1. LIST OF FIGURES
Figure 2.1: Map of South Africa showing the position of Mpumalanga
province.............................................................................................18
Figure 2.2: Sampling sites and the basic geology of the Sabie area....................20
Figure 2.3: View from north west to south east from between compartments
M-27a and M47a, of the Rhenosterhoek forest area.........................21
Figure 3.1: pHKCl values in forest soils of different ages and their
adjacent Grasslands, in the Eastern Transvaal and the Natal
Midlands.............................................................................................33
Figure 3.2: Acidity status in surface soils from commercial forest
plantations of different ages in the Eastern Escarpment....................35
Figure 3.3: Relationship between exchangeable Al (in aqueous solution
of 1M KCl) and pHKCl..........................................................................36
Figure 3.4: Changes in exchangeable basic cations / acidity ratio in soils in
relation to compartment age. The Age group of 0 to 10 consists of
forest compartments and their adjacent grassland soils.
(data source: current study, du Toit (1993) and Nowicki (1997)).......37
Figure 3.5: Amount of Al extracted by 1M KCl and 1M CuCl2 from the soil
collection............................................................................................38
Figure 3.6: Amount of Al removed by CuCl2 in relation to the organic
carbon (%) present in the soil collection............................................39
Figure 3.7: State of base saturation (BS) in grassland soils and forest soils
of different ages in the Eastern Escarpment and Natal Midlands......40
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2. Figure 4.1: Major cation composition of saturated paste extracts of the
soil collection. Concentrations (Y axis) are presented in mmolc/l.......47
Figure 4.2: Major anion composition of saturated paste extracts of the
soil collection. Concentrations (Y axis) are presented in mmolc/l.
Anion deficit was calculated as the difference between the sum
of inorganic cations (Figure 4.1) and anions......................................48
Figure 4.3: EC levels in surface soils of pine forest soils of different
ages and of their adjacent Grasslands...............................................50
Figure 4.4: Saturation indices of four selected minerals (quartz, kaolinite,
gibbsite and jurbanite) for three various MINTEQA2 modeling
outputs (With DOC&F, without DOC&F, Without DOC), at the
pH range of the saturated pastes.......................................................55
Figure 4.5: Changes of soil solution saturation indices as a factor of pH
(saturated paste) with respect to gibbsite and Al-OM complexes......56
Figure 4.6: Distribution of various Ca/Al ratios in soil solution of pine
forest surface soils of different ages and of grasslands in the
Sabie area..........................................................................................58
Figure 4.7: BC/AC ratio on the exchangeable sites and Ca/Al molar ratio in
soil solutions of forest compartments of different ages and of
natural grasslands in the Eastern Escarpment and the Natal
Middlands...........................................................................................64
Figure A1: Schematic map of the Rhenosterhoek plantation.................................I
Figure A2: Schematic map of the Blyfstaanhoogte plantation...............................II
Figure A3: Schematic map of the Grootfontein plantation....................................III
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3. Figure A4: Schematic map of the In Die Diepte plantation...................................IV
Figure C.1: pH values of saturated pastes and extracts of 22 surface soils
under pine plantations of different ages in the Sabie area,
Mpumalanga.....................................................................................XV
Figure C.2: pH values of three successive measurements in extracts of soil
solution for 11 surface soils under pine plantations of different
ages in the Sabie area, Mpumalanga................................................XV
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