Foliage biomass - sapwood (area and volume) relationships of Tectona grandis L.F. and Gmelina arborea Roxb.: silvicultural implications Ricardo Morataya 1,a , Glenn Galloway b,* , Frank Berninger 2,c , Markku Kanninen 3,d a Agreement Tropical AgriculturalResearch and Higher Education Center (CATIE) and University of Helsinki, CATIE, Turrialba, Costa Rica b TRANSFORMA Project (CATIE/COSUDE), CATIE, Turrialba, Costa Rica c Department of Forest Ecology, PO Box 27, 00014, University of Helsinki, Helsinki, Finland d Research Program Director CATIE, CATIE, Turrialba, Costa Rica Received 6 April 1998; accepted 6 July 1998 Abstract We developed foliage biomass to sapwood (area and volume) relationships for Tectona grandis L.F. and Gmelina arborea Roxb. growing in the Guanacaste province of Costa Rica. Strong linear relationships con®rmed the applicability of Shinozaki's pipe model theory to both of these fast-growing, tropical species. The linear models include data from 80 (40 per species) dominant, codominant, and suppressed trees that had been growing in un-, late and early thinned plantations and fence-row plantings. Results are applicable across a wide range of foliage biomass values. The relationships between foliage biomass and sapwood area and volume of the previous year's growth ring were also analyzed and were found to be highly signi®cant for T. grandis. Findings con®rm that silvicultural regimes of these species must allow individual trees to augment foliage biomass from an early age if sustained rapid diameter growth is desired. # 1999 Elsevier Science B.V. All rights reserved. Keywords: Pipe model; Teak plantations; Melina plantations; Thinning 1. Introduction Reforestation programs in many tropical countries have tended to emphasize plantation establishment and neglect intermediate operations such as thinning (Evans, 1992). This tendency has been con®rmed in a number of studies in Latin America countries includ- ing Guatemala (Zanotti et al., 1995), Costa Rica (Sa Ânchez, 1994; Vasquez and Ugalde, 1995), Nicar- agua (Centeno, 1993) and Ecuador (Galloway, 1987; Galloway et al., 1996) where only in recent years have thinning and pruning operations increased in estab- lished plantations. In Central America, a better understanding of stand dynamic processes made clear with data from a regio- Forest Ecology and Management 113 (1999) 231±239 *Corresponding author. Tel: +1-506-556-2703; fax: +1-506-556- 7730; e-mail: galloway@catie.ac.cr 1 Tel.: +1-506-556-6431; fax: +1-506-556-1533; e-mail: rmoratay@computo.catie.ac.cr 2 Tel.: +1-358-70851; e-mail: frank.berninger@helsinki.fi 3 Tel.: +1-506-556-1754; fax: +1-506-556-6255; e-mail: kanninen@computo.catie.ac.cr 0378-1127/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved. PII: S0378-1127(98)00429-0