Middle Elbe Research Articles

Microplastic analysis in sediments of the Elbe River by electrostatic separation and differential scanning calorimetry

This study presents the most extensive investigation of microplastic (MP) contents in sediment from the Elbe River. We employed electrostatic separation (ES) and differential scanning calorimetry (DSC) to overcome limitations of sample throughput and time-consuming analysis. In total 43 sediment samples were collected using a Van-Veen grab. Subsequently, coarse materials (d10 > 100 μm) and fine materials (d10 ≤ 100 μm) were enriched using ES and density separation. DSC was utilized for MP identification and quantification, based on the phase-transition signals of eight different polymers. MP presence was detected in 25 samples, with successful quantification in 12 samples. The MP content in coarse material samples from shoreline areas ranged from 0.52 to 1.30 mg/kg, while in fine material samples from harbor basins, it ranged from 5.0 to 44.6 mg/kg. The most prevalent polymers identified were LD-PE, HD-PE, PP, and PCL. These findings confirmed the suitability of DSC for analyzing MP in complex environmental samples. MP hotspots were identified in harbor basins, where natural sedimentation processes and increased anthropogenic activities contribute to MP accumulation. Additionally, industrial sewage potentially contributed to MP content in sediment samples. The highest pollution levels were observed in the middle Elbe, between the confluences of Mulde and Havel. Lowest MP contents were found in the lower Elbe, potentially influenced by tides. Future studies should focus on holistic investigations of selected river sections, encompassing sediment, water, and biota samples, rather than the entire catchment area. This approach would facilitate the generation of spatiotemporal data on MP distribution in freshwater streams. In addition, more research is needed to explore potential interactions between different MP and sediment types during DSC measurements.

Drivers for soil organic carbon stabilization in Elbe River floodplains

AbstractBackgroundFloodplains play an important role in the global carbon (C) cycle, particularly due to their large soil organic carbon (SOC) storage potential. However, a heterogeneous microrelief and anthropogenic landscape modifications complicate the understanding of stabilization processes of SOC in floodplains.AimDetermining the predominant drivers for SOC stabilization in Elbe River floodplain soils.MethodsWe measured SOC density fractions, microbial biomass, and mineralization characteristics in top‐ and subsoils of eight floodplain sites of the lower middle Elbe River.ResultsThe heavy fraction (HF) was the most important SOC pool, with a contribution of >64% at both depth intervals. With soil depth, HF pool size increased and the occluded light fraction (oLF) decreased, whereas the free LF (fLF) stayed the same. The contribution of the HF to SOC was positively related to fine texture (R2 = 0.64). Mineralizable C was negatively related to fine texture at both depth intervals. Both results suggest a positive effect of fine texture on SOC stabilization. The metabolic quotient was related to the amount of available SOC in the topsoil, but no relation was found in the subsoil. However, in top‐ and subsoil, the mineralization rate constant was positively related to the C/N ratios of the fLF and the oLF, indicating that the quality of fresh plant litter is an important energy source for microbial mineralization.ConclusionSedimentation of fine‐textured material is the most important driver for SOC stabilization rather than fresh plant litter input. Thus, SOC stabilization strongly depends on relief, flooding, and sedimentation.

Hydrological regime and forest development have indirect effects on soil fauna feeding activity in Central European hardwood floodplain forests

Soil fauna act as regulators of decomposition processes via their feeding activity, thereby playing an important role in regulating carbon cycling and sequestration. Hardwood floodplain forests are critically endangered habitats, but strongly contribute to carbon sequestration in Central Europe. In the present study, within a floodplain forest-development programme, we investigated the feeding activity of soil fauna via the Bait Lamina test in hardwood floodplain forests of the middle Elbe River in Germany in sites with different hydrological regimes and forest-development stages, with neighbouring grassland sites for comparison. While statistically significant differences in overall feeding activity between general hydrological regimes or forest development stages were not found, decreases in feeding activity with soil depth were strongly modulated by these factors, indicating more unfavourable conditions for soil fauna at increasing soil depth due to, e.g., anoxic conditions in floodplains of tributaries or low soil moisture content below the shallow rooting zone of grasslands. Registered effects of soil texture on soil fauna feeding activity were dependent on forest-tree density, and combined effects indicate that soil-fauna feeding activity varies with soil temperature during spring, but with soil moisture in early autumn. In conclusion, our results highlight the importance of the current abiotic conditions on soil-fauna feeding activities in floodplain forests, i.e. soil temperature, moisture and ground water level. Hydrological regime and forest development have a strong impact on the effect of these conditions, indirectly affecting soil fauna feeding activity and highlighting the multifactorial influence on soil fauna functional activity to be considered in floodplain-forest restoration programs.

Soil texture and pH affect soil CO2 efflux in hardwood floodplain forests of the lower middle Elbe River

AbstractFloodplain ecosystems play a significant role in the global carbon (C) cycle, particularly due to their C sink potential in hardwood floodplain forests. However, in these forests, interactions between a heterogeneous micro‐relief and anthropogenic landscape changes make estimating C loss through soil CO2 efflux difficult. To determine the drivers of soil CO2 efflux, we selected six hardwood floodplain forests at the lower middle Elbe River, which were distributed among different relief positions (low‐lying or high‐elevated) in the active and former flooding zone. We measured soil CO2 effluxes over a full year using the closed‐chamber method. Based on the response of soil CO2 efflux to soil moisture and temperature, annual efflux rates were determined, which were then related to soil properties, such as pH, texture, soil organic carbon (SOC) and nitrogen (N) content. Soil CO2 efflux ranged between 1006 (±99) and 2214 (±118) gC m−2 year−1. Maximum efflux occurred in a former floodplain forest that was disconnected from Elbe River water table fluctuations. SOC‐specific soil CO2 efflux (gC gSOC−1 year−1) was smallest in low‐lying forests of the active flooding zone and reflected by the appearance of redoximorphic mottling close to the soil surface. Fine texture (<6.3 μm), SOC and N were related positively and electric conductivity, C/N and pH negatively to total soil CO2 efflux. Soil pH and fine texture were the strongest univariate predictors for total soil CO2 efflux (both R2 = 0.59). Fine texture, pH and C/N ratio explained 66% of the variance in total soil CO2 efflux according to multiple linear regression. We conclude that, in hardwood floodplain forests, soil CO2 efflux is mainly controlled by fine texture and soil pH. Fine texture can be related to soil moisture and nutrient availability and may have a positive effect on the activity of microorganisms.Highlights Soil CO2 efflux ranged between 1006 (±99) and 2214 (±118) gC m2 year−1, whereby the maximum was measured in a disconnected floodplain forest Maximum soil CO2 efflux was measured in a disconnected floodplain forest SOC‐specific soil CO2 efflux was smallest in forests where redoximorphic mottling occurred close to the surface Fine texture (<6.3 μm) and pH were the strongest predictors for annual soil CO2 efflux

Are active and former floodplain soils of the lower middle Elbe similar? A study of soil characteristics and possible implications for forest restoration

The analyses of soil properties and processes under the consideration of the spatial complexity of floodplains is a key step in the preparation of floodplain restoration measures. In that context, we analyzed how hydrogeomorphology influences soil physicochemical properties and formation processes in hardwood floodplain forests at the local scale. Our analyses are based on, 44 mixed topsoil samples, 135 soil drillings (2.0 m depth) and 18 reference pits (1.6 m depth) distributed in 44 hardwood floodplain forests along 150 km of the middle Elbe River. We considered four hydrogeomorphic units (HGUs) along a lateral floodplain gradient. Two HGUs located in the active floodplain and defined by their morphology Active High (AH), and Active Low (AL), and two located in the former floodplain: seepage water influenced (FS), and disconnected from the river hydrology (FD). Our results indicate that the HGUs in the active floodplain benefit from a stronger connection to the river hydrology. Higher pHCaCl2 values in the active HGUs as well as expected higher total P contents due to river deposition result in increased phosphorous availability. Physicochemical parameters as lower pHCaCl2 and predominance of iron mottling found in the FD indicate increased P sorption, therefore lower Psol availability. However, HGUs in the former floodplain, particularly those disconnected from the river hydrology, are characterized by higher total carbon and nitrogen content. These results improve our understanding of the soil physicochemical dynamics and their interactions in the different hydrogeomorphic units, and could allow the evaluation of floodplain restoration measures based on soil nutrient distribution to increase the potential of restored forests to develop on the selected geographic setting.

The Rise of the White Serbia in the Light of the Merovingians’ Thuringia Policy

The study offers an analytical overview of the international relations in the territory of the Middle Elbe basin from the 530s until the early 8th century, specifically concerned with the policy of the Merovingian kings towards the former Thuringian kingdom lands and the issue of the rise of White Serbia. The author considers Frankish policy as an influencing factor in slavisation of the discussed region while examining the impact of a wider spectrum of possible factors, in particular, the changes in ecology and the Avar presence in the Middle Danube region. The chronology of the Serbian settlers’ arrival into the Middle Elbe valley as well as their political & legal status in that land are specified. The author discusses the issue of the White Serbs’ initial foreign policy orientation and investigates the causes, direction, time & consequences of its change. The main research content is complemented by the excurses on the climatic crisis of the Late Antique Little Ice Age and chosen aspects of the Avars’ & the White Serbs’ early ethnic history.
 The author develops W. Fritze’s hypothesis of the Merovingians’ active involvement and support of the Serbian immigration into the Middle Elbe and Saale region together with an idea of anti-Avar direction of this measure. Whereas, the results of the study have rejected the assumptions, that the Elbe Germans abandonment of the area to the east of the Elbe and Saale at the end of the third quarter of the 6th century was caused by the Frankish-Avar agreement or Slavic pressure. The author concludes that the first group of the Serbian settlers arrived to the Middle Elbe and Saale from the North-Western Bohemia during the Austrasian king Theudebert ІІ’s reign, probably, at the invitation of the famous Brunhilda, receiving the lands in Thuringia’s border zone as the Frankish foederati. The interconnection between the initial successes of the Merovingians’ Serbian policy in the east of Thuringia during the first decades of the 7th century and the settlement of the Croats & Serbs in the Balkans by the emperor Heraclius is revealed. It has been demonstrated that further expansion of the White Serbia’s territory from the 630s was of spontaneous nature and took place under the circumstances of the collapsed Merovingian control over Thuringia.

Adapting a Quercus robur allometric equation to quantify carbon sequestration rates on the Middle Elbe floodplain

Destructively sampling old Pedunculate oak (Quercus robur) trees on the active floodplain of the Middle Elbe to create an allometric equation to estimate carbon stocks (CS) and carbon sequestration rates (CSR) would defeat the purpose of protecting increasingly vulnerable and threatened primeval floodplain forests. To nondestructively estimate CS and CSR, we have adapted a two-parameter allometric equation which uses tree height (H) and diameter at breast height (DBH) (Dik 1984, Zianis et al. 2005) into a 1-parameter equation that requires only DBH to quantify stocks and annual changes in carbon stock (carbon sequestration rates) for individual Q. robur trees. The equations have also been adapted to estimate below- and above-ground carbon stocks of individual trees.The new method has:•Adapted a 2-parameter Quercus robur allometric equation which estimates tree volume to a 1-parameter equation which estimates above and below-ground carbon stock•Removed the requirement of tree height to reconstruct the carbon stock of trees at an annual timestep•An almost perfect linear relationship (Pearson R2= 0.998) between carbon sequestration rate and basal area increment (BAI)

The North or the South? Early medieval ceramics decorated with a zoned ornament – the result of local changes or interregional contacts?

The article underlines the need to re-discuss the prevailing views in archaeological literature on the provenance and transformation stages of completely wheel-turned ceramics decorated with zoned ornament. This class of ceramics was used in the Early Middle Ages (for about 100 years) by communities living in the area of southern Greater Poland and the north-eastern part of Lower Silesia. The previous ideas suggesting a close relationship between zoned ceramics and vessels produced in northern Bohemia are reconsidered, with the internal diversity of zoned ceramics being pointed out. We argue that inspiration in ceramics manufacturing came not only from the south (Bohemia), but also from the north (Pomerania) and the west (the middle Elbe region), and that there were also changes that appeared independently of these impulses in the ceramics production of small, native communities.

Factors controlling soil organic carbon stocks in hardwood floodplain forests of the lower middle Elbe River

We assessed key relationships of soil organic carbon (SOC) stocks to hydromorphic features, soil texture, C/N ratio, pH, and forest age in hardwood floodplain forests. Floodplain ecosystems play a significant role in the global carbon cycle, particularly due to their SOC storage potential. Interactions between heterogeneous micro-relief and anthropogenically affected vegetation and the hydrologic situation of floodplains make predicting SOC stocks difficult without field validation. Especially within hardwood floodplain forests, the controlling factors for SOC storage remain understudied, whereas these floodplain types can be the largest reservoir for carbon and have a substantial SOC sequestration potential. To determine the controlling factors for SOC storage, we selected 38 hardwood floodplain forest and 11 floodplain grasslands of the lower middle Elbe River and categorized them according to vegetation type (grassland, young forest, or old forest) and hydrologic situation (low-lying or high elevated and active or former floodplain). Profile SOC stocks were determined to a depth of 1 m, and topsoil SOC stocks were related to vegetation and soil characteristics, particularly pedological traits (e.g., hydromorphic features).Forest SOC stocks ranged between 99 and 149 t ha−1. SOC stocks decreased with depth throughout all categories and were unaffected by vegetation type within the same hydrologic situation. Vegetation parameters such as age, basal area, or leaf litter carbon stock had no direct effect on SOC stocks. An active connection to the river had the strongest effect on SOC stocks, with former floodplain sites storing 33% less SOC than the active sites. Within the active floodplains, low sites stored 50% more SOC than high sites. This effect was mainly controlled by relief-affected features such as flooding duration and fine texture, which also were the strongest univariate predictors for SOC stocks (R2 = 0.39 and 0.63). A multiple linear regression showed that fine texture, pH, C/N ratio and forest age can be used to explain 86% of variance in SOC stocks.We conclude that proxies for relief and sedimentation (i.e., hydromorphic features, flooding duration, soil texture, C/N ratio, and pH) are the strongest factors controlling SOC stocks in hardwood floodplain forests. Both can be related to allochthonous carbon inputs, increasing SOC stabilization through the accumulation of fine soil particles, and decreasing aerobic carbon mineralization potential through oxygen scarcity, while vegetation plays only a subordinate role.

Carbon Stocks of Hardwood Floodplain Forests along the Middle Elbe: The Influence of Forest Age, Structure, Species, and Hydrological Conditions

Hardwood floodplain (HF) forests can store a considerable amount of carbon (C), and floodplains may be good candidates for reforestation to provide natural C sinks. In this study, we use nondestructive inventory methods to estimate the C stocks of different tree species and C pools within HF forests of varying age and structure and located at sites differing in hydrological conditions (low and high active floodplain, seepage water zone, tributaries). The study was carried out along the Elbe river (Germany). Average C stocks for young plantations in the active floodplain were significantly lower (50.2 ± 10.8 SE Mg ha−1) than those of old dense (140.6 ± 11.6 SE Mg ha−1) and old sparse forests (180.4 ± 26.6 SE Mg ha−1) with comparable hydrological conditions. C stocks of old dense forests did not significantly vary from old sparse forests. Additionally, C stocks of old forests did not significantly vary according to hydrological conditions. The highest amount of C was stored in Quercus robur for all hydrological conditions. Ulmus laevis stored the second-highest amount of C on the active floodplain. We conclude that sparse and dense forests as well as forests under different hydrological conditions provide the same C storage function.

Defining the baseline for river restoration: comparing carabid beetle diversity of natural and human-impacted riparian habitats

Near-natural rivers and riparian ecosystems can represent biodiversity hotspots harbouring many highly specialised, rare and endangered species. During the past centuries, these habitats have been heavily degraded by anthropogenic use, and therefore river restoration is one of the most striking fields of action that is legally defined by the European Union Water Framework Directive. Successful restoration depends on realistic and specified targets that should be defined beforehand and founded on status quo surveys. We present a comparison of carabid beetle communities in riparian habitats of natural and managed river sites of the Mulde River in the Biosphere Reserve Middle Elbe. This endeavour is part of a unique multi-level revitalisation project. Pitfall trapping in 2016 and 2017 yielded 111 carabid species with many species of conservation concern in natural and managed habitats. However, Simpson diversity and functional diversity were lower in the latter. Both habitats harboured specific species assemblages with characteristic indicator species. Additionally, the trap location on slip-off slopes or cut banks was a significant driver of species composition. Our results indicate high ecological development potentials for the Mulde River, but restoration should consider differences between slip-off slopes and cut-off banks. We postulate that future restoration will foster population increases as well as a wider distribution of rare and endangered riparian habitat specialists.

Quality of Dissolved Organic Matter Driven by Autotrophic and Heterotrophic Microbial Processes in a Large River

Rivers are regarded as important sites for processing of dissolved organic matter (DOM) from terrestrial sources on its way to the ocean. However, little is known about the longitudinal change of DOM molecular composition in large rivers. Here we performed a Lagrangian sampling in the lower part of the Middle Elbe at low discharge conditions to test how DOM composition changes along the river stretch and how this is related to microbial processes. The concentration of dissolved organic carbon and fluorescence indices showed only subtle longitudinal differences. In contrast, ultra-high-resolution mass spectrometry analysis of riverine DOM detected pronounced changes in molecular composition. Also, chlorophyll a concentration, bacterial abundance, and bacterial production all increased downstream. The three microbial parameters were positively related to intensities of CHO and CHNO molecular formulas with high hydrogen/carbon and low oxygen/carbon ratios but negatively to several CHOS surfactants. To disentangle the role of autotrophic and heterotrophic processes, we developed a new approach and compared slopes from linear regression of DOM compound intensities versus chlorophyll a concentration and bacteria abundance. As a result, most of the positive related DOM compounds were produced by bacteria. In conclusion, longitudinal changes of river DOM seemed to be largely driven by microbial processes.

Bronze Age Beginnings – a Scalar View from the Global Outskirts

This article tracks the formation of the rich and socially complex Nordic Bronze Age (NBA),c.2000–1500bc, by applying a scalar methodology and using theentrepôtand early metalworking site of Pile in Scania as its point of departure. By regarding the Bronze Age as an ancient example of globalisation, Island Melanesia at the outskirts of contemporary globalisation is first examined to provide an analogue to the Nordic entrepreneurial and maritime culture into which metallurgy was first adopted. How did this northern margin become ‘Bronze Age’, and what impact did its inclusion have? Various scales, from local to Bronze-Age-global were found to intersect in the Pile hoard, and in similar sites near and far. Byc.2000bc, metals and other commodities travelled along well-established local, regional, and super-regional networks, which even incorporated the British Isles and Únětician hubs at the Middle Elbe–Saale. Back in Scandinavia, metal and metal-related culture provided a comparative advantage when navigating local competition for influence and leadership. The transculturally global was strategically appropriated locally, using the reinvention of tradition as a principal strategy. The first metal boom caused friction and slow social change, rather than a social revolution. The real tipping point came in 1600–1500bc, when the nearly full-blown NBA emerged, through engagement with a considerably expanded world. By this time, large amounts of metal were in circulation. Seen from the non-urban north, this unprecedented expansion of their world brought new opportunities but likely also deep social tensions. Thus, the effects of adopting metallurgy permeated society and connectivity at every level, even at the outskirts of the Bronze Age world.

Causes of death of beavers (Castor fiber) from eastern Germany and observations on parasites, skeletal diseases and tooth anomalies—a long-term analysis

The Eurasian beaver, Castor fiber, was nearly extirpated, and in Germany, the relict population at the Middle Elbe, was strictly protected. In the 1930s, the collection and analysis of carcasses of this then-endangered species began in Zerbst, Anhalt, and since 1957 was continued at the Zoological Institute of the University of Halle, Saxony-Anhalt. Records of varying detail from 1282 beavers found dead were recorded up to the year 2009. Here, this unique and valuable dataset is analysed coherently with the focus on the main causes of death separated by age class, sex, month and decade. Traffic accidents have been the major cause of mortality overall since the 1980s, while infections and inflammations have been the main natural cause, with fluctuating frequency during the decades and a peak in the 1950s. With the increased population size and distribution of beavers, routine collection and analysis of cadavers ceased in Halle in 2009. Here, it is argued however that irrespective of the conservation status of beavers, the regular post-mortem surveillance and analysis, of at least regional samples, allows for general health monitoring and provides knowledge about the prevalence of pathogens and parasites and their occurrence, or emergence, and information about contamination with toxins. Additionally, the specimens can contribute to collections for future studies.

Quaternary (triphenyl-) phosphonium compounds: Environmental behavior and toxicity

An analytical method based on high resolution mass spectrometry coupled with liquid chromatography (LC-HRMS) for 25 quaternary phosphonium compounds (QPCs) and derived phosphine oxides (POs) was developed and validated. To investigate the occurrence and fate of QPCs in the aquatic environment, water, suspended solids and sediments from the rivers Rhine and Elbe (upper and middle Elbe as well as tidal Elbe) were analyzed, as well as samples from tributaries bearing significant loads of QPCs. For the first time, the quaternary phosphonium compound tetrabutylphosphonium (Bu4P+) was detected. In the river Elbe concentrations were determined of up to 4700 ng/L (surface water) and 1000 μg/kg (sediment), respectively. Analysis of a time series of suspended solids (2005–2015) showed that QPCs have been present in the Elbe and Rhine catchment for at least one decade, with partly rising tendency. A degradation experiment with Rhine sediment revealed that triphenylphosphonium compounds (R-Ph3P+) and Bu4P+ are persistent in contact with sediment and suspended solids and tend to sorb onto sediment particles. Toxicological studies (reactive oxygen species (ROS) after substance exposure, Ames test, Micronucleus test, determination of cytotoxicity) with selected QPCs confirmed that all of them exhibit cytotoxicity and some even genotoxic potential at elevated concentrations, which emphasizes the need for an emission regulation of these compounds.

FloMan-MF: Floodplain Management for the Moor Frog − a simulation model for amphibian conservation in dynamic wetlands

We present a modeling approach to assess the impact of different conservation management options on the population dynamics of the moor frog (Rana arvalis, Amphibia, Anura) in dynamic river floodplains. The model is targeted at supporting amphibian conservation actions within floodplain management efforts for human flood protection. FloMan-MF is an individual-based, spatially explicit simulation model that combines three aspects: the hydrological dynamics of the landscape influenced by floods, frog reproductive behavior modeled through migration and selection of suitable reproduction sites (ponds), and population structure and trajectory over time. We validated each of the three systems and applied the baseline scenario to a two-year case study conducted in the Middle Elbe River floodplain (Germany). The FloMan-MF model aims to identify suitable compositions of floodplain ponds and habitat characteristics to optimize the reproductive habitat for moor frogs in a degraded floodplain. Therefore, to show potential applications of the model, we simulated floodplain habitat degradation and five different management scenarios. The population responded differently to each of the simulated management actions, ranging from rapid extinction to recovery with low numbers of individuals. The partly unexpected results reveal complex interactions in species-habitat interactions over time. According to our results, the establishment of dynamic temporary ponds seems to be a basic condition for population persistence of this species and can be realized within floodplain management activities. Extending the rationale and basic design of FloMan-MF to other amphibian species living in floodplains is straightforward.

Flood-event based metal distribution patterns in water as approach for source apportionment of pollution on catchment scale: Examples from the River Elbe

Summary With the implementation of European Water Frame Work Directive (EU-WFD), the pollution sources in the River Elbe were assessed by the River Basin Community Elbe (RBC Elbe). Contaminated old sediments played the most significant role for inorganic and organic pollution. In terms of further improvement of the water quality in the river system, a prioritization of the known pollution sources is necessary, with respect to the expected effect in the case of their remediation. This requires information on mobility of contaminated sediments. To create a tool that allows the assessment of pollution trends in the catchment area, event based flood investigations were carried out at a sampling site in the Middle Elbe. The investigations were based on a comparable, discharge related sampling strategy. Four campaigns were performed between 1995 and 2006. The majority of the investigated 16 elements (>80%) studied more intensively in 2006 reached its maximum concentration during the first five days of the event. Only the concentrations of B, Cl − , and U declined with increasing discharge during the flood. The aim of the study was to verify that each flood event is characterized by an internal structure of the water quality. This structure is formed by the appearance of maximum values of water quality parameters at different times during the event. It could be detected by descriptive and multivariate statistical methods. As a result, internal structure of the water quality during the flood was influenced primarily by the source of the metals in the catchment area and its distance from the sampling point. The transport of metals in dissolved, colloidal or particulate form and changes of their ratios during the flood were however, not decisive for the formation of the structure. Our results show that the comparison of the structures obtained from events in different years is indicative of the pollution trend in the catchment area. Exemplarily the trend of the metal pollution in the River Elbe will be discussed.

Dyke-slotting initiated rapid recovery of habitat specialists in floodplain mollusc assemblages of the Elbe River, Germany

Dyke openings are regarded as suitable measures for restoring biodiversity and ecosystem functioning in degraded floodplains. Nevertheless, only few studies evaluate the effects and success of such measures on biodiversity. The present work analyses the influence of one of the first dyke-slotting projects carried out along the Middle Elbe River (Germany) on floodplain mollusc assemblages. By applying a before-after-reference-control-impact-monitoring design, we specifically tested how species diversity and composition responded to the restoration measure. Floodplain reconnection led to a considerable increase in mollusc diversity. However, the overall community turnover was rather small only present among species with high soil humidity preferences. They mainly profited from the frequent floodings shifting species composition to be more hygrophilous and floodplain characteristic. Moderately hygrophilous and desiccation tolerant species were almost not affected by the dyke-slotting. Presumably, this can be explained by the already similar species composition of the active reference and the reactivated floodplain due to a high seepage water influence. So far, this indicates a successfully initiated recovery process. All in all, our results emphasize the crucial need of long-term monitoring to reveal the full ecological effects of restoration measures and the consideration of diversity-, community-, and species-level responses to evaluate restoration success.

Vegetation patterns of floodplain meadows along the climatic gradient at the Middle Elbe River

Central European floodplain meadows are characterised by flooding mainly in winter/spring and dry conditions over the summer. They harbour many rare and endangered plant species. We studied the vegetation of floodplain meadows along the regional climatic gradient of the Middle Elbe River. This gradient exhibits rather continental conditions in the south-east and oceanic conditions in the north-west. We aimed at detecting the influence of climate on the vegetation of floodplain meadows along this gradient.Along the Middle Elbe River (Germany), we recorded the vegetation of wet and mesic meadows in 2010. The results revealed differences in species composition especially in wet meadows: vegetation plots of wet meadows clustered in the DCA ordination according to their geographic location from west to east. Sample scores of DCA-axes of both meadow types correlated with the long-term means of climatic factors such as precipitation or temperature. While species numbers did not differ between study sites, evenness of mesic meadows was higher in the western part of the gradient.Indicative species of the sites were mainly common meadow species. Species typical for floodplain meadows were relatively evenly distributed along the gradient. Therefore, we confirm that the distribution of typical floodplain species is largely determined by hydrologic and land use conditions rather than by climatic factors. Therefore, we assume that typical floodplain meadow species at the Elbe River are relatively robust against direct climatic changes, as long as these changes do not exceed the range of the climatic gradient today. Concerning the total assemblages of floodplain meadows, those of wet meadows might be more vulnerable to climate change than those of mesic meadows. However, indirectly occurring changes caused by climate change, i.e. water-level changes due to an altered discharge regime of the Elbe River caused by altered precipitation patterns in the catchment, will affect all floodplain species.

Differential effects of reduced water potential on the germination of floodplain grassland species indicative of wet and dry habitats

AbstractFloodplain meadow ecosystems are characterized by high water level fluctuations and highly variable soil water potentials. Additionally, climate change scenarios indicate an increasing risk for summer drought along the northern Upper Rhine and the Middle Elbe River, Germany. While adult plants often persist even after strong changes in water availability, early life phases, such as seed germination and seedling establishment, might be more vulnerable. Therefore we tested whether reduced soil water potentials will affect the germination of meadow species and whether the response varies between (1) forbs indicative of wet and dry habitats and (2) seeds originating from sites along the rivers Elbe and Rhine. We exposed seeds of 20 floodplain meadow species with different moisture requirements from five plant families to a water potential gradient ranging from 0 to − 1.5 MPa. While across species germination percentage and synchrony decreased, germination time increased at reduced water potentials. Germination of the species indicative of dry habitats decreased more strongly, was slower and less synchronous at reduced water potentials than that of species indicative of wet habitats. Seeds from sites along the rivers Elbe and Rhine did not differ in their germination characteristics. We propose that species of wet sites follow an all-or-nothing-strategy with fast and synchronous germination to maximize competitive advantages, betting on a high probability of moist conditions for establishment (optimists). In contrast, species from dry sites appear to follow a bet-hedging strategy with a moisture-sensing mechanism for unsuitable conditions (pessimists), resulting in a slower and less synchronous germination.