Spatial and Temporal Characteristics of Rice Potential Productivity in Main Growing Regions of China.

The impact of spatial and temporal differences in climatic factors on rice productivity in China is highly uncertain because of its vast area and marked variation. The daily meteorological data during the years from 1961 to 1970 (1960s) and from 1996 to 2005 (2000s) of 351 weather stations in main rice growing regions of China were processed to obtain the daily meteorological surface data using softwares of ANUSPLIN and ARCGIS. The annual potential photosynthetic, photo-thermal and climatic productivities during rice-growing periods were calculated with the gradually descending model, and the spatial and temporal distribution characteristics of above three potential productivities between two decades (1960s and 2000s) were analyzed. Further, the spatial distribution characteristics of differences between potential photo-thermal and climatic productivities of 2000s, and between potential photo-thermal productivity of 2000s and high yield target were investigated. As compared with 1960s, the potential photosynthetic productivity in rice-growing periods of 2000s decreased by 5.33%, and the decreasing rates in the Northeast and Southwest China were lower than those in the Middle and South China. From 1960s to 2000s, the potential photo-thermal productivity during rice-growing periods increased in the Northeast and Southwest China, while decreased in most areas of the Middle and South China, with average decrement of 3.14% in main rice growing regions of China. Meanwhile, the potential climatic productivity during rice-growing periods of 2000s decreased in most areas of China as compared with 1960s, while increased in part of Middle and South China, with average decrement of 0.44% in main rice growing regions of China. The yield increment indices (within a range of 0 to 2.4) from the high yield target to the potential photo-thermal productivity were less than 1 in most areas of the single-cropping rice growing region, higher than 1 in most areas of the double-cropping rice growing region, and greater than 1.5 in most areas of South China. In addition, the differences between potential photo-thermal and climatic productivities in 2000s indicated that the high yields of rice in the Northeast China were more dependend on irrigation than in the Middle and South China. These results were helpful for further exploration of technical approaches to enhancing rice yields and for quantitative decision support for guiding national rice production in China.
Key words: Rice; Photosynthetic productivity, Photo-thermal productivity; Climatic productivity; Spatial distribution; Temporal distribution; Rice growing area; China