Modeling the diameter and locational distributions of branches within the crowns of loblolly pine trees

Abstract

Crown structure for 9- to 30-year-old loblolly pine was quantified via analysis of branch diameters and location, both along and around the bole, using observational data from 68 trees. The trees analyzed ranged in size from 11.1 to 31.6 cm in DBH and from 8.30 to 25.67 m in height, and were growing in Piedmont and Atlantic Coastal Plain stands ranging from 70 to 200 sq. ft. BA/acre. A series of equations was used to describe the diameter distribution of branches. Circular statistics were used to examine branching patterns around the bole.

A recursive system of 2 equations was developed in order to predict the total number of branches within a crown. A series of 3 equations was used to describe the average of and range in diameter within a whorl. Attempts at modeling the height above ground to branches (whorls) were unsuccessful; therefore, equidistant spacing was assumed. Similarly, predicting the number of branches within a whorl of a certain height was difficult, and overall percentages were employed.

Analysis of branch azimuths on a whole tree basis indicated a uniform distribution was appropriate (and not a “circular normal” distribution). Finally circular correlation was used to analyze rotational patterns within and between whorls, and a strong positive correlation was found for consecutive whorls of the same number of branches.

From this study it was concluded that modeling crown structure will be difficult, with much variation occurring among trees. More data are necessary to better refine the baseline work herein presented.