| Drought is one of the natural disasters with the highest frequency,the widest impact and the most serious loss.It has great harm to the economic and property safety of human society,especially in agricultural production and life.As a typical karst mountain landform,Guizhou belongs to the ecological fragile zone with rugged surface,thin soil layer and poor water retention capacity,and drought disasters often occur.Therefore,scientific evaluation of the risk of drought disaster and taking the measures to prevent and mitigate it is very important to improve the economic efficiency and improve the happiness index.In this study,the meteorological data of 19 meteorological stations in Guizhou Province were used to characterize meteorological drought and agricultural drought by standardized precipitation evapotranspiration index(SPEI)and crop water deficit index(CWDI),respectively.Based on Mann-Kendall test,moving average difference,wavelet cycle analysis and other methods,the trend,mutation characteristics,periodic characteristics and drought variation characteristics of SPEI sequence in tobacco growth period from 1958 to 2018 were analyzed.Based on the theory of natural disaster system and the principle of disaster risk assessment,combined with drought data and the economy,topography,population and tobacco planting area of each county and city,different indicators were reasonably selected to accurately construct the evaluation model from four aspects : risk of disasters,sensitivity of disaster environment,vulnerability of disaster-carrying entities and capacity to prevent and mitigate disasters.The tobacco drought risk zoning map of Guizhou Province was obtained by using GIS technology.The main conclusions are as follows :(1)The development law of meteorological drought in Guizhou was explored.The average annual precipitation in the growth period of Guizhou Province from1958 to 2018 was 312 mm.The unitary equation of precipitation with year was y =-0.4474 x + 1200.7,and the regression coefficient was negative.It can be seen that the precipitation in the growth period of Guizhou Province from 1958 to 2018 showed a decreasing trend with a drying trend,and the linear tendency rate was-4.47 mm / 10 a.The average precipitation is shown as zone I < zone II < zone III.Combined with the temperature data,it can be seen that the precipitation and temperature in Guizhou Province are positively correlated in different zones,that is,the temperature and precipitation decrease or increase together,and the higher the temperature,the more precipitation,and vice versa.The SPEI of the whole region showed a downward trend,indicating that the drought in Guizhou Province increased during the growth period of tobacco in the past 60 years,and the division fluctuated.The I and III areas showed a downward trend,and the II area showed an upward trend,which indicated that the drought in the II area of the study area had a tendency to reduce,and the I and III areas were aggravated.The mutation test of SPEI-6 sequence in Guizhou Province was carried out by M-K test and sliding T,and Guizhou Province was divided into three periods in recent60 years combined with diachronic climate records.From 1958 to 2018,the overall drought in Guizhou Province has a trend of shifting from northwest to southeast.From 1958 to 1975,the frequency of young drought was higher than that of the southeastern and southwestern regions,and the frequency of middle drought increased from the northeast to the southwest.During the tobacco growing period from 1976 to1991 in Guizhou Province,the frequency of light drought was higher in the western region,and there were fewer areas with severe drought.(2)Establishment and application of tobacco drought model in Guizhou provinceDuring the tobacco rooting period from 1958 to 2018,the highest frequency of light drought occurred in the northwest of Guizhou Province,and the trend of moderate drought decreased from southeast to northwest.The areas where severe drought occurred were distributed in the west and south-central,and the special drought was mainly concentrated in the northwest of Guizhou Province and Weining area.The light drought in the prosperous period is mainly concentrated in the west of Bijie,Liupanshui,the west of Southwest Guizhou and the southwest of Buyi Miao and Dong Autonomous Prefecture in southeastern Guizhou,and the northeast of Guizhou Province is prone to special drought.On the whole,the trend of special drought in the tobacco prosperous period in Guizhou Province is to strengthen from southwest to northeast;The light drought in the mature period is mainly concentrated in the middle and west of Bijie,Anshun area and the east of Qiannan Prefecture,with a wide range of areas where moderate drought occurs,and the lowest frequency is concentrated in the southeast of Tongren and the adjacent northwest of Qiandongnan Prefecture.The frequency of extreme drought in the west of the province is low,while in the east,on the contrary,the basic trend is gradually decreasing from east to west.On the whole,the drought frequency in the whole growth period increases from southwest to northeast.Drought risk in prosperous period: the high-risk area is concentrated in the southwest of Zunyi,and the low-risk area is in the northern part of Anshun.Drought risk in mature period: high-risk areas are mainly concentrated in the northwest of Zunyi,the east of southwest Guizhou and the southeast of Qiannan Prefecture.Drought risk in the whole growth period: the high-risk areas are mainly concentrated in Zunyi,the adjacent eastern Bijie and the central southwest Guizhou,the second high-risk areas are located in the western part of the province,and the low-risk areas are distributed in the southern part of Guiyang and the southeastern part of Anshun.Drought risk during rooting period : Weining and the north of Anshun are in low risk areas.Overall,the drought risk of tobacco rooting period shows a strong trend from southeast to northwest.Long-term drought risk : the high risk area is concentrated in the southwest of Zunyi,and the lower risk area is in the northern part of Anshun.Drought risk at maturity stage : High risk areas are mainly concentrated in the northwest of Zunyi and the east of southwest Guizhou and the southeast of Qiannan.The drought risk of the whole growth period : the high-risk areas are mainly concentrated in Zunyi and adjacent eastern Bijie and central Qianxinan Prefecture,the sub-high-risk areas are located in the western part of the province,and the low-risk areas are distributed in southern Guiyang and southeastern Anshun.(3)Comprehensive drought risk assessment and regionalization of tobacco in Guizhou ProvinceThe risk of drought disaster-causing factors in Guizhou province is obviously different from east to west,and it is generally characterized by high in the west and low in the east.The high exposure area is mainly in Weining area and some parts of central and southern Zunyi,which are distributed in blocks.On the whole,the exposure gradually increases from southwest to northeast.Liupanshui is the region with the lowest vulnerability;The ability of disaster prevention and mitigation from Zunyi city to the south shows a trend of first decreasing and then increasing,and from southwest to northeast it gradually increases.Guizhou tobacco comprehensive drought risk area,high risk area is located in the northern part of the province,showing a strip distribution.The low-risk area is divided into two parts,one is the vast majority of southeastern Guizhou and the southwest of Qiannan Prefecture,and the other is the southern part of Liupanshui.Generally speaking,the distribution law of tobacco comprehensive drought risk in Guizhou Province gradually decreases from south to north,and first increases and then decreases from west to east.The results can make clear the comprehensive drought risk in different regions,and play an important role in making drought prevention and drought relief plans and providing technical support for agricultural drought early warning.Based on the results of risk zoning,some suggestions on disaster prevention and mitigation of tobacco drought in Guizhou Province are given.High-risk areas: the government can appropriately increase artificial rainfall,build new agricultural water diversion projects,and actively improve smoke and water projects.Sub-high-risk area:Guiyang area strengthens the soil management ability of tobacco fields and does a good job in soil and water conservation.The water supply capacity in some areas of Tongren is seriously insufficient,so it is suggested to plan new reservoirs,rectify old reservoirs and improve tobacco drought resistance.Medium-risk area: There is a lot of precipitation in southwest Guizhou,so it is possible to appropriately increase field reservoirs and adjust planting structure.Sub-low and low-risk areas: Qiandongnan and Qiannan can introduce new tobacco varieties and adopt plastic film mulching technology to alleviate the impact of drought. |
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