根据研究观察,要延长绿化林的使用期,以降低更新衰死林的费用,只有用各种保护方法提高植物的抗性和削弱有害种的发展才有可能。营造县有抗性的林分,从选择植物种类开始,就要考虑到这些植物对于当地分布最多的病虫害的抗性。在苗圃培育造林树种时,应当做到多种多样,除了当地的种类以外,还要培育引进适于绿化建设基本要求的种和类型。营造具有抗性的林分,不仅要利用具有免疫力的植物种和类型,而且要配置合理。首先必须考虑植物本身对环境条件的需要。例如夏橡比红柞喜温、喜光、害土壤肥力:一些种很喜光,象刺槐、欧洲落叶松和西北利亚落叶松;对光要求严格的还 According to the research and observation, to extend the service life of green forests to reduce the costs of updating deciduous forests, it is only possible to improve plant resistance and impair the development of harmful species through various protection measures. To create county-resistant stands, beginning with the selection of plant species, consideration should be given to the resistance of these plants to the most widely distributed pests and diseases in the country. When nursery nursery afforestation tree species, should be done a variety, in addition to the local species, but also to cultivate the introduction of the basic requirements for greening species and types. Creating resistant stands requires not only the use of immune plant species and types, but also rational allocation. The first must consider the plant’s own need for environmental conditions. For example, summer acacia red oak hi warm, hi light, harm soil fertility: some kinds of hi light, such as acacia, European larch and korean larch; light also demanding