Summary
This study challenges the longstanding anthropogenic origin hypothesis for Amazonian Dark Earths by presenting geochemical and isotopic evidence suggesting natural alluvial deposition processes, rather than indigenous soil management, as the primary driver of their exceptional fertility. Whilst pre-Columbian artefacts at ADE sites indicate human habitation, the timing and composition of elevated phosphorus and calcium deposits, corroborated by neodymium and strontium isotope signatures, suggest indigenous peoples harnessed rather than engineered these naturally formed soils. The findings propose a fundamental reframing of human landscape influence in the Amazon and implications for sustainable tropical land use.
Regional applicability
The findings have limited direct relevance to UK farming systems, climate zones, and soil types. However, the methodological approach—combining geochemical analysis with isotope tracing to distinguish anthropogenic from natural soil enrichment—may inform UK soil archaeology and heritage land management studies.
Key measures
Phosphorus concentrations, calcium concentrations, trace element composition, stable isotope ratios of neodymium and strontium, radiocarbon activity of microcharcoal particles, spatial correlation analysis
Outcomes reported
The study analysed phosphorus, calcium, trace elements, and stable isotope ratios (neodymium, strontium) in Amazonian Dark Earth profiles compared to surrounding soils. Findings indicate exogenous mineral and carbon inputs from alluvial deposition predating human soil management by several millennia.
Topic tags
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