Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Doctorat → Espagne → 2016 → Modelización de la transpiración del olivo y el almendro en condiciones de déficit hídrico

Universidad de Córdoba (2016)

Modelización de la transpiración del olivo y el almendro en condiciones de déficit hídrico

García Tejera, Omar

Titre : Modelización de la transpiración del olivo y el almendro en condiciones de déficit hídrico

Modelling transpiration of olive and almond trees under water deficit conditions

Auteur : García Tejera, Omar

Université de soutenance : Universidad de Córdoba

Grade : Tesis Doctoral 2016

Résumé
The limitations of water for irrigation, has promoted the development of irrigation systems and crop management practices devoted to improve the efficient use of water. However, the best use of these tools requires a clear understanding of the components of the soilwater-plant system. In that sense, simulations models provide an excellent tool not only to synthesise the knowledge of each of the elements composing the system in a concise manner but to explore the interactions among them. The general objective of the present thesis is to develop a simulation model able to mimic the behaviour of each of the elements related to the water balance of tree crops under localised irrigation and submitted to any level of water stress. One of the main constrains when modelling the water balance of a tree relates to the parametrization of the water uptake capacity of the roots. The water uptake capacity of a single root is not a fixed value but it varies with soil water content or the soil temperature. Although the effect of temperature on radial root hydraulic specific resistance (Rp) (a measure of the uptake capacity of a root) is a known phenomenon, the impact of Rp variations expected from soil temperature changes over the tree root system is not. The first experiments developed studied the change in Rp in olive (Olea europaea L.) ‘Picual’ and a widely used hybrid rootstock for stone fruits, GF677, at five different temperatures, showing that a variation of 3 and 4.5 folds exists for olive ‘Picual’ and GF677 respectively in the range from 10 to 20 ºC. The functions obtained were scaled up to show the theoretical changes of total radial root system resistance in a common tree orchard in a Mediterranean climate at a daily and seasonal scale, using recorded soil temperature values. A difference between summer and winter of : 3.5 for olive ‘Picual’ and 9 folds for GF677 were observed. According to the results obtained it would therefore be advisable to assess them explicitly into soil-plant-atmosphere continuum (SPAC) models. SPAC models have been widely used to simulate water balance on trees. In these types of models the plant is regarded as an electric circuit composed of resistances in series or in parallel. As part of the present thesis a SPAC model for simulating tree transpiration (Ep) and water potential with variable water stress and water distribution in the soil have been formulated. As a special feature of this model, the soil is not only divided into several layers but also into different compartments, thus capturing the heterogeneity in root length and soil water content present in trees, especially those in which drip or any type of localised irrigation is used. The multi-compartment function for the soil and roots is coupled to a simplified representation of the canopy using a sun/shade approach, thus building up a complete supply-demand framework. The model was tested at two different scales. At a pot scale using a special lysimeter designed to accommodate split root young olive and almond (Prunnus dulcis Mill.) trees, and at a field scale on a hedgerow commercial olive orchard. In both experiment the model was able to successfully (lowest R2 = 0.81) simulate transpiration and leaf water potential when different levels of stress were imposed. The study of tree water balance during water stress conditions performed with the model revealed that at high root length densities it is the uptake capacity of the root what governs the water withdrawal by the root system and that root clumping might play a major role reducing the effective absorbing surface of the root system. Besides, at orchard level it was observed that the use of drip irrigation systems always limits the maximum attainable transpiration (Epmax) for a given environment, and that the degree of limitation would depends on the ratio of areas of roots and leaves and the vapour pressure deficit. Finally, a case study exercise with the model showed that two different irrigation strategies could be followed depending on the available water. If sufficient water is available to meet tree transpiration demand, one should wet a soil volume high enough to ensure that Ep is as close as possible to Epmax. Conversely, if a deficit is imposed, the strategy should be to reduce the wetted area in order to maximize the water routed to Ep The model proved to be a tool robust enough to capture the trend in Ep and in leaf water potential for trees submitted to different irrigation regimes and allows the study of the interactions among irrigation, tree Ep and the environment.

Mots Clés : Almendros, Cultivos arbóreos, Déficit hídrico, Eficiencia de uso del agua, Estrés hídrico, Ingeniería hidráulica, Modelos de simulación, Modelos SPAC, Olivos, Riegos

Présentation

Version intégrale (5,52 Mb)

Page publiée le 8 décembre 2016, mise à jour le 8 février 2019