Flow-divergence feedbacks control propagule retention by in-stream vegetation: the importance of spatial patterns for facilitation

• Published in: Aquatic Sciences
• Main Authors: Cornacchia, Loreta, van Der Wal, Daphne, van de Koppel, Johan, Puijalon, Sara, Wharton, Geraldene, Bouma, Tjeerd
• Other Authors: Royal Netherlands Institute for Sea Research (NIOZ), Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés (LEHNA), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE)-Centre National de la Recherche Scientifique (CNRS), Groningen Institute for Evolutionary Life Sciences Groningen (GELIFES), University of Groningen Groningen, Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, Spatial Ecology Department, Netherlands Institute of Ecology (NIOO-KNAW), School of Geography, Queen Mary University of London (QMUL)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: Aquatic macrophytes Bio-physical feedbacks Stress divergence Establishment Flume tank Hydrochory; aquatic macrophytes; bio-physical feedbacks; stress divergence; establishment; flume tank; hydrochory; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDE]Environmental Sciences; Groenlandia
• Online Access: https://univ-lyon1.hal.science/hal-02006278; https://univ-lyon1.hal.science/hal-02006278/document; https://univ-lyon1.hal.science/hal-02006278/file/Cornacchia2019-AqSc-HAL.pdf; https://doi.org/10.1007/s00027-018-0612-1

International audience Facilitation (enhancement of propagule retention in this case) is increasingly recognized as an important driver of biodiversity, but it is still unknown if facilitation during dispersal and colonization is affected by self-organized spatial pattern formation. We investigated the ability of in-stream submerged macrophyte patches to trap the vegetative propagules of three species (Berula erecta, Groenlandia densa, Elodea nuttallii in two size classes: 13–22 and 40–48 cm long), and to potentially benefit the colonization of these three species. We tested the effects of propagule traits, hydrodynamic forcing, and spatial patch configuration on propagule trapping. Propagule buoyancy was negatively correlated with trapping chance, while propagule size did not influence trapping. Species-specific differences in buoyancy were maintained for weeks after fragmentation. Propagule retention was interactive and conditional upon the interplay between incoming flow velocities and vegetation spatial patterning. In the flume experiment at low flows, a patchy configuration (one patch filling 66% of the flume width) retained more surface-drifting propagules (B. erecta, G. densa), than near-homogeneous cover (two patches close together, filling the entire flume width). In contrast, retention of sinking E. nuttallii propagules increased in the two-patch configurations. In flume and field releases where patches did not completely fill the channel width, water flowed around the patches rather than over or through them. This resulted in low-flow velocity areas within patches where canopies were upright and propagules were retained, and higher velocity flows around patches. In contrast, when vegetation filled the channel width, water could not be diverted laterally around the patches and preferentially flowed over them, causing the canopies to bend and reduce their trapping capacity. In flume experiments at high flows, retention of all species decreased, regardless of vegetation configuration, as propagules ...