Modelling within-region spatiotemporal variability in grapevine phenology with high resolution temperature data

Andrew Hall,John Blackman

doi:10.20870/oeno-one.2019.53.2.2450

Abstract

Aim: While it is well recognised that climate can vary spatially so that grapevine phenology significantly varies within a winegrowing region, the magnitude of temporal variability in climate determining factors to engender a significant difference in phenology over time can only currently be described in general terms. This study’s aim was to quantify and compare the temporal variability, and its interaction with spatial variability, in grapevine phenology and three derived viticulture climate indexes for three viticulture regions in eastern Australia with varying topographies, latitudes and continentalities.Methods and Results: Maximum and minimum temperature data were spatially interpolated to produce fine scale topoclimate maps at 30 m resolution for every day of a 20 year period from 1998 to 2018 for the three viticulture regions. Grapevine phenology modelling using a heat accumulation methodology was then applied to estimate growing season temperature, cool night index and post-harvest growing degree days (GDD) for every 30 m map pixel of the three regions in each of the 20 growing seasons.Conclusions: Summary statistics that quantify the spatial and year-to-year temporal variability and the interaction of spatial and temporal variability (i.e. spatiotemporal variability) demonstrated significant differences in grapevine phenology between each of three regions. The key conclusion was that within-region temporal variability in growing season temperature, cool night index and post-harvest GDD exceeded within-region spatial variability.Significance and impact of the study: This is the first study to quantify temporal variability in modelled grapevine phenology, compare this with the level of spatial variability and also consider the interaction of spatial and temporal variability in grapevine phenology within viticultural regions. This study opens many potential lines of further investigation into the effect of temporal variability on wine production and the cultural terroir factors that develop within a wine region as a result, particularly in the context of forecast future increases in inter-annual temperature variability.

Highlights

Sustainable production of winegrapes depends on suitable terroir, i. e. site characteristics combined with tailored viticultural practices (Wilson, 1998)
Interpolated daily maximum and minimum temperature data were acquired in raster format (i. e. maps made up of small individual units, each having a numerical value describing the temperature for the coincident actual location stored as 2D map arrays) for each day from July 1 1998 to June 30 2018 from the Australian Bureau of Meteorology (BOM) (2010) for a total of 15336 temperature datasets
Maps describing the level of temporal variability across the 20 years for the key indexes of growing season temperature, cool night index and post-harvest heat accumulation are presented in Figure 3 (Canberra District), Figure 4 (Orange) and Figure 5 (Yarra Valley)

Summary

INTRODUCTION

Sustainable production of winegrapes depends on suitable terroir, i. e. site characteristics combined with tailored viticultural practices (Wilson, 1998). Comparisons can be made with established regions with a similar climate to select appropriate varieties for new vineyard plantings based on historical temperature data (Jones, 2006a). Care needs to be taken when considering published historical climate data of a viticultural region, because within-region spatial variability in temperature can be significant. While spatial variability has been characterised in summaries of viticultural indexes used to compare growing conditions between regions, temporal variability in winegrape conditions has not. Instead of using averaged climate data and modelling this once, the current study ascertained temporal variability in production by modelling each year in the period individually, and summarising the key temperature derived viticulture indexes across the years. Consideration of spatiotemporal climatic variability may add value to future analyses of climate change effects on sustainable viticultural production

Case study region and cultivar

Phenological modelling

DISCUSSION