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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    The role of the starfish (Asterias rubens L.) predation in blue mussel (Mytilus edulis L.) seedbed stability
    Agüera García, A. - \ 2015
    Wageningen University. Promotor(en): Aad Smaal, co-promotor(en): Jeroen Jansen; Tim Schellekens. - Wageningen : Wageningen University - ISBN 9789462572164 - 170
    mytilus edulis - mossels - voortplanting - predatie - zaaibedden - predator prooi verhoudingen - waddenzee - aquacultuur - mytilus edulis - mussels - reproduction - predation - seedbeds - predator prey relationships - wadden sea - aquaculture

    Abstract

    Mussel beds are an important ecological component in the Wadden Sea. Mussels’ offspring settle massively in new suitable areas, forming seedbeds that may disappear again within months. The probability of a seedbed to survive the first winter is defined as seedbed stability; a definition that plays a very important role in the management of newly settled seedbeds. Many factors are important in the survival or extinction of seedbeds. Predation is thought to be particularly important during the first year after settlement and therefore key to survival. Many predators feed on mussel beds, but for most of them the potential to exterminate a seedbed is restricted by different factors such as prey selection or competition. Common starfish (Asterias rubens) are capable of concentrating/aggregating in high densities on mussel seedbeds making them an especially important factor limiting/affecting survival of mussel seedbeds. This study assesses the capacities of starfish as a mussel seed predator. It also provides tools and information to assess the risks of a seedbed being attacked and exterminated by starfish.

    In Chapter 2 the role of temperature and shading on winter predation was studied. The results showed that temperature limits feeding rate and feeding activity of starfish during winter. However, starfish feeding rate exhibited very high sensitivity to temperature changes. Light intensity affected both feeding rate and feeding activity. We conclude that starfish may not be an important factor destabilizing seedbeds during the average winter, but its importance may grow along with the increasing mean winter temperature due to climate change.

    In Chapter 3 the impact of salinity changes on predation performance and survival was assessed. Salinity is the main driver of species distributions in the Wadden Sea. Results show that salinity affected predation performance by reducing feeding activity and causing changes in prey selection. Moreover, as acclimation occurred, A. rubens predation performance improved in all treatments with survivors. We conclude that osmotic stress due to a salinity decreases determines A. rubens distribution, abundance and potential impact on the prey population. However this effect is influenced by the magnitude of the change in salinity and its timescale.

    In Chapter 4 the effect of tidal currents on predation rate was assessed, however, the chapter also tackles the role of hydrodynamic stress amelioration by mussels on the A. rubens population. The results suggest that mussels interact with their own predator beyond the role of food source, by ameliorating environmental stress, creating an additional dependence link between the foundation species and the predator, which potentially has major implications for ecosystem structure and stability.

    In Chapter 5, we assessed the role of mussel association with conspecifics at high densities on prey selection by A. rubens. We concluded that size selection does not always lead to an improvement in net profit. Size selection is a trade-off between energy yield and predation energy costs, which is affected by prey behaviour.

    The results of the prior chapters were integrated in Chapter 6 with field observations and literature to develop a simulation model. This model was designed to simulate growth of mussels and starfish, predation by starfish and mussel mortality. It can also be used to predict the likely effect of future environmental change scenarios on the potential impact of A. rubens on this important resource.

    In the general discussion, Chapter 7, previous literature, field data and the results from this thesis are summarised and reviewed to explain the spatial distribution of A. rubens in the Wadden Sea and the role of environmental conditions on A. rubens predation rate. Model simulations are used to answer the question: What is the role of A. rubens predation in mussel seedbed stability?

    Natuurlijke vijanden in de sierteelt : van uitzetten naar in stand houden
    Grosman, Amir - \ 2013
    ornamental horticulture - plant protection - biological control agents - predators - supplementary feeding - predator prey relationships - augmentation - pest resistance
    MEMO: Effecten van spieringvisserij op instandhoudingsdoelen Natura 2000 - gebied IJsselmeer
    Deerenberg, C.M. ; Geelhoed, S.C.V. - \ 2012
    Den Helder : IMARES (Rapport / IMARES Wageningen UR C023/12) - 19
    vissen - watervogels - predator prooi verhoudingen - broedvogels - visserijbeheer - natura 2000 - ijsselmeer - fishes - waterfowl - predator prey relationships - breeding birds - fishery management - natura 2000 - lake ijssel
    Het IJsselmeer is in het kader van de Natuurbeschermingswet 1998 (Nbwet) aangewezen als Natura 2000-gebied, waarvoor instandhoudingsdoelen o.a. voor een aantal visetende vogelsoorten is geformuleerd. Het gaat daarbij om de instandhoudingsdoelstellingen voor de broedvogels aalscholver en visdief en niet-broedvogels fuut, aalscholver, nonnetje, grote zaagbek, dwergmeeuw en zwarte stern (Minister van LNV, 2009). Omdat niet op voorhand uitgesloten kan worden dat de spieringvisserij significante effecten heeft op de doelstellingen voor visetende watervogels in het Natura 2000-gebied, is de spieringvisserij in het voorjaar vergunningplichtig.
    Is de hamster gebaat bij bejaging van de vos?
    Haye, M.J.J. la; Muskens, G.J.D.M. ; Kats, R.J.M. van; Kuiters, A.T. - \ 2008
    De Levende Natuur 109 (2008)5. - ISSN 0024-1520 - p. 187 - 191.
    hamsters - fauna - geïntroduceerde soorten - natuurlijke vijanden - predator prooi verhoudingen - vossen - hamsters - fauna - introduced species - natural enemies - predator prey relationships - foxes
    Om de kans op een succesvolle herintroductie van de Hamster zo groot mogelijk te maken, zijn de afgelopen jaren naast het aangepaste beheer ook andere beschermingsmaatregelen genomen, waaronder het afschieten van vossen. Het afschieten van vossen is controversieel. Voor tegenstanders van afschot speelt predatie door vossen slechts een marginale rol en is afschot van vossen dus niet nodig. Voorstanders van afschot menen dat de invloed van de vos op prooipopulaties dermate hoog is, dat afschot noodzakelijk is of kan bijdragen aan het beschermen van een bedreigde prooisoort
    Lieveheersbeestjes : heersers van de akkers?
    Lommen, S.T.E. ; Cuppen, J.G.M. - \ 2007
    Entomologische Berichten 67 (2007)6. - ISSN 0013-8827 - p. 260 - 263.
    landbouwkundige entomologie - biologische bestrijding - aphidoidea - coccinella septempunctata - adalia - propylea - akkerbouw - predator prooi verhoudingen - agricultural entomology - biological control - aphidoidea - coccinella septempunctata - adalia - propylea - arable farming - predator prey relationships
    Aphidofage lieveheersbeestjes zijn predatoren die voornamelijk leven van bladluizen. Deze lieveheersbeestjes worden regelmatig aangetroffen op akkers die geplaagd worden door bladluizen. Over hun effectiviteit als natuurlijke bestrijders van deze plaagsoorten bestaan wisselende rapporten. Een theoretisch model, ondersteunend door veldwaarnemingen en laboratoriumstudies, laat zien dat de biologie van lieveheersbeestjes niet is gericht op het uitroeien van de prooi. Dit maakt het moeilijk om bladluizen via natuurlijke bestrijding met aphidofage lieveheersbeestjes tot onder een economisch acceptabel niveau terug te brengen. Vormen van biologische bestrijding waarbij exotische of inheemse lieveheersbeestjes worden geïntroduceerd zijn soms op korte termijn effectief, maar hebben allebei belangrijke nadelen
    The least weasel (Mustela nivalis nivalis) in north-western Taimyr, Siberia, during a lemming cycle
    Broekhuizen, S. ; Mulder, J.L. ; Müskens, G.J.D.M. ; Popov, I.Y. - \ 2007
    Lutra 50 (2007)2. - ISSN 0024-7634 - p. 67 - 90.
    mustela nivalis - habitats - predator prooi verhoudingen - lemmingen - siberië - mustela nivalis - habitats - predator prey relationships - lemmings - siberia
    Gedurende de zomers van 2005 t/m 2007 werd op het Siberische schiereiland Taimyr de aanwezigheid van de dwergwezel onderzocht. De belangrijkste prooisoort van de dwergwezel is hier de Siberische lemming (Lemmus sibiricus).
    Synthesis agrobiodiversity - conservation and functionality
    Noordijk, J. ; Bruin, J. ; Rijn, P. van - \ 2007
    Entomologische Berichten 67 (2007)6. - ISSN 0013-8827 - p. 278 - 283.
    insecten - plagenbestrijding - landbouwkundige entomologie - natuurlijke vijanden - habitats - predatoren van schadelijke insecten - voedingsgedrag - nederland - predator prooi verhoudingen - functionele biodiversiteit - landschapselementen - agrobiodiversiteit - insects - pest control - agricultural entomology - natural enemies - habitats - predators of insect pests - feeding behaviour - netherlands - predator prey relationships - functional biodiversity - landscape elements - agro-biodiversity
    Biodiversity, including that of insects, should be preserve or even enhanced for its own sake, sometimes encouraged by international organizations. In agricultural areas an additional reason for its conservation is the ecological services it can provide to agriculture, including the natural control of crop pests. In this special issue of Entomologische Berichten studies focusing on each of the two aims are discussed. With special attention for the anthropod groups that play a role in pest control. Both aims can partly rely on conserving and improving the network of non-productive landscape elements, but for certain goals and insect groups specific measures will be required
    Hoe roofmijten hun prooi vinden met behulp van plantengeuren
    Boer, J.G. de; Dicke, M. - \ 2005
    Entomologische Berichten 65 (2005)4. - ISSN 0013-8827 - p. 112 - 117.
    phytoseiulus persimilis - tetranychus urticae - phaseolus lunatus - predator prooi verhoudingen - geurstoffen - insectenlokstoffen - phytoseiulus persimilis - tetranychus urticae - phaseolus lunatus - predator prey relationships - odours - insect attractants
    Plantengeuren die de planten afgeven na vraat door een herbivoor insect worden door hun natuurlijke vijanden gebruikt om hun prooi te vinden. Hierover is al meer dan 25 jaar onderzoek gedaan. Recent onderzoek in het tritrofe systeem van limaboonplanten (Phaseolus lunatus), spintmijten (Tetranychus urticae) en roofmijten (Phytoseiulus persimilis) heeft uitgewezen dat roofmijten met behulp van herbivoor-geïnduceerde plantengeuren hun prooi ook kunnen vinden in een omgeving met diverse soorten planten en herbivoren.
    Isolation and Identification of Kairomone(s) in the Daphnia-Scenedesmus System
    Holthoon, F.L. van - \ 2004
    Wageningen University. Promotor(en): Aede de Groot, co-promotor(en): Teris van Beek; E. van Donk. - Wageningen : S.n. - ISBN 9789085040668 - 154
    daphnia - predator prooi verhoudingen - waarschuwingsferomonen - isolatietechnieken - chemische structuur - fractionering - hplc - kernmagnetische resonantiespectroscopie - daphnia - predator prey relationships - alarm pheromones - isolation techniques - chemical structure - fractionation - hplc - nuclear magnetic resonance spectroscopy
    Infochemicals play an important role in interactions between living organisms in aquatic environments. Although the presence of these chemical cues is confirmed in more and more systems, the chemical structures of the compounds involved remain predominantly elusive and the identification of these compounds is essential to advance the research on chemical communication. An overview of chemical cues involving Daphnia (either as producer or receiver) is given and the progress towards their isolation and structure elucidation is described (Chapter 1). Most of the research so far has concentrated on the elucidation of kairomones produced by predators of Daphnia (especially Chaoborus and several species of fish). Less study has been devoted to the isolation of the infochemical exuded by Daphnia that causes colony formation in its prey Scenedesmus. One of the main aims of this study was the isolation and identification of this chemical cue. Colony formation in Scenedesmus only occurs when unicellular populations are exposed to either Daphnia or water that had contained Daphnia. It was concluded that the responsible cue had a chemical rather than a mechanical nature, since filtered Daphnia water also showed the colony formation activity. This colony formation was the basis for the development of a bioassay (Chapter 2). A bioassay is a test that is used to measure biological activity (in this case colony formation) of chemical mixtures or biological parameters. Colonies are indicated by high values and single cells are indicated by low values. Unfortunately over time a gradual decline of the difference between negative and positive controls was observed and efforts were undertaken to determine the cause for this decline. Several conditions were investigated (such as time, temperature, algae strain, culture medium, location, incubator, Erlenmeyer size, bacterial growth and microevolution). Additionally some general properties of the kairomone (such as thermal decomposition, biodegradation and concentration) were tested. A correlation between any of the above mentioned factors and the gradual decline of the difference between negative and positive controls was not found. Given that the bioassay was performed under such highly variable and not strictly controlled circumstances, this particular bioassay seems to be rather robust. However this does not defer from the fact that the quality of the bioassay did decline over time. Until the variable is identified that is responsible for the observed decline in difference between positive and negative controls, more care should be taken to standardise as many variables as possible. Despite its drawbacks, a bioassay still remains the best option to guide isolations of bioactive compounds through controlled experiments as long as observed differences are statistically significant. To find the most suitable and practical method for the analysis of Daphnia test water several sample pre-treatment methods were compared (Chapter 3), such as liquid-liquid extraction, solid-phase extraction, stir-bar sorptive extraction, solid-phase disk extraction. A test mixture with ten known natural compounds differing in polarity (log K o/w between -4.34 and 3.70) was used. The best method for small amounts of sample was either 'stirred' SPE or 'cartridge' SPE, but for large amounts of sample (sometimes up to 20 L) 'syringe' SPE was more suited. Consequently an SPE analysis protocol was developed that could elute the active compound in one fraction (Chapter 4). The experiments were performed with different concentrations of organic solvents and different sorbents (endcapped C 18 , MF C 18 , non-endcapped C 18 , C 8 , C 2, CN, ENV + and Oasis ® HLB). Endcapped C 18 was eventually chosen for further experiments (other sorbents did not perform better) and extracted with differing concentrations of methanol in water (50%, 85%) and pure methanol (100%). The chemical cue was most often recovered from the 85% aqueous methanol fraction, which indicates the cue is moderately non-polar.Biological activity was lost when active Daphnia water was partitioned at pH 12.0 against ethyl acetate. The aqueous and organic layer were both inactive, either by inactivation of the kairomone by the basic conditions in the aqueous layer or possibly more than one compound is present with synergistic effects. At lower pH (2.0 and 7.0) biological activity was recovered from the organic layer. This could be an indication that the active compound contains an anionic group. Experiments performed with ion exchange materials (SAX, SCX and Amberlite IRA-400) focused initially on the anion exchanger (SAX). However colony formation activity was recovered from the unretained fraction in contrast to what had been reported previously. This unexpected result prompted extraction with a cation exchanger (SCX). To exclude problems related to pH sensitive silica based sorbents, experiments were repeated on a resin based sorbent (Amberlite IRA-400),however a similar result was obtained as with the SAX sorbent. No satisfying explanation was found for the presence of biological activity in the unretained fractions and absence from the retained fractions, but different counterions on the ion exchangers could play a role. The enriched extracts obtained by SPE (C 18 ) were fractionated by high performance liquid chromatography. One fraction showed a significantly higher biological activity relative to the control ('Fraction C'). Further fractionation yielded three active fractions (C2, C3,C6). This could be an indication that more than one compound is responsible for the activity. Several natural products were biologically inactive when screened in the bioassay. They were, ecdysterone and juvenile hormone III (important hormones in other Crustaceae ), urea (proposed as kairomone in Daphnia - Scenedesmus system ), and geranic acid (reference compound). Although an assumption was made to ignore possible synergistic or additive effects in these experiments, the possibility of synergism or additivity should not be ignored, given that most likely more than one active fraction is present. At this point, due to the lack of reproducible and significant results from bioassay-guided separations, another way to identify possible candidates for the role of kairomone had to be used. Daphnia and control water were first extracted using SPE and then analysed with chromatographic techniques. Chromatograms of biologically active extracts were then compared with chromatograms of non-active control extracts to determine and recognise unique peaks (i.e. peaks only present in active Daphnia test water extracts). In an attempt to maximise the available data on the unknown colony inducing compound(s) several techniques were applied simultaneously, such as gas and liquid chromatography (Chapter 5). Several small unique peaks were recognised in the silylated extracts of Daphnia test water with GC-MS analysis. Some of these were tentatively identified as dodecanol, azelaic acid, sebacic acid and veratroylformic acid, but they did not induce colonisation. HPLC detection was performed not only with ultraviolet spectroscopy but also with evaporative light scattering and by electrospray ionisation-mass spectrometry to avoid overlooking compounds without a UV chromophore. LC analysis on four columns with different packings ensured that peaks were well separated on at least one column. Chromatograms with the best resolution were obtained on a C 18 column with an ACN-H 2 Ogradient and UV detection. High noise levels reduced the usefulness of ELS detection. Several peaks unique to 90% aqueous MeOH extracts of Daphnia test water were detected, but unfortunately not identified. Some of the recognised unique peaks ( B, G,K ) eluted in previously identified active regions ('Fraction C'). Especially peak B ([M-H] ¯ = 752.8 ?,lmax227 nm) was present in high amounts and well separated from neighbouring peaks. Therefore this peak was further analysed by liquid chromatography-nuclear magnetic resonance. Peaks from several extracts were trapped onto one SPE cartridge. This way a sufficient amount of analyte could be transferred into the NMR probe to allow recording of a 1-dimensional 1 H-spectrum. Unfortunately the spectrum did not lead to elucidation of the structure of peak B . One aliquot of this collected fraction was therefore analysed by high-resolution mass spectrometry and liquid-chromatography-quadrupole time-of-flight mass-spectrometry to obtain an accurate mass, while another aliquot was checked for biological activity in a bioassay. Unfortunately analysis with HRMS was unsuccessful and analysis with LC-QTOF has not yet yielded results. The peak with a possible pseudo molecular mass of 752.8 ([M-H] ¯) could not be detected. The other aliquot that was tested for biological activity in the bioassay showed significant differences between the negative control, positive control and peak B . This peak could therefore play a role in the induction of colonies in Scenedesmus , although it is still unclear whether it acts alone. Should peak B prove to be (partly) responsible for colony formation in Scenedesmus then the most important objective of this study has been partly reached, namely the isolation of kairomone(s) in the Daphnia - Scenedesmus system. This information will enable and facilitate research into the other objectives.
    Hunter and hunted
    Broekhuizen, S. - \ 2003
    Lutra 46 (2003)1. - ISSN 0024-7634 - p. 75 - 76.
    vleesetende dieren - prooi - predator prooi verhoudingen - boekbesprekingen - menselijke invloed - carnivores - prey - predator prey relationships - book reviews - human impact
    Bespreking van het nieuwste boek van Hans Kruuk (University Press Cambridge, 2002) over landroofdieren en de invloed die ze hebben op hun prooidiersoorten, inclusief de mens, en over de invloed die de mens heeft en heeft gehad op de landroofdieren
    Helpt Baars Perca fluviatilus Zwarte Stern Chlidonias niger?
    Tulp, Ingrid ; Leeuw, Joep de - \ 2002
    Limosa 75 (2002)3. - ISSN 0024-3620 - p. 123 - 126.
    laridae - osmerus - perca - perch - bass - birds - predators - predation - prey - predator prey relationships - foraging - fishery resources - population density - population ecology - distribution - spatial distribution - freshwater ecology - animal ecology - biological competition - animal competition - sterna - fish stocks - lake ijssel

    In autumn Black Terns make use of Lake IJsselmeer during their wing moult. In this period, yearling Smelt Osmerus eperlanus is their most important prey. The availability of Smelt is determined by several abiotic factors such as turbidity and light conditions. Smelt show a distinct diurnal pattern in vertical distribution, with concentrations at greater depths during the day and a more evenly distribution during twilight and night. In addition, seasonal variation can be large and horizontal distribution is very unpredictable. Since Black Terns can only feed in the upper centimetres of the water column, they depend on Smelt that are present in this layer. This makes it difficult to predict which proportion of the Smelt stock is actually available to Black Terns and other waterbirds. In a pilot project in which we aim to quantify the proportion of Smelt that is available as food for birds, we sampled fish in August 2002 in combined surface and bottom hauls. Most Smelt were found in the hauls that held many Perch, the main predator of Smelt, in the corresponding bottom hauls. The abundance of Black Terns in the surroundings of the sampling sites showed a positive correlation with the number of Smelt caught. Smelt seem to be chased towards the surface by hunting Perch, and are driven into reach of Black Terns. Therefore from the 'food for bird' perspective an optimum density of Perch is likely to exist. As a predator of Smelt, Perch is a direct competitor of waterbirds and high densities can result in a reduction of the Smelt stock. On the other hand a minimum density of predator fish is necessary to chase Smelt within reach of aerial fishing waterbirds. Using long term datasets on the relationship between Smelt stocks and their predators and detailed measurements on vertical distribution of Smelt, we aim to better understand this complex of factors, including the role of Perch/Pikeperch Stizostedion lucioperca fishery. This may lead to ecologically sensible recommendations for fish stock management.

    Interacties tussen visetende vogels en visserij: broodnijd een kwestie van dichtheidsafhankelijkheid
    Leeuw, J.J. de - \ 2001
    Limosa 74 (2001)2. - ISSN 0024-3620 - p. 69 - 72.
    osmerus - visserij - visbestand - vogels - roofvogels - prooi - predator prooi verhoudingen - voedselketens - biomassa - biologische productie - populatiedichtheid - populatiedynamica - seizoenvariatie - biologische mededinging - concurrentie tussen dieren - voedingsgedrag - populatie-ecologie - dierecologie - hydrobiologie - ijsselmeer - osmerus - fisheries - fishery resources - birds - predatory birds - prey - predator prey relationships - food chains - biomass - biological production - population density - population dynamics - seasonal variation - biological competition - animal competition - feeding behaviour - population ecology - animal ecology - hydrobiology - lake ijssel
    Nuancering van het veel verbreide idee van concurrentie tussen visetende vogels enerzijds en sport- en beroepsvisserij anderzijds. Een reconstructie van het seizoensverloop van productie, consumptie en biomassa van Spiering (Osmerus eperlanus) in het IJsselmeer laat zien dat dichtheidsafhankelijke processen (groei en sterfte) een zodanige rol spelen dat van concurrentie nauwelijks sprake is; alleen de aalscholvers ondervinden in het late voorjaar schade van de beroepsvisserij op spiering in het vroege voorjaar
    Steps towards food web management on farms
    Smeding, F.W. - \ 2001
    Wageningen University. Promotor(en): E.A. Goewie; A.H.C. van Bruggen; W. Joenje. - S.l. : S.n. - ISBN 9789058084149 - 137
    ecologie - landschapsecologie - landbouwbedrijven - bedrijfssystemen - biodiversiteit - predator prooi verhoudingen - biologische landbouw - ecologisch evenwicht - plantenecologische groepen - plagenbehandeling - agro-ecologie - ecology - landscape ecology - farms - farming systems - biodiversity - predator prey relationships - organic farming - ecological balance - plant ecological groups - pest management - agroecology

    This paper is the report of four years of research on the functional group composition of the animal community in relation to farm and ecological infrastructure (E.I.) management on organic arable farms. The results are mainly based on abundance data of ground dwelling arthropods obtained by pitfall trapping, density data of vegetation dwelling arthropods by vacuum sampling and density data of insectivorous birds by territory mapping. Arthropods were collected in wheat crops (representing the crop area) and on the adjacent canal bank (representing the E.I.); the bird, farm and E.I. variables were measured at the farm level. Study areas included in total 18 farms with varying extents of organic duration, crop rotation intensity, and quantity and quality of E.I.

    The hypothesis of the research was that the food web structure of an organic arable farm with long organic duration as well as with an improved E.I. ( i.e. enlarged, late mown), would show a higher abundance of meso- and macrofauna of both herbivorous and detritivorous functional groups. These enhanced primary groups were expected to carry a high predator abundance at both secondary ( i.e. invertebrates) as well as tertiary ( i.e. birds) levels. With regard to the crop areas it was found, in contradiction to the hypothesis, that herbivores were most abundant in crop areas of recently converted farms and of organic farms with intensive crop rotation; this herbivore abundance was associated with invertebrate predator abundance and species diversity. In accordance with the hypothesis, some evidence was found for increased detritivore and related epigeic predator abundance related to extensive crop management on the farms of long organic duration. Whilst studying the E.I., an increased abundance of vegetation dwelling predators and also detritivores was found in improved E.I. However K-herbivore numbers did not increase in the improved E.I. when they were compared to the traditionally managed E.I. The summer abundance of epigeic predators was also not related to an improved E.I. Field studies provided some evidence for the dispersal of functional groups, abundant in the E.I., towards the crop area. However, the effects of crop conditions on the arthropod abundance in the crop area were observed to offset the influence of the E.I. Bird studies at the farm level revealed positive correlation between bird functional groups and a combination of crop area and E.I. characteristics. Bird density was found to be positively associated with high arthropod abundance in the E.I. vegetation canopy. Observations also suggested positive correlation to an increased herbivory in the crop area of the long duration organic farms that had an intensive crop rotation.

    A proposal for a descriptive or topological farm food web is drawn from field observations as well as from references in literature. Predictions are made for four different farm food web structures that express four extremes of two environmental gradients, which correspond to the length of organic duration and the amount/quality of the E.I. With reference to field observations important themes in the food web theory are discussed, including the indirect effects of subsidised detrital food chains on herbivore abundance and consequently on bird abundance, as well as the possible effects of intra guild predation on arthropod functional group composition.

    The implications of the study are that organic duration and the amount/quality of the E.I. may contribute to improving ecosystem services and to aims based on nature conservation. However an optimisation of the farm food web with regard to ecosystem services may not necessarily improve nature conservation values. It is argued that increased understanding of the farm food web and its management is likely to support the development of multi-species agroecosystems that integrate improved ecosystem services and nature conservation goals.

    Ruim baan voor de vos: gevolgen voor grote natuurgebieden en het landelijk gebied
    Niewold, F.J.J. ; Jonkers, D.A. - \ 1999
    Wageningen : IBN-DLO, Instituut voor Bos- en Natuuronderzoek - 92
    vulpes vulpes - bescherming - dierecologie - predatoren - predator prooi verhoudingen - habitats - distributie - zoögeografie - natuurreservaten - platteland - nederland - vulpes vulpes - protection - animal ecology - predators - predator prey relationships - habitats - distribution - zoogeography - nature reserves - rural areas - netherlands
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