南京林业大学学报(自然科学版) ›› 2023, Vol. 47 ›› Issue (1): 47-56.doi: 10.12302/j.issn.1000-2006.202108030

所属专题: 智慧林业之森林参数遥感估测

• 专题报道Ⅰ:智慧林业之森林参数遥感估测 • 上一篇    下一篇

基于气候因子的杉木单木胸径生长模型构建

郭常酉1(), 郭宏仙2, 王宝华2,*()   

  1. 1.国家林业和草原局宣传中心,北京 100013
    2.宁夏大学农学院,宁夏 银川 750021
  • 收稿日期:2021-08-15 接受日期:2021-10-13 出版日期:2023-01-30 发布日期:2023-02-01
  • 通讯作者: 王宝华
  • 基金资助:
    国家自然科学基金项目(31470592)

Study on increment model of individual-tree diameter of Cunninghamia lanceolata in consideration of climatic factors

GUO Changyou1(), GUO Hongxian2, WANG Baohua2,*()   

  1. 1. Propaganda Center, State Forestry and Grassland Administration, Beijing 100013, China
    2. Agricultural College of Ningxia University, Yinchuan 750021, China
  • Received:2021-08-15 Accepted:2021-10-13 Online:2023-01-30 Published:2023-02-01
  • Contact: WANG Baohua

摘要: 【目的】 为准确预测湖南杉木的生长及制定经营管理措施,构建了考虑气候因子的杉木单木胸径生长混合效应模型。【方法】 基于湖南省第七、八次全国森林资源连续清查中73块样地的3 638株杉木数据,运用多元逐步回归的方法,考虑林木大小、竞争、立地和其他林分因子以及气候因子对杉木胸径生长的影响,分别以5年胸径增长量(D2-D1)、5年胸径增长量的自然对数[ln(D2-D1+1)]、5年胸径平方增长量的自然对数[ln(D22-D21+1)]、胸径平方增长量(D22-D21)为因变量构建模型,选择最优基础模型。在最优模型的基础上,引入样地随机效应,构建单水平线性混合效应模型,并引入3种常用的异方差函数和3种常用的自相关结构来消除模型的异方差和自相关,最后采用十折交叉验证的方法对模型的预估效果进行检验。【结果】 与其他3种因变量相比,因变量为ln(D22-D21+1)时模型表现最好,因此,因变量为ln(D22-D21+1)的模型为最优基础模型。根据模型结果可以看出,显著影响杉木胸径生长的变量主要包括期初胸径、大于对象木胸高断面积之和与期初胸径之比、每公顷断面积、坡向正弦值与海拔自然对数之积、年平均降雨量和1月平均最低温度。与最优基础模型相比,混合效应模型显著提高了模型的预测精度。同时,异方差函数和自相关矩阵的加入也明显改善了模型的拟合效果,其中以指数函数(exponent)和自回归移动平均结构[ARMA(1,1)]表现最好。在模型十折交叉检验中,混合效应模型也表现出较好的拟合效果。【结论】 气候因子对于湖南杉木单木胸径的生长有显著影响。与基础模型相比,引入样地随机效应构建单水平线性混合效应模型可以显著提高模型效果,所构建的模型可以为该区域杉木的科学经营提供支持。

关键词: 杉木, 单木胸径生长, 气候因子, 混合效应模型, 十折交叉验证

Abstract:

【Objective】 To accurately predict growth and formulate forest management strategies for Cunninghamia lanceolata in Hunan Province, a mixed-effects individual tree diameter increment model for Cunninghamia lanceolata was developed considering climatic factors. 【Method】 Based on the data of 3 638 observations in 73 plots from the 7th and 8th Chinese National Forest Inventory in Hunan Province, this study used the multiple stepwise regression method to introduce tree size, competition, site conditions, other stand variables, and climate factors as independent variables, and developed and evaluated four different dependent variables: i.e. 5-year diameter increment (D2-D1), the natural logarithm of 5-year diameter increment [ln(D22-D21+1)], the natural logarithm of 5-year squared diameter increment [ln(D22-D21+1)], and 5-year squared diameter increment (D22-D21). An optimal basic model was selected. A linear mixed-effects model with sample plots as random effects was then fitted. In addition, three commonly used variance functions and correlation structures were introduced to remove the heteroscedasticity of the residuals and autocorrelation. Finally, the 10-fold cross-validation method was used to assess predictive ability. 【Result】 Compared with the other three dependent variables, the model performed best with ln(D22-D21+1) as the dependent variable. Therefore, the model in which the dependent variable was ln(D22-D21+1) was selected as the optimal basic model. According to the results of the optimal basic model, the initial diameter, the ratio of the sum of the basal area of trees with diameters larger than the subject tree’s diameter to the initial diameter, stand basal area per hectare, the product of the sine of the slope and the natural logarithm of the altitude, mean annual precipitation, and mean minimum temperature in January significantly affected the increase in the diamteter of Cunninghamia lanceolata. Compared with the optimal basic model, the mixed-effects model showed a significantly improved prediction accuracy. Additionally, the introduction of variance functions and correlation structures also significantly improved the model’s performance, of which the exponent function (exponent) and ARMA(1,1) performed the best. In the 10-fold cross-validation, the mixed-effects model also showed better performance. 【Conclusion】 Climatic factors have a significant effect on the increase of diameter in Cunninghamia lanceolata. Compared with the basic model, the linear mixed-effects model with sample plots as random effects could greatly improve the model’s performance, and we hope that the model could provide support for the scientific management of Cunninghamia lanceolata in Hunan Province.

Key words: Cunninghamia lanceolata, individual-tree diameter increment, climate factor, mixed-effects model, 10-fold cross-validation

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