[Estimates of effective population size inPinus silvestris]

The effective population size for inbreeding has been estimated in a 70 years old population of Scotch Pine in three consecutive years to be 0.46, 0.55 and 0.61 respectively of the actual total population. The following formula was developed to determine differences among trees as regards their male or female flowering and their "maleness" and "femaleness":[Formula: see text] wheren e is the total effective population size for inbreeding,n e ' the male effective part,n e ″ the female effective part, andM a measure for monoecy ranging in values between zero (dioecy) and unity (ideal monoecy). The degree of monoecy was 70, 82 and 78 percent respectively in the three years.Correlation between male flowering over the three years was fairly strong; the same was found for female flowering. But correlation between male and female flowering was weak, both within the same year and over the three year period. Correlation of numbers of female strobili and numbers of ripe cones was weak also.The population model on which the above formulae is based is that of a clonal 'Seed Orchard' where seedlings of several clones are randomly distributed on evenly spaced plots.