Figure 6: Observed feedback at the community mosaic level. (a) Community mosaic of the Allier River with a predominant physical signature and (b) the Isère River with a predominant biotic signature on the alternate bars in the active tract.
Conclusion
The here presented results from various biogeomorphological investigations on French rivers underpin the important role played by riparian vegetation in such riverine ecosystems of the temperate zone in modulating hydrogeomorphological processes and fluvial landforms, as early advocated by Angela M. Gurnell. Her essential suggestions, having led at the time to some controversies, are now widely accepted and, as shown here, refined at different spatiotemporal scales as well as different ecosystem levels, from the individual/micro-form to the community mosaic/fluvial style.
Today, the fluvial biogeomorphological lessons learned from the French rivers, in addition to other studies in France, Europe and overseas, open new perspectives in the comprehensive study of riverine systems and their management considering feedback mechanisms between water, sediment and riparian plants. The here presented results, often obtained in close collaboration with Angela M. Gurnell, point to the need to better quantify, understand and model feedbacks between river morphodynamics and vegetation at nested spatiotemporal scales as well as its resilience aptitudes to disturbances. Indeed, the resilience of rivers may largely dependent on feedbacks between hydrogeomorphology and the dynamics of engineer populations, such as black poplar. Its comprehension, based on the biogeomorphological approach advocated, is needed to better predict future river evolutionary trajectories in the light of human pressures as well as restoration measures, climate and global change.
In addition, the different methods and approaches employed here and observations made, clearly helped, over the last twenty years, to contribute to the enlargement of the discipline of geomorphology to ecology and also to evolutionary ecology, endorsed by the biogeomorphological approach.