Relationship between Sunny Crown Volume Increment and Stem Cross-Sectional Area Increment at Sunny Crown Base for Hinoki Cypress, and its Application

摘要

Vertical distribution of stem cross-sectional area increment (CSAI) for hinoki cypress can be described by combination of two linear equations derived from three tree attributes: sunny crown length (SCL), stem volume increment (SVI), and CSAI at the base of sunny crown (CSAIscb). In this study, to propose a method for estimating CSAIscb, a relationship between CSAIscb and sunny crown volume increment (SCVQ was investigated. Data were obtained from 112 sample trees selected in six stands of even-agedhinoki cypress. The proportional relation can be assumed between SCVI and CSAIscb, and the relationship could be expressed by the regression equation: CSAIscb = 2.88 x 10 4SCVI. For each sampled tree, two vertical distributions of CSAI were obtained: oneis the distribution obtained by using CSAIscb estimated from the regression equation, and both of SCL and SVI observations, and the other is the distribution obtained by using observations of SCL, SVI, and CSAIscb. The two distributions were compared using root mean squared error (RMSE). Although the vertical distribution obtained by using CSAIscb estimate produced a larger RMSE value than that by using CSAIscb observation did, the difference in RMSE was small. In conclusion, the assumption of the proportional relationship between SCVI and CSAIscb provides a useful approach for predicting vertical distribution of CSAI for hinoki cypress.