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This paper presents the results of studies carried out on Ptelea trifoliata populations in the Wyszków Forest District in 1998 and 2013. P. trifoliata is a native species of North America (United States of America, northern part of Canada) and has a wide ecological range. However, it prefers fertile, wet soils and moderate light. In Europe, it is planted for its decorative value and is mainly found in synanthropic habitats (parks, graveyards, roadsides, fortifications) in Poland. The station of P. trifoliata is situated in the oak-hornbeam forest, Tilio-Carpinetum typicum, with a significant fraction of the stand consisting of Pinus sylvestris. Hop trees occur mainly along forest section lines and are rarely found inside the sections. In the last 15 years, an increase in the number and size of P. trifoliata clusters has been observed. The species spreads along forest section lines, which form a convenient migration route by creating favourable conditions for the germination and growth of seedlings (good access to light, fragments of bare soil). The presence of new individuals far from the pre-existing clusters indicates that the generative way of propagation dominates. Biometric measures indicate significant differences in length and width of whole leaves as well as leaflets, with leaves and leaflets of vegetative specimens significantly larger than generative ones.

As a consequence of the high rate of P. trifoliata expansion along forest section lines and occurrence of single specimens inside the forest sections, we assume this species to be potentially invasive.


Many ecological studies showed that species density (the number of species per unit area) in nonnative organism groups of the mountain areas decreases with increasing altitude. The aim of the paper is to determine the variability in the incidence of non-native plant species (neophytes) associated with the change in altitude and links of the invading taxons to reference habitat types, as well as their links to three ecologically very similar, however in natural conditions, different areas. In general, the most invaded habitats are those which are highly influenced by human activities. Firstly, data collection was conducted through field mapping of build-up areas in South-western Slovakia. Subsequently, with the assistance of ordination methods, we evaluated the level of association of invasive neophytes according to the set objectives. We found that altitude was an important factor determining variability of invasive neophytes’ occurrence. Total amount of habitats with invasive neophytes’ occurrence showed a linear increase along the altitudinal gradient. Many invasive neophytes adapted to abandoned habitats of upland territory were also able to grow along roads, and vice versa, abandoned and unused habitats of lowland areas created conditions for many typical invasive neophytes occurring along roads and habitats of gardens and yards. Railways of lowland areas provided habitats and means of spread of invasive woody neophytes. Gardens and yards were important sources of alien neophytes in all observed territories. Invasive neophyte Aster novi-belgii can be described as a very variable species tolerant to a wide range of factors limiting the spread of species along the elevation gradient.

publications recorded expansion of alien species (Ambrosia artemisiifolia L. (allergies!), Avena sterilis L. var. ludoviciana (Durieu) Fiori, Eleusine indica (L.). Gaertn., Iva xanthifolia Nutt., Senecio inaequidens DC.), spreading of species formerly cultivated for economic purposes (Asclepias syriaca L., Helianthus decapetalus L., Heracleum L. sp. div.) or medicinal and ornamental (Phytolacca americana L.) plants. Professor András Terpó is widely credited for his contribution to the taxonomic and chorologi- cal recognition of Arum genus variability in Europe

of species ( Fahrig, Merriam 1985 ; Franklin, Forman 1987 ; Freemark, Merriam 1986 ; Van Dorp, Opdam 1987 ; Hanski 1999 ; Eriksson, Ehrlén 2001 ). Landscape, according to the definition of the European Landscape Convention, is understood in this work in a physiognomic sense. The authors assumed that a landscape understood in this way, especially in lowland conditions and at a supra-local scale, is Land Use/ Land Cover (LULC). The share of individual patches of land use, and their composition and configuration in space, indicate the dominant type of landscape