Efficiency of Early Selections for Stem Volume and Predictions of Size Distributions of Selections in a Red Pine Spacing Trial

Simulated phenotypic selections for superior stem volume at age 34 were carried out in a red pine spacing trial between age 10 and age 34. The efficiency of selections increased exponentially with selection age and with diminishing initial spacing. Interactions between spacing, age, and the intensity of selection modified the overall efficiency of early selections. The probability that a tree would remain in a given relative size class during a 2-or 4-year-period increased with age when the initial spacing was less than 2.1 m. Wider spacings induced a decline in these probabilities. Realistic predictions of future size class distributions of trees selected for superior size at age 10 were generated from a maximum of 4 years growth information with the help of Markov chains (transition probability matrices). Age 34 standardized means of early selections could be estimated within 2% from a quadratic response surface with age, spacing, and selection intensity (%-select) as independent variables. For breeding purposes, selections at age 10 appeared more attractive than later selections. Predictions of age 10 to age 34 years correlations of stem volume based on these Markov chains produced realistic results for plantations planted at a 3.0 m square spacing and closer. For. Sci. 37(2):593-612.