Ruderal- und Adventivflora von Aufschüttungen in Bremen: sporadische Pracht auf vergänglichem Neuland

We investigated massive artificial deposits of soils, sands and debris, which accommodate a speciesrich urban flora in the municipal area of Bremen. They originate from extensive rearrangements of old port areas, large soil coverings of rubbish deposits or highway construction. The extended open areas are optimal colonization sites of typical annual, bi-annual and perennial species: local rurals as well as new adventitious invaders. Before the sites were finally sealed by roads and houses, many of the up to now rare species in the Bremen area are able to complete their reproduction cycle (e. g. Chenopodium hybridum, C. foliosum, Amaranthus blitum, Rumex salicifolius). Potentilla supina, Pastinaca sativa ssp. urens, Dittrichia graveolens and Carduus acanthoides were recorded in Bremen for the first time. Our results show that episodical but highly dynamic sites enrich the urban diversity considerably. Further periodical disturbance, turn-overs and displacements could preserve the high species diversity of early successional stands, which have become rare in our highly controlled urban landscape.