Response and adaptation of grapevine cultivars to hydrological conditions forced by a changing climate in a complex landscape

Soil water availability is one of the main components of the terroir concept, influencing crop yield and fruitcomposition in grapes. The aim of this work is to analyze some elements of the "natural environment" of terroir(climate and soil) in combination with the intra-specific biodiversity of yield responses of grapevine to wateravailability. From a reference (1961-90) to a future (2021-50) climate case, the effects of climate evolution onsoil water availability are assessed and, regarding soil water regime as a predictor variable, the potential spatialdistribution of wine-producing cultivars is determined.In a region of Southern Italy (Valle Telesina, 20,000 ha), where a terroir classification has been produced (Bonfanteet al., 2011), we applied an agro-hydrological model to determine water availability indicators. Simulations wereperformed in 60 soil typological units, over the entire study area, and water availability (= hydrological) indicatorswere determined. Two climate cases were considered: reference (1961-90) and future (2021-2050), the formerfrom climatic statistics on observed variables, and the latter from statistical downscaling of predictions by generalcirculation models (AOGCM) under A1B SRES scenario. Climatic data consist of daily time series of maximumand minimum temperature, and daily rainfall on a grid with a spatial resolution of 35 km.Spatial and temporal variability of hydrological indicators was addressed. With respect to temporal variability,both inter-annual and intra-annual (i.e. at different stages of crop cycle) variability were analyzed. Some cultivarspecificrelations between hydrological indicators and characteristics of must quality were established.Moreover, for several wine-producing cultivars, hydrological requirements were determined by means of yieldresponse functions to soil water availability, through the re-analysis of experimental data derived from scientificliterature. The standard errors of estimated requirements were determined.To assess cultivars adaptability, hydrological requirements were evaluated against hydrological indicators. Aprobabilistic assessment of adaptability was performed, and the inaccuracy of estimated hydrological requirementswas accounted for by the error of estimate and its distribution.Maps of cultivars potential distribution, i.e. locations where each cultivar is expected to be compatible withclimate, were derived and possible options for adaptation to climate change were defined.The 2021 - 2050 climate scenario was characterized by higher temperatures throughout the year and by asignificant decrease in precipitation during spring and autumn.The results have shown the relevant variability of soils water regime and its effects on cultivars adaptability.In the future climate scenario, a hydrological indicator (i.e. relative evapotranspiration deficit - RETD), averagedover the growing season, showed an average increase of 5-8 %, and more pronounced increases occurred in thephenological phases of berry formation and ripening. At the locations where soil hydrological conditions werefavourable (like the ancient terraces), hydrological indicators were quite similar in both climate scenarios andthe adaptability of the cultivars was high both in the reference and future climate case. The work was carriedout within the Italian national project AGROSCENARI funded by the Ministry for Agricultural, Food and ForestPolicies (MIPAAF, D.M. 8608/7303/2008)