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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    Time Trends in Age at Menarche and Related Non-Communicable Disease Risk during the 20th Century in Mexico
    Petersohn, Inga ; Zarate-Ortiz, Arli G. ; Cepeda-Lopez, Ana C. ; Melse-Boonstra, Alida - \ 2019
    Nutrients 11 (2019)2. - ISSN 2072-6643
    body mass index - diabetes mellitus - height - menarche - non-communicable disease

    Developed countries have shown a time trend towards a younger age at menarche (AAM), which is associated with increased risk of later obesity and non-communicable diseases. This study aimed to assess whether a time trend in AAM is associated with disease risk in Mexican women (n = 30,826), using data from the Mexican National Health Survey (2000). Linear and log binomial regression was used for nutritional and disease outcomes, while Welch⁻ANOVA was used to test for a time trend. AAM (in years) decreased over time (p < 0.001), with a maximal difference of 0.99 years between the 1920s (13.6 years) and 1980s (12.6 years ). AAM was negatively associated with weight (β = -1.01 kg; 95% CI -1.006, -1.004) and body mass index (BMI) (β = -1.01 kg/m²; -1.007, -1.006), and positively with height (β = 0.18 cm; 0.112, 0.231). AAM was associated with diabetes (RR = 0.95; 0.93, 0.98) and hypercholesterolemia (RR = 0.93; 0.90, 0.95), but not with hypertension, breast cancer or arthritis. In Mexico, AAM decreased significantly during the 20th century. AAM was inversely associated with adult weight and BMI, and positively with height. Women with a later AAM had a lower risk of diabetes and hypercholesterolemia.

    Flight height of seabirds : a literature study
    Jongbloed, R.H. - \ 2016
    IMARES (Report / IMARES C024/16) - 25
    sea birds - flight - height - animal behaviour - zeevogels - vliegen - hoogte - diergedrag
    OHN : Object Hoogten Nederland, de hoogte van alles wat boven het maaiveld uitsteekt
    Kramer, H. ; Clement, J. ; Mücher, C.A. - \ 2014
    Geo-Info 2014 (2014)3. - ISSN 1572-5464 - p. 18 - 21.
    bomen - gebouwen - meting - hoogte - gegevensbeheer - geografische informatiesystemen - trees - buildings - measurement - height - data management - geographical information systems
    Op locaties waar geen hoogtemetingen beschikbaar zijn, bevat het AHN geen hoogtegegevens. Reden genoeg voor Alterra om een vlakdekkend bestand te maken met alle hoogten boven maaiveld: het bestand Object Hoogte Nederland (OHN). Met OHN is het mogelijk om de vraag te beantwoorden "hoe hoog is deze boom"
    Maize yield and quality in response to plant density and application of a novel plant growth regulator
    Zhang, Q. ; Zhang, L. ; Evers, J.B. ; Werf, W. van der; Zhang, W. ; Duan, L. - \ 2014
    Field Crops Research 164 (2014). - ISSN 0378-4290 - p. 82 - 89.
    zea-mays l. - irrigated maize - spring wheat - grain-yield - corn - ethephon - height - climate - barley - ethyl
    Farmers in China have gradually increased plant density in maize to achieve higher yields, but this has increased risk of lodging due to taller and weaker stems at higher plant densities. Plant growth regulators can be used to reduce lodging risk. In this study, for the first time, the performance of a mixture of the plant growth regulators ethephon and diethyl aminoethyl hexanoate (DA-6), called EDAH is tested at different plant densities and in different cultivars. Grain yield, yield components and grain quality as well as plant height and lodging percentage were determined in two years (2012 and 2013), using two maize hybrids, ZD 958 and Pioneer 335 at densities of 4.5, 6.0, 7.5 and 9.0 plants m-2 with and without foliar application of EDAH at 7 expanded leaves stage. EDAH significantly increased grain yield (by 7.8–8.0%), kernel number per ear (by 2.9–4.0%) and 1000-kernel weight (by 3.3–5.1%). Lodging percentage increased with plant density and was decreased by EDAH application in 2013. Optimal density was 7.5 plants m-2. The number of ears per unit ground area increased linearly with plant density, but number of kernels per ear and kernel weight showed an optimum. The two tested cultivars differed in yield and quality. No effects of EDAH on grain quality parameters (protein, oil and starch content) were found. We conclude that EDAH can improve lodging resistance and yield in maize, and that the yield effect of EDAH also occurs if lodging is not reduced.
    Why trees and shrubs but rarely trubs?
    Scheffer, M. ; Vergnon, R.O.H. ; Cornelissen, J.H.C. ; Hantson, S. ; Holmgren, M. ; Nes, E.H. van; Xu, C. - \ 2014
    Trends in Ecology and Evolution 29 (2014)8. - ISSN 0169-5347 - p. 433 - 434.
    savanna - forest - transitions - height
    An analysis of the maximum height of woody plant species across the globe reveals that an intermediate size is remarkably rare. We speculate that this may be due to intrinsic suboptimality or to ecosystem bistability with open landscapes favouring shrubs, and closed canopies propelling trees to excessive tallness.
    Intercomparison of Methods for the Simultaneous Estimation of Zero-Plane Displacement and Aerodynamic Roughness Length from Single-Level Eddy-Covariance Data
    Graf, A. ; Boer, A. van de; Moene, A.F. ; Vereecken, H. - \ 2014
    Boundary-Layer Meteorology 151 (2014)2. - ISSN 0006-8314 - p. 373 - 387.
    frequency-response corrections - atmospheric boundary-layer - sonic anemometer data - tall vegetation - sensible-heat - surface - parameters - height - flux - temperature
    We applied three approaches to estimate the zero-plane displacement d through the aerodynamic measurement height z (with z = zm - d and zm being the measurement height above the surface), and the aerodynamic roughness length z0, from single-level eddy covariance data. Two approaches (one iterative and one regression-based) were based on the universal function in the logarithmic wind profile and yielded an inherently simultaneous estimation of both d and z0. The third approach was based on flux–variance similarity, where estimation of d and consecutive estimation of z0 are independent steps. Each approach was further divided into two methods differing either with respect to the solution technique (profile approaches) or with respect to the variable (variance of vertical wind and temperature, respectively). All methods were applied to measurements above a large, growing wheat field where a uniform canopy height and its frequent monitoring provided plausibility limits for the resulting estimates of time-variant d and z0. After applying, for each approach, a specific data filtering that accounted for the range of conditions (e.g. stability) for which it is valid, five of the six methods were able to describe the temporal changes of roughness parameters associated with crop growth and harvest, and four of them agreed on d to within 0.3 m most of the time. Application of the same methods to measurements with a more heterogeneous footprint consisting of fully-grown sugarbeet and a varying contribution of adjacent harvested fields exhibited a plausible dependence of the roughness parameters on the sugarbeet fraction. It also revealed that the methods producing the largest outliers can differ between site conditions and stability. We therefore conclude that when determining d for canopies with unknown properties from single-level measurements, as is increasingly done, it is important to compare the results of a number of methods rather than rely on a single one. An ensemble average or median of the results, possibly after elimination of methods that produce outliers, can help to yield more robust estimates. The estimates of z0 were almost exclusively physically plausible, although d was considered unknown and estimated simultaneously with the methods and results described above
    Linking size-dependent growth and mortality with architectural traits across 145 co-occurring tropical tree species
    Iida, Y. ; Poorter, L. ; Sterck, F.J. ; Kassim, A.R. ; Potts, M.D. ; Kubo, T. ; Kohyama, T.S. - \ 2014
    Ecology 95 (2014)2. - ISSN 0012-9658 - p. 353 - 363.
    rain-forest trees - mixed dipterocarp forest - functional traits - wood density - interspecific variation - demographic rates - severe drought - allometry - height - impact
    Tree architecture, growth, and mortality change with increasing tree size and associated light conditions. To date, few studies have quantified how size-dependent changes in growth and mortality rates co-vary with architectural traits, and how such size-dependent changes differ across species and possible light capture strategies. We applied a hierarchical Bayesian model to quantify size-dependent changes in demographic rates and correlated demographic rates and architectural traits for 145 co-occurring Malaysian rain-forest tree species covering a wide range of tree sizes. Demographic rates were estimated using relative growth rate in stem diameter (RGR) and mortality rate as a function of stem diameter. Architectural traits examined were adult stature measured as the 95-percentile of the maximum stem diameter (upper diameter), wood density, and three tree architectural variables: tree height, foliage height, and crown width. Correlations between demographic rates and architectural traits were examined for stem diameters ranging from 1 to 47 cm. As a result, RGR and mortality varied significantly with increasing stem diameter across species. At smaller stem diameters, RGR was higher for tall trees with wide crowns, large upper diameter, and low wood density. Increased mortality was associated with low wood density at small diameters, and associated with small upper diameter and wide crowns over a wide range of stem diameters. Positive correlations between RGR and mortality were found over the whole range of stem diameters, but they were significant only at small stem diameters. Associations between architectural traits and demographic rates were strongest at small stem diameters. In the dark understory of tropical rain forests, the limiting amount of light is likely to make the interspecific difference in the effects of functional traits on demography more clear. Demographic performance is therefore tightly linked with architectural traits such as adult stature, wood density, and capacity for horizontal crown expansion. The enhancement of a demographic trade-off due to interspecific variation in functional traits in the understory helps to explain species coexistence in diverse rain forests
    Trade-off between light interception efficiency and light use efficiency: implications for species coexistence in one-sided light competition
    Onoda, Y. ; Saluñga, J.B. ; Akutsu, K. ; Aiba, S.I. ; Yahara, T. ; Anten, N.P.R. - \ 2014
    Journal of Ecology 102 (2014)1. - ISSN 0022-0477 - p. 167 - 175.
    herbaceous plant community - temperate rain-forest - secondary forest - canopy structure - carbon gain - height - growth - photosynthesis - populations - stratification
    1. Taller plant species can pre-empt solar energy and suppress growth of subordinate species in vegetation stands, which is described through one-sided competition. Yet, in much of the world’s vegetation species of different statures coexist. This study aims to clarify the mechanisms underlying this apparent paradox. 2. We quantified how co-occurring species and individuals intercepted and used light for growth in a mature, warm-temperate evergreen forest. This was performed by determining the 3D distribution of foliage and light with a ground-based lidar system in combination with nondestructive measurements of plant growth. 3. Taller trees intercepted light more efficiently per unit of above-ground biomass than shorter trees did (=higher light interception efficiency, LIE). However, taller trees tended to have lower biomass production per unit light interception (=lower light use efficiency, LUE). Reduced LUE in taller trees was associated with their higher biomass allocation to nonphotosynthetic organs and probably with over-saturated light intensity for photosynthesis at high canopy positions. Due to the increased LIE and decreased LUE with tree heights, a trade-off between LIE and LUE was found, and this trade-off resulted in trees of different statures having similar relative growth rates. 4. Synthesis. Light competition drives trees to grow taller, and the light interception efficiency is higher in taller trees; however, this benefit comes at a cost of decreased efficiency of light use for growth. This trade-off allows trees of different statures to grow at proportionally comparable rates and may promote coexistence of tree species in one-sided light competition.
    Observational Support for the Stability Dependence of the Bulk Richardson Number across the Stable Boundary Layer
    Basu, S. ; Holtslag, A.A.M. ; Caporaso, L. ; Riccio, A. ; Steeneveld, G.J. - \ 2014
    Boundary-Layer Meteorology 150 (2014)3. - ISSN 0006-8314 - p. 515 - 523.
    self-correlation - resistance laws - surface fluxes - least-squares - model - height - regression - formulations - parameter - breakdown
    The bulk Richardson number (Ri Bh ; defined over the entire stable boundary layer) is commonly utilized in observational and modelling studies for the estimation of the boundary-layer height. Traditionally, Ri Bh is assumed to be a quasi-universal constant. Recently, based on large-eddy simulation and wind-tunnel data, a stability-dependent relationship has been proposed for Ri Bh . In this study, we analyze extensive observational data from several field campaigns and provide further support for this newly proposed relationship.
    Trait assembly of woody plants in communities across sub-alpine gradients: Identifying the role of limiting similarity
    Yan, B. ; Zhang, J. ; Liu, Y. ; Li, Z. ; Huang, X. ; Yang, W. ; Prinzing, A. - \ 2012
    Journal of Vegetation Science 23 (2012)4. - ISSN 1100-9233 - p. 698 - 708.
    functional traits - amazonian forest - neutral theory - niche - coexistence - height - growth - consequences - convergence - equivalence
    Questions - Plant species can be assembled into communities through habitat filtering or species competition, but their relative roles are still debated. We do not know whether there is limited similarity between co-existing species when accounting for the parallel effect of abiotic habitat filtering and biotic competition. By accounting for such effects, we test the predictions of three theories (classic niche theory, the Hubbell neutrality theory and the Scheffer and van Nes theory) of community assembly. Location - Two vegetation transitions (a grazing gradient and a timber line ecotone) in a sub-alpine area of western Sichuan Province, China (31° 51'N, 102° 41'E). Methods - We used a null model to investigate the above plant community assembly theories on two sub-alpine gradients of woody vegetation. In the null model, species traits were constrained between the maximum and minimum trait values of observed communities to test the principle of limiting similarity between co-existing species by testing for even spacing of traits. We analysed traits characterizing growth strategies of stems, leaves and twigs, measured at the level of individuals in situ. Results - After accounting for variations in trait range, it became evident that six out of eight traits showed significantly uneven spacing within some plots, notably towards the forest end of the gradient, i.e. under increased competition pressure among woody plants. The Wilcoxon rank test showed that seven out of eight traits were significantly unevenly spaced within plots. The two transitions studied showed surprisingly similar patterns, despite their dissimilar precise drivers.
    The impact of body mass index in old age on cause-specific mortality
    Hollander, E.L. de; Zutphen, M. van; Bogers, R.P. ; Bemelmans, W.J.E. ; Groot, C.P.G.M. de - \ 2012
    Journal of Nutrition, Health and Aging 16 (2012)1. - ISSN 1279-7707 - p. 100 - 106.
    obesity - overweight - men - consequences - underweight - guidelines - adiposity - whitehall - weight - height
    Objectives: To assess the association between Body Mass Index (BMI) and cause-specific mortality in older adults and to assess which BMI was associated with lowest mortality. Design: Prospective study. Setting: European towns. Participants: 1,980 older adults, aged 70-75 years from the SENECA (Survey in Europe on Nutrition and the Elderly: a concerted action) study. Measurements: BMI, examined in 1988/1989, and mortality rates and causes of death during 10 years of follow-up. Results: Cox proportional hazards model including both BMI and BMI2, accounting for sex, smoking status, educational level and age at baseline showed that BMI was associated with all-cause mortality (p0.3). The lowest all-cause mortality risk was found at 27.1 (95%CI 24.1, 29.3) kg/m2, and this risk was increased with statistical significance when higher than 31.4 kg/m2 and lower than 21.1 kg/m2. The lowest cardiovascular mortality risk was found at 25.6 (95%CI 17.1, 28.4) kg/m2, and was increased with statistical significance when higher than 30.9 kg/m2. Conclusion: In this study, BMI was associated with all-cause mortality risk in older people. This risk was mostly driven by an increased cardiovascular mortality risk, as no association was found for mortality risk from cancer or respiratory disease. Our results indicate that the WHO cut-off point of 25 kg/m2 for overweight might be too low in old age, but more studies are needed to define specific cut-off points.
    Wood density explains architectural differentiation across 145 co-occurring tropical tree species
    Iida, Y. ; Poorter, L. ; Sterck, F.J. ; Kubo, T. ; Kassim, A.R. ; Potts, M.D. ; Kohyama, T.S. - \ 2012
    Functional Ecology 26 (2012)1. - ISSN 0269-8463 - p. 274 - 282.
    mixed dipterocarp forest - life-history strategies - rain-forest - functional traits - adult stature - demographic rates - allometry - height - growth - size
    1. Because of its mechanical properties, wood density may affect the way that trees expand their stem and crown to exploit favourable light conditions in a mechanically stable way. From engineering theory and wood density properties, it is predicted that in terms of biomass investment, low-density wood is more efficient for vertical stem expansion, while high-density wood is more efficient for horizontal branch expansion. So far, these predictions have rarely been tested by empirical studies. 2. We tested these predictions for 145 co-occurring tree species in a Malaysian tropical rainforest. For each species, we selected trees across a broad size range and measured architectural dimensions (stem diameter, height of the lowest foliage and crown width). We used a hierarchical Bayesian model to estimate species-specific allometric relationships between architectural dimensions including estimated stem biomass. Then, we examined correlations between species wood density and estimated architectural variables at standardized heights. 3. When species were compared at standardized tree heights, wood density correlated negatively with stem diameter and positively with stem biomass at most reference heights. This indicates that species with low wood density produce thicker stems but at lower biomass costs. Wood density correlated positively with crown width and negatively with height of the lowest foliage, which indicates that high wood density species have wider and deeper crowns than low wood density species. These relationships were maintained at most reference heights. However, the relationship with crown width was nonsignificant above 18 m height. This may reflect large plastic response of lateral crown expansion to a local condition. 4. Wood density explains the trade-off between effective vertical stem expansion and horizontal crown expansion across co-occurring tropical tree species. Such mechanical constraints characterize the difference in tree architecture between low wood density species that show an efficient height expansion to attain better light conditions in the exposed canopy and high wood density species that show an efficient horizontal crown expansion to enhance current light interception and persistence in the shaded forest understorey. Our study thus suggests that the mechanical constraints set by wood density contribute to the co-existence of species differing in architecture and light capture strategy.
    A functional-structural model of rice linking quantitative genetic information with morphological development and physiological processes
    Xu, L.F. ; Henke, M. ; Zhu, J. ; Kurth, W. ; Buck-Sorlin, G.H. - \ 2011
    Annals of Botany 107 (2011)5. - ISSN 0305-7364 - p. 817 - 828.
    wheat triticum-aestivum - oryza-sativa l. - plant architecture - experimental populations - complex traits - growth-models - height - barley - yield - photosynthesis
    Background and Aims Although quantitative trait loci (QTL) analysis of yield-related traits for rice has developed rapidly, crop models using genotype information have been proposed only relatively recently. As a first step towards a generic genotype-phenotype model, we present here a three-dimensional functional-structural plant model (FSPM) of rice, in which some model parameters are controlled by functions describing the effect of main-effect and epistatic QTLs. Methods The model simulates the growth and development of rice based on selected ecophysiological processes, such as photosynthesis (source process) and organ formation, growth and extension (sink processes). It was devised using GroIMP, an interactive modelling platform based on the Relational Growth Grammar formalism (RGG). RGG rules describe the course of organ initiation and extension resulting in final morphology. The link between the phenotype (as represented by the simulated rice plant) and the QTL genotype was implemented via a data interface between the rice FSPM and the QTLNetwork software, which computes predictions of QTLs from map data and measured trait data. Key Results Using plant height and grain yield, it is shown how QTL information for a given trait can be used in an FSPM, computing and visualizing the phenotypes of different lines of a mapping population. Furthermore, we demonstrate how modification of a particular trait feeds back on the entire plant phenotype via the physiological processes considered. Conclusions We linked a rice FSPM to a quantitative genetic model, thereby employing QTL information to refine model parameters and visualizing the dynamics of development of the entire phenotype as a result of ecophysiological processes, including the trait(s) for which genetic information is available. Possibilities for further extension of the model, for example for the purposes of ideotype breeding, are discussed
    Increased searching and handling effort in tall swards lead to a Type IV functional response in small grazing herbivores
    Heuermann, N. ; Langevelde, F. van; Wieren, S.E. van; Prins, H.H.T. - \ 2011
    Oecologia 166 (2011)3. - ISSN 0029-8549 - p. 659 - 669.
    instantaneous intake rate - mammalian herbivores - foraging behavior - grass stems - density - serengeti - quality - biomass - height - models
    Understanding the functional response of species is important in comprehending the species’ population dynamics and the functioning of multi-species assemblages. A Type II functional response, where instantaneous intake rate increases asymptotically with sward biomass, is thought to be common in grazers. However, at tall, dense swards, food intake might decline due to mechanical limitations or if animals selectively forage on the most nutritious parts of a sward, leading to a Type IV functional response, especially for smaller herbivores. We tested the predictions that bite mass, cropping time, swallowing time and searching time increase, and bite rate decreases with increasing grass biomass for different-sized Canada geese (Branta canadensis) foraging on grass swards. Bite mass indeed showed an increasing asymptotic relationship with grass biomass. At high biomass, difficulties in handling long leaves and in locating bites were responsible for increasing cropping, swallowing, and searching times. Constant bite mass and decreasing bite rate caused the intake rate to decrease at high sward biomass after reaching an optimum, leading to a Type IV functional response. Grazer body mass affected maximum bite mass and intake rate, but did not change the shape of the functional response. As grass nutrient contents are usually highest in short swards, this Type IV functional response in geese leads to an intake rate that is maximised in these swards. The lower grass biomass at which intake rate was maximised allows resource partitioning between different-sized grazers. We argue that this Type IV functional response is of more importance than previously thought.
    Tree architecture and life-history strategies across 200 co-occurring tropical tree species
    Iida, Y. ; Kohyama, T.S. ; Kubo, T. ; Kassim, A.R. ; Poorter, L. ; Sterck, F.J. ; Potts, M.D. - \ 2011
    Functional Ecology 25 (2011)6. - ISSN 0269-8463 - p. 1260 - 1268.
    rain-forest trees - mixed dipterocarp forest - shade tolerance - allometry - growth - size - traits - height - heterogeneity - regeneration
    1. Tree architecture is thought to allow species to partition horizontal and vertical light gradients in the forest canopy. Tree architecture is closely related to light capture, carbon gain and the efficiency with which trees reach the canopy. Previous studies that investigated how light gradients drive differentiation in tree architecture have produced inconsistent results, partially because of the differences in which tree species and ontogenetic stages were studied. 2. We examined the relationship between stem diameter, tree height, foliage height, crown width and life-history strategy over a broad size range of 200 randomly selected, co-occurring tree species in a lowland rainforest in Peninsular Malaysia. We developed a hierarchical Bayesian model to account for both intra- and interspecific variation and describe the relationships among tree architectural variables. We analysed interspecific variation in tree architectural variables in relation to adult stature and light requirement for species regeneration as a function of tree size. 3. There was little interspecific variation in architectural variables, this is partly because of large intraspecific variation in response to canopy heterogeneity, but it also suggests architectural convergence within this community. However, interspecific analyses showed that, for large-statured species, small size classes had thinner stems with narrow and shallow crowns, whereas large-size classes had wider crowns. Light-demanding species (as indicated by high sapling mortality in shaded conditions) showed weak trends in tree architecture and were only characterized by wide crowns at intermediate sizes. 4. In summary, tree architectural traits overlapped across the species community. This suggests that architectural convergence and equalizing effects occur in this diverse tropical forest and that community-wide allometric equations can be used to describe forest height and carbon storage. Light resource partitioning also occurs, indicating stabilizing effects. Interspecific architectural variation in relation to adult stature supports the theory of the trade-off between early reproduction and vegetative growth. In closed rainforests, adult stature imposes a stronger force on architectural differentiation of species than regeneration light requirements.
    Akkerbouw onder hoogspanning : rapport over landbouwkundige gevolgen van 380 kV hoogspanningslijn Noord-Holland
    Reeuwijk, P. van; Voort, M.P.J. van der; Wolf, P.L. de - \ 2011
    Lelystad : Praktijkonderzoek Plant & Omgeving, Business Unit Akkerbouw, Groene Ruimte en Vollegrondsgroente - 42
    akkerbouw - elektrische energie - elektriciteitsvoorzieningen - kabels - effecten - elektrische leidingen - hoogte - arable farming - electrical energy - electricity supplies - cables - effects - power lines - height
    TenneT wil een hoogspanningslijn realiseren van Wateringen naar Beverwijk (TenneT, 2007). In 2011 start de inspraakprocedure. Het voorkeurstracé doorkruist een aantal landbouwgebieden. De Stichting van Bemmelenhoeve heeft Praktijkonderzoek Plant & Omgeving opdracht gegeven om de gevolgen in kaart te brengen voor akkerbouwbedrijven in de buurt van Hoofddorp
    Sensitivity of methods for estimating breeding values using genetic markers to the number of QTL and distribution of QTL variance
    Coster, A. ; Bastiaansen, J.W.M. ; Calus, M.P.L. ; Arendonk, J.A.M. van; Bovenhuis, H. - \ 2010
    Genetics, Selection, Evolution 42 (2010). - ISSN 0999-193X - 11 p.
    partial least-squares - linkage disequilibrium - dairy-cattle - selection - accuracy - height - loci - identification - association - prediction
    The objective of this simulation study was to compare the effect of the number of QTL and distribution of QTL variance on the accuracy of breeding values estimated with genomewide markers (MEBV). Three distinct methods were used to calculate MEBV: a Bayesian Method (BM), Least Angle Regression (LARS) and Partial Least Square Regression (PLSR). The accuracy of MEBV calculated with BM and LARS decreased when the number of simulated QTL increased. The accuracy decreased more when QTL had different variance values than when all QTL had an equal variance. The accuracy of MEBV calculated with PLSR was affected neither by the number of QTL nor by the distribution of QTL variance. Additional simulations and analyses showed that these conclusions were not affected by the number of individuals in the training population, by the number of markers and by the heritability of the trait. Results of this study show that the effect of the number of QTL and distribution of QTL variance on the accuracy of MEBV depends on the method that is used to calculate MEBV
    Respiratory function and other biological risk factors for completed suicide: 40 years of follow-up of European cohorts of the Seven Countries Study
    Giltay, E.J. ; Zitman, F.G. ; Menotti, A. ; Nissinen, A. ; Jacobs, D.R. ; Adachi, H. ; Kafatos, A. ; Kromhout, D. - \ 2010
    Journal of Affective Disorders 120 (2010)1-3. - ISSN 0165-0327 - p. 249 - 253.
    body-mass index - serum-cholesterol - united-states - lung-function - men - association - mortality - height - death - ideation
    Background - Prospective cohort studies on biological risk factors of completed suicide are scarce. We aimed to test which biological risk factors independently identify subjects at increased risk of suicidal death. Methods - In the prospective cohort of the Seven Countries Study, 5,321 middle-aged men from Finland, Serbia, Italy, and Greece were included. Completed suicide (ICD-8 codes E950-959) was assessed during 40 years of follow-up. Biological cardiovascular risk factors (including forced vital capacity [FVC] and height) were tested for their role as predictors in multivariable Cox models stratified by country. Results - There were 4518 deaths during follow-up, with 64 from suicide (1.4%). In univariable models, only FVC and height were strongly inversely related with suicide. Socio-economic status and being unmarried were potential confounders. In multivariable models taking these confounders into account, both a low FVC (0.30 for top vs. lowest quartile; 95% CI: 0.12–0.76; P = 0.006 for trend) and a low FVC/height ratio (0.37 for top vs. lowest quartile; 95% CI: 0.17–0.82; P = 0.004 for trend) were strongly inversely related with completed suicide. Limitations - Information on proximal causes, such as prior suicidal ideation, emotional distress and depression, was lacking at baseline. Conclusions - Poor respiratory function in middle-aged men was an independent risk factor for completed suicide
    Verfijning van de Basiskaart Natuur : segmentatie van luchtfoto's en het gebruik van het Actueel Hoogtebestand Nederland in duingebieden
    Hazeu, G.W. ; Oldengarm, J. ; Clement, J. ; Kramer, H. ; Sanders, M.E. ; Schmidt, A.M. ; Woltjer, I. - \ 2009
    Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu (WOt-rapport 102) - 94
    landgebruik - vegetatie - oppervlakte (areaal) - monitoring - inventarisaties - duingebieden - luchtfotografie - hoogte - natuurgebieden - land use - vegetation - acreage - monitoring - inventories - duneland - aerial photography - height - natural areas
    Dit rapport behandelt de verkenning naar de mogelijkheid om de vegetatieklassen van de Basiskaart Natuur (BKN) verder onder te verdelen op basis van vegetatiestructuurtypen. De verkenning heeft geleid tot de ontwikkeling van een methode om met behulp van segmentatie van luchtfoto’s en het Actueel Hoogtebestand Nederland (AHN) de duingebieden in Nederland verder onder te verdelen. Kaal duingebied, begroeid duingebied onderverdeeld naar drie vegetatiehoogteklassen en water in het duingebied zijn te onderscheiden. De onderverdeling van de BKN-klasse duinen, strand en zandplaten in meer subklassen is met gedetailleerde vegetatiekaarten voor drie deelgebieden gevalideerd. Verder geeft het rapport aan welke mogelijkheden er liggen om met het AHN de andere BKN-klassen bossen, heide, stuifzanden en rietmoerassen verder te verfijnen. Trefwoorden: vegetatiestructuurtypen, remote sensing, Actueel Hoogtebestand Nederland (AHN), duinen, Basiskaart Natuur (BKN), segmentatie luchtfoto’s
    Allometric growth relationships of East Africa highland bananas (Musa AAA-EAHB) cv. Kisansa and Mbwazirume
    Nyombi, K. ; Asten, P.J.A. van; Leffelaar, P.A. ; Corbeels, M. ; Kaizzi, C.K. ; Giller, K.E. - \ 2009
    Annals of Applied Biology 155 (2009)3. - ISSN 0003-4746 - p. 403 - 418.
    leaf-area estimation - biomass accumulation - radiation - crop - light - interception - morphology - fertilizer - diameter - height
    Highland bananas are an important staple food in East Africa, but there is little information on their physiology and growth patterns. This makes it difficult to identify opportunities for yield improvement. We studied allometric relationships by evaluating different phenological stages of highland banana growth for use in growth assessment, understanding banana crop physiology and yield prediction. Pared corms of uniform size (cv. Kisansa) were planted in a pest-free field in Kawanda (central Uganda), supplied with fertilizers and irrigated during dry periods. In addition, tissue-cultured plants (cv. Kisansa) were planted in an adjacent field and in Ntungamo (southwest Uganda), with various nutrient addition treatments (of N, P, K, Mg, S, Zn, B and Mo). Plant height, girth at base, number of functional leaves and phenological stages were monitored monthly. Destructive sampling allowed derivation of allometric relationships to describe leaf area and biomass distribution in plants throughout the growth cycle. Individual leaf area was estimated as LA (m2) = length (m) × maximum lamina width (m) × 0.68. Total plant leaf area (TLA) was estimated as the product of the measured middle leaf area (MLA) and the number of functional leaves. MLA was estimated as MLA (m2) = -0.404 + 0.381 height (m) + 0.411 girth (m). A light extinction coefficient (k = 0.7) was estimated from photosynthetically active radiation measurements in a 1.0 m grid over the entire day. The dominant dry matter (DM) sinks changed from leaves at 1118 °C days (47% of DM) and 1518 °C days (46% of DM), to the stem at 2125 °C days (43% of DM) and 3383 °C days (58% of DM), and finally to the bunch at harvest (4326 °C days) with 53% of DM. The allometric relationship between above-ground biomass (AGB in kg DM) and girth (cm) during the vegetative phase followed a power function, AGB = 0.0001 (girth)2.35 (R2 = 0.99), but followed exponential functions at flowering, AGB = 0.325 e0.036(girth) (R2 = 0.79) and at harvest, AGB = 0.069 e0.068(girth) (R2 = 0.96). Girth at flowering was a good parameter for predicting yields with R2 = 0.7 (cv. Mbwazirume) and R2 = 0.57 (cv. Kisansa) obtained between actual and predicted bunch weights. This article shows that allometric relationship can be derived and used to assess biomass production and for developing banana growth models, which can help breeders and agronomists to further exploit the crop's potential
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