Linking biogeomorphic feedbacks and hydrologic connectivity as key drivers of riverine ecosystem functioning

River corridors, i.e. channels and the adjacent floodplains, are hotspots of biodiversity and provide manifold ecosystem services. Their landscapes emerge from strong interactions between hydromorphology and vegetation. These biogeomorphic feedbacks not only shape planform development but also control riverine ecosystem functioning as underlying foundation of biodiversity and ecosystem service provision. Understanding these hydromorphology-vegetation interactions is central to the growing sub-discipline of biogeomorphology. Regular disturbances such as floods and droughts reorganize channels, generating pronounced spatiotemporal variability in hydrology and landform heterogeneity that promotes the recruitment of biogeomorphic keystone species such as Salix, Populus or Hippophae. Following establishment, these species can cross engineering thresholds, modify habitat conditions, and shape successional trajectories. The fluvial biogeomorphic succession model is a central framework for conceptualizing and studying these hydromorphology-vegetation feedbacks. Today, many rivers exhibit reduced geomorphic dynamics due to anthropogenic modifications and, simultaneously, face hydrologic change driven by climate change.
In our contribution, we apply the biogeomorphic succession model to the Naryn River in Kyrgyzstan, a still free flowing river on a length of more than 600 km. However, dams are under construction and expected to strongly modify hydromorphological and ecological dynamics in future. We found that within-channel hydrogeomorphic processes and disturbances exert a substantial – yet often overlooked – control on floodplain habitat development and their ability to provide ecosystem services. Even small changes amplified by biogeomorphic feedbacks can trigger the crossing of tipping points and shift ecosystem trajectories at reach scale. A fundamental mechanism is the determination of habitat availability for plant communities by the interplay of hydrologic connectivity and biogeomorphic feedbacks. Landforms arising from these feedbacks and associated with shallow groundwater are particularly important, acting as key habitat patches and biodiversity reservoirs along river corridors. Beyond the widespread anthropogenic influence on river corridors, climate change may shift discharge regimes and other boundary conditions, subtly reorganizing vegetation–hydromorphology couplings and potentially driving changes in river typology and riparian ecosystems. As biogeomorphic feedbacks and their response to anthropogenic river modifications and climate change are a key driver of riverine ecosystem functioning, it is crucial to further extend our existing scientific understanding and transform it into science-based, integrated river and floodplain management.