Grazing and disturbance as management tools in coastal slacks: consequences for soil organic matter, biodiversity and functional resilience

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Sand dune wetlands or slacks are biodiverse habitats supporting many rare UK plant, invertebrate and vertebrate species. They are a priority habitat for nature conservation in Europe. Grazing and disturbance are important in coastal habitats for maintaining this conservation value because they prevent succession towards scrub habitat, so appreciating their wider impacts is essential for directing management activities. We have good understanding of how these factors can alter aboveground communities but our knowledge on belowground biodiversity in these systems is limited, particularly in the context of interactions between plants and soil components and consequences for biogeochemical functioning. Earlier work characterised the accumulation of soil organic matter with slack age and documented changes in other soil properties (e.g. Jones et al. 2008). Few studies, however, have evaluated how soil microbial communities (Wasserstrom et al. 2017) and fauna (Butt & Chamberlain 2007) may develop, and whether altered belowground biodiversity and plant-soil interactions may drive changes in functional soil processes. Furthermore, there is pressing need to better understand how these changes may interact with different grazing or disturbance regimes. Using an established long-term experiment and wider network of study sites, this research will test links between organic matter quality, soil biodiversity and functional resilience in coastal systems, and provide unique belowground evidence to help optimise conservation management strategies. In summary, the aim of this PhD is to answer the following questions:1. What are the long-term impacts of grazing regime on organic matter quality, microbial and faunal composition in coastal dune slack soils? 2. Does the composition of soil biodiversity determine the capacity for biogeochemical functioning and its' resilience to climatic and hydrological fluctuations?3. Can management strategies be identified which optimise for plant communities, soil biodiversity and functional resilience?The project will focus on extensive dune slack systems at Ainsdale Sand Dunes National Nature Reserve, on the east coast of Lancashire. This location contains the Ainsdale Dune Slacks Long Term Experiment (LTE). This grazing experiment was established in 1974 and is the longest running dune slack wetland grazing experiment in the UK, consisting of sheep and rabbit exclosures. The proposal will build on earlier research at Ainsdale by Dr Millett (Millett & Edmondson 2013, 2015).