Response of underplanted European beech to shelterwood thinning at the northeasternmost forpost plantation in Europe

The projected northwards shift in the distribution suggests an expansion of European beech ( Fagus sylvatica L.) into the Baltics and an increase of its commercial potential there. Furthermore, recent studies have shown good long-term survival of underplanted, yet non-rereleased beech under the presumedly limiting climate of the eastern part of Latvia, thus supporting the advance of the thermophilic species. Hence, the estimation of the responses of the underplanted beech to shelterwood removal is a logical step in the assessment of the specie’s growth potential. To analyse the effect of conventionally managed mature coniferous shelterwood thinning on the growth of underplanted European beech, six thinning treatments (100, 75, and 50% of canopy, second canopy storey, second canopy storey with understorey removed, and the control) were tested in the 33-year-old northeasternmost experimental plantation in Europe. Growth responses were evaluated five years after the treatment, when beech was 38 years old. The survival and growth responses to shelterwood thinning and local characteristics at the tree and stand level were estimated using linear models. The post-treatment survival/mortality was independent, yet the dimensions of beech, particularly stem diameter, were significantly affected by shelterwood thinning intensity (positively). Regarding tree height, the response was somewhat weaker compared to that of stem diameter, while being disproportional to thinning intensity, with moderate thinning having the strongest positive effect. The estimated positive responsiveness of beech to shelterwood thinning suggested increasing growth potential of the species and expansion in the Baltics. Though the responses of beech were moderate probably due to the age and harsher climate.