| Summary: | Peatlands are important terrestrial stores ofcarbon and a principal source ofdissolved organic carbon (DOC) to the fluvial environment.. Whilst often regarded as a net carbon sink, enhanced DOC concentrations and an associated rise in the level of water discolouration observed in many artificially drained peatland catchments across Europe and North America suggests that continued degradation may shift the balance of the carbon budget, such that they become a net carbon source. Peatland restoration, in the form of drain blocking, is currently being undertaken in a number of these locations. However, a great deal of this work 'has been carried out on a pragmatic or even an ad-hoc basis, with a distinct lack of process-based assessment. Thus, very little is known about how such changes in land management affect DOC and colour dynamics.. In order to bridge this knowledge gap, this thesis examines a range of processes known to influence DOC/colour production and release. A variety of field monitoring and laboratory measurements were undertaken to assess the upland blanket peat within the Oughtershaw Beck catchment in the Yorkshire Dales National Park, UK. The installation of drainage ditches was found to reduce both the carbon storage potential of the peat and the quality of upland catchment waters. Drainage lowered the depth ofthe water table across the peat by an average of 10 em, enhanced the rate of microbial activity by 33 % and increased DOC and colour production in soil water solutions by 35 %, 'relative to an adjacent intact site that had not been drained. The greater level of aeration in the upper peat layers associated with a lowered water table also appeared to reduce the degree of surface saturation and the occurrence ·of overland flow (OLF), resulting in a greater volume of water being drawn down into the peat body. The reduced saturation levels caused the subsidence and compaction of the upper soil layers, which increased the bulk density and ultimately reduced the degree of macroporosity within the soil. ill turn, this is thought to have increased the residence time and surface area over which percolating waters flow, which is likely to have enhanced the degree of interaction with decompositional products, and thus the mobility of DOC/colour.
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