Charcoal Dispersal from Alpine Stallo Hearths in Sub-Arctic Sweden: Patterns Observed from Soil Analysis and Experimental Burning

Greger Hornberg,Lars Liedgren

doi:10.5539/ach.v4n2p29

Abstract

To evaluate dispersal patterns and concentrations of macroscopic charcoal particles around Stollo settlements in sub-arctic Scandinavia, their distributions following experimental burning and soil concentrations around an alpine Stollo settlement dating between AD 700 and 1150 were recorded. After the burning 98% of recorded particles were 0.1-0.5 mm long, 90% were dispersed within 40 m of the fire, their mean concentration 40 m from the fire was 0.14±0.08 particles/cm2 and the concentration decreased with increasing distance. At the settlement, 95% of recorded charcoal particles were 0.1-0.5 mm long, 94% were within 40 m of the hearths, the mean concentration declined with increasing distance, and concentrations were much lower than expected from the experimental burning (e.g. 17.6±2.4 particles/cm2, 40 m away). In conclusion: biological archives used for charcoal analysis in archaeological and vegetation history studies should be located ?40 m from settlements, and data obtained from charcoal analyses should be interpreted cautiously.

Highlights

1.1 Charcoal in Archaeological and Fire Ecology StudiesCharcoal found associated with archaeological sites is generally interpreted as originating from anthropogenic fires, such as large-scale burnings of vegetation to: increase the growth of grasses and herbs, and attract wild game (Mellars, 1976, Hörnberg et al, 1999); provide grazing for domestic animals (Emanuelsson & Segerström, 1998); or clear areas around settlements for construction and cultivation, e.g. in slash and burn cultivation (Wallin & Segerström, 1994, Larsson, 1995, Emanuelsson, 2001)
Sufficient charcoal be dispersed from a hearth inside a hut for it to be detectable in the vicinity of a settlement? Secondly, how far can charcoal produced in hearths disperse, and what is the resulting distribution pattern like? Thirdly, can fossil charcoal produced at the time of a Stállo settlement still be found in the soil around an alpine settlement today? based on the charcoal distribution pattern, is it possible to ascertain whether the particles derived from a hearth fire, from burning vegetation or from regional fires? To address these questions, an experimental burning was conducted and soil samples were collected from the surroundings of an ancient Stállo settlement with a known history
Over 90% of all charcoal particles were found within a radius of 40 m (Table 1), all particles between 0.5 mm and 1 mm were found within a radius of 20 m and all but one > 1 mm particle were recorded within 10 m of the hut

Summary

Introduction

1.1 Charcoal in Archaeological and Fire Ecology StudiesCharcoal found associated with archaeological sites is generally interpreted as originating from anthropogenic fires, such as large-scale burnings of vegetation to: increase the growth of grasses and herbs, and attract wild game (Mellars, 1976, Hörnberg et al, 1999); provide grazing for domestic animals (Emanuelsson & Segerström, 1998); or clear areas around settlements for construction and cultivation, e.g. in slash and burn cultivation (Wallin & Segerström, 1994, Larsson, 1995, Emanuelsson, 2001). It can be difficult to determine if the charcoal recorded at archaeological sites derives from anthropogenic or natural fires (Théry-Parisot et al, 2010). This has made it difficult to date ancient boreal settlements using charcoal because old particles may have combusted and new ones may have been produced by numerous natural fires that have affected the settlement area before and after their use (Liedgren et al, 2007). It is challenging to establish whether recorded charcoal derives from man-made or natural fires (Clark, 1988, Lynch et al, 2004, Théry-Parisot et al, 2010)

Objectives

Methods

Results

Discussion

Conclusion