Invasions by alien plants in the Czech Republic: a quantitative assessment across habitats
Occurrence of alien plant species in all major habitats of the Czech Republic was analysed using a data set of 20,468 vegetation plots, classified into 32 habitats according to the EUNIS classification. The plots contain on average 9% archaeophytes and 2.3% neophytes; for neophytes, this proportion is much smaller than 26.8% reported for the total flora of the country. Neophytes with the broadest habitat range were Impatiens parviflora (Balsaminaceae), Epilobium ciliatum (Onagraceae), Agrostis gigantea (Poaceae), Bidens frondosa (Asteraceae, EPPO List of invasive alien plants), Conyza canadensis (Asteraceae), Trifolium hybridum (Fabaceae), Robinia pseudacacia (Fabaceae), Medicago sativa (Fabaceae), Solidago canadensis (Asteraceae, EPPO List of invasive alien plants), Erigeron annuus (Asteraceae), Aster novi-belgii (Asteraceae), Cytisus scoparius (Fabaceae), Juncus tenuis (Juncaceae), Lupinus polyphyllus (Fabaceae, EPPO List of invasive alien plants) and Veronica persica (Scorphulariaceae). Most neophytes are found in a few habitats: only 5.6% of them were recorded in more than 10 habitats. By contrast, archaeophytes, and especially native species, tend to occur in a broader range of habitats. Highest numbers of aliens were found on arable land, in annual synantropic vegetation, trampled habitats and anthropogenic tall-forb stands. These habitats contain on average 22-56% archaeophytes and 4.4-9.6% neophytes. Neophytes are also common in artificial broadleaved forestry plantations; they also tend to constitute a high percentage of the cover in wet tall-forb stands, but are represented by fewer species there. Plots located in raised bogs, alpine grasslands, alpine and subalpine scrubs, and natural coniferous woodlands are entirely or practically free of alien species. The ratio between archaeophytes and neophytes was high in semi-natural dry and mesic grasslands and low in disturbed habitats with woody vegetation, such as artificial broadleaved forestry plantations, forest clearings and riverine willow stands. Results of this study do not support the hypothesis that species-rich communities are less prone to invasions, at least at the scale of vegetation plots.
Sources
Chytrý M, Pyšek P, Tichý L, Knollová I, Danihelka J (2005) Invasions by alien plants in Czech Republic: a quantitative assessment across habitats. Preslia, Praha, 77: 339-354.