Grapevine productivity modelling in the Portuguese Douro Region

In Portugal, and particularly in the Demarcated Region of Douro (DDR), wine production has a great tradition, producing the unique and worldwide famous Port wine as well as other remarkably good table wines. In this study the impact of projected climate change to wine production is analysed for the DDR. A statistical grapevine yield model (GYM) is developed using climate parameters as predictors. Statistically significant correlations are identified between annual yield and monthly mean temperatures and monthly precipitation totals during the growing cycle of grapevines. Close relationships between these climatic elements are found that influence the annual yield, with the GYM explaining over 50% of the total variance in the yield time series in recent decades. Furthermore, results point out a clear relationship between the vegetative cycle of grapevines and their basic climatic requirements: anomalously high (low) precipitations in March, during bud break, shoot and inflorescence development are favourable (adverse) to yield, while anomalously high temperatures in May (bloom) and June (berry development) favour yield. The GYM is applied to output from the regional climate model COSMO-CLM, which is shown to skilfully reproduce the GYM predictors. Considering ensemble simulations under the A1B emission scenario, a slight upward trend in yield is estimated to occur until about 2050, followed by a steep and continuous increase until the end of the 21st century, when yield is projected to be about 800 kg/ha above its current values. The results emphasise the potential of using GYM coupled with regional atmospheric models to assess variations in grapevine yield owed to climate change. Complementary studies are in process in order to evaluate possible phenological shifts and wine quality impacts.