Top-down growth modelling: a prototype for poplar plantations in Italy

Hybrid poplar plantations are one of the most important sources of timber and wood fibres in Italy and represent a significant alternative as sustainable use of agricultural land. Effective management of such plantations requires adequate growth and yield models. In light of this, the paper presents the fundamentals of a top-down growth and yield model for hybrid poplar (I-214 clone) plantations in Italy. In the top-down approach, standing volume, basal area, or other characteristics are the primary quantities predicted and these quantities are disaggregated into size-class, and, eventually, into individual-tree information. The basic element of the proposed prototype is the stand basal area growth equation. Stand age, current stand basal area, and site index are considered as predictors. If the current dbh distribution is also known, a second function estimates the size-class distribution of overall stand growth, projecting the dbh distribution to the end of the considered growth period. Individual competition indices do not contribute to the explanation of the growth variation at the tree level. Prototype predictions prove to be quite accurate: they are based on readily available forest inventory data, thus extracting knowledge from the wealth of accumulated long-term observations usually carried out in forestry.