Changes in carbon and inorganic nutrients after clear felling a rainforest in Malaysia and planting with Acacia mangium

The amounts of organic C, and N, P, K, Ca and Mg in the biomass and soils were investigated in two catchments in Sabah, Malaysia, that had formerly supported a dipterocarp rainforest before it was clear felled and planted with Acacia mangium. Trees in one catchment (W4) were manually felled and extracted. Trees in the other (W5), were also manually felled but extracted with crawler tractors. The slash was burnt in W5 before planting, which is the normal practice in this area. During the 10-year rotation period of the plantations, 95 Mg of organic carbon ha-1 were lost from the soil in both W4 and W5, corresponding to about 80% of the soil carbon at planting. About 1390 and 1190 kg N ha-1 were lost from the soil in W4 and W5 during this period, corresponding to 26 and 22% respectively of the initial amounts of nitrogen in the soil before planting. The amounts of plant-available P and Mg in W4 and W5, and Ca in W5 increased in the soil, in spite of the high amounts of nutrients taken up by plants. The content of plant-available K declined, probably due to leaching.