Fire caused demographic attrition of the Tasmanian palaeoendemic conifer Athrotaxis cupressoides
Bowman, DMJS and Bliss, A and Bowman, CJW and Prior, LD, Fire caused demographic attrition of the Tasmanian palaeoendemic conifer Athrotaxis cupressoides, Austral Ecology, 44, (8) pp. 1322-1339. ISSN 1442-9985 (2019) [Refereed Article]
The temperate island of Tasmania is a global centre of plant endemism, with relictual lineages that persist in topographically rugged, wet and cool refugia. An iconic example of these palaeoendemic plants is the slow‐growing conifer, Athrotaxis cupressoides D. Don (Cupressaceae). The geographic range of A. cupressoides has shrunk since European settlement because of destructive anthropogenic fires. Inscription of the Tasmanian Wilderness World Heritage Area in 1982 provided formal protection for Tasmania's palaeoendemic taxa, but they remain vulnerable to lightning‐ignited landscape fires, which are becoming more frequent due to climate change. We surveyed stands across the species’ range and found that stands damaged by fires in the 20th century had higher grass cover and were more exposed to hot northerly winds than unburnt stands. A recruitment bottleneck was evident, with juveniles absent in 28% of unburnt and 47% of burnt transects. Transects on small islands in lakes had lower herbivore densities and less evidence of fire than comparable mainland transects. However, the island transects had lower densities of A. cupressoides seedlings and saplings, despite similar densities of adult trees, suggesting factors other than fire and herbivory contribute to the poor regeneration. We also studied the effects of a lightning fire in 2016, finding it killed 68% of stems overall, with stems less than 30 cm diameter and those scarred by previous fires more likely to die. These findings of high adult mortality and poor regeneration following fire suggest that the geographic range of A. cupressoides will contract due to the increasing frequency of lightning‐ignited fires. Management responses to the increasing risk of landscape fires now include establishment of seed banks, restoration planting and use of irrigation to protect stands from active fires, in addition to rapid suppression of ignitions and targeted planned burning to reduce fuel loads in surrounding flammable vegetation.
fire severity, herbivory, regeneration, scat densities, stand structures, pencil pine, Tasmanian Wilderness World Heritage Area