Advances in phenology modelling of the grapevine

Abstract

Context of the study. Historical records of grapevine phenology have been collected over decades throughout different winegrowing regions. These records have demonstrated advances in key developmental stages such as budburst, flowering and veraison because of increased temperatures due to climate change. This context has driven a demand to improve modelling phenology to understand past, present and future impacts of climate change on grapevines, and to provide frameworks for adaptation.

Purpose of the study. To review the recent advances made in the development and use of grapevine phenology models and make recommendations for the best practice.

Material and methods. A suite of phenological models with different forms (linear and non-linear) have been tested to understand spatial and temporal variability and cultivar differences for historic, current and future trends. We evaluate different approaches for budburst, flowering and veraison. For the maturity phase the use of sugar concentrations as a proxy for phenology is considered, and assessment of nitrogen and water status for time to target sugar concentrations. Field manipulation of canopy and yield treatments were also used to evaluate impacts on model outcomes.

Results. Our findings demonstrate that research objectives should determine modelling approaches used.  Cultivar differences and diversity have been successfully characterised at different scales. While spatial and temporal diversity play an important role in phenological databases and within region variability, longer time series had the greater impact on model calibration and performance. Through model selection combined with climate change scenarios, future phenology predictions were possible, but under higher emission scenarios, model outcomes significantly diverged for non-linear and linear models. Leaf area: fruit weight ratios substantially modulated model predictions indicating the need to include this in impacts assessment as well as in adaptation strategies to delay sugar accumulation, a proxy used for maturity.  However, environmental factors of water nitrogen did not significantly impact sugar concentrations.

Significance of study. The collation of findings across a range of studies has provided insights into climate change impacts and adaptation strategies for the grapevine, emphasizing the importance of phenology records and ongoing model improvement to better understand climate change consequences in the future.