Effects of managed burning in comparison with vegetation cutting on dissolved organic carbon concentrations in peat soils

Abstract

Given the continuing concern about rising concentrations of dissolved organic carbon (DOC) in stream water leaving peat-covered catchments, this study has considered the impact of managed burning or cutting of Calluna vulgaris, a dominant vegetation cover in many UK peatlands. Pristine mature Calluna stands were compared with those that had been subject to cutting and or managed burning up to 5 years after intervention. The study measured the DOC concentration of both soil and surface runoff water over a period of 12 months in comparison with water table depth, conductivity, and pH. The results show the following: * The depth to the water table decreases upon both burnt and cut sites relative to controls in line with a change in evapotranspiration due to loss of vegetation. * The DOC concentration of surface runoff water was not significantly different (P < 0.05) between any of the treatments and the control. * The DOC concentration in soil water significantly (P < 0.05) decreased with both burning and cutting, but these differences could be explained by differences in water table and changes in flowpath through the soil profile. The study suggests that declines in soil water DOC concentration are brought about as different levels in the peat profile become the dominant source of water due to changes in the depth to water table. Changes in the depth to water table were brought about by changes in evapotranspiration that result from the loss of vegetation. The changes in water table mean that this mechanism may explain other observations of DOC concentration change with management. Cutting and burning may represent a management intervention that could be effective at reversing the current trends in DOC transfers from peat-covered catchments.