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Plantation forestry project

As part of the Gnangara Sustainability Strategy, the Forest Products Commission is undertaking the following project:

The project

There have been numerous studies of the impact of maritime pine (Pinus pinaster) plantations on recharge into the surface aquifers of the Gnangara groundwater system.

These studies have consistently demonstrated that dense plantations on the deep sandy profiles eliminate recharge to the aquifers. Conversely, maintaining the plantations at leaf areas below the point where maximum productivity is achieved allows recharge to occur.

The requirement for timber from the Gnangara, Pinjar and Yanchep plantations to maintain the wood flow to the Wesbeam Laminated Veneer Lumber Plant is the subject of a State Agreement, which requires that wood flows are maintained until 2029.

The agreement needs to be considered with any initiative that may increase the flow of water into the aquifer by changes to planned harvesting regimes. Adding to the complexity of the management of these plantations has been the discovery of an extensive European House Borer infestation. This has necessitated the selective clearfelling of some stands, which further reduces the options for modifying the overall management of the plantations.

This project will consider opportunities to change pine harvest regimes to increase groundwater recharge.

What will the project achieve?

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The project aims to:

  • Quantify the impacts of different harvesting strategies on likely wood flows from the existing plantations and thus water yields.
  • Identify whether there are specific areas where P. pinaster can be replanted in this region and determine the optimal practices for those areas for both water yield and quality.
  • Quantify the impact on wood flows and water yields of retaining areas of plantation for recreation and cultural heritage values.
  • Assess the impact of pine removal on the black cockatoo (Calyptorhynchus banksii) populations.

For more information on these and other projects, please contact us at gss@water.wa.gov.au