Base–Age Invariance Properties of Two Techniques for Estimating the Parameters of Site Index Models
Authors: Strub, Mike1; Cieszewski, Chris J.1
Source: Forest Science, Volume 52, Number 2, April 2006 , pp. 182-186(5)
Abstract:
Using eight hypothetical data points (four growth series with two observations each) the difference between two site index curve parameter estimation methods, the base–age invariant stochastic regression approach (BAI) and the method of all base ages (BAA), is illustrated. The anamorphic form of the Schumacher log-transform height–age equation is used for the comparison. The two estimation techniques are equivalent for the linear case of the model but produce different parameter estimates for its nonlinear form. For both linear and nonlinear cases the BAI approach produced a lower root-mean-squared error than the BAA method. Only the BAI approach produced unique estimates for the site-specific parameters of both model forms and both growth series.Document Type: Research article
Affiliations: 1: Mike Strub, Forest Biometrician, Weyerhaeuser Company, PO Box 1060, Hot Springs, AR 71902, and Adjunct Professor, Warnell School of Forest Resources, The University of Georgia, Athens, GA 30602-2152—Phone: (501) 624-8504; Chris J. Cieszewski, Associate Professor, Fiber Supply Assessment, Warnell School of Forest Resources, The University of Georgia, Athens, GA 30602-2152—Phone: (706) 542-8169; Fax: (706) 542-8356; biomat@smokey.forestry.uga.edu., Fax: (501) 624-8505, Email: mike.strub@weyerhaeuser.com.
