Delineation significance in viticultural zoning: examples in the Southern Côtes-du-Rhône

In order for a spatialized gestion of wine-producing areas, delineation of viticultural zones is needed. Viticultural zoning according to qualitative expression of varieties is a great concern for the wine professionals in the Southern Côtes-du­Rhône (lat. 43°50′-44°30′ North, long. 4°30′-5°10’East of Greenwich meridian). In this study, viticultural terroirs are regarded as parts of agricultural land, where harvest expression is likely to be homogeneous. Geographic information analysis, based on soil landscape characterization, is aimed at terroir spatial distribution modelling. Geographic data available are : field observations ; aerial photographs ; topographic, geological, and soil maps; Digital Elevation Model; satellite images. Terroir determination separately considers two objects: the soil landscape unit and the viticultural plot; both are described by about twenty environmental variables; 3 additional variables describe plots only. Multivariate clustering obtained from several classifications calculated on these variables, determines terroirs at two different scale and resolution levels: «global», from 55 soil landscape units; «local», from 91 plots. The terroirs interpolated from plot clusters are characterized by black Grenache harvest data measured over the course of 17 vintages (1982-1998): their harvest composition differ. Such locally defined terroirs are compared with the globally defined terroirs. Validity of global viticultural terroirs is discussed, in relation to variables influence and plot localization relevance.