Spider: spatial extrapolation of the vine water status at the whole denomination scale from a reference site

Abstract

<p style="text-align: justify;"><strong>Aim</strong> : The objective of this work was to test an approach to extrapolate the vine water status (<strong>Ψ</strong>) over a whole denomination. The method has already been tested at the field level, but it has never been validated on a spatial scale that large.</p><p style="text-align: justify;"><strong>Methods and results</strong> : The extrapolation model is based on an empirical approach that relies on a reference measurement and a spatial model of <strong>Ψ</strong>. Experiments were carried out over the 2946 ha of the denomination of Tavel (Gard, France). This site exhibits significant spatial variability in soil composition (three different soil units) and elevation, it is not irrigated and has a Mediterranean climate. This context leads to strong spatial variability in <strong>Ψ</strong>. Focusing on the most common grape variety used in the denomination, Grenache, a data base of predawn leaf water potential (PLWP) was built over three consecutive years (2008, 2009 and 2010). Respectively 10, 24 and 24 sites located throughout the denomination have been monitored for PLWP. The monitoring consisted respectively in 7, 10 and 9 measurement dates throughout the growing season. The spatial model was calibrated from 2009 and 2010 data and the prediction was tested on 2008 data. The results showed that the approach was completely transferable to a large territory like Tavel. The model significantly improved the quality of the prediction (R² = 0.9) compared to a conventional non-spatial method based on the mean values (R² = 0.61).</p><p style="text-align: justify;"><strong>Conclusion</strong>: On the basis of a single measurement taken at time “t” on a reference site, the model makes it possible to estimate <strong>Ψ</strong> on any site of the study area. The results, therefore, demonstrated the ability to extrapolate a PLWP measurement made on a reference site over the whole denomination constituted of three different soil units.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: This study represents a significant step since it demonstrates the existence of a spatial model of <strong>Ψ</strong> at a scale larger than the single field. It provides critical knowledge to consider the use of an empirical spatial model across a relatively large territory. This step opens up the possibility to provide spatial extrapolation model of <strong>Ψ</strong> based on data assimilation or existing data base.</p>

An overview of the recent approaches to terroir functional modelling, footprinting and zoning

“…A similar approach using δ 13 C measurements as ancillary variables enabled the extrapolation of stem water potentials for a rainfed vineyard with moderate water stress (Herrero-Langreo et al, 2013). These approaches may be transferable to a whole-vineyard scale (∼ 29 km 2 ), according to Baralon et al (2012), who constructed an important measurement database (58 fields monitored in all) over the course of three consecutive vintages. This approach considered a stratified sampling based on soil types, which is most effective when water restriction is high .…”

Spider&delta;: an empirical method to extrapolate grapevine (<em>Vitis vinifera</em> L.) water status at the whole denomination scale using &delta;¹³C as ancillary data

“…Vine water status can be highly variable at the withinfield level (van Leeuwen et al, 2006), at the vineyard level (Taylor et al, 2010) and, of course, at the whole appellation level (Baralon et al, 2012). Variability in vine water status induces a great variability of vine response in terms of vigour, yield, precocity and grape composition (Tisseyre et al, 2008).…”

“…This spatial model has been successfully tested at the within-field level (Acevedo-Opazo et al, 2010a) and at a vineyard level constituted of several blocks (Taylor et al, 2011). More recently, the model has been successfully tested at the whole denomination scale by Baralon et al (2012). At this scale, the approach was called SPIDER (SPatial extrapolation of the vIne water status at the whole DEnomination scale from a Reference site).…”

“…At this scale, the approach was called SPIDER (SPatial extrapolation of the vIne water status at the whole DEnomination scale from a Reference site). Note that in Baralon et al (2012), the term denomination refers to an appellation (a legally defined and protected geographical indication). The scale at which these authors have actually tested the approach is a small appellation of the south of France (Tavel) where climatic conditions where assumed homogeneous.…”

“…At this scale, SPIDER may be of particular interest as a decision support tool for field selection based on the water restriction experienced by the vines (Reynard et al, 2011) or for identifying zones where irrigation is most needed. However, as outlined by Baralon et al (2012), applying SPIDER at a large scale raised some practical limitations, of which the most important is the spatial resolution that is possible with such an approach. Indeed, the spatial resolution of the model is limited by the number of sites where a s coefficients are known.…”