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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    Natural Environments and Leisure among Rural–to–Urban Immigrants: An Application of Bourdieu's Concepts of Habitus, Social and Cultural Capital, and Field
    Horolets, Anna ; Stodolska, Monika ; Peters, Karin - \ 2018
    Leisure Sciences 41 (2018)4. - ISSN 0149-0400 - p. 313 - 329.
    capital - field - habitus - leisure - natural environments - rural-to-urban immigrants
    This study explored the use of natural environments for leisure among rural-to-urban immigrants by adopting Bourdieu's concepts of habitus, social and cultural capital, and field. Data were collected with the use of individual interviews with 27 participants, including Mexican immigrants in the United States, Ukrainian immigrants in Poland, Moroccan immigrants in the Netherlands, and Turkish immigrants in Germany. The findings showed that for some immigrants, practices of social capital maintenance became disconnected from recreation in natural environments, while for all participants, nature-related cultural capital had low transferability in a migratory situation. Depending on their position in a new social field, immigrants developed different strategies to use local natural environments for leisure. Some strategies contributed to preserving old habitus, while one strategy (finding substitutes) contributed to gradual changes in immigrants' nature-related habitus. We suggest that embodied and emplaced skills of using nature should be incorporated in the notion of cultural capital.
    Payment for Environmental Services: mobilising an epistemic community to construct dominant policy
    Rodriguez de Francisco, J.C. ; Boelens, R.A. - \ 2015
    Environmental Politics 24 (2015)3. - ISSN 0964-4016 - p. 481 - 500.
    ecosystem services - irrigation - politics - mexico - field
    The alleged capacity of Payment for Environmental Services (PES) to reach conservation policy goals, while reducing poverty in a cost-effective manner, makes it an extremely attractive development instrument for policymakers and international funding agencies. This article reconstructs the process of envisioning and building the National PES Strategy in Colombia. It reveals how this conservation policy has resulted from the mobilisation of the transnational/national PES epistemic community and its globally expanding discourse. The influential PES network generates internally defined standards of success that proceed without reference to empirical evidence as to the impacts of the implemented policies. PES adoption is influenced by regulatory instruments’ unsatisfactory outcomes, the ways in which market-environmentalist models induce profound indifference towards on-the-ground policy impacts, the discursive power and alignment properties of the PES policy epistemic community, and financial and political pressures by international banks and environmental NGOs.
    Interactions among drainage flows, gravity waves and turbulence: a BLLAST case study
    Román Cascón, C. ; Yagüe, C. ; Mahrt, L. ; Sastre, M. ; Steeneveld, G.J. ; Pardyjak, E. ; Boer, A. van de; Hartogensis, O.K. - \ 2015
    Atmospheric Chemistry and Physics 15 (2015). - ISSN 1680-7316 - p. 9031 - 9047.
    stable boundary-layer - intermittent turbulence - density-current - flux - field - wind - disturbances - simulations - stability - dynamics
    The interactions among several stable-boundary-layer (SBL) processes occurring just after the evening transition of 2 July 2011 have been analysed using data from instruments deployed over the area of Lannemezan (France) during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field campaign. The near-calm situation of the afternoon was followed by the formation of local shallow drainage flows (SDFs) of less than 10 m depth at different locations. The SDF stage ended with the arrival of a stronger wind over a deeper layer more associated with the mountain-plain circulation, which caused mixing and destruction of the SDFs. Several gravity-wave-related oscillations were also observed on different time series. Wavelet analyses and wave parameters were calculated from high resolution and accurate surface pressure data of an array of microbarometers. These waves propagated relatively long distances within the SBL. The effects of these phenomena on turbulent parameters (friction velocity and kinematic heat flux) have been studied through multi-resolution flux decomposition methods performed on high frequency data from sonic anemometers deployed at different heights and locations. With this method, we were able to detect the different time-scales involved in each turbulent parameter and separate them from wave contributions, which becomes very important when choosing averaging-windows for surface flux computations using eddy covariance methods. The extensive instrumentation allowed us to highlight in detail the peculiarities of the surface turbulent parameters in the SBL, where several of the noted processes were interacting and producing important variations in turbulence with height and between sites along the sloping terrain.
    Low-resolution modeling of dense drainage networks in confining layers
    Pauw, P.S. ; Zee, S.E.A.T.M. van der; Leijnse, A. ; Delsman, J.R. ; Louw, P.G.B. de; Lange, W.J. de; Oude Essink, G.H.P. - \ 2015
    Groundwater 53 (2015)5. - ISSN 0017-467X - p. 771 - 781.
    grondwaterstroming - watervoerende lagen - modellen - klimaatverandering - groundwater flow - aquifers - models - climatic change - aquifer - simulation - intrusion - seepage - florida - system - field - flow
    Groundwater-surface water (GW-SW) interaction in numerical groundwater flow models is generally simulated using a Cauchy boundary condition, which relates the flow between the surface water and the groundwater to the product of the head difference between the node and the surface water level, and a coefficient, often referred to as the “conductance.” Previous studies have shown that in models with a low grid resolution, the resistance to GW-SW interaction below the surface water bed should often be accounted for in the parameterization of the conductance, in addition to the resistance across the surface water bed. Three conductance expressions that take this resistance into account were investigated: two that were presented by Mehl and Hill (2010) and the one that was presented by De Lange (1999). Their accuracy in low-resolution models regarding salt and water fluxes to a dense drainage network in a confined aquifer system was determined. For a wide range of hydrogeological conditions, the influence of (1) variable groundwater density; (2) vertical grid discretization; and (3) simulation of both ditches and tile drains in a single model cell was investigated. The results indicate that the conductance expression of De Lange (1999) should be used in similar hydrogeological conditions as considered in this paper, as it is better taking into account the resistance to flow below the surface water bed. For the cases that were considered, the influence of variable groundwater density and vertical grid discretization on the accuracy of the conductance expression of De Lange (1999) is small.
    Surface water risk assessment of pesticides in Ethiopia
    Teklu, B.M. ; Adriaanse, P.I. ; Horst, M.M.S. ter; Deneer, J.W. ; Brink, P.J. van den - \ 2015
    Science of the Total Environment 508 (2015). - ISSN 0048-9697 - p. 566 - 574.
    predict insecticide concentrations - models fail - field - validation - exposure
    Scenarios for future use in the pesticide registration procedure in Ethiopia were designed for 3 separate Ethiopian locations, which are aimed to be protective for the whole of Ethiopia. The scenarios estimate concentrations in surface water resulting from agricultural use of pesticides for a small stream and for two types of small ponds. Seven selected pesticides were selected since they were estimated to bear the highest risk to humans on the basis of volume of use, application rate and acute and chronic human toxicity, assuming exposure as a result of the consumption of surface water. Potential ecotoxicological risks were not considered as a selection criterion at this stage. Estimates of exposure concentrations in surface water were established using modelling software also applied in the EU registration procedure (PRZM and TOXSWA). Input variables included physico-chemical properties, and data such as crop calendars, irrigation schedules, meteorological information and detailed application data which were specifically tailored to the Ethiopian situation. The results indicate that for all the pesticides investigated the acute human risk resulting from the consumption of surface water is low to negligible, whereas agricultural use of chlorothalonil, deltamethrin, endosulfan and malathion in some crops may result in medium to high risk to aquatic species. The predicted environmental concentration estimates are based on procedures similar to procedures used at the EU level and in the USA. Addition of aquatic macrophytes as an ecotoxicological endpoint may constitute a welcome future addition to the risk assessment procedure. Implementation of the methods used for risk characterization constitutes a good step forward in the pesticide registration procedure in Ethiopia. KEYWORDS: Aquatic ecosystems; Drinking water; Ecological risk assessment; Ethiopia; Exposure modelling; Pesticides; Tropics
    When Interaction Flows: An Exploration of Collective Creative Processes on a Collaborative Governance Board
    Oortmerssen, L.A. van; Woerkum, C.M.J. van; Aarts, N. - \ 2015
    Group & Organization Management 40 (2015)4. - ISSN 1059-6011 - p. 500 - 528.
    decision-making - team creativity - model - perspective - controversy - innovation - consensus - trust - field
    There is a growing awareness of the significance of collective creativity in dealing with the complex problems typical of today’s rapidly changing society. Whereas studies on collective creativity provide insight into what happens during creative episodes in terms of a changing meaning of the interaction content, they do not explain what happens in the conversational interaction process. To shed light on this, we introduce and define the concept of interaction flow. Interaction flow was observed during creative episodes in the board meetings of Platform Inspire, an innovation-oriented collaborative governance board in Western Europe. The concept of interaction flow makes collective creative episodes more observable and offers points of attention for facilitating these episodes. Keywords creativity, communication, collaboration, group or team dynamics
    Antibody response and risk factors for seropositvity in backyard poultry following mass vaccination against highly pathogenic avian influenza and Newcastle disease in Indonesia
    McLaws, M. ; Priyono, W. ; Bett, B. ; Al-Qamar, S. ; Claassen, I.J.T.M. ; Widiastuti, T. ; Poole, J. ; Schoonman, L. ; Jost, C. ; Mariner, J. - \ 2015
    Epidemiology and Infection 143 (2015)8. - ISSN 0950-2688 - p. 1632 - 1642.
    domestic poultry - h5n1 - ducks - surveillance - countries - efficacy - vaccines - vietnam - viruses - field
    A large-scale mass vaccination campaign was carried out in Java, Indonesia in an attempt to control outbreaks of highly pathogenic avian influenza (HPAI) in backyard flocks and commercial smallholder poultry. Sero-monitoring was conducted in mass vaccination and control areas to assess the proportion of the target population with antibodies against HPAI and Newcastle disease (ND). There were four rounds of vaccination, and samples were collected after each round resulting in a total of 27 293 samples. Sampling was performed irrespective of vaccination status. In the mass vaccination areas, 20–45% of poultry sampled had a positive titre to H5 after each round of vaccination, compared to 2–3% in the control group. In the HPAI + ND vaccination group, 12–25% of the population had positive ND titres, compared to 5–13% in the areas without ND vaccination. The level of seropositivity varied by district, age of the bird, and species (ducks vs. chickens).
    Strategic double cropping on Vertisols: A viable rainfed cropping option in the Indian SAT to increase productivity and reduce risk
    Nageswara Rao, V. ; Meinke, H.B. ; Craufurd, P.Q. ; Parsons, D. ; Kropff, M.J. ; Anten, N.P.R. ; Wani, S.P. ; Rego, T.J. - \ 2015
    European Journal of Agronomy 62 (2015). - ISSN 1161-0301 - p. 26 - 37.
    nitrogen - field - soil - management - tillage - residue - maize - wheat - yield - corn
    Our study suggests the possibility for transformational change in the productivity and risk profile of someof India’s rainfed cropping systems. In the semi-arid regions of Southern India, farmers traditionally cropsorghum or chickpea on Vertisols during the post-rainy season, keeping the fields fallow during the rainyseason. This practice avoids land management problems, but limits the potential for crop intensifica-tion to increase systems productivity. A long-term (15 year) experiment at ICRISAT demonstrated thatcropping during the rainy season is technically feasible, and that grain productivity of double croppedsorghum + chickpea (SCP–SCP) and mung bean + sorghum (MS–MS) sequential systems were higher thantheir conventional counterparts with rainy season fallow, i.e. fallow + post-rainy sorghum (FS–FS) and fal-low + post-rainy chickpea (FS–FCP). Without N application, mean grain yield of post-rainy sorghum in theMS–MS system was significantly greater (2520 kg ha-1per two-year rotation) than in the FS–FS system(1940 kg ha-1per two-year rotation), with the added benefit of the mung bean grain yield (1000 kg ha-1per two-year rotation) from the MS–MS system. In the SCP–SCP system the additional grain yield ofrainy sorghum (3400 kg ha-1per two-year rotation) ensured that the total productivity of this systemwas greater than all other systems. Double cropping MS–MS and SCP–SCP sequential systems had sig-nificantly higher crop N uptake compared to traditional fallow systems at all rates of applied nitrogen(N).The intensified MS–MS and SCP–SCP sequential systems without any N fertilizer applied recorded amuch higher median gross profit of Rs. 20,600 (US $ 375) and Rs. 15,930 (US $ 290) ha-1yr-1, respectively,compared to Rs. 1560 (US $ 28) ha-1yr-1) with the FS–FS system. Applying 120 kg of N ha-1considerablyincreased the profitability of all systems, lifting median gross profits of the sorghum + chickpea systemover Rs. 60,000 (US $ 1091) ha-1yr-1and the conventional system to Rs. 20,570 (US $ 374) ha-1yr-1. Thegross profit margin analysis showed that nitrogen is a key input for improving productivity, particularlyfor the double cropping systems. However, traditional systems are unviable and risky without N appli-cation in the variable climates of the semi-arid tropics. Together, our results show that on Vertisols insemi-arid India, double cropping systems increase systems’ productivity, and are financially more pro-fitability and less risky than traditional fallow post-rainy systems while further benefits can be achievedthrough fertilizer application.
    Water reform governmentality in Ecuador: Neoliberalism, centralization, and the restraining of polycentric authority and community rule-making
    Boelens, R.A. ; Hoogesteger van Dijk, J.D. ; Baud, M. - \ 2015
    Geoforum 64 (2015). - ISSN 0016-7185 - p. 281 - 291.
    rights - governance - politics - irrigation - andes - field
    In most Latin American countries, issues concerning water governance and control also reflect broader conflicts over authority and legitimacy between the state and civil society. What lies behind the diverse water policy reforms is not simply a question of governing water affairs but also a drive to control or co-opt water user groups. This paper examines the efforts by the present Ecuadorian government to ‘control water users’ through new forms of ‘governmentality’ (Foucault, 1991). We use the ‘cathedral and bazaar’ metaphor (Lankford and Hepworth, 2010) to illustrate government rationale and practices in water governance shifts in the last decades. We analyze how Rafael Correa’s government sets out to reshape the relations between state, market and society. In its ‘Twenty-first Century Socialism’ project, based on a proclaimed ‘Citizen Revolution’, actual policy reform does not reverse but rather transforms the process of neoliberalizing water governance – creating a hybrid bazaar-cathedral model. We argue that the current water govermentality project implements reforms that do not challenge established market-based water governance foundations. Rather it aims to contain and undermine communities’ autonomy and ‘unruly’ polycentric rule-making, which are the result of both historical and present-day processes of change. Interestingly, water user federations that emerged during the neoliberal wave of the last two decades now claim water control space and search for new forms of democratizing water governance. They act as agents who fiercely – yet selectively and strategically – oppose both elements of the State-centered (cathedral) and market-based (bazaar) water governance models
    Application of a visual soil examination and evaluation technique at site and farm level
    Sonneveld, M.P.W. ; Heuvelink, G.B.M. ; Moolenaar, S.W. - \ 2014
    Soil Use and Management 30 (2014)2. - ISSN 0266-0032 - p. 263 - 271.
    environmental-impact - indicators - quality - agriculture - framework - canada - field
    Visual soil examination and evaluation (VSEE) techniques are semi-quantitative methods that provide rapid and cost-effective information on soil quality. These are mostly applied at site or field level, but there is an increased need for soil quality indicators at farm level to allow integration with other sustainability indicators. The objectives of this study were to develop and apply a protocol for application of a VSEE technique at site level, to assess the VSEE observations against standardized laboratory analyses and to aggregate VSEE observations to farm level using an appropriate sampling design. The study was conducted at ten dairy farms in a reclaimed polder in the Netherlands with clay and organic soils. A stratified random sampling design was used to account for spatial variability in land use and soil series. VSEE was carried out using the Visual Soil Assessment approach. Results show that 81% of sites were assessed as good and the remainder as moderate to poor. For the clay soils, field observations of soil structure were significantly correlated with pH, bulk density, soil organic matter (SOM) and mean weight diameter of aggregates, whereas for organic soils, soil structure significantly correlated with pH, bulk density, organic C and SOM. The range in overall scores calculated at farm level was smaller than at site level, and most farms were assessed as good.
    Microwave assisted flow synthesis: Coupling of electromagnetic and hydrodynamic phenomena
    Patil, N.G. ; Benaskar, F. ; Meuldijk, J. ; Hulshof, L.A. ; Hessel, V. ; Schouten, J.C. ; Esveld, D.C. ; Rebrov, E.V. - \ 2014
    AIChE Journal 60 (2014)11. - ISSN 0001-1541 - p. 3824 - 3832.
    organic-synthesis macos - dry-media reactor - heat-transfer - thin-films - field - efficiency - catalysis
    This article describes the results of a modeling study performed to understand the microwave heating process in continuous-flow reactors. It demonstrates the influence of liquid velocity profiles on temperature and microwave energy dissipation in a microwave integrated milli reactor-heat exchanger. Horizontal cocurrent flow of a strong microwave absorbing reaction mixture (ethanol¿+¿acetic acid, molar ratio 5:1) and a microwave transparent coolant (toluene) was established in a Teflon supported quartz tube (i.d.: 3 × 10-3 m and o.d.: 4 × 10-3 m) and shell (i.d.: 7 × 10-3 m and o.d.: 9 × 10-3 m), respectively. Modeling showed that the temperature rise of the highly microwave absorbing reaction mixture was up to four times higher in the almost stagnant liquid at the reactor walls than in the bulk liquid. The coolant flow was ineffective in controlling the outlet reaction mixture temperature. However, at high flow rates it limits the overheating of the stagnant liquid film of the reaction mixture at the reactor walls. It was also found that the stagnant layer around a fiber optic temperature probe, when inserted from the direction of the flow, resulted in much higher temperatures than the bulk liquid. This was not the case when the probe was inserted from the opposite direction. The experimental validations of these modeling results proved that the temperature profiles depend more on the reaction mixture velocity profiles than on the microwave energy dissipation/electric field intensity. Thus, in flow synthesis, particularly where a focused microwave field is applied over a small tubular flow reactor, it is very important to understand the large (direct/indirect) influence of reactor internals on the microwave heating process.
    Management of irrigation frequency and nitrogen fertilization to mitigate GHG and NO emissions from drip-fertigated crops
    Abalos, D. ; Sanchez-Martin, L. ; Garcia-Torres, L. ; Groenigen, J.W. van; Vallejo, A. - \ 2014
    Science of the Total Environment 490 (2014). - ISSN 0048-9697 - p. 880 - 888.
    treated pig slurries - oxide emissions - n2o emissions - mediterranean climate - nitric-oxide - soil - water - potato - carbon - field
    Drip irrigation combined with split application of fertilizer nitrogen (N) dissolved in the irrigation water (i.e. drip fertigation) is commonly considered best management practice for water and nutrient efficiency. As a consequence, its use is becoming widespread. Some of the main factors (water-filled pore space, NH4+ and NO3-) regulating the emissions of greenhouse gases (i.e. N2O, CO2 and CH4) and NO from agroecosystems can easily be manipulated by drip fertigation without yield penalties. In this study, we tested management options to reduce these emissions in a field experiment with a melon (Cucumis melo L.) crop. Treatments included drip irrigation frequency (weekly/daily) and type of N fertilizer (urea/calcium nitrate) applied by fertigation. Crop yield, environmental parameters, soil mineral N concentrations and fluxes of N2O, NO, CH4 and CO2 were measured during 85 days. Fertigation with urea instead of calcium nitrate increased N2O and NO emissions by a factor of 2.4 and 2.9, respectively (P <0.005). Daily irrigation reduced NO emissions by 42% (P <0.005) but increased CO2 emissions by 21% (P <0.05) compared with weekly irrigation. We found no relation between irrigation frequency and N2O emissions. Based on yield-scaled Global Warming Potential as well as NO cumulative emissions, we conclude that weekly fertigation with a NO3--based fertilizer is the best option to combine agronomic productivity with environmental sustainability. Our study shows that adequate management of drip fertigation, while contributing to the attainment of water and food security, may provide an opportunity for climate change mitigation.
    Integrating chemical fate and population-level effect models of pesticides: the importance of capturing the right scales
    Focks, A. ; Horst, M.M.S. ter; Berg, E. van den; Baveco, H. ; Brink, P.J. van den - \ 2014
    Ecological Modelling 280 (2014). - ISSN 0304-3800 - p. 102 - 116.
    asellus-aquaticus l - potential application - lambda-cyhalothrin - life-history - growth - invertebrates - isopoda - field - ecotoxicology - biodiversity
    Any attempt to introduce more ecological realism into ecological risk assessment of chemicals faces the major challenge of integrating different aspects of the chemicals and species of concern, for example, spatial scales of emissions, chemical exposure patterns in space and time, and population dynamics and dispersal in heterogeneous landscapes. Although these aspects are not considered in current risk assessment schemes, risk assessors and managers are expressing increasing interest in learning more about both the exposure to and the effects of chemicals at landscape level. In this study, we combined the CASCADE-TOXSWA fate model, which predicts the fate of pesticides in an interconnected system of water bodies with variable hydrological characteristics, with the MASTEP mechanistic effect model, which simulates population dynamics and effects of pesticides on aquatic species at the scale of individual water bodies. To this end, we extrapolated MASTEP to the scale of realistic landscapes and linked it to dynamic exposure patterns. We explored the effects of an insecticide on the water louse Asellus aquaticus for a typical Dutch landscape covering an area of about 10 km2 containing 137 water bodies (drainage ditches) with a total length of about 65 km and different degrees of connectivity. Pesticide treatments used in potato crop were assumed to result in a spray-drift input of 5% (non-mitigated) and 1% (mitigated) of the amount of pesticide applied into parts of the water body network. These treatments resulted in highly variable exposure patterns both in space and time. The effects of the pesticide on the species were investigated by comparing two scenarios with low and high individual-level sensitivity. We found that downstream transport of the pesticide led to exposure of water bodies that did not receive direct spray-drift input, even though this particular pesticide was assumed to dissipate rapidly from water. The observed differences in population-level effects and recovery patterns ranged from no observable effects in the low spray-drift and low sensitivity scenario to severe reduction of abundances in the high spray-drift and high sensitivity scenario. These results illustrate the sensitivity of our modelling approach, but also show the need for precise calculations of pesticide inputs and model parameterisation. Our study demonstrates the potential of coupled fate-and-effect to explore realistic scenarios at the scale of heterogeneous landscapes. Such scenarios could include the application of multiple pesticides to one or more crop types. Spatial realism of the landscape represented in the model ensures realistic consideration of population growth and dispersal as the two main recovery mechanisms. Future options for the landscape-scale fate-and-effect simulation approach include exploring the effects of mitigation measures on the risk estimates at landscape scale and hence represent a step towards risk management.
    The challenge: Landscape ecotoxocologie and spatially explicit risk assessment
    Focks, A. - \ 2014
    Environmental Toxicology and Chemistry 33 (2014)6. - ISSN 0730-7268 - p. 1193 - 1193.
    field - stream - ecotoxicology - scale - model - need
    Salt-marsh erosion and restoration in relation to flood protection on the Wadden Sea barrier island Terschelling
    Loon-Steensma, J.M. van; Slim, P.A. ; Decuyper, M. ; Hu, Zhan - \ 2014
    Journal of Coastal Conservation 18 (2014)4. - ISSN 1400-0350 - p. 415 - 430.
    north norfolk - vegetation - succession - herbivory - estuary - defense - field
    This paper explores the impact of erosion and restoration measures on habitat development and on wave damping by a small salt marsh nestled alongside a dike on the Wadden island of Terschelling. The aim is to advance knowledge about the benefits and possible side-effects of salt-marsh restoration. Analysis of a time series of aerial photographs from 1944 to 2010 indicates that the salt marsh decreased steadily in size after maintenance of accretion works was terminated. In the western part of the marsh, which is accessible to sheep, vegetation is low (5–15 cm) and dominated by Salicornia europaea and by Spartina anglica. In the most intensively grazed parts, vegetation is very scarce. The eastern, inaccessible part of the salt marsh is covered by dense patches of the shrubby perennial Atriplex portulacoides and Spartina anglica (15–25 cm in height). SWAN wave models show that wave height at this location is significantly affected by the areal extent of the salt marsh as well as by the vegetation. High or dense vegetation are in the models nearly as effective in damping waves (with an initial height of 0.15 and 0.5 m) as widening the salt-marsh area by 350 m. A low density of low plants, as observed in the grazed part of the marsh, has almost no wave-damping effect. Even under conditions of sea level rise, a broader salt marsh vegetated with high plants significantly affects modelled wave height. Therefore, salt-marsh restoration is an adaptation measure worth exploring, though an array of effect types must be considered.
    Fitness consequences of larval exposure to Beauveria bassiana on adults of the malaria vector Anopheles stephensi
    Vogels, C.B.F. ; Bukhari, T. ; Koenraadt, C.J.M. - \ 2014
    Journal of Invertebrate Pathology 119 (2014). - ISSN 0022-2011 - p. 19 - 24.
    fungus metarhizium-anisopliae - entomopathogenic fungus - mosquito larvae - nosema-algerae - biocontrol agents - gambiae - infection - density - survival - field
    Entomopathogenic fungi have shown to be effective in biological control of both larval and adult stages of malaria mosquitoes. However, a small fraction of mosquitoes is still able to emerge after treatment with fungus during the larval stage. It remains unclear whether fitness of these adults is affected by the treatment during the larval stage and whether they are still susceptible for another treatment during the adult stage. Therefore, we tested the effects of larval exposure to the entomopathogenic fungus Beauveria bassiana on fitness of surviving Anopheles stephensi females. Furthermore, we tested whether larval exposed females were still susceptible to re-exposure to the fungus during the adult stage. Sex ratio, survival and reproductive success were compared between non-exposed and larval exposed A. stephensi. Comparisons were also made between survival of non-exposed and larval exposed females that were re-exposed to B. bassiana during the adult stage. Larval treatment did not affect sex ratio of emerging mosquitoes. Larval exposed females that were infected died significantly faster and laid equal numbers of eggs from which equal numbers of larvae hatched, compared to non-exposed females. Larval exposed females that were uninfected had equal survival, but laid a significantly larger number of eggs from which a significantly higher number of larvae hatched, compared to non-exposed females. Larval exposed females which were re-exposed to B. bassiana during the adult stage had equal survival as females exposed only during the adult stage. Our results suggest that individual consequences for fitness of larval exposed females depended on whether a fungal infection was acquired during the larval stage. Larval exposed females remained susceptible to re-exposure with B. bassiana during the adult stage, indicating that larval and adult control of malaria mosquitoes with EF are compatible.
    Effects of nursery management practices on morphological quality attributes of tree seedlings at planting: The case of oil palm (Elaeis guineensis Jacq.)
    Akpo, E. ; Stomph, T.J. ; Kossou, D. ; Omore, A.O. ; Struik, P.C. - \ 2014
    Forest Ecology and Management 324 (2014). - ISSN 0378-1127 - p. 28 - 36.
    container size - pot size - growth - fertilization - irrigation - substrate - purposes - manure - benin - field
    Even though oil palm production is associated with forest clearance and environmental degradation, it is also considered a potential carbon sink. For oil palm to fulfil its potential role in environmental sustainability, high quality seedlings are required. Nursery managers in Benin who produce oil palm seedlings for owners of small farms ignored recommended practices and developed their own. To evaluate the efficacy of their nursery management practices in terms of seedling growth, 2 experiments were conducted. Three polybag sizes (5 L, 8 L, and 15 L) in combination with 4 types of soil substrates and 3 fertiliser treatments were implemented in both experiments in a factorial design. Biomass (shoot, root, shoot-to-root ratio) and allometric (seedling height, number of leaves, length of most developed leaf, root-collar diameter) variables were measured 8 or 6 months after transplanting. Polybag size was the main factor determining oil palm seedling growth in both experiments. Applying 10 g fertiliser once a month was harmful to seedling survival with lethal effects in 5 L polybags. Arable soil with animal manure in 8 L polybags without any fertiliser supply sustained seedling growth well; this practice seemed to be the best balance between quality and production cost although 15 L polybags produced the best seedlings. Growth variables were highly correlated. Height and root-collar diameter constitute good candidates to estimate seedling biomass production non-destructively. The treatment effects on total biomass produced were similar for the 2 experiments. Given the observed large effects of polybag size on seedling growth, our findings suggest that fertiliser addition or substrate selection cannot overrule container size effects; the latter should be considered carefully for (forest and crop) tree seedling production in nurseries.
    Forced Engagements: Water Security and Local Rights Formalization in Yanque, Colca Valley, Peru
    Boelens, R.A. ; Seemann, M. - \ 2014
    Human Organization 73 (2014)1. - ISSN 0018-7259 - p. 1 - 12.
    climate-change - governance - politics - irrigation - community - bolivia - policy - andes - field
    For vulnerable groups in society, water insecurity and deficient water availability for food production commonly reflect unequal distribution of water volumes, quality, and services within unequal power structures. Water security is necessarily a political dilemma. Policy debates, however, tend to naturalize and de-politicize this concept. Instead of recognizing that water security and distribution belong to the realm of human interests, choices, negotiation, and power plays, they are often represented as following universal economic, legal, and natural-scientific rules. In this context, there is a widespread policy assumption that formally recognizing local, customary water rights is one important element to grant water security for marginalized user groups. This paper challenges this assumption and examines the illustrative case of a Peruvian Andes community, Yanque. We scrutinize formalization policies that claim to enhance water security for marginalized communities regarding (1) material water allocation and (re) distribution and (2) water rulemaking, legitimate authority, and cultural-political organization-both elements that stand central in formalization processes. We discuss the complex relationship between formal and alternative "water securities" and the cultural politics of rights recognition and show that uncritical formalization of local water rights often leads to weakening rather than strengthening local water security.
    Development of Xanthomonas fragariae populations and disease progression in strawberry plants after spray-inoculation of leaves
    Kastelein, P. ; Krijger, M.C. ; Czajkowski, R.L. ; Zouwen, P.S. van der; Schoor, R. van der; Jalink, H. ; Wolf, J.M. van der - \ 2014
    Plant Pathology 63 (2014)2. - ISSN 0032-0862 - p. 255 - 263.
    axonopodis pv. phaseoli - angular leaf-spot - survival - phyllosphere - rhizosphere - infection - field
    Xanthomonas fragariae is the causative agent of angular leaf spot disease of strawberry. Greenhouse experiments were conducted using a X. fragariae isolate tagged with a green fluorescent protein (GFP) for detailed population dynamic studies in and on leaves after spray-inoculation. The GFP-tagged bacteria were monitored with dilution plating of leaf washings and leaf extracts, and analysis of intact leaves using a non-invasive monitoring system called PathoScreen, based on laser radiation of fluorescent cells in plant tissues and signal recording with a sensitive camera. PathoScreen was also used to monitor bacteria grown on an agar medium after leaf printing. During the first 3 days after inoculation, bacterial populations washed off leaves rapidly decreased by at least a factor of 1000, after which populations remained stable until 14 days post-inoculation (dpi), when symptoms first started to appear. Thereafter, populations increased to a level of 1012 colony-forming units (CFU) g-1 of leaf material or higher. Similarly, densities in leaf extracts were low during the first 3 days after inoculation, at a level of 100–1000 CFU g-1 of leaf tissue. Gradually populations increased to a level of 109–1012 CFU g-1 at 28 dpi. Higher densities of epiphytic populations were found on the abaxial side than on the adaxial leaf side during the first 2 weeks after inoculation. After spray-inoculation of leaves, bacterial populations released from infected plants remained low until symptoms appeared, after which plants became highly infectious, in particular under high humidity
    Seasonal dependence of the urban heat island on the street canyon aspect ratio
    Theeuwes, N.E. ; Steeneveld, G.J. ; Ronda, R.J. ; Heusinkveld, B.G. ; Hove, L.W.A. van; Holtslag, A.A.M. - \ 2014
    Quarterly Journal of the Royal Meteorological Society 140 (2014)684. - ISSN 0035-9009 - p. 2197 - 2210.
    warmte - steden - stedelijke planning - warmtebalans - seizoenvariatie - meteorologie - nederland - heat - towns - urban planning - heat balance - seasonal variation - meteorology - netherlands - boundary-layer - energy-balance - climate zones - model - temperature - parameterization - simulation - schemes - cabauw - field
    In this paper we study the relation between the urban heat island (UHI) in the urban canyon and street geometry, in particular the aspect ratio. Model results and observations show that two counteracting processes govern the relation between the nocturnal UHI and the building aspect ratio: i.e. trapping of longwave radiation and shadowing effects. In general, trapping of longwave radiation supports the UHI, whereas shadowing effects reduce the UHI. The net effect depends on the UHI definition and the amount of available shortwave radiation penetrating the canyon. In summer, autumn and spring the shadowing effects can already reduce the UHI starting at an aspect ratio between 0.5 and 1. The analysis is carried out using several methods. Firstly, the single-column model version of the Weather Research and Forecasting model (WRF) is used extensively. Two separate runs, one rural and one urban, are used to estimate the UHI. Secondly, the urban canyon temperature at the two meter level is introduced, which allows for direct comparison between modelled and observed air temperatures within the urban canyon. Finally, the model is evaluated for all four seasons. The results of this research provide important insights for urban planning on how to use the aspect ratio to mitigate the UHI in the urban canyon
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