| Drought is the main agrometeorological disaster in China.The summer and autumn drought are mainly triggered by the combination of the strong evaporation,high temperature and the uneven spatial and temporal distributions of rainfall in the red soil region of the southern China.In addition,the red soil is sticky and heavy,the available water content is low,the summer autumn season is short,the duration of rainstorm is long,and the slope runoff coefficient is large,which further accelerate the slope land drought in the region.In recent years,the global warming,extreme weather and climate events have a tendency to increase.Severe seasonal drought events occur continuously in southern China,which have a serious impact on agricultural production and threaten food security in China.In order to promote the prevention and control of drought and the healthy development of agricultural production in this region,based on the meteorological data of Jiangxi Province and agricultural production materials of different administrative regions,this paper comprehensively and objectively analyzes and evaluates the regional seasonal drought situation from the drought frequency,drought range,drought intensity and drought change trend in different time scales.In this paper,the standardized precipitation evapotranspiration index(SPEI)is selected as the evaluation standard of drought based on the methods of crop yield residual(SYRS),Mann Kendall theory,multiple regression analysis and correlation analysis,the spatial-temporal pattern evolution characteristics of drought in Jiangxi Province were analyzed;the causes of drought are studied;the fluctuation rules of different crop yields and their temporal and spatial responses to drought were elaborated.(1)On the annual scale,the drought frequency in Jiangxi Province decreased from 1960s to 1980s,increased gradually after 1990s,and reached a peak at the beginning of the 21st century.In each season,the frequency of autumn drought and above middle drought were the highest,32.3%and 15.9%respectively.Jiujiang area in Northwest Jiangxi Province occurred more frequently.On the whole,spring drought and autumn drought increased,75%and 71%of the stations showed drying trend in spring and autumn respectively;summer drought and autumn drought were alleviated,and 82%and 96%of stations showed wetting trend in summer and winter respectively.The desiccation area in spring is more obvious in the north of Jiangxi Province,and in the south of Ganzhou in autumn.(2)There were 1963,1971,1978,1986,2003,2007 and 2011 in Jiangxi Province.The drought intensity was higher in 1960 s,1970 s and 2000 s,and lower in1980 s and 1990 s.The results showed that spring drought occurred for 5 years,and the highest drought intensity was 9.4 in 2000s;the highest drought intensity in 1980s was 9.0 in summer drought;the highest drought intensity was 11.8 in 1990 s in autumn drought for 7 years;the highest drought intensity was 19.0 in 1960 s in winter drought for 8 years.Since the 21st century,the risk of spring drought has increased greatly.(3)From the analysis of drought causes,rainfall was significantly positively correlated with relative humidity and SPEI(P<0.05),while the highest temperature,maximum wind speed and sunshine hours were significantly negatively correlated with drought(P<0.05).In each typical drought event,rainfall reduction and temperature rise were the main factors.The regression equation of rainfall,relative humidity and maximum wind speed can be established with spei through collinearity diagnosis.Rainfall is the most important factor contributing 70%of SPEI.(4)The yield per unit area of Jiangxi Province showed a very significant increase trend(R~2=0.63,P<0.01),with a linear growth of 83.21 kg/hm~2.However,the serious drought led to the serious decrease of grain yield.In 2003,Jiangxi Province had a serious drought,and the yield per unit area decreased by 821.69 kg/hm~2.The frequency of drought in Jiujiang is high,but the ability to resist drought is low,which leads to the biggest fluctuation of yield.The sensitivity of different crops to drought is different.There was a significant positive correlation between spei and the standardized yield residuals series(SYRS)in the growing season of one season mid season rice and double cropping late rice(P<0.05),and the most sensitive was from July to August.The results showed that drought from July to August had the greatest impact on yield.There was a significant negative correlation between SPEI and SYRS(P<0.05),indicating that waterlogging had a greater impact on the yield of double cropping early rice.For winter wheat and cotton,the sensitive period was November and April to May,respectively.To sum up,the degree of drought has been increasing since the 21st century,with frequent spring and autumn droughts.Although the increase of water conservancy facilities,alleviate the impact of drought on crops.However,climate warming has led to the aggravation of drought,and the drought threat faced by major crops has an increasing trend. |
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