Population dynamics in loblolly pine stands: changes in skewness and size inequality

Determined the changes in size inequality and asymmetry that occurred over 50 yr period in 16 even-aged, naturally seeded populations of Pinus taeda. Initial densities ranged from 618-28 861 stems/ha. In young stands size inequality was greater at higher plant densities; skewness of tree volumes was significantly greater at higher initial densities, whereas skewness of diameters was not; size inequality increased significantly prior to the onset of selt-thinning, then decreased during self-thinning; and skewness did not increase before self-thinning or significantly decrease during self-thinning. The two-parameter Weibull distribution only moderately effective at capturing the forms of the distributions observed. Correlations showed very close linear relationships among the Gini coefficient, the coefficient of variation, and the shape parameter of the Weibull distribution - both within and across different measures of tree size. All 3 statistics were correlated with initial density. Skewness coefficients for distributions of diameter, height and volume were not closely correlated with each other or with other population characteristics. Measures of inequality are more suitable for summarizing biologically important properties of tree populations than measures of skewness or skewness-sensitive parameters of probability distributions. -from Authors

Duke Scholars

Author Norman L. Christensen Environmental Sciences and Policy