Construction of site index equations for even aged stands of Tectona grandis (teak) from permanent plot data in India

A quantitative measure of the timber production potential of a given site may be provided by site index equations, which predict site index at a reference age from height and age information of a forest stand. Data from permanent sample plots laid down in even aged stands of Tectona grandis in six states of India were used to develop site index equations. Eleven growth functions were estimated from height-age data using the guide curve method and difference equation method with anamorphic and polymorphic formulations. The applied methods and estimated functions were compared with respect to residual variation, i.e., root mean square error (RMSE) from original data. The difference equation method gave lower RMSE than the guide curve method. A special solution of the difference equation derived from one of the growth functions, where a hyperbolic relationship between site index and a parameter was assumed, gave the best fit to the data. Site index curves with dominant heights in the 11-28 m range at a reference age of 25 years are presented.