Ruderal- und Saumgesellschaften des Okertals
Ruderal and skirt communities of the Oker valley (Southeast Lower Saxony) are investigated and documented by phytosociological releves. While in the upper part of the Harz mountains there are nearly no nitrophilous plant communities along the course of the river except the Alopecuretum aequalis, the river gravels in the foreland are settled by the Echio-Melilotetum. Grasslands poor in species like the Armerietuni halleri grow on elevated areas of the gravel banks. The northern part of the 'Okersteinfeld' is especially rich in species and communities: Cuscuto-Calystegietum, Urtico-Cruciatetum, Dipsacetum pilosi, Echio-Melilotetum, Cirsium eriophorum community, Onopordion communities, as well as liana dominated stands with Clematis vitalba, Humulus lupulus, or Coronilla varia. Thermophilous Vegetation (Onopordetum acanthii, Vicia tenuifolia community) is to be found at the steeps of the palatinate Werla. The middle course of the Oker from Schladen to Braunschweig is accompanied by Cuscuto-Calystegietum, Chaerophylletum bulbosi, Urtico-Cruciatetum and intermediates of them. The embankments of the lower course are settled by the Calystegio-Archangelicetum; Bidention communities are to be found only sporadically. Thalictrum flavum and Filipendula ulmaria communities are establishing on disused meadows in the valley. At the terrace edges interesting stands with geophytes like Allium carinatum or Tulipa sylvestris are to be found.