Terroir et variabilité microclimatique : pour une approche à l’échelle de la parcelle

The climatic component is one of the elements of the zoning of viticultural potential, alongside the geological and pedological components (Morlat, 1989; Lebon et al, 1993). Many climatic indices have thus been defined to estimate the potential for wine production at the scale of a region or a country (Carbonneau et al., 1992). The main climatic variables used are temperature and radiation. We note in particular the indices of Branas, Huglin and Ribereau-Gayon (Huglin, 1986). However, few studies have been undertaken on the spatial variability of microclimatic conditions at the scale of a vineyard, a valley, or even a municipality.

Today, faced with the need to be able to adapt to rapidly changing markets and competition, it seems increasingly necessary to better understand the pedoclimatic environment of the vineyard. A typical example of an effort in this direction is the bioclimatic zoning carried out in the department of Aude (Jacquinet, 1989). This approach, based on a dense network of meteorological stations, has made it possible to define various climatically homogeneous zones in this department. The zoning operation of the Champagne vineyard which has been in place since 1991 (Panigai and Langellier, 1992) also includes a climatic component, which is all the more crucial as this vineyard is at the northern limit of vine cultivation. . However, in this region where vines can be grown on steep slopes, it is necessary to ask the question of the spatial representativeness of the measurements made on a meteorological station. Indeed, due to differences in slope (which frequently exceed 10°, or 17%), exposure and altitude, meteorological variables can vary greatly a few hundred meters away.

In order to analyze the components of microclimatic variability within the vineyard, we compared the variability of climatic conditions at the regional scale and at the local scale (vine plot). Our approach consisted in comparing the data of two meteorological observation networks on two different and complementary spatial scales: the meteorological network of the Champagne vineyards, the objective of which is to estimate the mesoclimatic variations on the scale of the whole of the Champagne vineyard (area of ​​the order of 1000 km2), and a local network installed in the commune of Aÿ (Marne, France) intended to characterize the microclimatic variability and the differences in the development of the vine on the scale of the relief unit (1 km2). We have also introduced an intermediate scale, representing a zone that is physically well characterized and that one could think a priori to be homogeneous: the Marne valley. We were particularly interested in 3 variables: radiation, wind and temperature, which all have a decisive influence on the growth and development of the vine.