Spatial Characteristics of Diameter and Total Height in Juvenile Loblolly Pine (Pinus taeda L.) Plantations

Abstract

Abstract The spatial characteristics of diameter at breast height and total height were analyzed using data collected from a set of spacing trials planted with loblolly pines. These spacing trials were established at four locations in the Piedmont and Coastal Plain regions of Virginia and North Carolina in 1983. Trend surface analysis was employed to separate the systematic microsite variation from the variation incurred by intertree competition, and a simulation study was carried out to derive an empirical distribution for Moran statistics calculated from regression residuals. At the seedling period of stand development, the systematic environmental gradients had a dominant impact on the spatial patterns of dbh and total height; however, the impact of environmental gradients diminished as stands developed. Intertree competition was evident in the autocorrelation measures, i.e., Moran and Geary indices, which declined with increased density and with stand age. Moran index was statistically significant when competition was severe. Confounding of intertree competition and microsite variation effects made the spatial patterns of observation very complicated and difficult to describe mathematically. Autocorrelation was predominantly positive with total height, but mostly insignificant or negative with dbh in the juvenile period of loblolly pine stands, which suggests that total height is less sensitive to competition. For. Sci. 40(4):774-786.