Evaluation of winter chill requirement models using the observed apple tree phenology data in Kahriz (Urmia, Iran)

Document Type : Full Paper


1 Former Ph.D. Student, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran

2 Professor, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran


The flowering phase of apple trees is the most critical step in relation with low temperatures and frost events. Therefore, forecasting the time of flowering is important. If a model can predict the exact time of flowering, it would be feasible to care for flowers agianst late spring freezing (LSF). In this study, we evaluated three temperature-base chilling models namely: Chilling Hours (CH), Utah Model (UM) and Dynamic Model (DM) versus the observed phenological records of apple tree (13 years) in Kahriz (Urmia, Iran). The said models were applied to explain their efficiency and ability for predicting apple phenological dates. The study was performed for apple cultivars in Kahriz station by using phenological observations, daily minimum temperature and maximum screen temperature data (2002-2014). The winter chilling was determined by the three chilling models and remaining heat was estimated using the Growing Degree Hour concept. The model results showed that the Dynamic Model (DM) performed the best results in explaining apple flowering phenology stage with RMSE of lower than four days and relative errors less than 3%. Meanwhile, the probability of LSF was estimated by statistical distributions. By comparing the probability of frost occurrence with the date of the predicted flowering date, the risk of frost damage on apple flowering was determined. The results demonstrated that early flowering varieties, which their flower buds are activated before 25th of March, are exposed to LSF risk, with probability of 50 percent.


  1. Alburquerque, N., García-Montiel, F., Carrillo, A. & Burgos, L. (2008). Chilling and heat requirements of sweet cherry cultivars and the relationship between altitude and the probability of satisfying the chill requirements. Environmental and Experimental Botany, 64, 162-170.
  2. Bennett, J. (1950). Temperature and bud rest period: Effect of temperature and exposure on the rest period of deciduous plant leaf buds investigated. California Agriculture, 4, 11-16.
  3. Campoy, J., Ruiz, D. & Egea, J. (2011). Dormancy in temperate fruit trees in a global warming context: A review. Scientia Horticulturae, 130, 357-372.
  4. Cesaraccio, C., Spano, D., Snyder, R.L. & Duce, P. (2004). Chilling and forcing model to predict bud-burst of crop and forest species. Agricultural and Forest Meteorology. 126, 1-13.
  5. Darbyshire, R., Webb, L., Goodwin, I. & Barlow, S. (2011). Winter chilling trends for deciduous fruit trees in Australia. Agricultural and Forest Meteorology, 151, 1074-1085.
  6. Eccel, E., Rea, R., Caffarra, A. & Crisci, A. (2009). Risk of spring frost to apple production under future climate scenarios: the role of phenological acclimation. International Journal of Biometeorology, 53, 273-286.
  7. Farajzadeh, M., Rahimi, M., Kamali, G.A. & Mavrommatis, T. (2010). Modelling apple tree bud burst time and frost risk in Iran. Meteorological Applications, 17, 45-52.
  8. Fishman, S., Erez, A. & Couvillon, G. (1987). The temperature dependence of dormancy breaking in plants: computer simulation of processes studied under controlled temperatures. Journal of Theoretical Biology, 126, 309-321.
  9. FAOSTAT. (2015). Food and Agricultural Organisation of the United Nations, FAO statistical databases. http://faostat3.fao.org/browse/Q/QC/E
  10. Fox, D. (1981). Judging air quality model performance: A summary of the AMS workshop on dispersion models performance. Bulletin of the American Meteorological Society, 62, 599-609.
  11. Greenwood, D., Verstraeten, L., Draycott, A. & Sutherland, R. (1987). Response of winter wheat to N-fertiliser: Dynamic model. Fertilizer Research, 12, 139-156.
  12. Javanshah, A., Alipour, H. & Hadavi, F. (2005).  A model for assessing the chill units received in Kerman and Rafsanjan areas. Acta Horticulturae, 726, 221-226.
  13. Linvill, D.E. (1990). Calculating chilling hours and chill units from daily maximum and minimum temperature observations. HortScience, 25, 14-16.
  14. Luedeling, E. & Brown, P.H. (2011). A global analysis of the comparability of winter chill models for fruit and nut trees. International Journal of Biometeorology, 55, 411-421.
  15. Luedeling, E. & Gassner, A. (2012). Partial least squares regression for analyzing walnut phenology in California. Agricultural and Forest Meteorology, 158, 43-52.
  16. Luedeling, E. (2012). Climate change impacts on winter chill for temperate fruit and nut production: A review. Scientia Horticulturae, 144, 218-229.
  17. Luedeling, E., (2013). ChillR: statistical methods for phenology analysis in temperate fruit trees. R package. version 0.54.
  18. Luedeling, E., Gebauer, J. & Buerkert, A. (2009). Climate change effects on winter chill for tree crops with chilling requirements on the Arabian Peninsula. Climatic Change, 96, 219-237.
  19. MAJ, Ministry of Agriculture Jihad, Database Center. Iran (2015). http://www.maj.ir/Portal/Home/#
  20. Nekoonam, F., Fattahimoghadam, M. & A. Ebadi. (2012). A study of the environmental factors affecting some of the biological characteristics of flower in four iranian commercial apricot cultivars. Iranian Journal of Horticultural Science, 43, 175-187.
  21. Oukabli, A., Bartolini, S. & Viti, R. (2003). Anatomical and morphological study of apple (Malus X domestica Borkh.) flower buds growing under inadequate winter chilling. Journal of Horticultural Science & Biotechnology, 78, 580-585.
  22. Richardson, A.D., Keenan, T.F., Migliavacca, M., Ryu, Y., Sonnentag, O. & Toomey, M. (2013). Climate change, phenology, and phenological control of vegetation feedbacks to the climate system. Agricultural and Forest Meteorology, 169, 156-173.
  23. Saure, M. (1985). Dormancy release in deciduous fruit trees. Horticultural Reviews.7, 239-300.
  24. Shaeffer, D.L. (1980). A model evaluation methodology applicable to environmental assessment models. Ecological Modelling, 8, 275-295.
  25. Weinberger, J. (1950). Chilling requirements of peach varieties. Proceedings American Society for Horticultural Science, 56, 122-128.
  26. Yazdanpanah, H., Ohadi, D. & Soleimani, M. (2010). Forecasting different phenological phases of apple using artificial neural network. Journal of Research in Agricultural Science, 6, 97-106.
  27. Zhang, J. & Taylor, C. (2011). The Dynamic model provides the best description of the chill process on ‘Sirora’ pistachio trees in Australia. HortScience, 46, 420-425.
  28. Zhuang, W., Gao, Z., Wang, L., Zhong, W., Ni, Z. & Zhang, Z. (2013). Comparative proteomic and transcriptomic approaches to address the active role of GA4 in Japanese apricot flower bud dormancy release. Journal of Experimental Botany, 64, 4953-4966.