New stand of invasive neophyte Ambrosia artemisiifolia L. and its potential reproduction

A new stand, formed by some fifty individuals of Ambrosia artemisiifolia L., an invasive plant of alien origin, was discovered at the Katowice railway station (southern Poland), in 2011. Two years later, the stand (increased to more than 160 individuals in the meantime) was re-visited, phytosociological survey was made, and four soil cores (5 cm deep and 80 cm(2) surface area, each) were taken for seed bank studies. The phytosociological sampling revealed 28 co-occurring vascular species, most of them representing hemicryptophyte and geophyte life forms. According to Ellenberg's values, the species pool indicated sunny (L7 and L8 species dominating) and semi-dry (mainly F4 species) habitat for the common ragweed population, whereas Zarzycki's soil granulometric data reflected coarse-grained soil. Albedo of the soil was lower than that of the vegetation thus sparsely vegetated sites were considered as heat accumulating microhabitats that might support establishment of the thermophilic A. artemisiifolia. During soil seed bank analysis a high number of naturally opened fruits (dehiscent achenes) were found (718.75 per m(2)) most probably indicating frequent germination in previous years. Greenhouse germination tests proved successful germination of 125 individuals per m(2), which was considered enough to maintain the A. artemisiifolia stand at the station. The results call attention to a newly discovered, established population with increasing demography of A. artemisiifolia, a highly allergenic introduced weed of Poland.