Abstract
For centuries, traditional high-altitude oases in Oman have depended on the cultivation of deciduous fruit trees. This study explores the effects of climate change on winter chill (estimated as Chilling Hours—CH and Chill Portions—CP), a prerequisite to overcoming dormancy and initiating flowering, in three Omani oases. The results are compared with findings from an earlier study which reported a decrease in the numbers of CH in high-elevation oases by an average of 1.2–9.5 CH year−1 between 1983 and 2008. Location-specific weather data were obtained by merging 15 years of in situ recordings with 28 years of observations from an official weather station near the top of the investigated watershed. Between 1991 and 2018, scenarios of the past few decades show chill reductions by 75, 35 and 18% when estimated in CP at the oases of Masayrat ar Ruwajah (1030 m a.s.l.), Qasha’ (1640 m a.s.l.), and Al ‘Ayn (1900 m a.s.l.), respectively. Over the course of the twenty-first century, the lowest-elevation oasis at Masayrat ar Ruwajah is projected to lose virtually all winter chill, whereas, despite significant chill losses, conditions are expected to remain viable for some of the currently grown species in the higher-elevation oases. These projected changes will compromise the cultivation of temperate fruit trees in the near future, affecting the sustainability of Omani oases. Our methods support results from earlier work performed at these locations and provide an updated procedure for assessing climate change effects on temperature-dependent systems.
Highlights
Over the past decade, a range of studies has targeted the sustainability of oasis systems on the Arabian Peninsula, in Oman (Al-Kalbani et al 2016; Al-Rawahi et al 2017; Cariou 2017; Hüneburg et al 2019)
In all three oases of Wadi Muaydin, temperature records of the past 28 years indicated declining levels of winter chill. These declines were more pronounced when using Chilling Hours (CH) to quantify chill than when using Chill Portions (CP), the units of the Dynamic Model, and they increased with altitude when comparing absolute values
When analysing winter chill according to the Dynamic Model, the reduction between the 1991 and 2018 scenarios amounted to a decrease by 74%, with median values of 4.0 CP for 1991 and 1.0 CP for 2018
Summary
A range of studies has targeted the sustainability of oasis systems on the Arabian Peninsula, in Oman (Al-Kalbani et al 2016; Al-Rawahi et al 2017; Cariou 2017; Hüneburg et al 2019). The results of most studies have shown that the combination of carefully designed oasis infrastructure with well-textured human-made soils and socially organized irrigation (Siebert et al 2007; Wilkinson 1977) is a key characteristic of Arabian oases. Elaborate water management systems that avoid salinity buildup by regular leaching of salts from the soil profiles (Luedeling et al 2005) and a water-efficient three-storey cropping system (Al-Rawahi et al 2014; Golombek et al 2007) were proposed as important features for maintaining oasis sustainability. It has become clear that it is the combination of all these factors that has allowed these systems to persist through millennia, producing the provisioning, supporting, regulating and cultural ecosystem services necessary to preserve traditional oasis societies
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