Climate projections of chill hours and implications for olive cultivation in Minas Gerais, Brazil

Abstract

The objective of this work was to determine the accumulation of chill hours and to define the areas with aptitude for olive (Olea europaea) cultivation in the state of Minas Gerais, Brazil, as well as to analyze the impacts of climate change projections on chilling-hour requirements and climatic zoning, in two radiative forcing scenarios. The trigonometric method was used to quantify the number of chill hours, considering base temperatures (Tb) of 7.0, 9.5, and 13°C (high, medium, and low chill, respectively), and was applied to present climate (1983-2012) and to two future climate (2041-2070 and 2071-2100) conditions. The present climate data were obtained from 47 conventional weather stations, and the future climate data were obtained from three Earth system models (IPSL-CM5A-LR, MRI-CGCM3, and MIROC5). Future projections point to a decrease in the suitable areas for olive crop cultivation, particularly under representative concentration pathway (RCP) 8.5 and for olive cultivars with a high-chilling requirement (Tb=7.0ºC). Of the olive cultivars requiring medium chill (Tb=9.5ºC), only 2.6% (RCP 4.5) and 1.6% (RCP 8.5) will be suitable in the extreme south and in higher altitude areas of Minas Gerais, while, of those requiring low chill (Tb=13ºC), 11.8% (RCP 4.5) and 6.7% (RCP 8.5) will be suitable. If the climate projections become true, the cultivation of olive crops will be viable in the southern region and in higher altitude areas of the state of Minas Gerais.

Studying Parameters Affecting Accumulation of Chilling Units Required for Olive Winter Flower Induction

“…One simple model counts the number of hours below a certain base temperature: 7.2 • C [33,34]. Another, termed as the ''trigonometric approach', predicts different base temperatures depending on the chilling requirement of a cultivar: 7.0 • C, 9.5 • C, and 13 • C for high, medium, and low chilling requirements, respectively [35]. The De Melo-Abreu (DMA) model [36] initially developed for predicting the olive flowering date is similar in structure to the Utah model, with each hourly temperature contributing either a positive or negative amount of CU.…”

“…Recent publications focus on the effect of climate on the date of olive flowering [36,42]. Within traditional olive growing regions as well as other world regions, warmer WTRs will mean significantly less flowering and yield for some of the more popular olive cultivars [35,38], although some predictions show no potential reduction in flowering levels [40]. With this unknown future for olive production, a more precise model that can reliably predict the level of flowering in olives based on hourly winter temperatures may be a timely resource for both olive growers and researchers.…”