Height–diameter equation for first rotation eucalypt plantations in Portugal.

A height–diameter equation for eucalypt plantations was developed based on a tree dataset from trials and permanent plots located in the north and central coastal regions of Portugal. The total dataset was split into two datasets through restricted random sampling at the plot level. The equations selected in one data subset were evaluated with the other subset and vice versa. Harrison equation, fitted with the iteratively reweighted least squares method, in both versions—restricted and not restricted to pass through the point diameter–height (0, 1.30)—was selected. The first version was recommended for young plantations; it is age dependent and requires a measure of stand productivity. The second version was appropriate to use in commercial forest inventory where trees smaller than 4 cm diameter are not measured; it is age independent, density dependent and, also requires a measure of stand productivity. [Copyright &y& Elsevier]