Boreal Riparian Vegetation Under Climate Change

Riparian zones in boreal areas such as humid landscapes on minerogenic soils are characterized by diverse, productive, and dynamic vegetation which will rapidly react to climate change. Climate-change models predict that in most parts of the boreal region these zones will be affected by various combinations of increased temperature, less seasonal variation in runoff, increased average discharge, changes in groundwater supply, and a more dynamic ice regime. Increasing temperatures will favor invasion of exotic species whereas species losses are likely to be minor. The hydrologic changes will cause a narrowing of the riparian zone and, therefore, locally reduce species richness whereas effects on primary production are more difficult to predict. More shifts between freezing and thawing during winter will lead to increased dynamics of ice formation and ice disturbance, potentially fostering a more dynamic and species-rich riparian vegetation. Restoration measures that increase water retention and shade, and that reduce habitats for exotic plant species adjacent to rivers can be applied especially in streams and rivers that have been channelized or deprived of their riparian forest to reduce the effects of climate change on riparian ecosystems.     

漓江滨岸草带对径流泥沙的拦截效果

位于污染源和受纳水体之间的滨岸带对径流泥沙的过滤作用已经得到广泛认可,滨岸植被的存在能降低径流流速,增加土壤入渗,延缓产流时间,促使径流中的悬浮物质得到沉积。而关于漓江滨岸草带过滤作用的相关定量研究和应用尚未见报道。为探索影响草带过滤效果的影响因素,在广西漓江滨岸带内按不同植被条件、不同带宽布设6个试验小区,通过小区放水试验测定滨岸草带对径流泥沙的拦截效果。结果表明:草带能有效拦截径流悬浮物,对径流、泥沙的拦截率分别达到66%和68%,当草带宽度增加到10m时拦截率均达90%。带宽是影响径流泥沙拦截的主导因素。植被条件是影响拦截效果的又一重要因素,而初始含水量和入流泥沙浓度对拦截效果的影响较小。同一草带对泥沙的拦截效果优于径流的拦截效果,且二者之间存在密切的线性关系。     

Microbial ecology of the watery ecosystems of Evros river in North Eastern Greece and its influence upon the cultivated soil ecosystem

The aim of the present study was to evaluate the microbial ecosystem of cultivated soils along the Evros river in NE Greece. Evros river together with its derivative rivers constitute the capital source of life and sustainable development of the area. Along this riverside watery ecosystem systematic agro-cultures were developed such as wheat, corn and vegetable cultures. The evaluation of the ecosystem microbial charge was conducted in both axes which are the watery ecosystem and the riverside cultivated soil area. Considerable discrimination of water quality was observed when considering chemical and microbiological parameters of the Evros river ecosystem. Ardas river possesses a better water quality than Evros and Erythropotamos, which is mainly due to the higher quantities that these two rivers accumulate from industrial, farming and urban residues leading to higher degree of pollution.An increased microbial pollution was recorded in two of the three rivers monitored and a direct relation in microbial and chemical charging between water and cultivated-soil ecosystems was observed. The protection of these ecosystems with appropriate cultivated practices and control of human and animal activities will define the homeostasis of the environmental area.     

Plant invasions in the rivers of the Iberian Peninsula,south-western Europe: A review

Aquatic and riparian ecosystems are known to be highly vulnerable to invasive alien species (IAS), especially when subjected to human-induced disturbances. In the last three decades, we have witnessed a growing increase in plant invasions in Portugal and Spain (Iberian Peninsula, south-western Europe), with very detrimental economic, social and ecological effects. Some of these species, such as the giant reed (Arundo donax L.) and the water hyacinth (Eichhornia crassipes (Mart.) Solms-Laub.), number among the world's worst weeds. We present an appraisal of this invasive alien river flora and the most problematic aquatic weeds. We review various aspects of invasion ecology, including spatial and temporal patterns of invasion, species invasiveness, species traits of invasive weeds, and relationships between human disturbance in rivers and surrounding areas and invasibility, and contextualize them in overall state-of-the-art terms. We also acknowledge the use of IAS as bioindicators of the ecological quality of rivers, wetlands and riparian zones. Remote-sensing tools and Geographic Information Systems for detecting and monitoring IAS in Iberian rivers are presented.     

洱海入湖河流弥苴河下游氮磷季节性变化特征及主要影响因素

入湖河流携带污染物对洱海水环境的影响日益明显,对洱海入湖水量最大的河流——弥苴河下游水体氮磷进行了连续采样分析,以期为河口湿地建设和水质改善提供基础数据.结果表明:1)弥苴河水质介于地表水Ⅲ-Ⅴ类之间,主要污染物为氮和磷,其中总氮平均浓度为1.17 mg/L,最高浓度达到2.00 mg/L;总磷平均浓度为0.06 mg/L;2)弥苴河下游总氮、总磷浓度丰水期高于枯水期,并呈现出季节性变化规律;3)弥苴河下游水体总氮、总磷年均浓度远高于洱海水体总氮、总磷年均浓度,其中总氮高出2.10倍,总磷高出2.90倍;4)弥苴河下游河段非点源污染占据主导地位.     

流域尺度上河流水质与土地利用的关系

以苏子河流域内54个水质采样点为基点,生成6种尺度的河岸带缓冲区,并借助FRAGSTATS软件计算景观水平和类型水平上的8种景观指数.分别从景观空间格局与景观类型组成两方面,对景观指数与水质进行相关分析.结果表明:区域景观格局在不同缓冲区内对流域水质具有不同的效应.当缓冲区距离≤300 m时,旱地、建筑用地、水田为主要的景观类型组成,其面积比例、斑块数量、斑块密度、最大斑块指数、最大形状指数、景观斑块聚集度指数均较高,农田的连通性较高,对水质的影响较大.在距离河流较远的区域(缓冲区距离＞300 m),林地面积比例较高,林地聚集连通程度较好,对水质改善具有一定作用,但不明显.该流域耕地、建设用地等对水质有着关键的影响作用.     

Impact of riparian buffer zones on water quality and associated management considerations

Recent attention has focused on riparian forest buffer systems for filtering sediment, nutrients, and pesticides entering from upland agricultural fields. This paper summarizes the results of a field monitoring study done in Tokachikawa watershed in Hokkaido, Japan, Cisadane, Cianten and Citamyang sub-watersheds in Indonesia and Cauvery watershed, India to quantify the impact of riparian buffer zones on changes in stream water quality. A watershed approach was used to compare land use indicators – uplands, forests, riparian forest, livestock areas – to a wide range of surface water physical and chemical properties. Stream water physical property values increased from upstream to the confluence point, influenced by the upland and livestock land use activities. The greatest reduction in impairment of water quality was observed in buffer zones located along higher order streams where the gradient is very low, leading to slow groundwater movement. The lower stream water temperature in riparian buffer zones suggests that the shading effect is most pronounced in this area of the watershed. The results demonstrate the positive impact of forest buffer zones in reducing the influence of agricultural nutrients and chemicals on surface stream waters. Design and management considerations for establishing riparian zone land use are discussed.     

Seasonal and spatial distribution of dissolved and particulate organic carbon and bacteria in the bank of an impounding reservoir on the Enns River, Austria

1. Interstitial bacterial abundance, production and ectoenzyme activity were investigated over an annual cycle in an Austrian river when infiltration of oligotrophic river water into a river-bank was artificially enhanced. These microbial parameters were related to porewater chemistry and the concentration of particulate (POC) and dissolved organic carbon (DOC).
2. Porewater chemistry reflected the hydrodynamic mixing of infiltrating river water with riparian groundwater. Seasonal fluctuations in the microbial parameters resulted mainly from changes in temperature and organic matter supply. Seasonal change in porewater chemistry in the river-bank was detectable laterally only within the first metre of the sediment and decreased rapidly with increasing distance from the sediment–water interface.
3. The DOC concentration decreased only slightly during lateral transport through the aquifer, while total organic carbon (TOC) concentration as well as abundance and activity of interstitial bacteria were reduced by up to one order of magnitude within the top metre of the sediment. Retention of incoming particulate matter structured the lateral distribution pattern of TOC concentration. The POC and not the DOC pool was the main source of carbon for interstitial bacteria and, therefore, the quality of POC determines the distribution of microbial metabolism within the riparian zone.     

河岸无脊椎动物多样性维持机制研究进展

河岸是河流与陆地之间重要的生态界面,生物多样性丰富,但受到人为活动的严重威胁。无脊椎动物在河岸生物多样性中占有重要地位,发挥着非常重要的生态功能,也是水生生态系统和陆地生态系统之间物质和能量联系的重要纽带。尽管已有很多学者对河岸无脊椎动物群落进行了研究,但缺乏对河岸无脊椎动物多样性维持机制的总结。本文结合洪水和干旱、营养物质、微生境多样性、河岸植被、微气候梯度、食物资源以及河流空间梯度等影响因素,初步讨论和归纳了河岸无脊椎动物多样性的维持机制。周期性洪水和干旱引发了无脊椎动物的繁殖和迁移等行为,增加了河岸无脊椎动物群落周转率,为无脊椎动物创造了理想的条件。充足的营养物质使河岸具有较高的初级生产力,支撑了较高的无脊椎动物多样性。较高的微生境多样性为无脊椎动物提供了多样的生态位空间,孕育了特殊的河岸无脊椎动物种类。复杂的河岸植物群落不但是河岸无脊椎动物的食物来源之一,也为河岸无脊椎动物提供了多样的生态位空间和重要的避难场所。微气候环境的空间分异提供了复杂多样的生境条件,为水生无脊椎动物和陆生无脊椎动物种类在河岸共存创造了条件。跨越界面的资源补给增加了河岸无脊椎动物的食物可利用率,为河岸无脊椎动物提供了特殊的食物来源。这些因素在空间上呈现出明显的纵向梯度和侧向梯度,从更大尺度上为河岸无脊椎动物的多样化提供了条件。因此,探讨河岸无脊椎动物多样性的维持机制对于河岸生物多样性保护以及河流生态系统综合管理具有重要的指导意义。     

Variable flushing mechanisms and landscape structure control stream DOC export during snowmelt in a set of nested catchments

Stream DOC dynamics during snowmelt have been the focus of much research, and numerous DOC mobilization and delivery mechanisms from riparian and upland areas have been proposed. However, landscape structure controls on DOC export from riparian and upland landscape elements remains poorly understood. We investigated stream and groundwater DOC dynamics across three transects and seven adjacent but diverse catchments with a range of landscape characteristics during snowmelt (April 15–July 15) in the northern Rocky Mountains, Montana. We observed a range of DOC export dynamics across riparian and upland landscape settings and varying degrees of hydrologic connectivity between the stream, riparian, and upland zones. DOC export from riparian zones required a hydrologic connection across the riparian–stream interface, and occurred at landscape positions with a wide range of upslope accumulated area (UAA) and wetness status. In contrast, mobilization of DOC from the uplands appeared restricted to areas with a hydrologic connection across the entire upland–riparian–stream continuum, which generally occurred only at areas with high UAA, and/or at times of high wetness. Further, the relative extent of DOC-rich riparian and wetland zones strongly influenced catchment DOC export. Cumulative stream DOC export was highest from catchments with a large proportion of riparian to upland area, and ranged from 6.3 to 12.4 kg ha^?1 across the study period. This research suggests that the spatial/temporal intersection of hydrologic connectivity and DOC source areas drives stream DOC export.     

Riparian zones as havens for exotic plant species in the central grasslands

In the Central Grasslands of the United States, we hypothesized that riparian zones high in soil fertility would contain more exotic plant species than upland areas of low soil fertility. Our alternate hypothesis was that riparian zones high in native plant species richness and cover would monopolize available resources and resist invasion by exotic species. We gathered nested-scale vegetation data from 40 1 m²subplots (nested in four 1000 m² plots) in both riparian and upland sites at four study areas in Colorado, Wyoming, and South Dakota (a total of 320 1 m² subplots and 32 1000 m² plots). At the 1 m² scale, mean foliar cover of native species was significantly greater (P<0.001) in riparian zones (36.3% ± 1.7%) compared to upland sites (28.7% ± 1.5%), but at this small scale there were no consistent patterns of native and exotic species richness among the four management areas. Mean exotic species cover was slightly higher in upland sites compared to riparian sites (9.0% ± 3.8% versus 8.2% ± 3.0% cover). However, mean exotic species richness and cover were greater in the riparian zones than upland sites in three of four management areas. At the 1000 m² scale, mean exotic species richness was also significantly greater (P<0.05) in riparian zones (7.8 ± 1.0 species) compared to upland sites (4.8 ± 1.0 species) despite the heavy invasion of one upland site. For all 32 plots combined, 21% of the variance in exotic species richness was explained by positive relationships with soil % silt (t =1.7, P=0.09) and total foliar cover (t = 2.4, P=0.02). Likewise, 26% of the variance in exotic species cover (log₁₀ cover) was explained by positive relationships with soil % silt (t =2.3, P=0.03) and total plant species richness (t = 2.5, P=0.02). At landscape scales (four 1000 m² plots per type combined), total foliar cover was significantly and positively correlated with exotic species richness (r=0.73, P<0.05) and cover (r=0.74, P<0.05). Exotic species cover (log₁₀ cover) was positively correlated with log₁₀% N in the soil (r=0.61, P=0.11) at landscape scales. On average, we found that 85% (±5%) of the total number of exotic species in the sampling plots of a given management area could be found in riparian zones, while only 50% (±8%) were found in upland plots. We conclude that: (1) species-rich and productive riparian zones are particularly invasible in grassland ecosystems; and (2) riparian zones may act as havens, corridors, and sources of exotic plant invasions for upland sites and pose a significant challenge to land managers and conservation biologists.     

不同时空尺度下土地利用对洱海入湖河流水质的影响

土地利用与入湖河流水质的关系存在时空差异。以洱海西部入湖河流及其小流域为研究对象,综合空间分析和数理统计手段,探讨两者随空间尺度和时间变化的关系,结果表明:选取的小流域、河岸带30m缓冲区、河岸带60m缓冲区和河岸带90m缓冲区4种尺度下,对入湖河流水质影响显著的土地利用类型为建设用地和植被(包括林地和牧草地),影响最大的空间尺度为小流域尺度,河岸带30m缓冲区次之;小流域尺度下,建设用地面积百分比与入湖河流COD和TP浓度呈正相关,植被面积百分比与NH_4~+-N浓度呈负相关,响应土地利用的主要水质指标为TN和TP,回归调整系数分别为0.624和0.579;季节性关联分析表明建设用地与COD、NH_4~+-N、TP的回归关系在雨季强于旱季,植被与COD、TP的回归关系在雨季强于旱季,雨季建设用地和植被面积变化引起COD浓度变化更快。在流域管理中,针对植被覆盖率低、建设用地占比高的白鹤溪和中和溪应重点加强雨季土地利用管控,增加植被覆盖率,合理开发建设用地。     

密云水库上游流域土地利用与地表径流营养物的关系

定量刻画土地利用与水体营养物浓度的关系,有助于指导流域土地利用管理,以控制水体富营养化.以往研究较多关注土地利用的数量结构,对其强度、空间分布等刻画相对不足.本研究以密云水库上游流域为例,基于覆盖全流域52个子流域的水质采样,通过遥感解译和空间计算,提取土地利用强度、所处坡度、与河道及监测断面距离以及位置邻接关系等信息,构建土地利用与总氮、总磷和化学需氧量浓度的多元线性回归方程.结果表明: 土地利用与总氮、总磷和化学需氧量浓度回归方程的决定系数由未纳入任何信息的0.294、0.471和0.223分别增加到0.532、0.685和0.489,显著提高了模型的解释能力.在厘定每一空间位置土地利用对监测断面营养物浓度贡献率的基础上,比较与河道不同迁移路径距离下土地利用对营养物浓度的平均累积贡献率及面积累计百分比,确定了距离河道1 km范围内的河岸带为水体富营养化的关键控制范围.最后提出了优化农田施肥管理、加强牲畜粪便处理、建设林地过滤带和河岸缓冲带等水质污染控制和调控的措施建议.     

Managing riparian zones for river health improvement: an integrated approach

Riparian zones are among the most valuable ecosystems on the earth. They act as the ecological engineers that improve river health through delivering a range of ecosystem functions. Stream bank stabilization, pollutant and sediment buffering, temperature regulation, provision of energy to river food webs and communities, groundwater recharge and provision of ecological corridors and habitat for wildlife, are among major ecosystem functions of riparian zones that play a great role in river health. Besides these ecosystem functions, riparian zones also provide various ecosystem goods and services for human well-being. But in the current scenario, riparian zones are under severe threat due to agricultural activities, urbanization, river flow alteration, overexploitation, climate change, pollution, and biological invasion. In the present and probable future scenarios of declining river health and global environmental changes, there is a pressing need of an integrated approach for managing riparian zones. This review article aims to advocate an integrated approach for riparian zone management based on various components such as riparian condition assessment, policy framework, stakeholder’s participation, management practices, legislation, and awareness. Authors also discussed riparian zones in context of their concepts, features, functions, and threats.

     

A multi-scale assessment of the occurrence of exotic plants on the Olympic Peninsula,Washington

Abstract. Exotic plants were surveyed in 208 plots within the Dungeness and Hoh river watersheds on the Olympic Peninsula, Washington, USA. Landscape patch types included uplands (clearcuts, young and mature forests) and riparian zones (cobble bars, shrub patches, riparian forests, and alder flats). Patterns of exotic plant invasions were assessed between watersheds, between riparian and upland areas, among patch types, and within clearcuts. 52 exotic plant species were encountered, accounting for 23% of the flora in each watershed. In both watersheds, exotic species richness was approximately 33% greater in riparian zones than in uplands, and mean number and cover of exotic species were > 50% greater in riparian zones than in uplands. Among landscape patch types, richness and mean number and cover of exotics was highest in young riparian patches, intermediate in clearcuts and riparian forests, and lowest in young and mature forests. The exception to this was Hoh alder flats, which had the highest mean cover of exotic plants. Cover of exotic plants peaked in uplands 3 to 7 yr after clearcutting, then decreased with increased canopy closure. Disturbance type and time since disturbance were major factors influencing invasibility. Landscape patch size, position within watershed (distance from patch to human population centers, major highway, or river mouth), and environmental variables (slope, aspect, and elevation) were not important indicators of landscape patch invasibility. Riparian zones facilitated movement of exotic plants through landscapes, but did not appear to act as sources of exotic plants for undisturbed upland areas.     

Temporal patterns of water quality in the Pantanal floodplain and its contributing Cerrado upland rivers: implications for the interpretation of freshwater integrity

Water quality time series available for major tropical floodplains commonly have low temporal resolutions and irregular sampling frequencies. Here we examine such data using singular spectrum analysis, a non-parametric time series analysis technique, to assess the typical cyclical variations and long-term trends in upland Cerrado and lowland floodplain reaches of three rivers that are tributaries to the Pantanal in Brazil to evaluate ecological state and impact level, and develop recommendations for improved monitoring of Cerrado–Pantanal river systems. Both upland and lowland reaches have their average water quality cycles linked to a monocyclical hydrological regime. Amplitudes of nutrient concentrations (N, P) and Turbidity are higher in the uplands, whereas cyclical oxygen variations are up to two times higher in the floodplain reaches. SSA showed that trend extraction is possible for parameters with lower intra-annual variations and were found to be partially opposing (oxygen) in upland (negative trend) and floodplain (positive trend) stations. Land use intensification in the uplands is reflected by N concentrations in upland reaches. In the floodplain, the Paraguay river was found under a slight TN enrichment regime of about 0.02 mg L^?1 per year between 1995 and 2009. Assuming a fixed budget for institutional water quality monitoring, we recommend a reduction of the 150 registered sampling gauges by environmental agencies in the Brazilian Pantanal and its contribution area, 95 % of them with less than four samples per year, in favor of using the same resources for increased sampling frequency at a smaller number of sites.     

Variability in flood disturbance and the impact on riparian tree recruitment in two contrasting river systems

The vegetation within the riparian zone performs animportant ecological function for in-stream processes.In Australia, riparian zones are regarded as the mostdegraded natural resource zone due to disturbancessuch as river regulation and livestock grazing. Thisstudy looks at factors influencing vegetation dynamicsof riparian tree species on two contrasting riversystems in Western Australia. The Blackwood River insouth-western Australia is influenced by aMediterranean type climate with regular seasonalwinter flows. The Ord River in north-western Australiais characterized by low winter base flows andepisodic, extreme flows influenced by monsoon rains inthe summer. For both rivers, reproductive phenology ofstudied overstory species is timed to coincide withseasonal river hydrology and rainfall. An evendistribution of size classes of trees on the BlackwoodRiver indicated recruitment into the population iscontinual and related to the regular predictableseasonal river flows and rainfall. In contrast, on theOrd River tree size class distribution was clustered,indicating episodic recruitment. On both rivers treeestablishment is also influenced by elevation abovethe river, microtopography, moisture status and soiltype. In terms of vegetation dynamics riparianvegetation on the Ord River consists of long periodsof transition with short lived stable states incontrast to the Blackwood river where tree populationstructure is characterized by long periods of stablestates with short transitions.     

The role of micro-organisms in the ecological connectivity of running waters

1. Riparian zones hold a central place in the hydrological cycle, owing to the prevalence of surface and groundwater interactions. In riparian transition zones, the quality of exfiltrating water is heavily influenced by microbial activities within the bed sediments. This paper reviews the role of micro-organisms in biogeochemical cycling in the riparian-hyporheic ecotone. 2. The production of organic substances, such as cellulose and lignin, by riparian vegetation is an important factor influencing the pathways of microbial processing in the riparian zone. For example, anaerobic sediment patches, created by entrainment of allochthonous organic matter, are focal sites of microbial denitrification. 3. The biophysical structure of the riparian zone largely influences in-stream microbial transformations through the retention of organic matter. Particulate and dissolved organic matter (POM and DOM) is retained effectively in the hyporheic zone, which drives biofilm development and associated microbial activity. 4. The structure of the riparian zone, the mechanisms of POM retention, the hydrological linkages to the stream and the intensity of key biogeochemical processes vary greatly along the river continuum and in relation to the geomorphic setting. However, the present state of knowledge of organic matter metabolism in the hyporheic zone suggests that lateral ecological connectivity is a basic attribute of lotic ecosystems. 5. Due to their efficiency in transforming POM into heterotrophic microbial biomass, attached biofilms form an abundant food resource for an array of predators and grazers in the interstitial environments of rivers and streams. The interstitial microbial loop, and the intensity of microbial production within the bed sediments, may be a primary driver of the celebrated high productivity and biodiversity of the riparian zone. 6. New molecular methods based on the analysis of the low molecular weight RNA (LMW RNA) allow unprecedented insights into the community structure of natural bacterial assemblages and also allow identification and study of specific strains hitherto largely unknown. 7. Research is needed on the development and evaluation of sampling methods for interstitial micro-organisms, on the characterization of biofilm structure, on the analysis of the biodegradable matter in the riparian-hyporheic ecotone, on the regulation mechanisms exerted on microbiota by interstitial predators and grazers, and on measures of microbial respiration and other key activities that influence biogeochemical cycles in running waters. 8. Past experiences from large-scale alterations of riparian zones by humans, such as the River Rhine in central Europe, undeniably demonstrate the detrimental consequences of disconnecting rivers from their riparian zones. A river management approach that uses the natural services of micro-organisms within intact riparian zones could substantially reduce the costs of clean, sustainable water supplies for humans.     

Water allocation and climate-impacted riparian forest dynamics in the Ejina Oasis,Northwest China

Riparian forests in natural desert oases are extremely vulnerable to water shortages; of late these shortages have been associated with climate change and with increased human-led water allocation. This study covers a hundred-year history (1876–2017) of riparian forest growth at the Ejina Oasis, which is located in the lower reaches of the Heihe River basin of northwestern China. We collected tree cores from Populus euphratica, which is the major tree species found in the Ejina riparian forests. These samples allowed us to chart variations in riparian forest growth and to examine correlations between tree growth and local precipitation, temperature, drought indices, groundwater depth, and runoff volume from the middle reaches of the river. We found that groundwater depth (groundwater being mainly recharged by runoff) is the major factor limiting tree-stem radial growth. We compared runoff reconstruction series from upper reaches and P. euphratica radial growth in the lower reaches. We found a period of greatly decreased growth (1942–1951); which seems to have been due to human water diversion. We note that mountain runoff increased after 2000, but that riparian forest growth didn’t increase in tandem; the water that would otherwise have supported the forests had been diverted. Our study provides a warning for future water resource planning and suggests the desirability of policies that will balance the needs of natural ecosystems (riparian forests) with the requirements of artificial ecosystems (croplands).