Geoscience Reference
In-Depth Information
earths persists hundreds of years after they were abandoned, because it consists of
black carbon, as in soot or charcoal, coming from burnt biomass. In addition to
carbon they contain more phosphorus, nitrogen and calcium than the surrounding
soils. Fallows on Amazonian Dark Earths can be as short as 6 months, whereas
fallow periods on the surrounding forest soils need to be eight to 10 years long. The
size of the patches varies, ranging from small patches of less than one hectare
scattered within the normal upland soils, to areas of several km
2
stretched along
river bluffs and inter
uves. Terra preta often contains debris such as animal bone
fragments, turtle carapaces, shells, excrement, potsherds and remains of plants used
for houses, but the reason for their fertility are likely changes in the microbial
community due to the changes in substrate. They are currently investigated by soil
microbiologists.
Looking at the soil, it becomes clear that Amazonia
s rain forest is not a pristine
wilderness, but the location of probably the oldest ceramic
'
nds in the Americas, and
presumably, the world, dating to 5000 BCE
3500 BCE. Nearly continuous habitation
has been proven for a site near the mouth of the Amazon river, which was occupied as
early as 3500 BCE. Occupation of the Amazon, which has been widespread and is
documented in a multitude of known archaeological sites, ended with the European
conquest, or shortly thereafter. Agriculturalists who had by luck discovered how to
transform the infertile forest soils into useful ones, and then probably experimented to
create larger patches of this precious resource, vanished almost without trace. The
record of the Spanish explorer Francisco de Orellana, of his voyage down the Amazon
in 1542, where he provisioned himself by raiding villages along the river and reported
to have seen very large settlements standing on a slope on the northern shore of the
river near the Rio Madeira, has probably been wrongly dismissed.
The soils of the vanished people persist to date. Terra preta can be mined and is
sold by truckload or pot for gardening and agriculture. Scientists try to create dark,
fertile soils by inoculating rainforest soils with charcoal, with promising results.
The high carbon storage capacity of these soils makes them an interesting experi-
mental
-
eld for greenhouse gas policies.
3.3.2.4 Other Regions
The environmental histories of soils in South Asia, Africa, or Australia are less well
researched than those of China or Europe, and are often based solely on archaeo-
logical evidence. Nevertheless, some observations on soil classi
cations, soil
testing methods and diligent use of soils have been made and are available to the
non-specialist through overviews. Before turning to two such examples, the case of
Easter Island should brie
c island is a place
where phases of sustainable and unsustainable land-use are visible in the archae-
ological and pedological record.
44
Easter Island is one of the sites of successful
y be mentioned. The remote Paci
44
Bork and Mieth (
2006
).
