| Natural disasters are the concentrated embodiment of the negative man-land relationship.During the period of global warming,natural disasters occur more frequently,with greater intensity and more serious losses,which pose a threat to the ecological environment and human society.The research on the spatio-temporal features,causes and social effects of natural disasters is helpful to deeply grasp the law of disasters in order to prevent and reduce disasters,and maintain the normal operation of the ecological environment and society.Northern Shaanxi Province is sensitive to climate change and is of great significance in ecology,society and energy.During the Ming and Qing dynasties,the climatic conditions of the "Little Ice Age" were bad and became cold and dry as a whole.This paper studies the features and causes of natural disasters in this ecologically fragile area during the typical climate deterioration period of the Ming Dynasty,which can enrich the research cases of natural disasters in the past climate change period,gain an understanding of the natural-ecological-social feedback mechanism of disasters,and carry out "disaster learning" from past natural disasters.It is of practical significance to disaster prevention and control,environmental governance and the adjustment of human-land relationship under the background of global change.On the basis of collecting and collating the historical data of natural disasters in northern Shaanxi Province in Ming Dynasty,this paper comprehensively uses the methods of content analysis,mathematical statistics,wavelet analysis,Mann-Kendall test,ArcGIS spatial analysis,grey correlation analysis and social network analysis to study the temporal-spatial features,correlation and coupling between disasters,causes and social impacts of all kinds of natural disasters.The conclusions are as follows:(1)In Ming Dynasty,there were 404 natural disasters in northern Shaanxi Province.Drought was the main type of disaster.It occurred for 98 years,involving 1885 counties.In the level of drought,"moderate" is dominant,while "severe" and "severe" drought had a great impact on society.Drought has obvious distribution law in time,which was shown as follows:1)the frequency and county frequency of 10a showed a significant fluctuating upward trend,obviously showing four stages:less occurrence-widespread occurrence and increase-decrease-rapid increase,and the peak value of multiple and widespread occurrence appeared during the period of 1630-1644AD.2)on the seasonal scale,the incidence was high and widespread in summer,while more frequent in autumn and spring and the least in winter,and it also showed the characteristics of multiple occurrence and seasonal drought at the same time.3)the occurrence of drought had the periodicity of 6a,12a,25a and 66a.4)there was a sharp increase in frequency from 1400AD to 1409AD,and the increase was more obvious in 1430-1439AD.At the same time,the drought also had obvious spatial differentiation,which was higher in the south and lower in the north,and the high frequency area of drought was distributed in Luochuan-Huangling-Huanglong and Mizhi-Suide-Zizhou-Qingjian.Continuous drought often occurred in the middle and late Ming Dynasty,which played an indicative role in regional drought climate events.(2)Flood disasters occurred for 54 years,involving 313 counties,and the was mainly"moderate" grade,mostly in the middle and late Ming Dynasty,while "severe" were concentrated in the middle of Ming Dynasty.The temporal distribution law of flood disasters was shown as follows:1)the 10a frequency and county showed an obvious fluctuating upward trend,showing four stages:no disaster-more frequent occurrence-frequent occurrence-but the range decreases-rapidly increases.2)the seasonal features are obvious,which occurred more frequently in summer and autumn,especially in autumn,and the most in July and August(lunar calendar).3)the flood disaster had the periodicity of 6a and 32a.4)the frequency changed from less to more in 1380-1389AD,and the increase was more obvious in 1430-1439AD.Disasters also showed obvious differentiation in space,showing a point-like distribution of high-frequency centers,which were located in Yulin,Fuxian,Suide and Qingjian.(3)Famine was caused by drought,cold and low temperature,flood,insect,wind,hail and geological disasters,which occurred for 90 years.Drought caused the most famines(69 years)and the most extensive(976 counties).Famine had obvious distribution law in time,which was shown as follows:1)the 10a frequency and county showed a significant fluctuating upward trend,showing four stages:less occurrence,multiple occurrence,multiple occurrence,frequent occurrence and wide occurrence,and frequent and widespread occurrence in the middle and late Ming Dynasty.The peak occurred during the period from 1630AD to 1644AD.2)the occurrence of famine had the periodicity of 4a,9a,22a,40a.3)the frequency increased sharply from 1410AD to 1419AD.Spatially,it also showed obvious differentiation,and there were two high-frequency regions:Luochuan-Huangling-Huanglong-Fuxian and Mizhi-Suide-Zizhou-Qingjian.(4)Geological disasters occurred for 31 years in northern Shaanxi Province in Ming Dynasty,mainly mild and moderate,and few severe disasters,but the affected area was wide and the impact was great.The disasters'10a frequency showed a very significant upward trend as a whole.By comprehensively considering the frequency and the counties,the occurrence of disasters was divided into three stages:no disaster,increase and frequent,widespread.Spatially,there were relatively high frequency areas in Luochuan-Huangling-Huanglong,Mizhi-Suide-Zizhou-Qingjian,Yulin and Yan'an.Freezing disasters occurred for 28 years,mainly moderate and severe disasters,the most frequent and the strongest in the late Ming Dynasty.The disasters' 10a frequency showed a significant upward trend as a whole.By comprehensively considering the frequency and counties,the occurrence of disasters was divided into four stages:less occurrence,increase,no disaster,rapid increase.The seasonal characteristics of disasters were obvious,with the most frequent occurrence in autumn,followed by summer and winter,and less in spring.The spatial difference was obvious,and it occurs more frequently in the northern and central regions.Hail disasters occurred for a total of 32 years,mainly in the middle and late Ming Dynasty.The 10a frequency analysis showed that the overall trend was fluctuating and rising,with three stages of decrease-increase-stability.The hail disasters occurred mainly in summer,autumn and winter,especially in summer.In space,there were more in the north and east.Pest disasters occurred for a total of 32 years,mainly mild and moderate,while severe and severe insect disasters occurred in the middle and late Ming Dynasty.The 10a frequency analysis of disasters shows that the overall trend was an upward trend,which could be divided into four stages:less occurrence,increase,disaster-free,fluctuation increase.The seasonality was remarkable,mostly in summer and autumn.In space,Huangling and Qingjian were the most frequent.(5)The more natural disasters occur in the late Ming Dynasty,the more frequent and serious the disasters were:lighter disasters in the early Ming Dynasty,higher frequency and breadth in the middle period,and the most frequent and widespread in the later period.There was a significant seasonality in the year,which occurs in all four seasons,and was more concentrated and frequent in summer and autumn(accounting for 75.50%of the total).The spatial feature was significant,Yulin,Luochuan-Huangling-Huanglong,Mizhi-Suide-Zizhou-Qingjian were relatively high frequency areas.(6)There was a correlation and coupling relationship among natural disasters.In Ming Dynasty,the natural disasters formed a universal disaster network,and famine was located in the center of the network.There was a correlation among drought,flood,hail,freezing and wind disaster,and there was a coupling occurrence of many kinds of meteorological disasters.Meteorological disasters were related to famine,epidemic and insect pests.The coupling between various types of natural disasters was also shown in the clustering of time and space.The frequency of mass occurrence of disasters showed that there were 8 cluster occurrence periods,and there were differences in disaster composition types among different cluster occurrence periods,and the eighth group occurrence period at the end of Ming Dynasty was the most serious,which indicates the characteristics of cold and dry climate.Disasters frequently identify the spatial clustering of disasters,while the disaster clustering in Suide-Mizhi-Zizhou-Qingjian,Luochuan-Huanglong-Huangling,where the disaster clustering was related to the disaster-inducing environment and the disaster-bearing body.(7)The causes of disasters included natural factors,social factors and ecological environment factors.There was a negative correlation between the climate and the total frequency of natural disasters,and disasters occurred more frequently and widely in the period of cold and dry climate was relatively frequent and widespread in the period of cold and dry climate.Drought frequency,famine county,freezing disaster county had higher correlation with temperature,flood disaster frequency,pest disaster frequency,geological disaster county frequency,wind disaster county frequency and humidity correlation degree were higher.Geological and geomorphological factors played an important role in floods and geological disasters.The social factors included the number of population,the degree of land development and utilization and the degree of social fragility.The frequency of natural disasters changed in the same direction as the population increase:the faster the population increased,the more frequent disasters occurred.The impact of land use patterns was shown as follows:the development of land reclamation in the north echoes with the south-north movement of the center of gravity of disaster distribution.The failure of disaster relief measures reflected the increase of social vulnerability,which was an important reason why disasters become more frequent in the middle and late Ming Dynasty.The deterioration of ecological environment was mainly manifested in the decrease of forest and grassland vegetation and the aggravation of soil and water loss.The frequent and mass occurrence of natural disasters in the middle and late Ming Dynasty was related to the obvious deterioration of the regional ecological environment in this period.The interactive relationship among natural,ecological and social existence of natural disasters reflects the negative feedback chain formed by the natural-ecological-social system.(8)The frequent occurrence of disasters had seriously affected the regional population,economic development,social order,culture and so on.Cause the death and migration of the population,damage agriculture and urban economy,impact social order,shape beliefs,folklore and urban construction. |
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