This is the first complete inventory of alien vascular plant taxa for the Slovak Republic. The presented database contains information on family affiliation, residence status, invasion status, time of introduction, mode of introduction, planting purpose, abundance and distribution within phytogeographic regions, types of invaded habitats and syntaxa, and life forms and geographical origin of the alien taxa. In total, 21.5% of the total flora is made of up of alien taxa, comprised of 282 archaeophytes that make up 6.6% and 634 neophytes 14.9% of the total number of taxa, respectively. The majority of the alien taxa are casuals (57.6%), 39.1% are naturalized and 3.3% invasive. Most of them come from Europe (32.8%) and Asia (32.8%), followed by Africa (12.2%) and North America (10.8%). The database contains members of 98 families of which the Asteraceae, Brassicaceae, Fabaceae, Poaceae, Amaranthaceae and Rosaceae are the most represented. Almost 50% of the alien taxa are therophytes. Hemicryptophytes (26.3%) and phanerophytes (15.6%) are also abundant. More of the alien taxa were introduced deliberately (49.0%) than unintentionally (43.9%), and the majority were introduced as ornamental plants (55.9%). Of the total number of alien taxa, 45.2% are recorded from less than five localities. Most of them prefer human-made habitats; they are found in 137 phytosociological alliances, with those richest in alien taxa categorized as synanthropic vegetation.
A series of maps showing the level of invasion of the Czech Republic by alien plants was developed based on a quantitative assessment of the level of invasion of 35 terrestrial habitat types at different altitudes. The levels of invasion were quantified for 18,798 vegetation plots, using two measures: proportion of the species that are aliens and total cover of alien species. Separate assessments were made for archaeophytes and neophytes. Within each habitat, the level of invasion was related to altitude using generalized linear models. The level of invasion, depending on the measure used, decreased with altitude in 16 out of 20 habitats for archaeophytes and 18 out of 23 for neophytes. In two habitats, one measure of the level of invasion increased with altitude for archaeophytes. The values of the level of invasion predicted by generalized linear models for particular combinations of habitats and altitudes were projected onto a land-cover map and digital elevation map of the country. Four maps showing the level of invasion were produced, based on the proportion of the species that are archaeophytes or neophytes, and cover of archaeophytes and neophytes. The maps show that both archaeophytes and neophytes are most common in lowland agricultural and urban areas, whereas they are sparsely represented in mountainous areas. At middle altitudes, agricultural areas are more invaded than forested areas. Outside agricultural and urban areas, high levels of invasion are found especially in lowland sandy areas and river corridors.
Based on a combination of data from the Czech National Phytosociological Database and expert knowledge, a database of vascular plant species pools for 88 habitats, representative of the diversity of Czech vegetation, was compiled. This database contains 1820 native species, 249 archaeophytes and 278 neophytes, each assigned to one or more habitats. Besides the data on species occurrence in different habitats, the database contains information on a species’ ecological optimum in the habitat or its dominance. The largest pools of native species were found in rather rare habitats of dry and warm herbaceous or woody habitats at low altitudes, some of which contain > 530 species (maximum of 695 species for thermophilous forest fringes). These were followed by common habitats on mesic soils. The smallest pools of native species were in saline, aquatic and bog habitats ( 350 native species always contained > 5 archaeophytes and > 5 neophytes, and often many more. Two hundred and thirty two native species, 18 archaeophytes and 30 neophytes were identified as potential dominants in at least one habitat. However, potentially dominant species made up less than 3% of the species pool for 78 out of 88 habitats. Larger percentages (up to 14.6%) of potential dominants were included in habitats with small species pools and species-poor stands (e.g., aquatic, saline and mire habitats). The number of habitats in which a species occurred was used as a measure of its ecological range. Most ecological generalists were found among the native species, less among the archaeophytes and least among the neophytes. Out of the 36 species that occur as dominants in three or more habitats, 34 were native (many are grasses), onewas an archaeophyte (Cirsium arvense) and one was a neophyte (Impatiens parviflora).