Even-aged Scots pine-dominated plantations on nutrient-poor soils are common forest types in lowlands of Central Europe. However, the knowledge about spontaneous changes in forests floor vegetation, and correlated with it changes in species richness is still scarce. We focused our study at quantifying changes in forest floor vegetation in a 120-year chronosequence. The study was performed in the south-western part of Poland (Central Europe). Our data comprised 95 sample plots sized 200 m². The plots were located in 6 stand-age classes in homogenous forest sites.

The stands < 10 years showed the highest values for biodiversity indices. Species typical for old stands were also found in the youngest ones. The period of canopy closure resulted in decrease in species number and increase in bryophyte cover, and was followed by the increase in Pleurozium schreberi and Vaccinium myrtillus cover. The dominance of these species could be broken at middle age by Pteridium aquilinum, which declined in the oldest stands. Bryophytes with preference for humus-rich soil also occurred in the middle age class only. We attributed it to the soil-enriching effect of small woody debris provided by thinning. The dominance of Pleurozium schreberi and Vaccinium myrtillus in the oldest stands was correlated with the low level of biodiversity. While the oldest stands do not support any rare and specific species their conversion into a broad-leaved community could enhance spatial diversity of forest vegetation.

Keywords: Central Europe, clear-cutting, Pinus sylvestris, rotation period, temperate zone, succession, species diversity, secondary forests