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1.
The objective of this study was to determine the changing characteristics of soil surface roughness under different rainfall intensities and examine the interaction between soil surface roughness and different water erosion processes. Four artificial management practices (raking cropland, artificial hoeing, artificial digging, and contour tillage) were used according to the local agriculture customs of the Loess Plateau of China to simulate different types of soil surface roughness, using an additional smooth slope for comparison purposes. A total of 20 rainfall simulation experiments were conducted in five 1 m by 2 m boxes under two rainfall intensities (0.68 and 1.50 mm min?1) on a 15° slope. During splash erosion, soil surface roughness decreased in all treatments except raking cropland and smooth baseline under rainfall intensity of 0.68 mm min?1, while increasing for all treatments except smooth baseline under rainfall intensity of 1.50 mm min?1. During sheet erosion, soil surface roughness decreased for all treatments except hoeing cropland under rainfall intensity of 0.68 mm min?1. However, soil surface roughness increased for the artificial hoeing and raking cropland under rainfall intensity of 1.50 mm min?1. Soil surface roughness has a control effect on sheet erosion for different treatments under two rainfall intensities. For rill erosion, soil surface roughness increased for raking cropland and artificial hoeing treatments, and soil surface roughness decreased for artificial digging and the contour tillage treatments under two rainfall intensities. Under rainfall intensity of 0.68 mm min?1, the critical soil surface roughness was 0.706 cm for the resistance control of runoff and sediment yield. Under rainfall intensity of 1.50 mm min?1, the critical soil surface roughness was 1.633 cm for the resistance control of runoff, while the critical soil surface roughness was 0.706 cm for the resistance control of sediment yield. These findings have important implications for clarifying the erosive nature of soil surface roughness and harnessing sloped farmland. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
2.
结合土壤种子库萌发实验和幼苗库野外调查,研究塔里木河下游漫溢区土壤种子库和幼苗库特征及两者之间的差异,同时对不同微地形条件下两者多个生态指标进行分析比较。结果显示:（1）土壤种子库和幼苗库共发现有11科21属22种植物。土壤种子库有效种子密度为681±166个\5m-2,而幼苗库的密度为74±30株·m-2。土壤种子库和幼苗库均以多年生草本植物为主。（2）土壤种子库的Margalef指数值显著大于幼苗库,Simpson指数和Shannon-Wiener指数的值则略大于幼苗库。土壤种子库和幼苗库之间的物种相似度为0.553。（3）在不同微地形条件下,土壤种子库和幼苗库的密度和多样性指数变化趋势有所不同,但总体上均表现为土壤种子库大于幼苗库。 相似文献
3.
南极冰盖表面微地貌是大气与冰盖相互作用的直接产物,微地貌的形态特征、结构性质及其发展变化对南极冰盖表面的物质平衡、能量平衡以及冰盖记录大气信息的过程具有重要的影响,冰盖表面微地貌的结构性质以及空间分布的确定是计算南极冰盖物质平衡与能量平衡的重要依据,同时在南极冰芯钻探选址以及冰芯解译古气候信息时具有重要的参考价值。根据微地貌的形成方式将南极冰盖表面微地貌分为沉积型、侵蚀型、沉积间断型三类,介绍了南极冰盖表面常见的微地貌形态雪丘、雪纹、雪垄、雪窝以及光洁区的形态特征与结构性质,并对冰盖表面微地貌的分布规律特征进行了总结,文中重点对不同微地貌区域内的物质平衡与能量平衡特征进行了介绍,最后探讨了冰盖表面光洁区对南极冰芯选址的影响,并对未来南极微地貌研究进行了展望。 相似文献
4.
科尔沁沙地流动沙丘掘穴蚁（Formica cunicularia）筑丘活动及其对土壤的作用 总被引：1，自引：0，他引：1
以科尔沁沙地典型流动沙丘作为研究对象,通过调查不同坡度地形上掘穴蚁的蚁丘直径、密度和盖度分布,讨论了不同坡度地形对掘穴蚁筑丘活动的影响,并分析了掘穴蚁筑丘对不同坡度地形土壤的作用。结果表明,迎风坡和背风坡的坡底、坡中及丘顶对蚁丘直径、密度和盖度分布影响明显,其中蚁丘直径迎风坡坡中显著小于其他坡度地形（P<0.05）;密度和盖度分布顺序均表现为:丘顶>坡中>坡底。掘穴蚁筑丘改变了土壤性状,导致土壤含水量升高,pH值变小而电导率变大,有机质和全氮含量增加;微地貌条件下,蚁丘含水量和全氮含量迎风坡坡底较高,而蚁丘有机质含量背风坡坡底较高,但蚁丘土壤pH值和电导率丘顶较小。整个流动沙丘土壤基质均比较疏松,流动沙丘微环境易受风力作用而改变,从而影响掘穴蚁的筑丘活动分布,但不同坡度地形间蚁丘分布差异基本上均没有达到显著水平（P>0.05）。 相似文献
5.
During the filling of surface microrelief depressions the precipitation excess (precipitation minus infiltration and interception) is divided between surface storage and runoff, i.e. runoff starts before the surface depressions are filled. Information on the division of precipitation excess is needed for modelling surface runoff during the filling of surface depressions. Furthermore, information on the surface of the area covered with water is needed for calculating infiltration of water stored in soil surface depressions. Thirty‐two soil surface microreliefs were determined in Danish erosion study plots. The slope was c. 10% for all plots. Data were treated initially by removing the slope, after which 20 ‘artificial’ slopes (1–20%) were introduced producing 640 new data sets. Runoff during filling of the microrelief storage was calculated for each of the 640 data sets using a model developed for calculating surface storage and runoff from grid elevation measurements. Runoff started immediately after the first addition of water for all data sets. On a field scale, however, runoff has to travel some distance as overland flow and storage in smaller and larger depressions below the runoff initiation point must be taken into consideration. The runoff increases by intermittent steps. Whenever a depression starts to overflow to the border of the plot, the runoff jumps accordingly. In spite of the jumps, the distribution between surface storage and runoff was closely related to the quotient between precipitation excess and depression storage capacity. Surface area covered with water was exponentially related to the amount of water stored in surface depressions. Models for calculating surface storage and runoff from grid elevation measurements are cumbersome and require time‐consuming measurements of the soil surface microrelief. Therefore, estimation from roughness indices requiring fewer measurements is desirable. New improved equations for such estimations are suggested. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
6.
呼伦贝尔沙质草原风蚀坑研究（Ⅲ）: 微地貌和土层的影响 总被引：3，自引：3，他引：3
采用剖面测量,沿剖面选取不同微地貌部位测量土层厚度、坚实度、粒度构成,并进行室内统计比较和分析的方法,对呼伦贝尔沙质草原区风蚀坑的发育受微地貌部位和土层控制的情况进行了研究。发现在接近自然状态下风蚀坑主要发育于西南坡和南坡的上部和中部;由于翻耕、机动车道路等人类活动诱发,也形成于平坦的草地,北坡和东坡甚至低地。沙质草原区的土层中部存在一个粗化层,在失去草被和上部的土壤-根系层保护时特别容易遭受风蚀的侵害,形成风沙流破坏钙积层并导致风蚀坑的形成。沙质草原是生态地质环境脆弱区,呼伦贝尔沙质草原区的西坡、南坡的中上部,梁岗丘等微地貌部位是风蚀沙化的危险地带。干旱半干旱气候区沙质草原的土层是稀缺的自然资源,地表土壤-植物根系层是珍贵的生态系统。保护地表土层对于保护草地资源和生态环境,以及沙漠化防治具有极端重要性。 相似文献
7.
杭州湾北岸水下岸坡微地貌特征及其海床侵蚀指示意义 总被引：1，自引：0，他引：1
旁侧声纳图像和多波束水下地形测量清晰地揭示了杭州湾北岸水下岸坡4种微地貌形态,分别为冲沟、凹坑、沙波、光滑海底。金山深槽内海底扰动、切割十分强烈,微地貌以冲沟、凹坑为主,局部成沙波片发育。深槽外缘的水下平地微地貌特征主要表现为光滑海底和冲沟交替出现,局部也有沙波分布。旁侧声纳图像和底质综合分析表明杭州湾北岸水下地貌面貌是水动力和泥沙来源共同作用的结果：一方面,冲沟、凹坑和沙波代表的水流方向与涨潮流方向一致,指示了强劲的潮流对海床的侵蚀和改造;另一方面,由于底流水动力较强、底质沉积物粒径较细,冲沟得以普遍发育,而沙波仅在局部的砂质海床中出现。水下岸坡微地貌分布显示了海床侵蚀与地貌格局和水深条件密切相关,表现为主槽内冲刷和改造后再沉积作用较强,主槽外缘的水下平地冲刷作用明显变弱,出现弱能条件下的光滑海底;水下平地中,浅水区冲沟较为发育,深水区则以光滑海底为主。总体而言,杭州湾北岸水下岸坡侵蚀性微地貌广泛分布,海床处于侵蚀状态。 相似文献
8.
湖北省电线积冰微地形因子影响识别研究 总被引：2，自引：0，他引：2
电线积冰是影响电网正常运行的重要因素,研究电线积冰与微地形因子的关系对于电线积冰风险区划、电网建设可行性论证等具有重要指导意义。本文利用湖北省1：5万基础比例尺地形图数据和湖北省电网线路冰害故障调查统计数据,对电线积冰厚度与其对应的微地形因子进行相关性分析,识别对电线积冰有显著影响的微地形因子,分析电线积冰厚度与对其影响显著的微地形因子的定量关系,解析微地形因子对电线积冰敏感性等级。结果表明：地形起伏度、海拔高度、离水体远近程度、下垫面类型等是影响积冰厚度最显著的微地形因子;地形起伏度与积冰厚度呈乘幂函数关系,海拔高度与积冰厚度呈对数函数关系,离水体远近程度与积冰厚度呈分段函数关系,下垫面类型与积冰厚度无显式的函数关系,但积冰灾害发生点具有明显的随下垫面类型分布的特征;积冰厚度随地形起伏度、海拔高度的增加而增加,而其变化率和敏感性则逐渐减小;地形起伏度小于40 m时,其对积冰风险最敏感;海拔高度在25～100 m时,其对积冰风险最敏感;积冰厚度随离水体距离的增加呈先增后减的变化趋势,其变化率绝对值和敏感性也呈先增后减的变化趋势,当离开水体距离在2～2.7 km时,其对积冰风险最敏感;电线积冰灾害多发区域的下垫面主要为水体、林地,其次为农田和草地,水体对积冰风险的敏感性等级分别是林地、农田、草地的1.5、3.6和16.7倍。 相似文献
9.
One‐dimensional expression to calculate specific yield for shallow groundwater systems with microrelief 
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下载免费PDF全文 Although the importance to account for microrelief in the calculation of specific yields for shallow groundwater systems is well recognized, the microrelief influence is often treated very simplified, which can cause considerable errors. We provide a general one‐dimensional expression that correctly represents the effect of a microrelief on the total specific yield that is composed of the soil and surface specific yield. The one‐dimensional expression can be applied for different soil hydraulic parameterizations and soil surface elevation frequency distributions. Applying different van Genuchten parameters and a simple linear microrelief model, we demonstrate that the specific yield is influenced by the microrelief not only when surface storage directly contributes to specific yield by (partial) inundation but also when water levels are lower than the minimum surface elevation. Compared with a simplified representation of the soil specific yield, in which a mean soil surface is assumed for the calculation of soil specific yield, the correct representation can lead to lower as well as higher soil specific yields depending on the specific interaction of the soil water retention characteristics and the microrelief. The new equation can be used to obtain more accurate evapotranspiration estimates from water level fluctuations and to account for the effect of microtopographic subgrid variability on simulated water levels of spatially distributed hydrological models. Copyright © 2015 The Authors Hydrological Processes Published by John Wiley & Sons Ltd 相似文献
10.
Soil surface roughness contains two elementary forms, depressions and mounds, which affect water flow on the surface differently. While depressions serve as temporary water storage, mounds divert water away from their local summits. Although roughness impacts on runoff and sediment production have been studied, almost no studies have been designed explicitly to quantify the evolution of depressions and mounds and how this impacts runoff generation and sediment delivery. The objectives of this study were to analyze how different surface forms affect runoff and sediment delivery and to measure the changes in surface depressions and mounds during rainfall events. A smooth surface was used as the control. Both mounds and depressions delayed the runoff initiating time, but to differing degrees; and slightly reduced surface runoff when compared to the runoff process from the smooth surface. Surface mounds significantly increased sediment delivery, whilst depressions provided surface storage and hence reduced sediment delivery. However, as rainfall continued and rainfall intensity increased, the depression effect on runoff and erosion gradually decreased and produced even higher sediment delivery than the smooth surface. Depressions and mounds also impacted the particle size distribution of the discharged sediments. Many more sand‐sized particles were transported from the surface with mounds than with depressions. The morphology of mounds and depressions changed significantly due to rainfall, but to different extents. The difference in change had a spatial scale effect, i.e. erosion from each mound contributed to its own morphological change while sediments deposited in a depression came from a runoff contributing area above the depression, hence a much greater source area than a single mound. The results provide a mechanistic understanding of how soil roughness affects runoff and sediment production. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献