Oldenburg, Germany
Oldenburg, Germany

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Wiegleb G.,Sudan University of Science and Technology | Herr W.,IBL Umweltplanung GmbH | Zander B.,University of Applied Sciences Neubrandenburg | Broring U.,Sudan University of Science and Technology | And 2 more authors.
Limnologica | Year: 2015

In the present study, we present a synopsis of two macrophyte surveys of physiographic units in northwest Germany carried out over one decade. Data were used to test a set of hypotheses on macrophyte distribution at the regional level. Rank-frequency curves resembled the broken stick model. Twenty-one species of the 59 most frequent species occurred at high frequencies above 15%. Helophytes made up a high percentage (12 of 21) of the frequent species. Phalaris arundinacea was the most frequent species in both sampling periods. Most species showed no considerable change in frequency over time, among them the core hydrophytes. Spatial variation of species frequencies among physiographical units showed a unimodal distribution in relation to frequency. Spatial variation of frequencies of functional groups was significantly lower. Most uneven distribution among physiographical units was found in cryptogams. DCA ordinations of physiographical units showed a spatial gradient from alluvial plains to higher grounds units, which remained constant over time. CCA ordination of physiographical units in relation to environmental parameters identified two main axes, an altitudinal gradient and an alkalinity gradient. Species composition of units corresponded to the main landscape pattern of alluvial plains, glacial lowlands, and higher grounds on Mesozoic rock. Species diversity showed a complex behavior. Diverse units were found both in alluvial plains and glacial lowlands of intermediate elevation. The study may help defining regionally differentiated reference states for stream management, benchmarking indicator scores of species and avoiding application of assessment methods outside their range of applicability. © 2014 The Authors.


Bellebaum J.,Wiesenstrasse 9 | Kube J.,Dorfstr. 20 | Schulz A.,Institute Fur Angewandte OKosystemforschung GmbH | Skov H.,DHI | Wendeln H.,IBL Umweltplanung GmbH
Ornis Fennica | Year: 2014

Abundance of Long-tailed Ducks Clangula hyemalis wintering in the Pomeranian Bay wasmonitored between 1988 and 2014, using both ship-based and aerial surveys and correcting for distance dependent detection. Aerial surveys were conducted using an improved transect division and a double observer design to estimate detection probability near the transect line. As the latter probability was considerably below 1, we applied an additional correction factor for observer efficiency. After correcting for observer efficiency in aerial surveys, the two methodological approaches yielded similar densities, though an apparent underestimation in aerial surveys warrants further cross-validation. Density estimates from both platforms were merged for further analysis. After reaching peak levels in 1992 and 1993, Long-tailed Duck winter densities in the Pomeranian Bay declined by 82% until 2010. This decline was part of an overall decline in numbers throughout the Baltic Sea. An apparent increase since 2010, whichwas likely due to local ice-induced movements, indicates that habitats in the study area may still support high densities today.


Steffen K.,University of Gottingen | Becker T.,University of Gottingen | Becker T.,University of Trier | Herr W.,IBL Umweltplanung GmbH | Leuschner C.,University of Gottingen
Hydrobiologia | Year: 2013

This resampling study in 338 semi-permanent plots analyses changes in river macrophyte diversity in 70 water courses (small streams to medium-sized rivers) from four regions of the northwest German lowlands during the last six decades. The total macrophyte species pool decreased between the 1950s and 2010/2011 by 28% (from 51 to 37 species), mean plot-level species richness by 19% (from 4.7 to 3.8 species per relevé) and the number of red-listed species by 40% (from 30 to 18 species). Species loss was associated with marked change in species traits: species with presumably higher mechanical stress tolerance (indicated by low specific leaf area and short leaf longevity) are more abundant today. Nearly, half of the species present in the 1950s had either disappeared or been replaced by other species in the recent relevés. The dramatic impoverishment is likely a consequence of continued nutrient input that drove oligo- and mesotraphent species to extinction, and of restructuring and maintenance works in the water courses that reduced stagnant and undisturbed river habitats, where stress-intolerant species can persist. Efficient measures to reduce the nutrient load and to re-naturalise stream and river beds are urgently needed to halt and reverse the loss of macrophyte diversity. © 2013 The Author(s).


Demars B.O.L.,James Hutton Institute | Wiegleb G.,Sudan University of Science and Technology | Harper D.M.,University of Leicester | Broring U.,Sudan University of Science and Technology | And 2 more authors.
Water (Switzerland) | Year: 2014

The spatial structure and evolution of river networks offer tremendous opportunities to study the processes underlying metacommunity patterns in the wild. Here we explore several fundamental aspects of aquatic plant biogeography. How stable is plant composition over time? How similar is it along rivers? How fast is the species turnover? How does that and spatial structure affect our species richness estimates across scales? How do climate change, river management practices and connectivity affect species composition and community structure? We answer these questions by testing twelve hypotheses and combining two spatial surveys across entire networks, a long term temporal survey (21 consecutive years), a trait database, and a selection of environmental variables. From our river reach scale survey in lowland rivers, hydrophytes and marginal plants (helophytes) showed contrasting patterns in species abundance, richness and autocorrelation both in time and space. Since patterns in marginal plants reflect at least partly a sampling artefact (edge effect), the rest of the study focused on hydrophytes. Seasonal variability over two years and positive temporal autocorrelation at short time lags confirmed the relatively high regeneration abilities of aquatic plants in lowland rivers. Yet, from 1978 to 1998, plant composition changed quite dramatically and diversity decreased substantially. The annual species turnover was relatively high (20%-40%) and cumulated species richness was on average 23% and 34% higher over three and five years respectively, than annual survey. The long term changes were correlated to changes in climate (decreasing winter ice scouring, increasing summer low flows) and management (riparian shading). Over 21 years, there was a general erosion of species attributes over time attributed to a decrease in winter ice scouring, increase in shading and summer low flows, as well as a remaining effect of time which may be due to an erosion of the regional species pool. Temporal and spatial autocorrelation analyses indicated that long term hydrophyte biomonitoring, for the Water Framework Directive in lowland rivers, may be carried out at 4-6 years intervals for every 10 km of rivers. From multi-scale and abundance-range size analyses evidence of spatial isolation and longitudinal connectivity was detected, with no evidence of stronger longitudinal connectivity (fish and water current propagules dispersal) than spatial isolation (bird, wind and human dispersal) contrary to previous studies. The evidence for longitudinal connectivity was rather weak, perhaps resulting from the effect of small weirs. Further studies will need to integrate other aquatic habitats along rivers (regional species pool) and larger scales to increase the number of species and integrate phylogeny to build a more eco-evolutionary approach. More mechanistic approaches will be necessary to make predictions against our changing climate and management practices. © 2014 by the authors.


Wiegleb G.,TU Brandenburg | Broring U.,TU Brandenburg | Filetti M.,TU Brandenburg | Brux H.,IBL Umweltplanung GmbH | Herr W.,IBL Umweltplanung GmbH
Freshwater Biology | Year: 2014

Continuous multiyear data sets can help to detect long-term trends and allow predictions with respect to environmental and biological variables. While the use of taxon-based approaches for biomonitoring of watercourses is well established, little information exists concerning long-term variability of dominance and growth form composition of aquatic macrophyte communities. We analysed patterns in dominance and growth forms of macrophytes over a period of 21 years in relation to changes in water chemistry, disturbance regime and extreme weather conditions in two reference streams in the north-west German lowlands. Rank-abundance curves of annual observations indicated five core species. The pattern of abundance resembled a broken-stick rather than a log-normal distribution. The core species, which reached both the highest absolute and average cover values, were Sparganium emersum, Elodea canadensis, Callitriche hamulata, Potamogeton natans and Ranunculus peltatus. An analysis of change in dominance showed that in 67.5% of all observed cases, the same species became dominant in the subsequent year. Sparganium emersum (80.6%) and E. canadensis (68.8%) were the most successful species in retaining their relative dominance. Calculation of transition probabilities showed a strong attractor function of states dominated by Sparganium and Elodea. However, dominance patterns broke down over time and after 20 years, only one of the sites still showed the same dominance type. On average, dominance was preserved for around 4 years. Reaches were mostly dominated by six growth forms, namely vallisnerids, potamids, peplids, nymphaeids, myriophyllids and graminids. In each reach, two, three or five growth forms shared the highest cover percentages. An analysis of traits of successfully established and dominant species identified three strategies: a facultative wintergreen growth habit in combination with effective means of vegetative reproduction; strong maintenance traits (in particular rhizomes); short-life span in combination with seed and turion production. Strong oscillations of growth form types were observed. Six growth form clusters were defined, up to four of which may occur in one reach. Most frequent clusters were one characterised by strong vallisnerid dominance and another characterised by dominant potamids with peplids and myriophyllids. Both clusters showed the highest frequencies, durations and transition probabilities from other clusters. On average, growth form clusters persisted for 4.5 years. An analysis of the influence of environmental factors on growth form dynamics showed that chemical and physical parameters distinguish the sample sites but cannot explain the observed changes. We conclude that dynamics of species dominance as well as the occurrence of growth form assemblages are not controlled by physicochemical environmental factors such as nutrient composition at the scale of observation in this type of river. Instead, stochastic interactions between species characteristics and single disturbance events or weather extremes must be assumed. Implications for nature conservation, biomonitoring and reconstruction of reference sites are discussed. Continuous multiyear sampling is essential to understand the temporal behaviour of the system. © 2014 The Authors. Freshwater Biology published by John Wiley & Sons Ltd.


Marsh ditches were created for drainage and irrigation in marsh areas and are of great importance for the aquatic flora. The habitat conditions of aquatic plants underwent serious changes since 1970. Ditch structures have been adjusted to the requirements of machinery, their number has reduced and ditch maintenance has switched from manual to machine work. A comparison of data from the last 230 years shows the decline of the flora, but also the still existing floristic potential. This potential is vital to achievement of the goals of the European Water Framework Directive and provides the basis for conservation models.


Paetzold A.,IBL Umweltplanung GmbH | Paetzold A.,University of Sheffield | Smith M.,IBL Umweltplanung GmbH | Warren P.H.,IBL Umweltplanung GmbH | Maltby L.,IBL Umweltplanung GmbH
Ecology | Year: 2011

Resource subsidies between habitats are common and create the potential for the propagation of environmental impacts across system boundaries. However, recent understanding of the potential for subsidy-mediated cross-system impact propagations is limited and primarily based on passive flows of nutrients and detritus or short-term effects. Here, we assess the effects of sustained alterations in aquatic insect emergence (active subsidy pathway), due to chronic stream pollution, for riparian spiders. The sustained reduction in aquatic insect densities at the polluted reaches resulted in a marked decline in web spider population density and a shift in spider community composition. Our results provide the first evidence that stream pollution can control populations and community structure of terrestrial predators via sustained alterations in aquatic subsidies, emphasizing the role of subtle trophic linkages in the transmission of environmental impacts across ecosystem boundaries. © 2011 by the Ecological Society of America.

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