What determines plant species diversity in Central Africa?
Proosdij, Andreas S.J. van - \ 2017
Wageningen University. Promotor(en): M.S.M. Sosef, co-promotor(en): N. Raes; J.J. Wieringa. - Wageningen : Wageningen University - ISBN 9789463436618 - 161
plants - biodiversity - species diversity - species - distribution - biogeography - central africa - biosystematics - tropical rain forests - modeling - planten - biodiversiteit - soortendiversiteit - soorten - distributie - biogeografie - centraal-afrika - biosystematiek - tropische regenbossen - modelleren
Planet Earth hosts an incredible biological diversity. Estimated numbers of species occurring on Earth range from 5 to 11 million eukaryotic species including 400,000-450,000 species of plants. Much of this biodiversity remains poorly known and many species have not yet been named or even been discovered. This is not surprising, as the majority of species is known to be rare and ecosystems are generally dominated by a limited number of common species.
Tropical rainforests are the most species-rich terrestrial ecosystems on Earth. The general higher level of species richness is often explained by higher levels of energy near the Equator (latitudinal diversity gradient). However, when comparing tropical rainforest biomes, African rainforests host fewer plant species than either South American or Asian ones. The Central African country of Gabon is situated in the Lower Guinean phytochorical region. It is largely covered by what is considered to be the most species-rich lowland rainforest in Africa while the government supports an active conservation program. As such, Gabon is a perfect study area to address that enigmatic question that has triggered many researchers before: “What determines botanical species richness?”.
In the past 2.5 million years, tropical rainforests have experienced 21 cycles of global glaciations. They responded to this by contracting during drier and cooler glacials into larger montane and smaller riverine forest refugia and expanding again during warmer and wetter interglacials. The current rapid global climate change coupled with change of land use poses new threats to the survival of many rainforest species. The limited availability of resources for conservation forces governments and NGOs to set priorities. Unfortunately, for many plant species, lack of data on their distribution hampers well-informed decision making in conservation.
Species distribution models (SDMs) offer opportunities to bridge at least partly this knowledge gap. SDMs are correlative models that infer the spatial distribution of species using only a limited set of known species occurrence records coupled with high resolution environmental data. SDMs are widely applied to study the past, present and future distribution of species, assess the risk of invasive species, infer patterns of species richness and identify hotspots, as well as to assess the impact of climate change. The currently available methods form a pipeline, with which data are selected and cleaned, models selected, parameterized, evaluated and projected to other areas and climatic scenarios, and biodiversity patterns are computed from these SDMs. In this thesis, SDMs of all Gabonese plant species were generated and patterns of species richness and of weighted endemism were computed (chapter 4 & 5).
Although this pipeline enables the rapid generation of SDMs and inferring of biodiversity patterns, its effective use is limited by several matters of which three are specifically addressed in this thesis. Not knowing the true distribution limits the opportunities to assess the accuracy of models and assess the impact of assumptions and limitations of SDMs. The use of simulated species has been advocated as a method to systematically assess the impact of specific matters of SDMs (virtual ecologist). Following this approach, in chapter 2, I present a novel method to simulate large numbers of species that each have their own unique niche.
One matter of SDMs that is usually ignored but has been shown to be of great impact on model accuracy is the number of species occurrence records used to train a model. In chapter 2, I quantify the effect of sample size on model accuracy for species of different range size classes. The results show that the minimum number of records required to generate accurate SDMs is not uniform for species of every range size class and that larger sample sizes are required for more widespread species. By applying a uniform minimum number of records, SDMs of narrow-ranged species are incorrectly rejected and SDMs of widespread species are incorrectly accepted. Instead, I recommend to identify and apply the unique minimum numbers of required records for each individual species. The method presented here to identify the minimum number of records for species of particular range size classes is applicable to any species group and study area.
The range size or prevalence is an important plant feature that is used in IUCN Red List classifications. It is commonly computed as the Extent Of Occurrence (EOO) and Area Of Occupancy (AOO). Currently, these metrics are computed using methods based on the spatial distribution of the known species occurrences. In chapter 3, using simulated species again, I show that methods based on the distribution of species occurrences in environmental parameter space clearly outperform those based on spatial data. In this chapter, I present a novel method that estimates the range size of a species as the fraction of raster cells within the minimum convex hull of the species occurrences, when all cells from the study area are plotted in environmental parameter space. This novel method outperforms all ten other assessed methods. Therefore, the current use of EOO and AOO based on spatial data alone for the purpose of IUCN Red List classification should be reconsidered. I recommend to use the novel method presented here to estimate the AOO and to estimate the EOO from the predicted distribution based on a thresholded SDM.
In chapter 4, I apply the currently best possible methods to generate accurate SDMs and estimate the range size of species to the large dataset of Gabonese plant species records. All significant SDMs are used here to assess the unique contribution of narrow-ranged, widespread, and randomly selected species to patterns of species richness and weighted endemism. When range sizes of species are defined based on their full range in tropical Africa, random subsets of species best represent the pattern of species richness, followed by narrow-ranged species. Narrow-ranged species best represent the weighted endemism pattern. Moreover, the results show that the applied criterion of widespread and narrow-ranged is crucial. Too often, range sizes of species are computed on their distribution within a study area defined by political borders. I recommend to use the full range size of species instead. Secondly, the use of widespread species, of which often more data are available, as an indicator of diversity patterns should be reconsidered.
The effect of global climate change on the distribution patterns of Gabonese plant species is assed in chapter 5 using SDMs projected to the year 2085 for two climate change scenarios assuming either full or no dispersal. In Gabon, predicted loss of plant species ranges from 5% assuming full dispersal to 10% assuming no dispersal. However, these numbers are likely to be substantially higher, as for many rare, narrow-ranged species no significant SDMs could be generated. Predicted species turnover is as high as 75% and species-rich areas are predicted to loose many species. The explanatory power of individual future climate anomalies to predicted future species richness patterns is quantified. Species loss is best explained by increased precipitation in the dry season. Species gain and species turnover are correlated with a shift from extreme to average values of annual temperature range.
In the final chapter, the results are placed in a wider scientific context. First, the results on the methodological aspects of SDMs and their implications of the SDM pipeline are discussed. The method presented in this thesis to simulate large numbers of species offers opportunities to systematically investigate other matters of the pipeline, some of which are discussed here. Secondly, the factors that shape the current and predicted future patterns of plant species richness in Gabon are discussed including the location of centres of species richness and of weighted endemism in relation to the hypothesized location of glacial forest refugia. Factors that may contribute to the lower species richness of African rainforests compared with South American and Asian forests are discussed. I conclude by reflecting on the conservation of the Gabonese rainforest and its plant species as well as on the opportunities SDMs offer for this in the wider socio-economic context of a changing world with growing demand for food and other ecosystem services.
Unravelling aspects of spatial and temporal distribution of Verticillium dahliae in olive, maple and ash trees and improvement of detection methods
Keykhasaber, Mojtaba - \ 2017
Wageningen University. Promotor(en): Bart Thomma; Pierre de Wit, co-promotor(en): Jelle Hiemstra. - Wageningen : Wageningen University - ISBN 9789463430142 - 163
olea europaea - olives - acer - fraxinus - plant pathogenic fungi - verticillium dahliae - distribution - virulence - detection - olea europaea - olijven - acer - fraxinus - plantenziekteverwekkende schimmels - verticillium dahliae - distributie - virulentie - detectie
Vascular wilts caused by xylem-colonizing pathogens are among the most devastating plant diseases that affect a wide range of plant species worldwide. Information on the distribution of V. dahliae in infected trees helps to design an appropriate and efficient sampling method for reliable detection of the pathogen in diseased trees. In Chapter 3, the distribution of V. dahliae in young twigs and leaves of infected olive trees is studied by real-time quantification of V. dahliae DNA. Analysis of twig and leaf samples collected from different sides of the crown of infected olive trees showed a non-uniform distribution of the fungus within infected parts of diseased olive trees. It was demonstrated that testing of combined samples comprising subsamples from at least 5 twigs from different sides of the tree, or 5-10 random leaves, can reliably detect the pathogen. V. dahliae isolates that infect olive trees can be classified as defoliating (D) isolates that are highly virulent, or non-defoliating (ND) isolates that are generally less aggressive. Discrimination of these pathotypes is important in order to predict the severity of disease, and decide on appropriate disease management strategies. This is particularly important due to the alarming spread of highly virulent isolates of the D pathotype worldwide. In Chapter 4, a novel method is designed for accurate discrimination and sensitive detection of D and ND isolates of V. dahliae. Through comparative genomics of multiple D and ND isolates of V. dahliae a region was identified that is present in all sequenced ND isolates, while absent from all D isolates. Based on this presence-absence polymorphism, a set of primers was designed spanning this region that was able to generate differentially sized amplicons for isolates that belong to the different pathotypes. Additionally, a nested-PCR assay was designed to increase the sensitivity and improve detection of D and ND isolates in planta. In Chapter 5, the relation of the dynamics in pathogen distribution in infected plants to the differences in extent and severity of disease caused by D and ND isolates in resistant and susceptible olive genotypes is studied. To this end, the distribution of a D (V117) and a ND (V4) isolate of V. dahliae in root-inoculated young plants of a susceptible (Picual) and a partially resistant cultivar (Frantoio) of olive and its relationship to the disease progression was investigated using real-time PCR. The amount of pathogen DNA detected in the two cultivars correlated with their susceptibility to Verticillium wilt, with lower quantities of V4 and V117 DNA detected in ‘Frantoio’ than in ‘Picual’. Also quantities of pathogen DNA in V117-inoculated plants were higher than quantities of pathogen DNA in V4-inoculated plants. The distribution patterns of D and ND isolates in the lower, middle and top parts of tested olive cultivars showed that differences in symptom severity were related to amounts of the pathogen in lower and middle parts of the trees, since colonization of the pathogen in top parts of the stem of inoculated plants was minor and was not significantly different between treatments. Moreover, microscopic analysis of infection and colonization processes of V. dahliae in olive plants inoculated with GFP-labelled isolates revealed that colonization of the above ground tissues of infected olive plants is by means of conidia transported upward with the xylem sap stream. In Chapter 6 we investigated the spatial and temporal distribution of V. dahliae in relation to disease progression and recovery in stem-inoculated maple and ash trees. These species differ strongly in vascular anatomy with maple having a diffuse porous xylem anatomy whereas ash has a ring porous xylem anatomy. Results showed that that differences in the xylem anatomy of ash and maple did not significantly affect the speed and extent of the upward spread of the pathogen in stem-inoculated trees. Nevertheless, the xylem of ash trees is much less supportive for growth and survival of V. dahliae than that of maple trees, as in the year after inoculation disease incidence and also quantities of V. dahliae detected in maple trees were significantly higher than in ash trees. Moreover, V. dahliae could not be reisolated at all from ash trees that had recovered from disease. However, it could be detected by PCR in some cases in the xylem formed in the year of inoculation, never in the xylem formed in the year after inoculation. Nevertheless, V. dahliae easily could be detected in the wood of diseased ash and maple trees in the year after inoculation. Notably, despite the presence of a layer of terminal parenchyma cells between growth rings, in ash trees showing disease symptoms in the year after inoculation V. dahliae was present in the xylem of the new growth ring. It was also observed that in stem-inoculated trees V. dahliae can move downward from the point of inoculation into the root collar, which may provide an avenue for infection of new growth rings in ash trees.
North Sea mackerel egg survey in May and June 2015
Damme, C.J.G. van - \ 2015
IJmuiden : IMARES (Report / Centrum voor Visserijonderzoek (CVO) 15.010) - 39
makrelen - visseneieren - kuitschieten - distributie - visbestand - noordzee - mackerels - fish eggs - spawning - distribution - fishery resources - north sea
After technical problems prevented the North Sea mackerel egg survey to be carried out in 2014, a successful survey was carried out in May-June 2015. The survey was carried out on board ‘RV Tridens’. The expected mackerel spawning area was covered in each of four periods in east-west transects, separated by 1 degree. In total 260 valid plankton hauls with a Gulf VII plankton sampler were performed, as well as 3 fish hauls and 4 sets of flowmeter calibrations hauls.
Eutrophication, Nile perch and food-web interactions in south-east Lake Victoria
Cornelissen, I.J.M. - \ 2015
Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Leo Nagelkerke; R. Vijverberg. - Wageningen : Wageningen University - ISBN 9789462575660 - 163
lates niloticus - eutrofiëring - voedselwebben - interacties - visserijbiologie - visstand - dynamica - fytoplankton - distributie - voedingsgedrag - victoriameer - tanzania - lates niloticus - eutrophication - food webs - interactions - fishery biology - fish stocks - dynamics - phytoplankton - distribution - feeding behaviour - lake victoria - tanzania
The increasing eutrophication, the introduction of Nile perch (Lates niloticus) and the increasing fishing pressure has changed Lake Victoria tremendously the last century. Since the 1960s, eutrophication increased primary production, enabling an increase in fish production. However, eutrophication also created hypoxia pockets, which reduced the available habitats for fish. In addition, the endemic haplochromines declined, whereas the introduced Nile perch boomed in the 1980s. The Nile perch boom and increased fish production resulted in the largest freshwater fisheries of the world. However, it is unclear whether fish production can still increase with further eutrophication as maximum primary production rates may have been reached. Fish stocks fluctuate since the 1980s and in order to manage these, it is important to understand how eutrophication and fisheries affect the Nile perch population. The present study investigates the bottom-up effects of eutrophication on the Nile perch and food-web dynamics in south-east Lake Victoria. We analysed the level of eutrophication along an eutrophication gradient in the Mwanza Gulf. Phytoplankton biomass varied spatially and seasonally and was limited by nutrients in deep water and by light in shallow water. Fish distributions were dynamic, with environmental factors depth and temperature influencing Nile perch size structure and distribution patterns similarly on small and large spatial scales. Although prey densities of haplochromines and Caridina nilotica shrimp did not explain Nile perch distributions, ontogenetic diet shifts and composition were related to prey densities, suggesting an opportunistic feeding behaviour of Nile perch. Small Nile perch however, showed some preference to shrimp and Nile perch preferred haplochromines above Dagaa (Rastrineobola argentea) and juvenile Nile perch as fish prey. On a food-web level, the base of the food web was spatially and seasonally highly dynamic. The onset of rains caused a spatial differentiation in littoral/benthic and pelagic carbon sources, affecting the whole food web. Trophic levels of fish were related to the spatial variation in diet compositions. Although a large heterogeneity was found in water quality, fish distributions and food-web structure, bottom-up processes affected the food web similarly. Despite the ongoing nutrient load in Lake Victoria, water quality has improved since the 1990s. Climate forcing through increasing wind speeds increased visibility and oxygen levels. Global climate change will therefore be an important driver of the water quality and fish distributions of Lake Victoria.
Perspectives on the distribution of fresh food in emerging metropolises: the cases of Mexico City and Cairo
Waldhauer, N. ; Burgh, M. van der; Vorst, J.G.A.J. van der; Bing, X. ; Scheer, F.P. - \ 2015
Wageningen : Wageningen UR - Food & Biobased Research (Report / Wageningen UR Food & Biobased Research 1529) - ISBN 9789462573642 - 56
voedsel - distributie - voedseldistributieprogramma's - ketenmanagement - voedselketens - logistiek - efficiëntie - stedelijke gebieden - mexico - voedselzekerheid - voedselkwaliteit - voedselverspilling - duurzaamheid (sustainability) - food - distribution - food distribution programs - supply chain management - food chains - logistics - efficiency - urban areas - mexico - food security - food quality - food wastage - sustainability
The report consists of four main chapters. In chapter 2 a theoretical framework of urban food distribution is developed based on earlier projects, a literature study and interviews. This framework underlines the main elements of urban food distribution and serves as a theoretical outline for the following case studies and recommendations for improvement. Chapter 3 describes the current situation of fresh food distribution in the two chosen case studies Mexico City and Cairo using the framework of chapter 2 as a reference. Chapter 4 presents the conclusions from the case studies comparing the current situation of the respective urban fresh food distribution networks, assessing the performance of the system and stating the major challenges in both cities. Recommendations for intervention are given in chapter 5 taking into account the conclusions from the case studies, urban distribution initiatives and projects in Western European cities and expert interviews. Chapter 6 gives an outlook into further research.
Extensive literature search for preparatory work to support pan European pest risk assessment: Trichilogaster acaciaelongifoliae RC/EFS/ALPHA/2014/07
Derkx, M.P.M. ; Brouwer, J.H.D. ; Breda, P.J.M. van; Helsen, H.H.M. ; Hoffman, M.H.A. ; Hop, M.E.C.M. - \ 2014
Parma, It. : EFSA (EFSA supporting publication 2015- EN-764) - 71
acacia - acacia longifolia - houtachtige planten als sierplanten - distributie - onkruiden - invasieve exoten - geïntroduceerde soorten - biologische bestrijding - organismen ingezet bij biologische bestrijding - hymenoptera - risicoschatting - europa - acacia - acacia longifolia - ornamental woody plants - distribution - weeds - invasive alien species - introduced species - biological control - biological control agents - hymenoptera - risk assessment - europe
The European Commission is currently seeking advice from EFSA (Mandate M-2012-0272) to assess for Arabis mosaic virus, Raspberry ringspot virus, Strawberry latent ringspot virus, Tomato black ring virus, Strawberry mild yellow edge virus, Strawberry crinkle virus, Daktulosphaira vitifoliae, Eutetranychus orientalis, Parasaissetia nigra, Clavibacter michiganensis spp. michiganensis, Xanthomonas campestris pv. vesicatoria, Didymella ligulicola and Phytophthora fragariae the risk to plant health for the EU territory and to evaluate the effectiveness of risk reduction options in reducing the level of risk. In addition, the Panel is requested to provide an opinion on the effectiveness of the present EU requirements against these organisms laid down in Council Directive 2000/29/EC. As a consequence EFSA needs insight in the cropping practices of Citrus spp., Fragaria x ananassa, Ribes spp., Rubus spp., Vaccinium spp., Humulus lupulus, Vitis vinifera, Prunus armeniaca, P. avium, P. cerasus, P. domestica and P. persica, which are host plants for these pests. An extensive and systematic literature search was done in which scientific and grey/technical literature was retrieved from the 28 EU Member States, Iceland and Norway. All references were stored in EndNote libraries, separately for scientific literature and grey/technical literature. For each reference information is provided on the source/search strategy, the crop, the country, the topic (cropping practice, propagation, protection or irrigation (only for Citrus)) and protected cultivation vs. field production. Yields of references depended on the crop and on the country. Over 27,000 references were provided to EFSA. This allows EFSA to quickly find information on crop production, both indoors and outdoors, of all crops that were studied in this extensive literature search. The data can be used by EFSA for the present mandate, but are also an excellent basis for other current and future mandates.
Mogelijkheden voor de implementatie van het biomassawerf concept in de Greenport Betuwse Bloem : Deel 2. Het biomassawerf concept : voorbeelden, theorie & checklist
Annevelink, E. ; Gogh, J.B. van; Oever, M.J.A. van den; Dam, J.E.G. van; Bartels, P. - \ 2014
Wageningen : Wageningen UR - Food & Biobased Research (Rapport / Wageningen UR Food & Biobased Research 1478) - ISBN 9789461739933 - 57
logistiek - biomassa - ketenmanagement - distributie - biobased economy - betuwe - logistics - biomass - supply chain management - distribution - biobased economy - betuwe
Het project ‘Biomassawerf – verwerken van reststromen’ (BO-21.03-001) vormt een onderdeel van het Biobased gedeelte van het BO-programma Keteninnovaties Plantaardig (KIP) van het Ministerie van Economische Zaken. Deze nota is het tweede deel van de rapportage uit dit project, en is een vervolg op de nota: ‘Deel 1. Stakeholder analyse & biomassabeschikbaarheid’ (Annevelink et al., 2013). Het specifieke doel van dit tweede deelrapport is om enkele gevonden voorbeelden van het biomassawerf concept te schetsen, om de theorie verder uit te diepen en om een checklist op te stellen met stappen om tot een biomassawerf te komen.
Marine mammals in the Wider Caribbean - Current research and priorities for future studies
Lucke, K. ; Scheidat, M. ; Geelhoed, S.C.V. ; Debrot, A.O. - \ 2014
Den Helder : IMARES (Report / IMARES Wageningen UR C007/14) - 38
zeezoogdieren - distributie - populatiedynamica - beschermingsgebieden - kennisoverdracht - caribische zee - marine mammals - distribution - population dynamics - conservation areas - knowledge transfer - caribbean sea
Information on the distribution, abundance and ecology of marine mammal in the Wider Caribbean Region is scarce. This report aims at collating the on-going research in the Wider Caribbean Region, at identifying the most critical knowledge gaps that need to be addressed to inform and facilitate conservation actions and assess the most suitable research techniques to fill these knowledge gaps.
Mogelijkheden voor de implementatie van het biomassawerf concept in de Greenport Betuwse Bloem : deel 1. Stakeholder analyse & biomassabeschikbaarheid
Annevelink, E. ; Gogh, J.B. van; Dam, J.E.G. van; Bartels, P.V. - \ 2013
Wageningen : Wageningen UR - Food & Biobased Research (Rapport / Wageningen UR Food & Biobased Research 1416) - ISBN 9789461736970 - 75
biomassa - ketenmanagement - logistiek - distributie - biobased economy - betuwe - biomass - supply chain management - logistics - distribution - biobased economy - betuwe
Biomassawerven kunnen een centrale rol spelen bij de integrale aanpak van biomassaketens voor de biobased economy. Een biomassawerf heeft de rol om bij de aanbodkant verschillende soorten biomassastromen te verzamelen, eventueel voor te bewerken en ze vervolgens aan te bieden aan de verwerkingskant. Het hoofddoel van het project is te onderzoeken of het biomassawerfconcept haalbaar is om de beschikbaarheid van regionale biomassa voor economische verwerking te vergroten. Onderzoek moet uitwijzen hoe biomassawerven het beste kunnen worden opgezet, en hoe een netwerk van biomassawerven eruit zal komen te zien. Als case voor het onderzoek dient de Greenport Betuwse Bloem (GBB) in de Provincie Gelderland. Het subdoel van dit rapport is een nadere stakeholderanalyse van de GBB, waarbij de huidige situatie en wensen voor de toekomst in beeld worden gebracht. Verder is een inschatting gemaakt van de potentieel beschikbare biomassastromen binnen de GBB.
Making a better world: Carrier, retailer, and consumer support for sustainability initiatives in the context of urban distribution and retailing
Hofenk, D.J.B. - \ 2012
Open University. Promotor(en): J. Semeijn; J.M.M. Bloemer, co-promotor(en): M.J.H. van Birgelen. - Enschede : s.n. - ISBN 9789461914255 - 148
duurzaamheid (sustainability) - distributie - consumenten - marketing voor de detailhandel - kooplieden - transport - stedelijke gebieden - steden - nederland - sustainability - distribution - consumers - retail marketing - merchants - transport - urban areas - towns - netherlands
Consumenten zijn bereid om duurzame producten en duurzaam vervoer van producten naar winkels in de binnenstad te steunen, zelfs wanneer dit betekent dat ze meer moeten betalen voor producten. Maar dit geldt alleen als zij daartoe een morele verplichting voelen en de sociale druk niet te groot wordt. Winkeliers en transporteurs willen een dergelijke duurzame vorm van stedelijke distributie, zoals Binnenstadservice in Nijmegen, steunen als het initiatief vertrouwenwekkend is, zonder financieel nadeel. Dit stelt Dianne Hofenk op basis van haar promotieonderzoek naar factoren die de steun voor duurzame initiatieven voor stedelijke distributie en detailhandel beïnvloeden.
Ex-ante analyse wetsvoorstel stelsel van verantwoorde mestafzet
Koeijer, T.J. de; Luesink, H.H. ; Ham, A. van den - \ 2012
Den Haag : LEI Wageningen UR (Nota / LEI Wageningen UR : Onderzoeksveld Sector en ondernemerschap ) - 38
mestverwerking - dierlijke meststoffen - marketingkanalen - distributie - scenario-analyse - manure treatment - animal manures - marketing channels - distribution - scenario analysis
Invoering van verplichte mestverwerking kan op middellange termijn (2015) het tekort aan afzetmogelijkheden voor dierlijke mest oplossen en daarmee de druk op de mestmarkt opheffen. Een voorwaarde daarbij is dat de verwerkingscapaciteit van dierlijke mest zodanig toeneemt dat er niet langer sprake is van een tekort aan afzetmogelijkheden van mest.
North Sea mackerel egg survey: dutch participation may and June 2011
Damme, C.J.G. van - \ 2012
IJmuiden : IMARES (Report / IMARES Wageningen UR no. C026/12) - 32
makrelen - distributie - monitoring - kuitschieten - visseneieren - noordzee - mackerels - distribution - monitoring - spawning - fish eggs - north sea
Every three years an international North Sea survey is carried out by two European institutes, Institute for Marine Research (IMR) from Norway and Institute for Marine Resources and Ecosystem Studies (IMARES) from the Netherlands, to monitor the spatial and seasonal distribution of North Sea mackerel. In 2011 the North Sea mackerel egg survey was performed. The entire spawning area was sampled by IMR, Norway and IMARES, The Netherlands. The whole spawning area was sampled three times. IMARES covered the complete sampling area in the first period, in the second period IMR covered the northern part and IMARES the southern part of the spawning area. The third period the whole spawning area was covered by IMR. In total 190 ichthyoplankton samples were taken with a Gulf VII plankton torpedo with a Seabird CTD mounted on top. Additionally, adult fish samples for the estimation of fecundity and atresia were taken using a pelagic trawl. The survey was successful and IMARES managed to sample all but 3 of the planned stations. Numbers of mackerel eggs found in the samples were comparable to 2008. Total mackerel egg production in 2011 was 116*1012 and Spawning Stock Biomass (SSB) was estimated at 165*103 tons, which is slightly higher compared to 2008. Highest egg production was found in the first sampling week and it is possible that the beginning of mackerel spawning is missed.
Distributions of microorganisms in foods and their impact on food safety
Jongenburger, I. - \ 2012
Wageningen University. Promotor(en): Marcel Zwietering; Leon Gorris, co-promotor(en): Martine Reij. - S.l. : s.n. - ISBN 9789461732071 - 208
micro-organismen - distributie - voedingsmiddelen - voedselveiligheid - voedselmicrobiologie - representatieve monstername - flesvoedingsamenstelling - enterobacter sakazakii - microorganisms - distribution - foods - food safety - food microbiology - representative sampling - infant formulae - enterobacter sakazakii
The physical distributions of pathogens in foods influence the likelihood that a food product will cause illness, but knowledge about the physical distribution of microorganisms in foods and especially the heterogeneity therein is scarce. This Ph.D. research aims to increase the knowledge of microbial distributions in foods and therewith to provide better insights in their impact on public health and food safety management activities.
The research covers both theoretical investigations and practical experiments, focusing on powdered infant formula (PIF) as a suitable model product and the opportunistic pathogen Cronobacter spp. as a relevant microorganism in the practical experiments. The impact of spatial distributions of microorganisms, like homogeneous or more clustered distributions, on public health was investigated. Infrequent high doses were shown to mainly determine the probability of illness and also to dominate the arithmetic mean (mean of the counts) expressing the level of microorganisms present. The distribution of Cronobacter spp. in two industrial batches of PIF (a recalled batch and a reference batch) was quantified in detail. Additionally, batches of PIF on lab scale with well-mixed and localised contaminations of Cronobacter sakazakii were enumerated. In the recalled batch, the sample units were taken in the course of the filling time and the results showed that Cronobacter spp. were heterogeneously distributed. On local-scale, clusters of cells varying between 3 and 560 cells per cluster were present sporadically. Discrete and continuous statistical distributions were compared to model the enumeration data of the industrial and laboratory scale batches. Batches with low counts including zeros were fitted best by the Poisson-Lognormal distribution and Negative Binomial distribution. According to criteria proposed to compare the suitability of statistical distributions to model microbial distributions in foods, these two distributions had already been selected to be the most suitable candidates. Furthermore, the performances of random and systematic sampling ware compared to detect a localised contamination in a batch of food. Our calculations showed that systematic sampling rather than random sampling improved the sampling performance. Moreover, taking many small sample units systematically increased the probability to detect the localised contamination. Another systematic sampling strategy evaluated was stratified random sampling. Using the enumeration data of the recalled batch, stratified random sampling appeared to improve the detection probability of Cronobacter spp. as compared to random sampling. Generally, taking more and smaller sample units, while keeping the total sampling weight constant, improved the performance of the sampling plans.
The insights obtained in this thesis are considered to be relevant to a wide variety of dry products and to an extent also to other structured foods. They should be of use to food business operators to improve sampling and testing to verify control of their operation as well as to assess compliance of final products with food safety standards and guidelines before marketing. The results may equally be useful to governmental bodies setting and enforcing food safety standards (such as microbiological criteria) and conducting microbiological risk assessment.
Biologistiek: verminderering van knelpunten in de kleinschalige logistiek van biologische ketens
Bartels, P.V. ; Snels, J.C.M.A. - \ 2011
Wageningen UR Food & Biobased Research : Wageningen UR - Food & Biobased Research (Rapport / Wageningen UR Food & Biobased Research 1294) - ISBN 9789461730855 - 63
biologische landbouw - logistiek - distributie - landbouwproducten - biologische voedingsmiddelen - regionale voedselketens - workshops (programma's) - organic farming - logistics - distribution - agricultural products - organic foods - regional food chains - workshops (programs)
Het doel van het project “Biologistiek: vermindering van knelpunten in de kleinschalige logistiek van biologische ketens” is mogelijkheden aan te reiken aan de producenten van biologische producten om de verslogistiek van biologische landbouwproducten te optimaliseren door samenwerken en bundelen van de distributie. Door de optimalisatie wordt tevens een duurzamere en rendabelere distributie mogelijk. Hiervoor is een workshop georganiseerd, waarbij producenten en mogelijke partners in het vinden van oplossingen bij elkaar zaten.
Economische analyse van de mestmarkt; Opties voor het stimuleren van innovaties
Hoop, D.W. de; Bunte, F.H.J. ; Blokland, P.W. ; Kernebeek, H.R.J. van; Vrolijk, H.C.J. ; Luesink, H.H. ; Koeijer, T.J. de - \ 2011
Den Haag : LEI, onderdeel Wageningen UR (Rapport / LEI : Onderzoeksveld Sector en ondernemerschap ) - ISBN 9789086155293 - 57
dierlijke meststoffen - mestverwerking - distributie - economische analyse - landbouwprijzen - innovaties - prijsbepalende factoren - animal manures - manure treatment - distribution - economic analysis - agricultural prices - innovations - price determining factors
De mestmarkt speelt al decennialang een belangrijke rol in de Nederlandse agrarische sector. De kosten van mest hebben een grote invloed op de winstgevendheid en daarmee de concurrentiepositie van de Nederlandse veehouderijsector. Innovaties om de problemen op de mestmarkt structureel op te lossen blijven uit. Deze studie geeft een analyse van de kenmerken van de mestmarkt en de gevolgen voor de innovaties in de sector.
Europees kampioen agrologistiek
Simons, A.E. - \ 2011
Kennis Online 8 (2011)sept. - p. 3 - 5.
transport - agro-industriële ketens - agro-industriële sector - logistiek - distributie - transport - agro-industrial chains - agroindustrial sector - logistics - distribution
Nederland verdient jaarlijks ruim twaalf miljard euro aan agrologistiek, de handel en het transport van land- en tuinbouwproducten. Dertig procent van de grensoverschrijdende handel in Europa is in handen van Nederlandse handelaren en distributeurs. De komende jaren moeten trein en schip de dure vrachtwagen steeds meer vervangen.
Verduurzaming voedselproductie : transportbewegingen van het Nederlandse voedsel
Scheer, F.P. ; Groot, J.J. ; Snels, J.C.M.A. ; Simons, A.E. - \ 2011
Wageningen : Wageningen UR - Food & Biobased Research (Rapport / Wageningen UR Food & Biobased Research nr. 1267) - ISBN 9789461730770 - 26
transport - distributie - duurzaamheid (sustainability) - milieueffect - voedselproducten - veevervoer - transport - distribution - sustainability - environmental impact - food products - transport of animals
Beschreven is welke transportbewegingen het Nederlandse voedsel maakt, de plaatsen van bestemming, de manieren van transport, de omvang en wijze van het transport van levende dieren en de milieudruk die het transport oplevert.
Shortlist Master plan Wind Monitoring fish eggs and larvae in the southern North Sea: final report Part A en B
Damme, C.J.G. van; Hoek, R. ; Beare, D.J. ; Bolle, L.J. ; Bakker, C. ; Barneveld, E. van; Lohman, M. ; Os-Koomen, E. van; Nijssen, P.J.M. ; Pennock, I. ; Tribuhl, S.V. - \ 2011
IJmuiden : IMARES (Report / IMARES Wageningen UR C098/11) - 433
visseneieren - larven - distributie - monitoring - noordzee - fish eggs - larvae - distribution - monitoring - north sea
This report presents the results of twelve monthly ichthyoplankton surveys carried out from April 2010 until March 2011 in the southern North Sea. The aim of this study was to collect data on the temporal and spatial distribution of fish eggs and larvae on the Dutch Continental Shelf (NCP). However, since fish eggs and larvae are transported with the currents onto the NCP a larger area covering the majority of the southern North Sea was sampled during the surveys. Despite technical problems or bad weather conditions preventing the sampling of all planned stations during each survey, the coverage was good and the general trends in ichthyoplankton abundance became apparent. Fish eggs were found in all months but species and numbers varied per month across the southern North Sea. The highest abundance of fish eggs was found from January until May with fish eggs being found at all stations from April until July. Very few eggs were found between August and November. From December onwards abundance of eggs increased again. The pattern was the same on the NCP. In total 35 different species of fish eggs were found. Fish larvae were found in all months but species and numbers varied in a similar pattern to the fish eggs, except the highest abundance of larvae was found in December and January in the English Channel (mostly herring). Numbers of larvae in the southern North Sea increased from April until June and afterwards then gradually declined until November. After this the abundances increased again. Larvae were found at almost all stations from May until September. In October and November larvae were found at half of all the stations both in the whole sampling area and on the NCP. The patterns was the same on the NCP. In total 74 different species of fish larvae were found. Based on the results of a modelling study, a mitigating measure was issued by the Dutch authorities forbidding pile driving of offshore wind farm foundations from January to June, in order to ensure that negative effects on prey availability for birds and marine mammals within Natura 2000 areas are minimised. The results of the year-round monthly surveys show that from April until September fish larvae were found throughout the survey area, including the NCP, in varying numbers and varying species. Still in October and November larvae were found at half of the stations although at lower abundances. Even in December larvae were still found at a quarter of the stations on the NCP. Whilst the abundance of larvae was low in October and November, there are a few species with larvae present that are absent at other times of the year. These results on ichthyoplankton abundance and results of the experimental study on the effect of pile driving on fish larvae need to be combined. Ideally they should also be assessed with subsequent studies of ichthyoplankton transport and impact on the Natura 2000 sites. This unique study is the first to comprehensively sample and analyse the ichthyoplankton with monthly resolution in the southern North Sea. These data on spatial and temporal distribution of fish eggs and larvae can be used in modelling studies to assess the effects of human activities in the southern North Sea, on different fish stocks.
Evaluatie "VENLOg" (IN-114)
FBR-WUR, - \ 2010
TransForum - 3
verse producten - landbouwproducten - logistiek - agrodistributie - distributie - handel - landbouwindustrie - stadslandbouw - regionale ontwikkeling - regionale centra - fresh products - agricultural products - logistics - agro distribution - distribution - trade - agribusiness - urban agriculture - regional development - central places
Meer dan de helft van de wereldbevolking woont in grote bevolkingscentra gelegen in Delta’s. Deze delta’s zijn ook zeer geschikt voor productie. Kortom productie en afzet liggen voor een deel dicht bij elkaar (local to local) en zijn voor een deel global tussen de logistieke hotspots (global sourcing en distributie). Het samenkomen van alle vers stromen op bepaalde locaties is een logische ontwikkeling die gestuurd wordt door de ligging van grote bevolkingscentra en door de service eisen (responsiviteit, assortiment) die grote internationale afnemers vereisen. Deze clustering van gebundelde stromen, productie en consumptie is terug te vinden in het concept van metropolitan agriculture. Het project VENLOg gaat in op de logistieke problematiek van metropolitan agriculture, en kan op die manier de visie van TransForum versterken. Hoe, waar en met wie organiseer je nu logistieke knooppunten. De ambitie is om nieuwe triple P verbindingen te creëren binnen ketens (producenten, logistiek dienstverleners, handel, retail, vastgoed) en tussen agro-sectoren (transport, grondstoffen, energie- en afvalstromen). Multimodaal transport (water en rail-transport) kan worden ingezet om geconcentreerde logistieke stromen te vervoeren. Nieuwe combinaties van (product)stromen leiden tot een reductie van kilometers (en dus CO2-reductie) en de mogelijkheid om beter in te spelen op klantwensen (snellere levering).
Shortlist Masterplan Wind. Fish eggs and larvae in the southern North Sea: May 2010 cruise
Bolle, L.J. ; Hoek, R. ; Bakker, C. ; Os-Koomen, E. van - \ 2010
IJmuiden : IMARES (Report / IMARES Wageningen UR C063/10) - 16
visseneieren - larven - monitoring - distributie - noordzee - fish eggs - larvae - monitoring - distribution - north sea