Multiple charcoal profiles in a Scottish lake: taphonomy, fire ecology, human impact and inference

Sedimentary microscopic charcoal in lacustrine environments has received much attention, although this has been concerned largely with the deposition of modern charcoal or with distributions through time based on single profiles. Lake sediments are dynamic entities, however, and the phenomenon of sediment focusing, for example, will lead to the redistribution of pollen, spores and charcoal. The process may not always result in greatly altered fossil assemblage in percentage terms, but values for individual indicators, or their absolute values, may be affected strongly. This is investigated using multiple microscopic charcoal profiles covering many thousands of years from Black Loch, Fife, eastern Scotland. Relative and absolute measures of charcoal depiction are considered as a prelude to discussion of microscopic charcoal taphonomy in the context of a small lake, fire ecology and human impacts. The charcoal measures (concentrations, influx and charcoal to pollen ratios) all follow similar patterns, though with very different numerical values. Two cores have charcoal influx values of similar orders of magnitude for much of the Holocene, whereas quantities in two other cores vary by a factor of similar to 16 after 1000 cal BP. The differences between influx measures for total pollen and charcoal indicate that focusing effects between the two indicators are dissimilar. Correlations with pollen and spore taxa are explored and demonstrate the problems of discrepant data between profiles. Charcoal-pollen patterns for specific cultural periods are examined for one profile and they provide data suggesting that a direct fire-vegetation relationship for the site is unproven. The need to adopt a multi-causal approach to inference is emphasised. (C) 2000 Elsevier Science B.V. All rights reserved.