STEM TAPER ESTIMATIONS WITH ARTIFICIAL NEURAL NETWORKS FOR MIXED ORIENTAL BEECH AND KAZDAĞI FIR STANDS IN KARABÜK REGION, TURKEY

Oytun Emre Sakici,Gulay Ozdemir

doi:10.1590/01047760201824042572

Abstract

ABSTRACT Development of artificial neural network (ANN) models to estimate stem tapers of individual trees in mixed Fagus orientalis and Abies nordmanniana subsp. Equi-trojani stands distributed in Karabuk region of Turkey, and comparison of the ANN models with stem taper equations were aimed in this study. The measurements were obtained from 516 sample trees (238 for Oriental beech and 278 for Kazdagi fir) in mixed stands of Karabuk region. The measurements included diameter at breast height, tree height, diameter at stump height, and diameters at intervals of 1 m along the stem. In total, 45 ANN models and four stem taper equations were developed. Estimation performances of ANN models and stem taper equations were compared using relative rankings according to seven goodness-of-fit criteria. As a result, the ANN models were more successful in estimation of stem taper for both tree species. The most successful ANN model structures were (i) the model using logistic function in hidden layer with 10 nodes and hyperbolic tangent function in output layer for Fagus orientalis, and (ii) the model using logistic function in hidden layer with 10 nodes and linear function in output layer for Abies nordmanniana subsp. Equi-trojani.

Highlights

In order to know merchantable stand volume, which is one of the main components of forest dynamics, type and amount of the wood-based products obtained from the stands are important components of forest inventory which forms the basis of forest management (Barrio-Anta et al, 2007)
A total of 45 artificial neural network (ANN) models were developed using five number of nodes and nine transfer function pairs alternatives for both species. When these models were evaluated according to the statistical criteria, all alternatives containing logistic transfer function within output layer were unsuccessful for stem diameter estimations of both tree species
When the ANN models were ranked with these inappropriate alternatives, the evaluation of success of the other models was quite difficult

Summary

Introduction

In order to know merchantable stand volume, which is one of the main components of forest dynamics, type and amount of the wood-based products obtained from the stands are important components of forest inventory which forms the basis of forest management (Barrio-Anta et al, 2007). The success of accurate and reliable estimation of the stem volume of a tree and the volumes of the wood products obtained from trees coincides with the success in estimation of the stem diameters. Volume of a stem or any part of a standing tree can be accurately estimated depending on the stem taper estimation success for the subject tree. The most common approach to estimate stem diameters, which is the main variable to predict the volume of wood products more accurately, is to use stem taper equations (Fang et al, 2000; Diéguez-Aranda et al, 2006; Li and Weiskittel, 2010; Özçelik and CrecenteCampo, 2016). It has been stated that there are two main reasons for these studies; (i) the absence of a basic theory that would explain the change in stem forms of trees, and (ii) the need for a method that considers various wood products standards depending on the changing market conditions (Nevnham, 1988)

Methods

Results

Discussion

Conclusion