Global Advanced Research Journal of Agricultural Science (GARJAS) ISSN: 2315-5094
April 2015 Vol. 4(4): pp. 200-210
Copyright © 2015 Global Advanced Research Journals

 

Full Length Research Paper

Nonlinear mixed-effects models for the modeling the effects of growth rate on the transition of juvenile to mature wood in basic density in hinoki cypress (Chamaecyparis obtusa)

Takaaki Fujimoto *[1] And 2Junji Kimura

 

1Faculty of Agriculture, Tottori University, Tottori, 680-8553, Japan TEL&FAX: +81-857-31-5866

2Tohoku Regional Forest Office, Forestry Agency, Akita, 010-8550, Japan TEL&FAX: +81-18-836-2014

Corresponding Author’s E-mail: tafujimoto@muses.tottori-u.ac.jp;    

TEL&FAX: +81-857-31-5866

Accepted 16 March, 2015

 

Abstract

The aim of this study was to evaluate the effects of growth rate on the radial variation in basic density of hinoki cypress (Chamaecyparis obtusa) using a nonlinear mixed-effects model. Nineteen sample trees were harvested from two plots in which trees showed different growth rates within a 50-year-old hinoki stand. Ring widths and basic density were measured at 5-ring intervals. An asymptotic regression model that included the random effects of individual trees was fitted to describe the radial variation in basic density. A model including the fixed-effects of the plots as the covariate was also tested. The results indicated that the terms of the plots were highly significant; thus, the growth rate would affect the radial variation in basic density. The transition age was defined as the ring at which the basic density reached approximately 99% of the asymptote. The transition ages varied among trees, and ranged from 13.0 to 26.0. Analysis of variance revealed that the transition ages of trees in fast-growth plots were significantly younger than those of trees in slow-growth plots. These results imply that fast growth may be related to an early age of transition from juvenile to mature wood.

Keywords: Growth rate; Transition from juvenile to mature wood; Nonlinear mixed-effect model; Chamaecyparis obtusa

 


 

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