An evaluation of plant wax markers to reconstruct long-term vegetation change in peat bog deposits

Northern peatlands concentrated in boreal and subarctic regions store as much as one-third of global soil carbon and represent a highly important global carbon dioxide sink, with an amount of stored carbon representing 25-50% of current levels of atmospheric CO2. Their ability to continue to sequester carbon dioxide and their botanical composition under future global warming scenarios is uncertain, but research into their ability to store carbon during former periods of climate change can provide clues to their potential future response. It has already been shown that changes in the rate of carbon accumulation during the Medieval Warm Period and Little Ice Age in raised peat bogs was dependent upon the botanical composition of the peat forming plants. It is therefore vital to reconstruct the local peat forming vegetation when investigating long-term records of carbon accumulation, but this, unfortunately is not always possible, as plant macrofossils do not preserve well in blanket peat bogs and other boreal and subarctic peatland ecosystems. Given this, there is a pressing need to develop alternative techniques to reconstruct peat forming plants from extensive peat bog archive deposits which contain millennial records of carbon accumulation rate changes, and in this way reconstruct the spatial and temporal variability of carbon sequestration. This research seeks to redress this problem by testing the suitability of 'molecular fossils' preserved in peat profiles from UK blanket peat profiles (preservation of macrofossils is frequently poor in these deposits) to reconstruct the former vegetation components. If successful, the reward of this project will be improved understanding of species dependent carbon sequestration during previous periods of climate change, which could prove highly beneficial to inform future carbon management, both internationally and nationally (peat deposits in moorland areas represent the largest terrestrial carbon pool in the UK). Improved long-term base line data for the origin and nature of vegetation changes in peat bogs would also serve to guide and aid conservation of these threatened ecosystems, particularly blanket peat bogs. This would be highly beneficial to stakeholders charged with water collection, agriculture, sport, leisure, and tourism in moorland habitats where peat bog habitats occur. The techniques have excellent promise since their application in a PhD pilot project offered species level identification (of heather) in a buried soil deposit. Testing the value of plant wax biochemical markers as a proxy for peat-bog vegetation will involve three stages. The first stage will be to determine the chemical markers of living, reference material collected from a range of raised/blanket peat bog habitats. This will be followed by analyses of sub-fossil samples of known botanical composition and age from an extensively radiocarbon dated raised peat bog profile with excellent macrofossil preservation. These samples were investigated as part of a major EU 6th Framework funded project ('Accrotelm') and their timely availability represent an excellent opportunity to investigate the fossil plant wax biochemical signatures of samples of known botanical composition. Data on the modern/sub-fossil plant wax biochemical markers from known plant species will then be used in the final proof of concept stage to reconstruct the potential former local vegetation of a blanket peat sample of imperfectly known botanical composition. Peat bog deposits contain detailed records of carbon sequestration rate changes, and also provide proxy-climate data and long-term ecological records to inform conservation policies. UK scientists are world leaders in the analyses of these deposits, and this small project is closely aligned with three of NERC's current strategic science themes on Biodiversity, Sustainable Use of Natural Resources, and Knowledge Exchange to stakeholders.