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应用生态学报 ›› 2023, Vol. 34 ›› Issue (9): 2355-2362.doi: 10.13287/j.1001-9332.202309.005

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基于哑变量和分位数回归的兴安落叶松更新幼树的树高-胸径模型

吕乐乐1, 王文彬2, 董灵波1*   

  1. 1东北林业大学林学院, 森林生态系统可持续经营教育部重点实验室, 哈尔滨 150040;
    2日照市农业科学研究院, 山东日照 276800
  • 收稿日期:2023-06-01 修回日期:2023-07-28 出版日期:2023-09-15 发布日期:2024-03-16
  • 通讯作者: *E-mail: farrell0503@126.com
  • 作者简介:吕乐乐, 女, 1998年生, 硕士研究生。主要从事森林可持续经营研究。E-mail: 18811795715@163.com
  • 基金资助:
    “十四五”国家重点研发计划项目(2022YFD2200502)和黑龙江省头雁创新团队计划项目(森林资源高效培育技术研发团队)

Height-diameter models of regenerated saplings of Larix gmelinii based on dummy variable and quantile regression

LYU Lele1, WANG Wenbin2, DONG Lingbo1*   

  1. 1Ministry of Education Key Laboratory of Sustainable Forest Ecosystem Management, School of Forestry, Northeast Forestry University, Harbin 150040, China;
    2Agricultural Sciences Academy of Rizhao, Rizhao 276800, Shandong, China
  • Received:2023-06-01 Revised:2023-07-28 Online:2023-09-15 Published:2024-03-16

摘要: 本研究以大兴安岭地区翠岗林场2018—2019年55块固定样地2054株兴安落叶松幼树为对象,采用四分位数法将林分密度指数(SDI)划分为4个等级,即等级Ⅰ(SDI1<1863株·hm-2)、等级Ⅱ(1863≤SDI2<2155株·hm-2)、等级Ⅲ(2155≤SDI3<2459株·hm-2)和等级Ⅳ(SDI4≥2459株·hm-2),并采用哑变量方法引入SDI构建兴安落叶松幼树树高-胸径的哑变量模型和分位数回归模型。结果表明: 选取的5个代表性非线性树高曲线模型中,Richards模型的拟合效果最好,其Ra2、RMSE、MAE分别为0.7637、0.8250 m、0.5696 m;基于Richards模型构建的包含SDI的哑变量模型,其Ra2较基础模型提高了1.3%,而RMSE、MAE、AIC分别降低了2.1%、1.5%和11.2%;当分位点τ=0.5时,分位数回归模型的Ra2最大,RMSE、MAE、AIC最小,分别为0.7612、0.8294 m、0.5657 m、-767.19。相较于SDI1,SDI2~SDI4林分内幼树的树高分别增加5.6%、5.6%和11.3%。因此,合理调控兴安落叶松林的林分密度有利于增加更新幼树的高生长。

关键词: 哑变量, 分位数回归, 树高, 胸径, 林分密度指数

Abstract: Based on data collected from 2054 saplings of Larix gmelinii forest in 55 fixed plots in 2018-2019 in Cuigang Forestry Station, Daxing’anling area, we classified the stand density index (SDI) into four classes, i.e., Class Ⅰ (SDI1<1863 plants·hm-2), Class Ⅱ (1863 plants·hm-2≤SDI2<2155 plants·hm-2), Class Ⅲ (2155 plants·hm-2≤SDI3<2459 plants·hm-2) and Class Ⅳ (SDI4≥2459 plants·hm-2) by using the quartile method. We constructed a dummy variable model and quantile regression model for the height-breast diameter of saplings of L. gmelinii with dummy variable method introduced SDI. The results showed that among the five selected representative non-linear tree height curve models, the Richards model fitted the best, with Ra2, RMSE and MAE of 0.7637, 0.8250 m and 0.5696 m. The dummy variable model including the SDI constructed based on the Richards model showed a 1.3% increase in Ra2 compared with the base model, while RMSE, MAE, and AIC decreased by 2.1%, 1.5%, and 11.2%, respectively. When the quantile τ was 0.5, Ra2 of quantile regression model was the maximum, and RMSE, MAE, AIC was the minimum, being 0.7612, 0.8294 m, 0.5657 m, and -767.19, respectively. Compared with SDI1, sapling height in SDI2-SDI4 was increased by 5.6%, 5.6%, and 11.3%, suggesting reasonable that regulation of stand density was conducive to increase the height growth of saplings in regeneration.

Key words: dummy variable, quantile regression, tree height, diameter at breast height, stand density index