A Comparative Evaluation of Three Stem Profile Equations for Three Precious Tree Species in Southern China

Jun Jiang,Jie Li,Lifeng Pang,Angang Ming

doi:10.3390/f11060669

Abstract

Accurately describing the stem curve of precious tree species and estimating the quantity of various types of wood and their volume in the tropics can provide technical support for reasonable bucking. This study utilized Erythrophleum fordii, Castanopsis hystrix and Tectona grandis as study objects. Forty replicates of each species were used for a total of 120 individual trees. Their tape equations were constructed using simple tape equations, segmented taper equations and variable form taper equations. Statistical indicators were utilized to determine the best taper equation for the three types of precious tree species. A number of methods were compared and analyzed, including the index of correlation, the residual sum of squares, the mean prediction error, the variance of prediction errors and the root mean square error. Finally, a preliminary quantitative analysis was conducted to determine the trends of these three types of tree species. The result shows that the precision of the three predictions developed for each species is high, and, in particular, the segmented taper equations with optimized algorithms is the best. The tendency of the three species to vary was shown to be the highest for T. grandis in the range of 0.0 to 0.8 for its relative height, followed by E. fordii, while the variation of C. hystrix was the smallest. However, in the range of 0.8 to 1.0 relative height, the variation of Castanopsis hystrix was the largest, and the variation of both E. fordii and T. grandis were almost the same. Therefore, the segmented taper equations with optimization algorithms was recommended to fit the three types of tree species in the tropics. These types of equations can be used to estimate the stumpage and timber quantity and as a guide reasonable bucking for these three species.

Highlights

Precious tree species are primarily distributed in tropical provinces such as Guangxi and Fujian in China
The results showed that the variable exponent equation proposed by Lee et al [23] is more effective and can be used to describe the stem shape of larch plantations
The procedure used to assess the parameters of the model could be improved; because our objective was to build a soundly based model rather than to make precise and accurate predictions, we focused on the qualitative behavior of the model rather than on its statistical properties

Summary

Introduction

Precious tree species are primarily distributed in tropical provinces such as Guangxi and Fujian in China. Castanopsis hystrix, Erythrophleum fordii and Tectona grandis are primarily distributed in Guangxi, Guangdong, Fujian Provinces. These tree species are well known for the hardness of their wood, and its extreme resistance to corrosion, water and moisture. China only uses 5% of the world’s forest area and 3% of the world’s forest stock to support the growing wood consumption demand of 23% of the world’s population [2]. Many artificial timber forests are cultured to meet the increasing demands from civilians. Unreasonable tree species composition and low economic benefits cause challenges in utilizing the artificial timber forests

Objectives

Methods

Results

Discussion

Conclusion