|Authors: ||H. Kaufmann, M.M. Blanke|
|Keywords: ||sweet cherry (Prunus avium L.), chilling, climate change, chilling requirement, dormancy, global warming, phenology|
Cherry production in Europe may be hampered by climate change in terms of warmer winters resulting in insufficient chilling.
This contribution provides a brief introduction to winter chilling of fruit crops.
Therein, cherry was identified as one of the fruit crops with the highest possible chilling requirement.
The three chilling models are presented and the different ways of calculation explained.
The simplest model, Weinberger (1950) counts every hour between 0-7.2°C as one chilling hour (CH). The Utah model (1974) expands the temperature range to 1.4-12.4°C to calculate the chilling units (CU) and the temperatures are weighted; temperatures in excess of 16°C can nullify previously accumulated chill units.
The Dynamic model (1987), chilling portions (CP) are calculated based on assumptions of metabolic processes at a temperature range of (-2)-12°C with an optimal chilling effective range from 6 to 8°C. First results applying the three chilling models are presented to calculate winter chilling in a cherry orchard at Klein-Altendorf, Germany, and in an unheated greenhouse (average temperature increase by ca. 2°C) to simulate global warming.
When chilling was computed for the trees in the unheated greenhouse, the available chilling at 50°N increased by 12% (CU), 15% (CP) and 20% (CH), respectively.
In climate change predictions for other locations, the warmer winter temperatures often induce lack of chilling.
Options and limitations of counter measures in terms of cultivation methods such as microclimate manipulation, rest breaking agents, change of orchard location to a higher altitude and breeding are suggested and discussed.
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