Reintroduction of the dwarf bulrush (Typha minima Funck ex Hoppe) at the river revitalisation measure Stams-Rietz (Inn river, Austria)

Abstract

The dwarf bulrush (Typha minima Funk ex Hoppe) is considered as a sensitive target species in natural alpine river landscapes. It disappeared from many rivers due to straightening, thus reintroduction efforts for species conservation have been initiated. Recently, at the Inn river between Stams and Rietz, i.e. a section of about 3 kilometres, the river bed was widened up to 75 meters and a branch as well as a back water zone were created and bank protection was removed. This measure provides potential habitats for T. minima, thus its reintroduction was carried out in 2023 along the banks. Plants originated from an ex-situ culture from the Botanical Garden of the University of Innsbruck, where propagation was carried out with seeds from the Lech catchment. Only 2 weeks after the reintroduction of 1500 plants, a 100-year flood occurred, which washed away many plants and only 17 remained. Thus, additional specimens (n = 37) were planted. Overall, in November 2023 a total of 54 specimens were established and genetically characterised to assess the initial genetic composition for subsequent monitoring. In June and July 2024, again high flows affected the stocks. However, at several sites the stocks were able cope with these conditions and may form a new population along the Inn river.