Résumé
Plant water status monitoring during the vineyard growth cycle constitutes a basic parameter for both harvest quality and vineyard management. Unfortunately, the plant water status measurement requires skills and heavy devices which drastically limit the number of repetitions either in space or in time. Moreover, due to the significant spatial variability in viticulture, extrapolation of one local measurement to a larger scale, vine field or vineyard, is difficult. Therefore, the design of tools and methods to characterize and to assess the spatial variability of plant water status constitutes a big challenge. The aim of this paper is to propose an approach allowing the spatial variability of the plant water status to be assessed. This work proposes a complete literature review of previous works using different approaches to assess the vine water status. Based on this review, it leads to a conceptual approach considering the Spatial (S) and Temporal (T) variability of the plant water status assessment at a whole vineyard scale. This paper is divided into three sections: (i) description of plant water status reference methods based on direct measurements on the plant, (ii) plant water status assessment methods based on auxiliary information (i.e. weather, soil and plant vegetative expression), and finally (iii) a proposal for combining local reference measurement and auxiliary information to characterize the spatial variability of the vine water status at the vineyard scale. Taking into account restrictive assumptions, this paper points out the possibility to provide relevant spatial assessment of the vine water status. This possibility is illustrated with a simple example. This work gives an answer to the significant problem of vine water status assessment over space. It proposes an approach based high spatial resolution auxiliary information to extrapolate a measurement (PLWP or SWP) made at a given time on a reference site. This proposal determines the different steps for further investigations aiming at proposing a spatial model of vine water status.
L'évolution de l'état hydrique de la plante au cours du cycle végétatif est un paramètre important pour la gestion du vignoble et de la qualité de la vendange. Malheureusement, cette mesure fait appel à des dispositifs spécifiques particulièrement contraignants, ce qui limite fortement le nombre de mesures réalisables. La résolution spatiale et temporelle des mesures d'état hydrique est donc généralement faible. Compte tenu de la forte variabilité spatiale observée en viticulture, l'extrapolation de quelques mesures ponctuelles à une zone plus large peut s'avérer délicate. La conception d'outils et de méthodes qui permettent de caractériser cette variabilité constitue à la fois un enjeu et un défi. L'objectif de ce travail est de proposer une approche permettant d'estimer la variabilité spatiale de l'état hydrique des plantes.