Riparian plant guilds of ephemeral, intermittent and perennial rivers

Abstract

1. Plant functional types (or guilds) increasingly are being used to predict vegetation response to global changes. Continued human population growth coupled with projected warmer and drier climate will alter the hydrologic regimes of many arid-zone rivers, including intermittent rivers. We aimed to identify (i) woody plant guilds associated with distinct stream types of an arid region and (ii) plant traits indicating adaptation to the selective pressures of water availability and fluvial disturbance. 2. We used hierarchical clustering to identify 11 plant guilds from floodplains, terraces and uplands of eight Arizona rivers that vary in surface flow permanence, depth to ground water and intensity of fluvial disturbance. 3. Six guilds were riparian pioneers with small, wind-dispersed seeds, three guilds were late-seral, shade-tolerant riparian taxa with large animal-dispersed seeds, and two guilds were composed of desert xerophytes. Within the riparian pioneer and seral groups, guilds varied in water acquisition and productivity traits including wood density and rooting depth. 4. The community-weighted traits varied or covaried with water availability and fluvial disturbance. Root: shoot ratio, canopy height and leaf area were influenced strongly by water availability, with the latter two showing a nonlinear response to changes in water table depth. Leaf length increased, and wood density decreased, as sites become wetter and more fluvially disturbed. Communityweighted seed mass, seed dispersal and spinesence varied most strongly with elevation above thalweg (an indicator of decreasing fluvial disturbance). 5. These analyses will enable prediction of changes in the relative abundance of plant types and plant traits in response to changes in stream flow regimes, such as shifts towards greater intermittency. The distribution patterns of guilds among riparian habitat types emphasise the importance of focusing conservation efforts not only on the limited number of perennial rivers remaining in arid regions, but also on intermittent and ephemeral rivers with shallow water tables.

Seasonal and spatial variations of water use among riparian vegetation in tropical monsoon region of SW China

“…Such invasive species and lianas (e.g., M. vitifolia and H. scandens) are considered as pioneer species because they easily adapt and colonize a disturbed habitat (Stromberg & Merritt, 2016). However, the water use pattern of two invasive plants (C. odorata and T. diversifolia) was particularly different from other species in our study.…”

Riparian plant guilds become simpler and most likely fewer following flow regulation

“…The deciduous nutrient‐demanding plants stand out as being disfavoured in highly disturbed sites, as they contain species morphologically unfit to face floods. Similarly, traits related to fluvial disturbance are required to explain the riparian functional composition in Mediterranean and semi‐arid environments (Kyle & Leishman, ; Stromberg & Merritt, ).…”

The abundance and distribution of guilds of riparian woody plants change in response to land use and flow regulation

“…Trait‐based frameworks have been encouraged to provide a more general understanding of the adaptive strategies of riparian plants to the fluvial setting of rivers (Aguiar, Orestes Cerdeira, Martins, & Ferreira, ; Lawson, Fryirs, Lenz, & Leishman, ; Stromberg & Merritt, ), or to disturbance (Stahl et al., ), especially when shifts in species diversity following environmental changes are only rudimentarily understood (Kominoski et al., ). Several studies have reported clear relationships between riparian trait composition (rooting habit, seed mass and wood density) and water availability.…”