Modeling Tree Stem Volume of a Given Processible Diameter Class of Quercus phillyraeoides in Muroto Region, Kochi Prefecture

Abstract

Ubame oaks (Quercus phillyraeoides) are intensively processed into Binchoh charcoals in Kochi Prefecture. Quantifying the stem volume is necessary to estimate sustainable usage of the oak. The diameters of stems strongly relate to the specifications of the charcoal as well as the processibility of the stems into charcoals. Therefore, a stem volume model that enables us to estimate the volume for a given stem diameter distribution as well as the volume is desired. In this study, we measured the geometries of the oaks by felling in Muroto region, the major production of the Binchoh charcoal in Kochi Prefecture, and modeled the stem volume formula that estimates the volume for a given processible diameter. Stem volumes for a given processible diameter were approximated with linear regression model of D²H. A unified regression model that assumes linearity of the slopes and exponentiality of the x-intercepts with processible diameters slightly increased the root of mean square error but reduced AIC more than five. Estimations of this regression model and the actual stem volume measured were larger than the estimations of the stem volume table appropriate for the region and species and the volumes of Ubame oaks reported in Wakayama Prefecture.