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众多材料表明,林木的早晚期生长速度具有一定的相关性,而在一定年限内生长上的秩次变化并不太大。毛白杨是速生树种,品种试验中要求的半个轮伐期仅为7年左右,这就使我们用无性系的苗期表现预测其半个轮伐期时的生长具有一定的可靠性。如再把苗期表现与无性系原株性状相联系,其可靠性就可进一步提高。这样选出的初级良种可以填补正式良种选出前的品种空白,以提前推广应用于造林生产中。为此,我们于1986—1987年在全国毛白杨基地进行了毛白杨无性系苗期试验,综合试验结果及各无性系原株情况,选择确定了我省的毛白杨初级良种。
Numerous materials show that early and late forest growth rate has a certain relevance, but in a certain period of growth rankings change is not too large. Populus tomentosa is a fast-growing tree species, half of the species trials required rotation of only about 7 years, which allows us to use the clonal performance of the climatic half of its forecast when the rotation growth has some reliability. If the seedling performance and clonal traits linked to the original plant, its reliability can be further improved. The primary seed selected in this way can fill the gap of the species before the formal seed is selected, so as to promote the application in afforestation production in advance. Therefore, in 1986-1987, we conducted the seedling experiment of Populus tomentosa clones at the base of Populus alba in the whole country. Based on the comprehensive test results and the original strains of clones, we selected the primary cultivars of Populus tomentosa in our province.