Study on Evaluating a Standing Tree Used for Wooden Cultural Buildings – About the Method to Presume Size and Quality of the Timber

Abstract

In order to continue maintaining of cultural and historically valuable buildings, it is necessary to consider stocking of large sized and high quality timber. However, it is difficult to secure the timber for repair in Japan at present because the stock of the timber is assessed only by individual evaluation criteria. In order to maintain wooden cultural buildings, it is important to standardize the evaluation criteria. Purpose of this paper is to investigate individual evaluation criteria to selecting logs and in order to produce a timber required to maintain wooden structures. Moreover, it is intended to propose a criterion to selecting standing trees. For that purpose, we have selected logs at the timber market and have measured the size of their sapwood. The average sapwood width was calculated in order to predict a required size of a sawn timber. Then we measured the tree height and the diameter at breast height and upper parts of standing Japanese cypress trees growing at natural forests in Kiso area and using a three-order equation we have calculated their height curve and a relative taper-curve. Finally, we standardized the necessary size of the logs and the necessary size of the standing trees. As a result, we can now predict the size of standing trees as well as the size of the logs which are required to produce the wooden material quested to maintain historical wooden structures in Japan.