Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    How upward seepage of alkaline groundwater sustains plant species diversity of mesotrophic meadows
    Cirkel, D.G. - \ 2014
    Wageningen University. Promotor(en): Sjoerd van der Zee; J.P.M. Witte. - Wageningen : Wageningen University - ISBN 9789461739124 - 171
    hooiland - ecohydrologie - soortendiversiteit - alkalisch water - grondwater - kwel - biogeochemie - standplaatsfactoren - natuurgebieden - meadows - ecohydrology - species diversity - alkaline water - groundwater - seepage - biogeochemistry - site factors - natural areas
    Door kwelwater gevoede natte hooilanden, zoals blauwgraslanden, worden wel beschouwd als de Nederlandse kroonjuwelen van biodiversiteit. Ze zijn de afgelopen eeuw sterk achteruitgegaan, zowel in oppervlakte als in botanische kwaliteit. Tegenwoordig vindt men deze laagproductieve hooilanden alleen nog in beschermde natuurgebieden. Het gaat hierbij om veelal kleine reservaten, die geïsoleerd liggen in een intensief gebruikt agrarisch landschap. De hoge biodiversiteit van de hooilanden wordt verklaard door de toestroming van schoon en basenrijk grondwater. Die resulteert in relatief hoge en stabiele grondwaterstanden en, gecombineerd met een beperkte hoeveelheid infiltrerend regenwater, in kleinschalige waterkwaliteitsgradiënten in de bodem. Dit proefschrift verschaft een integraal inzicht in de hydrologische en biogeochemische relaties tussen kwelwater, infiltrerend neerslagwater en vegetatiepatronen. Dat inzicht is van belang voor het beheer van kwelafhankelijk graslanden, bijvoorbeeld doordat het kan bijdragen aan een juiste beoordeling van de ecohydrologische gevolgen van ingrepen in de waterhuishouding, van klimaatverandering en van de instroming van vervuild grondwater
    Laagveen en zeeklei 2010 : Dotterbloemhooilanden
    Hoek, D. van der; Riet, B. van de; Schie, M. - \ 2010
    S.n.
    graslanden - hooiland - weiden - caltha - vegetatiebeheer - natuurbeheer - grasslands - meadows - pastures - caltha - vegetation management - nature management
    Tot halverwege de vorige eeuw kwamen dotterbloemhooilanden veelvuldig voor, in de benedenlopen van beekdalen en het veengebied. Vanwege de rijke flora en fauna streven veel beheerders er naar ze terug te krijgen. Dit infoblad bekijkt de omstandigheden waaronder het mogelijk is dotterbloemhooilanden terug te krijgen en de mogelijke stimulerende maatregelen.
    Leidt bevloeiing van schraallanden tot eutrofiëring? [thema restauratie van natte schraallanden]
    Kemmers, R.H. ; Grootjans, A.P. ; Bakker, M. ; Baaijens, G.J. ; Nijp, J. ; Dijk, G. van - \ 2007
    De Levende Natuur 108 (2007)3. - ISSN 0024-1520 - p. 127 - 131.
    graslanden - ecologisch herstel - inundatie - hooiland - vegetatie - beekdalen - waterkwaliteit - ecohydrologie - overijssel - drenthe - grasslands - ecological restoration - flooding - meadows - vegetation - brook valleys - water quality - ecohydrology - overijssel - drenthe
    In het kader van obn onderzoek is in het Reestdal een experiment uitgevoerd om na te gaan of de oude praktijk van bevloeiing in aanmerking kon komen als effectgerichte maatregel tegen verdroging en verzuring van dotterbloemhooilanden. Bevloeiing zou de functie van kwel met de aanvoer van bufferende stoffen (kalium, calcium, ijzer) kunnen overnemen.
    Restauratie van schraallanden op veengronden door afgraven en vernatten [thema restauratie van natte schraallanden]
    Grootjans, A. ; Kemmers, R.H. ; Everts, H. ; Adema, E. - \ 2007
    De Levende Natuur 108 (2007)3. - ISSN 0024-1520 - p. 108 - 113.
    veengronden - bodemchemie - vegetatie - herstel - hooiland - hydrologie - plaggen steken - beekdalen - herstelbeheer - friesland - drenthe - peat soils - soil chemistry - vegetation - rehabilitation - meadows - hydrology - sod cutting - brook valleys - restoration management - friesland - drenthe
    Verdroging van veengronden is een veel voorkomend verschijnsel in beekdalen. Hoewel hydrologisch herstel een eerste vereiste is, zijn aanvullende maatregelen wenselijk. In deze obn bijdrage wordt verslag gedaan van ervaringen met het plaggen in De Lage Maden (Drentse Aa), De Barten (Linde) en De Wyldlannen (lage midden, Friesland)
    Utilization of seagrass habitats by juvenile groupers and snappers in Banten Bay, Banten Province, Indonesia
    Nuraini, S. ; Carballo, E.C. ; Densen, W.L.T. van; Machiels, M.A.M. ; Lindeboom, H.J. ; Nagelkerke, L.A.J. - \ 2007
    Hydrobiologia 591 (2007)1. - ISSN 0018-8158 - p. 85 - 98.
    unvegetated habitats - florida bay - fishes - recruitment - patterns - meadows - diel - abundance - selection - victoria
    Coastal development in Banten Bay, Indonesia, decreased seagrass coverage to only 1.5% of its surface area. We investigated the importance of seagrass as habitat for juvenile groupers (Serranidae) and snappers (Lutjanidae), by performing beam trawl hauls on a weekly basis in two seagrass locations and one mudflat area, and monthly trawl hauls in three different microhabitats (dense, mixed and patchy seagrass) in one of the seagrass locations. We studied the effects of location and microhabitat, as well as temporal patterns (diel, weekly and monthly) on the probability of occurrence and abundance of the most abundant grouper (Orange-spotted grouper, Epinephelus coioides) and snapper (Russell¿s snapper, Lutjanus russellii). We found that both species were almost exclusively found in seagrass locations, with a preference for microhabitats of high complexity (dense and mixed microhabitats). L. russellii had a higher probability of catch and abundance during the night, most probably because of its ability to avoid the beam trawl during daytime sampling. In addition there was an effect of week and month on the presence and abundance of both species, but patterns were unclear, probably because of high fishing pressure on juvenile groupers and snappers by push net fishermen. Groupers and snappers mainly fed on abundant shrimps, and to a lesser extent on fish. Moreover, juveniles find protection against predators in seagrass, which confirmed the critical role of quantity and quality of seagrass areas for juvenile groupers and snappers in Banten Bay.
    Goeree voor 1970: het land waar het leven goed was
    Sykora, K.V. - \ 2007
    Zuid-Hollands Landschap 3 (2007). - p. 12 - 13.
    landgebruik - natuurbescherming - graslandbeheer - duinen - vegetatie - plantenecologie - maaien - hooiland - begrazing - vegetatiebeheer - vegetatietypen - soortenrijkdom - zuidhollandse eilanden - zuid-holland - land use - nature conservation - grassland management - dunes - vegetation - plant ecology - mowing - meadows - grazing - vegetation management - vegetation types - species richness
    Wie door de duinen van Goeree wandelt, ziet grotendeels de duindoorn overwoekerd landschap. Diezelfde duinen bestonden voor 1970 vrijwel uitsluitend uit lage, soortenrijke duingraslanden, zoals nu nog in Westduinen, een terrein van Zuid Hollands Landschap, te zien is. Ook het landschap achter de zeereep zag er anders uit. Landschap en landgebruik hangen nauw samen. Professor Karlè Sýkora sprak met Henk Mastenbroek, hovenier te Ouddorp, die zich nog veel belangrijke details van het boerenleven op Goeree voor 1970 herinnert. Een samenleving waar hij met weemoed op terugkijkt
    Optimalisatie stikstofbemesting Engels raaigras : meerjarenverwerking deling van de stikstofbemesting
    Schoot, J.R. van der; Borm, G.E.L. ; Berg, W. van den - \ 2006
    Wageningen : Praktijkonderzoek Plant & Omgeving B.V. - 20
    graslanden - graslandbeheer - hooiland - toedieningshoeveelheden - gedeelde mestgiften - stikstofgehalte - stikstofmeststoffen - bemesting - grasslands - grassland management - meadows - application rates - split dressings - nitrogen content - nitrogen fertilizers - fertilizer application
    Om te komen tot een mogelijke verfijning van het N-advies voor Engels raaigras is in 2000 meerjarig bemestingsonderzoek gestart. In de proeven van 2000 en 2001 lag één object met gedeelde bemesting (tweede gift in vlagbladstadium). In 2002, 2003 en 2005 zijn in totaal zes stikstofproeven (klei en zand) geoogst van het tetraploïde ras Elgon. In de proeven lagen diverse basisgiften en zijn bijbemestingen van 30 en 60 kg N/ha in twee gewasstadia (DC32 en vlagbladstadium) toegediend. De effecten van de diverse giften en bijbemestingen op de gewasontwikkeling en zaadproductie zijn gevolgd. Voor het tetraploïde ras Elgon lijkt het oude bemestingsadvies aan de lage kant. Mede op basis van dit uitgevoerd onderzoek is het bemestingsadvies voor de rassen van het tetraploïde hooitype verhoogd naar 205-Nmin
    Structure, food and shade attract juvenile coral reef fish to mangrove and seagrass habitats: a field experiment
    Verweij, M.C. ; Nagelkerken, I. ; Graaff, D. de; Peeters, M. ; Bakker, E.J. ; Velde, G. van der - \ 2006
    Marine Ecology Progress Series 306 (2006). - ISSN 0171-8630 - p. 257 - 268.
    drum sciaenops-ocellatus - light-intensity - estuarine fish - predation - beds - meadows - communities - selection - assemblages - complexity
    Mangroves and seagrass beds are considered nurseries for juvenile fish, but little experimental evidence exists to elucidate which factors make them attractive habitats. A multifactorial field experiment on the use of these habitats by juvenile reef fish and their behaviour was performed during daytime with experimental units (EUs: 1 × 1 × 0.8 m), each representing a unique combination of the factors structure, shade, and food, using artificial seagrass leaves (AS) and artificial mangrove roots (AM). Diurnally active herbivores were most abundant in EUs containing food, and grazed on algae growing on the structures, but were not attracted to structures in the absence of food. The most abundant diurnally active zoobenthivores (Eucinostomus spp.) were present in highest numbers in any EU with food, where they fed on zoobenthos or rested on the bottom. The nocturnally active zoobenthivore/zooplanktivore Ocyurus chrysurus and the diurnally active piscivore Sphyraena barracuda were primarily attracted to structure, in which they rested and were not observed to feed. Haemulon flavolineatum was mainly attracted to AS, Lutjanus mahogoni was attracted to AS or shade, whereas L. apodus, O. chrysurus and S. barracuda were found in AM as well as in AS. The data suggest that during daytime, herbivores and diurnally active zoobenthivores are probably attracted to mangroves and seagrass beds primarily by food, and nocturnally active zoobenthivores by structure (in interaction with shade) that offers shelter from predation. S. barracuda is also attracted primarily to structure, but the larger individuals probably use this for ambush predation rather than for protection. In conclusion, our experiment clarifies that presence of structure, food and shade significantly contribute to the attractiveness of mangroves and seagrass beds to juvenile reef fish
    Unpalatable plants facilitate tree sapling survival in wooded pastures
    Smit, C. ; Ouden, J. den; Müller-Schärer, H. - \ 2006
    Journal of Applied Ecology 43 (2006)2. - ISSN 0021-8901 - p. 305 - 312.
    negative interactions - quercus-humilis - regeneration - competition - colonization - communities - vegetation - mountains - diversity - meadows
    Summary 1. In endangered wooded pasture ecosystems established tree saplings are frequently found in spatial association with protective structures, suggesting nurse effects. This associational resistance is thought to be a driving force behind tree regeneration in wooded pastures. Experimental evidence for associational resistance is, however, scarce. We studied the effects of unpalatable plants on tree sapling performance in a wooded pasture ecosystem in Switzerland and tested the associational resistance hypothesis experimentally. 2. We transplanted 600 Picea abies saplings of two size classes (5 cm and 10 cm) in plots: (i) with unpalatable plants (either Gentiana lutea or Cirsium acaule, representing a chemically and mechanically defended species, respectively); (ii) with one of both unpalatable plants clipped to the ground; and (iii) without any unpalatable plants. Grazing intensity was measured once in each plot and tree sapling performance was followed for 2 consecutive years. 3. Grazing intensity was significantly higher in plots without unpalatable plants, and significantly higher in plots with Cirsium than with Gentiana. Correspondingly, sapling survival (21¿5% and 10¿6% after 1 and 2 grazing years, respectively) was significantly higher near unpalatable plants, and significantly higher in plots with Gentiana than with Cirsium . Large tree saplings survived significantly better than small ones, and depended less on the unpalatable plants for survival. 4. Except for saplings planted near Gentiana, sapling removal by cows and horses was the major cause of death, the extent varying between unpalatable species and treatments. 5. The growth in height of the saplings was unaffected by the treatments. 6. Synthesis and applications. This study shows that unpalatable plants can enhance tree regeneration in wooded pastures. Sapling survival was significantly higher near unpalatable plants where grazing intensity was significantly lower. Protection against cattle is particularly important for small saplings. These results have important management implications for the endangered and disappearing wooded pastures in western Europe. Transplanting tree saplings near unpalatable plants could be an alternative reforestation technique in intensively grazed wooded pastures. On the other hand, removal of unpalatable plants and shrubs might prevent or slow down undesired tree encroachment in less intensively grazed areas. Key-words: associational resistance, cattle, Cirsium acaule, Gentiana lutea, grazing, Picea abies, tree regeneration
    The effectiveness of restoration measures in species-rich fen meadows=[De effectiviteit van herstelmaatregelen in blauwgraslanden]
    Hoek, D. van der - \ 2005
    Wageningen University. Promotor(en): Frank Berendse. - [S.l.] : S.n. - ISBN 9789085042440 - 136
    graslanden - hydrologie - grondwaterspiegel - vegetatie - voedingsstoffen - herstel - nederland - hooiland - plaggen steken - ecohydrologie - gelderland - gelderse vallei - achterhoek - grasslands - hydrology - water table - vegetation - nutrients - rehabilitation - netherlands - meadows - sod cutting - ecohydrology - gelderland - gelderse vallei - achterhoek
    In dit proefschrift worden de mechanismen geanalyseerd die de effectiviteit bepalen van enkele hydrologische maatregelen en plaggen op het herstel van soortenrijke, natte schraalgraslanden. Het veldonderzoek werd gedaan in de Bennekomse Meent en het Korenburgerveen. Voorafgaand is oriënterend (eco)hydrologisch onderzoek gedaan in het zuidelijk deel van de Gelderse Vallei
    Beperking van lachgasemissie uit beweid grasland; eindrapport voor reductieplan overige broeikasgassen landbouw cluster 1
    Kuikman, P.J. ; Groenigen, J.W. van; Velthof, G.L. ; Walvoort, D.J.J. ; Bolt, F.J.E. van der; Beek, C.L. ; Pol-van Dasselaar, A. van den - \ 2004
    Wageningen : Alterra (Alterra-rapport 560.1) - 46
    distikstofmonoxide - emissie - hooiland - graslanden - reductie - broeikaseffect - weiden - rundveevoeding - melkvee - nitrous oxide - emission - meadows - grasslands - reduction - greenhouse effect - pastures - cattle feeding - dairy cattle
    In het kader van het Reductie Plan Overige Broeikasgassen (ROB Landbouw) zijn de mogelijkheden voor het verminderen van de emissie van lachgas (N2O) bij optimalisern van beweiding bestudeerd. In de periode tussen augustus 2000 en juli 2002 zijn door middel van incubatie- en veldproeven de gevolgen van een aantal maatregelen op de N2O-emissie onderzocht en zijn emissiefactoren voor lachgasproductie bepaald. In dit rapport worden de belangrijkste resultaten van het onderzoek gepresenteerd; de gedetailleerde resultaten worden in aparte rapporten en publicaties beschreven. Perspectiefvolle maatregelen om de N2O-emissie te verminderen zijn onveranderd beperken van beweiding varierend van beperkt weiden gedurende het jaar, volledig opstallen en in het najaar na 1 september opstallen. Deze maatregelen verminderen de emissie van lachgas omdat er meer mest in de stal en opslag komt in plaats van in de wei en omdat er minder sterke verdichting van de bodem door vertrapping optreedt. Het draagvlak bij boeren is niet onverdeeld gunstig. Minder weiden betekent meer werk om de koeien binnen te halen voor de ondernemer, er is milieuwinst met minder nitraatuitspoeling en lager stikstofoverschot en ¿gebruik en risico op verhoogde emissie van methaan en ammoniak. De uitdaging voor de boer is om aan de wens van de samenleving dat koeien in de wei zijn tegemoet te komen tegelijkertijd met vermindering van de beweidingsduur.
    Lachgasemissie bij graslandvernieuwing in voor- of najaar; resultaten van een éénjarige meetcampagne
    Dolfing, J. ; Groot, W.J.M. de; Hoving, I.E. ; Kuikman, P.J. - \ 2004
    Wageningen : Alterra (Alterra-rapport 896) - 52
    distikstofmonoxide - emissie - graslanden - hooiland - graslandverbetering - grasmatverbetering - opnieuw zaaien - nitrous oxide - emission - grasslands - meadows - grassland improvement - sward renovation - resowing
    Jaarlijks wordt in Nederland ongeveer 10% van alle grasland gescheurd en opnieuw ingezaaid met gras of met andere gewassen. Als gevolg hiervan komen relatief grote hoeveelheden stikstof vrij waarvan een deel uitspoelt als nitraat of denitrificeert en verloren gaat. Dit verlies is afhankelijk van het tijdstip van scheuren en van het volggewas. Het is onduidelijk hoeveel van de stikstof die verloren gaat wordt omgezet in lachgas. In het voorliggende rapport worden de resultaten gepresenteerd van metingen die gedurende een volledig jaar zijn uitgevoerd binnen een veldexperiment naar graslandvernieuwing. Het experiment is uitgevoerd op een drietal locaties: Nij Bosma Zathe (zeeklei), Aver Heino (natte zandgrond; beekeerd) en Cranendonck (droge zandgrond; veldpodzol). Het doel van de meetcampagne was om de lachgasemissie te bepalen die het gevolg is van verschillende manieren van graslandvernieuwing bij verschillende bemestings-niveaus en grondsoorten. Het tijdstip waarop de graslandvernieuwing werd uitgevoerd beïnvloedt de emissie, maar het effect was niet consistent in de verschillende gronden. Het advies om tot scheuren in het voorjaar over te gaan om de vrijkomende stikstof zo veel mogelijk te benutten voor het volggewas blijkt niet a-priori gunstig voor de emissie van N2O en behoeft nuancering. De gegevens worden in de herinzaaiwijzer ingebouwd en op deze manier bij ondernemers onder de aandacht gebracht in termen van advies in het kader van goede landbouw praktijk. (http://www.pv.wur.nl/index.asp?producten/software/websoftware/herinzaaiwijzer/index.asp)
    Historische ecologie van hooimaatjes in "De Wildernis" (Overijssel)
    Dirkx, J. - \ 2002
    Wageningen : Alterra (Alterra-rapport 392) - 75
    hooiland - bevloeiing door onderwaterzetting - ecologie - landschap - geografie - geschiedenis - nederland - overijssel - ecohydrologie - historische ecologie - cultuurhistorie - historische geografie - natuurbehoud - natuurontwikkeling - meadows - flood irrigation - ecology - landscape - geography - history - netherlands - overijssel - ecohydrology - historical ecology
    In het natuurreservaat De Wildernis liggen enkele hooimaatjes die in het verleden werden bevloeid. Voor het nieuwe beheersplan dat Landschap Overijssel voor De Wildernis opstelt, heeft Alterra onderzocht wat de cultuurhistorische betekenis van deze hooimaatjes is en welke mogelijkheden er bestaan die betekenis te integreren met natuurbehoudsdoelen. De cultuurhistorische betekenis van de maatjes blijkt hoog. Het historisch-ecologische referentiebeeld, dat een van de uitkomsten van het onderzoek is, geeft bovendien aan dat integratie van behoud van cultuurhistorische waarden ook veel kansen biedt voor het ontwikkelen van natuurwaarden.
    At home on foreign meadows: the reintroduction of two Maculineae butterfly species
    Wynhoff, I. - \ 2001
    Wageningen University. Promotor(en): H.H.T. Prins; P.M. Brakefield. - S.l. : S.n. - ISBN 9789058084613 - 236
    lepidoptera - ecologie - introductie - heidegebieden - hooiland - natuurbescherming - nederland - lepidoptera - ecology - introduction - heathlands - meadows - nature conservation - netherlands
    Maculinea butterflies live as obligate parasites of specific Myrmica host ants in meadow and heathland habitat maintained by low intensity landuse. Changes in agriculture caused the decline and extinction of many populations. In The Netherlands, Maculinea nausithous and M. teleius disappeared in the 1970s. In 1990, they were reintroduced following the recommendations of the IUCN. This study focuses on the evaluation of this reintroduction into the nature reserve Moerputten in the province of Northern Brabant. Population establishment and dispersal were monitored and accompanied by research on the impact of the reintroduction on species-specific genetic composition and behaviour. Maculinea teleius immediately established itself on one meadow, where the population still occurs today. Maculinea nausithous , being the more mobile species, colonized habitat patches with the specific host ant at higher distances. Three subpopulations were founded.

    At the small spatial scale the females of both species were able to select habitat patches with host plants and host ants to deposit their eggs, rather then loosing many offspring by random oviposition. At the ladscape scale the occurence of the populations was also strongly related to the presence of the specific host ant species. However, through the limited dispersal capacity of the adults high quality patches at greater distance remain uncolonized. Genetic analysis showed that the new populations have not experienced a bottleneck in numbers following the translocation. However, the populations experienced selection due to changed ecological conditions at the founder site, but ecologically relevant traits were apparently not affected.

    The conservation of the reintroduced population should concentrate on keeping a high habitat quality on the colonized sites and enabling the development of metapopulations by improving the management of potential sites within colonization distance. Ultimately, the persistence of the populations depends on the availability of an extensive network of suitable habitat patches. This requires conservation management at a landscape scale. This study emphasizes that a carefully planned and implemented reintroduction can be a successful tool for species conservation if both small and large spatial scales are taken into account.

    Restoration of soil chemical conditions of fen-meadow plant communities by water management in the Netherlands.
    Hoek, D. van der; Braakhekke, W.G. - \ 1998
    In: European wet grasslands : biodiversity, management and restoration / Joyce, C.B., Wade, P.M., - p. 265 - 275.
    vegetatie - plantengemeenschappen - laagveengebieden - hooiland - bodemwater - bodem - nederland - herstel - aquatische ecosystemen - gelderland - vegetation - plant communities - fens - meadows - soil water - soil - netherlands - rehabilitation - aquatic ecosystems
    Het beheer van Thijsse's Hof; (4) Het droge duingrasland
    Londo, G. - \ 1997
    Groen : vakblad voor groen in stad en landschap 53 (1997)1. - ISSN 0166-3534 - p. 42 - 43.
    tuinen - parken - landgoederen - particulier eigendom - plantengemeenschappen - gematigde klimaatzones - graslanden - hooiland - weiden - graslanden, gematigde streken - geschiedenis - duinen - eolisch zand - noord-holland - kennemerland - gardens - parks - estates - private ownership - plant communities - temperate zones - grasslands - meadows - pastures - temperate grasslands - history - dunes - aeolian sands
    Seed dispersal in agricultural habitats and the restoration of species-rich meadows = Dispersie van zaden in cultuurlandschappen en het herstel van soortenrijke graslanden
    Dorp, D. van - \ 1996
    Agricultural University. Promotor(en): F. Berendse; J.M. van Groenendael. - S.l. : Van Dorp - ISBN 9789054855316 - 177
    plantengemeenschappen - gematigde klimaatzones - graslanden - hooiland - weiden - graslanden, gematigde streken - plantensuccessie - mens - migratie - planten - verspreiding - zaadverspreiding - flora - vegetatie - bescherming - conservering - natuurlijke graslanden - extensieve weiden - nederland - verstoring - plant communities - temperate zones - grasslands - meadows - pastures - temperate grasslands - plant succession - man - migration - plants - dispersal - seed dispersal - flora - vegetation - protection - conservation - natural grasslands - rangelands - netherlands - disturbance

    The restoration of species-rich meadows on former agricultural land in the Netherlands has a high priority, because these ecosystems have been disappearing rapidly due to eutrophication and acidification and falling water tables. In order to be able to restore such ecosystems on wet nutrient-poor soils, the suitability and accessibility of target sites have to be improved.

    The starting point for the restoration of species-rich meadows is frequently a soil that has been drained and enriched with fertilizers and polluted with pesticides for decades. Increasing the suitability of a site then involves ameliorating the habitat quality for the selected plant species by rewetting the soil, by reducing the availability of nutrients to plants through cutting and grazing and by removing the enriched topsoil, so that new individuals can establish. It is generally assumed that seeds are still available or will soon become available, This is not necessarily always the case. There are two alternative strategies by which plants may (re)colonize new sites; either through the germination of seeds buried in the soil or through the dispersal of seeds.

    In situations where soil seed banks have been depleted, dispersal of seeds from neighbouring sources via water, wind, animals and humans is the only natural option to restock a site with seeds. Since most grassland species have a limited dispersal capacity, the distances between seed sources and target sites become crucial. Ecological corridors could facilitate the dispersal of species in agricultural habitats if they satisfy the habitat requirements of the selected species.

    This thesis deals with a few aspects of the regeneration ecology of several meadow plant species (Chapters 1-5). Two questions are raised in particular: is it possible to restore species-rich meadows on previously farmed fields? and do ditch banks function as ecological corridors for species that are absent from a site undergoing restoration? To provide a contrast with typical grassland species, fleshy-fruited plant species and their specific dispersal characteristics have also been studied (Chapter 6).

    Chapter 1 describes the first phase of the restoration of species-rich meadows on former agricultural land in an intensively farmed landscape in the centre of the Netherlands. A comparison between the species pools of the former (pre1950) species-rich meadows, a set-aside area undergoing restoration and the ditch banks in the surrounding formed landscape, revealed that 106 out of the 145 meadow species of the former species-rich meadows were still present in refugia on ditch banks. Eighty-five out of these 145 meadow species have survived or already recolonized the set-aside area, but another 60 species has not yet recolonized the site due to insufficient seed dispersal, depleted soil seed banks and/or too few appropriate microsites in the vegetation for germination and establishment.

    An increase in the number of meadow species would be attainable if the accessibility and suitability of the site can be maximized. The effectiveness of the dispersal vectors water, humans and animals is extremely limited in the study area, leaving wind as the principal dispersal vector. Although some of the missing (extinct) species with long-range dispersal or permanent seed banks will reach the site without help, most species will not re-establish without being introduced deliberately.

    Chapter 2 analyses the dynamic distribution of ten perennial plant species typical of species-rich meadows in a Dutch agricultural landscape (220 ha). Mapping in 1990, 1991 and 1992 showed that ditch banks in the study area (comprising a set- aside area and the surrounding farmed landscape) form an important refugium for the selected species. Ditch banks were managed by regular mowing plus removal of the harvested biomass in the set-aside area and by grazing, mulching and dredging in the farmed landscape. In the setaside area, seven species were more frequent, whereas two species were less frequent. One species did not differ in frequency between the two areas.

    The distribution of the selected species varied greatly between years, suggesting frequent extinction and colonization events. This type of variation was expressed as E/C, i.e. the mean ratio of the number of extinctions and colonizations, The overall E/C index for all species and all years was 0.99. Four species appeared to be decreasing in distribution in the study area (E/C>1.0), six species appeared to be stable (E/C=1.0) or even increasing (E/C<1.0). A related index used was the proportion of cells that was occupied permanently (P/(T+P)).

    For the the selected plant species, the variation in the indices E/C and (P/(T+P)). was related to five life-history attributes (seed weight, dispersal mechanism, dispersal distance, ability to vegetatively spread and seed bank type) and proved to be not significantly associated. It is concluded that different combinations of life-history attributes (i.e. regeneration strategies) lead to species stability in this type of agricultural landscape.

    Chapter 3 explores the effects of five wind speeds (variable V: 2-13.5 m/s) and five release heights (variable H: 0.2-0.6 m) on the dispersal distances of seeds of six barochorous grassland perennials in a wind tunnel. The variation in dispersal distances within a seed population and between species with different aerodynamic attributes was expressed as 1-percentile, mode and 99-percentile values. Regression analyses showed that a model with three terms (V, V*H and V 2) best explained the variance in the dispersal distances across all species. According to the regression models, the dispersal distances of seeds in the tall of a frequency distribution (99-percentile values) increased exponentially with wind speed. At wind speeds of 14 m/s, predicted maximum distances were 10 to 15 m for small and relatively heavy spherical seeds and 20 to 30 m for large and relatively light cylindrical or disk-like seeds.

    A review of meteorological data showed that wind gusts>10 m/s at plant height occur at least annually. The long life-spans of plants of the selected species (up to several decades) suggests a large potential for long-range dispersal during their life-time. Individual populations appeared to be less isolated from other populations than can be inferred from distribution patterns of seed sources.

    Chapter 4 reports on the success of establishment after adding seeds of ten selected perennial plant species to a grassland undergoing restoration. The recolonization of former agricultural grasslands by perennial grassland species is assumed to be delayed or even prevented by a lack of seeds, by a lack of microsites offering opportunities for germination and establishment, or by both.

    Sampling the seed rain with sticky traps recorded the seeds of resident species and ubiquitous wind-dispersed species of the genera Betula, Cirsium and Epilobium. Given the spatial distribution of seed sources in the surrounding agricultural landscape and the limited dispersal capacity of the selected species, the fields of the restoration site are largely inaccessible. Lack of seeds was a major cause of their absence.

    Seeds of ten plant species were also added to a sward that was mown, clipped or from which the sod had been stripped. Established plants were allowed to grow for two years and then harvested. The establishment success of the selected species on sod-stripped plots was significantly higher than on mown or clipped plots. Differences between these treatments can be explained by the low density and short duration of gaps in the intact (mown and clipped) vegetation. Differences between species were related to seed weight; species with large heavy seeds had a significantly higher establishment success than species with small and light seeds. The lack of appropriate microsites, especially for species with small seeds, was another cause of their absence.

    Recruitment from old buried seeds is another recolonization route. Burial of seeds for two years revealed very low mortality rates in species with small, spherical and hard-coated seeds, and moderate mortality rates in species with seeds of high area/content ratios and direct germination. Species of the first group are expected to be frequently recruited from seeds buried in the soil when sod stripping has been applied.

    Chapter 5 explores the importance of linear landscape elements as ecological corridors. A cellular automaton model was built in order to determine the relative importance of the principal factors which determine the rate of migration of plants through corridors: the width and habitat quality of patches within a corridor (expressed as the population growth rate λ) and the dispersal capacity of plants (expressed as the slope αof the relationship between seed number and log-distance).

    Simulations with the model using different levels of the principal factors indicated highly significant and positive main effects of dispersal capacity, habitat quality and width of corridors on the rate of migration. Significant interactions existed for dispersal capacity x width and dispersal capacity x habitat quality, indicating that the effects of width and habitat quality depended on the dispersal capacity. In narrow corridors most of the dispersed seeds were deposited outside the corridor, which significantly reduced migration rates, especially for species with long-range dispersal of seeds. In wide corridors (up to 20 m), seed losses were much smaller and migration rates approximated those of continuous habitats. The contribution of the few longrange dispersed seeds to the rate of migration was significant when the quality of habitat patches was high. In all simulations, migration rates were <5 m/yr.

    Linear landscape elements are not effective corridors for plants with shortrange dispersal of seeds, because migration rates are low (<5 m/yr), high quality patches are few, and refugia and suitable habitat patches are frequently several kilometres apart, making a cohesive infrastructure for plants elusive.

    Chapter 6 deals with the dispersal interactions between fruit-eating birds and fleshy-fruited plants that grow on wooded banks in an agricultural landscape in Twenthe, Overijssel province, the Netherlands. Wooded banks are a characteristic feature of the landscape, but their density in the landscape is changing, i.e. in some areas wooded banks have been removed whereas new banks are being planted elsewhere. On average, there were 7 fleshy-fruited plant species per 100-m transect (the range was 2 to 14 species). The number of fleshy-fruited species of the transects did not correlate with the density of wooded banks or of woodland.

    Eight fruit-eating passerine bird species were regarded as the major avian seed dispersers. They were divided into longitudinal dispersers which carry the seeds of the majority of fleshy-fruited species over short (<0.1 km) distances only and transverse dispersers which carry the seeds of species with conspicuous fruit crops over larger distances (>0.1 km). Seed dispersal by longitudinal dispersers is limited to the network of wooded landscape elements whereas transverse dispersers frequently disperse seeds to and from dissimilar landscape elements.

    The bird-mediated seed rain on wooded banks was sampled in twelve transects by using 120 seed collectors and by systematically collecting bird droppings. The seed rain was dominated by Rubus fruticosus, Sorbus aucuparia, Rhamnus frangula, Lonicera periclymenum and Sambucus nigra. The density of the seed rain was 215 ± 68 seeds m -2. Most seeds (87,6%) were deposited during the fruiting period of the plant species involved; the rest (12.4%) was deposited when ripe fruits were no longer available or was deposited on transects where fruiting adults were absent and should be regarded as immigrants.
    In order to clarify the complex interactions between birds, plants and landscapes, the ecological differences between longitudinal and transverse dispersers deserve more attention. It will help to better predict the consequences of changing the density of wooded landscape elements on the species richness and distribution of fleshy-fruited plants in fragmented landscapes.

    Evaluation of flooding scenarios for riverine pastures along the river Dinkel, the Netherlands
    Hommel, P.W.F.M. ; Dirkx, G.H.P. ; Prins, A.H. ; Wolfert, H.P. ; Vrielink, J.G. - \ 1995
    In: Scenario studies for the rural environment : selected and edited proceedings of the symposium scenario studies for the rural environment, Wageningen, The Netherlands, 12 - 15 September 1994 / Schoute, J.T.H., Finke, P.A., Veeneklaas, F.R., - p. 555 - 559.
    graslanden - hooiland - weiden - plantengemeenschappen - herstel - natuurontwikkeling - beekdalen - overijssel - twente - grasslands - meadows - pastures - plant communities - rehabilitation - nature development - brook valleys - overijssel - twente
    On relatively high natural levees in the Dinkel valley a specific type of grassland is found: the Diantho-Armerietum (Dinkel pastures). This plant community is best developed on dry, nutrient-poor, sandy and relatively young soils. Occasional floodingis essential to the conservation and restoration of Dinkel pastures. The altitude above the bankful discharge water-level is of great importance. The lower zone is strongly influenced by the nutrient-rich surface water, the higher zones are vulnerable tosoil acidification. Maintaining the current flooding frequency is favourable to the conservation of existing Dinkel pastures; a higher frequency favours the development of new ones.
    Evaluatie van inundatie-scenario's voor rivierbegeleidende graslanden langs de Dinkel
    Hommel, P.W.F.M. ; Dirkx, G.H.P. ; Prins, A.H. ; Wolfert, H.P. ; Vrielink, J.G. - \ 1995
    In: Waarheen met het landelijk gebied? : geselecteerde en geredigeerde bijdragen aan het symposium 'Waarheen met het landelijk gebied?', Wageningen, 15 september 1994 / Schoute, J.F.T., van den Berg, L.M., Farjon, H., - p. 311 - 316.
    graslanden - hooiland - weiden - plantengemeenschappen - herstel - graslanden, gematigde streken - gematigde klimaatzones - dalen - natuurtechniek - natuur - overijssel - twente - grasslands - meadows - pastures - plant communities - rehabilitation - temperate grasslands - temperate zones - valleys - ecological engineering - nature - overijssel - twente
    Op de hogere oeverwallen langs de Dinkel komt een bijzonder graslandtype voor: Diantho-Armerietum of Dinkelgrasland. Dit graslandtype heeft zijn optimum op droge, schrale, leemarme, vrij jonge gronden. Incidentele inundaties zijn essentieel voor behoud en ontwikkeling van Dinkelgraslanden. De hoogteligging is hierbij van groot belang. Te laag gelegen zones worden sterk beonvloed door het voedselrijke rivierwater; te hoog gelegen zones zijn gevoelig voor bodemverzuring. Handhaving van de huidige overstromingsfrequentie biedt de beste kansen voor de ontwikkeling van nieuwe Dinkelgraslanden.
    Het Gallo-Trifolietum, een miskende associatie uit het Mergelland
    Schaminée, J.H.J. ; Zuidhoff, A.C. - \ 1995
    Natuurhistorisch Maandblad 84 (1995)4. - ISSN 0028-1107 - p. 90 - 96.
    kalkrijke gronden - graslanden - hooiland - weiden - plantengemeenschappen - graslanden, gematigde streken - gematigde klimaatzones - zuid-limburg - calcareous soils - grasslands - meadows - pastures - plant communities - temperate grasslands - temperate zones - zuid-limburg
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