Volume equations for Caucasian fir - Oriental spruce mixed stands in Ardanuç, Artvin

The objective of this study is to estimation of stem volume for Caucasian fir - Oriental spruce mixed stands in Artvin-Ardanuç region of Turkey. For this purpose, the data obtained from 213 felled sample trees in total, which are 107 Caucasian fir and 106 Oriental spruce, were used. The fitted equations were ranked according to goodness-of-fit criterias (adjusted coefficient of determination (R_(adj.)^2), standard deviation of residuals (Sy.x), average residuals (D ̅), average absolute residuals (|D ̅ |), absolute mean error percentage (OMH%) and total error percentage (TH%)) and the most successful equations were selected based on relative ranks. The R_(adj.)^2 values of the most successful single- and double-entry tree volume equations for Caucasian fir and Oriental spruce were 0.982 and 0.988 - 0.981 and 0.992, respectively. The best fitted tree volume equations were tested with independent data set for both tree species using “Wilcoxon T Test” within the border of Ardanuç Forest District Directorates, and concluded that these equations can be used for these stands at the 0.05 significant level. It is proposed to construct both single and double entry tree volume equations for the both tree species.