Catchment nutrient budgets and geological weathering in Eucalyptus regnans ecosystems in Victoria

The movement of water and nutrients (N, P, K, Na, Mg, and Ca) through Eucalyptus regnans dominated catchments in the Maroondah catchment near Melbourne were determined. Nutrient fluxes in precipitation and streamflow are discussed and used to prepare simple precipitation input – stream flow output catchment budgets. These budgets are similar to those found elsewhere in Australia and overseas with the exception of nitrogen. This was probably due to errors in measurement and incomplete quantification of nitrogen fluxes. Catchment sodium budgets were used to estimate geological weathering rates by two different methods. Both methods yielded similar results. Data from two other studies in Victorian forested catchments yielded results similar to those obtained from Maroondah. It was concluded that the bedrock weathering rate at Maroondah was approximately 700 kg ha-1 year-1 which is very similar to that found elsewhere. Nutrient inputs from geological weathering were then estimated and possible errors discussed.