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雁北地处内长城以北,为半干旱温带气候类型,自然植被稀少,风沙危害严重,农牧业产量低而不稳,农村生活较苦。从1958年以来,在风沙区和桑干河沿岸,营造了300多万亩小叶杨林。这些小叶杨林有效的制止了风沙危害,保护了农田,调节了气候,改善了生态环境,在促进农牧业增产丰收,保护工交生产方面,立下了汗马功劳。但是,由于立地条件太差,林木年龄偏大,很多林分已达成熟林或过熟林。所以大片小叶杨林生长衰退,形成“小老树”林,成片林木枯死,很多林地变成疏林和迹地,防护效益降低,某些地段再次出现风蚀现
Yanbei is located in the north of the Great Wall, a semi-arid temperate climatic type, natural vegetation is scarce, severe sand damage, low and unstable agricultural and livestock production, rural life is bitter. Since 1958, more than three million mu of Populus simonii have been created in the windy and sandy areas and along the Sanggan River. These Populus euphratica forest effectively stopped the harm of wind and sand, protected the farmland, tempered the climate and improved the ecological environment. It has made a lot of contributions in promoting the yield increase of agriculture and animal husbandry and protecting the production of industrial communication. However, due to the poor site conditions, the age of forest trees is too large and many forests have reached mature or over-mature forests. Therefore, the growth of large-leaf Poplar depression recession, the formation of “small old tree” forest, into a piece of forest dead, a lot of woodland into sparse forests and landmarks, protection effectiveness is reduced, and some sections appear once again wind erosion