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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    Urinary Excretion of N1-Methylnicotinamide and N1-Methyl-2-Pyridone-5-Carboxamide and Mortality in Kidney Transplant Recipients
    Deen, Carolien P.J. ; Veen, Anna van der; Gomes-Neto, António W. ; Geleijnse, Johanna M. ; Borgonjen van den Berg, Karin J. ; Heiner-Fokkema, M.R. ; Kema, Ido P. ; Bakker, Stephan J.L. - \ 2020
    Nutrients 12 (2020)7. - ISSN 2072-6643
    dietary intake - mortality - N1-methyl-2-pyridone-5-carboxamide - N1-methylnicotinamide - niacin status - renal transplantation - tryptophan - urinary excretion - vitamin B3

    It is unclear whether niacin nutritional status is a target for improvement of long-term outcome after renal transplantation. The 24-h urinary excretion of N1-methylnicotinamide (N1-MN), as a biomarker of niacin status, has previously been shown to be negatively associated with premature mortality in kidney transplant recipients (KTR). However, recent evidence implies higher enzymatic conversion of N1-MN to N1-methyl-2-pyridone-5-carboxamide (2Py) in KTR, therefore the need exists for interpretation of both N1-MN and 2Py excretion for niacin status assessment. We assessed niacin status by means of the 24-h urinary excretion of the sum of N1-MN and 2Py (N1-MN + 2Py), and its associations with risk of premature mortality in KTR. N1-MN + 2Py excretion was measured in a longitudinal cohort of 660 KTR with LS-MS/MS. Prospective associations of N1-MN + 2Py excretion were investigated with Cox regression analyses. Median N1-MN + 2Py excretion was 198.3 (155.9-269.4) µmol/day. During follow-up of 5.4 (4.7-6.1) years, 143 KTR died, of whom 40 due to an infectious disease. N1-MN + 2Py excretion was negatively associated with risk of all-cause mortality (HR 0.61; 95% CI 0.47-0.79; p < 0.001), and infectious mortality specifically (HR 0.47; 95% CI 0.29-0.75; p = 0.002), independent of potential confounders. Secondary analyses showed effect modification of hs-CRP on the negative prospective association of N1-MN + 2Py excretion, and sensitivity analyses showed negative and independent associations of N1-MN and 2Py excretion with risk of all-cause mortality separately. These findings add further evidence to niacin status as a target for nutritional strategies for improvement of long-term outcome in KTR.

    Neither poor nor cool : Practising food self-provisioning in allotment gardens in the Netherlands and Czechia
    Sovová, Lucie ; Veen, Esther J. - \ 2020
    Sustainability 12 (2020)12. - ISSN 2071-1050
    Allotment gardens - Alternative food networks - Coping strategy - Food self-provisioning - Practice theory - Quiet sustainability - Urban food

    While urban gardening and food provisioning have become well-established subjects of academic inquiry, these practices are given different meanings depending on where they are performed. In this paper, we scrutinise different framings used in the literature on food self-provisioning in Eastern and Western Europe. In the Western context, food self-provisioning is often mentioned alongside other alternative food networks and implicitly framed as an activist practice. In comparison, food self-provisioning in Central and Eastern Europe has until recently been portrayed as a coping strategy motivated by economic needs and underdeveloped markets. Our research used two case studies of allotment gardening from bothWestern and Eastern Europe to investigate the legitimacy of the diverse framings these practices have received in the literature. Drawing on social practice theory, we examined the meanings of food self-provisioning for allotment gardeners in Czechia and the Netherlands, as well as the material manifestations of this practice. We conclude that, despite minor differences, allotment gardeners in both countries are essentially 'doing the same thing.' We thus argue that assuming differences based on different contexts is too simplistic, as are the binary categories of 'activist alternative' versus 'economic need.'

    Stadslandbouw en plantenziekten
    Veen, E.J. ; Jansma, J.E. ; Vermeulen, T. ; Vlasakker, Paulien van de - \ 2020
    In: Plantgezondheid / Govers, Francine, Pieterse, Corné, Termorshuizen, Aad, Smit, Astrid, Stichting Biowetenschappen en Maatschappij (BWM) (Cahiers bio-wetenschappen en maatschappij 2) - p. 88 - 89.
    Ecological impact and cost-effectiveness of wildlife crossings in a highly fragmented landscape : a multi-method approach
    Sijtsma, Frans J. ; Veen, Eelke van der; Hinsberg, Arjen van; Pouwels, Rogier ; Bekker, Renée ; Dijk, René E. van; Grutters, Mark ; Klaassen, Raymond ; Krijn, Margriet ; Mouissie, Maarten ; Wymenga, Eddy - \ 2020
    Landscape Ecology 35 (2020)7. - ISSN 0921-2973 - p. 1701 - 1720.
    Cost-effectiveness - Defragmentation of road infrastructure - Ecoducts (wildlife crossing bridges) - Mixed-method evaluation - The Netherlands - Wildlife crossings

    Context: Road infrastructure construction is integral to economic development, but negatively affects biodiversity. To mitigate the negative impacts of infrastructure, various types of wildlife crossings are realized worldwide, but little is known about their effectiveness, and cost-effectiveness. Objective: The paper contributes to the methodological and empirical discussion on the effectiveness of wildlife crossings for enhancing the quality of surrounding nature and its cost-effectiveness by analyzing a large-scale wildlife-crossings program in the Netherlands. Method: A multi-criteria cost–benefit analysis is applied, comprised of monetary and non-monetary measures, and a mixed-method approach is used to determine ecological effects. Ecological effects are expressed in the standardized weighted hectare measurement of threat-weighted ecological quality area (1 T-EQA = 1 ha of 100% ecological quality, averagely threatened). Cost-effectiveness is calculated comparing the monetary costs of intervention with ecological benefits (Euro costs/T-EQA), for different types of wildlife crossings and for two other nature policies. Results: The Dutch habitat defragmentation program has induced an increase in nature value of 1734 T-EQA at a cost of Euro 283 million. Ecological gains per hierarchically ordered groups of measures differ strongly: The most effective are ecoducts (wildlife crossing bridges) followed by shared-use viaducts and large fauna tunnels. Ecoducts generated the largest gain in nature value, but were also the most costly measures. In terms of cost-effectiveness, both large fauna tunnels and shared-use viaducts for traffic and animals outperformed ecoducts. Conclusions: Ecoducts deliver ecologically, but their cost-effectiveness appears modest. Purchasing agricultural land for restoration of nature appears more cost-effective than building wildlife crossings. Yet, reducing environmental pressures or their effects on existing nature areas is likely to be most cost-effective.

    A comparative analysis of human adult testicular cells expressing stem Leydig cell markers in the interstitium, vasculature, and peritubular layer
    Eliveld, Jitske ; Daalen, Saskia K.M. van; Winter-Korver, Cindy M. de; Veen, Fulco van der; Repping, Sjoerd ; Teerds, Katja ; Pelt, Ans M.M. van - \ 2020
    Andrology (2020). - ISSN 2047-2919
    human testis - markers - propagation - stem Leydig cells

    Background: Origin of human adult Leydig cells (ALCs) is not well understood. This might be partly due to limited data available on the identification and location of human precursor and stem Leydig cells (SLCs) which hampers the study on the development of ALCs. Objectives: The aim of the present study was to investigate whether described human (PDGFRα, NGFR) and rodent (NES, PDGFRα, THY1, NR2F2) SLC markers are expressed by a common cell population within human adult testicular interstitial cells in vivo and before and after in vitro propagation. Materials and methods: Immunohistochemical analyses were used to identify localization of human adult testicular interstitial cells expressing described SLC markers. Next, interstitial cells were isolated and cultured. The percentage of cells expressing one or more SLC markers was determined before and after culture using flow cytometry. Results: NR2F2 and PDGFRα were present in peritubular, perivascular, and Leydig cells, while THY1 was expressed in peritubular and perivascular cells. Although NES and NGFR were expressed in endothelial cells, co-localization with PDGFRα was found for both in vitro, although for NGFR only after culture. All marker positive cells were able to undergo propagation in vitro. Discussion: The partly overlap in localization and overlap in expression in human testicular cells indicate that PDGFRα, NR2F2, and THY1 are expressed within the same ALC developmental lineage from SLCs. Based on the in vitro results, this is also true for NES and after in vitro propagation for NGFR. Conclusion: Our results that earlier described SLC markers are expressed in overlapping human interstitial cell population opens up further research strategies aiming for a better insight in the Leydig cell lineage and will be helpful for development of strategies to cure ALC dysfunction.

    Evaluation of diurnal responses of Tetradesmus obliquus under nitrogen limitation
    León-Saiki, G.M. ; Carreres, Benoit M. ; Remmers, Ilse M. ; Wijffels, René H. ; Martins dos Santos, Vitor A.P. ; Veen, Douwe van der; Schaap, Peter J. ; Suarez-Diez, Maria ; Martens, Dirk E. - \ 2020
    Algal Research 49 (2020). - ISSN 2211-9264
    Day/night cycles - Diurnal transcription changes - Microalgae - Nitrogen limitation - Scenedesmus obliquus - Starchless mutant

    Tetradesmus obliquus is an oleaginous microalga with high potential for triacylglycerol production. We characterized the biochemical composition and the transcriptional landscape of T. obliquus wild-type and the starchless mutant (slm1), adapted to 16:8 h light dark (LD) cycles under nitrogen limitation. In comparison to the nitrogen replete conditions, the diurnal RNA samples from both strains also displayed a cyclic pattern, but with much less variation which could be related to a reduced transcription activity in at least the usually highly active processes. During nitrogen limitation, the wild-type continued to use starch as the preferred storage compound to store energy and carbon. Starch was accumulated to an average content of 0.25 g·gDW −1, which is higher than the maximum observed under nitrogen replete conditions. Small oscillations were observed, indicating that starch was being used as a diurnal energy storage compound, but to a lesser extent than under nitrogen replete conditions. For the slm1 mutant, TAG content was higher than for the wild-type (average steady state value was 0.26 g·gDW −1 for slm1 compared to 0.06 g·gDW −1 for the wild-type). Despite the higher TAG content in the slm1, the conversion efficiency of photons into biomass components for the slm1 was only half of the one obtained for the wild-type. This is related to the observed decrease in biomass productivity (from 1.29 gDW·L−1·day−1 for the wild-type to 0.52 gDW·L−1·day−1 for the slm1). While the transcriptome of slm1 displayed clear signs of energy generation by degrading TAG and amino-acids during the dark period, no significant variation of these metabolites could be measured. When looking through the diurnal cycle, the photosynthetic efficiency was lower for the slm1 mutant compared to the wild-type especially during the second half of the light period, where starch accumulation occurred in the wild-type.

    Vers van Dichtbij : Hightech binnenmoestuin verrijkt verzorgingshuis
    Veen, E.J. ; Vlasakker, Paulien van de - \ 2020
    Uitblinkers 2020 (2020)14. - p. 10 - 11.
    Prosumption in Almere
    Veen, Esther - \ 2020
    Understanding the unseen food growers and gatherers
    The Care Farming Sector in The Netherlands: A Reflection on Its Developments and Promising Innovations
    Hassink, Jan ; Agricola, Herman ; Veen, Esther J. ; Pijpker, Roald ; Bruin, Simone R. De; Meulen, Harold A.B. van der; Plug, Lana B. - \ 2020
    Sustainability 12 (2020)9. - ISSN 2071-1050
    This paper describes the development of care farming in the Netherlands, one of the pioneering countries in this sector, where care farming has developed into a very diverse sector, with some farmers focussing primarily on agricultural production and others more specifically on providing care services. Care farms are increasingly open to a diversity of participants. The sector has become professionalised with the establishment of strong regional organisations and a steady growth increase in revenues, providing employment opportunities and boosting the economy of rural areas. In this paper, we highlight two promising innovations in care farming: education for school dropouts and the establishment of social farming activities in cities. These innovations face the challenge of connecting not only the agricultural and care sectors, but also the educational sector and the urban context. Initiators face a number of challenges, like trying to embed their activities in the educational sector, a mismatch in regulations and a lack of legitimacy in the case of education on care farms, as well as problems gaining access to land and a lack of recognition in the case of social farming in urban areas. However, the prospects are promising in both cases, because they match the changing demands in Dutch society and are able to integrate social, ecological and economic benefits. View Full-Text
    Deel mbo-ers kiest bewust voor duurzaam voedsel
    Kok, Carlijn de; Veen, E.J. - \ 2020
    Profiel, vakblad voor het MBO (2020)3. - p. 27 - 29.
    Sample for the Dutch FADN 2017
    Roskam, J.L. ; Meer, R.W. van der; Veen, H.B. van der - \ 2020
    Wageningen : Wageningen Economic Research (Wageningen Economic Research report 2020-036) - ISBN 9789463953764 - 27
    The FADN (Farm Accountancy Data Network) is a European instrument for evaluating the income of agricultural holdings and the impacts of the Common Agricultural Policy. The farms included in the Dutch FADN are a sample of agricultural and horticultural companies from the Agricultural Census. This report explains the background of the sample and the developments concerning the population and sample of 2017. All phases - from the determination of the selection plan, the recruitment of farms to the quality control of the final sample - are described in this report.
    Vitamine T van Tuinieren!
    Hiskemuller, Alexander ; Veen, Esther - \ 2020

    Genoemd in een artikel over 'Vitamine T van Tuinieren' in damesblad Margriet

    Fish Macrophages Show Distinct Metabolic Signatures Upon Polarization
    Wentzel, Annelieke S. ; Janssen, Joëlle J.E. ; Boer, Vincent C.J. de; Veen, Wouter G. van; Forlenza, Maria ; Wiegertjes, Geert F. - \ 2020
    Frontiers in Immunology 11 (2020). - ISSN 1664-3224 - 1 p.
    extracellular flux analysis - glycolysis - M1 M2 macrophage polarization - metabolic reprogramming - oxidative metabolism - oxidative phosphorylation (OXPHOS) - Seahorse - teleost

    Macrophages play important roles in conditions ranging from host immune defense to tissue regeneration and polarize their functional phenotype accordingly. Next to differences in the use of L-arginine and the production of different cytokines, inflammatory M1 macrophages and anti-inflammatory M2 macrophages are also metabolically distinct. In mammals, M1 macrophages show metabolic reprogramming toward glycolysis, while M2 macrophages rely on oxidative phosphorylation to generate energy. The presence of polarized functional immune phenotypes conserved from mammals to fish led us to hypothesize that a similar metabolic reprogramming in polarized macrophages exists in carp. We studied mitochondrial function of M1 and M2 carp macrophages under basal and stressed conditions to determine oxidative capacity by real-time measurements of oxygen consumption and glycolytic capacity by measuring lactate-based acidification. In M1 macrophages, we found increased nitric oxide production and irg1 expression in addition to altered oxidative phosphorylation and glycolysis. In M2 macrophages, we found increased arginase activity, and both oxidative phosphorylation and glycolysis were similar to control macrophages. These results indicate that M1 and M2 carp macrophages show distinct metabolic signatures and indicate that metabolic reprogramming may occur in carp M1 macrophages. This immunometabolic reprogramming likely supports the inflammatory phenotype of polarized macrophages in teleost fish such as carp, similar to what has been shown in mammals.

    Effectiveness of a peracetic acid solution on Escherichia coli reduction during fresh-cut lettuce processing at the laboratory and industrial scales
    Banach, J.L. ; Bokhorst-van de Veen, H. van; Overbeek, L.S. van; Zouwen, P.S. van der; Zwietering, M.H. ; Fels-Klerx, H.J. van der - \ 2020
    International Journal of Food Microbiology 321 (2020). - ISSN 0168-1605
    Cross-contamination - Disinfection - Food industry - Vegetables - Water

    Fresh leafy greens like lettuce can be consumed raw and are susceptible to foodborne pathogens if they become contaminated. Recently, the number of reported pathogenic foodborne outbreaks related to leafy greens has increased. Therefore, it is important to try to alleviate the human health burden associated with these outbreaks. Processing of fresh-cut lettuce, including washing, is a step in the supply chain that needs to be well controlled to avoid cross-contamination. Current measures to control the quality of lettuce during washing include the use of chemicals like chlorine; however, questions regarding the safety of chlorine have prompted research for alternative solutions with peracetic acid (PAA). This study evaluates the effectiveness of a PAA (c.a. 75 mg/L) solution on the reduction of a commensal E. coli strain during the washing of fresh-cut lettuce. Experiments were performed at the laboratory scale and validated at the industrial scale. We observed that the use of PAA was not adversely affected by the organic load in the water. The contact time and dose of the PAA showed to be relevant factors, as observed by the approximately 5-log reduction of E. coli in the water. Results showed that once introduced during washing, E. coli remained attached to the lettuce, thus supporting the need to control for pathogenic bacteria earlier in the supply chain (e.g., during primary production) as well as during washing. Moreover, our results showed that the use of PAA during washing did not have an apparent effect on the levels of fluorescent pseudomonads (FP) and total heterotrophic bacteria (THB) in lettuce. Overall, our results at the laboratory and industrial scales confirmed that during the processing of fresh-cut produce, where the accumulation of soil, debris, and other plant exudates can negatively affect washing, the use of a PAA (c.a. 75 mg/L) solution was an effective and safe wash water disinfectant that can potentially be used at the industrial scale.

    Naar klimaatbestendige agrarische bedrijven op veen en moerige gronden in de Veenkoloniën
    Verstand, Daan ; Bulten, Ellen ; Vijn, Marcel - \ 2020
    Wageningen : Stichting Wageningen Research, Wageningen Plant Research (WPR), Business unit Open Teelten (Rapport / Stichting Wageningen Research, Wageningen Plant Research (WPR), Business unit Open Teelten WPR 825) - 34
    Landbouwkundig gebruik van veen en moerige gronden leidt tot de uitstoot van broeikasgassen doordat veen oxideert. Dat gebeurt als de veenpakketten boven de grondwaterstand liggen. Tezamen stoten veen en moerige gronden in Nederland rond de zes megaton CO2 equivalenten per jaar uit. Binnen het Klimaatakkoord hebben alle sectoren, ook de landbouw, een opgave toegekend gekregen om een emissiereductie te realiseren. Veen en moerige gronden hebben de opgave om vanaf 2030 één megaton CO2 equivalenten minder uit te stoten per jaar. Dit rapport focust zich op mogelijkheden om bij te dragen aan de emissiereductie doelstelling van veen en moerige gronden die akkerbouwmatig gebruikt worden. Hierbij wordt er gefocust op de Veenkoloniën, waar veenpakketten in variabele diktes voorkomen en akkerbouw het gangbare landgebruik is, met bijbehorende grote ontwateringsdiepte. Dat leidt op plekken waar veel veen voorkomt tot een flinke bodemdaling van 1 a 2 cm per jaar. Dat resulteert in toenemende hoogteverschillen binnen percelen; de zandkoppen dalen niet mee, en de veenputten dalen juist steeds meer. Dit veroorzaakt droogte schade aan gewassen in droge tijden op de hoge plekken, en natschade in de lage plekken tijdens natte periodes. Het waterschap staat voor de beslissing voor de inrichting van het toekomstig watersysteem. Blijft akkerbouwmatig landgebruik, met bijbehorende lage waterstanden mogelijk? Of kunnen er andere vormen van landbouw plaatsvinden, waardoor er geen grote investeringen in het watersysteem gedaan hoeven te worden. Dit onderzoek draagt bij aan deze discussie. Er is in literatuur onderzoek gedaan naar maatregelen die de CO2 emissies van veengronden kunnen reduceren. Maatregelen zoals het onderwerken van veen en infiltratiedrainage zouden het huidige akkerbouw systeem in stand kunnen houden en tegelijkertijd een reductie van emissies realiseren. Er zijn ook maatregelen gevonden waarbij de functie akkerbouw wordt gewijzigd naar grasland, natte teelten of natte natuurgebieden. Voor dikke veenpakketten in lage plekken van de Veenkoloniën zijn natte teelten en natte natuur een goede oplossing. Bij de dunnere veengronden en moerige gronden kan het onderwerken van veen tot onder de grondwaterspiegel een oplossing zijn. De maatregelen zijn gecombineerd in een zestal ontworpen boerderij-varianten, elk met een specifieke focus. Deze zes zijn; internetboerderij, circulaire boerderij, koolstofboerderij, recreatieboerderij, veenproductenboerderij en de water- en energieboerderij. Zo biedt de internetboerderij technische oplossingen om het huidige systeem beter en fijnmaziger in te richten met infiltratiedrainage, terwijl de veeproductenboerderij zich op natte teelten als cranberries en lisdodde richt. Alle varianten zijn door experts gescoord op een aantal milieukundige en sociaal economische factoren, met een diffuus beeld als resultaat; de ene variant scoort erg goed op een reductie van emissies (de koolstofboerderij), terwijl de andere bijdraagt aan de verdiensten van de landbouw (internet boerderij). Helder is dat het gebied om maatwerk vraagt en er niet één maatregel of boerderij variant is die in het hele focus gebied toegepast kan worden. Dat komt mede door de variatie aan veendikte in ruimtelijke zin en omdat de boerderijvarianten nichemarkten aan zullen moeten boren. In het vervolgonderzoek wordt hier samen met belanghebbende verder naar gekeken.
    Positioning Strategies for Animal-Friendly Products: A Social Dilemma Approach
    Riemsdijk, Lenka van; Ingenbleek, Paul T.M. ; Veen, Gerrita van der; Trijp, Hans C.M. van - \ 2020
    Journal of Consumer Affairs 54 (2020)1. - ISSN 0022-0078 - p. 100 - 129.

    Many consumers express concerns about the welfare of animals in agriculture, but often refrain from purchasing animal-friendly alternatives that address their concerns. To support consumers in making choices in line with their values and attitudes, this study approaches consumer animal-friendly product choice as a dilemma between maximizing the buyer's self-interest and maximizing societal interest. To address this social dilemma, we developed and tested positioning strategies that reinforce the animal welfare label with complementary consumption values (functional, emotional, social, and epistemic). The results from a choice experiment with Dutch chicken meat shoppers showed that two strategies—emotional and epistemic—effectively increase consumer value perceptions. These insights imply that animal-friendly products positioned to invoke emotion or curiosity drive consumers towards animal-friendly product choices, and that these strategies are most effective for consumers who base their choice solely on maximizing either self-interest or societal interest.

    Rhizosphere and litter feedbacks to range-expanding plant species and related natives
    Manrubia, Marta ; Putten, Wim H. van der; Weser, Carolin ; Veen, Ciska G.F. - \ 2020
    Journal of Ecology 108 (2020)1. - ISSN 0022-0477 - p. 353 - 365.
    litter feedback - novel communities - plant range expansion - plant–soil feedback - rhizosphere feedback

    Plant–soil feedback (PSF) results from the net legacy effect that plants leave in the composition of soil communities and abiotic soil properties. PSF is induced by the rhizosphere and by litter inputs into the soil, however, we have little understanding of their individual contributions. Here, we examine feedback effects from the rhizosphere of living plants, decomposing litter and their combination. We used four pairs of climate warming-induced range-expanding plant species and congeneric natives, and examined PSF effects on plant biomass production, as well as on decomposition in their new range. We tested the hypothesis that the plant rhizosphere provides less negative feedback to range-expanders than to the congeneric natives, and that feedback mediated by litter decomposition does not provide such a difference because decomposers might be less specialized than pathogens. To determine PSF, we used soil from the congener species within each pair as an ‘away’ soil to indicate whether range-expanders may have lost their specialized soil biota upon arrival in the novel range. Our results show that although range-expanding plant species and their congeneric natives developed neutral PSF in both rhizosphere- and litter-conditioned soils, two of the four range-expanders produced more biomass than natives in soils conditioned by litter, that is, soils with high nutrient content. Shoot litter from two out of four range-expanding species decomposed more than that of natives, but decomposition was unaffected by soil conditioning. Synthesis. We compared PSF effects of range-expanders and congeneric natives mediated via both the rhizosphere and litter using the congeneric species as a control. Under those conditions, PSF effects were neutral and not affected by plant origin. Therefore, we conclude that studies not comparing within plant genera may overestimate the impact of plant origin on PSF. Still, even under those conditions range-expanders appeared to benefit more from high soil nutrient availability than natives, thus providing a possible advantage over congeneric natives.

    Nonlinear responses of soil nematode community composition to increasing aridity
    Xiong, Dan ; Wei, Cun Zheng ; Wubs, Jasper E.R. ; Veen, G.J. ; Liang, Wenju ; Wang, Xiaobo ; Li, Qi ; Putten, Wim H. Van der; Han, Xingguo - \ 2020
    Global Ecology and Biogeography 29 (2020)1. - ISSN 1466-822X - p. 117 - 126.
    aridity - biodiversity - global climate change - grassland transect - nonlinear response - soil nematode community

    Aim: Increasing aridity under global change is predicted to have a profound impact on the structure and functioning of terrestrial ecosystems, yet we have a poor understanding of how belowground communities respond. In order to understand the longer term responses of different trophic levels in the soil food web to increasing aridity, we investigated the abundance, richness and community similarity of the soil nematode community along a 3,200 km aridity gradient. Location: A transect across semi-arid and arid grasslands in Northern China, where the aridity ranges from.43 to.97. Time period: July and August 2012. Major taxa studied: Soil-borne Nematoda. Methods: We used generalized additive (mixed) models to analyse the abundance, richness and community similarity patterns of soil nematodes. We used structural equation modelling (SEM) to disentangle the direct and indirect environmental drivers (aridity, soil and plant variables) of the nematode community. Results: The abundance, richness and similarity of nematode communities declined nonlinearly with increasing aridity. The most pronounced decline in nematode richness and community similarity occurred in arid conditions (aridity >.80). However, the shape of the response to aridity differed among nematode feeding groups. In arid conditions, the abundance and richness of bacterial feeders were less sensitive to changes in aridity than for fungal feeders. The SEM analysis revealed that nematode community responses to aridity were not mediated via changes in plant and soil variables, but instead were affected directly by aridity. Main conclusions: Our results showed that in mesic grasslands, increasing aridity primarily caused a decline in nematode abundance, whereas increasing aridity in xeric grasslands led to a loss of nematode diversity. The nonlinear responses of nematodes to aridity could also result in nonlinear shifts in ecosystem functioning, because soil nematodes operate at various trophic levels in the soil food web, thereby influencing the performance of plants, soil biodiversity and biogeochemical cycling.

    Sharing a meal: a diversity of performances engendered by a social innovation
    Dagevos, Marianne ; Veen, E.J. - \ 2020
    Journal of Urbanism 13 (2020)1. - ISSN 1754-9175 - p. 97 - 113.
    This paper explores the dynamics between social innovations and socio-spatial transformations using practice theory as linking pin. Social innovations, such as the case study of a meal sharing platform here presented, are considered as proposals. Using social practice theory as a theoretical lens enables us to explain how the principles of the proposal’s design are moderated and appropriated by its users. Consequently, familiar routinized practices expand, becoming more complex and hybrid. It is in the performance of the practice that this complexity is revealed. Specific focus is on the socio-spatial transfor-mations that social innovations propose. This paper shows how tactics of appropriation can result in trespassing the boundaries between private and public, and between domestic and communitarian space. This way, we connect social innovations to DIY-urbanism, show-ing how citizens appropriate urban space.
    Malaria mosquitoes use leg push-off forces to control body pitch during take-off
    Veen, Wouter G. van; Leeuwen, Johan L. van; Muijres, Florian T. - \ 2020
    Journal of Experimental Zoology Part A: Ecological and Integrative Physiology 333 (2020)1. - ISSN 2471-5638 - p. 38 - 49.
    aerodynamics - Anopheles coluzzii - computational fluid dynamics

    Escaping from a blood host with freshly acquired nutrition for her eggs is one of the most critical actions in the life of a female malaria mosquito. During this take-off, she has to carry a large payload, up to three times her body weight, while avoiding tactile detection by the host. What separates the malaria mosquito from most other insects is that the mosquito pushes off gently with its legs while producing aerodynamic forces with its wings. Apart from generating the required forces, the malaria mosquito has to produce the correct torques to pitch-up during take-off. Furthermore, the fed mosquito has to alter the direction of its aerodynamic force vector to compensate for the higher body pitch angle due to its heavier abdomen. Whether the mosquito generates these torques and redirection of the forces with its wings or legs remains unknown. By combining rigid-body inverse dynamics analyses with computational fluid dynamics simulations, we show that mosquitoes use leg push-off to control pitch torques and that the adaption of the aerodynamic force direction is synchronized with modulations in force magnitude. These results suggest that during the push-off phase of a take-off, mosquitoes use their flight apparatus primarily as a motor system and they use leg push-off forces for control.

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