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The effect of moorland management on the release of dissolved organic carbon (DOC) from blanket peat is currently a topic of great interest in the UK. A recent paper by Chapman et al. (Biogeochemistry, doi:, 2010) reports on changes in humic colour/DOC concentrations in surface waters draining 15 upland peat catchments in the North Pennines (UK) over two decades, and examines the possible underlying drivers of those changes. Chapman et al. identify significant variation in water colour between adjacent catchments and over time. One potential driver of changes in DOC is managed moorland burning, and Chapman et al. state that their study provides evidence that burning has no effect on colour in upland catchment drainage waters. This observation counters a recent series of papers showing strong links between new moorland burn management on blanket peat soils and colour/DOC in catchment drainage waters. We have reviewed the methodological approach and results presented by Chapman et al. that relate to the assessment of managed burning, and show significant errors in the data used in their analysis. This has resulted in conclusions being drawn about the role of managed burning in DOC release that are not supported by evidence. [ABSTRACT FROM AUTHOR]

This study compares the spatial and temporal variability of water colour for fifteen sub-catchments of the River Nidd, northeast England, in 1986 and 2006/2007. Between 1986 and 2006/2007, mean annual water colour increased in all the sub-catchments. However, there was considerable variation in the increase, which ranged from 22 to 155%. Statistical analysis revealed that the sub-catchments could be split into two 'types' based on water chemistry and therefore dominant source of runoff; type 1 where flow was dominated by runoff from peat and type 2 where a greater contribution of flow appears to originate from mineral soil horizons, as indicated by the higher silicon, base cation concentrations and pH values. Largest proportional increases in water colour were observed in the sub-catchments that had the smaller mean annual water colour values in 1986 which were, in general, the type 2 sub-catchments. The higher rate of water colour increase in the type 2 catchments, in comparison to the type 1 catchments, may be related to changes in adsorption of dissolved organic carbon (DOC) within the mineral horizons of the organo-mineral soils on the lower catchment slopes possibly as a result of changes in acid sulphur deposition. [ABSTRACT FROM AUTHOR]

Many catchment management schemes in the UK have focussed on peatland restoration to improve ecosystem services such as carbon sequestration, water quality and biodiversity. The effect of these schemes on dissolved organic carbon (DOC) flux is critical in understanding peatland carbon budgets as well as the implications for drinking water treatment. In many catchments, however, peatland areas are not the only source of DOC, meaning that their significance at the full catchment scale is unclear. In this paper we have evaluated the importance of different land uses as sources of DOC by combining three datasets obtained from the Exe catchment, UK. The first dataset comprises a weekly monitoring record at three sites for six years, the second, a monthly monitoring record of 25 sites in the same catchment for one year, and the third, an assessment of DOC export from litter and soil carbon stocks. Our results suggest that DOC concentration significantly increased from the peaty headwaters to the mixed land-use areas (ANOVA F = 12.52, p < 0.001, df = 2), leading to higher flux estimates at the downstream sites. We present evidence for three possible explanations: firstly, that poor sampling of high flows may lead to underestimation of DOC flux, second, that there are significant sources of DOC besides the peatland headwaters, and finally, that biological- and photo-degradation decreases the influence of upstream DOC sources. Our results provide evidence both for the targeting of catchment management in peatland areas as well as the need to consider DOC from agricultural and forested areas of the catchment., (Copyright © 2019 Elsevier B.V. All rights reserved.)