322 New Zealand Journal of Forestry Science 32(3) New Zealand Journal of Forestry Science 32(3): 322–333 (2002) PRELIMINARY SITE INDEX MODELS FOR NATIVE ROBLE (NOTHOFAGUS OBLIQUA) AND RAULÍ (N. ALPINA) IN CHILE GUILLERMO TRINCADO V* Institute for Forest Management, Austral University, Casilla 567, Valdivia, Chile ANDRES KIVISTE Estonian Agricultural University, Department of Forest Management, Kreutzwaldi 5, EE-2400 Tartu, Estonia and KLAUS VON GADOW Institute for Forest Management, Georg-August-University Göttingen, Büsgenweg 5, 37077 Göttingen, Germany (Received for publication 14 January 2002; revision 11 October 2002) ABSTRACT Few growth models have been published relating to native tree species in Chile. The objective of this study was to develop site index curves for two of the most valuable native species in Chile — Roble (Nothofagus obliqua (Moerb.) Oerst.) and Raulí (Nothofagus alpina Oerst. et Endl.). The study was based on stem analysis data. The method used for the reconstruction of each stem profile corresponded to one proposed previously. Site index models were generated using the difference equation method. The resulting site index systems revealed different growth patterns for both species. Among the two light- demanding species, Raulí is characterised by better initial growth. Keywords: site index; polymorphic curves; difference equation method. INTRODUCTION Studies carried out in natural forests in Chile indicate that the forest communities with the highest commercial value are the second-growth forests, known as renovales (Ulloa 1984). The ecology and structural characteristics of the renovales, which cover a total area of about 300 000 ha (CONAF & CONAMA 1999), have been described by several authors and will not be repeated here (Wadsworth 1976; Corvalán 1977; Puente et al. 1979; Donoso 1981; CONAF 1994). The most important species in the second-growth forests, and those that represent a high proportion of the trees, belong to the genus Nothofagus. The most valuable species are Nothofagus obliqua (Roble) and N. alpina (Raulí). Because of the large area, * Current address: Department of Forestry, Virginia Polytechnic and State University, Blackburg, Virginia 24061, United States