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核桃是经济价值很高的木本油料树种,近年来发展很快。但在发展中存在一个严重的问题,就是幼树越冬后常常发生枝条从上而下的枯死现象,老乡把这种现象叫“抽条”。在北京郊区,一般1-2年生的核桃苗百分之百的发生抽条,3-10年生的幼树也很严重。在幼树“抽条”较重时,影响生长和发育,逐渐形成小老苗,在管理不及时的情况下造成死亡;“抽条”轻的引起树形紊乱,呈扫帚状,从而影响生长和结果。例如,北京地区从1962年以
Walnut is a woody oilseed species with high economic value and has developed rapidly in recent years. However, there is a serious problem in development. It is the phenomenon that the young trees often die from the top to the bottom after the winter is over. The villagers call this phenomenon “drawing.” In the suburbs of Beijing, 1 to 2 years old walnut seedlings are generally one hundred percent sprouting, 3-10 year-old young trees are also very serious. When sapling is heavier, it will affect the growth and development, and gradually form small seedlings, which will cause death under the condition that the management is not timely. The “drawing” lightly causes the disorder of the tree, which is broom-like, thus affecting the growth And the result. For example, Beijing area from 1962 to