NGS Data of Local Soil Bacterial Communities Reflecting the Ditch Profile of a Neolithic Rampart from Hachum (Germany)

An archaeological exposure near Hachum, featuring a ditch profile interpreted as part of a Neolithic earthwork, was characterized using DNA analyses of bacterial 16S rRNA from soil samples. The NGS data from 13 sampling points at different positions and depths within the trench profile were compared with regard to the percentage distribution of phyla and the frequency of occurrence of individual bacterial types (genera or operational taxonomic units, OTUs). Characteristic differences between parts of the trench profile became apparent based on correlations of OTU abundances as well as the occurrence of specific types. In particular, a high similarity in bacterial communities was observed among samples from intermediate trench depths, while a markedly different composition was found in the area of the central trench bottom. These findings indicate that the trench must have remained open for a certain period of time and was later filled relatively homogeneously. The results showed that the middle and lower parts of the ditch fill could be clearly distinguished from each other and from the surrounding area based on the composition of soil bacterial DNA. Genera detected predominantly in the lower part of the ditch suggest that, after the ditch was completed, organic matter, animal dung, and possibly even human feces were accumulated at the bottom. The investigations demonstrate that analyses of soil bacterial communities can provide valuable insights into the history and function of a Neolithic earthwork and, more generally, represent an important additional source of information for interpreting archaeological contexts that are devoid of or poor in finds.