Die tausendjährige Geschichte des Teesdalio-Arnoseridetums
Developments in the techniques used in studying past vegetation and the availability of good sample material enable the reconstruction, in considerable detail, of former plant communities on the basis of fossil material. In exceptional circumstances, it is even possible to reconstruct a community to the level of association, i.e. the basic syntaxonomic unit. This is illustrated by reference to the Teesdalio-Arnoseridetum, a community of winter cereals. The reconstructions are based on the results of pollen analyses of plaggen soils (Plaggenesch) and macrofossil analyses of carbonized cereals (generally dominated by rye) with particular reference being paid to the weed component. It is shown that the Teesdalio-Arnoseridetum community developed during the early Medieval period on poor soils. This development was associated with the introduction of winter rye, which was cultivated year after year on the same fields in the Pleistocene areas, south of the North Sea. As a result of application of fertilizers and crop rotation, this association has become, in recent times, poor in character species and, indeed, is threatened with extinction.