地理研究  2016 , 35 (1): 195-202 https://doi.org/10.11821/dlyj201601017

Orginal Article

土壤侵蚀研究中的景观连通度:概念、作用及定量

刘宇

中国科学院地理科学与资源研究所,中国科学院生态系统网络观测与模拟重点实验室,北京 100101

Landscape connectivity in soil erosion research: Concepts, implication and quantification

LIU Yu

Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China

收稿日期: 2015-06-17

修回日期:  2015-10-26

网络出版日期:  2016-01-23

版权声明:  2016 《地理研究》编辑部 《地理研究》编辑部

基金资助:  国家自然科学基金项目(41301032)

作者简介:

作者简介:刘宇(1981- ),男,贵州六盘水人,博士,助理研究员,研究方向为景观格局与生态过程、生态遥感与生态系统评估。E-mail: liuyu@igsnrr.ac.cn

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摘要

土壤侵蚀过程是广泛存在的地表物质运移、再分配过程,受景观格局的调控。关于景观格局与土壤侵蚀之间相互关系的研究众多,但耦合景观格局与土壤侵蚀过程的概念框架和有效工具比较少。景观连通度在斑块、坡面到流域等多个尺度上影响土壤侵蚀的发生和发展,是深刻影响土壤侵蚀过程的关键景观格局特征。从景观连通度的概念、分类着手,分析了景观连通度在土壤侵蚀过程中的作用,阐述了土壤侵蚀研究中定量景观连通度的方法,总结了基于土壤侵蚀过程定量景观连通度的两类主要途径:景观连通度指数方法和融合景观连通度概念的分布式土壤侵蚀模型。景观连通度概念及其定量在方法论上将景观格局与土壤侵蚀过程联系起来,是景观格局—土壤侵蚀相互作用研究的有效工具。

关键词: 景观连通度 ; 土壤侵蚀 ; 景观格局 ; 土壤保持

Abstract

Soil erosion widely occurs across earth surface. It is a redistribution process of sediment over landscapes, and mitigated by landscape pattern. Landscape pattern data can be easily extracted from satellite imageries. However, due to the missing of a concrete conceptual framework, as well as effective tools linking landscape pattern with soil erosion processes, it is difficult to untangle their interactions explicitly. Landscape connectivity is a key landscape characteristic, and plays a critical role in soil erosion process. It shapes the occurrence and evolution of soil erosion from patch to watershed level. In this review, the concept, categorizing, and effect of landscape connectivity are summarized in the context of soil erosion. The connectivity indices and the spatially distributed soil erosion model are the two dominant approaches that can be used to link soil erosion with landscape pattern. Connectivity indices quantify the physical coupling among landscape units, and the functional connectivity, indicating the water or sediment delivery between landscape units. The spatially distributed soil erosion models explicitly incorporate landscape connectivity by taking landscape connectivity indices as parameters, implicitly modelling the in situ sediment production and sediment routing between source areas and sink areas, or along the flow path ways determined by topography. The connectivity concept frameworks effectively linking landscape pattern and soil erosion, and undoubtedly, provide an operational solution for unfolding the interaction between landscape pattern shifts and soil erosion dynamic.

Keywords: landscape connectivity ; soil erosion ; landscape pattern ; soil conservation

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刘宇. 土壤侵蚀研究中的景观连通度:概念、作用及定量[J]. , 2016, 35(1): 195-202 https://doi.org/10.11821/dlyj201601017

LIU Yu. Landscape connectivity in soil erosion research: Concepts, implication and quantification[J]. 地理研究, 2016, 35(1): 195-202 https://doi.org/10.11821/dlyj201601017

1 引言

土壤侵蚀是陆地生态系统中普遍发生且具有广泛生态环境效应的地表物质运移过 程[1],是土壤学、地貌学、水文学、生态学等多个学科共同关注的地表过程。在格局—过程—尺度及等级为核心的景观生态学[2]研究中,土壤侵蚀与景观格局的相互作用是典型的例子。除降雨、土壤物理和化学属性等因素外,土壤侵蚀过程中发挥抑制或促进功能的景观单元在空间上的配置格局控制着土壤侵蚀过程的发生和发展[3,4]。因此,定量描述景观单元空间分布格局的指标可指示土壤侵蚀状况或者发生风险[5-7],可与泥沙输移建立定量的表达关系[8,9]。景观连通度(landscape connectivity)是描述景观格局的重要概念,在揭示景观格局的生态效应(如物种迁移、扩散)方面[10,11]产生了丰硕的成果,也逐渐被应用于反映土壤侵蚀的景观格局描述,涉及的空间尺度从小区[5,6]、坡面[6,12]、流域到区域[13,14]。尽管景观连通度对土壤侵蚀具有深刻的影响,而在土壤侵蚀研究中应用景观连通度概念近年来才开始受到关注。但对景观连通度概念仍然存在多样化、不一致的理解,在景观连通度的定量方法上仍处于探索阶段,景观连通度的作用在土壤保持实践中尚未明确提出。基于景观连通度与土壤侵蚀的相互作用,从概念、表征及其在土壤侵蚀过程中的作用三个方面对景观连通度进行阐述和探讨。

2 土壤侵蚀研究中的景观连通度概念

土壤侵蚀受不同景观功能单元空间配置和组成的控制。与生物过程不同,土壤侵蚀是具有空间方向性(沿地形梯度方向或风向、水流方向等)、主控因素和强度存在尺度依赖和临界现象的地表物质运移过程[15]。景观连通度是影响土壤侵蚀过程的重要因素[16]。近年来,景观连通度概念在降雨侵蚀,特别是大尺度泥沙输移研究中得到广泛应用[17,18]。从水文学和地貌学中发展起来的景观连通度概念在土壤侵蚀研究中应用最为广泛,大致包括三种:① 描述流域内地形单元间空间邻接关系的景观结构连通度;② 刻画径流从景观中一个地方到另一个地方运动通道的畅通程度的水文连通度;③ 指示泥沙及其上附着污染物在流域内的物理传输、且随颗粒大小变化的泥沙连通度[17]。景观结构连通度在一定的时间尺度上(月、季度、年)通常被看作静态的,适合反映给定景观格局下产流产沙和水沙输移的平均状态。水文连通度和泥沙连通度通常是高度动态的,依赖于降雨过程和具体的景观属性状态,适合于描述次降雨等短时内的景观连通状况。面向土壤侵蚀过程的景观连通度以径流和水分横向运移、土壤颗粒的剥离和沿地表的移动为目标过程。高强度的降雨、陡峭的地形以及低粗糙度的裸露土壤有利于增强景观单元或景观位置间的径流和泥沙输送,对应较高的景观连通度。地形洼地、植被斑块、人类建筑设施等起到阻碍作用的景观单元削弱水沙输送路径的有效连通[11,12,19],形成较低的景观连通度。

总体上,对降雨侵蚀过程而言,景观连通度有两个方面的涵义:① 景观结构连通度:径流、泥沙产生斑块(“源”斑块)内部以及斑块间在水流路径方向上的相互连通和泥沙产生区与泥沙输送目的地(库塘、湖泊、河道等)之间联系通道的畅通程度[6,14];② 景观功能连通度:景观中不同位置通过径流和泥沙输送联系的程度,通常可用不同位置间径流、泥沙输送频率、输送量或径流量表征[20,21]。在土壤侵蚀过程中,景观结构连通与功能连通之间存在反馈关系,即结构上的连通制约着功能上的连通,而后者作为重要的干扰方式,可改变前者[22]

3 景观连通度在土壤侵蚀中的作用

土壤侵蚀过程在多个尺度受到包括地形格局、土地覆被格局等景观格局的控制。塑造景观连通状态是景观格局控制土壤侵蚀发生、发展的主要途径之一[23],如低入渗斑块之间在水流路径方向上的连通、坡面与沟道之间通过泥沙输送路径建立的连通,沟道网络之间的连通等[16,24]。根据土壤侵蚀的发生和发展,可将其划分为两个相互衔接的子过程:物质供给过程和物质搬运—沉积过程,即泥沙的产生过程和在景观中的再分配过程。物质供给过程指土壤颗粒在外力作用下的原位剥离;物质搬运—沉积过程指土壤物质在降雨、径流、重力、风等作用下的输送和在地形洼地、平坦部位、植被阻碍体中沉积的过程。在土壤颗粒的原位剥离过程中,景观连通度通过影响径流侵蚀能力而影响土壤颗粒原位剥离。在泥沙传输过程,景观连通度影响着水沙向区外传输的难易程度。景观中某位置上游低入渗、高产流区域之间的连通,以及其与上游集水区的有效连通可增强土壤物质的剥离。下游泥沙输送路径上低阻力单元的连通则有利于泥沙向区外输出[6]

从斑块到流域、区域等多尺度的实验[25-28]和模型模拟研究[29,30]表明,随着尺度的变化,土壤侵蚀受不同类型景观连通的影响。斑块尺度上,斑块内部结构控制着土壤侵蚀过程,其差异会非线性地放大侵蚀产沙[31]。小区和坡面尺度上,径流、泥沙源区的连通主导着侵蚀的发生和发展[16],因而径流、产沙与源区的连通度指标具有很好的相关性[6]。子集水区尺度,响应单元间的空间连通度及其与排水路径的连通程度是泥沙传输的主导因素;小流域/沟道网络水平上,沟道网络的连通度是关键[16]。集水区和小流域尺度上,植被斑块、地形洼地等地表单元控制坡面产流、产沙区域与坡底沟道的连通度,制约着坡面泥沙向沟道的输送[32]。在流域和景观尺度,土壤物质在景观中的搬运—沉积是关注的主要土壤流失过程。地形洼地、大面积植被带、水坝、山前洪积扇、河心滩等景观单元间的连通度制约着泥沙运移[11]。如洼地将坡面与河道分隔,洪积扇植被带将沟道与主河道阻断等。这些要素在泥沙输移过程中发挥着开关的作用,决定了任何时刻的有效流域面积[11]

4 土壤侵蚀过程导向的景观连通度定量

土壤侵蚀研究对景观连通度的定量大多是通过对观测实验的经验总结而发展起来的。景观连通度指数和具有模拟泥沙传输功能的土壤侵蚀模型是表达景观连通度的两个主要的途径[33]。景观连通度指数方法基于侵蚀过程机理,利用遥感或地面制图方法获取的景观类型,结合景观类型的土壤保持功能,通过描述景观功能单元之间的空间关系,或将景观属性与其他侵蚀影响因素联系起来,构建耦合过程的景观连通度测度指标[12,34]。土壤侵蚀模型则将景观连通度表征参数直接作为模型的参数,或在模拟产流产沙和径流、泥沙输移过程中考虑景观阻滞功能异质性、隐式地表达景观连通度概念,如在考虑景观阻滞功能异质性的条件下模拟泥沙沿汇流路径的输移。

4.1 景观连通度指数

随着景观格局信息获取能力的增强,景观格局指数成为反映土壤侵蚀状况的便捷工具[35,36]。由于土壤侵蚀过程的复杂性和景观格局指数本身的局限性,当前许多基于斑块—基底—廊道范式构建的景观指数与土壤侵蚀变量之间不存在确定的定量关系[37],而根据土壤侵蚀过程构建的景观格局指数是较好的选择。相对于土壤侵蚀模型而言,结合景观信息和侵蚀过程机理构建的景观格局指数对输入数据要求低,而指示意义明确。在土壤侵蚀研究中,景观连通度指数主要从景观单元间的空间耦合关系[12],或景观单元间水沙传输可能性、频率和量级等方面着手构建[6,18]。前者即为景观空间结构连通度指数,多用于静态的景观连通度描述;后者为景观功能连通度,随降雨、土壤含水量等驱动因素变化而具有较高的时间动态特征,过程意义更为明显,在一定程度上可视为一些土壤侵蚀模型的简化。

4.1.1 景观空间结构连通度指数 景观空间结构连通度指数以土地利用/覆被、景观水文属性数据、地形等空间数据为基础,在对景观类型土壤保持功能定性或定量的基础上建立。“源”、“汇”景观功能分类与地表水沙输送方向相结合是构建景观连通度指数的主要方向。植被斑块、坑洼、以及人工水沙拦阻设施等阻滞侵蚀发展的景观单元被视为水沙的“汇”,而裸露土壤斑块、低入渗区等增强土壤侵蚀的景观单元则为径流、泥沙的“源”。径流、泥沙的“源”区域内部的连通,以及其与植被斑块、坑洼等“汇”单元之间在水沙输送方向上的空间配置决定着景观连通的方式和程度。基于此,Ludwig等在小区尺度上将地表分为阻碍和非阻碍单元,将沿下坡方向非阻碍单元连续毗邻的距离作为基本参数,构建了方向性渗透指数(directional leakiness index,DLI)来反映小区尺度给定植被覆盖格局下的水、沙留滞能力[5]。坡面尺度泥沙的输移方向大致是沿坡面向下,因此地表泥沙“源”、“汇”类型单元在下坡方向的连通可增强土壤侵蚀。据此,Mayor等提出Flowlength指数来定量从裸露土壤等土壤侵蚀的“源”开始至坑洼、植被斑块等“汇”终止的地表水流路径长度来定量小区、坡面和小型集水区尺度景观连通度[6]。该指数将植被斑块看作完全的“汇”。然而,低于一定植被覆盖度阈值的稀疏植被和缺乏近地表植被覆盖的植被覆盖区同样可发生较强的侵蚀。认识到这一点,Liu等将地表覆被类型的土壤保持能力作为权重,改进了Flowlength指数[38]。基于植被覆被度与土壤流失之间的负指数关系,Ludwig等以遥感获取的植被覆盖度为参数改进了DLI指数,构建了CDLI(cover-based directional leakiness index)[39]。DLI和CDLI指数都是基于规则小区提出的,具有归一化、输入数据少、有一定的过程描述,方便应用。但将泥沙输移方向设定为平行坡面向下限制了在地形复杂的坡面或在集水区尺度的应用。为此,Ludwig等用地形提取的水流方向作为泥沙输移方向,提出了基于植被覆盖度和地形的LI指数(leakiness index)[4],增强了对侵蚀过程中物质输移的表达。

上游来水是立地土壤侵蚀的主要驱动力之一。因此,上游集水区面积是表达立地土壤侵蚀强度的有效指标。定量与上游集水区连通的程度是构建面向土壤侵蚀的景观连通度指数所采取的又一种策略。研究表明,景观中任一位置的侵蚀量与上游汇水面积呈指数关系,上游集水区面积越大的景观位置土壤侵蚀强度越大[18]。上游集水区内的植被、土壤、地形坡度以及坑洼、堤埂、降雨特征等因素决定着景观中任意位置与上游集水区的实际连通状况,即实际集水区面积并不一定与通过分水岭确定的上游集水区完全等同,实际有效连通的区域只是集水区内的部分区域(有效集水区)[11,20,34]。基于此,Fryirs等采用有效集水区面积来表达泥沙输移相关的流域景观连通度[34]。Imeson等则用植被覆盖调节后上游有效集水区面积与上坡集水区面积之比作为景观连通度的表征[12]

4.1.2 景观功能连通度指数 在土壤侵蚀过程中,空间结构上互不直接邻接的景观位置或景观单元也可通过水沙输移连通。Jain等结合景观单元是否在空间上邻接和单元间是否存在物质输送,提出概念性的景观连通度定量方法[40]。对空间上邻接的景观单元,景观连通度由空间上邻接的面积(Ap)和单元间物质传输量(im)决定了式(1)。空间上不邻接的景观单元间的连通度(C)取决于景观单元间物质传输的驱动力(E)和间隔距离(d),可用式(2)表示:

C=Ap×im(1)

C=E/d(2)

土壤侵蚀过程包括侵蚀产沙和泥沙在景观中的输移两个过程,具有区内和区外两方面的效应[1,41]。因此,水力侵蚀区土壤侵蚀过程涉及的景观连通包括与上游水、沙输入区的连通和与下游水沙输出区的连通,即径流、泥沙从位置A输移到位置B的概率取决于两个要素:A处上游流域的地表特征(土壤可蚀性、粗糙度、坡度、土地利用/覆被等)和A、B位置间径流、泥沙输送通道上的地表特征。基于这样的框架,Borselli等提出了式(3)来表示A、B间连通的可能性[18]

式中:A为上坡集水区面积; S̅W̅分别为上坡集水区平均坡度(m/m)和权重系数(无量纲); diSiWi分别为位置A、B间第i个栅格的长度(m)、坡度(m/m)和权重系数(无量纲,可用植被覆盖因子、地表粗糙度等代替)。通过对式(3)分子分母取对数,构造了分布式的景观泥沙连通指数(IC),将侵蚀产沙与泥沙输出结合起来,因而具有较强的过程基础。IC实质上是一个结合侵蚀产沙与泥沙输移的简化模型。遵循类似的考虑,Fu等基于土地利用类型的土壤保持功能差异及其相对于出口(坡底、河道等)的距离,构建了多尺度土壤流失评价指数,将这两方面结合起来评价坡面到流域的土壤流失[14]

总的来看,土壤侵蚀过程导向的景观连通度指数大多考虑了土壤侵蚀过程中发挥作用的多种地表因素,从立地土壤侵蚀产沙驱动力或结合泥沙传输过程中的阻力出发构建,以概化的方式反映了景观格局控制土壤侵蚀过程的机制。但土壤侵蚀具有临界[14,42]、尺度依赖[24]和过程时空维度上复杂[43]的特点,这需要对侵蚀过程的细致描述才能反映出来。而目前的景观连通度指数大多基于低频的景观信息,刻画的是给定景观格局下土壤侵蚀的平均状态,对土壤侵蚀过程的非线性变化特征、侵蚀特征的尺度更替反映不足。

4.2 融合景观连通度的土壤侵蚀模拟模型

土壤侵蚀模拟模型是土壤侵蚀研究的主要工具和主要内容之一。景观连通度在大量的分布式土壤侵蚀模型中得到隐式地表达,如WATEM/SEDEM模型[44]、Lapsus[45]、LISEM[46]等。此类模型一般基于水流路径和降雨、水流侵蚀—搬运能力模拟产沙和泥沙在景观中的传输过程来实现对景观连通度的表达,且对降雨、土地利用/覆被等因素导致的景观连通变化具有很好的反映。在WATEM/SEDEM模型中,产沙量用RUSLE模型模拟,泥沙在景观中的输移则通过模拟地表覆被特征控制的泥沙传输能力(transport capacity,TC)模拟。RUSLE模型中的坡长因子实质上是对与上坡连通度的考虑,空间化的植被覆盖因子和土壤保持措施因子则是对侵蚀抑制功能的表达。TC模拟中使用上坡汇水面积、植被泥沙传输系数等参数。WATEM/SEDEM通过产沙量和传输能力的对比确定泥沙沿地形决定的水流路径的传输和沉积:当产沙量与上游来沙量之和大于传输能力,则泥沙输出量等于传输能力,净沉积发生;反之则泥沙全部输出,净侵蚀发生。由此将地形格局、植被覆盖格局、土壤保持措施影响的空间异质性涵盖在内,定量了流域内景观位置之间、景观单元间的泥沙传输量,从而表达了景观连通度。Lapsus模型中将地表径流能量作为泥沙输移的驱动力,适合模拟短时到长期的土壤侵蚀[45]。与WATEM/SEDEM类似,Lapsus模型通过泥沙输入量与泥沙传输能力的大小关系确定泥沙沉积和沿水流路径方向的输出。在泥沙沿水流路径的传输模拟中,Lapsus模型采用了多流向算法,更好表达了地形的汇聚和分散[45]。LISEM模型是一个物理意义较强的侵蚀模型,产沙和泥沙传输能力同样也是模拟泥沙在景观中传输的基础,它很好地模拟了径流和悬移泥沙沿给定输送网络的传输[25]。总而言之,这些模型通过考虑上坡汇水区地表格局特征、立地条件和沿传输通道的景观功能异质性、以泥沙沉积—输出模拟为基础隐式地表达了景观结构和功能连通度。

在土壤侵蚀模型中将景观连通度指数作为一个因子是土壤侵蚀模拟模型反映景观连通状况的另一个途径。Vigiak等将景观连通度指数与坡面最大侵蚀产沙量结合起来,构建坡面侵蚀产沙的估算模型[9]。刘宇等将RUSLE模型与景观连通度指数结合,构建指示流域泥沙输出的模型,直观地将景观连通度与侵蚀模型结合起来[13]。虽然融合了景观连通度概念的土壤侵蚀模拟模型能充分反应景观格局对土壤侵蚀的作用,但地表信息、降雨数据的时空精细程度,尤其是地形数据的精度,显著影响模型的准确性。此外,土壤侵蚀过程中的临界现象、尺度依赖和多因素相互作用仍然是模型模拟面临的重大挑战。尽管如此,此类模型反映了土壤侵蚀过程的分布式特点,描述了各景观位置间通过泥沙输移建立的联系和景观格局在土壤侵蚀发生、发展中的作用,对以水土保持为目标的景观格局设计具有很好的应用价值。

5 结论与讨论

土壤侵蚀是受景观格局控制的地表物质再分配过程。对于降雨驱动的土壤侵蚀,景观连通度是在多个空间尺度和时间尺度影响土壤侵蚀过程的重要景观格局特征。因此,定量景观连通度可作为描述景观格局与土壤侵蚀相互作用的桥梁。基于土壤侵蚀过程构建景观连通度指数和发展融合景观连通度概念的土壤侵蚀模型,是耦合景观连通度和土壤侵蚀的两个途径。以景观连通度定量指标作为参数,或基于水流路径和降雨、水流侵蚀—搬运能力模拟产沙和泥沙在景观中的传输是土壤侵蚀模型中表达景观连通度的方式。景观指数方法简单易行,而模型方法则过程机理清晰。

尽管如此,土壤侵蚀过程中的临界现象等非线性特征、尺度依赖和多因素复杂相互作用使得两种景观连通度描述途径面临诸多挑战。为增强景观连通度定量指标和模型在土壤侵蚀研究中的有效性,对土壤侵蚀过程对驱动变量的临界、非线性响应特征的表达需要强化,这也是景观格局定量方法研究土壤侵蚀过程的难点。地形、降雨、植被覆盖、土壤质地、土壤水分等是土壤侵蚀的主要影响因子,具有较高的时空变异性,因而土壤侵蚀在强度、形式等方面也具有高度的时空变异性。因此,在描述景观连通度的研究中,应加强景观连通度对高度空间异质的土壤侵蚀驱动因素的非线性响应的表达方法研究,探索尺度更替对景观连通度的影响。景观连通度指数是非常便捷易行的工具,高时空分辨率的景观属性获取是提高其景观连通度表达能力的需求。因此,需要加强高时空分辨率景观信息和驱动因子状态参量的获取方法研究。随着高时空分辨率对地观测技术和平台的发展,遥感技术成为获取较高时空分辨率的植被覆盖、降雨甚至地形信息的有效途径。但影响土壤侵蚀的土壤质地、土壤水分,尤其是植被地下部分的相关特征信息难以大范围、高频率获取,成为制约景观格局定量方法刻画土壤侵蚀时空动态特征重要方面。有必要将高时空分辨率对地遥感监测与地面定位观测和调查相结合,发展土壤质地、水分以及植被地下特征的遥感反演方法。

The authors have declared that no competing interests exist.


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https://doi.org/10.3969/j.issn.1672-3007.2014.02.016      URL      [本文引用: 1]      摘要

以丹江口水库以上的汉江流域为 例,利用植被覆盖度、坡度加权的上游有效汇流面积空间分布型式和驱动-阻力耦合空间分布拟合函数2个指标,评价水蚀流域土地覆被格局土壤保持能力,并基于 研究区14个子流域水文站泥沙资料进行验证。结果表明:汉江干流沿岸河谷盆地和丹江口水库周边丘陵区子流域是研究区城镇和农田的主要分布区,植被覆盖度 低,距离汉江较近,当前覆被格局土壤保持能力相对较低,是河流泥沙的主要直接来源地;有效汇流面积空间分布型式和驱动-阻力耦合空间分布拟合函数能有效反 映流域泥沙输出,可作为评价流域土地覆被格局土壤保持能力的指标。该评价方法基于土地覆被格局与土壤侵蚀的作用机制,简单易行,可为评价土地覆被格局土壤 保持能力、土地覆被格局变化的土壤侵蚀效应提供一种简捷的途径。

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https://doi.org/10.3969/j.issn.1672-3007.2014.02.016      URL      [本文引用: 1]      摘要

以丹江口水库以上的汉江流域为 例,利用植被覆盖度、坡度加权的上游有效汇流面积空间分布型式和驱动-阻力耦合空间分布拟合函数2个指标,评价水蚀流域土地覆被格局土壤保持能力,并基于 研究区14个子流域水文站泥沙资料进行验证。结果表明:汉江干流沿岸河谷盆地和丹江口水库周边丘陵区子流域是研究区城镇和农田的主要分布区,植被覆盖度 低,距离汉江较近,当前覆被格局土壤保持能力相对较低,是河流泥沙的主要直接来源地;有效汇流面积空间分布型式和驱动-阻力耦合空间分布拟合函数能有效反 映流域泥沙输出,可作为评价流域土地覆被格局土壤保持能力的指标。该评价方法基于土地覆被格局与土壤侵蚀的作用机制,简单易行,可为评价土地覆被格局土壤 保持能力、土地覆被格局变化的土壤侵蚀效应提供一种简捷的途径。
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Ecosystems, 2007, 10(6): 987-998.

https://doi.org/10.1007/s10021-007-9074-3      Magsci      [本文引用: 1]      摘要

<a name="Abs1"></a>The importance of the spatial pattern of vegetation for hydrological behavior in semiarid environments is widely acknowledged. However, there is little empirical work testing the hypothetical covariation between vegetation spatial structure and hillslope water and sediment fluxes. We evaluated the relationships between vegetation structural attributes (spatial pattern, functional diversity), soil surface properties (crust, stone, plant, and ground cover, and particle size distribution) and hillslope hydrologic functioning in a semiarid Mediterranean landscape; in particular, we tested whether decreasing patch density or coarsening plant spatial pattern would increase runoff and sediment yield at the hillslope scale. Runoff and sediment yield were measured over a 45-month period on nine 8&nbsp;×&nbsp;2-m plots that varied in vegetation type and spatial pattern. We grouped vegetation into functional types and derived plant spatial pattern attributes from field plot maps processed through a GIS system. We found that there was an inverse relationship between patch density and runoff, and that both runoff and sediment yields increased as the spatial pattern of vegetation coarsened. Vegetation pattern attributes and plant functional diversity were better related to runoff and sediment yield than soil surface properties. However, a significant relationship was found between physical crust cover and plant spatial pattern. Our results present empirical evidence for the direct relationship between the hydrologic functioning of semiarid lands and both the spatial pattern and the functional diversity of perennial vegetation, and suggest that plant spatial pattern, physical crust cover, and functional diversity may be linked through feedback mechanisms.
[9] Vigiak O, Borselli L, Newham L T H, et al.

Comparison of conceptual landscape metrics to define hillslope-scale sediment delivery ratio.

Geomorphology, 2012, 138(1): 74-88.

https://doi.org/10.1016/j.geomorph.2011.08.026      URL      [本文引用: 2]      摘要

The aim of this study was to evaluate four metrics to define the spatially variable (regionalised) hillslope sediment delivery ratio ( HSDR ). A catchment model that accounted for gully and streambank erosion and floodplain deposition was used to isolate the effects of hillslope gross erosion and hillslope delivery from other landscape processes. The analysis was carried out at the subcatchment (~40km 2 ) and the cell scale (400m 2 ) in the Avon-Richardson catchment (3300km 2 ), south-east Australia. The four landscape metrics selected for the study were based on sediment travel time, sediment transport capacity, flux connectivity, and residence time. Model configurations with spatially-constant or regionalised HSDR were calibrated against sediment yield measured at five gauging stations. The impact of using regionalised HSDR was evaluated in terms of improved model performance against measured sediment yields in a nested monitoring network, the complexity and data requirements of the metric, and the resulting spatial relationship between hillslope erosion and landscape factors in the catchment and along hillslope transects. The introduction of a regionalised HSDR generally improved model predictions of specific sediment yields at the subcatchment scale, increasing model efficiency from 0.48 to >0.6 in the best cases. However, the introduction of regionalised HSDR metrics at the cell scale did not improve model performance. The flux connectivity was the most promising metric because it showed the largest improvement in predicting specific sediment yields, was easy to implement, was scale-independent and its formulation was consistent with sedimentological connectivity concepts. These properties make the flux connectivity metric preferable for applications to catchments where climatic conditions can be considered homogeneous, i.e. in small-medium sized basins (up to approximately 3000km 2 for Australian conditions, with the Avon-Richardson catchment being at the upper boundary). The residence time metric improved model assessment of sediment yields and enabled accounting for climatic variability on sediment delivery, but at the cost of greater complexity and data requirements; this metric might be more suitable for application in catchments with important climatic gradients, i.e. large basins and at the regional scale. The application of a regionalised HSDR metric did not increase data or computational requirements substantially, and is recommended to improve assessment of hillslope erosion in empirical, semi-lumped erosion modelling applications. However, more research is needed to assess the quality of spatial patterns of erosion depicted by the different landscape metrics.
[10] Bélisle M.

Measuring landscape connectivity: The challenge of behavioral landscape ecology.

Ecology, 2005, 86(8): 1988-1995.

https://doi.org/10.1890/04-0923      URL      [本文引用: 1]      摘要

The recognition of behavior as a link between process and pattern in landscape ecology is exemplified by the concept of functional connectivity: the degree to which the landscape facilitates or impedes movement among resource patches. In this paper, I first argue that the actual operational definitions of this concept as applied to animal movement are not fully consistent with its formal definition. For instance, I question that a high likelihood of movement among the different points of primary habitat implies a high connectivity and contend that such a view can lead to misinterpretations. I also address two more hurdles to the measurement of functional connectivity: the fact that functional connectivity may not be equal along all axes and directions of movement and individual variation in functional connectivity within a given landscape. These points bring me to suggest that the concept of functional connectivity be bridged to the one of travel costs used in behavioral ecology. This would help define unequivocal operational definitions of functional connectivity as its measurement would then be dictated by its ecological role within specific models (e.g., travel costs within group membership models of foraging theory). I argue further that this ecological role shall in turn determine the motivation underlying the movement of individuals, implying that the latter should preferably be standardized when measuring functional connectivity in the field. I finally present some methods to do so. These include translocation and playback experiments, food-titration and giving-up densities experiments, and manipulating feeding and breeding site locations and success.
[11] Prugh L R.

An evaluation of patch connectivity measures.

Ecological Applications, 2009, 19(5): 1300-1310.

https://doi.org/10.1890/08-1524.1      URL      PMID: 19688936      [本文引用: 5]      摘要

Measuring connectivity is critical to the study of fragmented populations. The three most commonly used types of patch connectivity measures differ substantially in how they are calculated, but the performance of these measures has not been broadly assessed. Here I compare the ability of nearest neighbor (NN), buffer, and incidence function model (IFM) measures to predict the patch occupancy and colonization patterns of 24 invertebrate, reptile, and amphibian metapopulations. I predicted that NN measures, which have been criticized as being overly simplistic, would be the worst predictors of species occupancy and colonization. I also predicted that buffer measures, which sum the amount of habitat in a radius surrounding the focal patch, would have intermediate performance, and IFM measures, which take into account the areas and distances to all potential source patches, would perform best. As expected, the simplest NN measure (distance to the nearest habitat patch, NHi) was the poorest predictor of patch occupancy and colonization. Contrary to expectations, however, the next-simplest NN measure (distance to the nearest occupied [source] patch, NSi) was as good a predictor of occupancy and colonization as the best-performing buffer measure and the general IFM measure Si. In contrast to previous studies suggesting that area-based connectivity measures perform better than distance-based ones, my results indicate that the exclusion of vacant habitat patches from calculations is the key to improved measure performance. I highlight several problems with the parameterization and use of IFM measures and suggest that models based on NSi are equally powerful and more practical for many conservation applications.
[12] Imeson A C, Prinsen H A M.

Vegetation patterns as biological indicators for identifying runoff and sediment source and sink areas for semi-arid landscapes in Spain. Agriculture,

Ecosystems & Environment, 2004, 104(2): 333-342.

[本文引用: 5]     

[13] 刘宇, 吴炳方, 曾源, .

耦合过程和景观格局的土壤侵蚀水环境影响评价

. 应用生态学报, 2013, 24(9): 2581-2589.

Magsci      [本文引用: 2]      摘要

<div style="line-height: 150%">将景观格局的作用纳入到土壤侵蚀的生态环境影响评估中,具有方法上的实用意义,可为水体泥沙源区识别、评价立地侵蚀对目标水体的泥沙输出风险和流域景观格局对土壤流失抑制潜力提供一种途径.本文将RUSLE模型作为模拟立地土壤侵蚀强度的工具,考虑植被覆盖和地形对泥沙输送的阻滞作用,从点(栅格)和子流域两个尺度,采用景观格局表征方法定量评估南水北调中线水源区土壤侵蚀对河流、水库的影响.在点(栅格)尺度提出土壤侵蚀影响强度(<em>I</em>)指标表征土壤侵蚀对水体的泥沙输出风险;在流域尺度利用反映流域景观格局留滞泥沙能力的渗透指数(LI)指示泥沙进入水体的风险.结果表明: 耦合景观格局信息和侵蚀过程的指标能空间分布式地有效反映立地土壤侵蚀对水体泥沙输入的影响强度;LI与流域平均景观阻滞、平均植被覆盖度呈显著的指数关系, 子流域输沙模数与LI呈显著的指数回归关系.说明基于土壤侵蚀过程表征景观格局、将景观格局信息与景观土壤保持功能结合起来的评价方法,可为土壤侵蚀风险评价提供新途径.</div><div style="line-height: 150%">&nbsp;</div>

[Liu Yu, Wu Bingfang, Zeng Yuan, et al.

Assessment of the impacts of soil erosion on water environment based on the integration of soil erosion process and landscape pattern.

Chinese Journal of Applied Ecology, 2013, 24(9): 2581-2589.]

Magsci      [本文引用: 2]      摘要

<div style="line-height: 150%">将景观格局的作用纳入到土壤侵蚀的生态环境影响评估中,具有方法上的实用意义,可为水体泥沙源区识别、评价立地侵蚀对目标水体的泥沙输出风险和流域景观格局对土壤流失抑制潜力提供一种途径.本文将RUSLE模型作为模拟立地土壤侵蚀强度的工具,考虑植被覆盖和地形对泥沙输送的阻滞作用,从点(栅格)和子流域两个尺度,采用景观格局表征方法定量评估南水北调中线水源区土壤侵蚀对河流、水库的影响.在点(栅格)尺度提出土壤侵蚀影响强度(<em>I</em>)指标表征土壤侵蚀对水体的泥沙输出风险;在流域尺度利用反映流域景观格局留滞泥沙能力的渗透指数(LI)指示泥沙进入水体的风险.结果表明: 耦合景观格局信息和侵蚀过程的指标能空间分布式地有效反映立地土壤侵蚀对水体泥沙输入的影响强度;LI与流域平均景观阻滞、平均植被覆盖度呈显著的指数关系, 子流域输沙模数与LI呈显著的指数回归关系.说明基于土壤侵蚀过程表征景观格局、将景观格局信息与景观土壤保持功能结合起来的评价方法,可为土壤侵蚀风险评价提供新途径.</div><div style="line-height: 150%">&nbsp;</div>
[14] Fu Bojie, Zhao Wenwu, Chen Liding, et al.

A multiscale soil loss evaluation index.

Chinese Science Bulletin, 2006, 51(4): 448-456.

Magsci      [本文引用: 4]     

[15] Zehe E, Sivapalan M.

Threshold behaviour in hydrological systems as (human) geo-ecosystems: Manifestations, controls, implications.

Hydrology and Earth System Sciences, 2009, 13(7): 1273-1297.

https://doi.org/10.5194/hess-13-1273-2009      URL      PMID: 11198184      [本文引用: 1]      摘要

In this paper we review threshold behaviour in environmental systems, which are often associated with the onset of floods, contamination and erosion events, and other degenerative processes. Key objectives of this review are to (a) suggest indicators for detecting threshold behavior, (b) discuss their implications for predictability, (c) distinguish different forms of threshold behavior and the...
[16] Cammeraat E L H.

Scale dependent thresholds in hydrological and erosion response of a semi-arid catchment in southeast Spain

. Agriculture, Ecosystems & Environment, 2004, 104(2): 317-332.

https://doi.org/10.1016/j.agee.2004.01.032      URL      [本文引用: 4]      摘要

Land degradation and soil erosion are perceived as important problems in the dryland zones of the Mediterranean. Three-year measurements of hydrological and soil erosion data from a series of nested experimental watersheds in a semi-arid area of SE Spain are discussed. The aim was to study the role and effects of thresholds on the spatial connections between different system compartments, such as response units and sub-catchments that act at different levels of scale (plot to watershed scale). It was also the aim to quantify runoff and erosion at these different scales. Several types of thresholds are described and these are related to vegetation type and pattern, soil surface roughness, distance to the main channel, land use and tillage effects (intrinsic properties of the landscape) as well as rainfall intensity, duration and depth (external influence). The expansion of runoff generating areas under Hortonian overland flow is discussed in relation to vegetation structure and rainfall. Results showed that runoff and sediment yield results highly depend on the vegetation structure. The relation between rainfall intensity and rainfall depth and the hydrological response were established at five levels of scale. Three spatio-temporal process domains were analysed: the spot- and plot-processes at the finest scale, the hillslope, micro- and sub-catchment processes at the intermediate scale and catchment scale and main channel network processes at the broadest scale. An event with a 5-year recurrence period is discussed to illustrate the importance of scale related thresholds, explaining the relative importance of high intensity rainfalls. Soil erosion was found to be a magnitude larger on terraced valley bottoms (2500-3000gm -2 ) when compared to the semi-natural hillslopes, where erosion figures were less than 10gm -2 . This indicated that the contribution of sediment from terraced cultivated lands is important and are an underestimated part of the sediment budget of semi-arid catchments.
[17] Bracken L J, Croke J.

The concept of hydrological connectivity and its contribution to understanding runoff-dominated geomorphic systems.

Hydrological Processes, 2007, 21(13): 1749-63.

https://doi.org/10.1002/hyp.6313      URL      [本文引用: 2]      摘要

The term 'connectivity' is increasingly being applied in hydrological and geomorphological studies. Relevant research encompasses aspects of landscape connectivity, hydrological connectivity and sedimentological connectivity. Unlike other disciplines, notably ecology, published studies show no consensus on a standard definition. This paper provides an overview of how existing research relates to the concept of connectivity in both ecology and hydrology by proposing and evaluating a conceptual model of hydrological connectivity that includes five major components: climate; hillslope runoff potential; landscape position; delivery pathway and lateral connectivity. We also evaluate a proposed measure of connectivity called the volume to breakthrough to quantify changing connectivity between different environments and catchments.
[18] Borselli L, Cassi P, Torri D.

Prolegomena to sediment and flow connectivity in the landscape: A GIS and field numerical assessment.

Catena, 2008, 75(3): 268-277.

https://doi.org/10.1016/j.catena.2008.07.006      Magsci      [本文引用: 4]      摘要

<h2 class="secHeading" id="section_abstract">Abstract</h2><p id="">This paper presents two new definitions of sediment and water flux connectivity (from source through slopes to channels/sinks) with examples of applications to sediment fluxes. The two indices of connectivity are operatively defined, one (IC) that can be calculated in a GIS environment and represents a connectivity assessment based on landscape's information, and another that can be evaluated in the field (FIC) through direct assessment. While IC represent a potential connectivity characteristic of the local landscape, since nothing is used to represent the characteristics of causative events, FIC depend on the intensities of the events that have occurred locally and that have left visible signs in the fields, slopes, etc.</p><p id="">IC and FIC are based on recognized major components of hydrological connectivity, such as land use and topographic characteristics. The definitions are based on the fact that the material present at a certain location A reaches another location B with a probability that depends on two components: the amount of material present in A and the route from A to B. The distance to B is weighted by the local gradient and the type of land use that the flow encounters on its route to B, while the amount of material present in A depends on the catchment surface, slope gradient and type of land use of said catchment.</p><p id="">Although IC and FIC are independent from each other, and are calculated using different equations and different inputs, they complement each other. In fact, their combined use improves IC's accuracy. Hence, connectivity classes can afterward be rated using IC alone.</p><p id="">This procedure has been applied in a medium-size watershed in Tuscany (Italy) with the aim of evaluating connectivity, identifying connected sediment sources and verifying the effects of mitigation measures.</p><p id="">The proposed indices can be used for monitoring changes in connectivity in areas with high geomorphological or human induced evolution rates.</p>
[19] Molina A, Govers G,

Van den Putte A, et al. Assessing the reduction of the hydrological connectivity of gully systems through vegetation restoration: field experiments and numerical modelling.

Hydrology and Earth System Sciences, 2009, 13(10): 1823-1836.

https://doi.org/10.5194/hess-13-1823-2009      URL      [本文引用: 1]      摘要

Restoration of degraded land in the Southern Ecuadorian Andes has led to alterations in the functioning of degraded catchments. Recovery of vegetation on areas affected by overgrazing, as well as the reforestation or afforestation of gully areas have given rise to modifications of hydrological connectivity within the catchments. Recent research has highlighted the ability of gully channels to trap sediment eroded from steep slopes, especially if vegetation is established along the gully bed. However, vegetation cover not only induces sediment deposition in the gully bed, but may also have a potential to reduce runoff water volume. The performance of gully beds in reducing the transfer of runoff was investigated by conducting controlled concentrated flow experiments in the field. Experimental field data for nine gullies were derived by pouring concentrated inflow into the upstream end and measuring the outflow at the downstream end of the channel. Two consecutive flow experiments per gully were carried out, so that data for dry and wet soil conditions were collected. The hydrological response to concentrated flow was estimated for each experiment by calculating its cumulative infiltration coefficient, IC (%). The results showed a great difference in IC between dry and wet soil conditions. The IC for wet soil conditions was on average 24%, whereas it was 60% for dry conditions. Gullies with more than 50% surface vegetation cover exhibit the highest cumulative infiltration coefficients (81% for dry runs, and 34% for wet runs), but runoff transmission losses were not as clearly related to Correspondence to: A. Molina (molina armando@hotmail.com) vegetation cover as sediment storage as shown in Molina et al. (2009). The experimental field data of 16 experiments were used to calibrate a hydrological model developed by Fiener and Auerswald (2005) in order to simulate the transfer of concentrated flow along the gully beds. The calibrated model was able to simulate the transfer of runoff water well, as the error on the simulated total outflow volumes is below 13% for 15 out of 16 cases. However, predicting infiltration amounts is difficult: the high sensitivity of model results to some crucial hydraulic parameters (runoff width, hydraulic conductivity and sorptivity) is one of the reasons why the relationships between model parameter values and gully features are relatively weak. The results obtained from the field experiments show that gully systems are key elements in the hydrological connectivity of degraded landscapes. The transfer of overland flow and sediment from the slopes towards the river system highly depends on the presence/absence of vegetation in the gully beds and should therefore be accounted for in assessments of landscape degradation and/or recovery.
[20] Fryirs K A, Brierley G J, Preston N J, et al.

Buffers, barriers and blankets: The (dis)connectivity of catchment-scale sediment cascades.

Catena, 2007, 70(1): 49-67.

https://doi.org/10.1016/j.catena.2006.07.007      Magsci      [本文引用: 2]      摘要

<h2 class="secHeading" id="section_abstract">Abstract</h2><p id="">Catchment configuration and the nature of connectivity within and between landscape compartments affect the operation of sediment cascades and geomorphic responses to disturbance events of differing magnitude and frequency. This paper introduces the concept of landform impediments, termed buffers, barriers and blankets, that impede sediment conveyance by limiting the connectivity between landscape compartments. Buffers restrict sediment delivery to channels, barriers inhibit sediment movement along channels, and blankets drape channel or floodplain surfaces affecting the accessibility of sediment to entrainment. These features operate as a series of switches which turn on/off processes of sediment delivery, determining the effective catchment area at any given time. Using previously documented examples, the role of these features in affecting the operation of sediment cascades in a low relief, passive landscape setting such as the Australian landmass is contrasted to examples from high relief, uplifting settings in New Zealand. The Australian examples are further explored by examining how changes to landscape connectivity brought about by human disturbance since European settlement have impacted upon landscape sensitivity and prospects for river recovery. This approach to analysis of impediments to sediment conveyance is generic and can be applied in any environmental setting.</p>
[21] Heckmann T, Schwanghart W G.

Geomorphic coupling and sediment connectivity in an alpine catchment: Exploring sediment cascades using graph theory.

Geomorphology, 2013, 182(2): 89-103.

https://doi.org/10.1016/j.geomorph.2012.10.033      URL      [本文引用: 1]      摘要

Through their relevance for sediment budgets and the sensitivity of geomorphic systems, geomorphic coupling and (sediment) connectivity represent important topics in geomorphology. Since the introduction of the systems perspective to physical geography by , a catchment has been perceived as consisting of landscape elements (e.g. landforms, subcatchments) that are coupled by geomorphic processes through sediment transport. In this study, we present a novel application of mathematical graph theory to explore the network structure of coarse sediment pathways in a central alpine catchment. Numerical simulation models for rockfall, debris flows, and (hillslope and channel) fluvial processes are used to establish a spatially explicit graph model of sediment sources, pathways and sinks. The raster cells of a digital elevation model form the nodes of this graph, and simulated sediment trajectories represent the corresponding edges. Model results are validated by visual comparison with the field situation and aerial photos. The interaction of sediment pathways, i.e. where the deposits of a geomorphic process form the sources of another process, forms sediment cascades, represented by paths (a succession of edges) in the graph model. We show how this graph can be used to explore upslope (contributing area) and downslope (source to sink) functional connectivity by analysing its nodes, edges and paths. The analysis of the spatial distribution, composition and frequency of sediment cascades yields information on the relative importance of geomorphic processes and their interaction (however regardless of their transport capacity). In the study area, the analysis stresses the importance of mass movements and their interaction, e.g. the linkage of large rockfall source areas to debris flows that potentially enter the channel network. Moreover, it is shown that only a small percentage of the study area is coupled to the channel network which itself is longitudinally disconnected by natural and anthropogenic barriers. Besides the case study, we discuss the methodological framework and alternatives for node and edge representations of graph models in geomorphology. We conclude that graph theory provides an excellent methodological framework for the analysis of geomorphic systems, especially for the exploration of quantitative approaches towards sediment connectivity.
[22] Turnbull L, Wainwright J, Brazier R E.

A conceptual framework for understanding semi-arid land degradation: Ecohydrological interactions across multiple-space and time scales.

Ecohydrology, 2008, 1(1): 23-34.

[本文引用: 1]     

[23] Schröder B.

Pattern, process, and function in landscape ecology and catchment hydrology-how can quantitative landscape ecology support predictions in ungauged basins (PUB)?.

Hydrology and Earth System Sciences, 2006, 10(6): 967-979.

[本文引用: 1]     

[24] Cammeraat L H.

A review of two strongly contrasting geomorphological systems within the context of scale.

Earth Surface Processes and Landforms, 2002, 27(11): 1201-1222.

https://doi.org/10.1002/esp.421      URL      [本文引用: 2]      摘要

Abstract Scale issues are often addressed in contemporary geo-ecological studies and form one of the major challenges in the fields of physical geography, hydrology and ecology. In this paper the application of hierarchy theory and response units is proposed as an approach towards scale-transcending environmental studies on degradation and geomorphological development. Goals of the research were to establish which processes are important at what spatio-temporal scale, how hydro-geomorphological response is influenced by biological processes and whether hierarchy theory and the response unit approach can be used as an up-scaling methodology. Results from two climatologically and geomorphological different regions are discussed, one dominated by water shortage (SE Spain) and the other by water surplus (Luxembourg). In both cases detailed process research was carried out at scales ranging from the micro-plot to the catchment. Process research was concentrated on understanding and quantifying sediment and water transfer through the geo-ecosystems studied. Outcomes showed that in both cases the role of biological processes was important in the hydrological and degradation response of both areas. This was not only true for the finest scale levels but also had its impact on the emerging properties and response at the hillslope and catchment level. Connectivity of runoff-generating and runoff-absorbing areas was important on all scale levels. Connectivity is dominated by both the rainfall magnitude requency uration characteristics and physically and biologically controlled thresholds, which range from initial soil moisture contents, vegetation patterns or soil biological activity, to the presence of water harvesting structures. The complex interrelationships of the processes involved showed that linear up-scaling from fine to broad scale is impossible, as many thresholds and non-linear processes are involved at specific scales. The identified response units are used to integrate these complex relationships in a relatively manageable way, and may provide a useful framework for up-scaling, and for understanding catchment hydro-geomorphological response and development. Copyright © 2002 John Wiley & Sons, Ltd.
[25] Boer M, Puigdefábregas J.

Effects of spatially structured vegetation patterns on hillslope erosion in a semiarid mediterranean environment: A simulation study.

Earth Surface Processes and Landforms, 2005, 30(2): 149-167.

[本文引用: 2]     

[26] Parsons A J, Brazier R E, Wainwright J, et al.

Scale relationships in hillslope runoff and erosion.

Earth Surface Processes and Landforms, 2006, 31(11): 1384-1393.

https://doi.org/10.1002/esp.1345      URL      摘要

Abstract Eight runoff plots, located within a small catchment within the Walnut Gulch Experimental Watershed, southern Arizona, were constructed to test the argument that sediment yield (kg m -2 ) decreases as plot length increases. The plots ranged in length from 2 m to 27&middot;78 m. Runoff and sediment loss from these plots were obtained for ten natural storm events. The pattern of sediment yield from these plots conforms to the case in which sediment yield first increases as plot length increases, but then subsequently decreases. Data from the present experiment indicate that maximum sediment yield would occur from a plot 7 m long. Analysis of both runoff and sediment yield from the plots indicates that the relationship of sediment yield to plot length derives both from the limited travel distance of individual entrained particles and from a decline in runoff coefficient as plot length increases. Particle-size analysis of eroded sediment confirms the role of travel distance in controlling sediment yield. Whether in response to the finite travel distance of entrained particles or the relationship of runoff coefficient to plot length, the experiment clearly demonstrates that the erosion rates for hillslopes and catchments cannot be simply extrapolated from plot measurements, and that alternative methods for estimating large-area erosion rates are required. Copyright © 2006 John Wiley & Sons, Ltd.
[27] Zheng Fen Li.

Effect of vegetation changes on soil erosion on the Loess Plateau.

Pedosphere, 2006, 16(4): 420-427.

https://doi.org/10.1016/S1002-0160(06)60071-4      URL      摘要

Vegetation is one of the key factors affecting soil erosion on the Loess Plateau. The effects of vegetation destruction and vegetation restoration on soil erosion were quantified using data from long-term field runoff plots established on the eastern slope of the Ziwuling secondary forest region, China and a field survey. The results showed that before the secondary vegetation restoration period (before about 1866-1872), soil erosion in the Ziwuling region of the Loess Plateau was similar to the current erosion conditions in neighboring regions, where the soil erosion rate now is 8000 to 10000t km^(-2) year^(-1). After the secondary vegetation restoration, soil erosion was very low; influences of rainfall and slope gradient on soil erosion were small; the vegetation effect on soil erosion was predominant; shallow gully and gully erosion ceased; and sediment deposition occurred in shallow gully and gully channels. In modern times when human activities destroyed secondary forests, soil erosion increased markedly, and erosion rates in the deforested lands reached 10000 to 24000t km^(-2) year^(-1), which was 797 to 1682 times greater than those in the forested land prior to deforestation. Rainfall intensity and landform greatly affected the soil erosion process after deforestation. These results showed that accelerated erosion caused by vegetation destruction played a key role in soil degradation and eco-environmental deterioration in deforested regions.
[28] Descroix L, González B J L, Viramontes D.

Gully and sheet erosion on subtropical mountain slopes: Their respective roles and the scale effect.

Catena, 2008, 72(3): 325-339.

https://doi.org/10.1016/j.catena.2007.07.003      Magsci      [本文引用: 1]      摘要

<h2 class="secHeading" id="section_abstract">Abstract</h2><p id="">As most mountains in tropical and subtropical zones, the Western Sierra Madre suffers active present erosion, which may create some constraints to the social and economic development in the area.</p><p id="">The objectives of this study of soil degradation in the Western Sierra Madre, are to determine the respective roles of gully and sheet erosion. This research is based on field observations, field measurements of runoff and, soil losses at the plot, as well as the watershed scales as an analysis of an exhaustive census of the few gullies located in an experimental area.</p><p id="">Measured soil losses in the Western Sierra Madre are high although there are few gullies. Most of the sediment yield seems to originate in widespread degraded areas where stoniness is the main evidence of a previous stage of erosion. Previously overgrazing and deforestation were determined as the factors of the appearance of new soil surface characteristics which explain the high runoff and sediment productions. The soil compacted by cattle trampling reduces infiltration. The decrease of the vegetation cover triggers a rise in the splash effect and thus, a soil sealing.</p><p id="">These processes induce an increase in runoff and soil losses. The main erosion type has been described as sheet erosion: it is characterised by the removal of fine soil particles and the remains of gravels, pebbles and blocks, which constitute a pavement on the soil. Gullies generally appear on the bottom of wide valleys and depressions, where soils are thick. It is shown that sheet erosion is two orders of magnitude higher than gully erosion at the hillslope scale.</p><p id="">Due to the spatial distribution of land use and the geological context such as the heavily degraded areas close to the main rivers, the reduction of runoff and soil loss rates within the extension of a considered area, commonly observed in hydrology, only applies up to the elementary catchments scale (1 to 50&nbsp;km<sup>2</sup>). Above this area, runoff coefficient and soil loss rates increase.</p>
[29] de Vente J, Poesen J.

Predicting soil erosion and sediment yield at the basin scale: Scale issues and semi-quantitative models

. Earth-Science Reviews, 2005, 71(1): 95-125.

https://doi.org/10.1016/j.earscirev.2005.02.002      URL      [本文引用: 1]      摘要

Basin sediment yield is the product of all sediment producing processes and sediment transport within a basin. Consequently, the prediction of basin sediment yield should take into consideration all different erosion and sediment transport processes. However, traditional physics-based, conceptual, and empirical or regression models have not been able to describe all these processes due to insufficient systems knowledge and unfeasible data requirements. Therefore, the applicability of these models at the basin scale is troublesome. This paper first illustrates the relation between basin area, dominant erosion processes, and sediment yield by a combination of measured sediment yield at different spatial scales in Mediterranean environments. This clearly reveals that soil erosion rates measured at one scale are not representative for sediment yield at another scale level. Second, the most important semi-quantitative models developed for erosion and sediment yield assessments at the basin scale are reviewed. Most of these models use environmental factors to characterise a drainage basin in terms of sensitivity to erosion and sediment transport. Six of the nine models discussed (PSIAC, FSM, VSD, Gavrilovic, CSSM, WSM) include sheet-, rill-, gully, bank erosion, landslides, and connectivity, at least partly, in the assessment of basin sediment yield. The low data requirements and the fact that practically all significant erosion processes are considered makes them especially suited for estimating off-site effects of soil erosion. The other three models (EHU, CORINE, FKSM) focus mainly on sheet and rill erosion and provide quantitative descriptions of the sensitivity to erosion at basin or even regional scales. These models thus focus mainly on on-site problems of soil erosion. Most of the semi-quantitative models might benefit from a more quantitative description of factors used to characterise the basin. Though an equilibrium should be found between the extra effort and increase in model performance, the increased availability of spatially distributed topographic data as well as high-resolution satellite imagery will probably make this feasible in the near future. (c) 2005 Elsevier B.V. All rights reserved.
[30] Onori F, De Bonis P, Grauso S.

Soil erosion prediction at the basin scale using the revised universal soil loss equation (RUSLE) in a catchment of Sicily (southern Italy).

Environmental Geology, 2006, 50(8): 1129-1140.

https://doi.org/10.1007/s00254-006-0286-1      Magsci      [本文引用: 1]      摘要

<a name="Abs1"></a>Soil erosion by water is a serious problem in southern Italy, particularly in Sicily which is one of the Italian administrative regions prone to desertification. Soil erosion not only affects soil quality, in terms of agricultural productivity, but also reduces the availability of water in reservoirs. This study was conducted in the Comunelli catchment in south-central Sicily, to predict potential annual soil loss using the revised universal soil loss equation (RUSLE) and to test the reliability of this methodology to predict reservoirs siltation. The RUSLE factors were calculated for the catchment using survey data and rain gauge measurement data. The <i>R</i>-factor was calculated from daily, monthly and annual precipitation data. The <i>K</i>-factor was calculated from soil samples collected in May and November 2004. The LS topographic factor was calculated from a 20&nbsp;m digital elevation model. The <i>C</i>- and <i>P</i>-factors, in absence of detailed data, were set to 1. The results were compared with those obtained from another soil loss estimation method based on <sup>137</sup>Cs and with the soil loss estimated from the sediment volume stored in the Comunelli reservoir between 1968 and 2004.
[31] Ludwig J A, Bartley R, Hawdon A A, et al.

Patch configuration non-linearly affects sediment loss across scales in a grazed catchment in north-east Australia.

Ecosystems, 2007, 10(8): 839-845.

https://doi.org/10.1007/s10021-007-9061-8      URL      [本文引用: 1]      摘要

A principle of the cross-scale interaction (CSI) framework is that disturbance-induced landscape changes resulting in coarser-grained spatial structure may non-linearly amplify transfer processes across scales. We studied suspended sediment losses at two spatial scales (0.24 m2 plots and ca. 0.25 ha hillslopes of about 140 m in length) in a semiarid savanna landscape to determine whether the spatial structure of grassy and bare soil areas introduced a non-linear amplification of sediment loss. Sediment loss rates from 0.24 m2 bare plots averaged 1.527 t ha-1 y-1, which was 23 times the loss rate from nearby grassy plots (0.066 t ha-1 y-1). These rates were then extrapolated linearly to two hillslopes separated by only 200 m and having similar total grass cover, slope and soil type but differing in the spatial structure of bare soil patches. The coarse-grained hillslope had a large bare patch on its lower slope, whereas the fine-grained hillslope had no bare soil patches when quantified at a 4 m grid-cell resolution. Measured sediment loss from the fine-grained hillslope averaged 0.050 t ha-1 y-1, whereas the average sediment loss from the coarse-grained hillslope was 2.133 t ha-1 y-1. By linearly extrapolating from the plot scale, the expected sediment loss for the fine-grained hillslope was 0.066 t ha-1 y-1, which is similar to that observed. The expected sediment loss for the coarse-grained hillslope was 0.855 t ha-1 y-1, where linear extrapolation assumed a 46:54 ratio of bare to grassy plots and that the spatial arrangement of plots does not affect sediment loss processes. For the coarse-grained hillslope observed sediment loss is 2.5 times greater than that expected by linear extrapolation from the plot scale. This result indicates a cross-scale interaction related to spatial configuration of patches. We suggest that there were non-linearities in hillslope ecohydrological transfer processes (runoff, erosion) across scales due to a specific patch configuration that greatly amplified sediment loss because the pattern failed to slow runoff and retain sediment before it entered a creek. This example supports the CSI framework and indicates the importance of considering the effect of spatial structure when predicting system dynamics at different scales.
[32] Jencso K G, McGlynn B L, Gooseff M N, et al.

Hydrologic connectivity between landscapes and streams: Transferring reach-and plot-scale understanding to the catchment scale.

Water Resources Research, 2009, 45(2): 262-275.

https://doi.org/10.1029/2008WR007225      URL      [本文引用: 1]      摘要

The relationship between catchment structure and runoff characteristics is poorly understood. In steep headwater catchments with shallow soils the accumulation of hillslope area (upslope accumulated area (UAA)) is a hypothesized first-order control on the distribution of soil water and groundwater. Hillslope-riparian water table connectivity represents the linkage between the dominant catchment...
[33] Bracken L J, Wainwright J, Ali G A, et al.

Concepts of hydrological connectivity: Research approaches, pathways and future agendas

. Earth-Science Reviews, 2013, 119: 17-34.

https://doi.org/10.1016/j.earscirev.2013.02.001      URL      Magsci      [本文引用: 1]      摘要

For effective catchment management and intervention in hydrological systems a process-based understanding of hydrological connectivity is required so that: i) conceptual rather than solely empirical understanding drives how systems are interpreted; and ii) there is an understanding of how continuous flow fields develop under different sets of environmental conditions to enable managers to know when, where and how to intervene in catchment processes successfully. In order to direct future research into process-based hydrological connectivity this paper: i) evaluates the extent to which different concepts of hydrological connectivity have emerged from different approaches to measure and predict flow in different environments; ii) discusses the extent to which these different concepts are mutually compatible; and iii) assesses further research to contribute to a unified understanding of hydrological processes. Existing research is categorised into five different approaches to investigating hydrological connectivity: i) evaluating soil moisture patterns (soil moisture connectivity); ii) understanding runoff patterns and processes on hillslopes (flow-process connectivity); iii) investigating topographic controls (terrain-connectivity) including the impact of road networks on hydrological connectivity and catchment runoff; iv) developing models to explore and predict hydrological connectivity; and v) developing indices of hydrological connectivity. Analysis of published research suggests a relationship between research group, approach, geographic setting and the interpretation of hydrological connectivity. For further understanding of hydrological connectivity our knowledge needs to be developed using a range of techniques and approaches, there should be common understandings between researchers approaching the concept from different perspectives, and these meanings need to be communicated effectively with those responsible for land management. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.
[34] Fryirs K A, Brierley G J, Preston N J, et al.

Catchment-scale (dis)connectivity in sediment flux in the upper Hunter catchment, New South Wales, Australia.

Geomorphology, 2007, 84(s3-s4): 297-316.

https://doi.org/10.1016/j.geomorph.2006.01.044      URL      [本文引用: 3]      摘要

(Dis)connectivity within and between landscape compartments affects the extent and rate of transfer of energy and matter through catchments. Various landforms may impede sediment conveyance in a river system, whether laterally to the channel (termed buffers) or longitudinally along the channel itself (termed barriers). A generic approach to analysis of landscape (dis)connectivity using slope threshold analysis in GIS, tied to air photograph interpretation and field mapping of buffers and barriers, is tested in the upper Hunter catchment, Australia. Under simulated conditions, effective catchment area, which is a measure of the proportion of a catchment that has the potential to contribute sediment to the channel network, varies from 73% to just 3% of the total catchment area for differing subcatchments in the upper Hunter. This variability can be explained by the spatial distribution and assemblage of buffers and barriers in each subcatchment. Multiple forms of disconnectivity are evident in some subcatchments, such that when one buffer or barrier is breached, other features still impede sediment transfer within the system. The importance of the position of buffers and barriers within any given subcatchment is emphasised. Spatial variability in valley width exerts a critical control on catchment connectivity, with more efficient sediment conveyance in narrow valleys relative to wider valleys characterised by piedmonts, terraces, fans and extensive floodplains in which conveyance is impeded. This variability reflects the landscape history and geological setting of each subcatchment. The framework developed in this paper can be used to assess the impact of natural or human-induced buffers and barriers on catchment-scale sediment flux in any landscape setting, providing a physical template atop which other biogeochemical fluxes could be examined.
[35] 刘前进, 于兴修.

北方土石山区土壤侵蚀强度垂直景观格局: 以沂蒙山区为例

. 地理研究, 2010, 29(8): 1471-1483.

Magsci      [本文引用: 1]      摘要

<p>以具北方土石山区典型特征的沂蒙山区为例,在分析土壤侵蚀过程的基础上,选取具生态学意义的侵蚀强度景观格局指数,从垂直维度上分析侵蚀景观格局变化特征。结果表明:土壤侵蚀景观格局具有显著垂直分带性。50~200带为低侵蚀稳定区,人类活动影响大,缀块成片分布,连通性强,形状较规则;400~800带为高侵蚀稳定区,自然因素起主导作用,缀块密度大且分散,形状较复杂;200~400带为侵蚀景观急剧变化区,侵蚀程度随高程增加而增大,自然因素作用增强。微度与轻度侵蚀景观、强烈与极强烈侵蚀景观具相同垂直变化趋势,此两组侵蚀景观变化趋势的差异主要分布于低于300带和高于500带处;中度侵蚀景观变化趋势可视为前两组侵蚀景观变化趋势的过渡。</p>

[Liu Qianjin, Yu Xingxiu.

Vertical landscape pattern on soil erosion intensity in the rocky area of northern China: A case study in the Yimeng Mountainous Area, Shandong.

Geographical Research, 2010, 29(8): 1471-1483.]

Magsci      [本文引用: 1]      摘要

<p>以具北方土石山区典型特征的沂蒙山区为例,在分析土壤侵蚀过程的基础上,选取具生态学意义的侵蚀强度景观格局指数,从垂直维度上分析侵蚀景观格局变化特征。结果表明:土壤侵蚀景观格局具有显著垂直分带性。50~200带为低侵蚀稳定区,人类活动影响大,缀块成片分布,连通性强,形状较规则;400~800带为高侵蚀稳定区,自然因素起主导作用,缀块密度大且分散,形状较复杂;200~400带为侵蚀景观急剧变化区,侵蚀程度随高程增加而增大,自然因素作用增强。微度与轻度侵蚀景观、强烈与极强烈侵蚀景观具相同垂直变化趋势,此两组侵蚀景观变化趋势的差异主要分布于低于300带和高于500带处;中度侵蚀景观变化趋势可视为前两组侵蚀景观变化趋势的过渡。</p>
[36] Ouyang Wei, Skidmore A K, Hao Fanghua, et al.

Soil erosion dynamics response to landscape pattern.

Science of the Total Environment, 2010, 408(6): 1358-1366.

https://doi.org/10.1016/j.scitotenv.2009.10.062      URL      PMID: 19922979      [本文引用: 1]      摘要

Simulating soil erosion variation with a temporal land use database reveals long-term fluctuations in landscape patterns, as well as priority needs for soil erosion conservation. The application of a multi-year land use database in support of a Soil Water Assessment Tool (SWAT) led to an accurate assessment, from 1977 to 2006, of erosion in the upper watershed of the Yellow River. At same time, the impacts of land use and landscape service features on soil erosion load were assessed. A series of supervised land use classifications of Landsat images characterized variations in land use and landscape patterns over three decades. The SWAT database was constructed with soil properties, climate and elevation data. Using water flow and sand density data as parameters, regional soil erosion load was simulated. A numerical statistical model was used to relate soil erosion to land use and landscape. The results indicated that decadal decrease of grassland areas did not pose a significant threat to soil erosion, while the continual increase of bare land, water area and farmland increased soil erosion. Regional landscape variation also had a strong relationship with erosion. Patch level landscape analyses demonstrated that larger water area led to more soil erosion. The patch correlation indicated that contagious grassland patches reduced soil erosion yield. The increased grassland patches led to more patch edges, in turn increasing the sediment transportation from the patch edges. The findings increase understanding of the temporal variation in soil erosion processes, which is the basis for preventing local pollution.
[37] 刘宇, 吕一河, 傅伯杰.

景观格局—土壤侵蚀研究中景观指数的意义解释及局限性

. 生态学报, 2011, 30(1): 267-275.

URL      [本文引用: 1]      摘要

景观格局分析是景观生态学研究的重要组成部分.景观指数是景观格 局分析的有力工具.近年来,景观格局与土壤侵蚀关系的相关研究增多,常规景观格局指数得到应用.但针对土壤侵蚀过程的景观指数意义解释不足,景观指数在刻 画景观格局-土壤侵蚀过程关系存在局限.选择了连接性、多样性、边界/斑块密度、形状4个方面的12个常用景观指数,对这些指数在景观格局-土壤侵蚀过程 关系研究中的意义进行阐述,对指数应用的局限性及其原因进行了分析.景观数据属性、景观指数本身性质和土壤侵蚀过程的复杂性使得常规景观格局指数在景观格 局-土壤侵蚀关系研究中存在不足.这3方面的影响使得常规景观格局指数与土壤侵蚀表征变量之间不存在确定的关系,从而难以通过景观指数来表征景观土壤侵蚀 特征.缺乏土壤侵蚀过程基础是常规景观指数在土壤侵蚀研究应用中存在局限的主要原因.因此,构建基于土壤侵蚀过程的景观指数是景观格局-土壤侵蚀关系研究 的需要和新的发展方向.

[Liu Yu,Lv Yihe,Fu Bojie.

Implication and limitation of landscape metrics in delineating relationship between landscape pattern and soil erosion.

Acta Ecologica Sinica, 2011, 30(1): 267-275.]

URL      [本文引用: 1]      摘要

景观格局分析是景观生态学研究的重要组成部分.景观指数是景观格 局分析的有力工具.近年来,景观格局与土壤侵蚀关系的相关研究增多,常规景观格局指数得到应用.但针对土壤侵蚀过程的景观指数意义解释不足,景观指数在刻 画景观格局-土壤侵蚀过程关系存在局限.选择了连接性、多样性、边界/斑块密度、形状4个方面的12个常用景观指数,对这些指数在景观格局-土壤侵蚀过程 关系研究中的意义进行阐述,对指数应用的局限性及其原因进行了分析.景观数据属性、景观指数本身性质和土壤侵蚀过程的复杂性使得常规景观格局指数在景观格 局-土壤侵蚀关系研究中存在不足.这3方面的影响使得常规景观格局指数与土壤侵蚀表征变量之间不存在确定的关系,从而难以通过景观指数来表征景观土壤侵蚀 特征.缺乏土壤侵蚀过程基础是常规景观指数在土壤侵蚀研究应用中存在局限的主要原因.因此,构建基于土壤侵蚀过程的景观指数是景观格局-土壤侵蚀关系研究 的需要和新的发展方向.
[38] Liu Yu, Fu Bojie, Lv Yihe, et al.

Linking vegetation cover patterns to hydrological responses using two process-based pattern indices at the plot scale.

Science China: Earth Sciences, 2013, 56(11): 1888-1898.

https://doi.org/10.1007/s11430-013-4626-1      URL      [本文引用: 1]      摘要

Vegetation cover pattern is one of the factors controlling hydrological processes.Spatially distributed models are the primary tools previously applied to document the effect of vegetation cover patterns on runoff and soil erosion.Models provide precise estimations of runoff and sediment yields for a given vegetation cover pattern.However,difficulties in parameterization and the problematic explanation of the causes of runoff and sedimentation rates variation weaken prediction capability of these models.Landscape pattern analysis employing pattern indices based on runoff and soil erosion mechanism provides new tools for finding a solution.In this study,the vegetation cover pattern was linked with runoff and soil erosion by two previously developed pattern indices,which were modified in this study,the Directional Leakiness Index(DLI)and Flowlength.Although they use different formats,both indices involve connectivity of sources areas(interpatch bare areas).The indices were revised by bringing in the functional heterogeneity of the plant cover types and the landscape position.Using both artificial and field verified vegetation cover maps,observed runoff and sediment production on experiment plots,we tested the indices' efficiency and compared the indices with their antecedents.The results illustrate that the modified indices are more effective in indicating runoff at the plot/hillslope scale than their antecedents.However,sediment export levels are not provided by the modified indices.This can be attributed to multi-factor interaction on the hydrological process,the feedback mechanism between the hydrological function of cover patterns and threshold phenomena in hydrological processes.
[39] Ludwig J A, Eager R W, Liedloff A C, et al.

A new landscape leakiness index based on remotely sensed ground-cover data.

Ecological Indicators, 2006, 6(2): 327-336.

https://doi.org/10.1016/j.ecolind.2005.03.010      Magsci      [本文引用: 1]      摘要

<h2 class="secHeading" id="section_abstract">Abstract</h2><p id="">A new continuous, cover-based, directional leakiness index, CDLI, is described that has a number of advantages over a binary-based, directional leakiness index, DLI, previously described in this journal. These indices are monitoring tools aimed to indicate the potential for gently sloping, arid and semi-arid landscapes to retain, not leak, resources, such as soils. To compute DLI, pixels in remotely sensed images had to be classified as being either vegetation patches or open interpatches. This simple binary classification procedure is unrealistic for images with relatively large pixels (e.g., 30-m pixel Landsat), where a single pixel is likely to be a mix of denser vegetation patches and more open interspaces. This mix of patch and interpatch within a pixel can be represented as proportional ground-cover. Because CDLI is based on these ground-cover data, which can vary continuously between 0&ndash;100%, it is an index of landscape leakiness that is applicable to larger scale, remotely sensed imagery. Using Landsat imagery, we illustrate how CDLI is useful for comparing the potential leakiness of four Australian arid and semi-arid sites differing in rangeland condition. When imagery is available for specific landscape sites through time, CDLI can be used to monitor changes in the potential leakiness of these sites. However, both CDLI and DLI assume that resource flows are one-directional, which restricts their application to images acquired from relatively gentle, uniform landscapes. A leakiness index applicable to landscapes with hilly terrain is being developed.</p>
[40] Jain V, Tandon S K.

Conceptual assessment of (dis)connectivity and its application to the Ganga River dispersal system.

Geomorphology, 2010, 118(s3-s4): 349-358.

https://doi.org/10.1016/j.geomorph.2010.02.002      URL      [本文引用: 1]      摘要

Connectivity in river dispersal systems is an important evolving concept and helps in understanding their dynamics. In this study, the types of connectivity have been defined on the basis of two components, namely &ldquo;physical contact&rdquo; and &ldquo;transfer of material.&rdquo; Based on this, four types of connectivity are recognized. These are (a) active connected system, (b) inactive connected system, (c) partially active connected system, and (d) disconnected system. Connectivity indices have been proposed based on the process understanding of different types of connectivity. This conceptual understanding of connectivity has been applied to the Ganga dispersal system, a large river system. Results of the connectivity analysis on the Ganga dispersal system reveal that different sets of data such as sediment budgets, geochemical isotopic data and radiogenic (U&ndash;U&ndash;Th) data are noncoherent. Therefore, developing rigorous and well constrained quantitative multidisciplinary data sets is needed to have a better understanding of connectivity at multiple spatio-temporal scales in large river dispersal systems; this would ultimately help model the dynamics of such systems.
[41] Lal R.

Soil erosion and the global carbon budget.

Environment International, 2003, 29(4): 437-450.

https://doi.org/10.1016/S0160-4120(02)00192-7      URL      PMID: 12705941      [本文引用: 1]      摘要

Soil erosion is the most widespread form of soil degradation. Land area globally affected by erosion is 1094 million ha (Mha) by water erosion, of which 751 Mha is severely affected, and 549 Mha by wind erosion, of which 296 Mha is severely affected. Whereas the effects of erosion on productivity and non-point source pollution are widely recognized, those on the C dynamics and attendant emission of greenhouse gases (GHGs) are not. Despite its global significance, erosion-induced carbon (C) emission into the atmosphere remains misunderstood and an unquantified component of the global carbon budget. Soil erosion is a four-stage process involving detachment, breakdown, transport/redistribution and deposition of sediments. The soil organic carbon (SOC) pool is influenced during all four stages. Being a selective process, erosion preferentially removes the light organic fraction of a low density of <1.8 Mg/m(3). A combination of mineralization and C export by erosion causes a severe depletion of the SOC pool on eroded compared with uneroded or slightly eroded soils. In addition, the SOC redistributed over the landscape or deposited in depressional sites may be prone to mineralization because of breakdown of aggregates leading to exposure of hitherto encapsulated C to microbial processes among other reasons. Depending on the delivery ratio or the fraction of the sediment delivered to the river system, gross erosion by water may be 75 billion Mg, of which 15-20 billion Mg are transported by the rivers into the aquatic ecosystems and eventually into the ocean. The amount of total C displaced by erosion on the earth, assuming a delivery ratio of 10% and SOC content of 2-3%, may be 4.0-6.0 Pg/year. With 20% emission due to mineralization of the displaced C, erosion-induced emission may be 0.8-1.2 Pg C/year on the earth. Thus, soil erosion has a strong impact on the global C cycle and this component must be considered while assessing the global C budget. Adoption of conservation-effective measures may reduce the risks of C emission and sequester C in soil and biota.
[42] Lobkovsky A E, Jensen B, Kudrolli A, et al.

Threshold phenomena in erosion driven by subsurface flow.

Journal of Geophysical Research, 2004, 109(F4): 357-370.

https://doi.org/10.1029/2004JF000172      URL      [本文引用: 1]      摘要

Abstract: We study channelization and slope destabilization driven by subsurface (groundwater) flow in a laboratory experiment. The pressure of the water entering the sandpile from below as well as the slope of the sandpile are varied. We present quantitative understanding of the three modes of sediment mobilization in this experiment: surface erosion, fluidization, and slumping. The onset of erosion is controlled not only by shear stresses caused by surfical flows, but also hydrodynamic stresses deriving from subsurface flows. These additional forces require modification of the critical Shields criterion. Whereas surface flows alone can mobilize surface grains only when the water flux exceeds a threshold, subsurface flows cause this threshold to vanish at slopes steeper than a critical angle substantially smaller than the maximum angle of stability. Slopes above this critical angle are unstable to channelization by any amount of fluid reaching the surface.
[43] Helming K, Auzet A V, Favis-Mortlock D.

Soil erosion patterns: evolution, spatio-temporal dynamics and connectivity.

Earth Surface Processes and Landforms, 2005, 30(2): 131-132.

[本文引用: 1]     

[44] Van Rompaey A J J, Verstraeten G, Van Oost K, et al.

Modelling mean annual sediment yield using a distributed approach.

Earth Surface Processes and Landforms, 2001, 26(11): 1221-1236.

https://doi.org/10.1002/esp.275      URL      [本文引用: 1]      摘要

Abstract In this paper a spatially distributed model for the calculation of sediment delivery to river channels is presented (SEDEM: SEdiment DElivery Model). The model consists of two components: (1) the calculation of a spatial pattern of mean annual soil erosion rates in the catchment using a RUSLE (Revised Soil Erosion Equation) approach; and (2) the routing of the eroded sediment to the river channel network taking into account the transport capacity of each spatial unit. If the amount of routed sediment exceeds the local transport capacity, sediment deposition occurs. An existing dataset on sediment yield for 24 catchments in central Belgium was used to calibrate the transport capacity parameters of the model. A validation of the model results shows that the sediment yield for small and medium sized catchments (10鈥5000 ha) can be predicted with an average accuracy of 41 per cent. The predicted sediment yield values with SEDEM are significantly more accurate than the predictions using a lumped regression model. Moreover a spatially distributed approach allows simulation of the effect of different land use scenarios and soil conservation techniques. Copyright © 2001 John Wiley & Sons, Ltd.

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