CR 58:257-266 (2014)  -  DOI: https://doi.org/10.3354/cr01197

ABSTRACT: This study examined the structure and trends in climate parameters that were important for grapevine growing between 1950 and 2009 in the wine-growing region of Styria in NE Slovenia. The study also included the dynamics of grape ripening and the timing of harvest for 4 varieties grown in the region between 1980 and 2009. Temperature and precipitation characteristics from 3 stations (Celje, Jeruzalem, and Maribor) in the region were organized into annual and growing-season periods and were used to assess the effects on the different varieties and on wine quality. Based on the data associated with the content of soluble solids, total acidity, and the recommended date of harvest for a particular year, trends towards earlier maturity of 12-25 d were observed. In general, temperature changes were more significant after 1980 than between 1950 and 1979. The mean annual and seasonal temperatures (1980-2009) increased significantly, by 0.4 to 0.6°C per decade. The average growing-season warming rates were driven particularly by changes in maximum temperatures, with significant increases in the number of days with T_max > 30°C. Growing-season warming has also resulted in changes in heat accumulation indices, with significant increases since 1980. Changes in temperature parameters show strong correlations with harvest dates and fruit composition. Trends toward higher sugar levels and lower total acidity are a consequence of higher temperatures during the ripening of the berries. Grapes now ripen at temperatures that are approximately 1.2-1.8°C higher than 30 yr ago. For varieties that ripen early, the temperatures are predicted to become too hot to produce high-quality wines.

KEY WORDS: Climate change · Temperature · Vine varieties · Grape maturity · Slovenia