The climate change influences and trends on the grapevine growing in Southern Romania: A long-term study

The topography and pedoclimatic conditions in Romania are diverse and in many places highly favourable for viticulture. In the past 21 years it was observed that the climate slowly changed, with a visible impact on grape quality. The influence of climate change on grape growing depends however on the vineyard location, relief and soil, multiple combination of varieties and rootstocks, water supply, as well as viticultural practices. The influence of the climate change was studied during a long period of time, between 1998 and 2018, in our experimental vineyard at UASVM Bucharest (N Lat.: 44 degrees 47'07"; E Long.: 26 degrees 076'28"; elevation 87m), located in the Southern part of Romania. The observations made during last twenty one years on qualitative and quantitative parameters of the most widespread Romanian grape variety, Feteasca regala grafted on the Kober 5 BB rootstock, along with the calculated values for the usual climatic indices describing viticultural climate, showed some significant climate changes in comparison with a reference period between 1961 and 1997 taken from the existent scientific literature. Our observations during past twenty years reveal a trend of increase in all studied temperature-dependent climatic indices during the grape growing season, with a large variation in the absolute minimum temperatures during winter, which suggests a shift towards an increased thermal amplitude between summer and winter temperatures in certain years. Compared with the reference period (1961-1997), an increase in the following temperature-dependent indices was observed: +0.75 degrees C for the average annual temperature; +0.78 degrees C for average temperature in the growing season; +2.37 degrees C for average maximum temperature in the warmest month; +2.11 degrees C for average maximum temperature in the summer; +234 units in Huglin index; +173 units in Winkler index and +0.35 degrees C in Cool night index. These climate changes bring important variations of grape yield due to the minimum temperatures during winter and significant reduction of total acidity, along with a significant increase of sugar concentration. This study aids to understand and anticipate the rate of climate change in Southern Romania, the extent of the changes in grape quality and the interventions required to maintain constant grape and wine quality.