Grapevine Phenology and Climate Change: Relationships and Trends in the Veneto Region of Italy for 1964–2009

Abstract

A long-term (1964–2009), multiple Vitis vinifera L. cultivar data set has provided a comprehensive assessment of cultivar similarities/differences in phenological timing and growth phases and relationships with climate and climate change in the Veneto region of Italy. The budbreak to harvest period for the cultivars studied covered mid-April to late September, averaging 156 days but varying 55 days across cultivars. The main phenological events and intervals between events exhibited a 25 to 45 day variation between the earliest and latest years, with the bloom to veraison growth interval showing the lowest vintage-to-vintage variation. From 1964–2009, trends of 13 to 19 days earlier were found for bloom, veraison, and harvest dates, while budbreak exhibited high interannual variation and no trend. There were similar characteristics and trends for the main phenological events for early, middle, and late maturing cultivars, although early maturing cultivars changed at a higher rate. Changes in climate in the region led to significant breakpoints in the phenology time series, averaging 1990–1991 across all cultivars, with early and middle cultivars shifting sooner than late cultivars. Growing season average temperatures warmed 2.3°C from 1964–2009, while annual and seasonal precipitation amounts did not change significantly. From 1964–2009, the growing period climate differences were 2.0°C between the years with the shortest and the longest budbreak to harvest intervals. The combined trends in phenology and climate resulted in an average shift of eight days per 1.0°C of warming. The extremely warm summer of 2003 (compressed growth intervals) and warm spring of 2007 (shifts in phenological timing) provide analog conditions to those projected for later this century.