DIAMETER AND HEIGHT DISTRIBUTIONS IN GENETICALLY IMPROVED PINUS-RADIATA

Diameter and height distributions for Pinus radiata D. Don trees grown from seed lots representing a range of genetic improvement were compa red at midrotation (age 14 or 15) in seven large-plot trials at six si tes. In one of the trials, comparisons were made at year 5 and annuall y from age 8 to 16. These an the first data from plantation conifers c omparing tree size distributions of commercially planted seed lots. Di fferences among seed lots for quadratic mean diameter and mean height were statistically significant and generally reflected the expected le vel of genetic improvement. Standard deviation, skewness, and kurtosis were not significantly different among seed lots. However, diameter d istributions of higher rated seed lots sometimes appeared very slightl y more skewed to the right and flatter than the lower rated seed lots, a similar tendency observed as stands age. Models used to predict dia meter distribution from stand parameters are not likely to require mod ification for genetically improved seed lots.