HOLOCENE FIRE IN THE SCOTTISH HIGHLANDS: EVIDENCE FROM MICROSCOPIC AND MACROSCOPIC CHARCOAL RECORDS

It has been hypothesised that the mid-Holocene pine (Pinus sylvestris L.) decline in the Scottish Highlands was the result of a change in the fire regime of the region. The wet climate of the Highlands and the predominantly non-forested condition of the area today does not lead one to intuitively imagine fire as a dominant ecological process. Scottish pine forests, however, are known to burn and in forested regions of the world under similar climatic conditions, fire is the predominant landscape-pattern forming disturbance process. To date, it has been largely unknown whether fire was a prevalent factor in Scotland over the course of the Holocene and what impact it may have had on the development of vegetation communities.

Both macroscopic and microscopic charcoal and pollen analyses are presented from four Holocene lake sedimentary sequences in the Scottish Highlands. Three macroscopic charcoal size fractions were examined (³ 500 mm, 250-500 mm and 125-250 mm). Comparison of macroscopic charcoal abundance profiles from these four disparate sites in the Highlands with those from areas of known fire activity indicates that landscape-level burning did occur in the Scottish Highlands throughout the Holocene. Charcoal abundance was found to be strongly correlated with vegetation composition at all four of the sites examined. These results reveal that pine abundance in the Highlands is not related to fire history, as had been postulated, but is instead predominantly related to heath development. Abundance profiles of the three different macroscopic charcoal size fractions were found to be strongly correlated. Microscopic charcoal abundance, however, was more variable and was, therefore, determined to be a less accurate measure of local catchment-scale burning within the region.