Managing genetic resources of lodgepole pine in west-central Alberta: patterns of isozyme variation in natural populations and effects of forest management

Abstract Needle tissue, collected from 30 individuals in each of 57 stands of lodgepole pine from west-central Alberta, Canada, was analyzed by starch gel electrophoresis for eight enzyme systems encoding 12 putative loci, which displayed a total of 51 allozymes. In unmanaged (fire-origin, unthinned) stands there were no differences in genetic diversity among elevations (breeding regions) and there was no relationship between geographic distance and genetic identity. Ordination of allelic frequencies showed that there was little population differentiation related to elevation or management prescription. For harvest-origin stands there were no significant differences in genetic diversity between regeneration methods (natural regeneration versus planting); nor was there any effect of pre-commercial thinning on genetic diversity of fire- or harvest-origin stands. Harvest-origin stands had significantly lower average population genetic diversity than unmanaged (fire-origin, unthinned) stands (expected heterozygosity, H exp ; effective number of alleles, n e ) and also showed lower total expected ( H T ) (6% less) and observed heterozygosity ( H O ) (9% less). Unmanaged (fire-origin, naturally regenerated, unthinned) stands had significantly greater H exp and n e than harvest-origin (unthinned) stands of similar age that were planted. For the high elevation breeding region harvest-origin stands showed lower allelic richness than average for a similar sample size of stands from the region; this was due mainly to missing rare (frequency H T (15%), H O (15%), alleles per locus (2.25 versus 4.00) and % polymorphic loci (42% versus 75%) and were missing 47% of all alleles and 78% of rare alleles.