To evaluate the relative importance of each predictor,
regression coeffcients were recalculated on the
standardized values of predictors and SI. The weight
of each predictor was expressed as percent of the sum
of the absolute values of regression coef®cients. The
variable having the greatest effect on site index estimation
was annual rainfall (37.2%), followed by water
surplus (32.9%), clay content in the horizon 25±50 cm
below ground (11.8%), calcium-carbonate content in
the horizon 25±50 cm below ground (10.6%) and
east±west component of aspect (7.6%).