مدلسازي تاثير تغيير اقليم بر رفتار گلدهي زعفران (Crocus sativus L.)

Modelling the impact of climate change on flowering behaviour of Saffron {Crocus sativus L.)

Flowering in saffron take places in two separate stages, both triggered by temperature as the main driving force. Based on the existing evidence about the temperature rise due to global warming it seems that flowering behaviour of saffron could be affected by future climate change in production areas. In order to study the flowering responses of saffron to temperature rise a model for simulation of flowering behaviour was developed. Using this model development rate and duration at each flowering stage in response to 0.5, 1.0, 1.5 and 2 °C increase in mean daily temperature above the current records was simulated. In the model development rate (.DR) is calculated based on maximum DR at optimum temperature (DRm1, DRm2) multiplied by a specific temperature function for each stage (ft1, ft2). Duration of each flowering stage was then estimated as the reciprocal of the calculated development rates. The value of DRm1 and ft] was estimated from evidences in the literature at optimum temperature of 23-25 °C. DRm2 and ft 2 was calculated by fitting 5-parameter function to the saffron development rate and temperature data were collected from farmers fields located in production areas. Using these data the minimum, optimum and maximum temperatures for the second stage of flowering was estimated as 15.5, 18.0 and 22.5 °C, respectively with maximum development rate of 0.0289 day-1. Simulation results indicated that the effect of temperature rise on reducing development rate was similar for both flowering stages and hence flowering duration will be increased by 32 to 38 days per 1 °C increase in mean daily temperature. Therefore, temperature rise by 1.5-2.0 °C due to climate change results in postponing time of flower emergence until early to late December in the main saffron production regions of Khorasan provinces.