| Forest fires are intrinsic components of boreal forest ecosystems and harvesting is widespread, with different types of silvicultural practices used to maintain species and populations. It has been hypothesized that forest fires, and silvicultural practices may reduce genetic diversity of regenerated populations. We chose the boreal tree species white spruce [Picea glauca (Moench) Voss] as a model system to test this hypothesis.;To investigate whether different silvicultural practices influence genetic diversity of regenerating forest, I compared population genetic parameters of white spruce trees from old-growth forest, natural regeneration, plantation populations, and tree improvement selections in Saskatchewan. The allelic- and genotype-based genetic diversity of old-growth and natural regeneration was higher than that of plantations and tree improvement selections; however, differences were not statistically significant.;To determine whether wildfires result in subsequent changes to a population's genetic diversity and structure, I compared the genetic diversity of two post-fire young regeneration stands and their adjacent post-fire old-growth stands in Prince Albert National Park of Canada. Allelic- and genotype-based genetic diversity parameters showed a similar level of genetic diversity in post-fire young regeneration and post-fire old-growth stands.;Lastly, to determine how landscape and population connectivity (via gene flow) shape population structure of a species, nine populations of white spruce were sampled from a contiguous landscape (covering 1600 km2) in northern Saskatchewan. The vast majority of genetic diversity (∼96%) was maintained within populations and little differentiation (∼4.4%) existed among populations. I did not detect a correlation between genetic distance and geographic distance. UPGMA and Bayesian analyses, however, revealed differentiation among the studied populations.;In conclusion, wildfires did not significantly alter genetic diversity parameters in white spruce, likely due to high dispersal of pollen and seeds from neighbouring forests. Old-growth and natural regeneration showed slightly higher genetic diversity than plantations and tree-improvement selections. Populations sampled from a contiguous landscape from northern Saskatchewan were found well-connected genetically. The results of this study have significance for the conservation and sustainable management of white spruce genetic resources. |
