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

Aim: To quantify the responses of alpha and beta diversity to multivariate gradients, incorporating variation in environmental and management variability in coastal dune slacks. Location: United Kingdom dune slacks. Methods: Plant community composition, plant nutrient status and soil characteristics were measured for 164 quadrats in 41 dune slacks across 12 coastal sand dune systems. Data were collated on climate and atmospheric deposition. Hydrological regimes at daily resolution were modelled and calibrated using daily-to-monthly site measurements, from which we calculated quadrat-level hydrological metrics. Alpha diversity (richness, Shannon diversity and Pielou's evenness) metrics and beta diversity (turnover and nestedness) for species and genera were calculated across three spatial levels from sand dune system (highest) to dune slack to quadrat (lowest). Results: Diversity patterns depended on the spatial and taxonomic level considered. At smaller spatial levels (between dune slacks and between quadrats), alpha and beta diversity varied along gradients driven by soil characteristics, water table depth and atmospheric deposition. At larger spatial levels (between sand dune systems), patterns of beta diversity were a consequence of plant nutrient status. There was little variability in alpha diversity along this same gradient, with only small changes in Pielou's species evenness. Patterns at a coarser taxonomic level (genus) mirrored those at the species level. Main conclusion: We show that patterns of variation in plant diversity are dependent on the spatial level considered, but taxonomic level made little difference in understanding these patterns. Therefore, if we do not consider patterns across different spatial levels, important environmental and management drivers could be missed. The high biodiversity value and degree of threat to these European protected habitats makes such understanding invaluable for their conservation

Pony trails, hydrology and habitat restoration: aspects of the ecology of Petalophyllum ralfsii in a Welsh oceanic dune system

Introduction: This study investigated the ecology of Petalophyllum ralfsii in an oceanic dune system, including relationships with grazing livestock, hydrology and habitat restoration. Methods: The study site was two large slacks at Newborough Warren, NW Wales, UK. In areas of one slack, there are 6-yr-old ‘restoration scrapes’, where vegetation was stripped to restore early successional habitat. Since 2001, both slacks have had continuous conservation grazing, primarily by ponies. Locations of P. ralfsii were recorded using high-precision GPS. Vegetation was recorded by relevés and hydrology investigated from dipwell data. Results: Petalophyllum ralfsii was recorded at 1322 locations, mostly along pony trails, but also in sparsely vegetated depressions and restoration scrapes. The most frequent associates were Carex flacca, Didymodon tophaceus, Equisetum variegatum and Ptychostomum pseudotriquetrum. Wetter locations could be flooded for prolonged periods in some winters. Drier locations did not flood at all during the five winters of the study. Within occupied 5 × 5 m grid cells, vertical range of locations was no more than 16 cm. Locations in restoration scrapes are confined to areas where the water table is relatively high. Conclusions: Livestock grazing had a major positive impact on P. ralfsii. Trampling along pony trails provided competitive release and, due to greater soil bulk density, prolonged water availability at the surface. Ponies likely provided directed dispersal into suitable microhabitats via transport of diaspores on their hooves. Restoration scrapes have been colonised by P. ralfsii, but the population is small, likely related, at least in part, to water availability

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."

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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