Long-term records of dissolved organic carbon flux from peat-covered catchments: evidence for a drought effect?

This study considers three long records of dissolved organic carbon (DOC) flux from two catchments with peat-covered headwaters. The catchments vary in size from 11 to 818 km(2) and the records are at least 12 years old, with one record going back to 1965. The study compares both annual and monthly DOC flux records with a range of hydroclimatic indicators in order to test which component of droughts may contribute to increasing DOC flux. The study found that: (1) there was no significant correlation between any of the proposed drought variables and DOC flux in any of the study catchments over periods of up to 34 years; (2) the most important variable for explaining the DOC flux was the runoff from the catchments overlying a seasonal cycle and an underlying upward trend was present in some records; (3) the residual time-series, after removal of the best-fit models, showed no evidence of increased production after times of severe drought. The lack of any evidence for any additional biogeochemical reactions associated with drought supports evidence that DOC loss from peat is limited by its solubility and that its production is fast on the time-scale of runoff events. Copyright (C) 2008 John Wiley & Sons, Ltd.