Two-tiered methodology for the assessment and projection of mine vegetation rehabilitation against mine closure restoration goal

摘要

Reinstatement of a 'self-sustaining native ecosystem' is an increasingly common revegetation goal for open-cut mines in Australia. This is usually applied as a regulatory requirement for mine closure, with some mines aiming for a high standard of 'ecological restoration'. There is a growing appreciation that ecological restoration outcomes of mine rehabilitation are unachievable within the life of a mine and that assessment methodologies are subjective and inadequate to provide the high degree of confidence 'needed for mine closure. Here we elaborate on the integration of the BioCondition assessment and the Ecosystem Dynamics Simulator (EDS) trajectory methodologies. We also demonstrate an alternative early relinquishment assessment criteria similar to that used for early recruitment of regrowth native vegetation that exhibit structural characteristics of undisturbed native vegetation into remnant status in Queensland. We used ten age cohorts of rehabilitation ranging from three to 22 years at Meandu coal mine, south-east Queensland. All the sites gained average BioCondition scores ranging from 19 to 44 out of possible score of 65. Growth trajectories indicated decline in species and basal area on all sites in the next three decades as the dense stock of short-lived acacia species senesce and die. None of the sites are projected to meet self-sustaining status by 2072, but there is evidence in some of a progression. All the sites except two (K2.3 and SW2) are projected to achieve remnant vegetation status by 2062. Applying the remnant vegetation criteria results in shorter timeframes and robustly evaluates whether sites are progressing towards the self-sustaining ecosystem mine closure goal.