Trade-Offs Related to Ecosystem Engineering: A Case Study on Stiffness of Emerging Macrophytes

Abstract

Abstract. Biologically mediated modifications of the abiotic environment, also called ecosystem engineering, can significantly affect a broad range of ecosystems. Nevertheless, remarkably little work has focused on the costs and benefits that ecosystem engineers obtain from traits that underlie their ecosystem engineering capacity. We addressed this topic by comparing two autogenic engineers, which vary in the degree in which they affect their abiotic environment via their physical structure. That is, we compared two plant species from the intertidal coastal zone (Spartina anglica and Zostera noltii), whose shoots are exposed to similar currents and waves, but differ in the extent that they modify their environment via reduction of hydrodynamic energy. Our results indicate that there can be trade-offs related to the traits that underlies autogenic ecosystem engineering capacity. Dissipation of hydrodynamic forces from waves was roughly a factor of three higher in vegetation with stiff leaves compared to those with flexible leaves. Drag was highest and most sensitive to hydrodynamic forces in stiff vegetation that does not bend with the flow. Thus, shoot stiffness determines both the capacity to reduce hydrodynamic energy (i.e., proxy for ecosystem engineering capacity) and the drag that needs to be resisted (i.e., proxy for associated costs). Our study underlines the importance of insight in the trade-offs involved in ecosystem engineering as a first step toward understanding the adaptive nature of ecosystem engineering.

Plant resistance to mechanical stress: evidence of an avoidance–tolerance trade‐off

“…Hydrodynamic traits were measured in a unidirectional flow flume (full description in Bouma et al, 2005). The width of the straight working section of the flume was 30 cm and the height of the water column was 25 cm.…”

“…The width of the straight working section of the flume was 30 cm and the height of the water column was 25 cm. Drag was measured using a force transducer (WL|Delft Hydraulics, Delft, the Netherlands, described in Bouma et al, 2005). A hole fitting the size of the transducer was made in the bottom of the flume so that the transducer was placed underneath with its top part perfectly level with the bottom of the flume.…”

Wave Attenuation at a Salt Marsh Margin: A Case Study of an Exposed Coast on the Yangtze Estuary

“…Furthermore, remaining salt marshes are at risk of drowning (Roman et al 1997;Reed 2002) as a result of global sea-level rise (Douglas et al 2001) and a local reduction in (riverine) sediment supply (Yang et al 2006). The ability of salt marshes to accrete in response to sea-level rise by trapping sediment is strongly dependent on the attenuation of waves and currents (Friedrichs and Perry 2001;Leonard and Reed 2002;Bouma et al 2005a). Hence, from the perspective of both coastal defense and salt marsh management, an in-depth understanding is needed of the way in which waves are attenuated by salt marshes.…”

“…Flume experiments have shown that wave damping by salt marshes is strongly affected by vegetation characteristics (e.g., Bouma et al 2005aBouma et al , 2010. Flumes are, however, of limited use for studying the effect of flooding height on wave attenuation.…”

Risk reduction by combining nature values with flood protection?

“…29,31], but also by the height [32], stem diameters and configuration of the branches and leaves. For example, dissipation was roughly three times higher in vegetation with stiff leaves than in vegetation with flexible leaves [33]. Therefore, some saltmarsh plant species are more effective in wave damping than others.…”