Fluvial biogeomorphological feedbacks from plant traits to the landscape: lessons from French rivers in line with A.M. Gurnell’s influential contribution

Abstract

Research in fluvial biogeomorphology largely aims to promote our understanding of the interactions between riparian vegetation and fluvial morphodynamics within riverine ecosystems. Starting at the end of last century, Angela M. Gurnell has made a major contribution to fluvial geomorphology by considering, in addition to water flow and sediment transport, explicitly riparian, and later also aquatic vegetation and thus significantly promoted the fluvial biogeomorphological approach from its beginnings until today. The objective of the present paper is to present a set of studies and results obtained over the last twenty years by the authors and many collaborators, including Angela M. Gurnell, on a panel of French rivers: Tech, Garonne, Isère and Allier Rivers. In particular, feedback mechanisms between fluvial morphodynamics and riparian vegetation dynamics were investigated directly in the field and also using high resolution remote sensing at the scale of individual plants, populations, communities and landscapes, as well as during semi-controlled ex situ experiments at the scale of individual plants. Collectively, the authors’ research conducted over the past 20 years contributed to elucidate some key aspects of the feedback dynamics between the lowest and highest levels of the riparian ecosystem organisation. This article presents and discusses those key aspects. The gradually obtained results contributed to better understand and quantify feedbacks between river morphodynamics and vegetation at nested spatiotemporal scales, from plant species traits to the riverine landscape. Furthermore, the biogeomorphological approach advocated for more than twenty years now, has clearly helped to contribute to the enlargement of the discipline of geomorphology to ecology as well as evolutionary ecology, and to the development of a more integrative vision to study earth surface processes.