Site index curves for leucaena [Leucaena leucocephala (Lam.) De Wit] in agreste of Pernambuco

The main goal of this work was to set and compare site index curves for leucena [Leucaena leucocephala (Lam.) de Wit] variety Hawaii (cv K8) in Agreste of Pernambuco. The data set came from Empresa Pernambucana de Pesquisa Agropecuaria (IPA), Experimental Station of Caruaru, in which 544 trees cultivated with and without organic compound were measured 19 times during the period of 1990 - 2003. The models of Schumacher, Chapman-Richards, Silva-Bailey, Mitscherlich, Weibull and Clutter-Jones were tested and compared. To select the best equations, the Index of Fit (IF), standard error of estimate (S-yx %), identity model test and the graphic of residuals distribution were used and results show that the model of Clutter-Jones provided a better IF for both treatments. The graphic of residual distribution did not show tendency among the models. The model identity test showed no differences among the models tested. As Schumacher's model has been used frequently in forestry and presented the smallest number of parameters, it deserves special focus in studies of site index.