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    长白落叶松人工林地位指数及立地形的比较研究

    Comparison between site index and site form for site quality evaluation of Larix olgensis plantation

      摘要
    • 摘要:
      目的以吉林省长白落叶松人工林为对象，分析立地形与地位指数及其与林分生产力之间的关系，检验立地形评价长白落叶松人工林立地质量的可行性。
      方法基于168块固定样地的314个观测数据，提出了基准胸径确定的方法，即以胸径-年龄的逻辑斯蒂方程为基础，求其拐点纵坐标(即为基准胸径)。以理查兹生长方程分别拟合优势高-年龄、优势高-优势胸径的导向曲线，分别计算各样地的地位指数与立地形，并分析立地形与地位指数以及二者与林分生产力之间的关系。
      结果立地形与地位指数回归方程的决定系数R2为0.3627，RMSE为1.9930m，平均绝对误差MAE为1.5632m。地位指数、立地形与生产力的相关系数分别为0.6764和0.3203。采用等距划分的方法将计算所得的地位指数与立地形划分为8个等级，地位指数从1至8级各等级所占比例分别为0.64%、3.82%、12.74%、24.84%、32.48%、19.43%、5.10%、0.96%；立地形从1至8级各等级所占比例分别为0%、1.59%、9.24%、42.36%、44.90%、1.91%、0%、0%。
      结论对于落叶松人工林来说，立地形只能解释36.27%的地位指数变异；地位指数与生产力的相关性远大于立地形与生产力的相关性。对立地形与地位指数采用等距划分的方法进行立地质量等级划分，立地质量等级均呈现出中间多、两头少的趋势，但各等级的样地数量差异较大。总体来说，本研究中立地形不宜作为长白落叶松人工林立地质量评价的指标。

       

      Abstract:
      ObjectiveThis study aims to examine whether site form is a valid method for site quality evaluation of Larix olgensis plantations through analyzing the relationship between site form as well as site index and site productivity.
      MethodWe put forward the method of determining the reference diameter at breast height(DBH) on the basis of DBH-age logistic growth equation with 314 observation data from 168 permanent sample plots of Larix olgensis plantations, and the reference DBH was calculated as the DBH at inflection point of the growth equation. We separately developed the dominant height-age and dominant height-DBH guide curves with the Richards growth equation, calculated the site index and site form for each plot, analyzed the correlation between site index and site form, and the correlation between both of them and productivity.
      ResultThe result showed that the coefficient of determination R2 with the regression equation between site index and site form was 0.3627, RMSE was 1.9930m and MAE was 1.5632m. The correlation coefficients between site index, site form and productivity were 0.6764 and 0.3203, respectively. We successively classified the site index and site form into 8 grades at equal interval. The proportion from grade 1 to grade 8 by site index was 0.64%, 3.82%, 12.74%, 24.84%, 32.48%, 19.43%, 5.10%, 0.96%; and the proportion from grade 1 to grade 8 by site form was 0%, 1.59%, 9.24%, 42.36%, 44.90%, 1.91%, 0%, 0%.
      ConclusionFor Larix olgensis plantations, site form could only explain 36.27% variation of site index, the correlation between site index and productivity was much larger than that of site form and productivity. The classified site quality grades by the site index and site form roughly showed the same trend in proportion at most grades, i.e. most sample plots were at the middle grade and few sample plots at both ends. But the number of sample plots in most site quality grades differs greatly. In general, we do not recommend site form as a method for site quality evaluation with Larix olgensis plantation.

       

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