Abstract
Propagule dispersal is fundamental to the colonization of new habitats, metapopulation connectivity, and gene flow and thus enables saltmarsh species to cope with global change. In this study, mesocosm and flume experiments were used to quantify the effects of different dispersal units (i.e. seed, spikelet, inflorescence, and plant fragment-containing seeds) and abiotic conditions on the dispersal processes of 4 globally distributed saltmarsh species: Salicornia europaea, Scirpus maritimus, Spartina anglica, and Elymus athericus. The results showed that (1) moving seawater has a species-specific effect on buoyancy, leading to prolonged floatability of high tidal-flat species E. athericus and reduced floatability of pioneer species; (2) tidal currents increase dispersal speed, whereas wind can have additive or antagonistic effects on current-dominated dispersal speed depending on its direction; (3) wave action reduces dispersal speed, but this effect becomes smaller with increasing wave magnitudes and/or applied co-directional wind; (4) dispersal speed may vary depending on the physical forcing and type and morphology of the dispersal units, but the largest species effect is related to the period in which units remain buoyant; and (5) the dispersal potential of saltmarsh species in wind wave-dominated coastal environments can be ordered as follows: E. athericus > S. maritimus > S. anglica > S. europaea. This study provides valuable guidance for future numerical hydrodynamic models of saltmarsh dispersal and establishment, allowing more accurate prediction of the distributional responses of saltmarsh species to climate change, thereby supporting appropriate management and restoration strategies.
Highlights
Salt marshes are increasingly valued because of their capacity to form elevated biogeomorphic landscapes by attenuating hydrodynamic energy (Bouma et al 2005, 2007, Temmerman et al 2007)
The saltmarsh species Salicornia europaea, Scirpus maritimus (Scirpus), Spartina anglica (Spartina), and Elymus athericus (Elymus) were selected as representatives of common functional species in salt marshes worldwide (Fig. 1; for Salicornia see e.g. Ellison 1987; for Scirpus see e.g. entity is the less likely it is that it can be supported by Charpentier et al 2000; for Spartina see e.g. Cao et the surface tension of water (Vogel 1988)
As expected, flooding regimes had a speciesspecific effect on the buoyancy of the dispersal units over time (Fig. 3)
Summary
Salt marshes are increasingly valued because of their capacity to form elevated biogeomorphic landscapes by attenuating hydrodynamic energy (Bouma et al 2005, 2007, Temmerman et al 2007). The actual dispersal potential of these dispersal units might be mirrored by their morphological properties such as mass and shape (Chang et al 2008, Friess et al 2012). These dispersal units have traditionally been excluded from assessments of the saltmarsh propagule dispersal ability, evidence suggests that they may be important for dispersal (Ingrouille & Pearson 1987, Bockelmann et al 2003, Minchinton 2006, Strong & Ayres 2013). We aimed to provide a more complete understanding of saltmarsh dispersal strategies by comparing the dispersal behaviors of such dispersal units with those of isolated seeds under abiotic conditions
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