River Connectivity Affects Submerged and Floating Aquatic Vegetation in Floodplain Wetlands

Abstract

The submerged and floating plant communities in floodplain wetlands of the Upper Columbia River have never been described. To explore mechanisms behind the influence of the annual flood pulse on vegetation, we investigated how species group into flood response guilds whose distributions vary along a connectivity gradient between 44 floodplain wetlands and the river, how connectivity influences water and sediment, and to what degree the effect of connectivity on vegetation is mediated by its effects on these environmental variables. We characterised assemblages with cluster and indicator species analysis, as well as non-metric scaling ordination and tested a structural equation model, which defined the relationship between assemblage composition, sediment and water quality, and connectivity to the river. We found four assemblages, each associated with different water and sediment conditions, and positioned at differing degrees of connectivity. The model provided a good fit to the data. We conclude that in highly connected floodplain wetlands the direct effect of flooding supersedes the influence of water and sediment quality in structuring vegetation assemblages. Yet where flooding is less intense, these environmental variables resume their structuring role.

Morphological forms of two macrophytes (yellow water-lily and arrowhead) along velocity gradient

“…Along with the water depth increased the content of dissolved organic matter. Nuphar lutea tolerates high organic substrate and nutrient level (Rooney et al 2013). Free floating forms mange better in such limited light conditions of water (Steffen et al 2013).…”

“…Differences in morphology of Sagittaria sagittifolia and Nuphar lutea result in the different rigidity of their tissues (Sukhodolova & Sukhodolov 2012;Steffen et al 2013). Nuphar lutea produces very long rhizomes that make plants resistant to the flow pressure (Rooney et al 2013). Furthermore, yellow water-lily was described in literature as mowing-tolerant species (Steffen et al 2013).…”

“…Aquatic plants adapt to hydrodynamic stress, including floods and changes in velocity, through the variety of changes in their morphology, life history and behaviour (Rooney et al 2013).…”

Anthropogenic impacts on vegetation diversity and spatial floral composition of the swamp forest associated with the tropical river basin

“…Today also wetlands are containing a large part of the world's as a biological heritage (Goldewijk, 2004;Hermoso et al, 2012;Rooney et al, 2013). Wetlands have been identified as a most dynamic ecosystem among other natural ecosystems.…”

Realised and predicted changes in the invertebrate benthos after restoration of connectivity to the floodplain of a large river

“…Bornette, Amoros & Lamouroux, 1998;Aarts et al, 2004;Lasne, Lek & Lafaille, 2007;Gli nska-Lewczuk, 2009;Leigh & Sheldon, 2009). Lateral connectivity encapsulates an array of processes, such as the intensity and timing of shear stress; nutrient, organic matter and sediment fluxes; and the import and export of propagules and predators, that ultimately drives the structure and function of the biota in floodplain waterbodies (Amoros & Bornette, 1999, 2002Leigh & Sheldon, 2009;Rooney, Carli & Bayley, 2013).…”