Quarry Rehabilitation (Revegetation)

By on August 10, 2017

The following is a summary of the Quarry Rehabilitation presentation given by STEVE MUECK (Senior Consultant Botanist, Biosis) at the CMPA Progressive Rehabilitation Management Workshop held in February 2017.

Rehabilitation Context
Firstly discussed was the context for rehabilitation: the type of quarry, for example, sand, gravel or rock and the location: for example, peri-urban or rural; and of course existing vegetation (introduced /native vegetation).

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Rehabilitation Objectives

The second step is to establish the rehabilitation objectives: introduced vegetation versus native vegetation.
Creating a novel environment (through quarrying) will mean that:
• This is unlikely to be suitable for the pre-quarry vegetation community hence what ecological vegetation classes are to be planted.
• There will be new habitat types such as steep slopes which will have value for different species to the original vegetation.
• Objectives will need to be established such as how many species are required and the resulting structure.
• Susceptibility to weed invasion will be dependent on the local weed load.
• There may be a change in hydrology, for example, the likelihood of a wetland in the quarry floor due to ground water discharge.
• There will be changed soil structure with any re-used topsoil possibly requiring time to stabilise.
• There may be changed soil biology: soil is more than decomposed rock with bacteria and fungi required in order for plants to grow.
• Comparisons with broadly similar contexts in the surrounding landscape may assist in species / vegetation community selection.
• There may be community succession whereby one plant is used to improve conditions for another.

Climatic Context
• Establish the total rainfall: tropical, temperate, semi-arid etc.
• Seasonality of climate.
• Extremes in the climate will influence whether rehabilitation will succeed or fail.
• Climate change can influence what is reasonable to plant.
• There are limited opportunities for successful  establishment of vegetation.

Availability of suitable plants for revegetation
Are local plants chosen or whatever is available? Availability will be driven by:
• The demand for the site’s indigenous vegetation for example, grassland rehabilitation.
• Determining suitable vegetation.
• Whether planting tube stock, direct seeding or both.
• The number of plants required will be dependent on the context, for example, a weedy environment will need more work and more plants.
• The final point is to do things once and so plan revegetation well.

Understand the Process
A thorough understanding of the approval, planning and preparation processes is likely to lead to successful revegetation.
• Clear achievable objectives and goals from approval to exit.
• Every site is different so start small, revegetation works can be expensive – some trial and error may be required to get it right.
• Site preparation – stored soil, mulch, weed matting, and brush matting.
• Secure source of plants (lag time for collection and growing).
• Regular monitoring of revegetation enables an understanding of current progress and the ability to report success.

What works and what may not

Sand Quarry
• Salvage and reuse top soil as soon as possible.
• Brush cutting and lay out.
• Supplementary planting.
• On-site nursery.
• Lower areas likely to be wetter and so the vegetation community will change.

Hard Rock
• Wetlands in the quarry floor can be a great biodiversity asset (e.g. Growling Grass Frog breeding).
• Cliffs can be a rare habitat useful to some species (e.g. Peregrine Falcon).
• Use colonising species to establish early vegetation structure (e.g. Wattles fix nitrogen and help establish soil structure, grasses provide erosion control).
• Do not try to undertake revegetation all at once: if it is wrong then it is a waste of resources.

General do’s and don’ts
• Do not agree to the impossible to get approval – regulators need to be realistic.
• Vegetation communities can take decades to establish and may need to go through many stages.
• Rehabilitation requires careful planning and preparation.
• Starting physical rehabilitation is one thing – starting revegetation is another (it may take a year or two to get ready to start planting native vegetation).
• Each site is different and plants can behave differently so do not try to do everything at once. What works in one place may not in another – learn through progressive rehabilitation.

 

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Thank you to Steve Mueck, Biosis.

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