| 苗木分级方法比较 |
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| 引用本文： | 常培英,刘曼玲.苗木分级方法比较[J].山西农业大学学报(自然科学版),1984(2). |
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| 作者姓名： | 常培英 刘曼玲 |
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| 作者单位： | 山西农业大学林学系，山西农业大学林学系 |
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| 摘 要： | 本文采用主分量分析法和聚类分析法对283株华北落叶松二年生留床苗(2—0)进行了苗木分级方法的比较。283株样苗是按照随机抽样原则取得的。每株样苗分别测量了下述六个因子:苗高(x_1);地径(x_2);侧枝数(x_3~-);主根长(x_4);鲜重(x_5)重心高(x_6)——苗木重心至顶芽的距离。进行比较的方法有:六因子(x_1—x_6),四因子(x_1,x_2,x_5,x_6)和二因子(x_1,x_2)主分量分析法与逐步聚类分析法。比较结果:(1) 由于六种分级法之间差异均不显著,所以在苗木分级时主分量法与逐步聚类法都可以采用;(2) 地径、鲜重、重心高和苗高所含苗木质量的信息量较多,因此这四个因子可作为苗木分级的主要因子;(3) 主分量分析法工作量较大,并且比较复杂,不便于生产上使用,但在选择因子方面可为聚类法提供依据;(4) 地径、苗高二因子也可反映苗木质量的主要信息,苗木分级时采用这两个因子可使分级工作简化。
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COMPARISON OF THE METHODS OF GRADING OF FOREST SEEDLINGS |
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| Abstract: | Analytical methods of Principal Components and Clustering were adopted to compare for grading methods of the 283 sample seedlings of two-year-North China Larch(2-0). Seedlings were taken by random sampling. Six indexes were determined Height of seedling(x_1); diameter at foot(x_2); number of branch(x_3) length of top root(x_4); fresh weight(x_5); height of cent of grayity(x_6) distance from centre of gravity to top shoot. Analytical methods of Principal Components and Step-by-Step Clustering of Gindexes(x_1-x_6) of princapal Components and Step-by-Step Clustering of 6 indexes(x_1-x_6); 4 indexes(x_1, x_2, x_5 x_6) and 2 indexes(x_1, x_2)are compared, Resultsare: (1) The differences between 6 methods of grading are not significant. Analytical methods of principal Components and step-by-Step Clustering can be adopted when seedling are graded (2) Diameter at foot, fresh weight, height of centr of gravity and height of seedling can be used as main indexes for grading of forest seedling, sinci more in formations of seedling uality are obtained. (3) The heavy and complex calculations of the principal Component analysis method made it unfittobe used in proouction, but it can providie basis for clustering in choosing indexes; (4) Diameter at foot and height of seedling can also refeict main information of seedling quality. Grading can be simplified when they are adopted. |
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