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京郊地处我国北部冬麦区的边缘,属于暖温带大陆性季风气候,冬冷夏热,极端最低气温一般在-18—-20℃,个别地区曾低至-27.4℃,早春气温很不移定,倒春寒频率较高。因此,有的年份容易发生冻害,导致小麦死苗减产。建国以来已发生六次全市性大冻害,减产都在三成以上.1977—1981年五年就连续发生三次冻害,越冬死茎率达20—30％。小麦生长后期常受高温逼熟的影响,促使茎叶早衰,籽粒灌浆时间缩短,粒重明显降低。尤其在春季
The suburbs of Beijing are located on the fringe of the winter wheat area in the northern part of China. They belong to the warm temperate continental monsoon climate. The winters are cold and hot in summer. The extreme minimum temperature is generally -18 to 20 degrees centigrade. In some areas, the temperature dropped to as low as -27.4 degrees centigrade. In late spring cold frequency higher. Therefore, some years prone to frost damage, resulting in reduced production of wheat dead seedlings. Since the founding of the People’s Republic of China, six major freeze-offs have taken place in the city, with a reduction in production of more than 30% .Three years of freeze-frost injury occurred in five consecutive years from 1977 to 1981, with 20-30% dead-wintering stalks. The late growth of wheat often under the influence of high-temperature ripening, promote premature leaf stems and leaves, grain filling time shortened, grain weight decreased significantly. Especially in spring