甘肃河西走廊临泽小枣冻害成因及防治对策

进入21世纪的短短几年里,甘肃河西走廊临泽小枣就遭受了2次冻害,2008年的冻害比2003年更为严重,位于临泽县北部的四个乡镇的枣粮间作地,全部幼树和绝大部分大树树冠均冻死、绝产.冻害程度调查表明,临泽县南部乡镇轻,北部乡镇重;村庄宅旁轻,枣粮间作地重;靠近林带和小网格林带内轻,远离林带和大网格林带内重;背风面轻,迎风面重.气象资料分析得出,2003年冻害是由于2002年12月下旬的低温所致;2008年冻害是1月下旬到2月上旬的低温所致,冻害期间,最大风力为西北风,吹得最多的是东北风.通过与正常年份气温的比较分析得出,临泽小枣安全越冬的临界气温为-20.0℃,2d日平均温度低于-20℃的低温即可使临泽小枣遭受冻害,但≤1d的-20℃以下的低温对临泽小枣不产生冻害;温度越低,枣树能忍受的时间越短,可忍受的极端最低气温为-27℃.加强绿洲防护体系建设,大力发展村旁、路旁、渠旁、宅旁等四旁枣树种植,及根据天气预报采取应急措施是防止临泽小枣发生冻害的主要对策.

Cause of freezing damage and prevention strategies to Linze jujube in Hexi Corridor region of Gansu Province

Linze jujube suffered from twice freezing damage in the few years of 21st century, and the freezing damage in 2008 was severer than that in 2003. All seedlings and crown of most big trees in jujube/crop inter-cropping field of four towns which located in the north of Linze County were freezed to death and had not yields. The investigation of freezing damage shows that, the freezing damage degree of towns which located in the south of Linze County is slight and the towns which located in the north of Linze County is serious; the side of villages and houses is slight and jujube/crop inter-cropping field is serious; the freezing damage degree of jujube trees which is close to forest belt and in the small grid forest belt is slight, and the damage which kept away form forest belt and in the big grid forest belt is serious; the leeward side is slight and the windward side is serious. The analysis of weather data concludeds that the freezing damage in 2003 is resulted from the low temperature of the last ten days of December in 2002; and the low temperature from the last ten days of January to the first ten days of February result in freezing damage of 2008, the direction of most great wind is northwest and the direction with most frequent wind is northeast in the period of freezing damage. Compared with the temperatures in normal years, we conclude that the critical temperature that Linze jujube could live through winter safely is -20.0℃, and it would suffer from freezing damage when average temperature of two days is lower than -20.0℃, but temporary low temperature would not cause freezing damage, and the lower the temperature, the shorter the tolerated time, and the extreme lowest temperature that it could tolerate is -27℃. The main strategies that could prevent freezing damage are to strengthen the construction and protection of oasis shelter belt, to develop planting of jujube trees beside villages, roads, canals, houses, and to take some urgent measures according to weather forecast.