شبیه سازی عملکرد غده سیب زمینی در شرایط تغییر اقلیم با استفاده از مدل WOFOST

Simulation of Potato Tuber Performance under Climate Change Conditions Using the WOFOST Model
Background and Objectives
In this research, to evaluate the consequences of climate change on the yield of potato tuber, from the statistics of the production level and the area under cultivation of potatoes in Ardabil, Tabriz, Shahrekord, Hamadan, Jiroft, Kohnouj, Manojan, Isfahan, Sanandaj and Shiraz stations in the statistical period of 2015- 1361 was used. The mentioned regions are among the main centers of potato production in the country and account for 62.72% of the cultivated area and 68.27% of the country's potato production. In this research, the production and performance data of 10 meteorological stations inside Iran were used and the data of the fifth report of the Representative Concentration Pathway scenarios (RCPs) in the period of 2011-2100 have been used to evaluate the consequences of climate change on potato tuber yield.
Methodology
In order to prepare field data for calibration and determining the validity of the WOFOST model in potential conditions (conditions without water and food restrictions, disease and weed control) the data of the research projects of the agricultural research centers of Hamedan regions , Isfahan, Ardabil, Shiraz, Tabriz, Shahrekord, Jiroft, Kohnouj, Manojan and Sanandaj, which are the main centers of potato production in Iran, were collected during 2010-2014 and used as a base or monitoring period. This information includes planting date, phenological stages from planting to germination, germination to flowering and germination to physiological maturity of the potato plant in each of the regions. In order to calibrate the WOFOST model using field data, from phenological and performance data in the years 2010, 2011 and 2013 were used to calibration of the model, and from phenological and performance data in the years 2012 and 2014 were used to determine the validity of the model. In order to calibrate and determine the validity of the WOFOST model in the study areas, it is first necessary to adjust the potato plant parameters (coefficients) for different climatic conditions. Therefore, the creation of the plant file, which is the most sensitive part of WOFOST model calibration, was done for tuber performance. In this study, WOFOST ver 7.1 was used, which was developed by the Agrobiology and Soil Fertility Research Center and the Netherlands Agricultural Research Center at Wageningen University. WOFOST is derived from another model called SUCROS. This model uses parameters and functions to describe the effects of temperature, radiation and water stress on the main processes of crop growth. The outputs of the model include the final yield, leaf area index, crop growth rate, dry matter accumulation rate in each organ, and development stages with one-day intervals. The calibration of the model and the determination of the coefficients of the model were done in such a way that the expected performance of the tuber was simulated by the WOFOST model. Parameters of Specific leaf area as a function of development stage (SLATB), Maximum leaf CO2 assimilation rate as a function of development stage of the crop (AMAXTB), efficiency of conversion into leaves (CVL), efficiency of conversion into roots (CVR), efficiency of conversion into stems (CVS) and Lower threshold temperature for emergence (TBASEM), which were necessary for the simulation of gland function, were calibrated and determined based on the permissible range of model coefficients changes and using resources. Then, in order to simulate the potential performance of the potato plant for all 10 study areas and every five years, with conventional planting dates and also with a range of planting dates (three dates) separately and a total of 150 the load was executed.
Findings
According to the yield potential results of potato tuber obtained from the data collected during five years, the average yield for the 10 studied stations in the calibration stage was 46190.09 kg/ha and 44434.3 kg/ha for the validation data. In the model implementation stage, the average yield during these five years for the 10 studied stations was 45919.3 kg/ha for calibration and 43812.95 kg/ha for the validation stage by the model. Therefore, by evaluating the statistical indicators, the WOFOST model has high accuracy for simulating performance in all regions.
Conclusion
The results of the simulation of the yield of potato tuber under the future climate conditions indicated a decrease in yield in the studied areas. Thus, the greatest decline in performance was observed in the period of 2071-2099 and under the RCP8.5 scenario. In the studied areas, on average, the highest yield decrease was related to Ardebil station with 2396.5 kg/ha and Hamedan with 1816.9 kg/ha, and the lowest yield decrease belonged to Sanandaj station with 813.2 kg/ha and Isfahan station with 981.8 kg/ha. On average, in the 10 studied areas, a decrease in potato tuber yield was observed by 1436.3 kg/ha. Reducing the length of the potato ripening period has the biggest contribution in reducing the potato tuber yield. The results obtained from the simulation of the yield of potato tubers show that in parallel with the increase in temperature, the yield of the tubers also decreases, so that for one degree Celsius increase in the average annual temperature, the yield of the tubers will decrease by 3.77%. .