Alluvial Forest Succession

Germination, establishment and distribution of hardwood riparian forest species - Basics for a process-oriented modelling of the riparian forest succession

Due to far-reaching interventions in the hydrology of rivers and alluvial plains and a significant intensification of agricultural use, habitats in alluvial zones are among the most threatened habitats in Germany and Europe. According to the floodplain status report for Germany, the proportion of near-natural alluvial forests is only about 1% of recent river floodplains. In the National Strategy on Biological Diversity, the "restoration, re-dynamisation and development" of floodplain forests is mentioned as one of the objectives in the area of "rivers and floodplains".

Dike realignments are the most effective method to reactivate formerly hydrologically dynamic floodplain areas. Individual back dikes have already been carried out, e.g. at the Mittelelbe near Lenzen, further back dikes are being implemented or planned. At the time of the dike realignment, the areas mostly have arable land or grassland and thus plant species communities that have not been exposed to a near-natural flooding regime for a long time. Therefore, a secondary succession takes place after a recirculation.How this takes place under hydrodynamic conditions that are no longer natural is unclear with regard to reclaimed areas and predictions are therefore difficult.

Alluvial forests naturally represent the climatic plant communities of the alluvial habitats of Central Europe. This means that in the absence of human use, softwood and hardwood floodplain forests would establish themselves in the active floodplain areas. Which of these two types of alluvial forest is characteristic depends on the prevailing hydrodynamics. Thereafter, the softwood floodplain forests occupy the deeper and longer flooded areas, while the hardwood floodplain forests occupy the higher and shorter floodplain areas. Thus, the species population is selected according to the respective flooding tolerance. However, this scheme is greatly simplified, as the occurrence of floodplain forests also depends on stochastic events, such as colonisation, and the availability of open soil.  

Against this background, i) the current distribution of typical wood species of the floodplain forest is determined, ii) the regeneration of these species along the prevailing hydrological gradients is investigated and iii) the influence of flooding duration and time on the establishment of wood species of the floodplain forest is recorded in detail.
 

Project information

Duration: 2016-2019

Project participants: PD Dr. Tobias W. Donath, Dr. Kristin Ludewig (Professur für Landschaftsökologie und Landschaftsplanung, Justus-Liebig-Universität Giessen)

Supporter: Federal Institute of Hydrology (BfG)