Ecohydrology of dune wetlands

Biodiversity is declining at an unprecedented rate, which will have significant impact on human health and well-being. Dune slacks are low-lying seasonal wetland habitats within coastal sand dunes. They are rich in biodiversity and expected to be sensitive to environmental changes due to complex interactions between hydrology and plant community compositions. However, there has been a lack of research in UK dune slacks exploring these interactions. Therefore, this thesis examines the relationship between plant communities and the underlying hydrological and environmental controls across UK dune slacks.In Chapter 2 (methods chapter), I summarise the data collection, processing and groundwater modelling undertaken across 41 dune slacks in 12 coastal sand dunes systems, which underpin Chapter 3 and 5. I also summarise the data collection, processing and groundwater modelling undertaken across six dune slacks in one coastal sand dune system in north west England, which underpin Chapter 4. The outputs from this research are important for management, as they provide invaluable information on the plant communities present and the long-term hydrological regime of key UK sand dune systems.In Chapter 3, I investigated plant community responses to environmental and hydrological drivers across spatial scales (coastal sand dune site, dune slack and plot) and taxonomic resolutions (species and genus) in UK dune slacks. Findings from this investigation show that ‘local’ environmental factors such as water table depth are important in shaping plant communities. Additionally, the response of genus data was similar to species data, therefore in the search for biodiversity short cuts genus data may be used.In Chapter 4, I investigated species-specific responses and plant community responses to fine-scale hydrological variability in a coastal sand dune system in north west England (Ainsdale Sand Dunes). I found that hydrology is an important driver in dune slack communities between dune slacks. However, not all plant communities within a dune slack are structured by fine-scale hydrological variation, demonstrating the complexity of plant composition patterns. In addition to successional processes, topographic variation within slacks appears to impact plant community composition and diversity. Therefore, to maximise habitat space for many species, topographically varied dune slacks need to be created.In Chapter 5, I explored how environmental drivers affect the relationship between a commonly used ecological indicator (Ellenberg moisture - F) and water table depth across UK dune slacks. Findings from this investigation demonstrate that Ellenberg F is a powerful biological indicator of soil hydrology in an ecological context, but other factors can alter this relationship. From a practical perspective these findings help us to understand which abiotic and biotic factors modify the relationship between Ellenberg F and hydrological regime, which aids interpretation of Ellenberg F-values at a sand dune site level.The results presented here improve our understanding of the underlying hydrological and environmental control of UK dune slack plant communities. Additionally, this research provides a basis for future ecological and hydrological dune slack studies within the UK.</div

Data for - Environmental modifiers of the relationship between water table depth and Ellenberg’s indicator of soil moisture.

These datasets are those described in Dwyer et al. 2021. Environmental modifiers of the relationship between water table depth and Ellenberg’s indicator of soil moisture. The authors are currently undertaking further analysis of these data, but are open to further collaborative projects. If you are interested in using these data, please contact authors.</p

Prey capture by the non-native carnivorous pitcher plant Sarracenia purpurea across sites in the Britain and Ireland.

Data for - Prey capture by the non-native carnivorous pitcher plant Sarracenia purpurea across sites in the Britain and Ireland. Includes: site locations, prey capture per pitcher, synthesis of prey capture from exsiting studies globally.</p

Environmental modifiers of the relationship between water table depth and Ellenberg’s indicator of soil moisture

Ellenberg indicator values for plant species are widely used metrics in ecology, providing a proxy measure of environmental conditions, without direct measurements. They integrate environmental conditions over time since species will only persist where conditions are favourable. Ellenberg moisture (F) values summarise the hydrological environment experienced by plants. However, the relationship between indicator values and hydrological metrics appears to be influenced by a range of other abiotic and biotic factors, limiting our ability to fully interpret Ellenberg F. Focussing on Ellenberg F, we evaluated how the unweighted mean plant community F value to hydrology, specifically water table depth, is influenced by other environmental factors, ground cover type and alpha diversity in UK seasonal coastal wetlands (dune slacks). As expected, water table depth had the strongest influence on unweighted mean Ellenberg F. We show that unweighted mean Ellenberg F was more sensitive to changes in water table levels for plant communities that were more nutrient limited, when the organic matter layer was thicker and there was less bare ground cover. Unweighted mean Ellenberg F was consistently lower for a given water table depth, when there was lower atmospheric nitrogen deposition, lower loss of ignition (a measure of organic matter content) and more diverse plant communities. These findings help us to better interpret what Ellenberg F indicator values tell us about hydrological conditions, by understanding the factors which alter that relationship

Fine‐scale hydrological niche segregation in coastal dune slacks

Questions: Hydrological niche segregation is widespread and has been found across a range of different habitats. Different plant species can occupy distinct hydrological niches, and as a result fine-scale variability in hydrology can structure plant communities. However, these patterns may not be as clear in habitats where differences in hydrology are more short-lived, such as coastal dune slacks. We explored the extent that the hydrological regime structures dune slack plant communities. Location: Ainsdale Coastal Sand Dune National Nature Reserve, UK. Methods: Six hundred quadrats were surveyed, 100 in each of six coastal dune slacks. Water table levels are recorded monthly in each slack. Metrics summarising hydrological regime were calculated and adjusted for each quadrat based on elevation. We tested the relationship between water table depth, plant communities and topography across and within dune slacks. Results: Half (three) of the slacks showed a significant influence of hydrology on plant community composition. The three that did not were the ones that varied least topographically and contained less diverse plant communities. We also provide indirect evidence of niche segregation by modelling species-specific responses between mean water table depth and probability of species presence. Conclusions: We demonstrate that hydrology is a dominant driver of plant community composition across dune slacks. However, plant communities are not always structured by hydrology, demonstrating the complexity of vegetation patterns. Topographic variation appears to impact plant community patterns, as do successional processes, highlighting the need to create diverse habitats for slack restoration and management

Data for - "Fine-scale hydrological niche segregation in coastal dune slacks."

Data for "Fine-scale hydrological niche segregation in coastal dune slacks." Contains all data used in this publication. Details in Read Me file (MetaData for fine-scale hydrological niche segregation in dune slacks)

Data for - Patterns of variation in plant diversity vary over different spatial levels in seasonal coastal wetlands

Data and associated code for data analysis for the paper.  Patterns of variation in plant diversity vary over different spatial levels in seasonal coastal wetlands. Working title was: Local environmental factors control alpha and beta diversity of coastal dune slack plant communities.</p