Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Pathologists and entomologists must join forces against forest pest and pathogen invasions
    Jactel, Hervé ; Desprez-Loustau, Marie Laure ; Battisti, Andrea ; Brockerhoff, Eckehard ; Santini, Alberto ; Stenlid, Jan ; Björkman, Christer ; Branco, Manuela ; Dehnen-Schmutz, Katharina ; Douma, Jacob C. ; Drakulic, Jassy ; Drizou, Fryni ; Eschen, René ; Franco, José Carlos ; Gossner, Martin M. ; Green, Samantha ; Kenis, Marc ; Klapwijk, Maartje J. ; Liebhold, Andrew M. ; Orazio, Christophe ; Prospero, Simone ; Robinet, Christelle ; Schroeder, Martin ; Slippers, Bernard ; Stoev, Pavel ; Sun, Jianghua ; Dool, Robbert van den; Wingfield, Michael J. ; Zalucki, Myron P. - \ 2020
    NeoBiota 58 (2020). - ISSN 1619-0033 - p. 107 - 127.
    Capacity building - Detection - Disease - Exotic - Forest health - Fungi - Identification - Insects - Interdisciplinarity - Management

    The world's forests have never been more threatened by invasions of exotic pests and pathogens, whose causes and impacts are reinforced by global change. However, forest entomologists and pathologists have, for too long, worked independently, used different concepts and proposed specific management methods without recognising parallels and synergies between their respective fields. Instead, we advocate increased collaboration between these two scientific communities to improve the long-term health of forests. Our arguments are that the pathways of entry of exotic pests and pathogens are often the same and that insects and fungi often coexist in the same affected trees. Innovative methods for preventing invasions, early detection and identification of non-native species, modelling of their impact and spread and prevention of damage by increasing the resistance of ecosystems can be shared for the management of both pests and diseases. We, therefore, make recommendations to foster this convergence, proposing in particular the development of interdisciplinary research programmes, the development of generic tools or methods for pest and pathogen management and capacity building for the education and training of students, managers, decision-makers and citizens concerned with forest health.

    Autonomous and informed decision-making : The case of colorectal cancer screening
    Douma, Linda N. ; Uiters, Ellen ; Verweij, Marcel F. ; Timmermans, Danielle R.M. - \ 2020
    PLoS ONE 15 (2020)5. - ISSN 1932-6203

    Introduction It is increasingly considered important that people make an autonomous and informed decision concerning colorectal cancer (CRC) screening. However, the realisation of autonomy within the concept of informed decision-making might be interpreted too narrowly. Additionally, relatively little is known about what the eligible population believes to be a 'good' screening decision. Therefore, we aimed to explore how the concepts of autonomous and informed decision-making relate to how the eligible CRC screening population makes their decision and when they believe to have made a 'good' screening decision. Methods We conducted 27 semi-structured interviews with the eligible CRC screening population (eighteen CRC screening participants and nine non-participants). The general topics discussed concerned how people made their CRC screening decision, how they experienced making this decision and when they considered they had made a 'good' decision. Results Most interviewees viewed a 'good' CRC screening decision as one based on both reasoning and feeling/intuition, and that is made freely. However, many CRC screening non-participants experienced a certain social pressure to participate. All CRC screening non-participants viewed making an informed decision as essential. This appeared to be the case to a lesser extent for CRC screening participants. For most, experiences and values were involved in their decision-making. Conclusion Our sample of the eligible CRC screening population viewed aspects related to the concepts of autonomous and informed decision-making as important for making a 'good' CRC screening decision. However, in particular the existence of a social norm may be affecting a true autonomous decision-making process. Additionally, the present concept of informed decision-making with its strong emphasis on making a fully informed and well-considered decision does not appear to be entirely reflective of the process in practice. More efforts could be made to attune to the diverse values and factors that are involved in deciding about CRC screening participation.

    Substantial differences occur between canopy and ambient climate : Quantification of interactions in a greenhouse-canopy system
    Westreenen, A. van; Zhang, N. ; Douma, J.C. ; Evers, J.B. ; Anten, N.P.R. ; Marcelis, L.F.M. - \ 2020
    PLoS ONE 15 (2020)5. - ISSN 1932-6203 - p. e0233210 - e0233210.

    Organ temperature and variation therein plays a key role in plant functioning and its responses to e.g. climate change. There is a strong feedback between organ, especially leaf, temperature and the climate within the canopy (canopy climate), which in turn interacts with the climate outside the canopy (ambient climate). For greenhouses, the determinants of this interplay and how they drive differences between canopy and ambient climate are poorly understood. Yet, as many experiments on both regular greenhouse crops and field crops are done in greenhouses, this is crucial to know. Therefore, we designed an experiment to quantify the differences between ambient and canopy climate and leaf temperature. A path analysis was performed to quantify the interactions between components of the greenhouse canopy-climate system. We found that with high radiation the canopy climate can be up to 5°C cooler than the ambient climate, while for cloudy days this was only 2°C. Canopy relative humidity (RH) was up to 25% higher compared to ambient RH. We showed that radiation is very important for these climate differences, but that this effect could be partly counteracted by turning off supplementary light (i.e. due to its indirect effects e.g. changing light distribution). Leaf temperature was substantially different, both higher and lower, from the canopy air temperature. This difference was determined by leaf area index (LAI), temperature of the heating pipe and the use of supplementary light, which all strongly influence radiation, either shortwave or thermal radiation. The difference between leaf and ambient air temperature could be decreased by decreasing the LAI or increasing the temperature of the heating pipe.

    Generalized AIC and chi-squared statistics for path models consistent with directed acyclic graphs
    Shipley, Bill ; Douma, Jacob C. - \ 2020
    Ecology 101 (2020)3. - ISSN 0012-9658
    Akaike Information Criterion - d-separation - directed acyclic graph - maximum likelihood - model selection - path analysis - piecewise SEM

    We explain how to obtain a generalized maximum-likelihood chi-square statistic, X2 ML, and a full-model Akaike Information Criterion (AIC) statistic for piecewise structural equation modeling (SEM); that is, structural equations without latent variables whose causal topology can be represented as a directed acyclic graph (DAG). The full piecewise SEM is decomposed into submodels as a Markov network, each of which can have different distributional assumptions or functional links and that can be modeled by any method that produces maximum-likelihood parameter estimates. The generalized X2 ML is a function of the difference in the maximum likelihoods of the model and its saturated equivalent and the full-model AIC is calculated by summing the AIC statistics of each of the submodels.

    No evidence of flowering synchronization upon floral volatiles for a short lived annual plant species: Revisiting an appealing hypothesis
    Fricke, Ute ; Lucas-Barbosa, Dani ; Douma, Jacob C. - \ 2019
    BMC Ecology 19 (2019)1. - ISSN 1472-6785
    Flowering onset - Flowering synchronization - Phenology - Plant-plant communication

    Background: Self-incompatible plants require simultaneous flowering mates for crosspollination and reproduction. Though the presence of flowering conspecifics and pollination agents are important for reproductive success, so far no cues that signal the flowering state of potential mates have been identified. Here, we empirically tested the hypothesis that plant floral volatiles induce flowering synchrony among self-incompatible conspecifics by acceleration of flowering and flower opening rate of non-flowering conspecifics. We exposed Brassica rapa Maarssen, a self-incompatible, in rather dense patches growing annual, to (1) flowering or non-flowering conspecifics or to (2) floral volatiles of conspecifics by isolating plants in separate containers with a directional airflow. In the latter, odors emitted by non-flowering conspecifics were used as control. Results: Date of first bud, duration of first flower bud, date of first flower, maximum number of open flowers and flower opening rate were not affected by the presence of conspecific flowering neighbors nor by floral volatiles directly. Conclusions: This study presents a compelling approach to empirically test the role of flower synchronization by floral volatiles and challenges the premises that are underlying this hypothesis. We argue that the life history of the plant as well as its interaction with pollinators and insect herbivores, as well as the distance over which volatiles may serve as synchronization cue, set constraints on the fitness benefits of synchronized flowering which needs to be taken into account when testing the role of floral volatiles in synchronized flowering.

    Variation in plastic responses to light results from selection in different competitive environments-A game theoretical approach using virtual plants
    Bongers, Franca J. ; Douma, Jacob C. ; Iwasa, Yoh ; Pierik, Ronald ; Evers, Jochem B. ; Anten, Niels P.R. - \ 2019
    PLoS Computational Biology 15 (2019)8. - ISSN 1553-734X - p. e1007253 - e1007253.

    Phenotypic plasticity is a vital strategy for plants to deal with changing conditions by inducing phenotypes favourable in different environments. Understanding how natural selection acts on variation in phenotypic plasticity in plants is therefore a central question in ecology, but is often ignored in modelling studies. Here we present a new modelling approach that allows for the analysis of selection for variation in phenotypic plasticity as a response strategy. We assess selection for shade avoidance strategies of Arabidopsis thaliana in response to future neighbour shading signalled through a decrease in red:far-red (R:FR) ratio. For this, we used a spatially explicit 3D virtual plant model that simulates individual Arabidopsis plants competing for light in different planting densities. Plant structure and growth were determined by the organ-specific interactions with the light environment created by the vegetation structure itself. Shade avoidance plastic responses were defined by a plastic response curve relating petiole elongation and lamina growth to R:FR perceived locally. Different plasticity strategies were represented by different shapes of the response curve that expressed different levels of R:FR sensitivity. Our analyses show that the shape of the selected shade avoidance strategy varies with planting density. At higher planting densities, more sensitive response curves are selected for than at lower densities. In addition, the balance between lamina and petiole responses influences the sensitivity of the response curves selected for. Combining computational virtual plant modelling with a game theoretical analysis represents a new step towards analysing how natural selection could have acted upon variation in shade avoidance as a response strategy, which can be linked to genetic variation and underlying physiological processes.

    Plant slaat alarm met geur
    Douma, J.C. - \ 2019
    Planten communiceren via geurstoffen, kunnen we die boodschap kraken?
    Douma, J.C. - \ 2019
    Wageningen : Wageningen University & Research
    What makes a volatile organic compound a reliable indicator of insect herbivory?
    Douma, Jacob C. ; Ganzeveld, Laurens N. ; Unsicker, Sybille B. ; Boeckler, Andreas ; Dicke, Marcel - \ 2019
    Plant, Cell & Environment 42 (2019)12. - ISSN 0140-7791 - p. 3308 - 3325.
    biogenic volatile organic compound (BVOC) - emission - herbivore induced plant volatile (HIPV) - hydroxyl radical - nitrate radical - oxidation - ozone - Populus nigra

    Plants that are subject to insect herbivory emit a blend of so-called herbivore-induced plant volatiles (HIPVs), of which only a few serve as cues for the carnivorous enemies to locate their host. We lack understanding which HIPVs are reliable indicators of insect herbivory. Here, we take a modelling approach to elucidate which physicochemical and physiological properties contribute to the information value of a HIPV. A leaf-level HIPV synthesis and emission model is developed and parameterized to poplar. Next, HIPV concentrations within the canopy are inferred as a function of dispersion, transport and chemical degradation of the compounds. We show that the ability of HIPVs to reveal herbivory varies from almost perfect to no better than chance and interacts with canopy conditions. Model predictions matched well with leaf-emission measurements and field and laboratory assays. The chemical class a compound belongs to predicted the signalling ability of a compound only to a minor extent, whereas compound characteristics such as its reaction rate with atmospheric oxidants, biosynthesis rate upon herbivory and volatility were much more important predictors. This study shows the power of merging fields of plant–insect interactions and atmospheric chemistry research to increase our understanding of the ecological significance of HIPVs.

    Analysing continuous proportions in ecology and evolution: A practical introduction to beta and Dirichlet regression
    Douma, Jacob C. ; Weedon, James T. - \ 2019
    Methods in Ecology and Evolution 10 (2019)9. - ISSN 2041-210X - p. 1412 - 1430.
    beta regression - Dirichlet regression - fractions - non-count proportions - one augmented - proportions - transformations - zero augmented

    Proportional data, in which response variables are expressed as percentages or fractions of a whole, are analysed in many subfields of ecology and evolution. The scale-independence of proportions makes them appropriate to analyse many biological phenomena, but statistical analyses are not straightforward, since proportions can only take values from zero to one and their variance is usually not constant across the range of the predictor. Transformations to overcome these problems are often applied, but can lead to biased estimates and difficulties in interpretation. In this paper, we provide an overview of the different types of proportional data and discuss the different analysis strategies available. In particular, we review and discuss the use of promising, but little used, techniques for analysing continuous (also called non-count-based or non-binomial) proportions (e.g. percent cover, fraction time spent on an activity): beta and Dirichlet regression, and some of their most important extensions. A major distinction can be made between proportions arising from counts and those arising from continuous measurements. For proportions consisting of two categories, count-based data are best analysed using well-developed techniques such as logistic regression, while continuous proportions can be analysed with beta regression models. In the case of >2 categories, multinomial logistic regression or Dirichlet regression can be applied. Both beta and Dirichlet regression techniques model proportions at their original scale, which makes statistical inference more straightforward and produce less biased estimates relative to transformation-based solutions. Extensions to beta regression, such as models for variable dispersion, zero-one augmented data and mixed effects designs have been developed and are reviewed and applied to case studies. Finally, we briefly discuss some issues regarding model fitting, inference, and reporting that are particularly relevant to beta and Dirichlet regression. Beta regression and Dirichlet regression overcome some problems inherent in applying classic statistical approaches to proportional data. To facilitate the adoption of these techniques by practitioners in ecology and evolution, we present detailed, annotated demonstration scripts covering all variations of beta and Dirichlet regression discussed in the article, implemented in the freely available language for statistical computing, r.

    ‘Beperkte scope’ natuurlijke vijanden vraagt om geïntegreerde actie. Positieve neveneffecten breedwerkende groene middelen.
    Messelink, G.J. ; Douma, Jenette - \ 2019
    Ecological significance of light quality in optimizing plant defence
    Douma, Jacob C. ; Vries, Jorad de; Poelman, Erik H. ; Dicke, Marcel ; Anten, Niels P.R. ; Evers, Jochem B. - \ 2019
    Plant, Cell & Environment 42 (2019)3. - ISSN 0140-7791 - p. 1065 - 1077.
    Brassica nigra - competition - functional–structural plant modelling - growth-defence trade-off - herbivory - plant defence - red to far-red ratio - shade avoidance

    Plants balance the allocation of resources between growth and defence to optimize fitness in a competitive environment. Perception of neighbour-detection cues, such as a low ratio of red to far-red (R:FR) radiation, activates a suite of shade-avoidance responses that include stem elongation and upward leaf movement, whilst simultaneously downregulating defence. This downregulation is hypothesized to benefit the plant either by mediating the growth-defence balance in favour of growth in high plant densities or, alternatively, by mediating defence of individual leaves such that those most photosynthetically productive are best protected. To test these hypotheses, we used a 3D functional–structural plant model of Brassica nigra that mechanistically simulates the interactions between plant architecture, herbivory, and the light environment. Our results show that plant-level defence expression is a strong determinant of plant fitness and that leaf-level defence mediation by R:FR can provide a fitness benefit in high densities. However, optimal plant-level defence expression does not decrease monotonically with plant density, indicating that R:FR mediation of defence alone is not enough to optimize defence between densities. Therefore, assessing the ecological significance of R:FR-mediated defence is paramount to better understand the evolution of this physiological linkage and its implications for crop breeding.

    Touch and plant defence : volatile communication with neighbours
    Douma, Jacob C. ; Anten, Niels P.R. - \ 2019
    Journal of Experimental Botany 70 (2019)2. - ISSN 0022-0957 - p. 371 - 374.
    Plants use many cues to get the latest news on their environment, from different parts of the light spectrum predicting future shading by neighbours, to volatiles released by insect-infested plants preparing neighbouring plants for future attack, or touch providing information about impending mechanical stress or herbivore attacks. Markovic et al. (2019) have now shown that gentle touching of leaves leads to emission of volatiles that can activate the same set of defence genes in neighbouring plants as were up-regulated in the touched plant.
    Legacy effects of diversity in space and time driven by winter cover crop biomass and nitrogen concentration
    Barel, J.M. ; Kuijper, T.W.M. ; Boer, W. de; Douma, Bob ; Deyn, G.B. de - \ 2018
    Journal of Applied Ecology 55 (2018)1. - ISSN 0021-8901 - p. 299 - 310.
    1. Plant diversity can increase nitrogen cycling and decrease soil-borne pests, which are feedback mechanisms influencing subsequent plant growth. The relative strength of these mechanisms is unclear, as is the influence of preceding plant quantity and quality. Here, we studied how plant diversity in space and time influences subsequent crop growth.
    2. During 2 years, we rotated two main crops (Avena sativa, Cichorium endivia) with four winter cover crop (WCC) species in monocultures and mixtures. We hypothesized that, relative to monocultures, WCC mixtures promote WCC biomass (quantity) and nitrogen concentration (quality), soil mineral nitrogen, soil organic matter, and reduce plant-feeding nematode abundance. Additionally, we predicted that preceding crops modified WCC legacies. By structural equation modelling (SEM), we tested the relative importance of WCC shoot biomass and nitrogen concentration on succeeding crop productivity directly and indirectly via nitrogen cycling and root-feeding nematode abundance.
    3. WCC shoot biomass, soil properties and succeeding Avena productivity were affected by first-season cropping, whereas subsequent Cichorium only responded to the WCC treatments. WCC mixtures’ productivity and nitrogen concentration showed over- and under-yielding, depending on mixture composition. Soil nitrogen and nematode abundance did not display WCC mixture effects. Soil organic matter was lower than expected after Raphanus sativus + Vicia sativa mixture. Subsequent Avena productivity depended upon mixture composition, whereas final Cichorium productivity was unresponsive to WCC mixtures. SEM indicated that WCC legacy effects on subsequent Avena (R2 = 0.52) and Cichorium (R2 = 0.59) productivity were driven by WCC biomass and nitrogen concentration, although not by the quantified soil properties.
    4. Synthesis and applications. Through understanding plant–soil feedback, legacy effects of plant species and species mixtures can be employed for sustainable management of agro-ecosystems. Biomass and nitrogen concentration of plants returned to the soil stimulate subsequent plant productivity. Winter cover crop quantity and quality are both manipulable with mixtures. The specificity of spatial and temporal diversity effects warrants consideration of plant species choice in mixtures and rotations for optimal employment of beneficial legacy effects.
    Data from: Legacy effects of diversity in space and time driven by winter cover crop biomass and nitrogen concentration
    Barel, J.M. ; Kuijper, T.W.M. ; Boer, W. de; Douma, J.C. ; Deyn, G.B. de - \ 2017
    crop rotation - soil oranic matter - soil mineral nitrogen - plant-feeding nematodes - plant-soil feedback - plant productivity - agroecology - winter cover crops - agriculture - plant diversity - Avena sativa - Cichorium endivia - Lolium perenne - Trifolium repens - Raphanus sativus - Vicia sativa
    Plant diversity can increase nitrogen cycling and decrease soil-borne pests, which are feedback mechanisms influencing subsequent plant growth. The relative strength of these mechanisms is unclear, as is the influence of preceding plant quantity and quality. Here, we studied how plant diversity in space and time influences subsequent crop growth. During 2 years, we rotated two main crops (Avena sativa, Cichorium endivia) with four winter cover crop (WCC) species in monocultures and mixtures. We hypothesized that, relative to monocultures, WCC mixtures promote WCC biomass (quantity) and nitrogen concentration (quality), soil mineral nitrogen, soil organic matter, and reduce plant-feeding nematode abundance. Additionally, we predicted that preceding crops modified WCC legacies. By structural equation modelling (SEM), we tested the relative importance of WCC shoot biomass and nitrogen concentration on succeeding crop productivity directly and indirectly via nitrogen cycling and root-feeding nematode abundance. WCC shoot biomass, soil properties and succeeding Avena productivity were affected by first-season cropping, whereas subsequent Cichorium only responded to the WCC treatments. WCC mixtures’ productivity and nitrogen concentration showed over- and under-yielding, depending on mixture composition. Soil nitrogen and nematode abundance did not display WCC mixture effects. Soil organic matter was lower than expected after Raphanus sativus + Vicia sativa mixture. Subsequent Avena productivity depended upon mixture composition, whereas final Cichorium productivity was unresponsive to WCC mixtures. SEM indicated that WCC legacy effects on subsequent Avena (R2 = 0.52) and Cichorium (R2 = 0.59) productivity were driven by WCC biomass and nitrogen concentration, although not by the quantified soil properties. Synthesis and applications. Through understanding plant–soil feedback, legacy effects of plant species and species mixtures can be employed for sustainable management of agro-ecosystems. Biomass and nitrogen concentration of plants returned to the soil stimulate subsequent plant productivity. Winter cover crop quantity and quality are both manipulable with mixtures. The specificity of spatial and temporal diversity effects warrants consideration of plant species choice in mixtures and rotations for optimal employment of beneficial legacy effects.
    Grain legume cultivation and children’s dietary diversity in smallholder farming households in rural Ghana and Kenya
    Jager, I. de; Abizari, Abdul Razak ; Douma, J.C. ; Giller, K.E. ; Brouwer, I.D. - \ 2017
    Grain legume cultivation and children’s dietary diversity in smallholder farming households in rural Ghana and Kenya
    Jager, I. de; Abizari, Abdul Razak ; Douma, J.C. ; Giller, K.E. ; Brouwer, I.D. - \ 2017
    In: Abstracts: IUNS21st International Congress of Nutrition. - Karger (Annals of Nutrition & Metabolism suppl 2) - ISBN 9783318061925 - p. 1319 - 1319.
    Grain legume cultivation and children’s dietary diversity in smallholder farming households in rural Ghana and Kenya
    Jager, Ilse de; Abizari, Abdul Razak ; Douma, Jacob C. ; Giller, Ken E. ; Brouwer, Inge D. - \ 2017
    Food Security 9 (2017)5. - ISSN 1876-4517 - p. 1053 - 1071.
    Children - Dietary diversity - Ghana - Kenya - Legume production - SEM analysis
    Boosting smallholder food production can potentially improve children’s nutrition in rural Sub-Saharan Africa through a production-own consumption pathway and an income-food purchase pathway. Rigorously designed studies are needed to provide evidence for nutrition impact, but are often difficult to implement in agricultural projects. Within the framework of a large agricultural development project supporting legume production (N2Africa), we studied the potential to improve children’s dietary diversity by comparing N2Africa and non-N2Africa households in a cross-sectional quasi-experimental design, followed by structural equation modelling (SEM) and focus group discussions in rural Ghana and Kenya. Comparing N2Africa and non-N2Africa households, we found that participating in N2Africa was not associated with improved dietary diversity of children. However, for soybean, SEM indicated a relatively good fit to the posteriori model in Kenya but not in Ghana, and in Kenya only the production-own consumption pathway was fully supported, with no effect through the income-food purchase pathway. Results are possibly related to differences in the food environment between the two countries, related to attribution of positive characteristics to soybean, the variety of local soybean-based dishes, being a new crop or not, women’s involvement in soybean cultivation, the presence of markets, and being treated as a food or cash crop. These findings confirm the importance of the food environment for translation of enhanced crop production into improved human nutrition. This study also shows that in a situation where rigorous study designs cannot be implemented, SEM is a useful option to analyse whether agriculture projects have the potential to improve nutrition.
    When does it pay off to prime for defense? A modeling analysis
    Douma, Jacob C. ; Vermeulen, Peter J. ; Poelman, Erik H. ; Dicke, Marcel ; Anten, Niels P.R. - \ 2017
    New Phytologist 216 (2017)3. - ISSN 0028-646X - p. 782 - 797.
    Community - Fitness - Insect herbivory - Plant competition - Priming - Volatiles
    Plants can prepare for future herbivore attack through a process called priming. Primed plants respond more strongly and/or faster to insect attack succeeding the priming event than nonprimed plants, while the energetic costs of priming are relatively low. To better understand the evolution of priming, we developed a simulation model, partly parameterized for Brassica nigra plants, to explore how the fitness benefits of priming change when plants are grown in different biotic environments. Model simulations showed that herbivore dynamics (arrival probability, arrival time, and feeding rate) affect the optimal duration, the optimal investment and the fitness benefits of priming. Competition for light increases the indirect costs of priming, but may also result in a larger payoff when the nonprimed plant experiences substantial leaf losses. This modeling approach identified some important knowledge gaps: herbivore arrival rates on individual plants are rarely reported but they shape the optimal duration of priming, and it would pay off if the likelihood, severity and timing of the attack could be discerned from the priming cue, but it is unknown if plants can do so. In addition, the model generated some testable predictions, for example that the sensitivity to the priming cue decreases with plant age.
    Semi-natural habitats support biological control, pollination and soil conservation in Europe. A review
    Holland, John M. ; Douma, Jacob C. ; Crowley, Liam ; James, Laura ; Kor, Laura ; Stevenson, David R.W. ; Smith, Barbara M. - \ 2017
    Agronomy for Sustainable Development 37 (2017)4. - ISSN 1774-0746
    Agricultural policy - Agricultural research - Agroecology - Ecosystem services - Experimental design - Integrated pest management - Pollinators - Sustainable agriculture
    Semi-natural habitats are integral to most agricultural areas and have the potential to support ecosystem services, especially biological control and pollination by supplying resources for the invertebrates providing these services and for soil conservation by preventing erosion and run-off. Some habitats are supported through agri-environment scheme funding in the European Union, but their value for ecosystem service delivery has been questioned. An improved understanding of previous research approaches and outcomes will contribute to the development of more sustainable farming systems, improve experimental designs and highlight knowledge gaps especially for funders and researchers. Here we compiled a systematic map to allow for the first time a review of the quantity of evidence collected in Europe that semi-natural habitats support biological control, pollination and soil conservation. A literature search selected 2252 publications, and, following review, 270 met the inclusion criteria and were entered into the database. Most publications were of pest control (143 publications) with less on pollination (78 publications) or soil-related aspects (31). For pest control and pollination, most publications reported a positive effect of semi-natural habitats. There were weaknesses in the evidence base though because of bias in study location and the crops, whilst metrics (e.g. yield) valued by end users were seldom measured. Hedgerows, woodland and grassland were the most heavily investigated semi-natural habitats, and the wider landscape composition was often considered. Study designs varied considerably yet only 24% included controls or involved manipulation of semi-natural habitats. Service providers were commonly measured and used as a surrogate for ecosystem service delivery. Key messages for policymakers and funders are that they should encourage research that includes more metrics required by end users, be prepared to fund longer-term studies (61% were of only 1-year duration) and investigate the role of soils within semi-natural habitats in delivering ecosystem services.
    A risk categorisation and analysis of the geographic and temporal dynamics of the European import of plants for planting
    Eschen, René ; Douma, Bob ; Grégoire, Jean Claude ; Mayer, François ; Rigaux, Ludovic ; Potting, Roel P.J. - \ 2017
    Biological Invasions 19 (2017)11. - ISSN 1387-3547 - p. 3243 - 3257.
    Biosecurity - Harmful organisms - International trade - Pathway risk analysis - Plants for planting - Prioritisation

    The international trade in plants for planting (P4Ps) is a major pathway for the introduction of plant pests. The global trade in P4Ps is both voluminous and highly diverse, but there is little detailed knowledge about its diversity and dynamics. This makes it difficult to assess the risks associated with this trade and to prioritise high-risk commodities (genus-origin combinations) for detailed inspection or regulation. Using the ISEFOR database, this paper describes the diversity and dynamics of P4P imports into the EU, based on genus-level data for lots imported into fourteen Member States that provided this data for different periods between 2005 and 2014, totalling over 30Bn plants and over 7500 commodities. There was great variety, as well as complementarity, in terms of the imported genera, origins and commodities among the countries. Two-thirds of the imported commodities changed every year. Based on the 10-year data from the Netherlands, the greatest importer of live plants in the dataset, we developed a risk categorisation approach for prioritising the highest risk commodities, based on risk associated information concerning the imported genus and the history of trade with respect to the exporting countries, genera and type of plant material traded. Application of this risk categorisation led to the identification of a modest number of commodities that represent elevated risk, to which more inspection resources can be allocated while lower-risk commodities could be subject to less-intensive phytosanitary inspections.

    A new metric to assess the predictive accuracy of multinomial land cover models
    Douma, Bob ; Cornwell, William K. ; Bodegom, Peter M. van - \ 2017
    Journal of Biogeography 44 (2017)6. - ISSN 0305-0270 - p. 1212 - 1224.
    Cohen's kappa - Kappa multinomial - Land cover - Model predictive accuracy - Multinomial models - Multiple class AUC - Validation

    Aim: The earth's land cover is often represented by discrete classes, and predicting shifts between these classes is a major goal in the field. One increasingly common approach is to build models that predict land cover classes with probabilities rather than discrete outcomes. Current assessment approaches have drawbacks when applied to these types of models. In this paper we present a new metric, which assesses agreement between model predictions and observations, while correcting for chance agreement. Location: Global. Methods: κmultinomial is the product of two metrics: the first component measures the agreement in the ranks of the predicted and observed classes, the other specifies the certainty of the model in the case of discrete observations. We analysed the behaviour of κmultinomial and two alternative metrics: Cohen's Kappa (κ) and an extension of the area under receiver operating characteristic Curve to multiple classes (mAUC) when applied to multinomial predictions and discrete observations. Results: Using real and synthetic datasets, we show that κmultinomial - in contrast to κ - can distinguish between models that are very far off versus slightly off. In addition, κmultinomial ranks models higher that predict observed classes with an onaverage higher probability. In contrast, mAUC gives the same score to models that are perfectly able to discriminate among classes of outcomes regardless of the certainty with which those classes are predicted. Main conclusions: With κmultinomial we have provided a tool that directly uses the multinomial probabilities for accuracy assessment. κmultinomial may also be applied to cases where model predictions are evaluated against multiple sets of observations, at multiple spatial scales, or compared to reference models. As models develop we assess how well new models perform compared to the real world.

    Development of a pathway model to assess the exposure of European pine trees to pine wood nematode via the trade of wood
    Douma, J.C. ; Werf, W. Van Der; Hemerik, L. ; Magnusson, C. ; Robinet, C. - \ 2017
    Ecological Applications 27 (2017)3. - ISSN 1051-0761 - p. 769 - 785.
    biological invasion - Bursaphelenchus xylophilus - coniferous wood - Monochamus - pest risk analysis - pine wilt disease - risk reduction options - wood trade
    Pine wood nematode (PWN), Bursaphelenchus xylophilus, is a threat for pine species (Pinus spp.) throughout the world. The nematode is native to North America, and invaded Japan, China, Korea, and Taiwan, and more recently Portugal and Spain. PWN enters new areas through trade in wood products. Once established, eradication is not practically feasible. Therefore, preventing entry of PWN into new areas is crucial. Entry risk analysis can assist in targeting management to reduce the probability of entry. Assessing the entry of PWN is challenging due to the complexity of the wood trade and the wood processing chain. In this paper, we develop a pathway model that describes the wood trade and wood processing chain to determine the structure of the entry process. We consider entry of PWN through imported coniferous wood from China, a possible origin of Portuguese populations, to Europe. We show that exposure increased over years due to an increase in imports of sawn wood. From 2000 to 2012, Europe received an estimated 84 PWN propagules from China, 88% of which arose from imported sawn wood and 12% from round wood. The region in Portugal where the PWN was first reported is among those with the highest PWN transfer per unit of imported wood due to a high host cover and vector activity. An estimated 62% of PWN is expected to enter in countries where PWN is not expected to cause the wilt of pine trees because of low summer temperatures (e.g., Belgium, Sweden, Norway). In these countries, PWN is not easily detected, and such countries can thus serve as potential reservoirs of PWN. The model identifies ports and regions with high exposure, which helps targeting monitoring and surveillance, even in areas where wilt disease is not expected to occur. In addition, we show that exposure is most efficiently reduced by additional treatments in the country of origin, and/or import wood from PWN-free zones. Pathway modelling assists plant health managers in analyzing risks along the pathway and planning measures for enhancing biosecurity.
    A novel way to understand plant species preferences in relation to groundwater discharge conditions using a trait-based approach
    Knaap, Yasmijn A.M. Van der; Douma, Jacob C. ; Aerts, Rien ; Ek, Remco Van; Bodegom, Peter M. van - \ 2016
    Ecohydrology 9 (2016)4. - ISSN 1936-0584 - p. 549 - 559.
    Canopy height - Clonal growth - Leaf phosphorus content - N:P ratio - Nutrient availability - P availability - Seed mass - Seepage

    Groundwater discharge sites harbour characteristic and often rare plant communities that differ substantially from groundwater recharge sites. It is not known which abiotic conditions at these sites drive the differences in community composition. A trait-based approach, which relates species traits to abiotic conditions, may provide insight in this relationship and improve conservation management of these characteristic communities. We used this approach to identify the following: (i) dominant abiotic conditions that shape plant communities at discharge sites and (ii) characteristic traits associated with these abiotic conditions. First, we performed a (qualitative) literature survey to relate plant traits to various abiotic conditions at discharge sites. Second, we performed a meta-analysis to quantitatively test the trait selection at discharge sites. For the meta-analysis, we compiled a species discharge preference database (n=170), based on literature and field data. We performed linear regression to relate traits to species discharge preference. Only 5 out of the 11 traits tested (low leaf phosphorus content, high leaf N:P, low rate of clonal reproduction, low maximum height and high seed mass) were significantly related to discharge preference, while the explained variance was low (R2<0.09). Our results suggest the following: (i) Despite the inclusion of traits specifically related to prevailing local environmental conditions, beyond commonly applied traits, hardly any differences were revealed; this indicates a need for more comprehensive eco-physiological understanding (and information on the selection of combinations of traits). (ii) A trait-based approach may not be highly distinctive in environments differing in only a few specific characteristics.

    Apprécions-nous correctement? : Réponse aux violences sexuelles en République Démocratique du Congo: une comparaison entre 2011 et 2014
    Douma, Nynke ; Hilhorst, D.J.M. ; Matabaro, Jocelyne - \ 2016
    London : Secure Livelihoods Research Consortium (Report 9) - 74 p.
    Getting the balance right? : Sexual violence response in the Democratic Republic of Congo: a comparison between 2011 and 2014
    Douma, Nynke ; Hilhorst, D.J.M. ; Matabaro, Jocelyne - \ 2016
    London : Secure Livelihoods Research Consortium (Report 9) - 66 p.
    Trouver un juste equilibre? : Réponse à la violence sexuelle en République démocratique du Congo: resumé
    Douma, Nynke ; Hilhorst, D.J.M. ; Matabaro, Jocelyne - \ 2016
    London : Secure Livelihoods Research Consortium (Rapport 9) - 12 p.
    Application of a wood pathway model to assess the effectiveness of options for reducing risk of entry of oak wilt into Europe
    Robinet, Christelle ; Douma, Bob ; Piou, Dominique ; Werf, Wopke van der - \ 2016
    Forestry 89 (2016)4. - ISSN 0015-752X - p. 456 - 472.

    The oak wilt fungus, Ceratocystis fagacearum, is native to North America, and is a threat to oaks in Europe. Therefore, the European Union has regulated the importation of oak wood from the US into Europe. We developed a pathway model to calculate the exposure of oak trees in Europe to the fungus under different regulatory scenarios and thus evaluate the effectiveness of the measures. The model describes the import, inspection and treatments of wood, as well as the trade among European countries and processing to sawn wood, final product and residues. The model quantifies the frequency of escape of the fungus from wood with a vector, and the transfer to host trees. Existing regulations reduce exposure by a factor >30 000 compared with a scenario without regulation. Exposure is highest around European ports and during transportation of wood across Europe. Wood treatments and shipment to a restricted set of ports are effective measures, each reducing exposure by more than 90%. Pathway modelling is a promising tool to study entry pathways of alien tree pests and evaluate risk reduction options: it provides a systematic and transparent approach but is limited by availability of biological data.

    Pathway models for analysing and managing the introduction of alien plant pests - an overview and categorization
    Douma, J.C. ; Pautasso, M. ; Venette, R.C. ; Robinet, C. ; Hemerik, L. ; Mourits, M.C.M. ; Schans, J. ; Werf, W. van der - \ 2016
    Ecological Modelling 339 (2016). - ISSN 0304-3800 - p. 58 - 67.
    Alien plant pests are introduced into new areas at unprecedented rates through global trade, transport, tourism and travel, threatening biodiversity and agriculture. Increasingly, the movement and introduction of pests is analysed with pathway models to provide risk managers with quantitative estimates of introduction risks and effectiveness of management options. Pathway models vary greatly in mathematical form, level of detail, treatment of uncertainty and variability, as well as terminology. We conducted an overview and cluster analysis of pathway models to guide risk assessors, risk managers and model developers. We performed divisive hierarchical clustering on models retrieved from the peer-reviewed and grey literature to characterise and categorize the currently used modelling approaches. We distinguish two clusters of models based on product volume flows and two clusters of models based on the movement of individual agents. The first cluster of flow-based models describes a flow of infested material from origins to destinations according to fixed partitioning coefficients. These deterministic models can account for consequences of parameter variability and uncertainty. The second and third clusters of pathway models incorporate stochasticity in processes, and are respectively flow-based or agent-based. Models in the fourth cluster account for interactions between agents and nodes in the pathway. Conceptually, there are no fundamental differences between epidemic network models and this last cluster of pathway models. The choice of pathway model depends on the aim of the risk assessment, the available time, expertise and data. Models in clusters 2, 3, and 4 add sophistication and insight in variability to pathway analysis, but under time and data constraints, key objectives of risk assessors and managers can be addressed with models in cluster 1. The four clusters represent a comprehensive and fit for purpose toolbox of models
    Development of probabilistic models for quantitative pathway analysis of plant pests introduction for the EU territory
    Douma, J.C. ; Robinet, C. ; Hemerik, L. ; Mourits, M.C.M. ; Roques, A. ; Werf, W. van der - \ 2015
    European Food Safety Authority - 435
    gewasbescherming - landen van de europese unie - plantgezondheid - siergewassen - stochastische modellen - bouwhout - vermeerderingsmateriaal - invasieve exoten - plantaardige producten - waarschijnlijkheid - risicoschatting - risicovermindering - plantenplagen - plant protection - european union countries - plant health - ornamental crops - stochastic models - building timbers - propagation materials - invasive alien species - plant products - probability - risk assessment - risk reduction - plant pests
    The aim of this report is to provide EFSA with probabilistic models for quantitative pathway analysis of plant pest introduction for the EU territory through non-edible plant products or plants. We first provide a conceptualization of two types of pathway models. The individual based PM simulates an individual consignment (or a population of such consignment) by describing the stochastic change in the state of the individual consignment over time and space. The flow-based PM, simulates the flow of infested product over time and space, without distinguishing individual consignments. We show how these two conceptualisations are mathematically related, and present, as a show case, both models for cut flowers. Second, we developed PMs for five product groups: round wood, sawn wood, cut flowers, plants for planting and seeds. For each product group we have developed a case-study (combination of product, origin and pest) to illustrate the use of the pathway models: (1) oak wood from the USA and Ceratocystis fagacearum, (2) Coniferous sawn wood from China and Bursaphelenchus xylophilus, (3) Cut orchids from Thailand and Thrips palmi, (4) Pot orchids from Thailand and Thrips palmi, and (5) Tomato seeds and Clavibacter michiganensis subsp. michiganensis from outside the European Union. An uncertainty analysis on the models shows that the pest species-specific parameters appear to be sensitive and uncertain. Third, a practical guidance is provided on i) how to develop a PM, ii) the application of PMs in @Risk (a plugin for MS Excel), and iii) application in R. Finally, future research topics are defined. Further work is needed on interpretation of results, linking quantitative outcomes of pathway modelling to pest risk scoring guidance, and evaluation of management options using pathway models.
    Early-season crop colonization by parasitoids is associated with native vegetation, but is spatially and temporally erratic
    Bianchi, F.J.J.A. ; Walters, B.J. ; Hove, A.L.T. ; Cunningham, S.A. ; Werf, W. van der; Douma, J.C. ; Schellhorn, N.A. - \ 2015
    Agriculture, Ecosystems and Environment 207 (2015). - ISSN 0167-8809 - p. 10 - 16.
    terebrans hymenoptera-ichneumonidae - managing ecosystem services - biological-control - bemisia-tabaci - pest-control - agricultural landscapes - habitats - biodiversity - populations - arthropods
    Semi-natural habitats in agricultural landscapes may support parasitoid populations that provide biocontrol services by suppressing populations of crop pests, but little is known about the spatial pattern and variability of these services at different levels of scale. Here we investigate the rarely studied phenomenon of early-season crop colonization by parasitoids and the relationship with the surrounding landscape. We assessed parasitism of whiteflies by placing whitefly infested cotton seedlings in remnant vegetation, arable land 25–125 m from remnant vegetation, and arable land further than 400 m from remnant vegetation. Twelve to twenty sentinel plants were exposed in a 25 × 25 m grid pattern in plots in each habitat. The experiment was conducted at 18 locations across two landscapes and repeated three times in a 2-week period in 2007 and 2008. Parasitism was observed during the first three days after the introduction of the whitefly infested seedlings and was in all cases caused by Encarsia spp. The mean number of parasitized whitefly per plant was 0.106 ± 0.025 and was highest on cotton plants placed in remnant vegetation, declining with increasing distance from remnant vegetation. A regression model with land use and meteorological variables received more statistical support from the data than models with only landscape and time period as factors. Parasitism levels were influenced by the proportion of remnant vegetation, grassland, as well as wind, temperature, dew point temperature and year. Early-season colonization of whitefly infested seedlings by parasitoids was erratic and characterized by large spatial (inter-plant and inter-plot) and temporal variation. Our study confirms that remnant vegetation function as reservoirs for parasitoids and that parasitoids can penetrate arable fields beyond 125 m within 3 days. However, variation in the occurrence of parasitism makes it difficult to predict parasitoid colonization at a specific place and time. Therefore, field-based scouting for pests and parasitoids is necessary, even in landscapes with a high biocontrol potential.
    Global patterns of plant root colonization intensity by mycorrhizal fungi explained by climate and soil chemistry
    Soudzilovskaia, N.A. ; Douma, J.C. ; Akhmetzhanova, A.A. ; Bodegom, P.M. van; Cornwell, W.K. ; Moens, E.J. ; Treseder, K.K. ; Tibbett, M. ; Wang, Y.P. ; Cornelissen, J.H.C. - \ 2015
    Global Ecology and Biogeography 24 (2015)3. - ISSN 1466-822X - p. 371 - 382.
    ectomycorrhizal fungi - arbuscular mycorrhizas - ecosystem development - temperature stress - growth-responses - cold-storage - nitrogen - phosphorus - carbon - metaanalysis
    Aim Most vascular plants on Earth form mycorrhizae, a symbiotic relationship between plants and fungi. Despite the broad recognition of the importance of mycorrhizae for global carbon and nutrient cycling, we do not know how soil and climate variables relate to the intensity of colonization of plant roots bymycorrhizal fungi. Here we quantify the global patterns of these relationships. Location Global. Methods Data on plant root colonization intensities by the two dominant types of mycorrhizal fungi world-wide, arbuscular (4887 plant species in 233 sites) and ectomycorrhizal fungi (125 plant species in 92 sites),were compiled frompublished studies. Data for climatic and soil factors were extracted from global datasets. For a given mycorrhizal type, we calculated at each site the mean root colonization intensity bymycorrhizal fungi across all potentiallymycorrhizal plant species found at the site, and subjected these data to generalized additive model regression analysis with environmental factors as predictor variables. Results We show for the first time that at the global scale the intensity of plant root colonization by arbuscular mycorrhizal fungi strongly relates to warm-season temperature, frost periods and soil carbon-to-nitrogen ratio, and is highest at sites featuring continental climates with mild summers and a high availability of soil nitrogen. In contrast, the intensity of ectomycorrhizal infection in plant roots is related to soil acidity, soil carbon-to-nitrogen ratio and seasonality of precipitation, and is highest at sites with acidic soils and relatively constant precipitation levels. Main conclusions We provide the first quantitative global maps of intensity of mycorrhizal colonization based on environmental drivers, and suggest that environmental changes will affect distinct types of mycorrhizae differently. Future analyses of the potential effects of environmental change on global carbon and nutrient cycling via mycorrhizal pathways will need to take into account the relationships discovered in this study.
    Bordetella pertussis: an underreported pathogen in pediatric respiratory infections, a prospective cohort study
    Brink, G. van den; Wishaupt, J.O. ; Douma, J.C. ; Hartwig, N.G. ; Versteegh, F.G.A. - \ 2014
    Bmc Infectious Diseases 14 (2014). - ISSN 1471-2334 - 10 p.
    suspected pertussis - holmesii dna - illness - diagnosis - children - tests
    Background: The incidence of pertussis has been increasing worldwide. In the Netherlands, the seroprevalence has risen higher than the reported cases, suggesting that laboratory tests for pertussis are considered infrequently and that even more pertussis cases are missed. The objective of our study was to determine the frequency of pertussis in clinically unsuspect cases compared to suspect cases with the intention of finding clinical predictors. Methods: The present prospective cohort study was part of a controlled clinical trial evaluating the impact of molecular diagnostics on clinical decision making in pediatric respiratory infections, performed during 2 winter seasons. For this study, in the first season pertussis was only tested in case of clinical suspicion, in the second season, pertussis was also tested without clinical suspicion. Multivariate and univariate analysis were performed using SPSS 18 and Statistical software ‘R’. Results: In the two seasons respectively 22/209 (10,5%) and 49/373 (13,1%) cases were clinically suspected of pertussis. Bordetella pertussis was detected by real time RT-PCR in respectively 2/22 (9,1%) and 7/49 (14,3%) cases. In the second season an additional 7 cases of pertussis were found in clinically unsuspected cases (7/257 = 2,7%). These additional cases didn’t differ in clinical presentation from children without a positive test for pertussis with respect to respiratory symptoms. Conclusions: Pertussis in children sometimes mimics viral respiratory tract infections. If pertussis diagnostics are based on clinical suspicion alone, about 1 in 5 cases (19%) is missed. Despite widely accepted clinical criteria, paroxysmal cough is not a good predictor of pertussis. To prevent spreading, physicians should include B. pertussis in routine diagnostics in respiratory tract infections. Keywords: Bordetella pertussis, Whooping cough, Respiratory tract infections, Polymerase chain reaction, Child
    A fully traits-based approach to modeling global vegetation distribution
    Bodegom, P.M. van; Douma, J.C. ; Verheijen, L.M. - \ 2014
    Proceedings of the National Academy of Sciences of the United States of America 111 (2014)38. - ISSN 0027-8424 - p. 13733 - 13738.
    earth system model - climate-change - plant traits - economics spectrum - functional traits - amazonian forest - photosynthesis - classification - co2 - acclimation
    Dynamic Global Vegetation Models (DGVMs) are indispensable for our understanding of climate change impacts. The application of traits in DGVMs is increasingly refined. However, a comprehensive analysis of the direct impacts of trait variation on global vegetation distribution does not yet exist. Here, we present such analysis as proof of principle. We run regressions of trait observations for leaf mass per area, stem-specific density, and seed mass from a global database against multiple environmental drivers, making use of findings of global trait convergence. This analysis explained up to 52% of the global variation of traits. Global trait maps, generated by coupling the regression equations to gridded soil and climate maps, showed up to orders of magnitude variation in trait values. Subsequently, nine vegetation types were characterized by the trait combinations that they possess using Gaussian mixture density functions. The trait maps were input to these functions to determine global occurrence probabilities for each vegetation type. We prepared vegetation maps, assuming that the most probable (and thus, most suited) vegetation type at each location will be realized. This fully traits-based vegetation map predicted 42% of the observed vegetation distribution correctly. Our results indicate that a major proportion of the predictive ability of DGVMs with respect to vegetation distribution can be attained by three traits alone if traits like stem-specific density and seed mass are included. We envision that our traits-based approach, our observation-driven trait maps, and our vegetation maps may inspire a new generation of powerful traits-based DGVMs.
    Low investment in sexual reproduction threatens plants adapted to phosphorus limitation
    Fujita, Y. ; Olde Venterink, H. ; Bodegom, P.M. van; Douma, J.C. ; Heil, G.W. ; Hölzel, N. ; Jablonska, E. ; Kotowski, W. ; Okruszko, T. ; Pawlikowski, P. ; Ruiter, P.C. de; Wassen, M.J. - \ 2014
    Nature 505 (2014). - ISSN 0028-0836 - p. 82 - 86.
    vegetatie - flora - soortendiversiteit - voortplantingsgedrag - ecosystemen - wetlands - veenplanten - bodem-plant relaties - stikstof - fosfaat - waterbeheer - bedreigde soorten - europa - azië - vegetation - flora - species diversity - reproductive behaviour - ecosystems - wetlands - bog plants - soil plant relationships - nitrogen - phosphate - water management - endangered species - europe - asia - n-p stoichiometry - biological stoichiometry - endangered plants - mineral-nutrition - community biomass - european flora - life-history - patterns - traits
    Plant species diversity in Eurasian wetlands and grasslands depends not only on productivity but also on the relative availability of nutrients, particularly of nitrogen and phosphorus1–4. Here we show that the impacts of nitrogen:phosphorus stoichiometry on plant species richness can be explained by selected plant life-history traits, notably by plant investments in growth versus reproduction. In 599 Eurasian siteswithherbaceous vegetationwe examined the relationship between the local nutrient conditions and community-mean life-history traits. We found that compared with plants in nitrogen-limited communities, plants in phosphorus-limited communities invest little in sexual reproduction (for example, less investment in seed, shorter flowering period, longer lifespan) and have conservative leaf economy traits (that is, a low specific leaf area and a high leaf dry-matter content). Endangered species weremore frequent in phosphorus-limited ecosystems and they too invested little in sexual reproduction. The results provide new insight into how plant adaptations to nutrient conditions can drive the distribution of plant species in natural ecosystems and can account for the vulnerability of endangered species.
    Fragility by choice? A scoping mission in Burundi, South Sudan and Uganda, a synthesis report on research commissioned by the Dutch Consortium for Rehabilitation (DCR)
    Frerks, G.E. ; Douma, P. - \ 2013
    Den Haag : Dutch Consortium for Rehabilitation - 80 p.
    Meer maatregelen nodig voor natuurbehoud
    Wamelink, Wieger - \ 2013
    Natuurbehoud onder EU-norm
    Wamelink, Wieger - \ 2013
    De lente barst alleen nog maar in ons hoofd los
    Vliet, Arnold van - \ 2013
    Eikenprocessierups dit jaar later door kou
    Vliet, Arnold van - \ 2013
    De lente barst alleen nog maar in ons hoofd los
    Vliet, Arnold van - \ 2013
    De lente barst alleen nog maar in ons hoofd los
    Vliet, Arnold van - \ 2013
    De lente barst alleen nog maar in ons hoofd los
    Vliet, Arnold van - \ 2013
    De lente barst alleen nog maar in ons hoofd los
    Vliet, Arnold van - \ 2013
    De lente barst alleen nog maar in ons hoofd los
    Vliet, Arnold van - \ 2013
    De lente barst alleen nog maar in ons hoofd los
    Vliet, Arnold van - \ 2013
    De lente barst alleen nog maar in ons hoofd los
    Vliet, Arnold van - \ 2013
    De lente barst alleen nog maar in ons hoofd los
    Vliet, Arnold van - \ 2013
    De lente barst alleen nog maar in ons hoofd los
    Vliet, Arnold van - \ 2013
    De lente barst alleen nog maar in ons hoofd los
    Vliet, Arnold van - \ 2013
    De lente barst alleen nog maar in ons hoofd los
    Vliet, Arnold van - \ 2013
    De lente barst alleen nog maar in ons hoofd los
    Vliet, Arnold van - \ 2013
    De lente barst alleen nog maar in ons hoofd los
    Vliet, Arnold van - \ 2013
    Natuur ligt drie weken achter op schema van afgelopen twaalf jaar
    Vliet, Arnold van - \ 2013
    Kou in april niet abnormaal
    Vliet, Arnold van - \ 2013
    Hallo, snotterseizoen
    Vliet, Arnold van - \ 2013
    Verlandschapping stad levert winst op (interview met S. Lenzholzer)
    Lenzholzer, Sanda - \ 2013
    Effectiveness of innovation grants to smallholder agricultural producers: an explorative systematic review
    Ton, G. ; Grip, K. de; Klerkx, L.W.A. ; Rau, M.L. ; Douma, M. ; Friis-Hansen, E. ; Triomphe, B. ; Waters-Bayer, A. ; Wongtschowski, M. - \ 2013
    London : EPPI-Centre, Social Science Research Unit, Institute of Education, University of London - ISBN 9781907345548 - 115
    premies - verbeteringssubsidies - boeren - innovaties - familiebedrijven, landbouw - grants - improvement grants - farmers - innovations - family farms
    Grants for agricultural innovation are common but grant funds specifically targeted to smallholder farmers remain relatively rare. Nevertheless, they are receiving increasing recognition as a promising venue for agricultural innovation. They stimulate smallholders to experiment with improved practices, to become proactive and to engage with research and extension providers. The systematic review covered three modalities of disbursing these grants to smallholder farmers and their organisations: vouchers, competitive grants and farmer-led innovation support funds. The synthesis covers, among others, innovation grant systems in Malawi (Agricultural Input Subsidy Programme), Latin America (several Challenge Funds for Farmer Groups), Uganda (National Agricultural Advisory Services ), and Colombia (Local Agricultural Research Committees - CIAL).
    Corporate Social Responsibility: the role of public policy. A systematic literature review of the effects of government supported interventions on the corporate social responsibility (CSR) behaviour of enterprises in developing countries. IOB Study
    Ingram, V.J. ; Grip, K. de; Ruijter de Wildt, M.J.M. de; Ton, G. ; Douma, M. ; Boone, J.A. ; Hoeven, J.T. van - \ 2013
    Den Haag : Department (IOB), Ministry of Foreign Affairs of the Netherlands (IOB Study 377) - ISBN 9789053284384 - 136
    Succession-induced trait shifts across a wide range of NW European ecosystems are driven by light and modulated by initial abiotic conditions
    Douma, Jacob C. ; Haan, Martin W.A. de; Aerts, Rien ; Witte, Jan Philip M. ; Bodegom, Peter M. van - \ 2012
    Journal of Ecology 100 (2012)2. - ISSN 0022-0477 - p. 366 - 380.
    Chronosequences - Determinants of plant community diversity and structure - Functional ecosystem characteristics - Initial abiotic conditions - Meta-analysis - Plant strategy axes - Succession trajectories - Trajectory partitioning

    For truly predictive community ecology, it is essential to understand the interplay between species traits, their environment and their impacts on the composition of plant communities. These interactions are increasingly understood for various environmental drivers, but our understanding of how traits, in general, change during succession is still modest. We hypothesize that (initial) abiotic conditions other than light drive the successional dynamics of other traits. The idea that different initial abiotic conditions lead to different trait trajectories during succession was predicted long ago but has never been tested for traits. In this study, we compared the successional (decades to centuries) trait trajectories of 19 ecosystem types in low-altitude NW Europe using a database including >4700 plots. We tested which traits (out of a total of 12, including those associated with light competition strategies) show consistent shifts across ecosystems. Additionally, we investigated, through a novel partitioning of trait differences (using partial principal component analyses), whether abiotic factors can explain trait shifts that occur over and above light-induced trait shifts. We show that canopy height, woodiness, leaf size and seed mass increase, and flowering onset and flowering duration decrease consistently with succession across ecosystems, while leaf economic traits and life span showed a mixed response during succession. Accounting for the effect of height revealed that the initial and prevailing abiotic conditions - particularly soil moisture - co-determine trait shifts during succession. Therefore, different initial starting conditions may lead to different trajectories in trait space, most notably due to the differential response of specific leaf area (SLA), leaf nitrogen content and life span. For example, SLA decreases in seres that become drier over time (initially very wet), while it increases in seres that become wetter over time (initially very dry). Synthesis. Our novel approach of partitioning successional trait shifts between the influence of competition for light and other abiotic factors showed that trajectories of ecosystems through trait space can be explained by a combination of the two: a universal response to changing light availability and a specific response depending on initial abiotic conditions.

    Disturbance and resource availability act differently on the same suite of plant traits : Revisiting assembly hypotheses
    Douma, J.C. ; Shipley, B. ; Witte, J.P.M. ; Aerts, R. ; Bodegom, P.M. van - \ 2012
    Ecology 93 (2012)4. - ISSN 0012-9658 - p. 825 - 835.
    Canopy height - Community assembly - Disturbance - Germination onset - Leaf economic traits - Nutrient availability - Relative growth rate - Seed mass - Structural equation modeling - The Netherlands

    Understanding the mechanisms of trait selection at the scale of plant communities is a crucial step toward predicting community assembly. Although it is commonly assumed that disturbance and resource availability constrain separate suites of traits, representing the regenerative and established phases, respectively, a quantification and test of this accepted hypothesis is still lacking due to limitations of traditional statistical techniques. In this paper we quantify, using structural equation modeling (SEM), the relative contributions of disturbance and resource availability to the selection of suites of traits at the community scale. Our model specifies and reflects previously obtained ecological insights, taking disturbance and nutrient availability as central drivers affecting leaf, allometric, seed, and phenology traits in 156 (semi-) natural plant communities throughout The Netherlands. The common hypothesis positing that disturbance and resource availability each affect a set of mutually independent traits was not consistent with the data. Instead, our final model shows that most traits are strongly affected by both drivers. In addition, trait-trait constraints are more important in community assembly than environmental drivers in half of the cases. Both aspects of trait selection are crucial for correctly predicting ecosystem processes and community assembly, and they provide new insights into hitherto underappreciated ecological interactions.

    Towards a functional basis for predicting vegetation patterns; incorporating plant traits in habitat distribution models
    Douma, Jacob C. ; Witte, Jan Philip M. ; Aerts, Rien ; Bartholomeus, Ruud P. ; Ordoñez, Jenny C. ; Venterink, Harry Olde ; Wassen, Martin J. ; Bodegom, Peter M. van - \ 2012
    Ecography 35 (2012)4. - ISSN 0906-7590 - p. 294 - 305.
    vegetation types - geographical distribution - ecological modeling - prediction - traits - habitats - netherlands

    Reliably predicting vegetation distribution requires habitat distribution models (HDMs) that are ecologically sound. Current correlative HDMs are increasingly criticized because they lack sufficient functional basis. To include functional information into these models, we integrated two concepts from community ecology into a new type of HDM. We incorporated: 1) species selection by their traits in which only those species that pass the environmental filter can be part of the community (assembly theory); 2) that the occurrence probability of a community is determined by the extent to which the community mean traits fit the required traits as set by the environment. In this paper, our trait-based HDM is presented and its predictive capacity explored. Our approach consists of two steps. In step 1, four plant traits (stem-specific density and indicator values for nutrients, moisture and acidity) are predicted from four dominant environmental drivers (disturbance, nutrient supply, moisture supply and acidity) using regression. In step 2, these traits are used to predict the occurrence probability of 13 vegetation types, covering the majority of vegetation types across the Netherlands. The model was validated by comparison to the observed vegetation type for 263 plots in the Netherlands. Model performance was within the range of conventional HDMs and decreased with increasing uncertainty in the environment-trait relationships and with an increasing number of vegetation types. This study shows that including functionality into HDMs is not necessarily at the cost of model performance, while it has several conceptual advantages among including an increased insight in the functional characteristics of the vegetation and sources of unpredictability in community assembly. As such it is a promising first step towards more functional HDMs. Further development of a trait-based HDM hinges on replacing indicator values by truly functional traits and the translation of these relationships into mechanistic relationships.

    Going beyond limitations of plant functional types when predicting global ecosystem-atmosphere fluxes : Exploring the merits of traits-based approaches
    Bodegom, P.M. van; Douma, J.C. ; Witte, J.P.M. ; Ordoñez, J.C. ; Bartholomeus, R.P. ; Aerts, R. - \ 2012
    Global Ecology and Biogeography 21 (2012)6. - ISSN 1466-822X - p. 625 - 636.
    Assembly theory - Bioclimatic limits - DGVM - Earth system models - Functional traits - Habitat filtering - Land surface model - PFT - Plant strategies - Trait convergence

    Aim Despite their importance for predicting fluxes to and from terrestrial ecosystems, dynamic global vegetation models have insufficient realism because of their use of plant functional types (PFTs) with constant attributes. Based on recent advances in community ecology, we explore the merits of a traits-based vegetation model to deal with current shortcomings. Location Global. Methods A research review of current concepts and information, providing a new perspective, supported by quantitative analysis of a global traits database. Results Continuous and process-based trait-environment relations are central to a traits-based approach and allow us to directly calculate fluxes based on functional characteristics. By quantifying community assembly concepts, it is possible to predict trait values from environmental drivers, although these relations are still imperfect. Through the quantification of these relations, effects of adaptation and species replacement upon environmental changes are implicitly accounted for. Such functional links also allow direct calculation of fluxes, including those related to feedbacks through the nitrogen and water cycle. Finally, a traits-based model allows the prediction of new trait combinations and no-analogue ecosystem functions projected to arise in the near future, which is not feasible in current vegetation models. A separate calculation of ecosystem fluxes and PFT occurrences in traits-based models allows for flexible vegetation classifications. Main conclusions Given the advantages described above, we argue that traits-based modelling deserves consideration (although it will not be easy) if one is to aim for better climate projections.

    Global quantification of contrasting leaf life span strategies for deciduous and evergreen species in response to environmental conditions
    Ommen Kloeke, A.E.E. van; Douma, J.C. ; Ordoñez, J.C. ; Reich, P.B. ; Bodegom, P.M. van - \ 2012
    Global Ecology and Biogeography 21 (2012)2. - ISSN 1466-822X - p. 224 - 235.
    Deciduous - Evaporative demand - Evergreen - Favourable period - Growing season - Leaf habit - Leaf life span - Mixed model analysis - N-mineralization - Temperature

    Aim Species with deciduous and evergreen leaf habits typically differ in leaf life span (LLS). Yet quantification of the response of LLS, within each habit, to key environmental conditions is surprisingly lacking. The aim of this study is to quantify LLS strategies of the two leaf habits under varying temperature, moisture and nutrient conditions, using a global database. We hypothesize that deciduous LLS reflects the length of the growing season, avoiding unfavourable conditions regardless of the cause. Evergreen species adjust to unfavourable periods and amortize lower net carbon gains over several growing seasons, with increasing LLS associated with increasingly short favourable versus unfavourable season lengths. Location Global. Methods Data on LLS and environmental variables were compiled from global datasets for 189 deciduous and 506 evergreen species across 83 study locations. Individual and combined effects of measures of seasonality of temperature, water and nutrient availability on length of the growing season and on LLS were quantified using linear mixed models. The best models for predicting LLS were obtained using Akaike's information criterion (AIC) and ΔAIC. Results The LLS of deciduous and evergreen species showed opposite responses to changes in environmental conditions. Under unfavourable conditions, deciduous LLS decreases while evergreen LLS increases. A measure of temperature alone was the best predictor of the growing season. The LLS of deciduous species was independent of environmental conditions after expressing LLS in relation to the number of growing seasons. Evergreen species, on the other hand, adjusted to unfavourable conditions by increasing LLS up to four growing seasons. Contrary to expectations, variation in LLS was best explained solely by temperature, instead of by combined measures of temperature, moisture and nutrient availability. Shifts in the photosynthesis to respiration balance might provide a physiological explanation. Main conclusions Temperature, and not drought or nutrient availability, is the primary driver of contrasting responses of LLS for different leaf habit types.

    A lot of hype, less effective aid
    Douma, N.W. ; Hilhorst, D.J.M. - \ 2012
    Fond de commerce? Sexual violence assistance in the Democratic Republic of Congo
    Douma, N. ; Hilhorst, D.J.M. - \ 2012
    Wageningen : Wageningen University, Disaster Studies
    Fond de commerce?: Sexual violence assistance in the Democratic Republic of Congo
    Douma, N.W. ; Hilhorst, D. - \ 2012
    Wageningen : Disaster Studies (Occasional paper 02) - 78 p.
    Fond de commerce?: Assistance aux victimes de violences sexuelles en République Démocratique du Congo
    Douma, N.W. ; Hilhorst, D. - \ 2012
    Wageningen : Disaster Studies (Occasional paper 03) - 86 p.
    A combination of functionally different plant traits provides a means to quantitatively predict a broad range of species assemblages in NW Europe
    Douma, J.C. ; Aerts, R. ; Witte, J.P.M. ; Bekker, R.M. ; Kunzmann, D. ; Metselaar, K. ; Bodegom, P.M. van - \ 2012
    Ecography 35 (2012)4. - ISSN 0906-7590 - p. 364 - 373.
    vegetatietypen - plantenecologie - vegetation types - plant ecology - relative growth-rate - community ecology - strategies - diversity - convergence - divergence - patterns - model - components - nitrogen
    Assembly theory predicts that filtering processes will select species by their attributes to build a community. Some filters increase functional similarity among species, while others lead to dissimilarity. Assuming converging processes to be dominant within habitats, we tested in this study whether species assemblages across a wide range of habitats can be distinguished quantitatively by their mean trait compositions. In addition, we investigated how many and which traits are needed to describe the differences between species assemblages best. The approach has been applied on a dataset that included 12 plant traits and 7644 vegetation releves covering a wide range of habitats in the Netherlands. We demonstrate that due to the dominant role of converging processes 1) the functional composition can explain up to 80% of the floristic differences between species assemblages using seven plant traits, showing that plant trait combinations provide a powerful tool for predicting the occurrence of species assemblages across different habitats; 2) to achieve a high performance, traits should be taken from different strategy components, i.e. traits that are functionally orthogonal, which does not necessarily coincide with low trait-trait correlations; 3) the different strategy components identified in this study correspond to the strategy components of some conventional plant ecological strategy schemes (PESS) schemes to describe the variation between individual species. However, some PESS merge traits into one strategy component that are shown to be functionally different when predicting species assemblages. If such PESS is used to predict assemblages, this leads to a loss in predictive capacity. Potentially, our new approach is globally applicable to quantify community assembly patterns. However this needs to be tested.
    Value chain partnerships: A process-based view on how partnerships generate institutional change
    Vellema, S. ; Wijk, J. van; Roo, N. de; Douma, M. ; Drost, S. - \ 2012
    Looking beyond upgrading: How value chains partnerships create institutional change
    Vellema, S. ; Wijk, J. van; Roo, N. de; Douma, M. ; Drost, S. - \ 2012
    Quantifying the functional responses of vegetation to drought and oxygen stress in temperate ecosystems
    Douma, J.C. ; Bardin, V. ; Bartholomeus, R.P. ; Bodegom, P.M. van - \ 2012
    Functional Ecology 26 (2012)6. - ISSN 0269-8463 - p. 1355 - 1365.
    plant traits - soil-conditions - water-balance - strategies - patterns - aerenchyma - submergence - communities - tolerance - climate
    1. Our understanding of the generality of plant functional responses to water availability is limited; current field studies use either very rough approximations of water and oxygen availability or only focus on water-stressed ecosystems. Studies that relate species' responses to a surplus of water are limited to controlled experiments. 2. The aim of this study was to investigate how traits are selected along a gradient of soil moisture, ranging from oxygen-stressed to drought-stressed. We tested 15 traits: eight leaf traits, two root traits, two seed traits and three allometry traits and related their community means to process-based measures of drought stress and oxygen stress for 171 plots in the Netherlands. Because the trait values had been taken from a large database, an independent field survey was carried out to validate the relationships thus derived. 3. We show that root porosity and seed floating capacity are mostly strongly related, although still moderately, to oxygen and drought stress (R-2 = 27% and 42%, respectively). Leaf traits responded weakly to either of the stressors. The field survey yielded similar relationships. Trait combinations were much more closely related to oxygen or drought stress than individual traits, suggesting that there are multiple trait solutions at a given level of water and oxygen stress. 4. The relatively weak relationships found between traits and water-related stressors contrast with the strong control of other environmental drivers (disturbance, nutrients) on traits and suggest that these strong constraints imposed by other environmental drivers necessitate varied solutions to cope with water availability.
    Eplucher l'Oignon : Pour une filière oignon nigérienne compétitive et inclusive
    Schrader, T.H. ; Vugt, S.M. van; Roo, N. de; Salifou, L. ; Douma, A. ; Daddy, A. ; Ouédraogo, Z. ; Sarr, M. ; Adjobo, R.A. - \ 2012
    Wageningen : Wageningen UR Centre for Development Innovation; SNV Niger, FCMN-Niya, Agri-Bilan - 63
    Trends in veterinary antibiotic use in the Netherlands 2004-2012
    Bondt, N. ; Puister-Jansen, L.F. ; Ge, L. ; Veen, H.B. van der; Bergevoet, R.H.M. ; Douma, B.E. ; Vliet, A.L.J. van; Wehling, K.W. - \ 2012
    Den Haag : LEI Wageningen UR (LEI 12-109) - 26
    veehouderij - varkenshouderij - pluimveehouderij - rundveehouderij - antibiotica - dosering - monitoring - antibioticaresistentie - livestock farming - pig farming - poultry farming - cattle husbandry - antibiotics - dosage - monitoring - antibiotic resistance
    The objective of this study is to obtain detailed insight into the trends in the exposure of farm animals to antibiotics. This is done by monitoring both overall sales data at the national level and usage data per animal species: pigs, poultry, veal calves, other cattle and sheep.
    Trends in veterinary antibiotic use in the Netherlands 2005-2011
    Bondt, N. ; Puister-Jansen, L.F. ; Ge, L. ; Veen, H.B. van der; Bergevoet, R.H.M. ; Douma, B.E. ; Vliet, A.L.J. van; Wehling, K.W. - \ 2012
    Den Haag : LEI Wageningen UR
    antibiotica - veehouderij - dierhouderij - vee - diergeneeskunde - veterinaire praktijk - dierenwelzijn - diergezondheid - antibiotics - livestock farming - animal husbandry - livestock - veterinary science - veterinary practice - animal welfare - animal health
    During the period 2009-2011 the total sales of antibiotics dropped nearly 32%, from 495 tonnes in 2009 to 338 tonnes in 2011 (FIDIN, 2012). This far exceeds the policy objective for 2011 set by the Dutch government, i.e., a 20% reduction in antibiotic use compared with 2009. Survey data on antibiotic use per animal species indicate a decrease in all five livestock sectors examined in 2011.
    Multi-Stakeholder processes, service delivery and state institutions; Synthesis report
    Stel, N. ; Boer, D. de; Hilhorst, D. ; Haar, G. van der; Molen, I. van der; Douma, N.W. ; Herman Mostert, R. - \ 2012
    The Hague : Peace Security and Development Network - 96 p.
    How do bryophytes govern generative recruitment of vascular plants?
    Soudzilovskaia, Nadejda A. ; Graae, Bente J. ; Douma, Jacob C. ; Grau, Oriol ; Milbau, Ann ; Shevtsova, Anna ; Wolters, Loes ; Cornelissen, Johannes H.C. - \ 2011
    New Phytologist 190 (2011)4. - ISSN 0028-646X - p. 1019 - 1031.
    Allelopathy - Bryophyte - Generative recruitment - Germination - Moisture - Plant-plant interaction - Seedling - Temperature

    Interactions between vascular plants and bryophytes determine plant community composition in many ecosystems. Yet, little is known about the importance of interspecific differences between bryophytes with respect to their effects on vascular plants. We compared the extent to which species-specific bryophyte effects on vascular plant generative recruitment depend on the following underlying mechanisms: allelopathy, mechanical obstruction, soil moisture and temperature control. We sowed 10 vascular plant species into monospecific mats of six chemically and structurally diverse bryophytes, and examined 1-yr seedling recruitment. Allelopathic effects were also assessed in a laboratory phyto-assay. Although all bryophytes suppressed vascular plant regeneration, there were significant differences between the bryophyte species. The lack of interactions indicated the absence of species-specific adaptations of vascular plants for recruitment in bryophyte mats. Differences between bryophyte species were best explained by alterations in temperature regime under bryophyte mats, mostly by reduced temperature amplitudes during germination. The temperature regime under bryophyte mats was well predicted by species-specific bryophyte cushion thickness. The fitness of established seedlings was not affected by the presence of bryophytes. Our results suggest that climatically or anthropogenically driven changes in the species' composition of bryophyte communities have knock-on effects on vascular plant populations via generative reproduction.

    Estimate of veterinary antibiotic usage in the Netherlands in 2011
    Bondt, N. ; Puister-Jansen, L.F. ; Veen, H.B. van der; Bergevoet, R.H.M. ; Douma, B.E. ; Vliet, A.L.J. van; Wehling, K.W. - \ 2011
    Den Haag : LEI, onderdeel van Wageningen UR - 4
    dierhouderij - antibiotica - veterinaire producten - verkoopbaar volume - toepassing - statistische analyse - animal husbandry - antibiotics - veterinary products - merchantable volume - application - statistical analysis
    The information presented on the MARAN website is based on a collation of data from ongoing surveillance systems on the sales and use of antimicrobial agents in animal husbandry in the Netherlands.
    Veterinary antibiotic usage in the Netherlands in 2010
    Bondt, N. ; Puister-Jansen, L.F. ; Veen, H.B. van der; Bergevoet, R.H.M. ; Douma, B.E. ; Vliet, A.L.J. van; Wehling, K.W. - \ 2011
    Wageningen : Wageningen UR - 17
    veehouderij - antibiotica - toepassing - marktonderzoek - overheidsbeleid - antibioticaresistentie - livestock farming - antibiotics - application - market research - government policy - antibiotic resistance
    The objective of this study is to obtain detailed insight into the exposure of farm animals to antibiotics, by monitoring both sales data at the national level and more specifically data per animal species. The results of the study can be used by the Ministry of Economic Affairs, Agriculture and Innovation for policy evaluation. In addition, the usage data might play a role in explaining trends in resistance that have become apparent.
    Linking biodiversity conservation to market-led development: a case study of the Right Rooibos Initiative, South Africa
    Douma, M. ; Hawkins, H.S. ; Vellema, S. - \ 2010
    Den Haag : Ministerie van Buitenlandse Zaken (IChA working paper no. 2) - 40
    This series of Working Papers is a result of the Partnership Programme between the Netherlands’ Ministry of Foreign Affairs Government and Wageningen UR. The project ‘Inclusive Chains for Agro biodiversity IChA’ collaborated with partners in 5 countries: Colombia, Ghana, Namibia, South Africa and Thailand Two questions are pertinent to facilitate better practice and eventually better the market access within the Rooibos industry: 1) Is Right Rooibos effective economically, socially and environmentally, and 2) Are existing certification schemes enabling or constraining regarding biodiversity conservation and better practice in general, and how can they be improved? Both of these questions are interrelated and fall within the general GCA mandate. This study focuses on the latter aim. Thus this study aims to 1) create an understanding of how events around the Right Rooibos and various potential certification schemes emerged, who was involved in these events and how different stakeholders, with varying backgrounds and expertise, shaped that process, and to 2) determine whether certification schemes presently developing around Rooibos are perceived by stakeholders as enabling or constraining regarding biodiversity conservation and better practice in general. determine whether certification schemes presently developing around Rooibos are perceived by stakeholders as enabling or constraining regarding biodiversity conservation and better practice in general.
    Les 25 Résolutions de Konni
    Vugt, S.M. van; Schrader, T.H. ; Roo, N. de; Daddy, A. ; Douma, A. ; Salifou, M.L. - \ 2010
    Wageningen : Wageningen UR Centre for Development Innovation - 47
    Niger is the largest exporter of onions in West Africa. More than 100.000 Nigerian peasants cultivate onions. For them and all the other operators within the chain (intermediaries, tradesmen, shipping agents), the onion is an important source of income. SNV Niger, and Wageningen UR Centre for Development Innovation in the Netherlands, in collaboration with FCMN Niya and Agri-Bilan, initiated an action research titled “Peeling the onion”. The goal of this action-research is to identify possibilities of collective action for all the actors in the value chain of the onion. The research focusses on ‘leverages’ to induce changes which make the onion subsector in one time more competitive, inclusive and sustainable. After this first phase, we shared our results during this participative workshop in Birni Konni in the area of Tahoua. Moreover one stimulated the dialogue between the various actors within the value chain of the onion resulting in the 25 resolutions of Konni! This report is the result of this workshop and dialogues.
    Multi-stakeholder processes, service delivery and state institutions : theoretical framework & methodologies : working paper
    Noor, M. ; Douma, N.W. ; Haar, G. van der; Hilhorst, D. ; Stel, N. - \ 2010
    Maastricht, Wageningen : Peace Security and Development Network - 69
    Public private cooperation fragile states: Report on field research mission to North Kivu and Ituri
    Douma, P. ; Bolhuis, E.E. ; Klaver, D.C. ; Zawadi, Y. - \ 2009
    Wageningen : Wageningen UR Centre for Development Innovation - 70 p.
    This field study is part of the Schokland project to research among others the possibilities for Public Private Cooperation (PPC) in stimulating Economic Growth in Fragile States. Fragile states are relatively far behind in achieving the Millennium Development Goals (MDGs) and in order to reduce fragility in the long run, it is essential to stimulate economic growth. PPC is defined in this project as a form of collaboration between the Netherlands Government, the Netherlands private sector and Dutch NGOs with local stakeholders with the aim to see what complementary roles these actors can play in socio-economic recovery processes in fragile and post conflict states. The overall research consists of a central research, an economic mission and a so-called decentral field research, to which category this study belongs. This field research concerns the Eastern DRC component, notably fieldwork in North Kivu and the Ituri district of the Province Oriental. The primary objective of this decentralised study was to identify options for (Dutch) private sector and public sector actors to engage in post conflict settings, what sectors are potentially interesting for foreign (Dutch) investment and how local state and non-state stakeholders could participate in future PPCs. Furthermore, the study aims to assess the potential contribution of public–private cooperation to fair and sustainable economic development and to conflict transformation.
    The impact of humanitarian assistance on livelihoods affected by humanitarian crisis in Uganda: An analysis of communities' and humanitarian actors' perspectives on socio-cultural dynamics in the Acholi and Nango entry points
    Frerks, G.E. ; Douma, P. ; Hollander, T. - \ 2009
    Utrecht : Centre for Conflict Studies, Makarere University and Gulu University - 52 p.
    The struggle after combat, the role of NGOs in DDR processes: synthesis study
    Klem, B. ; Douma, P. ; Frerks, G. ; Gompelman, G. ; Laar, S. van de - \ 2008
    The Hague : Cordaid - 44 p.
    Divortium 1967 : Sociologische faktoren van invloed op echtscheiding [Sociological factors influencing divorce 1967]
    Douma, W.H. ; Suy, L. - \ 2007
    Landbouwuniversiteit Wageningen
    sociology - family life - women - sexual behaviour - personality - marriage - sociology of the family
    Detailed background data on own husband, parents and ex-husband / religious attitude / experiences during courtship / premarital sexual relations / what happened after divorce ( house, children ) / relationships with both families / friends / problems in financial matters / different hobbies / children / drinking problems of self and husband / personality descriptions of former husband and self / reasons for divorce ( also for husband's wife ). Background variables: basic characteristics/ household characteristics/ occupation/employment/ education/ religion
    Family in the changing village, 1960-1972
    Douma, W.H. - \ 2007
    Landbouwuniversiteit Wageningen
    sociology - family life - housing - sociology of the family
    Contacts with inhabitants of second houses / opinion on different aspects of village / necessary facilities in village / preference of living near the town / use of car / opinion on future of village / attitude towards renovated old houses and their owners. Background variables: basic characteristics/ residence/ characteristics of parental family/household/ occupation/employment/ education/ religion/ consumption of durables/ readership, mass media, and 'cultural' exposure/ organizational membership
    Spatial patterns in savanna trees and grasses due to herbivory
    Douma, J.C. ; Langevelde, F. van; Groen, T.A. ; Vijver, C.A.D.M. van de; Prins, H.H.T. - \ 2007
    In: Spatial matters : how spatial patterns & processes affect savanna dynamics / Groen, T.A., Wageningen : Wageningen University - ISBN 9789085046905 - p. 57 - 71.
    Netwerk legt fundament voor systeem van snelle signalering dierziekten in varkenshouderij
    Douma, E. - \ 2007
    Local peace initiatives in Ituri, DRC
    Frerks, G.E. ; Douma, P. - \ 2007
    Wageningen : Wageningen University (Pax Christi Best practice study 3) - ISBN 9789076657080 - 60 p.
    The contribution of mosses to the carbon and water exchange of artic ecosystems: quantification and relationships with system properties
    Douma, J.C. ; Wijk, M.T. van; Lang, S.I. ; Shaver, G.R. - \ 2007
    Plant, Cell & Environment 30 (2007)10. - ISSN 0140-7791 - p. 1205 - 1215.
    simulated environmental-change - photosynthetic co2 flux - leaf-area index - reflectance properties - dioxide exchange - boreal forest - global change - tundra - alaska - vegetation
    Water vapour and CO2 exchange were measured in moss-dominated vegetation using a gas analyser and a 0.3 × 0.3 m chamber at 17 sites near Abisko, Northern Sweden and 21 sites near Longyearbyen, Svalbard, to quantify the contribution of mosses to ecosystem level fluxes. With the help of a simple light-response model, we showed that the moss contribution to ecosystem carbon uptake varied between 14 and 96%, with an average contribution of around 60%. This moss contribution could be related to the normalized difference vegetation index (NDVI) of the vegetation and the leaf area index (LAI) of the vascular plants. NDVI was a good predictor of gross primary production (GPP) of mosses and of the whole ecosystem, across different moss species, vegetation types and two different latitudes. NDVI was also correlated with thickness of the active green moss layer. Mosses played an important role in water exchange. They are expected to be most important to gas exchange during spring when leaves are not fully developed
    Netwerk Snelle Signalering Dierziekten
    Anonymous, ; Douma, E. - \ 2006
    'Are we making a difference?' Cordaid policy and practice in addressing complex political emergencies: the case of Sudan
    Douma, N. ; Hilhorst, D.J.M. - \ 2006
    In: Working on Peace-Building and Conflict Prevention: Experiences and dilemmas of Dutch NGOs / Schennink, B., van der Haar, G., Amsterdam : Dutch University Press - ISBN 9789036100519 - p. 47 - 84.
    Controlling light-use by Rhodobacter capsulatus continuous cultures in a flat-panel photobioreactor
    Hoekema, S. ; Douma, R.D. ; Janssen, M.G.J. ; Tramper, J. ; Wijffels, R.H. - \ 2006
    Biotechnology and Bioengineering 95 (2006)4. - ISSN 0006-3592 - p. 613 - 626.
    purple nonsulfur bacterium - a-stat technique - hydrogen-production - photosynthetic bacterium - rhodopseudomonas-palustris - growth - energy - photoproduction - optimization - cultivation
    The main bottleneck in scale-up of phototrophic fermentation is the low efficiency of light energy conversion to the desired product, which is caused by an excessive dissipation of light energy to heat. The photoheterotrophic formation of hydrogen from acetate and light energy by the microorganism Rhodobacter capsulatus NCIMB 11773 was chosen as a case study in this work. A light energy balance was set up, in which the total bacterial light energy absorption is split up and attributed to its destinations. These are biomass growth and maintenance, generation of hydrogen and photosynthetic heat dissipation. The constants defined in the light energy balance were determined experimentally using a flat-panel photobioreactor with a 3-cm optical path. An experimental method called D-stat was applied. Continuous cultures were kept in a so-called pseudo steady state, while the dilution rate was reduced slowly and smoothly. The biomass yield and maintenance coefficients of Rhodobacter capsulatus biomass on light energy were determined at 12.4 W/m(2) (400-950 nm) and amounted to 2.58 x 10(-8) +/- 0.04 x 10(-8) kg/J and 102 +/- 3.5 W/kg, respectively. The fraction of the absorbed light energy that was dissipated to heat at 473 W/m(2) depended on the biomass concentration in the reactor and varied between 0.80 and 0.88, as the biomass concentration was increased from 2.0 to 8.0 kg/m(3). The process conditions were estimated at which a 3.7% conversion efficiency of absorbed light energy to produced hydrogen energy should be attainable at 473 W/m(2)
    Lichenrijke stuifzanden in Noord-Limburg : verleden, heden en toekomst
    Ketner-Oostra, H.G.M. ; Douma, B.E. ; Ancker, H. van den; Jungerius, P.D. - \ 2005
    Natuurhistorisch Maandblad 94 (2005)6. - ISSN 0028-1107 - p. 109 - 116.
    geomorfologie - geologie - landschapsecologie - vegetatie - eolisch zand - korstmossen - plantengeografie - noord-limburg - geomorphology - geology - landscape ecology - vegetation - aeolian sands - lichens - phytogeography - noord-limburg
    Tijdens een vooronderzoek over mogelijk herstel van stuifzandvegetatie in de gemeente Bergen zijn vier natuurterreinen onderzocht waarvan de gegevens terug te vinden waren bij eerder onderzoek (Cleef en Kers, 1968). Een vergelijking is gemaakt met recent uitgevoerd onderzoek (Van den Acker, 2002). Het betreft een 90 ha groot verstuivingslandschap binnen Nationaal Park de Maasduinen
    Beyond conflict : Peacebuilding practices of Cordaid
    Douma, N. ; Hilhorst, D.J.M. - \ 2004
    The Hague : Cordaid - 69 p.
    Differential modulation of enterocyte-like Caco-2 cells after exposure to short-chain fatty acids
    Malago, J.J. ; Koninkx, J.F.J.G. ; Douma, P.M. ; Dirkzwager, A. ; Veldman, K.T. ; Hendriks, H.G.C.J.M. ; Dijk, J.E. van - \ 2003
    Food Additives and Contaminants 20 (2003)5. - ISSN 0265-203X - p. 427 - 437.
    phaseolus-vulgaris isolectins - small-intestinal-mucosa - sodium-butyrate - colon-cancer - ulcerative-colitis - dietary fiber - rat colon - colonocytes - inhibition - metabolism
    The response of intestinal epithelial cells to short-chain fatty acids, which are increasingly used as food additives, was investigated. Human small intestinal epithelial cell model Caco-2 cells were exposed to formate, propionate and butyrate to assess their effect on cellular growth, metabolism, differentiation and protection against bacteria. The Caco-2 cells were entirely grown in the different short-chain fatty acids and respective growth patterns were determined. Differentiated cells were exposed to 0-20 mM short-chain fatty acids for 48 h and changes in DNA, RNA, (glyco)protein syntheses, sucrase isomaltase activity, transepithelial electrical resistance and protection against Salmonella enteritidis were measured. The short-chain fatty acids, altered linearly and differentially the growth pattern ranging from stimulation by formate to inhibition by butyrate. Formate inhibited cellular metabolism. Low concentrations of up to 5 mM propionate and 2 mM butyrate stimulated metabolism, while higher doses were inhibitory. Formate had no effect on sucrase isomaltase enzyme activity and transepithelial electrical resistance, whereas propionate and butyrate increased these markers of differentiation. Infection with S. enteritidis did not benefit from the short-chain fatty acid-induced transepithelial electrical resistance. It is concluded that formate, propionate and butyrate selectively and differentially modulate growth characteristics, cellular metabolism, sucrase isomaltase activity and transepithelial electrical resistance in a concentration- and carbon atom-related fashion. The short-chain fatty acid-induced transepithelial electrical resistance does not confer protection against S. enteritidis.
    Voorraad in beweging : kansen voor intermodaal transport van verse producten?
    Douma, S.R. - \ 2000
    Wageningen : ATO LEI (Rapport / ATO B486) - 46
    transport - verse producten - transport - fresh products
    Weergave van natuurrampen in Nederlandse dagbladen
    Hilhorst, D. ; Belloni, H. ; Douma, N. ; Holla, J. ; Kuiper, G. - \ 2000
    Wageningen : Wageningen Disaster Studies (Disaster Sites 5) - 45
    natuurrampen - wereld - gevaren - journalistiek - tijdschriften - verslagen - nederland - natural disasters - world - hazards - journalism - journals - records - netherlands
    Corticosterone modifies muscarinic receptor immunoreactivity in rat hippocampus
    Douma, B.R. ; Jansen, K. ; Korte, S.M. ; Buwalda, B. ; Zee, E.A. van der; Luiten, P.G. - \ 1999
    Neuroscience Letters 268 (1999). - ISSN 0304-3940 - p. 41 - 44.
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