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Dieback Forest Rehabilitation
 
Phytophthora dieback has a widespread distribution throughout the jarrah forest. In some areas the effect of the disease is very high with the death of many jarrah trees, Banksia trees and understorey plants. The worst affected sites have been termed as ‘graveyards’ due to the presence of dead tree stags.
 
In 1987 Alcoa made a commitment to work with state government departments to rehabilitate these sites that were present within the mining area. Alcoa continues to jointly manage the program with the Department of Environment and Conservation (DEC) and provide financial support.
 
The program aims to improve the structure of the vegetation community and improve the general aesthetics of the sites. This will increase the potential of the forest to meet all its pre-existing land uses, which include water catchment and provision of fauna habitats.
 
To determine a site's suitability for dieback forest rehabilitation (DFR), it is individually assessed and a suitable treatment for its condition is prescribed. If the site is a dieback graveyard the treatment may involve breaking up and loosening the surface of the soil, planting the area with trees, and seeding it with an understorey legume mix. For sites with a productive understorey but many deaths in the overstorey, disturbances to the healthy plants are minimised by only planting seedlings and doing little soil disturbance treatment.
 
Sites that are very degraded, but have a low likelihood of success with current treatments, are not treated. At Willowdale, for example, the majority of non-mining dieback forest occurs on "black gravel" areas – these are areas where the topsoil contains a high proportion of black gravel and where we know current treatments will not be successful.  Research projects by Murdoch University have investigated what plants, animals and fungi occur on these sites. A second research project is developing and assessing tree establishment techniques.
 
A workshop was held in 2006 to discuss the rehabilitation of these degraded sites and to identify opportunities to improve the DFR program. The workshop was attended by wide range of stakeholders including representatives from government departments, research institutions, non-government organisations, neighbours and community conservation groups. The workshop participants supported the continuation of projects to understand the ecology of these dieback affected gravel sites.  As a result of the workshop, a research scientist has been funded by Alcoa for 3 years to study these sites.
 
Rehabilitated dieback forest sites are monitored to determine if the applied treatments have successfully established trees and seeded legumes. The sites are assessed two years after the treatment, and both the DEC and Alcoa review the results to determine whether they warrant any changes to our current treatments. Some sites have been re-monitored at five-years-old to ensure site improvement has been maintained.
 


A dieback graveyard site.

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A dieback graveyard site.

Research, black Gravel site

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Research is underway to determine the best treatment for Willowdale Mine's dieback infected black gravel areas.