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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    Modelling food security : Bridging the gap between the micro and the macro scale
    Müller, Birgit ; Hoffmann, Falk ; Heckelei, Thomas ; Müller, Christoph ; Hertel, Thomas W. ; Polhill, J.G. ; Wijk, Mark van; Achterbosch, Thom ; Alexander, Peter ; Brown, Calum ; Kreuer, David ; Ewert, Frank ; Ge, Jiaqi ; Millington, James D.A. ; Seppelt, Ralf ; Verburg, Peter H. ; Webber, Heidi - \ 2020
    Global environmental change : human and policy dimensions 63 (2020). - ISSN 0959-3780
    Agent-based models - Crop models - Economic equilibrium models - Food security - Land use - Model integration - Multi-scale interactions - Social-ecological feedbacks

    Achieving food and nutrition security for all in a changing and globalized world remains a critical challenge of utmost importance. The development of solutions benefits from insights derived from modelling and simulating the complex interactions of the agri-food system, which range from global to household scales and transcend disciplinary boundaries. A wide range of models based on various methodologies (from food trade equilibrium to agent-based) seek to integrate direct and indirect drivers of change in land use, environment and socio-economic conditions at different scales. However, modelling such interaction poses fundamental challenges, especially for representing non-linear dynamics and adaptive behaviours. We identify key pieces of the fragmented landscape of food security modelling, and organize achievements and gaps into different contextual domains of food security (production, trade, and consumption) at different spatial scales. Building on in-depth reflection on three core issues of food security – volatility, technology, and transformation – we identify methodological challenges and promising strategies for advancement. We emphasize particular requirements related to the multifaceted and multiscale nature of food security. They include the explicit representation of transient dynamics to allow for path dependency and irreversible consequences, and of household heterogeneity to incorporate inequality issues. To illustrate ways forward we provide good practice examples using meta-modelling techniques, non-equilibrium approaches and behavioural-based modelling endeavours. We argue that further integration of different model types is required to better account for both multi-level agency and cross-scale feedbacks within the food system.

    Research challenges for cultural ecosystem services and public health in (peri-)urban environments
    Chen, Xianwen ; Vries, Sjerp de; Assmuth, Timo ; Dick, Jan ; Hermans, Tia ; Hertel, Ole ; Jensen, Anne ; Jones, Laurence ; Kabisch, Sigrun ; Lanki, Timo ; Lehmann, Irina ; Maskell, Lindsay ; Norton, Lisa ; Reis, Stefan - \ 2019
    Science of the Total Environment 651 (2019). - ISSN 0048-9697 - p. 2118 - 2129.
    Cultural ecosystem services - Nature-based solutions - Public health - Urban green/blue infrastructure

    Urbanization is a global trend, and consequently the quality of urban environments is increasingly important for human health and wellbeing. Urban life-style is typically associated with low physical activity and sometimes with high mental stress, both contributing to an increasing burden of diseases. Nature-based solutions that make effective use of ecosystem services, particularly of cultural ecosystem services (CES), can provide vital building blocks to address these challenges. This paper argues that, the salutogenic, i.e. health-promoting effects of CES have so far not been adequately recognised and deserve more explicit attention in order to enhance decision making around health and wellbeing in urban areas. However, a number of research challenges will need to be addressed to reveal the mechanisms, which underpin delivery of urban CES. These include: causal chains of supply and demand, equity, and equality of public health benefits promoted. Methodological challenges in quantifying these are discussed. The paper is highly relevant for policy makers within and beyond Europe, and also serves as a review for current researchers and as a roadmap to future short- and long-term research opportunities.

    Embolism resistance drives the distribution of Amazonian rainforest tree species along hydro-topographic gradients
    Oliveira, Rafael S. ; Costa, Flavia R.C. ; Baalen, Emma van; Jonge, Arjen de; Bittencourt, Paulo R. ; Almanza, Yanina ; V. Barros, Fernanda de; Cordoba, Edher C. ; Fagundes, Marina V. ; Garcia, Sabrina ; Guimaraes, Zilza T.T.M. ; Hertel, Mariana ; Schietti, Juliana ; Rodrigues-Souza, Jefferson ; Poorter, Lourens - \ 2019
    New Phytologist 221 (2019)3. - ISSN 0028-646X - p. 1457 - 1465.
    drought vulnerability - forest resilience - functional ecology - hydrological niches - P - phosphorus - tropical forests - water table

    Species distribution is strongly driven by local and global gradients in water availability but the underlying mechanisms are not clear. Vulnerability to xylem embolism (P50) is a key trait that indicates how species cope with drought and might explain plant distribution patterns across environmental gradients. Here we address its role on species sorting along a hydro-topographical gradient in a central Amazonian rainforest and examine its variance at the community scale. We measured P50 for 28 tree species, soil properties and estimated the hydrological niche of each species using an indicator of distance to the water table (HAND). We found a large hydraulic diversity, covering as much as 44% of the global angiosperm variation in P50. We show that P50: contributes to species segregation across a hydro-topographic gradient in the Amazon, and thus to species coexistence; is the result of repeated evolutionary adaptation within closely related taxa; is associated with species tolerance to P-poor soils, suggesting the evolution of a stress-tolerance syndrome to nutrients and drought; and is higher for trees in the valleys than uplands. The large observed hydraulic diversity and its association with topography has important implications for modelling and predicting forest and species resilience to climate change.

    The power and pain of market-based carbon policies : a global application to greenhouse gases from ruminant livestock production
    Henderson, B. ; Golub, A. ; Pambudi, D. ; Hertel, T. ; Godde, C. ; Herrero, M. ; Cacho, O. ; Gerber, P. - \ 2018
    Mitigation and Adaptation Strategies for Global Change 23 (2018)3. - ISSN 1381-2386 - p. 349 - 369.
    Carbon policy - Greenhouse gases - Mitigation - Ruminants
    The objectives of this research are to assess the greenhouse gas mitigation potential of carbon policies applied to the ruminant livestock sector [inclusive of the major ruminant species—cattle (Bos Taurus and Bos indicus), sheep (Ovis aries), and goats (Capra hircus)]—with particular emphasis on understanding the adjustment challenges posed by such policies. We show that market-based mitigation policies can greatly amplify the mitigation potential identified in marginal abatement cost studies by harnessing powerful market forces such as product substitution and trade. We estimate that a carbon tax of US$20 per metric ton of carbon dioxide (CO2) equivalent emissions could mitigate 626 metric megatons of CO2 equivalent ruminant emissions per year (MtCO2-eq year−1). This policy would also incentivize a restructuring of cattle production, increasing the share of cattle meat coming from the multiproduct dairy sector compared to more emission intensive, single purpose beef sector. The mitigation potential from this simple policy represents an upper bound because it causes ruminant-based food production to fall and is therefore likely to be politically unpopular. In the spirit of the Paris Agreement (UNFCCC 2015), which expresses the ambition of reducing agricultural emissions while protecting food production, we assess a carbon policy that applies both a carbon tax and a subsidy to producers to manage the tradeoff between food production and mitigation. The policy maintains ruminant production and consumption levels in all regions, but for a much lower global emission reduction of 185 MtCO2-eq year−1. This research provides policymakers with a quantitative basis for designing policies that attempt to trade off mitigation effectiveness with producer and consumer welfare.
    Sustainable Nitrogen Management in Denmark
    Dalgaard, Tommy ; Brock, S. ; Graversgaard, Morten ; Hansen, Brigitte ; Hashemi, F. ; Häsler, B. ; Hertel, O. ; Hutchings, N.J. ; Jacobsen, B.H. ; Stoumann Jensen, L. ; Kjeldsen, Chris ; Olesen, J.E. ; Schjorring, J.K. ; Sigsgaard, T. ; Stubkjaer Andersen, P. ; Termansen, Mette ; Vejre, H. ; Vestergaard Odgaard, M. ; Vries, W. de; Wiborg, I.A. - \ 2017
    In: Innovative solutions for sustainable management of nitrogen. - Aarhus University and the dNmark.org Research Alliance - ISBN 9788793398825 - p. 13 - 16.
    Innovative solutions for sustainable management of nitrogen : Conference proceedings
    Dalgaard, Tommy ; Olesen, J.E. ; Schjorring, J.K. ; Jensen, J.S. ; Vejre, H. ; Andersen, P.S. ; Gundersen, P. ; Jacobsen, B.H. ; Jensen, J. ; Häsler, B. ; Termansen, Mette ; Hertel, O. ; Brock, S. ; Kronvang, B. ; Svenning, Jens Christian ; Sigsgaard, T. ; Hansen, B. ; Thorling, L. ; Højberg, A.L. ; Wiborg, I.A. ; Piil, K. ; Kjeldsen, Chris ; Graversgaard, Morten ; Hutchings, N. ; Vries, W. de; Christensen, J. ; Mukendi, T. - \ 2017
    - 142 p.
    The need for improved maps of global cropland
    Fritz, S. ; See, L. ; Justice, C. ; Becker-Reshef, I. ; Bydekerke, L. ; Cumani, R. ; Defourny, P. ; Erb, K. ; Foley, J. ; Gilliams, S. ; Gong, P. ; Hansen, M. ; Hertel, T. ; Herold, M. ; Herrero, M. ; Kayitakire, F. ; Latham, J. ; Leo, O. ; MCCallum, I. ; Obersteiner, M. ; Ramankutty, N. ; Rocha, J. ; Tang, H. ; Thornton, P. ; Vancutsem, C. ; Velde, M. van der; Wood, S. ; Woodcock, C. - \ 2013
    EOS: Transactions, American Geophysical Union 94 (2013)3. - ISSN 0096-3941 - p. 31 - 32.
    Food security is a key global concern. By 2050, the global population will exceed 9 billion, and a 50% increase in annual agricultural output will be required to keep up with demand. There are significant additional pressures on existing agricultural land through increased competition from the biofuel sector and the need to elevate feed production, which is being driven by higher levels of meat consumption in low- and middle-income countries
    The impact of environmental and climate constraints on global food supply
    Eickhout, B. ; Meijl, H. van; Tabeau, A.A. ; Stehfest, E. - \ 2009
    In: Economic Analysis of Land Use in Global Climate Change Policy / Hertel, T., Rose, S., Tol, R., USA : Routledge - ISBN 9780415773089
    A New Representation of Agricultural Production Technology in GTAP
    Huang, Jikun ; Tongeren, F.W. van; Dewbre, J. ; Meijl, H. van - \ 2004
    Objectives This paper seeks to improve the treatment of the agriculture sector in GTAP. It will incorporate into GTAP an agricultural production technology consistent to the maximum degree practicable with that currently employed in the Organization for Economic Co-operation and Development¿s (OECD) Policy Evaluation Matrix (PEM) model. Policy reform simulations in a sector as complex as agriculture often require a variety of different models. Consistency between the different approaches is important. The assumptions about economic behavior should be transparent and similar in spirit across the different models. The focus of this paper will be on the way OECD agricultural policies are represented in GTAP. This is important to preserve consistency relative to existing PEM analysis, in particular with respect to the issue of decoupling. Approach The most important concern is the modeling of land allocation and the influence of policy on those decisions. The base version of GTAP represents land allocation in a nested constant elasticity of transformation (CET) structure similar to, but not as detailed as in PEM. PEM distinguishes different types of land and ¿this allows for detailed representation of land-based policies. In this paper, GTAP is modified to include a three level CET land use structure. The differentiation between different land types according to the crop being farmed and demand for pasture land also implies a supply response that may not always be in line with the supply response generated by a standard GTAP model. The newly developed land allocation system is calibrated to land supply elasticities from the same literature survey (OECD 2001) used to calibrate the PEM model. In the standard GTAP model there is no specificity for agricultural capital or labor. This assumption is defensible for analyses where the assumed adjustment horizon is sufficiently long term. However, for the short/medium term adjustment horizon usually adopted for OECD simulations, it is necessary to modify GTAP in order to recognize that these factors are to some degree sector specific and adjustments are therefore ¿sluggish¿. A common assumption in CGE models, including GTAP, is that intermediate inputs are combined with primary factors in fixed proportions. In PEM, all purchased inputs are assumed substitutable and used in variable proportions with primary factors depending on relative prices. Hertel and Keeney (2003) have modified GTAP to represent this kind of factor substitution, incorporating PEM substitution elasticities in the model. This approach will be adopted for this paper. Preliminary Findings This study should result in a more realistic modeling of the agricultural sector in GTAP. In particular, this study should find that, based on the literature survey, agricultural supply response is more inelastic for specific land using activities than in the standard GTAP model. For example, land used in rice is much less substitutable than land used in wheat production. For an equivalent policy shock, supply response between crops will be more inelastic, and changes in crop prices will be more pronounced. In summary, aggregate supply response for land using sectors (principally agriculture) will be more inelastic (more sector specificity for land use), and rental rate differences will be more pronounced (with implications for welfare distribution).
    Induction and characterization of micronuclei in plant cells : perspectives for micronucleus-mediated chromosome transfer = Inductie en karakterisering van microkernen in plantecellen : perspectieven voor chromosoom overdracht via microkernen
    Verhoeven, H.A. - \ 1989
    Agricultural University. Promotor(en): A. van Kammen; B. de Groot. - S.l. : Verhoeven - 117
    cytologie - plantenfysiologie - genetische modificatie - recombinant dna - celfysiologie - cytology - plant physiology - genetic engineering - recombinant dna - cell physiology

    In this thesis, micronucleation in plant cells has been investigated and systems for isolation and transfer of organelles have been established.
    The discovery, described in chapter two, that the phosphoric amide herbicide amiprophos-methyl induced micronuclei at a high frequency in cell suspensions of N.plumbaginifolia, has opened the possibility to develop a microcell-mediated chromosome transfer system analogous to that in mammalian cell lines. In mammalian cells, micronuclei are induced by prolonged exposure of cells to spindle toxins (colchicine, Colcemid), resulting in up to 60% micronucleated cells (Matsui et al., 1982). Micronucleated cells are isolated by the "shake-off' method, and subjected to high speed centrifugation, which results in fractionation of the cells into microcells, containing micronulei with one or a few chromosomes. Subsequently, microcells are fused to the recipient cells. The transferred chromosomes were found to remain intact and mitotically stable (Fournier, 1982). This technique has hitherto not been available for plant cells or protoplasts, due to the lack of efficient procedures to induce micronuclei. Gamma-irradiation is now often used in the construction of monochromosomal addition lines by somatic hybridization (Bates et al., 1987), to induce chromosome damage which promotes chromosome elimination from one of the fusion partners. As has been pointed out in the introduction (chapter one), ionizing radiation induces chromosome rearrage ments, deletions and insertions (Menczel et al., 1982). From research on mammalian cells, it is known that these phenomena occur with a lower frequency after microcell-mediated chromosome transfer (Fournier, 1981). If microprotoplasts would become available for plant genetic manipulation, transfer of a limited number of chromosomes by microprotoplast fusion would offer an alternative to the use of gamma-irradiation. With the finding that APM induces micronuclei at high frequency in plants, transfer of low numbers of chromosomes after micronucleation can now be tested for use in plant genetic manipulation. The APM treatment was found to be reversible, as was demonstrated by washing the cell suspension cultures free from APM. After washing, normal growth and cell division were soon resumed, with some abnormal, multipolar spindles in the first division after washing. This observation is in good agreement with the the reversible inhibition of microtubule polymerization by APM (Falconer and Seagull, 1987). This low cytotoxicity makes APM a useful tool in the induction of micronuclei in plants.

    The flow cytometric analysis of the nuclear DNA content of APM-treated cel suspension cultures of N.plumbaginifolia, revealed the presence of many micronuclei with a DNA content equivalent to one metaphase chromosome (which consists of both sister chromatids). Similar observations have been made in micronucleated rat kangaroo cells after treatment with Colcemid (Sekiguchi et al., 1978). Sorting of the micronuclei on the basis of the fluorescence of ethidium-bromide, followed by analysis of the DNA content by Feulgen staining (chapter three), shows that it is possible to separate micronuclei on the basis of their DNA content by flowcytometry, like it has been shown for isolated plant metaphase chromosomes. Chromosome identification is sometimes possible with isolated metaphase chromosomes (de Laat and Blaas, 1984; Conia et al., 1987a; 1987b). Identification of chromosomes present in a particular micronucleus is not possible. This is due to different degrees of chromosome decondensation in the micronuclei (which influences the fluorescence signal of the fluorochrome -DNA complex by quenching), and due to the various combinations of chromosomes in micronuclei containing more than one metaphase chromosome. This is illustrated by the DNA histograms of isolated micronuclei in chapter two, which lack the specific chromosome peaks, present in metaphase chromosome preparations (chapter four). When micronuclei are present in large numbers, the overall DNA histogram will show no appreciable contribution of a particular type of chromosome combination in micronuclei, since chromosome grouping appears to be a random process, as was shown by the analysis of the number of micronuclei per cell in chapter two, and by cytological data in chapter two and three. Furthermore, the reduction of the number of micronuclei per micronucleated cell, which appears to be the consequence of fusion of micronuclei into a lobed restitution nucleus, gives rise to even more combinations of chromosomes.

    The processes, involved in the formation of micronuclei, are studied in chapter three and four. The effects of the anti-microtubular herbicides APM, oryzalin and the alkaloid colchicine, used for metaphase arrest and induction of micronuclei in mammalian cells, on the mitotic index and micronueleus formation are compared. The disruption of the spindle by direct inhibition of microtubule assemble is responsible for the accumulation of cells at metaphase. The concentrations of the inhibitors required for complete metaphase arrest, vary from 3 μM for APM and oryzalin to 500 μM for colchicine, as a consequence of differences in binding specificity (Hertel et al., 1980; Dustin 1984). The differences in the percentage of ball metaphases indicate specific effects of the above mentioned inhibitors on chromosome scattering. Apart from the disruption of the microtubules, APM and oryzalin have been shown to influence the accumulation of calcium in the mitochondria (Hertel et al., 1981). Moreover, oryzalin disturbs the active excretion of calcium by the plasma membrane. These combined effects result in an increased cytoplasmic calcium concentration (Hertel et al., 1980), which will be higher after oryzalin treatment than after APM treatment, due to the reduction of active calcium excretion by oryzalin. Our 'data suggest that the APM or oryzalin induced increase of the cytoplasmic calcium concentration is involved in both formation and fusion of micronuclei. Colchicine, which does not influence the cytoplasmic calcium concentration, is not effective in the induction of micronuclei. The higher cytoplasmic calcium levels after oryzalin treatment, would increase the fusogenic properties of the nuclear membranes, which would explain why micronuclei exist for a shorter time after oryzalin treatment as compared to APM treatment. This hypothesis will be tested in future experiments by treatments with the calcium ionophore A23187 in combination with the calcium-specific chelator ethyleneglycolbis- (2-aminoethylether)-N,N'-tetra acetic acid (EGTA), with simultaneous measurements of the cytoplasmic calcium concentrations with the new calcium specific fluorochromes Fluo-3 and Rhod-2 (Haugland, 1989).

    In order to obtain both large numbers of micronucleated cells, and large numbers of micronuclei per micronucleated cell, the
    effect of DNA synthesis inhibitors was investigated. The results in chapter five show, that a considerable increase in the number of micronucleated cells can be achieved by HU or APH treatments, and that the time at which micronuclei appear can be controlled. The results further indicate that metaphases have to be exposed to APM for at least 12h, before micronucleation occurs, and that their lifetime is in the same order. These data demonstrate that it is possible to manipulate the conditions of the treatments in order to obtain either a high yield of metaphase chromosomes, or a high yield of micronuclei, with little contamination by micronuclei or chromosomes, respectively. In this way, it becomes possible to determine the moment at which the number of micronuclei per cell is at its maximal value.

    The isolation and characterization of microprotoplasts from micronucleated suspension cells is described in chapter six. Data obtained from DNA content measurements and flow cytometry demonstrate the presence of up to 40% of subprotoplasts with a DNA content less than the G1-level of the APM treated suspension cells. This indicates that genome fractionation has occurred, and the data on the FDA-staining show that most of the subprotoplasts still possess an intact plasma membrane, since FDA can not be retained by vacuolar membranes only (Lesney, 1986). The viability of the microprotoplasts and other types of subprotoplasts is indicated by the successful culture after gradient fractionation. As it is impossible to measure the DNA-content of microprotoplasts in a non-destructive way, no preselection could be performed to use only microprotoplasts for fusion. In a mass fusion system, the smallest microcells will be the least likely to fuse when electrofusion is used, because their small diameter will prevent alignment and membrane breakdown, which are both related to particle diameter (Zimmermann et al., 1982). Individual selection and fusion could overcome this problem (Koop et al., 1983). This control is essential for the efficient application of microprotoplasts, since the DNA content per microprotoplast will depend upon the DNA content per micronucleus in the cell suspension. Microprotoplast fusion will result in transfer of a part of the total number of chromosomes, directly followed by spontaneous chromosome elimination when two distantly related species are fused, since chromosome elimination seems to be directed by genome dose effects (Graves, 1984; Gilissen et al., 1989). Sofar no successful fusion experiments have been performed, which makes it impossible at the moment to comment on the usefulness of microprotoplasts in chromosome transfer. However, fusion experiments with karyoplasts indicate that it is possible to perform fusions in a controlled way (Spangenberg et al., 1987).

    In addition to the microprotoplast fusion, microinjection was developed for transfer of organelles and micronuclei. Glass needles with a large orifice (5pM) were prepared, along with a pressure system, based on the application of mercury. With the injection system, described in chapter seven, it is possible to suck donor material from a donor protoplast, and inject this directly into the recipient. The data on the complementation of the albino tobacco by injection of mature green chloroplasts or etiolated plastids, indicate that protoplasts can survive the injection treatment, and that the injected plastids can be replicated by the recipient. In this way, the organelles to be transferred are not subjected to damaging isolation procedures and they can be preselected visually. Selective transfer of organelles offers a number of advantages when compared to fusion techniques, or transfer of isolated genes. One of the advantages is the protective nature of the membranes associated with chloroplasts, mitochondria and nuclei. Although structural integrity and functionality has been demonstrated for isolated chloroplasts and mitochondria, it is not known whether isolated organelles are still physiologically intact. The isolation of intact nuclei from plant cells has also been described, with data indicating their structural integrity, as well as their ability to transfer genes into recipient protoplasts (Saxena et al., 1986). Transfer of marker genes does not necessarily implicate the functional integrity of isolated nuclei, since transfer of marker genes can be achieved by uptake of isolated genomic DNA. Preliminary results obtained from experiments with microinjection of micronuclei, indicate that it is possible to remove micronuclei from the donor by suction. Sofar, transfer into a recipient has not been achieved. The kanamycine- resistance, which was introduced into N.plumbaginifolia by transformation with Agrobacterium tumefaciens , will be used as selectable marker after transfer of micronuclei. The transfer of chromosomes will be tested with species specific repetitive DNA probes, which are able to discriminate between the donor genome N.plumbaginifolia and the recipient (either Lycopersicon esculentum or Solanum tuberosum ) . Several probes with the required specificity have already been characterized, from a series of highly repetitive sequences, isolated from N.plumbaginifolia (data not shown).

    With the methods, described in this thesis, the transfer of chromosomes via micronuclei has come within reach. Future work will focus on achieving transfer, and study the fate of the introduced micronuclei. This should provide an answer whether micronuclei can be used as chromosome carriers in plants, as has already been shown in mammalian somatic cell genetics.

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