| The cultivation of crops for the survival and development of human beings and the status of the country's economy is no doubt.As we all know,the harvest of crops mainly depends on the environment,so crops are venerable to the natural disasters.Nowadays,the global climate change makes the crop growth is more sensitive to the environment and the situation is more severe.Crops biological disasters are one of the important types of natural disasters.In recent decades,the losses caused by crop biological disasters have been increasing year by year.However,the law of occurrence of crop biological disasters is still relatively backward in disaster prevention and mitigation.The research of crop biological disaster in China is imperative.Chongqing has the largest agricultural population and the largest proportion of agriculture in the national economy.In 2014,the city's agricultural population of 2003.08 million,available cultivated land of about 243.84 million hectares,per capital arable land is only 0.07 hectares.The stable production of crops played a crucial role for the smooth and rapid development of Chongqing's economy.However,in the past 20 years,due to global warming,changes in farming systems and human tillage activities and other factors,the Chongqing crop biological disasters showed a significant increase in the trend.Therefore,it is necessary to have a research of crop area by time variation and occurrence rate of crops in Chongqing.The time variation of crop yield loss is caused by crop biological disasters.The comprehensive analysis of crop biological disasters and the analysis of the effect of crop biological disaster will produce/make a good influence on prevention and mitigation of it.In this paper,we use the linear trend method,the Hurst index method,the Morelet wavelet analysis method and the gray GM(1,1)prediction model method to investigate the interannual and interdecadal units in Chongqing from 1950 to 2012,respectively.The time variation characteristics of the area and incidence of crop biological disasters in Chongqing,the time variation characteristics of crop losses and damage caused by biological disasters in Chongqing,and the time variation characteristics of disaster prevention and control effect after prevention and control of crop diseases in Chongqing;And the weight of the crop biological disaster in Chongqing was determined by the method of analytic hierarchy process,and the comprehensive analysis of the crop biological disaster in Chongqing was carried out.In this paper,we make the following conclusions:(1)Time variation and incidence of crop biological disasters in Chongqing was as follows: the area and occurrence rate of crop diseases and insect pests and rodents in Chongqing showed a significant upward trend,and the area and occurrence rate of crop weeds were declining.The incidence of crop pests and diseases,weed damage,rodents were quasi-6 years and 23 years of shock cycle,quasi-5 years,10 years and 23 years of the oscillation cycle,quasi-23 years of the oscillation cycle;The Hurst indices of the time series of crop diseases and insect pests and rodent morbidity were 0.9047 and 0.8063,which indicates that the future incidence of pest and rodent diseases in Chongqing is increasing continuously.The GM(1,1)forecast of crop biological disasters in Chongqing showed that the occurrence rate of pests,,weed damage and rodents in crops was 5084.87,1599.79 and 423.82 thousand hectares in 2022,respectively,and the incidence rates were 155.73%,48.46% and 13.72.(2)The temporal variation characteristics of crop losses and damage caused by biological disasters in Chongqing are as follows: The loss of food crops and the damage caused by crop pests and diseases and rodent diseases in Chongqing are showing an increasing trend.And the loss and damage degree of the grain crops caused by the weeds damage showed a decreasing trend.The damage degree of food crops caused by pests and diseases,weeds and rodents was quasi-9 and 23 years,quasi-4-year oscillation period;The Hurst index of the time series of food crop damage caused by pests,weeds and rodent deasease was 0.9023,0.6119 and 0.7814 respectively,which indicated that the overall trend of damage to food crops caused by future biological disasters in Chongqing is consistent with that of the past.There were obvious upward trend of oil crop damage and damage degree caused by pests and diseases,weeds diseases in Chongqing.The damage degree of oil crops caused by pests and diseases,weeds diseases was basically 10 years and 25 years respectively.The Hurst index of the damage period of oil and crop caused by pests and diseases,weeds was 0.8959 and 0.573,which indicated that the trend of oil crops' damage by future pests and diseases,weeds diseases in Chongqing was consistent with that of the past.The loss and damage degree of other crops caused by pests and diseases in Chongqing showed an increasing trend,and the other crop losses and damage caused by the weeds decreased;And the damage degree of other crops caused by pests and diseases,weeds was 27 years of shock cycle,quasi-5 years and quasi-27 years of the shock cycle;pests and diseases,weeds caused by other crop damage time series of Hurst index were 0.7597 and 0.6105,indicating that the future of Chongqing pests and diseases,weeds caused by the overall trend of damage to the oil crop is consistent with the past.The results showed that the loss of food crops caused by pests,weeds and rodents was 259488.15 tons,38601.53 tons and 42008.89 tons respectively in 2022.The damage rate of food crops caused by pests,weeds and rodents was 139.87 kg / ha,21.18 kg / ha and 22.95 kg / ha;pests and diseases caused,weeds by the loss of oil crops were 15915.34 tons and 6367.69,respectively.And the degree of damage were 55.56 kg / ha,22.12 kg / ha;The loss of pests and diseases,weeds caused by other crops was 175082.38 tons and 36561.14 tons,respectively,the damage degree of 130.14 kg / ha,33.22 kg / ha.(3)The area of disease prevention and control of crop diseases and insect pests,weeds in Chongqing showed an increasing trend,and the area of control of rodents was increasing,and the control rate was decreasing.The food crop pests and diseases,weeds damage after the recovery of the amount of recovery and disaster reduction rate showed an upward trend,the average annual recovery of the loss and disaster reduction rates were 891229.71 tons and 80.51%,115887.49 tons and 71.3%.Crop weeds control after losses increased,an average annual loss of 150945.89 tons,after treatment and reduction rate decreases,the annual reduction rate of 51.69%;oil crop pests and diseases,weeds,after the control of the wicked and the reduction of the rate of disaster reduction and the rate of increase in the rate of disaster reduction,the average annual loss rate is 150945.89 tons and the annual reduction of losses and disaster reduction rates were 14076.99 tons and 69.19%,7627.73 tons and 66.13% respectively.The recoverable losses and disaster reduction rates of other crops and pests and diseases,weeds in Chongqing were increasing,and their annual loss and the rate of disaster reduction were 272210.32 tons and 75.95%,37563.96 tons and 60.63% respectively.(4)The effects of crop diseases and pests,weeds diseases and rodents on the intensity of crop disaster in Chongqing were 0.637,0.1047 and 0.2583 respectively.There are 10 times,7 times,4 times and 3 times of the number of years of light disaster,moderate disaster,heavy disaster and catastrophic disaster in Chongqing City from 1989 to 2012.The forecast shows that there will be three heavy and catastrophic disasters in Chongqing during 2017-2032,which would be during 2017-2019,2025-2027 and 2031-2032 respectively. |
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