Refining the growing season temperature parameter for use in winegrape suitability analysis

Abstract

Background and Aims A region's suitability for viticulture is commonly categorised by thermal-based bioclimatic indices during the growing season, of which the growing season temperature (GST) is the most widely used. Growing season temperature thresholds, however, were developed for a specific region and therefore may not translate to other established wine regions, including Australia. This paper aims to investigate and refine the application of GST in modelling spatial suitability of existing wine regions in south-east Australia. Methods and Results Locations suitable for winegrapes according to traditional GST were mapped and compared with established wine regions. Inconsistencies were identified, and a range of refinements was applied in order to improve the spatial representation. Conclusions This study highlights the benefit of three improvements to the GST parameter in order to successfully represent Australian wine regions. First, a latitude adjustment was applied to the GST to account for varying day length. Second, significant temporal variability in GST over the last 15–20 years was identified, highlighting the challenge of selecting a period that represents ‘average conditions’ for such studies. Third, in order to model the spatial extent of Australian wine regions, the inclusion of a ‘hot’ GST classification (19–22°C) was needed. Significance of the Study These refinements allow for the successful quantification of climatic conditions for Australian viticulture. Refined GST thresholds can be applied to future climate projections, providing the industry with vital information and guidance on how to react and adapt to the challenges of climate change.