[en] Landscape Ecological Survey of the Bipindi-Akom II ... - ITTO

eddish mottles mottles occur, occur, starting starting between between 20 20 and and 50 cm depth. depth. Iron Iron concretions occur in in the deeper
subsoils, starting between between 50 to 100 cm depth. depth.
Locally on summits, steep upper slopes or very steep hill slopes, moderately deep to very deep,
gravelly and stony soils occur as inclusions within the Ebom soils. These have clay contents in
the the subsoils subsoils of 40 40 to to 50% and and are are less less deeply deeply and and less less intensively weathered weathered than than the the typical typical
Ebom Ebom soils. soils. At the present scale scale of the survey, these soils could not be mapped separately.
The Ebom soils are typically found in the uplands and isolated hills in the central and northern
regions regions of the TCP TCP area area at at altitudes altitudes between between 350 and and 500 m asl. asl. Complexes Complexes of the Ebom Ebom with with
Nyangong Nyangong soils are found in the uplands above 500 m.
Full profile descriptions with analytical data of the Ebom soils are given in Annex IV.
5.2.3 Ehimimhang Ebimimbang soils
The Ebimimbang soils are are moderately moderately deep to very deep, moderately moderately well well to well well drained, drained,
yellowish yellowish brown brown sandy clay clay loams to sandy clays with sand to sandy loam topsoils and with
gravelly subsoils. They are developed on coarse grained gneisses and migmatites. They are
characterized characterized by by sandy sandy topsoils topsoils and and a a clay clay increase increase with with depth depth of 15 to 20% 20% which which generally
occurs occurs within within 20 20 cm cm of the surface. The The depth depth of the moderately moderately deep deep soils (50-100 cm) cm) is is
limited by weathering bedrock, plinthite or high concentrations of gravel (both iron concretions
or or quartz quartz gravel).
The topsoils are 5 to 10 cm thick, with colours in the range of dark greyish brown to black and
generally with about 20% clay clay but clay percentages percentages as as low as 9% occur as well. well. The subsurface
horizons horizons are 5 to to 10 cm thick, have yellowish brown to dark brown colours and have clay
percentages percentages of 16 to 25 %, but in places less. As silt contents are low, sand contents of tops oils
and and subsurface subsurface horizons horizons are high.
Subsoils have yellowish brown colours with a range from light yellowish brown to strong brown
and commonly have about 40% clay. Clay contents ranges between 30 and 64%. Reddish
mottles start to appear appear between about about 15 and 40 cm depth. In places plinthite occurs with in 150
cm, cm, starting starting between between 75 and 140 cm cm depth. depth. Iron Iron concretions concretions occur occur in in the the deeper deeper subsoils, subsoils,
starting starting at at irregular irregular depths, depths, appearing appearing between between 15 and 140 cm cm from from the the surface surface downwards. downwards. Next Next
to these concretions, quartz gravel and pieces of rotten rock occur in the deeper subsoils giving
them them a texture of slightly gravelly to gravelly sandy clay loams to sandy clays.
In In the the survey survey area, area, the the Ebimimbang soils typically typically occur occur at at altitudes below below 350 350 m and and are thus thus
found found on on the the dissected erosional erosional plains, plains, uplands uplands and and isolated isolated hills hills in in this altitude zone. zone. Valley Valley
bottom bottom soils occupy occupy up up to to 15% of these areas but could usually not be mapped separately as
most most valley valley bottoms bottoms are are narrow narrow « 250 250 m).
Annex IV gives full profiles descriptions with analytical data of the Ebimimbang soils.
5.2.4 Valley Bottom soils
The valley bottoms are dominated by moderately deep to very deep, poorly to very poorly
drained drained soils soils developed developed in unconsolidated recent recent alluvium. alluvium. The The soil soil profiles profiles are stratified
showing showing alternations alternations of sand, loam and and clay clay layers. layers. Sand, Sand, however, however, is dominant. Flooding, Flooding, high high
ground water water levels and and locally locally greyish greyish colours colours are characteristics characteristics of this soil soil type. type. Depth Depth of
groundwater level and soil texture could be used for further subdivision of these soils, although
at reconnaissance scale scale this this is not feasible.
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