论文部分内容阅读
树木的寿命是有限的,当林木达到一定年龄时,就会逐渐衰弱以至死亡,林带的结构也就逐渐稀疏,防护效益就会逐渐降低,甚至完全失去防护作用。为了保证防护效益的永续性,必须建立新的林带以代替自然衰老的旧林带。 张家口坝上总土地面积2,072万亩,现有林面积283万多亩,其中防护林成林面积50多万亩。树种以杨树为主。早期营造的林带,已达成熟龄,基本停止生长,极待采伐更新。但由于对林带更新缺乏经验,有的仅采取“拔大毛”进行疏伐,未能有效地更
The life span of trees is limited. When the trees reach a certain age, they will gradually weakened and even die, and the structure of forest belts will gradually become sparse, and the protective benefits will be gradually reduced or even completely lost. In order to ensure the sustainability of protection benefits, we must establish a new forest belt to replace the old natural aging forest belt. Zhangjiakou dam total land area of 2072 acres, the existing forest area of more than 2.83 million mu, of which more than 50 million mu of shelterbelts forest area. Poplar-based trees. Early to create a forest belt, has reached mature age, the basic stop growing, pending cutting updates. However, due to the lack of experience in updating the forest belt, some have only adopted “pulling big hair” for thinning and failing to effectively and more effectively