studying and analyzing strong spring frostbite phenomenon of pistachio gardens in yazd province

pistachio is one of the most important export items in iran, comprising more than 23% of iran non-oil exports. yazd is considered as the second biggest province of iran from the viewpoint of pistachio production, standing after kerman province. since frostbite phenomenon, especially, strong spring frostbite, has incurred many damages into pistachio gardens of this area, it is necessary to study frostbite in this province; since being aware of the phenomenon and its occurrence time can help the farmers in preventing and reducing damages caused by frostbite. the objective of this project is to study and analyze strong spring frostbite in pistachio gardens and zone it in yazd province. for this purpose, we used the daily statistics of the minimum temperature in 16 meteorological stations of the province and its neighborhood during a common 18-year statistical period (1993-2010). in order to zone spring frostbite intensity of pistachio, we counted the number of days having frostbite in each station with three weak (1 to -10c), mediate (-1.1 to -30c) and strong (-30c and less) thresholds and after studying the relation between the number of frostbite days and altitude, we plotted the frostbite area maps in arc gis medium. in addition, we extracted temperature drop times with 1, 0 and -10c thresholds as the effective temperatures on pistachio in florescence stage and plotted its zoning maps. the results of this research show that pistachio gardens of all stations under investigation except tabas station including yazd and bafgh stations experience weak frostbite, while the remaining stations experience weak, mediate and strong frostbite in spring season. therefore, south and southwestern stations (dehshir, marvast, ashkezar, ardakan and bahadran) are considered as a dangerous region for agriculture especially pistachio gardens in terms of occurrence of different frostbite intensities. temperature drop time in 1, 0 and -10c reveals that 10c temperature drop ends from 23 to 28 march and 00c temperature drop ends since 22 to 27 march and -10c temperature drop ends since 21 to 28 march in yazd province.