Spatio-temporal Pattern,climatic Background And Social Influence Of Locust Plagues In Shaanxi And Gansu Provinces During Ming And Qing Dynasties

The course of Chinese history has been accompanied by various natural disasters,among which droughts,floods and locust plagues had a great impact on ancient Chinese agricultural production and social development.Previous studies on historical locust plagues mainly focused on overall comprehensive analysis.In recent years,there have been increasing studies on historical locust plagues in terms of chronology,region and typical cases.Especially in the regional research,the study area mainly focuses on the eastern part of China.However,as one of the early agricultural birthplaces of the Chinese nation,there are few studies on locust plagues in Shaanxi-Gansu region,which has an important military strategic position.Based on this,this paper collected the historical data of Ming and Qing dynasties,and established and improved the locust plague database in Shaanxi and Gansu.From the two aspects of nature and society,with the aid of statistical analysis and spatial analysis methods,we reconstruct time sequences of dynasties,months,grade(strength),frequency(size),the number of county,examine the spatio-temporal patterns,climate background and social impacts from locust plagues,and reveal the governance ideas and measures for prevention and control of locust plagues.The results indicated:(1)Temporal dynamics.There were 122 locust plague years and 350 locust plague counties in Shaanxi-Gansu region.Locust plague mainly occurred from March to September in the lunar calendar,and June and July were still the high incidence period.Locust plagues of grade 1 and 2 were mostly frequently occurred.The occurrence of locust plagues in Shaanxi and Gansu had obvious fluctuation and evolution stages,and the frequency of locust plagues on the whole presented an upward trend of fluctuation.Three large outbreaks of locust plague occurred in Shaanxi-Gansu region,and the 17 th century was the period with the largest number of locust plague outbreaks.The results of wavelet analysis showed that there were long cycles of about 30 a and 50 a,and short cycles of 3a and 10 a.(2)Spatial pattern.The distribution of locust plague in Shaanxi and Gansu Provinces had obvious regional differentiation,and the distribution of locust plague in different periods and counties was different,but the distribution of locust plague in Shaanxi-Gansu was similar on the whole,which was mainly concentrated in the monsoon area in southeastern Gansu and the Weihe River Basin in Guanzhong Plain and South Shaanxi.The locust plague center moved to the west in Gansu while moved to the south in Shaanxi.In the trend analysis,Gansu province showed a trend of low west and high east in the east-west direction,and high north and low south in the south-north direction.Shaanxi province presented a smooth line in the east-west direction and a trend of north high and south low in the north-south distribution.(3)Climate background.The outbreak of locust plague was obviously related to the temperature.The outbreak of locust plague occurred during the cold temperature period,and the cold and warm climate of the previous winter would affect the survival rate of locust eggs,thus affecting the occurrence of locust plague in the next year.The locust plague sequences corresponded to the dry and wet sequences in reverse phase,that is,when the precipitation decreased,the drought would be intensified,and the number of locust plague counties also increased.The sequence of locust plagues had a good positive phase correspondence with Nino3 index,and the high incidence period of locust plagues was also the period of El Nino prevalence,indicating that there was a remote correlation between locust plagues and El Nino phenomenon,which may be attributed to the relation chain of "El Nino-northwest China drought-locust plagues".The statistical data of drought,flood and locust confirmed the close close relationship between locust plague and drought.(4)Social impact.Large scale locust plagues directly led to crop loss and food shortage,which on the one hand caused rice price to rise and the economy to deteriorate,on the other hand,it caused the phenomenon of hunger,and the occurrence of famine,which may further cause the epidemic to spread,ten followed by population decline and greater social unrest.Therefore,the social impact caused by the locust plague is a series of chain reactions on food security,economic fluctuation and social stability,etc.,which may lead to greater social unrest and political crisis if the government does not handle it properly.Including artificial prevention,agricultural prevention and other measures to control locust,from the emperor down to the common people,there was the ideology of sorcery,although the government made clear that was not practical,but did not explicitly deny this practice.