Figure 5: Observed feedback at the community level. (a) Herbaceous and arboreous communities in the active tract of the Tech River and (b) the Allier River. Photographs: Dov Corenblit (a) and Franck Vautier (b).
Landscape-level feedbacks: biological versus physical forcing in contrasted hydrogeomorphological contexts
At the scale of the fluvial landscape, our research was carried out primarily on the Tech, Allier and Isère Rivers, using two and three-dimensional spatiotemporal analyses with GIS, stereo and multi-image photogrammetry and LiDAR. These three rivers differ in their morphodynamics and the level of anthropogenic pressure. The Tech is a Mediterranean torrential river with a very irregular hydrogeomorphological regime. Anthropogenic pressure has led to channel bed vertical incision, lateral stabilization of its banks and therefore to a certain loss of dynamics despite the virulence of flash floods. The Allier is a high-energy river that is, in its lower section (RNNVA) still relatively free to move laterally in a wide meander belt. The Isère River is a high-energy river that has was laterally confined with huge embankments. This resulted in a channel mostly straightened and migrating alternate bars progressively stabilizing and heavily colonized by vegetation.
Spatial analyses of the feedback between colonization/vegetation succession dynamics and landscape/fluvial style dynamics on these three rivers have made it possible to highlight different types of responses and effects of riparian vegetation at the landscape scale and thus to estimate the impact of local feedbacks (at the scale of traits and population) on the organization of the habitat mosaic over few decades (Fig. 6).