Changes in water colour between 1986 and 2006 in the headwaters of the River Nidd, Yorkshire, UK: a critique of methodological approaches and measurement of burning management.

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]