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Comparison of Some Soil Chemical Properties in Four Terminalia superba Plantations and a Natural Tropical Forest in Mayombe, Congo

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A comparative study was carried out in Mayombe, between the soil of the natural forest and the soil under four Terminalia superba plantations of 7, 12, 32 and 48 years old. Ten composite soil samples were collected from ten systematically located squares (1 mי, four cores from each square) in each plantation. The goal was to evaluate the impact of reforestation on soil pH, exchangeable cations, base saturation, CEC and phosphorus in the 0-10 em layer. The results showed that soil pH was 4.63 in natural forest and between 4.97 and 5.84 in plantations. Ca content was higher in the 7 year old plantation (7.83 cmol kg-I) than in natural forest (3.14 cmol kg-I). Mg was 3.27 cmol kg-I in the young plantation and 1.41 cmol kg-I in forest. K exhibited a low content in the plantations and high content in natural forest. Base saturation varied between 48.6 and 100%. The CEC was almost a steady state. All soil properties showed an initial increase in the seven years after reforestation. The increase was followed by a general decrease with aging of plantations. Despite this decline, the positive Deterioration Index (DI) recorded suggested that reforestation with T. superba slightly improved the soil attributes, except in the case ofK and CEC in which a negative DI was obtained

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