Single- and double-entry volume equations for Crimean pine stands in Kastamonu Regional Directorate of Forestry

The aim of this study was to develop single- and double-entry over-bark and under-bark stem volume equations for pure and natural Crimean pine (Pinus nigra J.F.Arnold subsp. pallasiana (Lamb.) Holmboe) stands in Kastamonu Regional Directorate of Forestry. A total of 227 sample trees taken from available sites, densities, and ages were measured for over-bark and under-bark stem volumes. Seven single-entry and twelve double-entry stem volume equations were fitted for over-bark and under-bark stem volume estimations, separately. The fitted equations were ranked according to four goodness-of-fit criteria (coefficient of determination (R2), root mean square error (RMSE), mean absolute error (MAE) and Akaike information criterion (AIC)), and the most successful equations were selected based on relative ranks. Among the tested equations, the most successful single- and double-entry equations for both over-bark and under-bark stem volume estimations were equations 4 and 8, respectively. The R2 values for these equations were 0.964 and 0.994 for over-bark stem volume and 0.957 and 0.992 for under-bark stem volume, respectively. With the developed single- and double-entry equations, over-bark and under-bark stem volumes of individual trees can be estimated in the Crimean pine stands of Kastamonu Regional Directorate of Forestry