BASAL AREA GROWTH OF INDIVIDUAL TREES - A MODEL DERIVED FROM A REGIONAL LONGLEAF PINE GROWTH STUDY

An individual tree basal area increment (BAI) model for thinned, even- aged stands of naturally regenerated longleaf pine (Pinus palustris Mi ll.) is presented. The model is an intrinsically nonlinear equation, w hich is constrained so that it performs within the bounds of biologica lly reasonable outputs for any combination of values for the independe nt variables. All parameters in the equation were estimated simultaneo usly. This is a departure from the more traditional potential-times-mo difier approach in which parameters for a potential growth function ar e estimated from a sample of trees exhibiting the fastest growth. Inde pendent variables used to describe BAI are stand basal area, the compe titive position of an individual tree within the stand calculated as t he sum of the basal areas of all trees larger than the subject tree, m ean age of dominant and codominant trees, and individual tree diameter outside-bark at breast height. Noticeably absent from the model is an independent variable that explicitly characterizes site differences.