Niche construction within riparian corridors. Part I: Exploring biogeomorphic feedback windows of three pioneer riparian species (Allier River, France)

• Published in: Geomorphology (Amsterdam, Netherlands) Netherlands), 2018-03, Vol.305, p.94-111
• Main Authors: Hortobágyi, Borbála, Corenblit, Dov, Steiger, Johannes, Peiry, Jean-Luc
• Format: Article
• Language: English
• Subjects: Biodiversity and Ecology; Biogeomorphic feedback window; Environment and Society; Environmental Sciences; Environmental studies; Establishment area; Geography; Global Changes; Humanities and Social Sciences; Longitudinal and transverse gradients of alluvial bars; Riparian Salicaceae species
• ISSN: 0169-555X; 1872-695X
• DOI: 10.1016/j.geomorph.2017.08.048

Within riparian corridors, biotic-abiotic feedback mechanisms occur between woody vegetation strongly influenced by hydrogeomorphic constraints (e.g., sediment transport and deposition, shear stress, hydrological variability), fluvial landforms, and morphodynamics, which in turn are modulated by the established vegetation. During field investigations in spring 2015, we studied 16 alluvial bars (e.g., point and lateral bars) within the dynamic riparian corridor of the Allier River (France) to assess the aptitude of three pioneer riparian Salicaceae species (Populus nigra L., Salix purpurea L., and Salix alba L.) to establish and act as ecosystem engineers by trapping sediment and constructing fluvial landforms. Our aim is to empirically identify the preferential establishment area (EA; i.e., the local areas where species become established) and the preferential biogeomorphic feedback window (BFW; i.e., where and to what extent the species and geomorphology interact) of these three species on alluvial bars within a 20-km-long river reach. Our results show that the EA and BFW of all three species vary significantly along the longitudinal profile, i.e., upstream-downstream exposure on the alluvial bars, as well as transversally, i.e., the main hydrological connectivity gradient from the river channel toward the floodplain. In the present-day context of the Allier River, P. nigra is the most abundant species, appearing to act as the main engineer species affecting landform dynamics at the bar scale; S. purpurea is established and acts as an ecosystem engineer at locations on alluvial bars that are most exposed to hydrosedimentary flow dynamics, while S. alba is established on the bar tail close to secondary channels and affects the geomorphology in mixed patches along with P. nigra. Our study highlights the role of functional trait diversity of riparian engineer species in controlling the extent of fluvial landform construction along geomorphic gradients within riparian corridors exposed to frequent hydrogeomorphic disturbances. •Populus nigra, Salix purpurea and alba are engineer species of the Allier River.•Species' establishment areas vary along two major gradients on alluvial bars.•Species' biogeomorphic feedback windows vary along two gradients on alluvial bars.•Biosedimentation depends according to species and their physiognomy.•Important biogeomorphic role of functional trait diversity of riparian engineers