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Hoewel libellen regelmatig geïnvenlariseerd worden, is er nog weinig bekend over de relatie tussen het voorkomen van (groepen van) libellen en typen ven-ecosystemen. De ibellenfauna verschilt van ven tot ven. De vraag is nu oÍ bepaalde typen vennen gekarakteriseerd kunnen worden door een specifeke combinatie van libellensoorten, oftewel een soortgemeenschap

Nu de digitalisering en informatisering van onze samenleving snel toenemen, ontstaat de vraag of de overheid haar geo-informatiebeleid moet aanpassen en deze informatie ook vrij beschikbaar moet stellen aan burgers en organisaties zodat maatschappelijke (en economische) ontwikkelingen niet worden geremd. Onduidelijk is echter welke maatschappelijke effecten kunnen worden verwacht indien de overheid dit doet. In dit artikel worden de resultaten van een korte verkennende studie gepresenteerd. Kortom: de toegang van burgers en overheden tot geo-informatie

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).

Herintroductie van soorten is zo oud als natuurbescherming in Nederland. Circa honderd jaar ervaring heeft echter geleerd dat herintroducties niet alleen complex, tijdrovend en kostbaar zijn, maar ook dat ze vaak mislukken. Daarom maakten PRI en Alterra een afweging voor toekomstige herintroducties, gebaseerd op ecologische en populatie-genetische overwegingen

De Kathager Beemden liggen in de noordelijke helft van Zuid-Limburg, op de flanken van het Geleenbeekdal, gemeente Nuth. Van de 40 ha met een reservaatbestemming is ruim de helft in eigendom en beheer bij Natuurmonumenten; de rest is particulier bezit. In dit artikel wordt een gedetaillerd overzicht gegeven van de vegetatie in twee graslandpercelen op de oostelijke dalflank, waar op talrijke punten water uittreedt

Ook voor de natuur zijn nu al veranderingen zichtbaar ten gevolge van klimaatverandering; een tijdige reactie is gewenst. Het natuurbeleid zal zich door de toenemende onvoorspelbaarheid mindewr moeten richten op het behoud van specifieke soorten en meer op het creëren van gunstige condities

In recent decades, the West European population of Black-tailed Godwits, Limosa limosa limosa, has declined in size at a quite alarming rate, while the Icelandic population, L. l. islandica, has undergone a rapid increase in population size. These two populations have been the subject of a great deal of research, much of which has been focused on understanding the causes and consequences of the contrasting population trends. In 2007, a workshop was held during the annual conference of the International Wader Study Group at La Rochelle, France, with the aims of identifying the likely causes of the population changes and providing recommendations for future actions to improve the conservation of both populations. The available evidence strongly suggests that changes in productivity as a consequence of agricultural intensification are the most likely driver of the decline in L. l. limosa, although the concentration of much of the population in just a few sites in winter and spring is likely to exacerbate their vulnerability to future habitat changes. Agricultural and climatic changes are implicated in the expansion of L. l. islandica, and the availability of both intertidal mudflats and wet grasslands as foraging habitats appears to be very important across much of the winter range of this population. A series of recommendations for actions to conserve both populations are provided, including improving agricultural land management and protecting key passage and winter sites and habitats.

Tree species can affect the soil they are growing on and this might influence their fitness. The New Zealand gymnosperm tree species kauri (Agathis australis (D. Don) Lindl.) which grows in mixed angiosperm–gymnosperm forests has a substantial effect upon the soil. We studied the hypotheses that: (1) low soil moisture availability below mature kauri trees hampers growth of kauri seedlings and angiosperm seedlings, (2) low nutrient availability below kauri trees hampers only angiosperm seedlings, and (3) angiosperm seedlings are hampered more than kauri seedlings by the conditions below kauri trees. We tested these hypotheses by planting seedlings of kauri and mapau (Myrsine australis (A. Rich) Allan) under kauri trees and applying the following treatments: removal of herbs, removal of litter, removal of nutrient limitation, and elimination of root competition of mature kauri trees. The results indicate that low soil moisture availability, or the combination of low soil moisture availability and low nutrient fertility, hampers the growth of kauri as well as mapau seedlings below kauri trees. The mapau seedlings are hampered relatively more than the kauri seedlings which might result in an increased relative fitness of the latter.

Models of the annual development cycle of trees in boreal and temperate regions were reviewed and classified on the basis of their ecophysiological assumptions. In our classification we discern two main categories of tree development: 1) fixed sequence development, which refers to irreversible ontogenetic development leading to visible phenological events such as bud burst or flowering, and 2) fluctuating development, which refers to reversible physiological phenomena such as the dynamics of frost hardiness during winter. As many of the physiological phenomena are partially reversible, we also describe integrated models, which include aspects of both fixed-sequence and fluctuating development. In our classification we further discern simple E-models, where the environmental response stays constant, and more comprehensive ES-models, where the environmental response changes according to the state of development. On the basis of this model classification, we have developed an operational modelling framework, in which we define an explicit state variable and a corresponding rate variable for each attribute of the annual cycle considered. We introduce a unifying notation, which we also use when presenting a selection of previously published models. To illustrate the various developmental phenomena and their modelling, we have carried out model simulations. Finally, we discuss the ecophysiological interpretation of the model variables, methodological aspects of the empirical development and testing of the models, the introduction of new aspects to the modelling, other closely related models, and applications of the models.

De samenstelling en het beheer van het omringende landschap kunnen bijdragen aan de effectiviteit van natuurlijke vijanden in het reguleren van plagen in gewassen. Uit ons onderzoek blijkt een duidelijke relatie tussen groenblauwe dooradering van het landschap en de mate van plaagbeheersing in de akkers. Aanwezigheid tot op honderden meters van bepaalde elementen van groenblauwe dooradering gaat samen met een verhoogde plaagbeheersing. Zo blijkt bijvoorbeeld bos tot op vijfhonderd meter van invloed te zijn op de parasitering van koolmotrupsen. Door een nieuwe analysemethode kan plaagbeheersing als landschapsdienst nu ook ruimtelijk en kwantitatief in beeld worden gebracht

Op 6 september 2007 verbleven de drie eerstgenoemde auteurs een aantal dagen op Rottumerplaat in verband met een vegetatieonderzoek. En passant werden enige korstmossen en mossen verzameld. De (korst)- mosflora van de grote Waddeneilanden is goed bekend (voor een mossenoverzicht, zie Van Tooren 2004). Mossen en korstmossen van het onbewoonde eiland Rottumerplaat bleven echter lang buiten beeld. En dat is niet verwonderlijk: Rottumerplaat is een belangrijk rustgebied voor vogels en zeehonden en niet vrij toegankelijk.

Previous studies have shown that preen wax composition in some sandpipers shifts from the usual monoesters to diesters during the breeding season, possibly to reduce the ability of mammalian predators to find nests using olfactory cues. To investigate further the relationship between incubation and wax secretion, we examined seven sandpiper species with different incubation patterns (species in which both sexes incubate, in which only males incubate and in which only females incubate). During the breeding period, diester preen wax was secreted almost exclusively by the incubating sex in species with uniparental incubation, and by both sexes in species with biparental incubation. These findings suggest that diester preen waxes have a function that is directly related to incubation. Unexpectedly, in female-incubating Curlew Sandpiper Calidris ferruginea and Buff-breasted Sandpiper Tryngites subruficollis, some males also secreted diester preen waxes during the breeding period. This suggests that some males may in fact incubate, that these waxes may be a remnant from their evolutionary past when both sexes incubated, or that males need to be olfactorally cryptic because they are involved in the making of nest scrapes. The seasonal pattern of preen wax composition was also studied in captive male, female and female-mimicking male (`faeder¿) Ruff Philomachus pugnax. Captive female Ruff changed preen wax composition from monoesters to diesters in the spring despite the fact that no incubation took place. This suggests that circannual rhythms rather than actual incubation behaviour may trigger the shift to diester waxes. All captive male Ruff, including the faeders, continued to secrete monoesters, supporting the hypothesis that only the incubating sex secretes diesters.

De ecosysteembenadering is ook geschikt voor een beoordeling op meerdere ruimtelijke schaalniveaus tegelijkertijd. De benadering is door de TCB uigewerkt voor het bodemecosysteem, maar is ruimer toepasbaar. Dat laten TCB en Alterra in deze bijdrage zien

In 1979 werd opnieuw begrazing door schapen toegepast. Uit veldwaarnemingen blijkt dat diverse plantensoorten die reeds aanwezig waren vóór de begrazing, zich over het terrein hebben verspreid, maar dat er vrijwel geen nieuwe soorten zijn bijgekomen tussen 1977 en 2005. In het kader van het Overlevingsplan Bos en Natuur (OBN) wordt sinds medio 2004 onderzoek verricht naar het functioneren en het herstel van dergelijke hellingschraallandcomplexen in Zuid-Limburg

Om meer zicht te krijgen op de eigendomsverhoudingen en het historisch landgebruik rond het bosreservaat Kerperbos (onderdeel van het Vijlenerbos) is eerst de kadastrale kaart van circa 1840 gedigitaliseerd. Veldnamen blijken vroeger anders toegepast te zijn. Vervolgens is in het bosreservaat en aangrenzende delen, samen circa 40 ha, in de periode 2003-2007 de mosflora in kaart gebracht. Dit artikel doet daar uitgebreid verslag van

Rubus canduliger is described as a new regional bramble species belonging to the series Discolores. It has been recognized in the Netherlands as a distinct species for more than 70 years but identified as the central European R. grabowskii. The latter, however, differs by its tapering prickles, regular leaves with longer petiolule of the terminal leaflet, broader, often pyramidal inflorescence, and white or pink flowers with carpels hairy at the top. R. canduliger has a well-defined range north of the Rhine river around Arnhem where it occurs in urban and other disturbed habitats. Historical events, e.g. transport of young trees in the 16th century may explain most records south of the Rhine river, 25¿50 km outside the main range. The ecology and phytosociology of the new bramble are discussed. Its distribution is compared to R. trichanthus, another regional species with a similar range as R. canduliger, but occurring in more natural habitats. In pseudogamous European blackberries (Rubus section Rubus = R. fruticosus agg.), range size is considered to be related to the age of the species. Several widespread species have disjunct distribution ranges that are suggested to be the result of long-distance dispersal by migratory birds but unintentional anthropogenic transport of seeds may be involved as well. We hypothesize that in northwestern Europe fragmentation of continuous ranges of widespread species was caused by ongoing deforestation and subsequent degradation (acidification) of originally base-rich sandy and loamy soils from the Iron Age onward. Many regional species, however, have originated and spread in the resulting man-made landscapes. A classification of range types of brambles differing in size and internal structure is presented.

The rapid developments in computer techniques and the availability of large datasets open new perspectives for vegetation analysis aiming at better understanding of the ecology and functioning of ecosystems and underlying mechanisms. Information systems prove to be helpful tools in this new field. Such information systems may integrate different biological levels, viz. species, community and landscape. They incorporate a GIS platform for the visualization of the various layers of information, enabling the analysis of patterns and processes which relate the individual levels. An example of a newly developed information system is SynBioSys Europe, an initiative of the European Vegetation Survey (EVS). For the individual levels of the system, specific sources are available, notably national and regional Turboveg databases for the community level and data from the recently published European Map of Natural Vegetation for the landscape level. The structure of the system and its underlying databases allow user-defined queries. With regard to its application, such information systems may play a vital role in European nature planning, such as the implementation the EU-program Natura 2000. To illustrate the scope and perspectives of the program, some examples from The Netherlands are presented. They are dealing with long-term changes in grassland ecosystems, including shifts in distribution, floristic composition, and ecological indicator values.

Op basis van een vangpotonderzoek wordt de relatie tussen het voorkomen van loopkeversoorten, abiotische factoren en de vegetatie beschreven. Het onderzoek werd uitgevoerd in 2004 in de Millingerwaard. Er kan geconcludeerd worden dat bepaalde loopkeversoorten alleen bij een bepaald type vegetatie voorkomt

1. Positive effects of fish on algal biomass have variously been attributed to cascading top-down effects and to nutrient enrichment by fish excretion. 2. Here, we used a combination of field and laboratory approaches to test an additional hypothesis, namely that the physical resuspension of settled algal cells by fish enhances algal biomass and alters community composition. 3. A multi-lake survey showed that phytoplankton biomass and the fraction of motile algae increased with the concentration of inorganic suspended solids. This correlation could not be explained by wind-induced resuspension because of the small size of the lakes. 4. In an enclosure experiment, chlorophyll-a concentration, phytoplankton abundance and inorganic suspended solids increased significantly in the presence of Cyprinus carpio (common carp), but only if the fish had access to the sediment. No such effects were seen when a net prevented carp reaching the sediment. 5. The effects of enhanced nutrients and reduced zooplankton grazing as a result of fish feeding could not (fully) explain these observations, suggesting that the resuspension by carp of settled algae from a surface film on the sediment was the major factor in the outcome of the experiment. 6. An increase in diatoms and green algae (organisms with a relatively large sedimentation velocity) only in enclosures where carp could reach the sediment supported this view. 7. Several lines of evidence indicate that fish-induced resuspension of algal cells from the sediment is an important mechanism that affects phytoplankton biomass and community composition in shallow lakes.

This study aims to reveal whether complexity, namely, community and trophic structure, of chronically stressed soil systems is at increased risk or remains stable when confronted with a subsequent disturbance. Therefore, we focused on a grassland with a history of four centuries of patchy contamination. Nematodes were used as model organisms because they are an abundant and trophically diverse group and representative of the soil food web and ecosystem complexity. In a field survey, a relationship between contaminants and community structures was established. Following, two groups of soil mesocosms from the field that differed in contamination level were exposed to different disturbance regimes, namely, to the contaminant zinc and a heat shock. The zinc treatment revealed that community structure is stable, irrespective of soil contamination levels. This implies that centuries of exposure to contamination led to adaptation of the soil nematode community irrespective of the patchy distribution of contaminants. In contrast, the heat shock had adverse effects on species richness in the highly contaminated soils only. The total nematode biomass was lower in the highly contaminated field samples; however, the biomass was not affected by zinc and heat treatments of the mesocosms. This means that density compensation occurred rapidly, i.e., tolerant species quickly replaced sensitive species. Our results support the hypothesis that the history of contamination and the type of disturbance determine the response of communities. Despite that ecosystems may be exposed for centuries to contamination and communities show adaptation, biodiversity in highly contaminated sites is at increased risk when exposed to a different disturbance regime. We discuss how the loss of higher trophic levels from the entire system, such as represented by carnivorous nematodes after the heat shock, accompanied by local biodiversity loss at highly contaminated sites, may result in detrimental effects on ecosystem functions. © 2007 by the Ecological Society of America.

Brachypodium xcugnacii, the hybrid of B. pinnatum and B. sylvaticum, has originated spontaneously in a vegetation with the parental species at the transition between calcareous grassland and scrub in the first author's ecological experimental garden in Scherpenzeel (The Netherlands) in a vegetation gradient between calcareous grassland and scrub. The hybrid has chromosome number 23, which is intermediate to that of the parental species (being 28 and 18, respectively). The features of B. xcugnacii are largely intermediate to those of the parental species. In 2006, a plant with intermediate features was also found in the southern part of the Province of Limburg, The Netherlands. Presumably, this plant also belongs to B. xcugnacii, even though this has not yet been confirmed by chromosome research

Few ecotoxicological studies on mammals use non-destructive methodologies, despite the growing ethical concern over the use of destructive sampling methods. In the present study we assessed exposure of hedgehogs (Erinaceus europaeus) to polychlorinated biphenyls (PCBs), dichloro-diphenyl-trichloroethanes (DDTs), hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB), by investigating concentrations of these compounds in soils and hedgehog hair from seven study sites around the urban area of Antwerp, Belgium. No relationships were observed between organochlorine compound concentrations in soils and hair from the different study areas. Furthermore, the individual variation of contamination levels in hair within study sites was high, especially for HCHs and HCB, and hair and soil had different relative profiles for PCBs, DDTs and HCHs. Our results show that concentrations of organochlorine compounds in soils alone are not predictive of the risk of these pollutants to hedgehogs and that tissue analyses are preferred to soil analyses in exposure and risk assessment studies.

Soorten kunnen het beste beschermd worden door de biotoop waarin ze voorkomen goed te beheren. Daarnaast zal er aandacht besteed moeten worden aan het behoud van de meest kwetsbare en bedreigde soorten (rode lijstsoorten). Verreweg de meeste soorten van de recente rode lijst leven als parasiet in nesten van andere soorten. Dat roept de vraag op, of deze soorten niet gemakkelijker te beschermen zouden zijn door hun gastheer te beschermen

The implications of habitat fragmentation go beyond changes in the size and composition of suitable habitat patches. In fragmented landscapes, "matrix permeability" influences the dispersal of organisms, thereby affecting the persistence of populations in such landscapes. We investigated the effect of habitat composition on the movement of adult and recently metamorphosed juvenile common frogs (Rana temporaria) emigrating from a pond in an agricultural landscape. One question driving our research was: do the numbers of captured individuals differ between habitat types? Such a difference would indicate avoidance of or preference for certain habitats. A subsidiary question was: does the response to landscape composition differ between adults and juveniles? We found significant differences in the numbers of frogs trapped in various habitat types. Adult and juvenile common frogs preferred extensive meadows and hedgerows above other habitat types. Arable land was the most avoided habitat type, but short-cut pastures and road verges were also avoided. For instance, almost 10 times more juveniles and four times more adults were caught in meadows than in arable land. Hedgerows were also frequented often, with four times more juveniles and 2.2 times more adults captured compared to arable land. Juveniles displayed more clear-cut preference and avoidance of habitat types than adults. These findings suggest that intensively farmed landscapes form a larger barrier for juveniles than for adults, from which we conclude that different life stages of the same species may react differently to matrix composition. The demonstrated influence of matrix composition on frog dispersal underlines the importance of having well-connected habitat networks to ensure the sustainability of amphibian communities in agricultural landscapes.

De mogelijkheid van dubbele bevruchting bij de otter wordt nader beschouwd nadat bij een in mei 2005 doodgereden otter ook 3 blastocysten naast 3 morula's in de baarmoeder werden aangetroffen. Dit gelijktijdig voorkomen van verschillende ontwikkelingsstadia van bevruchte eicellen duidt namelijk op herhaalde bevruchting in verschillende perioden van de oestrus

Wapendragers en stamboorders zijn in de landelijke inventarisatie 2006 van insectenplagen de meest opvallende aantasters op bomen en struiken in het stedelijk en landschappelijk groen. Nieuw is een Japanse schildluis. De eikenprocessierups werd het meest gemeld

In de media komen niet zelden doemscenario's over de effecten van klimaatverandering naar buiten. Hoe waarschijnlijk is dit verdwijnen van boomsoorten uit het Nederlandse bos; en is grootschalige sterfte wel aan de orde. Dit artikel behandelt diverse boomsoorten (beuk, es, haagbeuk, winterlinde, esdoorn) in relatie tot de bodemsoort (zandgrond, leemgrond en kleigrond)

In deze beschouwing (een vervolg op het voorgaande artikel van De Waal) wordt nader ingegaan op de samenhang tussen fysiotopen en de daaraan verbonden begroeiingen, en wordt deze verbondenheid met een aantal voorbeelden toegelicht. En wel uit verschillende fysisch-geografische eenheden. 1. Begroeiing van tichelrestruggen van uiterwaarden in het rivierengebied; 2. Begroeiing op hoge zandgronden; Begroeiing uit het Zuid-Limburgse Heuvelland

Verhoogde concentraties van verontreinigingen in een bodem zijn niet direct afleesbaar in het veld. Zo zien de uiterwaarden van de Waal er landschappelijk prima uit, maar toch worden hier steenuilen gevonden met verhoogde concentraties PCB's en cadmium. Het vaststellen van risico's van verontreinigingen in natuurgebieden blijkt ingewikkeld te zijn door allerlei variaties in tijd, ruimte en ecologische structuren

The very rare water mite Arrenurus berolinensis is reported for the first time for the Netherlands. The species was found in a peat pit in the province of Overijssel in 2006. Previous records originate from Berlin (1896) and Eastern Prussia (1907), nowadays the Russian enclave Kaliningrad. In addition, the first description of the female is provided, which had not been reported before

dendrogeomorphological approach is presented, using wood characteristics of native oak (Quercus robur L.) to infer dynamics of aeolian sediment transport in drift-sand areas. Wood samples, taken from oaks in two drift-sand areas, were analysed to study changes in tree-ring pattern and wood anatomy as a consequence of burying or exposure from drift sand. In all cases, the wood of the sampled oaks showed sudden changes in anatomy and tree-ring width due to burial by drift sand or subsequent exposure after erosion of the new soil surface. After aerial stems became covered by drift sand, the wood lost its characteristic ring-porous features, and tree rings became strongly reduced in width with less distinct ring boundaries. Buried stems that became exposed after erosion showed an abrupt increase in ring width and turned distinctly ring porous again. Roots that were exposed also adopted clear ring-porous features, increased in ring width and anatomically resembled aerial stem wood. Using tree-ring analysis, it is possible to precisely date sand deposition and erosion events by detecting the concurrent changes in anatomy of woody structures. This study indicates the high potential of dendrogeomorphology as a tool to study drift-sand dynamics with a high temporal, i.e. annual, resolution for a period going back as long as the maximum age of the trees present (in this study at least 250 years). Since the signals of past deposition and erosion events are conserved in the wood, this is the only method that can be used to reconstruct drift-sand dynamics when the actual landforms are no longer present.

Two methods were developed for the generation of cisgenic apples. Both have been successfully applied producing trees. The first method avoids the use of any foreign selectable marker genes; only the gene-of-interest is integrated between the T-DNA border sequences. The second method makes use of recombinase-based marker excision. For the first method we used the MdMYB10 gene from a red-fleshed apple coding for a transcription factor involved in regulating anthocyanin biosynthesis. Red plantlets were obtained and presence of the cisgene was confirmed. Plantlets were grafted and grown in a greenhouse. After 3 years, the first flowers appeared, showing red petals. Pollination led to production of red-fleshed cisgenic apples. The second method used the pM(arker)F(ree) vector system, introducing the scab resistance gene Rvi6, derived from apple. Agrobacterium-mediated transformation, followed by selection on kanamycin, produced genetically modified apple lines. Next, leaves from in vitro material were treated to activate the recombinase leading to excision of selection genes. Subsequently, the leaf explants were subjected to negative selection for marker-free plantlets by inducing regeneration on medium containing 5-fluorocytosine. After verification of the marker-free nature, the obtained plants were grafted onto rootstocks. Young trees from four cisgenic lines and one intragenic line, all containing Rvi6, were planted in an orchard. Appropriate controls were incorporated in this trial. We scored scab incidence for three consecutive years on leaves after inoculations with Rvi6-avirulent strains. One cisgenic line and the intragenic line performed as well as the resistant control. In 2014 trees started to overcome their juvenile character and formed flowers and fruits. The first results of scoring scab symptoms on apple fruits were obtained. Apple fruits from susceptible controls showed scab symptoms, while fruits from cisgenic and intragenic lines were free of scab., Frontiers in Plant Science, 6, ISSN:1664-462X

De gaswinning vanaf de locaties Moddergat, Lauwersoog en Vierhuizen kan effecten hebben op het Natura 2000 gebied Waddenzee. Uit voorzorg vindt de winning plaats volgens het ‘Hand aan de kraan’ principe. In dat kader vindt een uitgebreide monitoring plaats van biotische en abiotische parameters, om te controleren of gaswinning vanaf de bovengenoemde locaties geen meetbaar nadelig effect heeft op de instandhoudingsdoelstellingen van de speciale beschermingzone Waddenzee, waaronder een groot aantal vogelsoorten waarvoor het gebied is aangewezen.

Dynamics of populations may be synchronized at large spatial scales, indicating driving forces acting beyond local scales, but may also vary locally as a result of site-specific conditions. Conservation measures for fragmented and declining populations may need to address such local effects to avoid local extinction before measures at large spatial scales become effective. To assess differences in local population dynamics, we aimed to determine the demographic drivers controlling population trends in three remaining populations of the Northern Wheatear Oenanthe oenanthe in the Netherlands, as a basis for conservation actions. An integrated population model (IPM) was fitted to field data collected in each site in 2007–2011 to estimate fecundity, survival and immigration. Sites were 40–120 km apart, yet first-year recruits were observed to move between some of the sites, albeit rarely. All three populations were equally sensitive to changes in fecundity and first-year survival. One population was less sensitive to adult survival but more sensitive to immigration. A life table response experiment suggested that differences in immigration were important determinants of differences in population growth between sites. Given the importance of immigration for local dynamics along with high philopatry, resulting in low exchange between sites, creating a metapopulation structure by improving connectivity and the protection of local populations are important for the conservation of these populations. Site-specific conservation actions will therefore be efficient and, for the short term, we propose different site-specific conservation actions.

De gaswinning vanaf de locaties Moddergat, Lauwersoog en Vierhuizen kan effecten hebben op het Natura 2000 gebied Waddenzee. Uit voorzorg vindt de winning plaats volgens het ‘Hand aan de kraan’ principe. In dat kader vindt een uitgebreide monitoring plaats van biotische en abiotische parameters, om te controleren of gaswinning vanaf de bovengenoemde locaties geen meetbaar nadelig effect heeft op de instandhoudingsdoelstellingen van de speciale beschermingzone Waddenzee, waaronder een groot aantal vogelsoorten waarvoor het gebied is aangewezen.

Jaarlijks wordt in opdracht van het ministerie van Economische Zaken de Nederlandse otterpopulatie genetisch gemonitord. Daarmee wordt een vinger aan de pols gehouden wat betreft de ontwikkeling van de genetische status van de populatie. Deze vorm van monitoring, gebaseerd op DNA-profielen op basis van DNA geïsoleerd uit verse spraints (uitwerpselen), maakt het tevens mogelijk veranderingen in de ruimtelijke verspreiding en de populatieomvang van jaar tot jaar te volgen. De monitoringsronde van 2013/2014 laat zien dat de populatie verder is gegroeid naar een aantal van ca. 140 individuen. Echter, de genetische variatie binnen individuen is sterker afgenomen vergeleken met voorafgaande jaren. Onderdeel van deze monitoring is ook autopsie van dode otters, waarbij wordt gekeken naar de doodsoorzaak en de belangrijkste lichaamskenmerken. Knelpuntlocaties waar otters worden doodgereden worden in beeld gebracht. Er is een sterke toename van het jaarlijkse aantal verkeersslachtoffers. Deze lijkt gelijke tred te houden met de toename van de populatieomvang.

Op de Reijerscamp bij Wolfheze zijn de effectiviteit van bodemtransplantaties en het uitstrooien van maaisel voor het ontwikkelen van heide en heischraal grasland op een voormalig landbouwgebied vergeleken. Deze natuurherstelmaatregelen zijn toegepast en getest in gebieden waar de toplaag van de bodem (de voormalige bouwvoor) is afgegraven en in niet-afgegraven gebieden. Wat zijn de resultaten van dit experiment en welke meerwaarde levert bodemtransplantatie voor natuurontwikkeling op?

Jaarlijks wordt in opdracht van het ministerie van Economische Zaken de Nederlandse otterpopulatie genetisch gemonitord. Daarmee wordt een vinger aan de pols gehouden wat betreft de ontwikkeling van de genetische status van de populatie. Deze vorm van monitoring, gebaseerd op DNA-profielen op basis van DNA geïsoleerd uit verse spraints (uitwerpselen), maakt het tevens mogelijk veranderingen in de ruimtelijke verspreiding en de populatieomvang van jaar tot jaar te volgen. De monitoringsronde van 2013/2014 laat zien dat de populatie verder is gegroeid naar een aantal van ca. 140 individuen. Echter, de genetische variatie binnen individuen is sterker afgenomen vergeleken met voorafgaande jaren. Onderdeel van deze monitoring is ook autopsie van dode otters, waarbij wordt gekeken naar de doodsoorzaak en de belangrijkste lichaamskenmerken. Knelpuntlocaties waar otters worden doodgereden worden in beeld gebracht. Er is een sterke toename van het jaarlijkse aantal verkeersslachtoffers. Deze lijkt gelijke tred te houden met de toename van de populatieomvang.

Under natural conditions the zonation of woody species in floodplains is to a large extent determined by hydrological conditions. Flood survival varies even among closely related species of the same genus. Most studies that quantify flood survival of seedlings and saplings of European floodplain species focus on species of the genera Salix and Populus, while few studies on saplings of Quercus robur, Fraxinus excelsior, Crataegus monogyna have been carried out, and even less on comparing these species groups. We performed a comparative observational study on the presence of saplings (