Projection of phenology response to climate change in rainfed vineyards in north-east Spain

- Temperature and precipitation changes in Mediterranean climate under RCP4.5 and RCP8.5 scenarios.
- Changes in water available for vines under rainfed conditions under climate change.
- Relationships between grape phenology and climatic variables.
- Effects of temperature and water available changes on grape phenology.

The aim of this research was to predict the changes in vine phenology of some white grape varieties when rainfed vineyards are subjected to climate change. The research was conducted in the north east of Spain, in an area with a Mediterranean climate. Temperature and precipitation changes under two Representative Concentration Pathway (RCP) scenarios - RCP4.5 and RCP8.5 - were simulated based on an ensemble of models. Water losses by runoff were predicted using the WEPP model and changes in evapotranspiration were estimated according to the predicted changes in temperature, wind speed and solar radiation for the same scenarios. Dates of budbreak, bloom, veraison and harvest of three varieties were evaluated: Chardonnay, during the period 1998-2012; and Parellada and Macabeo during the period 1998-2009. Projections for 2030, 2050 and 2070 were made based on the observed phenological dates and the heat accumulation needed to reach each stage and water available recorded in different periods along the growing cycle. An advance of all phenological dates was predicted, higher for veraison and harvest than for the earlier stages and higher for Parellada than for Macabeo and Chardonnay. These stages may advance up to 10 and 16 days, respectively, for 2050 and up to 12 and 20 days for 2070 under the RCP4.5 scenario. Under RCP8.5 scenario, the advance by 2070 could be up to 23 and 28 days. These changes resulted in a shortening of the periods between phenological dates (>10 days), higher for Parellada than for Chardonnay and Macabeo. The results also showed an additional advance of bloom for Chardonnay and Macabeo associated with decreasing water available, and an advance of veraison and harvest for all three varieties, associated with decreasing water available, particularly between budbreak and bloom and between bloom and veraison, depending on the variety.