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There is increasing recognition that soils fulfil many functions for society. Each soil can deliver a range of functions, but some soils are more effective at some functions than others due to their intrinsic properties. In this study we mapped four different soil functions on agricultural lands across the European Union. For each soil function, indicators were developed to evaluate their performance. To calculate the indicators and assess the interdependencies between the soil functions, data from continental long‐term simulation with the DayCent model were used to build crop‐specific Bayesian networks. These Bayesian Networks were then used to calculate the soil functions' performance and trade‐offs between the soil functions under current conditions. For each soil function the maximum potential was estimated across the European Union and changes in trade‐offs were assessed. By deriving current and potential soil function delivery from Bayesian networks a better understanding is gained of how different soil functions and their interdependencies can differ depending on soil, climate and management. Highlights: When increasing a soil function, how do trade‐offs affect the other functions under different conditions?Bayesian networks evaluate trade‐offs between soil functions and estimate their maximal delivery.Maximizing a soil function has varied effects on other functions depending on soil, climate and management.Differences in trade‐offs make some locations more suitable for increasing a soil function then others. [ABSTRACT FROM AUTHOR]

Many estuaries exhibit seasonality in the estuary-scale distribution of suspended particulate matter (SPM). This SPM distribution depends on various factors, including freshwater discharge, salinity intrusion, erodibility, and the ability of cohesive SPM to flocculate into larger aggregates. Various authors indicate that biotic factors, such as the presence of algae and their excretion of sticky transparent exopolymer particles (TEP), affect the flocculation and erosion processes. Consequently, seasonality in these biotic factors may play a role in the observed seasonality in SPM. Whereas the impact of abiotic factors on seasonality in SPM is well studied, the relative contribution of biotically induced seasonality is largely unknown. In this study, we employ two approaches to assess the aggregated importance of biotically induced seasonality in flocculation and erosion on seasonality in SPM in the Scheldt estuary. In the first approach, we focus on seasonality of in situ observations in the Scheldt estuary of turbidity, floc size, Chlorophyll-a, and TEP, showing that the abiotic parameters show seasonality, while seasonality in TEP is ambiguous. The second approach concerns a reverse engineering method to calibrate biotically affected parameters of a coupled sediment transport-flocculation model to turbidity observations, allowing us to compare the modeled SPM concentrations to the observations. Driven by seasonality in freshwater discharge, the model captures the observed seasonality in SPM without requiring biotically induced seasonality in flocculation and erosion, which is supported by the absence of seasonality in TEP. [ABSTRACT FROM AUTHOR]

Macrophytes are important organisms in running water systems, having a decisive role in ecological processes and interactions. Their temporal and spatial distribution in streams can be highly variable, and this is often determined by flow velocity. In this study, macrophyte growth, morphology and nutrient stoichiometry were studied monthly during one growing season in reaches with different flow velocity and flow velocity distribution and, as a result, different distributional plant patterns in an Austrian lowland stream, dominated by evergreen macrophyte species, Berula erecta. Flow velocity, water depth, fine sediment layer depth and metabolism were measured in the stream and the correlation with plant biomass and morphological traits was tested. We aimed to study differences between reaches with different distributional plant patterns and whether common interactions between macrophytes and flow velocity can also be observed when vegetation is evergreen. Plant biomass showed seasonal variation, with the highest values in June and the lowest in February. In the reach with low flow velocity and homogeneous macrophyte distribution, biomass peaked in summer and plant morphology changed with the seasons, whereas biomass and morphology in the reach with high flow velocity and patchy distribution were more constant throughout the year. Plant carbon, nitrogen and phosphorus content were higher in spring and autumn than in summer, whereas biogenic silica accumulated over the course of the growth season. Stream metabolism was strongly correlated with macrophyte biomass, and this correlation was stronger in the reach with homogeneous macrophyte distribution than in the reach with a patchy distribution. Moreover, average leaf area and stem length were positively correlated with fine sediment layer depth, and negatively with flow velocity. The results stress the importance of macrophyte growth and morphology in river processes like metabolism, hydromorphology and nutrient dynamics: especially plant morphology plays an important role in macrophyte–flow interactions. [ABSTRACT FROM AUTHOR]

Aquatic macrophytes can have a significant impact on their associated community of epiphytic algae and bacteria through the provisioning of structural habitat complexity through different growth forms, the exudation of nutrients and the release of allelochemicals. In turn, this effect on epiphytic biofilm biomass and nutrient content has a potential effect on the macroinvertebrates that depend on epiphyton as a food source.We studied the effect of living macrophytes and their growth form on biofilm development in a semi‐controlled replicated microcosm experiment. Conditions of a nutrient‐poor water layer and nutrient‐rich sediment were created to study the effects of nutrient exudation by living macrophytes. We compared biofilm quantity and quality on structurally simple (Vallisneria spiralis) versus complex (Egeria densa) living plants and artificial analogues. Subsequently, the biofilm that had developed on the plants was fed, in a laboratory growth experiment, to two species of macroinvertebrate grazers (the snail Haitia acuta and the mayfly nymph Cloeon dipterum). This enabled us to assess if and how the macrophyte‐induced effects on the epiphyton can influence macroinvertebrate grazers.Living macrophytes were found to have a significant effect on epiphytic algal cover, which was mostly expressed by a lower cover on living macrophytes compared to their artificial analogues. Additionally, epiphyton cover on artificial macrophytes was found to be higher on complex structures compared to simple ones, yet this was not observed on living macrophytes. Plant specific traits, such as the release of allelopathic substances, competition for nutrients and DIC, and the amount of CaCO3 deposition on plant surfaces might explain these results.The density of epiphytic bacteria was found to be negatively correlated with biofilm Ca content from macrophytes in every treatment except living E. densa, which differed in leaf anatomy from the other plants by possessing polar leaves. Furthermore, biofilm on living macrophytes had lower C:N:P molar ratios compared to that on artificial plants, which is likely to be explained by nutrient exudation by the living plants. Although it was expected that a more nutritious biofilm would lead to increased grazer growth, this was observed only for H. acuta on E. densa. Because biofilm quantity was not a limiting factor, this lack of effect may be caused by compensatory feeding.It can be concluded that, depending on their traits, living macrophytes can have a positive effect on macroinvertebrate grazers by providing a large surface area for colonisation by epiphytic algae and bacteria, by improving biofilm stoichiometry and by stimulating bacterial growth. [ABSTRACT FROM AUTHOR]

Microhabitat suitability models are useful tools to enhance the reintroduction success of fish. Since 2008, a translocation and reintroduction program has been carried out in Flanders to prevent substantial loss of genetic variability in the Cottus perifretum (bullhead) population, and to meet the goals set by the Habitat Directive. To this end, habitat suitability of potential headstreams was assessed on a macrohabitat and microhabitat scale prior to the reintroduction. On a macrohabitat scale, water quality, habitat structure, food availability, and fish community were screened. Based on microhabitat models for bullhead in the summer period, microhabitat suitability was assessed in headstreams where macrohabitat characteristics showed a high potential for success. Both macro‐ and microhabitat assessment showed that reintroduction of bullheads in the Nellebeek, Bruelbeek, and Mollendaalbeek would most likely lead to self‐sustaining populations. For the Sint‐Annabeek, the microhabitat suitability model, considering depth and stream velocity, estimates that 7.5–9.5% of the headstream is suitable for bullhead. However, when substratum is taken into account, the microhabitat suitability index shows that only 4.3–5.8% of the brook is suitable. The current habitat quality and quantity in the Sint‐Annabeek is estimated to support a mean total population of 812 bullheads. However, the microhabitat suitability can be substantially improved by the artificial deposition of medium‐sized gravel (5–50 mm) and large gravel (50–100 mm). By doing so, the mean estimated population size could increase up to 1,330 individuals. Our results show that habitat improvement is necessary prior to the reintroduction of bullheads in the Sint‐Annabeek. [ABSTRACT FROM AUTHOR]

Abstract: Tidal marsh vegetation is increasingly valued for its role in ecosystem‐based coastal protection due to its wave dissipating capacity. As the efficiency of wave dissipation is known to depend on specific vegetation properties, we quantified how these morphological, biochemical, and biomechanical properties of tidal marsh vegetation are, in turn, affected by wave exposure. This was achieved by field measurements at two locations, with contrasting wave exposure, in the brackish part of the Scheldt Estuary (SW Netherlands), where Scirpus maritimus is the dominant pioneer species. Our results show that shoots from more wave‐exposed conditions developed significantly shorter and thicker stems than the ones growing in more sheltered conditions. Furthermore, we show that the more exposed shoots are more flexible whereas the shoots growing in more sheltered conditions are stiffer. This may indicate plasticity in response to wave exposure following a stress‐avoidance strategy. Increasing stiffness was shown to be related to enhanced biogenic silica and lignin contents of the shoot tissue. These properties might affect the wave‐attenuating capacity of the marsh as stiff plants are known to mitigate waves more effectively than flexible ones. However, we also found higher shoot densities on the exposed site, which may partly explain why higher relative wave attenuation rates were found on the exposed site, despite the presence of more flexible individual shoots. This study highlights that the efficiency of wave attenuation by tidal marsh vegetation ultimately depends on mutual interactions between waves and plasticity in morphological, biochemical, and biomechanical plant properties. [ABSTRACT FROM AUTHOR]

Accelerated mass loss from the Greenland ice sheet leads to glacier retreat and an increasing input of glacial meltwater to the fjords and coastal waters around Greenland. These high latitude ecosystems are highly productive and sustain important fisheries, yet it remains uncertain how they will respond to future changes in the Arctic cryosphere. Here we show that marine-terminating glaciers play a crucial role in sustaining high productivity of the fjord ecosystems. Hydrographic and biogeochemical data from two fjord systems adjacent to the Greenland ice sheet, suggest that marine ecosystem productivity is very differently regulated in fjords influenced by either land-terminating or marine-terminating glaciers. Rising subsurface meltwater plumes originating from marine-terminating glaciers entrain large volumes of ambient deep water to the surface. The resulting upwelling of nutrient-rich deep water sustains a high phytoplankton productivity throughout summer in the fjord with marine-terminating glaciers. In contrast, the fjord with only land-terminating glaciers lack this upwelling mechanism, and is characterized by lower productivity. Data on commercial halibut landings support that coastal regions influenced by large marine-terminating glaciers have substantially higher marine productivity. These results suggest that a switch from marine-terminating to land-terminating glaciers can substantially alter the productivity in the coastal zone around Greenland with potentially large ecological and socio-economic implications. [ABSTRACT FROM AUTHOR]

Quantification of ecosystem services ( ES) is an important step in operationalizing the concept for management and decision-making. With the exponential increase in ES research, ES have become a 'catch-all phrase', which some suggest has led to a poorly defined, impractical and ambiguous concept. An overview of the methods used in ES quantification is needed to examine their scientific rigour and provide guidelines for selecting appropriate measures., We present a systematic review of 405 peer-reviewed ES research papers to address the question: 'Is the biophysical and socio-economic reality of ES adequately quantified? First, we considered whether ES measures are scientifically rigorous enough by considering four predefined criteria (the type of data used, quantification of uncertainty, validation done and data reported). Secondly, using a novel approach, we determined which part of the ES cascade was measured: the ecosystem property, function, service, benefit or value., Our results showed that each of the 21 ES analysed had on average 24 different measures, which may indicate the complex reality of ES and/or suggest a potential lack of consensus on what constitutes an ES. We found that uncertainty is often not included and validation mostly missing., When analysing which part(s) of the ES cascade each measure corresponded to, we found that for regulating ES, ecosystem properties and functions (ecological aspects) are more commonly quantified (67% of measures). Conversely for provisioning ES, benefits and values (socio-economic aspects) are more commonly quantified (68%). Cultural ES are predominantly quantified using scores (35%)., In conclusion, ES appear to be poorly quantified in many cases, as often only one side of the cascade is considered (either the ecological or socio-economic side) and oversimplified and variable indicators are often used., Policy implications. This review provides a detailed overview of ecosystem services ( ES) quantification (ranging from simple scores to advanced methods) with the aim to support future ES quantification and ultimately the successful application of the ES concept. [ABSTRACT FROM AUTHOR]

Based on an analysis in the frequency domain of the governing equation of oxygen dynamics in aquatic systems, we derive a new method for estimating gross primary production (GPP) from oxygen time series. The central result of this article is a relation between time averaged GPP and the amplitude of the diel harmonic in an oxygen time series. We call this relation the Fourier method for estimating GPP. To assess the performance and accuracy of the method, we generate synthetic oxygen time series with a series of gradually more complex models, and compare the result with simulated GPP. We demonstrate that the method is applicable in systems with a range of rates of mixing, air-water exchange and primary production. We also apply the new method to oxygen time series from the Scheldt estuary (Belgium) and compare it with 14C-based GPP measurements. We demonstrate the Fourier method is particularly suited for estimating GPP in estuarine and coastal systems where tidal advection has a large imprint in observed oxygen concentrations. As such it enlarges the number of systems where GPP can be estimated from in situ oxygen concentrations. By shifting the focus to the frequency domain, we also gain some useful insights on the effect of observational error and of stochastic drivers of oxygen dynamics on metabolic estimates derived from oxygen time series. [ABSTRACT FROM AUTHOR]

The biogeochemical cycling of silicon (Si) along the land-to-ocean continuum is studied by a variety of research fields and for a variety of scientific reasons. However, there is an increasing need to refine the methodology and the underlying assumptions used to determine biogenic silica (BSi) concentrations. Recent evidence suggests that contributions of nonbiogenic sources of Si dissolving during alkaline extractions, not corrected by standard silicate mineral dissolution correction protocols, can be substantial. The ratio between dissolved Si and aluminum (Al) monitored continuously during the alkaline extraction can be used to infer the origin of the Si fractions present. In this study, we applied both a continuous analysis method (0.5 M NaOH) and a traditional 0.1 M Na2CO3 extraction to a wide array of samples: (1) terrestrial vegetation, (2) soils from forest, cropland and pasture, (3) lake sediments, (4) suspended particulate matter and sediments from rivers, (5) sediments from estuaries and salt marshes and (6) ocean sediments. Our results indicate that the 0.1 M Na2CO3 extraction protocol can overestimate the BSi content, by simultaneously dissolving Si fractions of nonbiogenic origin that may represent up to 100% of the Si traditionally considered as biogenic, hampering interpretation especially in some deeper soil horizons, rivers and coastal oceanic sediments. Moreover, although the term amorphous Si was coined to reflect a growing awareness of nonbiogenic phases we show it is actually inappropriate in samples where silicate minerals may account for a large part of the extracted Si even after linear mineral correction. [ABSTRACT FROM AUTHOR]

In recent years, it has become increasingly clear that two-way interactions between organisms and landscape-forming processes play a key role in the evolution of many aquatic ecosystems. To be able to compare sedimentation processes among different environments, a standardized method that is generally applicable is necessary. Current methods are usually designed for one environment only or are unreliable in the presence of vegetation. This paper presents the functionality of a plate sediment trap with a lid in combination with a filter paper, which enables the measurement of sedimentation rates in both permanently subaqueous environments and periodically flooded wetlands. We first present the trap design and demonstrate its functionality. No significant differences were found between replicates, nor was there any indication of a trap size effect on the sedimentation rate. Secondly, we demonstrate its applicability in periodically flooded and permanently subaqueous environments and in the presence or absence of vegetation. It is concluded that the use of a standardized method and equipment makes it possible to compare (bio)geomorphological changes in totally different environments. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT Aquatic plants (macrophytes) can have a large effect on river hydraulics and geomorphology. Though, the extent to how plant morphological plasticity actively influences these feedbacks has received little scientific attention. The nymphaeid macrophyte species Nuphar lutea (L.) Smith is characterized by a distinct leaf duality. Floating leaves shade most of the submerged leaves thereby limiting light penetration in the water. Despite their apparent negligible photosynthetic role, submerged leaves of N. lutea remain intact during summer and contribute a significant part to the total biomass. Our results indicate that the submerged leaves are crucial in plant-flow interactions and hence in the engineering potential of the plant, i.e. the capacity to locally reduce flow velocities and to promote sedimentation, including organic matter deposition. Plant individuals growing in running river water were compared to individuals from adjacent oxbow lake water. The number and size of submerged leaves were significantly higher for river standing individuals and the accumulated sediment contained significantly more organic matter, total nitrogen and total phosphorus, and was characterized by a lower carbon/nitrogen ratio and a finer grain size. We therefore argue that the submerged N. lutea canopy in rivers has the ability to create a high-nutrient, low hydrodynamic environment, resembling the conditions found in oxbow lakes. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Question How does the interaction between silicon ( Si) and vegetation affect local and global ecological processes, higher levels of ecological organization, and terrestrial- and watershed-scale Si fluxes? Location We selected several ecosystems throughout the world, from river headwaters to estuaries, being examples of (i) terrestrial vegetation, (ii) aquatic and floodplain vegetation, and (iii) tidal wetland vegetation. Methods We provide examples of the importance of linking Si use by terrestrial and aquatic vegetation, to larger-scale Si flux consequences towards and through rivers. Cross-disciplinary studies achieve the best understanding of vegetation effects on the global Si cycle, and the role of Si as a plant functional trait. Conclusion Si use by plants has not always received the research attention of other elements. Yet, today the importance of Si for plant functioning is slowly becoming better understood. Silicon is a crucial element for many plant species, being important for decomposition processes, plant competitiveness and stress tolerance. The inclusion by vegetation scientists of Si uptake as a plant functional trait is important to assess links between plant physiology, plant distribution and plant tolerance to environmental changes, but also to understand the role of vegetation on Si fluxes through the watershed. However, lack of knowledge regarding the biological control of the Si cycle hinders accurate quantification. Only a concerted effort bringing scientists together from a broad array of disciplines will provide this new direction for research on vegetation- Si cycling. [ABSTRACT FROM AUTHOR]

Macrophytes are important in the biogeochemistry of flowing rivers, although most information so far has relied on measurements of nutrients in plant tissues. This yields only indirect information on the nutrient uptake fluxes by roots and shoots and about nutrient translocation between roots and shoots. Here, we studied nitrogen uptake through experiments with enriched 15 N stable isotopes., Two macrophytes ( Potamogeton natans and Ranunculus fluitans) were grown in a closed race track-shaped flume, allowing us to control the hydraulic conditions in and around the plants. Overall ammonium uptake rates (μmol g−1 dry mass h−1) were higher for R. fluitans than P. natans., In addition to differences between the species, the spatial position of individuals within the plant patch and water flow were also important in explaining ammonium uptake. Thus, ammonium uptake was high at the leading edge of the patch and increased with velocity., Plant characteristic, such as the angle at which the plants bent in the flow, was also correlated with ammonium uptake. Differences in nutrient uptake associated with hydrodynamic parameters raised the question of how the two are related. For both species, uptake was not correlated with Reynolds stress, indicating the poor effect of turbulent mixing in determining ammonium uptake. [ABSTRACT FROM AUTHOR]

ABSTRACT The long-term (10-100 years) evolution of tidal channels is generally considered to interact with the bio-geomorphic evolution of the surrounding intertidal platform. Here we studied how the geometric properties of tidal channels (channel drainage density and channel width) change as (1) vegetation establishes on an initially bare intertidal platform and (2) sediment accretion on the intertidal platform leads to a reduction in the tidal prism (i.e. water volume that during a tidal cycle floods to and drains back from the intertidal platform). Based on a time series of aerial photographs and digital elevation models, we derived the channel geometric properties at different time steps during the evolution from an initially low-elevated bare tidal flat towards a high-elevated vegetated marsh. We found that vegetation establishment causes a marked increase in channel drainage density. This is explained as the friction exerted by patches of pioneer vegetation concentrates the flow in between the vegetation patches and promotes there the erosion of channels. Once vegetation has established, continued sediment accretion and tidal prism reduction do not result in significant further changes in channel drainage density and in channel widths. We hypothesize that this is explained by a partitioning of the tidal flow between concentrated channel flow, as long as the vegetation is not submerged, and more homogeneous sheet flow as the vegetation is deeply submerged. Hence, a reduction of the tidal prism due to sediment accretion on the intertidal platform, reduces especially the volume of sheet flow (which does not affect channel geometry), while the concentrated channel flow (i.e. the landscape forming volume of water) is not much affected by the tidal prism reduction. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Spatial self-organisation of ecosystems is the process by which large-scale ordered spatial patterns emerge from disordered initial conditions through local feedbacks between organisms and their environment. Such process is considered important for ecosystem functioning, providing increased productivity, resistance and resilience against environmental change. Although spatial self-organisation has been found for an increasing number of ecosystems, it has never been shown so far for aquatic river vegetation. Here we explore the existence of spatial self-organisation of freshwater macrophyte patches in a typical lowland river (Belgium), showing that the underlying mechanisms for pattern formation are scale-dependent feedbacks between plant growth, water flow and local river bed erosion and sedimentation. The mapping of vegetation patches showed that the frequency distribution of patch sizes is governed by a power-law function, suggesting that the patches are self-organised. Scale-dependent feedbacks, likely to lead to this self-organised pattern, were demonstrated with a mimic experiment. Both positive and negative feedbacks on plants were confirmed by a transplantation experiment. Placing vegetation patch mimics in the river showed experimentally that on a short range (within and behind the mimics) flow reduction and increased sedimentation occurred, while on a larger range (next to patches) the flow was accelerated and decreased sedimentation took place. By transplanting macrophytes within, next to and further away from existing patches, it was proven that the conditions within the patches favoured the survival and growth of transplants (i.e. short-range positive feedback), while the conditions just next to patches led to decreased survival and growth (i.e. long-range negative feedback). [ABSTRACT FROM AUTHOR]

Silica (Si) is of great concern to agronomists because it has a beneficial effect on plant resistance to various stresses, enabling yield optimization in economically important crop species. Yet biogenic silica (BSi) cycling in soils controls a large part of the Si export fluxes to rivers and oceans. Despite the importance of agricultural-harvest- related Si removal, previous studies have not addressed this topic thoroughly. By performing a detailed quantification of agricultural Si export in Western Europe's Scheldt River basin, we show that harvest not only disrupts BSi cycling but also introduces an agricultural Si pathway, with major export Si fluxes as compared with BSi production in climax forest communities and grasslands. Harvesting substantially changes terrestrial Si cycling because reconstitution of BSi to soils in litter fall is prevented. The agricultural Si loop clearly constitutes an important flow of BSi out of terrestrial ecosystems - one that is currently unrecognized in global biogeochemical Si cycling. [ABSTRACT FROM AUTHOR]

Summary 1. Macrophytes in running waters experience an often dynamic and harsh environment. To avoid breakage, plants have to reduce the experienced drag force. However, by reducing leaf area, photosynthetic production is less. Aquatic plants therefore have to find a balance between reducing drag and maintaining photosynthetic capacity. 2. In the experiments in this study, we assessed to what extent different morphological strategies (emergent vs. submerged) were able to minimize drag while maximizing leaf area. 3. From our measurements, it is clear that with increasing water velocities, emergent plant species have a drag value three to four times higher than submerged species. 4. To test the versatility of leaves, leaves were removed and their effect on drag and bending was investigated. Almost 60% of the drag is contributed by the leaves, and stems bend less when leaves are removed. 5. Because high submerged leaf area increases not only plant drag but also photosynthetic yield, a trade-off between both parameters was investigated in the function of stream velocity. Emerged species had a more favourable trade-off at low stream velocities. However, with increasing stream velocity, submerged species could reduce their drag more in comparison with blunt objects. Within these submerged species, a clear distinction was seen between those ( Potamogeton natans) concentrating their leaf area on or just beneath the water surface ( Stuckenia pectinata) and those with more or less evenly distributed biomass ( Callitriche platycarpa and Ranunculus penicillatus). 6. These results indicate that aquatic plants with an emergent strategy are able to take better advantage of zones with reduced hydraulic forces than submerged plants. Additionally, this plant occurrence will be determined by the relationship between total plant drag and root strength. [ABSTRACT FROM AUTHOR]

1. The extent to which seedling recruitment contributes to local functional diversity depends on the environmental filters operating in a plant community. Classical community assembly models assume that habitat constraints and competition act like hierarchical filters with habitat filtering as the dominant one. Alternative models assume a synergic interaction since responses to environmental stress and competition may impose physiological trade-offs in plants. 2. River floodplains are an ideal system to test the relationship between habitat and competition filtering in community (re)assembly, as flooding causes changes in both habitat stress (waterlogging, resulting in anoxia and toxicity) and competition (dieback of vegetation) on one hand and acts as an effective seed dispersal vector on the other hand. 3. We conducted a mesocosm experiment on early community assembly from a pool of 34 floodplain species covering a wetness gradient. Seed mixtures were sown in a full factorial design with water level, canopy and mowing as controlling factors. We measured the biomass of all species after one growing season and determined germination and seedling growth traits, both outside (response to waterlogging/no waterlogging) and in a growth-chamber (response to light/darkness). 4. Species recruitment was analysed in relation to the controlling factors and measured functional traits using co-inertia analysis. Furthermore we analysed the effects of the controlling factors on several aspects of functional diversity. 5. There was no establishment in grass sward, unless mowing was applied. Species-rich communities only developed when germination and early establishment phases occurred on waterlogged bare soil. High water level did not suppress establishment but reduced the total biomass and lowered inter-specific competition. The effect of mowing on species richness depended upon the interplay between waterlogging and canopy. 6. Establishment success under canopy required seedling strategies to tolerate shade. The elimination of typical wetland specialists from oxic mesocosms was clearly an effect of their poorer and/or slower germination and lower competitive abilities in comparison to non-wetland plants, leading to their disappearance in this low-stress environment. 7. Our results indicate that single stress factors can enhance species richness and functional diversity through limiting competition but a synergic interaction of different stresses can lead to reduced richness. [ABSTRACT FROM AUTHOR]

•Although silica (Si) is not an essential element for plant growth in the classical sense, evidence points towards its functionality for a better resistance against (a)biotic stress. Recently, it was shown that wetland vegetation has a considerable impact on silica biogeochemistry. However, detailed information on Si uptake in aquatic macrophytes is lacking. •We investigated the biogenic silica (BSi), cellulose and lignin content of 16 aquatic/wetland species along the Biebrza river (Poland) in June 2006 and 2007. The BSi data were correlated with cellulose and lignin concentrations. •Our results show that macrophytes contain significant amounts of BSi: between 2 and 28 mg BSi g−1. This is in the same order of magnitude as wetland species (especially grasses). Significant antagonistic correlations were found between lignin, cellulose and BSi content. Interestingly, observed patterns were opposite for wetland macrophytes and true aquatic macrophytes. •We conclude that macrophytes have an overlooked but potentially vast storage capacity for Si. Study of their role as temporal silica sinks along the land–ocean continuum is needed. This will further understanding of the role of ecosystems on land ocean transport of this essential nutrient. [ABSTRACT FROM AUTHOR]

The article presents a study which investigates the use of one-dimensional (1D) heat transport models to measure the amount of exchange fluxes in groundwater and surface water. It states that measurement is required to preserve the water ecosystem. It cites that simulations of 1D transient heat flow were performed on Aa River in Flanders, Belgium and on Lake 77 in Lusatia, Germany. Among the methods and equipment used include seepage meters, thermal method and vertical temperature.

1. In recent years, European water management policies have promoted floodplain rehabilitation for flood mitigation purposes. This could provide opportunities for the restoration of valuable floodplain meadows. However, during restoration projects, it is essential to understand the effects of the measures undertaken. In this study, we focus on the interaction between flood frequency and mowing in determining species composition of temperate lowland floodplain meadows. We hypothesized that the interaction of regular flooding with annual mowing would result in higher species richness than annual mowing or regular flooding alone. 2. We compared the composition of annually mown and non-mown vegetation located in floodplain sites differing in flood frequencies. The presence of different plant growth forms and functional types was investigated in order to explain the mechanisms underlying the differences found. 3. Both flood frequency and mowing affected species composition. However, flood regime was less important than mowing regime. 4. Mowing was shown to strongly affect species composition by reducing productivity and competitiveness and offering opportunities for weak competitors. Annually mown sites harboured higher numbers of smaller species compared to non-mown sites which supported higher populations of tall graminoid species. CSR strategists (where C is competitiveness, S is stress-tolerance and R is ruderality) were most common in mown sites, demonstrating that mowing imposes a moderate degree of disturbance and nutrient stress. 5. Only the combination of frequent flooding with annual mowing clearly increased species richness. This can be attributed to the fact that mowing provides the necessary gaps for germination of flood imported seeds. 6. Synthesis and applications. Apart from focusing on the restoration of flood dynamics, managers should pay attention to the implementation and maintenance of extensive land management practices to ensure sustainable restoration results. Note that many European riparian sites have been abandoned during the last 20 years as a result of changes in policies and agricultural markets, yet annual disturbance and/or the creation of open vegetation gaps through annual mowing are necessary in order to maintain species-rich vegetations in these systems. The evaluation of possible administrative options bringing together the interests of farmers and conservationists is an important challenge in determining the restoration and preservation of these valuable floodplain habitats. [ABSTRACT FROM AUTHOR]

We investigated long-term trends (1965-2002) in dissolved inorganic nutrients in the tidal part of the Scheldt estuary (Belgium, The Netherlands). Annually averaged concentrations of dissolved silicate (DSi), dissolved inorganic nitrogen (DIN), and phosphate (DIP) increased significantly until the mid-1970s, after which they declined linearly at rates of 0.6, 2.9, and 0.3 µmol L-1 yr-1, respectively. This co-occurred with a deterioration followed by a restoration of water column oxic conditions. Because of the differences in the reduction rate of DSi (1.2% yr-1), DIN (1.7% yr-1), and DIP (5.4% yr-1), the N:P and Si:P ratios more than doubled from 1980 to 2002. The Si:N ratio varied from 0.2 to 0.4 and was positively correlated with river discharge. The part downstream from the confluence of the main rivers was a net sink for DSi during the entire period but evolved from a net sink to a net source for DIP, while the reverse was true for DIN. This differential behavior of the estuary with respect to DIN and DIP strongly buffered the altered loadings to the upper estuary. The input of oxygen-consuming substances at the head of the estuary triggered a sequence of oxidation reactions. In the early 1970s, high loadings of ammonium and organic matter caused oxygen depletion and intense water-column denitrification in the upstream part and intense nitrification downstream, with a nitrate maximum succeeding a nitrite peak. With oxic conditions improving and the input of ammonium decreasing, water-column denitrification declined, the nitrification front migrated upstream, and the estuary evolved from a net producer of nitrite to a net consumer. Now, at the beginning of the 21st century, nitrate behaves almost conservatively over the entire estuary. [ABSTRACT FROM AUTHOR]

We quantified the fate and transport of watershed-derived ammonium in a tidal freshwater marsh fringing the nutrient-rich Scheldt River in a whole-ecosystem 15N labeling experiment. 15N-NH4+ was added to the floodwater entering a 3,477 m² tidal marsh area, and marsh ammonium processing and retention were traced in six subsequent tide cycles. We present data for the water phase components of the marsh system, in which changes in concentration and isotopic enrichment of NO3-, NO2-, N2O, N2, NH4+, and suspended particulate nitrogen (SPN) were measured in concert with a mass balance study. Simultaneous addition of a conservative tracer (NaBr) confirmed that tracer was evenly distributed, and the Br- budget was almost closed (115% recovery). All analyzed dissolved and suspended N pools were labeled, and 31% of added 15N-NH4+ was retained or transformed. Nitrate was the most important pool for 15N, with nitrification accounting for 30% of 15N-transformation. In site whole-ecosystem nitrification rates were four to nine times higher than those in the water column alone, implying a crucial role for the large reactive marsh surface area in N-transformation. Under conditions of low oxygen concentrations and high ammonium availability, nitrifiers produced N2O. Our results show that tidal freshwater marshes function not only as nutrient sinks but also as nutrient transformers. [ABSTRACT FROM AUTHOR]

The Long-Term Vision for the Schelde estuary was determined as“the development of a healthy and multifunctional estuarine water system that can be utilized in a sustainable way for human needs.” This Dutch–Flemish managerial plan sets quality targets for the condition of the estuary by the year 2030 and the management measures to achieve them. Targets were developed and integrated from three central perspectives: accessibility of the ports, safety against floods in the densely populated catchment, and ecosystem health. This study focuses on the ecological rehabilitation of the estuary and the creation of sustainable nature, seeking possible alliances with security measures against floods, navigation requisites for port activities, and enhancement of the estuary's educational and recreational values. The estuary and its valley were subdivided into ecologically relevant zones. Key parameters were identified, and a conceptual rehabilitation model was developed, based on a problem analysis. Goals were set in a semiquantified way for most attributes of the estuarine functioning and prioritized for each zone. Rehabilitation measures with maximal contribution to the priority goals were identified for each zone. Spatial analysis of the study area indicated optimal areas for the implementation of these measures. To exemplify the array of possibilities on an ecosystem level, two different rehabilitation plans were proposed, each from a different approach. The potential contribution to the rehabilitation of the estuary was compared for both alternatives. [ABSTRACT FROM AUTHOR]

By the approval of the European Bird Directive (79/ 409/EEC) in 1979 and the Habitat Directive (92/43/EEC) in 1992, nature protection has become an important part of European law with direct consequences for land use,industrial development and agriculture. If a member state reclaims an area that is protected by these directives,it has to take compensational measures. When such an area includes saline grasslands that require very specific abiotic conditions, a place with similar conditions must be available to re-establish those grasslands at another location in a sustainable way. This will limit the number and extent of possible sites for compensation. In the conflict between economy and ecology in the Schelde polders, Flanders has chosen to expand the port of Antwerp in the polders at the left Schelde bank and destroy a protected saline grassland site. As a consequence, it has to compensate for this loss.Therefore, we made a detailed study of the hydrology, geology and soil conditions of the endangered saline grassland site. The same was done in four possible compensation sites, all situated in nearby polders. We found that the presence of upwelling groundwater flowing through a saline peat layer is necessary for the occurrence of saline grasslands. Only in one of the four possible compensation sites, called Muggenhoek, we found such conditions. So, we indicate this place as a possible site for the re-creation of saline grasslands and give some recommendations for their development. [ABSTRACT FROM AUTHOR]

Many tidal marshes have been lost by past land use changes, but are nowadays increasingly restored and created to provide valuable ecosystem services such as nature‐based flood and erosion protection along estuarine shorelines. To be functional for flood and shoreline erosion protection, restored and created tidal marshes should develop erosion resistant sediment beds. Here, we investigated which factors drive the spatial variations in sediment strength and erosion resistance in a developing tidal marsh restoration site. Our results show that decreasing tidal inundation frequency, decreasing sedimentation rate, and better drainage led to stronger consolidation in deeper sediment layers. This consolidation resulted in greater sediment strength, quantified here by shear strength and penetration resistance. Generally, sediment strength was greater when sediment had higher bulk density, while a higher water and fine fraction (= clay and silt) content decreased sediment strength. Overall, all measurement locations were relatively erosion resistant, likely caused by the dense root network and cohesive sediment. To restore or create resilient tidal marshes for nature‐based flood and shoreline erosion protection, we should thus aim for sites with relatively low tidal inundation frequency, moderate sedimentation rates, and cohesive sediment mixtures of clay, silt, and sand, which are well drained and have potential for vegetation establishment. These conditions have a high likelihood of resulting in restored or created tidal marshes that contribute to nature‐based flood and shoreline erosion protection. [ABSTRACT FROM AUTHOR]

Describes the use of the abundance/biomass comparison (ABC) method for detecting environmental stress such as pollution on macrozoobenthos and bird communities in the Netherlands and Belgium. Environmental stress related to a long tidal exposure time of the plot or to human disturbance; Difficulty of using the method in estuarine areas.

We studied the seasonal exchange of biogenic silica (BSi) and dissolved silica (DSi) between a freshwater and a saltwater tidal marsh and the adjacent coastal waters. Export of DSi was observed from both tidal marshes, whereas BSi was imported in association with suspended solids. The export of DSi was highest (23.4% and 123.8% in the freshwater and saltwater marsh, respectively) in summer when DSi concentrations were low in the nearby coastal waters. Combined data from both marshes suggested a logarithmic decrease in DSi export with increasing DSi concentrations in the inundating waters. BSi import was observed year round in the freshwater marsh, but only in summer in the saltwater marsh. The results show that DSi export from tidal marshes, both freshwater and salt water, contributes significantly to estuarine Si availability in summer and provide new insights regarding potential linkages between tidal marshes and secondary production in nearby coastal waters. [ABSTRACT FROM AUTHOR]