引种是丰富林木资源,提高林业生产水平,实现林木速生、丰产、优质的重要手段。七十年代中期,引进的河南白榆已成为我区平原营造用材林、防护林以及四旁绿化的树种之一。经过十多年的生产实践,河南白榆在抗性方面表现出了一些缺陷。因此,对白榆种源的选择上产生了意见分歧。一种认为,河南白榆生长状况良好,可以大力发 Introduction is an important means of enriching tree resources, raising the level of forestry production, and achieving the fast-growing, high-yielding and high-quality trees. The mid-seventies, the introduction of Henan elm has become plains in our district to create timber forests, shelterbelts and green trees on one side. After more than ten years of production practice, Henan elm shows some defects in resistance. Therefore, the selection of white elm species have had different opinions. One thinks, Henan elm growing in good condition, you can vigorously hair