Gp. Buchert et al., EFFECTS OF HARVESTING ON GENETIC DIVERSITY IN OLD-GROWTH EASTERN WHITE-PINE IN ONTARIO, CANADA, Conservation biology, 11(3), 1997, pp. 747-758
Genetic diversity measures at 54 isozyme loci coding for 16 enzymes in
megagametophytes were compared between preharvest and postharvest gen
e pools of two adjacent virgin, old-growth (similar to 250 years) stan
ds of eastern white pine (Pinus strobus L.) in the Galloway Lake Old P
ine Area of central Ontario. The concurrence of genetic diversity chan
ges between the stands suggests that real and repeatable genetic erosi
on occurred in these gene pools as a result of harvesting. The total a
nd mean number of alleles detected in each stand were reduced by appro
ximately 25% after tree density reduction of 75%. The percentage of po
lymorphic loci dropped by about 33% from preharvest levels. About 40%
of the low frequency (0.25 > p greater than or equal to 0.01) alleles
and 80% of the rare (p < 0.01) alleles were lost from each stand becau
se of harvesting. Hypothetical multilocus gametic diversity was reduce
d by about 40% in each stand after harvesting. Latent genetic potentia
l of each stand was reduced by about 50%, suggesting that the ability
of these gene pools to adapt to changing environmental conditions may
have been compromised. Heterozygosity estimates in the postharvest sta
nds did not reflect reductions in allelic richness due to harvesting.
Observed heterozygosity increased by 12% in one stand after harvesting
, even though other genetic diversity measures decreased. Gene frequen
cy changes due to harvesting imply that gene pools of naturally regene
rated progeny stands may be quite different from the original parental
stands. Silvicultural practices should ensure that the gene pools of
remaining pristine old-growth stands have been reconstituted in the re
generating stands.