Functional challenges of reed bed restoration in the large Alpine lakes
References
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Abstract
Lacustrine reed beds are structuring habitats of riparian zones, providing shelter and breeding grounds for numerous species while ensuring major biogeochemical functions that support environmental quality. Beyond carbon sequestration, they also contribute to the nitrogen cycle by modulating its availability through nutrient transformations linked to the activity of plant and microbial communities in the sediments. Aquatic reed beds have significantly declined in large Alpine lakes, mainly as a result of shoreline development and water level regulation. Research conducted by the Lake Ecosystems Research and Development Unit (ECLA) shows that nitrogen regulation in riparian zones is closely dependent on hydrology and the presence of reeds. Nitrification, the aerobic transformation of ammonium into nitrate by bacteria, remains very limited when sediments are continuously submerged, whereas the assimilation of ammonium by reeds constitutes a major sink, significantly reducing its concentration in sediments down to a depth of 30 cm. These results highlight that reed bed restoration cannot rely solely on replanting but requires an integrated approach combining ecological engineering and hydrological management to restore biogeochemical processes and associated ecosystem services. Our findings thus provide operational guidance for future restoration actions and help strengthen the resilience of riparian ecosystems in the face of global change.