Heat Injury Risk Assessment for Single-Cropping Rice in the Middle and Lower Reaches of the Yangtze River under Climate Change

Under global warming, the risk of heat injury for crops increases, which leads to increasing instability in agricultural production. In this study, based on phenological observation data and yield data during 1981-2011 and daily meteorological data during 1961-2011 in the middle and lower reaches of the Yangtze River (MLRYR), the risk of heat injury for single-cropping rice in this area and its response to climate change were assessed and analyzed. The risk was decomposed into such elements as hazard, exposure, vulnerability, and disaster prevention/mitigation capacity, in accordance with natural disaster risk assessment theory and the formation mechanisms of agrometeorological disasters. First, a hazard assessment model was established to identify spatiotemporal variations of the heat injury in the MLRYR during 1961-2011, and the relationship between heat injury hazard and air temperature was analyzed to identify the response of hazard to climate change. It was found that the heat injury haz-ard of single-cropping rice was positively correlated with the mean and maximum temperatures during the rice heading period of 20 days, with the hazard increasing sharply when the mean temperature exceeded 26.5℃ and the maximum temperature exceeded 31℃. Then, exposure, vulnerability, and disaster preven-tion/mitigation capacity were also quantitatively examined. The results show that vulnerability and hazard were the two most important factors in the heat injury risk assessment for single-cropping rice at most stations in the MLRYR. The risk assessment considering only the first three natural elements produced high-risk values ( 0.46) mainly in the northeast of the study area. By adding the regional capability in disaster prevention/mitigation into account, the risk assessment produced high-risk values in a much smaller area in the northeast but some-what larger areas in the southwest of the study domain. In general, the risk of heat injury differed greatly within the MLRYR. Particular rice varieties should be adopted for specific regions, according to the local risk features quantified by this study. Under the warming climate, the risk of heat injury for single-cropping rice is likely to continue to increase.