油松人工林相容性生长联立方程组模型构建

Construction of Compatible Growth Simultaneous Equations Model for Pinus tabuliformis Plantation

  • 摘要: 以西宁市周边山地人工林为研究对象,利用近2年森林资源更新调查数据,构建油松林相容性生长联立方程组模型,采用似乎不相关回归法求解模型参数,并对模型进行异方差修正,最后检验所构建的相容性生长联立方程组模型预测精度及适应性。结果表明:相容性生长联立方程组模型对平均胸径、平均树高和每公顷断面积的预估精度均在93%以上,MSE和TRE值均在 ± 2%以内,卡方检验结果远远小于临界值,预测效果优于独立拟合模型。在油松中幼龄林阶段,胸径、树高和断面积生长均与林分密度指数和地位级指数正相关;胸径、树高生长对地位级指数更敏感,而断面积生长对林分密度指数更敏感。基于模型预测结果,油松林分胸径快速增长期在5~25 a,年均生长量为0.33 cm;树高快速增长期在5~30 a,年均生长量为0.23 m;断面积在15 a之前增速最快,年均生长量为0.13 m2/hm2。本研究所构建的油松林相容性生长联立方程组模型预测精度高,可用来预测西宁市及相似生态区油松林分胸径、树高和断面积生长,为林分生长及收获预估、科学合理经营提供参考。

     

    Abstract: Taking the mountain plantation around Xining City as the research object, and using the forest resources update survey data in the past 2 years, a compatible growth simultaneous equation systems model of Pinus tabuliformis forest was constructed. The seemingly unrelated regression method was used to solve the model parameters. And the heteroscedastic correction was made to the model. Finally, testing the predicting effect and adaptability of the compatible growth simultaneous equation systems model. The results showed that the prediction accuracy of compatible growth simultaneous equation systems model for stand mean diameter, mean height and basal area were all above 93%, the MSE and TRE were within ± 2%, and the Chi-square test results were far less than the critical value. The prediction effect of compatible stand growth equation systems model was better than that of independent fitting model. At the young stage of P. tabuliformis, the diameter, tree height and basal area were positively correlated with stand density index and site class index. The diameter and tree height growth were more sensitive to the site class index, while the basal area growth was more sensitive to the stand density index. Based on the model prediction results, the rapid growth period of diameter of P. tabuliformis is 5–25 a, and the average annual growth is 0.33 cm. The rapid growth period of tree height is 5–30 a, and the average annual growth is 0.23 m. The basal area grows fastest before 15 a, with an annual growth rate of 0.13 m2/hm2. The compatible growth simultaneous equation systems model of P. tabuliformis forest constructed in the study has high predicting effect, which can be used to predict the growth of diameter, tree height and basal area of P. tabuliformis stand in Xining City and similar ecological areas, providing reference for the prediction of stand growth and harvest and scientific and reasonable management.

     

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