Studies On Spatial And Temporal Variations Of Most Optimum Leaf Area Index Of Rice In Main Growing Regions Of China

Agricultural production is determined by climate change. In the past50years, China’s average surface temperature was increased, while the total amount of solar radiation was decreased. Because of wider regional distribution and great differences between ecological zones, the effects of climate change on rice production were not the same in main growing regions of china.As the global climate change, climatic conditions of heading changed caused by the safe date of maturity changed, result in optimum leaf area index changed. Analyze the influence of climate change on leaf area index in China to make clear optimum leaf area index of different ecological zones in order to set the target yield.In this study, by using the active accumulated temperature of grain filling required, minimum limit temperature of maturity and optimum temperature for heading,the safe date of maturity and the best heading-grain filling period were calculated. Temporal and spatial variation of safe date of maturity and the best heading-grain filling period were analyzed combined with geographic information systems (GIS). Based on this fact, natural light intensity of heading stage is obtained. According to modified Mosi-Formula, optimum leaf area index of heading stage of different years were simulated. Results of this study were presented as follows:1. China rice Security maturity roughly zonal distribution of early gradually from south to north, northeast earliest, in mid-September. The safe date of maturity was zonality distribution, earlier gradually from south to north. The safe date of maturity in northeast china was the earliest, in mid September. The safe date of maturity in Sichuan Basin was mid-October; and in Yunnan plateau was late October. In the middle and lower Yangtze Region, single cropping rice ripening in the last ten-day period of October to early November, double-cropping late rice matured in early November. South China which was the latest, double-cropping late rice ripening in the last ten-day period of November. The distribution trend of the best heading stage was same as maturity.For northeast region earliest to be late July to early August, Sichuan Basin and Yunnan-Guizhou Plateau to be late August to early September. In the middle and lower yangtze river, the best heading date of single cropping rice was the early of middle of September, which of double-cropping late rice was the last ten-day period of September. For double-cropping late rice in South China, the best heading date was early October.2. From1960to2007, the general safe date of maturity was delayed. Average delay in the past50years was Id. The delaying tendency inYunnan-Guizhou Plateau, Northeast, South region was more obvious. The high value area of safe date delaying was Yunnan-Guizhou Plateau, which delayed9d for the past50years. The safe date of maturity in South region had delayed6.5d for the past50years, while for Northeast, delayed6d. The safe date of maturity in Sichuan basin had delayed4.5d for the past50years. In middle-lower yangtze area, single cropping rice delayed2.5d, double-cropping late rice delayed1.5d.The best heading date were also delayed. Compared with the safe date of maturity, the delayed trend of best heading date was increased. From1961to2007, the average best heading date was delayed7d. The delayed trend of Yunnan-Guizhou Plateau was most obvious, delayed9.5d average. Single cropping rice in middle-lower yangtze area delayed8d. Double-cropping late rice in South China delayed7d, while that in northeast delayed7d.The delayed trend of best heading of double-cropping late rice of middle-lower yangtze area was least, which delayed5.5d.3. From1960to2007, the optimum LAI of heading stage was increased. Compared with the1960s, the optimum LAI of northeast region increased by an average of2.1, the Yunnan-Guizhou Plateau and Sichuan Basin increased by an average of2.6, the middle and lower Yangtze Region increased by an average of2.85±0.05, while that of southern China increased about3.0.The high values of leaf area index were the middle and lower Yangtze Region, south China and low altitude of Yunnan-Guizhou Plateau. In2000s, leaf area index for high yielding fields was about8.0, while light and heat resources were abundant, optimum leaf area of heading stage could reach9.0. The low value range of leaf area index were high altitude of Yunnan-Guizhou Plateau (>2000m), the optimum LAI only about4.4. The optimum LAI of rice in cold area such as Northeast area was also low, which was about5.3.