Impacts of dieback at Pine Lake, Tasmania

Abstract

The possibility of a new plant disease in alpine plant communities was identified in 1994, following an investigation of dead and dying plants in the Central Plateau Conservation Area. Seven areas of dieback were identified within the affected catchment and monitored. Symptoms included leaf discolouration, loss of foliage and plant death. No disease of this type has previously been recorded in the Australian alpine environment. Temporal and spatial patterns in disease development along with evidence of lesions on plant roots suggested a soil and water-borne pathogen could be contributing to the dieback. A species of Phytophthora was isolated from plant material collected at the site. Investigations have focussed on whether plants at the limits of their range have been more susceptible to a combination of below-average rainfall, above-average temperatures and the presence of pathogens. Initial rapid development of disease symptoms suggested the potential for local extinction of species, including Tasmanian endemics such as Athrotaxis cupressoides, and significant alteration to community structure through a loss or substantial reduction in the tree and shrub layers. However, longer term monitoring suggests short-term disease events followed by recovery of surviving plants with only localised impacts. Management actions have been concentrated on containment, monitoring impacts and investigation of the cause of the dieback.