Pedogenesis and pre-Colombian land use of “Terra Preta Anthrosols” (“Indian black earth”) of Western Amazonia
Introduction
The Terra Preta Anthrosols of Amazonia (Indian black earth) are mainly Oxisols, Ultisols and Inceptisols with an anthropic A horizon. They have been described by Katzer (1933), Gourou (1949), Sombroek (1966), Ranzani et al. (1970), Eden et al. (1984) and Andrade (1986), yet many aspects of their origin remain obscure. Detailed studies of these precolonial anthropogenic soils can help answer questions about population distribution, soil carrying capacity, settlement pattern and land uses of ancient Amazonian peoples. According to Roosevelt (1997), the history and ecology of Amazonian habitats are of theoretical and practical relevance to the conservation of the vast tropical rainforest, and yet they are poorly documented. According to radiocarbon dating of Terra Preta sites (Hilbert, 1968), these pre-Colombian societies inhabited the Amazon valley and its main tributaries between 2400±75 and 1525±58 years BP.
Terra Preta Anthrosols in the lower Amazon valley and lower Tapajós have been chemically studied by Kern (1988), Kern and Kampf (1989), Zech et al. (1990), Pabst (1991), Kern and Costa (1997) and Glaser (1999) among others, but little is known about the Terra Preta sites of the middle Amazon valley. Near Manaus, there are many discontinuous patches of well-drained Tertiary Plateau, where Xanthic Oxisols (Latosols) are overlain by black earth deposits pedogenically transformed, containing archaeological artifacts such as pottery fragments, weathered bones and organic remains. The extent of these patches of high fertility epipedons is of local and regional importance, and has been considered as an indication of former sustainable land use (Smith, 1980; Glaser, 1999). Even today, anthrosols are intensively cultivated by local population (the“caboclos”), highlighting its importance to the Amazonian social and ecological landscape (Fig. 1).
The aim of this paper is to relate selected chemical, physical and mineralogical attributes of Terra Preta Anthrosols (TPA) with aspects of precolonial land use and the origin of TPA. Also, TPA attributes were compared with neighbouring nonanthropogenic soils, ranging from the Tertiary Plateau to the floodplain of middle Amazon, emphasizing the pedogeomorphological relationships of their occurrence and implications for precolonial human societies.
Section snippets
Material and methods
We studied seven soils along a toposequence ranging from the Tertiary Plateau (regionally called Terra Firme) down to the Amazon river floodplain (regionally called várzea), in the Iranduba district, near Manaus, Amazonas, Brazil (Fig. 2). The soils were classified in the Brazilian System of Soil Classification (EMBRAPA, 1999) and Soil Taxonomy (USDA, 1999), respectively, as Anthropic Yellow Podzolic (Anthropic Xanthic Kandiudult) (P1), Anthropic Yellow Latosol (Anthropic Xanthic Kandiudox)
Chemical and physical characteristics
The five soils from the Tertiary Plateau and its border (P1 to P5; Fig. 2) are generally dystric in subsurface, and dominated by kaolinite in the clay fraction, similar to those developed from preweathered sediments on the Tertiary Plateau elsewhere in Brazil (Resende et al., 1995) Table 1, Table 2. The two nonanthropogenic soils, P4 and P5, have high levels of Al3+ in the exchange complex. At the surface, the anthropogenic A horizons of P1, P2 and P3 show a distinct eutrophic character, with
Conclusions
The investigated chemical, mineralogical and micropedological attributes, such as high available P and mica flakes in pottery remains of the Terra Preta, indicate that the allochthonous materials in the Terra Preta Anthrosols have their source in the neighbouring floodplain soils and from the Amazon river. Amazon floodplain soils were the only source of soil material for pottery, since 2:1 minerals are not found in upslope Tertiary Plateau soils.
The total and available P contents of
Acknowledgements
The authors are grateful for the careful reviews and comments by Prof. J. Catt and Dr. G. Guggenberger on earlier version of this paper. This work has been partially supported by CAPES-Brazil and CNPq, during Prof. Schaefer's sabbatical in Western Australia.
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