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Ervaringen met vegetatie en begrazing in kustsystemen, met name de zandige kwelders van Schiermonnikoog. Zo komen ganzen voor op de jonge onbeweide kwelder. De effecten van beweiding met vee op het gebruik van kwelders in mei door ganzen zijn geïnventariseerd in het gehele internationale waddengebied. De vraag of kwelders wel of niet beweid moeten worden is geen goede. Beweiding is geen doel op zich. Aldus de hoogleraar coastal ecology, die het belang van een veldstation, zoals Rijksuniversiteit Groningen dat op Schermonnikoog heeft, hoog inschat

In dit artikel worden enkele belangrijke spelers in het Waddengebied nader beschouwd: Raad voor de Wadden; Waddenacademie; Het Tij Geleerd en Waddenfonds. Op dit moment lijkt het een doolhof waarin een duidelijke wegwijzer in de vorm van regie ontbreekt

Dit afsluitende artikel (binnen een themanummer) geeft aanknopingspunten voor de beleids- en beheerpraktijk die voortvloeien uit het stimuleringsprogramma biodiversiteit NWO. De conclusies zijn geclusterd rond vier aspecten van biodiversiteit: veranderingen in ruimte, tijd en databeheer; functionaliteit; de strijd om ruimte; maatschappelijke inpassing. Het programma heeft geresulteerd in 17 proefschriften en ruim 80 artikelen; gekozen is voor disciplines, waarin Nederland voorop loopt (functionele biodiversiteit, dispersie van soorten en natuurbeheer en natuurherstel)

In the past, arable fields were established locally on the alvar on Öland. Several persisted until the present time, but some of them were abandoned shorter or longer ago. We found a series of arable fields forming a chronosequence: still cultivated, ca. 20 years abandoned, ca. 50 years abandoned, and never cultivated. Species of man-influenced habitats gradually disappeared from the former arable fields, but a few persisted after 50 years. A group of alvar species had re-established after 20 years, but others did not re-establish even after 50 years of abandonment, although they are present in the local species pool. We found no evidence of dispersal as a constraint for re-establishment.

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Since the introduction of the term ecosystem engineering by Jones et al. many studies have focused on positive, facilitative interactions caused by ecosystem engineering. Much less emphasis has been placed on the role of ecosystem engineering in causing negative interactions between species. Here, we report on negative interactions between two well known ecosystem engineers occurring at the interface of salt marsh and intertidal flat (i.e. common cordgrass Spartina anglica and lugworms Arenicola marina), via modification of their joint habitat. A field survey indicated that, although both species share a common habitat, they rarely co-occur on small spatial scales (, Since the introduction of the term ecosystem engineering by Jones et al. many studies have focused on positive, facilitative interactions caused by ecosystem engineering. Much less emphasis has been placed on the role of ecosystem engineering in causing negative interactions between species. Here, we report on negative interactions between two well known ecosystem engineers occurring at the interface of salt marsh and intertidal flat (i.e. common cordgrass Spartina anglica and lugworms Arenicola marina), via modification of their joint habitat. A field survey indicated that, although both species share a common habitat, they rarely co-occur on small spatial scales (

Bij twee voormalige landbouwgebieden achter de Groninger kust is de mogelijkheid onderzocht om hier brakwater vegetatie te herstellen. Dit om een geleidelijker overgang van zout naar zoet te verkrijgen. Omdat de zaadbank in de bodem onvoldoende doelsoorten bevatte, is er geëxperimenteerd met het inbrengen van achtergebleven materiaal uit de vloedlijnen. De mogelijkheden voor brakwater vegetatie zijn onderzocht in de Emmapolder en de Klutenplas in Noord Groningen

Kennis van de verbreiding van diasporen (zaden en vegetatieve delen) van kwelderplanten is van groot belang voor de planning en beheer van ontpolderingsprojecten, waarbij middels het doorsteken van dijken of zomerkaden voormalig ingepolderde gebieden worden blootgesteld aan getijdenwater met als doel de kweldervegetatie te herstellen

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Radboud University, Aquatic Ecology & Environmenta, 22 juni 2005, Promotores : Bakker, J.P., Groenendael, J.M. van Co-promotor : Smolders, A.J.P., Contains fulltext : 33142.pdf (publisher's version ) (Open Access)

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Specialization can become detrimental to a discipline if it fosters intellectual isolation. A bibliographic analysis of several research areas in plant ecology (invasion biology, succession ecology, gap/patch dynamics, and global change effects on plants) revealed that plant ecologists do not regularly make use of the findings and insights of very similar studies being conducted in other research subdisciplines, nor do they try to make their findings and insights easily accessible to researchers in other areas. Invasion papers were least likely to be cross-linked (6%) with other fields, whereas gap/patch dynamics papers were most likely to be cross-linked (15%). This tendency toward intellectual isolation may be impeding efforts to achieve more powerful generalizations in ecology by reducing the number of potentially productive exchanges among researchers. In this paper, we illustrate this problem using the example of several speciality areas that study vegetation change. We argue that, rather than characterizing studies of vegetation change on the basis of what distinguishes them from one another, plant ecologists would benefit from concentrating on what such studies have in common. As an example, we propose that several speciality areas of plant ecology could be reunified under the term ecology of vegetation change. Individual researchers, journals, and ecological societies all can take specific steps to increase the useful exchange of ideas and information among research areas. Promoting rapid and more effective communication among diverse researchers may reduce the proliferation of narrow theories, concepts, and terminologies associated with particular research areas. In this way, we can expedite our understanding of the ecological mechanisms and consequences associated with plant communities.

Complexity theory predicts that local feedback processes may strongly affect the organization of ecosystems on larger spatial scales. Whether complexity leads to increased resilience and stability or to increased vulnerability and criticality remains one of the dominant questions in ecology. We present a combined theoretical and empirical study of complex dynamics in mineralogenic salt marsh ecosystems that emerge from a positive feedback between clay accumulation and plant growth. Positive feedback induces self-organizing within the ecosystem, which buffers for the strong physical gradient that characterizes the marine-terrestrial boundary, and improves plant growth along the gradient. However, as a consequence of these self-organizing properties, salt marshes approach a critical state as the edge of the salt marsh and the adjacent intertidal flat becomes increasingly steep and vulnerable to wave attack. Disturbance caused, for instance, by a storm may induce a cascade of vegetation collapse and severe erosion on the cliff edge, leading to salt marsh destruction. Our study shows that on short timescales, self-organization improves the functioning of salt marsh ecosystems. On long timescales, however, self-organization may lead to destruction of salt marsh vegetation. [KEYWORDS: emergence ; positive feedback ; salt marsh development ; self-organization], Complexity theory predicts that local feedback processes may strongly affect the organization of ecosystems on larger spatial scales. Whether complexity leads to increased resilience and stability or to increased vulnerability and criticality remains one of the dominant questions in ecology. We present a combined theoretical and empirical study of complex dynamics in mineralogenic salt marsh ecosystems that emerge from a positive feedback between clay accumulation and plant growth. Positive feedback induces self-organizing within the ecosystem, which buffers for the strong physical gradient that characterizes the marine-terrestrial boundary, and improves plant growth along the gradient. However, as a consequence of these self-organizing properties, salt marshes approach a critical state as the edge of the salt marsh and the adjacent intertidal flat becomes increasingly steep and vulnerable to wave attack. Disturbance caused, for instance, by a storm may induce a cascade of vegetation collapse and severe erosion on the cliff edge, leading to salt marsh destruction. Our study shows that on short timescales, self-organization improves the functioning of salt marsh ecosystems. On long timescales, however, self-organization may lead to destruction of salt marsh vegetation. [KEYWORDS: emergence ; positive feedback ; salt marsh development ; self-organization]

De afgelopen decennia hebben zich periodiek jonge duintjes ontwikkeld op het strand. In de beschutting daarvan trad een aanzet op tot de vorming van een groen strand, maar dat was kleinschalig en steeds van korte duur. De afgelopen jaren is vrij plotseling een groen strand ontstaan met een oppervlakte van enkele honderden hectares. Hoe komt zoiets bijzonders tot stand?

Item does not contain fulltext, 1 Restored floodplains and backwaters lacking a viable propagule bank, may need flood pulses to facilitate inward dispersal of diaspores. Temporal patterns of hydrochorous plant dispersal are, however, not well known. 2 Diversity and abundance of diaspores dispersed in a water body over 12 months were quantified using a 200 mum net in order to: (i) test for a relationship between discharge and the number of species and diaspores dispersed; (ii) examine the effect of seed buoyancy and seed release period on the length of the dispersal period; and (iii) test whether diaspores of species that disperse during a similar period of the year are characterized by similar dispersal and dormancy traits. 3 A total 359 188 individuals of 174 vascular species developed from 144 samples, with most (90%) from vegetative diaspores and only 10% from seeds. Mean number of species and diaspores varied between months in parallel with discharge levels. Stepwise multiple regression analysis showed that both seed buoyancy and seed release influenced dispersal periods. 4 In general, species that dispersed most diaspores in spring and summer had non-dormant seeds, a shorter seed release period and a shorter seed dispersal period than species whose dormant seeds dispersed in autumn and winter. Vegetative diaspores were dispersed on average over 8 months, indicating their importance to long-distance dispersal. Several species dispersed both generative and vegetative diaspores, often in different seasons. 5 Our results may assist the planning of regenerative processes in riverine wetlands at landscape scales, as dispersal phenology, and discharge rates must be taken into consideration. Vegetative diaspores may be more important than seeds, although the latter may extend the species dispersal period into other seasons. Temporal heterogeneity in diaspore dispersal influences the identity of diaspores reaching restored habitats.

Gedurende de periode 1994-2001 zijn de effecten van ontgrondingen onderzocht in negen gebieden. Deze terreinen zijn representatief voor de verschillende uitgangssituaties van de Nederlandse zandgronden, voor de ontwikkelingsmogelijkheden van het abiotische milieu. In een aantal gebieden is de gehele bouwvoor verwijderd tot op het zand. Elders is lokaal de toplaag verwijderd

In dit artikel wordt ingegaan op de voorkeur van rotganzen (Branta bernicla) voor bepaalde habitats en op de gevolgen van verschillende beheersvormen op het voorkomen op de Waddeneilanden Ameland en Schiermonnikoog

Ingegaan wordt op relevante ruimtelijke dimensies in relatie tot diversiteit van soorten, de verbindingen tussen habitats en het herstel, en problemen in abiotische condities

The upper courses of brook valley systems harbour Nardo-Galion saxatilis communities characteristic of oligotrophic soils under low-intensity farming. Most of these communities have disappeared under intensified farming i.e. application of fertilizers. We studied the possibilities of restoration i.e. re-establishment of the former plant community by adopting various cutting regimes after the cessation of fertilization in 1972. The various cutting regimes revealed different effects after 25 yr. Regimes with cutting every second year with or without removal of the swath, and complete abandonment deviated from the other regimes that included annual haymaking with different frequency and timing. The latter group of cutting regimes came closer to the community of an adjacent field where fertilization stopped in 1967. This field in turn harboured several Nardo-Galion species after 25 yr of annual cutting, and showed more resemblance with a local reference community (at a distance of 500 m) that had not been fertilized since the 1940s. The local reference still does not match poorly developed Nardo-Galion saxatilis communities found in the region of ca. 50 km around the study area, and is far from well developed Nardo-Galion communities in the same region. The study site still harbours several species characteristic of eutrophic soil and few species characteristic of oligotrophic soil after 25 yr of annual cutting and removal of the swath. The soil seed bank harbours only few target species. Although species characteristic of oligotrophic soil are present in an adjacent field and Nardo-Galion saxatilis species occur at 500 m, they have not (yet) established in the target area.Nomenclature: van der Meijden(1990) ., The upper courses of brook valley systems harbour Nardo-Galion saxatilis communities characteristic of oligotrophic soils under low-intensity farming. Most of these communities have disappeared under intensified farming i.e. application of fertilizers. We studied the possibilities of restoration i.e. re-establishment of the former plant community by adopting various cutting regimes after the cessation of fertilization in 1972. The various cutting regimes revealed different effects after 25 yr. Regimes with cutting every second year with or without removal of the swath, and complete abandonment deviated from the other regimes that included annual haymaking with different frequency and timing. The latter group of cutting regimes came closer to the community of an adjacent field where fertilization stopped in 1967. This field in turn harboured several Nardo-Galion species after 25 yr of annual cutting, and showed more resemblance with a local reference community (at a distance of 500 m) that had not been fertilized since the 1940s. The local reference still does not match poorly developed Nardo-Galion saxatilis communities found in the region of ca. 50 km around the study area, and is far from well developed Nardo-Galion communities in the same region. The study site still harbours several species characteristic of eutrophic soil and few species characteristic of oligotrophic soil after 25 yr of annual cutting and removal of the swath. The soil seed bank harbours only few target species. Although species characteristic of oligotrophic soil are present in an adjacent field and Nardo-Galion saxatilis species occur at 500 m, they have not (yet) established in the target area.Nomenclature: van der Meijden(1990) .

In dit artikel wordt ingegaan op de mogelijkheid om melkvee te houden op grasland zonder enige bemesting en met diverse andere beperkingen. Een verkorte weergave van Gronings onderzoek in het stroomdal van de Drentsche Aa

In het project Noord-Friesland Buitendijks zal natuurontwikkeling plaatsvinden door verkweldering van bestaande zomerpolders. Over de kansen voor de ontwikkeling van kweldervegetatie: de vegetatie in de kwelder buiten de zomerpolder; de zaadvoorraad in de bodem; mogelijke verspreiding van zaden door getijdestromingen; mogelijke rol van ganzen bij het transport van kiemkrachtige zaden