Seabird mediated link between marine and terrestrial ecosystems

• Main Author: Guy, Matthew
• Other Authors: Park, Kirsty, Johnson, David, Gilbert, Lucy, Macaulay Development Trust
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Stirling 2019
• Subjects: Great Skua; plant community; invertebrate community; meta-ecosystems; decomposition; mineralization; Sea birds Ecology; Microbial ecology; Biodiversity; Great skua
• Online Access: http://hdl.handle.net/1893/31793; http://dspace.stir.ac.uk/bitstream/1893/31793/1/Guy-M_2019_Seabird-Mediated-Link-Between-Marine-and-Terrestrial-Ecosystems.pdf

The meta-ecosystem concept describes spatial coupling of ecosystems through flows of energy material and organisms across ecosystem boundaries. Mobile species can act as biotic vectors to facilitate the movement of these items between ecosystems and can be essential to maintaining the meta-ecosystem. Global biodiversity and species movement are under increasing pressures of anthropogenic activity. A greater understanding of how mobile species influence the functioning of the meta-ecosystem will provide a better insight to how changes in one ecosystem may influence coupled ecosystems across landscapes. Throughout this thesis I use the marine-terrestrial meta-ecosystem connected by the seabird great skua as a model system to investigate this. I use a combination of observational and manipulation experiments to determine the effects on plant nutrient assimilation, soil processes, plant community assemblage and dynamics and invertebrate community assemblage. I show that great skuas transport large quantities of essential plant nutrients into the terrestrial ecosystem through faeces and pellets. This feeds into plant nutrition regardless of species and life history traits and potentially reduces the reliance of heather and tormentil on mycorrhizae symbionts for nutrient acquisition. This nutrient deposition has little influence over the functioning of the soil biota: the increase in soil nutrient pools varied, mineralization was unaffected by great skua abundance and the rate of decomposition and nutrient release from litter was largely determined by the litter quality rather than where the litter was buried. This also indicates that plants are accessing nutrients rapidly and directly from faeces through abiotic pathways and the excess is lost through surface run-off or leached through the soil. Above ground I demonstrated that this increased nutrient availability and disturbance both play a role in rapidly shifting the plant community from dwarf shrub and tall acid grassland communities to short, ruderal, graminoid ...