人们常说“树大自然直”。这话对于单轴分枝的树种来说尚有可能,而对于白榆、刺槐等合轴分枝的树种来讲就另当别论。因为白榆和刺槐的第一侧芽往往抽枝很弱或不发枝,由下部第三、四侧芽萌发出的旺枝代替,到了第二年,新梢又被下部另一侧枝代替,所以树干往往弯曲、分杈多、主干矮,如不及时整形修枝,很难长成有用之材。因此,适度地整形修枝是白榆、刺槐幼林抚育中的重要措施之一。其修枝的原则是:控制竞争枝,保持主干的顶端优势;调整冠高比例,保留一定树冠长度;增加叶面积,促进光合作用。 (一) 控制竞争枝。竞争枝是与主梢粗 People often say that “trees are nature straight.” This statement is possible for uniaxial branch species, while for elm, locust and other co-axial branches in terms of species is another matter. Because the first side buds of elm and black locust are often weakened or not sprouted, replaced by the sprouting buds of the third and fourth buds in the lower part. In the second year, the new shoots are replaced by the other branches of the lower part, so the trunk Often bent, bifurcated more, the backbone short, if not timely shaping pruning, it is difficult to grow into useful material. Therefore, it is one of the important measures to cultivate white elm and young black locust in the process of proper shaping and pruning. The principle of pruning is: control competition branches, to maintain the backbone of the top edge; crown height adjustment, to maintain a certain canopy length; increase leaf area and promote photosynthesis. (A) control competition branch. Competition branch is with the main shoot thick