The relationship between vegetation and morphology in saltmarsh restoration schemes

Managed realignment, where coastal flood defences are breached or lowered to introduce tidal inundation to the coastal hinterland, is becoming an increasingly popular approach to coastal management to restore saltmarsh environments and compensate for habitat and ecosystem service loss elsewhere. Despite the popularity of managed realignment, there is increasing evidence that restored sites have a lower abundance and diversity of key plant species in comparison to natural saltmarshes. This has been associated with poor drainage within restored sites caused by reduced sub-surface hydrological connectivity and lower topographic variability, with the typical morphology within restored sites being more representative of an agricultural field than a saltmarsh environment. A potential cause of this is the use of constructed channels and existing drainage ditches in the site design, with few sites utilising remnant pre-reclamation intertidal drainage channels. This approach might restrict drainage and prevent widespread sedimentation and seed dispersal impacting the plant communities that can colonise, and consequently the delivery of targeted ecosystem services.

Despite the suggested link between site drainage and vegetation, the relationship between plant assemblage, health, and cover in relation to site morphology has not been empirically assessed. This project will address this fundamental knowledge gap through an assessment of UK managed realignment sites. Vegetation health and coverage will be assessed utilising a range of vegetation indices, derived from open access satellite data, and on-site vegetation surveys. These will be compared to assessments of the sediment properties and distance to creek features and the breach area to provide a site-scale spatial and temporal evaluation of the relationship between morphology and vegetation. Following this, sites and areas of interest will be assessed further using an Unmanned Aerial System to provide high resolution (cm-scale) measurements of plant communities in comparison to subtle, yet important, variations in topography.

Findings from this study will provide a new insight into the relationship between morphology and vegetation in saltmarsh restoration schemes, and with implications for the design and construction of future sites to maximise site evolution and ecosystem service delivery. The project will involve extensive fieldwork and travel to sites around the UK. The student will also be expected to conduct laboratory and remote sensing analysis as part of the project. The student will be encouraged to dissemination research findings during the project through attendance at relevant conferences and symposia, alongside publishing scientific papers in appropriate peer-reviewed journals.

https://www.reading.ac.uk/ges/staff/dr-jonathan-dale