Linking fluvial biogeomorphology to evolutionary ecology: a focus on pioneer riparian trees

摘要

In streams, riparian trees such as poplars or willows respond to the flood regime, but they also control hydrogeomorphological processes and the dynamics of river forms. It is now recognized that feedbacks between riparian trees and hydrogeomorphological processes occur during their lifetime. These feedbacks lead to the emergence of biogeomorphological units such as fluvial islands, banks and levels of vegetated alluvial plain. Based on our empirical observations and a synthesis of the most recent discoveries in geomorphology, plant ecology and evolutionary ecology, we present the four stages of co-construction between riparian forests and fluvial forms. We describe the close bidirectional coupling between biological and geomorphological components as a "biogeomorphological life cycle" during which the biological development of the plant requires a series of geomorphological changes of river beds under biotic control. We emphasize that riparian trees that grow in dense stands protect each other from mechanical stresses linked to flow and sediment transport. Together, they also trap fine sediment, organic matter and nutrients more effectively. Thus, they strengthen their ability to survive, to exploit resources and to reach sexual maturity between exceptional high magnitude floods, which corresponds to a facilitation interaction.