Figure 2: Multi-scale theoretical model of the feedback between riparian vegetation dynamics and river morphodynamics.
Individual plant and population level feedbacks: response and effect traits of Populus nigra
In settings exposed to high tractive forces and sediment erosion or burial during floods, high temperatures and hydric stress during summer low flows, such as on alluvial bars, the completion of the life cycle of certain woody pioneer riparian species such as P. nigra requires a progressive modification of hydrogeomorphological conditions and habitat, from germination to sexual maturity. The latter is reached when the habitat and its topographic surface attain higher, more stable levels, characterized by the deposition and accumulation of finer sediments, nutrients, and organic matter, and less exposed to the risk of destruction by floods.
Individual plants may form together at the colonization stage more or less compact and monospecific woody populations which are very relevant for the study of biogeomorphological feedback from the individual to population levels. In riparian contexts in the European Northern hemisphere, P. nigra has become a model species for field studies but also ex situ experiments (Figs. 3 and 4).