Dynamic Temperature Index Of Freeze Injury Of Winter Wheat

The main characteristic of global climate change is the warming of the climate.Extreme climate events and climate stress increase,which pose serious threats for the production of winter wheat.Freezing damage is one of the main meteorological disasters that affect winter wheat production.Establishing a scientific and reasonable winter wheat freeze injury index for predict frost damage can provide a scientific and rational basis for winter wheat monitoring,forecasting,and defense measures to ensure the safe production of food in China.Using the winter wheat freezing injury records(total of 113),the daily average temperature of the growing season,and yield data from 23 agricultural meteorological observatories in Hebei Province from 1980 to 2007,adopt the case analysis method,according to the temperature adaptability and frost damage effect of winter wheat,the time of cold injury and the type of frost damage were divided according to the principle of dynamic and relative change,and the index of frost damage was set up in different periods and types to determine the index algorithm and index value.Based on this index system,a probabilistic forecasting model of winter wheat frost damage based on Bayesian networks was established.The model was verified by using Luancheng as an example.The main results are as follows:(1)The time of winter wheat frost damage was divided into three periods before wintering,wintering,and early spring.(2)The type of frost damage according to the magnitude of severe temperature reduction,the length of low temperature duration,and the degree of change in temperature before and after the winter season were:Severe drop in temperature before winter,insufficiency of accumulated temperature,early warm later slants cold;Sudden cooling type in winter,winter type long cold type,winter freeze-thaw type;Early spring temperature drop type,low temperature type,freeze-thaw type.(3)Intensity of temperature drop within 5 days(Tdrop5);ratio of accumulated temperature before winter to accumulated temperature averaged(?TV+);number of days during which temperature anomaly was >0 in continuous 20 days(DTa+),and the number of days in which 20 days of continuous temperature anomaly was less than 0(DTa-);The ratio of the accumulated temperature at 0°C to averaged(?TV-),the ratio between the days of winter and averaged(DWV),the ratio of the days of daily average temperature anomaly <0 to the entire winter period(DVTa-),and the average daily temperature the number of days for flat >0(DTa+),the number of days for which continuous daily average air temperature is less than 0(DTa-).And determine the index value of the type of frost damage in each period.(4)The dynamic freeze injury indicators established in the winter wheat field in the northern wheat region of 2013-2016 were used to test the indicators of dynamic freeze injury,demonstrating that these indicators can basically predict the occurrence of frost damage.(5)The freezing and injurious rules of winter wheat from 1980 to 2007 in Hebei Province were analyzed.Freeze injury of winter wheat occurred in 16 years from 1980 to 2007.The incidence of frost damage was the highest in the 1980 s.Freezing damage was distributed in most of the winter wheat regions;it decreased in the 1990s;increased after 2000,mainly in Central and southern Hebei Province.(6)Based on the dynamic indicators of winter wheat freezing damage,a prediction model of winter wheat frost damage based on Bayesian network was established.Based on the analysis of the temperature of Luancheng from 1981 to 2011,the number of frost damages of each type was calculated according to the index of frost damage,and the volatility yield of winter wheat in the corresponding year was calculated and compared.The results showed that in addition to part of the year the total number of frost damage and wave dynamic yield relationship is complex,the other years are negative correlation obviously,the model has a good effect.