Issues related to the detection of boundaries

Ecotones are inherent features of landscapes, transitional zones, and play more than one functional role in ecosystem dynamics. The delineation of ecotones and environmental boundaries is therefore an important step in land-use management planning. The delineation of ecotones depends on the phenomenon of interest and the statistical methods used as well as the associated spatial and temporal resolution of the data available. In the context of delineating wetland and riparian ecosystems, various data types (field data, remotely sensed data) can be used to delineate ecotones. Methodological issues related to their detection need to be addressed, however, so that their management and monitoring can yield useful information about their dynamics and functional roles in ecosystems. The aim of this paper is to review boundary detection methods. Because the most appropriate methods to detect and characterize boundaries depend of the spatial resolution and the measurement type of the data, a wide range of approaches are presented: GIS, remote sensing and statistical ones.     

The influences of land-use changes on hydrology and riparian environment in a northern Japanese landscape

Temporal changes in a hydrological system and riparian ecosystem were examined with reference to land-use conversion in order to clarify the linkages between these two systems. First, the hydrological system of the Toikanbetsu River basin was divided into three components that measure water retention, inundation and conveyance. Variation in the hydrological system was expressed as a basis of delineating the three components and estimating their functions. The rainfall-runoff system was also examined using a model which can predict responses of surface-, subsurface- and base flows on rainfall intensity. Second, areas and fragmentation of the riparian forests, maximum stream temperature in summer and amount of coarse woody debris (CWD) were selected as parameters indicating the condition of the riparian ecosystem. Temporal changes in stream temperature and amount of CWD were estimated using multiple regression analysis and analysis of variance, respectively. The results indicated that the hydrological system has been altered since the 1970s, increasing flood peaks by 1.5–2.5 times and shortening peak appearance by 7 hours. Riparian forests have been disappearing since the 1960s due to extensive development of agricultural lands and river channelization. The summer maximum stream temperature increased from 22 °C in 1947 to 28 °C at present. The amount of CWD should substantially decrease with river channelization and associated forest cutting. Fish favoring cool water, such as masu salmon, could survive in 1947 although they are forced to migrate to cooler forested upstream tributaries now. The ecological systems were closely related to and distinctly altered by land-use. Finally, we propose a new perspective for understanding the two interrelated systems. Riparian ecosystems can be restored by restoring water retention and inundation functions, which also reduce the flood hazard generated by elevated flood peaks.     

塔里木河干流荒漠河岸林植物群落多元分析及其土壤环境解释

应用对应分析(CA)与典范对应分析(CCA)排序方法,对塔里木河干流荒漠河岸林植物群落进行了多元统计分析,并给出各群落类型的土壤环境定量解释。结果表明:塔里木河干流荒漠河岸林地区多数物种出现频次不高,物种丰富度低;CCA排序结果显示出土壤含水率、总盐、HCO3-是决定植物群落分异的主导土壤环境因子,得到CCA第一轴、第二轴与环境因子之间的多元回归方程,并将样地划分为4种群落类型,定量地揭示研究区植物群落类型的分布与土壤环境之间的关系。     

Plant Community Influences on Intermittent Stream Stability in the Great Plains

The composition of the greenline plant community is linked to the stability of riparian ecosystems. Cool season exotic grasses are invading native plant communities across the northern Great Plains, potentially compromising streambank stability and increasing the risk of erosion within riparian ecosystems. To determine how the species composition of the greenline community impacts stream type and the risk of streambank erosion, thirty five reaches across five watersheds were sampled to determine the dominant greenline vegetation. At each reach, a cross-section was sampled to determine stream type, greenline vegetation, and risk of streambank erosion. Channel types were delineated using Rosgen’s classification of natural rivers. Canopy cover and composition was assessed using the line point intercept method along a 30.5 m transect in the greenline community. Plants recorded were grouped by their wetland indicator status for the central Great Plains. The Bank Erosion Hazard Index (BEHI) was used to assess the streams risk of erosion by calculating the difference between the bank height and bank full height, average plant rooting depth and density, bank angle degree, and the dominant texture of the bank material. Bank height ratio (BHR) was assessed as a measure of streambank stability and floodplain connectivity. A Nonmetric Multidimensional Scaling ordination was performed to analyze plant community influences. Analysis of the data determined that the most stable stream types (E and C channels), lower BEHI scores, and stable bank height ratios were associated with high amounts of litter and facultative wet species. In comparison, unstable F channels were associated with early successional species and bare ground. Sites with the higher BEHI scores were associated with greenlines comprised of upland and facultative upland and saline tolerant species. Late successional facultative wetland species were found to provide the most protection to intermittent streambanks.     

Variation of Soil and Water Volumes in Riparian Jungle Soils of Brazil

The objective of this work is to study the relation between humidity, density, porosity and shrinkage of the floodplain soil and riparian vegetation and their ability to store water. For this purpose, two locations for every type of soils were evaluated. Both were placed at the Agronomy University （Faculdade de Cidncias Agron6micas） in SAo Manuel, State of SAo Paulo, Brazil. The floodplain soil was vegetated with Southern Cattail （Typha domingensis）. In both places, soil samples were collected from several depths： 0, 30, 60 and 100 cm. Results show that lower soil density values （0.15 g/cm3） with organic texture and high porosities values （up to 86.2%） were found in samples with the highest organic material content in the floodplain soil. For this field experiment, flood plains soils （characterised as basin gley soils） presented high volumetric instability with a retratibility of 67.49% and higher water storage capacities compared to riparian stands soils （characterised as fluvic neosoils）.     

滨岸缓冲带截留污染物机理和效果的研究进展

滨岸缓冲带是指与河流（包括湿地和湖泊）相邻的对污染物、沉积物和洪水具有一定缓冲功能的水陆生态系统交错带,是一种重要的控制面源污染和保护水体环境的方法。滨岸缓冲带的研究存在较多的方向和不同的立足点。为了更好地总结和梳理已有研究成果,该文通过大量的文献调研,构建了滨岸缓冲带的研究框架,从其作用机理、结构、功能与效果等方面对国内外的有关研究和实践进行了系统分析和总结,并提出了未来的研究展望。     

城市河岸带综合评价——以福州市南台岛为例

应用模糊评价模型,从生态安全性与景观适宜性两方面对城市河岸带进行综合评价研究.其中生态安全性评价是对近岸水域、岸坡带、近岸陆域3个横向地带选取指标,景观适宜性评价则是从视觉环境、景观构成等方面选取指标,从而构建了城市河岸带综合评价指标体系.以福州南台岛为例,结合南台岛河岸带的特点将其分为6个景观河段分别进行综合评价,结...     

三峡水库消落带淹水—落干交替下紫色土力学特性变化模拟

三峡水库消落带在高压淹水浸泡和干湿交替作用下,土壤力学特性必然发生变化,影响土体抗侵蚀性能,破坏库岸稳定性。目前对消落带土壤力学特性变化及其对淹水—落干驱动的响应尚不明确。以三峡水库消落带广泛分布的紫色土为研究对象,模拟水压作用和淹没—出露交替过程,研究紫色土应力—应变和抗剪强度参数对高压淹水和干湿交替作用的响应。结果表明:水柱压力、干湿交替次数和干湿交替幅度都能显著驱动紫色土力学特性发生变化。与对照组相比,随着水柱压力增加,紫色土刚度逐渐增强,黏聚力降低幅度变小,内摩擦角增大。随干湿交替次数增加,紫色土刚度逐渐减小;内摩擦角有所增大,黏聚力的变化趋势与之相反,且随干湿交替次数的增加而显著降低。随干湿交替幅度增加,抗剪强度迅速降低(相同围压下),黏聚力增大,内摩擦角降低;与对照组相比,干湿交替幅度越小,土壤的内摩擦角增大越多,黏聚力降低越多。     

河岸带不同植被下土壤酶特征及其去污效果

通过测定河岸带常见植被类型下的土壤酶活性,比较其去污效果,分析土壤酶活性与TN、TP、NH4＋-N、COD等农业面源污染物去除率的相关性。结果表明,不同植被类型表层土壤酶活性存在显著差异（P〈0.05）,灌草、草本酶活性较大,乔灌草次之,乔草最小,而不同植被河岸带对农业面源污染物的去除率也表现出基本相同的规律,因此对农业面源污染去除效果最好的河岸带植被类型配置应为灌草或草本（芦苇）;不同植被深层土壤酶活性基本不存在显著差异。由相关性分析可知,TN、NH4＋-N去除率与表层土壤脲酶活性呈显著相关关系,而COD去除率与土壤脲酶的相关性不显著;TP、COD去除率与土壤磷酸酶活性的相关性显著。研究结果为利用土壤酶活性强度作为评价河岸带净化效果的指标提供了理论依据。     

河岸带植被对非点源氮、磷以及悬浮颗粒物的截留效应

选取草地河岸带和人工林地河岸带,开展了人工模拟农田施肥和径流污染物截留效果的现场试验。分别采集地表径流和渗透水水样,测定分析了总磷(TP)、总氮(TN)、氨氮(NH4—N)以及固体颗粒物的浓度。结果表明,草地河岸带对地表径流TP的截留效果显著优于林地河岸带,草地和林地河岸带对氮元素的截留效果趋于一致;河岸带对地表径流和渗透水中TN,TP和NH4—N的截留率是相似的;草地河岸带对固体颗粒物的截留效果优于林地河岸带;河岸带越宽,其截污功能越强;人为干扰造成了人工林地河岸带截污能力的减弱。并提出了河岸带管理的相关建议。