Anthropogenic soil and settlement organisation in the Bolivian Amazon

Abstract

Anthropogenic soils known as Amazonian Dark Earths (ADEs) have long been known as a key component of subsistence systems for various pre-Columbian Amazonian populations. Often treated as a single category, ADE systems consist of two broad anthrosols (human-modified soils): the darker ADE (traditionally known as terra preta) and a lighter brown Amazonian Brown Earth (ABE; traditionally known as terra mulata). Data on the characteristics and spatial distribution of these anthrosols are severely lacking. Transects of soil test pits at the Triunfo and Versalles archaeological sites in the Iténez Forest, in the Bolivian Amazon, show variability in the distribution of soil types, revealing aspects of settlement organisation and resource management. Geochemical, isotopic and archaeobotanical data from an ADE, ABE and control soil profile from the Triunfo site, established ca. 500 cal BCE, characterise the two anthrosols as distinct components of a polyculture agroforestry subsistence system that combines anthropogenic soil fertilisation, closed-canopy forest enrichment, limited forest clearance for crop cultivation and low-severity fire management.

Legacies of Indigenous land use and cultural burning in the Bolivian Amazon rainforest ecotone

“…Versalles is located on the banks of the Iténez River (known as the Guaporé River in Brazil), within the tropical forest on the northern border of the forest reserve. Today, Versalles is inhabited by an Itonama-speaking Indigenous community, which is built atop a pre-Columbian Indigenous settlement [76]. Archaeological and terrestrial palaeoecological research was conducted at the Triunfo site on the southwestern shore of LV, which includes a mosaic of anthropogenically enriched ADE/ABE soils surrounded by a ditch and embankment earthwork, known as a zanja , and a double ditch ring village [76].…”

“…Today, Versalles is inhabited by an Itonama-speaking Indigenous community, which is built atop a pre-Columbian Indigenous settlement [76]. Archaeological and terrestrial palaeoecological research was conducted at the Triunfo site on the southwestern shore of LV, which includes a mosaic of anthropogenically enriched ADE/ABE soils surrounded by a ditch and embankment earthwork, known as a zanja , and a double ditch ring village [76].

Figure 1Regional study map of Laguna Versalles.

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“…A four-week archaeological excavation was conducted in 2017 at the archaeological site of Triunfo located on the southwest shore of LV (figure 1) to recover cultural material, establish construction chronology of earthworks and assess site formation history [76]. Ceramic material was analysed following standard procedures to assess changes in form, paste and decoration, and compared to regional collections (electronic supplementary material, figure S1).…”

“…A transect of soil test pits, running perpendicular from the lake, was assessed for cultural material and for the presence, depth and intensity of anthropogenic soil. Three soil test pits were excavated along the transect for archaeobotanical, geochemical and isotopic sampling representing ADE, ABE and nearby ferralsol soils used as control sample [76]. Archaeobotanical analysis of the samples (phytoliths and macrocharcoal) was conducted following standard procedures [64,76].…”

“…Three soil test pits were excavated along the transect for archaeobotanical, geochemical and isotopic sampling representing ADE, ABE and nearby ferralsol soils used as control sample [76]. Archaeobotanical analysis of the samples (phytoliths and macrocharcoal) was conducted following standard procedures [64,76]. Full archaeobotanical analysis is presented elsewhere [5,76], with key results being discussed below.…”