86 research outputs found
35 jaar beheer Drentsche Aa:Evaluatie natuurontwikkeling en aanbevelingen voor verbetering
No full textDe ecologen Henk Everts, Ab Grootjans, Jan Bakker en Piet Schipper wijden zich al bijna een halve eeuw aan het in kaart brengen van de natuur in het Drentsche Aa-gebied. Ter afsluiting van hun werk hebben ze alle gegevens naast elkaar gezet en vergeleken. De gestelde doelen voor de Drentsche Aa worden in het onderzoek geëvalueerd door trends tussen 1980 en 2015 te relateren aan veranderingen in de waterhuishouding en het beheer. Hiervoor zijn vier vegetatiekarteringengebruikt uitgevoerd in de periode tussen 1982 en 2015. De interpretatie van de gegevens is zowel gericht op de vegetatie van de habitattypenals op die van Dotterbloemhooilanden en Grote zeggenmoerassen met tellingenvan broedvogels en tellingen van libellen en dagvlinders.Op basis van de resultaten worden aanbevelingen gedaan om maatregelen te treffen die op korte en lange termijn nodig zijn. Belangrijk zijn onder meer maatregelen ter bescherming van de laatste voedselarmeinfiltratiegebieden, en maatregelen om diffuse vervuiling verder terug te dringen en de effecten van klimaatverandering op te vangen
35 jaar beheer Drentsche Aa:Evaluatie natuurontwikkeling en aanbevelingen voor verbetering
No full textDe ecologen Henk Everts, Ab Grootjans, Jan Bakker en Piet Schipper wijden zich al bijna een halve eeuw aan het in kaart brengen van de natuur in het Drentsche Aa-gebied. Ter afsluiting van hun werk hebben ze alle gegevens naast elkaar gezet en vergeleken. De gestelde doelen voor de Drentsche Aa worden in het onderzoek geëvalueerd door trends tussen 1980 en 2015 te relateren aan veranderingen in de waterhuishouding en het beheer. Hiervoor zijn vier vegetatiekarteringengebruikt uitgevoerd in de periode tussen 1982 en 2015. De interpretatie van de gegevens is zowel gericht op de vegetatie van de habitattypenals op die van Dotterbloemhooilanden en Grote zeggenmoerassen met tellingenvan broedvogels en tellingen van libellen en dagvlinders.Op basis van de resultaten worden aanbevelingen gedaan om maatregelen te treffen die op korte en lange termijn nodig zijn. Belangrijk zijn onder meer maatregelen ter bescherming van de laatste voedselarmeinfiltratiegebieden, en maatregelen om diffuse vervuiling verder terug te dringen en de effecten van klimaatverandering op te vangen
Van venen, mensen, water en vuur
No full textContains fulltext :
65644_van_vemew.pdf (Publisher’s version ) (Open Access)With bibliogr., inaugural address Radboud University Nijmegen20 p
Vegetation Re-development After Fen Meadow Restoration by Topsoil Removal and Hay Transfer
No full textWe investigated the effects of different restoration treatments on the development of fen meadow communities: (1) depth of topsoil removal, with shallow (circa 20 cm) and deep (circa 40 cm) soil removal applied, (2) transfer of seed-containing hay, and (3) access of large animals. We carried out a full factorial experiment with all combinations of these factors and monitored it for 4 years. We studied the effect of seed availability in the soil seed bank on species abundance in the vegetation and compared it to the effect of species introduction by hay. We observed large differences in species composition between different treatments after 4 years. The combination of hay transfer, deep soil removal, and exclusion of large animals resulted in a community with highest similarity to the target vegetation. We found that the transfer of seeds with hay had a larger effect on species abundance than the soil seed bank. Hay transfer appeared to have important consequences on vegetation development because it speeded up the establishment of the target vegetation.
Restoration of Natural and Semi-Natural Wetland Systems in Central Europe: Progress and Predictability of Developments
No full textAfter almost 40 years of experience in wetland restoration in Central Europe in which vegetation changes have been monitored by means of permanent plots or vegetation maps, some light can be shed on the intrinsic dynamics of such ecosystems, showing the limits of restoration and constraints in its manipulation. Sometimes such constraints in the restoration process can be identified, mostly being constraints in nutrient availability or in the water regime, but unexpected changes can also be the result of intrinsic species fluctuations or invasive species. Unexpected vegetation developments are sometimes undesired, can be very persistent and may indicate that environmental conditions are not suitable for target communities. Unexpected developments also illustrate the limits in restoration ecology. Very often the restoration process simply proceeds along successional pathways we did not anticipate. Theories about such alternative pathways can be explored using prediction models, such as cellular automata, which can handle the results of biomonitoring very efficiently. Biomonitoring during 40 years, however, has also shown that a certain amount of unpredictability has to be taken for granted, both in natural wetlands and in areas under restoration.
Performance of four Dactylorhiza species over a complex trophic gradient
No full textSpontananeous distribution and survival in experimental plots of four marsh orchids (Dactylorhiza spp.) in a hay-meadow complex were related to mineral composition of groundwater, soil nutrient availability and species composition of the vegetation. Differences in Ca2+ contents of the groundwater pointed to the discharge of various groundwater flows in the meadow. Soil fertility and extent of N limitation, measured with the phytometer Cirsium palustre, varied with position on the gradient. Total N content of the soil and levels of exchangable K+ and NH4+ were correlated to organic matter content. Highest total P levels were found in areas with a pronounced discharge of mineral-rich groundwater. Concentration of available P was higher in wet than in drier sites. Natural abundance and survival of introduced Dactylorhiza maculata (L.) Soo plantlets was highest in Juncus acutiflorus-dominated transitions between meadows and Parvocaricetea marsh. These were characterized by the occurrence of a water type of intermediate mineral content and by low soil fertility, limited by N and P. Survival of D. praetermissa (Druce) Soo showed exactly the opposite pattern to that of D. maculata, It had its optimal spontaneous abundance in more fertile parts of the meadow influenced by discharge of groundwater with an intermediate mineral content. D. majalis (Rchb, f) Hunt Be Summerh. also occurred in the more fertile parts of the meadow, but showed an optimum in drier stands associated with discharge of highly calcareous groundwater. The phosphorus-pool of these soils was high, but the availability of phosphate was low. The soil fertility of D. majalis site was limited by N. D. incarnata (L.) Soo occurred mainly in transitions between basiphilous small sedge vegetation and productive hay meadow stands. The species occurred at fertile but waterlogged soils with high concentrations of NH4+. The presence of base-rich groundwater with a high pH apparently prevents the species from ammonium toxicity. None of the species occurred in degenerated (drained) and acidified meadow sites.</p
Performance of four Dactylorhiza species over a complex trophic gradient
No full textSpontananeous distribution and survival in experimental plots of four marsh orchids (Dactylorhiza spp.) in a hay-meadow complex were related to mineral composition of groundwater, soil nutrient availability and species composition of the vegetation. Differences in Ca2+ contents of the groundwater pointed to the discharge of various groundwater flows in the meadow. Soil fertility and extent of N limitation, measured with the phytometer Cirsium palustre, varied with position on the gradient. Total N content of the soil and levels of exchangable K+ and NH4+ were correlated to organic matter content. Highest total P levels were found in areas with a pronounced discharge of mineral-rich groundwater. Concentration of available P was higher in wet than in drier sites. Natural abundance and survival of introduced Dactylorhiza maculata (L.) Soo plantlets was highest in Juncus acutiflorus-dominated transitions between meadows and Parvocaricetea marsh. These were characterized by the occurrence of a water type of intermediate mineral content and by low soil fertility, limited by N and P. Survival of D. praetermissa (Druce) Soo showed exactly the opposite pattern to that of D. maculata, It had its optimal spontaneous abundance in more fertile parts of the meadow influenced by discharge of groundwater with an intermediate mineral content. D. majalis (Rchb, f) Hunt Be Summerh. also occurred in the more fertile parts of the meadow, but showed an optimum in drier stands associated with discharge of highly calcareous groundwater. The phosphorus-pool of these soils was high, but the availability of phosphate was low. The soil fertility of D. majalis site was limited by N. D. incarnata (L.) Soo occurred mainly in transitions between basiphilous small sedge vegetation and productive hay meadow stands. The species occurred at fertile but waterlogged soils with high concentrations of NH4+. The presence of base-rich groundwater with a high pH apparently prevents the species from ammonium toxicity. None of the species occurred in degenerated (drained) and acidified meadow sites
Restoration of Natural and Semi-Natural Wetland Systems in Central Europe:Progress and Predictability of Developments
No full textAfter almost 40 years of experience in wetland restoration in Central Europe in which vegetation changes have been monitored by means of permanent plots or vegetation maps, some light can be shed on the intrinsic dynamics of such ecosystems, showing the limits of restoration and constraints in its manipulation. Sometimes such constraints in the restoration process can be identified, mostly being constraints in nutrient availability or in the water regime, but unexpected changes can also be the result of intrinsic species fluctuations or invasive species. Unexpected vegetation developments are sometimes undesired, can be very persistent and may indicate that environmental conditions are not suitable for target communities. Unexpected developments also illustrate the limits in restoration ecology. Very often the restoration process simply proceeds along successional pathways we did not anticipate. Theories about such alternative pathways can be explored using prediction models, such as cellular automata, which can handle the results of biomonitoring very efficiently. Biomonitoring during 40 years, however, has also shown that a certain amount of unpredictability has to be taken for granted, both in natural wetlands and in areas under restoration
Restoration of Natural and Semi-Natural Wetland Systems in Central Europe:Progress and Predictability of Developments
No full textAfter almost 40 years of experience in wetland restoration in Central Europe in which vegetation changes have been monitored by means of permanent plots or vegetation maps, some light can be shed on the intrinsic dynamics of such ecosystems, showing the limits of restoration and constraints in its manipulation. Sometimes such constraints in the restoration process can be identified, mostly being constraints in nutrient availability or in the water regime, but unexpected changes can also be the result of intrinsic species fluctuations or invasive species. Unexpected vegetation developments are sometimes undesired, can be very persistent and may indicate that environmental conditions are not suitable for target communities. Unexpected developments also illustrate the limits in restoration ecology. Very often the restoration process simply proceeds along successional pathways we did not anticipate. Theories about such alternative pathways can be explored using prediction models, such as cellular automata, which can handle the results of biomonitoring very efficiently. Biomonitoring during 40 years, however, has also shown that a certain amount of unpredictability has to be taken for granted, both in natural wetlands and in areas under restoration
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