Predicting the Impact of Climate Change on Pistachio Chilling Requirements in Yazd Province, Iran

Articles in Press

Document Type : Original Research Article

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Department of Humanities and Social Sciences, Faculty of Geography, Yazd University, Yazd, Iran

Abstract

Pistachio (Pistacia vera L.) production in arid regions depends critically on sufficient winter chilling to ensure regular budbreak and stable yields. This study assesses current and future winter chill for major pistachio cultivars in Yazd Province, central Iran, under ongoing climate warming. Three chill models were evaluated: the Chilling Hours model (temperatures between 0 and 7.2 °C), the Utah model, and the Positive Utah model. Observed three-hourly and daily minimum and maximum temperatures from seven synoptic stations (2003–2020) were combined with statistically downscaled projections from the CanESM2 global climate model under three emissions scenarios (RCP2.6, RCP4.5, RCP8.5) for 2021–2050. The Chilling Hours model, driven by mean daily temperature, showed the best performance, with the lowest errors and highest correlation with observed chill-related phenology, and mean temperature outperformed minimum and maximum temperature as a predictor of chill accumulation. Projections indicate a general decline in winter chilling across Yazd Province, with reductions in seasonal chilling hours and a tendency toward earlier chill accumulation in autumn. Low-chill cultivars such as ‘Kale Ghochi’ are projected to remain largely suitable, whereas high-chill cultivars, including ‘Akbari’ and ‘Fandoghi’, face increasing chill deficits, threatening their long-term viability. These results highlight the need for adaptation measures, including promotion of low-chill cultivars, site selection in cooler microclimates, and improved phenological modeling for risk management.

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Sustainable Earth Trends

Articles in Press, Accepted Manuscript
Available Online from 27 June 2026

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