Abstract
Both above- and below-ground plant traits are known to modulate feedbacks between vegetation and river morphodynamic processes. However, how they collectively influence vegetation establishment on gravel bars remains less clear. Here we develop a numerical model that couples above- and below-ground vegetation dynamics with hydromorphological processes. The model dynamically links plant growth rate to water table fluctuations and includes plant mortality by uprooting and burial. We considered a realistic hydrological regime and used the model to simulate the coevolution of alternate gravel bars and vegetation that displays trade-offs in investment of above- and below-ground biomass. We found that a balanced plant growth above- and below-ground facilitates vegetation to establish on steady, stable bars, because it allows plants to develop traits that maximise growth performance during low flow periods and thus survival during floods. Regardless of the growth strategy, vegetation could not establish on migrating bars because of large plant loss by uprooting during floods. These findings add on previous studies suggesting that morphodynamic processes play a key role on determining plant trait distributions and highlight the importance of including the dynamics of both above- and below-ground plant traits for predicting shifts between bare and vegetated states in river bars.
Highlights
Both above- and below-ground plant traits are known to modulate feedbacks between vegetation and river morphodynamic processes
A clear understanding on how vegetation types may influence river ecomorphodynamics remains limited to a handful of studies[15,26]
Our results indicate that the effect of different growth strategies can be significant for river bar ecomorphodynamics and varies depending on the steady and migrating nature of bars
Summary
Both above- and below-ground plant traits are known to modulate feedbacks between vegetation and river morphodynamic processes How they collectively influence vegetation establishment on gravel bars remains less clear. Regardless of the growth strategy, vegetation could not establish on migrating bars because of large plant loss by uprooting during floods These findings add on previous studies suggesting that morphodynamic processes play a key role on determining plant trait distributions and highlight the importance of including the dynamics of both above- and below-ground plant traits for predicting shifts between bare and vegetated states in river bars. A clear understanding on how (functional) vegetation types may influence river ecomorphodynamics remains limited to a handful of studies[15,26] Both above- and below-ground plant traits contribute to plant’s ability to interact with hydromorphological processes and cope with specific d isturbances[10,16,17]. Model applications tend to simplify the natural variability of the hydrological regime, overlooking the combined effects of floods with different magnitude, duration, and frequency on vegetation survival, and of water table fluctuations during low flow periods on vegetation growth
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