Water stress,transpiration and leaf area index in eucalypt plantations in a bauxite mining area in south-west Australia

The clearing of native forests for open cut mining for bauxite is a potential cause for severe modification of the hydrological cycle. In the Darling Range, Western Australia, jarrah (Eucalyptus marginata Sm.) woodlands are being cleared for mining and are being replaced with plantations of other eucalypts. The plantation trees, which were up to 8 years old, showed no greater water stress than those of the original forest. The leaf area index of older plantation trees was usually higher than that of the original, mature forest. Transpiration rate was estimated on twigs enclosed briefly in a transpiration chamber. Prior test showed that this method was appropriate for comparisons in field grown eucalypts. Field measurements of stratified samples showed little difference in transpiration rate per unit leaf area between plantation forests and original forests. For the last 3 months of the dry season, however, transpiration per unit area of leaves was depressed by 25% in the plantation forest.