Categorized maturity index for viticultural zoning: A case study for Iberia

Abstract

Optimal climatic demands of different winegrape varieties are specific to each viticultural region. In this context, an innovative category analysis is used as a zoning tool, depicting the suitability of a particular region for winemaking. In this study, we assess the “optimum viticultural year” based on a set of pre-established bioclimatic indices. By combining this knowledge with the different classes of the degree-day based Huglin Index, a single multi-purpose index is developed. Hence, the CMI (Categorized Maturity Index) is split into four non-overlapping categories for viticultural zoning (0 – Unsuitable in 50% of the years; 1 – Suitable for early maturing varieties; 2 – Suitable for intermediate maturing varieties; 3 – Suitable for late maturing varieties). As a case study, the CMI is calculated over the Iberian Peninsula using climatic variables (daily temperatures and precipitations) obtained from an observational gridded dataset (E-OBS) over the period of 1961-2000. A 16-member ensemble of model transient experiments (produced by the ENSEMBLES project) is used for assessing climate change projections over the region (following the SRES A1B scenario). Results show that climate change may have detrimental impacts in some Iberian wine regions (e.g. Alentejo/Vidigueira and Granja-Amareleja, Condado de Huelva, Jerez, Montilla-Moriles, Bullas, Ribera del Guadiana), by increasing drought and cumulative thermal effects during the growing season. These changes may represent an important limitation to grapevine development, making adaptation/mitigation strategies crucial. On the other hand, high altitude and coastal regions (e.g. Vinho Verde, Rías Baixas) may benefit from warmer and dryer future climates in both wine quality and new potential vineyard areas. These climate change driven-scenarios provided by the CMI are thereby a valuable tool for viticultural zoning over the Iberian Peninsula or over any other wine region.