The interplay between grape ripening and weather anomalies in Northern Italy – A modelling exercise

Abstract

Current climate change is increasing inter- and intra-annual variability in atmospheric conditions leading to grapevine phenological shifts as well as altered grape ripening and composition at ripeness.This study aims to i) detect weather anomalies within a long-term time series, ii) model grape ripening revealing altered traits in time to target specific ripeness thresholds for four Vitis vinifera cultivars, and iii) establish empirical relationships between ripening and weather anomalies with forecasting purposes. The Day of the Year (DOY) to reach specific grape ripeness targets was determined from time series of sugar concentrations, total acidity and pH collected from a private company in the period 2009–2021 in North-Eastern Italy. Non-linear regression models were fitted over a time series of ripening parameters on a calendar time basis and assessed for modelling efficiency (EF) and error of prediction (RMSE) in four grapevine cultivars (Merlot, Cabernet-Sauvignon, Glera and Garganega). For each vintage and cultivar, advances or delays in DOY to target specified ripeness thresholds were assessed with respect to the average ripening dynamics. A thirteen years’ long meteorological series monitored at a ground weather station using hourly air temperature and rainfall data was analysed. Climate statistics were obtained and for each time interval (month, bimester) weather anomalies were identified. A linear regression analysis was performed to assess correlations between ripening and weather anomalies. For each cultivar, ripeness advances or delays expressed in the number of days to target the specific ripening threshold were assessed in relation to registered weather anomalies and the specific reference time interval in the vintage. Precipitation of the warmest month and temperature anomalies during late spring (May–June) and during the warmest month (August) we found to be important to understanding the effect of climate change on sugar ripeness. Maximum and minimum temperatures of the May–June bimester and maximum temperatures of the warmest month best correlate with altered total acidity evolution and pH increment during the ripening process. A new modelling framework is presented using historical data that supports management decisions by better understanding past impacts and forecasting for the future.

Grape Berry Responses to Sequential Flooding and Heatwave Events: A Physiological, Transcriptional, and Metabolic Overview

“…Considering that both acids are known to decrease after véraison [117] and taking into account their variations also at T4, our data fully match the known trends (Figure 10). Moreover, lower values with respect to the control were observed for both acids in the F berries, most likely due to their advanced ripening, and also in the heat wave-stressed samples, consistent with previous studies claiming the negative effects of high temperatures and global warming on berry acidity [23,[118][119][120]. Concerning the other sugar compounds, all grouping together in the heatmap, the situation reflected quite well the SSC shown above in Figure 2, especially at T4, when the C and F berries showed the highest values.…”

Weather Variables for Within-Vineyard Awareness of Botrytis Risk

“…Te most severe epidemic observed in this study (Kay site 1-1) was associated with a relatively rapid rate of disease increase (Figure 1(a)), disease-conducive weather, a relatively high crop load, and a long late-season interval. Six rainfall events ≥1 mm from March 1 may have also slowed the development of berry total soluble solids [54]. Berries with splits or other visible injuries were largely absent at Kay site 1-1, suggesting the symptoms were an expression of accumulated latent infections [8].…”

“…In Tasmania, a protracted fowering period of 2-3 weeks [63] can coincide with multiple periods of surface moisture favouring cohorts of latent infection. Use of environmental conditions between E-L 19 and E-L 31, such as mean daily maximum air temperature (Table 3), is relevant to fowering phenology and fruit set in Australia and New Zealand, with likely fow on efects to berry size, bunch architecture, and grape maturity dynamics [54]. Tis interval is also sufciently long to reveal the pattern and slope of the accumulating daily BI, knowledge that could be used to justify a prebunch closure fungicide application at a time when sufcient spray coverage of grape berries is still achievable.…”

Alpine Viticulture and Climate Change: Environmental Resources and Limitations for Grapevine Ripening in Valtellina, Italy

“…Results highlighted that viticultural activity in Valtellina is strongly affected by the interannual variability of environmental conditions [45][46][47]. Additionally, this should be considered to define effective agronomical management of the vineyard [48,49].…”