(Introduction):

Long-term research on the growth and timber yield of plantations with forest species native to tropical dry forest is scarce, despide the fact that many of these species a real potential for commercial timber production is recognized.

(Objective):

Build a local classification system based on the growth of dominant height for Samanea saman by using site index curves, to facilitate management works with this native species in the tropical dry forest of Liberia, Costa Rica.

(Methodology):

The dominant height-age data, used to construct the dominant height and site index curves, were obtained from permanent plots, which were measured annually for 21 years. Eight regression models used in the forest literature were tested. The models were statistically analyzed; in addition, the estimated values were plotted versus the observed values to graphically evaluate the fit of the data.

(Results):

The most satisfactory model was that of Prodan (1951) with R 2 adj of 93.72 %, MSE = 3.9706, SEE = 1.9926 and MAE = 1.4830 for a P-value of (0.00001) at a confidence level of 95 %. The average curve adjusted by the Prodan model at first presents an inclination that suggests a rapid initial growth, with a first section of the curve that rises quickly until the age of 8; then, a second section between the ages of 9 and 14, where it continues to grow with a lower rate.

(Conclusions):

The Prodan model has an appropriate fit for permanent plot data. The proposed classification system took as its base age 15 years to construct the curves corresponding to site indices 9, 12, 15 and 18, which cover the entire observed site quality range.