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美国《Fo-rest Farmer》1981年10期介绍了一种改造低价阔叶林建立珍贵混交林的方法。这种方法整地费用低,并能从砍伐小径材得到直接收益。美国林业部门为了评价这种方法的可行性,选择低价柞林作了试验。他们先把试验地上胸高直径10厘米以上的柞树都伐掉,然后划出24个面积0.4公顷的小班,其中18个小班按每一树种6个小班顺次栽植拉当松、美国五针松和美国椴,另外6个小班作对照,让它们天然更新。每个处理中选三个小班用杀树剂处理留下的1.5米以上的天然生树木。4年后,人工栽植的树木成活率都很高。栽植拉当松的小班,经杀树剂处理的,拉当松在林分组成中的比例占78%,不用杀树剂的拉当松占41%。对于栽植美国五针松和美国椴的小班,则还需透光抚育。至于对照小班,主要只能靠萌条更新有经济价值的树种。
The United States “Fo-rest Farmer” 1981 the 10th introduced a transformation of low-cost broad-leaved forest to establish precious mixed forest method. This method of land preparation costs low, and can get direct benefits from cutting trails. In order to evaluate the feasibility of this method, the U.S. Department of Forestry selected the low-cost turtle forest for testing. They first cut the oak tree with a diameter of 10 cm or more on the test ground and then cut out 24 small classes with an area of 0.4 hectares. Among them, 18 small classes were planted successively with 6 small classes of each species, American linden, another 6 small classes as a control, so that they are naturally updated. Choose three small classes for each treatment with the tree to leave behind 1.5 meters of natural raw trees. Four years later, the survival rate of artificial trees are high. Cedar pine planted small class, after killing the tree, the proportion of pine needles in the forest composition accounted for 78%, do not kill the agent of pine accounted for 41%. Transplanting is also needed for small classes of American pine and American linden. As for the control of small classes, mainly by Meng sprouting to update the species of economic value.