Projected climate change effects on apple phenological development

Abstract: The Western Cape region of South Africa is identified as an area that will be influenced directly and significantly by projected climate change in future. Higher mean, maximum and minimum temperatures and more frequent, warmer hot and less frequent, cold days are predicted. High temperature extremes have increased, whereas low temperature extremes have decreased significantly. Rainfall trends are more difficult to indicate and show little consistency across the Western Cape region. Extreme rainfall events will become more frequent, especially in spring and summer, with a reduction in extremes in autumn. Thus, depending on when during the season these changes will occur, and which climatic parameters are involved, the effect of the changes will impact differently on fruit production – specifically apples. The phenological development of fruit trees is to a great extent genetically controlled; however it is influenced and even shifted when temperature changes are significant during the sensitive periods. Dormancy in apple trees has been mentioned specifically as a sensitive stage that will impact on fruit production due to climate change. Similarly, a change in rainfall patterns will impact on this sensitive stage. The objective of this study is to quantify the predicted climate changes and integrate these scenarios with present phenological phases of apples in two climatically contrasting production areas in the Western Cape. Once we have identified the main phenological stages expected to be affected, the impact of these changes on fruit production will be discussed.