Comment on: 'burning management and carbon sequestration of upland heather moorland in the UK'

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Date: Feb. 2010
From: Australian Journal of Soil Research(Vol. 48, Issue 1)
Publisher: CSIRO Publishing
Document Type: Article
Length: 3,012 words
Lexile Measure: 1510L

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A recent paper by Farage et al. (2009) on burning management and carbon sequestration of an upland heather (Calluna vulgaris) moorland addresses an important subject that is currently under much debate in the UK. Many of the upland moorland systems in the UK have organic soils and store considerable quantities of carbon. Estimates of the total carbon stored in these soils vary depending on the assumptions made for soil depth, geographical area, bulk density and carbon content (see Chapman et al. 2001) but a recent reappraisal suggests they store in the region of 3000 Mt carbon (SEERAD 2007). Large areas of these systems are managed by burning, either for red grouse habitat or for sheep grazing (Yallop et al. 2006). The use of fire for managing this land is highly controversial (Tucker 2003; Pearce 2006; Davies et al. 2008a) and the debate has become polarised; the effect of burning on carbon budgets is an important component of this debate (Davies et al. 2008a). Research that estimates the impact of burning on carbon sequestration is urgently needed and the paper by Farage et al. is already being used as evidence that, to quote their abstract, 'careful burning management at this site does not have a major detrimental effect on the carbon budget'. Although Farage et al. are careful to point out that their results apply only to the one particular site, Mossdale Moor, where measurements were made, their conclusions are inevitably being used by landowners and moorland managers elsewhere in the country as evidence to defend the practice of management by burning and ultimately may be used as evidence in the policy decision-making processes (e.g. Scottish Government 2009). It is therefore crucial that a paper on such an important topic should be placed in an appropriate context.

Unfortunately, their estimates of the amount of carbon in vegetation that is consumed in a fire appear to be extreme and thus atypical of this type of management fire. For example, they report a very high amount of biomass remaining after the fires (given as 1262 g/[m.sup.2] in the text but as 1149 g/[m.sup.2] in their table 1), which is remarkable for a management fire in 15-year-old heather. This contrasts with our own data from 26 experimental fires, typical of those used in management, in similar vegetation in which we recorded a mean of only 277 g/[m.sup.2] of heather remaining with a maximum of 940 g/[m.sup.2] in one late-mature-phase stand (Table 1). This late-mature-phase stand was itself atypical in that the heather stems had collapsed such that a high proportion of the dead and fine fuel was close to the ground, un-aerated, and remained too damp to burn. The only situation in which more fuel than this could remain after a fire is burning in very old heather (late mature and degenerate phases; Gimingham 1988) in which the coarse woody stems comprise a significant proportion of the total biomass but remain unburned and in which a deep layer of mosses and litter has accumulated...

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Gale Document Number: GALE|A222313811