Case Study: Some Lessons From the Early Development of Native Forest Rehabilitation at Three Surface Mine Complexes in Australia

Abstract

Abstract:The rehabilitation of forest and other woody vegetation ecosystems on mineral extraction sites is common place and a major post-mining land use throughout Australia. Owing to the need for government certification (under Australian Government and State legislation) for mine closure, monitoring of the establishing forests or other woody ecosystems is typically undertaken using agreed completion criteria which are predictive of rehabilitation future achievement. The collation and review of the monitoring results for the early development of the rehabilitated forests at three surface mines provide an opportunity to identify key processes and practices that might be used to enhance the achievements in Australia and elsewhere. The monitoring results for two rehabilitation schemes in subtropical Queensland (mineral sand and coal) and one in Western Australia (bauxite) were examined. Whilst it is evident that woody vegetation comprising several native tree and shrub species can be readily established, the resulting vegetation communities in the early development of the forest vegetation can be notably different in their composition and structure to the target and/or locally occurring native types. It is concluded that forest structural formation in combination with species composition, are of importance in establishing the predicted trajectory of the developing forest type, ecosystem, functioning, and sustainability. Species composition is likely to influence initial forest structure and the need for intervention practices, such as thinning, that may be required to achieve the necessary structural formation and ultimately the targeted native forest types. The principles established are likely to universally apply irrespective of the mineral and climatic types examined.

Extended ecosystem function analysis — the next step for mine rehabilitation appraisals

“…Despite the apparent attainment of a stabilised ecosystem, the dense scrub structure was not the vegetation and ecosystem for the target regionally important native sand dune heath/forest described by Gravina et al 2011, and Smith and Nichols 2011. It also exhibited no evidence or indication of community renewal for its future stability as a vegetation type (Humphries 2016). This situation is not unique to the mineral sand rehabilitation and is evident in rehabilitation elsewhere.…”

“…In the examples cited and reported by Tongway (n.d.(b)), Lacy et al (2008), DnA Environmental (2013, 2014) and EBS Ecology (2013), there is no requirement to characterise the developing vegetation community, structure and condition. While the soil surface may be nutrient rich, stable and have a high infiltration capacity, the vegetation present may not be a type that meets the rehabilitation and completion criteria objectives and/or may not be sustainable as has been pointed out for some forest rehabilitation schemes (Humphries 2016). For example, the sheoak (Alocasuarina) dominated stands on rehabilitated mineral sand mines in Queensland (Gravina et al 2011) are likely to have scored highly in the LOI and the LFA/EFA methodology.…”

“…Currently, such data are not routinely collected as part of the LFA/EFA process, and where they are collected they are typically not being used to determine the type of vegetation ecosystems being assessed and to identify significant species and assemblages. Using this type of data it was possible to project the likely development trajectory of forest rehabilitation and achievement of the objectives and criteria at three mines (Humphries 2016). Given the establishment was not reflecting those of the target assemblages, such data would enable the identification of the need for changes in establishment practice and any necessary intervention to achieve the rehabilitation objectives, as described by Grigg and Grant (2009), Gravina et al 2011, and Smith and Nichols (2011).…”

“…It tells us, for example, whether the ecosystem is tree, shrub, herbaceous or cryptogam based, whether it is a closed or open system, and whether it is changing from one to another form. Using vegetation structural formation data it was possible to determine the current development trajectory of forest rehabilitation and achievement of the objectives and completion criteria at three mines, and enabled the identification of the critical need for intervention to achieve the rehabilitation objectives (Humphries 2016).…”

“…Eyre et al (2011) have published a useful classification for vegetation structural formations that could be applied to determine the nature and development of establishment on mine sites. It is currently deployed in Queensland as part of its regional ecosystem descriptions and classifications, and has been advocated for forest ecosystems in Queensland and Western Australia (Humphries 2016).…”