Above‐ground and below‐ground Salix dynamics in response to river processes

Abstract

Abstract:Riparian vegetation influences hydraulic and morphodynamic river processes and may contribute to sediment stabilization. In turn, vegetation recruitment and growth on non-cohesive fluvial deposits strongly depends on river hydrology and the ability of roots to develop and to anchor efficiently to resist flow erosion. In this paper, we examine the above-ground and the belowground seasonal growth dynamics of Salix cuttings in relation to local river hydrodynamics and morphodynamics, on the basis of a detailed and unique data set. During the two season-long campaigns in 2009 and 2010, 1188 and 1152 cuttings, respectively, were organized in square plots and planted on a gravel island of the restored reach of the River Thur (Neunforn, Thurgau, Switzerland). Each year, all cuttings were monitored almost regularly from the beginning until the end of the growing season (April-September). Root development statistics were also obtained from high-resolution scanner analysis of carefully uprooted samples from selected plots. Our results show how cutting survival and the nature and strength of correlations between island topography and cutting growth statistics depend on river hydrology. An empirical functional form that links root development based on the measured main stem length is then proposed for predictive purposes. Cutting mortality following flood events is shown to depend nonlinearly on both erosion and deposition processes, whereas it appears more linearly related to the magnitude of the bed shear stress distribution generated by the maximum seasonal flood. This analysis allows an identification of an important threshold for plant survival within different erosion and deposition regimes, which explains the spatial and temporal distribution of the surviving cuttings within the plots. These results have practical implications, for instance, for evaluating, planning and managing the use of riparian trees in restoration projects.

Swiftness of biomorphodynamics in Lilliput- to Giant-sized rivers and deltas

“…This was a prudent approach because the settling, survival, growth, and mortality of vegetation were insufficiently understood for the purpose of quantitative spatial modelling. Recent efforts target these unknowns in field measurements and field experiments (Kui et al, 2014;Pasquale et al, 2014), and in numerical modelling with explicit description of the life cycle of riparian eco-engineering tree species (van Oorschot et al, 2014). Here, eco-engineering species significantly change their environment, for example by increasing flow resistance, capture, stabilization, or mobilization of sediment and by increasing the stability of channel banks.…”

Evidence of increase in woody vegetation in a river corridor, Northwest England, 1984–2007

“…Stromberg, Lite, & Dixon, 2010). Types and zonation of riparian vegetation are strongly controlled by hydrological regime (Osterkamp, Hupp, & Stoffel, 2012;Sandercock & Hooke, 2010;Tabacchi et al, 2009), and occurrence of floods can affect recruitment and survival (Pasquale, Perona, Francis, & Burlando, 2014;Perona et al, 2009). Succession, particularly on river bars, is well known .…”

“…Succession, particularly on river bars, is well known . Much recent research has focused on the mechanisms and dynamics of growth and survival and interaction with processes (Bertoldi et al, 2009;Crouzy, Edmaier, Pasquale, & Perona, 2013;Gilvear, Francis, Willby, & Gurnell, 2007), including research on Salix species (Pasquale et al, 2014).…”

Effects of hydropeaking waves’ offsets on growth performances of juvenile Salix species

“…Cuttings of S. viminalis were adopted as laboratory prototypes of a representative woody riparian species to be grown within plastic rhizopods (e.g., Francis et al, 2005;Pasquale et al, 2012Pasquale et al, , 2014. Fig.…”