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Title: Generating carbon credits through application of the enzymic latch mechanism in peatland carbon sequestration
Author: Dunn, Christian
Awarding Body: Bangor University
Current Institution: Bangor University
Date of Award: 2013
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Northern hemisphere peatlands are the most efficient carbon stores of any terrestrial ecosystem holding around 455 Pg of carbon - twice the amount found in the world's forest biomass. Such stocks accumulate because phenolic inhibitors in the peat-soil slow the rate of decomposition to below that of photosynthetic production. The disproportionate importance of phenolics in peatlands is related to the unique properties of waterlogged peat soils suppressing the activity of phenol oxidase; one of the few enzymes capable of breaking these inhibitors down. This permits accumulation of phenolic compounds that are potent inhibitors of hydrolase enzymes - major agents in the breakdown of organic matter. Phenol oxidases can therefore be considered an 'enzymic latch' holding in place climate-changing amounts of carbon. However, anthropogenic impacts and the effects of global warming are switching these organic wetlands from carbon sinks to significant sources of greenhouse gases (GHG); namely, carbon dioxide (CO2) and methane (CH4). This study investigates the possibility of manipulating the enzymic latch in order to strengthen the suppression of decomposition in peatlands and thereby maximising their carbon sequestering abilities. It was found that adjusting the levels of photosynthetically active radiation (PAR) various peatland plants were subjected to did not alter the activity of phenol oxidases, as was hypothesised (due to the expected increase in root exudation brought about by maximised photosynthetic activity). Results also showed that managing floral communities of peatlands to strengthen the enzymic latch (by increasing phenolic concentrations and/or decreasing phenol oxidase activities) only produced a modest increase in carbon sequestration. Directly amplifying the levels of phenolics in the peat-matrix though proved to have a highly significant effect on suppressing enzymic decomposition and the resulting biogenic release of carbon-based trace gases. It was shown that although exudates from wood fragments were able to produce these inhibitory effects, adding a solution of high molecular weight industrially produced lignin (calcium lignosulphonate) was the most effective method of supplementing peat samples to achieve maximum suppression of organic matter breakdown. This effect was observed in peat taken from both temperate and boreal locations. Results from this study revealed that if supplementary phenolics were added to global peatlands as a method of geoengineering the additional amounts of carbon sequestered by peatlands could be transformed into 'carbon credits' to an estimated value of £42.25 billion.
Supervisor: Freeman, Christopher Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available