Locating Amazonian Dark Earths (ADE) Using Satellite Remote Sensing – A Possible Approach

Amazonian Dark Earths (ADE) are the result of pre- Columbian humans' occupation of the Amazon Basin and are related to the need for fertile soils for growing crops (e.g. Glaser and Woods 2004). ADE soils contain highly elevated levels of organic matter, mostly in the form of very slowly decomposing charcoal, which retains water and nutrients, and makes ADE some of the most fertile soils in the world (Kern et al. 2003; Lehmann et al. 2003). When productivity of plants grown on ADE soil was contrasted with typical Amazonian soils, Major et al. (2005) found that maize yields were as much as 63 times greater, weed cover was 45 times greater, and plant species diversity was up to 11 times greater than for adjacent typical Amazonian soils. ADE soils contain up to 70 times more SOM than typical Amazonian soils (Mann 2002). Woods and McCann (1999) have shown that nutrient transfers from outside of ADE sites are necessary to explain current nutrient levels in ADE soils, suggesting that the formation of these soils ultimately became an intentional effort on the part of prehistoric Amerindian populations to improve the quality of their farmland. These nutrient sources may have been plant and animal food wastes, fish bones and other un-used fish matter, or human excrement, as well as a host plant materials used for fuel and construction. The presence of algae in ADE from c.1150 BP and later suggests that silt from riverbanks was incorporated into the ADE soils in at least one location (Mora et al. 1991).