Land-water Ecotones Research Articles

Monitoring and control of water-ecological space in the Dongting Lake region

The territorial spatial planning in the new era strengthens the control of different functional spaces and emphasizes integrated and coordinated development of each functional space. Therefore, it is important to monitor the “structure-function” characteristics of water-ecological space based on the context of territorial spatial planning and develop a management and control framework. Based on land use and social statistics, and with the help of ArcGIS analysis, this paper examined the structure and function of the water-ecological space in the Dongting Lake study for 2010, 2015, and 2020, generating a control framework and proposing key initiatives. The main results are as follows: 1) The overall scale of the water ecological space in the Dongting Lake study is over 7,300 km2. Water bodies had the largest share, followed by coastal terrestrial areas, while the land-water ecotone was the smallest. There was a small decrease in the water ecological space during the study period. Yueyang had the largest overall scale of water ecological space, while Linli had the smallest. 2) The comprehensive function of water ecological space in the Dongting Lake study was about 0.4000, increasing somewhat during the study period. Among the units, the comprehensive function value was highest in Yuanjiang City, while Jincheng City had the lowest. 3) From the structural elements of water ecological space, scientific planning of functional zoning of water ecological space should be carried out and combined with the delineation of “three zones and three lines.” Key initiatives such as multi-scale and multi-level planning and control, use control and access restrictions, determination of water ecological space ownership, pollution control and accountability, and comprehensive water ecological treatment and restoration should be promoted.

Research progress on key processes of nitrogen cycling under soil-plant-microbial interactions in the water-level-fluctuation zone of the Three Gorges Reservoir

流域氮污染问题是世界面临的共同难题,大型水利水电工程极大地改变了流域氮循环过程。三峡水库作为我国重要的优质淡水资源库,却面临着支流水华频繁暴发的水安全问题。如何有效削减氮污染并维持水库消落带生态系统的稳定性,是三峡水库生态安全运行中亟待解决的实际问题。水库消落带作为邻近水体的“生物地球化学循环热区”,在营养元素循环、面源污染截留、温室气体排放等过程中扮演着重要角色。随着生物信息学、分子生物学等新型研究手段在环境研究中广泛应用,氮循环过程与机理得到了更微观的诠释,氮循环功能微生物的多样性和生态位分化等方面的研究也取得了突出成果。本文基于对三峡水库消落带土壤-植物-微生物作用下的氮循环关键过程所开展的最新研究,结合消落带水陆交错的特殊环境条件,综述水库消落带中氮循环的关键过程和机理,分析水库消落带对流域水环境和温室气体排放的潜在影响,并对未来消落带亟待解决的问题做了进一步展望,以期为大型水库消落带生态系统的综合管理提供科学支撑。;Nitrogen pollution in watersheds is a serious problem all over the world. Large hydropower projects have greatly altered the nitrogen cycle in watersheds. The water in Three Gorges Reservoir, as our national precious freshwater resources, is facing safety issues caused by frequent outbreaks of algal blooms in tributaries. How to reduce nitrogen pollution effectively and maintain the stability of the water-level-fluctuation zone (WLFZ) is a practical issue to be solved urgently, especially to achieve the ecological operation of the Three Gorges Reservoir. As the biogeochemical cycle hotspot of the adjacent basin, the reservoir WLFZ plays an important role in the process of nutrient cycling, non-point source pollution interception, and greenhouse gas emissions. With the wide application of new research techniques, such as bioinformatics and molecular biology in environmental research, the process and mechanism of nitrogen cycle have been interpreted more microcosmically, and the research on the diversity and niche divergence of nitrogen cycle functional microorganisms has also made great achievements. Our study is based on the latest research progress of nitrogen cycle process, related soil-plant-microorganism interactions in the land-water ecotones. In addition, this review has summarized the process and mechanism of nitrogen cycle in the reservoir WLFZ, analyzed the potential impact of the reservoir WLFZ on the water environment and greenhouse gas emissions. In order to provide scientific supports for the integrated management on WLFZ ecosystem of large reservoirs, we made a further outlook on the problems to be solved in the future.

Probing the Response of the Amphibious Plant Butomus umbellatus to Nutrient Enrichment and Shading by Integrating Eco-Physiological With Metabolomic Analyses.

Amphibious plants, living in land-water ecotones, have to cope with challenging and continuously changing growth conditions in their habitats with respect to nutrient and light availability. They have thus evolved a variety of mechanisms to tolerate and adapt to these changes. Therefore, the study of these plants is a major area of ecophysiology and environmental ecological research. However, our understanding of their capacity for physiological adaptation and tolerance remains limited and requires systemic approaches for comprehensive analyses. To this end, in this study, we have conducted a mesocosm experiment to analyze the response of Butomus umbellatus, a common amphibious species in Denmark, to nutrient enrichment and shading. Our study follows a systematic integration of morphological (including plant height, leaf number, and biomass accumulation), ecophysiological (photosynthesis-irradiance responses, leaf pigment content, and C and N content in plant organs), and leaf metabolomic measurements using gas chromatography-mass spectrometry (39 mainly primary metabolites), based on bioinformatic methods. No studies of this type have been previously reported for this plant species. We observed that B. umbellatus responds to nutrient enrichment and light reduction through different mechanisms and were able to identify its nutrient enrichment acclimation threshold within the applied nutrient gradient. Up to that threshold, the morpho-physiological response to nutrient enrichment was profound, indicating fast-growing trends (higher growth rates and biomass accumulation), but only few parameters changed significantly from light to shade [specific leaf area (SLA); quantum yield (φ)]. Metabolomic analysis supported the morpho-physiological results regarding nutrient overloading, indicating also subtle changes due to shading not directly apparent in the other measurements. The combined profile analysis revealed leaf metabolite and morpho-physiological parameter associations. In this context, leaf lactate, currently of uncertain role in higher plants, emerged as a shading acclimation biomarker, along with SLA and φ. The study enhances both the ecophysiology methodological toolbox and our knowledge of the adaptive capacity of amphibious species. It demonstrates that the educated combination of physiological with metabolomic measurements using bioinformatic approaches is a promising approach for ecophysiology research, enabling the elucidation of discriminatory metabolic shifts to be used for early diagnosis and even prognosis of natural ecosystem responses to climate change.

Fish assemblages respond to forest cover in small Amazonian basins

The removal of native forest affects stream characteristics, processes, and organisms at the local scale. We compared the structure of fish assemblages between microbasins impacted by deforestation and those in pristine condition in the Amazonian Machado River basin, Brazil. Fish were collected with seine and dip nets along an 80-m stretch of 28 streams. At each site, we recorded physical, chemical, and land-water ecotone variables. We collected 6,586 specimens of 109 species, being 39 and 18 of them exclusively of forested and deforested streams, respectively. Non-significant differences were found for abundance and species richness between forested and deforested streams. A total of four main trophic groups were identified. Carnivores were more abundant in forested streams, whereas herbivores, omnivores and detritivores species were the most abundant in deforested streams. The deforested streams showed higher abundance and richness of algae and periphyton consumers, while forested streams presented higher abundance and richness of invertebrate consumers. Forested streams presented longer foodchains, higher occurrence and abundance of species that have more specialized habits and are intolerant to degraded environments, whereas generalist and tolerant species predominated in deforested streams. We conclude that species composition in Amazonian streams predictably responds to the degree of forest cover.

Presence and identification of <i>Legionella</i> and <i>Aeromonas</i> spp. in the Great Masurian Lakes system in the context of eutrophication

Growing anthropopressure over the last several decades has resulted in rapid progressive eutrophication of the Great Masurian Lakes (GML) system located in northeastern Poland. In our studies, we investigated whether there is a relationship between the occurrence of pathogenic bacteria: Legionella spp. and Aeromonas spp., not explored so far in the waters of GML system, and the trophic status of the studied lakes. The GML system of glacial origin includes lakes connected by natural and artificial channels, and it extends from north to south for approximately 100 kilometers. Water samples were taken during the summer, subsequently spring and autumn seasons from 15 lakes in land-water ecotones. At all sampling sites, basic in situ measurements of physicochemical parameters were recorded. The amounts of chlorophyll a, nitrogen, phosphorus, dissolved organic carbon were also measured. The trophic state index (TSI) of the sampling sites was also estimated. The real-time PCR technique enabled the determination of the presence and abundance of Legionella spp. and Aeromonas spp. The results clearly showed that several environmental water quality parameters, associated with eutrophication, and among them: nitrogen, phosphorus, chlorophyll, ammonium concentration, conductivity, turbidity, water transparency, highly affected the presence and abundance of the detected pathogenic bacteria in the studied lakes. Special attention should be paid to the high impact of water eutrophication on the number of pathogenic microorganisms, which result both from human activities in lakes and climate change.

Early ecosystem responses to watershed restoration along a headwater stream

Along many streams, natural riparian vegetation has been replaced by agricultural fields or plantations resulting in ecosystem alterations due to changes of the interactions across the land-water ecotone. We studied the effect of restoration interventions by removing a dense spruce plantation in a 25 m wide zone along a 4 km section of a headwater stream. Water discharge, nutrient and total organic carbon concentrations were unaffected by the intervention, which only involved 0.7% of the catchment area. Focusing on the oxygen dynamics within several sections of the stream revealed that the stream water was generally oxygen under-saturated both before and after the restoration reflecting the dominance of heterotrophy over photoautotrophy typical of small streams. Oxygen saturation was tightly coupled to water discharge, with anoxia or hypoxia developing during low summer flow, and levels just below saturation during high autumn-spring flow at low temperature and low metabolism. Stream-near felling increased incident irradiance and reduced the duration and extent of summer hypoxia despite unaltered discharge, temperature and concentration of total organic carbon. Increased incident irradiance was accompanied by higher oxygen saturation in open sections compared to control sections with intact tree cover. Diel oxygen changes followed incident irradiance during low summer flow, while alterations at high winter flow were caused by changes in temperature-dependent oxygen solubility and high reaeration. In conclusion, we show that anoxic or hypoxic oxygen levels occur in warm, low-flow summer periods and this stress is reduced when intense shading from spruce plantation is removed and in-stream oxygen production is stimulated.

Responses of fish assemblages to subtle elevations in headwater streams in southwestern Amazonia

This study aimed to characterize species composition and abundance of fish assemblages of low-order streams of the Machado River Basin and to identify the main environmental factors associated to fish assemblages along the elevational gradient. Fishes were collected by seine and dip nets, along an 80-m stretch of 71 streams. In each site, we recorded physical, chemical, and land–water ecotone variables. We collected 22,702 specimens of 91 species. Species richness and abundance varied negatively with elevation. Ordination and similarity analyses detected that streams located in higher and middle elevation ranges differed in species composition from those in the lower elevation range. Almost one-third of the recorded species were selected as indicator species. Species of the families Trichomycteridae, Cichlidae, Gymnotidae, and Characidae were closely associated with the land–water ecotone and structural characteristics of lower elevation range, whereas several other Characidae species were more abundant in middle elevation range, where aquatic vegetation cover and conductivity values were higher. By assuming that composition and relative abundance of fish respond to environmental changes, hydrological characteristics may be viewed as environmental filters for stream assemblages by ultimately selecting the pool of species able to reach for specific elevation ranges and meet their biological requirements.

Do Mining Activities Significantly Affect Feeding Behavior of Freshwater Benthic Macroinvertebrates? A Case Study in South Sardinia (Italy)

We investigated the cascading effects of chemical contaminants on alder leaf detritus quality and the exploitation of this feeding resource by benthic macroinvertebrates (isopods, gastropods, and mayfly nymphs). Trophic behavior and energetics of benthic macroinvertebrates were used to evaluate the effects of contaminants on detritus exploitation. A two-way factorial nested experimental design was used to statistically quantify how leaf detritus origin (polluted and unpolluted streams) and the pollution level of the site selected for microbial conditioning of the detritus could affect the feeding resource quality for aquatic benthic macroinvertebrates, as measured by their trophic behavior (i.e. food selection) and exploitation (i.e. food ingestion). Alder leaves collected from a polluted stream in a former mining area (South-Sardinia, Italy) had Cd, Pb, and Zn concentrations up to 10 times that of leaves collected from an unpolluted stream. When benthic macroinvertebrates were given the option to choose, they all selected leaves from the unpolluted stream and/or those conditioned in the unpolluted stream. Ingestion rates were also significantly affected by both considered factors: leaf origin and conditioning. In addition, synergistic effects strongly increased the chemical contaminant stress on the leaf detritus quality. These results show that the terrestrial component of land–water ecotones affected by mining can be a relevant indirect pathway of chemical stress to benthic macroinvertebrate species.

Nutrient availability and nutrient use efficiency in plants growing in the transition zone between land and water.

The transition zone between terrestrial and freshwater habitats is highly dynamic, with large variability in environmental characteristics. Here, we investigate how these characteristics influence the nutritional status and performance of plant life forms inhabiting this zone. Specifically, we hypothesised that: (i) tissue nutrient content differs among submerged, amphibious and terrestrial species, with higher content in submerged species; and (ii) PNUE gradually increases from submerged over amphibious to terrestrial species, reflecting differences in the availability of N and P relative to inorganic C across the land-water ecotone. We found that tissue nutrient content was generally higher in submerged species and C:N and C:P ratios indicated that content was limiting for growth for ca. 20% of plant individuals, particularly those belonging to amphibious and terrestrial species groups. As predicted, the PNUE increased from submerged over amphibious to terrestrial species. We suggest that this pattern reflects that amphibious and terrestrial species allocate proportionally more nutrients into processes of importance for photosynthesis at saturating CO2 availability, i.e. enzymes involved in substrate regeneration, compared to submerged species that are acclimated to lower availability of CO2 in the aquatic environment. Our results indicate that enhanced nutrient loading may affect relative abundance of the three species groups in the land-water ecotone of stream ecosystems. Thus, species of amphibious and terrestrial species groups are likely to benefit more from enhanced nutrient availability in terms of faster growth compared to aquatic species, and that this can be detrimental to aquatic species growing in the land-water ecotone, e.g. Ranunculus and Callitriche.

Evaluating Sentinel-2 for Lakeshore Habitat Mapping Based on Airborne Hyperspectral Data.

Monitoring of lakeshore ecosystems requires fine-scale information to account for the high biodiversity typically encountered in the land-water ecotone. Sentinel-2 is a satellite with high spatial and spectral resolution and improved revisiting frequency and is expected to have significant potential for habitat mapping and classification of complex lakeshore ecosystems. In this context, investigations of the capabilities of Sentinel-2 in regard to the spatial and spectral dimensions are needed to assess its potential and the quality of the expected output. This study presents the first simulation of the high spatial resolution (i.e., 10 m and 20 m) bands of Sentinel-2 for lakeshore mapping, based on the satellite’s Spectral Response Function and hyperspectral airborne data collected over Lake Balaton, Hungary in August 2010. A comparison of supervised classifications of the simulated products is presented and the information loss from spectral aggregation and spatial upscaling in the context of lakeshore vegetation classification is discussed. We conclude that Sentinel-2 imagery has a strong potential for monitoring fine-scale habitats, such as reed beds.

Food sources of macro-invertebrates in an important mangrove ecosystem of Vietnam determined by dual stable isotope signatures

Dual stable isotope signatures (δ13C and δ15N) were applied to determine the contribution of mangrove materials and other organic carbon sources to the invertebrate community in an ecologically important mangrove ecosystem of Vietnam. We have analyzed 181 specimens of 30 invertebrate species and found δ13C and δ15N ranging from −14.5 to −26.8‰ and from 1.3 to 12.1‰, respectively. From taxa measured for stable isotopes, polychaete, gastropods, bivalves, and grapsid crabs living in mangrove forest showed relative low δ13C values, while fiddler crabs inhabiting in the land–water ecotone showed the highest δ13C values. The δ13C showed that just a few mangrove inhabitants directly relied on the mangrove materials. The wide ranges of δ13C and δ15N signatures indicated that the invertebrates utilized heterogeneous diets, comprising benthic microalgae, marine phytoplankton, particulate organic matter, sediment organic matter, mangrove detritus, and meiofauna and rotten animal tissues as the supplemental nutrient food sources. Moreover, the significant correlation between δ13C values and body sizes of invertebrates showed that snails Littoraria melanostoma and Terebralia sulcata, bivalve Glauconome virens, and portunid crab Scylla serrata exhibited ontogenetic shifts in diets. The present study showed that adjacent habitats such as tidal flat and mangrove creeks seem to contribute an important microalgal food resource for invertebrates and highlighted the need for conservations of mangrove forests and the adjacent habitats.

Shaping of an agricultural landscape to increase water and nutrient retention

One of the most important phenomena, from the point of view of sustainable development of the countryside, is the worsening quality and diminishing quantity of water resources. The agriculture-induced pressure on ecosystems tends to increase while hunger and malnutrition of global population grows, expected to reach 2 billion persons by 2050. Moreover, there is no more land that could be utilized for this purpose. Widespread appearance of erosion, pollution of ground and surface waters and shortages of water resources is therefore expected. This seeks for an urgent need for a new approach to environmental management. For this purpose, not only technical measures, but also natural mechanisms, involving physical and biological processes must be used. This paper presents the results of investigations carried out in Wielkopolska (Poland) and in the Gumera (Gumara) catchment (Ethiopia) on climate and land use changes, and their impacts on water quantity and quality. Possibilities to counteract the worsening of water conditions are presented. Long-term investigations show that proper shaping of landscape structures, mainly by creation of shelterbelts, strips of meadows, land-water ecotones and small water bodies, and improving soil structure by increasing organic matter content, is one of the best tools for achieving this goal.

Ecohydrology for a sustainable future in Africa – the cases of Ethiopia, Kenya and Tanzania

The productivity of some African lands has declined by 50% due to soil erosion and desertification over the period 2000–2010. Yield reductions may range from 2% to 40% (8% in average). This leads to increasing starvation of people, where only in Sub-Saharan Africa (SSA) the number of hungry people reached 212 million. In Ethiopia about 90% of arable lands is in mountainous areas, where live 90% of the human population and 60% of all livestock. The highlands exposed to improper agricultural practices has been heavily degraded in the last century. The country faces environmental challenges such as land degradation, limited quantity and quality of water resulting from progressive deforestation, improper agricultural practices and urbanization. Similar problems are touching other African countries, especially in the East Africa. To overcome these problems, efforts have been made to launch afforestation and conservation programs; however, success to date has been limited. Harmonization of ecohydrological principles with the existing efforts has been planned. The Gumera River basin has been chosen to be one of the ecohydrological demonstration sites. The Kenyan-Tanzanian border area is also an area of interest due to the large seasonal migrations of large mammals depending on water availability. Lake Naivasha in Kenya is used to demonstrate possible measures for restoration of land-water ecotone functions of Cyperus papyrus by restoration of hydrological regime in the tributaries deltas. This paper uses three cases to discuss the importance of ecohydrology for problem solving in Africa. Establishment of the regional centre for ecohydrology is being proposed.

Animal species diversity at a land–water ecotone in Mongolia

The biodiversity of wetland ecosystems has received scant attention in Mongolia. We measured amphibian and macroinvertebrate species diversity at a complicated land–water ecotone of a pond within a wetland complex in Shaamar during July 2005. From our study area (0.5-ha grassland and an adjacent pond), we sampled 4,926 animals including 1 mammal, 4 amphibian, and 26 aquatic macroinvertebrate (>2 mm) species with a biomass of 4,444 g. Among these, a backswimmer (Notonectidae sp. 1) was a dominant species, representing 65% of the total number of animals collected (3,209) and 22% of the mass (999 g). Our study area was small but contained 4 amphibian species (Hyla japonica, Ranaamurensis, Bufo raddei, and Salamandrellakeyserlingii) in a mixed community with Shannon Diversity Index (H′) of 1.678 and Pielou’s Evenness Index (J′) of 1.211. No larvae or tadpoles of any amphibian species were found in the pond, indicating their early metamorphosis. H′ and J′ with 26 macroinvertebrate species were estimated to be 1.828 and 0.561, respectively. This suggests that low macroinvertebrate species diversity relative to high species richness is due to low evenness resulting from considerable numbers of a backswimmer. In 6 sites sampled in the pond, mean water pH revealed high alkalinity (range 9.01–10.45). The presence of our taxa in a highly alkaline environment indicates that they may be alkaliphilic.

Substrate Availability May Be More Important than Aquatic Insect Abundance in the Distribution of Riparian Orb‐web Spiders in the Tropics

ABSTRACTSpiders that are abundant along streams may depend on energy subsidies across land–water ecotones, but the effects of season and habitat structure on this trophic linkage remain poorly understood in the tropics. We carried out surveys and a manipulative experiment to investigate the effects of season and substrate availability on the distribution of riparian orb‐web spiders in Hong Kong, southern China. In the surveys, spider abundance, prey, substrate use, and web orientation were recorded. The experiment involved installation of in‐stream artificial substrates (ropes and bamboo poles) to increase substrate availability for web attachment. We found no seasonal difference in web abundance, but seasonal differences were observed for the prey on webs: aquatic insects (mostly Ephemeroptera and chironomid midges) contributed 69 percent of total prey collected during the wet season, but only 38 percent during the dry season. Most webs (50–80%) were < 0.5 m above the water and 45–51 percent of them tended to be orientated horizontally to the water surface and supported by overhanging vegetation and boulders. The addition of artificial substrates resulted in a 23–34 percent increase in the number of webs at the four treatment sites compared to controls, indicating that availability of web‐building substrates is a critical determinant of the spider distribution. Our results suggest that riparian zones are potential ‘hotspots' of food availability for spiders, and that the aquatic insect subsidy allows this habitat to support increased densities of spiders when the constraint of substrate availability is relaxed.

Feeding habits of Thoracocharax stellatus (Characiformes: Gasteropelecidae) in the upper rio Tocantins, Brazil

The silver hatchetfish Thoracocharax stellatus is one of the approximately 200 fish species recorded for the upper rio Tocantins, in the region where it was impounded by the Serra da Mesa hydroelectric dam. Analysis of the stomach contents of 88 specimens revealed a diet consisting almost entirely of insects (99.6%), most of which were terrestrial (87.6%). Ants, beetles, and mayflies were the main food items. Dawn and dusk seemed to be the periods of highest foraging activity for T. stellatus. As a specialist on terrestrial insects, this species has a close connection with the region near the river bank, where prey is provided from the associated riparian vegetation. Despite the impoundment and depletion of the land-water ecotone observed in later stages of reservoir formation, no significant changes in the diet of the few remnant specimens were recorded, which seems to indicate little feeding flexibility. Thus, feeding seemed to be an overriding factor for the displacement of this species after river impoundment.

A trophic cascade in a macrophyte‐based food web at the land–water ecotone

AbstractTrophic cascades may purportedly be more common in aquatic than terrestrial food webs, but herbivory on freshwater vascular plants has historically been considered low. Water lilies are an exception, suffering severe grazing damage by leaf beetles. To test whether a central prediction of cascade models—that predator effects propagate downwards to plants—operates in a macrophyte‐based food web, we experimentally manipulated predation pressure on a key herbivore of water lilies in the littoral zone of a lake in Michigan, USA. Field experiments comprised combinations of caging treatments to alter the number of predators (larvae of the ladybird beetleColeomegilla maculata) that hunt the grazers of the macrophytes (larvae of the leaf beetlesGalerucella nymphaeae) on the leaves of the water lilyNuphar advena. Predatory larvae of the ladybird beetles significantly reduced grazing damage to water‐lily leaves by 35–43%. The predators reduced plant damage chiefly via density‐mediated effects, when lower densities of grazers translated to significant declines in plant damage. Plant damage caused by the surviving herbivores was less than predicted from individual grazing rates under predator‐free conditions. This suggests that trait‐mediated effects may possibly also operate in this cascade. The observed strong effect of predators on a non‐adjacent trophic level concurs with an essential component of the trophic cascade model, and the cascade occurred at the ecotone between aquatic and terrestrial habitats:Nupharis an aquatic macrophyte with emergent and floating leaves, whereas both beetle species are semi‐terrestrial and use the dry, emergent and floating leaves of the water lily as habitat. Also, the cascade is underpinned by freshwater macrophytes—a group for which trophic processes have often been underappreciated in the past.

Ecological integrity of river–floodplain systems—assessment by dragonfly surveys (Insecta: Odonata)

AbstractDragonflies are reliable indicators of the ecological quality of land–water ecotones, habitat heterogeneity and the hydrological dynamics of water bodies. In recent years, surveys of dragonfly communities have become a powerful tool for the ecological assessment of floodplain areas. The goal of this paper is to present a new approach towards assessing the ecological integrity of river–floodplain systems by analysing resident breeding dragonfly species. The methodology is based on experiences with existing approaches using macroinvertebrates as bioindicators, in particular, calculations of saprobic indices, longitudinal zonation and functional feeding group patterns. In addition to the total number of species and the number of sensitive species, the ‘Odonate Habitat Index’ (OHI) is a key element of the assessment method. It indicates characteristic features of a river–floodplain system, such as connectivity aspects, flow dynamics and terrestrialization processes. The OHI is calculated from the species‐specific habitat values (expressing habitat preferences), abundances and the species‐specific indication weight, which distinguishes eurytopic from stenotopic species. The comparison of the status quo with a reference condition allows an assessment of individual water bodies and/or of a whole area in a five‐tiered classification scheme. The approach presented may also be used for the evaluation of restoration measures (e.g. reconnection of side arms) and for the definition of management objectives. Apart from the methodological framework, the results of a first application of this approach are presented in the paper as well. The study areas were selected floodplain systems of the Austrian section of the Danube and man‐made inshore structures of the impounded Danube section in Vienna. Copyright © 2001 John Wiley & Sons, Ltd.

Metals in sediment and water of three reed(Phragmites australis(Cav.) Trin. ex Stend.) stands

In the frame of the research program EUREED (Effects of interaction between eutrophication and major environmental factors on the ecosystem stability of reed (Phragmites australis) vegetation in European land-water ecotones), three reed stands, established near Alcacer do Sal, Lagoa de Albufeira and Montargil, were studied. The stands were monitored monthly between December 1993 and December 1994 for productivity, soil and water chemistry. The relationship between the concentration of some metals in soil and water and its influence on the stability of the reed vegetation was studied. Environmental factors, such as salinity, negative redox potential on the root system and high Cu, Na and Zn concentrations in soil did not affect the normal development of reed vegetation and its capability to recover after mechanical damage.

Die-back of Phragmites australis in European wetlands: an overview of the European Research Programme on Reed Die-back and Progression (1993–1994)

Reed ( Phragmites australis (Cav.) Trin. ex Steudel) is one of the dominant plant species in European land-water ecotones. During the past decades reed belts have died back, especially in central and eastern Europe. The aim of the European Research Programme on Reed Die-back and Progression (EUREED), was to examine how increasing eutrophication, changed water table management, temperature, reduced genetic variation and their interactions may contribute to reed die-back. Eutrophication appeared to be a key factor, but the effects on P. australis were indirect, via the accumulation and decay of litter and allogenous organic matter, rather than acting directly via disturbed carbohydrate cycling or reduced porosity of the aerenchymous plant tissue. The formation of toxic byproducts of decomposing litter in anoxic environment, such as acetic acid, may reduce reed vigour. Sulphide may act as a principal toxin especially at brackish sites, such as Lake Fert, Hungary. There were large differences in genetic variability. However, populations from eutrophic sites did not grow faster and were not more plastic than populations from oligotrophic sites. Variation within populations could be large as compared to variation between populations when exposed to nitrogen, liquid manure and litter. DNA-fingerprinting showed differences between land and water reeds. This may be due to a differential selective force during establishment, e.g., when the water table recovers after a drawdown. Selection by water table during establishment could affect the susceptibility of clones in the mature stage for indirect effects of eutrophication. It was concluded that in stagnant water bodies the present water table management enforces the effects of eutrophication on the reed die-back. In addition, local disturbances, such as the mechanical mowing of reeds may enhance reed die-back.