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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    Hydrological drought and wildfire in the humid tropics
    Taufik, Muh - \ 2017
    Wageningen University. Promotor(en): R. Uijlenhoet, co-promotor(en): Henny van Lanen. - Wageningen : Wageningen University - ISBN 9789463436359 - 99
    wildfires - drought - humid tropics - wetlands - hydrology - prediction - water management - natuurbranden - droogte - humide tropen - wetlands - hydrologie - voorspelling - waterbeheer

    Drought is a recurrent hazard, which has happened throughout human history, and it is anticipated to become more severe in multiple regions across the world. Drought occurs in all climate regimes from humid to dry and from hot to cold. Drought is often viewed through its impact on environment and society, including wildfire, which is the topic of this study. The nature of such impacts differs remarkably from region to region. Although drought does not directly cause wildfire, it provides favorable conditions for wildfire ignition and spread. When drought coincides with strong El Niño events in the humid tropics, e.g. Southeast Asia, the impacts worsen through uncontrolled forest fires affecting the global carbon cycle. These include reduction of the carbon stock, intensifying the haze hazard, and other severe socio-economic impacts in Southeast Asia, including areas far away from the burnt area, e.g. Singapore because of fires in Sumatra.

    There still remains a serious lack of scientific understanding about the fundamental role of drought in fire-generating processes. Most research, so far, suggests that climate controls wildfire occurrence in the humid tropics. However, this climate-centered approach, which is reflected in contemporary drought-fire related indices, overlooks soil and hydrological processes beneath the surface across the humid tropics. There is also uncertainty about the relative roles of climate variability and human activities in influencing the nature and distribution of drought-related wildfires. Hence, the general objective of this PhD research is to examine how characterization of hydrological drought under natural and human-modified conditions can improve understanding of wildfires in general in the humid tropics.

    Chapter 2 discusses the contribution of humans to an increase of hydrological drought severity in the tropical peatland of Southeast Asia. Climate variability induces drought in the region, however, human activities (human-modified drought) may increase its severity. Analyzing long time series of simulated historical groundwater levels from selected regions in Southeast Asia, which were validated against some years with observations, revealed that human interference (through canalization and land-use change) has amplified drought severity. The drought amplification due to human interference was at least double that of climate-induced drought. The amplification is even higher when peatland is converted into acacia plantation. Further, research findings suggest that even if the Paris Agreement target is met, drought risk of peatlands remains high unless sustainable water management receives top priority in the region.

    Chapter 3 deals with how an existing, well-known drought-fire related index, i.e. the Keetch-Byram Drought Index (KBDI), is modified to improve applicability in the humid climate environment of Southeast Asia. The improvement includes: (i) adjustment of the drought factor to the local climate, and (ii) addition of the water table depth as a dynamic factor to fine-tune the drought index. The results indicate that the modified Keetch-Byram Drought Index (mKBDI) performed well in predicting fire hazard. Furthermore, the research identified a critical water table depth, which represents maximum fire hazard (0.85 m for the wetland forest of South Sumatra). Below this value hazard does not increase anymore. The mKBDI could be more widely applied, if pedotransfer functions would be developed that link easily-obtainable soil properties to the parameters of the water table factor.

    Chapter 4 shows that wetland transformation (i.e. through canalization and land-use change) not only affects hydrological drought (Chapter 2), but also influences fire behaviour. In Southeast Asia, expansion of agricultural cropland and forest plantations has changed the landscape of wetlands. The findings showed that the transformation into acacia plantation has amplified the fire hazard from 4% (under natural conditions) to 17%. An even higher amplification (40% fire hazard) is expected under poor water management, that is, uncontrolled drainage. The findings derived from this observation-based modeling experiment suggest that improved water management (controlled drainage with higher dry season surface water levels) can minimize fire susceptibility.

    Chapter 5 explains the importance of hydrology for fire hazard studies. Borneo is selected to investigate the added value of including hydrological variables in fire hazard prediction approaches. More than 300 statistical models were tested, and the results showed that models that include hydrological variables better predict area burnt than those solely based on climate indicators/indices. Further, modelling evidence shows amplifying wildfires and greater area burnt in response to El Niño Southern Oscillation (ENSO) strength, when hydrology is considered. These results highlight the importance of considering hydrological drought for wildfire prediction. I recommend that hydrology should be considered in future studies of the impact of projected ENSO strength, including effects on tropical ecosystems and biodiversity conservation.

    The contributions of this thesis research to science are summarized and synthesized in Chapter 6. First, the research identified that fire hazard studies would benefit from adding hydrology, which is reflected in the improved model performance when hydrological variables are integrated. Next, the research revealed that humans play a substantial role in modifying groundwater drought characteristics, hence amplifying the fire hazard in Southeast Asia. Further, the chapter identified several relevant research findings, including the model choice, which should consider the simplicity and the applicability of the model. Another finding demonstrated that controlling canal water level through canal blocking is a practical water management tool to restore degraded wetland. This restored wetland would benefit some endemic species. However, the restored wetland still faces high drought severity. Hence they remain more fire-prone until the un-impacted hydrology condition is achieved. Finally, this research suggest that currently widely-used drought indices (such as FWI) require improvements in their model structure, which means integration of hydrological variables to increase their applicability for fire hazard studies in the humid tropics.

    Eindrapportage Veerkracht van Melkvee I : verandering van dynamiek, voorspellende kracht
    Dixhoorn, Ingrid van; Mol, Rudi de; Werf, Joop van der; Reenen, Kees van - \ 2016
    Wageningen : Wageningen UR Livestock Research (Livestock Research rapport 956) - 94
    melkkoeien - melkvee - gustperiode - lactatie - rundveeziekten - diergezondheid - diergedrag - dierfysiologie - gegevens verzamelen - voorspelling - rundveeteelt - dairy cows - dairy cattle - dry period - lactation - cattle diseases - animal health - animal behaviour - animal physiology - data collection - prediction - cattle farming
    The transition period is a critical phase in the life of dairy cows. Early identification of cows at risk for disease would allow for early intervention and optimization of the transition period. Based on the theory of resilience of biological systems we hypothesize that the level of vulnerability of an individual cow can be quantified by describing dynamical aspects of continuously measured physiological and behavioural variables. To examine the relationship between the risk to develop diseases early in lactation and dynamic patterns of high-resolution, physiological and behavioural data, were continuously recorded in individual cows before calving. Dynamic, quantitative parameters for high-resolution physiological and behavioural measures, continuously acquired during the dry period have predictive value for the risk of cows to develop diseases during the early lactation period. Our results suggest that quantitative parameters derived from sensor data may reflect the level of resilience of individual cows.
    Multi-population genomic prediction
    Wientjes, Y.C.J. - \ 2016
    Wageningen University. Promotor(en): Roel Veerkamp; Mario Calus. - Wageningen : Wageningen University - ISBN 9789462576193 - 267
    cum laude - dairy cattle - genomics - prediction - quantitative trait loci - genetic improvement - breeding value - selective breeding - animal breeding - animal genetics - melkvee - genomica - voorspelling - loci voor kwantitatief kenmerk - genetische verbetering - fokwaarde - selectief fokken - dierveredeling - diergenetica
    Cum laude graduation
    Expert knowledge in geostatistical inference and prediction
    Truong, N.P. - \ 2014
    Wageningen University. Promotor(en): Peter de Ruiter, co-promotor(en): Gerard Heuvelink. - Wageningen : Wageningen University - ISBN 9789462570283 - 156
    geostatistiek - biometrie - ruimtelijke statistiek - statistische inferentie - voorspelling - bayesiaanse theorie - deskundigen - kriging - geostatistics - biometry - spatial statistics - statistical inference - prediction - bayesian theory - experts - kriging

    Geostatistics provides an efficient tool for mapping environmental variables from observations and layers of explanatory variables. The number and configuration of the observations importantly determine the accuracy of geostatistical inference and prediction. Data collection is costly, and coarse sampling may lead to large uncertainties in interpolated maps. In such case, additional information may be gathered from experts who are knowledgeable about the spatial variability of environmental variables. Statistical expert elicitation has gradually become a mature research field and has proved to be able to extract from experts reliable information to form a sound scientific database. In this thesis, expert knowledge has been elicited and incorporated in geostatistical models for inference and prediction. Various extensions to the expert elicitation literature were required to make it suitable for elicitation of spatial data. The use of expert knowledge in geostatistical research is promising, yet challenging.

    Runoff, discharge and flood occurrence in a poorly gauged tropical basin : the Mahakam River, Kalimantan
    Hidayat, H. - \ 2013
    Wageningen University. Promotor(en): Remko Uijlenhoet, co-promotor(en): Ton Hoitink. - S.l. : s.n. - ISBN 9789461737434 - 114
    oppervlakkige afvoer - afvoer - overstromingen - monitoring - tropen - modellen - rivieren - cartografie - voorspelling - kalimantan - indonesië - runoff - discharge - floods - monitoring - tropics - models - rivers - mapping - prediction - kalimantan - indonesia

    Tidal rivers and lowland wetlands present a transition region where the interests of hydrologists and physical oceanographers overlap. Physical oceanographers tend to simplify river hydrology, by often assuming a constant river discharge when studying estuarine dynamics. Hydrologists, in turn, generally ignore the direct or indirect effects of tides in water level and discharge records. This thesis aims to improve methods to monitor, model and predict discharge dynamics in tidal rivers and lowland wetlands, by focussing on the central and lower reaches of the River Mahakam (East Kalimantan, Indonesia), and the surrounding lakes area. The 980-km long river drains an area of about 77100 km2 between 2°N - 1°S and 113°E - 118°E. Due to its very mild bottom slope, a significant tidal influence occurs in this river. The middle reach of the river is located in a subsiding basin, parts of which are below mean sealevel, featuring peat swamps and about thirty lakes connected to the river via tie channels.

    Upstream of the lakes area, at about 300 km from the river mouth, an acoustic Doppler current profiler (H-ADCP) has been horizontally deployed at a station near the city of Melak (Chapter 2). The H-ADCP profiles of velocity are converted to discharge adopting a new calibration methodology. The obtained time-series of discharge show the tidal signal is clearly visible during low flow conditions. Besides tidal signatures, the discharge series show influences by variable backwater effects from the lakes, tributaries and floodplain ponds. The discharge rate at the station exceeds 3250 m3s-1 with a hysteretic behaviour. For a specific river stage, the discharge range can be as high as 2000 m3s-1. Analysis of alternative types of rating curves shows this is far beyond what can be explained from kinematic wave dynamics. Apart from backwater effects, the large variation of discharge for a specified river stage can be explained by river-tide interaction, impacting discharge variation especially in the fortnightly frequency band.

    A second H-ADCP station has been setup in the lower reach of the Mahakam, near the city of Samarinda, where the tidal discharge amplitude generally exceeds the discharge related to runoff (Chapter 3). Conventional rating curve techniques are inappropriate to model river discharge at this tidally influenced station. As an alternative, an artificial neural network (ANN) model is developed to investigate the degree to which tidal river discharge at Samarinda station can be predicted from an array of level gauge measurements along the tidal river, and from tidal level predictions at sea. The ANN-based model produces a good discharge estimation, as established from a consistent performance during both the training and the validation periods, showing the discharges can be predicted from water levels only, once that a trained model is available. The ANN models perform well in predicting discharges up to two days in advance.

    Chapter 4 addresses the role of backwater effects and tidal influences on discharge time-series used to calibrate a rainfall-runoff model. The HBV rainfall-runoff model is implemented for the Mahakam sub-catchment upstream of Melak (25700 km2). In a first approach, the model is calibrated using a discharge series derived from the H-ADCP measurements from Melak station. In a second approach, discharge estimates derived from a rating curve are used to calibrate the model. Adopting the first approach, a comparatively low model efficiency is obtained, which is attributed to the backwater and tidal effects that are not captured in the model. The second approach produces a relatively higher model efficiency, since the rating curve filters the backwater effects out of the discharge series. Seasonal variation of terms in the water balance is not affected by the choice for one of the two calibration strategies, which shows that backwaters do not have a systematic seasonal effect on the river discharge.

    To allow for investigation of the causes of backwater effects, satellite radar remote sensing is employed to monitor water levels in wetlands (Chapter 5). A series of Phased Array L-band Synthetic Aperture Radar (PALSAR) images is used to observe the dynamics of the Mahakam River floodplain. To analyze radar backscatter behavior for different land cover types, several regions of interest are selected, based on land cover classes. Medium shrub, high shrub, fern/grass, and degraded forest are found to be sensitive to flooding, whereas peat forest, riverine forest and tree plantation backscatter signatures only slightly change with flood inundation. An analysis of the relationship between radar backscatter and water levels is carried out. For lakes and shrub covered peatland, for which the range of water level variation is high, a good water level-backscatter correlation is obtained. In peat forest covered peatland, subject to a small range of water level variation, water level-backscatter correlations are poor, limiting the ability to obtain a floodplain-wide water surface topography from the radar images.

    Chapter 6 continues to investigate the degree in which satellite radar remote sensing can serve to distinguish between dry areas and wetlands, which is a difficult task in densely vegetated areas such as peat domes. Flood extent and flood occurrence information are successfully extracted from a series of radar images of the middle Mahakam lowland area. A fully inundated region is easily recognized from a dark signature on radar images. Open water flood occurrence is mapped using a threshold value taken from radar backscatter of the permanently inundated areas. Radar backscatter intensity analysis of the vegetated floodplain area reveals consistently higher backscatter values, indicating flood inundation under forest canopy. Those observations are used to establish thresholds for flood occurrence mapping in the vegetated area. An all-encompassing flood occurrence map is obtained by combining the flood occurrence maps for areas with and without vegetation.

    Chapter 7 synthesizes the findings from the previous chapters. It is concluded that the backwater effects and subtle tidal influences may prevent the option to predict river discharge using rating curves, which can best be interpreted as a stage-runoff relationship. H-ADCPs offer a promising alternative to monitor river discharge. For a tidal river, an ANN model can be used as a tool for data gap filling in an H-ADCP based discharge series, or even to derive discharge estimates solely from water levels and water level predictions. Discharge can be predicted several time-steps ahead, allowing water managers to take measures based on forecasts. The stage-runoff relationship derived from a continuous series of H-ADCP based discharge estimates may be expected to be much more accurate than a similar rating curve derived from a small number of boat surveys. The flood occurrence map derived from PALSAR images can offer a detailed insight into the hydroperiod, the period in which a soil area is waterlogged, and flood extent of the lowland area, illustrating the added value of radar remote sensing to wetland hydrological studies. In future work, radar-based floodplain observations may serve to calibrate hydrodynamic models simulating the processes of flooding and emptying of the lakes area.

    Een beoordelingslijst voor de complexiteit van modellen en bestanden
    Voorn, G.A.K. van; Walvoort, D.J.J. ; Knotters, M. ; Bogaart, P.W. ; Houweling, H. ; Janssen, P.H.M. - \ 2011
    Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu (WOt-paper 11) - 6
    biometrie - modellen - voorspelling - evaluatie - kwaliteit - onzekerheid - biometry - models - prediction - evaluation - quality - uncertainty
    Het Planbureau voor de Leefomgeving (PBL) maakt bij beleidsevaluaties en verkenningen gebruik van numerieke rekenmodellen die - voor een deel – samen worden ontwikkeld met Wageningen UR. De complexiteit van deze rekenmodellen neemt in het algemeen steeds verder toe. Het idee daarbij is dat het toevoegen van meer processen en variabelen aan een model leidt tot een groter toepassingsgebied, nauwkeuriger uitkomsten en dus tot betere voorspellingen. WOT-paper 11 geeft een beschrijving van een methode om de balans tussen (de complexiteit van) een rekenmodel, de toepassing en de beschikbare data te verbeteren.
    Koppelingen in het NHI
    Veldhuizen, A.A. ; Mulder, H.M. ; Verkaik, J. - \ 2011
    Alterra : Deltares - ISBN 9789490070007 - 28
    agrohydrologie - hydrologie - grondwaterstand - voorspelling - modellen - agrohydrology - hydrology - groundwater level - prediction - models
    Dit rapport doet verslag van de werkzaamheden van Alterra en Deltares aan de koppelingen binnen het Nederlands Hydrologisch Instrumentarium (NHI) en tussen het NHI en het agrohydrologische effectmodel AGRICOM.
    Evenwichtsanalyse modelcomplexiteit : een verkennende studie
    Bogaart, P.W. ; Voorn, G.A.K. van; Akkermans, L.M.W. - \ 2011
    Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu (WOt-werkdocument 226) - 49
    biometrie - modellen - voorspelling - evaluatie - kwaliteit - onzekerheid - biometry - models - prediction - evaluation - quality - uncertainty
    Dit werkdocument omvat een verkennende studie om de mogelijkheden te evalueren van de verhouding tussen de complexiteit van een model of bestand, de ondersteunende data, en de toepassing. Dit verhoudingsconcept wordt als „evenwicht¿ aangeduid. Doel is een reductie in de onzekerheid in voorspellingen door modellen en bestanden. In dit document wordt een prototype van een evaluatielijst voorgesteld. Deze lijst is gebaseerd op de relevante punten die een rol spelen bij evenwicht. De lijst bestaat uit twee sublijsten, die elk uit onderdelen met vragen bestaan. De ene sublijst is gebaseerd op de bestaande evaluatielijst voor „status A¿, die gebruikt wordt in de kwaliteitsborging bij de WOT Natuur & Milieu onderdeel van Wageningen UR. De andere sublijst omvat relevante kernvragen voor „evenwicht¿ die nog niet operationeel zijn. Elk onderdeel is gekoppeld aan een fase in de modelleercyclus, behalve het overkoepelende onderdeel „schaal¿. De discussie beschrijft het projectvervolg, waarin wordt beoogd om de evaluatielijst te toetsen aan casussen en de kennis van experts.
    Predicting soil nitrogen supply : relevance of extractable soil organic matter fractions
    Ros, G.H. - \ 2011
    Wageningen University. Promotor(en): Willem van Riemsdijk, co-promotor(en): Erwin Temminghoff; Ellis Hoffland. - [S.l.] : S.n. - ISBN 9789085858829 - 243
    mineralisatie - organische stikstof - bodem - organisch bodemmateriaal - bodemonderzoek - voorspelling - bodemtestwaarden - beoordeling - oogstresten - mineralization - organic nitrogen - soil - soil organic matter - soil testing - prediction - soil test values - assessment - crop residues

    Predicting the potential of soils to supply N is of considerable importance to maximize agricultural N use efficiency and to minimize environmental losses. This research examines and evaluates the current soil testing approach, which uses extractable organic N (EON) fractions to predict soil N supply, using isotopic 15N tracing, multivariate statistics and meta-analytical techniques.
    Almost all 20 EON fractions that have been developed during recent decades significantly reflect the potential of soils to supply N, in spite of the strong differences in size and composition of EON due to extraction methodology. The EON fractions have therefore been considered as highly bio-available N pools in soil. However, most of them performed either worse than or similarly to total N as predictor of soil N supply, and the uncertainty of the predicted soil N supply (even under controlled environmental conditions) is still too big for serious improvement of fertilizer management.
    A micro-diffusion method is developed to estimate gross EON fluxes in order to investigate the biochemical basis for observed relationships between EON and soil N supply. The fate of EON fractions in N mineralization, in particular those fractions that are obtained with weak hydrolyzing salt solutions, is comparable to that of dissolved organic N (DON). Both DON and EON can be considered as (intermediate) decomposition waste products in an abiotic and biotic controlled equilibrium with total N.
    Therefore, their relationship with soil N supply likely reflect that both DON, EON, and soil N supply are mutually dependent on total N.
    The dependency of soil N supply on methodological and environmental issues strongly encourages more effort to be put into validation and up-scaling, particularly regarding the quantification of the differences between laboratory and field experiments. A combination of soil testing with simulation modeling is necessary to account for the numerous environmental factors controlling soil N supply. The exact EON fraction that can be used in such an approach is less important and practical considerations may be decisive to select one for routine application in soil analysis.
    In conclusion, a holistic approach, which considers spatial and temporal variability of both soil N supply and crop N demand, may provide a successful approach to improving fertilizer management at the farm-scale.

    Genomic selection in dairy cattle
    Roos, A.P.W. de - \ 2011
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): B.J. Hayes; Roel Veerkamp. - [S.l. : S.n. - ISBN 9789085858539 - 184
    melkvee - selectief fokken - genetische verbetering - veredelingsprogramma's - fokwaarde - genetische merkers - haplotypen - voorspelling - dierveredeling - genexpressieanalyse - genotyping - dairy cattle - selective breeding - genetic improvement - breeding programmes - breeding value - genetic markers - haplotypes - prediction - animal breeding - genomics - genotyping
    The objectives of this Ph.D. thesis were (1) to optimise genomic selection in dairy cattle with respect to the accuracy of predicting total genetic merit and (2) to optimise a dairy cattle breeding program using genomic selection. The study was performed using a combination of real data sets and simulations. Real data sets consisted of dense marker genotypes of progeny tested bulls that had accurate phenotypes derived from their daughters’ performance records. Through cross-validation, the reliability of genomic predictions was assessed for Bayesian models that fitted either marker genotypes, ancestral haplotypes or genomic relationships. Haplotype-based methods gave the most reliable predictions and provided opportunities to limit computer requirements for analysing very large data sets. The reliability of genomic predictions across breeds was studied using simulated marker data. The data was simulated such that it showed the same the patterns of linkage disequilibrium (LD) as observed within and between Holstein, Angus, and Jersey cattle from the Netherlands, Australia, and New Zealand. It was concluded that the most reliable genomic predictions can be obtained when the reference populations of each breed are combined, whereas for diverged breeds at least 300,000 markers are required to ensure that the LD between markers and QTL persists across breeds. Using a simulated genomic selection scheme, it was shown that the annual rate of genetic gain in dairy cattle may double compared to current progeny test schemes, without compromising the rate of inbreeding. To achieve such a high rate of genetic gain, the generation interval needs to be reduced significantly, as young bulls will prove to be superior to progeny tested bulls. It is expected that in the near future many animals will be genotyped and very high marker densities will be inferred by imputation techniques. This may result in genomic predictions that are persistent across breeds and generations. Large scale genotyping of cows may enable genomic selection for novel traits and the integration of genomic information in herd management processes.
    Normering van de belasting situatie droogte : een gestandaardiseerde methode om periodes van droogte en natheid weer te geven
    Oostindie, K. ; Wesseling, J.G. ; Ritsema, C.J. - \ 2010
    Wageningen : Alterra (Alterra-rapport ) - 42
    neerslag - droogte - bodemwater - hydrologische gegevens - voorspelling - dijken - veengronden - west-nederland - precipitation - drought - soil water - hydrological data - prediction - dykes - peat soils - west netherlands
    Indien actuele maandelijkse neerslaghoeveelheden worden vergeleken met historische neerslagreeksen, dan kan men, gebruik makend van statistische technieken, inzichtelijk maken hoe de desbetreffende maand afwijkt ten opzichte van het langjarig gemiddelde. Er kan een kansberekening worden uitgevoerd, waardoor het mogelijk is de hoeveelheid neerslag te classificeren als droog, normaal, of nat. Voor 3 neerslagstations in west Nederland zijn deze analyses uitgevoerd. Bovendien is met behulp van HYDRUS-2D een dijkvak doorgerekend. Hierbij is gezocht naar relaties tussen de neerslaganalyses en berekende grondwaterstanden, waterafstotendheid en bodemvochtgehaltes.
    Achtergronden en mogelijkheden tot voorspellen van vruchtrui bij appel en peer : resultaten van een literatuuronderzoek
    Maas, F.M. - \ 2010
    Randwijk : Praktijkonderzoek Plant & Omgeving, Bloembollen, Boomkwekerij en Fruit - 24
    malus - appels - pyrus - peren - vruchtval - voorspelling - literatuuroverzichten - fruitteelt - malus - apples - pyrus - pears - fruit drop - prediction - literature reviews - fruit growing
    In een literatuurstudie werd gezocht naar de achtergronden van vruchtzetting en vruchtrui bij appel en peer. Er wordt een overzicht gegeven van vier modellen die zijn ontwikkeld en in de literatuur zijn beschreven om de mate van vruchtrui, zowel de natuurlijke rui als die volgend op een behandeling met chemische dunmiddelen, te voorspellen.
    Voorspelling van de bemestende waarde (N) van runderdrijfmest
    Boer, H.C. de; Bloem, J. - \ 2010
    Lelystad : Wageningen UR Livestock Research (Rapport / Wageningen UR Livestock Research 359) - 21
    rundveehouderij - mest - drijfmest - graslanden - voorspelling - stikstofmeststoffen - stikstof - bodemchemie - laboratoriumdiagnose - bemesting - cattle husbandry - manures - slurries - grasslands - prediction - nitrogen fertilizers - nitrogen - soil chemistry - laboratory diagnosis - fertilizer application
    Voor de praktijk lijkt het niet langer nodig om voor de voorspelling van de N-opname van grasland uit runderdrijfmest (eerste vier sneden na bemesting) nog gebruik te maken van het gehalte organische N. Het gebruik van minerale N lijkt te volstaan. Wel dient er duidelijk onderscheid gemaakt te worden tussen onvergiste en covergiste drijfmest. De rekenregels in de Bemestingsadviesbasis kunnen op basis van deze informatie aangepast worden.
    Effectieve bestrijding van Phytophthora infestans bij minimaal fungicidengebruik met behulp van waarschuwingssystemen (Parapluplan; 2009)
    Schepers, H.T.A.M. ; Spruijt, J. ; Evenhuis, A. ; Kessel, G.J.T. - \ 2009
    Lelystad : Praktijkonderzoek Plant & Omgeving, Sector AGV - 39
    solanum tuberosum - aardappelen - phytophthora infestans - voorspelling - fungiciden - geïntegreerde bestrijding - gewasbescherming - solanum tuberosum - potatoes - phytophthora infestans - prediction - fungicides - integrated control - plant protection
    De P. infestans-populatie wordt steeds agressiever, de cyclus wordt korter en er kan een snellere uitbreiding van de epidemie optreden als niet wordt ingegrepen. Bestrijding van Phytophthora in de teelt van aardappelen vraagt daardoor steeds meer aandacht. Het ontwikkelen van strategieën die zowel rekening houden met doseringsverlaging, rasresistentie, gecombineerde bestrijding Alternaria en Phytophthora, milieu en kosten vindt over meerdere jaren in veldproeven plaats op verschillende locaties in Nederland met verschillende teeltomstandigheden en verschillende klimatologische omstandigheden. Ieder jaar zijn er enkele aanpassingen in proefopzet, gebaseerd op de nieuwste inzichten uit Phytophthora onderzoek (Parapluplan Phytophthora). Het onderzoek werd uitgevoerd in opdracht van het Ministerie van Landbouw.
    Assessing ecological quality of shallow lakes: does knowledge of transparency suffice?
    Peeters, E.T.H.M. ; Franken, R.J.M. ; Jeppesen, E. ; Moss, B. ; Bécares, E. ; Hansson, I. ; Romo, S. ; Kairesalo, T. ; Gross, E.M. ; Donk, E. van; Noges, T. ; Irvine, K. ; Kornijów, R. ; Scheffer, M. - \ 2009
    Basic and Applied Ecology 10 (2009)1. - ISSN 1439-1791 - p. 89 - 96.
    meren - eutrofiëring - deskundigen - waterbeheer - modellen - regressieanalyse - voorspelling - herstel - waterkwaliteit - eu regelingen - richtlijnen (directives) - kaderrichtlijn water - aquatische ecosystemen - lakes - eutrophication - experts - water management - models - regression analysis - prediction - rehabilitation - water quality - eu regulations - directives - water framework directive - aquatic ecosystems - hypertrophic lake - expert judgment - danish lakes - fish
    The European Water Framework Directive (WFD) requires that all aquatic ecosystems in their member states should reach `good¿ ecological quality by 2015. To assess ecological quality, the WFD requires the definition of reference conditions using biological, physical and chemical indicators and the assignment of each water body to one of five quality classes using these indicators. Elaborate assessment schemes using large sets of variables are now being developed. Here we address the question whether all this is really needed and what the simplest assessment approach would be for the case of shallow lakes. We explore the relationships between the quality class assigned to a lake by experts in shallow lake ecology and a rich set of biological, physical, and chemical data. Multinomial logistic regression analyses were carried out based on data from 86 shallow lakes throughout Europe that were sampled in 2000 and/or 2001. Ecological quality of shallow lakes judged by experts was strongly correlated to physical and chemical variables associated with light regime and nutrients and much less to biological variables. Our regression model showed that ecological quality of this set of shallow lakes judged by experts could be predicted quite well from water transparency expressed as Secchi depth and that other variables did not contribute to it significantly. According to the WFD, lakes should at least have a `good¿ ecological quality. Quality judged by experts and predicted quality were similar for 78% of the lakes with respect to meeting this standard. As a cautionary note we stress that Secchi depth alone will be a less useful indicator if effects of stressors other than eutrophication (e.g. lake acidification and toxic pollution) are to be considered.
    Verkenning van de mogelijkheden voor de ontwikkeling van een metamodel voor de uitspoeling van stikstof uit landbouwgronden
    Salm, C. van der; Hoogland, T. ; Walvoort, D.J.J. - \ 2008
    Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu (WOt-werkdocument 110) - 71
    landbouwgronden - stikstof - uitspoelen - modellen - denitrificatie - voorspelling - immobilisatie - verliezen uit de bodem - agricultural soils - nitrogen - leaching - models - denitrification - prediction - immobilization - losses from soil
    Op basis van een groot aantal runs van SWAP/ANIMO is een metamodel voor de voorspelling van de stikstofuitspoeling ontwikkeld. In deze studie zijn twee verschillend benaderingen gevolgd om een metamodel te ontwikkelen: (i) een (statistisch) model waarbij de modelstructuur gebaseerd is op de procesformulering een eenvoudig massabalans model voor stikstof en (ii) een zuiver statistisch model waarvoor variabelen zijn gebruikt waarvan verwacht wordt dat zij de stikstofuitspoeling beïnvloeden (landgebruik, Gt, bodemtype, N.input ed.). De verklaarde variantie voor de stikstofuitspoeling was bij beide modellen laag (40.6 en 60.9 %). De matige perfomance van de metamodellen lijkt sterk samen te hangen met de sterke variatie van de (im)mobilisatie en denitrificatiefluxen in het moedermodel. Deze variatie kan slechts beperkt verklaard worden aan de hand van simpele parameters als bodemtype, landgebruik en Gt.
    CASCADE model predicts exposure at different locations within catchments
    Adriaanse, P.I. - \ 2007
    stroomgebieden - oppervlaktewater - pesticiden - blootstelling - waterverontreiniging - modellen - voorspelling - risicoschatting - eu regelingen - kaderrichtlijn water - ecotoxicologie - watersheds - surface water - pesticides - exposure - water pollution - models - prediction - risk assessment - eu regulations - water framework directive - ecotoxicology
    Aquatic life is protected from pesticide stress by two EU directives. It is not clear whether the ecotoxicological criteria from both directives can be met and what will be the consequences for Dutch agriculture. That is why the CASCADE model has been developed, using as much as possible existing models
    Automatic prediction of high-resolution daily rainfall fields for multiple extents: the potential of operational radar
    Schuurmans, J.M. ; Bierkens, M.F.P. ; Pebesma, E.J. ; Uijlenhoet, R. - \ 2007
    Journal of Hydrometeorology 8 (2007)6. - ISSN 1525-755X - p. 1204 - 1224.
    radar - regen - hydrologie - modelleren - voorspelling - hydrologische gegevens - meettechnieken - meteorologische waarnemingen - radar - rain - hydrology - modeling - prediction - hydrological data - measurement techniques - meteorological observations - gauge data - stochastic interpolation - geostatistics - variability - design - scales - model
    This study investigates the added value of operational radar with respect to rain gauges in obtaining high-resolution daily rainfall fields as required in distributed hydrological modeling. To this end data from the Netherlands operational national rain gauge network (330 gauges nationwide) is combined with an experimental network (30 gauges within 225 km2). Based on 74 selected rainfall events (March¿October 2004) the spatial variability of daily rainfall is investigated at three spatial extents: small (225 km2), medium (10 000 km2), and large (82 875 km2). From this analysis it is shown that semivariograms show no clear dependence on season. Predictions of point rainfall are performed for all three extents using three different geostatistical methods: (i) ordinary kriging (OK; rain gauge data only), (ii) kriging with external drift (KED), and (iii) ordinary collocated cokriging (OCCK), with the latter two using both rain gauge data and range-corrected daily radar composites¿a standard operational radar product from the Royal Netherlands Meteorological Institute (KNMI). The focus here is on automatic prediction. For the small extent, rain gauge data alone perform better than radar, while for larger extents with lower gauge densities, radar performs overall better than rain gauge data alone (OK). Methods using both radar and rain gauge data (KED and OCCK) prove to be more accurate than using either rain gauge data alone (OK) or radar, in particular, for larger extents. The added value of radar is positively related to the correlation between radar and rain gauge data. Using a pooled semivariogram is almost as good as using event-based semivariograms, which is convenient if the prediction is to be automated. An interesting result is that the pooled semivariograms perform better in terms of estimating the prediction error (kriging variance) especially for the small and medium extent, where the number of data points to estimate semivariograms is small and event-based semivariograms are rather unstable.
    Understanding and prediction of stable atmospheric boundary layers over land
    Steeneveld, G.J. - \ 2007
    Wageningen University. Promotor(en): Bert Holtslag, co-promotor(en): B.J.H. van de Wiel. - [S.l.] : S.n. - ISBN 9789085047162 - 199
    atmosfeer - klimaatfactoren - modellen - voorspelling - meteorologische factoren - grenslaagmeteorologie - aardoppervlak - atmosferische grenslaag - atmosphere - climatic factors - models - prediction - meteorological factors - boundary-layer meteorology - land surface - atmospheric boundary-layer
    The main objective of this thesis is to contribute to further understanding of the stable boundary layer (SBL) over land, and its representation in atmospheric models. A SBL develops during night due to radiative surface cooling. Observations in the SBL are difficult since many different physical processes can play a role. These processes are turbulent mixing, radiative transport, a coupling with the vegetation and underlying soil, drainage flows, gravity waves, fog, and aspects of land use heterogeneity. Therefore, the understanding and the representation of the SBL in weather forecast and climate models is relatively poor, especially for calm nights. In this thesis, a detailed column model of the atmosphere-land surface system is used to represent the atmospheric boundary layer over land and ice. As such, LES results and CASES99 field observations are used for comparison and model evaluation. It turns out that the degree of land-surface coupling plays a key role in forecasting the SBL. Also, the sensitivity of the radiation transfer model to vertical resolution is examined. It is found that the SBL can be satisfactorily modelled (except for the low-level jet (LLJ) and intermittency of the turbulence) if the geostrophic wind speed, advection, subsidence, and vegetation and soil properties are known, and if relatively high vertical resolution is used near the surface (both in the soil and in the atmosphere). The column model is used to study the nighttime 2m temperature increase due to additional CO2 as function of wind speed. Observations show that the temperature increase is similar for windy and calm nights, although this is somewhat counterintuitive. Model results confirm that the temperature increase is indeed similar for windy and calm nights. Next an intercomparison study of limited area weather forecast models (COAMPS, MM5, HIRLAM) is performed for CASES-99. Large errors occur in the forecasted minimum temperature, SBL height and diurnal temperature range. Models that account for a realistic interaction with the land surface are advantageous. A sufficient large domain is required to forecast the LLJ, and the forecasted surface cooling is very sensitive to the choice of the radiation scheme, especially for calm nights. Overall it is possible to upgrade the model performance by using the lessons learnt with the column model. In the thesis, also the role of orographic drag on the SBL is explored. It is shown that orography of 10 m amplitude can produce drag as large as the turbulent drag. Accounting for this in a model gave sufficient cyclone filling and a better forecast of the SBL structure and LLJ. The thesis concludes with studies of the SBL height. Dimensional analysis is used to derive a new and robust formulation for the SBL height for a broad range of latitude land-use conditions.
    Reducing prediction uncertainty of weather controlled systems
    Doeswijk, T.G. - \ 2007
    Wageningen University. Promotor(en): Gerrit van Straten, co-promotor(en): Karel Keesman. - [S.l.] : S.n. - ISBN 9789085046134 - 174
    weersvoorspelling - weersbeïnvloeding - modellen - voorspelling - schatting - bedrijfssystemen - onzekerheid - weather forecasting - weather control - models - prediction - estimation - farming systems - uncertainty
    In closed agricultural systems the weather acts both as a disturbance and as a resource. By using weather forecasts in control strategies the effects of disturbances can be minimized whereas the resources can be utilized. In this situation weather forecast uncertainty and model based control are coupled. In this thesis a model of a storage facility of agricultural produce is used as an example for a weather controlled system.

    The first step in reducing prediction uncertainty is taken by reducing the uncertainty in the weather forecast itself. A Kalman filter approach is used for this purpose. Weather forecast uncertainty is significantly reduced up to 10 hours for temperature, up to 32 hours for wind speed and up to 3 hours for global radiation by using this approach.

    For a linearized model of the storage facility error propagation rules have been derived. The uncertainty of the output can therefore be analytically calculated. The medium range weather forecast, up to ten days ahead , consists of an ensemble of 50 forecasts. The mean and variance of these forecasts are used for model prediction and model output uncertainty prediction. Furthermore, by using optimal control in conjunction with a cost criterion, the uncertainty of the system state is incorporated into the cost criterion. As a result the control inputs shift towards parts with less uncertainty in the weather forecast. Finally, a numerical risk evaluation showed that if feedback is applied, as in receding horizon optimal control, the cost increase is limited to 5% for a 24 hour feedback interval.

    Mathematical models are always an approximation of the real system. Model uncertainties arise in the model structure and/or in unknown parameter values. If measurements from the system are present, the model is fitted to the data by changing parameter values. Generally, parameters that are nonlinear in system model output are estimated by nonlinear least-squares (NLS) optimization algorithms. For systems that rational in their parameters a reparameterization method is proposed such that the new parameters can be estimated with ordinary least squares. As a result a modified predictor appears. In the noise free case this leads to the exact parameter estimates whereas a nonlinear least squares approach might end up in a local minimum. If noise is present, however, the linear estimates might be biased and the modified predictor has only a limited range. Because after linear reparameterization the data structure generally becomes errors-in-variables a bias compensated total least squares approach is used. The predictive performance of the modified predictor in this case largely improves and is regarded as a powerful alternative to the existing least squares methods.

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