Jean-Pascal Goutouly

Why climate change will not dramatically decrease viticultural suitability in main wine-producing areas by 2050

Hannah et al. (1) recently published a comprehensive study showing substantial impacts of climate change on viticultural suitability, leading to potential ecological issues. We agree that expansion of viticulture into new areas can lead to a decrease in biodiversity and that an increase in water use for irrigation might lead to major freshwater conservation impacts. However, we disagree with the alarming statement that suitability for winegrowing of main wine-producing areas worldwide will dramatically decrease over the next 40 y. We point out major methodological flaws in ref. 1, mostly linked to (i) the misuse of bibliographical data to compute suitability index, (ii) underestimation of adaptations of viticulture to warmer conditions, and (iii) the inadequacy of the monthly time step in the …

Abundance weighting for improved vegetation mapping in row crops: application to vineyard vigour monitoring

We present a complete framework for vigour mapping in row crops by multispectral remote sensing. The main contribution consists of taking into account vegetation abundance in the computation of vigour indexes. Though developed in a viticulture context, the proposed algorithm is generic enough to be adapted to any row crop, especially in horticulture. The algorithm takes advantage of both spectral and spatial features extracted from image data. Spectral information is used at pixel level by an independent component analysis (ICA) based algorithm to process vegetation abundance maps. As for spatial information, deformable models are used to fit a network of rectangles to individual plants. Both spectral information and spatial information are then combined to compute abundance-weighted vigour indexes that are assigned to specific plants. Resulting measurements are then used for within-block vigour mapping. A validation procedure is carried out on experimental vine plots. It is shown that the use of vegetation abundance by itself or as a weight in the computation of vegetation indexes improves the accuracy of vigour assessment in row crops.

Mapping Grapevine (Vitis vinifera L.) Water Status during the Season Using Carbon Isotope Ratio (δ13C) as Ancillary Data

Vine water status is a major parameter for vine management because it affects both wine quality and yield. In order to optimize vineyard management and harvesting practices, it is necessary to characterize vineyard water status spatial variability. This work aims at establishing an empirical spatial model for stem water potential (ΨStem) with ancillary data based on vine water status. Carbon isotope ratio (δ13C) measured at harvest was selected as ancillary data because it reflects only the effect of vine water status variations integrated over the season and is not impacted by other factors such as vine nitrogen status. The proposed model was applied at the intrablock level. It is based on the spatial extrapolation of a ΨStem value measured at a reference site using δ13C values collected over the block. Measurements of ΨStem and δ13C were carried out over three consecutive years on 96 locations within the block. ΨStem values obtained with a spatial model were more accurate than ΨStem values obtained with a nonspatial model, indicating the relevancy of δ13C values to account for spatial variability of vine water status. Results show that operational maps of vine water status can be obtained by means of a spatial model, in which δ13C values from a previous season are used as ancillary data. Maps can be updated at any given time during the season by carrying out a limited number of ΨStem measurements in selected locations. This model offers a tool to monitor vine water status and to implement management practices while considering vine water status intrablock variability.