Ecosystem services in coastal wetlands: Investigating bio- and hydro-mechanical traits of salt marsh vegetation

Abstract

<p>Biodiversity and nature conservation play an increasingly important role with growing societal awareness, which is reflected in current European legislative frameworks such as the Marine Strategy Framework Directive or the Water Framework Directive, calling for integrative solutions and restoration of good environmental status. Salt marshes provide ecosystem services which can help mitigate climate change and sea level rise threats and simultaneously address coastal squeeze problems. The periodical submergence due to tidal changes creates a special ecosystem with different zones delineated by a landward increasing marsh elevation, which are inhabited by different plant and animal communities. In addition to their ecological value, salt marshes provide coastal protection, as they dissipate wave energy and stabilize otherwise exposed coastal soil lining sea dikes.  </p><p>The "Gute Küste Niedersachsen" research project investigates which environmental properties account for livable and safe coastal conditions along temperate climate coastlines, focusing on the symbiosis of human settlements, nature conservation and sustainable coastal protection. Specifically, the identification of vegetation-mediated ecosystem services within salt marshes at the North Sea coast of Lower Saxony, Germany is addressed here. The overarching goal of the transdisciplinary project is to gain knowledge of natural or nature-based systems and their processes within real-world laboratories at the coast to incorporate proven ecosystem services into standardized coastal protection design guidelines and promote integrated coastal zone management.</p><p>Methods include field observations and experiments, hydraulic laboratory experiments and numerical simulations over the course of 5 years. During the first years, a systematic observation of vegetation regarding distribution patterns, growth, density, and bio-mechanical (e.g. flexural rigidity, area moment of inertia) as well as root properties (e.g. root length density, tensile strength) and their respective seasonality is conducted. Through comprehensive monitoring covering large areas of halophytic meadows, a physical model of heterogeneous salt marshes will be developed. Simultaneous measurements of environmental parameters covering waves, currents and soil properties yield a comprehensive data set for analysis, numerical and analytical modeling purposes. </p><p>Hydraulic experiments modeling the wave-vegetation-soil interaction will be devised based on field data, developing dynamically and geometrically scaled vegetation surrogates. Besides vegetation properties aboveground, a focus will be on previously sparsely considered root system effects that is hypothesized to govern erosional processes in salt marshes.</p>

From seasonal field study to surrogate modeling: Investigating the biomechanical dynamics of Elymus sp. in salt marshes

“…For this, water absorbing properties and the influence of air and water temperature should be considered (Behalek et al 2018). Storage conditions and duration, humidity, and orientation of the print while stored can play a role in plastic deformations (Keimer et al 2022). The quality of the print in regard to anisotropy, including postcuring after printing and during storage time, should be evaluated in detail, especially for small structures (Ahmad et al 2020; Štaffová et al 2022).…”

“…This includes the material variation owing to temperature and water absorption. Increasing and decreasing the outer diameter 0.2 mm with constant printing conditions was shown in Keimer et al (2022), which resulted in inconclusive changes. Therefore, investigating changes in the geometry of surrogates should continue with distinct differences. In this study, the outer diameter for the green plants is only 5% higher than for brown plants, but Young's modulus is 50% higher, indicating a change in mechanical properties of the tissue.…”

“…To refer to the investigated mixtures in this study, the percentage of "Type D Flex" will be used: 0%, 30%, 50%, 70%, 90%, and 100%. The layers were printed with a height of 0.1 mm and a UV light exposure time of 3.0 s. The printing settings were kept consistent for all prints to ensure the best comparability (Keimer et al 2022). The test specimen was printed in an upright position without support structures.…”

“…This includes the material variation owing to temperature and water absorption. Increasing and decreasing the outer diameter 0.2 mm with constant printing conditions was shown in Keimer et al (2022), which resulted in inconclusive changes. Therefore, investigating changes in the geometry of surrogates should continue with distinct differences.…”