Modeling the diameter and locational distribution of branches within the crowns of loblolly pine trees in unthinned plantations

Abstract

Crown structure for 9- to 30-year-old loblolly pine (Pinustaeda L.) trees in unthinned plantations was quantified via analysis of branch diameters and location, both along and around the bole, using data from 68 trees. The trees ranged in size from 11.1 to 31.6 cm in diameter at breast height and from 8.30 to 25.67 m in total height, and were growing in Piedmont and Atlantic Coastal Plain stands. Three equations were used to describe the diameter distribution of branches. Circular statistics were used to examine branching patterns around the bole. A system of two equations was developed to predict the total number of branches within a crown. A series of three equations was used to describe the mean of and range in diameters within a whorl. Attempts at modeling the height above ground to branches (whorls) were unsuccessful; therefore, equal height growth per year was assumed and whorls were placed within each year of growth in concordance with the literature. 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 that a uniform, or regular, 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 is difficult, with much variation occurring among trees.