Effects of forest harvesting nutrient removals on soil nutrient reserves

Intensive harvesting of native eucalypt forests is carried out in the Eden area in the south east coastal region of New South Wales, Australia. Soil nutrient capital and nutrient removals in forest harvesting were estimated together with potential impacts of these removals on the nutrient capital balance. Soils were anlysed from eighty sites for phosphorus fractions, including organic phosphorus fractions, and total and exchangeable cations. Based on typical forest harvesting systems, it was found that 3-4 kg phosphorus would be removed per hectare. Due to equilibrium between the various soil phosphorus components, depletion would not be solely from the more available pools. It is expected that at least four forest rotations (320 years) would be required before any detectable change would occur, within forest communities. A similar depletion estimate was calculated for the potentially most vulnerable cation, calcium. The other nutrient cations, magnesium and potassium had considerably greater reserves.