Spatial and temporal evolution characteristics of drought in Guangxi during sugarcane growth period based on SPEI

China is the third largest sugar producer in the world, and sugar industry is the most important economic pillar industries in south China. Drought is one of the most serious agro-meteorological disasters affecting sugarcane production. Under the background of climate change, to analyze the temporal and spatial evolution characteristics of drought in sugarcane planting area is of great significance for disaster prevention and improving the ability of sugarcane production to cope with climate change. In this paper, Guangxi Zhuang Autonomous Region which is located in 104°26′-112°04′E，20°54′-26°24′N was taken as the research area. Temperature and precipitation data from 1971 to 2017 and the standardized precipitation evapotranspiration index (SPEI) were used to analyze the drought characteristics. Firstly, historical typical drought events and measured soil relative humidity were used to verify the applicability of SPEI to sugarcane drought monitoring. Then, taking the sugarcane growth stages including seedling stage, tillering stage, stem elongation stage, maturity stage and whole growth stage as time scale, and considering the difference of sugarcane sowing time, the spatial and temporal evolution characteristics and variation rules of light drought, medium drought, severe drought and extreme drought in different sugarcane planting areas in Guangxi were analyzed by climate trend rate, wavelet analysis and GIS spatial technology. The results showed that the occurrence time and intensity of typical drought events during 2003 to 2011 in sugarcane planting area were good fit with SPEI, and the correlation between soil moisture of 0cm to 50cm depths and SPEI were good in each sugarcane growth period and the whole growth period and most of them passed the significance level test, all this indicates that SPEI could reflect drought objectively. The climate trend rate analysis showed that, from 1971 to 2017, the drought trend of sugarcane was the strongest at the tilling stage, the second at the seedling stage, the weakest at the stem elongation stage, while the mature stage showed a wet trend. The wavelet analysis results showed that, for the time scale of 10 to15 a, there were about 4 to 6 dry-wet cycles in each sugarcane growth stages, and for the time scale of 0 to 5 a, dry-wet cycles alternation were more obvious. There were great differences in each growth period, and the change of stem elongation and seedling stage were more obvious than those of tilling stage and technological maturity stage. From the seedling stage to the maturity stage, the spatial distribution characteristics and variation rules of drought in the sugarcane growing areas in Guangxi were of great difference. Generally speaking, drought frequency is highest in maturity stage and lowest in tillering stage and similar in stem elongation and seedling stage. Frequency of light drought was high for all sugarcane growth stage and relative low for medium drought, severe drought and extreme drought, furthermore, frequency of middle drought was obviously higher in stem elongation stage and maturity stage than other growth stages. For sugarcane seedling stage and stem elongation stage, drought frequency was higher in northern Guangxi than other areas, while for tillering stage and maturity stage, drought frequency was higher in central Guangxi.