Genetic diversity and genetic structure of adult and buried seed populations of Betula maximowicziana in mixed and post-fire stands

The genetic diversity and genetic structure of plant populations are influenced by processes of regeneration. Assessing the genetic composition of populations regenerated by different modes is important for successful forest management and conservation. In this study, we compared the genetic diversity and genetic structure of six populations in mixed stands with those of four post-fire stands of the noble hardwood species Betula maximowicziana. We collected plant tissues from 491 adults and 266 seedlings, germinated from soil samples, for a total of 10 populations, and genotyped them using 11 microsatellite loci. Genetic diversity parameters (e.g., HE, Rs, FIS) in the post-fire stands were similar to those in the mixed stands. In contrast, other parameters, including the number of private alleles (PA), the number of loci showing significant linkage disequilibrium (LD) and effective population size (Ne) differed between the mixed and post-fire stands. The average PA, LD and Ne values were 1.2, 2.0 and 315.7, respectively, for the mixed stands, and 0.3, 5.0 and 282.2, respectively, for the post-fire stands. Evidence of a significant bottleneck was detected in two of four adult populations in the post-fire stands, possibly as a result of a catastrophic founder effect due to fire disturbance on their genetic constitution. Buried seed populations maintained the same level of genetic variability as adult populations, but with lower genetic differentiation among them. Spatiotemporal gene flow, characterized by wind-mediated dispersal and the persistence of viable seeds in the soil, are key factors maintaining the genetic diversity of B. maximowicziana populations. Our study reveals that post-fire stands and buried seeds will be useful genetic resources in the future.