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Railway territories are man-made habitats forming corridors for non-native species migration. In this study, we assessed non-native species occurrence in plant communities along a railway route of the Bialowieza Primeval Forest in Poland in relation to adjacent plant community type and microhabitat (embankment western and eastern sides of the railway track, intertrack space). An 11-km fragment of a narrow-gauge railway route in the western part of the Bialowieza Primeval Forest was investigated. This fragment was divided into 416 sections where all observed non-native species were identified, and all individuals, ramets and tussocks were counted. We discovered 12 non-native taxa, most of which (8 species) originated from North America. The highest average number of non-native species per section was recorded in the vicinity of the Circeo-Alnetum community. Statistically, more non-native species occurred on the western embankment than on the eastern one and in the intertrack space. The use of the narrow-gauge railway in the Bialowieza Forest has increased the risk of establishment of invasive species in local plant communities. The Bialowieza Forest is a refuge for native biodiversity of the utmost importance. Thus, continuous monitoring of the occurrence of non-native species is necessary for the preservation of native plant communities in the vicinity of the narrow-gauge railway route assessed in this study.

Invasive plant species pose a threat to the diversity of natural habitats. The extent of the changes depends, among others, on soil properties, settlement time and the degree of coverage of sites by an invasive species. The objective of this study was to determine changes in the habitats of Solidago canadensis at two localities in Poland that differ in soil fertility and acidity. The content of organic carbon, nitrogen and phosphorus, as well as pH were analysed from soil samples collected from the sites invaded by S. canadensis and from the control sites. The composition and species richness of vascular plant communities at the same sites were also determined. The analyses revealed an increase in the soil organic carbon content and in the C/N ratio at the sites invaded by S. canadensis. The presence of S. canadensis also reduced the number of vascular plant species, mainly annuals and perennials. Thus, an increase in S. canadensis cover results in soil degradation and habitat homogenization.

This study examined a non-soil seed bank deposited inside the tussock cores of Carex cespitosa, a perennial plant with a tussock growth form. Based on the vertical structure of the seed bank in 20 tussock cores, the history of changes in plant species composition during succession in an unmowed grassland in the Bialowieza National Park was reconstructed. Three horizontal layers were distinguished in each tussock core: upper (corresponding to the initial forest stage), middle (transitory stage—forb and swamp communities) and bottom (early successional stage—grassland). The results showed that seeds of both the parental species and other species were stored inside the C. cespitosa tussock cores. More than 50,000 seedlings were found, representing 42 vascular plant species. The highest number of seedlings was recorded in the middle layer. Seedlings of swamp species were dominant in the upper layer, whereas seedlings of grassland species were dominant in the other layers. The highest number of C. cespitosa seedlings was observed in the upper layer. The most common seedlings in the middle layer belonged to the species Epilobium palustre, Lythrum salicaria and Cirsium palustre. In the bottom layer, the most common species of seedlings were grassland species, e.g. Lychnis flos-cuculi and Ranunculus repens. The protected seed bank inside this tussock species reflected recorded changes in species composition of these grasslands through time. Seed banks in this and other tussock-forming species represent a potentially useful tool for reconstructing recent developmental history of plant communities.

This study deals with population dynamics of Cirsium rivulare (brook thistle) present in a meadow that undergoes succession as a result of former disuse. The effect of the following in the succession, currently dominant clonal species and necromass on the performance of the brook thistle population (presence, size of clusters and reproduction) was investigated. The regression stage, the Cirsium rivulare population had attained after mowing, was discontinued. Different kinds of influence from the contiguous species on the brook thistle population could be identified. In the case of Filipendula ulmaria and Carex cespitosa , Cirsium rivulare clusters were found to be present on the edge of the dominant patches. In case of Carex acutiformis patches brook thistle ramets did not form clusters but were present among the sedge ramets. No Cirsium rivulare ramets were found in Phragmites australis and willow ( Salix cinerea , S. pentandra and S. aurita ) patches. The highest number of generative brook thistle ramets were observed in a Carex acutiformis patch, whereas the highest number of inflorescences on the shoots of the analysed species were identified in the patch dominated by Filipendula ulmaria . Experimental vegetation gaps were created in patches dominated by various species to determine the effect of necromass on the presence of Cirsium rivulare seedlings. A considerable rise in the number of Cirsium rivulare seedlings was noted in Carex acutiformis and Filipendula ulmaria patches following necromass removal in comparison with plots containing necromass. On the other hand, removing the necromass and foliage did not contribute to an increase in the numbers of brook thistle seedlings in the patch dominated by Cirsium rivulare itself.

Cirsium rivulare is a perennial plant that forms patches consisting of ramets resulting from sexual reproduction by seeds and asexual propagation by rhizome fragmentation. We examined the relationship between the size of patches and genetic differentiation of ramets within and between patches. Ramet genotypes were identified using microsatellites. From among 216 ramets examined in the studied population, 123 had a unique genotype, while 93 were clonal, i.e., their genotype was present in at least two ramets. The frequency of ramets with clonal genotypes was 43% and the frequency of unique genotypes was 57%. Ramets with identical genotypes were dominant in small patches. Large patches consisted of ramets with both unique and clonal genotypes, usually with the predominance of the latter. A molecular variance analysis showed the highest level of variance between ramets and the lowest between patches. Additionally, 21.02% of the total variance was recorded between ramets and within patches. The size of patches was correlated with the number of clonal ramets and the number of unique ramets, but it was not correlated with the clonality index. This population of C. rivulare is currently in a phase of decline from 30 years of vegetation transformation, and there appears to have been an increase in sexual propagation based growth over clonal propagation based growth. Hence, a predominance of ramets with unique genotypes was observed. This can happen as a result of disintegration of large patches and formation of gaps between them. These gaps become convenient places for seed germination and the subsequent development of seedlings.

The paper presents results of a study on the response of species growing in experimental gaps in the patches dominated by Carex acutiformis, C. cespitosa and Salix cinerea. The study was performed in a meadow area subjected to the process of succession in the Reski Range in the Białowieski National Park. Four patterns of seedlings recruitment in the experimental gaps were distinguished: pattern I - great number of seedlings with high richness of species, pattern II - great number of seedlings with low richness of species, pattern III - low number of seedlings with great richness of species and pattern IV - low number of seedlings with low richness of species.