Abstract:
Objective Based on the national permanent forest plots, the basic average tree height - diameter models of Cunninghamia lanceolate was established by province for predicting tree height .
MethodsThere was a total of 23 239 samples distributed in 15 provinces in this study. Eighteen candidate base growth equations were used to fit height-diameter relationship in each province. The coefficient of determination (R2), mean absolute error (MAE), mean relative error (MRE) and root mean square error (RMSE) combing with the residual plots were used for model evaluation. In addition, the 5-fold method was used to test the optimal model in each province.
Result The best height-diameter model in each province was not the same. The best model for Chinese fir in Sichuan, Yunnan, Chongqing, Shanxi, Zhejiang, Jiangxi, Hunan and Guangxi was the Mitscherlich equation. For Jiangsu, Anhui, Henan and Fujian, the best model was the Hossfeld equation. And for Guangdong, Hubei and Guizhou, the best model was hyperbolic equation, Logistic equation and Gompertz equation, respectively. The R2 of the model ranged from 0.602 to 0.807, MAE ranged from 0.94 to 1.53 m, MRE ranged from −4.72 to −2.93%, RMSE ranged from 1.23 to 2.00 m, and MPE ranged from 0.50 to 2.77. These models performed well and had biological significance, which indicated that these models could be used as the basic height-diameter models of C. lanceolate plantation in each province
Conclusion height-diameter models of C. lanceolate distributed in 15 provinces are developed in this study, which simulates well the average tree height of C. lanceolate in each province, and can be used as basic models of height-diameter for C. lanceolate plantation in each province in China.