Abstract: 【Objective】To identify the temporal and spatial changes of photo-thermal resources during the growing season and key development stages of winter wheat in China so as to mitigate the impacts of climate change on wheat production in China by adjusting cropping system and crop distribution according to changing trends of photo-thermal resources.【Method】Daily data of temperature and sunshine hours of 47 years (1961-2007) from 264 meteorological stations in the winter wheat growing regions in China were used to calculate daily active temperature (＞0℃) and daily total global radiation. The theoretical dates when winter wheat reaches its main development stages were determined based on the accumulated active temperature required by each development stage. Photo-thermal resources (the growth degree days (GDD), the thermal time (TT), the total global radiation, and the product of thermal effectiveness and global radiation (TEP)) for the whole growing season and the key development stages were then calculated. The grid data were obtained by means of inverse distance weight spatial interpolation using ArcGIS (v9.3).【Result】During the 1961-2007, the theoretical sowing date of winter wheat delayed averagely by 0.5 d•10a-1, that of heading and ripening became earlier averagely by 1.6 d•10a-1 and 1.7 d•10a-1, respectively, and the whole growing season was shortened averagely by 2.2 d•10a-1. During winter wheat growing season, the GDD and the total TT increased averagely by 7.8℃•d•10a-1 and 0.6 d•10a-1, respectively, the total global radiation decreased averagely by 39.69 MJ•m-2•10a-1 (by -2.34%•10a-1), and the TEP decreased averagely by 10.18 MJ•m-2•10a-1 (by -1.22%•10a-1). From sowing to heading, the GDD and the total TT increased averagely by 6.2 ℃•d•10a-1 and 0.57 d•10a-1, respectively, the total global radiation decreased averagely by 27.7 MJ•m-2•10a-1 (by -2.72%•10a-1), and the TEP decreased averagely by 5.2 MJ•m-2•10a-1 (by -1.18%•10a-1). From heading to ripening, the GDD and the total TT increased averagely by 1.6 ℃•d•10a-1 and 0.05 d•10a-1, respectively, the total global radiation decreased averagely by 12 MJ•m-2•10a-1 (by -1.78%•10a-1), and the TEP decreased averagely by 4.97 MJ•m-2•10a-1 (by -1.26%•10a-1).【Conclusion】During the 1961-2007, in the North region and in Mid-eastern Shandong Province of Huang-Huai region for winter wheat growing, the decreases of both TEP and the length of wheat growing season indicate that changes in photo-thermal resources had negative effects on winter wheat potential productivity in these regions. In the rest regions (the Southwest, the Middle and Lower Reaches of the Yangtze River, the Huang-Huai, and the South) for winter wheat growing, the increased TEP had a positive impact on winter wheat potential productivity whereas the shortened growing season had a negative impact on winter wheat potential productivity, hence, the impacts of changes in photo-thermal resources on winter wheat potential productivity is positive or negative can only be determined by resorting to quantitative analysis using crop growth simulation models.

Key words: winter wheat, development stage, GDD, photo-thermal resources, photo-thermal potential productivity