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The SE-Veluwe is a forested area in The Netherlands consisting mainly of Pinus and heathlands and includes mono- and mixed species stands of Fagus sylvatica, Quercus robur, Q. petraea, Picea abies, Pseudotsuga menziesii, Betula pubescens and B. pendens. In this area, forest managers differ in management targets. Managers with a productivity-oriented target feel limited in meeting their target because neighbouring managers with biodiversity as main target do not or insufficiently control ungulate levels. The objective of this study was to assess to what extent ungulate herbivores affect natural regeneration and to gain insight in the spatial interactions between ungulate grazing, forest management and natural regeneration. This was assessed using the model FORSPACE, which is a process-based and spatial-explicit simulation model that integrates the impacts of ungulate grazing (cattle, horse, red deer, fallow deer, roe deer and wild boar) and forest management. We found that spatial interactions caused important local differences including: (i) spatial effects due to forest management; (ii) spatial interactions between ungulate species; (iii) spatial effects due to the distribution of seed sources of trees; and (iv) spatial interactions between plant species and grazing intensity. In general, we conclude that the effects of forest management on regeneration of trees are much more profound than that of ungulate grazing and browsing. Moreover, there are relatively small differences in the effects of the ungulates at very low to very high densities. (c) 2006 Elsevier B.V. All rights reserved.

Het gaat bijzonder slecht met veel vogels van het agrarisch gebied. Zowel weidevogels als akkervogels staan zwaar onder druk. Vogelbescherming Nederland, SOVON en de Ornothologische Unie hielden een studiedag in Leiden (maart 2006). Dit artikel doet verslag van (onderzoeks)bevindingen vanuit CML, SOVON, Alterra, Radboud Universiteit en Altenburg & Wymenga

`Farming for Nature¿, a relatively new policy instrument being tried out in the Netherlands, is evaluated. The concept has been designed to allow dairy farmers to improve nature conservation on their farms. Under the scheme, no manure, fertilizer, or feed - concentrates or roughage - may be imported into farm systems from external sources. The feasibility of such a self-sustaining system and the conditions required for it to deliver the desired results, are explored with a farm-based linear programming model known as FIONA (Farm based Integrated Optimization Model for Nature and Agriculture). The model is explained and applied to `de Langstraat¿, a region in southern Netherlands

Ongoing large-scale habitat disturbance requires quick identification of conservation priorities such as targeting sites rich in species and/or endemics. Biodiversity assessments are time consuming and expensive, so surveys often rely on partial sampling. Optimal use should be made of all currently available sources of information, but methodological differences between surveys hamper direct comparison. Because diversity depends on spatial scale, diversity characteristics of different sites are best compared on the basis of species-area relationships. As a result of the incompleteness of sampling, the observed species-area relationship deviates from the "true" species-area relationship.In this paper, we identify five key factors affecting the shape of the species-area relationship due to incomplete sampling: (1) the total spatial extent of the observations, (2) the spatial distribution of the observations, (3) the proportion of the total extent sampled, (4) the proportion of the individuals in the sampled area included in the survey, and (5) the proportion of the included individuals successfully identified. We outline how methodologically different surveys can be combined to optimize the use of existing data in the evaluation of conservation needs, particularly for tropical forests.As an illustration, we analyzed four methodologically different botanical surveys in the same area of old growth lowland forest in South Cameroon with the aim of reconciling these surveys. The four surveys were (1) reconnaissance scale vegetation mapping, (2) detailed botanical assessment (all individuals), (3) incomplete botanical assessment (10% individuals), and (4) herbarium collections.By correcting for the five key factors we were able to match the results of the four different biodiversity surveys. The five key factors affected the recorded number of species and endemics differently; partial sampling of extent (3) and individuals (4) and partial identification of individuals (5) were the three most important factors.We conclude that reconciliation of biodiversity assessments is possible if the differences between methods can be accounted for. We advocate reliable documentation of survey methods, especially the five key factors, because it greatly enhances the potential of combining methodologically different surveys for comparative biodiversity analyses.

1. Sampling and processing of benthic macroinvertebrate samples is time consuming and expensive. Although a number of cost-cutting options exist, a frequently asked question is how representative a subset of data is of the whole community, in particular in areas where habitat diversity is high (like Dutch surface water habitats). 2. Weighted averaging was used to reassign 650 samples to a typology of 40 community types, testing the representativeness of different subsets of data: (i) four different types of data (presence/absence, raw, (2)log- and ln-transformed abundance), (ii) three subsets of 'indicator' taxa (taxa with indicator weights 4-12, 7-12, and 10-12) and (iii) single taxonomic groups (n = 14) by determining the classification error. 3. (2)log- and ln-transformed abundances resulted in the lowest classification error, whilst the use of qualitative data resulted in a reduction of 10% of the samples assigned to their original community type compared to the use of ln-transformed abundance data. 4. Samples from community types with a high number of unique indicator taxa had the lowest classification error, and classification error increased as similarity among community types increased. Using a subset of indicator taxa resulted in a maximum increase of the classification error of 15% when only taxa with an indicator weight 10-12 were included (error = 49.1%). 5. Use of single taxonomic groups resulted in high classification error, the lowest classification error was found using Trichoptera (68%), and was related to the frequency of the taxonomic group among samples and the indicator weights of the taxa. 6. Our findings that the use of qualitative data, subsets of indicator taxa or single taxonomic groups resulted in high classification error implies low taxonomic redundancy, and supports the use of all taxa in characterising a macroinvertebrate community, in particular in areas where habitat diversity is high.

We assessed the trophic status of Leptodora kindtii in the food web of a shallow, eutrophic lake in which 0+ age group fish were the main predators. The mean biomass of 0+ fish during three successive years varied from 0.39 g dry wt m(-2) in the first year to 0.05 g dry wt m(-2)in the second year to 2.49 g dry wt m(-2) in the third year. In the years with high fish biomass, densities of small-bodied (

The term ‘critical body residue’ (CBR) was defined as the lowest observed total body concentration of a contaminant in an organism, which is associated with the occurrence of adverse toxic effects in either individuals or populations of a defined age or stage of development. In this study, internal toxicity thresholds were determined for copper in the clitellated adult stage of earthworms ( Lumbricus rubellus and Aporrectodea caliginosa ). The objective was to assess the applicability of CBRs as a practical tool in soil quality assessment of contaminated sites and as a means of a sustainable protection of earthworm fauna. Laboratory studies showed that body concentrations of Cu were generally in agreement with the chemically available CaCl 2 -extractable fraction in soil, but that there was also some evidence of internal pH-related homeostatic regulation. Toxicological correlates of body Cu concentrations with adverse effects on cocoon production (fecundity) suggested an approximate sublethal internal threshold of about 40 mg kg −1 , with mortality occurring at about 60 mg kg −1 . Adult L. rubellus sampled from areas with a wide range of metal pollution showed body Cu concentrations with a minimum of 8 mg kg −1 and a maximum of 60 mg kg −1 . Beyond this apparent physiological tolerance range, environmental management directed at optimal earthworm population survival may not be sustainable in contaminated fields. Studies of L. rubellus colonizing a metal-contaminated experimental sludge-treated field showed that a reduced rate of colonization can already be associated with an average body Cu concentration of 25 mg kg −1 . However, in this particular field situation mixture effects of other metals that were also present in the soil and the occurrence of avoidance behaviour during colonization may have contributed to this low internal toxicity threshold. It is concluded that the CBR approach seems to be a feasible option for use as a tool in a bioavailability-based soil quality assessment, even for essential trace metals like copper, but that further insight may be needed to establish the uncertainty and reliability of the application in environmental quality assessment and decision making.

Overzicht van insectenplagen in bos en landschap, het stedelijk gebied niet inbegrepen. Een onderverdeling per provincie en naar soort plaag (bladvretende, naaldvretende insecten, houtboorders en bastkevers, zuigende, bladminerende en galvormende insecten)

In this study, we measured the ethoxy-resorufin-O-deethylase (EROD) activity in primary hepatocytes of the common green frog Rana esculenta as a biomarker for cytochrome P4501A induction. We exposed hepatocytes derived from male and female frogs to several halogenated aromatic hydrocarbons, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,4,7,8-pentachlorodibenzofuran (PCDF), polychlorinated biphenyls (PCB-126, PCB-118). and polycyclic aromatic hydrocarbons such as benzo[a]pyrene (BaP), chrysene, anthracene, and pyrene. Exposure to PCB-118, anthracene, and pyrene, up to 1 μ M, did not induce EROD activity, whereas TCDD and PCDF induced EROD activity maximally. In our primary frog hepatocytes, exposure to chrysene and BaP resulted in median effective concentration values (EC50) in the high nM range (82-1035 nM). Exposure to TCDD, PCDF and PCB-126 resulted in EC50 values of 0.4 to 8, 0.07 to 0.7, and 3 to 133 nM, respectively, which is in the same range as EC50 values found in primary hepatocytes of birds. Compared to our frog hepatocytes, primary rat hepatocytes seem to be more sensitive to TCDD, chrysene. and BaP.

In de afgelopen jaren zijn er in Nederland in het wild enkele vondsten en zichtwaarnemingen gedaan van katten die kenmerken vertoonden van de wilde kat (Felis silvestris). Deze waarnemingen worden onder de loep genomen

An extensive study was carried out in the Netherlands on the occurrence of a number of estrogenic compounds in surface water, sediment, biota, wastewater, rainwater and on the associated effects in fish. Compounds investigated included natural and synthetic hormones, phthalates, alkylphenol(ethoxylate)s and bisphenol-A. The results showed that almost all selected (xeno-)estrogens were present at low concentrations in the aquatic environment. Locally, they were found at higher levels. Hormones and nonylphenol(ethoxylate)s were present in concentrations that are reportedly high enough to cause estrogenic effects in fish. Field surveys did not disclose significant estrogenic effects in male flounder (Platichthys flesus) in the open sea and in Dutch estuaries. Minor to moderate estrogenic effects were observed in bream (Abramis brama) in major inland surface waters such as lowland rivers and a harbor area. The prevalence of feminizing effects in male fish is largest in small regional surface waters that are strongly influenced by sources of potential hormone-disrupting compounds. High concentrations of plasma vitellogenin and an increased prevalence of ovotestes occurred in wild male bream in a small river receiving a considerable load of effluent from a large sewage treatment plant. After employing in vitro and in vivo bioassays, both in situ and in the laboratory, we conclude that in this case hormones (especially 17α-ethynylestradiol) and possibly also nonylphenol(ethoxylate)s are primarily responsible for these effects. © 2005 Elsevier Ltd. All rights reserved.

Er ontstaat in Nederland bijna onzichtbaar een infrastructuur voor dieeren: dassentunnels, ree-uitstapplaatsen, faunagoten, natuurbruggen, ecoducten. Boomblad geeft een overzicht van ontwikkelingen rond de barri¿rewerking van het wegenstelsel, de gevonden oplossingen en het gedrag van dieren

Beschrijving van zwenkgras Festuca pallens, zoals dat voorkomt in herbariummateriaal van Nederlandse bodem in de collectie van het Nationaal Herbarium Nederland (NHN) te Leiden

In the Netherlands Bryum torquescens is known mainly from calcareous soils and limestone in the southernmost part of the country. Most records date from the 19th century. The species was rediscovered in chalk grasslands in this same area (1995 and 2002) and in adjacent Belgium (1987).

Hoofdlijnen uit de Staatsbosbeheer studie over de ontwikkeling van loofhout in het Robbenoordbos. Het gehele bos is na de inundatie weer geheel ingeplant in de oorspronkelijke opzet. De studie vermeldt groei, ondergroei, bodemgesteldheid, gemengd bos

De hamsterpopulatie was in Zuid-Limburg in 1999 zover achteruit gegaan, dat een fokprogramma is gestart, met daarnaast een hamstervriendelijk beheer van leefgebieden. Dit artikel gaat in op de genetische processen die spelen bij de sterke afname in omvang en evalueert de mogelijke consequenties van het fokken en uitzetten van verwante dieren

Many cities are expanding rather fast. As a result several green areas vanished, while the remaining ones are getting more and more under urban pressure. Changes in the size and configuration of green urban areas will affect the liveability of a city for citizens, as well as the local survival probability of many plant and animal species. In order to keep the city liveable and healthy not only water, energy and waste flows should be managed properly, but also green urban areas. Area, connectivity and quality of habitat patches are crucial for the survival of many species. Therefore, biotope types should be maintained in a proper setting of a network, which makes the exchange of individuals of species with a poor dispersal capacity possible. For getting public support for the maintenance of nature quality of green areas a good communication between responsible authorities and citizens is conditional. Monitoring of nature quality is necessary in order to keep biodiversity at a high level. A monitoring programme can be part of an Ecological Policy Plan of the city.

Dit artikel geeft resultaten van veldonderzoek op militaire terreinen op de Veluwe (Oldebroek, Doornspijk). Het blijkt, dat er sprake is van verjonging van jeneverbessen in heidevegetaties

In veel natuurgebieden is begrazing de belangrijkste beheermaatregel. Desondanks blijven er veel vragen: wat betekent deze vorm van begrazing voor de soortendiversiteit en de bescherming van bedreigde soorten, en waar worden de beste resultaten geboekt? Waar liggen de knelpunten en hoe kan hier met gerichte beheermaatregelen gestuurd worden. Hoe verhoudt zich dit beheer tot de Habitatrichtlijn

Sinds 2002 worden in Zuid-Limburg hamsters geherintroduceerd in speciaal ingerichte leefgebieden. Na drie jaar monitoren is inzicht verkregen in de leefwijze van de korenwolf (Cricetus cricetus)

We determined accumulated heavy metal concentrations (Cd, Pb, Cu, Zn) of earthworms in moderately contaminated floodplain soils. Both soil and mature earthworms were sampled before and after flooding and earthworm species were identified to understand species specific differences in bioconcentration. Accumulated metal concentrations in floodplain earthworms differed before and after flooding. Differences in uptake and elimination mechanisms, in food choice and living habitat of the different earthworm species and changes in speciation of the heavy metals are possible causes for this observation. Regression equations taken from literature, that relate metal accumulation by earthworms in floodplains as a function of metal concentration in soil, performed well when all species specific data were combined in an average accumulation, but did not address differences in accumulation between earthworm species. The accumulation of metals by earthworms is species dependent and affected by flooding.

Noord-Nederland kent tientallen kilometers steentaluds van zeeweringen (strekdammen, zeedijken) die tot dusver nauwelijks plantensociologisch aandacht kregen. Dit artikel doet uitgebreid verslag van de gevonden vegetatietypen. Daarbij blijkt de Crambo een unieke plantengemeenschap te zijn

In het natuurbeheer is het streven naar meer natuurlijkheid een belangrijke doelstelling geworden. Maar keuze voor een bepaalde mate van natuurlijkheid is geen garantie voor het behoud van een 'bijbehorende' biodiversiteit. Wil een beheerder echt de biodiversiteit bewaren, dan zal hij eerst meer moeten weten over de ecologische eigenschappen van de soorten. Zo blijkt uit praktijkvoorbeelden (Beekbergerwoud, Rhederoord), afkomstig uit het bosreservatenonderzoek, dat Alterra uitvoert in opdracht van LNV in zestig gebieden, verspreid door het land

Knowledge of the interactions between organisms within trophic groups is important for an understanding of the role of biodiversity in ecosystem functioning. We hypothesised that interactions between bacterivorous nematodes of different life history strategies would affect nematode population development, bacterial community composition and activity, resulting in increased N mineralization. A microcosm experiment was conducted using three nematode species (Bursilla monhystera, Acrobeloides nanus and Plectus parvus). All the nematode species interacted with each other, but the nature and effects of these interactions depended on the specific species combination. The interaction between B. monhystera and A. nanus was asymmetrically competitive (0,-), whereas that between B. monhystera and P. parvus, and also A. nanus and P. parvus was contramensal (+, -). The interaction that affected microcosm properties the most was the interaction between B. monhystera and P. parvus. This interaction affected the bacterial community composition, increased the bacterial biomass and increased soil N mineralization. B. monhystera and P. parvus have the most different life history strategies, whereas A. nanus has a life history strategy intermediate to those of B. monhystera and P. parvus. We suggest that the difference in life history strategies between species of the same trophic group is of importance for their communal effect on soil ecosystem processes. Our results support the idiosyncrasy hypothesis on the role of biodiversity in ecosystem functioning.

Increased insight into the factors that determine the importance of dispersal limitation on species richness and species composition is of paramount importance for conservation and restoration ecology. One way to explore the importance of dispersal limitation is to use seed-sowing experiments, but these do not enable the screening of large sets of species and habitats. In the present paper we present a complementary approach based on comparing small plots with larger regions with regard to species composition and distribution of functional traits. We developed a GIS tool based on ecological and geographical criteria to quantify species pools at various spatial scales. In this GIS tool, containing floristic, large databases, phytosociological and functional information are exploited. Our premise is that differences in the nature of the species in local and regional species pools with regard to functional traits can give important clues to the processes at work in the assembly of communities. We illustrate the approach with a case study for mesotrophic hay meadows (Calthion palustris). We tested the effects of differences in frequency in the local Habitat Species Pool and differences in dispersal and persistence traits of species on local species composition. Our results show that both species pool effects and functional traits affect the probability of occurrence in small plots. Species with a high propagule weight have, given the frequency in the Local Habitat Species Pool, a lower probability of occurrence in small plots. The probability of local occurrence, however, is increased by the ability to form a persistent soil seed bank and by adult longevity. This provides support for the view that the degree of dispersal limitation is dependent on the degree of spatial isolation of the focal site relative to source populations and moreover that species inherently differ in the degree to which dispersal limitation is a limiting factor for local occurrence.

Door natuurontwikkeling langs grote rivieren wordt ruimte geboden aan natuurlijke processen als overstroming, erosie, sedimentatie en begrazing. De vestiging van struik- en boomsoorten (ooibos) maakt onderdeel uit van deze spontane natuurontwikkeling. In 2001 is onderzoek gestart langs de Waal bij Beuningen, waarbij gekeken wordt naar het proces van spontane vestiging van houtige soorten in relatie tot de overstromingskarakteristiek van de rivier en de begrazing door runderen en paarden

Long-distance seed dispersal is generally assumed to be important for the regional survival of plant species. In this study, we quantified the importance of long-distance seed dispersal for regional survival of plant species using wind dispersal as an example. We did this using a new approach, by first relating plant species' dispersal traits to seed dispersal kernels and then relating the kernels to regional survival of the species. We used a recently developed and tested mechanistic seed dispersal model to calculate dispersal kernels from dispersal traits. We used data on 190 plant species and calculated their regional survival in two ways, using species distribution data from 36,800 1 km2-grid cells and 10,754 small plots covering the Netherlands during the largest part of the 20th century. We carried out correlation and stepwise multiple regression analyses to quantify the importance of long-distance dispersal, expressed as the 99-percentile dispersal distance of the dispersal kernels, relative to the importance of median-distance dispersal and other plant traits that are likely to contribute to the explanation of regional survival: plant longevity (annual, biennial, perennial), seed longevity, and plant nutrient requirement. Results show that long-distance dispersal plays a role in determining regional survival, and is more important than median-distance dispersal and plant longevity. However, long-distance dispersal by wind explains only 1-3% of the variation in regional survival between species and is equally important as seed longevity and much less important than nutrient requirement. In changing landscapes such as in the Netherlands, where large-scale eutrophication and habitat destruction took place in the 20th century, plant traits indicating ability to grow under the changed, increasingly nutrient-rich conditions turn out to be much more important for regional survival than seed dispersal.

Deze publicatie zet een traditie voort, die begon met "Rode lijst van plantengemeenschappen in Waddengebied" (Westhoff 1993), vervolgens overzichten in Kwartaalbericht milieustatistieken (Van Duuren en Schaminée), met vervolgens de uitgaves De vegetatie van Nederland (1995-1999). De huidige uitgave is een initiatief vanuit Rijkswaterstaat (Adviesdienst Geo-Informatie en ICT), vanwege hun vegetatiebeheer in het kust- en rivierengebied

In 1997 the worm Aulodrilus japonicus was identified for the first time in The Netherlands. This article gives more information on distribution, microhabitat and life history

Nowadays many teenagers are brought to school by car and spend a great deal of their free time watching TV and playing computer games. Lack of opportunities to experience nature may influence their perception of nature. Do they miss the flower-rich grasslands and the meadow birds of the past? Do they miss the variety of plants and water animals in the ditches? If we want to convince young people that it is important to conserve biodiversity we have to find out what kinds of preconceptions, ideas and beliefs they have about environmental issues. Are they worried about deterioration of the environment and loss of nature? A survey was conducted among approximately 400 Dutch schoolchildren (age: 8–16 years) in order to test their feelings about deterioration of the environment and the extinction of species. The majority of pupils answered that they regret the extinction of species more or less, especially popular ones. For a minority it does not matter at all. The proportion of pupils who expressed indifference to the pollution of air, water and soil was 7%, 10% and 13%, respectively. Dying of the forest was taken very seriously by approximately 60% of the pupils; this percentage increased after a slide of a dead forest was shown. A similar result was obtained in respect to the assumed extinction of a common plant species: it was taken more seriously after some information was given. More than half of the pupils predicted a bad future for the Netherlands. However, this pessimistic view can be changed into a more optimistic one by stimulating activities to improve the environment. The fact that most pupils judged their own future positive may indicate that they feel to have some control on the quality of their own life.

In de Nederlandse flora's worden de grofbladerige schapengrassen met lange naalden samengevat onder een taxon, dat enkel sporadisch in Frankrijk voorkomt. Onderzoek is gedaan naar herbariummateriaal in Nederland, de naam van de soorten die hier voorkomen

Op 4 oktober 2004 overleed Dr. Anne van Wijngaarden op 78-jarige leeftijd in zijn huis bij Millac- Carlux, Frankrijk. Hij was een van de Nederlandse oprichters van de Vereniging voor Zoogdierkunde en Zoogdierbescherming. Nadat zijn eindexamen op de middelbare school wilde Anne aanvankelijk geologie studeren, maar toen de verplichte excursies te duur bleken, werd het biologie. Nog voordat hij doctoraal-examen had gedaan, kreeg hij een baan bij de Plantenziektenkundige Dienst. Zijn eerste opdracht bestond uit een studie van de biologie en van methodes ter bestrijding van de woelrat (Arvicola terrestris). Het onderzoek naar verspreiding, habitatkeuze, voedselkeuze en voortplantingsgedrag van twee ondersoorten of vormen van dezelfde soort, de woelrat of waterrat (Arvicola terrestris terrestris) en de molmuis (Arvicola terrestris sherman) , mondde uit in een proefschrift (1954) en vormde het begin van zijn levenswerk: geografisch-ecologisch onderzoek van Nederlandse zoogdieren. Van Wijngaarden breidde zijn studie naar de woelrat verder uit met onderzoek naar de veldmuis (Microtus arvalis), met nadruk op habitatkeuze, populatiedynamiek en intra- en interspeciefieke concurrentie. Samen met collega Herman de Vries, begon hij daarnaast met het verzamelen verspreidingsgegevens van andere kleine Nederlandse zoogdieren. Braakballen van uilen waren hierbij een belangrijke bron van informatie en samen met De Vries werd een determineertabel voorbereid voor inheemse insecteneters en knaagdieren aan de hand van schedelmateriaal. Van Wijngaarden begon tevens met het verzamelen van gegevens over de verspreiding van vleermuizen in kerkgebouwen. In 1957 stapte Van Wijngaarden over naar het Rijksinstituut voor Veldbiologisch Onderzoek ten behoeve van het Natuurbehoud (RIVON), waar hij hoofd werd van de afdeling Zoölogie. Zijn belangrijkste taak was het vullen van kennisleemten met betrekking tot de verspreiding en habitatkeuze van zoogdieren. Hij richtte zich in eerste instantie op de meeste bedreigde soorten: de das (Meles meles), de otter (Lutra lutra), de Noordse woelmuis (Microtus oeconomus) en vleermuizen die overwinteren in boomholten of in kelders of die op kerkzolders voorkomen. Hij droeg daarnaast bij aan de inventarisaties van overwinterende vleermuizen in Limburgse mergelgroeven, en nam tevens de kartering van een aantal van deze groeven ter hand. Hij gaf leiding aan vele studenten, die hem bijstonden in het verzamelen van verspreidingsgegevens van zoogdieren. Als resultaat van deze noeste arbeid verscheen in 1971 de eerste verspreidingsatlas van Nederlandse zoogdieren. Van Wijngaarden interesseerde zich niet alleen in zoogdieren zelf, maar ook in hun invloed op de vegetatie. Hij werd een van de initiators van het onderzoek in Nederland naar de effecten van begrazing door grote herbivoren in natuurterreinen en uit productie genomen akkers. Van Wijngaarden was ook een van de pleitbezorgers van herintroductie van de bever (Castor fiber) in Nederlandse rivierdelta¿s. Van Wijngaarden hield zich naast zijn onderzoek aan Nederlandse zoogdieren, ook bezig met internationale beschermingsaspecten van zoogdieren. Onder auspiciën van de IUCN deed hij onderzoek naar de monniksrob (Monachus monachus), en naar de status van de bever in Europa. In 1968 organiseerde hij een expeditie naar Spitsbergen om deel te nemen aan internationaal onderzoek naar de verspreiding en ecologie van de ijsbeer (Ursus maritimus). Hij droeg bij aan een inventarisatie van de status van bedreigde Europese zoogdieren, voor de Raad van Europa, hetgeen gepubliceerd werd als supplement van het ¿Handbuch der Säugetiere Europas¿. Hij droeg bij aan een veldgids voor de niet-vliegende zoogdieren in de bossen van de Guianas. Van Wijngaarden redigeerde daarnaast verschillende buitenlandse boeken om deze beschikbaar te maken voor het Nederlandse publiek, onder meer de ¿Guide to mammal tracks¿ van Dahlstrøm en Bang (1973) en de volumes X-XIII van Grzimeks Tierleben over zoogdieren (1973-1975). In 1985 ging Van Wijngaarden, gedwongen door de gevolgen van een tien jaar eerder opgelopen hoofdblessure, vervroegd met pensioen. Hij hield zich niet meer bezig met zoogdierkunde en werd een actief lid van de Franse Botanische Vereniging.

Op verzoek van Staatsbosbeheer onderzocht Alterra de mogelijkheden voor het realiseren van een ecologische hoofdstructuur. Met twee hoofdaandachtspunten: van de Flevopolders naar de Veluwe en van de Veluwerand / Utrechtse Heuvelrug (traject Veenendaal Doesburg) naar Duitsland en omgeving Mook

Contains fulltext : 60338.pdf (Publisher’s version ) (Closed access) 1 Local plant communities can only function within a metacommunity context if they are connected by appropriate dispersal vectors, accommodating the transport of propagules between sites. The capacity for long-distance dispersal may be a key factor in the survival of local populations, especially in fragmented landscapes, and hence may have a large impact on local species composition. Dispersal vectors with a large efficiency for long-distance dispersal included in this study are: water, wind, large mammals and birds. 2 We tested the hypothesis that variation in dispersal traits across plant communities is related to the position of the communities along major environmental gradients. This hypothesis was tested for (i) separate long-distance dispersal vectors and (ii) multiple dispersal vectors (the number of potential long-distance dispersal vectors per species). 3 To quantify linkages between dispersal traits and environmental gradients, we coupled a data base containing dispersal attributes with another data base, containing 40 000 local vegetation descriptions aggregated into 123 plant communities. For each dispersal vector, the proportions of species that have access to this vector per community (weighted trait scores) were projected along three major environmental gradients: soil moisture, nutrient availability and light availability. 4 The potential importance of individual dispersal vectors showed clear differences along the three environmental gradients, with the greatest differences along the light availability gradient. The differences in dispersal traits probably reflect environmental constraints on the availability or efficiency of individual dispersal vectors. 5 The ability to be dispersed by multiple dispersal vectors is a common phenomenon in most plant communities (an average of 2.15 vectors per species). The mean number of potential long-distance dispersal vectors per species increases with light availability. This probably implies that plant communities differ in their response to both habitat fragmentation and habitat restoration. 6 Despite differences in trait spectra among communities, all dispersal syndromes are represented in nearly all communities. An important consequence of this complementarity in dispersal traits is that species within the same community may experience different connectivity. 7 The results emphasize the need for dispersal models based upon multiple dispersal vectors that explicitly include parameters for habitat characteristics.

Agapetus fuscipes is a caddisfly that only seems to occur in unimpacted streams and therefore can be a suitable indicator species for natural conditions. The species has decreased in the Netherlands because of human activities which caused organic pollution and hydromorphological degradation. Literature was reviewed to study the autecology and life cycle of A. fuscipes in order to reveai the ecological requirements of this species. By taking Agapetus fuscipes as an example, it is shown that the autecology and life cycle of an indicator species can give important clues for its presence in unimpacted and absence in impacted streams Agapetus fuscipes is a caddisfly that only seems to occur in unimpacted streams and therefore can be a suitable indicator species for natural conditions. The species has decreased in the Netherlands because of human activities which caused organic pollution and hydromorphological degradation. Literature was reviewed to study the autecology and life cycle of A. fuscipes in order to reveal the ecological requirements of this species. By taking Agapetus fuscipes as an example, it is shown that the autecology and life cycle of an indicator species can give important clues for its presence in unimpacted and absence in impacted streams. A. fuscipes is very susceptible to organic pollution and to a lesser degree to discharge dynamics (dropping water level and discharge peaks). The species copes with dynamic discharge events by maintaining a high population density and recolonisation of disturbed habitats from refuges. However, the vulnerability of the species strongly depends on the life stage of the animals (e.g., the ability to migrate, the oxygen demand and the habitat requirements differ between instars). Although several adaptations to dynamic conditions, a high frequency of discharge peaks or a long period of drought can cause the population to decline. Once a population has totally disappeared from a stream it will take the species a long time to recolonise the stream because of its low dispersion capacity. To protect this species stream restoration should focus on water quality (avoid organic pollution and agricultural run off) and on stabilising the discharge by taking care of natural infiltration in the catchment area instead of fast removal of rain water by drainage systems.

Mapping and monitoring salt marshes in the Netherlands are important activities of the Ministry of Public Works (Rijkswaterstaat). The Survey Department (Meetkundige Dienst) produces vegetation maps using aerial photographs. However, it is a time-consuming and expensive activity. The accuracy of the conventional vegetation map derived using aerial photograph interpretation (API) is estimated to be approximately 43%. An alternative method is demonstrated that uses an expert system to combine airborne hyperspectral imagery with terrain data derived from radar altimetry. The accuracy of the vegetation map generated by the expert system increased to 66%. When hyperspectral imagery alone was used to classify coastal wetlands, an accuracy of 40% was achieved - comparable to the accuracy of the API-derived vegetation map. An analysis of the efficiency of the proposed expert system showed that the speed of map production is increased by using the new method. This means that digital image classification using the expert system is an objective and repeatable method superior to the conventional API method.

Data from 24 water management districts and the rivers Rhine and Meuse in the Netherlands were used to study geographical distribution, relative occurrence, and environmental requirements of 76 aquatic oligochaetes (families Tubificidae, Naididae, and Lumbriculidae) (Annelida, Clitellata). Approximately 50% of the 76 species that occur in the Netherlands are uncommon, rare, or very rare. The other half of the species are common, very common or abundant. The abundant species are: Stylaria lacustris, Ophidonais serpentina, Limnodrilus claparedeianus, Limnodrilus hoffmeisteri, and Lumbriculus variegatus. With the exception of several brackish water species (those restricted in distribution to water management districts close to the sea that are influenced by salt water influx) and specific running water species (restricted mainly to the eastern part of the Netherlands), most of the species occurred throughout the whole Netherlands. The species distribution was related to environmental variables using ordination. In general, species distribution was correlated with either large waters with high chloride and phosphorus concentrations and a high hydrogen ion concentration (as pH), or with small forested (running) waters in more natural (undeveloped) areas that occasionally become intermittent. Vegetation cover was positively correlated with several swimming species in the family Naididae. While the distribution of aquatic oligochaetes in some families occurring in the Netherlands is known to some extent, the occurrence and distribution of rare and small taxa, particularly those that are difficult to identify taxonomically, is virtually unknown. Some of the rare oligochaete taxa, especially those associated with unique habitats, have received only cursory attention. Also in the data studied, the observations of the more rare species were too few to draw conclusions. To improve our knowledge of oligochaete distribution in the Netherlands, additional research should focus on rare species associated with special habitats and water types (natural areas) and those taxa in poorly known families. The standardisation of sampling and processing methodologies, particularly the use of nets and sieves with fine-meshed screening, will ensure the collection of the smaller species of oligochaetes. Subsequently, oligochaetes should be identified to species level by experienced taxonomists trained in oligochaete identification. Finally, many aquatic oligochaete species are identifiable only when sexually mature and therefore the time of year in which samples are collected is critical to the accurate representation of true oligochaete diversity at any given site. For analysing the relation between species and environmental variables the best option is to use composite data from spring and autumn.

Winter flooded rice fields can serve as substitute habitat for migratory waterfowl. Not much is known about the effects of the foraging waterfowl on nutrient cycling in rice production systems. This study quantifies the effect of foraging waterfowl on decomposition of rice residue and N-cycling in a winter flooded rice field in the Sacramento Valley, California. Along two transects in a field, pairs of control plots and exclosure plots, which excluded waterfowl, were set up. The original straw residue within the inner 2 m2 of the 3 m ×3 m plots was replaced by 15 N labeled straw residue. The labeled residue was subsequently followed into the light fraction and mineral fraction of the soil through the winter flooding period. Foraging waterfowl increased the loss of 15 N from the residue from 83 to 89%, but did not affect the mass decomposition and loss of total N of the residue. No significant effect of the waterfowl was seen in the recovery of the residue N in the total soil N pool and in the light fraction, although there was a low recovery of residue N within these pools in the control treatments. The recovery of residue N in the NH4+-N pool after winter flooding was significantly lower in the presence of waterfowl. The increased loss of residue N and lower recovery of residue N in the presence of waterfowl may indicate that the rate of N-cycling was increased. A better understanding of the N-cycle in winter flooded rice fields in the presence of waterfowl is needed to assess the potential benefits of winter flooding for the rice farmers.

The main objective of the European Union (EU) funded project AQEM1was to develop a framework of an assessment system for streams in Europe based on benthic macroinvertebrates that fulfils the requirements of the EU Water Framework Directive. Initial assessment methods for 28 European stream types and more generally applicable tools for stream biomonitoring in Europe were generated. The development of the system was based on a newly collected data set covering stream types in Austria, the Czech Republic, Germany, Greece, Italy, The Netherlands, Portugal and Sweden. Altogether, 901 benthic invertebrate samples were taken using a standardised multi-habitat sampling procedure and a large number of parameters describing the streams and their catchments was recorded for all sampling sites. From the stream and catchment characteristics measures of stress were derived. A large number of metrics was tested independently for each of the stream types, to identify the response of each metric to degradation of a site. This process resulted in up to 18 core metrics for the individual stream types, which were combined into a different multimetric index in each country. The multimetric AQEM assessment system is used to classify a stream stretch into an Ecological Quality Class ranging from 5 (high quality) to 1 (bad quality) and often provides information on the possible causes of degradation. AQEM provides a taxa list of 9557 European macroinvertebrate taxa with associated autecological information, a software package for performing all the calculations necessary for applying the multimetric AQEM assessment system and a manual describing all aspects of the application of the system from site selection to data interpretation.

The present study aims to investigate whether taxa with a small distribution range or taxa with low abundances indicate specific habitats or a high ecological quality and what the effect is if these taxa are excluded from ecological assessment. We compared autecological features between stream dwelling taxa with a mean abundance >5 individuals per sample and a mean abundance \\le5 individuals per sample as well as between taxa with a small distribution range and taxa with a large distribution range. The number of rare taxa (either with a small distribution range or with low abundances) in a sample was related to the ecological quality classes. To test the effect of exclusion of rare taxa we constructed 8 data sets all including 142 samples of Dutch lowland streams. From each data set we stepwise excluded taxa that had low abundances or taxa that were known to be restricted in their distribution range. With help of the AQEM assessment software we calculated the final ecological quality classes and the metrics that were included in the multimetric for the original data and the 8 selected data sets. Autecological features of the taxa within the different selections showed that taxa with small distribution ranges were often running water taxa, living on stones and gravel and indicating oligosaprobic water conditions in contrast to taxa that had a large distribution range. There were only small differences between taxa with low and high abundances. However, current velocity preference was lower for taxa with abundance \\le5 individuals per sample, saprobic values were higher and scores for typical stream habitats, such as lithal, psammal and akal were lower compared to high abundant taxa. If taxa with low abundances were excluded a higher ecological quality class was achieved in most cases, while excluding taxa with a small distribution range resulted in lower ecological quality classes. In conclusion, excluding taxa with a small distribution range led to worse ecological quality classes because these taxa have special autecological features that often indicate natural streams. On the other hand, excluding taxa with low abundances resulted in higher ecological quality classes because these taxa indicate more disturbed situations and because the number of taxa per sample was strongly reduced. Although the documentation of rare taxa (either with low abundances or with small distribution ranges) is often time and cost-intensive regarding field work, laboratory work, data processing, and analyses, the indicative power of these taxa for natural circumstances is essential and therefore rare taxa should be included in ecological assessment studies.

De landbouw kan een belangrijke rol blijven vervullen in het beheer van het landelijk gebied. Om dat te kunnen, moet aan een ingrijpend omvormingsproces vorm worden gegeven. De stelling van Vereijken dat de landbouw uit Nederland zal en mag verdwijnen, doet geen recht aan de groene potentie van deze bedrijfstak. Zorg voor natuur en landschap is niet alleen een boerenzaak, maar een maatschappelijke zaak

Tongvaren (Asplenium scolopendrium) is in Nederland voornamelijk bekend als muurplant, maar komt incidenteel ook als bosplant voor. De Sint-Pietersberg herbergt echter een rijke groeiplaats, zowel als rots- als bosplant. De plek laat tevens zien wat zo'n driekwart eeuw spontane bosontwikkeling in de omgeving van een verlaten mergelgroeve kan opleveren