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River Floodplain (river + floodplain)
Kinds of River Floodplain Selected AbstractsThe Temporal Asynchrony of Planktonic Cladocerans Population at Different Environments of the Upper Paraná River FloodplainINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 6 2008Erica Mayumi Takahashi Abstract The aim of this study was to investigate the existence of synchronic fluctuation patterns in cladoceran populations of the Upper Paraná River floodplain. The following hypothesis were tested: (i) the populations of a given species present the same fluctuation pattern in abundance for different environments and (ii) synchrony is higher when we consider subsets of neighboring environments or those belonging to the same category (e.g., lagoons, rivers). Samplings were performed every three months from February 2000 to November 2002 at 11 sites. To evaluate spatial synchrony, the intraclass correlation coefficient was used. The results showed no significant correlation for the most abundant species, meaning that fluctuation patterns of planktonic cladocerans were asynchronous. Asynchrony indicated that the influence of floods and regional climatic factors was not strong enough to synchronize the populations, suggesting that local factors were more important than regional effects in determining zooplankton abundance patterns. The implications of these results are that the observations from a single environment cannot be extrapolated to other environments in a manner that would allow its use as a sentinel site. This means that a monitoring program for floodplain systems, or at least for the Paraná River floodplain, has to comprise greater spatial extents. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of Environmental Heterogeneity on the Structure of Testate Amoebae (Protozoa, Rhizopoda) Assemblages in the Plankton of the Upper Paraná River Floodplain, BrazilINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 2 2003Luiz Felipe Machado Velho Abstract In freshwater environments, testate amoebae are usually found associated with macrophytes and sediments and many studies have suggested that their occurrence in plankton samples is accidental. This implies that predictable patterns detected in planktonic assemblages should not be observed in testate amoebae assemblages. This hypothesis was tested in this study. Plankton samples were collected from different environments in the Upper Paraná River floodplain. Results show that patterns in species composition and abundance of testate amoebae are predictable, and that dominant species tend to present characteristic shell morphology in hydrologically different environments. We suggest that testate amoebae must be routinely included in plankton ecology studies, at least in floodplain environments. [source] Effects of spatial variations in source areas upon dust concentration profiles during three wind erosion events in AustraliaEARTH SURFACE PROCESSES AND LANDFORMS, Issue 10 2001H. J. Butler Abstract Dust storms are a major contributor to soil erosion in inland Australia, and the Simpson Desert,Channel Country region is one of the most active wind erosion regions. While information is available on wind erosion rates at the land-type level, little is known about the influence that spatial variations in the erodibility within a land type have on the resulting dust concentration profile. A Gaussian plume model, DSIS, is presented along with tower-based dust data, to describe the influence of different spatial combinations of dust source areas, during three dust events on the Diamantina River floodplain in Western Queensland, Australia. Copyright © 2001 John Wiley & Sons, Ltd. [source] Productivity of American robins exposed to polychlorinated biphenyls, Housatonic River, Massachusetts, USAENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2003Miranda H. Henning Abstract American robins (Turdus migratorius) breeding in the Housatonic River (MA, USA) watershed were studied in the field in 2001 to determine whether productivity was adversely affected by exposure to polychlorinated biphenyls (PCBs), as would be suggested by extrapolation from laboratory studies on other avian species. The study involved identifying nests within the Housatonic River floodplain (target area) and in reference areas beyond foraging distance of the floodplain, monitoring clutch size and number hatched and fledged, collecting eggs and nestlings for analysis for PCBs, and testing for differences in productivity between populations. One hundred and six active robin nests were monitored. Although concentrations of PCBs in target specimens were more than two orders of magnitude greater than in reference specimens, the only statistically significant differences in productivity were inconsistent with an exposure-related effect. First-generation productivity of exposed robins was within the range of natural background variation. Bioequivalence tests confirmed that first-generation productivity was statistically and biologically equivalent in target and reference robins. These findings contrast with extrapolations from laboratory studies of other avian species. [source] Adaptive management of an environmental watering event to enhance native fish spawning and recruitmentFRESHWATER BIOLOGY, Issue 1 2010A. J. KING Summary 1. A common goal of many environmental flow regimes is to maintain and/or enhance the river's native fish community by increasing the occurrence of successful spawning and recruitment events. However, our understanding of the flow requirements of the early life history of fish is often limited, and hence predicting their response to specific managed flow events is difficult. To overcome this uncertainty requires the use of adaptive management principles in the design, implementation, monitoring and adjustment of environmental flow regimes. 2. The Barmah-Millewa Forest, a large river red gum forest on the Murray River floodplain, south-east Australia, contains a wide variety of ephemeral and permanent aquatic habitats suitable for fish. Flow regulation of the Murray River has significantly altered the natural flood regime of the Forest. In an attempt to alleviate some of the effects of river regulation, the Forest's water regime is highly managed using a variety of flow control structures and also receives targeted Environmental Water Allocations (EWA). In 2005, the largest environmental flow allocated to date in Australia was delivered at the Forest. 3. This study describes the adaptive management approach employed during the delivery of the 2005 EWA, which successfully achieved multiple ecological goals including enhanced native fish spawning and recruitment. Intensive monitoring of fish spawning and recruitment provided invaluable real-time and ongoing management input for optimising the delivery of environmental water to maximise ecological benefits at Barmah-Millewa Forest and other similar wetlands in the Murray-Darling Basin. 4. We discuss possible scenarios for the future application of environmental water and the need for environmental flow events and regimes to be conducted as rigorous, large-scale experiments within an adaptive management framework. [source] Behavioural responses of a south-east Australian floodplain fish community to gradual hypoxiaFRESHWATER BIOLOGY, Issue 3 2007DALE G. MCNEIL Summary 1. Hypoxic conditions occur frequently during hot, dry summers in the small lentic waterbodies (billabongs) that occur on the floodplains of the Murray-Darling River system of Australia. Behavioural responses to progressive hypoxia were examined for the native and introduced floodplain fish of the Ovens River, an unregulated tributary of the Murray River in south-east Australia. 2. Given the high frequency of hypoxic episodes in billabongs on the Ovens River floodplain, it was hypothesised that all species would exhibit behaviours that would confer a degree of hypoxia-tolerance. Specifically, it was hypothesised that as hypoxia progressed, gill ventilation rates (GVRs) would increase and aquatic surface respiration (ASR) would become increasingly frequent. Fish were subjected to rapid, progressive hypoxia from normoxia to anoxia in open tanks. 3. All tested species exhibited behaviours consistent with their use of potentially hypoxic habitats. As hypoxia progressed, GVRs increased and all species, with the exception of oriental weatherloach, began to switch increasingly to ASR with 90% of individuals using ASR at various oxygen concentrations below 1.0 mg O2 L,1. Australian smelt, redfin perch and flat-headed galaxias were the first three species to rise to ASR, with 10% of individuals using ASR by 2.55, 2.29 and 2.21 mg O2 L,1 respectively. Goldfish and common carp were the last two species to rise to ASR, with 10% of individuals using ASR by 0.84 and 0.75 mg O2 L,1 respectively. In contrast to other species, oriental weatherloach largely ceased gill ventilation and used air-gulping as their primary means of respiration during severe hypoxia and anoxia. 4. Australian smelt, redfin perch and flat-headed galaxias were unable to maintain ASR under severe hypoxia, and began exhibiting erratic movements, termed terminal avoidance behaviour, and loss of equilibrium. All other species continued to use ASR through severe hypoxia and into anoxia. Following a rise to ASR, GVRs either remained steady or decreased slightly indicating partial or significant relief from hypoxic stress for these hypoxia-tolerant species. 5. Behavioural responses to progressive hypoxia amongst the fish species of the Ovens River floodplain indicate a generally high level of tolerance to periodic hypoxia. However, species-specific variation in hypoxia-tolerance may have implications for community structure of billabong fish communities following hypoxic events. [source] The Temporal Asynchrony of Planktonic Cladocerans Population at Different Environments of the Upper Paraná River FloodplainINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 6 2008Erica Mayumi Takahashi Abstract The aim of this study was to investigate the existence of synchronic fluctuation patterns in cladoceran populations of the Upper Paraná River floodplain. The following hypothesis were tested: (i) the populations of a given species present the same fluctuation pattern in abundance for different environments and (ii) synchrony is higher when we consider subsets of neighboring environments or those belonging to the same category (e.g., lagoons, rivers). Samplings were performed every three months from February 2000 to November 2002 at 11 sites. To evaluate spatial synchrony, the intraclass correlation coefficient was used. The results showed no significant correlation for the most abundant species, meaning that fluctuation patterns of planktonic cladocerans were asynchronous. Asynchrony indicated that the influence of floods and regional climatic factors was not strong enough to synchronize the populations, suggesting that local factors were more important than regional effects in determining zooplankton abundance patterns. The implications of these results are that the observations from a single environment cannot be extrapolated to other environments in a manner that would allow its use as a sentinel site. This means that a monitoring program for floodplain systems, or at least for the Paraná River floodplain, has to comprise greater spatial extents. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of Environmental Heterogeneity on the Structure of Testate Amoebae (Protozoa, Rhizopoda) Assemblages in the Plankton of the Upper Paraná River Floodplain, BrazilINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 2 2003Luiz Felipe Machado Velho Abstract In freshwater environments, testate amoebae are usually found associated with macrophytes and sediments and many studies have suggested that their occurrence in plankton samples is accidental. This implies that predictable patterns detected in planktonic assemblages should not be observed in testate amoebae assemblages. This hypothesis was tested in this study. Plankton samples were collected from different environments in the Upper Paraná River floodplain. Results show that patterns in species composition and abundance of testate amoebae are predictable, and that dominant species tend to present characteristic shell morphology in hydrologically different environments. We suggest that testate amoebae must be routinely included in plankton ecology studies, at least in floodplain environments. [source] Interactive controls of herbivory and fluvial dynamics on landscape vegetation patterns on the Tanana River floodplain, interior AlaskaJOURNAL OF BIOGEOGRAPHY, Issue 9 2007Lem G. Butler Abstract Aim, We examined the interactive effects of mammalian herbivory and fluvial dynamics on vegetation dynamics and composition along the Tanana River in interior Alaska. Location, Model parameters were obtained from field studies along the Tanana River, Alaska between Fairbanks (64°50.50, N, 147°43.30, W) and Manley Hot Springs (65°0.0, N, 150°36.0, W). Methods, We used a spatially explicit model of landscape dynamics (ALFRESCO) to simulate vegetation changes on a 1-year time-step. The model was run for 250 years and was replicated 100 times. Results, Increases in herbivory decreased the proportion of early successional vegetation and increased the proportion of late successional vegetation on the simulated landscape. Erosion and accretion worked as antagonists to herbivory, increasing the amount of early successional vegetation and decreasing the amount of late successional vegetation. However, the interactive effects of herbivory and erosion/accretion were especially important in determining system response, particularly in early seral vegetation types. High erosion rates, when coupled with low herbivory, greatly increased the proportion of willow on the landscape. When coupled with high herbivory, however, they greatly increased the proportion of alder on the landscape. At low levels of herbivory, alder abundance peaked at intermediate levels of erosion/accretion. Main conclusions, Neither erosion/accretion nor herbivory produced consistent landscape patterns that could be predicted independently of the other. These findings underscore the importance of the interactive effects of biotic and abiotic disturbances in shaping large-scale landscape vegetation patterns in boreal floodplain ecosystems , systems traditionally thought to be driven primarily by abiotic disturbance alone. [source] Relationships between fish assemblages, macrophytes and environmental gradients in the Amazon River floodplainJOURNAL OF FISH BIOLOGY, Issue 3 2003P. Petry During the flood season of 1992,1993, 139 species of fishes were collected from a floodplain lake system in the central Amazon Basin. Fish species distribution was examined relative to abiotic variables in seven vegetation strata on Marchantaria Island, Solimões River. Both environmental variables and species distributions were influenced by a river channel to floodplain-interior gradient. Species diversity was significantly higher in vegetated areas than in unvegetated areas, with deeper water Paspalum repens stands harbouring the highest diversity. As a result, species richness and catches were positively related to habitat complexity, while catch was also negatively related to dissolved oxygen (DO) and water depth. Low DO and shallow waters appeared to act as a refuge from predation. Fish assemblages were related to water chemistry, but species richness was not. Canonical correspondence analysis provided evidence that floodplain fish assemblages formed by the 76 most common species were influenced by physical variables, macrophyte coverage and habitat complexity, which jointly accounted for 67% of the variance of fish species assemblages. Omnivores showed no pattern relative to the river channel to floodplain-interior gradient while detritivores were more likely to be found at interior floodplain sites and piscivores closer to the river. Piscivores could be further separated into three groups, one with seven species associated with free-floating macrophytes in deep water, a second with five species found in shallow waters with rooted grasses and a third with six open water orientated species. The results suggest that fish assemblages in the Amazon floodplain are not random associations of species. [source] Temporal distribution and composition of the ichthyoplankton from Leopoldo's Inlet on the Upper Paraná River floodplain (Brazil)JOURNAL OF ZOOLOGY, Issue 4 2002Reinaldo José de Castro Abstract Temporal distribution and composition of ichthyoplankton and their relationships with some environmental variables of Leopoldo's Inlet (Ressaco do Leopoldo) on the upper Paraná River floodplain, southern Brazil, were analysed. Samples were taken from February 1991 to February 1992, and 3480 larvae were collected. The highest density of larvae was observed in November 1991 (36.79 larvae/10 m3) at night (night/day ratio 7: 1). Species composition showed a predominance of Characiformes (80%). There was a high density (4.28 larvae/10 m3) of Bryconamericus stramineus throughout almost the whole study period. The majority of the species were more frequently collected at night. Pearson's correlation indicated a relationship between larval density, temperature, and pluviometric index. Leopoldo's Inlet, whose ichthyofauna is mainly composed of grazing and resident species, shows favourable conditions for fish reproduction and development. [source] A fish kill event, hypoxia and other limnological impacts associated with early wet season flow into a lake on the Mary River floodplain, tropical northern AustraliaLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 3-4 2003Simon A. Townsend Abstract The Mary River, in the Australian wet/dry tropics, flows seasonally to inundate a coastal floodplain. In the dry season, the river reduces to a series of disconnected lakes located along the main river channel. This paper examines the impact of riverine inflow, at the beginning of the wet season, on the limnology of Shady Camp Lake, and addresses broader water quality management issues. The first wet season flow of Mary River carried a high biological oxygen demand that reduced the lake's oxygen concentration. The resulting hypoxic conditions prompted fish avoidance behaviour and caused the death of at least 200 fish. There is no evidence of any direct anthropogenic pollution causing the event. After reaching near anoxic conditions, dissolved oxygen concentrations recovered several weeks later, although they remained low. The water quality of the Mary River was characterized by an initial pulse of water with high concentrations of organic carbon, suspended particulate material, colour, total nitrogen and total phosphorus. Phytoplankton biomass, measured as chlorophyll a, did not increase because of nitrogen limitation attributed to low nitrate and ammonia concentrations in the inflow waters. The low concentrations of available nitrogen were probably a result of denitrification, which would have been enhanced by the warm temperatures and low oxygen concentrations. The oxygen sag in Shady Camp Lake caused by the inflow of the Mary River exemplifies the vulnerability of floodplain channel lakes to riverine waters and underscores the need to manage catchment practices to minimize the concentration of labile organic material in the river and its associated oxygen demand. [source] Does stand structure influence susceptibility of eucalypt floodplain forests to dieback?AUSTRAL ECOLOGY, Issue 3 2010SHAUN C. CUNNINGHAM Abstract Forest dieback is a worldwide problem that is likely to increase with climate change and increasing human demands for resources. Eucalyptus camaldulensis forests are an acute example of forest dieback, with 70% of the Victorian Murray River floodplain in some state of dieback. If we are to halt dieback in these floodplain forests, we need to understand what makes stands susceptible to dieback. Forest diebacks are often related to stand structure, with dieback more severe in senescent or high-density stands. We determined whether certain stand structures make these forests more susceptible to dieback. We undertook an extensive survey of 176 stands across 100 000 ha of forest, covering the range of stand condition on this floodplain. Large and small trees (20-, 40-, 80- and 120-cm diameter) showed a similar reduction in the probability of being alive with decreasing stand condition. A slight improvement in stand condition was found at higher densities and basal areas, which may reflect the higher productivity or younger age of these stands. Stand condition was moderately, positively correlated with longitude, with stand condition being higher in the east of the Murray River floodplain where flooding frequencies are currently higher. This suggests that dieback of these floodplain forests would be more effectively mitigated by increased water availability through flooding than by altering stand structure. [source] Fish community characteristics of the lower Gambia River floodplains: a study in the last major undisturbed West African riverFRESHWATER BIOLOGY, Issue 2 2009VASILIS LOUCA Summary 1.,The Gambia River is the last major West African river that has not been impounded. However, a hydroelectric dam is being constructed and substantial changes to the hydrology and ecology of the system are expected. 2.,Little information is available on the impact of water impoundments in semi-arid regions on downstream floodplain fish communities, due to the scarcity of pre-intervention data. Because profound impacts on physical habitat, salinity and nutrient transport can occur downstream of such impoundments, a knowledge of the species-habitat associations of biota such as fishes is necessary for understanding likely changes and how to limit them. 3.,Fish were sampled using cast and hand nets along two transects on the floodplain, and with fyke nets in two ,bolongs' (creeks) from May to November 2005 and 2006 in the lower reaches of the Gambia River, close to the salt water front where ecological changes due to the construction of the dam are likely to be pronounced. 4.,Greatest fish species richness was associated with low conductivity, low pH and deep water. Bolongs held greater species richness compared with other floodplain habitats, probably because they acted as conduits for fish moving on and off the floodplain. Species richness and catch biomass increased rapidly following the first rains and then declined. 5.,Using a multivariate analysis, three main species groups were identified on the floodplain; one associated with deeper water, one with less brackish water and one with shallow, open water. Tilapia guineensis was the commonest species on the floodplains. 6.,The floodplains provide nursery habitats as many fish captured were immature, particularly for species where adults are mainly encountered in the main channel. Several small-sized floodplain specialists were also represented by a high proportion of mature individuals. 7.,Impoundment is expected to reduce seasonal flooding of the floodplain in the lower Gambia River, downstream of the impoundment, resulting in reduced occurrence of aquatic habitats, especially bolongs, together with lower dissolved oxygen and increased salinity, leading to alteration of the floodplain fish communities, benefiting salt-tolerant species, reducing overall species richness and probably reducing floodplain fish production. [source] Waterlogging and canopy interact to control species recruitment in floodplainsFUNCTIONAL ECOLOGY, Issue 4 2010Wiktor Kotowski Summary 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. [source] Rivers as resources, rivers as borders: community and transboundary management of fisheries in the Upper Zambezi River floodplainsTHE CANADIAN GEOGRAPHER/LE GEOGRAPHE CANADIEN, Issue 3 2007JAMES ABBOTT This article examines the recent convergence of community-based and transboundary natural resource management in Africa. We suggest that both approaches have potential application to common-pool resources such as floodplain fisheries. However, a merging of transboundary and community-based management may reinforce oversimplifications about heterogeneity in resources, users, and institutions. A scalar mismatch between the ecosystem of concern in transboundary management and local resources of concern in community-based management, as well as different colonial and post-colonial histories contribute to this heterogeneity. We describe a fishery shared by Namibia and Zambia in terms of hybrid fisheries management. We examine settlement patterns, fishermen characteristics, sources of conflict, and perceptions regarding present and potential forms of fisheries management in the area. We also consider the implications that initiatives to manage resources on the local and ecosystem scale have for these fishing livelihoods. Our findings indicate that important social factors, such as the unequal distribution of population and fishing effort, as well as mixed opinions regarding present and future responsibility for fisheries management will complicate attempts to implement a hybrid community-transboundary management initiative. Les rivières comme ressources, les rivières comme frontières: la gestion communautaire et transfrontière dans la plaine inondable du bassin supérieur de la rivière Zambezi Cet article examine l'état actuel du processus de convergence en Afrique entre gestions communautaire et transfrontalière des ressources naturelles. Nous laissons entendre que les deux approches ont le potentiel pour servir à la gestion de ressources halieutiques communes situées par exemple dans les plaines inondable. Par contre, la fusion des modes de gestion communautaire et transfrontaliers pourrait renforcer l'idée selon laquelle l'hétérogénéité des ressources, usagers et institutions est plus simple qu'elle ne l'est en réalité. Un décalage entre l'écosystème en question dans la gestion transfrontalière et les ressources locales en question dans la gestion communautaire, en plus des diverses histoires coloniales et post-coloniales, contribuent à cette hétérogénéité. Une description de la pêche que partagent la Namibie et la Zambie est présentée en termes d'une gestion hybride de la pêcherie. Nous examinons les schémas de peuplement, les traits distinctifs des populations de pêcheurs, les sources de conflit et les perceptions à l'égard des modes actuels et potentiels de gestion de la pêcherie dans la région. Nous étudions les conséquences que des initiatives en matière de gestion des ressources à l'échelle locale et à celle de l'écosystème peuvent avoir sur ces moyens de subsistance. Les résultats semblent montrer que des facteurs sociaux importants, comme la distribution inégale de la population et l'effort de pêche, ainsi que des opinions partagées concernant l'exercice des responsabilités dans la gestion de la pêcherie peuvent compliquer la tâche de mise en uvre d'une initiative de gestion communautaire et transfrontalière hybride. [source] Biological and ecological traits of benthic freshwater macroinvertebrates: relationships and definition of groups with similar traitsFRESHWATER BIOLOGY, Issue 2 2000Philippe Usseglio-Polatera Summary 1Relating species traits to habitat characteristics can provide important insights into the structure and functioning of stream communities. However, trade-offs among species traits make it difficult to predict accurately the functional diversity of freshwater communities. Many authors have pointed to the value of working with groups of organisms as similar as possible in terms of relationships among traits and have called for definition of groups of organisms with similar suites of attributes. 2We used multivariate analyses to examine separately the relationships among 11 biological traits and among 11 ecological traits of 472 benthic macroinvertebrate taxa (mainly genera). The main objective was to demonstrate (1) potential trade-offs among traits; (2) the importance of the different traits to separate systematic units or functional groupings; and (3) uniform functional groups of taxa that should allow a more effective use of macroinvertebrate biological and ecological traits. 3We defined eight groups and 15 subgroups according to a biological trait ordination which highlighted size (large to small), reproductive traits (K to r strategists), food (animal to plant material) and feeding habits (predator to scraper and/or deposit feeder) as ,significant' factors determining the ordination of taxa. This ordination partly preserved phylogenetic relationships among groups. 4Seven ecological groups and 13 ecological subgroups included organisms with combinations of traits which should be successively more adequate in habitats from the main channel to temporary waters, and from the crenon to the potamic sections of rivers, and to systems situated outside the river floodplain. These gradients corresponded to a gradual shift from (1) rheophilic organisms that lived in the main channel of cold oligotrophic mountain streams to (2) animals that preferred eutrophic habitats of still or temporary waters in lowlands. The groups with similar ecological traits had a more diverse systematic structure than those with similar biological traits. 5Monitoring and assessment tools for the management of water resources are generally more effective if they are based on a clear understanding of the mechanisms that lead to the presence or absence of species groups in the environment. We believe that groups with similar relationships among their species traits may be useful in developing tools that measure the functional diversity of communities. [source] Flood events overrule fertiliser effects on biomass production and species richness in riverine grasslandsJOURNAL OF VEGETATION SCIENCE, Issue 5 2007Boudewijn Beltman Abstract Question: Do severe winter flood events lift the nutrient limitation of biomass production in a river floodplain? How does this affect plant species richness? How long do the effects last? Location: Floodplain grassland on calcareous sandy loam near river Rhine in The Netherlands. Methods: Plots were fertilised with four treatments (control, N, P, N+P) for 21 years; plant species composition, vegetation biomass and tissue nutrient concentrations were determined every year between 1985 and 2005. Results: Fertilisation with N generally increased biomass production and reduced species richness, but these effects varied over time. During the first four years of the experiment, biomass production appeared to be co-limited by N and P, while N fertilisation dramatically reduced plant species richness; these effects became weaker subsequently. Following two extreme winter floods in 1993,94 and 1994,95 and a drought in spring 1996, the effects of fertilisation disappeared between 1998 and 2001 and then appeared again. Flooding caused an overall reduction in species richness (from c. 24 to 15 species m -2) and an increase in biomass production, which were only partly reversed after ten years. Conclusions: Long time series are necessary to understand vegetation dynamics and nutrient limitation in river floodplains, since they are influenced by occasional flood and drought events, whose effects may persist for more than ten years. A future increase in flooding frequency might be detrimental to species richness in floodplain grasslands. [source] Parallel changes in genetic diversity and species diversity following a natural disturbanceMOLECULAR ECOLOGY, Issue 6 2009GUILLAUME EVANNO Abstract We examined the spatial and temporal variation of species diversity and genetic diversity in a metacommunity comprising 16 species of freshwater gastropods. We monitored species abundance at five localities of the Ain river floodplain in southeastern France, over a period of four years. Using 190 AFLP loci, we monitored the genetic diversity of Radix balthica, one of the most abundant gastropod species of the metacommunity, twice during that period. An exceptionally intense drought occurred during the last two years and differentially affected the study sites. This allowed us to test the effect of natural disturbances on changes in both genetic and species diversity. Overall, local (alpha) diversity declined as reflected by lower values of gene diversity HS and evenness. In parallel, the among-sites (beta) diversity increased at both the genetic (FST) and species (FSTC) levels. These results suggest that disturbances can lead to similar changes in genetic and community structure through the combined effects of selective and neutral processes. [source] A review of the importance of freshwater inflow to the future conservation of Lake St LuciaAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 7 2009A. K. Whitfield Abstract 1.Lake St Lucia, the oldest formally protected estuary in the world is under threat from historic and present manipulation of freshwater supplies to the system. 2.Constraints to the functioning of the ecosystem began in 1914 with the commencement of draining and canalization of the Mfolozi Swamp to open up the swamp and river floodplain for sugar cane cultivation. Warner's Drain was completed in 1936 and the sediment filtering capability of the swamp on river floodwaters was effectively removed. This resulted in exceptionally high sediment loads from the Mfolozi River entering directly into the St Lucia system and the river was therefore diverted southwards and provided with a separate estuary mouth. This deprived St Lucia of its single largest freshwater supply. 3.During the past 50,60 years, increasing freshwater abstractions from the Mkhuze, Mzinene, Hluhluwe and Nyalazi rivers have contributed to the increasingly severe salinity extremes experienced by Lake St Lucia. In the past decade, desiccation of large areas of False Bay, North and South Lake has occurred, due primarily to natural estuary mouth closure combined with a prolonged drought and unnaturally low freshwater inflows during the closed phase. These events have pushed the system into an extreme state that has not been recorded previously and would not have occurred if Mfolozi River water had been available to the St Lucia system over this drought period. 4.Forestry plantations have further exacerbated the freshwater supply situation, although recent removal of pine plantations on the eastern and western shores of the lake are likely to help restore groundwater flows to the system. 5.This review explores the possibility of relinking the Mfolozi River, once the Mfolozi floodplain swamp has been re-established, to the St Lucia system, thereby bringing urgently needed fresh water to this threatened World Heritage Site. Copyright © 2009 John Wiley & Sons, Ltd. [source] Terrestrial invertebrates inhabiting lowland river floodplains of Central Amazonia and Central Europe: a reviewFRESHWATER BIOLOGY, Issue 4 2002JOACHIM ADIS 1.,Amazonian terrestrial invertebrates produce high population densities during favourable periods and may suffer a drastic decrease during occasional floods and droughts. However, the monomodal, predictable flood pulse of the larger Amazonian rivers favours the development of morphological (respiratory organs, wing-dimorphism), phenological (synchronization of life cycles, univoltine mode of life), physiological (flooding ability, gonad dormancy, alternating number of developmental stages), and behavioural adaptations (migration, temporal diving) with numerous interactions. 2.,In lowlands of Central Europe, the flood pulse of large rivers is less predictable than in Central Amazonia and is superimposed by the seasonal light/temperature pulse (summer/winter regime). Some terrestrial invertebrates show physiological resistance against inundation or drought, phenologies fitting the normal annual rhythm of water level fluctuation (quiescence or diapause of eggs or adult invertebrates), high dispersal ability and migration. However, most species survive simply using a `risk strategy', combining high reproduction rates, dispersal and reimmigration following catastrophic events. 3.,The diversity of species in terrestrial invertebrates is lower in lowland riverine ecosystems of Central Amazonia and Central Europe compared with the respective uplands because of flood stress in these systems. However, floodplains in Central Amazonia possess a greater number of endemic species in comparison with Central European floodplains because of long periods of fairly stable climatic conditions in comparison with large palaeoclimatic changes in Central Europe. [source] Medieval environmental impacts and feedbacks: The lowland floodplains of England and WalesGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 3 2010John Lewin Because of their varying channel styles (braided, meandering, and anastomosing) medieval lowland floodplains in England and Wales provided varying opportunities for defense, settlement, river crossing, and resource exploitation. In turn, these activities altered the character of channels and floodplains, with medieval and later development obscuring the former variety of floodplains themselves. The changing nature of river floodplains is reviewed using archaeological, documentary, and geomorphological evidence. Anastomosing channels and floodplain wetlands have now all but disappeared but were formerly of considerable significance; also discussed are interactions involving flooding, fording, bridging, modifications to channels and their dimensions, and those arising from accelerated soil erosion,most of which peaked in the medieval period when floodplains were significantly transformed. Deliberately or inadvertently, dynamic floodplain landforms were interactively involved with human development during a critical time period in a totality of ways not previously fully identified. © 2010 Wiley Periodicals, Inc. [source] Using cosmogenic beryllium,7 as a tracer in sediment budget investigationsGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 2 2002W. H. Blake Recent advances in the use of the environmental radionuclides caesium,137 and unsupported lead,210 to quantify medium, and longer,term rates of erosion and sediment accumulation have proved of considerable value in catchment sediment budget investigations. However, there remains a need to explore the potential for using other shorter,lived radionuclides to provide evidence of sediment mobilisation, transport and storage over shorter timescales and particularly for individual events. This contribution reports the results of a study aimed at exploring the potential for using beryllium,7 (7Be, t½= 53.3 days) to meet this requirement. The study investigated the use of 7Be as a sediment tracer in three key components of the sediment budget, namely, soil erosion and sediment mobilisation from slopes, the transport, storage and remobilisation of fine sediment in river channels and overbank deposition on river floodplains. The results presented clearly demonstrate the potential for using 7Be to obtain information on short,term and event,based sediment redistribution rates for use in catchment sediment budget investigations. [source] Do dams and levees impact nitrogen cycling?GLOBAL CHANGE BIOLOGY, Issue 8 2005Simulating the effects of flood alterations on floodplain denitrification Abstract A fundamental challenge in understanding the global nitrogen cycle is the quantification of denitrification on large heterogeneous landscapes. Because floodplains are important sites for denitrification and nitrogen retention, we developed a generalized floodplain biogeochemical model to determine whether dams and flood-control levees affect floodplain denitrification by altering floodplain inundation. We combined a statistical model of floodplain topography with a model of hydrology and nitrogen biogeochemistry to simulate floods of different magnitude. The model predicted substantial decreases in NO3 -N processing on floodplains whose overbank floods have been altered by levees and upstream dams. Our simulations suggest that dams may reduce nitrate processing more than setback levees. Levees increased areal floodplain denitrification rates, but this effect was offset by a reduction in the area inundated. Scenarios that involved a levee also resulted in more variability in N processing among replicate floodplains. Nitrate loss occurred rapidly and completely in our model floodplains. As a consequence, total flood volume and the initial mass of nitrate reaching a floodplain may provide reasonable estimates of total N processing on floodplains during floods. This finding suggests that quantifying the impact of dams and levees on floodplain denitrification may be possible using recent advances in remote sensing of floodplain topography and flood stage. Furthermore, when considering flooding over the long-term, the cumulative N processed by frequent smaller floods was estimated to be quite large relative to that processed by larger, less frequent floods. Our results suggest that floodplain denitrification may be greatly influenced by the pervasive anthropogenic flood-control measures that currently exist on most majors river floodplains throughout the world, and may have the potential to be impacted by future changes in flood probabilities that will likely occur as a result of climate shifts. [source] Numerical simulation of overbank processes in topographically complex floodplain environmentsHYDROLOGICAL PROCESSES, Issue 4 2003A. P. Nicholas Abstract This article presents results from an investigation of the hydraulic characteristics of overbank flows on topographically-complex natural river floodplains. A two-dimensional hydraulic model that solves the depth-averaged shallow water form of the Navier,Stokes equations is used to simulate an overbank flow event within a multiple channel reach of the River Culm, Devon, UK. Parameterization of channel and floodplain roughness by the model is evaluated using monitored records of main channel water level and point measurements of floodplain flow depth and unit discharge. Modelled inundation extents and sequences are assessed using maps of actual inundation patterns obtained using a Global Positioning System, observational evidence and ground photographs. Simulation results suggest a two-phase model of flooding at the site, which seems likely to be representative of natural floodplains in general. Comparison of these results with previous research demonstrates the complexity of overbank flows on natural river floodplains and highlights the limitations of laboratory flumes as an analogue for these environments. Despite this complexity, frequency distributions of simulated depth, velocity and unit discharge data closely follow a simple gamma distribution model, and are described by a shape parameter (,) that exhibits clear systematic trends with changing discharge and floodplain roughness. Such statistical approaches have the potential to provide the basis for computationally efficient flood routing and overbank sedimentation models. Copyright © 2002 John Wiley & Sons, Ltd. [source] Flood events overrule fertiliser effects on biomass production and species richness in riverine grasslandsJOURNAL OF VEGETATION SCIENCE, Issue 5 2007Boudewijn Beltman Abstract Question: Do severe winter flood events lift the nutrient limitation of biomass production in a river floodplain? How does this affect plant species richness? How long do the effects last? Location: Floodplain grassland on calcareous sandy loam near river Rhine in The Netherlands. Methods: Plots were fertilised with four treatments (control, N, P, N+P) for 21 years; plant species composition, vegetation biomass and tissue nutrient concentrations were determined every year between 1985 and 2005. Results: Fertilisation with N generally increased biomass production and reduced species richness, but these effects varied over time. During the first four years of the experiment, biomass production appeared to be co-limited by N and P, while N fertilisation dramatically reduced plant species richness; these effects became weaker subsequently. Following two extreme winter floods in 1993,94 and 1994,95 and a drought in spring 1996, the effects of fertilisation disappeared between 1998 and 2001 and then appeared again. Flooding caused an overall reduction in species richness (from c. 24 to 15 species m -2) and an increase in biomass production, which were only partly reversed after ten years. Conclusions: Long time series are necessary to understand vegetation dynamics and nutrient limitation in river floodplains, since they are influenced by occasional flood and drought events, whose effects may persist for more than ten years. A future increase in flooding frequency might be detrimental to species richness in floodplain grasslands. [source] Policies, plans, practice, and prospects: irrigation in northeastern SyriaLAND DEGRADATION AND DEVELOPMENT, Issue 2 2007F. Hole Abstract Over the past half-century the agricultural landscape of northeastern Syria has been transformed, due in large part to the introduction of significant irrigation to the steppe. At the beginning of this period, irrigation was confined almost entirely to river floodplains and natural depressions. The steppe was dominated by wintertime rain-fed agriculture and year-round grazing. The introduction of diesel-powered wells and, subsequently, state-operated dam and canal systems, has led to the expansion of both wintertime and summertime irrigation on the steppe away from the floodplain. The sustainability of these irrigation projects has always been suspect. Even as technologies for water extraction have allowed for previously impossible patterns of cultivation, the combination of declining water quality, a deepening water-table, and degradation-prone soils have limited crop yields and led to the rapid abandonment of many steppe farms. The actual trajectory of land-use in the region is determined by social and political forces as well as by hydrology and surficial geology. In this paper we examine recent land-use history in the watersheds of two tributaries of the Euphrates River, the Balikh and Khabur. A review of historical drivers of development in the region is combined with satellite analyses to provide an overview of the structure and dynamics of land-use in this water-limited region. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||||||||