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柳树是平原地区重要的绿化造林树种,其中乔木型柳树被广泛用于营造用材林、防护林及风景林。现有柳树人工林产量很低,如湖滩地(江苏洪泽湖)15年生垂柳(Salix babylonica)人工林平均树高仅6.3米,平均胸径7.5厘米,材积年平均生长量仅1.2立方米/公顷;生长较好的林分,22年生平均树高12.8米,平均胸径17.5厘米,材积年平均生长量只有4.6立方米/公顷;江滩地17年生早柳(S. matsudana)人工林,年平均材积生长量只有5.57立方米/公顷(湖北黄岗赤壁林场长江江滩);生长较好的早柳人工林,14年生年平均生长量也只有7.5立方米/公顷(山东泰安汶河河漫滩地)。在国外,优良的无性系年平均材积生长量可高达20立方米/公顷。南斯拉夫选育的白柳(S. alba)无性系7年生,年平均高生长为2.06米,胸径生长为2.54厘米,苏联乌克兰林业与农林土壤改良研究所选育的爆竹柳(S. fragilis)×白柳优良无性系,4年生树高6.8米,胸径18.8厘米;白柳×爆竹柳优良无性系,4年生树高7.2米,胸径17.3厘米。因此,选育优良无性系,
Willow is an important afforestation tree species in the plains, of which the arbor-type willow is widely used to create timber forests, shelter forests and scenic forests. The current production of willow plantations is very low. For example, the average tree height of 15-year-old Salix babylonica plantations in Lakeland (Hongze Lake, Jiangsu Province) is only 6.3 meters, the average diameter at breast height is 7.5 cm, and the average annual volume of annual growth is only 1.2 cubic meters per hectare ; The average growth diameter of the 22-year-old tree was 12.5 meters, average diameter at breast height was 17.5 cm, annual volume of annual growth was only 4.6 cubic meters / hectare; the average annual volume of S. matsudana plantation The growth rate is only 5.57 cubic meters per hectare (the Red River Forest Farm in Huanggang, Huanggang, Hubei). The better-growing early willow plantation also has an average annual growth rate of only 7.5 cubic meters per hectare at the 14th annual birthplace. In foreign countries, the annual average volume growth of fine clones can reach as high as 20 cubic meters per hectare. The S. alba clones bred by Yugoslavia were 7-year-old with an average annual growth of 2.06 meters and a diameter at breast height of 2.54 cm. S. fragilis × white willow birch bred by the Institute of Forestry, Farming and Forestry Improvement, Excellent clones, 4-year-old tree height 6.8 meters, diameter 18.8 cm; white willow × firecracker excellent clone, 4-year-old tree height 7.2 meters, 17.3 cm in diameter. Therefore, breeding excellent clones,