Impacts of climate change on cv. Glera buds’ fruitfulness – 18 years of monitoring in the Conegliano-Valdobbiadene area, Italy

Abstract

Context and purpose of the study. The vine is generally a very fertile plant when compared to other tree species. However, there are varietal, environmental and cultural effects that can affect bud fruitfulness. Since vine productivity can vary greatly from one year to the next, in the recent climate change scenario this study focused on: i) highlighting the magnitude of fluctuations in bud fruitfulness; ii) determining the influence of the occurrence of extreme weather events and the most significant time windows on fruitfulness; iii) to develop predictive models to support winegrowers.

Material and methods. In ten Glera vineyards in the Valdobbiadene area from 2006 to 2023, field data of buds’ fruitfulness were recorded in spring (BBCH 53) on the first 10 buds and expressed as: potential fruitfulness, real fruitfulness, n. blind buds and n. sterile buds. These data were related to 61 indices of climate extremes proposed by the WMO calculated on 18 years’ time series of the nearby weather stations on an annual and monthly basis. Since bud fruitfulness, the result of the flower induction process, is influenced by the meteorological trend of two successive years, field fruitfulness data were compared with indices calculated both on the current season and on the previous one.

Results. The intensity and duration of thermal anomalies (summer days, frost days), heat waves and tropical nights, temperature excursions, drought events and excess water and warm winters significantly influenced buds’ fruitfulness in an even opposite way in relation to the period in which they occur. Not only does the trend of the previous year significantly affect the degree of fruitfulness but also that of the first months of the season (influencing the last stages of gametogenesis). Not only does the trend of the previous year significantly affected the degree of fruitfulness but also that of the early months of the year (influencing the last stages of gametogenesis). Predictive models have been developed both for a single variable and using Multiple Linear Regressions (MLR) being able to effectively estimate the degree of fruitfulness and the extent of appearance of blind and sterile buds. The results obtained represent an important tool for assessing the impact of climate change on viticulture, understanding which environmental variables are decisive on flower induction and providing support to winegrowers to plan pruning and estimate vineyard yield.