Integrating morphodynamic and ecological processes to understand and predict the response of salt marshes to sea-level change and reduced sediment supply

整合形态动力学和生态过程，了解和预测盐沼对海平面变化和沉积物供应减少的响应

• 批准号: 313881250
• 负责人: Professor Dr. Kai Jensen, since 11/2019
• 金额: --
• 依托单位: Biozentrum Klein Flottbek und Botanischer Garten
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/313881250?language=en
• 关键词: Integrating; morphodynamic; ecological; processes; understand

Salt marshes are coastal sedimentary systems which are important for wave attenuation and coastal protection. In general, many salt marshes can adjust to sea level rise (SLR), because increased inundation frequencies lead to enhanced sediment deposition and accretion. However, on a decadal time scale complex morphological responses of tidal marshes might evolve in times of global change due to spatial and temporal variable sediment deposition rates. Sediment deposition and accretion rates and patterns in salt marshes are affected by external environmental factors such as the tidal range, storm frequency and sediment supply, many of which will be altered by environmental change. Internal factors such as elevation and distance to the sediment source affect sediment deposition rates and patterns on the local scale. Additionally, vegetation was found to increase sediment deposition by reducing flow velocity. Increased sediment deposition and the resulting surface-elevation change in turn promote vegetation change and increase biomass production, which leads to more sediment trapping and thus to a positive feedback loop of sediment dynamics and vegetation. Various morphodynamic models considering these factors have been proposed to predict changes in surface elevation of tidal marshes. These models reach from zero-dimensional point models to landscape scale models. Furthermore, both models based on empirical field measurements and statistical analysis, and physical models based on hydrodynamic equations are available. Many of these models also attempt to include the effect of vegetation on flow and sediment deposition. Yet, many biophysical interactions between marsh vegetation and hydro-morphological processes, and effects of heterogeneous vegetation patterns on sediment fluxes are poorly understood. For example, models mostly focus on homogeneous low marshes, but vegetation structure strongly differs between marsh zones and forms heterogeneous patterns. Most importantly, models generally assume that vegetation is static, while morphological marsh development is indeed also a main driver of vegetation succession, leading to changes in vegetation properties which in turn also affect sediment dynamics as outlined above. We propose to improve morphodynamic marsh models by integrating feedback loops between sediment and vegetation dynamics for salt marshes in the Wadden Sea. These models will be better able to predict marsh response to different climate change scenarios (WP A/B). Furthermore, they will be a useful tool for decision making in the context of coastal protection measures (WP C). We propose a three year project for two PhD-students. PhD-student A would focus on empirical and physical modelling of sediment deposition and accretion. PhD-student B would develop a predictive habitat distribution model for salt marsh vegetation.

盐沼是一种海岸沉积体系，对波浪衰减和海岸防护具有重要作用。一般来说，许多盐沼可以适应海平面上升（SLR），因为增加的淹没频率导致增加的沉积物沉积和加积。然而，在一个十年的时间尺度上，复杂的形态响应的潮汐沼泽可能会演变的全球变化的时间，由于空间和时间可变的沉积物沉积速率。盐沼沉积物的沉积和堆积速率和模式受外部环境因素的影响，如潮差、风暴频率和沉积物供应，其中许多因素会因环境变化而改变。诸如海拔和到沉积物来源的距离等内部因素影响到当地沉积物的沉积速率和模式。此外，植被被发现通过降低流速来增加沉积物沉积。沉积物增加和由此产生的地表海拔变化反过来又促进植被变化和增加生物量生产，从而导致更多的沉积物截留，从而形成沉积物动态和植被的正反馈循环。考虑这些因素的各种形态动力学模型已被提出来预测潮滩表面高程的变化。这些模型从零维点模型到景观尺度模型。此外，这两个模型的基础上经验的现场测量和统计分析，和物理模型的基础上的流体动力学方程。许多模型还试图包括植被对水流和泥沙沉积的影响。然而，沼泽植被和水文形态过程之间的许多生物物理相互作用，以及异质植被格局对沉积物通量的影响知之甚少。例如，模型大多集中在均匀的低沼泽，但植被结构强烈不同的沼泽地带，形成异质模式。最重要的是，模型通常假设植被是静态的，而沼泽形态的发展确实也是植被演替的主要驱动力，导致植被特性的变化，这反过来又影响到上文所述的沉积动力学。我们建议改进形态动力学沼泽模型，通过整合沉积物和植被动态之间的反馈回路，在瓦登海盐沼。这些模型将能够更好地预测沼泽对不同气候变化情景的反应（WP A/B）。此外，它们将是在沿海保护措施（WP C）方面进行决策的有用工具。我们提出了一个为期三年的项目为两个博士生。博士生A将侧重于沉积物沉积和加积的经验和物理建模。博士生B将为盐沼植被开发一个预测栖息地分布模型。