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Determination of stem standing volume is very useful for both sustainable management of timber resources and practical purposes in forestry. Brutian pine (Pinus brutia Ten.) and black pine (Pinus nigra Arnold.) are important raw material of forest products industry of Turkey. With ever changing market conditions, there is a need to accurately estimate tree volumes utilizing multiple upper stem merchantability limits. This is not currently possible with the existing total stem volume tables for these three species. Nowadays, taper equations are the best way to estimate volume for saw timber and biomass purposes. In this study, variable exponent taper equations evaluated and fitted to data come from 253 destructively sampled trees which were collected in natural brutian pine and black pine stands in Egirdir district. For this aim, the taper equations of Lee et al. (2003), Kozak (2004), and Sharma and Zhang (2004) were used. A second-order continuous-time autoregressive error structure was used to correct the inherent autocorrelation in the hierarchical data. The proposed models generally performed better for Merchantable tree volume. Results show that the Kozak (2004) taper equation was superior to the other equations in predicting diameter and merchantable height, while The Sharma and Zhang (2004) taper model provided the best predictions for merchantable volume than the other models. The one of the important results of this study, the importance of checking fit statistics of taper equations for both diameters and volume estimationsAs a results, Sharma and Zhang (2004) taper model recommended for estimating diameter at a specific height, height to a specific diameter along the stem, and merchantable volume for brutian pine and black pine stands in Egirdir analyzed. |
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