Lj. Osher et Sw. Buol, RELATIONSHIP OF SOIL PROPERTIES TO PARENT MATERIAL AND LANDSCAPE POSITION IN EASTERN MADRE DE DIOS, PERU, Geoderma, 83(1-2), 1998, pp. 143-166
Properties of soils in the eastern part of Madre de Dies, Peru, were c
haracterized and related to landscape position and parent material tex
ture. Level uplands, dissected side slopes and recent flood plains dom
inate the topography in this region. Soil textures vary from clayey to
sandy, depending on the texture of sedimentary materials from which e
ach pedon formed. Parent material textural variation is a result of di
fferences in the energy of the meandering rivers that deposited the an
cient alluvium. Fourteen soil profiles were described and sampled in t
he field and analyzed in the laboratory. Data for eight soil profiles
representative of the region are presented here. The profiles include
soils formed in both sandy and fine-textured parent materials and soil
s with moisture status ranging from well drained to poorly drained. So
il moisture conditions vary with position on the landscape, such that
as distance from streams increases, average depth to the fluctuating w
ater table decreases. Redoximorphic features are present in all minera
l soils. The average depth to redoximorphic features is least in locat
ions furthest from streams. Soils in landscape positions that are poor
ly or somewhat poorly drained contain significant amounts of plinthite
. In all soils, kaolinite is the dominant mineral in the < 0.2 mu m fr
action, while quartz is the dominant mineral in very fine and fine san
d fractions. All soils have low cation exchange capacity (CEC), low ba
se saturation, and acid pH. Coarse-textured spodic soils with well dev
eloped zones of iron and organic matter translocation are formed in re
cent sand deposits of flood plains of 2nd-order streams. Organic soils
are found in the wetlands associated with flood plains of some 3rd-or
der streams. Most properties of these soils appear to be controlled by
the textures of their sedimentary parent materials and by their posit
ion on the landscape. The soils classify as Paleustults, Plinthaquults
, Kandiustults, Placaquods and Troposaprists according to Soil Taxonom
y. New subgroups of Paleustult are proposed. (C) 1998 Elsevier Science
B.V.