Exploring the key drivers of riparian woodland successional pathways across three European river reaches

Abstract

International audienceClimate change and river regulation are negatively impacting riparian vegetation. To evaluate these impacts, process‐based models are preferred over data‐driven approaches. However, they require extensive knowledge about ecohydrological processes. To facilitate the implementation of such process‐based models, the key drivers of riparian woodland successional pathways across three river reaches, in Austria, Portugal, and Spain, were explored, employing two complementary approaches. The principal component analyses highlighted the importance of the physical gradients determining the placement of the succession phases within the riparian and floodplain zones. The generalized additive models revealed that the initial and pioneer succession phases, characteristic of the colonization stage, appeared in areas highly morphodynamic, close in height and distance to the water table, and with coarse substrate, whereas elder phases within the transitional and mature stages showed incremental differences, occupying less dynamic areas with finer substrate. The Austrian site fitted well the current successional theory (elder phases appearing sequentially further up and distant), but at the Portuguese site, the tolerance of the riparian species to drought and flash flood events governed their placement. Finally, at the Spanish site, the patchy distribution of the elder phases was the remnants of formative events that reshaped the river channel. These results highlight the complex relationships between flow regime, channel morphology, and riparian vegetation. The use of succession phases, which rely on the sequential evolution of riparian vegetation as a response to different drivers, may be potentially better reproducible, within numerical process‐based models, and transferable to other geographical regions

Species composition and plant traits: Characterization of the biogeomorphological succession within contrasting river corridors

“…Other converging pathways were identified earlier, within the FBS model (Corenblit et al, ), as well as by other authors, without referring to the FBS model (Bendix & Hupp, ; Egger et al, ). This stresses the importance of identifying specific physical (hydrogeomorphological) and/or biological drivers for the successional pathway or trajectory considered (Muñoz‐Mas et al, ).…”

The Recruitment Niche Predicts Plant Community Assembly Across a Hydrological Gradient Along Plowed and Undisturbed Transects in a Former Agricultural Wetland

“…For example, in wetland communities, this disturbance does not necessarily kill the seeds, but can induce a spatial storage effect that favorably influences the species richness of seeds, seed abundance, and germination ability at the community level when compared to an undisturbed landscape (Devictor et al, 2007). Hydrological gradients also interact with interspecific interactions and competition to determine undisturbed community assemblages (Muñoz-Mas et al, 2017) and have been found to create differences in seed density and species diversity (Bekker et al, 2000). It is, therefore, necessary to consider the relationship between hydrological gradients and anthropogenic disturbance, such as plowing, to understand and predict the plant community that emerges and establish, which can be especially useful in the ecological restoration of previously disturbed sites.…”

Relier la biogéomorphologie fluviale à l’écologie évolutive : un focus sur les arbres riverains pionniers

“…At this fourth stage, the biogeomorphological entities have reached their stage of exosystemic maturity as functional units with many interacting species (e.g., bacteria, mycorrhiza, insects, invertebrates, plants) capable of supporting the nutritional requirements and sexual reproduction of the large mature trees. Only exceptional floods and lateral erosion of the banks or anthropogenic activities are capable to cause the complete destruction of such stabilized and resistant biogeomorphological entities (Jourdain et al, 2017;Martínez-Fernández et al, 2017;Muñoz-Mas et al, 2017). We suggest that the vegetated islands, banks and floodplains are potentially the result of a positive niche construction (Odling-Smee et al, 2003) by pioneer engineer trees.…”

“…Les entités biogéomorphologiques ont atteint leur stade écosystémique de maturité en tant qu'unité fonctionnelle de l'écosystème riverain comportant de nombreuses espèces en interaction (e.g., bactéries, mycorhizes, invertébrées, insectes, plantes) capables de soutenir les besoins nutritifs et la reproduction sexuée des grands arbres matures. Désormais, seules les crues exceptionnelles, l'érosion latérale des chenaux pendant des débits à pleins bords, ou les activités anthropiques sont en mesure de causer leur destruction complète (Dufour et Piégay, 2010 ;Jourdain et al, 2017 ;Martínez-Fernández et al, 2017 ;Muñoz-Mas et al, 2017). La durée de la phase écologique dépend ainsi de la fréquence et de la magnitude des crues destructrices, mais aussi du degré de mobilité latérale du ou des chenaux qui peut causer, par sapement latéral, la destruction de ces entités biogéomorphologiques (Jourdain et al, 2017).…”