Temporal And Spatial Variation Characteristics Of Drought And Its Impact On Crop Production In Guangxi

Drought is a universal natural disaster with slow development and wide impact.As a system directly affected by weather and climate change,drought will directly affect crop production and threaten food security.As an agricultural region in southwest China,Guangxi was often affected by drought in the long-term development process,which threatens the agricultural production and social and economic stability of Guangxi.It was of great significance to systematically study the temporal and spatial variation characteristics of drought in this region and its impact on crop production,so as to stabilize crop yield and prevent its growth process from being affected by drought.Based on monthly temperature and precipitation data in Guangxi from 1961 to 2017,the spatial and temporal distribution characteristics of drought and flood were revealed by using the standardized precipitation evapotranspiration index(SPEI),which represents multiple time scales,from four aspects of drought frequency,drought station frequency,drought intensity and maximum drought duration.Using meteorological factors,geographical environment factors,El Nino-Southern Oscillation(ENSO)event and relative number of sunspots,the main influencing factors of drought were discussed by means of correlation analysis,spatial inverse distance weighted interpolation and linear change analysis.Finally,drought index was combined with crop standardized yield residual series(SYRS)to quantitatively analyze the impact of drought on crop production,and reveal the critical time nodes and spatial locations of severe drought.The main conclusions are as follows:(1)The drought trend in Guangxi increased in annual scale,growing season,spring and autumn,and the annual scale showed three major periods: 1961-1969,1983-1993 and 2000-2012.Spatially,the drought trend increased mainly in northwest Guangxi,southwest and north Guangxi in spring,central Guangxi in summer,northeast Guangxi in autumn,and south central Guangxi in growing season.The drought frequency in Guangxi increased in autumn,while the extreme drought events occurred frequently in winter.Moderate and severe drought occurred frequently in northwest and northeast Guangxi,and extreme drought occurred frequently in northeast and central Guangxi.The drought station frequency shows that Guangxi was dominated by local drought,and its high value was gradually transferred to autumn and winter,and the degree was gradually deepened.The longest drought duration in Guangxi reached 4months,which occurred in 1987,1988,1989,1992,1998,2000 and 2005 respectively.The longest drought duration on the interdecadal scale reached 5 months,which occurred in the1980 s and 1990 s respectively.The spatial distribution pattern of the longest drought duration was high in the east and low in the west,and Liujiang station and Weizhoudao station reached the maximum.(2)Drought was significantly correlated with precipitation,evapotranspiration,relative humidity,sunshine duration and other meteorological factors,and the correlation coefficient between precipitation and drought is the largest.The spatial distribution pattern of correlation coefficient was high in northeast China and low in southwest China.The precipitation in northeast Guangxi has the greatest influence on drought.When ENSO event occurred,the probability of drought and flood events in Guangxi was about 59%,and the correlation coefficients of Sea surface temperature anomalies(STTA)and SPEI were the largest in annual scale,spring and autumn,especially in autumn,the drought events in western and central Guangxi were most affected by SSTA changes.The relative number of sunspots and SPEI showed a special alternating relationship of "positive-negative-positive-negative-positive" in five periods,which were positive before 1961-1970.It was negative from 1970 to 1980;Positive from 1980 to 1989;Negative between 1989 and 1999;After 2000,the positive and negative relationship between the relative number of sunspots and SPEI coefficient alternates from one week to 10 years.The ecological environment of Guangxi was fragile,the spatial and temporal distribution of regional precipitation was extremely uneven.The hills and depressions developed in carbonate rocks are widely distributed,and the soil water retention capacity was poor,which was prone to drought and flood disasters.(3)SYRS of grain crops showed that there were 11 years of low yield,among which the years of high yield were 1978,1986 and 1988 respectively,and the yield in 1988 was the highest.The grain yield in central and northwestern Guangxi showed an upward trend,with the highest increasing rate and coefficient of variation in Chongzuo and Laibin areas.SYRS of cash crops showed a total of 15 years of yield reduction,and the high yield year was 2000.The abnormal grain yield was closely related to the drought in the medium time scale(4-7 months)from April to May,and the flood in the short and medium time scale(4-5 months)in August.The yield anomalies of cash crops are closely related to the drought in medium time scale(4-7 months)from June to September and the flood in long time scale(6-12 months)from January to June.The SPEI values in short and medium time scale are more advantageous for detecting drought and flood events.(4)The crop yield in spring and autumn was mainly affected by drought,in summer by flood.The areas with the highest risk of drought are mainly located in the northwest and central part of Guangxi.The responses of crop yields to drought and flood events differed spatially over time,with large areas of drought correlation and sensitivity shifting from southeast to northwest from spring to autumn.The results will help to better understand the impact of drought on crops in Guangxi,provide information for policymakers,and the method is expected to be applied to other crops in other regions.