Restoring Banksia woodland communities after pine forestry in a biodiversity hotspot, Western Australia

Background/Question/Methods

This study assesses the potential of returning native Banksia woodlands to areas of the Pinus pinaster Ait. (Maritime Pine) pine plantations on the Gnangara Mound, a vital water source north of Perth, Western Australia. It will provide crucial knowledge essential in the continuing development of restoration techniques that maximise the establishment of Banksia woodland species, which are increasingly threatened by clearing for urbanisation and mining. This study will extend Banksia woodland restoration techniques developed to date and apply them to the old field environment of pine plantations, aiming to determine if the 50 year persistence of pine plantations has irreversibly affected the soil environment and its ability to sustain the former Banksia woodland ecosystem. Study areas include: topsoil seedbank analyses; physical and chemical soil analyses; seedling establishment, survival, health and physiology trials; combined with an overall ecosystem health analysis utilising invertebrate and mycorrhizal activity sampling.

Results/Conclusions

Soil testing at 500 mm increments to the water table at three different sites show elevated acidity, phosphorus (P) and organic carbon levels within P. pinaster soils which may impact native Banksia woodland restoration. Mechanically ground P. pinaster pine needles at high concentrations impede native species germination. Areas of cleared pine that remain fallow result in reduced emergence of native species. Invasive weed species management is of particular concern to combat the rapid recruitment and growth of non native species in areas of cleared pine left fallow. With the State government of Western Australia planning to replace 23, 000 hectares of P. pinaster plantations to protect and enhance a subsoil potable water source, native Banksia woodland will need to be restored at a rate of 1,000 hectares per year.  Thus this study will provide key information for maximising restoration efforts of this biodiverse ecosystem. The work will provide information to aid the recovery of this iconic ecosystem assemblage with special conservation value in the southwest Australian biodiversity hotspot.