Abstract: Based on the data of daily meteorological factors in winter, winter wheat freezing injury and winter wheat cultivars in Hebei Province from 1981 to 2010, the three types of climatic indexes of winter wheat freezing injury, including severe temperature downing in early winter, winter with long cold days and freezethawing, were established by using rank sum test and Bayesian discriminant analysis. According to the risk analysis principle and probability density function, the climatic models of risk probability index for winter wheat freezing injury were set up, and the freezing risk of winter wheat in Hebei was assessed. The results showed that the freezing injury due to severe temperature downing in early winter was affected mainly by the variation range of temperature and the extreme minimum temperature during the temperature downing process. The freezing injury due to winter with long cold days was influenced mainly by the cold intensity of winter season, including the number of days of winter wheat overwintering stage, the mean temperature, the number of days with the minimum temperature being lower than the critical temperature, and the accumulated negative temperature during the same period. The freezing injury due to freezethawing was affected mainly by the extreme minimum temperature in the microthermal process with daily average temperature above 0 ℃. The major risk of winter wheat freezing injury in the north Hebei was due to winter with long cold days, and the high and subhigh risks of such freezing injury mainly occurred in the middlenorth part of Tangshan and Qinhuangdao and northwest of Baoding. The main risk of winter wheat freezing injury in the middle and south Hebei was freezethawing and severe temperature downing in early winter, and the high and subhigh risks of such freezing injury mainly occurred in the east part of Xingtai and Handan, and northwest part of Baoding.

Key words: Henan Province, carbon footprint, spatial distribution, farmland ecosystem