Pedo-antrocological characteristics of anthropogenically transformed soils in a case study of the Bolgar historical and archaeological complex in the Republic of Tatarstan (Russia)

Abstract

The study was conducted within the Bolgar historical and archaeological complex in the Republic of Tatarstan, with the aim to determine contents and distribution of antrocomass, i.e., charred particles in anthropogenically transformed soils of different ages and types of genesis. The study materials included a garden soil layer of the 20th century, an urban cultural layer of the 13th century and two buried arable soils – the upper soil of the 9th–10th centuries (Bolgar culture) and the lower soil of the 5th–7th centuries AD (Imen’kovo culture). People of the Bolgar culture were familiar with beneficial effects of wood ash and used it together with charred crushed bone as a mixed wood-bone ash fertilizer. The same principle was utilized for the improvement of soil fertility in the 20th century garden soil. Generally, the antrocomass accumulation was shown to be only an optional characteristic of anthropogenically transformed soils, e.g., it was absent at the early stage (5th–7th centuries) of arable land use. The particle-size distribution and the degree of preservation of charcoal particles were predetermined by the genesis of soil horizon, i.e., the ‘turbational’ type was associated with a higher degree of charcoal fragmentation as compared to the ‘sedimentational’ type.