A “terroir” study, based on the “Basic Terroir Unit” concept (B.T.U.), has been realized in the french vineyard of Anjou (Loire Valley). In the characterization of B.T.U.’s natural factors, the geological component (geological stage and lithology) is the first key used to B.T.U. identification. The second affects the soil and its variability. A ground model has been elaborated as suitable to mapping small areas showing a sufficient homogeneous vine behavior. This pattern, based on the soil depth and the weathering intensity of the parent rock, allows to distinguish three main type of environments : “ rock, alteration, alterite”.
Furthermore, a viticultural survey based on parcels has been carried out and coupled to the characterization and mapping of B.T.U. The data crossing, by an information geographic system (I.G.S.), of these two approaches allowed an analysis of the wine growers empirical perception and valorization of “terroir”.
The survey has been realized among all wine-growers’ home, in the twelve main viticultural municipalities of the studied area. The different kinds of questions were about to : the socio-economical farm aspects, the vine and its ecophysiological behavior, the viticultural and oenological wine grower practices, the wine grower’s soil empirical knowledge, the climate and the parcel potentiality. Most questions presented three modalities of answers for each variable : “in the average, higher or lower than the average”. Results were treated with two methods : crossing selection and multiple factor analysis. These analysis were realized at two scales : the first one which was the ground model " rock, alteration, alterite " applied in the whole studied area, so called “general ground model” ; and the second one which was the B.T.U. for the both main geological systems : the metagrauwacke of the brioverian period and the green to grey sandstone schist of the ordovician-devonian period. At the first scale, the wine growers have well differentiated the both opposite rock and alterite environments, by climatic (air temperature, frost risk), pedoclimatic (temperature and soil moisture regime) and pedological (soil depth and stone content) criteria. The environment “ alteration ” is less well characterized from the survey but also from the characterization method of natural factors. The vine behavior (bud break earliness, canopy development in the both normal year and dry year) is also influenced, according to the survey, by the environment type. Wine growers have partly integrated these detected differences between parcels on their viticultural (grape variety, number of selection for grape harvesting) and oenological practices (kind of wine, vinification and marketing of wine per parcel, yeast using).
The analysis at the B.T.U. scale have confirmed the pertinence of the ground model “ rock, alteration, alterite ” on the perception of pedologic and pedoclimatic characteristics and a great influence of the geological system on the local climatic factors and on the vine behavior.
The coherence of results between these two approaches (survey and integrated characterization) would allow the data acquisition, per survey, about several variables that are not directly collected during the B.T.U. mapping phasis.
AttachmentsNo supporting information for this article