Predicting the crown shape of loblolly pine trees

A model to predict the crown shape of loblolly pine (Pinus taeda L.) trees in stands is presented. Crown shape changes due to growth, competition, and age are modeled as functions of changes in individual tree characteristics. An average symmetrical vertical cross-sectional profile is assumed for practicality, which consists of outer and inner shape functions. The outer shape is modeled with a second-degree polynomial constrained to equal zero at the crown tip. Its flexibility allows the vertical movement of maximum crown radius due to competition. The essentially cone-shaped inner defoliated area of a loblolly pine crown is modeled as a straight line. The equation system allows determination of key crown measures such as maximum crown radius and its height, crown volume, and crown surface area. Fitted equations presented are valid for unthinned loblolly pine in Louisiana, U.S.A., stands, but the model, methodology, and results should be useful more generally.