| ABSTRACT | Temperate fruit and nut trees (such as apple, peach, cherry and others) develop survival mechanisms to overcome winter cold stress, creating a yearly cycle of growth and dormancy. They require cultivar-specific chilling and heat requirements during the dormant period to produce economically viable yields. Timing and accumulation rate of chill and heat enable to predict the spring flowering timing. Hence, long-term phenological observations are useful to downscale atmospheric conditions to the local agriculture. The location of Israel on the border between Mediterranean climate and semi-arid climate limits the potential areas for deciduous growth. The risk of not fulfilling the chill requirements is high since the winter chill level is already close to its lower limit for successful yield. For that reason deciduous fruit trees are grown in Israel above heights of 600m (preferably closer to 1000m) in the Judean, the Galilean and the Golan mountains.No studies using trees phenology have been carried out in Israel to evaluate the response to variations in chill and heat accumulation rates. This study identifies the temperature variables, including accumulated chill portions and heat hours in the winter and spring and their temporal distribution that explain the flowering timing and yield of sweet cherry (Prunus avium) in Israel. First, the flowering dates of cherries of two cultivars, grown at the Golan Heights at 730m, are correlated with seasonal chill and heat accumulation between 1998 and 2017, using the Dynamic Model and a simple Growing Degree Hour (GDH) Model. No significant trend was found in the GDH, the minimum, the maximum and daily average temperatures for the winter season at the orchard location in the Golan Heights, for this period. In order to assess possible effects of climate change, we estimate winter chill and heat accumulation for the future (2050-2070), using two COSMO-CLM models with different resolutions (0.44° and 0.0715°), taken from the CORDEX-MENA domain, for the RCP4.5 scenario. The results will be presented. An increase of winter temperatures, i.e., a decline in winter chill, may become critical and may overcome the positive influence of an increase in heat accumulation even for the high mountains of Israel. Inadequate chilling may cause delays in flowering and leaf emergence and finally in fruit quality and yields. Identifying of such delays may serve as an early-warning indicator that the future productivity may be threatened by climate change. Assessments of this type may be used by growers, producers and policy-makers to develop adaptation strategies such as selecting adopted cultivars or changing the type of agricultural crop. |