The Importance of Plant Traits on River Processes and How to Incorporate them into Revegetation Strategies
Sharon Bywater-Reyes1*, Rebecca Diehl2, Li Kui3, John Stella4, and Andrew Wilcox5
1Earth and Atmospheric Sciences, University of Northern Colorado, Box 100, 501 20th St., Greeley, CO 80639, USA, sharon.bywaterreyes@unco.edu
2Diehl, Rebecca, Gund Institute for Environment, The University of Vermont, Burlington, VT 05405, USA, Rebecca.Diehl@uvm.edu
3Kui, Li, Marine Science Institute, The University of California Santa Barbara, Santa Barbara, CA 93106, USA, li.kui@ucsb.edu
4Stella, John, Forest and Natural Resource Management, SUNY-ESF, Syracuse, NY 13210, USA, stella@esf.edu
5Wilcox, Andrew, Department of Geosciences, University of Montana, Missoula, MT 5981, USA, Andrew.Wilcox@mso.umt.edu
The strength of interactions between plants and river processes is dependent on plant traits such as stem density, plant frontal area, and stem bending properties. A combination of flow regulation, river management, and exotic species invasion have altered the distribution of vegetation in many waterways, with subsequent shifts in the distribution of plant traits. For example, in most U.S. Southwest waterways, Tamarix has invaded, displacing native pioneer vegetation such as Populus. Our team investigated whether plant-trait differences between Tamarix and Populus differentially affect hydraulics, sediment transport, and river morphology with a combination of flume, field, and remote sensing approaches spanning the individual seedling to river-corridor scales. We found that Tamarix requires more force to bend compared to Populus, has greater stem densities and a different crown morphology, resulting in a greater influence on near-bed flow velocities, and subsequently sediment transport (greater aggradation rates). In the Bill Williams (Arizona) watershed, at the patch and corridor scales, remote sensing observations confirmed greater aggradation for denser vegetation patches. Furthermore, long-term channel adjustments were faster for Tamarix versus Populus dominated reaches. More broadly, because the plant traits that influence hydraulics and sediment transport are correlated to plant functional traits (e.g., specific leaf area and stem-tissue density), they should be explicitly considered in riparian management and restoration efforts. Restoration designs should use a collaborative approach that includes the views of fluvial geomorphologists and riparian ecologists such that plants are distributed in a manner with desirable outcomes.