Risk division on winter wheat suffering from spring wet damages in Jiangsu Province

Wet damage in spring has been one of the important agro-meteorrological disasters in the winter wheat production of Jiangsu Province.In order to reveal the occurrence pattern of the disaster,forage its appropriate monitoring and forewarning indicators,evaluate its hazard risk scientifically and provide the decision-making basis for the prevention from its disaster and the mitigation of its loss,in this paper,three meteorological factors such as ten-day precipitation,ten-day sunshine time,and ten-day rainfall days were selected to characterize the wet damage in spring and their data in all springs during 1960 to 2008 were calculated and used to analyze the relationship between the wet damage and the climate yield of winter wheat in the different regions of Jiangsu Province combined with the path analysis,a statistical method.A wet damage index was quoted to differentiate the effect of wet damage on the yield of winter wheat in the different regions of the province.An hazard risk index of wet damage and its division indicators with three risk grades were suggested to evaluate the hazard risks of the wet damage and decide their regional divisions in the province.Consequently,some results were obtained from this paper.At first,the ten-day precipitation and ten-day rainfall days in spring were remarkable positive related to the climatic yields of winter wheat in the dfferent regions of the province but the ten-day sunshine time was eminent negative related to the climatic yields.The ten-day precipitation and ten-day sunshine time were two direct factors influencing on the climatic yield of winter wheat but the ten-day rainfall days had indirect effect.Secondly,the quoted index model of wet damage and its suggested hazard risk index model reflected perfectly the occurrence frequencies of wet damage and the loss situations of winter wheat yield in the different regions of the province.Under the assistance of Arc GIS 9.3,a software of geographical information system,the spatial analysis on the hazard risk index of wet damage showed that the regional difference of the risk index in Jiangsu Province was obvious,the maximum value areas of the risk index distributed in most part of South Jiangsu Province and the western part of the region between the Yangtze River and the Huaihe River,the minmum value areas were the coast regions along the Yellow Sea and the regions surronding Taihu and the moderate value areas situated in the middle part of the region between the Yangtze River and the Huaihe River and the northern part of North Jiangsu Province.Thirdly,the risk indexes of wet damage and the drop percentages in winter wheat yield in the different regions of the province were synthesized as their risk division indicators of the wet damage and the whole province was divided into the regions of three hazard risk type such as the high hazard risk regions covered the south part of Jiangsu Province and the western part of the region between the Yangtze River and the Huaihe River(giving priority to the region surrounding Honzehu Lake),the moderate hazard risk regions inclued the northwestern part of the province and Lixiahe river regions and the low hazard risk regions situated in Lianyungang Region and the north part of Yancheng Region.