The aim of this work was to investigate the frequency and intensity of extreme weather events in various centers from Romania’s viticultural regions: winter frost, extreme temperatures during the growing season and summer droughts. Winter frost damaging the vine is a significant risk to grape production, mainly in the plains and lowlands to the foothills. The frequency of winter frost damaging the vine has increased during the last decades, in the context of climate change. Also, there has been found a significant increase in the number of hot days (Tmax > 30°C) and very hot days (Tmax > 35°C). The evolution of these extreme events was followed in Craiova, Constanta, Bucharest, Timisoara, Cluj-Napoca, Oradea and Iasi, between 1977 and 2015. The long term study (18 years) conducted in the experimental plantation of the University of Agronomic Sciences and Veterinary Medicine Bucharest revealed their influence on vine. During the last two decades, there has been registered a trend of increasing the frequency and intensity of winter frost, damaging vine (Tmin < -20°C), heat waves (number of days with Tmax > 30°C and > 35°C) and droughts that adversely affect viticulture, production and quality of grapes and wine. The highest warming trends were observed for northern viticultural regions (Transylvania and Moldavia) and for the seaside. Although the intensification of heat waves increases sugar accumulation in the berries, they trigger a significant reduction in grape production and in titrable acidity, requiring corrections and resulting in unbalanced wines. Meanwhile, droughts trigger production decrease. To avoid negative effects on vine, it is necessary to take measures, both on a short, medium and long term.
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∘47′07′′; E Long.: 26∘076′28′′; elevation 87 m), 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, Fetească regală 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 ∘C for the average annual temperature; +0.78 ∘C for average temperature in the growing season; +2.37 ∘C for average maximum temperature in the warmest month; +2.11 ∘C for average maximum temperature in the summer; +234 units in Huglin index; + 173 units in Winkler index and +0.35 ∘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.
Twenty-three new Romanian table grapes varieties were analysed for their phenological behaviour, quantitative characteristics (bunch weight, berry weight, their length and width, grape yield), sugar accumulation, titratable acidity, and ºBrix / acid ratio during three consecutive years (2015-2017). The higher temperatures recorded during the study period determined an advance in the development of the main phenophases, especially the grapes’ harvest maturity. Absolute minimum temperatures during winter, damaging the vine, have significantly affected grape yield. As a consequence of earlier phenology and lower yields due to frost damage, harvest was advanced between 2 and 4 weeks than the average. The results obtained in this study favoured five remarkable genotypes for their very good quality of grape (‘Victoria’, ‘Tamina’, ‘Xenia’, ‘Napoca’ and ‘Augusta’). These varieties are distinguished by the highest values for bunch and berry weight (between 300-500 g and 5.5-8.4 g, respectively), berries’ size uniformity, the sugar content between 15.45-21.53 ºBrix and balanced ºBrix / acid ratio. Lately, the high temperatures during the grape maturation period have led to increased accumulations of sugar in berries, to reduced acidity, which affects the sugar-acidity balance; a more careful choice of grape harvest time is needed.
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