Using forest growth trajectory modelling to complement BioCondition assessment of mine vegetation rehabilitation

摘要

The standard rehabilitation objective for open-cut mines in Queensland is to establish a self-sustaining native forest ecosystem. Consequently, mine regulators and managers need tools to project whether sites are likely or not to meet agreed completion criteria and to ensure timely remedial interventions. The Ecosystem Dynamics Simulator (EDS) is such a tool capable of modelling forest dynamics and projecting long-term growth of woody species only. Here, the model was applied to rehabilitation sites aged between 5 and 22 years in Meandu open-cut coal mine in southeast Queensland. EDS projected structural characteristics for trees (height, diameter, basal area, foliage pro-jective cover and stem density) and tree species composition as a function of rehabilitation age. Projected stand growth attributes were assessed against BioCondition benchmarks developed from eucalypt (Eucalyptus/ Corymbid) remnant forests adjacent to the mine. Growth trajectories indicated that sites with ＞30% eucalypt basal area composition were more likely to develop into euca-lypt-dominated self-sustaining ecosystems compared with sites that were initially dominated by acacias (Acacia spp.). Projections suggested that some benchmark attributes such as number of large eucalypt trees would take more than 70 years to be met. The application of EDS provided a framework to support decisions on early remedial intervention and assess the risk associated with lease relin-quishment.