The value of the archaeobotanical analysis of desiccated plant remains from old buildings: methodological aspects and interpretation of crop weed assemblages

Plant material like threshing remains has been used systematically as filling and insulation material in buildings for a long time. Such plant material can be found in several places, for example in floor cavities (internal floor deposits, Fehlböden) or in beam holes. For the first time in Switzerland, desiccated plant material like this has been investigated. In this article the analysis of the material from three different sites is presented, each dated to a different period, from the late medieval period to the time just before the industrial revolution. The samples consisted of chaff from Triticum spelta in bulk, and smaller amounts of other cereals such as T. monococcum, Avena sativa, Panicum miliaceum and Secale cereale, plus various weeds. The assemblages in the late medieval samples show evidence of three-field rotation: the high percentage of grassland species is interpreted as an indicator of the fallow land phase within the three-field system. A higher ratio of annual to perennial plants in the more modern samples indicates the development of more intensive tillage and cultivation. Methodological questions regarding sampling strategies of the floor cavity subsamples are investigated. The analyses suggest that the volume of these subsamples should be more than two litres.