Direct Seeding achieves rehabilitation objectives for an operational sand mine in Southeast Queensland: A case study

Abstract

Direct seeding is increasingly recognised as a practical method for ecological restoration; however, its application in post-mining rehabilitation remains limited due to concerns regarding establishment reliability, species performance, and cost-effectiveness. This study evaluates the effectiveness of direct seeding for mine rehabilitation at an operational sand mine in Southeast Queensland, with a focus on achieving compliance with Queensland's Progressive Rehabilitation and Closure Plan (PRCP) requirements. A seed mix comprising 10 native woody species—including primary and secondary koala food trees (Eucalyptus and Corymbia spp.)—and five native grass species was applied across two sites with contrasting land-use histories. Vegetation establishment was monitored over a 36-month period, with performance assessed in terms of species richness, plant density, and the influence of non-native vegetation. At the Native Vegetation Site, canopy tree densities substantially exceeded PRCP targets (5200 vs. 600 stems/ha), and key koala food trees also surpassed their respective benchmarks. In contrast, native grass establishment was lower than anticipated, potentially reflecting dormancy constraints, site-specific soil properties, and competition with exotic species. At the Pasture Site, the dominance of Chloris gayana (Rhodes grass) significantly inhibited native plant recruitment, highlighting the importance of targeted weed management. A cost analysis indicated that direct seeding was approximately 30 % more cost-effective than tubestock planting, while supporting greater species and structural diversity. These findings demonstrate that, when implemented with appropriate site preparation and management, direct seeding represents a scalable, economically viable, and ecologically robust strategy for post-mining landscape rehabilitation.