Assessment and mapping of heat stress affecting the saffron In South Khorasan Province

Climate is the most important determinants for the geographical distribution of plant species such as saffron. The thermal stress is one of the most important factor in reducing the yield of agricultural products. South Khorasan province as a center for saffron production suffers from thermal stresses. In this study, data was used from the province synoptic and climatology stations which provided valid data. Then, analysis was conducted to identify the stressful behavior that was harmful to the Saffron. For this purpose, the maximum temperature thresholds were categorized as somewhat critical (35 to 40 degrees), critical (40 to 45 degrees) and supercritical (more than 45 ° C) groups. In the next stage, a program was written in Matlab software to extract these days from the maximum temperature database of the selected stations. Using the 90th percentile, the threshold for hot days was determined for each station. Than the maps for hot stress and maximum temperature zoning were drawn in GIS environment. The results show that the hot period months have the greatest critical and supercritical days and the critical days also has increased in March. The occurrence of stressful days has increased in recent years that might affect the flowering and yield of saffron. The South, West and Central parts of the province have possessed the greatest number of supercritical days which have reached 177 days in July in the West of province. Reduced crop yields in the stressful centers in recent years, is amongst the consequences of heat stress in the province.