Evaluation of stem taper models fitted for Japanese cedar (Cryptomeria japonica) in the subtropical forests of Jeju Island, Korea

Abstract

This study was conducted to evaluate the performance of the five stem taper models in predicting the diameter over bark at any given height (d) and total volume of Japanese cedar (Cryptomeria japonica D.Don) in the subtropical forests of Korea. The four fit statistics used in this study were standard error of estimate (SEE), mean bias ((Formula presented.)), mean absolute bias (MAB), and coefficient of determination (R2). For the lack-of-fit statistics, SEE, MAB, and (Formula presented.) of the five models in predicting d in the different relative height classes and in predicting the total volume in the different diameter at breast height (D) classes were determined. Results of the model evaluation indicated that the Kozak88 stem taper model had the best performance in most of the fit statistics followed by Kozak02 stem taper model. The Kozak88 model also provided the best performance in the lack-of-fit statistics having the best SEE, MAB, and (Formula presented.) in predicting d in most of the relative height classes. This model consistently performed well in estimating the total volume of Japanese cedar in the different D classes as compared to other stem taper and volume models. These stem taper equations could serve as a management tool for forest managers to accurately predict the d, merchantable stem volumes, and total stem volumes of the standing trees of Japanese cedar in the southern plantation of Korea.