Height–age and height–diameter relationships for monocultures and mixtures of eastern cottonwood clones

Data from an eastern cottonwood clonal mixing study in Mississippi and Kentucky, USA, were used to test the effects of planting locations and genetics (clonal proportions) on height–age and height–dbh functions. Planting locations, which accounted for 5.6% of the variation in observed dominant height growth ( p=0.0001), were more important than clonal proportions, which accounted for only 1.0% of the variation ( p=0.0077). Interactions between clones in mixtures were not significant ( p=0.9178), but three cases of over- and undercompensation paralleled those observed for basal area. Planting locations were associated with differences in maximum height in the height–dbh function and clonal proportions were associated with differences in height of trees with smaller than average dbh. Although statistically significant, the effects of planting locations and clonal proportions were not important enough to incorporate into the final height–dbh model.