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Northern peatlands are important stores of carbon. Following mechanical harvesting, peatlands are often abandoned. The plant communities on cutover peatlands are species-poor and large parts of these sites can remain bare for long periods of time. We currently have little understanding of carbon dynamics in cutover peatlands. This thesis reports various experiments undertaken on a cutover peatland investigating rates of decomposition of different litter types at different water-tables; the influence of plant species on litter decomposition; fungal communities. associated with different litter types; pelow-ground fluxes of recent plant assimilate . and the fate of inputs of below-ground labile carbon. Inputs of carbon from plant litter were dominated by Gal/una vulgaris. Litter type was more important than depth to water-table in determining litter decomposition; over 18 months, there was no· difference between losses of carbon in the litter of four vascular plants, but Sphagnum auriculatum showed very little change in carbon content. Fungal community composition was also more influenced by litter type than water-table. Carbon, nitrogen and phosphorus were all significant factors in explaining fungal community composition but over 75% of the variation was unexplained by these litter quality variables. Living plants did not effect rates of litter decomposition or community composition of fungi ,. colonising litter. ·Inputs of 13C. root extracts from different plant species were used equally by micro-organisms. The first use of in situ 13C pulse labelling on a peatland showed that most of the 13C pulse was lost via shoot respiration, with a third of 13C remaining in the shoot biomass after 2 months. Although there were no significant differences between the DOC associated with the three different plant species studied, there was considerable variation in the quantities and dynamics of carbon allocated to this pool. Fluxes of 13C from peat respiration were low in comparison with the other carbon pools. Key words: carbon; peat; cutover peatland; carbon dioxide; carbon flux; Gal/una vulgaris; Eriophorum angustifolium; Eriophorum vaginatum; Sphagnum auriculatum; decomposition; fungal community composition; 13C pulse labelling.

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