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西吉县位于黄河中游,是我国水土流失很严重的地区之一,由于地处高寒、干旱、无霜期短,因而制约着树木的生长与发展。解放三十年来,全县人工造林面积为46.88万亩,保存面积只有7.40万亩,保存率仅为15.8%。在造林工作中又由于未能解决适地适树问题,所以该县人工林资源不仅数量少,而且树种单一,多为杨树,生物产量低,因而生态环境不良。为了扩大森林资源,改善环境条件,自1981—1986年北京林业大学与西吉县
Xiji County, located in the middle reaches of the Yellow River, is one of the areas where soil erosion is very serious in our country. Due to its high altitude, drought and short frost-free period, Xiji County restricts the growth and development of trees. In the three decades since the liberation, the area of artificial afforestation in the county has reached 468,800 mu, with a preserved area of only 74,000 mu and a preservation rate of only 15.8%. In the afforestation work, the problem of suitable tree-planting can not be solved. Therefore, the resources of plantation in this county are not only small in quantity, but also single in tree species, mostly poplar, with low biological yield and poor ecological environment. In order to expand forest resources and improve environmental conditions, from 1981 to 1986 Beijing Forestry University and Xiji County