The socio-ecological legacies of centuries-old charcoal making practices in a mountain forest of the northern Pyrenees

Abstract

Centuries of charcoal making has profoundly shaped European mountain forest ecosystems. However, it remains difficult to assess this impact due to a lack of knowledge about the full operational sequence and related silvicultural systems. To accurately reconstruct such practices and shed light on the resulting legacies, we carried out an interdisciplinary study in the Bernadouze forest, a 46 ha mountain forest of European beech (Fagus sylvatica L.) in the French Pyrenees. We performed a multi-proxy analysis of 7990 charcoal fragments from 28 charcoal kilns to assess the long-term changes in forest composition and structure, but also in harvesting practices and related silvicultural systems. In addition, we assessed the legacy of such practices on the forest’s main features, by evaluating the biodiversity on 13 one-hectare plots using the Index of Potential Biodiversity (IBP). The 18 radiocarbon dates showed that charcoal making took place at least from the 9th-10th c. to the 19th-20th c. Beech and silver fir (Abies alba Mill.) were the main species used. We discerned sustainable silvicultural practices performed over the centuries without significant change. Charcoal burners harvested well calibrated wood pieces mostly from the end of the growing season until the early spring, and charred after a seasoning period. The forest was managed as a beech coppice with fir standard before being progressively transformed, between the mid 15th-mid 17th c. period, into a monospecific beech coppice, probably treated in a coppice selection system. While this management allowed forest cover to be continuously sustained, it also resulted in the homogeneity of the forest today, both in composition and structure, and led to low hosting capacity for biodiversity. Nevertheless, this ancient forest, which constitutes a high biocultural legacy due to immemorial use rights, needs dedicated management.