Mapping and assessing Phytophthora cinnamomi dieback in the eastern Otways

The plant pathogen Phytophthora cinnamomi causes severe declines in Australian native vegetation, loss of susceptible flora, degradation of fauna habitat, fauna declines and ecosystem deterioration. The disease Phytophthora dieback has been listed as a Key Threatening Process to Australian biodiversity under the EPBC Act 1999. Research on the impacts of the pathogen in the eastern Otways has been undertaken since the 1970s, yet knowledge gaps have been identified when considering the mapping of the disease?s current occurrence and location of significant uninfested refuges within the Great Otway National Park. The objective of this research was to identify and map the spread of P. cinnamomi within the Anglesea Heathy Woodlands. Floristic data was recorded to assess species composition/cover between uninfested, infested and post-infested vegetation. Significant declines in susceptible species cover have led to increases in resistant sedges and grasses, suggesting that susceptible species are not recovering following infestation. The density of susceptible keystone species Xanthorrhoea australis (Austral grass-tree) was recorded in order to correlate basal area with Normalized Difference Vegetation Index (NDVI) satellite imagery. This study has identified significant uninfested refuges of X. australis and demonstrated NDVI to be an effective tool in mapping P. cinnamomi spread across the landscape. Further research is required to improve the accuracy of results so the need for extensive on-ground vegetation surveying can be reduced. Through identification of uninfested remnants, management techniques including strategic phosphite application, wash-down facilities and track closures can be implemented to reduce disease spread and conserve significant biodiversity within the Great Otway National Park.