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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Nitrous oxide and methane emissions from optimized and alternative cereal cropping systems on the North China Plain: A two-year field study
Gao, B. ; Ju, X.T. ; Su, F. ; Meng, Q.F. ; Oenema, O. ; Christie, P. ; Chen, X.P. ; Zhang, F.S. - \ 2014
Science of the Total Environment 472 (2014). - ISSN 0048-9697 - p. 112 - 124.
greenhouse-gas emissions - n2o emissions - soil - management - maize - fertilizer - fluxes - agriculture - balance - intensity
The impacts of different crop rotation systems with their corresponding management practices on grain yield, greenhouse gas emissions, and fertilizer nitrogen (N) and irrigation water use efficiencies are not well documented. This holds especially for the North China Plain which provides the staple food for hundreds of millions of people and where groundwater resources are polluted with nitrate and depleted through irrigation. Here, we report on fertilizer N and irrigation water use, grain yields, and nitrous oxide (N2O) and methane (CH4) emissions of conventional and optimized winter wheat-summer maize double-cropping systems, and of three alternative cropping systems, namely a winter wheat-summer maize (or soybean)-spring maize system, with three harvests in two years; and a single spring maize system with one crop per year. The results of this two-year study show that the optimized double-cropping system led to a significant increase in grain yields and a significant decrease in fertilizer N use and net greenhouse gas intensity, but the net greenhouse gas N2O emissions plus CH4 uptake and the use of irrigation water did not decrease relative to the conventional system. Compared to the conventional system the net greenhouse gas emissions, net greenhouse gas intensity and use of fertilizer N and irrigation water decreased in the three alternative cropping systems, but at the cost of grain yields except in the winter wheat-summer maize-spring maize system. Net uptake of CH4 by the soil was little affected by cropping system. Average N2O emission factors were only 0.17% for winter wheat and 0.53% for maize. In conclusion, the winter wheat-summer maize-spring maize system has considerable potential to decrease water and N use and decrease N2O emissions while maintaining high grain yields and sustainable use of groundwater.
Mapping and monitoring High Nature Value farmlands: Challenges in European landscapes
Lomba, A. ; Guerra, C. ; Alonso, J. ; Honrado, J.P. ; Jongman, R.H.G. ; McCracken, D. - \ 2014
Journal of Environmental Management 143 (2014). - ISSN 0301-4797 - p. 140 - 150.
common agricultural policy - plant-species richness - land-use - biodiversity conservation - farm-management - intensity - intensification - conflicts - systems - cover
The importance of low intensity farming for the conservation of biodiversity throughout Europe was acknowledged early in the 1990s when the concept of ‘High Nature Value farmlands’ (HNVf) was devised. HNVf has subsequently been given high priority within the EU Rural Development Programme. This puts a requirement on each EU Member State not only to identify the extent and condition of HNVf within their borders but also to track trends in HNVf over time. However, the diversity of rural landscapes across the EU, the scarcity of (adequate) datasets on biodiversity, land cover and land use, and the lack of a common methodology for HNVf mapping currently represent obstacles to the implementation of the HNVf concept across Europe. This manuscript provides an overview of the characteristics of HNVf across Europe together with a description of the development of the HNVf concept. Current methodological approaches for the identification and mapping of HNVf across EU-27 and Switzerland are then reviewed, the main limitations of these approaches highlighted and recommendations made as to how the identification, mapping and reporting of HNVf state and trends across Europe can potentially be improved and harmonised. In particular, we propose a new framework that is built on the need for strategic HNVf monitoring based on a hierarchical, bottom-up structure of assessment units, coincident with the EU levels of political decision and devised indicators, and which is linked strongly to a collaborative European network that can provide the integration and exchange of data from different sources and scales under common standards. Such an approach is essential if the scale of the issues facing HNVf landscapes are to be identified and monitored properly at the European level. This would then allow relevant agrienvironmental measures to be developed, implemented and evaluated at the scale(s) required to maintain the habitats and species of high nature conservation value that are intimately associated with those landscapes.
Dealing with consumer differences in liking during repeated exposure to food; typical dynamics in rating behavior
Horst, G.J. ter; Renken, R. ; Nanneti, L. ; Dalenberg, J.R. ; Wijk, R.A. de - \ 2014
PLoS ONE 9 (2014)3. - ISSN 1932-6203
in-home consumption - k-means - elderly adults - mere exposure - acceptance - intensity - flavor - young - pleasantness - preferences
Consumers show high interindividual variability in food liking during repeated exposure. To investigate consumer liking during repeated exposure, data is often interpreted on a product level by averaging results over all consumers. However, a single product may elicit inconsistent behaviors in consumers; averaging will mix and hide possible subgroups of consumer behaviors, leading to a misinterpretation of the results. To deal with the variability in consumer liking, we propose to use clustering on data from consumer-product combinations to investigate the nature of the behavioral differences within the complete dataset. The resulting behavioral clusters can then be used to describe product acceptance. To test this approach we used two independent data sets in which young adults were repeatedly exposed to drinks and snacks, respectively. We found that five typical consumer behaviors existed in both datasets. These behaviors differed both in the average level of liking as well as its temporal dynamics. By investigating the distribution of a single product across typical consumer behaviors, we provide more precise insight in how consumers divide in subgroups based on their product liking (i.e. product modality). This work shows that taking into account and using interindividual differences can unveil information about product acceptance that would otherwise be ignored.
Effect of patches of woody vegetation on the role of fire in tropical grasslands and savannas
Langevelde, F. van; Groot, C. de; Groen, T.A. ; Heitkonig, I.M.A. ; Gaigher, I. - \ 2014
International Journal of Wildland Fire 23 (2014)3. - ISSN 1049-8001 - p. 410 - 416.
south-africa - neotropical savanna - semiarid woodland - national-park - tree cover - ecosystems - intensity - frequency - dynamics - plants
In tropical grasslands and savannas, fire is used to reduce woody vegetation expansion. Woody vegetation in these biomes is often patchily distributed, and micro-climatic conditions can largely vary locally with unknown consequences for fire effects. We hypothesized that (1) fire has higher temperature and maintains high temperatures for a longer period at the windward side than at the leeward side of wooded patches, (2) this difference increases with patch size, (3) fire has a larger effect on woody vegetation at the windward side than at the leeward side of wooded patches, and (4) this effect increases with patch size. We planted tree seedlings around wooded patches in a grassland and burnt these plots. We found that fire had a lower temperature and had an elevated temperature for a shorter time period at the leeward side of wooded patches than at the windward side. Also, we found smaller effect of fire on the seedlings at the leeward side. We conclude that patches of woody vegetation can have a large effect on the role of fire in tropical grasslands and savannas. This effect suggests a ⿿safe zone� for seedlings at the leeward side, which consequently promotes woody vegetation expansion. This paper contributes to understanding of the effect of patchiness of woody vegetation on the role of fire in tropical grasslands and savannas in reducing woody vegetation expansion.
An estimate of potential threats levels to soil biodiversity in EU
Gardi, C. ; Jeffery, S.L. ; Saltelli, A. - \ 2013
Global Change Biology 19 (2013)5. - ISSN 1354-1013 - p. 1538 - 1548.
new-zealand flatworm - habitat fragmentation - ecosystem function - earthworms - diversity - europe - intensification - resilience - intensity - corridors
Life within the soil is vital for maintaining life on Earth due to the numerous ecosystem services that it provides. However, there is evidence that pressures on the soil biota are increasing which may undermine some of these ecosystem services. Current levels of belowground biodiversity are relatively poorly known, and so no benchmark exists by which to measure possible future losses of biodiversity. Furthermore, the relative risk that each type of anthropogenic pressures places on the soil biota remains unclear. Potential threats to soil biodiversity were calculated through the use of a composite score produced from data collected from 20 international experts using the budget allocation methodology. This allowed relative weightings to be given to each of the identified pressures for which data were available in the European Soil Data Centre (ESDC). A total of seven different indicators were used for calculating the composite scores. These data were applied through a model using ArcGIS to produce a spatial analysis of composite pressures on soil biodiversity at the European scale. The model highlights the variation in the composite result of the potential threats to soil biodiversity. A sensitivity analysis demonstrated that the intensity of land exploitation, both in terms of agriculture and use intensity, as well as in terms of land-use dynamics, were the main factors applying pressure on soil biodiversity. It is important to note that the model should not be viewed as an estimate of the current level of soil biodiversity in Europe, but as an estimate of pressures that are currently being exerted. The results obtained should be seen as a starting point for further investigation on this relatively unknown issue and demonstrate the utility of this type of model which may be applied to other regions and scales.
Texture and savoury taste influences on food intake in a realistic hot lunch time meal
Forde, C.G. ; Kuijk, N.L. van; Thaler, T. ; Graaf, C. de; Martin, N. - \ 2013
Appetite 60 (2013). - ISSN 0195-6663 - p. 180 - 186.
bite size - energy-intake - portion size - questionnaire - satiation - weight - young - consumption - intensity - healthy
Background: Previous studies with model foods have shown that softer textures lead to higher eating rates and higher ad libitum food intake and higher intensity of salt taste has been shown to result in a lower ad libitum food intake. These observations have yet to be replicated in the context of realistic solid hot meal components. Aim: The objective of the present study was to assess the effect of texture and taste on the ad libitum intake of a realistic hot lunchtime meal. Methods: The meals consisted of potatoes, carrots, steak and gravy varied according to a 2 (texture: mashed vs. whole) x 2 (taste: standard taste vs. strong taste) design. The texture dimension referred to mashed potatoes, mashed carrots and pieces of steak vs. whole boiled potatoes, whole boiled carrots and whole steak. The taste was varied by manipulating the taste intensity of the gravy to be either standard or high intensity savoury taste. The current study used a between groups, single course ad libitum design whereby subjects were recruited for a one off meal study, during which their food intake was measured. The four groups consisted of about 40 subjects (mashed, standard, n = 37; mashed, savoury n = 39; whole, standard n = 40; and whole, savoury n = 41) matched for age (average age = 44.8 +/- 5.3), gender (on average 19 males and 20 females), normal BMI (average 22.6 +/- 1.7) and dietary restraint score (DEBQ score = 1.74 +/- 0.6). Results: The results showed that the estimated means of the intake of the two mashed conditions was 563.2 +/- 20.3 g and intake of whole meal was 527.5 +/- 20.0 g (p = 0.23). The texture effect was significant in the higher savoury condition with an average of 91 g less food consumed in the solid-savoury meal than in the mashed savoury meal. This effect was not replicated in the standard gravy condition, with no significant difference between solid and mashed textures. This was reflected in an interaction effect that was approaching significance (p = 0.051). The estimated mean eating rate in the two mashed conditions was 57.0 +/- 2.5 g and was significantly higher than the whole meal condition (47.2 +/- 2.5 g (p <0.05), with no difference in eating rate between the standard and savoury gravy conditions. Discussion: Although interpretation was made difficult by the between groups design and the interaction between taste * texture, the results nonetheless confirm the effect of texture on eating rate and ad libitum intake for solid savoury meal components. The impact of taste on ad libitum intake of a solid meal remains unclear. We conclude that people consumed more of the meal when the food was simultaneously mashed and savoury. Food texture may be used to produce slower eating rates that result in a reduced overall energy intake within a realistic hot lunchtime meal. (C) 2012 Elsevier Ltd. All rights reserved.
Hot fire, cool soil
Stoof, C.R. ; Moore, D. ; Fernandes, P. ; Stoorvogel, J.J. ; Fernandes, R. ; Ferreira, A.J.D. ; Ritsema, C.J. - \ 2013
Geophysical Research Letters 40 (2013)8. - ISSN 0094-8276 - p. 1534 - 1539.
south-eastern australia - intensity - behavior - forest - temperatures - variability - erodibility - germination - california - vegetation
Wildfires greatly increase a landscape's vulnerability to flooding and erosion events by removing vegetation and changing soils. Fire damage to soil increases with increasing soil temperature, and, for fires where smoldering combustion is absent, the current understanding is that soil temperatures increase as fuel load and fire intensity increase. Here, however, we show that this understanding that is based on experiments under homogeneous conditions does not necessarily apply at the more relevant larger scale where soils, vegetation, and fire characteristics are heterogeneous. In a catchment-scale fire experiment, soils were surprisingly cool where fuel load was high and fire was hot and, conversely, soils were hot where expected to be cooler. This indicates that the greatest fire damage to soil can occur where fuel load and fire intensity are low rather than high, and has important implications for management of fire-prone areas prior to, during, and after fire events.
A modelling approach for the assessment of the effects of Common Agricultural Policy measures on farmland biodiversity in the EU27
Overmars, K.P. ; Helming, J.F.M. ; Zeijts, H. van; Jansson, T. ; Terluin, I.J. - \ 2013
Journal of Environmental Management 126 (2013). - ISSN 0301-4797 - p. 132 - 141.
land-use change - intensity - dynamics - europe
In this paper we describe a methodology to model the impacts of policy measures within the Common Agricultural Policy (CAP) on farm production, income and prices, and on farmland biodiversity. Two stylised scenarios are used to illustrate how the method works. The effects of CAP measures, such as subsidies and regulations, are calculated and translated into changes in land use and land-use intensity. These factors are then used to model biodiversity with a species-based indicator on a 1 km scale in the EU27. The Common Agricultural Policy Regionalised Impact Modelling System (CAPRI) is used to conduct the economic analysis and Dyna-CLUE (Conversion of Land Use and its Effects) is used to model land use changes. An indicator that expresses the relative species richness was used as the indicator for biodiversity in agricultural areas. The methodology is illustrated with a baseline scenario and two scenarios that include a specific policy. The strength of the methodology is that impacts of economic policy instruments can be linked to changes in agricultural production, prices and incomes, on the one hand, and to biodiversity effects, on the other – with land use and land-use intensity as the connecting drivers. The method provides an overall assessment, but for detailed impact assessment at landscape, farm or field level, additional analysis would be required.
Measuring fast-temporal sediment fluxes with an analogue acoustic sensor: a wind tunnel study
Poortinga, A. ; Minnen, J. van; Keijsers, J.G.S. ; Riksen, M.J.P.M. ; Goossens, D. ; Seeger, K.M. - \ 2013
PLoS ONE 8 (2013)9. - ISSN 1932-6203
eolische processen - sediment - windtunnels - meettechnieken - aeolian processes - wind tunnels - measurement techniques - inland drift-sand - aeolian transport - erosion - velocity - cloud - soil - validation - efficiency - intensity - saltation
In aeolian research, field measurements are important for studying complex wind-driven processes for land management evaluation and model validation. Consequently, there have been many devices developed, tested, and applied to investigate a range of aeolian-based phenomena. However, determining the most effective application and data analysis techniques is widely debated in the literature. Here we investigate the effectiveness of two different sediment traps (the BEST trap and the MWAC catcher) in measuring vertical sediment flux. The study was performed in a wind tunnel with sediment fluxes characterized using saltiphones. Contrary to most studies, we used the analogue output of five saltiphones mounted on top of each other to determine the total kinetic energy, which was then used to calculate aeolian sediment budgets. Absolute sediment losses during the experiments were determined using a balance located beneath the test tray. Test runs were conducted with different sand sizes and at different wind speeds. The efficiency of the two traps did not vary with the wind speed or sediment size but was affected by both the experimental setup (position of the lowest trap above the surface and number of traps in the saltation layer) and the technique used to calculate the sediment flux. Despite this, good agreement was found between sediment losses calculated from the saltiphone and those measured using the balance. The results of this study provide a framework for measuring sediment fluxes at small time resolution (seconds to milliseconds) in the field.
In aeolian research, field measurements are important for studying complex wind-driven processes for land management evaluation and model validation. Consequently, there have been many devices developed, tested, and applied to investigate a range of aeolian-based phenomena. However, determining the most effective application and data analysis techniques is widely debated in the literature. Here we investigate the effectiveness of two different sediment traps (the BEST trap and the MWAC catcher) in measuring vertical sediment flux. The study was performed in a wind tunnel with sediment fluxes characterized using saltiphones. Contrary to most studies, we used the analogue output of five saltiphones mounted on top of each other to determine the total kinetic energy, which was then used to calculate aeolian sediment budgets. Absolute sediment losses during the experiments were determined using a balance located beneath the test tray. Test runs were conducted with different sand sizes and at different wind speeds. The efficiency of the two traps did not vary with the wind speed or sediment size but was affected by both the experimental setup (position of the lowest trap above the surface and number of traps in the saltation layer) and the technique used to calculate the sediment flux. Despite this, good agreement was found between sediment losses calculated from the saltiphone and those measured using the balance. The results of this study provide a framework for measuring sediment fluxes at small time resolution (seconds to milliseconds) in the field.
Environmental factors driving the effectiveness of European agri-environmental measures in mitigating pollinator loss – a meta-analysis
Scheper, J.A. ; Holzschuh, A. ; Kuussaari, M. ; Potts, S.G. ; Rundlöf, M. ; Smith, H. ; Kleijn, D. - \ 2013
Ecology Letters 16 (2013)7. - ISSN 1461-023X - p. 912 - 920.
agricultural landscapes - farmland biodiversity - species richness - conservation - communities - management - bees - intensity - countries - schemes
In Europe, agri-environmental schemes (AES) have been introduced in response to concerns about farmland biodiversity declines. Yet, as AES have delivered variable results, a better understanding of what determines their success or failure is urgently needed. Focusing on pollinating insects, we quantitatively reviewed how environmental factors affect the effectiveness of AES. Our results suggest that the ecological contrast in floral resources created by schemes drives the response of pollinators to AES but that this response is moderated by landscape context and farmland type, with more positive responses in croplands (vs. grasslands) located in simple (vs. cleared or complex) landscapes. These findings inform us how to promote pollinators and associated pollination services in species-poor landscapes. They do not, however, present viable strategies to mitigate loss of threatened or endangered species. This indicates that the objectives and design of AES should distinguish more clearly between biodiversity conservation and delivery of ecosystem services. Keywords: Agri-environmental schemes, ecological contrast, ecosystem services, landscape context, land-use intensity, pollinators.
Pesticide use and biodiversity conservation in the Amazonian agricultural frontier
Schiesari, L. ; Waichman, A. ; Brock, T.C.M. ; Adams, C. ; Grillitsch, B. - \ 2013
Philosophical Transactions of the Royal Society B. Biological sciences 368 (2013)1619. - ISSN 0962-8436
land-use - natural enemies - south-america - deforestation - landscape - brazil - risk - sustainability - intensity
Agricultural frontiers are dynamic environments characterized by the conversion of native habitats to agriculture. Because they are currently concentrated in diverse tropical habitats, agricultural frontiers are areas where the largest number of species is exposed to hazardous land management practices, including pesticide use. Focusing on the Amazonian frontier, we show that producers have varying access to resources, knowledge, control and reward mechanisms to improve land management practices. With poor education and no technical support, pesticide use by smallholders sharply deviated from agronomical recommendations, tending to overutilization of hazardous compounds. By contrast, with higher levels of technical expertise and resources, and aiming at more restrictive markets, large-scale producers adhered more closely to technical recommendations and even voluntarily replaced more hazardous compounds. However, the ecological footprint increased significantly over time because of increased dosage or because formulations that are less toxic to humans may be more toxic to other biodiversity. Frontier regions appear to be unique in terms of the conflicts between production and conservation, and the necessary pesticide risk management and risk reduction can only be achieved through responsibility-sharing by diverse stakeholders, including governmental and intergovernmental organizations, NGOs, financial institutions, pesticide and agricultural industries, producers, academia and consumers.
Taste-nutrient relationships in commonly consumed foods
Dongen, M.V. van; Berg, M.C. van den; Vink, N. ; Kok, F.J. ; Graaf, C. de - \ 2012
The British journal of nutrition 108 (2012)1. - ISSN 0007-1145 - p. 140 - 147.
body-weight - energy-balance - sweeteners - sucrose - flavor - intensity - receptors - nutrition - sweetness - behavior
Taste is expected to represent a food's nutrient content. The objective was to investigate whether taste acts as nutrient-sensor, within the context of the current diet, which is high in processed foods. Intensities of the five basic tastes of fifty commonly consumed foods were rated by nineteen subjects (aged 21.0 (SD 1.7) years, BMI 21.5 (SD 2.0) kg/m(2)). Linear regression was used to test associations between taste and nutrient contents. Food groups based on taste were identified using cluster analysis; nutrient content was compared between food groups, using ANOVA. Sweetness was associated with mono- and disaccharides (R-2 0.45, P <0.01). Saltiness and savouriness were correlated, with r 0.92 (P
Impact of grazing management on hibernating caterpillars of the butterfly Melitaea cinxia in calcareous grasslands
Noordwijk, C.G.E. ; Flierman, D.E. ; Remke, E. ; Wallis de Vries, M.F. ; Berg, M.P. - \ 2012
Journal of Insect Conservation 16 (2012)6. - ISSN 1366-638X - p. 909 - 920.
life-history strategies - restoration management - seminatural grasslands - intraguild predation - phytophagous insects - species-diversity - conservation - intensity - herbivores - vegetation
Semi-natural grasslands are increasingly grazed by large herbivores for nature conservation purposes. For many insects such grazing is essential for the conservation of their habitat, but at the same time, populations decrease at high grazing intensity. We hypothesised that grazing management may cause increased butterfly mortality, especially for life-stages with low mobility, such as hibernating caterpillars. To test this, we measured the effect of sheep grazing on overwinter larval survival. We used the Glanville fritillary (Melitaea cinxia), which has gregarious caterpillars hibernating in silk nests, as a model species. Caterpillar nests were monitored throughout the hibernating period in calcareous grassland reserves with low and high intensity sheep grazing and in an ungrazed control treatment. After grazing, 64 % of the nests at the high intensity grazing treatment were damaged or missing, compared to 8 and 12 % at the ungrazed and low intensity grazing treatment, respectively. Nest volume and caterpillar survival were 50 % lower at the high intensity grazing treatment compared to both ungrazed and low intensity grazing treatments. Nest damage and increased mortality were mainly caused by incidental ingestion of the caterpillars by the sheep. It is likely that grazing similarly affects other invertebrates, depending on their location within the vegetation and their ability to actively avoid herbivores. This implies that the impact of grazing strongly depends on the timing of this management in relation to the phenology of the species. A greater focus on immature and inactive life-stages in conservation policy in general and particularly in action plans for endangered species is required to effectively preserve invertebrate diversity.
Estimation of rain kinetic energy from radar reflectivity and/or rain rate based on a scaling formulation of the raindrop size distribution
Yu, N. ; Boudevillain, B. ; Delrieu, G. ; Uijlenhoet, R. - \ 2012
Water Resources Research 48 (2012)4. - ISSN 0043-1397 - 13 p.
soil-erosion - spectra - model - intensity - cloud - precipitation - france
This study offers an approach to estimate the rainfall kinetic energy (KE) by rain intensity (R) and radar reflectivity factor (Z) separately or jointly on the basis of a one- or two-moment scaled raindrop size distribution (DSD) formulation, which contains (1) R and/or Z observations and (2) the dimensionless probability density function (pdf) of a scaled raindrop diameter. The key point is to explain all variability of the DSD by the evolution of the explaining moments (R and Z); hence the pdf is considered as constant. A robust method is proposed to estimate the climatological values of the parameters with a 28 month DSD data set collected in the Cévennes-Vivarais region of France. Three relationships (KE-R, KE-Z, and KE-RZ), which link the observations (R and/or Z) to rainfall kinetic energy (KE), are established. As expected, the assessment using the disdrometer data indicates that (1) because of the proximity of the moment orders, the KE-Z relationship exhibits less variability than the KE-R relationship and (2) the combination of R and Z yields a significant improvement of the estimation of KE compared to the single-moment formulations. Subsequently, a first attempt to spatialize the kinetic energy using radar and rain gauge measurements is presented for a convective event, showing a promising potential for erosion process studies. Different from the application with the disdrometer data, the performance of the KE-Z relationship degrades compared to the KE-R relationship as a result of a bias and/or the sampling characteristics of the radar data
Effects of Visual Priming on Taste-Odor Interaction
Beilen, M. van; Bult, J.H.F. ; Renken, R. ; Stieger, M.A. ; Thumfart, S. ; Cornelissen, F. ; Kooijman, V.M. - \ 2011
PLoS ONE 6 (2011)9. - ISSN 1932-6203 - 9 p.
olfactory perception - sucrose solutions - perceived flavor - color - sweetness - discrimination - intensity - mixtures - texture - vision
Little is known about the influence of visual characteristics other than colour on flavor perception, and the complex interactions between more than two sensory modalities. This study focused on the effects of recognizability of visual (texture) information on flavor perception of odorized sweet beverages. Participants rated the perceived sweetness of odorized sucrose solutions in the presence or absence of either a congruent or incongruent visual context. Odors were qualitatively reminiscent of sweet foods (strawberry and caramel) or not (savoury). Visual context was either an image of the same sweet foods (figurative context) or a visual texture derived from this product (non-figurative context). Textures were created using a texture synthesis method that preserved perceived food qualities while removing object information. Odor-taste combinations were rated sweeter within a figurative than a non-figurative context. This behaviour was exhibited for all odor-taste combinations, even in trials without images, indicating sustained priming by figurative visual context. A non-figurative context showed a transient sweetening effect. Sweetness was generally enhanced most by the strawberry odor. We conclude that the degree of recognizability of visual information (figurative versus non-figurative), influences flavor perception differently. Our results suggest that this visual context priming is mediated by separate sustained and transient processes that are differently evoked by figurative and non-figurative visual contexts. These components operate independent of the congruency of the image-odor-taste combinations.
Photosynthetic efficiency of Chlamydomonas reinhardtii in flashing light
Vejrazka, C. ; Janssen, M.G.J. ; Streefland, M. ; Wijffels, R.H. - \ 2011
Biotechnology and Bioengineering 108 (2011)12. - ISSN 0006-3592 - p. 2905 - 2913.
quantum yield - photobioreactors - microalgae - cyanobacteria - cultivation - dependence - intensity
Efficient light to biomass conversion in photobioreactors is crucial for economically feasible microalgae production processes. It has been suggested that photosynthesis is enhanced in short light path photobioreactors by mixing-induced flashing light regimes. In this study, photosynthetic efficiency and growth of the green microalga Chlamydomonas reinhardtii were measured using LED light to simulate light/dark cycles ranging from 5 to 100¿Hz at a light-dark ratio of 0.1 and a flash intensity of 1000¿µmol¿m-2¿s-1. Light flashing at 100¿Hz yielded the same photosynthetic efficiency and specific growth rate as cultivation under continuous illumination with the same time-averaged light intensity (i.e., 100¿µmol¿m-2¿s-1). The efficiency and growth rate decreased with decreasing flash frequency. Even at 5¿Hz flashing, the rate of linear electron transport during the flash was still 2.5 times higher than during maximal growth under continuous light, suggesting storage of reducing equivalents during the flash which are available during the dark period. In this way the dark reaction of photosynthesis can continue during the dark time of a light/dark cycle. Understanding photosynthetic growth in dynamic light regimes is crucial for model development to predict microalgal photobioreactor productivities. Biotechnol. Bioeng. 2011;108: 2905–2913. © 2011 Wiley Periodicals, Inc
Fast and simple model for atmospheric radiative transfer
Seidel, F.C. ; Kokhanovsky, A.A. ; Schaepman, M.E. - \ 2010
Atmospheric Measurement Techniques 3 (2010). - ISSN 1867-1381 - p. 1129 - 1141.
aerosol retrieval - transfer code - scattering - polarization - reflectance - quantities - intensity - radiance - light - 6s
Radiative transfer models (RTMs) are of utmost importance for quantitative remote sensing, especially for compensating atmospheric perturbation. A persistent trade-off exists between approaches that prefer accuracy at the cost of computational complexity, versus those favouring simplicity at the cost of reduced accuracy. We propose an approach in the latter category, using analytical equations, parameterizations and a correction factor to efficiently estimate the effect of molecular multiple scattering. We discuss the approximations together with an analysis of the resulting performance and accuracy. The proposed Simple Model for Atmospheric Radiative Transfer (SMART) decreases the calculation time by a factor of more than 25 in comparison to the benchmark RTM 6S on the same infrastructure. The relative difference between SMART and 6S is about 5% for spaceborne and about 10% for airborne computations of the atmospheric reflectance function. The combination of a large solar zenith angle (SZA) with high aerosol optical depth (AOD) at low wavelengths lead to relative differences of up to 15%. SMART can be used to simulate the hemispherical conical reflectance factor (HCRF) for spaceborne and airborne sensors, as well as for the retrieval of columnar AOD
Editor's Choice: Unveiling below-ground species abundance in a biodiversity experiment: a test of vertical niche differentation among grassland species
Semchenko, M. ; Mommer, L. - \ 2010
Journal of Ecology 98 (2010)5. - ISSN 0022-0477 - p. 1 - 1.
plant competition - interspecific competition - community ecology - traits - growth - intensity - gradient - survival - density - ability
P>1. Currently, there is a debate among plant ecologists on the concepts of the intensity of competition and the importance of competition, which is central to many issues of modern plant population ecology and plant community ecology. 2. It is problematic that the current measures of intensity and importance of competition, typically, are reported as dimensionless indices because they hide the fact that both indices are functions of plant density and the level of the environmental gradient. 3. Here, a new formulation of the concepts is suggested, which explicitly highlights the functional dependencies on plant density and the level of the environmental gradient. The new measures are a generalization of the previous indices and correspond to the previous indices in the case of a simple experimental design. 4. The suggested measures of the intensity and importance of competition are exemplified using data from a response surface competition experiment between Agrostis capillaris and Festuca ovina along a herbicide gradient, where the expected clear effect of plant density was demonstrated. 5. Synthesis. As the suggested measures of the intensity and importance of competition explicitly highlight the functional dependencies on plant density and the level of the environmental gradient, we think that they will help to ensure a closer connection between experimental plant ecology and the attempts to model plant populations and communities.
Photosynthetic efficiency of Chlorella sorokiniana in a turbulently mixed short light-path photobioreactor
Kliphuis, A.M.J. ; Winter, L. de; Vejrazka, C. ; Martens, D.E. ; Janssen, M.G.J. ; Wijffels, R.H. - \ 2010
Biotechnology Progress 26 (2010)3. - ISSN 8756-7938 - p. 687 - 696.
spirulina-platensis cyanobacteria - rotating cylinders - growth-inhibition - cell densities - cultures - flow - productivity - co2 - intensity - stability
To be able to study the effect of mixing as well as any other parameter on productivity of algal cultures, we designed a lab-scale photobioreactor in which a short light path (SLP) of (12 mm) is combined with controlled mixing and aeration. Mixing is provided by rotating an inner tube in the cylindrical cultivation vessel creating Taylor vortex flow and as such mixing can be uncoupled from aeration. Gas exchange is monitored on-line to gain insight in growth and productivity. The maximal productivity, hence photosynthetic efficiency, of Chlorella sorokiniana cultures at high light intensities (1,500 µmol m-1 s-1) was investigated in this Taylor vortex flow SLP photobioreactor. We performed duplicate batch experiments at three different mixing rates: 70, 110, and 140 rpm, all in the turbulent Taylor vortex flow regime. For the mixing rate of 140 rpm, we calculated a quantum requirement for oxygen evolution of 21.2 mol PAR photons per mol O2 and a yield of biomass on light energy of 0.8 g biomass per mol PAR photons. The maximal photosynthetic efficiency was found at relatively low biomass densities (2.3 g L-1) at which light was just attenuated before reaching the rear of the culture. When increasing the mixing rate twofold, we only found a small increase in productivity. On the basis of these results, we conclude that the maximal productivity and photosynthetic efficiency for C. sorokiniana can be found at that biomass concentration where no significant dark zone can develop and that the influence of mixing-induced light/dark fluctuations is marginal
Adverse effectsof agricultaral intensification and climate change on breeding habitat quality of Blacktailed Godwits Limosa l. limosa in the Netherlands
Kleijn, D. ; Schekkerman, H. ; Dimmers, W.J. ; Kats, R.J.M. van; Melman, T.C.P. ; Teunissen, W.A. - \ 2010
Ibis 152 (2010)3. - ISSN 0019-1019 - p. 475 - 486.
farmland bird populations - lapwing vanellus-vanellus - agri-environment schemes - grassland management - chicks - eggs - biodiversity - intensity - britain - europe
Agricultural intensification is one of the main drivers of farmland bird declines, but effects on birds may be confounded with those of climate change. Here we examine the effects of intensification and climate change on a grassland breeding wader, the Black-tailed Godwit Limosa l. limosa, in the Netherlands. Population decline has been linked to poor chick survival which, in turn, has been linked to available foraging habitat. Foraging habitat of the nidifugous chicks consists of uncut grasslands that provide cover and arthropod prey. Conservation measures such as agri-environment schemes aim to increase the availability of chick foraging habitat but have not yet been successful in halting the decline. Field observations show that since the early 1980s, farmers advanced their first seasonal mowing or grazing date by 15 days, whereas Godwits did not advance their hatching date. Ringing data indicate that between 1945 and 1975 hatching dates advanced by about 2 weeks in parallel with the advancement of median mowing dates. Surprisingly, temperature sums at median mowing and hatching dates suggest that while the agricultural advancement before 1980 was largely due to agricultural intensification, after 1980 it was largely due to climate change. Examining arthropod abundance in a range of differently managed grasslands revealed that chick food abundance was little affected but that food accessibility in intensively used tall swards may be problematic for chicks. Our results suggest that, compared with 25 years ago, nowadays (1) a much higher proportion of clutches and chicks are exposed to agricultural activities, (2) there is little foraging habitat left when chicks hatch and (3) because of climate change, the vegetation in the remaining foraging habitat is taller and denser and therefore of lower quality. This indicates that for agri-environment schemes to make a difference, they should not only be implemented in a larger percentage of the breeding area than the current maxima of 20–30% but they should also include measures that create more open, accessible swards
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