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.
Keywords: Fluvial biogeomorphology, biogeomorphological
feedback, riparian vegetation, Populus nigra , black poplar,
ecosystem engineer, plant traits.
Introduction
In order to fully understand river behaviour and trajectories of change,
Angela M. Gurnell early pointed out the need to study interactions
between the biological and physical compartments of ecosystems, i.e.,
the responses of organisms to the physical environment and their effects
on that physical environment (Gurnell and Gregory, 1984, 1995; Gurnell,
1995). Research in fluvial biogeomorphology largely aims to promote our
understanding of the interactions between riparian vegetation and
fluvial morphodynamics within riparian ecosystems. Angela M. Gurnell has
made a major contribution by considering explicitly vegetation, first
riparian (living vegetation, propagules and large woods) and then
aquatic, in addition to water flow and sediment transport into fluvial
geomorphology and thus to promote the fluvial biogeomorphological
approach from the end of the last century until today (e.g., far from
exhaustive: Gurnell, 1997; Gurnell et al., 2000, 2001, 2004, 2005, 2006,
2012, 2013, 2016a, 2016b, 2018, 2019; Gurnell and Petts, 2002, 2006;
Gurnell, 2014; Gurnell and Grabowski, 2016; Gurnell and Bertoldi, 2020;
Gurnell and Bertoldi, 2022). A bibliographic research on the Web of
Science (all databases) using the combined terms ”riparian vegetation” +
”geomorphology” + ”river*” showed that out of a total number of 711
articles archived on 11th November 2023, more than
12% were authored or co-authored by A.M. Gurnell, which represents
86 articles. The second-best score is 33 articles (Fig. 1).
The biogeomorphological approach applied to rivers is necessarily
ambitious because requires skills in geomorphology and plant ecology and
because the modalities of interactions between hydrogeomorphological
components and riparian vegetation are multiple and nested at various
spatiotemporal scales. Thanks to Angela M. Gurnell’s influential
research and contribution to fundamental and applied river sciences,
fluvial biogeomorphology is now well situated at the interface between,
geomorphology, ecology and river management (e.g., Gurnell et al.
2016a,b).