长期以来,城市绿化多采用单行或双行列植方式,安置植物种类时,偏重乔木的栽植,忽视灌木和花卉的配置。道路分层绿化,是用乔木、灌木搭配的方法,利用自然植物群落中的植物个体,相互依存、互相竞争的习性,形成层次多变、高低错落的垂直和水平混合结构,组成人工群落。在植物安排上,要注意适当密植,促使树丛及早郁闭,成片栽植时,力求疏密有致。种类搭配上,考虑阳性与阴性,速生与慢生相结合。例如, For a long time, urban afforestation mostly adopts single row or double row planting. When planting plant species, the emphasis is placed on the planting of trees and the disposition of shrubs and flowers. Hierarchical afforestation is a method of using trees and shrubs to make use of the individual, interdependent, and competing habits of natural plant communities to form vertical and horizontal mixed structures of varying levels and high and low levels, thus forming an artificial community. Arrangements in plants, we should pay attention to appropriate close planting, prompting the bushes closed early, into a piece of planting, and strive to sparseness and dedication. With the type, consider positive and negative, fast-growing and slow life combination. E.g,