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Francone, C.; Katul, G.G.; Cassardo, C.; Richiardone, R. |
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Title |
Turbulent transport efficiency and the ejection-sweep motion for momentum and heat on sloping terrain covered with vineyards |
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Journal Article |
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Year |
2012 |
Publication |
Agricultural and Forest Meteorology |
Abbreviated Journal  |
Agricultural and Forest Meteorology |
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Volume |
162-163 |
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98-107 |
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Keywords |
coherent motion; cumulant expansions; heat and momentum transfer; sloping terrain; vineyards; planar fit method; boundary-layers; reynolds stress; dense canopies; plant canopies; flow; fluxes; forest; fields; hills |
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In boundary layer flows, it is now recognized that the net momentum and mass exchange rates are dominated by the statistical properties of ejecting and sweeping motion often linked to the presence of coherent turbulent structures. Over vineyards, three main factors impact the transport properties of such coherent motion: presence of sloping terrain, variations in leaf area index (LAI) during the growing season, and thermal stratification. The effect of these factors on momentum and heat transport is explored for three vineyard sites situated on different slopes. All three sites experience similar seasonal variation in LAI and mean wind conditions. The analysis is carried out using a conventional quadrant analysis technique and is tested against two models approximating the joint probability density function (JPDF) of the flow variables. It is demonstrated that a Gaussian JPDF explains much of the updraft and downdraft statistical contributions to heat and momentum transport efficiencies for all three sites. An incomplete or truncated third-order cumulant expansion method (ICEM) of the JPDF that retains only the mixed moments and ignores the skewness contributions describes well all the key properties of ejections and sweeps for all slopes, LAI, and stability classes. The implication of these findings for diagnosing potential failures of gradient-diffusion theory over complex terrain is discussed. Because only lower order moments are needed to describe the main characteristics of the JPDF, the use of the Moving Equilibrium Hypothesis (MEH) to predict these moments from the locally measured sensible heat flux and friction velocity is explored. Provided the planar fit coordinate transformation is applied to the data, the MEH can describe these statistical moments at all three sites regardless of terrain slopes and LAI values. (C) 2012 Elsevier B.V. All rights reserved. |
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0168-1923 |
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CropM |
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MA @ admin @ |
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4471 |
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Mueller, L.; Schindler, U.; Shepherd, T.G.; Ball, B.C.; Smolentseva, E.; Hu, C.; Hennings, V.; Schad, P.; Rogasik, J.; Zeitz, J.; Schlindwein, S.L.; Behrendt, A.; Helming, K.; Eulenstein, F. |
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Title |
A framework for assessing agricultural soil quality on a global scale |
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Journal Article |
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Year |
2012 |
Publication |
Archives of Agronomy and Soil Science |
Abbreviated Journal |
Archives of Agronomy and Soil Science |
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58 |
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sup1 |
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S76-S82 |
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Keywords |
soil quality; indicators; muencheberg soil quality rating |
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This paper provides information about a novel approach of rating agricultural soil quality (SQ) and crop yield potentials consistently over a range of spatial scales. The Muencheberg Soil Quality Rating is an indicator-based straightforward overall assessment method of agricultural SQ. It is a framework covering aspects of soil texture, structure, topography and climate which is based on 8 basic indicators and more than 12 hazard indicators. Ratings are performed by visual methods of soil evaluation. A field manual is then used to provide ratings from tables based on indicator thresholds. Finally, overall rating scores are given, ranging from 0 (worst) to 100 (best) to characterise crop yield potentials. The current approach is valid for grassland and cropland. Field tests in several countries confirmed the practicability and reliability of the method. At field scale, soil structure is a crucial, management induced criterion of agricultural SQ. At the global scale, climate controlled hazard indicators of drought risk and soil thermal regime are crucial for SQ and crop yield potentials. Final rating scores are well correlated with crop yields. We conclude that this system could be evolved for ranking and controlling agricultural SQ on a global scale. |
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0365-0340 |
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CropM, TradeM, ftnotmacsur |
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MA @ admin @ |
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4589 |
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Dumont, B.; Vancutsem, F.; Seutin, B.; Bodson, B.; Destain, J.-P.; Destain, M.-F. |
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Title |
Simulation de la croissance du blé à l’aide de modèles écophysiologiques: Synthèse bibliographique des méthodes, potentialités et limitations |
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Journal Article |
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2012 |
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Biotechnologie, Agronomie, Société et Environnement |
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Biotechnologie, Agronomie, Société et Environnement |
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163 |
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376-386 |
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crops; growth; soil; Triticum; wheats; calibration; optimization methods |
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Crop models describe the growth and development of a crop interacting with its surrounding agro-environmental conditions (soil, climate and the close conditions of the plant). However, the implementation of such models remains difficult because of the high number of explanatory variables and parameters. It often happens that important discrepancies appear between measured and simulated values. This article aims to highlight the different sources of uncertainty related to the use of crop models, as well as the actual methods that allow a compensation for or, at least, a consideration of these sources of error during analysis of the model results. This article presents a literature review, which firstly synthesises the general mathematical structure of crop models. The main criteria for evaluating crop models are then described. Finally, several methods used for improving models are given. Parameter estimation methods, including frequentist and Bayesian approaches, are presented and data assimilation methods are reviewed. |
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French |
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CropM, ftnotmacsur |
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MA @ admin @ |
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4584 |
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Author |
Francone, C.; Cassardo, C.; Richiardone, R.; Confalonieri, R. |
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Title |
Sensitivity Analysis and Investigation of the Behaviour of the UTOPIA Land-Surface Process Model: A Case Study for Vineyards in Northern Italy |
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Journal Article |
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Year |
2012 |
Publication |
Boundary-Layer Meteorology |
Abbreviated Journal |
Boundary-Layer Meteorology |
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144 |
Issue |
3 |
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419-430 |
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energy balance; hydrological balance; land-surface model; morris method; vegetation cover; vitis vinifera l.; atmosphere transfer scheme; environmental-models; energy-balance; uncertainty; simulation; canopy |
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We used sensitivity-analysis techniques to investigate the behaviour of the land-surface model UTOPIA while simulating the micrometeorology of a typical northern Italy vineyard (Vitis vinifera L.) under average climatic conditions. Sensitivity-analysis experiments were performed by sampling the vegetation parameter hyperspace using the Morris method and quantifying the parameter relevance across a wide range of soil conditions. This method was used since it proved its suitability for models with high computational time or with a large number of parameters, in a variety of studies performed on different types of biophysical models. The impact of input variability was estimated on reference model variables selected among energy (e.g. net radiation, sensible and latent heat fluxes) and hydrological (e.g. soilmoisture, surface runoff, drainage) budget components. Maximum vegetation cover and maximum leaf area index were ranked as the most relevant parameters, with sensitivity indices exceeding the remaining parameters by about one order of magnitude. Soil variability had a high impact on the relevance of most of the vegetation parameters: coefficients of variation calculated on the sensitivity indices estimated for the different soils often exceeded 100 %. The only exceptions were represented by maximum vegetation cover and maximum leaf area index, which showed a low variability in sensitivity indices while changing soil type, and confirmed their key role in affecting model results. |
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0006-8314 1573-1472 |
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CropM |
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MA @ admin @ |
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4470 |
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Jing, Q.; Bélanger, G.; Baron, V.; Bonesmo, H.; Virkajärvi, P.; Young, D. |
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Title |
Regrowth simulation of the perennial grass timothy |
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Journal Article |
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Year |
2012 |
Publication |
Ecological Modelling |
Abbreviated Journal |
Ecol. Model. |
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232 |
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64-77 |
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biomass; carbohydrate; leaf area index; n uptake; reserve-dependent growth; temperature; nutritive-value; carbohydrate reserves; phleum-pratense; catimo model; leaf-area; nitrogen-fertilization; spring harvest; meadow fescue; tall fescue; growth |
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Several process-based models for simulating the growth of perennial grasses have been developed but few include the simulation of regrowth. The model CATIMO simulates the primary growth of timothy (Phleum pratense L), an important perennial forage grass species in northern regions of Europe and North America. Our objective was to further develop the model CATIMO to simulate timothy regrowth using the concept of reserve-dependent growth. The performance of this modified CATIMO model in simulating leaf area index (LAI), biomass dry matter (DM) yield, and N uptake of regrowth was assessed with data from four independent field experiments in Norway, Finland, and western and eastern Canada using an approach that combines graphical comparison and statistical analysis. Biomass DM yield and N uptake of regrowth were predicted at the same accuracy as primary growth with linear regression coefficients of determination between measured and simulated values greater than 0.79, model simulation efficiencies greater than 0.78, and normalized root mean square errors (14-30% for biomass and 24-34% for N uptake) comparable with the coefficients of variation of measured data (1-21% for biomass and 1-25% for N uptake). The model satisfactorily simulated the regrowth LAI but only up to a value of about 4.0. The modified CATIMO model with its capacity to simulate regrowth provides a framework to simulate perennial grasses with multiple harvests, and to explore management options for sustainable grass production under different environmental conditions. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved. |
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0304-3800 |
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CropM, LiveM |
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MA @ admin @ |
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4473 |
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