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雁北地区从建国初期到六十年代,共营造以小叶杨为主的杨树人工林二百万亩,但生长缓慢,甚至有将近一半的林分濒于死亡,防护效益急剧下降。鉴于已经失去改造时期,急需进行大规模更新。但是,如何使新造的林分不再形成“小老树”,并使之达到速生丰产的目的,在七十年代初期尚无成功的经验。我们从1976年起对这一重大问题进行了研究。结合本区的具体条件,采用比较先进的造林技术和管理措施,建立了210亩试验林,取得了较好的效果,现将几年来的试验结果归纳整理如下:
From the early days of the founding of the People’s Republic of China to the 1960s, a total of two million mu of poplar plantations were poplar-populated in the Yanbei area. However, the area was slow to grow. Nearly half of the forests were even on the verge of death and the protection efficiency dropped sharply. In view of the lost transformation period, a large-scale update is urgently needed. However, there is no successful experience in the early 1970s as to how to make newly established stands no longer form “little old trees” and achieve the goal of quick and high yield. We have studied this major issue since 1976. Based on the specific conditions in this area, 210-acre experimental forest was set up with more advanced afforestation techniques and management measures, and good results were obtained. The results of the experiments over the years are summarized as follows: