Risk Assessment Of Heat Injury For Single-cropping Rice In The Middle And Lower Reaches Of The Yangtze River

The Middle and Lower Reaches of the Yangtze River region(MLRYR) is one of the major rice producing areas in China. Under the background of global warming, risk of high temperature stress of rice increases, which lead to the increased instability of agricultural production. Therefore, it is of great significance to make risk assessment of heat injury for single-cropping rice in MLRYR and its response to climate change. In this paper, based on phonological observation data and yield data records during 1981—2011 and daily meteorological data during 1961—2011 in MLRYR, interannual variability of agricultural climate resources, temporal spatial distribution of temperature tendency rate and decadal heat injury for single-cropping rice was analyzed. In accordance with the theory of “Four Elements” including hazard of the natural disaster, vulnerability and exposure of the disaster-affected body and the disaster prevention and mitigation capacity of human beings, four models were established. On the basis of high temperature days, hazard model was established and decadal spatial distribution maps of hazard in the latest 50 years were made to analyze hazard variability. Considering the sensitivity and adaptability, we used variation coefficient of yield reduction rate in disaster year, thermal variation index and regional agricultural economy development level as vulnerability evaluation indexes, and built the vulnerability evaluation model. The ratio of planting area and agricultural acreage was selected as exposure index and exposure model was established. Agricultural machinery total power per unit area, per capita net income of farmers and rural electricity consumption per unit area are factors in provincial statistical yearbook that can reflect level of agricultural modernization. We selected these three factors as disaster prevention and mitigation capacity assessment indexes. Disaster prevention and mitigation capacity assessment model was established on the basis of comprehensive weighted evaluation to assess the disaster prevention and mitigation capacity in MLRYR. “Three Elements” and “Four Elements” risk assessment index system of heat injury for single-cropping rice in the MLRYR were established, respectively. The relationship between hazard of heat injury and air temperature was analyzed to identify the response of risk to climate change. Result showed that:(1) Hazard and vulnerability of heat injury are the two most important factors in the risk assessment model in most sites;(2) Areas with high risk values in “Three Elements” model are mainly in the northeast of research areas with risk index of more than 0.57 while those with medium and low values are mostly in the west of Hunan, Anhui, central of Hubei and east as well as west of research areas, respectively. Areas with high risk values in “Four Elements” model are mainly in the northwest of Hunan with risk index of more than 0.57 while those with medium values are in most sites in research areas.(3) Hazard of heat injury of single-cropping rice was positively correlated with temperature of 20 days during heading period. Results indicated that the risk of heat injury increases with temperature quickly when the highest temperature exceed 31℃ or the average temperature exceed 26.5 ℃.Risk of heat injury in different regions of MLRYR had significant differences. Suitable variety types should be selected and disaster prevention and mitigation capacity of human beings should be improved according to local risk features.