Populus nigra L. establishment and fluvial landform construction: biogeomorphic dynamics within a channelized river |
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| Authors: | Dov Corenblit Johannes Steiger Gaspard Charrier José Darrozes Virginia Garófano‐Gómez Alexandre Garreau Eduardo González Angela M Gurnell Borbála Hortobágyi Frédéric Julien Luc Lambs Sébastien Larrue Thierry Otto Erwan Roussel Franck Vautier Olivier Voldoire |
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| Institution: | 1. Université Clermont Auvergne, Université Blaise Pascal, GEOLAB, Clermont‐Ferrand, France;2. CNRS, UMR 6042, GEOLAB – Laboratoire de géographie physique et environnementale, Clermont‐Ferrand, France;3. Université Paul Sabatier, CNRS, UMR 5563, GET – Géosciences Environnement Toulouse, Université Toulouse III, Toulouse, France;4. Université Paul Sabatier, INP;5. CNRS, UMR 5245, ECOLAB – Laboratoire écologie fonctionnelle et environnement, Université Toulouse III, Toulouse, France;6. Department of Biological Sciences, University of Denver, Denver, CO, USA;7. School of Geography, Queen Mary, University of London, London, UK;8. Université Clermont Auvergne, Université Blaise Pascal, Maison des Sciences de l'Homme, Clermont‐Ferrand, France;9. CNRS, USR 3550, MSH, Clermont‐Ferrand, France |
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| Abstract: | Populations of the riparian pioneer species Populus nigra L. which establish on alluvial bars within river channels modulate sediment dynamics and fluvial landforms. Dense cohorts of P. nigra have colonized gravel point bars along the channelized River Garonne, France, during the last 20 years and have enhanced the vertical, lateral and longitudinal development of the bars. For this period, the geomorphic characteristics of two wooded point bars on this laterally stable river are closely linked to the spatial distribution and intensity of establishment and resistance of different cohorts of P. nigra. Furthermore, P. nigra colonization dynamics were controlled by engineer effects of this same species. This relationship is illustrated by a significant correlation between key geomorphic and biological variables measured in situ and characterized with a set of four aerial photographs taken between 2000 and 2010. The development of wooded point bars, which are discrete biogeomorphic units, over the studied period, appear to result from a specific biogeomorphic positive feedback of matter aggregation and vegetation establishment related to sediment trapping and stabilization by pioneer engineer plants. We propose a conceptual model of biogeomorphic unit construction for channelized, lateral stable rivers. We consider the resultant biogeomorphic units as functional from an ecological point of view because P. nigra enhances at the cohort scale (i) its own inherent capacity to resist hydrogeomorphic disturbances, and (ii) its resilience capacity as a result of successful colonization, especially downstream of mature poplar stands. Copyright © 2016 John Wiley & Sons, Ltd. |
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| Keywords: | fluvial landform biogeomorphology black poplar vegetation establishment ecosystem engineer |
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