我盟自六十年代初期开始引种华北落叶松,到目前全盟已发展到42万多甫,其中国营林场占60％。引种最早的苏木山林场,华北落叶松保存面积6万多亩,30％已郁闭成林。由于初植密度过大,影响正常生长,急需进行间伐,因此,准确地确定抚育间伐起始年限、间 Since the beginning of the 1960s, our Union has introduced the Larix principis-rupprechtii. Up till now, the alliance has developed to more than 420,000, of which 60% are state-owned forest farms. Introduction of the earliest Mt forest, Larix principis-rupprechtide preservation area of ​​60,000 acres, 30% closed forest. Due to the initial planting density is too large, affecting the normal growth, the need for thinning, therefore, accurately determine the beginning of tending thinning interval