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我国目前共有森林面积14.457亿亩,中幼龄林面积9.7亿亩,占森林总面积的67％,其中国营林场和林业局有中幼龄林4亿亩。中幼龄林抚育间伐是一项重要技术措施。现有的中幼龄林林分密度很大,人工林每亩五、六百株,飞播林和天然林有的每亩达上千株。因此,林内透光条件差,林木营养面积不足,生长不良,极易发生雪压、风折和病虫等自然
At present, China has a total of 1.4457 billion mu of forest area and a middle-aged and young-age forest area of 970 million mu, accounting for 67% of the total forest area. Among them, the state-owned forest farms and the Forestry Bureau have 400 million mu of young and middle-aged forests. Middle-aged forest tending thinning is an important technical measure. The current density of middle-aged and young stands is very large. There are five or six hundred plants per acre in the plantation, and some one thousand in aerial and natural forests. Therefore, poor light transmission in the forest, lack of forest nutrient area, poor growth, prone to snow pressure, wind and pests and other natural