Genetic variation in southern Idaho ponderosa pine progeny tests after 11 years /

Comparisons were made among 268 half-sib families of ponderosa pine from 37 southwest Idaho populations at four test sites.Data involved 8-and 11-year height, the percentage of trees damaged by snow, and the percentage of trees with straight stems.Analyses of variance evidenced population differentiation for height at both ages but not for the percentages of snow-damaged or straight-stemmed trees.Differences among populations accounted for about 20 percent of the genetic variance; most of the genetic variance occurred within populations.Multiple regression analyses were made to relate population differentiation to geographic and ecologic variables.The data suggested that elevation of the seed source controlled differentiation; latitude and longitude were secondary; and habitat types were not important.From these results, it was concluded that seed for afforestation should not be transferred more than 450 m elevation, 1.7 degrees longitude, and 2.2 degrees latitude.Quantitative genetic analyses provided estimates of family her itabilities in 11-year height that ranged from 0.37 to 0.53 for the various planting sites.These heritabilities imply that genetic gains of about 7 percent can be expected readily in the 11-year height of progenies of selected families CONTENTS