Desiccated diaspores from building materials: methodological aspects of processing mud brick for archaeobotanical studies and first results of a study of earth buildings in southwest Hungary

Earth buildings are among the richest sources of archaeobotanical materials from the recent past. Thus, mudbrick constructions are extremely rich in plant materials, especially chaff, straw, fruits and seeds. Recovery of these remains enables us to gain a comprehensive insight into the contemporary floras of past settlements and their surroundings. Mudbricks from southwest Hungary which were 100–150 years old and were used there as traditional natural building materials, were examined in this research from an archaeobotanical point of view. Techniques were used that mostly come from modern seed bank research, and the most efficient processing methods were tested and further developed. Different flotation procedures were compared and the minimum sample volume was also determined. A new sodium chloride (common salt) flotation method was developed, providing a useful separation procedure for the recovery of plant remains and diaspores (seeds) from mudbrick. The effectiveness of sodium chloride is similar to other chemicals used in seed bank research, but much more economical. The minimum and optimum sample volumes are 2,500–3,500 cm 3 ; these are necessary to recover most of the taxa preserved in the bricks. A trend in the recovery of different sized seeds was also observed, revealing that the recovery of smaller seeds was less successful. Using the sodium chloride method, more than 18,000 desiccated diaspores were recovered and identified from 212 kg of mudbrick samples, from the period between 1850 and 1930. A total of 249 taxa were identified, most of which are weedy taxa connected to cereal and ruderal weed plant communities.