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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Top-down pressure on a coastal ecosystem by harbor seals
Aarts, Geert ; Brasseur, Sophie ; Poos, Jan Jaap ; Schop, Jessica ; Kirkwood, Roger ; Kooten, Tobias Van; Mul, Evert ; Reijnders, Peter ; Rijnsdorp, Adriaan D. ; Tulp, Ingrid - \ 2019
Ecosphere 10 (2019)1. - ISSN 2150-8925 - p. e02538 - e02538.
demersal fish - diet - harbor seal - impact - intertidaL - Phoca vitulina - predation pressure - sealing - Subtidal - top-down regulation - top predator
Historic hunting has led to severe reductions of many marine mammal species across the globe. After hunting ceased, some populations have recovered to pre-exploitation levels and may have regained their prominent position as top predator in marine ecosystems. Also, the harbor seal population in the international Wadden Sea grew at an exponential rate following a ban on seal hunting in 1960s, and the current number ~38,000 is close to the historic population size. Here we estimate the impact of the harbor seal predation on the fish community in the Wadden Sea and nearby coastal waters. Fish remains in fecal samples and published estimates on the seal’s daily energy requirement were used to estimate prey selection and the magnitude of seal consumption. Estimates on prey abundance were derived from demersal fish surveys, and fish growth was estimated using a Dynamic Energy Budget model. GPS tracking provided information on where seals most likely caught their prey. Harbor seals hauling-out in the Dutch Wadden Sea fed predominantly on demersal fish, for example, flatfish species (flounder, sole, plaice, dab), but also on sandeel, cod, and whiting. Although harbor seals acquire the majority of prey further offshore in the adjacent North Sea, and only spend 14% of their diving time in the Wadden Sea, seal predation was still estimated to cause an average annual mortality of 43% of the remaining fish in the Wadden Sea and 60% in the nearby shallow coastal waters (<20 m). There were however large sources of uncertainty in the estimated impact of seals on fish, including the migration of fish between the North Sea and Wadden Sea, and catchability estimates of the fish survey sampling gear, particularly for sandeel and other pelagic fish species. Our estimate suggested a considerable top-down pressure by harbor seals on demersal fish. However, predation by seals may also alleviate density-dependent competition between the remaining fish, allowing for increased fish growth, and partly compensating for the reduction in fish numbers. This study shows that recovering coastal marine mammal populations could become an important component in the functioning of shallow coastal ecosystems.
SCAR Conference 2017: 2017 "Research and innovation policy, state-of-play and the role of SCAR in the European Bioeconomy", 4-5 December 2017, Tallinn
Bunthof, Christine - \ 2017
SCAR - CASA - Bioeconomy - impact - policy - representation - inclusion - inclusiveness - policy development
On 4 and 5 December 2017, the second conference of the Standing Committee for Agricultural Research (SCAR) took place in Tallinn, Estonia, entitled "Research and innovation policy, state-of-play and the role of SCAR in the European Bioeconomy". The conference focused on the work and impact of SCAR on European and national policy development and representation and inclusion challenges for SCAR. It hosted over sixty-five participants from twenty-seven countries and was co-organised by the Estonian presidency of the Council of the European Union and SCAR CASA.
Stakeholder initiatives in flood risk management : exploring the role and impact of bottom-up initiatives in three ‘Room for the River’ projects in the Netherlands
Edelenbos, Jurian ; Buuren, Arwin Van; Roth, Dik ; Winnubst, Madelinde - \ 2017
Journal of Environmental Planning and Management 60 (2017)1. - ISSN 0964-0568 - p. 47 - 66.
citizen initiatives - flood management - governance - impact - stakeholders

In recent years stakeholder participation has become a popular topic in flood management. Little is known about how and under which circumstances local stakeholders initiate and develop successful flood management strategies and how governmental actors respond to them. Drawing on theories of social movements, stakeholder participation, and citizenship, this paper analyses how local stakeholder initiatives in the Dutch ‘Room for the River’ programme evolve and, in turn, influence such governmental plans and actions. The description and comparative analysis of the three cases leads to three conclusions: first, in all cases, forms of local self-organization play a role, but its impacts are highly dependent on the mix of strategies chosen. Second, forms of coproduction between local stakeholders and government actors are the most viable strategy to realize the positive impact of local initiatives. Third, government agencies tend to react to local initiatives defensively. Much depends on timing and connecting to the right people.

Strategies to adapt to climate change in the Central Rift Valley of Ethiopia: landscape impact assessment for on-farm adaptation
Bitew, A.M. - \ 2015
Wageningen University. Promotor(en): Leo Stroosnijder, co-promotor(en): Saskia Keesstra. - Wageningen : Wageningen University - ISBN 9789462574625 - 170
klimaatverandering - klimaatadaptatie - landschap - impact - ecologische beoordeling - ethiopië - climatic change - climate adaptation - landscape - impact - ecological assessment - ethiopia

PhD Thesis Title: Strategies to adapt to climate change in the Central Rift Valley of Ethiopia: landscape impact assessment for on-farm adaptation


Alemayehu Muluneh Bitew

Agriculture and the economies of Ethiopia are highly sensitive to climatic fluctuations. Rainfall is the most important determinant of Ethiopia’s economic success or failure from year to year. A 10% decrease in seasonal rainfall from the long-term average generally translates into a 4.4% decrease in the country’s food production. Studies indicate that future climate change scenario by 2050 could also cause Ethiopian GDP to be 8-10% smaller than under a no-climate change baseline. The Central Rift Valley (CRV) of Ethiopia is a potential food producing area and yet one of the most drought prone areas in the country and already face an enormous food security challenge. The main objective of this study was, therefore, to quantify changes in current and future growing season rainfall characteristics including rainfall extremes and to evaluate their impacts with the intension of evaluating and developing potential adaptation options for maize cropping in the drought-prone CRV of Ethiopia. Projections for future climate in the CRV suggested that the Belg rainfall which is already erratic, occurring very late or failing altogether for the current climate will continue to decrease during the rest of this century which makes future Belg crop production very difficult. But, the Kiremt season total rainfall is likely to show an increase. Our field experiment and modelling has proven that for the current climate and future projections supplemental irrigation can avoid total crop failure in drought years and is a viable option to improve food security in the Rift Valley dry lands of Ethiopia. Furthermore, shifting sowing period of maize from the current Belg season (April or May) to the first month of Kiremt season (June) can offset the predicted yield reduction caused by climate change.

Using selection index theory to estimate consistency of multi-locus linkage disequilibrium across populations
Wientjes, Y.C.J. ; Veerkamp, R.F. ; Calus, M.P.L. - \ 2015
BMC Genetics 16 (2015). - ISSN 1471-2156
genomic breeding values - genetic-relationship information - quantitative trait loci - dairy-cattle breeds - prediction - accuracy - haplotype - markers - impact - lines
The potential of combining multiple populations in genomic prediction is depending on the consistency of linkage disequilibrium (LD) between SNPs and QTL across populations. We investigated consistency of multi-locus LD across populations using selection index theory and investigated the relationship between consistency of multi-locus LD and accuracy of genomic prediction across different simulated scenarios. In the selection index, QTL genotypes were considered as breeding goal traits and SNP genotypes as index traits, based on LD among SNPs and between SNPs and QTL. The consistency of multi-locus LD across populations was computed as the accuracy of predicting QTL genotypes in selection candidates using a selection index derived in the reference population. Different scenarios of within and across population genomic prediction were evaluated, using all SNPs or only the four neighboring SNPs of a simulated QTL. Phenotypes were simulated using different numbers of QTL underlying the trait. The relationship between the calculated consistency of multi-locus LD and accuracy of genomic prediction using a GBLUP type of model was investigated.
The accuracy of predicting QTL genotypes, i.e. the measure describing consistency of multi-locus LD, was much lower for across population scenarios compared to within population scenarios, and was lower when QTL had a low MAF compared to QTL randomly selected from the SNPs. Consistency of multi-locus LD was highly correlated with the realized accuracy of genomic prediction across different scenarios and the correlation was higher when QTL were weighted according to their effects in the selection index instead of weighting QTL equally. By only considering neighboring SNPs of QTL, accuracy of predicting QTL genotypes within population decreased, but it substantially increased the accuracy across populations.
Consistency of multi-locus LD across populations is a characteristic of the properties of the QTL in the investigated populations and can provide more insight in underlying reasons for a low empirical accuracy of across population genomic prediction. By focusing in genomic prediction models only on neighboring SNPs of QTL, multi-locus LD is more consistent across populations since only short-range LD is considered, and accuracy of predicting QTL genotypes of individuals from another population is increased.
Firms’ willingness to invest in a water fund to improve water-related ecosystem services in the Lake Naivasha basin, Kenya
Mulatu, D.W. ; Oel, P.R. van; Veen, A. van der - \ 2015
Water International 40 (2015)3. - ISSN 0250-8060 - p. 463 - 482.
tropical forestry projects - environmental services - market actors - payments - management - behavior - private - choice - impact
A valuation scenario was designed using a contingent-valuation approach and presented to decision makers in business firms in Kenya’s Lake Naivasha basin to test how applicable a water fund might be as a potential financing mechanism for a payment for water-related ecosystem services scheme. The findings indicate that measuring a firm’s willingness to invest in ecosystem services could help determine whether a firm would invest and engage with other stakeholders to pool their investments in ecosystem services. Linking the institutional decision-making behaviour of a firm and its willingness to invest in a water fund is the novelty of this article.
Characterisation of hydroclimatological trends and variability in the Lake Naivasha basin, Kenya
Odongo, V.O. ; Tol, C. van der; Oel, P.R. van; Meins, F.M. ; Becht, R. ; Onyando, J.O. ; Su, Z. - \ 2015
Hydrological Processes 29 (2015)15. - ISSN 0885-6087 - p. 3276 - 3293.
long-term persistence - time-series - hurst phenomenon - climatic-change - impact - identification - hydrology - ethiopia - water - precipitation
Recent hydro-climatological trends and variability characteristics were investigated for the Lake Naivasha basin with the aim of understanding the changes in water balance components and their evolution over the past 50¿years. Using a Bayesian change point analysis and modified Mann–Kendall tests, time series of annual mean, maximum, minimum, and seasonal precipitation and flow, as well as annual mean lake volumes, were analysed for the period 1960–2010 to uncover possible abrupt shifts and gradual trends. Double cumulative curve analysis was used to investigate the changes in hydrological response attributable to either human influence or climatic variability. The results indicate a significant decline in lake volumes at a mean rate of 9.35¿×¿106¿m3¿year-1. Most of the river gauging stations showed no evidence of trends in the annual mean and maximum flows as well as seasonal flows. Annual minimum flows, however, showed abrupt shifts and significant (upward/downward) trends at the main outlet stations. Precipitation in the basin showed no evidence of abrupt shifts, but a few stations showed gradual decline. The observed changes in precipitation could not explain the decline in both minimum flows and lake volumes. The findings show no evidence of any impact of climate change for the Lake Naivasha basin over the past 50¿years. This implies that other factors, such as changes in land cover and infrastructure development, have been responsible for the observed changes in streamflow and lake volumes.
Potential of extensification of European agriculture for a more sustainable food system; the case for nitrogen and livestock
Grinsven, J.J.M. van; Erisman, J.W. ; Vries, W. de; Westhoek, H. - \ 2015
Environmental Research Letters 10 (2015)2. - ISSN 1748-9326 - 10 p.
dairy farms - management - intensification - welfare - trends - impact - costs - meat - pig
Most global strategies for future food security focus on sustainable intensification of production of food and involve increased use of nitrogen fertilizer and manure. The external costs of current high nitrogen (N) losses from agriculture in the European Union, are 0.3–1.9% of gross domestic product (GDP) in 2008. We explore the potential of sustainable extensification for agriculture in the EU and The Netherlands by analysing cases and scenario studies focusing on reducing N inputs and livestock densities. Benefits of extensification are higher local biodiversity and less environmental pollution and therefore less external costs for society. Extensification also has risks such as a reduction of yields and therewith a decrease of the GDP and farm income and a smaller contribution to the global food production, and potentially an i0ncrease of global demand for land. We demonstrate favourable examples of extensification. Reducing the N fertilization rate for winter wheat in Northwest Europe to 25–30% below current N recommendations accounts for the external N cost, but requires action to compensate for a reduction in crop yield by 10–20%. Dutch dairy and pig farmers changing to less intensive production maintain or even improve farm income by price premiums on their products, and/or by savings on external inputs. A scenario reducing the Dutch pig and poultry sector by 50%, the dairy sector by 20% and synthetic N fertilizer use by 40% lowers annual N pollution costs by 0.2–2.2 billion euro (40%). This benefit compensates for the loss of GDP in the primary sector but not in the supply and processing chain. A 2030 scenario for the EU27 reducing consumption and production of animal products by 50% (demitarean diet) reduces N pollution by 10% and benefits human health. This diet allows the EU27 to become a food exporter, while reducing land demand outside Europe in 2030 by more than 100 million hectares (2%), which more than compensates increased land demand when changing to organic farming. We conclude that in Europe extensification of agriculture is sustainable when combined with adjusted diets and externalization of environmental costs to food prices.
What reported food-evoked emotions may add: A model to predict consumer food choice
Gutjar, S. ; Dalenberg, J.R. ; Graaf, C. de; Wijk, R.A. de; Palascha, A. ; Renken, Remco J. ; Jager, G. - \ 2015
Food Quality and Preference 45 (2015). - ISSN 0950-3293 - p. 140 - 148.
consumption experience - responses - satisfaction - liking - taste - package - questionnaires - behavior - design - impact
Food-evoked emotions provide information that goes beyond the information from traditional hedonic ratings. The objectives of our study were: (i) to investigate how intrinsic (sensory) and extrinsic (packaging) cues affect consumers’ emotional responses to foods, and (ii) to explore whether emotional responses to these cues combined with liking, predict actual food choice. Participants (n = 103) rated emotional responses to seven products under a blind taste, a package and a package and taste condition using the EsSense Profile™. During the blind taste condition participants also scored liking of the products. Test products were breakfast drinks and desserts. Food choice was measured in two different breakfast sessions reflecting a different choice context. In one choice context, products were presented blind to taste, after which participants chose one out of the seven foods to consume for breakfast. In the other choice context, participants based their choice on the package of the seven foods without tasting them. Results showed that emotions evoked by food products could be organised in a two-dimensional space, representing a valence (pleasantness) and an activation/arousal dimension. Specific emotional profiles generated for products differed across the blind taste, package and the package and taste condition, meaning that intrinsic and extrinsic product properties elicit in part different emotions. Liking and valence together had the strongest predictive value for product choice based on the product’s taste. The combination of liking, valence and arousal had the strongest predictive value for package-based choice. In conclusion, food-evoked emotions add predictive value to solely liking ratings, and may guide consumers’ product choice behaviour.
Eight challenges in modelling infectious livestock diseases
Brooks-Pollock, E. ; Jong, M. de; Keeling, M.J. ; Klinkenberg, D. ; Wood, J.L.N. - \ 2015
Epidemics 10 (2015). - ISSN 1755-4365 - p. 1 - 5.
mouth-disease - great-britain - bovine tuberculosis - virus transmission - avian influenza - dynamic-model - uk foot - cattle - epidemic - impact
The transmission of infectious diseases of livestock does not differ in principle from disease transmission in any other animals, apart from that the aim of control is ultimately economic, with the influence of social, political and welfare constraints often poorly defined. Modelling of livestock diseases suffers simultaneously from a wealth and a lack of data. On the one hand, the ability to conduct transmission experiments, detailed within-host studies and track individual animals between geocoded locations make livestock diseases a particularly rich potential source of realistic data for illuminating biological mechanisms of transmission and conducting explicit analyses of contact networks. On the other hand, scarcity of funding, as compared to human diseases, often results in incomplete and partial data for many livestock diseases and regions of the world. In this overview of challenges in livestock disease modelling, we highlight eight areas unique to livestock that, if addressed, would mark major progress in the area.
Towards a set of design principles for developing oral presentation competence: A synthesis of research in higher education
Ginkel, S.O. van; Gulikers, J.T.M. ; Biemans, H.J.A. ; Mulder, M. - \ 2015
Educational Research Review 14 (2015). - ISSN 1747-938X - p. 62 - 80.
presentation skills - communication competence - feedback - students - impact - intervention - apprehension - performance - reflection - anxiety
Developing oral presentation competence is an essential objective in higher education. However, a comprehensive picture of effective learning environment characteristics for encouraging oral presentation performance is lacking hitherto. This review identifies and classifies relevant studies with the aim of deducing a set of design principles with underlying conceptual and empirical argumentations for developing this competence. Fifty-two publications from the last 20 years were selected through a systematic search in four scientific databases. Subsequently, all studies were categorized with respect to student characteristics, learning environment characteristics, learning processes and outcomes. The synthesis of these studies resulted in the formulation of seven design principles, addressing the instruction, learning and assessment sides of the learning environment. These design principles include the following learning environment characteristics: learning objectives, learning task, behaviour modelling, opportunity to practice, intensity and timing of feedback, peer assessment and self-assessment. Finally, an agenda for future research is discussed.
Effect of feed-related farm characteristics on relative values of genetic traits in dairy cows to reduce greenhouse gas emissions along the chain
Middelaar, C.E. van; Berentsen, P.B.M. ; Dijkstra, J. ; Arendonk, J.A.M. van; Boer, I.J.M. de - \ 2015
Journal of Dairy Science 98 (2015)7. - ISSN 0022-0302 - p. 4889 - 4903.
life-cycle assessment - genomic selection - economic values - milk-production - methane - cattle - mitigation - impact - level - model
Breeding has the potential to reduce greenhouse gas (GHG) emissions from dairy farming. Evaluating the effect of a 1-unit change (i.e., 1 genetic standard deviation improvement) in genetic traits on GHG emissions along the chain provides insight into the relative importance of genetic traits to reduce GHG emissions. Relative GHG values of genetic traits, however, might depend on feed-related farm characteristics. The objective of this study was to evaluate the effect of feed-related farm characteristics on GHG values by comparing the values of milk yield and longevity for an efficient farm and a less efficient farm. The less efficient farm did not apply precision feeding and had lower feed production per hectare than the efficient farm. Greenhouse gas values of milk yield and longevity were calculated by using a whole-farm model and 2 different optimization methods. Method 1 optimized farm management before and after a change in genetic trait by maximizing labor income; the effect on GHG emissions (i.e., from production of farm inputs up to the farm gate) was considered a side effect. Method 2 optimized farm management after a change in genetic trait by minimizing GHG emissions per kilogram of milk while maintaining labor income and milk production at least at the level before the change in trait; the effect on labor income was considered a side effect. Based on maximizing labor income (method 1), GHG values of milk yield and longevity were, respectively, 279 and 143 kg of CO2 equivalents (CO2e)/unit change per cow per year on the less efficient farm, and 247 and 210 kg of CO2e/unit change per cow per year on the efficient farm. Based on minimizing GHG emissions (method 2), GHG values of milk yield and longevity were, respectively, 538 and 563 kg of CO2e/unit change per cow per year on the less efficient farm, and 453 and 441 kg of CO2e/unit change per cow per year on the efficient farm. Sensitivity analysis showed that, for both methods, the absolute effect of a change in genetic trait depends on model inputs, including prices and emission factors. Substantial changes in relative importance between traits due to a change in model inputs occurred only in case of maximizing labor income. We concluded that assumptions regarding feed-related farm characteristics affect the absolute level of GHG values, as well as the relative importance of traits to reduce emissions when using a method based on maximizing labor income. This is because optimizing farm management based on maximizing labor income does not give any incentive for lowering GHG emissions. When using a method based on minimizing GHG emissions, feedrelated farm characteristics affected the absolute level of the GHG values, but the relative importance of the traits scarcely changed: at each level of efficiency, milk yield and longevity were equally important. Key words: breeding, milk yield, longevity, economic value.
Loss of Plant Species Diversity Reduces Soil Erosion Resistance
Berendse, F. ; Ruijven, J. van; Jongejans, E. ; Keesstra, S.D. - \ 2015
Ecosystems 18 (2015)5. - ISSN 1432-9840 - p. 881 - 888.
biodiversity loss - productivity - ecology - stability - future - impact
In many estuarine areas around the world, the safety of human societies depends on the functioning of embankments (dikes) that provide protection against river floods and storm tides. Vegetation on land-side slopes protects these embankments from erosion by heavy rains or overtopping waves. We carried out a field experiment to investigate the effect of plant species diversity on soil loss through erosion on a simulated dike. The experiment included four diversity treatments (1, 2, 4, and 8 species). In the third year of the experiment, we measured net annual soil loss by measuring erosion losses every 2 weeks. We show that loss of plant species diversity reduces erosion resistance on these slopes: net annual soil loss increased twofold when diversity declines fourfold. The different plant species had strongly diverging effects on soil erosion, both in the single-species and in the multi-species plots. Analysis of the dynamics of the individual species revealed that the main mechanism explaining the strong effects of plant species diversity on soil erosion is the compensation or insurance effect, that is, the capacity of diverse communities to supply species to take over the functions of species that went extinct as a consequence of fluctuating environmental conditions. We conclude that the protection and restoration of diverse plant communities on embankments and other vegetated slopes are essential to minimize soil erosion, and can contribute to greater safety in the most densely populated areas of the world. Key words: plant species diversity; soil erosion; plant competition; insurance effect; compensation effect.
ERP in agriculture: Lessons learned from the Dutch horticulture
Verdouw, C.N. ; Robbemond, R.M. ; Wolfert, J. - \ 2015
Computers and Electronics in Agriculture 114 (2015). - ISSN 0168-1699 - p. 125 - 133.
critical success factors - enterprise systems - future internet - supply chains - management - impact - model - perspective - innovation - adoption
Farming nowadays is a complex managerial task that imposes stringent requirements on farm management information systems. In other sectors, Enterprise Resource Planning (ERP) systems are widely implemented to meet such requirements. This paper assesses the applicability of ERP systems in the agri-food domain by investigating the experiences of agri-food companies that already have implemented an ERP system. More specifically, the research has analyzed the drivers and barriers for adoption of ERP in the Dutch horticultural sector. The results show that the alignment of ERP with the specific characteristics and requirements of a company is a crucial challenge in order to capitalize the benefits of ERP. The study also shows that it is possible to deal with this challenge. The majority of the respondents (62%) is positive about of the match of the specific ERP solution with the company’s business processes during implementation. Most of these respondents have implemented a system that includes a sector-specific layer around a standard ERP solution. Moreover, it is concluded that a proper management of the orientation, selection and implementation processes is of crucial importance for a successful adoption.
How good is good enough? Data requirements for reliable crop yield simulations and yield-gap analysis
Grassini, P. ; Bussel, L.G.J. van; Wart, J. van; Wolf, J. ; Claessens, L. ; Yang, H. ; Boogaard, H.L. ; Groot, H.L.E. de; Ittersum, M.K. van; Cassman, K.G. - \ 2015
Field Crops Research 177 (2015). - ISSN 0378-4290 - p. 49 - 63.
pedo-transfer functions - daily solar-radiation - water-use efficiency - climate-change - distribution maps - weather data - corn-belt - maize - model - impact
Numerous studies have been published during the past two decades that use simulation models to assesscrop yield gaps (quantified as the difference between potential and actual farm yields), impact of climatechange on future crop yields, and land-use change. However, there is a wide range in quality and spatialand temporal scale and resolution of climate and soil data underpinning these studies, as well as widelydiffering assumptions about cropping-system context and crop model calibration. Here we present anexplicit rationale and methodology for selecting data sources for simulating crop yields and estimatingyield gaps at specific locations that can be applied across widely different levels of data availability andquality. The method consists of a tiered approach that identifies the most scientifically robust require-ments for data availability and quality, as well as other, less rigorous options when data are not availableor are of poor quality. Examples are given using this approach to estimate maize yield gaps in the stateof Nebraska (USA), and at a national scale for Argentina and Kenya. These examples were selected torepresent contrasting scenarios of data availability and quality for the variables used to estimate yieldgaps. The goal of the proposed methods is to provide transparent, reproducible, and scientifically robustguidelines for estimating yield gaps; guidelines which are also relevant for simulating the impact of cli-mate change and land-use change at local to global spatial scales. Likewise, the improved understandingof data requirements and alternatives for simulating crop yields and estimating yield gaps as describedhere can help identify the most critical “data gaps” and focus global efforts to fill them. A related paper(Van Bussel et al., 2015) examines issues of site selection to minimize data requirements and up-scalingfrom location-specific estimates to regional and national spatial scales.
From field to atlas: Upscaling of location-specific yield gap estimates
Bussel, L.G.J. van; Grassini, P. ; Wart, J. van; Wolf, J. ; Claessens, L. ; Yang, H. ; Boogaard, H.L. ; Groot, H.L.E. de; Saito, K. ; Cassman, K.G. ; Ittersum, M.K. van - \ 2015
Field Crops Research 177 (2015). - ISSN 0378-4290 - p. 98 - 108.
climate-change - weather data - crop yields - input data - resolution - model - scale - impact - maize - systems
Accurate estimation of yield gaps is only possible for locations where high quality local data are available,which are, however, lacking in many regions of the world. The challenge is how yield gap estimates basedon location-specific input data can be used to obtain yield gap estimates for larger spatial areas. Hence,insight about the minimum number of locations required to achieve robust estimates of yield gaps atlarger spatial scales is essential because data collection at a large number of locations is expensive andtime consuming. In this paper we describe an approach that consists of a climate zonation scheme supple-mented by agronomical and locally relevant weather, soil and cropping system data. Two elements of thismethodology are evaluated here: the effects on simulated national crop yield potentials attributable tomissing and/or poor quality data and the error that might be introduced in scaled up yield gap estimatesdue to the selected climate zonation scheme. Variation in simulated yield potentials among weatherstations located within the same climate zone, represented by the coefficient of variation, served as ameasure of the performance of the climate zonation scheme for upscaling of yield potentials.We found that our approach was most appropriate for countries with homogeneous topography andlarge climate zones, and that local up-to-date knowledge of crop area distribution is required for selectingrelevant locations for data collection. Estimated national water-limited yield potentials were found to berobust if data could be collected that are representative for approximately 50% of the national harvestedarea of a crop. In a sensitivity analysis for rainfed maize in four countries, assuming only 25% coverageof the national harvested crop area (to represent countries with poor data availability), national water-limited yield potentials were found to be over- or underestimated by 3 to 27% compared to estimateswith the recommended crop area coverage of =50%. It was shown that the variation of simulated yieldpotentials within the same climate zone is small. Water-limited potentials in semi-arid areas are anexception, because the climate zones in these semi-arid areas represent aridity limits of crop productionfor the studied crops. We conclude that the developed approach is robust for scaling up yield gap estimatesfrom field, i.e. weather station data supplemented by local soil and cropping system data, to regional andnational levels. Possible errors occur in semi-arid areas with large variability in rainfall and in countrieswith more heterogeneous topography and climatic conditions in which data availability hindered full application of the approach.
Empty pockets, empty ponds? Disadoption of water harvesting technologies in Ethiopia
Wakeyo, M.B. ; Gardebroek, C. - \ 2015
Journal of Arid Environments 120 (2015). - ISSN 0140-1963 - p. 75 - 86.
supplemental irrigation - agricultural extension - semiarid region - adoption - systems - productivity - africa - impact - china - soil
This study analyses disadoption of water harvesting technologies in Ethiopia where the average disadiption rate in the sample areas is as high as 42%. Given that Ethiopia is a drought-prone country with 95% of its crop production being rain-fed, such a high disadoption rate for irrigation technologies is surprising and urges investigation. Using panel data on 332 Ethiopian farm households collected in 2005 and 2010 we estimate a logit model to identify factors underlying disadoption. We find farm-household, economic, technology-specific, and natural condition variables that relate to disadoption. Mainly, shortage of plastic-sheets, altitude, and distance to market increase disadoption whereas education, experience with water harvesting (learning-by-doing), farm profit, availability of family labour, access to credit, ease of selling output, growing perennial crops, and distance from natural water sources decrease the probability of disadiption. There is no evidence that malaria has a significant effect on disadoption. Based on these findings, improved supply of plastic sheets and motor pumps, and advise to afmers on appropriate crops, credit and improved market accesses could ontribute to decreasing disadoption of water harvesting technologies.
Site-specific dynamics in remnant populations of Northern Wheatears Oenanthe oenanthe in the Netherlands
Oosten, H.H. van; Turnhout, C. van; Hallmann, C.A. ; Majoor, F. ; Roodbergen, M. ; Schekkerman, H. ; Versluijs, R. ; Waasdorp, S. ; Siepel, H. - \ 2015
Ibis 157 (2015)1. - ISSN 0019-1019 - p. 91 - 102.
spatial synchrony - environmental correlation - scale - dispersal - birds - immigration - landscape - density - impact - space
Dynamics of populations may be synchronized at large spatial scales, indicating driving forces acting beyond local scales, but may also vary locally as a result of site-specific conditions. Conservation measures for fragmented and declining populations may need to address such local effects to avoid local extinction before measures at large spatial scales become effective. To assess differences in local population dynamics, we aimed to determine the demographic drivers controlling population trends in three remaining populations of the Northern Wheatear Oenanthe oenanthe in the Netherlands, as a basis for conservation actions. An integrated population model (IPM) was fitted to field data collected in each site in 2007–2011 to estimate fecundity, survival and immigration. Sites were 40–120 km apart, yet first-year recruits were observed to move between some of the sites, albeit rarely. All three populations were equally sensitive to changes in fecundity and first-year survival. One population was less sensitive to adult survival but more sensitive to immigration. A life table response experiment suggested that differences in immigration were important determinants of differences in population growth between sites. Given the importance of immigration for local dynamics along with high philopatry, resulting in low exchange between sites, creating a metapopulation structure by improving connectivity and the protection of local populations are important for the conservation of these populations. Site-specific conservation actions will therefore be efficient and, for the short term, we propose different site-specific conservation actions.
Basic principles of analysing biological and technical variation in non-destructive data
Tijskens, L.M.M. ; Schouten, R.E. ; Konopacki, P. ; Jongbloed, G. - \ 2015
Computers and Electronics in Agriculture 111 (2015). - ISSN 0168-1699 - p. 121 - 126.
keeping quality - postharvest - variance - behavior - impact - color - fruit - age
More and more, the omnipresent variation between individual items in a batch is taken into account by using special analysing techniques like mixed effects and indexed regression. In this paper the assumptions upon which these techniques are based, are explained, based on a simulated data set. The most important issue is the separation of biological variation and the technical variation (or measuring error). The techniques are further elucidated with some examples from practise (skin colour apples in storage, softening of melons in storage and water loss in plums, melons and mandarins), to show the increased reliability of the analyses. Since variation is always present in any measured data set, the techniques are applicable in all fields working with living material.
Analysing chemical-induced changes in macroinvertebrate communities in aquatic mesocosm experiments: a comparison of methods
Szöcs, E. ; Brink, P.J. van den; Lagadic, L. ; Caquet, T. ; Roucaute, M. ; Auber, A. ; Bayona, Y. ; Liess, M. ; Ebke, P. ; Ippolito, A. ; Braak, C.J.F. ter; Brock, T.C.M. ; Schäfer, R.B. - \ 2015
Ecotoxicology 24 (2015)4. - ISSN 0963-9292 - p. 760 - 769.
fresh-water microcosms - fungicide carbendazim - pond mesocosms - responses - insecticide - models - impact - chlorpyrifos - zooplankton - conclusions
Mesocosm experiments that study the ecological impact of chemicals are often analysed using the multivariate method ‘Principal Response Curves’ (PRCs). Recently, the extension of generalised linear models (GLMs) to multivariate data was introduced as a tool to analyse community data in ecology. Moreover, data aggregation techniques that can be analysed with univariate statistics have been proposed. The aim of this study was to compare their performance. We compiled macroinvertebrate abundance datasets of mesocosm experiments designed for studying the effect of various organic chemicals, mainly pesticides, and re-analysed them. GLMs for multivariate data and selected aggregated endpoints were compared to PRCs regarding their performance and potential to identify affected taxa. In addition, we analysed the inter-replicate variability encountered in the studies. Mesocosm experiments characterised by a higher taxa richness of the community and/or lower taxonomic resolution showed a greater inter-replicate variability, whereas variability decreased the more zero counts were encountered in the samples. GLMs for multivariate data performed equally well as PRCs regarding the community response. However, compared to first axis PRCs, GLMs provided a better indication of individual taxa responding to treatments, as separate models are fitted to each taxon. Data aggregation methods performed considerably poorer compared to PRCs. Multivariate community data, which are generated during mesocosm experiments, should be analysed using multivariate methods to reveal treatment-related community-level responses. GLMs for multivariate data are an alternative to the widely used PRCs
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