Risk Assessment Of Cold And Hot Damage For Double-season Early Rice(dser) In Lower-middle Reaches Of The Yangtze Rive Basin

Agricultural meteorological disasters are the important factors which threaten the national food security. Risk assessment on agro-meteorological disasters is the main research direction of guaranteeing agricultural production. Yangtze River basin is the largest double-season early rice (DSER) planting area in China, its DSER output accounts for more than half of the country’s total production. This region is located in central China, where hydrothermal resources are relatively abundant, but the seasonal distribution is uneven. Temperature swings in spring and hot days emerge frequently in summer, causing DSER’s cold and hot damage and affecting final yield. Therefore, it is emergency to carry out risk assessment of cold and hot damage of DSER.The research is based on the meteorological data during 1961-2012, agricultural meteorological data during 1981-2010 and social statistics data of DSER growing region in lower-middle reaches of the Yangtze River Basin. Using jointing stage as the partition, the growing season is separated into earlier stage and later stage. The methods of statistical analysis, Mann-Kendall and wavelet analysis are applied to analysis spatial and temporal distribution of early cold damage, late cold damage and late hot damage. Then we can identify the regional multiple disasters risk. Laying the foundation of the formation mechanism of natural disaster risk, we constructed the evaluation models to assess hazard, vulnerability, exposure and disaster prevention and mitigation capacity. Weight coefficients of risk assessment model are calculated by entropy weight evaluation method. Weight coefficients of risk assessment model are calculated by entropy weight evaluation method. The results of the multi-risk assessment model is valuable for decision making to release disaster risks. The main conclusions are as follows:(1) Temporal and spatial distribution of severe weather:for temporal variation, cold damage is severe at booting stage in 1970s, at tillering stage in 1980s, at flowering stage in 1990s and hot damage is severe in 2000s. For spatial distribution, cold damage at tillering stage, booting stage and flowering stage are serious in the central and western area, the northern area, eastern and western area respectively. Hot damage at flowering stage is serious in eastern area, and for filling stage, it is serious in northern, central and eastern of the study area. The distribution of cold damage and hot damage is mainly related to the terrain.(2) Hazard assessment results show that:the best DSER growing condition is in Hunan and Jiangxi. Hazard in Hunan and Jiangxi is the lowest, followed by Hubei, and Zhejiang is worst. Flowering and tilling stage in Hunan, tillering and filling stage in Jiangxi, booting and filling stage in Hubei and flowering and filling stage in Zhejiang are the critical periods for disaster prevention and reduction.(3) Vulnerability assessment results show that:mid-east Zhejiang, mid-south Jiangxi and Hubei planting area are the low vulnerable area. The vulnerability index in Northeastern of Jiangxi is quite high, followed by Ningxiang and Chaling of Hunan province.(4) Exposure assessment results show that:DSER planting area ratio is high in the eastern of Hunan and northeastern of Jiangxi, which means high exposure and high minacity to the rice production. The exposure is lower in Zhejiang and Hubei, and it won’t have high impacts on DSER yield.(5) Disaster prevention and mitigation capacity assessment result show that:Disaster prevention and mitigation capacity is highest in Zhejiang province. It is relatively higher in central Hunan, western Hubei and southern Jiangxi. Disaster prevention and mitigation capacity is lower in the other area(6) Risk assessment results show that:mid-west Zhejiang, northeast Jiangxi and central Hunan are divided into high-risk areas. Southern Hunan, southeastern Jiangxi, eastern Hubei and eastern Zhejiang are roughly divide into the low-risk and the other area are divided into medium risk areas.Based on the results of risk identification and risk assessment of cold and hot damage for DSER in lower-middle reaches of the Yangtze River Basin, we put forward the disaster reduction suggests for each province. In order to release the risk, in mid-west Zhejiang it is useful to breed anti-disaster DSER species, adjust the sowing period or replant single-season rice. For northeastern Jiangxi, increasing the investment of local agriculture is needed. It is necessary to adjust the planting structure in Hunan. Science and technical inputs in Hubei should be increased to reduce the risk.