Tidal Freshwater Forest Restoration at the European Elbe Estuary: Initial Establishment Success of Salix Species

ABSTRACT: Restoration of tidal freshwater forest is required according to European legislation for biodiversity conservation and compensation for human impact on estuaries. A large-scale project was set up to compensate for channel deepening at the port of Hamburg, the third largest port in Europe. The relief was modelled to allow tidal dynamics, and 2680 willows (genus Salix) were planted for a tidal freshwater forest in autumn 2022. Six characteristic Salix species were planted in different habitats at the restoration site. After one year, 75% of the individuals were established, whereas S. viminalis showed the highest establishment percentage (85.7), followed by S. rubens (72.6), S. triandra (70.7), S. alba (60.3), S. purpurea (51.3), and S. fragilis (37.7). The species diversity in the different habitats (stream valley meadow, reed stands, wet sinks, bar ground, in small bays, at tidal creeks) was preserved. The species differed in growth parameters and planting habitats: Salix alba and S. purpurea showed drought damage, but S. alba responded with resprouting; S. alba was least affected, whereas S. viminalis was most affected by browsing but similarly responded with strong resprouting. Salix triandra showed browsing damage but did resprout less. Salix fragilis and S. rubens behaved intermediary. The study demonstrates the initial establishment success of the Salix species one year after plantation with important implications for initial restoration management of tidal freshwater forest in European estuaries.