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在经营条件比较好,水源方便,劳力和资金充足的地方,应积极推广这种造林方法,特别是“四旁”植树和营造速生丰产林,采用这种造林方法,经济效益尤为突出。然而这些造林方法,技术性强、标准高、投资较大、耗劳力多,条件不成熟的地方,不应盲目推广,只有在条件具备的情况下,才能收到事半功倍的效果。杨树主要分布在北半球暖温带,在植物分类学上属杨柳科杨属。在杨属内,又分胡杨派、白杨派、青杨派、黑杨派和大叶杨派五大类。据统计,世界杨树主要自然种有100多种,其中青杨派和黑杨派就占80多种。
Where operating conditions are good, water sources are convenient, labor and capital are sufficient, such methods of afforestation should be actively promoted. In particular, planting trees around the “four sides” and creating fast-growing and high-yield forests should be actively promoted. Such afforestation methods are particularly effective in economic efficiency. However, these methods of afforestation should not be blindly promoted in areas with strong technical skills, high standards, large investment, labor-intensive conditions and immature conditions. Only when the conditions are met can they receive a multiplier effect. Poplar is mainly distributed in the warm temperate in the northern hemisphere, belongs to genus of poplar in the plant taxonomy. Within the genus of Populus, there are five categories of Hu Yang, Poplar, Qingyang, Black Poplar and Yeh Yeung. According to statistics, there are more than 100 species of poplar in the world, of which more than 80 are Populus and Black Poplar.