| In the context of global climate change,extreme weather events such as drought occur frequently.The drought research of food crops has long become an important research topic in the field of Agrometeorology in the world.Potato is the fourth most important food crop in the world.The sing-cropping region in the northern China is the dominant potato producing area in China.Drought is the main factor affecting the potato yield in this area.Taking potato drought in the sing-cropping region in the northern China as the research object,this paper constructs potato drought index based on crop water deficit in different growth periods by using meteorological data,historical disaster data and growth periods data of potato drought from 1981 to 2015;Through the methods of historical disaster inversion,independent sample T-test,cumulative probability inverse function and K-Means cluster analysis,the drought level index threshold of potato in different growth periods was calibrated;Through the comparative analysis method of reserved independent verification samples,the effectiveness of potato drought level index was verified.The main conclusions are as follows:1)Based on the precipitation and water demand of potato in different growth periods,the potato drought index was constructed.The independent T-test results of the disaster samples and disaster free samples in the three growth periods of potato show that there are significant differences between the disaster samples and disaster free samples in the three growth periods,which shows that the drought index constructed in this paper can effectively characterize the drought disasters in different growth periods of potato in the study area.2)The thresholds of mild,moderate and severe drought index in potato seeding—emergence period are 0.75≤DI<0.82,0.82≤Di<0.94 and DI≥0.94 respectively;The threshold values of mild,medium and severe drought index during emergence—bloom period are 0.63≤DI<0.74,0.74≤DI<0.88 and DI≥0.88 respectively;The threshold values of mild,medium and severe drought level index in bloom—harvesting period are 0.50≤DI<0.58,0.58≤DI<0.69 and DI≥0.69 respectively.The drought trigger thresholds of potato in seeding—emergence period,emergence—bloom period and bloom—harvesting period are0.75,0.63 and 0.5 respectively.3)Based on the reserved potato drought verification samples,the identification results of the constructed potato drought level index were verified.The results showed that:The proportion of drought identified by the index of seeding—emergence period is 84.6%,and the proportion of drought level identification degree is completely consistent,that is the potato drought level identification results are the same as the actual drought level,is 69.2%;the proportion belonged to basically consistent,that is although the identification result of drought level is different from the actual drought level,but there is no cross level difference,is 15.4%.The proportion of drought identified by the index of emergence—bloom period and bloom—harvesting period are 95.7% and 90.0% respectively.The proportions of drought lever identification in emergence—bloom period and bloom—harvesting period completely consistent with the actual drought level are 78.3% and 75.0% respectively,the proportions belonged to basically consistent are 17.4% and 15.0% respectively.4)From 1981 to 2015,the drought index of potato in the sing-cropping region in the northern China showed a gradual downward trend;from the interannual variation of drought index in different growth periods of typical sites,the potato drought index in different sites showed an upward trend with the increase of years in the bloom—harvesting period;in terms of spatial distribution,generally speaking,the frequency of drought in the whole region is higher in the western region than in the East.The western region is more likely to be affected by severe drought during bloom—harvesting period,and the eastern and central regions are more likely to be affected by light drought during emergence—flowering period. |
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