Stem Taper Equations for Estimating Merchantable Volume of Lebanon Cedar Trees in the Taurus Mountains, Southern Turkey

摘要

Taper models are one of several necessary components in modern forest inventory and/or management planning systems, giving information on diameter at any point along the tree stem. This information can be used to estimate stem volume and to classify the structure of the tree. This study aimed to assess the performance of different types of taper equations for predicting tree diameter at a specific height, height to a specific diameter, and merchantable volume for Lebanon cedar (Cedrus libani A. Rich.). Ten commonly used and well-known taper functions were evaluated. Appropriate statistical procedures were used in model fitting to account for the problems of autocorrelation and multicollinearity in the hierarchical data that are associated with the construction of taper models. The compatible segmented model of Clark et al. (USDA For. Serv., Res. Pap. SE-282, Southern Research Station, Asheville, NC, 1991) was superior to the other equations in describing the stem profile, estimating height to a specific diameter, and estimating merchantable volume for Lebanon cedar when upper stem diameter measurements were available, whereas the taper equation of Fang et al. (For. Sci. 46: 1-12, 2000) performed well when those measurements were unavailable. The equation of Kozak (For. Chron. 80: 507-515, 2004) had lower R-2 and higher root mean square error and Akaike information criterion values compared with those for the other taper equations. In general, segmented taper equations provided more accurate predictions than variable-form models. The equations developed in this study are fundamental tools for use in forestry practices and can help forest managers in the area of study.