Deeper mine site soil covers the root to revegetation success

New research by Federation University will help ensure the success of coal mine site rehabilitation in a changing climate. 

 

With climate models projecting a warmer and drier climate future for Victoria, the consequences for vegetation soil covers on rehabilitated coal mines is likely to be significant: soil drought conditions could affect the survival and density of the vegetation cover, in addition to increased erosion risk for rehabilitated landform stability.

 

The research, commissioned by the Cooperative Research Centre for Transformations in Mining Economies (CRC TiME) with support from the Victorian Government and Federation University, details that increasing the depth of soil covers allows vegetation to grow roots deeper to endure drought conditions. 

 

The underlying coal beneath the soil covers have great potential to store water, providing water to plants over extended periods of drought conditions.

Vegetation planted on deeper cover therefore has a much greater chance to endure drought conditions.

 

The project team used measured data and hydrological modelling to simulate soil moisture and water flux, with data revealing the importance of fracture flow of water through coal. 

 

Climate conditions from 2021 in the Latrobe Valley were extrapolated to simulate future climate scenarios, and these were used to guide soil column experiments to assess soil water content and plant growth.

 

Vegetation was planted in the soil columns and a range of soil cover and climate 

scenarios were modelled.

 

What the project team around Professor Baumgartl and Dr Filipović found was heartening: plants under drought conditions grew their roots deeper searching for and extracting water from the coal below. 

 

Professor Baumgartl notes the impact these new data could have on mine site rehabilitation for industry: “To most effectively rehabilitate landforms that can withstand future climate conditions, increasing the depth of soil cover designs – to a certain point – could be a means to provide more opportunity for vegetation to establish and thrive in the long term.”

 

CRC TiME CEO Dr Guy Boggs noted the national need to implement new technologies for risk reduction and value creation across the life cycle of mines: “Mine closure plans rely on new techniques to reduce liabilities and lower costs for rehabilitation. Thomas and Vilim’s work on soil covers complements our work on native seed sourcing and procurement training – particularly for 

regional and First Nations businesses – as well as our trials in developing functioning soils, more efficient and effective ecological monitoring, and pit lake risk reduction.”

Future studies should consider surface runoff for sloping rehabilitated areas, and its effect on erosion and water distribution.

 

The pattern of coal fractures also needs to be investigated through tailored field trials, as their effect on root growth is vital.

 

CRC TiME is supported by the Australian Government Department of Industry, Science and Resources Cooperative Research Centre Program.