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.