Modeling juvenile growth of loblolly pine plantations is important for a better understanding of the whole process of stand development and helping to schedule appropriate silvicultural treatments for young stands. This paper evaluates spacing treatment effects on young loblolly pine trees and presents individual tree growth models for loblolly pine plantations. Using data from spacing trials (plot size ranging from 1.22 x 1.22 to 3.66 x 3.66 m(2)) for loblolly pine plantations, a generalized randomized block design (GRBD) analysis was conducted to test spacing treatment and site quality effects on young tree growth. It is shown that planting density and site quality have significant influence, and spacing rectangularity is negligible. Based on the Bertalanffy differential equation and biologically reasonable assumptions regarding density and site quality effects on tree growth, a general projection model for individual tree diameter and height was developed. A stochastic model for generalizing tree height predictions within each diameter class was proposed. Models for crown ratio, and initial diameter distribution were also developed. The models were estimated with spacing trial data from young loblolly pine plantations. Validation results for these models showed that they are appropriate for predicting the juvenile growth of loblolly pine plantations where competing vegetation has been controlled in a similar manner to these spacing trials.
