Investigations on recent and subfossil salt-marsh vegetation of the East Frisian barrier islands in the southern North Sea (Germany)
Freund, Holger; Petersen, Jö rg; Pott, Richard
Investigations into the distribution and long-term dynamics of salt-marsh vegetation were carried out on the East Frisian barrier islands of Juist and Langeoog, Germany. These investigations were based on the comparison of vegetation maps made at various times in the mid and later twentieth century, monitoring by permanent plots, present-day vegetation mapping combined with precise altimetry, and the application of various palaeoecological techniques including pollen, diatom and plant macrofossil analyses. The last mentioned techniques enabled salt-marsh vegetation dynamics to be studied over a time span of up to two millennia. Selected data were digitised, geo-referenced and processed using GIS in order to establish scenarios of potential vegetation development in salt marshes depending, for example, on sea-level fluctuations or de-embankments. In the present study, it is shown that the salt-marsh vegetation of the East Frisian islands have been influenced by sea-level fluctuations, and by people and their cattle since the Middle Ages. However, the composition of particular vegetation units has remained more or less stable, with the changes being confined to the spatial pattern of the plant communities. The main recent change is that associated with summer-dike construction in the saltmarsh area "Sommerpolder" on Langeoog. This strongly influenced the vegetation patterns which have been monitored since the beginning of diking.