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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Aquatic ecology 13 (1979), S. 113-115 
    ISSN: 1573-5125
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A brief account of investigations into the biomass and cumulative annual net production of two EuropeanRuppia species in localities in S.-Finland, The Netherlands and S.-France is given. TheRuppia decline in eutrophicated waters due to excessive phytoplankton growth is discussed.
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  • 2
    ISSN: 1573-5125
    Keywords: fens ; wetlands ; biomass production ; nitrogen deposition ; nutrient enrichment ; eutrophication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Species-rich floating fen ecosystems in former turf ponds in the western part of The Netherlands are subject to nitrogen enrichment because of high atmospheric N deposition (50 kg ha−1,Y−1,). and supply of polluted river water in dry summer periods. Further, some fens have become more influenced by rain water because downward seepage to the groundwater has increased due to hydrological alterations. This paper describes changes in plant biomass production by comparing seasonal maximum biomass values for 15 fen sites determined with standard procedures in 1981 and 1988. Fen sites in different polders showed different species composition, which is related to differences in hydrology and history of fen management among the polders. The ‘mid-succession’ fens (type 1) which are characteristically N-limited have shown a biomass increase in spite of the annual mowing regime, which shows that these fens are becoming enriched with nitrogen. There are indications that the role of phosphorus as a limiting factor increases in these fens, and that a shift of N-limited towards P-limited phanerogam growth occurs. This may bring these fens eventually in the ‘late-succession’ stage, as presently found in Het Hol (type 2). The fens in this stage are P-limited and have a different species composition. It was concluded that the mesotrophic fens in the Vechtplassen area, characterized by a species-rich vegetation, can only persist in their eutrophicated environment if they are located in a groundwater discharge area and if they are annually harvested in the summer. If all fens in the area, will eventually become P-limited it is expected that the species composition will change to a more uniform ’late-succession’ vegetation type.
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  • 3
    ISSN: 1573-5125
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary The "Ooypolder" is situated in a bend of the river "Waal" a branch of the Rhine near the town of Nijmegen. This town has been built on a ridge formed by pleistocene glaciers. The soil of the "Ooypolder" consists of a 2–5 meter thick surface layer of holocene river-clay on many pleistocene layers of sand and gravel. The surface drainage of the region, protected by the river-dike against the "Waal" ("Ooyse Bandijk", fig. 1) is directed to "Het Meer" from which it is pumped into the "Waal". Groundwater movements are strongly influenced by the "Waal". At high river-levels "Waal"-water infiltrates into the "Ooypolder", at low levels the polder loses groundwater to the river (fig. 2). With some delay the groundwater follows closely the river-level. Groundwater movements from the hills of Nijmegen (fig. 2) to the "Ooypolder" and "Waal" are not proved. Among the surface waters (fig. 1) "Oude Waal" is an old branch of the "Waal"; "Bizonbaai" is formed by sand dredging and "Viswater" by clay and sand dredging. At river-levels above 11 meter N.A.P. (sea level, mean tide) the "Oude Waal" and "Bizonbaai" are in open connection with the "Waal". Both are completely flooded by the "Waal" once in 2 and 10 years respectively, at very high levels of the river. "Viswater", protected against the "Waal" by the river-dike ("Ooyse Bandijk") (fig. 1), is a completely closed basin. The influence of the "Waalwater" upon the water in the Ooypolder is correlated with the chloride concentration. The concentration in the water of the "Waal" is 50 mg Cl−/1 at high discharge and 300 mg Cl−/1 at very low discharge, caused by salt wastes of French mines. The actual chloride concentration in "Bizonbaai" and "Oude Waal" is the result of the last filling with river-water, the dilution by rain-water (ca. 4 mg Cl−/1) and the infiltration of river-water at sudden high river-levels. At 12 June, this infiltration of river-water was clearly visible on the slopes of the "Bizonbaai" after a sharp rise of the river-level (fig. 3), caused by rain-storms in Germany.
    Notes: Konklusies Het water in de Ooypolder wordt sterk beïnvloed door het water van de Waal. Dit komt vooral in de chlorideconcentratie tot uiting. De concentratie in het Waalwater varieert tussen 50 mg Cl−/1 bij hoge afvoer en 300 mg Cl−/1 bij zeer lage afvoer. Zowel Oude Waal als Bizonbaai staan ieder jaar bij hoge afvoer in open verbinding met de Waal en worden bij zeer hoge afvoeren gemiddeld één maal in de respectievelijk 2 en 10 jaar door de Waal doorstroomd. In de periode met normale en lage afvoer wordt de chlorideconcentratie in Bizonbaai en Oude Waal verlaagd door toevoer van regenwater met een chlorideconcentratie van ca. 4 mg Cl−/1 (LEEFLANG, 1938) en verhoogd door kwelwater vanuit de Waal bij snelle stijgingen van het rivierpeil. De Bizonbaai ontvangt in verhouding tot de Oude Waal minder regenwater door verschil in afwaterend gebied terwijl door de korte afstand tot de Waal de invloed van het kwelwater in de Bizonbaai groter zal zijn dan in de Oude Waal. De chlorideconcentratie in het Viswater was in juni ca. 23 mg Cl−/1, bij een onderzoek in december 1961 (DE VOORN, 1961) werd een chlorideconcentratie van 25 mg Cl−/1 aan het oppervlak en 30 mg Cl−/1 bij de bodem gemeten. Gezien deze lage en stabiele chlorideconcentraties is de invloed van het Waalwater op het Viswater gering.
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  • 4
    ISSN: 1573-5052
    Keywords: Carbon ; Fens ; Global change ; Organic matter ; Peat ; Succession
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper investigates the rates of peat accumulation associated with different phases in the succession from open water to carr forest in shallow ponds created by peat dredging in The Netherlands. Four phases had been recognized in a previous study of aerial photographs for the period 1937–1990, i.e. open water (Aq), reed swamp (SA), brownmoss quaking fen (BM) and carr forest (CF). Peat accumulation rates were estimated by relating the amounts of organic matter stored to the data on the successional history for 21 different sites. The organic matter accumulation rates were highest in the SA phase (1.12 kg m-2 y-1 on a dry weight basis), intermediate in the BM and CF phases (0.49 and 0.58 kg m-2 y-1), and lowest in the Aq phase (0.26 kg m-2 y-1). These values are high in comparison with values determined for fen ecosystems with stratigraphic methods in combination with radiocarbon dating. The accumulation rates were inversely related to the average duration of the successional phases, suggesting that peat accumulation is a major driving force behind the succession.
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  • 5
    ISSN: 1573-5052
    Keywords: Carr ; Peatland ; Species composition ; The Netherlands ; Vegetation ; Wetland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Quaking fens and floating forests in the Westbroek Polder, the Netherlands, have seed banks with an estimated mean total seed density of 920 and 690 seeds m-2, respectively. Fifty nine species were found in two or more quaking fens of which 39 were also found in their seed banks. Fifty species were found in two or more floating-forests and 31 of these were also found in their seed banks. The seed banks of fens and forests had 36 species in common. The seed banks of fens and forests were more similar (Spearman rank order correlation coefficients of 0.64 on the basis of percent presence and 0.61 on the basis of mean seed density in the seed bank and mean species cover in the vegetation) than were the seed banks and vegetation of either fens or forests (0.46 and 0.46 for fens; 0.26 and 0.23 for forests). When the tree canopy is removed from a floating forest to try to restore it to a quaking fen, it is predicted that a total of 47 species from the floating-forest understory will persist. Eleven of these species are not present in fens. Fifteen additional species can become established potentially from the forest seed banks. Sixteen species found in fens, however, are predicted to be missing from cleared sites. Of these 16 species, 7 are uncommon aquatic-and fen species.
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  • 6
    ISSN: 1573-515X
    Keywords: fens ; management ; nitrogen ; phosphorus ; productivity ; vegetation ; wetlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A fertilization experiment was carried out in 3 mesotrophic fens to investigate whether plant growth in these systems is controlled by the availability of N, P or K. The fens are located in an area with high N inputs from precipitation. They are annually mown in the summer to prevent succession to woodland. Above-ground plant biomass increased significantly upon N fertilization in the two “mid”-succession fens studied. In the “late”-succession fen that had been mown for at least 60 years, however, plant biomass increased significantly upon P fertilization. The mowing regime depletes the P pool in the soil, while it keeps N inputs and outputs in balance. A long-term shift occurs from limitation of plant production by N toward limitation by P. Hence, mowing is a suitable management tool to conserve the mesothrophic character of the fens.
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  • 7
    ISSN: 1573-5117
    Keywords: wetland characteristics ; threats ; conservation ; rehabilitation ; management ; ecological research ; The Netherlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Wetlands are among the worlds' most important, but also most threatened, environmental resources. Wetland losses have been in progress particularly from the industrial revolution onwards, because wetland functions could not successfully compete for space with other land uses. Wetlands became recently foci of conservation efforts because of the increased awareness of their importance in water management and wildlife conservation, and because of the diversity of their habitats. The Netherlands are relatively rich in wetlands: 16% of its' territory is regarded as internationally important wetland and 7% has been registered as such. The major Dutch wetland types are: coastal ecosystems, large riverine systems, base-rich freshwater systems, and nutrient-poor freshwater systems. Most threats to the Dutch wetlands are of man-made origin. They comprise: (1) Changes in hydrology leading to changed discharges, currents and desiccation; (2) Acidification; (3) Eutrophication; and (4) Toxification. Long-term threats are largely climate-change related, and concern temperature rise and the UV-B increase in irradiation. General conservation goals also apply to wetlands but Ramsar-registered wetlands have a special status. Conservation of the Dutch wetlands is difficult, because of the high population density of the country and its inherent threats. However, ecological targets and standards are increasingly set in national Policy Plans and international agreements. Rehabilitation and creation of wetlands is presently widely advocated, and sometimes realised. For ecological research, the sustainability of wetlands should get top priority. Such a research programme would focus on understanding the underlying ecological processes in natural and man-dominated wetland systems to prescribe conservation, rehabilitation and management strategies that would enhance the sustainability of these systems. Within this framework special attention should be directed to studies (1) At the ecosystem level of ecosystem parameters, of which natural oscillations and trends in time, and on which the impact of disturbances are quantified. Particularly these studies, in which often simulation models are used as tools for interpretation, can provide the basis for extrapolations in space and time; (2) On adaptation capacity and mechanisms of (groups of) species to extreme environmental conditions; (3) On (mutual) relationships between plants, animals and microorganisms (e.g. competition, grazing and mineralization); (4) On dispersion between small wetlands. For the contemporary quantitative assessment of the long-term effects of climate changes, the effects of temperature rise and increase in UV-B irradiation on individual species, communities and ecosystems should also be studied.
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  • 8
    ISSN: 1573-5117
    Keywords: brackish water ; aquatic macrophytes ; supra-littoral pools
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fifty brackish supra-littoral pools bordering the Waddenzee were studied. The structure of plant communities (Potamogeton pectinatus L., Ranunculus baudotii Godr. and Zannichellia pedunculata Rchb.) is discussed in relation to water level fluctuations, chlorinity and water transparency. Chlorinity tolerances of the macrophytes (7 species) are discussed. The macrofauna was studied semi-quantitatively. The aquatic Coleoptera had the greatest diversity (24 species). A distinct relationship between the number of Coleoptera species and the percentage of macrophyte coverage was found. The distribution patterns of the most frequent species with respect to chlorinity categories are shown in histograms. The number of aquatic Heteroptera species is also discussed in relation to chlorinity and vegetation coverage. Less important macrofaunal groups (the Crustacea, Mollusca and Odonata) occurred in low species numbers.
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  • 9
    ISSN: 1573-515X
    Keywords: nitrogen ; phosphorus ; mineralization ; productivity ; peatlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Release of inorganic nitrogen and phosphorus in the soil of a peatland (fen) in The Netherlands was measured by means of an in situ incubation technique. Three sampling stations were chosen along a gradient in the plant productivity and water chemistry of the fen. The station with the highest biomass production was located near the ditch that supplied the fen with water in amounts matching water losses through evaporation and downward percolation to the groundwater. Water chemistry at this station strongly resembled that of the ditch water. The two stations remote from the ditch had much lower plant biomass, and significantly lower pH, conductivity, and calcium and bicarbonate concentrations. The vegetation at these two stations was characterized by a thick Sphagnum carpet. The release of inorganic N and P was much faster at the two stations remote from the ditch than at that located near the ditch. The differences in mineralization rate are probably due to the differences in water chemistry; phosphates are more soluble at low than at high pH. The fast N mineralization at stations with a thick Sphagnum carpet may be related to the chemical composition of Sphagnum litter. The difference in productivity is not explained by the N and P mineralization rates. Direct supply of N and P from the ditch are probably the main cause of the high productivity at the station bordering the ditch.
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  • 10
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a typical Dutch polder landscape the effects of nutrient transport from cultivated grassland to mesotrophic fen communities were studied. In a comparative approach, biomass production and nutrient (N, P and K) uptake were determined monthly in four fens and a hayfield differeing in productivity and species composition. The interstitial ground water was sampled every two weeks for determinations of inorganic nutrient concentrations. The differences in productivity between the fens were clearly reflected in the amount of N, P and K taken up in the above-ground vegetation. N and P proved to be limiting plant growth in the fens, whereas K was the main limiting factor in the hayfield. The ground water welling up from the sandy bottom into the fens proved to be rich in ammonia (3–5 ppm). There are strong indications that this continual seepage leads to a considerable input of N into the fens but not to a higher productivity, as the ammonia is absorbed by the lowermost peat layers covering the sand. At this moment, the differences in productivity between the fens must be caused by differences in the rates of mineralization of the superficial peat layer. The degree of fixation of the floating vegetation mat, determining whether or not low water levels lead to an aerated soil top layer, is important in this respect. Within a period of decades, however, the continuous inflow of ammonia may eventually cause an increase in the productivity and a change in the species composition of the fens.
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