Effect of forest plantation of some species of Shorea on soil fertility properties

The performance of forest tree growth depends largely on the soil factors, particularly when the climatic and topographicall factors are optimum for the tree species. On the other hand vegetation (including forest trees) is capable of affecting some soil characteristics. So the interrelationship between soil-forest three is very close. Attention and investigation on forest three species having potential for improving physico-chemical soil fertility are now being increased particularly by foresters and forest plantation managers. This is very interesting because the soil resources should be used without destruction of its productivity. This investigation is conducted to predict which species of the 3 species of Shorea, i.e. S. pinanga, S. compressa and S. palembanica has the best effect on both physical and chemical soil fertility, in order to seek species of forest three which have potentials as soil improver or soil conserver. The result showed that better effect on soil physical condition ie: on soil porosity soil permeability and bulk density was found for S. palembanica, but not on soil chemical fertility. No different effect of the three planted species is found on the following soil chemical properties: soil reaction (pH values range from 5.12-5.66); organic carbon 2.2 percent (01-0 cm depth) to 1.2-1.6 percent (10-20 cm depth), total N: 0.4 percent (0-10 cm) and 0.2 percent (10-20 cm), content of potassium, magnessium and calcium. All of these parameters show similar results. Also the CEC of the soils are not affected by the planted species. For these soil parameters all species had positive effect except on potassium. Base on the content of nutrients of the forest floor, the best species for soil fertility conservation is found for S. pinanga. Under this forest stand the contents of three important nutrients, i.e. phosphorus (P), nitrogen (N) and potassium (K) were: 225.2 kg/ha, 1241 kg/ha and 1290.6 kg/ha respectively and then followed by S. compressa. It is concluded that S. pinanga, S. compressa and S. palembanica have positive effects on chemical soil properties except on the soil potassium content. The best species for soil fertility conservation through nutrient cycle will be S. pinanga followed by S. compressa. It is suggested that these tree species of Shorea should be chosen for reforestation and man made forest extensification because of their capability to maintain and to conserve soil feritlity level during their growth