While the red beech mostly overshadows springs and spring rivulets, it cannot withstand the waterlogging and occasional high water on the banks of the Wupper and the larger brooks. Here, black alder and ash can thrive as narrow riverine forests bordering the river and streams. With its efficient root aeration system, the alder is well adapted to changing water levels. The broad lateral roots of the ash that transition to strong tap roots enable it to thrive in dense and damp soils. Its fine roots propagate in the better aerated upper soil layers. If high water is only seldom and irregular, oak-hornbeam forests prevail along the banks in place of the riverine forests.
The highly changeable environmental conditions in riverine forests produce a microcosmic mosaic of varied locational characteristics. Riverine forests are therefore among Europe’s most species-rich and vital habitats.
In addition to numerous amphibians, reptiles and insects, they also offer excellent living conditions to many bird species.