Archaeobotanical analysis of plant macroremains

Archaeobotanical analysis of plant macroremains

Analysis of plant macroremains deals with separation and determination of plant macroremains (seeds, fruits, needles, buds etc.) excavated from archaeological situations. The aim of this analysis is to determine a range of cultural plants and also to reconstruct past agrotechnical practices and processes and agricultural systems (e. g. rotation of cultural plants). Given he fact that mainly local sources of plants were used in the past, the assemblages of macroremains can provide important information concerning the characteristics of vegetation growing in the past in the surrounding of researched sites. The analysis of plant macroremains also provides information about the process of domestication of particular plants. Furthermore, it informs about specific characters of particular archaeological context (e.g. about local fossilisation conditions). The plant macroremains collected from the archaeological contexts also provide information concerning wild and domesticated plant sources used as food, source of energy or for other (e.g. technological) purposes. Under certain conditions, the archaeobotanical proxies can serve as a source of knowledge about seasonality of researched sites, especially in the situation when combined with other kinds of environmental proxies (e.g. pollen, fauna, annual tree rings…).

Plan macroremains usually preserve on archaeological sites thanks to unaccomplished burning. Fire has been since the Prehistory necessary part of all settlements and also of many burial places. Plan macroremains carbonisation usually happens during meal preparation, fires of settlements or during refuse combustion. Archaeological contexts containing carbonized organic macroremains thus belong to the most common on archaeological sites. Organic part of plant corpses is usually formed mainly by polysaccharides such as cellulose or lignin. Carbonization of polysaccharides results into a carbon skeleton sometimes containing also residual starch, lipids and DNA. Carbon skeleton is resistant against chemical and biological disruption; however, it is prone to mechanical damage.

Environment poor in oxygen slows down decomposition of plant remains. Wet environment is favourable for plan macroremains preservation. Lakes, river arms, marches, bogs, fens and water ditches contain wet sediments in the proximity of archaeological sites, which enable preservation of plant macroremains.

Plant macroremains often preserve also in places with specific chemism. For example, during metal (bronze, iron or silver) corrosion toxic salts and metal oxides appear, which can result in slowing down or even stopping of plant remains decomposition. Heavily salted sediments can also contain mineralised seeds pervaded with these salts.

Absence of water also slows down the process of plant remains decomposition. Preservation of dry plant remains is typical for arid regions. Dry plant remains present in wood-brick constructions of still existing buildings represent a special case of plant macroremains preservation. For example, unburnt daub of preserved Medieval and Early Modern houses can contain rich assemblages of dried plant remains.

Information concerning plants growing in past at particular archaeological sites can be received also indirectly from plant imprints on the daub, pottery or brick fragments. Plant material was frequently added in clay used for production of these kind of artefacts as bonding agent. In compare to the plant macroremains analysis, the plant imprints analysis is a great source of information also about soft vegetative plant tissues, such as leaves, straw or chaff, which appear otherwise just sporadically in archaeological contexts.

Analyses of plant macroremains are in a frame of the ERCA Centre guaranteed by Mgr. Petr Kočár from the Archaeological Institute of the Czech Academy of Sciences in Prague.

 

Achene of the hemp plant (Cannabis sativa), Veselí nad Moravou site, castle from the 13th century.

 

Germinated caryopsis of the common barley (Hordeum vulgare), Chanovice site, castle, Early Modern Age (scanning electron microscopy).

Stone of the grapevine (Vitis vinifera), Ledčice site – Early Middle Age (photographed with a use of the binocular magnifying glass).