白榆是我国的固有树种,分布面积广,栽培历史悠久。由于它具有适应性强、生长快、用途广等优良特性,已成为我国东北、华北、西北及江淮平原等地区“四旁”绿化、用材林、防护林和盐碱地造林的重要树种。白榆在长期的系统发育过程中,由于异花授粉、自然和人工选择及环境条件等作用的结果,种内形成了多种多样的变型,它们 White elm is an indigenous tree species in our country with a wide distribution and a long history of cultivation. Because of its good adaptability, fast growth, wide use and other fine features, it has become an important tree species in afforestation of “four sides”, timber forests, shelterbelts and saline-alkali lands in Northeast China, North China, Northwest China and the Jianghuai Plain. In the long-term phylogenetic process, Ulmus pumila grows in a variety of forms due to the effects of cross-pollination, natural and artificial selection and environmental conditions,