An investigation, comparison, and development of individual tree competition models

A new individual tree competition model based on the zone of influence principle was developed and tested on data from two young loblolly pine plantation stands. Analyses indicated that, depending on stand, diameter distribution and spatial arrangement, the model acted either as a competition advantage or as a competition disadvantage model. Attempts to discover the nature of the change in behavior of the model within stands over time were made by considering model parameters as functions of time and observing their change. The attempt was unsuccessful due to the limited number of years for which data were available. Comparisons of the developed model with two zone of influence models selected from the literature verified that, at least for the data used in this study, the selected comparison models could also serve as either a competitive advantage or disadvantage model, depending upon stand conditions. Also, neither comparison model predicted diameter increments with the same degree of precision as did the developed model.

An additional effort was made to define an individual tree competition model based on volume overlaps between the crowns.