Burning management and carbon sequestration of upland heather moorland in the UK

Abstract

The use of fire in land management has come under increasing scrutiny with regard to its potential effects on sustainability and climate change. Moorlands in the United Kingdom have traditionally used rotational burning of the heather (Calluna vulgaris) to improve the grazing and habitat, especially for grouse (Lagopus lagopus scoticus). However, these ecosystems overlie carbon-rich soils and concerns have been raised about the merits of this practice. In order to assess the impact of rotational burning on carbon balance, an investigation was undertaken on a grouse moor in the Yorkshire Dales, UK. This showed that the quantity of carbon stored above ground in heather biomass ranged from 600 to 1325 g C/m2 (typical for UK upland heaths). However, the national UK carbon inventory assumes 200 g C/m2, thereby appearing to underestimate considerably the importance of these habitats for carbon storage above ground. Analysis of 2 burns in subsequent years showed that 16 ± 4% and 24 ± 5% (± s.e.) of the above-ground material was consumed in the fires, resulting in the direct release of 103 ± 22 and 201 ± 62 g/m2 of carbon, respectively. Indirect carbon losses, which other studies have shown to be primarily due to erosion, were estimated to release another 5–21 g C/m2.year. The significance of other major greenhouse gas fluxes was assessed for the whole system using published parameters and models. We show that, over the burning cycle of 15–20 years, losses of carbon from burning are <10% of the total losses of carbon from the system, implying that careful burning management at this site does not have a major detrimental effect on the carbon budget, which for this moor lies within the range of an annual net loss of 34 g C/m2.year to a net uptake of 146 g C/m2.year.