Soil Bacterial Communities as Indicators of Anthropogenic Impact: Insights from an Early Medieval Settlement Pit Beneath the Church of Golmsdorf (Germany)

Soil samples obtained during an archaeological investigation accompanying renovation works on the village church of Golmsdorf were analyzed for the composition of soil bacterial communities using 16S rRNA sequencing. The bacterial composition of an early medieval settlement pit discovered at depth beneath the floor of the nave proved to be particularly noteworthy in relation to the archaeological context. The composition of DNA coding for 16S rRNA from this settlement pit reflects the incorporation of plant material, most likely mixed with ruminant manure and possibly additional animal remains. Archaeologically, this can be interpreted as evidence for human use of the immediate surroundings of the pit during its backfilling, together with livestock keeping. This finding clearly demonstrates the ecological “memory” of soil bacteria with respect to the prehistoric past and the human impact on the soil at that time. In contrast, bacterial taxa associated with organic material and livestock are scarcely present—or absent altogether—in soil samples taken immediately beneath the church floor. Instead, these samples show a high proportion of salt-tolerant and halophilic bacteria, which corresponds well with the observed high electrical conductivity values of this material. This pattern is interpreted as a consequence of the incorporation of construction material residues into the soil during building activity at the church in the late Middle Ages or 17th-century construction phases. The results overall demonstrate that NGS-based analyses of soil bacterial communities can provide valuable insights into human influence on soil material in both historical and prehistoric contexts, offering important additional information for archaeological interpretation.