Middle Bronze Age land use practices in the north-western Alpine foreland – A multi-proxy study of colluvial deposits, archaeological features and peat bogs

This paper aims to reconstruct Middle Bronze Age (MBA) land use practices in the north-western Alpine foreland (SW Germany, Hegau). We used a multi-proxy approach including the biogeochemical proxies from colluvial deposits in the surrounding of the well-documented settlement site of Anselfingen and offsite pollen data from two peat bogs. This approach allowed in-depth insights into the MBA subsistence economy and shows that the MBA in the north-western Alpine foreland was a period of establishing settlements with sophisticated land management and land use practices. The reconstruction of phases of colluvial deposition was based on ages from optically luminescence (OSL) and radiocarbon (AMS 14C) dating from multi-layered colluvial deposits and supports the local archaeological record with the first phase of major colluvial deposition occurring during the MBA followed by phases of colluvial deposition during the Iron Age, the Medieval period, and modern times. The onsite deposition of charred archaeobotanical remains and animal bones from archaeological features, as well as polycyclic aromatic hydrocarbons (PAHs), charcoal spectra, phytoliths, soil microstructure, urease enzymatic activity, microbial biomass carbon (Cmic) and heavy metal contents, were used as proxies for onsite and near-site land use practices. The charcoal spectra indicate MBA forest management which favoured the dominance of Quercus in the woodland vegetation in the surrounding area north of the settlement site. Increased levels of 5ß stanols (up to 40 %) and the occurrence of pig bones (up to 14 %) support the presence of a forest pasture mainly used for pig farming. In the surrounding area south of the settlement, an arable field with a buried MBA plough horizon (2Apb) could be verified by soil micromorphological investigations and high concentrations of grass phytoliths from leaves and stems. Agricultural practices (e.g. ploughing) focussed on five stable cereal crops (Hordeum distichon/vulgare, Triticum dicoccum, Triticum monococcum, Triticum spelta, Triticum aestivum/turgidum), while the presence of stilted pantries as storage facilities and of heat stones indicate post-harvest processing of cereal crops and other agrarian products within the settlement. In the area surrounding the settlement, increased levels of urease activity, compared to microbial biomass carbon (up to 2.1 µg N µg Cmic−1), and input of herbivorous and omnivorous animal faeces indicate livestock husbandry on fallow land. The PAH suites and their spatial distribution support the use of fire for various purposes, e.g. for opening and maintaining the landscape, for domestic burning and for technical applications. The offsite palynological data support the observed change in onsite and near-site vegetation as well as the occurrence of related land use practices. During the Early and Middle Bronze Age fire played a major role in shaping the landscape (peak of micro-charcoal during the MBA) and anthropogenic activities promoted oak dominated forest ecosystems at the expense of natural beech forests. This indicates a broader regional human influence in the north-western Alpine foreland at low and mid altitude inland sites during the Middle Bronze Age.