Natural Regeneration, Genetic Diversity, and Provenance of Introduced Fagus sylvatica L. Stands in Latvia

European beech (Fagus sylvatica L.) has a wide distribution range through Central and Western Europe, and is tolerant to a range of environmental factors and shade. Due to the high wood quality and growth rate, there is increasing interest in the cultivation of this species in Northern Europe, and European beech is appropriate for closer-to-nature forestry management practices, where shade-tolerant species are essential. Latvia is located to the north of the natural range of European beech, but stands have been successfully established in the 19th century, using reproductive material of unknown origin. This study investigated the natural regeneration, genetic diversity, population structure, and provenance of Latvian F. sylvatica populations from two areas in western Latvia-Skede and Kaleti. Parent-offspring analyses did not identify a decrease in genetic diversity parameters in the naturally regenerated offspring, indicating that natural regeneration has not decreased the genetic viability of these populations. The three stands located in Skede were genetically very similar (pairwise Fst values ranged from 0.004 to 0.007). The Kaleti stand was more differentiated from the Skede stands (pairwise Fst values with the Skede stands ranged from 0.047 to 0.051), and the genetic diversity was low (He = 0.638). This is probably a result of the use of reproductive material collected from a very limited number of individuals to establish this stand, which also prevented the determination of the origin of this material. The Skede stand was compared to German, Polish, and Swedish F. sylvatica populations, and a Bayesian clustering analysis indicated that the most likely provenance of the Skede stand in Latvia was from southern Germany.