Chorological spectra of arable weed vegetation types in the Czech Republic

A data set of 2,730 phytosociological releves was used for a comparison of the basic chorological characteristics of the main vegetation types of weed vegetation in the Czech Republic. All releves were classified by the Cocktail method into the alliances: Caucalidion, Scleranthion annul, Veronico-Euphorbion, Oxalidion fontanae, Spergulo-Erodion and Arnoseridion minimae. The proportions of native species, archaeophytes and neophytes, as well as the proportion of species with particular distribution range types were calculated for each releve. The weed vegetation in the data set contained 560 species: 38.3% of them were native, 56.2% were archaeophytes and 5.5% were neophytes. The highest proportion of natives was found for the weed vegetation of poor sandy soils (alliance Arnoseridion minimae) and of humid areas (alliance Oxalidion fontanae). The highest proportion of archaeophytes was found in the thermophilous weed vegetation of Caucalidion and Spergulo-Erodion alliances, and the highest proportion of neophytes in Spergulo-Erodion alliance. Czech weed vegetation is predominantly composed of species of Euroasian temperate range type. These species prevail in weed vegetation of alliances Scleranthion annui and Oxalidion fontanae. Macaronesian-Mediterranean range types and Oriental-Turcestani-Mediterranean range types make up 25-38% of all weed species growing in the Czech Republic. These Mediterranean species dominate in the weed vegetation of alliances Caucalidion and Arnoseridion minimae, followed by alliances Veronico-Euphorbion and Spergulo-Erodion. The proportion of central European species is similar (about 10%, of species) in all the compared vegetation types except Spergulo-Erodion, where these species are rarer (only 5%). Other chorological types arc scarcely present in the weed vegetation of the Czech Republic.