The European beech is a major component of central European forests, and the eastern limit of its range lies in Poland. However, the Holocene migration of the beech is not yet finished, especially in NE Poland, so the northern distribution of the beech continues to change. The main goal of this study was to determine if the beech will reach its northern limit in the future.
The investigation was carried out in 18 beech stands in Poland. To study the status of the health of the trees, circular plots were established in grids of different sizes. The basal beech stand area ranged from 3.7 m2 ha-1 to 31.2 m2 ha-1. The density of trees exceeded a hundred trees per hectare in most of the plots (61%), and the average degree of defoliation was not greater than 60% in all of the investigated stands. Environmental conditions influenced defoliation of beech trees (Fisher's test, F = 4.0204; P <0.0001). The vitality of the beech trees varied between stands (Kruskal-Walis test, H = 139.7433, P <0.0001) and was rather good in 56% of the study plots. Seedlings and saplings were observed in all of the investigated stands, and they covered from 5 to 39% and 21 to 80% of the study plots, respectively. Spontaneous beech regeneration was widespread and differed from stand to stand as well as within stands in all of the study plots. The number of tall seedlings in most of the study plots (56%) was greater than 10,000 individuals per hectare. The factors limiting beech regeneration were stand density and herb cover, and the number of beech seed trees influenced the quantity of small seedlings. Beech tree density positively influenced the number of small seedlings, and the strength of the correlation was moderate and statistically significant (Pearson correlation, r = 0.349). Beech tree density influenced the vitality of tall and small saplings (Pearson's correlations, r = 0.673 and r = 0.361, respectively). The spontaneous regeneration and strong vitality of seedlings and saplings suggests that beech can create stable stands in the future and that it is an expansive tree species both within its continuous range and at the limit of its distribution. It is quite possible that beech will reach its north-eastern limit in Poland in the future.