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SOILS

Introduction
Geologically, Kebun Cina Forest Reserve consists of sedimentary rocks dominated by sandstone interbedded with mudstone known as Sandakan Formation. It forms prominent scarps and ridges with moderate dipslopes of sandstone cuestas. The sandstone is soft, grey to bluish grey, weathering yellow to brown. It is fine to medium grained, with quartz being the dominant mineral.
In a forest ecosystem, soil influences the formation of plant communities, and their species and structural diversity. The type of vegetation on a soil is likely to have a marked influence on soil fertility because different vegetations produce litter of different chemical composition. In Kebun Cina Forest Reserve, three types of soils, viz, Acrisol, Podzol and Lithosol, are found.
 

Acrisol
 
Over a large area of Kebun Cina Forest Reserve, one can see that soils are bright coloured with red or yellow hues due to the presence of appreciable amounts of iron oxides and/or hydroxides and sometimes aluminuim hydroxide. Both colours can exist at different level in the same profile. Under the FAO-UNESCO soil classification, these soils are known as Acrisol . Some of its characteristics are the marked increase in clay content with depth, high acidity that decreases with depth and low plant nutrient content. The deepest and most well drained Acrisol comprises an A horizon (an accumulation of well decomposed organic matter intimately associated with the mineral fraction and normally darker than the adjacent underlying horizon), an E horizon (concentration of sand and silt resulting from loss of silicate clay and a lighter colour) and a B horizon (mineral horizon in which the rock structure is obliterated and there is concentration of silicate clay) . The shallow A horizon is composed of loamy sand with bleached sand grains and humus; thus it is an important source of nutrients for plant growth. This soil layer overlies a deep brownish yellow loamy sand E horizon often with transitional EB horizon passing to B horizons of yellowish red sandy clay loam. On steeper slopes, the A and E horizons are often partially eroded so that the B horizon occurs much closer to the surface.
 

Podzol
 
Another soil type that can be found In the area is podzolic soil which has sandy texture and is well or excessively drained. This soil is typically formed on base-deficient, often highly siliceous, parent material. It comprises surface O layers of acid leaf litter; a shallow humic sandy A horizon; and a grey, strongly leached sandy E horizon which is sharply separated from the moderately fine to coarse textured spodic B horizon. Underlying the spodic horizon is the B horizon that has more clay which may be the result of sequential deposition. This soil has a pH of 4 to 5 and generally contains a low level of plant nutrients except in the surface horizon which is rich in organic matter.
 

Lithosol
Lithosol is restricted to the steepest slope and occurs mainly on upper slopes and also on incised lower slope. This soil occurs in association with outcrops of sandstones and the thickness is about 10 cm on the surface. It becomes hard and massive when dry partly because there is too little organic carbon. Soil erosion and excessive dryness during drought are the main limitations of this soil.
 

 

The information provided above is based on the poster(s) displayed at Kebun Cina Gallery.

Click the following link(s) to view the poster(s).

 

  
 
 
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