影响深度为0—40 cm;(2)在垂直剖面上降雨前坡面、降雨后坡面及降雨后坳沟,三者土壤水分均在表层为降低型,中间为稳定型,深层分别为波动型、增长型和降低型;(3)表层(0—40 cm)降雨前坡面与降雨后坡面和坳沟均有显著性差异,表层土壤水分与其他各土层之间差异显著(P<0.05);(4)沿坡长方向降雨前后坡面表层土壤水分变化趋势相同且与降雨后坳沟变化趋势相反,在10—50 m坡长三者的深层土壤水分变化趋势一致。研究结果可为坡面尺度土壤水分优化管理提供参考依据。
Background, aim, and scope Soil moisture （SM） is a key factor for soil erosion, plant growth and vegetation recovery on the Loess Plateau. The high spatial and temporal variation of SM not only determines related to hydrological processes and ecological function, but also has an important impact on the quality and service of the ecosystem. In turn, the regime of SM was dominated by a series environmental factors, including meteorological factors （i.e., rainfall, evaporation, wind speed, etc.）, topography, soil texture, plant roots and so on, at a wide range of spatial and time scales. At slope scales, micro-topography （i.e., swale, ridge） and rainfall events are two of the factors highly affecting SM. In order to evaluate their impact on the spatial distribution of SM （0-5 m）, we selected a typical slope （which contains two swales and three ridges） at Gutun watershed, which located at the middle part of the Loess Plateau of China, to conduct research work. The mean annual rainfall is 530.9 mm and mean annual temperature is 10.6℃. Material and method We collected soil samples to a depth of 5 m on the slope by using high-density sampling strategy combined with classical statistics. Three columns with 10-m-spacing were arranged on the ridges, and two columns with 15-m-spacing were arranged in the swales. A total of 27 samples points were selected. At each sampling point, sample were collected at every 10 cm from 0 to 200 cm depth, and every 20 cm from 200 cm to 500 cm. Totally, we collected 35 samples at each point. During the sampling period, there was continuous rainfall, which provided us with an opportunity to assess the impact of rainfall on SM. In order to make the test comparable, we used the oven drying method to determine SM and Excel 13.0 and SPPS 17.0 to conduct data calculation and statistical analysis. Results （1） The effect depth of rainfall on SM was 0- 40 cm. （2） In the vertical direction, SM in the ridges with before-rainfall, the ridges with after-rainfall and the swales with after-rainfall demonstrated a decline type for upper layer, a stable type for middle layer, multiple types for deep layer, respectively. （3） SM in 0--40 cm differed significantly between the ridges with before-rainfall, and the ridges with after-rainfall and the swales with after-rainfall, SM between 0-40 cm layer and other soil layers was also significant. （4） Along the slope, SM had a similar trend between the ridges with before-rainfall and the ridges with after-rainfall, which was different from that of the swales with after-rainfall; in the slope length of 10--50 m, SM indicated a similar trend. Discussion The surface SM changes drastically and significantly differs from the deep SM, mainly owed to rainfall, evaporation and other eco-hydrological processes. Along the profile, the vertical trends of deep SM are different, which may be related to micro-topography （i.e., swale, ridge）, rainfall events, plant ages and corresponding root systems, soil texture and structure. Conclusions Micro-topography and rainfall events had a significant impact on SM. The response of SM in the slope to rainfall event can reach 40 cm. Deep SM in the slope can be divided into three layers-the lower layer, the stabilization layer, and the fluctuating layer. With the increase of slope length, the response of SM to micro-topography increased. Recommendations and perspectives Understanding the relationships between SM and micro-topography and rainfall event is necessary not only for local farmers to improve land use efficiency but also for rational use of limited soil water resources. Especially, this study can provide a reference for the optimal water management at slope scale.
出处
《地球环境学报》
CSCD
2017年第4期357-366,共10页
Journal of Earth Environment
基金
国家自然科学基金项目(41530854
41571130083
41471189)
陕西省青年科技新星项目(2013KJXX-09)~~
关键词
微地形
坡面
降雨
土壤含水量
黄土高原
micro-topography
slope
rainfall
soil water content
the Loess Plateau
