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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    Satellite Earth observation data to identify anthropogenic pressures in selected protected areas
    Nagendra, H. ; Mairota, P. ; Marangi, C. ; Lucas, R. ; Dimopoulos, P. ; Honrado, J.P. ; Niphadkara, M. ; Mücher, C.A. ; Tomaselli, V. ; Panitsa, M. ; Tarantino, C. ; Manakos, I. ; Blonda, P. - \ 2015
    International Journal of applied Earth Observation and Geoinformation 37 (2015). - ISSN 0303-2434 - p. 124 - 132.
    ecosystem services - species richness - biodiversity - conservation - forest - lidar - classifications - management - predictor - invasions
    Protected areas are experiencing increased levels of human pressure. To enable appropriate conservation action, it is critical to map and monitor changes in the type and extent of land cover/use and habitat classes, which can be related to human pressures over time. Satellite Earth observation (EO) data and techniques offer the opportunity to detect such changes. Yet association with field information and expert interpretation by ecologists is required to interpret, qualify and link these changes to human pressure. There is thus an urgent need to harmonize the technical background of experts in the field of EO data analysis with the terminology of ecologists, protected area management authorities and policy makers in order to provide meaningful, context-specific value-added EO products. This paper builds on the DPSIR framework, providing a terminology to relate the concepts of state, pressures, and drivers with the application of EO analysis. The type of pressure can be inferred through the detection of changes in state (i.e. changes in land cover and/or habitat type and/or condition). Four broad categories of changes in state are identified, i.e. land cover/habitat conversion, land cover/habitat modification, habitat fragmentation and changes in landscape connectivity, and changes in plant community structure. These categories of change in state can be mapped through EO analyses, with the goal of using expert judgement to relate changes in state to causal direct anthropogenic pressures. Drawing on expert knowledge, a set of protected areas located in diverse socio-ecological contexts and subject to a variety of pressures are analysed to (a) link the four categories of changes in state of land cover/habitats to the drivers (anthropogenic pressure), as relevant to specific target land cover and habitat classes; (b) identify (for pressure mapping) the most appropriate spatial and temporal EO data sources as well as interpretations from ecologists and field data useful in connection with EO data analysis. We provide detailed examples for two protected areas, demonstrating the use of EO data for detection of land cover/habitat change, coupled with expert interpretation to relate such change to specific anthropogenic pressures. We conclude with a discussion of the limitations and feasibility of using EO data and techniques to identify anthropogenic pressures, suggesting additional research efforts required in this direction.
    Effects of Dichrostachys cinerea (L.) Wight & Arn (Fabaceae) on herbaceous species in a semi-arid rangeland in Zimbabwe
    Mudzengi, C. ; Kativu, S. ; Dahwa, E. ; Poshiwa, X. ; Murungweni, C. - \ 2014
    Nature Conservation 7 (2014). - ISSN 1314-6947 - p. 51 - 60.
    plant - invasibility - vegetation - invasions - ecosystem - botswana
    Anthropogenic alteration of an environment and other disturbance regimes may enable the expansion of some native species into new geographical areas, a phenomenon observed with Dichrostachys cinerea. Five D. cinerea invaded sites, each approximately one hectare in size were assessed for the effects of D. cinerea on native herbaceous species diversity, richness, basal cover, litter cover, top hamper and plant vigour. The same attributes were studied in five uninvaded sites adjacent to, and equal in size to each invaded site. Forty herbaceous species were identified in the area. There were significant differences (P <0.05) noted in species richness, basal cover, litter cover, top hamper, plant vigour, and species diversities between invaded and uninvaded sites, with uninvaded sites recording higher values than invaded sites. Altitude, erosion and the edaphic variables pH, N, P and K, which were included as explanatory variables, also differed significantly (P
    Invasion Biology and Ecosystem Theory: Insights from a Continent in Transformation
    Prins, H.H.T. ; Gordon, I.J. - \ 2014
    Cambridge : Cambridge University Press - ISBN 9781107035812 - 530
    invasies - invasieve soorten - ecologie - ecosystemen - planten - dieren - australazië - invasions - invasive species - ecology - ecosystems - plants - animals - australasia
    Many conservationists argue that invasive species form one of the most important threats to ecosystems the world over, often spreading quickly through their new environments and jeopardising the conservation of native species. As such, it is important that reliable predictions can be made regarding the effects of new species on particular habitats. This book provides a critical appraisal of ecosystem theory using case studies of biological invasions in Australasia. Each chapter is built around a set of 11 central hypotheses from community ecology, which were mainly developed in North American or European contexts. The authors examine the hypotheses in the light of evidence from their particular species, testing their power in explaining the success or failure of invasion and accepting or rejecting each hypothesis as appropriate. The conclusions have far-reaching consequences for the utility of community ecology, suggesting a rejection of its predictive powers and a positive reappraisal of natural history.
    A suite of models to support the quantitative assessment of spread in pest risk analysis
    Robinet, C. ; Kehlenbeck, H. ; Kriticos, D.J. ; Baker, R.H.A. ; Battisti, A. ; Brunel, S. ; Dupin, M. ; Eyre, D. ; Faccoli, M. ; Ilieva, Z. ; Kenis, M. ; Knight, J. ; Reynaud, P. ; Yart, A. ; Werf, W. van der - \ 2012
    PLoS ONE 7 (2012)10. - ISSN 1932-6203
    diabrotica-virgifera-virgifera - western corn-rootworm - long-distance dispersal - population expansion - economic-impact - pitch canker - invasions - asterisk - climate - europe
    Pest Risk Analyses (PRAs) are conducted worldwide to decide whether and how exotic plant pests should be regulated to prevent invasion. There is an increasing demand for science-based risk mapping in PRA. Spread plays a key role in determining the potential distribution of pests, but there is no suitable spread modelling tool available for pest risk analysts. Existing models are species specific, biologically and technically complex, and data hungry. Here we present a set of four simple and generic spread models that can be parameterised with limited data. Simulations with these models generate maps of the potential expansion of an invasive species at continental scale. The models have one to three biological parameters. They differ in whether they treat spatial processes implicitly or explicitly, and in whether they consider pest density or pest presence/absence only. The four models represent four complementary perspectives on the process of invasion and, because they have different initial conditions, they can be considered as alternative scenarios. All models take into account habitat distribution and climate. We present an application of each of the four models to the western corn rootworm, Diabrotica virgifera virgifera, using historic data on its spread in Europe. Further tests as proof of concept were conducted with a broad range of taxa (insects, nematodes, plants, and plant pathogens). Pest risk analysts, the intended model users, found the model outputs to be generally credible and useful. The estimation of parameters from data requires insights into population dynamics theory, and this requires guidance. If used appropriately, these generic spread models provide a transparent and objective tool for evaluating the potential spread of pests in PRAs. Further work is needed to validate models, build familiarity in the user community and create a database of species parameters to help realize their potential in PRA practice
    The emergence of enlightened anthropocentrism in ecological resoration
    Keulartz, J. - \ 2012
    Nature and Culture 7 (2012)1. - ISSN 1558-6073 - p. 48 - 71.
    ecosystem services - changing environment - crowded planet - biodiversity - conservation - management - sustainability - millennium - invasions - paradigm
    Over the past decade a shift can be noticed from ecological restoration to ecological design, where ecological design stands for a technocratic approach that courts hubris and mastery rather than humility and self-restraint. Following Eric Higgs, this shift can be seen as a “hyperactive and heedless response“ to global environmental change, especially climate change. The new technocratic approach may be best characterized as enlightened (or prudential) anthropocentrism, where nature is only allowed that degree of agency which is required to deliver the services that are essential for human well-being. It is not only questionable if we have the scientific and technical abilities to purposeful design ecosystems that will serve our needs, but also if the new approach will be sufficient to protect biodiversity in the long run.
    Klimaatverandering trapt af
    Bron, W.A. - \ 2010
    Nature Today 2010 (2010)16-06.
    invasies - geïntroduceerde soorten - planten - klimaatverandering - insect-plant relaties - invasions - introduced species - plants - climatic change - insect plant relations
    Klimaatverandering zet exotische planten aan tot het uitbereiden van hun leefgebied en verhoogt zo de kans op 'woekersoorten'. Of deze planten van een ander continent of gewoon van hetzelfde afkomstig zijn, maakt niet uit. Zulke soorten delen drie eigenschappen die hen onoverwinnelijk kunnen maken in een nieuw gebied: in vergelijking met hun inheemse verwanten hebben ze minder ondergrondse vijanden en meer hulp tegen de plantenetende insecten. Tim Engelkes van het Nederlands Instituut voor Ecologie (NIOO-KNAW) promoveert woensdag 16 juni 2010 in Wageningen op dit onderzoek.
    Meer winterschade: De Amerikaanse ribkwal is verdwenen
    Bragt, P.H. van - \ 2010
    Nature Today 2010 (2010)09-07.
    geïntroduceerde soorten - invasies - kwal (weekdier) - kustwateren - kou - introduced species - invasions - jellyfish - coastal water - cold
    Sinds 2006 is de Amerikaanse ribkwal een exotische gast in onze zoute wateren. Hij vestigde zich meteen explosief langs de hele Nederlandse kust en ook elders op onder andere de Duitse, Deense en Zuid-Noorse kust en de Baltische Zee. Vooral in de Oosterschelde en Grevelingen kwam hij in 2007 en 2008 in onmeetbare hoeveelheden voor. Zoveel zelfs dat men vreesde dat deze nieuwe wereldburger van onze faunalijst een ecologische ramp zou gaan veroorzaken. Vorig jaar was er al sprake van een relatieve daling van het aantal ribkwallen in onze kustwateren. Nu lijken ze zowel uit de Zeeuwse Delta als in de Waddenzee zijn verdwenen. Het is aannemelijk dat de twee recente strenge winters en dan vooral de langdurige winter van 2009-2010 de Amerikaanse ribkwal uit onze kustwateren heeft verdreven.
    Climate warming, plant invasions and plant-enemy interactions
    Engelkes, T. - \ 2010
    Wageningen University. Promotor(en): Wim van der Putten, co-promotor(en): T.M. Bezemer; J.A. Harvey. - [S.l. : S.n. - ISBN 9789085856771 - 128
    invasies - geïntroduceerde soorten - planten - klimaatverandering - schistocerca gregaria - myzus persicae - insect-plant relaties - invasions - introduced species - plants - climatic change - schistocerca gregaria - myzus persicae - insect plant relations
    The climate is changing and temperatures are predicted to further increase in the future. Species respond to these changes by either adapting to the local warmer conditions and/or range shifting to higher latitudes. Some of these successful range shifting plants can become invasive in their new range. Therefore, there is a conceptual analogy of successful range shifts and biological invasions originating from other continents. Intra-continental plant species shift their ranges within the same contiguous land mass from which they originate. Inter-continental species originate from other continents from where they have been introduced before expanding in their new range. The aim of this thesis is to gain a better understanding of the plant-insect interactions that may contribute to the success of exotic plants that have expanded their ranges due to climate warming. More specifically I aimed to clarify whether climate warming-induced range expanding exotic plants are less suitable than native congener plants and whether these plants suffer less from aboveground enemies than native congener plants. In addition, I investigated if inter –and intra-continental exotic plant species differed in their suitability and if they responded differently to potential aboveground enemies.

    In the first greenhouse experiment, I tested the hypothesis that inter- and intra-continental exotic plants and phylogenetically related native plants from the same habitat do not respond differently to two aboveground polyphagous herbivores. Further I tested if intra- and inter-continental exotic plants experience less negative soil feedback than related native plants. I grew fifteen plant species with and without naive polyphagous locusts (Schistocerca gregaria) and cosmopolitan aphids (Myzus persicae) and exposed all plants to soils from their invaded range in order to test the feedback from the soil community to plant biomass production. My results show that that both inter –and intra-continental exotic plants on average were better defended against aboveground and belowground enemies than related native plant species. This suggests that successful range expanding plants may include species with invasive properties.

    Exotic plants have been shown to have neutral to positive soil feedbacks, while native plants experience negative effects from their soil biota. Belowground interactions can influence aboveground interactions and may change the relationships between exotic plants and their enemies. I examined how the performance of the two aboveground polyphagous herbivores S. gregaria and M. persicae species was influenced by feedback interactions between the plants and their soil biota and compared these responses in intra- and inter-continental exotic and related native plants. Locust mass was negatively affected by the plant specific soil community and larger on native than on exotic plants. Locust survival was also higher on native plants, but not affected by soil type. There were no differences between inter –and intra-continental plants. Aphid population size was not affected by soil type, but was highest on the intra-continental range expander. The body size of M. persicae was larger on control than on soils with specific plant communities and not affected by plant origin.

    One way of measuring the release of exotic plants from natural enemies is by comparing their herbivore loads with related plants that are native in the invaded range. These loads can be influenced by top down control of insect predators and parasitoids. In the field, I examined herbivore loads and predator pressure on two exotic (inter-continental and intra-continental) and two related native plant species. I found smaller herbivore loads on the exotic plant species than on the related native plants. Moreover, the herbivores on the exotic plants had a higher predator pressure than herbivores on the phylogenetically related native plants. These results imply that both types of exotic plants have a double advantage: enhanced bottom-up and top-down control of herbivores.

    Finally, I set up a field experiment to test the effect of herbivory on communities of exotic and native plants. I created ten communities with six exotic plant species and their phylogenetically related native species that co-occur in the same riverine habitat. Half of the communities were exposed to herbivory and the other half was grown in a herbivory-free environment. This study was done in order to test if exotic plants may dominate invaded plant communities exposed to aboveground herbivory and if this advantage of the exotic plants under herbivory would disappear when all plants were free of herbivores. Herbivory reduced aboveground plant biomass by almost half. However, exotic plants did not become the exclusive dominants in these communities, as some native species were well protected against aboveground herbivory as well. Plant species varied considerably in their responses to herbivory resulting in changes in community ranking. Interestingly, the proportional biomass contributions to the community were similar for exotic and native plant species and also not different between inter –and intra-continental plants. I conclude that release from aboveground enemies is not the only factor explaining the invasive success of intra- and inter-continental exotic plant species.

    In conclusion, climate warming-induced range expanding plant species originating from the same continent may possess invasive properties comparable to introduced inter-continental exotic plants. In the greenhouse and in the field, both inter- and intra-continental exotic plant species were more resistant against aboveground herbivores than native plants. In the greenhouse, the exotic plants suffered less from herbivory than related natives, although this did not result in their absolute dominance in the field when exposed to herbivory. Therefore, aboveground enemy exposure is not the only factor predicting the invasive success of intra- and inter-continental exotic plant species.
    Risk assessment on the possible introduction of three predatory snails (Ocinebrellus inornatus, Urosalpinx cinerea, Rapana venosa in the Dutch Wadden Sea
    Fey-Hofstede, F.E. ; Brink, A.M. van den; Wijsman, J.W.M. ; Bos, O.G. - \ 2010
    Texel : IMARES (Report / IMARES Wageningen UR no. C032/10) - 88
    mariene ecologie - geïntroduceerde soorten - invasies - effecten - aquatische ecologie - waddenzee - marine ecology - introduced species - invasions - effects - aquatic ecology - wadden sea
    Recently three alien invasive predatory snails have been found in the Dutch marine waters, which are identified by the Ministry of Agriculture, Nature and Food Quality as potential high risk species due to their possible impact on bivalve species (TRCPD/2009/3587). These are: Japanese oyster drill Ocinebrellus inornatus (syn: Ceratostoma inornatum, Ocenebra japonica), American oyster drill Urosalpinx cinerea and Asian rapa whelk Rapana venosa. In this report we describe the potential ecological and economical risks of introduction of the three alien invasive predatory snails in the Nature 2000 Wadden Sea area.
    Savanna aliens
    Masocha, M. - \ 2010
    Wageningen University. Promotor(en): Andrew Skidmore; Herbert Prins, co-promotor(en): Milena Holmgren Urba. - [S.l. : S.n. - ISBN 9789085856191 - 161
    savannen - ecosystemen - invasies - onkruiden - houtige onkruiden - gedegradeerd land - habitat vernietiging - isoptera - verbranden - geografische informatiesystemen - ecologische verstoring - verstoord land - monitoring - afrika - terrestrische ecosystemen - milieumonitoring - savannas - ecosystems - invasions - weeds - woody weeds - degraded land - habitat destruction - isoptera - burning - geographical information systems - ecological disturbance - disturbed land - monitoring - africa - terrestrial ecosystems - environmental monitoring
    Numerous alien plant species are invading African savannas causing loss of biodiversity and altering ecosystem functioning. The ecological factors and underlying mechanisms causing these invasions are poorly understood. This hinders invasive species management and biodiversity conservation. In this thesis, a range of approaches (i.e., field measurements, a greenhouse experiment, field experiments, a long-term burning experiment, remote sensing, and Geographical Information System (GIS) techniques) was used to understand how the availability of two key resources limiting primary productivity in African savannas (water and nutrients) and how major disturbances (i.e., fire, grazing) determine the invasion of these systems by alien plant species.
    Otiorhychus meridionalis, een nieuwe invasieve snuitkeversoort voor de fauna van Nederland (Coleoptera: Curculionidae)
    Heijerman, Th. ; Hellingman, S. - \ 2009
    Entomologische Berichten 69 (2009)3. - ISSN 0013-8827 - p. 95 - 100.
    coleoptera - curculionidae - otiorhynchus - invasies - ecologie - verspreiding - insectenplagen - schade - coleoptera - curculionidae - otiorhynchus - invasions - ecology - dispersal - insect pests - damage
    Wederom kan een nieuwe invasieve plaagsoort voor Nederland worden gemeld. Weer betreft het een soort uit het snuitkevergenus Otiorhynchus, namelijk O. meridionalis. Dit is de zesde soort van dit in economisch opzicht belangrijke genus die Nederland heeft bereikt. In deze bijdrage worden de nieuwe vondsten gepresenteerd en wordt kort aangegeven hoe deze soort herkend kan worden en wat de verspreiding en voedselvoorkeur zijn van deze soort
    Literatuurstudie naar de biologie, impact en mogelijke bestrijding van twee invasieve soorten: de rode Amerikaanse rivierkreeft (Procambarus clarkii) en de geknobbelde Amerikaanse rivierkreeft (Orconectes virilis)
    Roessink, I. ; Hudina, S. ; Ottburg, F.G.W.A. - \ 2009
    Wageningen : Alterra (Alterra-rapport 1923) - 61
    rivierkreeft - geïntroduceerde soorten - invasies - waterbeheer - veenweiden - aquatische ecosystemen - utrecht - crayfish - introduced species - invasions - water management - peat grasslands - aquatic ecosystems - utrecht
    Dit literatuuronderzoek is een onderdeel van een breed opgezet onderzoek in het veenweidegebied naar de invloed van rivierkreeften op het ecosysteem. Specifiek wordt ingegaan op de verschillende eigenschappen van twee soorten die voor mogelijke problemen zorgen in het beheergebied van de waterschappen in het westelijk veenweidegebied, te weten de rode- (Procambarus clarkii) en de geknobbelde Amerikaanse rivierkreeft (Orconectes virilis). Het is van belang om de gevonden resultaten steeds weer in hun oorspronkelijke context te bezien. Zo is het overgrote deel van de hier gepresenteerde studies naar P. clarkii uitgevoerd in Zuid-Europa (Portugal, Spanje, Italië) en de daar geobserveerde mechanismen en kenmerken kunnen zeker van toepassing zijn op populaties in Nederland. Echter, ze kunnen ook zeker afwijken omdat hier nu eenmaal andere klimatologische of hydrologische omstandigheden heersen. De resultaten uit Zuidelijke streken geven derhalve mogelijkheden weer die van toepassing kunnen zijn op noordelijke populaties, geen absolute zekerheden.
    Vegetation-plot data and databases in Europe: an overview
    Schaminée, J.H.J. ; Hennekens, S.M. ; Chytrý, M. ; Rodwell, J.S. - \ 2009
    Preslia 81 (2009)3. - ISSN 0032-7786 - p. 173 - 185.
    environmental-conditions - plant-communities - classification - biodiversity - information - invasions - habitats - system
    During the last decade many electronic databases of vegetation plots, mainly phytosociological relevés, were established in different European countries. These databases contain information which is extremely valuable for both testing various macroecological hypotheses and for nature conservation surveying or monitoring. The aim of this paper is to provide estimates of the number of vegetation plots there are in Europe, how many are stored in an electronic format and to assess their distribution across European countries and regions.We sent a questionnaire to the managers of national or regional databases of vegetation plots and other prominent vegetation ecologists. Meta-data obtained in this way indicate that there are > 4,300,000 vegetation-plot records in Europe, of which > 1,800,000 are already stored electronically. Of the electronic plots, 60% are stored in TURBOVEG databases. Most plot records probably exist in Germany, the Netherlands, France, Poland, Spain, Czech Republic, Italy, UK, Switzerland and Austria. The largest numbers of plots per unit area are in the Netherlands, Belgium, Denmark and countries of central Europe. The most computerized plots per country exist in the Netherlands (600,000), followed by France, the Czech Republic and the UK. Due to its strong phytosociological tradition, Europe has many more vegetation plots than any other part of the world. This wealth of unique ecological information is a challenge for future biodiversity studies. With the alarming loss in biodiversity and environmental problems like global warming and ongoing changes in land use, there is an urgent need for wide-scale scientific and applied vegetation research. Developments of information systems such as SynBioSys Europe and facilitation of data flow between the national and regional databases should make it easier to use these vegetation-plot data
    Exotische waterplant cabomba groeit explosief
    Vliet, A.J.H. van - \ 2009
    Nature Today 2009 (2009)1-5-2009.
    cabomba - geïntroduceerde soorten - invasies - nieuwe soorten - verspreiding - schadelijke waterplanten - nadelige gevolgen - bestrijdingsmethoden - cabomba - introduced species - invasions - new species - dispersal - aquatic weeds - adverse effects - control methods
    De cambomba of waterwaaier is een waterplant die oorspronkelijk uit Zuid-Amerika komt. De plant wordt veel als aquariumplant gebruikt en sinds 1986 is hij voor het eerst in het Nederlandse oppervlaktewater aangetroffen
    Exoot gesignaleerd : risicoperceptie van invasieve exoten en draagvlak voor maatregelen hiertegen
    Breukers, A. ; Slobbe, R.B. - \ 2009
    Den Haag : LEI Wageningen UR (Rapport / LEI : Werkveld 5, Milieu, natuur en landschap ) - ISBN 9789086153015 - 79
    geïntroduceerde soorten - biodiversiteit - nadelige gevolgen - plagenbestrijding - economische evaluatie - perceptie - cerambycidae - sciurus carolinensis - boomkwekerijen - invasies - phytophthora ramorum - groenbeheer - introduced species - biodiversity - adverse effects - pest control - economic evaluation - perception - cerambycidae - sciurus carolinensis - forest nurseries - invasions - phytophthora ramorum - management of urban green areas
    Dit rapport bevat een verkenning van de risicoperceptie van invasieve exoten en het draagvlak voor maatregelen hiertegen onder betrokken partijen. Uit deze verkenning blijkt dat de risicoperceptie hoog is onder partijen die economische gevolgen ondervinden van invasieve exoten. De risicoperceptie is laag als de gevolgen niet direct duidelijk zijn of niet als schadelijk worden ervaren. Een hoge risicoperceptie leidt over het algemeen tot een hoog draagvlak voor maatregelen, al speelt ook de verwachte effectiviteit van maatregelen daarbij een rol. Bepalend voor de risicoperceptie en het draagvlak voor maatregelen zijn gebrek aan kennis, biodiversiteit als collectief goed, tegenstrijdige belangen en tekortkomingen in wet- en regelgeving
    Plants on the move: plant-soil interactions in poleward shifting plant species
    Grunsven, R.H.A. van - \ 2008
    Wageningen University. Promotor(en): Frank Berendse; Wim van der Putten, co-promotor(en): Elmar Veenendaal. - [S.l.] : S.n. - ISBN 9789085852513 - 140
    planten - plantenecologie - plantensuccessie - invasies - soorten - bodem - interacties - rizosfeer - bodemflora - bodemfauna - klimaatverandering - bodem-plant relaties - plants - plant ecology - plant succession - invasions - species - soil - interactions - rhizosphere - soil flora - soil fauna - climatic change - soil plant relationships
    As a result of recent global climate change, areas that have previously been climatically unsuitable for species have now become suitable new habitats. Many plant-species are expanding their range polewards, colonizing these newly available areas. If these species are able to expand their range faster than their natural enemies they can become released from these limiting factors. A similar mechanism has been reported for invasive plant species, introduced into foreign continent, which are often found to be released from natural enemies.
    An example of an invasive plant species that is introduced into a foreing contintinent is Carpobrotus edulis. This species was found to be negatively affected by the soil community collected in the native range, while the soil communities from the invaded range did not have an effect on plant performance compared to a sterilized control. I hypothesized that a similar reduction of the negative effects of the soil community can occur when plant species shift their range. This hypothesis was tested in a greenhouse experiment. I compared plant-soil feedbacks of three plant species that have recently expanded their range into The Netherlands, with three related native species. The non-native species experienced a significantly less negative effect of plant-soil feedback than the native plant species.
    Concurrently with these range shifts local climate is changing and this might affect plant-soil feedback as well. In order to test this plant-soil feedbacks of six range expanding and six related native species were compared at two temperatures, 20°C and 25°C daytime temperature. While again native species showed a more negative plant-soil feedback than the non-native species, temperature did not affect the strength or direction of plant-soil feedback.
    Besides pair wise comparisons between native and non-native species in the invaded range, comparisons between the native and non-native range of a range expanding plant can be used to test for effects of range shifts on plant-soil interactions. Rhizosphere soil was collected from populations of Tragopogon dubius in both the native and the recently colonized range. The soil communities from the native range had a more negative effect on plant performance than the soil communities from the invaded range as compared to sterilized controls. T. pratensis, which is native to the entire studied range, did not show this pattern.
    As plant-soil interactions are the net effect of many positive and negative factors the less negative effect of plant-soil feedback can be either a result of more positive or less negative effects of the soil community. One of the mutualistic groups of organisms, the arbuscular mycorrhizal fungi (AMF) are known to be a major factor contributing to ecosystem functioning and to the maintenance of plant biodiversity and the most important soil-borne mutualists for many plants. I therefore focus on this group of soil organisms. I compared the association of T.dubius with AMF in the new part of its range with T. pratensis native to this area. Three measures for plant-fungal affinity were compared between these two plant species; the density of AMF propagules able to colonize the plant, the percentage of root length colonized by arbuscular mycorrhiza, and the composition of the resulting AMF community in the roots. This was done for four replicate soil inocula from different sites in The Netherlands. The two plant species did not differ in any of the tested factors. As there are no differences in the association with the most important mutualist the observed differences in plant-soil interaction are likely an effect of release from negative components in the soil community, e.g. soil pathogens, but further studies are needed to test this.
    Alterations in biotic interactions, through climate change and range shifts, such as a release of soil-borne natural enemies, can have significant effects on the performance of plants. Predictions of future ranges and impact of range expanding plant species on invaded ecosystems can therefore not be accurately made without a thorough understanding of its biotic interactions and the way these interactions are changed by the range shifts.

    Wegvisproef Japanse oesters in de Oosterschelde : eindrapportage
    Wijsman, J.W.M. ; Dubbeldam, M. ; Kluijver, M.J. de; Zanten, E. van; Smaal, A.C. - \ 2008
    Yerseke : IMARES (Rapport / Wageningen IMARES C063/08) - 95
    crassostrea gigas - geïntroduceerde soorten - invasies - oosterschelde - monitoring - vangmethoden - crassostrea gigas - introduced species - invasions - eastern scheldt - monitoring - trapping
    De Japanse oester, een exoot voor onze wateren, is in 1964 voor het eerst geïntroduceerd in de Oosterschelde ten behoeve van de oesterkwekers na de massale sterfte van platte oesters tijdens de strenge winter van 1962/1963. Sindsdien heeft deze soort zich ontwikkeld tot een dominante soort. In het voorjaar van 2006 is er een praktijkproef gestart om te onderzoeken of het noodzakelijk, zinvol en mogelijk is om de steeds verder oprukkende Japanse oesters (Crassostrea gigas) in de Oosterschelde te beheren. In het kader van deze proef is hiertoe 50 ha oesterbank (12,5 miljoen kg), verdeeld over vier locaties in de Oosterschelde weggevist door de Zeeuwse mosselvloot. De oesters zijn gestort op nabijgelegen stortlocaties alwaar de verwachting was dat de oesters zouden afsterven door verstikking. Het doel van deze proef is om na te gaan hoe effectief het bestand op geselecteerde proeflocaties kan worden verwijderd en eventueel hergebruikt d.m.v. toepassing van de mosselkor, tegen welke kosten, welke milieueffecten (morfologie, sedimentsamenstelling, bodemdiergemeenschap en vogels) dit met zich meebrengt en in welk tempo positieve (herstel sediment en oorspronkelijke bodemfauna) en negatieve effecten (herstel Japanse oester) zich voordoen. Dit eindrapport beschrijft de resultaten van de wegvisproef en de monitoring die in twee jaar erop volgend is uitgevoerd.
    Massaal voorkomen van Obolodiplosis robiniae (Diptera: Cecidomyidae), een nieuwe galmugsoort voor Nederland
    Roskam, H. ; Aa, H. ; Bijkerk, J. ; Ellis, W. ; Moraal, L.G. - \ 2008
    Entomologische Berichten 68 (2008)1. - ISSN 0013-8827 - p. 27 - 28.
    cecidomyiidae - diptera - nieuwe soorten - robinia pseudoacacia - invasies - habitats - nederland - geïntroduceerde soorten - cecidomyiidae - diptera - new species - robinia pseudoacacia - invasions - habitats - netherlands - introduced species
    Galinsecten zijn doorgaans trage volgers van hun waardplanten wanneer deze door de mens naar andere arealen worden overgebracht. Om die reden laten veel gallenzoekers exoten links liggen – er is immers toch niets op te vinden. Resultaten is wel dat hierdoor nieuwe vondsten te laat kunnen worden opgemerkt. Zo kon het gebeuren dat een paar maanden geleden op de oorspronkelijk uit Amerika afkomstige Robinia pseudoacacia in verbazend grote aantallen de Nearctische galmuggensoort Obolodiplosis robiniae werd aangetroffen in de tuin van een van de auteurs. Vervolgens gingen de auteurs op zoek en werd de galg verspreid over heel Nederland aangetroffen
    Dispersie : herstelde petgaten en de rol van dispersie
    Didderen, K. - \ 2007
    Wageningen : Alterra (Alterra-rapport 1564) - 67
    aquatische gemeenschappen - moerassen - plassen - herstel - dispersie - invasies - ecologie - vissen - waterkwaliteit - macrofauna - noordwest-overijssel - biologisch waterbeheer - aquatic communities - marshes - ponds - rehabilitation - dispersion - invasions - ecology - fishes - water quality - macrofauna - noordwest-overijssel - biological water management
    Als herstelmaatregelen in oppervlaktewateren succesvol worden uitgevoerd, blijkt vaak dat de gewenste soorten niet of slechts gedeeltelijk terugkeren, ondanks gunstige abiotische omstandigheden. De oorzaak ligt waarschijnlijk in de mogelijkheden van de soorten, om de afstand af te leggen tussen het herstelgebied en dichtstbijzijnde populatie. In dit onderzoek is specifiek nagegaan hoe het dispersievermogen is van indicatorsoorten in petgaten
    Indicatoren voor 'Convention on biodiversity 2010'. Indicatoren voor het invasieproces van exotische organismen in Nederland
    Weijden, W.J. van der; Leewis, R. ; Bol, P. ; Melman, T.C.P. - \ 2007
    Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu (WOt-werkdocument 53.6) - 42
    biodiversiteit - invasies - geïntroduceerde soorten - soorten - nederland - indicatoren - biodiversity - invasions - introduced species - species - netherlands - indicators
    Nederland en de Europese Unie zijn ondertekenaar van de Convention on Biodiversity (CBD). Eén van de thema’s van die conventie is ‘Alien Invasive Species'. Evenals in andere landen neemt in Nederland het aantal exoten hand over hand toe. Doel van dit CML document is het presenteren van mogelijke indicatoren voor het proces van bioinvasies in verschillende ecosystemen in Nederland (zoet en zout water, en land) en voor hun impact op natuur, economie en volksgezondheid. Het gaat daarbij om indicatoren die uitstijgen boven het niveau van de individuele soort en die meetbaar zijn tegen redelijke (meer) kosten
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