Effective population size as a parameter closely correlating with the genetic
and genotypic diversity of the seed orchard output is an important indicator
of seed orchard functioning. It is determined by the variation of male and
female gametic contributions of parental genotypes (including those outside
the seed orchard), influenced by the variation in male and female gamete
production, reproductive phenology, pollen dispersal within seed orchard and
other factors. We assessed male and female fecundity, as well as temporal
course of male and female flowering in two seed orchards of Pinus nigra
ARNOLD and Fraxinus excelsior L./F. angustifolia VAHL. in Slovakia. In both
cases, male and female gametic contributions of plus-tree clones were modeled
on the basis of fecundity and flowering phenology, and were used to calculate
status number as an estimator of effective population size. In the seed
orchard of Pinus nigra, marker-aided verification of clonal fidelity revealed
unexpectedly high proportion of misplaced ramets (29.9%) and alien genotypes
(44.4%). Monitoring of reproductive processes in 2002 and 2003 showed high
variation in both male and female fecundity, and pollen shedding preceding
female receptivity in Pinus nigra. All these factors contributed to a very
low relative status effective number, representing 8.6% to 38.6% of the
population census (depending from the management option in relation to
misplaced and alien genotypes). In the mixed seed orchard of Fraxinus
excelsior and F. angustifolia, the proportion of misplaced and alien
genotypes was much lower (22.4% and 12.3%, respectively). However, a high
fecundity variation and protogyny resulted in a low relative status number
(18.8% to 29.5% of the census number of clones) also in this seed orchard.
Practical implications of these findings are shortly discussed and practical
management options are proposed.