一、引言白杨是我国普通树种,但有特具的优点,种类丰富其多数品种既耐寒旱、宜于高山地区生长,又耐温润、利于低窪地带栽培;树形紧密利于防风,根株坚韧便于固土防冲,并且繁殖简便,生长迅速,易于成材,在农林和工业上都有相当的贡献。由于我国森林早经破坏,全国各地山区釀成不同程度的冲刷;在北部与西北部因乾早造成的风沙侵蚀,为害甚烈,为了维护农田,保障生产,防护林的营造为当前迫切任 I. INTRODUCTION Poplar is an ordinary tree species in our country, but it has special advantages. Its variety is rich in most varieties of which are resistant to cold and drought. It is suitable for growing in mountainous areas and is resistant to temperature and moisture and conducive to cultivation in low-lying areas. Soil anti-red, and the breeding of simple, rapid growth, easy to become useful, in agriculture and forestry and industry have a considerable contribution. Due to the early destruction of forests in our country, mountainous areas in different parts of the country lead to different degrees of erosion. In the northern and northwestern parts of the country, wind and sand erosion caused by drought is very damaging. In order to maintain farmland and ensure production,