Patterns in branch permeability with crown depth and permeability at the top of the main stem were analyzed for loblolly pine (Pinus taeda L.) trees from families selected on the basis of growth rate (fast, slow) and crown size (large, small). Analysis of variance with levels of crown size nested within levels of growth rate was used to test for differences in main stem permeability. Permeability at the top of the stem averaged 2.010 12 m 2 . There were no significant differences in permeability between families selected for fast and slow growth, but permeability was significantly lower for families selected for large crowns than for families selected for small crowns. Branch permeability averaged 0.7410 12 m 2 and decreased significantly with crown depth. Large-crown families had higher overall branch permeability than small-crown families. Average permeability in branches did not differ significantly between fast-and slow-growing families. Large crown-families had significantly larger current leaf area: total leaf area ratios in the lower two-thirds of the crown, and a weak but significant association was found between permeability and current leaf area: total leaf area ratios for a given relative crown depth. Our results suggest that ecotypic and adaptive processes simultaneously affect the overall patterns of stem and branch permeability in loblolly pine families.
The objective of this study is to evaluate the fit of Johnson's SB distribution function to vertical foliage distributions of variously aged and treated loblolly pine trees when the function is fit with two percentiles of the observed distributions. Foliage distributions are linked to various stand properties, and straightforward means of quantifying foliage distribution may lead to a convenient method of characterizing forest stands using remote sensing technology such as LiDAR. Regression analyses indicate that the 15th and 50th percentiles of the distributions were best correlated with variables of crown structure and tree age. Skewness and kurtosis of the distributions calculated with the function's parameters also varied with crown structure and age. Cumulative fractions of leaf area calculated with fitted SB functions matched measured values well; cumulative values of absolute leaf area showed less correspondence with measured values, but residuals of both centered around zero. Incompatibilities between the continuous SB function and the irregular and discrete nature of foliage distribution of single trees occasionally produced large prediction errors. Based on these results, the SB function fitted with the two-percentile method suitably describes the vertical distribution of leaf area of a wide variety of loblolly pine trees. FOR. SCI. 51(2):93–101.
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