| Abstract: | The meliorated Oberes Rhinluch fen is used by agriculture as grassland with maize-cultivation on about 30 % of its area. In the ditch system of this area with water levels of 30 to 150 there were observed 67 taxa of aquatic plants and marsh plants, of which about 15 achieve covering degrees of more than 3 % and form 80 … 90 % of the biomass. Biomasses of between 20 … 184 g/m2 dry weight (Lemna) and 504 … 1612 g/m2 (Phragmites) are obtained in pure populations. In mixed populations the biomasses amount to between 304 and 916 g/m2 dry weight. According to their density and orientation, riparian copses and trees cause a more or less intense overshadowing of ditches, resulting in a considerable reduction of the biomass of macrophytes. By copses and trees on the south side of the waters the light available may be reduced to 30 %, from which a reduction of the biomass to 10 … 30 % results. By means of such planting it is possible to control the growth of plants in order to reduce the necessary and very expensive weed-removal and bottom-clearing actions. |
